JP2015058685A - Laminate film and method for manufacturing the same, back sheet for solar cell module, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate film having a coating layer having excellent moisture heat resistance in adhesion and fewer defects on a surface thereof, a back sheet for a solar cell module, and a solar cell module capable of maintaining stable power generation efficiency.SOLUTION: A laminate film 11 includes: a coating layer 1 which is formed by applying a coating liquid containing a polyolefin resin, a fluorine-based surfactant, and at least one compound selected from nonionic surfactants other than a fluorine-based surfactant and anionic surfactants other than a fluorine-based surfactant, on at least one surface of a polyester film, and then at least once stretching the polyester film; and the stretched polyester film 2. The back sheet for a solar cell module, and the solar cell module include the laminate film.

Description

  The present invention relates to a laminated film and a method for producing the same, a back sheet for a solar cell module, and a solar cell module.

  Polyester films are used in various fields such as back sheets for solar cell modules, optical films, tracing films, packaging films, magnetic tapes, and insulating tapes. When used in these applications, generally, a polyester film is often used as a laminated film in which another film having functionality is bonded or a coating layer is provided on the film surface. However, since the polyester film itself does not have adhesiveness, a film layer such as an easy-adhesion layer is laminated on the polyester film and laminated through the film layer.

Usually, the coating layer is formed by an off-line coating method or an in-line coating method. In particular, in the in-line coating method, by providing the coating layer before or during the stretching process of the polyester film, there is an advantage that the adhesion between the polyester film and the coating layer can be further enhanced.
For example, Patent Documents 1 and 2 disclose a method in which a coating layer containing a polyester resin, an acrylic resin, a urethane resin, or the like is formed during stretching by an in-line coating method.

  On the other hand, polyolefin resin is used as a material for the coating layer because it has excellent heat and moisture resistance and adhesiveness. For example, Patent Documents 3 and 4 disclose a coating layer containing a polyolefin-based resin. Here, the coating layer is formed by an off-line coating method.

  On the other hand, it is known to use a surfactant in the coating solution in order to improve the surface state of the coating layer. For example, Patent Document 5 discloses a method for improving the leveling property at the time of coating by adding a surfactant to a coating solution containing a polyurethane resin for a coating layer formed by coating by an in-line coating method. ing.

  Further, Patent Document 6 describes a method for improving adhesion and improving the surface state by adding a specific amount of a surfactant to a coating liquid containing a polyolefin resin.

  Patent Documents 7 and 8 describe a solar cell in which an undercoat layer-forming coating solution containing a polyolefin binder, an oxazoline-based crosslinking agent, and a nonionic surfactant is applied to a PET substrate by an in-line coating method. A backsheet is disclosed.

JP 2005-178313 A JP-A-7-17885 JP 2013-26340 A JP 2013-38412 A JP 2011-168053 A JP2013-21273A JP2013-58748A International Publication No. 2013/024902

  The laminated films described in Patent Documents 1 and 2 do not have sufficient moisture and heat resistance of the coating layer, and when the laminated film is used under high-temperature and high-humidity conditions, the adhesiveness tends to decrease.

  When the coating layer is formed by the in-line coating method in order to further improve the adhesion between the coating layer described in Patent Documents 3 and 4 and the polyester film, surface defects such as holes and bumps (projections) frequently occur in the coating layer. easy. When a coating layer is formed in the middle of stretching using the in-line coating method, the coating layer is stretched together with the polyester film, so that defects are also increased. Therefore, as in Patent Documents 3 and 4, in the offline coating method, the defect is so small that it does not cause a problem. However, if the in-line coating method is employed in order to improve the adhesiveness, it is considered that the defect becomes large.

  Even with the method described in Patent Document 5, it is difficult to suppress defects in the coating layer using the polyolefin resin. In addition, the heat and humidity resistance of the coating layer is not sufficient, and when the laminated film is used under high temperature and high humidity conditions, the adhesiveness is lowered. In particular, the moisture and heat resistance required for the solar cell backsheet is high, and the coating layer described in Patent Document 5 has insufficient moisture and heat resistance.

Moreover, when the coating layer described in Patent Document 6 is formed in the middle of stretching by an in-line coating method, surface defects such as holes and bumps (projections) are still likely to occur in the coating layer. If there are surface defects such as holes or bumps in the coating layer, the adhesiveness of the defective part will be poor, so if the laminated film is laminated with another member through the coating layer, it may cause a floating failure, and When another functional layer is applied to the surface, the designability is impaired as a point defect.
Even in the solar cell backsheet described in Patent Documents 7 and 8, surface defects may occur in the undercoat layer.
From the above, a laminated film having excellent surface moisture resistance and excellent surface resistance is desired.

  An object of the present invention is to provide a laminated film having a coating layer having excellent moisture and heat resistance and having few defects on its surface, a method for producing the same, a back sheet for a solar cell module, and a solar that can maintain stable power generation efficiency. It is to provide a battery module.

Specific means for achieving the object is as follows.
<1> Polyester resin coating solution containing at least one selected from polyolefin resins, fluorosurfactants, nonionic surfactants other than fluorosurfactants, and anionic surfactants other than fluorosurfactants A coating layer formed by stretching the polyester film at least once after coating on at least one surface of the film;
A stretched polyester film;
A laminated film having
<2> The laminated film according to <1>, wherein the polyolefin resin is an acid-modified polyolefin resin.
<3> The mass ratio of the fluorosurfactant, nonionic surfactant, and anionic surfactant contained in the coating layer to the polyolefin resin is a [mass%], b [mass%], and c [mass], respectively. %], The laminated film according to <1> or <2> satisfying the following formulas (1) and (2).
0.2 ≦ a + b + c ≦ 5.0 (1)
0.1 ≦ (b + c) /a≦10.0 (2)
<4> The laminated film according to any one of <1> to <3>, in which the coating layer contains all of the fluorosurfactant, the nonionic surfactant, and the anionic surfactant.
<5> The laminated film according to any one of <1> to <4>, wherein the polyolefin resin contains 0.1 to 10% by mass of a structure derived from an unsaturated carboxylic acid or an anhydride thereof.
<6> The laminated film according to <5>, wherein the unsaturated carboxylic acid or an anhydride thereof is acrylic acid, methacrylic acid, or an anhydride of acrylic acid or methacrylic acid.
<7> The laminated film according to any one of <1> to <6>, wherein the polyolefin resin contains 0.1 to 25% by mass of a structure derived from an unsaturated carboxylic acid ester.
<8> The laminated film according to <7>, wherein the unsaturated carboxylic acid ester is a methyl ester, an ethyl ester, or a butyl ester.
<9> The laminated film according to any one of <1> to <8>, wherein the polyolefin resin is a copolymer of ethylene, an unsaturated carboxylic acid ester, an unsaturated carboxylic acid, or an anhydride thereof.
<10> The polyolefin resin is a copolymer of ethylene, an acrylate ester and acrylic acid or an anhydride thereof, or a copolymer of ethylene, a methacrylate ester and acrylic acid or an anhydride thereof <1> to <9> The laminated film according to any one of the above.
<11> The laminated film according to any one of <1> to <10>, wherein the coating layer has a structure derived from a crosslinking agent having an oxazoline group.
<12> The laminated film according to <11>, wherein the crosslinking agent having an oxazoline group is water-soluble. <13> A back sheet for a solar cell module, comprising the laminated film according to any one of <1> to <12>.
<14> a transparent front substrate on which sunlight is incident;
An element structure portion including a solar cell element and a sealing material for sealing the solar cell element, which is disposed on the side opposite to the side on which sunlight is incident on the front substrate,
The solar cell module backsheet according to <13>, which is disposed on the side opposite to the side on which the front base material of the element structure portion is located,
Including solar cell module.
<15> Polyester resin coating solution containing at least one selected from polyolefin resins, fluorosurfactants, nonionic surfactants other than fluorosurfactants, and anionic surfactants other than fluorosurfactants Applying on at least one side of the film;
By stretching the polyester film on which the coating film is formed at least once, on the stretched polyester film, at least selected from polyolefin resins, fluorosurfactants, nonionic surfactants and anionic surfactants Forming a coating layer containing one kind;
The manufacturing method of the laminated | multilayer film which has this.
<16> The method for producing a laminated film according to <15>, wherein the coating liquid is an aqueous dispersion.
<17> As the coating solution, when the solid content in the coating solution is X [g], and the precipitation amount when the coating solution is filtered through a filter having a pore diameter of 10 μm is Y [g], the following formula (3 The method for producing a laminated film according to <15> or <16>, in which a coating liquid satisfying 0.01 ≦ C ≦ 0.50 is satisfied.
C = (Y / X) × 100 (3)

  According to the present invention, a laminated film having a coating layer with excellent moisture and heat resistance and having few defects on the surface, a method for producing the same, a back sheet for a solar cell module, and a solar capable of maintaining stable power generation efficiency A battery module is provided.

It is the schematic which shows an example of a structure of the laminated | multilayer film of this invention. It is the schematic which shows an example of a structure of the solar cell module backsheet of this invention. It is the schematic which shows an example of a structure of the solar cell module of this invention.

Hereinafter, the laminated film, the back sheet for a solar cell module (hereinafter sometimes referred to as a back sheet) and the solar cell module of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the figure, the same code | symbol is attached | subjected to the member (component) which has the same or corresponding function, and description is abbreviate | omitted suitably.
As a result of intensive studies to solve the above problems, the present inventors have surprisingly found that the coating layer has a polyolefin, a fluorosurfactant, a nonionic surfactant, and an anionic surfactant. By containing at least one kind other than the fluorosurfactant selected from the above, and forming the coating layer by in-line coating, a laminated film having a coating layer having excellent heat and moisture resistance of adhesion and having few surface defects is obtained. I found that I can do it.
The reason why the coating layer in the laminated film of the present invention is excellent in heat and moisture resistance of adhesion and has few surface defects is not clear, but is presumed as follows.

-Moist heat resistance of adhesion-
Since polyolefin resin does not have a hydrolyzing structure, it is excellent in heat and moisture resistance. Since polyolefin resin is relatively soft (low elastic modulus and large elongation), it absorbs the material difference of thermal shrinkage / expansion that occurs when wet heat is stored after pasting other members and prevents floating.
On the other hand, polyolefin has strong electrostatic repulsion and suppresses aggregation in latex, so that the coating solution is kept uniform, the uniformity of the coating layer is high, and uneven distribution of adhesion is unlikely to occur. For example, combining an acid-modified polyolefin and an oxazoline cross-linking agent is considered to improve the cohesive strength in the film and improve the adhesion between the polyester film and the coating layer, thereby improving the adhesion.

-Prevention of surface defects-
By using a fluorosurfactant and a nonionic surfactant or a fluorosurfactant and an anionic surfactant in combination, hole-like defects and bumpy defects can be significantly reduced. Although the mechanism of the reduction is not clear, (1) the optimization of the adsorption state of the surfactant on the surface of the latex particles of the acid-modified polyolefin resin suppresses the latex agglomeration and reduces the bump-like defects. (2) It is considered that a uniform leveling of the coating liquid occurs due to the reduction of the surface tension, and hole-like defects are reduced. Since the nonionic surfactant and the anionic surfactant act on (1) and the fluorosurfactant acts on (2), it is considered that the combined use of these surfactants is extremely effective.
Hereinafter, the laminated film of the present invention will be specifically described.

[Laminated film]
The laminated film of the present invention contains at least one selected from polyolefin resins, fluorine-based surfactants, and nonionic surfactants other than fluorine-based surfactants and anionic surfactants other than fluorine-based surfactants. After the coating liquid is applied on at least one surface of the polyester film, the coating liquid has a coating layer formed by stretching the polyester film at least once, and a stretched polyester film.

FIG. 1 schematically shows an example of the configuration of the laminated film of the present invention. A laminated film 11 of the present invention shown in FIG. 1 is formed on a polyester film 2 with a polyolefin resin, a fluorosurfactant, and a nonionic surfactant other than the fluorosurfactant (hereinafter simply referred to as “nonionic surfactant”). And a coating layer 1 containing at least one selected from anionic surfactants other than fluorine-based surfactants (hereinafter sometimes simply referred to as “anionic surfactants”). It is formed by a coating method.
The in-line coating method is a manufacturing method in which a film is continuously formed without winding a film in a series of film forming processes such as a resin extrusion process, a stretching process, a coating process, and a stretching process. The in-line coating method is distinguished from an off-line coating method in which a film is wound in the middle of the film forming process and then separately applied.
In the in-line coating method, a stretching process is provided after the coating process. When a plurality of stretching processes are provided, the stretching process may be provided before the coating process. However, in the in-line coating method, the stretching process is always provided once after the coating process. For example, a longitudinal stretching process may be provided after the application process, and a lateral stretching process may be provided thereafter, or an application process may be provided after the longitudinal stretching process, and a lateral stretching process may be provided thereafter. In addition, a transverse stretching process may be provided before the longitudinal stretching process, and each stretching process may be provided in a plurality of steps.

  In addition, when a laminated film is produced by an in-line coating method, portions along both edges of the laminated film have low thickness uniformity, and thus are usually cut out and recycled as a raw material for a polyester film. Therefore, if the polyolefin film contained in the coating layer is mixed in the polyester film that is the base of the laminated film, and the same kind of polyolefin resin as the coating layer is contained in the polyester film, the laminated film is formed by an in-line coating method. It can be judged that it was produced.

  A coating layer is formed by apply | coating a coating liquid on a polyester film, and extending | stretching. Here, the coating solution contains, as a surfactant, a fluorosurfactant and at least one selected from a nonionic surfactant and an anionic surfactant. The coating layer thus formed contains a polyolefin resin, a fluorosurfactant, and at least one selected from a nonionic surfactant and an anionic surfactant.

A release layer may be further formed on the surface of the film layer of the laminated film. Since the coating layer has adhesiveness, if it is exposed, it may adhere to an unintended article or the coating layer itself may deteriorate. Therefore, in order to physically and chemically protect the coating layer, a release layer is provided on the surface of the coating layer, and when used, the release layer is peeled off to expose the coating layer, and then another member. Can be laminated.
Examples of the release layer include those in which a release agent layer such as silicone is applied to various plastic films to form a release agent layer, and a polypropylene film alone, which is used as a release sheet for ordinary pressure-sensitive adhesive sheets Can be used.

  Moreover, you may provide another functional layer on the surface of the coating layer of a laminated film. For example, functional layers such as a hard coat layer, an antireflection layer, an antifouling layer, an electric resistance layer, and a barrier layer can be laminated. Thereby, the laminated | multilayer film of this invention can be used for various uses.

(Coating layer)
The coating layer 1 is a layer formed on the surface of a stretched polyester film, containing at least one selected from a polyolefin resin, a fluorosurfactant, and a nonionic surfactant and an anionic surfactant. A coating layer functions as an easily bonding layer which adhere | attaches a polyester film and another functional layer.

The thickness of the coating layer is preferably 0.01 to 0.5 μm. The thickness of the coating layer is preferably 0.01 μm or more, more preferably 0.03 μm or more, and further preferably 0.05 μm or more. The thickness of the coating layer is preferably 0.5 μm or less, more preferably 0.3 μm or less, and further preferably 0.2 μm or less.
The coating layer may have a structure of two or more layers, and in the case of a structure of two or more layers, the total thickness is preferably within the above range. By setting the thickness of the coating layer within the above range, it is possible to obtain a coating layer that is excellent in adhesiveness and does not impair the functionality of the laminated film.

<Polyolefin resin>
The coating layer contains a polyolefin resin as a binder, and preferably contains an acid-modified polyolefin. The acid-modified polyolefin is preferably a modified product obtained by bonding a carboxylic acid or a carboxylic acid anhydride to a homopolymer or copolymer of an olefin component.

  The olefin component that is the main component of the acid-modified polyolefin resin is not particularly limited, but an alkene having 2 to 6 carbon atoms such as ethylene, propylene, isobutylene, 2-butene, 1-butene, 1-pentene, 1-hexene is preferable, Mixtures of these may be used. Among these, in order to improve adhesiveness, alkenes having 2 to 4 carbon atoms such as ethylene, propylene, isobutylene, and 1-butene are more preferably used, ethylene and propylene are further preferable, and ethylene is most preferably used. Among ethylene, low density ethylene having a branched structure is particularly preferably used.

In the present invention, the acid-modified polyolefin resin is preferably a resin that is acid-modified with an unsaturated carboxylic acid or an anhydride thereof.
Examples of unsaturated carboxylic acid components include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, and the like, as well as unsaturated dicarboxylic acid half esters and half amides. It is done. Of these, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferable, and acrylic acid and maleic anhydride are particularly preferable.
The unsaturated carboxylic acid component only needs to be copolymerized in the acid-modified polyolefin resin, and the form thereof is not limited. Examples of the copolymerization state include random copolymerization, block copolymerization, and graft copolymerization (grafting). Modification).

  The content of the structure derived from the unsaturated carboxylic acid or anhydride thereof in the acid-modified polyolefin resin is 0.1 to 20% by mass, preferably 0.1 to 10% by mass, and 0.5 to 10% by mass. More preferably, 1-5 mass% is more preferable, and 2-4 mass% is further more preferable. If the content of the unsaturated carboxylic acid or its anhydride in the acid-modified polyolefin resin is 0.1% by mass or more, it is easy to form an aqueous dispersion, and if it is 20% by mass or less, the deterioration of weather resistance is suppressed. can do.

  In addition, the acid-modified polyolefin resin tends to be excellent in mechanical properties and weather resistance when the molecular weight is large. Accordingly, the melt flow rate (MFR) value (according to JIS K7210: 1999) at 190 ° C. and 2160 g load, which is a measure of molecular weight, is preferably 500 g / 10 min or less, more preferably 300 g / 10 min or less, and 100 g / 10 More preferred is less than or equal to minutes. Moreover, 0.001 g / 10min or more is preferable, 0.05g / 10min is more preferable, 0.1g / 10min is still more preferable. If the melt flow rate is 300 g / 10 min or more, the deterioration of weather resistance and acid rain resistance is suppressed, and if it is 0.001 g / 10 min or more, it is difficult to be restricted by the production surface when the resin is made high molecular weight. .

  The acid-modified polyolefin resin tends to have better weather resistance when the melting point is higher. Accordingly, the melting point of the acid-modified polyolefin resin is preferably 70 ° C. or higher, more preferably 75 to 200 ° C., and further preferably 80 to 170 ° C. If the melting point of the acid-modified polyolefin resin is 70 ° C. or higher, a decrease in adhesion at a high temperature is suppressed, and if it is 200 ° C. or lower, aqueous dispersion is easy.

  In the present invention, the acid-modified polyolefin resin preferably contains an unsaturated carboxylic acid ester or (meth) acrylic acid ester component in order to obtain sufficient adhesion to the filler.

  As the unsaturated carboxylic acid ester component, ester components such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, and crotonic acid are preferable. Of these, acrylic acid and methacrylic acid ester components are preferred.

  In addition, examples of the (meth) acrylic acid ester component include esterified products of (meth) acrylic acid and alcohols having 1 to 30 carbon atoms, and (meth) acrylic acid and carbon are particularly easy to obtain. An esterified product with an alcohol having a number of 1 to 20 is preferred.

  Specific examples of the (meth) acrylic acid ester component include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, (meth ) Octyl acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, and the like. Mixtures of these may be used. Among these, from the viewpoint of easy availability and adhesiveness, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl acrylate, octyl acrylate are more preferable, ethyl acrylate, More preferred is butyl acrylate, and particularly preferred is ethyl acrylate. In addition, “(meth) acrylic acid˜” means “acrylic acid˜ or methacrylic acid˜”.

  The content of the structure derived from the unsaturated carboxylic acid ester or (meth) acrylic acid ester component in the acid-modified polyolefin resin is preferably 0.1 to 25% by mass, and more preferably 1 to 20% by mass. Preferably, it is 2-18 mass%, More preferably, it is 3-15 mass%. When the content of the unsaturated carboxylic acid ester or (meth) acrylic acid ester component is 0.1% by mass or more, a decrease in adhesiveness is suppressed, and when the content is 25% by mass or less, a decrease in weather resistance and acid resistance is suppressed. Is done.

  The unsaturated carboxylic acid ester or (meth) acrylic acid ester component only needs to be copolymerized in the acid-modified polyolefin resin, and the form thereof is not limited. Examples of the state of copolymerization include random copolymerization, block Examples thereof include copolymerization and graft copolymerization (graft modification). Among them, the acid-modified polyolefin resin is preferably an ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid or ternary copolymer thereof, and in particular, the acid-modified polyolefin resin includes ethylene and acrylic acid ester. A terpolymer of acrylic acid or its anhydride or a terpolymer of ethylene, methacrylic acid ester and acrylic acid or its anhydride is preferred.

Specific examples of the acid-modified polyolefin resin include a copolymer of ethylene, (meth) acrylic acid ester and maleic anhydride (such a copolymer is referred to as “ethylene- (meth) acrylic acid ester-maleic anhydride copolymer”). The same applies hereinafter.), Ethylene-propylene- (meth) acrylic acid ester-maleic anhydride copolymer, ethylene-butene- (meth) acrylic acid ester-maleic anhydride copolymer, propylene-butene- ( (Meth) acrylic acid ester-maleic anhydride copolymer, ethylene-propylene-butene- (meth) acrylic acid ester-maleic anhydride copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene -Maleic anhydride copolymer, ethylene-propylene-maleic anhydride copolymer, ethylene -Maleic anhydride copolymer, propylene-butene-maleic anhydride copolymer, ethylene-propylene-butene-maleic anhydride copolymer, etc., among them ethylene- (meth) acrylic acid ester-maleic anhydride A copolymer is most preferred. The form of the copolymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc., but a random copolymer and a graft copolymer are preferred from the viewpoint of easy availability.
Some acid-modified polyolefin resins are commercially available. Specific examples of commercially available products include Bondine HX-8210, HX-8290, TL-8030, LX-4110, AX8390 (manufactured by Arkema), Arrow Base SA-1200, SB-1010, SE-1013N, SE1200 (and above). Unitika Ltd.).

  In the present invention, the acid-modified polyolefin resin for forming the coating layer is preferably an aqueous dispersion in order to improve the weather resistance and acid resistance, and to easily reduce the thickness of the coating layer. An aqueous dispersion is preferable because it facilitates mixing of a crosslinking agent and the like.

  In addition, the number average particle diameter of the acid-modified polyolefin resin in the aqueous dispersion is preferably 1 μm or less, for reasons such as easy to make various performance surfaces and thickness uniform when coating, and 0.5 μm or less. Is more preferably 0.2 μm or less, and particularly preferably 0.1 μm or less.

<Basic compound>
The coating layer preferably further contains a basic compound having a boiling point of 200 ° C. or lower. The basic compound functions to improve the dispersibility of the acid-modified polyolefin resin in the aqueous coating solution. Since the acid-modified polyolefin resin is water-insoluble, a basic compound is used for dispersion in the aqueous coating solution. That is, the basic compound can make the acid-modified polyolefin resin into an aqueous dispersion.

  The basic compound neutralizes the carboxyl group in the acid-modified polyolefin resin in the aqueous coating solution. Aggregation between the fine particles is prevented by the electric repulsion between the carboxyl anions generated by the neutralization, and the aqueous dispersion is stabilized, whereby the dispersibility is improved. The basic compound used for this invention should just be a thing which can neutralize a carboxyl group. The basic compound added for such a purpose functions as an aqueous agent.

  In the aqueous dispersion, the carboxyl group in the acid-modified polyolefin resin is preferably neutralized with a basic compound. Aggregation between the fine particles is prevented by the electric repulsive force between the carboxyl anions generated by neutralization, and stability is imparted to the aqueous dispersion. Any basic compound can be used as long as it can neutralize the carboxyl group, but a volatile basic compound having a boiling point of 200 ° C. or lower is preferably used.

The addition amount of the basic compound having a boiling point of 200 ° C. or less added to the aqueous coating solution is preferably 0.5 to 3.0 times equivalent to the carboxyl group in the acid-modified polyolefin resin. It is more preferably 8 to 2.5 times equivalent, and further preferably 1.01 to 2.0 times equivalent.
Moreover, it is preferable that content of the basic compound whose boiling point contained in a film layer is 200 degrees C or less is 0.1-2.5 times equivalent with respect to the carboxyl group in acid-modified polyolefin resin. It is more preferably 3 to 2.0 times equivalent, and still more preferably 0.3 to 1.5 times equivalent.

  By making the addition amount of a basic compound more than the said lower limit, the addition effect of an effective basic compound can be acquired and a favorable aqueous dispersion can be obtained. Moreover, the softening of a coating layer can be prevented by making the addition amount of a basic compound below the said upper limit.

  As the basic compound, a volatile compound having a boiling point of 200 ° C. or less is preferably used. The boiling point of the basic compound may be 200 ° C. or less, preferably 180 ° C. or less, and more preferably 160 ° C. or less. Further, the boiling point of the basic compound is preferably −40 ° C. or higher, and more preferably 0 ° C. or higher. By making the boiling point of the basic compound not more than the above upper limit, the basic compound can be volatilized when the polyester film coated with the coating layer forming coating solution is heated in the drying step. Moreover, the ratio which a basic compound volatilizes from an aqueous coating liquid before application | coating can be decreased by making a boiling point more than the said lower limit.

  The volatile basic compound having a boiling point of 200 ° C. or lower is preferably ammonia or an organic amine compound. Specific examples of the organic amine compound include triethylamine, N, N-dimethylethanolamine, aminoethanolamine, N-methyl-N, N-diethanolamine, isopropylamine, iminobispropylamine, ethylamine, diethylamine, and 3-ethoxypropylamine. , 3-diethylaminopropylamine, sec-butylamine, propylamine, methylaminopropylamine, 3-methoxypropylamine, monoethanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine and the like.

  Further, in the aqueous dispersion, it is preferable to add an organic solvent at the time of aqueous formation in order to promote the aqueous formation of the acid-modified polyolefin resin and reduce the dispersed particle size. The amount of the organic solvent to be used is preferably 40% by mass or less, more preferably 1 to 40% by mass, further preferably 2 to 35% by mass, and 3 to 30% by mass with respect to the mass of the aqueous coating solution. Particularly preferred. When the amount of the organic solvent is 40% by mass or less, the aqueous coating solution can be regarded as an aqueous medium, the environmental load is small, and the deterioration of the stability of the aqueous dispersion is suppressed. It should be noted that the organic solvent added at the time of making the aqueous solution may be appropriately reduced by distilling it out of the system by a solvent removal operation called stripping. There is no effect.

  The organic solvent used in the present invention preferably has a boiling point of 30 to 250 ° C, particularly preferably 50 to 200 ° C. These organic solvents may be used in combination of two or more. In addition, when the boiling point of the organic solvent is 30 ° C. or higher, the rate of volatilization when the resin is made aqueous is small, and the efficiency of aqueous formation is sufficiently increased. An organic solvent having a boiling point of 250 ° C. or lower can be easily scattered from the resin coating film by drying, and a decrease in water resistance of the coating film is suppressed.

  Among organic solvents, ethanol, n-propanol, isopropanol, n-butanol, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, and the like are highly effective in promoting the aqueous formation of resins and are easy to remove the organic solvent from the aqueous medium. Ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl ether are preferred, and ethanol, n-propanol, and isopropanol are particularly preferred from the viewpoint of low temperature drying property.

  In the present invention, the method for obtaining the aqueous dispersion is not particularly limited. For example, as exemplified in JP-A No. 2003-119328, each component described above, that is, an acid-modified polyolefin resin, a basic compound, water, and, if necessary, an organic solvent can be preferably sealed. A method of heating and stirring in a container can be employed, and this method is most preferred. According to this method, the acid-modified polyolefin resin can be satisfactorily made into an aqueous dispersion without substantially adding a non-volatile water-based auxiliary.

  The resin solid content concentration in the aqueous dispersion is not particularly limited, but is preferably 1 to 60% by mass with respect to the total mass of the aqueous dispersion in terms of ease of coating and ease of adjustment of the thickness of the coating layer, 2-50 mass% is more preferable, and 5-30 mass% is further more preferable.

<Surfactant>
The coating layer contains, as a surfactant, a fluorosurfactant and at least one selected from a nonionic surfactant and an anionic surfactant.

(1) Fluorosurfactant A fluorosurfactant is a surfactant having a perfluoroalkyl group in the molecule, such as perfluoroalkylcarboxylate, perfluoroalkylsulfonate, perfluoroalkylphosphorus. Anionic type such as acid ester; Amphoteric type such as perfluoroalkyl betaine; Cationic type such as perfluoroalkyltrimethylammonium salt; Contains perfluoroalkylamine oxide, perfluoroalkylethylene oxide adduct, perfluoroalkyl group and hydrophilic group Nonionic types such as oligomers containing perfluoroalkyl groups and lipophilic groups, oligomers containing perfluoroalkyl groups, hydrophilic groups and lipophilic groups, urethanes containing perfluoroalkyl groups and lipophilic groups Be mentioned . Moreover, the fluorine-type surfactant described in each gazette of Unexamined-Japanese-Patent No. 62-170950, 62-226143, and 60-168144 is also mentioned suitably.
Fluorosurfactants are trade names such as Megafac manufactured by DIC, Surflon manufactured by Asahi Glass, Novec manufactured by Asahi Glass, and Zonyls manufactured by EI Dupont Nemeras & Company. Are commercially available.
In particular, sodium = bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfonite oxysuccinate is preferable.

The amount of the fluorosurfactant contained in the coating layer is preferably 0.03% by mass to 2.0% by mass, and 0.05% by mass to 1.5% by mass with respect to the mass of the acid-modified polyolefin resin. % Is more preferable, and 0.1% by mass to 1.0% by mass is more preferable.
By making the amount of the fluorosurfactant not more than the above upper limit value, it is possible to keep good adhesion between the coating layer and other members, and by making the amount not less than the above lower limit value, the surface of the coating layer The shape can be improved.

(2) Nonionic surfactant The nonionic surfactant used for the coating layer is not particularly limited as long as it is other than a fluorosurfactant, and a conventionally known one can be used. For example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, sorbitan fatty acid partial esters, pentaerythritol Fatty acid partial esters, propylene glycol mono fatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters, Polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N N- bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid ester, trialkylamine oxide, polyethylene glycol, copolymers of polyethylene glycol and polypropylene glycol.

The amount of the nonionic surfactant contained in the coating layer is preferably 0.1% by mass to 3.0% by mass with respect to the mass of the acid-modified polyolefin resin, and 0.2% by mass to 2.5% by mass. %, More preferably 0.5% to 2.0% by weight.
By making the amount of the nonionic surfactant not more than the above upper limit value, it is possible to maintain good adhesion between the coating layer and other members, and by making the amount not less than the above lower limit value, the surface of the coating layer The shape can be improved.

(3) Anionic surfactant The anionic surfactant used for the coating layer is not particularly limited as long as it is other than a fluorosurfactant, and a known one can be used. For example, fatty acid salts, abietic acid salts, hydroxyalkane sulfonates, alkane sulfonates, dialkyl sulfosuccinate esters, linear alkyl benzene sulfonates, branched alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl phenoxy poly Oxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N-oleyl taurine sodium salt, N-alkyl sulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated beef oil, fatty acid alkyl esters Sulfates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fatty acid monoglyceride sulfates, polyoxyethylene alcohol Ruphenyl ether sulfates, polyoxyethylene styryl phenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, styrene / maleic anhydride Examples thereof include partial saponification products of polymers, partial saponification products of olefin / maleic anhydride copolymers, and naphthalene sulfonate formalin condensates.

The amount of the anionic surfactant contained in the coating layer is preferably 0.1% by mass to 3.0% by mass with respect to the weight of the acid-modified polyolefin resin, and 0.2% by mass to 2.5% by mass. %, More preferably 0.5% to 2.0% by weight.
By making the amount of the anionic surfactant not more than the above upper limit value, it is possible to keep good adhesion between the coating layer and other members, and by making the amount not less than the above lower limit value, the surface of the coating layer The shape can be improved.

(4) Content of surfactant It is preferable that the coating layer contains all of a fluorosurfactant, a nonionic surfactant, and an anionic surfactant.
The mass ratio of the fluorosurfactant, nonionic surfactant, and anionic surfactant contained in the coating layer to the acid-modified polyolefin resin is a [mass%], b [mass%], and c [mass%], respectively. ], It is preferable that the following formulas (1) and (2) hold.
0.2 ≦ a + b + c ≦ 5.0 (1)
0.1 ≦ (b + c) /a≦10.0 (2)

  a + b + c, that is, by making the total amount of the surfactant not more than the above upper limit value, it is possible to ensure adhesion between the coating layer and other members, and to suppress surface defects, and not less than the above lower limit value. By doing so, surface defects can be suppressed.

  (B + c) / a, that is, the surface defects can be suppressed by setting the ratio of the nonionic surfactant and the anionic surfactant to the fluorosurfactant to the above upper limit value or less, and the above lower limit value or more. By doing so, surface defects can be suppressed, and adhesion between the coating layer and other members can be ensured.

<Crosslinking agent>
The coating layer is preferably crosslinked by a crosslinking agent.
Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. From the viewpoint of ensuring adhesion with a polyester film after aging with wet heat, a crosslinking agent selected from a carbodiimide crosslinking agent, an oxazoline crosslinking agent, an isocyanate crosslinking agent, and an epoxy crosslinking agent is preferable, and in particular, an oxazoline crosslinking agent ( Compounds having an oxazoline group) are preferred.

Specific examples of the oxazoline-based crosslinking agent include, for example, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2. -Oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2'-bis- (2-oxazoline), 2,2'-methylene-bis -(2-oxazoline), 2,2'-ethylene-bis- (2-oxazoline), 2,2'-trimethylene-bis- (2-oxazoline), 2,2'-tetramethylene-bis- (2- Oxazoline), 2,2'-hexamethylene-bis- (2-oxazoline), 2,2'-octamethylene-bis- (2-oxazoline), 2,2'-ethylenebis- (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), 2,2 '(1,3-phenylene) -bis- (2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- There is (2-oxazolinyl norbornane) sulfide. Furthermore, (co) polymers of these compounds can also be preferably used.
These may be used alone or in combination of two or more.

The oxazoline-based crosslinking agent is preferably aqueous such as water-soluble and / or water-dispersible from the viewpoint of excellent mixing stability with the aqueous dispersion of acid-modified polyolefin resin, and more preferably water-soluble. Here, “water-soluble” means that it can be dissolved in water at a certain concentration or more.
The polymerization method of the polymer oxazoline-based crosslinking agent is not particularly limited, and a known method can be employed. For example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, or the like in an aqueous medium can be used. By these methods, an aqueous solution or an aqueous dispersion can be obtained. It is preferable that the oxazoline-based cross-linking agent of these polymers does not substantially contain a non-volatile aqueous additive to improve adhesion and weather resistance.

  The molecular weight of the polymer oxazoline-based crosslinking agent is preferably 1000 to 80000 in terms of number average molecular weight, more preferably 3000 to 60000, still more preferably 5000 to 40000, particularly preferably 8000 to 30000, most preferably 10,000 to 20000. preferable. When the number average molecular weight is 1000 or more, the adhesiveness and weather resistance tend to be improved. When the number average molecular weight is 80000 or less, the production of the polymer is easy.

  As the oxazoline-based crosslinking agent, commercially available products may be used. For example, aqueous dispersion type Epocross “K-1010E”, “K-1020E”, “K-1030E”, K2010E, K2020E, K2030E, aqueous solution type WS500, WS700 [Epocross Series manufactured by Nippon Shokubai Co., Ltd.] and the like can be used.

  The content of the crosslinking agent with respect to the total solid mass of the composition for forming a coating layer is preferably 10% by mass to 75% by mass, more preferably 15% by mass to 60% by mass, and 20% by mass. A range of ˜50 mass% is particularly preferred. When the content of the cross-linking agent is 5% by mass or more, a sufficient cross-linking effect is obtained, and a decrease in strength of the coating layer and poor adhesion can be suppressed. On the other hand, the pot life fall of the composition for film layer formation can be prevented because it is 50 mass% or less.

(Polyester film)
The polyester film 2 used by this invention is comprised including polyester. The kind of polyester is not particularly limited, and a known polyester can be used.

  The polyester is preferably a saturated polyester. By using a saturated polyester, a polyester film that is superior in terms of mechanical strength as compared with a film using an unsaturated polyester can be obtained. Examples of the polyester include 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 the linear saturated polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate, of which polyethylene terephthalate (PET) or Polyethylene-2,6-naphthalate (PEN) is particularly preferable in terms of a balance between mechanical properties and cost, and polyethylene terephthalate is more particularly preferable.

  The polyester may be a homopolymer or a copolymer. Further, polyester may be blended with a small amount of other types of resin, such as polyimide. Further, as the polyester, a crystalline polyester capable of forming anisotropy when melted may be used.

  From the viewpoint of heat resistance and viscosity, the molecular weight of the polyester is preferably 5000 to 30000, more preferably 8000 to 26000, and particularly preferably 12,000 to 24,000. As the weight average molecular weight of the polyester, a value in terms of polymethyl methacrylate (PMMA) measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent can be used.

The polyester can be obtained by reacting a dicarboxylic acid or an ester-forming derivative thereof with a low molecular weight aliphatic diol or a high molecular weight diol.
Examples of the dicarboxylic acid or its ester-forming derivative include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, paraphenylene dicarboxylic acid, dimethyl terephthalate, dimethyl isophthalate, dimethyl orthophthalate, dimethyl naphthalene dicarboxylate, and paraphenylene. And dimethyl dicarboxylate. These may be used alone or in combination of two or more.

Examples of the low molecular weight aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, and 1,5-pentane. Examples include diol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol. These may be used alone or in combination of two or more.
Examples of the high molecular weight diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyhexamethylene glycol. These may be used alone or in combination of two or more.

Examples of the crystalline polyester composed of the above components include polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and butanediol terephthalate polytetramethylene glycol copolymer. These may be used alone or in combination of two or more.
Particularly preferred among aromatic polyesters are those using terephthalic acid or naphthalenedicarboxylic acid as the main component as the dicarboxylic acid, and those having ethylene glycol or cyclohexanedimethanol as the main component as the diol, more preferably polyethylene terephthalate. Polyethylene naphthalate and polycyclohexanedimethylene terephthalate, more preferably polyethylene terephthalate and polyethylene naphthalate.

  Polyester can be synthesized by a known method. For example, polyester can be synthesized by a known polycondensation method or ring-opening polymerization method, and any of transesterification and direct polymerization can be applied.

  When the polyester used in the present invention is a polymer or copolymer obtained by a condensation reaction mainly comprising an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof, An aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof can be produced by an esterification reaction or an ester exchange reaction and then a polycondensation reaction. Moreover, the carboxylic acid value and intrinsic viscosity of the polyester can be controlled by selecting the raw material and reaction conditions.

In order to effectively advance the esterification reaction or transesterification reaction and polycondensation reaction, it is preferable to add a polymerization catalyst during these reactions.
As a polymerization catalyst for polymerizing polyester, Sb-based, Ge-based, and Ti-based compounds are preferable, and Ti-based compounds are particularly preferable from the viewpoint of keeping the carboxyl group content within a predetermined range. In the case of using a Ti-based compound, an embodiment in which polymerization is performed by using the Ti-based compound as a catalyst in a range of 1 ppm to 30 ppm, more preferably 3 ppm to 15 ppm is preferable. When the proportion of the Ti-based compound is within the above range, the terminal carboxyl group can be adjusted to the following range, and the hydrolysis resistance of the polymer substrate can be kept low.

  Examples of the synthesis of polyester using a Ti compound include Japanese Patent Publication No. 8-301198, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 3997756, Japanese Patent No. 3996226, Japanese Patent No. 3997866, Japanese Patent No. 39968671, The methods described in Japanese Patent No. 40000867, Japanese Patent No. 4053837, Japanese Patent No. 4127119, Japanese Patent No. 4134710, Japanese Patent No. 4159154, Japanese Patent No. 4269704, and Japanese Patent No. 431538 can be applied.

  The polyester is preferably solid-phase polymerized after polymerization. Thereby, a preferable carboxylic acid value 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, solid-phase polymerization is described in 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, Japanese Patent No. 4167159, etc. The method can be applied.

  The temperature of the solid phase polymerization is preferably 170 to 240 ° C, more preferably 180 to 230 ° C, and further preferably 190 to 220 ° C. The solid phase polymerization time is preferably 5 to 100 hours, more preferably 10 to 75 hours, and further preferably 15 to 50 hours. The solid phase polymerization is preferably performed in a vacuum or in a nitrogen atmosphere.

  The molecular weight of the polyester is preferably a weight average molecular weight (Mw) of 5,000 to 100,000, more preferably 8,000 to 80,000, and particularly preferably 12,000 to 60,000 from the viewpoints of heat resistance and viscosity. As the weight average molecular weight of the polyester, a value in terms of polymethyl methacrylate (PMMA) measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent can be used.

The terminal carboxyl group content in the polyester (the carboxylic acid value of the polyester, hereinafter referred to as AV (Acid Value)) is preferably 25 eq / ton (equivalent / ton) or less, more preferably 20 eq / ton or less, based on the polyester. More preferably, it is 16 eq / ton or less, and particularly preferably 15 eq / ton or less. When the terminal carboxyl group content is 25 eq / ton or less, the hydrolysis resistance and heat resistance of the polyester film can be maintained. The lower limit of the terminal carboxyl group content is 2 eq in that the adhesiveness (adhesiveness) between the layer (for example, white layer) formed when the laminated film of the present invention is used as a back sheet for a solar cell module is maintained. / Ton or more is desirable.
The terminal carboxyl group content in the polyester can be adjusted by polymerization catalyst species, polymerization time, and film forming conditions (film forming temperature and time). The terminal carboxyl group content is H.264. A. Pohl, Anal. Chem. 26 (1954) 2145, and can be measured by a titration method. Specifically, the polyester is dissolved in benzyl alcohol at 205 ° C., a phenol red indicator is added, and titrated with a solution of sodium hydroxide in water / methanol / benzyl alcohol to determine the carboxylic acid value (eq / ton) can be calculated.

The terminal hydroxyl group content in the polyester is preferably 120 eq / ton or less, more preferably 90 eq / ton or less, based on the polyester. When the hydroxyl group content is 120 eq / ton or less, the reaction between the carbodiimide having a bulky functional group and the hydroxyl group is suppressed, and it reacts preferentially with the carboxyl group, thereby further reducing the carboxylic acid value. The lower limit of the hydroxyl group content is preferably 20 eq / ton or more from the viewpoint of adhesion to the upper layer.
The hydroxyl group content in the polyester can be adjusted by the polymerization catalyst species, the polymerization time, and the film forming conditions (film forming temperature and time). As the terminal hydroxyl group content, a value measured by ¹ H-NMR using a deuterated hexafluoroisopropanol solvent can be used.

  Moreover, the intrinsic viscosity (IV; Intrinsic Viscosity) of the polyester in the present invention is preferably 0.65 to 0.95 dl / g, more preferably 0.68 to 0.90 dl / g, and 0.70 to 0.85 dl / g. g is particularly preferred. The intrinsic viscosity of the polyester is preferably not more than the above lower limit value from the viewpoint of improving the film forming property and improving the thickness uniformity.

  The intrinsic viscosity (IV) of the polyester is a mixture of all the polyesters when there are two or more kinds of polyesters used in film formation (for example, when using the recovered polyester described in JP2011-256337A). It is preferable that the intrinsic viscosity of the obtained polyester satisfy the above range.

The intrinsic viscosity (IV) of the polyester is obtained from the following formula from the solution viscosity measured at 25 ° C. by dissolving the polyester in orthochlorophenol.
ηsp / C = [η] + K [η] ² · C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the mass of dissolved polymer per 100 ml of solvent (1 g / 100 ml in this measurement), and K is the Huggins constant (0.343) The solution viscosity and the solvent viscosity are measured using an Ostwald viscometer.

  Although the thickness of the polyester film in this invention changes with uses, when using the laminated | multilayer film of this invention as a member of a solar cell module backsheet, it is preferable that it is 25-300 micrometers, and it is 120-300 micrometers. More preferred. By setting the thickness of the polyester film to the above lower limit value or more, sufficient mechanical strength can be obtained, and by making the thickness not more than the above upper limit value, a merit in cost can be obtained.

  The polyester film in the present invention is stretched at least once after applying a coating solution for forming a coating layer on the film, but is preferably biaxially stretched, and is plane biaxially stretched. It is particularly preferable as compared with stretching such as tubular, and it is particularly preferable that sequential biaxial stretching is performed.

(Laminated film manufacturing method)
The laminated film of the present invention contains at least one selected from polyolefin resins, fluorine-based surfactants, and nonionic surfactants other than fluorine-based surfactants and anionic surfactants other than fluorine-based surfactants. A step of applying the coating liquid on at least one surface of the polyester film, and a polyester film on which the coating film has been formed is stretched at least once, whereby the polyolefin resin and the fluorosurfactant are stretched on the stretched polyester film. And forming a coating layer containing at least one selected from a nonionic surfactant and an anionic surfactant.

The laminated film of the present invention can be produced, for example, by the following method.
When manufacturing a polyester film, the polyester resin used as a raw material is first dried in a drying process. A drying process is a process dried by heating a polyester resin. As for the temperature of drying, 100-200 degreeC is more preferable, More preferably, it is 120-180 degreeC, More preferably, it is 150-180 degreeC.

In this invention, the polyester resin used as the raw material of a polyester film may contain the film for reproduction | regeneration. When the polyester resin includes a film for regeneration, it is preferable to provide a cutting step before the drying step. The cutting step is a step of cutting a film for reproduction such as an edge portion of a film or a defective film so as to have a certain size or less. By cutting the film for reproduction so as to have a certain size, the time required for the next process can be shortened.
Moreover, when the polyester resin of a raw material contains the film for reproduction | regeneration, it is preferable that the film for reproduction | regeneration is 20-80 mass% with respect to a polyester resin, and it is more preferable that 25-75 mass% is contained. 30 to 70% by mass is more preferable.

  After the drying step, the polyester resin is put into a kneader and kneaded. For kneading, various kneaders such as a single screw extruder, a twin screw extruder, a Banbury mixer, and a Brabender can be used. Among these, it is preferable to use a twin screw extruder. The kneading temperature is preferably from the crystal melting temperature (Tm) of the polyester resin to Tm + 80 ° C., more preferably Tm + 10 to Tm + 70 ° C., and further preferably Tm + 20 to Tm + 60 ° C. The kneading atmosphere may be in air, in vacuum, or in an inert air stream, but more preferably in vacuum or in an inert air stream.

The kneaded polyester resin is put into a single-screw or twin-screw extruder and heated and melted there. In this case, the heating and melting temperature is preferably a crystal melting temperature (Tm) to Tm + 80 ° C. or less of the polyester resin, more preferably Tm + 5 to Tm + 60 ° C., and further preferably Tm + 10 to Tm + 50 ° C.
The melting time is preferably 1 to 30 minutes, more preferably 1 to 20 minutes, and further preferably 3 to 15 minutes. Thereafter, the melted polyester resin is discharged from the die into a soft sheet.

  The polyester sheet discharged from the die is preferably passed through a melt pipe, a gear pump, and a filter. It is also preferable to provide a static mixer in the melt pipe to promote mixing of the resin and additives.

The polyester sheet is extruded onto a casting roll, cooled and solidified, and formed into a film. The film thus obtained becomes a polyester sheet of a cast film (unstretched original fabric).
The temperature of the casting roll is preferably 0 to 60 ° C, more preferably 5 to 55 ° C, and still more preferably 10 to 50 ° C. At this time, in order to improve the adhesion between the melt and the cooling drum and improve the flatness, it is also preferable to use an electrostatic application method, an air knife method, water coating on the cooling drum, or the like. Further, in order to efficiently perform cooling, cold air may be blown from above the cooling drum.

  The polyester sheet is sent to a longitudinal stretching machine and stretched longitudinally. Then, both ends are gripped by the left and right clips of the transverse stretching machine, and the polyester film is stretched laterally while being sent to the winder side.

The coating layer is formed on the surface of the polyester film by coating before the stretching process or during the stretching process. When a coating process is provided in the process between the stretching processes, at least one stretching process is provided after the coating process.
For example, when the coating step is provided before stretching in the longitudinal and lateral directions, it may be performed sequentially as coating → longitudinal stretching → lateral stretching, coating → transverse stretching → longitudinal stretching, and simultaneously in two directions after the coating step. It may be stretched. Also, it is stretched in multiple stages, such as coating → longitudinal stretching → longitudinal (transverse) stretching → transverse stretching, longitudinal stretching → coating → longitudinal (transverse) stretching → transverse stretching, longitudinal stretching → longitudinal (transverse) stretching → coating → transverse stretching. It is also preferable.

When the coating layer is formed by application, it is preferable to apply an aqueous solution or an aqueous dispersion (latex).
Since acid-modified polyolefin is water-insoluble, basic compounds such as alkali metals, ammonia, and amine compounds are mixed in the aqueous solution or aqueous dispersion (latex) as a neutralizing agent that imparts dispersion stability. Is done.
The coating solution is expressed by the following formula (3) when the solid content in the coating solution is X [g], and the precipitation amount when the coating solution is filtered through a filter having a pore diameter of 10 μm is Y [g]. It is preferable that the rubber solidification rate C [%] represented satisfies 0.01 ≦ C ≦ 0.50.
C = (Y / X) × 100 (3)
There is no restriction | limiting in particular as an application | coating method, Well-known methods, such as bar coater application | coating and slide coater application | coating, can be used.

  The coating layer is formed by applying a coating solution on the polyester film and then curing it by drying. When the coating layer has a two-layer structure, it is preferable to dry after coating the second layer.

The longitudinal stretching is preferably performed at Tg (glass transition temperature) −10 to Tg + 50 ° C., more preferably T to Tg + 40 ° C., and further preferably Tg + 10 to Tg + 35 ° C.
The longitudinal draw ratio is preferably 2 to 5 times, more preferably 2.5 to 4.5 times, and still more preferably 3 to 4 times.

  After longitudinal stretching, cooling is preferred, Tg-50 to Tg is preferred, Tg-45 to Tg-5 ° C is more preferred, Tg-40 to Tg-10 ° C is more preferred. Such cooling may be brought into contact with a cooling roll or may be blown with cold air.

Thereafter, when performing transverse stretching, the transverse stretching is preferably performed using a tenter. In the tenter, lateral stretching can be performed by expanding the clip in the width direction while conveying the heat treatment zone while holding both ends of the polyester film with the clip.
A preferable stretching temperature is Tg to Tg + 100 ° C., more preferably Tg + 10 to Tg + 80 ° C., and further preferably Tg + 20 to Tg + 70 ° C.
The transverse draw ratio is preferably 2 to 5.5 times, more preferably 2.5 to 5 times, and still more preferably 3 to 4.5 times.

  A polyester sheet preheating step may be provided before the stretching step. The preheating temperature is preferably Tg-50 to Tg + 30 ° C of the polyester, more preferably Tg-40 to Tg + 15 ° C, and still more preferably Tg-30 to Tg. Such preheating may be brought into contact with a heating roll, a radiant heat source (IR (infrared) heater, halogen heater, etc.) may be used, or hot air may be blown.

  In addition, in this invention, after apply | coating the coating liquid for film layer formation to at least one surface of a polyester film, a series of processes extended | stretched are called film forming processes.

After the stretching step, it is preferable to heat-set and relax the film after the stretching treatment. The heat setting means that the film is subjected to heat treatment at about 180 to 210 ° C. (more preferably 185 to 210 ° C.) for 1 to 60 seconds (more preferably 2 to 30 seconds).
The heat setting is preferably carried out in the state of being gripped by the chuck in the tenter after the transverse stretching. In this case, the chuck interval is performed at the width at the end of the transverse stretching, further widened, or reduced in width. May be. By performing heat setting, microcrystals can be generated, and mechanical properties and durability can be improved.

It is preferable to perform a relaxation treatment following the heat setting. The thermal relaxation treatment is a treatment for shrinking the film by applying heat to the film for stress relaxation.
In the thermal relaxation treatment, relaxation is preferably performed in at least one of length and width, and the amount of relaxation is preferably 1 to 15% (ratio to the width after lateral stretching) in both length and width, more preferably 2 to 10%, still more preferably. Is 3-8%.
The relaxation temperature is preferably Tg + 50 to Tg + 180 ° C., more preferably Tg + 60 to Tg + 150 ° C., and still more preferably Tg + 70 to Tg + 140 ° C.

  The thermal relaxation is preferably performed at −100 to Tm−10 ° C., more preferably Tm−80 to Tm−20 ° C., and even more preferably Tm−70 to Tm−35 ° C. when the melting point of the polyester is Tm. is there. This promotes the formation of crystals and improves the mechanical strength and heat shrinkability. Furthermore, hydrolysis resistance is improved by heat setting at Tm-35 ° C. or lower. This is to suppress the reactivity with water by increasing the tension (binding) without destroying the orientation of the amorphous part where hydrolysis is likely to occur.

Lateral relaxation can be performed by reducing the width of the tenter clip. Moreover, longitudinal relaxation can be implemented by narrowing the interval between adjacent clips of the tenter. This can be achieved by connecting adjacent clips in a pantograph shape and shrinking the pantograph. Moreover, after taking out from a tenter, it can also heat-process and relieve | moderate, conveying with low tension. The tension is preferably 0 to 0.8 N / mm ² per cross-sectional area of the film, more preferably 0 to 0.6 N / mm ² , and still more preferably 0 to 0.4 N / mm ² . 0 N / mm ² can be carried out by providing two or more pairs of nip rolls during conveyance and slacking them in a suspended manner.

  The film coming out of the tenter is trimmed at both ends held by the clip, and after being subjected to knurling (embossing) at both ends, the film is wound up. A preferable width is 0.8 to 10 m, more preferably 1 to 6 m, and still more preferably 1.5 to 4 m. The thickness is preferably 30 to 300 μm, more preferably 40 to 280 μm, still more preferably 45 to 260 μm. Such adjustment of the thickness can be achieved by adjusting the discharge amount of the extruder or adjusting the film forming speed (adjusting the speed of the cooling roll, the stretching speed linked to this).

  Reproduction films such as trimmed film edges are collected and recycled as a resin mixture. The film for reproduction becomes a film raw material for the laminated film of the next lot, and returns to the drying process as described above, and the manufacturing process is sequentially repeated.

As will be described later, the laminated film of the present invention can be suitably used not only as a protective sheet for a solar cell module (back sheet for a solar cell module) but also for other uses.
The laminated film of the present invention can also be used as a laminate provided with another coating layer.

[Back sheet for solar cell module]
The back sheet for a solar cell module of the present invention includes the above-described laminated film. Since the laminated film of the present invention has high adhesion heat and heat resistance and few surface defects, when used in a back sheet for a solar cell module, the power generation efficiency of the solar cell module is impaired over a long period of time or the design property is impaired. Can be suppressed.

A back sheet for a solar cell module can be formed by laminating, for example, the following functional layer on the laminated film of the present invention.
In addition, when laminating | stacking a functional layer, it is preferable to provide an easily bonding layer in between. Moreover, it is preferable to surface-treat the surface of a laminated film before laminating | stacking a functional layer, for example, a flame treatment, a corona treatment, a plasma treatment, an ultraviolet treatment etc. can be given.
FIG. 2 schematically shows an example of the configuration of the solar cell module backsheet of the present invention. The back sheet 12 for a solar cell module shown in FIG. 2 has the reflective layer 3 and the overcoat layer 4 laminated on the film layer 1 side of the laminated film 11 described above, and the back layer 5 and the back surface protective layer 6 on the polyester film 2 side. It is configured by stacking.

<Reflective layer (colored layer)>
In the back sheet of the present invention, it is preferable to provide the light reflecting layer 3 on the inner side surface (side to be bonded to the sealing material). By providing the reflective layer, it is possible to reflect the light that has passed through the solar cell and reaches the back sheet out of the sunlight incident on the solar cell module, and return it to the solar cell. Thereby, power generation efficiency can be improved.
Further, the reflective layer preferably has an adhesive strength of 10 N / cm or more, more preferably 20 N / cm or more, with respect to the sealing material.

(binder)
As the binder for the reflective layer, acrylic, polyester, polyurethane, polyolefin polymers and the like can be used, and among these, polyolefin polymers are preferred.

  Some polyolefin-based binders that can be used in the reflective layer are commercially available. Specific examples of commercially available products include Bondine HX-8210, HX-8290, TL-8030, LX-4110, AX8390 (manufactured by Arkema), Arrow Base SA-1200, SB-1010, SE-1013N, SE1200 (and above). Unitika Ltd.).

(Crosslinking agent)
The reflective layer preferably contains an epoxy-based, isocyanate-based, oxazoline-based, carbodiimide-based or the like crosslinking agent in order to further improve the adhesion with the sealing material.
Of these cross-linking agents, carbodiimide cross-linking agents and oxazoline cross-linking agents are particularly preferable from the viewpoint of ensuring adhesion after wet heat aging. The carbodiimide crosslinking agent used in the present invention is a compound having one or more carbodiimide groups in the molecule.

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

  The oxazoline-based crosslinking agent used in the present invention is a compound having two or more oxazoline groups in the molecule.

The oxazoline-based crosslinking agent used in the present invention may be a low molecular compound or a (co) polymer.
Moreover, Epocros WS-700, Epocros WS-500, Epocros K-2020E (all made by Nippon Shokubai Co., Ltd.) etc. can be used as a commercial item.

  When using an oxazoline-based crosslinking agent, it is preferable to use a catalyst such as an onium salt in combination. Specific examples of the onium salt catalyst include benzyltriethylammonium chloride, diammonium hydrogen phosphate, and boron tetrafluoride diphenylmethylsulfonium. These catalysts are preferably added in an amount of 0.5 to 5% by mass relative to the crosslinking agent. When the addition amount of the catalyst with respect to the crosslinking agent is 0.5% by mass or more, a sufficient crosslinking accelerating effect is obtained, and when it is 5% by mass or less, the pot life of the coating liquid is prolonged, and the occurrence of coloring can be suppressed. it can.

(Pigments and reflectance)
It is preferable to add a white pigment to the reflective layer of the present invention for the purpose of increasing the reflectance.
Preferred examples of the white pigment include titanium oxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin and talc. Of these, titanium oxide is particularly preferable from the viewpoints of whiteness, reflectance, and durability. Titanium oxide has three types of crystal systems of rutile, anatase, and brookite, but those having a rutile crystal structure are preferred because of their high refractive index, whiteness, and low photocatalytic activity.

(Other additives)
You may add well-known additives, such as surfactant and antiseptic | preservative, to a reflection layer as needed.
Examples of the surfactant include known surfactants such as anionic and nonionic surfactants. Examples of the anionic surfactant include sodium alkyl sulfate and sodium alkylbenzene sulfonate, and examples of the nonionic surfactant include polyoxyethylene alkyl ether. Also preferred are fluorosurfactants such as sodium perfluoroalkyl sulfate.

(Film thickness)
The thickness of the reflective layer is preferably 3 to 10 μm, more preferably 4 to 8 μm.
By making the thickness of the reflective layer in the range of 3 to 10 μm, it is possible to achieve both necessary reflectance and adhesiveness.

(Application method)
A method for forming the reflective layer by coating is not particularly limited, and a known coating method such as a roll coating method, a bar coater method, a slide die method, or a gravure coater method can be used.
There is no restriction | limiting also in the solvent of a coating liquid, You may use organic solvent type solvents like methyl ethyl ketone, toluene, and xylene, or you may use water as a solvent. Considering that the environmental load is small, a coating solution using water as a solvent is preferable. Solvents may be used alone or in combination. In particular, in the case of an aqueous solvent, it may be used as a mixed solvent obtained by adding a small amount of a water-miscible organic solvent to water.
Although there is no restriction | limiting in particular also in drying of a reflection layer, It is preferable to dry about 1 to 10 minutes at the temperature of about 120-200 degreeC from a viewpoint of shortening of drying time. When the drying temperature is 120 ° C. or higher, the drying time can be shortened, which is advantageous in production. It can suppress that the planarity of the backsheet obtained as it is 200 degrees C or less is impaired.

<Overcoat layer>
In the back sheet of the present invention, the overcoat layer 4 may be provided on the reflective layer 3 for the purpose of improving the adhesion with the sealing material.

(binder)
As the binder for the overcoat layer, those mentioned as the binder for the reflective layer can be preferably used.

(Crosslinking agent)
As the crosslinking agent for the overcoat layer, those mentioned as the crosslinking agent for the reflective layer can be preferably used.

(Other additives)
As other types of additives for the overcoat layer, those mentioned as the additive for the reflective layer can be preferably used.

(Film thickness)
The film thickness of the overcoat layer is preferably in the range of 0.1 to 1.0 μm, more preferably 0.2 to 0.8 μm. By setting the thickness of the overcoat layer in the range of 0.1 to 1.0 μm, it is possible to obtain strong adhesiveness with the sealing material.

(Application method)
As the coating method, the solvent, and the drying method of the coating liquid for forming the overcoat layer, those described in the reflective layer can be preferably used.

<Back layer>
The back sheet of the present invention is preferably provided with a back surface layer 5 for protecting the polyester film on the outer surface (the surface opposite to the solar cell side).

(binder)
As the binder for the back layer, it is preferable to use a silicone-based composite polymer described below from the viewpoint of durability and adhesion to the support. The silicone-based composite polymer of the present invention (hereinafter sometimes referred to as “composite polymer”) is a polymer that is copolymerized with a — (Si (R ¹ ) (R ² ) —O) _n — moiety in the molecule. A polymer containing a structural portion.

  Some silicone-based composite polymers that can be used in the present invention are commercially available. Specific examples of commercially available products include Ceranate WSA 1060, 1070 (manufactured by DIC Corporation), Polydurex H7620, H7630, H7650 (manufactured by Asahi Kasei Chemicals Corporation) and the like.

(Crosslinking agent)
It is preferable to add a crosslinking agent to the back layer of the present invention in order to improve the adhesion to the polyester film. As the kind of the cross-linking agent, those described for the reflective layer can be used.

(UV absorber)
It is preferable to add an ultraviolet absorber to the back layer of the present invention.
Examples of ultraviolet absorbers include, for example, salicylic acid-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based ultraviolet absorbers, hindered amine-based ultraviolet stabilizers, and the like in the case of organic ultraviolet absorbers. . Specifically, for example, salicylic acid-based pt-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy -5-sulfobenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, benzotriazole 2- (2'-hydroxy-5) '-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6 (2H benzotriazol-2-yl) phenol], a cyanoacrylate Ethyl-2-cyano-3,3′-diphenyl acrylate), others, and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy]- Phenol, hindered amine-based bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetra Examples include methylpiperidine polycondensate, nickel bis (octylphenyl) sulfide, and 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate. It is done.

Examples of inorganic ultraviolet absorbers include metal oxides such as titanium oxide, zinc oxide, and cerium oxide, and carbon-based components such as carbon, fullerene, carbon fiber, and carbon nanotube. Among these, titanium oxide is particularly preferable from the viewpoints of cost and durability.
The amount of the UV absorber added to the back layer varies depending on the type of the UV absorber, but is preferably in the range of 0.2 to 5 g / m ² , more preferably 0.3 to 3 g / m ² .

(Other additives)
A white pigment may be added to the back layer for the purpose of supplementing the reflectance of the reflective layer. Regarding the type of white pigment, the white pigment described in the reflective layer can be preferably used.
The addition amount of the white pigment in the back layer is in the range of 0.3 to 10 g / m ² , more preferably 4 to 9 g / m ² . By making the addition amount 0.3 to 10 g / m ² , both good adhesiveness and improved reflectance can be achieved. In addition, when using a titanium oxide as a white pigment, it can serve as a pigment and a ultraviolet absorber.
As the types of other additives in the back layer, the types of additives described in the reflective layer can be preferably used.

(Film thickness)
The thickness of the reflective layer of the present invention is preferably 3 to 12 μm, more preferably 4 to 8 μm. By making the thickness of the back surface layer in the range of 3 to 12 μm, both necessary durability and adhesiveness can be achieved.

(Application method)
As the coating method, solvent, and drying method of the coating liquid for forming the back layer, those described in the reflective layer can be preferably used.

<Back side protective layer>
In the backsheet of the present invention, the back surface protective layer 6 may be provided on the back surface layer 5 for the purpose of further improving the durability.

<Binder>
The binder for the back surface protective layer of the present invention is preferably a fluoropolymer from the viewpoint of durability.
The fluorine-based polymer that can be preferably used in the present invention is a polymer containing a fluorine-containing monomer in the main chain or side chain. The fluorine-containing monomer may be contained in either the main chain or the side chain, but is preferably contained in the main chain from the viewpoint of durability.
Specific examples of the monomer containing fluorine include ethylene tetrafluoride, ethylene chloride trifluoride, vinylidene fluoride, vinyl fluoride, hexafluoropropylene, fluorine-containing alkyl vinyl ether (eg, perfluoroethyl vinyl ether), fluorine-containing ester ( Perfluorobutyl methacrylate, etc.).

  Some fluoropolymers that can be used in the present invention are commercially available. Specific examples of commercially available products include Lumiflon LF200 (manufactured by Asahi Glass Co., Ltd.), Zeffle GK570 (manufactured by Daikin Industries, Ltd.), Obligard SW0011F (manufactured by AGC Co-Tech Co., Ltd.), and the like.

(Crosslinking agent)
In order to improve the adhesion to the back surface layer, it is preferable to add a crosslinking agent to the back surface protective layer of the present invention. As the kind of the cross-linking agent, those described for the reflective layer can be used.

(Slip agent)
You may add a slipping agent to the back surface protective layer of this invention as needed.
Examples of the slip agent include synthetic wax compounds, natural wax compounds, surfactant compounds, inorganic compounds, organic resin compounds, and the like. Among these, a compound selected from a synthetic wax compound, a natural wax compound, and a surfactant compound is preferable from the viewpoint of the surface strength of the back surface protective layer.

As the slip agent, a commercially available product may be used. Specifically, as a synthetic wax-based slip agent, for example, Chemipearl series (for example, Chemipearl W700, W900, W950, etc.) manufactured by Mitsui Chemicals, Inc. And Polylon P-502, Hymicron L-271, Hydrin L-536 manufactured by Chukyo Yushi Co., Ltd., and the like. Examples of natural wax-based lubricants include Hydrin L-703-35, Cellosol 524, and Cellosol R-586 manufactured by Chukyo Yushi Co., Ltd.
Examples of the surfactant-based slip agent include NIKKOL series (for example, NIKKOL SCS, etc.) manufactured by Nikko Chemicals Co., Ltd., and Emar series (for example, EMAL 40, etc.) manufactured by Kao Corporation.

(Colloidal silica)
You may add colloidal silica to the back surface protective layer of this invention as needed.
The colloidal silica that can be used in the present invention is one in which fine particles mainly composed of silicon oxide are present in a fine particle state using water, unitary alcohols or diols, or a mixture thereof as a dispersion medium.
The colloidal silica particles have an average primary particle size of about several nm to 100 nm. The shape of the colloidal silica particles may be spherical, or may be one in which these are connected in a bead shape. Specific examples of the colloidal silica particles include, for example, Snowtex ST-20, ST-30, ST-40, ST-C, ST-N, ST-20L, ST-O, ST-OL, manufactured by Nissan Chemical Industries, Ltd. ST-S, ST-XS, ST-XL, ST-YL, ST-ZL, ST-OZL, ST-AK, Snowtex-AK series, Snowtex-PS series, and Snowtex-UP can be mentioned.

(Other additives)
As other types of additives for the back surface protective layer, those described for the reflective layer can be preferably used.

(Film thickness)
The thickness of the back surface protective layer of the present invention is in the range of 0.5 to 6 μm, more preferably 1 to 5 μm. If the thickness of the back surface protective layer is 0.5 μm or more, the durability is sufficient, and if it is 6 μm or less, it is advantageous in terms of cost.

(Application method)
As the coating method, the solvent, and the drying method of the coating liquid for forming the back surface protective layer, those described in the reflective layer can be preferably used.

<Heat treatment>
The backsheet of the present invention may be heat treated at any point in the manufacturing process. The heat treatment can be performed at an arbitrary time after, for example, forming any one of a white layer (reflection layer), an overcoat layer, a back surface layer, and a back surface protective layer. The most preferred method is after all these layers are formed. There is no restriction | limiting in particular about the form which heat-processes, A sheet | seat form or a roll form may be sufficient. The heat treatment temperature is preferably about 30 to 80 ° C., and the time is preferably about 24 to 72 hours.

[Solar cell module]
The solar cell module of the present invention is configured by providing the back sheet for a solar cell module of the present invention described above or the back sheet for a solar cell module manufactured by the method of manufacturing the back sheet for solar cell module described above. Yes. As a preferred embodiment of the present invention, a solar cell element that converts light energy of sunlight into electrical energy is disposed between a transparent front substrate on which sunlight is incident and the above-described solar cell module backsheet of the present invention. The solar cell element is disposed between the front substrate and the back sheet, and is sealed and bonded with a sealing material such as ethylene-vinyl acetate. 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. FIG. 3 schematically shows an example of the configuration of the solar cell module of the present invention. The solar cell module 31 of the present invention shown in FIG. 3 is disposed on the transparent front base material 21 on which sunlight enters, and on the opposite side of the front base material 21 from the side on which sunlight enters. The element structure portion including the element 23 and the sealing material 22 for sealing the solar cell element 23 and the back for the solar cell module of the present invention disposed on the opposite side of the element structure portion to the side where the front substrate 21 is located. And a sheet 12.

  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 front board | substrate 21 should just have the light transmittance which sunlight can permeate | transmit, and can be suitably selected from the base material which permeate | transmits light. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. For such a substrate, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used.

  Examples of the solar cell element 23 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, and gallium-arsenide. Various known solar cell elements such as II-VI group compound semiconductor systems can be applied.

  In the case of the solar cell module provided with the back sheet for the solar cell module of the present invention, the coating layer on the polyester film has an adhesive force excellent in moisture and heat resistance and has few surface defects, so that it is exposed to the thermal environment and ultraviolet rays. Even if it is done, it is excellent in adhesiveness with a polyester film or an adjacent layer, and can maintain stable power generation efficiency over a long period of time.

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

[Example 1]
(Polyester resin polymerization)
According to Example 1 of Unexamined-Japanese-Patent No. 2011-208125, the polyester resin was polymerized and used as the raw material pellet of a laminated polyester film.

(Preparation of aqueous coating solution for forming coating layer)
In a 1 L pressure-resistant glass container equipped with a stirrer and a heater, 50.0 g (10% by mass) of Nucrel N1214 (Mitsui / DuPont Polychemical Co., Ltd.), which is a copolymer resin of ethylene and methacrylic acid, is used as a raw material. ), 175.0 g (35% by mass) of n-propanol as an organic solvent, 12.7 g (3 times equivalent / COOH) of 28% aqueous ammonia as a basic compound, and 262.3 g of distilled water were respectively sealed. The stirring blade was rotated and mixed at a rotational speed of 400 rpm. Precipitation of resin granules was not observed at the bottom of the container, and it was confirmed that the container was in a floating state. Therefore, the entire glass container was covered with a heat insulating material, the heater was turned on, the system temperature was set to 170 ° C., and the mixture was further stirred for 60 minutes. Thereafter, the heater was turned off and cooled to 80 ° C. by natural cooling while stirring at a rotational speed of 400 rpm. At this time, the time required to lower the system temperature from 120 ° C. to 80 ° C. was 1 hour. Then, the heat insulating material of the glass container was removed, and the lower half of the glass container was immersed in water and cooled with water. Stirring was stopped when the system internal temperature became 35 ° C. or lower, and the content in the glass container was filtered with a 460 mesh stainless steel filter to obtain an aqueous dispersion having a solid content of 25%. Various characteristics of the aqueous dispersion are shown in Table 1.

Next, a coating solution having the following composition was prepared using the aqueous dispersion.
-Acid-modified olefin aqueous dispersion: 24 parts by mass (concentration: 25% by mass)
・ Fluorosurfactant: 1.2 parts by mass (sodium bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfonite oxysuccinate, concentration 1% by mass)
-Nonionic surfactant: 1.8 parts by mass (Naroacty CL95, manufactured by Sanyo Chemical Industries, Ltd., concentration 1% by mass)
Oxazoline-based crosslinking agent: 4.0 parts by mass (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., concentration: 25% by mass)
・ Distilled water: 69.0 parts by mass

(Formation of laminated film)
The laminated film has at least one non-fluorinated surfactant selected from an acid-modified polyolefin resin, a fluorosurfactant, and an anionic surfactant and a nonionic surfactant on one surface of the polyester film. It obtained by apply | coating the aqueous coating liquid containing and extending | stretching and forming a coating layer.

-Extrusion molding-
The polyester resin pellets were dried to a moisture content of 20 ppm or less, then charged into a hopper of a 50 mm diameter twin-screw kneading extruder, melted at 270 ° C., and extruded. The melt (melt) was passed through a gear pump and a filter (pore diameter: 20 μm), and then extruded from a die onto a cooling roll at 20 ° C. to obtain an amorphous sheet (unstretched film). The extruded melt was brought into close contact with the cooling roll using an electrostatic application method.

-Stretching and coating-
The unstretched film extruded and solidified by the above method was sequentially biaxially stretched by the following method to obtain a laminated polyester film having a thickness of 250 μm.

<Stretching method>
(A) Longitudinal stretching The unstretched film was passed between two pairs of nip rolls having different peripheral speeds and stretched in the longitudinal direction (conveying direction). The preheating temperature was 75 ° C., the stretching temperature was 90 ° C., the stretching ratio was 3.4 times, and the stretching speed was 3000% / second.
(B) over the coating longitudinal stretched base (longitudinally stretched film), the coating liquid, solids after drying so that the 0.3 g / m ^2, was coated with a bar coater.
(C) Transverse stretching The longitudinally stretched and coated longitudinally stretched film was stretched laterally using a tenter under the following conditions.
<Conditions>
Preheating temperature: 110 ° C
Stretching temperature: 120 ° C
Stretch ratio: 4.2 times Stretch speed: 70% / second

-Heat fixation / thermal relaxation-
Then, the biaxially stretched film after finishing longitudinal stretching and lateral stretching was heat-set under the following conditions. Further, after heat setting, the tenter width was reduced and heat relaxation was performed under the following conditions.
<Heat setting conditions>
Heat setting temperature: 215 ° C
Heat setting time: 2 seconds <thermal relaxation conditions>
Thermal relaxation temperature: 210 ° C
Thermal relaxation rate: 2%

-Winding-
After heat setting and heat relaxation, both ends were trimmed by 10 cm. Then, after extruding (knurling) with a width of 10 mm at both ends, it was wound up with a tension of 25 kg / m. The width was 1.5 m and the winding length was 2000 m.

[Example 2]
A laminated film was produced in the same manner as in Example 1 except that the nonionic surfactant was changed to the anionic surfactant shown below.
Anionic surfactant (Lapisol A-90, manufactured by NOF Corporation, concentration 1% by mass)

[Comparative Example 1]
In Comparative Example 1, a laminated film was produced in the same manner as in Example 1 except that a urethane resin was produced with reference to Example 1 of JP 2011-168053 A and used as a binder resin for the coating layer.

[Comparative Examples 2 to 5]
A laminated film was produced in the same manner as in Example 1 except that the type and addition amount of the surfactant were changed as shown in Table 1.

[Comparative Example 6]
A laminated film was produced in the same manner as in Example 1 except that the off-line coating method was used as the coating method for the coating layer forming coating solution.

[Examples 3 to 14]
A laminated film was produced in the same manner as in Example 1 except that the type and addition amount of the surfactant were changed as shown in Table 1.

[Examples 15 to 17]
A laminated film was produced in the same manner as in Example 14 except that the acid-modified polyolefin resin in the coating layer was changed as shown below.

Example 15
Bondin TX8030
(Low density ethylene-ethyl acrylate-maleic anhydride terpolymer, manufactured by Arkema)

Example 16
Bondin LX4110
(Low density ethylene-ethyl acrylate-maleic anhydride terpolymer, manufactured by Arkema)

Example 17
Bondin AX8390
(Low density ethylene-ethyl acrylate-maleic anhydride terpolymer, manufactured by Arkema)

[Example 18]
A laminated film was produced in the same manner as in Example 16 except that the type of the crosslinking agent was changed to the material shown below.
Carbodiimide compound (Carbodilite V-02-L2, manufactured by Nisshinbo Industries Inc., solid content: 40% by mass)

[Example 19]
A laminated film was produced in the same manner as in Example 16 except that the crosslinking agent was not used.

[Example 20]
A laminated film was produced in the same manner as in Example 1 except that the nonionic surfactant was changed to the one shown below.
・ Nonionic surfactant (EMALEX 707, manufactured by Nippon Emulsion Co., Ltd., concentration 1% by mass)

[Example 21]
A laminated film was produced in the same manner as in Example 1 except that the nonionic surfactant was changed to the one shown below.
-Acetylene diol type nonionic surfactant (Surfinol 485, manufactured by Air Products Japan, concentration 1% by mass)

[Example 22]
A laminated film was produced in the same manner as in Example 2 except that the anionic surfactant was changed to that shown below.
・ Anionic surfactant (Sanded BL, manufactured by Sanyo Chemical Co., Ltd., concentration 1% by mass)

[Example 23]
A laminated film was produced in the same manner as in Example 2 except that the anionic surfactant was changed to that shown below.
Anionic surfactant (Newcol 291-M, manufactured by Nippon Emulsifier Co., Ltd., concentration 1% by mass)

[Example 24]
A laminated film was produced in the same manner as in Example 1 except that the fluorosurfactant was changed to the one shown below.
Fluorosurfactant: Perfluoroalkylcarboxylic acid potassium salt (Surflon S-111, manufactured by Asahi Glass Co., Ltd., concentration 1% by mass)

[Example 25]
A laminated film was produced in the same manner as in Example 14 except that the acid-modified polyolefin resin was changed as shown below.
・ Bondyne HX8140
(Low density ethylene-ethyl acrylate-maleic anhydride terpolymer, manufactured by Arkema)

(Evaluation method)
[Evaluation of adhesion before wet heat storage]
The obtained laminated film was cut into 20 mm width × 150 mm length to prepare two sample pieces. These two sample pieces are arranged so that the coating layers face each other, and an EVA (ethylene vinyl acetate copolymer resin) sheet (an EVA sheet manufactured by Mitsui Chemicals Fabro Co., Ltd.) cut into a 20 mm width × 100 mm length therebetween. : RC02B) was sandwiched and hot-pressed using a vacuum laminator (vacuum laminator manufactured by Nisshinbo Co., Ltd.) to adhere to EVA. The bonding conditions at this time were as follows.
Using a vacuum laminator, vacuum was applied at 150 ° C. for 3 minutes, and then pressure was applied for 10 minutes for adhesion.

  Thus, a sample for adhesion evaluation was obtained in which the 50 mm portion from one end of the two sample pieces adhered to each other was not bonded to EVA, and the EVA sheet was bonded to the remaining 100 mm portion.

  The EVA non-adhered portion of the obtained sample for adhesion evaluation (portion of 50 mm from one end of the sample piece) is sandwiched between upper and lower clips with Tensilon (RTC-1210A manufactured by ORIENTEC), with a peeling angle of 180 ° and a pulling speed of 300 mm / min A tensile test was performed to measure the adhesion strength, and the ranking was performed according to the following evaluation criteria based on the measured adhesion strength. Of these, ranks A and B are practically acceptable ranges.

(Evaluation criteria)
A: Adhesion was very good (10 N / mm or more)
B: Adhesion was good (3 N / mm or more and less than 10 N / mm)
C: Adhesion was slightly poor (less than 3 N / mm)

[Adhesion evaluation after wet heat storage]
The adhesion evaluation sample was subjected to a moisture heat resistance test at 120 ° C., 100%, 60 hr, and the adhesion evaluation sample after the moisture heat resistance test was evaluated by the above-described peel test method.

[Surface]
About the surface of the coating layer of a laminated | multilayer film, 10m length x full width (1.5m) was visually observed, and the planar shape was ranked according to the following evaluation criteria. Among these, ranks A, B, and C are practically acceptable ranges.
(Evaluation criteria)
A: The surface defect was less than 1 / m ² .
B: Surface defects were 1 / m ² or more and less than 3 / m ² .
C: Surface defects were 3 / m ² or more and less than 5 / m ² .
D: The surface defects were 5 / m ² or more and less than 10 / m ² .
E: Surface defects were 10 / m ² or more.

[Rubber coagulation rate]
Regarding the mechanical stability of the coating solution, that is, the aqueous dispersion, the rubber coagulation rate was evaluated by the Marlon test method with reference to the former JIS K 6392.
The coating solution, which has been allowed to stand in a temperature-controlled room (15 ° C.) for 1 hour or longer and filtered with a 380 mesh filter cloth, is weighed 100.0 g to obtain a measurement sample. Was used to measure the rubber coagulation rate. The load on the polyethylene liner was 25 kg, rotation was started at 2000 rpm, and 15 minutes later, the coating solution in the Marlon cup was filtered through a weighed pore size filter of 10 μm. Further, the precipitate was taken out by washing with pure water, sufficiently washed with pure water, and then dried in a drying oven at 105 ° C. until a constant weight was obtained. Then, it cooled to room temperature in the desiccator, and weighed to the precision of 0.1 mg. The solid content of the coating solution was X [g], the precipitation amount was Y [g], and the rubber coagulation rate C [%] with respect to the solid content in the coating solution was measured by the following formula (3).
C = (Y / X) × 100 (3)

  Table 1 shows the configuration of the coating layer in Examples and Comparative Examples, and Table 2 shows the evaluation results.

[Preparation of back sheet]
<Formation of reflective layer>
-Preparation of titanium dioxide dispersion-
Each component shown in the composition of the following titanium dioxide dispersion was mixed, and the mixture was subjected to dispersion treatment for 1 hour by a dynomill type disperser.
(Composition of titanium dioxide dispersion)
Titanium dioxide (white pigment, volume average particle size 0.42 μm) 39.9 parts [Taipeku R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content 100%]
Polyvinyl alcohol: 16.0 parts [PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10%]
・ Surfactant [Demol EP, manufactured by Kao Corporation, solid content: 25%] ・ ・ ・ 0.5 part ・ Distilled water ・ ・ ・ 51.6 parts

-Preparation of coating solution for forming a reflective layer-
Each component shown below was mixed to prepare a coating solution for forming a reflective layer.
(Composition of coating solution for reflection layer formation)
-Titanium dioxide dispersion (dispersion of white pigment) ... 80.0 parts-Silanol-modified polyvinyl alcohol ... 19.2 parts [R1130, manufactured by Kuraray Co., Ltd., solid content: 7%]
・ Polyoxyalkylene alkyl ether (surfactant) ・ ・ ・ 3.0 parts [Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1%]
Oxazoline compound (crosslinking agent) 2.0 parts [Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25%]
・ Distilled water: 7.8 parts

-Formation of reflective layer-
The obtained coating solution for forming a reflective layer was applied to one surface (surface on the coating layer side) of the laminated film and dried at 180 ° C. for 1 minute, so that the amount of white pigment (titanium dioxide) was 5.5 g / A reflective layer having a thickness of m ² and a thickness of 5.5 μm was formed.

<Formation of back layer>
-Preparation of pigment dispersion-
Each component in the following composition was mixed, and the mixture was subjected to dispersion treatment for 1 hour using a dynomill type disperser.
(Composition of pigment dispersion)
Titanium dioxide (white pigment, volume average particle size 0.42 μm) 39.9 parts [Taipek R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content: 100%]
Polyvinyl alcohol: 16.0 parts [PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10%]
・ Surfactant [Demol EP, manufactured by Kao Corporation, solid content: 25%] ・ ・ ・ 0.5 part ・ Distilled water ・ ・ ・ 51.6 parts

-Preparation of coating solution for back layer formation-
Each component shown in the composition below was mixed to prepare a coating solution for forming the back surface layer.
(Composition of the coating solution for forming the back layer)
-Acrylic / silicone binder (silicone resin) ... 362.3 parts [Ceranate WSA-1070, manufactured by DIC, solid content: 40%]
Carbodiimide compound (crosslinking agent) 48.3 parts [Carbodilite V-02-L2, manufactured by Nisshinbo Co., Ltd., solid content: 40%]
Surfactant: 9.7 parts [Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1%]
・ Pigment dispersion liquid: 157.0 parts
・ Distilled water ... 422.7 parts

-Formation of back layer-
The obtained back surface layer-forming coating solution was applied to the other surface of the laminated film (opposite surface on which the coating layer was formed) so that the amount of the silicone resin was 3.0 g / m ² in terms of the coating amount. And dried at 180 ° C. for 1 minute to form a back layer having a dry thickness of 3 μm.

<Formation of back surface protective layer>
-Preparation of coating solution for forming the back surface protective layer-
Each component shown to the following composition was mixed and the coating liquid for back surface protective layer formation was prepared.
(Composition of the coating solution for forming the back surface protective layer)
-Fluorine binder (fluorine resin) ... 362.3 parts [Obligato SW0011F, manufactured by AGC Co-Tech, solid content: 40%]
-Carbodiimide compound (crosslinking agent) 24.2 parts [Carbodilite V-02-L2, manufactured by Nisshinbo Industries, Ltd., solid content: 40%]
-Surfactant ... 24.2 parts [Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1%]
・ Distilled water ... 703.8 parts

-Formation of back surface protective layer-
The obtained coating solution for forming the back surface protective layer was applied on the back surface layer so that the amount of the fluororesin was 2.0 g / m ² in terms of the coating amount, dried at 180 ° C. for 1 minute, and dried. A back protective layer having a thickness of about 2 μm was formed.

  With the above method, a reflective layer was formed on one surface of the laminated film obtained in Example 1, and a back surface layer and a back surface protective layer were formed on the opposite surface to prepare a back sheet.

  When the laminated film shown in Example 1 was used, a back sheet excellent in adhesiveness and design was obtained.

[Production of solar cell module]
3 mm thick tempered glass, EVA sheet (RC02B manufactured by Mitsui Chemicals Fabro Co., Ltd.), crystalline solar cell, EVA sheet (RC02B manufactured by Mitsui Chemicals Fabro Co., Ltd.) and manufactured in Example 1 The back sheet for the solar cell module using the laminated film thus prepared was superposed in this order, and hot pressing was performed using a vacuum laminator (manufactured by Nisshinbo Co., Ltd., vacuum laminating machine) to bond the EVA and each member. As a bonding method, a vacuum laminator was used for vacuuming at 150 ° C. for 3 minutes, and then pressure was applied for 10 minutes for bonding.

  When the produced crystalline solar cell module was operated for power generation, a solar cell module with high power generation efficiency and excellent design was obtained over a long period of time.

1 Coating layer
2 Polyester film 3 Reflective layer 4 Overcoat layer 5 Back surface layer 6 Back surface protective layer 11 Laminated film 12 Back sheet 21 for solar cell module Transparent front base material 22 Sealing material 23 Solar cell element 31 Solar cell module

Claims (17)

A coating liquid containing at least one selected from a polyolefin resin, a fluorosurfactant, and a nonionic surfactant other than a fluorosurfactant and an anionic surfactant other than a fluorosurfactant After coating on one surface, a coating layer formed by stretching the polyester film at least once;
The stretched polyester film;
A laminated film having   The laminated film according to claim 1, wherein the polyolefin resin is an acid-modified polyolefin resin. The mass ratios of the fluorosurfactant, the nonionic surfactant, and the anionic surfactant contained in the coating layer to the polyolefin resin are a [mass%], b [mass%], and c, respectively. The laminated film according to claim 1 or 2, which satisfies the following formulas (1) and (2) when [% by mass] is set.
0.2 ≦ a + b + c ≦ 5.0 (1)
0.1 ≦ (b + c) /a≦10.0 (2)   The laminated film according to any one of claims 1 to 3, wherein the coating layer includes all of the fluorine-based surfactant, the nonionic surfactant, and the anionic surfactant.   The laminated film according to any one of claims 1 to 4, wherein the polyolefin resin contains 0.1 to 10% by mass of a structure derived from an unsaturated carboxylic acid or an anhydride thereof.   The laminated film according to claim 5, wherein the unsaturated carboxylic acid or an anhydride thereof is acrylic acid, methacrylic acid, or an anhydride of acrylic acid or methacrylic acid.   The laminated film according to any one of claims 1 to 6, wherein the polyolefin resin contains 0.1 to 25 mass% of a structure derived from an unsaturated carboxylic acid ester.   The laminated film according to claim 7, wherein the unsaturated carboxylic acid ester is a methyl ester, an ethyl ester, or a butyl ester.   The laminated film according to any one of claims 1 to 8, wherein the polyolefin resin is a copolymer of ethylene, an unsaturated carboxylic acid ester, and an unsaturated carboxylic acid or an anhydride thereof.   The polyolefin resin is a copolymer of ethylene, an acrylic ester and acrylic acid or an anhydride thereof, or a copolymer of ethylene, a methacrylic ester and acrylic acid or an anhydride thereof. 10. The laminated film according to any one of 9 above.   The laminated film according to any one of claims 1 to 10, wherein the coating layer has a structure derived from a crosslinking agent having an oxazoline group.   The laminated film according to claim 11, wherein the crosslinking agent having an oxazoline group is water-soluble.   The back sheet | seat for solar cell modules provided with the laminated | multilayer film of any one of Claims 1-12. A transparent front substrate on which sunlight is incident;
An element structure portion including a solar cell element and a sealing material for sealing the solar cell element, disposed on the opposite side of the front base material from which sunlight is incident;
The back sheet for a solar cell module according to claim 13, which is disposed on a side opposite to a side on which the front base material is located of the element structure portion,
Including solar cell module. A coating liquid containing at least one selected from a polyolefin resin, a fluorosurfactant, and a nonionic surfactant other than a fluorosurfactant and an anionic surfactant other than a fluorosurfactant Applying on one side;
The polyolefin resin, the fluorosurfactant, the nonionic surfactant, and the anionic interface are formed on the stretched polyester film by stretching the polyester film on which the coating film is formed at least once. Forming a coating layer containing at least one selected from active agents;
The manufacturing method of the laminated | multilayer film which has this.   The method for producing a laminated film according to claim 15, wherein the coating liquid is an aqueous dispersion. When the solid content in the coating solution is X [g] and the amount of precipitation when the coating solution is filtered through a filter having a pore diameter of 10 μm is Y [g], the following formula (3) The manufacturing method of the laminated | multilayer film of Claim 15 or Claim 16 which uses the coating liquid with which the rubber solidification rate C [%] represented by these satisfy | fills 0.01 <= C <= 0.50.
C = (Y / X) × 100 (3)