JP2013058746A - Polymer sheet for solar cell and manufacturing method therefor, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer sheet for a solar cell having excellent manufacturing suitability in which adhesion is excellent between a polymer base material and a polymer layer provided thereon.SOLUTION: The polymer sheet for a solar cell has a first polymer layer containing at least one kind of binder polymer selected from fluorine polymer and silicon polymer on a polymer base material, and a second polymer layer including, on the polymer base material layer of the first polymer layer, a structural portion derived from a crosslinking agent having at least one kind of binder polymer selected from fluorine polymer and silicon polymer, and an oxazoline group for crosslinking the binder polymer, where the equivalence [meq/g] of oxazoline group to the binder polymer is more than 0 and less than 1.

Description

  The present invention relates to a solar cell polymer sheet provided on the opposite side of a solar cell element to a solar light incident side, a method for producing the same, and a solar cell module.

  In general, a solar cell module has a structure in which a glass / front sheet on which sunlight is incident / a sealant / a solar cell element / a sealant / a backsheet (hereinafter also referred to as BS) is laminated in this order. doing. Specifically, in the solar cell module, the solar cell element is generally embedded with a resin (sealing material) such as EVA (ethylene-vinyl acetate copolymer), and a solar cell protective sheet is further adhered thereon. Configured to structure. Moreover, as this protective sheet for solar cells, conventionally, a polyester film, particularly a polyethylene terephthalate (hereinafter referred to as PET) film has been used.

  However, when used for a long time as a protective sheet for solar cells, especially a back sheet (BS) for a solar cell that is the outermost layer, a general PET film is likely to peel off on the solar cell. In a single-layer BS, if it is placed for a long time in an environment that is exposed to wind and rain such as outdoors, peeling is likely to occur between the BS and a sealing material such as EVA. Conventionally, a laminate-type BS in which a weather-resistant film is bonded to the outermost layer side of a base film such as PET has been used for the problem of weather resistance. Among the laminated laminates, the most widely used was a fluorine-based polymer film such as a polyvinyl fluoride film.

  However, when a fluoropolymer film is used as a polymer sheet for a laminate type solar cell, the adhesion (adhesiveness) between the polyester film and the fluoropolymer film is weak, and it tends to peel off when used for a long period of time. There was a problem. On the other hand, in recent years, a coating type back sheet in which a composition containing a fluorine-based polymer is applied on a PET base film has been developed (see Patent Documents 1 to 5). For example, Patent Document 2 discloses a polymer sheet in which a polyethylene terephthalate support having a specific thickness and a weathering layer that is a fluorine-containing polymer layer are laminated by coating.

  On the other hand, in addition to the weather resistant layer, various other functional layers have been laminated on the polymer sheet for solar cells. For example, in Patent Document 6, white inorganic fine particles such as titanium oxide are added to the back sheet, a white layer having light reflection performance is laminated, and light passing through the cell is irregularly reflected and returned to the cell to generate power. A method for improving the efficiency is described. Furthermore, in order to obtain strong adhesion between the back sheet and the EVA sealing material, a polymer layer such as an easy adhesion layer may be provided on the outermost layer of the back sheet. In this regard, Patent Document 6 describes a technique for providing a thermal adhesive layer on a white polyethylene terephthalate film.

  Thus, the present situation is that the protective sheet for solar cells, which tends to be multilayered, is more likely to cause the problem of adhesion between the layers as the number of laminated layers increases. Furthermore, in recent years, solar cells have been used for a long time in harsh places such as outdoors, from the viewpoint of increasing the power generation efficiency of solar cells and from the viewpoint of reducing the cost by integrating and installing them. Also, the durability is required for the adhesion between the layers.

  On the other hand, for the purpose of improving the curability of the curable resin composition, Patent Document 7 discloses a compound having a plurality of 2-oxazoline groups in the molecule and a plurality of carboxyl groups in the molecule. A curable resin composition containing a compound and a catalyst is described.

JP 2010-95640 A JP 2010-53317 A JP 2007-35694 A International Publication No. 2008/143719 Pamphlet JP 2010-053317 A Japanese Patent Laid-Open No. 2003-060218 JP 05-25361 A

However, conventional laminated films and laminated structure supports as described in the above-mentioned prior art documents such as Patent Documents 1 and 2 are still unsatisfactory from the viewpoint of adhesion between layers required for solar cells in recent years. It is enough. Furthermore, further improvement is demanded for improvement in adhesion when a polymer layer containing a polymer such as a fluoropolymer and a silicone polymer is applied.
Moreover, the curable resin composition as described in Patent Document 7 uses a highly reactive compound such as an acrylic resin as a main binder as a compound having a carboxyl group. For this reason, it is difficult to apply the said curable resin composition to the solar cell use as which a weather resistance is requested | required.

  The present invention has been made in view of the above circumstances, and has excellent adhesion between a polymer substrate and a polymer layer provided on the polymer substrate, and a polymer sheet for solar cells excellent in production suitability. It is an object to provide a manufacturing method thereof and a solar cell module having stable power generation efficiency.

Specific means for solving the above problems are as follows.
<1> A first polymer layer containing at least one binder polymer selected from a fluoropolymer and a silicone polymer on a polymer substrate, and the fluoropolymer provided on the polymer substrate side of the first polymer layer And at least one binder polymer selected from silicone polymers, and a structural part derived from a crosslinking agent having an oxazoline group that crosslinks the binder polymer, and the equivalent amount [meq / g] of the oxazoline group to the binder polymer is And a second polymer layer that is greater than 0 and less than 1.

<2> The solar cell polymer sheet according to <1>, wherein the first polymer layer contains an onium compound.
<3> The polymer sheet for solar cells according to <1> or <2>, wherein the second polymer layer contains an onium compound.
<4> The polymer sheet for solar cells according to any one of <1> to <3>, wherein the first polymer layer is an outermost layer.
<5> The sun according to any one of <1> to <4>, wherein at least one of the first polymer layer and the second polymer layer contains a water-miscible organic solvent having a boiling point of 99 ° C. or less. It is a polymer sea for batteries.

<6> The polymer sheet for solar cells according to any one of <1> to <5>, wherein the polymer base material contains an end-capping agent.
<7> The polymer sheet for solar cells according to any one of <1> to <6>, wherein the polymer base material contains a carbodiimide-based end-capping agent.
<8> The polymer sheet for solar cells according to any one of <1> to <7>, wherein the polymer substrate contains fine particles that are inorganic particles or organic particles.
<9> The polymer sheet for solar cells according to any one of <1> to <8>, wherein the polymer base material has a laminated structure including two or more layers having different content rates of fine particles that are inorganic particles or organic particles. It is.

<10> At least one of the first polymer layer and the second polymer layer has a boiling point of 99 ° C. selected from methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and acetone. The polymer sheet for solar cells according to any one of <1> to <9>, which contains the following water-miscible organic solvent.

<11> On a polymer substrate, an equivalent of oxazoline group [meq / g] containing at least one binder polymer selected from a fluoropolymer and a silicone polymer, and a crosslinking agent having an oxazoline group. ], A step of applying a coating solution having a value greater than 0 and less than 1 and drying, followed by curing to form a second polymer layer, and a fluoropolymer and a silicone polymer are selected on the second polymer layer And a step of forming a first polymer layer by applying and drying a coating solution containing at least one binder polymer.

<12> The method for producing a polymer sheet for a solar cell according to <11>, wherein the coating liquid used in the step of forming the first polymer layer contains an onium compound.
<13> The method for producing a polymer sheet for solar cells according to <11> or <12>, wherein the coating liquid used in the step of forming the second polymer layer contains an onium compound.
<14> The curing time of the polymer layer in the step of forming the first polymer layer and the step of forming the second polymer layer are both in the range of 1 minute to 30 minutes. <11> to <13> The manufacturing method of the polymer sheet for solar cells of any one of these.

<15> The coating liquid used for forming at least one of the first polymer layer and the second polymer layer is a binder polymer containing a water-miscible organic solvent having a boiling point of 99 ° C. or less in the coating liquid. It is a manufacturing method of the polymer sheet for solar cells as described in any one of <11> to <14> which is an aqueous coating liquid containing 0.1 mass%-30 mass% with respect to the total mass.
<16> The coating solution used for forming at least one of the first polymer layer and the second polymer layer is at least selected from methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and acetone. The polymer sheet for solar cells according to any one of <11> to <15>, which contains one kind of water-miscible organic solvent having a boiling point of 99 ° C. or less.

<17> The polymer sheet for solar cell according to any one of <1> to <10> or the polymer sheet for solar cell according to any one of <11> to <16>. It is a solar cell module provided with the polymer sheet for solar cells made.

<18> a transparent front substrate on which sunlight is incident, a cell structure portion provided on the front substrate and having a solar cell element and a sealing material for sealing the solar cell element;
The polymer sheet for solar cells according to any one of <1> to <10>, provided on the side opposite to the side where the front substrate is located of the cell structure portion, and disposed adjacent to the sealing material. Or the polymer sheet for solar cells manufactured by the manufacturing method of the polymer sheet for solar cells of any one of <11>-<16>.

ADVANTAGE OF THE INVENTION According to this invention, the polymer sheet for solar cells which was excellent in the adhesiveness of a polymer base material and the polymer layer provided on this polymer base material, and was excellent in manufacture aptitude, and its manufacturing method can be provided.
Moreover, according to this invention, the solar cell module which has the stable electric power generation efficiency can be provided.

  Hereinafter, the polymer sheet for solar cells of the present invention, the manufacturing method thereof, and the solar cell module will be described in detail.

In this specification, when referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, the plurality of the components present in the composition unless otherwise specified. It means the total amount of substance.
In the present specification, a numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In this specification, the term “process” is not only an independent process, but is included in the term if the purpose of the process is achieved even when it cannot be clearly distinguished from other processes.

[Polymer sheet for solar cells]
The polymer sheet for solar cells of the present invention comprises a first polymer layer containing at least one binder polymer selected from a fluoropolymer and a silicone polymer on a polymer substrate, and the polymer of the first polymer layer. The substrate side includes at least one binder polymer selected from a fluoropolymer and a silicone polymer, and a structural part derived from a crosslinking agent having an oxazoline group that crosslinks the binder polymer, and the oxazoline for the binder polymer The polymer sheet for solar cells which has the 2nd polymer layer whose group equivalent [meq / g] is more than 0 and less than 1.

In the present invention, the first polymer layer that is a constituent layer of the polymer sheet is a layer containing at least one binder polymer selected from a fluoropolymer and a silicone polymer, and the second polymer layer is At least one binder polymer selected from a fluoropolymer and a silicone polymer, and a cross-linking agent having an oxazoline group, and the equivalent [meq / g] of the oxazoline group to the binder polymer is 0 By making the layer into a specific range in which the content of the cross-linking agent exceeding 1 and less than 1 is relatively low, excellent adhesion between the polymer layer and the polymer substrate is exhibited. Moreover, the adhesiveness between the polymer layer and the polymer substrate in the present invention is excellent in sustainability.
Furthermore, in a preferred embodiment of the present invention, the first polymer layer and / or the second polymer layer contains an onium compound, so that the polymer has excellent adhesion between the polymer layer and the polymer substrate. The solvent resistance of the layer can also be improved.
Thereby, when a solar cell module is comprised using the polymer sheet for solar cells of this invention, while being able to obtain favorable electric power generation performance, power generation efficiency can be kept stable over a long period of time.

  The first and second polymer layers in the present invention may be a weather resistant layer exposed to an external environment, that is, a back layer, when a solar cell module is configured using the polymer sheet for solar cells of the present invention. preferable. The first polymer layer is preferably the outermost layer.

  Hereinafter, each constituent element in the polymer sheet for solar cell of the present invention will be described in more detail in the order of the polymer substrate, the first polymer layer, the second polymer layer, the layer configuration, and the characteristics of the polymer sheet for solar cell. do.

(Polymer substrate)
The polymer sheet for solar cells of the present invention has a polymer substrate.
Examples of the polymer substrate include polyester, polyolefin such as polypropylene and polyethylene, or fluorine-based polymer such as polyvinyl fluoride. Among these, polyester is preferable from the viewpoint of cost and mechanical strength.

<Polyester>
The polyester used as the polymer substrate (support) in the present invention 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. Among these, polyethylene terephthalate or polyethylene-2,6-naphthalate is particularly preferable from the viewpoint of balance between mechanical properties and cost.

  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 is preferred in which the Ti-based compound is polymerized by using it as a catalyst so that the Ti element conversion value is in the range of 1 ppm to 30 ppm, more preferably 3 ppm to 15 ppm. When the amount of Ti compound used is within the above range in terms of Ti element, the terminal carboxyl group can be adjusted to the following range, and the hydrolysis resistance of the polymer 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, Patent No. 3,996,871, Patent No. 4000086, Patent No. 4053837, Patent No. 4,127,119, Patent No. 4,134,710, Patent No. 4,159,154, Patent No. 4,269,704, Patent No. 4,313,538 and the like can be applied.

The carboxyl group content in the polyester is preferably 55 equivalent / t (tons; the same applies hereinafter) or less, more preferably 35 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). When the carboxyl group content is 55 equivalents / t or less, hydrolysis resistance can be maintained, and a decrease in strength when subjected to wet heat aging can be suppressed to be small.
“Equivalent / t” represents a molar equivalent per 1 ton.
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 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 method described in Japanese Patent No. 4167159 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.

The polyester substrate in the present invention is preferably a biaxially stretched film from the viewpoint of mechanical strength.
For example, the polyester base material in the present invention is obtained by melt-extruding the above polyester into a film and then cooling and solidifying with a casting drum to form an unstretched film. The unstretched film is longitudinally at Tg to (Tg + 60) ° C. A biaxially stretched film that is stretched once or twice or more so that the total magnification is 3 to 6 times, and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C. Preferably there is.
Furthermore, what was heat-processed for 1 to 60 second at 180-230 degreeC as needed may be used.

As for the thickness of a polymer base material (especially polyester base material), about 25 micrometers-about 300 micrometers are preferable. If the thickness is 25 μm or more, the mechanical strength is good, and if it is 300 μm or less, it is advantageous in terms of cost.
In particular, the polyester base material has a tendency that the hydrolysis resistance deteriorates as the thickness increases, and the durability during long-term use tends to decrease. In the present invention, the thickness is 120 μm or more and 300 μm or less, and When the carboxyl group content in the polyester is 2 to 35 equivalents / t, the effect of improving wet heat durability is further exhibited.

<End sealant>
The polymer substrate may contain one or more end capping agents.
The content in the case where the polymer substrate contains a terminal blocking agent is preferably 0.1% by mass to 10% by mass with respect to the total mass of the polymer contained in the polymer substrate, and more preferably 0.8%. It may be 2% by mass to 5% by mass, more preferably 0.3% by mass to 2% by mass.

  Hydrolysis of the polymer is accelerated by the catalytic effect of hydrogen ions generated from the terminal carboxyl group, etc. Therefore, in order to improve hydrolysis resistance (weather resistance), an end-capping agent that reacts with the terminal carboxyl group is added. Can be effective. When the content of the end-capping agent is within the above range, it can be avoided that the end-capping agent acts as a plasticizer for the polymer and the mechanical strength and heat resistance of the polymer substrate are lowered.

  Examples of the terminal blocking agent include an epoxy compound, a carbodiimide compound, an oxazoline compound, and a carbonate compound. A carbodiimide having high affinity with a polymer suitable for a polymer substrate such as polyester and high end-capping ability is preferred.

  When the end capping agent (particularly carbodiimide end capping agent) has a high molecular weight, volatilization during melt film formation can be reduced. The molecular weight is preferably 200 to 100,000 in terms of weight average molecular weight, more preferably 2000 to 80,000, and still more preferably 10,000 to 50,000. When the weight average molecular weight of the end-capping agent (particularly carbodiimide end-capping agent) is 100,000 or less, it is easy to uniformly disperse in the polymer, and the weather resistance improving effect can be sufficiently exhibited. When the weight average molecular weight of the end-capping agent is 200 or more, volatilization during extrusion and / or film formation can be suppressed, and an effect of improving weather resistance can be exhibited.

-Carbodiimide terminal blocker-
The carbodiimide terminal blocking agent is a carbodiimide compound having a carbodiimide group. The carbodiimide compound includes a monofunctional carbodiimide and a polyfunctional carbodiimide. Examples of monofunctional carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide and di-β-naphthylcarbodiimide. Preferably, they are dicyclohexyl carbodiimide and diisopropyl carbodiimide.

  As the polyfunctional carbodiimide, a carbodiimide having a polymerization degree of 3 to 15 is preferably used. Specifically, 1,5-naphthalene carbodiimide, 4,4′-diphenylmethane carbodiimide, 4,4′-diphenyldimethylmethane carbodiimide, 1,3-phenylene carbodiimide, 1,4-phenylene diisocyanate, 2,4-tolylene Carbodiimide, 2,6-tolylene carbodiimide, mixture of 2,4-tolylene carbodiimide and 2,6-tolylene carbodiimide, hexamethylene carbodiimide, cyclohexane-1,4-carbodiimide, xylylene carbodiimide, isophorone carbodiimide, isophorone carbodiimide, Dicyclohexylmethane-4,4′-carbodiimide, methylcyclohexanecarbodiimide, tetramethylxylylene carbodiimide, 2,6-diisopropylphenylcarbodiimide, or , And the like can be exemplified 3,5-triisopropyl-2,4-carbodiimide.

  Since the carbodiimide compound generates an isocyanate gas by thermal decomposition, it is preferable that the terminal blocking agent is a carbodiimide compound having high heat resistance. In order to improve heat resistance, the higher the molecular weight (degree of polymerization) of the carbodiimide compound, the more preferable, and the terminal of the carbodiimide compound preferably has a structure with high heat resistance. Since the carbodiimide compound is likely to be further thermally decomposed once it is thermally decomposed, in the production of the polymer substrate, it is possible to devise such as making the extrusion temperature of the polymer as low as possible.

  In an embodiment, the carbodiimide compound used as a terminal blocking agent preferably has a cyclic structure (for example, those described in JP 2011-153209 A). These can exhibit the same effect as the above high molecular weight carbodiimide even at a low molecular weight. This is because the terminal carboxyl group of the polymer and the cyclic carbodiimide undergo a ring-opening reaction, one of which reacts with this terminal carboxyl group, and the other of the ring-opening reacts with the other terminal carboxyl group to increase the molecular weight, thereby generating an isocyanate gas. It is because it can suppress.

In one embodiment, the terminal blocking agent, which is a carbodiimide compound having a cyclic structure, preferably includes a cyclic structure in which a first nitrogen and a second nitrogen of a carbodiimide group are bonded by a bonding group. In one embodiment, the end-capping agent has at least one carbodiimide group adjacent to the aromatic ring, and the first nitrogen and the second nitrogen of the carbodiimide group adjacent to the aromatic ring are bound by a linking group. It is preferably a carbodiimide containing a cyclic structure (also called an aromatic cyclic carbodiimide).
The aromatic cyclic carbodiimide may have a plurality of cyclic structures.
The aromatic cyclic carbodiimide is preferably an aromatic carbodiimide having no ring structure in which the first nitrogen and the second nitrogen of two or more carbodiimide groups are bonded by a linking group in the molecule, that is, a monocyclic ring. Can be used.

  The cyclic structure has one carbodiimide group (—N═C═N—), and the first nitrogen and the second nitrogen are bonded by a bonding group. One cyclic structure has only one carbodiimide group. For example, when there are a plurality of cyclic structures in the molecule, such as a spiro ring, one cyclic structure bonded to a spiro atom is included in each cyclic structure. As long as it has a carbodiimide group, the compound may have a plurality of carbodiimide groups. The number of atoms in the cyclic structure is preferably 8 to 50, more preferably 10 to 30, further preferably 10 to 20, and particularly preferably 10 to 15.

  Here, the number of atoms in the cyclic structure means the number of atoms directly constituting the cyclic structure. For example, the number of atoms is 8 for an 8-membered ring, and the number of atoms is 50 for a 50-membered ring. . When the number of atoms in the cyclic structure is 8 or more, the cyclic carbodiimide compound can maintain stability and can be suitable for storage and use. Although there is no special restriction | limiting regarding the upper limit of the number of ring members from a reactive viewpoint, It is preferable that a cyclic carbodiimide compound is 50 or less from a viewpoint which can suppress the cost increase by synthetic difficulty. From this point of view, the range of the number of atoms in the cyclic structure is preferably 10-30, more preferably 10-20, and even more preferably 10-15.

  Specific examples of the carbodiimide sealant having a cyclic structure include the following compounds. However, the present invention is not limited to the following specific examples.

~ Epoxy terminal blocker ~
The epoxy end-capping agent is an epoxy compound. Preferable examples of the epoxy compound include glycidyl ester compounds and glycidyl ether compounds.

  Specific examples of the glycidyl ester compound include benzoic acid glycidyl ester, t-Bu-benzoic acid glycidyl ester, P-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycidyl ester, and lauric acid glycidyl ester. , Glycidyl palmitate, glycidyl behenate, glycidyl versatate, glycidyl oleate, glycidyl linoleate, glycidyl linolein, glycidyl behenol, glycidyl stearol, diglycidyl terephthalate, isophthalic acid Diglycidyl ester, phthalic acid diglycidyl ester, naphthalenedicarboxylic acid diglycidyl ester Ter, methylterephthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diglycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, sebacic acid diglycidyl ester, dodecane Examples thereof include dionic acid diglycidyl ester, octadecanedicarboxylic acid diglycidyl ester, trimellitic acid triglycidyl ester, and pyromellitic acid tetraglycidyl ester. These epoxy terminal blockers can be used alone or in combination of two or more.

  Specific examples of the glycidyl ether compound include phenyl glycidyl ether, O-phenyl glycidyl ether, 1,4-bis (β, γ-epoxypropoxy) butane, 1,6-bis (β, γ- Epoxypropoxy) hexane, 1,4-bis (β, γ-epoxypropoxy) benzene, 1- (β, γ-epoxypropoxy) -2-ethoxyethane, 1- (β, γ-epoxypropoxy) -2-benzyl Oxyethane, 2,2-bis- [р- (β, γ-epoxypropoxy) phenyl] propane and 2,2-bis- (4-hydroxyphenyl) propane and 2,2-bis- (4-hydroxyphenyl) Examples thereof include bisglycidyl polyether obtained by the reaction of bisphenol such as methane and epichlorohydrin. These can use 1 type (s) or 2 or more types.

-Oxazoline-based end-capping agent-
The oxazoline-based end-capping agent is an oxazoline compound. As the oxazoline compound, a bisoxazoline compound is preferable, and specifically, 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), and 2,2′-bis. (4,4-dimethyl-2-oxazoline), 2,2′-bis (4-ethyl-2-oxazoline), 2,2′-bis (4,4′-diethyl-2-oxazoline), 2,2 '-Bis (4-propyl-2-oxazoline), 2,2'-bis (4-butyl-2-oxazoline), 2,2'-bis (4-hexyl-2-oxazoline), 2,2'- Bis (4-phenyl-2-oxazoline), 2,2'-bis (4-cyclohexyl-2-oxazoline), 2,2'-bis (4-benzyl-2-oxazoline), 2,2'-p- Phenylenebis (2-oxazoline), 2,2'-m- Enylene bis (2-oxazoline), 2,2'-o-phenylene bis (2-oxazoline), 2,2'-p-phenylene bis (4-methyl-2-oxazoline), 2,2'-p-phenylene bis (4,4-dimethyl-2-oxazoline), 2,2′-m-phenylenebis (4-methyl-2-oxazoline), 2,2′-m-phenylenebis (4,4-dimethyl-2-oxazoline) ), 2,2′-ethylenebis (2-oxazoline), 2,2′-tetramethylenebis (2-oxazoline), 2,2′-hexamethylenebis (2-oxazoline), 2,2′-octamethylene Bis (2-oxazoline), 2,2′-decamethylenebis (2-oxazoline), 2,2′-ethylenebis (4-methyl-2-oxazoline), 2,2′-tetramethylenebis (4,4 - Methyl-2-oxazoline), 2,2′-9,9′-diphenoxyethanebis (2-oxazoline), 2,2′-cyclohexylenebis (2-oxazoline) and 2,2′-diphenylenebis ( 2-oxazoline) and the like. Among these, 2,2′-bis (2-oxazoline) is most preferably used from the viewpoint of reactivity with polyester. Furthermore, as long as the objective of this invention is achieved, the bisoxazoline compound mentioned above may be used individually by 1 type, or may use 2 or more types together.

  Such a terminal blocking agent is introduced into the polymer substrate by a method such as kneading into a polymer contained in the polymer substrate. The above effect can be obtained by reacting the end-capping agent and the polymer molecule in direct contact. Even if the end-capping agent is added to the coating layer on the polymer substrate, the polymer and the end-capping agent do not react.

<Fine particles that are inorganic particles or organic particles>
The polymer constituting the polymer substrate may contain fine particles that are inorganic particles or organic particles. Thereby, the reflectance (whiteness) of light can be improved and the power generation efficiency of a solar cell can be improved.

  The average particle size of the fine particles is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 5 μm, and still more preferably 0.15 μm to 1 μm, and the content is 0% by mass to 50% with respect to the total mass of the polymer. The mass may be 1% by mass, preferably 1% by mass to 10% by mass, and more preferably 2% by mass to 5% by mass. When the average particle size of the fine particles is 0.1 μm to 10 μm, the whiteness of the polymer substrate is easily set to 50 or more. When the content of the particles is 1% by mass or more, the polymer substrate whiteness is easily set to 50 or more. When the content of the fine particles is 50% by mass or less, the mass of the polymer substrate does not become too large and is easy to handle in processing. In addition, the average particle diameter and content here refer to the weighted average value based on the average value of each layer, when a polymer base material is a multilayer structure. That is, the average particle diameter is calculated by (average value of particle diameter of each layer) × (thickness of each layer / thickness of all layers) for each layer, and the sum is obtained. (Average value of quantity) × (thickness of each layer / thickness of all layers) is calculated for each layer and indicates the sum total.

The average particle size of the fine particles is determined by an electron microscope method. Specifically, the following method is used.
The fine particles are observed with a scanning electron microscope, the magnification is appropriately changed according to the size of the fine particles, and the photographed image is enlarged and copied. Next, the outer circumference of each particle is traced for at least 200 fine particles selected at random. The equivalent circle diameter of the particles is measured from these trace images with an image analyzer. The average of the measured values is defined as the average particle size.

The fine particles may be either inorganic particles or organic particles, or a combination of both. Thereby, the reflectance of light can be improved and the power generation efficiency of a solar cell can be improved.
Suitable inorganic particles include, for example, wet and dry silica, colloidal silica, calcium carbonate, aluminum silicate, calcium phosphate, alumina, magnesium carbonate, zinc carbonate, titanium oxide, zinc oxide (zinc white), antimony oxide, and oxidation. Cerium, zirconium oxide, tin oxide, lanthanum oxide, magnesium oxide, barium carbonate, zinc carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, titanium mica, talc, clay, Among these inorganic particles that can include kaolin, lithium fluoride, or calcium fluoride, titanium dioxide or barium sulfate is preferable. The titanium oxide may be either anatase type or rutile type. In addition, the surface of the fine particles may be subjected to an inorganic surface treatment using alumina, silica or the like, or may be subjected to an organic surface treatment using a silicon compound or alcohol.

Among these fine particles, titanium dioxide is preferable. When the polymer base material contains this, the polymer sheet can exhibit excellent durability even under light irradiation. Specifically, when UV irradiation is performed at 63 ° C., 50% Rh, irradiation intensity of 100 mW / cm ² for 100 hours, the elongation at break is preferably 35% or more, more preferably 40% or more. Since the polymer sheet of this embodiment can suppress photodecomposition and deterioration, it is more suitable as a back surface protective film for solar cells used outdoors.

  Titanium dioxide includes those having a rutile crystal structure and those having an anatase crystal structure. In one embodiment, it is preferable to add fine particles mainly composed of rutile-type titanium dioxide to the polymer substrate. The anatase type has a very high spectral reflectance of ultraviolet rays, whereas the rutile type has a characteristic that the absorption rate of ultraviolet rays is large (spectral reflectance is small). The present inventor pays attention to such a difference in spectral characteristics in the crystal form of titanium dioxide, and can improve the light resistance in the polymer sheet for protecting the back surface of the solar cell by utilizing the ultraviolet absorption performance of rutile titanium dioxide. I found out that I can do it. In this embodiment, excellent film durability under light irradiation can be obtained without substantially adding other ultraviolet absorbers. Therefore, problems such as contamination due to bleeding out of the ultraviolet absorbent and a decrease in adhesion are unlikely to occur.

  Here, the fine particle “mainly composed of rutile type titanium dioxide” means that the mass of rutile type titanium dioxide in all titanium dioxide particles exceeds 50% by mass with respect to the total mass of titanium dioxide particles. Moreover, it is preferable that the amount of anatase type titanium dioxide in all the titanium dioxide particles with respect to the total titanium dioxide particle mass is 10 mass% or less, More preferably, it is 5 mass% or less, Most preferably, it is 0 mass% or less. When the content of the anatase type titanium dioxide is not more than the above upper limit value, the amount of rutile type titanium dioxide in the total titanium dioxide particles can be ensured, so that the ultraviolet absorption performance can be ensured. Since anatase-type titanium dioxide has a strong photocatalytic action, this action also tends to reduce the light resistance of the polymer sheet. Rutile titanium dioxide and anatase titanium dioxide can be distinguished by X-ray structure diffraction and spectral absorption characteristics.

  The surface of the rutile titanium dioxide fine particles may be subjected to an inorganic surface treatment using alumina, silica or the like, or may be subjected to an organic surface treatment using a silicon compound or alcohol. Prior to blending rutile titanium dioxide into the polyester composition, particle size adjustment, coarse particle removal, and the like may be performed using a purification process. Examples of industrial means for the purification process include pulverizing means such as a jet mill and a ball mill, and classification means such as dry or wet centrifugation.

  The organic fine particles that can be contained in the polymer substrate are preferably those that can withstand the heat during film formation. For example, fine particles made of a cross-linked resin, specific examples include fine particles made of polystyrene cross-linked with divinylbenzene.

Various conventionally known methods can be used as a method for adding fine particles into the polymer substrate. The typical methods are listed below.
(1) A method of adding fine particles before the end of the ester exchange reaction or esterification reaction at the time of synthesizing the polymer constituting the polymer substrate, or adding fine particles before starting the polycondensation reaction.
(2) A method in which fine particles are added to a polymer and melt kneaded.
(3) Producing master pellets (or master batches (MB)) in which a large amount of fine particles are added in the methods (1) and (2) above, kneading these with a polymer not containing fine particles, A method of containing a predetermined amount of fine particles in the obtained product.
(4) The method of using the master pellet of said (3) as it is.
In an embodiment, a master batch method (MB method: (3) above) including mixing polyester resin and fine particles in an extruder in advance is preferable. In addition, a method can be employed in which MB and the fine particles, which have not been dried in advance, are introduced into an extruder and degassed moisture and air. Preferably, the increase in the acid value of the polymer can be suppressed by preparing MB using a polymer that has been slightly dried in advance. Examples of such a method include a method of extruding while degassing, a method of extruding without sufficiently degassing with a sufficiently dried polymer, and the like.

  For example, when preparing MB, it is preferable to reduce the moisture content of the polymer to be introduced in advance by drying. Drying conditions are preferably 100 ° C. to 200 ° C., more preferably 120 ° C. to 180 ° C., for 1 hour or longer, more preferably 3 hours or longer, and even more preferably 6 hours or longer. Thereby, it is sufficiently dried so that the moisture content of the polymer such as polyester is preferably 50 ppm or less, more preferably 30 ppm or less. The premixing method is not particularly limited, and may be a batch method or a single-screw or biaxial or more kneading extruder. When producing MB while degassing, melt the polymer at a temperature of 250 ° C. to 300 ° C., preferably 270 ° C. to 280 ° C., and provide one, preferably two or more degassing ports in the pre-kneader, It is preferable to adopt a method such as performing continuous suction deaeration of 0.05 MPa or more, more preferably 0.1 MPa or more, and maintaining the reduced pressure in the mixer.

  In an embodiment, the polymer substrate may contain a large number of fine voids inside. Thereby, higher whiteness can be suitably obtained. In that case, the apparent specific gravity is 0.7 or more and 1.3 or less, preferably 0.9 or more and 1.3 or less, more preferably 1.05 or more and 1.2 or less. When the apparent specific gravity is 0.7 or more, the polymer sheet has a waist and can be easily processed during the production of the solar cell module. If the apparent specific gravity is 1.3 or less, the mass of the polymer sheet is small, which can contribute to weight reduction of the solar cell.

  The fine cavities can be formed from a thermoplastic resin that is incompatible with the fine particles and / or a polymer constituting the polymer substrate described below. The term “cavity derived from a thermoplastic resin that is incompatible with the fine particles or polymer” means that there are voids around the fine particles or the thermoplastic resin. For example, it is confirmed by a cross-sectional photograph of the polymer substrate by an electron microscope. can do.

  The resin that can be added to the polymer base material for forming a cavity is preferably a resin that is incompatible with the polymer constituting the polymer base material, which can scatter light and increase the light reflectance. When the polymer constituting the polymer substrate is polyester, preferred incompatible resins include polyolefin resins such as polyethylene, polypropylene, polybutene, and polymethylpentene, polystyrene resins, polyacrylate resins, polycarbonate resins, and polyacrylonitrile resins. , Polyphenylene sulfide resin, polysulfone resin, cellulose resin, and fluorine resin. These incompatible resins may be homopolymers or copolymers, and two or more incompatible resins may be used in combination. Among these, polyolefin resins and polystyrene resins such as polypropylene and polymethylpentene having a low surface tension are preferable, and polymethylpentene is more preferable. Since polymethylpentene has a relatively large difference in surface tension from polyester and a high melting point, it has a low affinity with polyester and easily forms voids (cavities) in the polyester film-forming process.

When the polymer substrate contains an incompatible resin, the amount thereof is 0% by mass to 30% by mass with respect to the entire polymer substrate, more preferably 1% by mass to 20% by mass, and still more preferably 2%. The range is from mass% to 15 mass%. When the content is 30% by mass or less, the apparent density of the entire polymer base material can be secured, so that film breakage or the like hardly occurs during stretching, and good productivity can be obtained.
When adding fine particles, the average particle size of the fine particles is preferably 0.1 μm to 10 μm, more preferably 0.1 μm to 5 μm, and still more preferably 0.15 μm to 1 μm. When the average particle size is 0.1 μm or more, reflectance (whiteness) can be secured, and when the average particle size is 10 μm or less, a decrease in mechanical strength due to voids can be avoided. The content of the fine particles is 0 to 50% by mass, preferably 1 to 10% by mass, and more preferably 2 to 5% by mass with respect to the total mass of the polymer substrate. When the content is 50% by mass or less, a decrease in mechanical strength due to voids can be avoided. When the polymer constituting the polymer substrate is polyester, preferable fine particles include those having a low affinity with polyester, specifically, barium sulfate and the like.

<Layer structure of polymer substrate>
The polymer substrate may be a single layer or may have a laminated structure of two or more layers.
As an example of the laminated structure in the polymer substrate, it is preferable to combine a high whiteness (a layer with a lot of voids and fine particles) and a low whiteness layer (a layer with a small amount of voids and fine particles). Although the light reflection efficiency can be increased in a layer containing a large amount of voids or fine particles, a decrease in mechanical strength (embrittlement) is likely to occur due to voids or fine particles, and it is preferable to combine with a layer having low whiteness to compensate for this. For this reason, it is preferable to use a layer with high whiteness for the outer layer of a polymer base material, and it may be used for one side of a polymer base material, and may be used for both surfaces of a polymer base material. When a high white layer using titanium dioxide as fine particles is used as the outer layer of the polymer base material, titanium dioxide has a UV absorbing ability, so that the effect of improving the light resistance of the polymer base material can be obtained.
One suitable polymer base material is a polymer base material having a laminated structure including two or more layers having different contents of fine particles, which are inorganic particles or organic particles.

  When the layer having high whiteness is a layer comprising fine particles, the content of fine particles is preferably 5% by mass or more and 50% by mass or less, and more preferably 6% by mass or more and 20% by mass or less with respect to the mass of the entire layer. . When the high whiteness layer is a layer formed by cavity formation, the apparent specific gravity of the high whiteness layer is preferably 0.7 or more and 1.2 or less, more preferably 0.8 or more and 1.1 or less. On the other hand, when the layer with low whiteness is a layer containing fine particles, the content of fine particles with respect to the mass of the entire layer is preferably 0% by mass or more and less than 5% by mass, more preferably 1% by mass or more and 4% by mass. % Or less is more preferable. When the high whiteness layer is a layer formed by cavity formation, the low whiteness layer preferably has an apparent specific gravity of 0.9 or more and 1.4 or less and has a higher apparent specific gravity than the high white layer, and more preferably. Has an apparent specific gravity of 1.0 to 1.3 and higher than that of the high white layer. The low white layer may not contain fine particles or cavities.

  As a preferable laminated structure that the white polymer substrate may have, a high white layer / low white layer, a high white layer / low white layer / high white layer, a high white layer / low white layer / high white layer / low white layer, high Examples include white layer / low white layer / high white layer / low white layer / high white layer.

The thickness ratio of each layer in the laminated structure is not particularly limited, but the thickness of each layer is preferably 1% or more and 99% or less, more preferably 2% or more and 95% or less of the total layer thickness. Within this range, it is easy to obtain the effects of improving the reflection efficiency and imparting light resistance (UV). The thickness of all layers of the polymer substrate is not particularly limited as long as it can be formed as a film, but is usually in the range of 20 μm to 500 μm, preferably 25 μm to 300 μm.
As a laminating method for producing a polymer substrate having a laminating structure, a so-called coextrusion method using two or three or more melt extruders is preferably used.

  In certain embodiments, it is also preferred to use a fluorescent whitening agent such as thiofediyl to increase the whiteness of the white polymer substrate. A preferable addition amount is 0.01% by mass or more and 1% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, and further preferably 0.1% by mass with respect to the total mass of the white polymer substrate. % Or more and 0.3% by mass or less. If it is 0.01% by mass or more, the effect of improving the light reflectivity is easily obtained, and if it is 1% by mass or less, it is possible to avoid a decrease in reflectance due to yellowing due to thermal decomposition during extrusion. As such a fluorescent whitening agent, for example, OB-1 (trade name) manufactured by Eastman Kodak Co., Ltd. can be used.

In one embodiment, the white polymer substrate has an illuminance: 100 mW / cm ² , a temperature: 60 ° C., a relative humidity: 50% RH, and an irradiation time: 48 hours. Preferably it is less than 5. The Δb value is more preferably less than 4 and even more preferably less than 3. This is useful in that the color change can be reduced even if it is irradiated with sunlight for a long time. Such an effect is prominent in a solar battery module in which a polymer sheet is laminated on a solar battery cell as a back sheet, particularly when irradiated from the polymer sheet side.

<Surface treatment>
The polymer substrate is preferably in a form in which surface treatment is performed by corona treatment, flame treatment, low-pressure plasma treatment, atmospheric pressure plasma treatment, or ultraviolet treatment. By performing these surface treatments, it is possible to further improve the adhesion (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 can increase adhesion by increasing carboxyl groups and hydroxyl groups on the surface of polymer substrates (for example, polyester substrates). However, crosslinking agents (especially oxazoline or carbodiimide compounds that are highly reactive with carboxyl groups) can be used. When the crosslinking agent is used in combination, stronger adhesiveness can be obtained. This is more remarkable in the case of corona treatment.

Corona treatment is usually performed by applying high frequency and high voltage between a metal roll (dielectric roll) coated with a derivative and an insulated electrode to cause dielectric breakdown of the air between the electrodes. Is ionized to generate a corona discharge between the electrodes. And it performs by passing a polymer base material between this corona discharge.
In an embodiment, the corona treatment conditions are preferably a gap clearance of 1 to 3 mm between the electrode and the dielectric roll, a frequency of 1 to 100 kHz, and an applied energy of about 0.2 to 5 kV · A · min / m ^2. .

(First polymer layer)
The polymer sheet for solar cells of the present invention has a first polymer layer containing at least one binder polymer selected from a fluoropolymer and a silicone polymer.
The first polymer layer is a layer that can function as a weather-resistant layer.

<Binder polymer>
The first polymer layer contains at least one binder polymer selected from a fluoropolymer and a silicone polymer (hereinafter sometimes referred to as “specific binder” as appropriate). In the first polymer layer, the specific binder is contained as a main binder. Here, the main binder in the first polymer layer is a binder having the largest content in the first polymer layer.

  In the first polymer layer, the fluoropolymer and the silicone polymer may be used alone or in combination of two or more. Moreover, when using together a fluoropolymer and a silicone polymer, you may select and use together 2 or more types of polymers from any one of a fluoropolymer and a silicone polymer, or it is 1 type from both a fluoropolymer and a silicone polymer. Or you may select 2 or more types and use together.

~ Fluoropolymer ~
The fluoropolymer that the first polymer layer can contain as the specific binder is not particularly limited as long as it is a polymer having a repeating unit represented by-(CFX ¹ -CX ² X ³ )-(however, X ¹ , X ² and X ³ represent a hydrogen atom, a fluorine atom, a chlorine atom, or a perfluoroalkyl group having 1 to 3 carbon atoms.

  Examples of fluoropolymers include polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), polyvinyl fluoride (hereinafter sometimes referred to as PVF), and polyvinylidene fluoride (hereinafter referred to as PVDF). ), Polychloroethylene trifluoride (hereinafter sometimes referred to as PCTFE), polytetrafluoropropylene (hereinafter sometimes referred to as HFP), and the like.

  These fluoropolymers may be a homopolymer obtained by polymerizing a single monomer, or may be a copolymer obtained by copolymerizing two or more kinds. Examples thereof include a copolymer of tetrafluoroethylene and tetrafluoropropylene (abbreviated as P (TFE / HFP)), a copolymer of tetrafluoroethylene and vinylidene fluoride (abbreviated as P (TFE / VDF)), etc. Can be mentioned.

Furthermore, as a specific binder used for the first polymer layer, a fluorocarbon monomer represented by-(CFX ¹ -CX ² X ³ )-and another monomer (non-fluorine-containing monomer) were copolymerized. It may be a polymer. Specific examples of fluorocarbon monomers include ethylene tetrafluoride, ethylene trifluoride, vinylidene fluoride, vinyl fluoride, hexafluoropropylene, fluorine-containing alkyl vinyl ethers (eg, perfluoroethyl vinyl ether), fluorine-containing esters. Etc. (perfluorobutyl methacrylate, etc.). Specific examples of the non-fluorine-containing monomer include ethylene, alkyl vinyl ether (eg, ethyl vinyl ether, cyclohexyl vinyl ether), and carboxylic acid (eg, acrylic acid, methacrylic acid, hydroxybutyme vinyl ether, etc.). When the fluoropolymer is a polymer obtained by copolymerizing a fluorocarbon monomer and a non-fluorine-containing monomer), the content of the fluorine-containing monomer with respect to the total mass of the fluoropolymer is preferably 30% by mass to 98% by mass, more Preferably it is 40-80 mass%. Sufficient durability can be acquired as the ratio of a fluorine-containing monomer is 30 mass% or more. Further, from the viewpoint of the stability of polymerization, it is preferably 98% by mass or less.
Examples of polymers obtained by copolymerization of fluorocarbon monomers and non-fluorine-containing monomers are copolymers of tetrafluoroethylene and ethylene (abbreviated as P (TFE / E)), copolymer of tetrafluoroethylene and propylene. Copolymer (abbreviated as P (TFE / P)), copolymer of tetrafluoroethylene and vinyl ether (abbreviated as P (TFE / VE)), copolymer of tetrafluoroethylene and perfluorovinyl ether (P (TFE / FVE)) Abbreviation), a copolymer of chlorotrifluoroethylene and vinyl ether (abbreviated as P (CTFE / VE)), a copolymer of chlorotrifluoroethylene and perfluorovinyl ether (abbreviated as P (CTFE / FVE)), tetrafluoro Hexafluoropropylene, a copolymer obtained by copolymerizing ethylene, ethylene and acrylic acid Copolymer formed by copolymerizing tetrafluoroethylene, copolymer formed by copolymerizing hexafluoropropylene, tetrafluoroethylene and ethylene, and formed by copolymerizing chlorotrifluoroethylene and perfluoroethyl vinyl ether. A copolymer, a copolymer formed by copolymerizing chlorotrifluoroethylene, perfluoroethyl vinyl ether and methacrylic acid, a copolymer formed by copolymerizing chlorotrifluoroethylene and ethyl vinyl ether, and chlorotrifluoroethylene A copolymer obtained by copolymerizing ethyl vinyl ether and methacrylic acid, a copolymer obtained by copolymerizing vinylidene fluoride, methyl methacrylate and methacrylic acid, and a copolymer obtained by copolymerizing vinyl fluoride, ethyl acrylate and acrylic acid. And the like.
Among these, a copolymer obtained by copolymerizing chlorotrifluoroethylene and perfluoroethyl vinyl ether, a copolymer obtained by copolymerizing chlorotrifluoroethylene, perfluoroethyl vinyl ether and methacrylic acid, chlorotrifluoro Copolymer made by copolymerizing ethylene and ethyl vinyl ether, Copolymer made by copolymerizing chlorotrifluoroethylene, ethyl vinyl ether and methacrylic acid, Copolymerized vinylidene fluoride, methyl methacrylate and methacrylic acid And a copolymer obtained by copolymerizing vinyl fluoride, ethyl acrylate and acrylic acid.
Among them, a copolymer obtained by copolymerizing chlorotrifluoroethylene and ethyl vinyl ether, and a copolymer obtained by copolymerizing chlorotrifluoroethylene, ethyl vinyl ether and methacrylic acid are more preferable.

  These fluoropolymers may be used by dissolving the polymer in an organic solvent or by dispersing polymer fine particles in water. The latter is preferred because of its low environmental impact. The aqueous dispersions of fluoropolymers are described in, for example, Japanese Patent Application Laid-Open Nos. 2003-231722, 2002-20409, and 9-194538.

Moreover, you may use the commercial item marketed as a fluoropolymer. Specific examples of commercially available products include Lumiflon (registered trademark) LF200 (manufactured by Asahi Glass Co., Ltd.), Zeffle (registered trademark) GK570 (manufactured by Daikin Industries, Ltd.), Obligard SW0011F (trade name, manufactured by AGC Co-Tech Co., Ltd.) and the like. is there.
The molecular weight of the fluoropolymer can be about 2000 to 1000000 in terms of polystyrene-converted weight average molecular weight, and preferably about 3000 to 300000.

~ Silicone polymer ~
The silicone polymer that can be contained in the first polymer layer is a polymer having a (poly) siloxane structure in the molecule. Here, the “siloxane structure” means a structure containing at least one siloxane bond. “Polysiloxane structure” means a structure in which a plurality of siloxane bonds are continuous. The term “(poly) siloxane structure” encompasses siloxane structures and polysiloxane structures within its scope. The expressions “the polymer has a siloxane structure in the molecule” and “the polymer has a (poly) siloxane structure in the molecule” mean that the polymer contains a siloxane structure or a polysiloxane structure in the molecule.
In a preferred embodiment, the silicone polymer has a (poly) siloxane structural unit represented by the following general formula (1) as a (poly) siloxane structure, as a (poly) siloxane structure.

In the general formula (1), R ¹ and R ² each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group. Here, R ¹ and R ² may be the same or different, and the plurality of R ¹ and R ² may be the same or different from each other. n represents an integer of 1 or more.

In the part of “— (Si (R ¹ ) (R ² ) —O) _n —” ((poly) siloxane structural unit represented by the general formula (1)) which is a (poly) siloxane segment in the polymer, R ¹ and R ² may be the same or different and each represents a hydrogen atom, a halogen atom, or a monovalent organic group.

“— (Si (R ¹ ) (R ² ) —O) _n —” is a (poly) siloxane segment derived from various (poly) siloxanes having a linear, branched or cyclic structure.

Examples of the halogen atom represented by R ¹ and R ² include a fluorine atom, a chlorine atom, and an iodine atom.

The “monovalent organic group” represented by R ¹ and R ² is a group that can be covalently bonded to an Si atom, and may be unsubstituted or may have a substituent. Examples of the monovalent organic group include an alkyl group (e.g., methyl group, ethyl group), an aryl group (e.g., phenyl group), an aralkyl group (e.g., benzyl group, phenylethyl), and an alkoxy group (e.g. : Methoxy group, ethoxy group, propoxy group, etc.), aryloxy group (eg, phenoxy group etc.), mercapto group, amino group (eg: amino group, diethylamino group etc.), amide group and the like.

Among them, R ¹ and R ² are each independently a hydrogen atom, a chlorine atom, a bromine atom, an unsubstituted or substituted carbon number of 1 in terms of adhesion to an adjacent layer and durability in a wet and heat environment. To 4 alkyl groups (especially methyl and ethyl groups), unsubstituted or substituted phenyl groups, unsubstituted or substituted alkoxy groups, mercapto groups, unsubstituted amino groups, and amide groups are more preferred. Is an unsubstituted or substituted alkoxy group (preferably an alkoxy group having 1 to 4 carbon atoms) from the viewpoint of durability in a moist heat environment.

  The n is preferably 1 to 5000, and more preferably 1 to 1000.

Specific examples of the portion of “— (Si (R ¹ ) (R ² ) —O) _n —” ((poly) siloxane structural unit represented by the general formula (1)) in the silicone polymer include dimethyldimethoxysilane Hydrolysis condensate containing hydrolysis condensate, hydrolysis condensate containing hydrolysis condensate of dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane, hydrolysis condensate of dimethyldimethoxysilane / vinyltrimethoxysilane Hydrolysis condensate containing, hydrolysis condensate containing dimethyldimethoxysilane / 2-hydroxyethyltrimethoxysilane hydrolysis condensate, hydrolysis condensate of dimethyldimethoxysilane / 3-glycidoxypropyltriethoxysilane Hydrolysis condensate contained, dimethyldimethoxysilane / diphenyl / dimeth It is hydrolyzed condensate containing Shishiran γ- methacryloxypropyltrimethoxysilane hydrolyzed condensate of trimethoxysilane. Among these, hydrolyzed condensate containing hydrolyzed condensate of dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane and hydrolyzed condensate of dimethyldimethoxysilane / diphenyl / dimethoxysilane γ-methacryloxytrimethoxysilane Hydrolysis condensates are preferred.
The ratio of “— (Si (R ¹ ) (R ² ) —O) _n —” ((poly) siloxane structural unit represented by the general formula (1)) in the polymer is based on the total mass of the polymer. In particular, it is preferably 15 to 85% by mass, and in particular, the strength of the first polymer layer surface is improved, and scratches and scratches are prevented from being generated. From the viewpoint of better durability, a range of 20 to 80% by mass is more preferable. When the ratio of the (poly) siloxane structural unit is 15% by mass or more, the strength of the surface of the first polymer layer is improved, and scratches caused by scratches, scratches, collisions of flying pebbles, etc. can be prevented, Moreover, it can be excellent in adhesiveness with adjacent materials such as the second polymer layer. Suppression of the occurrence of scratches improves weather resistance, and effectively enhances peeling resistance, shape stability, and adhesion durability when exposed to a moist heat environment, which are easily deteriorated by heat and moisture. Moreover, a liquid can be kept stable as the ratio of a (poly) siloxane structural unit is 85 mass% or less. These effects can be more remarkable when the content of the (poly) siloxane structural unit is in the range of 20% by mass to 80% by mass.

When the silicone polymer in the present invention is a copolymer having a (poly) siloxane structural unit and other structural units, the mass of the (poly) siloxane structural unit represented by the general formula (1) in the molecular chain is as follows. The case where it contains 15-85 mass% by a ratio and 85-15 mass% by a mass ratio for a non-siloxane type structural unit is preferable. By containing such a copolymer, the film strength of the first polymer layer is improved, the occurrence of scratches due to scratching, scratching, etc. is prevented, and the adhesion to the polymer substrate forming the support, that is, heat and The peel resistance, shape stability, and durability in a moist heat environment, which are easily deteriorated when moisture is applied, can be dramatically improved as compared with the prior art.
When the silicone polymer is a copolymer having a (poly) siloxane structural unit and another structural unit, a portion of “— (Si (R ¹ ) (R ² ) —O) _n —” in the silicone polymer ( The molecular weight of the (poly) siloxane structural unit represented by the general formula (1) is about 30000 to 1000000 in terms of polystyrene-converted weight average molecular weight, and preferably about 50000 to 300000.

  As the copolymer, a siloxane compound (including polysiloxane in its range) and a compound selected from a non-siloxane monomer or a non-siloxane polymer are copolymerized and represented by the general formula (1) ( A block copolymer having a poly) siloxane structural unit and a non-siloxane structural unit is preferred. In this case, the siloxane compound and the non-siloxane monomer or non-siloxane polymer to be copolymerized may be one kind alone or two or more kinds.

The non-siloxane structural unit (derived from the non-siloxane monomer or non-siloxane polymer) copolymerized with the (poly) siloxane structural unit is not particularly limited except that it does not have a siloxane structure, and is arbitrary. Any of the polymer segments derived from the polymer may be used. Examples of the polymer (precursor polymer) that is a precursor of the polymer segment include various polymers such as a vinyl polymer, a polyester polymer, and a polyurethane polymer.
Among these, vinyl polymers and polyurethane polymers are preferable, and vinyl polymers are particularly preferable because they are easy to prepare and have excellent hydrolysis resistance.

Typical examples of the vinyl polymer include various polymers such as an acrylic polymer, a carboxylic acid vinyl ester polymer, an aromatic vinyl polymer, and a fluoroolefin polymer. Among these, acrylic polymers are particularly preferable from the viewpoint of design freedom. As monomers constituting the acrylic polymer, esters of acrylic acid (eg, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, etc.) or esters of methacrylic acid (eg, methyl methacrylate, butyl methacrylate, hydroxyethyl acrylate) , Glycidyl methacrylate, dimethylaminoethyl methacrylate, etc.). Further monomers include carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, styrene, acrylonitrile, vinyl acetate, acrylamide, divinylbenzene, etc. Among them, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate methyl methacrylate , Butyl methacrylate, hydroxyethyl acrylate, acrylic acid or methacrylic acid are preferred.
Specific examples of the acrylic polymer include methyl methacrylate / ethyl acrylate / acrylic acid copolymer, methyl methacrylate / ethyl acrylate / 2-hydroxyethyl methacrylate / methacrylic acid copolymer, methyl methacrylate / butyl acrylate / 2- Examples thereof include a bidoxyethyl methacrylate / methacrylic acid / γ-methacryloxytrimethoxysilane copolymer or a methyl methacrylate / ethyl acrylate / glycidyl methacrylate / acrylic acid copolymer.
The polymer constituting the non-siloxane structural unit may be used alone or in combination of two or more. Furthermore, the individual polymers may be homopolymers or copolymers.
The molecular weight of the polymer, which is a precursor of the polymer segment constituting the non-siloxane structural unit, is about 3000 to 1000000 in terms of polystyrene-converted weight average molecular weight, and more preferably about 5000 to 300000.

  The precursor polymer constituting the non-siloxane structural unit is preferably one containing at least one of an acid group and a neutralized acid group and / or a hydrolyzable silyl group. Among such precursor polymers, the vinyl polymer includes, for example, (a) a vinyl monomer containing an acid group and a vinyl monomer containing a hydrolyzable silyl group and / or a silanol group. (2) a method of reacting a polycarboxylic acid anhydride with a vinyl polymer containing a previously prepared hydroxyl group and hydrolyzable silyl group and / or silanol group, 3) Utilizing various methods such as a method in which a vinyl polymer containing an acid anhydride group and a hydrolyzable silyl group and / or silanol group prepared in advance is reacted with a compound having active hydrogen (water, alcohol, amine, etc.). Can be prepared.

  The precursor polymer can be produced and obtained using, for example, the method described in paragraph Nos. 0021 to 0078 of JP-A-2009-52011.

  The silicone polymer may be used alone or in combination with other polymers. When other polymers are used in combination, the content ratio of the polymer containing the (poly) siloxane structure in the present invention is preferably 30% by mass or more, more preferably 60% by mass or more of the total binder amount. The content ratio of the polymer containing the (poly) siloxane structure is 30% by mass or more, thereby improving the strength of the surface of the layer, preventing the occurrence of scratches due to scratching or scratching, and adhesion to the polymer substrate. In addition, it is more excellent in durability under humid heat environment.

  The molecular weight of the silicone polymer is preferably 5,000 to 100,000, and more preferably 10,000 to 50,000.

For the preparation of the silicone polymer, (i) a method of reacting a precursor polymer with a polysiloxane having a structural unit represented by the general formula (1), (ii) in the presence of the precursor polymer, the R ¹ and A method such as a method of hydrolyzing and condensing a silane compound having the structural unit represented by the general formula (1) in which R ² is a hydrolyzable group can be used.
Examples of the silane compound used in the method (ii) include various silane compounds, and alkoxysilane compounds are particularly preferable.

When the silicone polymer is prepared by the method (i), for example, water and a catalyst are added to the mixture of the precursor polymer and polysiloxane as necessary, and the temperature is about 20 to 150 ° C. for about 30 minutes to 30 hours ( Preferably, it can be prepared by reacting at 50 to 130 ° C. for 1 to 20 hours. As a catalyst, various silanol condensation catalysts, such as an acidic compound, a basic compound, and a metal containing compound, can be added.
Moreover, when preparing a silicone polymer by the method of said (ii), for example, water and a silanol condensation catalyst are added to the mixture of a precursor polymer and an alkoxysilane compound, and it is 30 minutes-30 minutes at the temperature of about 20-150 degreeC. It can be prepared by performing hydrolytic condensation for about an hour (preferably at 50 to 130 ° C. for 1 to 20 hours).

  Preferred examples of silicone polymers include hydrolysis condensates in which the (poly) siloxane structural unit contains a hydrolysis condensate of dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane, dimethyldimethoxysilane / diphenyl / dimethoxysilane γ-methacrylate. It consists of one of the hydrolytic condensates of loxytrimethoxysilane, and the polymer structure part copolymerized with the (poly) siloxane structural unit is ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate methyl methacrylate, methyl methacrylate, butyl Examples include a composite polymer that is an acrylic polymer composed of a monomer component selected from methacrylate, hydroxyethyl acrylate, acrylic acid, and methacrylic acid. The (poly) siloxane structural unit contains a hydrolysis condensate containing a hydrolysis condensate of dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane and a monomer component selected from methyl methacrylate, ethyl acrylate, acrylic acid, and methacrylic acid. And a composite polymer that is an acrylic polymer.

  Commercially available products may be used as the silicone polymer, for example, SERATE series produced by DIC Corporation [eg, SERATE WSA1070 (polysiloxane structural unit content ratio: 30% by mass acrylic / silicone Resin, WSA 1060 (polysiloxane structural unit content: 75 mass%), etc.], Asahi Kasei Chemicals H7600 series (H7650, H7630, H7620 etc.), JSR Co., Ltd. inorganic / acrylic composite An emulsion or the like can be used.

-Other binders-
Moreover, you may use together other binder polymers other than specific binders, such as an acrylic resin, a polyester resin, a polyurethane resin, and a polyolefin resin, in the range which does not exceed 50 mass% of all the binders in a 1st polymer layer.

  60-95 mass% is preferable, as for the total content of the binder polymer containing the specific binder in a 1st polymer layer, 75-95 mass% is further more preferable, and 80-93 mass% is especially preferable.

<Crosslinking agent>
It is preferable that the 1st polymer layer in this invention has the structure part derived from the crosslinking agent which bridge | crosslinks between the said specific binders. That is, the first polymer layer can be formed using a crosslinking agent capable of crosslinking between the binder polymers. By crosslinking with a crosslinking agent, adhesion after wet heat aging, specifically adhesion to a polymer substrate when exposed to a wet heat environment, and adhesion between layers can be further improved.

  As the crosslinking agent applied to the first polymer layer, a compound having an oxazoline group is preferable. Specific examples of the compound having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2- Oxazoline, 2-isopropenyl-4-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- (Oxazolinyl norbornane) sulfide and the like. Furthermore, (co) polymers of these compounds are also preferably used.

  Specific examples of the compound having an oxazoline group as a copolymer include a copolymer composed of 2-isopropenyl-2-oxazoline, methoxypolyethylene glycol methacrylate and methyl acrylate, 2-isopropenyl-2-oxazoline, Copolymer comprising methoxypolyethylene glycol methacrylate and methyl methacrylate, 2-isopropenyl-2-oxazoline, copolymer comprising methoxypolyethylene glycol methacrylate and ethyl acrylate, 2-isopropenyl-2-oxazoline Copolymer of monoesterified product of methacrylic acid and polyethylene glycol and methyl methacrylate, 2-isopropenyl-4-oxazoline, methoxypolyethylene glycol methacrylate and methyl methacrylate Polymers, mention may be made of a copolymer comprising 2-isopropenyl-4-oxazoline and acrylic acid methoxypolyethylene glycol and methyl methacrylate. These copolymers can be particularly suitably used as a crosslinking agent applied to the first polymer layer.

  Further, as commercially available compounds having an oxazoline group, Epocros K2010E, K2020E, K2030E, WS-500, WS-700 (all manufactured by Nippon Shokubai Chemical Co., Ltd.) and the like can be used.

  Only 1 type may be sufficient as the compound which has an oxazoline group in a 1st polymer layer, and 2 or more types may be used together.

  Moreover, in the range which does not impair the effect of this invention, you may use together crosslinking agents, such as an epoxy type, an isocyanate type, a melamine type, and a carbodiimide type.

In the case where the first polymer layer includes a cross-linked structure by a cross-linking agent, it is preferable to include a structural part derived from 0.5 to 50% by mass of the cross-linking agent with respect to the specific binder contained in the first polymer layer. It is more preferable to include a structural part derived from 30% by mass of the crosslinking agent, and it is particularly preferable to include a structural part derived from 5% to 20% by mass of the crosslinking agent.
When the addition amount 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 first polymer layer, and when it is 50% by mass or less, Long pot life.

<Onium compound>
The first polymer layer preferably contains an onium compound from the viewpoint of improving solvent resistance.

Examples of the onium compounds include ammonium salts, sulfonium salts, oxonium salts, iodonium salts, phosphonium salts, nitronium salts, nitrosonium salts, diazonium salts, and the like.
Specific examples of the onium compound include, for example, monoammonium phosphate, diammonium phosphate, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium p-toluenesulfonate, ammonium sulfamate, ammonium imidodisulfonate, tetrabutylammonium chloride, and benzyl chloride. Ammonium salts such as trimethylammonium chloride, triethylbenzylammonium chloride, tetrabutylammonium tetrafluoride, tetrabutylammonium hexafluoride, tetrabutylammonium perchlorate, tetrabutylammonium sulfate; trimethylsulfonium iodide, trimethyl boron tetrafluoride Sulfonium, boron tetrafluoride diphenylmethylsulfonium, boron tetrafluoride benzyltetramethylenesulfonium, hexafluoride Sulfone salts such as Timon 2-butenyltetramethylenesulfonium, antimony hexafluoride 3-methyl-2-butenyltetramethylenesulfonium; oxonium salts such as boron trifluoride trimethyloxonium; diphenyliodonium chloride, boron tetrafluoride diphenyl Iodonium salts such as iodonium; phosphonium salts such as antimony cyanomethyl tributylphosphonium hexafluoride and boron tetrafluoride ethoxycarbonylmethyltributylphosphonium; nitronium salts such as nitronium tetrafluoride; nitrosonium salts such as nitrosonium tetrafluoride; A diazonium salt such as 4-methoxybenzenediazonium chloride;
Among these onium compounds, ammonium salts such as ammonium phosphate and benzylammonium chloride are more preferable from the viewpoints of safety, pH, and price.

  Only one type of onium compound in the first polymer layer may be used, or two or more types may be used in combination.

  The content of the onium compound in the first polymer layer is preferably 0.5% by mass to 10% by mass with respect to the total amount of the binder polymer contained in the first polymer layer, and 1% by mass to 5% by mass. % Is more preferable.

<Water-miscible organic solvent with a boiling point of 99 ° C. or lower>
The first polymer layer may contain at least one water-miscible organic solvent having a boiling point of 99 ° C. or lower. By containing a low-boiling organic solvent, the crosslinking reaction between the polymer containing the specific binder contained in the first polymer layer and the compound having an oxazoline group is promoted, and the solvent resistance is further improved.

  Water miscibility means having water solubility, and refers to the property of being arbitrarily mixed with water.

  A boiling point of 99 ° C. or lower means that it is easier to remove than water, which is the main solvent in a coating solution that is suitably prepared as an aqueous coating solution, and a solvent component that is more easily removed from the system than water. It is estimated that the cross-linking reaction is improved by inclusion.

  The water-miscible organic solvent having a boiling point of 99 ° C. or lower is not particularly limited except for the boiling point. For example, alcohol solvents (monohydric alcohols and dihydric or higher polyhydric alcohols), ketone solvents, ether solvents A solvent, an ester solvent, etc. can be mentioned.

Examples of the alcohol solvent include methyl alcohol (bp: 65 ° C.), ethyl alcohol (bp: 78 ° C.), n-propyl alcohol (bp: 97 ° C.), i-propyl alcohol (bp: 82 ° C.), t -Butyl alcohol (bp: 82 degreeC) etc. are mentioned, C1-C3 monohydric alcohol etc. are mentioned suitably.
Examples of the ketone solvent include ketone compounds having 3 to 5 carbon atoms such as acetone (bp: 56 ° C.), methyl ethyl ketone (bp: 80 ° C.), and 2-butanone (bp: 79.5 ° C.). .
Examples of the ether solvent include diethyl ether (bp: 35 ° C.), tetrahydrofuran (bp: 66 ° C.), and the like.
Examples of the ester solvent include ethyl acetate (bp: 70 ° C.), isopropyl acetate (bp: 88-91 ° C.), and the like.
The “bp” indicates a boiling point.

  Among the above, the water-miscible organic solvent is a monohydric alcohol having 1 to 3 carbon atoms and 3 to 3 carbon atoms from the viewpoint of improving the crosslinking reactivity between the polymer and the oxazoline-based crosslinking agent, and hence the solvent resistance. A solvent selected from 5 ketone compounds is preferable, and methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, or acetone is more preferable.

  When the first polymer layer contains a water-miscible organic solvent having a boiling point of 99 ° C. or less, only one type may be used, or two or more types may be used in combination.

When the first polymer layer contains a water-miscible organic solvent, the content of the water-miscible organic solvent contained in the polymer layer is the total of the binder polymer including the specific binder contained in the first polymer layer. 0.0001 mass%-30 mass% are preferable with respect to mass, and 0.1-5 mass% is more preferable.
Since water-miscible organic solvents are volatilized, the storage environment is preferably within a closed container at room temperature for one week.

  A surfactant, a filler, and the like may be further added to the first polymer layer as necessary.

<Surfactant>
As the surfactant that can be used for the first polymer layer, a known surfactant such as an anionic or nonionic surfactant can be used.
When a surfactant is added to the first polymer layer, the addition amount is preferably 0.1 to 15 mg / m ² , more preferably 0.5 to 5 mg / m ² . When the addition amount of the surfactant is 0.1 mg / m ² or more, generation of repellency can be suppressed and good layer formation can be obtained, and when it is 15 mg / m ² or less, adhesion can be performed satisfactorily. .

~ Filler ~
A filler may be further added to the first polymer layer. As the filler, known fillers such as colloidal silica and titanium dioxide can be used. The addition amount of the filler is preferably 20% by mass or less, more preferably 15% by mass or less, with respect to the binder contained in the first polymer layer. When the addition amount of the filler is 20% by mass or less, the planar shape of the first polymer layer can be kept better.

~ Thickness ~
The thickness of the first polymer layer in the present invention is preferably in the range of 0.8 μm to 12 μm, particularly preferably in the range of about 1.0 μm to 10 μm.

~position~
In the polymer sheet for solar cells of the present invention, another layer may be laminated on the first polymer layer. However, from the viewpoint of improving the durability of the protective sheet, reducing the weight, reducing the thickness, and reducing the cost. Therefore, the first polymer layer is preferably the outermost layer of the polymer sheet for solar cells of the present invention.

(Second polymer layer)
The polymer sheet for solar cells of the present invention includes at least one binder polymer selected from a fluoropolymer and a silicone polymer, and a structural portion derived from a crosslinking agent having an oxazoline group that crosslinks the binder polymer, and It has the 2nd polymer layer whose equivalent [meq / g] of the said oxazoline group with respect to a binder polymer is more than 0 and less than 1. The second polymer layer is a layer that can function as a weather-resistant layer together with the first polymer layer.

  The second polymer layer can be formed using other components depending on the case, and the components differ depending on the application. The first polymer layer can constitute an undercoat layer, a colored layer that bears the function of reflecting sunlight, imparting appearance design, and the like.

The second polymer layer may be, for example, a layer that improves the adhesion between the polymer substrate and the first polymer layer, that is, a layer that functions as a so-called undercoat layer.
The second polymer layer can be configured as a reflective layer that reflects sunlight toward the incident side, for example. In that case, the second polymer layer can be constituted by further using a colorant such as a white pigment.

<Binder polymer>
The second polymer layer includes at least one binder polymer selected from a fluoropolymer and a silicone polymer.
The at least one binder polymer selected from the fluoropolymer and silicone polymer contained in the second polymer layer is synonymous with the specific binder contained in the first polymer layer as the main binder, and the details thereof are also the same. . The details of the content of the specific binder polymer are the same as in the case of the first polymer layer except that the “first polymer layer” is replaced with “second polymer layer”. As a specific specific binder, the same specific binder that can be contained in the first polymer layer can be suitably applied. The specific binder contained in the second polymer layer may be the same as or different from the specific binder contained in the first polymer layer.

  The total content of the binder polymer including the specific binder in the second polymer layer is preferably 60 to 95% by mass, more preferably 75 to 95% by mass, and particularly preferably 80 to 93% by mass.

<Crosslinking agent>
The 2nd polymer layer in this invention has the structure part derived from the crosslinking agent which bridge | crosslinks between the said specific binders. That is, the second polymer layer can be formed using a crosslinking agent capable of crosslinking between the binder polymers. By crosslinking with a crosslinking agent, adhesion after wet heat aging, specifically adhesion to a polymer substrate when exposed to a wet heat environment, and adhesion between layers can be further improved.

A compound having an oxazoline group is applied to the second polymer layer as a crosslinking agent.
As the compound having an oxazoline group in the second polymer layer, the same compound as the compound having an oxazoline group in the first polymer layer can be suitably applied.

  As for the compound which has an oxazoline group in a 2nd polymer layer, only 1 type may be sufficient and 2 or more types may be used together.

The equivalent [meq / g] of the oxazoline group to the specific binder in the second polymer layer is more than 0 and less than 1, and preferably 0.45 or more and less than 1.
When the equivalent [meq / g] of the oxazoline group to the specific binder is in the above range, the adhesion between the polymer substrate and the polymer layer provided thereon can be specifically improved.

  Moreover, in the range which does not impair the effect of this invention, you may use together crosslinking agents, such as an epoxy type, an isocyanate type, a melamine type, and a carbodiimide type.

  The second polymer layer preferably includes a structural part derived from 0.5 to 50% by mass of a crosslinking agent with respect to the specific binder (main binder) of the second polymer layer, and is preferably 3 to 30% by mass of crosslinking. It is further preferable to include a structural part derived from an agent, and it is particularly preferable to include a structural part derived from 5 to 20% by mass of a crosslinking agent. When the addition amount of the crosslinking agent is 0.5% by mass or more with respect to the specific binder (main binder) of the second polymer layer, sufficient crosslinking is performed while maintaining the strength and adhesiveness of the second polymer layer. An effect is acquired and the pot life of a coating liquid can be kept long as it is 50 mass% or less.

<Onium compound>
The second polymer layer preferably contains an onium compound from the viewpoint of improving solvent resistance.
Examples of the onium compound that can be applied to the second polymer layer include the same onium compounds that can be applied to the first polymer layer.

  Only one type of onium compound in the second polymer layer may be used, or two or more types may be used in combination.

  The content of the onium compound in the second polymer layer is preferably 0.5% by mass to 10% by mass with respect to the total amount of the binder polymer contained in the second polymer layer, and 1% by mass to 5% by mass. % Is more preferable.

<Water-miscible organic solvent with a boiling point of 99 ° C. or lower>
The second polymer layer may contain at least one water-miscible organic solvent having a boiling point of 99 ° C. or lower. By containing a low-boiling organic solvent, the crosslinking reaction between the binder polymer containing the specific binder contained in the second polymer layer and the compound having an oxazoline group is promoted, and the solvent resistance is further improved.

  The water-miscible organic solvent having a boiling point of 99 ° C. or less that can be contained in the second polymer layer is synonymous with the water-miscible organic solvent having a boiling point of 99 ° C. or less that can be contained in the first polymer layer. Is the same. The details of the content of the water-miscible organic solvent having a boiling point of 99 ° C. or lower are the same as in the case of the first polymer layer except that “first polymer layer” is read as “second polymer layer”. . Specific examples of the water-miscible organic solvent having a boiling point of 99 ° C. or lower are preferably the same as the specific binder that can be contained in the first polymer layer. The water-miscible organic solvent having a boiling point of 99 ° C. or less contained in the second polymer layer may be the same as or different from the specific binder contained in the first polymer layer.

<Other additives>
You may add surfactant, a filler, etc. to a 2nd polymer layer as needed.

~ Surfactant ~
As the surfactant, a known surfactant such as an anionic or nonionic surfactant can be used. When adding surfactant, the addition amount is preferably 0.1 to 10 mg / m ² , more preferably 0.5 to 3 mg / m ² . When the addition amount of the surfactant is 0.1 mg / m ² or more, generation of a repellency is suppressed and good layer formation is obtained, and when it is 10 mg / m ² or less, the polymer substrate and the first polymer Adhesion with other layers such as a layer can be performed satisfactorily.

~ Filler ~
A filler may be further added to the second polymer layer. As the filler, known fillers such as colloidal silica and titanium dioxide can be used. The addition amount of the filler is preferably 20% by mass or less, more preferably 15% by mass or less per binder contained in the second polymer layer. When the addition amount of the filler is 20% by mass or less, the planar shape of the second polymer layer can be kept better.

~ Thickness ~
The thickness of the second polymer layer is preferably 0.05 μm to 10 μm. If the thickness of the second polymer layer is 0.05 μm or more, the durability is sufficient, and a sufficient adhesive force between the polymer substrate and the first polymer layer can be secured. On the other hand, when the thickness of the second polymer layer is 10 μm or less, the surface shape is hardly deteriorated, and the adhesive force with other layers such as the first polymer layer is sufficient. When the thickness of the second polymer layer is in the range of 0.05 μm to 10 μm, both the durability and the surface shape of the second polymer layer are compatible, and the adhesion between the polymer substrate and the first polymer layer is enhanced. In particular, a range of about 1.0 μm to 10 μm is preferable.

~ Back layer ~
It is preferable to constitute the first and second polymer layers in the present invention as a back layer (weather-resistant layer). In a solar cell having a laminated structure of a battery-side substrate (= transparent substrate on which sunlight is incident (glass substrate or the like) / element structure portion including solar cell elements) / polymer sheet for solar cells, the back layer is supported. It is the back surface protective layer distribute | arranged to the opposite side to the side facing the said battery side board | substrate of the polymer base material which is a body. In the present invention, since the first and second polymer layers contain a specific binder, adhesion to the polymer substrate and adhesion between the polymer layers are improved, and further, deterioration resistance in a humid heat environment is obtained. . Therefore, the form in which the first polymer layer in the present invention is disposed as the outermost layer farthest from the polymer substrate is preferable.

  Other components that can be included in the back layer may include pigments used in the colored layer, in addition to the surfactants and fillers described above. Details of these other components and pigments and preferred embodiments will be described later.

~ Colored layer ~
The first polymer layer in the present invention may be a colored layer (preferably a reflective layer). In this case, the first polymer layer further contains a pigment. The second polymer layer may be a colored layer (preferably a reflective layer). In this case, the second polymer layer further contains a pigment. The colored layer may further include other components such as various additives as necessary. Hereinafter, the case where the first polymer layer is a colored layer may be referred to as a first colored layer, and the case where the second polymer layer is a colored layer may be referred to as a second colored layer. Only one of the first polymer layer and the second polymer layer may be a colored layer, or both may be colored layers. The following description is common to the first and second colored layers.

  As a function of the colored layer, first, by reflecting the light that has passed through the solar cells and reaches the back sheet without being used for power generation out of the incident light, and returns the solar cells to the solar cells, Increasing the power generation efficiency, secondly, improving the decorativeness of the appearance when the solar cell module is viewed from the side on which sunlight enters (front side), and the like. In general, when the solar cell module is viewed from the front side, a back sheet can be seen around the solar cell, and by providing a colored layer on the back sheet, the decorativeness can be improved and the appearance can be improved.

-Pigment-
The colored layer in the present invention can contain at least one pigment.
Examples of the pigment include inorganic pigments such as titanium dioxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, ultramarine blue, bitumen, and carbon black, and organic pigments such as phthalocyanine blue and phthalocyanine green. It can be appropriately selected and contained.

  Of the pigments, a white pigment is preferred when the polymer layer is formed as a reflective layer that reflects light that has entered the solar cell and passed through the solar cell and returns it to the solar cell. As the white pigment, titanium dioxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc and the like are preferable.

The content in the colored layer of the pigment is in ^the range of 2.5g / ^{m 2} ~8.5g / m 2 is preferred. When the pigment content is 2.5 g / m ² or more, necessary coloring can be obtained, and reflectance and decorative properties can be effectively provided. Further, when the content of the pigment in the colored layer is 8.5 g / m ² or less, the planar shape of the colored layer is easily maintained and the film strength is excellent. Among them, the content of the pigment is in ^the range of 4.5g / ^{m 2} ~8.0g / m 2 is more preferable.

  The average particle diameter of the pigment is preferably 0.03 μm to 0.8 μm in volume average particle diameter, and more preferably about 0.15 μm to 0.5 μm. When the average particle size is within the above range, the light reflection efficiency is high. The average particle diameter is a value measured by a laser analysis / scattering particle size distribution measuring apparatus LA950 (manufactured by Horiba, Ltd.).

  In any case of the first colored layer and the second colored layer, the content of the binder component (including the specific binder) is preferably in the range of 15 to 200% by mass, and 17 to 100% by mass with respect to the pigment. % Range is more preferred. When the content of the binder is 15% by mass or more, the strength of the colored layer is sufficiently obtained, and when it is 200% by mass or less, the reflectance and the decorativeness can be kept good.

~ Physical properties ~
When a white pigment is added as a pigment to the colored layer to form a reflective layer, the light reflectance at 550 nm on the surface on which the colored layer and the easy-adhesion layer described later are provided is preferably 75% or more. . The light reflectivity is the ratio of the amount of light incident from the surface of the easy-adhesion layer to the amount of incident light reflected from the reflection layer and emitted again from the easy-adhesion layer. Here, light having a wavelength of 550 nm is used as the representative wavelength light.
When the light reflectance is 75% or more, the light that passes through the cell and enters the cell can be effectively returned to the cell, and the effect of improving the power generation efficiency is great. The light reflectance can be adjusted to 75% or more by controlling the content of the colorant in the range of 2.5 to 30 g / m ² .

(Other functional layers)
The polymer sheet for solar cells of the present invention may have other functional layers in addition to the polymer substrate and the first and second polymer layers. As another functional layer, an undercoat layer and an easy adhesion layer can be provided.

[Undercoat layer]
In the polymer sheet for solar cells of the present invention, an undercoat layer may be provided between the polymer substrate (support) and the second polymer layer. The thickness of the undercoat layer is preferably in the range of 2 μm or less, more preferably 0.05 μm to 2 μm, and still more preferably 0.1 μm to 1.5 μm. When the thickness is 2 μm or less, the planar shape can be kept good. Moreover, it is easy to ensure required adhesiveness because thickness is 0.05 micrometer or more.

  The undercoat layer can contain a binder. As the binder, for example, polyester, polyurethane, acrylic resin, polyolefin, or the like can be used. In addition to the binder, the undercoat layer is added with an epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, oxazoline-based crosslinking agent, anionic or nonionic surfactant, silica filler, etc. Also good.

There is no particular limitation on the method for applying the undercoat layer and the solvent of the coating solution used.
As a coating method, for example, a gravure coater or a bar coater can be used.
The solvent used for the coating solution may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.
The coating may be performed on the polymer substrate after biaxial stretching, or may be performed by stretching in a direction different from the initial stretching after coating on the polymer substrate after uniaxial stretching. Furthermore, you may extend | stretch in 2 directions, after apply | coating to the base material before extending | stretching.

  If the polymer sheet for solar cells of this invention is a method which can contact the said sealing agent of the battery side board | substrate with which the solar cell element was sealed with the sealing material, and can arrange | position the 1st polymer layer side suitably, Can be selected and manufactured. Especially, formation of the 1st and 2nd polymer layer can be most suitably performed with the manufacturing method of the polymer sheet for solar cells of this invention mentioned later.

[Colored layer]
In addition to the first and second polymer layers, the polymer sheet for solar cells of the present invention may further be provided with a colored layer (preferably a reflective layer) substantially free of the specific binder. The colored layer in this case (hereinafter sometimes referred to as a third colored layer) contains at least a polymer component other than the specific binder and a pigment, and further contains other components such as various additives as necessary. Can be configured. The details of the pigment and various additives are as described above for the case where the first or second polymer layer is formed as a colored layer. The polymer component other than the specific binder is not particularly limited and can be appropriately selected according to the purpose.

  The term “substantially free” means that the specific binder is not actively contained in the colored layer. Specifically, the content of the specific binder in the colored layer is 15% by mass or less. Preferably, the specific binder is not contained (the content is 0 (zero) mass%).

[Adhesive layer]
It is also preferable that the polymer sheet for solar cells of the present invention is further provided with an easily adhesive layer. The easy-adhesion layer is particularly preferably provided on the colored layer. The easy-adhesion layer is a layer for firmly bonding the solar cell polymer sheet to a sealing material (preferably EVA) for sealing a solar cell element (hereinafter also referred to as a power generation element) of the battery side substrate (battery body). It is.

  The easy-adhesion layer can be formed using a binder and inorganic fine particles, and may further include other components such as additives as necessary. The easy-adhesion layer is 10 N / cm or more (preferably 20 N / cm or more) with respect to an ethylene-vinyl acetate (EVA: ethylene-vinyl acetate copolymer) -based sealing material that seals the power generation element of the battery side substrate. It is preferable that it is comprised so that it may have the adhesive force of (). When the adhesive force is 10 N / cm or more, it is easy to obtain wet heat resistance capable of maintaining adhesiveness.

  The adhesive strength can be adjusted by a method of adjusting the amount of the binder and inorganic fine particles in the easy-adhesive layer, a method of applying a corona treatment to the surface of the back sheet that adheres to the sealing material, and the like.

-Binder-
The easy-adhesion layer can contain at least one binder.
Examples of the binder suitable for the easy-adhesive layer include polyester, polyurethane, acrylic resin, polyolefin, and the like. Among these, acrylic resin and polyolefin are preferable from the viewpoint of durability. As the acrylic resin, a composite resin of acrylic and silicone is also preferable.

  Examples of preferred binders include Chemipearl S-120 and S-75N (both manufactured by Mitsui Chemicals) as specific examples of polyolefins, and Jurimer ET-410 and SEK-301 (both Nippon Pure Chemical ( As a specific example of the composite resin of acrylic and silicone, Ceranate WSA1060, WSA1070 (both manufactured by DIC Corporation) and H7620, H7630, H7650 (both manufactured by Asahi Kasei Chemicals Corporation) and the like can be given.

The content of the binder in the easy-adhesive layer is preferably in the range of 0.05 to 5 g / m ² . Especially, the range of 0.08-3 g / m < ² > is more preferable. The content of the binder, 0.05 g / m ² or more is desired as easy adhesion obtained to that, better surface state is obtained when the is 5 g / m ² or less.

-Fine particles-
The easily adhesive layer can contain at least one kind of inorganic fine particles.
Examples of the inorganic fine particles include silica, calcium carbonate, magnesium oxide, magnesium carbonate, and tin oxide. Among these, fine particles of tin oxide and silica are preferable in that the decrease in adhesiveness when exposed to a humid heat atmosphere is small.

  The particle size of the inorganic fine particles is preferably about 10 to 700 nm, more preferably about 20 to 300 nm in terms of volume average particle size. When the particle size is within this range, better easy adhesion can be obtained. The particle size is a value measured by a laser analysis / scattering particle size distribution measuring apparatus LA950 (manufactured by Horiba, Ltd.).

  There is no restriction | limiting in particular in the shape of an inorganic fine particle, Any things, such as a spherical form, an indeterminate form, and a needle shape, can be used.

The content of the inorganic fine particles is in the range of 5 to 400% by mass with respect to the binder in the easy-adhesive layer. When the content of the inorganic fine particles is 5% by mass or more, good adhesiveness can be maintained when exposed to a moist heat atmosphere, and when it is 400% by mass or less, the surface state of the easily adhesive layer is more favorable. Become.
Among these, the content of the inorganic fine particles is preferably in the range of 50 to 300% by mass.

-Crosslinking agent-
The easily adhesive layer can contain at least one crosslinking agent.
Examples of the crosslinking agent suitable for the easily adhesive layer include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among these, an oxazoline-based cross-linking agent is particularly preferable from the viewpoint of ensuring adhesiveness after wet heat aging. Specific examples of the oxazoline-based crosslinking agent include the same specific examples as described in the above-mentioned polymer layer section.

  As content in the easily bonding layer of a crosslinking agent, 5-50 mass% is preferable with respect to the binder in an easily bonding layer, Most preferably, it is 20-40 mass%. When the content of the crosslinking agent is 5% by mass or more, a good crosslinking effect can be obtained, and the strength and adhesiveness of the colored layer can be maintained. When the content is 50% by mass or less, the pot life of the coating liquid Can be kept long.

-Additives-
If necessary, the easily adhesive layer may further contain a known matting agent such as polystyrene, polymethylmethacrylate, or silica, or a known surfactant such as anionic or nonionic.

-Method of forming easy-adhesive layer-
The easy-adhesive layer can be formed by a method in which a polymer sheet having easy adhesive properties is bonded to a substrate, or a method by coating. Especially, the method by application | coating is preferable at the point which is easy and can form in a thin film with uniformity. As a coating method, for example, a known coating method such as a gravure coater or a bar coater can be used. The coating solvent used for preparing the coating solution may be water or an organic solvent such as toluene or methyl ethyl ketone. A coating solvent may be used individually by 1 type, and may mix and use 2 or more types.

Although there is no restriction | limiting in particular in the thickness of an easily-adhesive layer, Usually, 0.05-8 micrometers is preferable, More preferably, it is the range of 0.1-5 micrometers. When the thickness of the easy-adhesion layer is 0.05 μm or more, necessary easy adhesion can be suitably obtained, and when it is 8 μm or less, the surface shape becomes better.
The easy-adhesion layer needs to be transparent so as not to reduce the effect of the colored layer.

~ Physical properties ~
Moreover, the polymer sheet for solar cells of the present invention has an adhesive force with the sealing material after storage for 48 hours in an atmosphere of 120 ° C. and 100% RH, with respect to the adhesive force with the sealing material before storage, It is preferable that it is 75% or more. As described above, the polymer sheet for solar cells of the present invention includes a predetermined amount of binder and a predetermined amount of inorganic fine particles with respect to the binder, and has an adhesive force of 10 N / cm or more with respect to the EVA-based sealing material. By having the easy-adhesion layer, an adhesive strength of 75% or more before storage can be obtained even after the storage. Thereby, as for the produced solar cell module, peeling of a backsheet and the fall of the power generation performance accompanying it are suppressed, and long-term durability improves more.

[Method for producing polymer sheet for solar cell]
The method for producing the polymer sheet for solar cells of the present invention is not particularly limited, but can be suitably produced by the following method for producing a polymer sheet for solar cells of the present invention.

  That is, the method for producing a polymer sheet for a solar cell of the present invention comprises, on a polymer substrate, at least one binder polymer selected from a fluoropolymer and a silicone polymer, and a crosslinking agent having an oxazoline group, and Applying a coating solution having an equivalent [meq / g] of the oxazoline group to the binder polymer of more than 0 and less than 1 and drying and then curing to form a second polymer layer (second step) And a coating liquid containing at least one binder polymer selected from a fluoropolymer and a silicone polymer is applied onto the second polymer layer and dried to form the first polymer layer. Forming (first polymer layer forming step).

  As described above, the polymer sheet for solar cell of the present invention can form the first and second polymer layers of the present invention and, if necessary, an easily adhesive layer on a polymer substrate. Any method may be used.

  In addition, the 1st and 2nd coating liquid for polymer layers is a coating liquid containing the above-mentioned essential component and arbitrary component. Details of the polymer substrate and the components constituting each coating liquid are as described above.

  As a suitable coating method for the first and second polymer layer coating solutions, for example, a gravure coater or a bar coater can be used. In the present invention, the polymer layer coating solution is applied directly on the surface of the polymer substrate or through an undercoat layer having a thickness of 2 μm or less, and the polymer layer (for example, a colored layer (preferably a reflective layer) is preferably coated on the polymer substrate. Layer) or back layer).

  The first and second polymer layers can be formed by a method in which a polymer sheet is bonded to a polymer substrate, a method in which the polymer layer is coextruded when forming the polymer substrate, a method by coating, or the like. Especially, the method by application | coating is preferable at the point which is easy and can form in a thin film with uniformity. In the case of 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 an aqueous system using water as a coating solvent, or a solvent system 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.
In addition, when the polymer layer coating solution contains a “water-miscible organic solvent having a boiling point of 99 ° C. or lower” described later as an organic solvent, the amount of “water-miscible organic solvent having a boiling point of 99 ° C. or lower” is as described above. The “water-miscible organic solvent having a boiling point of 99 ° C. or lower” is adjusted to an amount satisfying the content range.

  One of the preferred embodiments of the coating solution for the polymer layer is that the water-miscible organic solvent having a boiling point of 99 ° C. or less is 0.1% by mass to 30% by mass with respect to the total mass of the binder polymer contained in the coating solution. % Water-based coating solution. It is preferable that at least one of the first polymer layer and the second polymer layer is formed using the aqueous coating solution. When the content of the water-miscible organic solvent in the coating solution for forming the polymer layer is 30% by mass or less, it is advantageous in terms of precipitation, filterability, and solvent environment. The content of the water-miscible organic solvent in the coating liquid for forming a polymer layer is 0.1% by mass to 30% by mass, more preferably 0.1% by mass to 10% by mass, further based on the binder polymer. Preferably it is 0.1 mass%-5 mass%. When the content of the water-miscible organic solvent is 0.1% by mass or more, it means that the water-miscible organic solvent is positively contained, and it is easy to remain in the formed layer. The preferred range of the content of the water-miscible organic solvent in the coating liquid for forming a polymer layer is the same for the coating liquid for forming either the first polymer layer or the second polymer layer.

  Specific examples of the water-miscible organic solvent having a boiling point of 99 ° C. or lower include the same specific examples as described in the section of the polymer layer.

  In a polymer layer coating solution containing a compound having an oxazoline group as a crosslinking agent, the crosslinking reaction between the polymer and the compound having an oxazoline group proceeds better due to the inclusion of the water-miscible organic solvent. Excellent solvent resistance is obtained.

  The second polymer layer is dried under desired conditions after the application of the polymer layer coating solution, and then the dried coating film is further cured. Also about a 1st polymer layer, after drying on desired conditions, it is preferable to harden the coating film after drying further.

  As a method for curing the polymer layer, a heating method is suitable. Although it does not specifically limit as heating temperature, 50 to 200 degreeC is preferable and 150 to 200 degreeC is more preferable. The curing time for curing the first or second polymer layer is preferably 1 minute to 30 minutes, and the production suitability is more preferably 1 minute to 2 minutes.

  In a preferred embodiment of the first polymer layer and the second polymer layer in the present invention, the first polymer layer and the second polymer layer are formed in forming the first polymer layer and the second polymer layer. The aspect which forms a 2nd polymer layer on a polymer base material, and forms a 1st polymer layer on this 2nd polymer layer following this is mentioned.

  Moreover, in this invention, the hardening time at the time of forming a 1st polymer layer and a 2nd polymer layer can all be 1 minute-2 minutes. That is, in the present invention, a polymer layer having sufficient adhesion can be formed even when the curing time is set to a relatively short time as described above. Further, when the first polymer layer and the second polymer layer further contain an onium compound, the solvent resistance as well as sufficient adhesion can be improved. Thus, the polymer sheet for solar cells of the present invention has excellent production suitability.

<Solar cell module>
The solar cell module of the present invention is configured by providing the polymer sheet for solar cell of the present invention described above or the polymer sheet for solar cell manufactured by the method for manufacturing the polymer sheet for solar cell described above. As a preferred embodiment of the present invention, a solar cell element that converts light energy of sunlight into electric energy is disposed between the transparent front substrate on which sunlight enters and the polymer sheet for solar cells of the present invention described above. The solar cell element is sealed and bonded with a sealing material such as ethylene-vinyl acetate between the front substrate and the back sheet. That is, a cell structure portion having a solar cell element and a sealing material for sealing the solar cell element is provided between the front substrate and the back sheet.

  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 transparent substrate only needs to have a light-transmitting property through which sunlight can pass, and can be appropriately selected from base materials that transmit 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.

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

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. In the examples, “part” is based on mass.
In the following, the volume average particle size was measured using a laser analysis / scattering particle size distribution measuring apparatus LA950 (manufactured by Horiba, Ltd.).

<Production of polymer substrate>
As polymer base materials used in Examples and Comparative Examples, PET-1, PET-2, PET-3, PET-4, and PET-5 were produced as follows.

-Preparation of PET-1-
[Step 1] -Esterification-
A slurry of 100 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals Co., Ltd.) and 45 kg of ethylene glycol (manufactured by Nippon Shokubai Chemical Industry Co., Ltd.) is charged in advance with about 123 kg of bis (hydroxyethyl) terephthalate, temperature 250 ° C., pressure 1 . The esterification reaction tank maintained at 2 × 10 ⁵ Pa was sequentially supplied over 4 hours to carry out the esterification reaction, and after the completion of the supply, the esterification reaction was carried out over an additional hour. 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, with respect to the resulting polymer. After stirring for 5 minutes, an ethylene glycol solution of cobalt acetate and manganese acetate was added in the obtained polymer so that the cobalt element equivalent value and the manganese element equivalent value were 30 ppm and 15 ppm, respectively. After further stirring for 5 minutes, a 2% by mass ethylene glycol solution of a titanium alkoxide compound was added so that the converted value of titanium element was 5 ppm in the resulting polymer to obtain a low polymer. Five minutes later, a 10% by mass ethylene glycol solution of ethyl diethylphosphonoacetate was added so that the phosphorus element conversion value was 5 ppm in the obtained 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-
The pellets obtained above were held in a vacuum vessel maintained at 40 Pa at a temperature of 220 ° C. for 30 hours for solid phase polymerization.

[Step 4] -Production of film-like polymer substrate (support)-
The pellets after undergoing solid-phase polymerization as described above were melted at 280 ° C. and cast on a metal drum to produce an unstretched base having a thickness of 2.5 mm. Thereafter, the film was stretched 3 times in the longitudinal direction at 90 ° C., and further stretched 3.3 times in the transverse direction at 120 ° C. Thus, a biaxially stretched polyethylene terephthalate support (hereinafter referred to as “PET-1”) having a thickness of 300 μm was obtained.
The carboxyl group content of PET-1 was 14 eq / t. The carboxyl group content of the polyethylene terephthalate support was determined by the following method.

<< Measurement of carboxyl group content >>
A weight w [g] of about 0.1 g of the support was measured, put in a round bottom flask containing 5 mL of benzyl alcohol, and kept in an atmosphere at a temperature of 205 ° C. for 24 hours in a stoppered state. The contents were then added to 15 mL of chloroform. A solution obtained by adding a small amount of phenol red indicator to this solution was titrated with a benzyl alcohol solution of potassium hydroxide having a concentration of 0.01 N / L. The amount of potassium hydroxide solution required for titration was set to ymL, and the carboxyl group content (COOH group content) of the biaxially stretched PET support was determined by the following formula (A). In addition, it calculated | required similarly to PET-1 also about the carboxyl group content in PET-2-5 mentioned later.
Carboxyl group content (eq / t) = 0.01 × y / w Formula (A)

-Production of PET-2-
-Preparation of end-capping agent-containing master batch pellet (MB-I)-
9 kg of solid-phase-polymerized pellets obtained in the preparation of PET-1 were dried in advance in an atmosphere of 120 ° C. and 10 ⁻³ torr (0.1333 Pa) for 8 hours.
1 kg of the following end-capping agent A is added to the dried pellets, supplied to a vent type biaxial extruder, kneaded and extruded at 275 ° C. while degassing, and 10% by mass of the end-capping agent A A master batch pellet (MB-I) (diameter: about 3 mm, length: about 7 mm) was prepared.
End sealant A:
N, N′-dicyclohexylcarbodiimide, Mw = 206, carbodiimide end-capping agent

-Production of support-
Using the mixed pellet obtained by mixing 96 mass% of the solid-phase-polymerized pellet of PET-1 and 4 mass% of the master batch pellet MB-I, in the same manner as in Step 4 in the production of PET-1, A biaxially stretched polyethylene terephthalate support (PET-2) having a thickness of 250 μm was obtained. The carboxyl group content of PET-2 was 8 eq / t.

-Production of PET-3-
-Preparation of end-capping agent-containing master batch pellet (MB-II)-
Instead of the end-capping agent A used in the preparation of PET-2, the end-capping agent-containing master batch pellet (MB-) was used in the same manner as in the preparation of PET-2 except that the following end-capping agent B was used. II) was obtained.
End sealant B:
JP, 2011-153209, A cyclic carbodiimide compound with the following structure manufactured by the method of paragraph numbers [0174] and [0175], Mw = 516.

-Production of support-
Using the mixed pellet obtained by mixing 92% by mass of the solid-phase-polymerized pellet of PET-1 and 8% by mass of the master batch pellet (MB-II), the same procedure as in Step 4 in the production of PET-1 was performed. Thus, a biaxially stretched polyethylene terephthalate support (PET-3) having a thickness of 250 μm was obtained. The carboxyl group content of PET-3 was 8 eq / t.

-Preparation of PET-4-
-Production of master batch pellets containing titanium dioxide (MB-III)-
50 kg of solid-phase-polymerized pellets obtained in the preparation of PET-1 were previously dried in an atmosphere of 120 ° C. and 10 ⁻³ torr (0.1333 Pa) for 8 hours.
A mixture of 50 kg of rutile titanium dioxide having an average particle size of 0.3 μm (electron microscopic method) mixed with pellets after drying is supplied to a vent type twin screw extruder, kneaded and extruded at 275 ° C. while degassing, A master batch pellet (MB-III) (diameter: about 3 mm, length: about 7 mm) containing 50% by mass of titanium oxide was produced. The carboxyl group content of this master batch pellet was 15 eq / t. The average particle diameter of the titanium dioxide fine particles was measured by the following method.

<< Measurement of average particle diameter of titanium dioxide fine particles >>
The titanium dioxide fine particles are observed with a scanning electron microscope (SEM), the magnification is appropriately changed according to the size of the particles, and a photograph taken is enlarged and copied. Next, the major axis and minor axis of each particle are measured for at least 100 randomly selected fine particles. The average value of the major axis and the minor axis is defined as the particle size of the particle. The particle diameter of each particle is determined, and the average value of 100 particles is defined as the average particle diameter of the titanium dioxide fine particles.

-Production of support-
Using the mixed pellet obtained by mixing 80% by mass of the solid phase polymerized pellet of PET-1 and 20% by mass of the master batch pellet (MB-III), the same procedure as in Step 4 in the production of PET-1 was performed. Thus, a biaxially stretched polyethylene terephthalate support (PET-4) having a thickness of 250 μm was obtained. The carboxyl group content of PET-4 was 14 eq / t.

-Production of PET-5-
As shown below, using the solid phase polymerized pellets obtained by the production of PET-1 and the master batch pellets (MB-III) obtained by the production of PET-4, respectively, A layer, B Except co-extrusion of the layer and the C layer, a 250 μm thick double-stretched polyethylene terephthalate support (PET-5) having a laminated structure of the A layer, the B layer, and the C layer was performed in the same manner as in Step 4 in the production of PET-1. ) The thicknesses of the A layer, the B layer, and the C layer are as shown below. Moreover, the carboxyl group content of PET-5 was 15 eq / t.
(A layer)
Pellets: Solid-phase polymerized pellets obtained by the production of PET-1 are used alone.
Thickness: about 50μm
(B layer)
Pellet: A mixed pellet obtained by mixing 64% by mass of a solid-phase polymerized pellet obtained by the production of PET-1 and 36% by mass of a master batch pellet (MB-III) is used.
Thickness: about 150μm
(C layer)
Pellets: Solid-phase polymerized pellets obtained by the production of PET-1 are used alone.
Thickness: about 50μm

  Using the PET-1 to PET-5 obtained as described above, each polymer sheet of Examples and Comparative Examples was prepared as follows.

[Example 1-1]
A reflective layer, an easy-adhesion layer, and first and second polymer layers were formed on the PET-1 obtained above as follows to prepare a polymer sheet of Example 1-1.

<Formation of reflective layer>
-Preparation of pigment dispersion-
Components in the following composition were mixed, and the mixture was subjected to a dispersion treatment for 1 hour by a dynomill type disperser.
<Composition of pigment dispersion>
・ Titanium dioxide (volume average particle size = 0.42 μm) 39.9% by mass
(Taipeke R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content 100% by mass)
・ Polyvinyl alcohol: 8.0% by mass
(PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10% by mass)
・ Surfactant ... 0.5% by mass
(Demol EP, manufactured by Kao Corporation, solid content: 25% by mass)
・ Distilled water: 51.6% by mass

-Preparation of reflection layer coating solution 1-
Components in the following composition were mixed to prepare a reflection layer coating solution 1.
<Composition of coating solution 1>
-The above pigment dispersion: 80.0 parts-Polyacrylic resin aqueous dispersion: 19.2 parts (Binder: Jurimer ET410, manufactured by Nippon Pure Chemicals Co., Ltd., solid content: 30% by mass)
Polyoxyalkylene alkyl ether: 3.0 parts (Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
Oxazoline compound (crosslinking agent, H-1) 2.0 parts (Epocross WS-700, manufactured by Nippon Shokubai Chemical Industry Co., Ltd., solid content: 25% by mass)
・ Distilled water: 7.8 parts

-Formation of reflective layer-
The obtained coating solution 1 for the reflective layer was applied onto the above PET-1, dried at 180 ° C. for 1 minute, and a white layer (reflective layer) having a titanium dioxide content of 6.5 g / m ² as a pigment layer. ) Was formed.

<Easily adhesive layer>
-Preparation of easy-adhesion layer coating solution-
Components in the following composition were mixed to prepare a coating solution for an easily adhesive layer.
<Composition of coating solution>
-Polyolefin resin aqueous dispersion: 5.2 parts (Binder: Chemipearl S-75N, manufactured by Mitsui Chemicals, solid content: 24% by mass)
Polyoxyalkylene alkyl ether 7.8 parts (Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
Oxazoline compound (crosslinking agent, H-1) 0.8 parts (Epocross WS-700, manufactured by Nippon Shokubai Chemical Industry Co., Ltd., solid content: 25% by mass)
Silica fine particle aqueous dispersion: 2.9 parts (Aerosil OX-50, manufactured by Nippon Aerosil Co., Ltd., volume average particle diameter = 0.15 μm, solid content: 10% by mass)
・ Distilled water ... 83.3 parts

-Formation of an easily adhesive layer-
The obtained coating solution was applied on the reflective layer so that the binder amount was 0.09 g / m ² and dried at 180 ° C. for 1 minute to form an easy-adhesive layer.

<Surface treatment (corona treatment)>
On the side where the reflective layer and the easy-adhesion layer in PET-1 were not formed, corona treatment was performed under the following conditions.

<Corona treatment>
・ Equipment: Solid state corona treatment machine 6KVA model made by Pillar Co. ・ Gap clearance between electrode and dielectric roll: 1.6 mm
・ Processing frequency: 9.6 kHz
Processing speed: 10 m / min Processing strength: 0.75 kV / A / min / m ²

<First and second polymer layers>
-Formation of first and second polymer layers-
On the side subjected to the corona treatment in PET-1, the second polymer layer coating liquid A obtained from the following was applied so that the binder amount was 5.1 g / m ² in terms of wet coating amount. Dry for 2 minutes and cure to form a second polymer layer with a dry thickness of 8.5 μm. Next, on the second polymer layer, the first polymer layer coating solution B obtained from the following was applied such that the binder amount was 1.3 g / m ² in terms of wet coating amount, and dried at 150 ° C. for 2 minutes. And cured to form a first polymer layer having a thickness of 1.6 μm.

[Preparation of second coating liquid A for polymer layer]
Components in the following composition were mixed to prepare a second coating liquid A for polymer layer.
<Composition of coating liquid A>
-Silicone polymer aqueous dispersion (Ceranate WSA1070, manufactured by DIC Corporation, solid content concentration 37.4% by mass) ... 45.9 parts-Crosslinker having oxazoline group (Epocross WS-700, Nippon Shokubai Chemical Industry ( Co., Ltd., solid content: 25% by mass) ... 7.7 parts, polyoxyalkylene alkyl ether ... 2.0 parts (Naroacty CL95, Sanyo Chemical Industries, Ltd., solid content: 1% by mass )
The following pigment dispersion: 33.0 partsDistilled water: 11.4 parts

~ Preparation of pigment dispersion ~
After mixing the following components, the mixture was subjected to a dispersion treatment for 1 hour using a Dinomill type disperser.
<Composition>
・ Titanium dioxide (volume average particle diameter = 0.42 μm) 39.9% by mass
(Taipeke R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content 100% by mass)
・ Polyvinyl alcohol: 8.0% by mass
(PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10% by mass)
・ Surfactant ... 0.5% by mass
(Demol EP, manufactured by Kao Corporation, solid content: 25% by mass)
・ Distilled water: 51.6% by mass

[Preparation of Coating Solution B for First Polymer Layer]
Components in the following composition were mixed to prepare a first coating liquid B for polymer layer.
<Composition of coating solution>
・ Fluoropolymer aqueous dispersion (Obligard SW0011F, AGC Co-Tech Co., Ltd., solid content concentration 36.1% by mass) ・ ・ ・ 45.9 parts ・ Crosslinking agent having oxazoline group (Epocross WS-700, Nippon Shokubai Chemical Industry Co., Ltd.) 7.7 parts, polyoxyalkylene alkyl ether ... 2.0 parts (Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1) mass%)
-The above pigment dispersion ... 33.0 parts-Distilled water ... 11.4 parts

[Examples 1-2 to 1-3, Comparative Examples 1-1 to 1-6]
In Example 1-1, the specific binder and the oxazoline group were added so that the equivalent amount (meq / g) of the oxazoline group to the binder in the second polymer layer and the first polymer layer was a value described in Table 1. Except having changed the usage-amount of the crosslinking agent to have, it carried out similarly to Example 1-1, and produced the polymer sheet of Examples 1-2 to 1-3 and Comparative Examples 1-1 to 1-6.

[Examples 2-1 to 2-3, comparative examples 2-1 to 2-6]
In Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-6, the fluoropolymer aqueous dispersion used for the first polymer layer was replaced with a silicone polymer aqueous dispersion (Ceranate WSA1070, DIC Corporation). Examples 2-1 to 2-2, in the same manner as in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-6, except that the solid content concentration was changed to 37.4% by mass. 3, and polymer sheets of Comparative Examples 2-1 to 2-6 were produced.

(Evaluation)
About each polymer sheet produced in Examples 1-1 to 1-3, Examples 2-1 to 2-3, Comparative Examples 1-1 to 1-6, and Comparative Examples 2-1 to 2-6, The evaluation results of the following evaluation are shown in Table 1.

(1) Evaluation of adhesion obtained in Examples 1-1 to 1-3, Examples 2-1 to 2-3, Comparative Examples 1-1 to 1-6, and Comparative Examples 2-1 to 2-6 Six scratches were made on each of the obtained polymer sheets on the side where the first and second polymer layers were formed with a single-edged razor to form 25 squares. 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 back layer was ranked according to the following evaluation criteria according to the number of peeled cells. Evaluation ranks 3 to 5 are practically acceptable ranges.

<Evaluation criteria>
5: No peeling occurs 4: The peeled squares are zero, but the scratch part is slightly peeled off.
3: The square which peeled was less than 1 square.
2: The square which peeled was 1 square or more and less than 5 squares.
1: The square which peeled was 5 squares or more.
What is permitted in practice is classified into evaluation ranks 3 to 5.

  As shown in Table 1, each of the polymer sheets of Examples 1-1 to 1-3 and Examples 2-1 to 2-3 is a polymer excellent in adhesion in comparison with the comparative example. It turns out that it is a sheet. Moreover, it turns out that the polymer sheet of each Example is excellent also about production suitability.

[Examples 3-1 to 3-13]
For the second polymer layer coating liquid A and the first polymer layer coating liquid B used in Example 1-2, the onium compounds listed in Table 2 were further mixed with the binder ratios listed in Table 2 ( The polymer sheets of Examples 3-1 to 3-13 were produced in the same manner as in Example 1-2, except that the addition was performed so that the amount was (mass%).

[Examples 4-1 to 4-11]
For the second polymer layer coating solution A and the first polymer layer coating solution B used in Example 2-2, the onium compounds listed in Table 2 were further mixed with the binder ratios listed in Table 2 ( The polymer sheets of Examples 4-1 to 4-11 were produced in the same manner as in Example 2-2, except that the addition was made so that the amount was (mass%).

[Examples 5-1 to 5-5]
The specific binder and the oxazoline group so that the equivalent (meq / g) of the oxazoline group to the binder is the value described in Table 3 with respect to the first coating solution for the polymer layer used in Example 4-3. In the second polymer layer coating solution, ethanol (a water-miscible organic solvent having a boiling point of 99 ° C. or lower) is used with the binder ratio (see Table 3). The polymer sheets of Examples 5-1 to 5-5 were produced in the same manner as in Example 4-3, except that the amount was changed so as to be 5% by mass.

[Examples 5-6 to 5-9]
With respect to the 1st coating liquid for polymer layers used for Example 4-3, it has a specific binder and an oxazoline group so that the equivalent (meq / g) of the oxazoline group with respect to a binder may become the value described in Table 3. A cross-linking agent and an onium compound were used, and ethanol (water-miscible organic solvent having a boiling point of 99 ° C. or lower) was added so as to have a binder ratio (% by mass) shown in Table 3, and the film thickness. The polymer sheets of Examples 5-6 to 5-9 were produced in the same manner as in Example 4-3 except that was changed as described in Table 3.

[Examples 5-10 to 5-13]
Ethanol (a water-miscible organic solvent having a boiling point of 99 ° C. or less) was further added to the first polymer layer coating solution used in Examples 5-6 to 5-9 to the binder ratio (mass) shown in Table 3. %), Polymer sheets of Examples 5-10 to 5-13 were produced in the same manner as in Examples 5-6 to 5-9.

[Examples 5-14 to 5-15]
Except for adjusting the amount of distilled water to the first polymer layer coating solution used in Examples 5-10 to 5-11, the solution concentration (% by mass) shown in Table 3 was obtained. In the same manner as in Examples 5-10 to 5-11, polymer sheets of Examples 5-14 to 5-15 were produced.

[Examples 5-16 to 5-19]
Except having changed the polymer base material (PET-1) used for Example 5-11 into the polymer base material of Table 3, it is the same as Example 5-11, and Examples 5-16 to 5-5 Seventeen polymer sheets were prepared. The polymer substrate (PET-1) used in Example 5-11 was changed to the polymer substrate shown in Table 3, and the Ti content in the second polymer layer was changed as shown in Table 3. Except for the above, polymer sheets of Examples 5-18 to 5-19 were produced in the same manner as Example 5-11.

(Evaluation)
About each of the coating liquid for the first and second polymer layers prepared in Examples 3-1 to 3-11, Examples 4-1 to 4-11, and Examples 5-1 to 5-19, and The following evaluation was performed about each polymer sheet produced in these Examples. The evaluation results are shown in Tables 2 and 3.

(1) Evaluation of adhesion <1a> Adhesion before wet heat aging In the same manner as the evaluation of adhesion performed on the polymer sheet prepared in Example 1-1, Examples 3-1 to 11-11, Each polymer sheet produced in Examples 4-1 to 4-11 and Examples 5-1 to 5-19 was evaluated for adhesion before wet heat aging. The evaluation results are shown in Tables 2 and 3.

<1b> Adhesiveness after wet heat aging Each polymer sheet produced in Examples 3-1 to 11-11, Examples 4-1 to 4-11, and Examples 5-1 to 5-19 is 120 After maintaining for 48 hours under the environmental conditions of 100 ° C. and 100% RH, after adjusting the humidity for 1 hour under the environment of 25 ° C. and 60% RH, the same evaluation as in the above “(1a) Adhesion before wet heat aging” The adhesion was evaluated by the method. The evaluation results are shown in Tables 2 and 3.

(2) Evaluation of solvent resistance First and third polymer sheets prepared in Examples 3-1 to 3-11, Examples 4-1 to 4-11, and Examples 5-1 to 5-19 The surface on the side where the second polymer layer is formed (the surface of the first polymer layer forming the outermost layer) was rubbed with a cotton swab soaked with ethanol. The solvent resistance was ranked according to the following evaluation criteria based on the number of rubbing times in which dissolution (peeling) of the polymer layer occurred. Evaluation ranks 3 to 5 are practically acceptable ranges. The evaluation results are shown in Tables 2 and 3.

<Evaluation criteria>
5: 100 or more, or not dissolved at all (no peeling occurs)
4: 50 times or more and less than 100 times 3: 30 times or more and less than 50 times 2: 11 times or more and less than 30 times 1: 10 times or less What is permitted in practice is classified into evaluation ranks 3 to 5 .

(3) Evaluation of filterability of coating solution The coating solution to be evaluated was fed at 50 mL / min, and the pressure when filtered through a filter film (pore size 1.0 μm filter) manufactured by Pall Co., Ltd. Evaluation was performed according to the following evaluation criteria. Evaluation ranks 3 to 5 are practically acceptable ranges. The evaluation results are shown in Table 2 and Table 3 below.
<Evaluation criteria>
5: No pressure rise (0.1 kgf / cm ² less than / 2L flow-through)
4: pressure rise (0.1 kgf / ccm ² or 0.5 kgf / cm ² less than / 2L flow-through)
3: Increase in pressure (0.5 kgf / cm ² or more and less than 1.0 kgf / cm 2/2 L flow)
2: pressure rise (1.0 kgf / cm ² or more 2.0 kgf / cm ² less than / 2L flow-through)
1: Pressure increase (2.0 kgf / cm ² or more / 2L flow)

  As shown in Tables 2 and 3, Examples 3-1 to 3-13, Examples 4-1 to 4-11, and Example 5 further containing an onium compound in the first and second polymer layers. It can be seen that each of the polymer sheets -1 to 5-19 is excellent in solvent resistance and excellent in adhesiveness. Moreover, it turns out that the polymer sheet of each Example is excellent also about production suitability.

(Example 6-1)
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.), Example 1-1 The polymer sheets prepared in (1) were superposed in this order, and hot-pressed using a vacuum laminator (Nisshinbo Co., Ltd., vacuum laminating machine) to adhere to EVA. At this time, the polymer sheet produced in Example 1-1 was disposed so that the easy-adhesion layer was in contact with the EVA sheet. Moreover, the adhesion method is as follows.
In this way, a crystalline solar cell module was produced. When the produced solar cell module was operated for power generation, it showed good power generation performance as a solar cell.
<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.

(Examples 6-2 to 6-46)
In Example 6-1, polymer sheets were prepared in Examples 1-2 to 1-3, Examples 2-1 to 2-3, Examples 3-1 to 3-11, and Examples 4-1 to 4-11. A solar cell module of Examples 6-2 to 6-46 was produced in the same manner as in Example 5-1, except that the polymer sheet prepared in Examples 5-1 to 5-19 was used. did.
When the power generation operation was performed using the obtained solar cell module, all showed good power generation performance as a solar cell.

Claims (18)

  A first polymer layer containing at least one binder polymer selected from a fluoropolymer and a silicone polymer on a polymer substrate; and provided on the polymer substrate side of the first polymer layer; At least one binder polymer selected from silicone polymers, and a structural part derived from a crosslinking agent having an oxazoline group that crosslinks the binder polymer, and an equivalent amount of the oxazoline group to the binder polymer [meq / g] And a second polymer layer that is greater than 0 and less than 1.   The polymer sheet for solar cells according to claim 1, wherein the first polymer layer contains an onium compound.   The polymer sheet for solar cells according to claim 1 or 2, wherein the second polymer layer contains an onium compound.   The polymer sheet for solar cells according to any one of claims 1 to 3, wherein the first polymer layer is an outermost layer.   5. The solar cell according to claim 1, wherein at least one of the first polymer layer and the second polymer layer contains a water-miscible organic solvent having a boiling point of 99 ° C. or less. Polymer sheet.   The polymer sheet for solar cells according to any one of claims 1 to 5, wherein the polymer base material contains an end-capping agent.   The polymer sheet for solar cells according to any one of claims 1 to 6, wherein the polymer substrate contains a carbodiimide-based end-capping agent.   The polymer sheet for solar cells according to any one of claims 1 to 7, wherein the polymer substrate contains fine particles that are inorganic particles or organic particles.   The polymer sheet for solar cells according to any one of claims 1 to 8, wherein the polymer base material has a laminated structure including two or more layers having different contents of fine particles that are inorganic particles or organic particles.   At least one of the first polymer layer and the second polymer layer has a boiling point of 99 ° C. or less selected from methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and acetone. The polymer sheet for solar cells of any one of Claims 1-9 containing the water miscible organic solvent of these. The polymer substrate contains at least one binder polymer selected from a fluoropolymer and a silicone polymer, and a crosslinking agent having an oxazoline group, and an equivalent amount of the oxazoline group to the binder polymer [meq / g] Is applied, dried and then cured to form a second polymer layer, and the second polymer layer is selected from a fluoropolymer and a silicone polymer. Applying a coating solution containing at least one binder polymer and drying the coating solution to form a first polymer layer;
The manufacturing method of the polymer sheet for solar cells which has this.   The manufacturing method of the polymer sheet for solar cells of Claim 11 with which the coating liquid used for the process of forming a said 1st polymer layer contains an onium compound.   The manufacturing method of the polymer sheet for solar cells of Claim 11 or Claim 12 in which the coating liquid used for the process of forming a said 2nd polymer layer contains an onium compound.   The curing time of the polymer layer in the step of forming the first polymer layer and the step of forming the second polymer layer are both in the range of 1 minute to 30 minutes. The manufacturing method of the polymer sheet for solar cells of any one of Claims 1.   The coating liquid used to form at least one of the first polymer layer and the second polymer layer is a binder polymer containing a water-miscible organic solvent having a boiling point of 99 ° C. or less. The method for producing a polymer sheet for a solar cell according to any one of claims 11 to 14, which is an aqueous coating solution containing 0.1% by mass to 30% by mass with respect to the total mass.   The coating liquid used for forming at least one of the first polymer layer and the second polymer layer is at least one selected from methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and acetone. The polymer sheet for solar cells according to any one of claims 11 to 15, comprising a water-miscible organic solvent having a seed boiling point of 99 ° C or lower.   The solar cell manufactured by the manufacturing method of the polymer sheet for solar cells of any one of Claims 1-10, or the polymer sheet for solar cells of any one of Claims 11-16. A solar cell module provided with a polymer sheet for a battery. A transparent front substrate on which sunlight is incident;
A cell structure portion provided on the front substrate and having a solar cell element and a sealing material for sealing the solar cell element;
The polymer for solar cells of any one of Claims 1-10 provided in the opposite side to the side in which the said front substrate is located of the said cell structure part, and arrange | positioned adjacent to the said sealing material. The polymer sheet for solar cells manufactured by the manufacturing method of the sheet | seat or the polymer sheet for solar cells of any one of Claims 11-16,
Solar cell module with