JP5995769B2 - Laminated film, back sheet for solar cell module, and solar cell module - Google Patents

Description

  The present invention relates to a laminated film, a back sheet for a solar cell module, and a solar cell module. Specifically, the present invention relates to a laminated film used for a solar cell module backsheet, which has both adhesiveness and reworkability. The present invention also relates to a method for producing the laminated film.

  Generally, a solar cell module is formed by laminating glass or a front sheet / transparent filling material (sealing material) / solar cell element / sealing material / back sheet (BS) in this order from the light-receiving surface side on which sunlight enters. It has a structure. Specifically, the solar cell element is generally embedded in a resin (sealing material) such as EVA (ethylene-vinyl acetate copolymer), and a back sheet for a solar cell module is further adhered thereon. Composed. The back sheet for a solar cell module is provided in the outermost layer of the solar cell module and functions to protect the solar cell element.

The back sheet for a solar cell module has a configuration in which a polyester film is used as a support and an adhesive layer is laminated thereon. When assembling the solar cell module, the back sheet for the solar cell module and the EVA film are bonded via the adhesive layer. As an adhesive layer for adhering the solar cell module backsheet and the EVA film, an EVA adhesive layer having a thickness of about 100 μm is generally used (for example, Patent Document 1).
Also, it has been proposed to use an adhesive layer having a two-layer structure as such an adhesive layer (for example, Patent Document 2). Here, the total thickness of the adhesive layer having a two-layer structure is about several tens to 100 μm.

  As described above, the solar cell module is assembled by laminating the solar cell module backsheet and the EVA film via the adhesive layer. However, since the step of bonding the solar cell module backsheet and the EVA film is a step requiring skill, in the bonding step, there are many cases where a bonding error such as a wrong bonding position occurs. Since expensive members are used for each member of the solar cell module, when a mistake in attaching the back sheet for the solar cell module occurs, the solar cell module back sheet is once peeled off from the EVA film and then attached again. Work (rework) of attaching may be performed.

JP 2012-253164 A International Publication No. 2011/073819 Pamphlet

  However, when a laminated film used for a conventional back sheet for a solar cell module is bonded to an adherend such as an EVA film, there is a problem that the rework operation cannot be performed smoothly. In general, a laminated film and an EVA film are required to have high adhesion because they are placed in a harsh environment for a long time. On the other hand, when performing a rework work, when peeling a laminated film from an EVA film, it is calculated | required to have moderate peelability. In other words, in order to smoothly perform the rework work, the laminated film is required to have peelability while having excellent adhesion, but the conventional laminated film is more suitable than the EVA film. There is a problem that the rework work cannot be performed smoothly because it does not have good adhesion and peelability.

  In order to solve such problems of the prior art, the present inventors have proceeded with studies for the purpose of providing a back sheet for a solar cell module having both adhesiveness and peelability.

As a result of intensive studies to solve the above problems, the present inventors have found a support, a first adhesive layer laminated on at least one surface of the support, and a first adhesive layer. In the laminated film having the second adhesive layer laminated on the side opposite to the support, the average film thickness of the first adhesive layer and the second adhesive layer is within a predetermined range, and the first By defining the ratio of the average film thickness of the first adhesive layer to the total average film thickness of the adhesive layer and the second adhesive layer, a laminated film having both adhesion and reworkability can be obtained. I found. Further, the present inventors have found that such a laminated film can be produced by forming the first adhesive layer by an in-line coating method, and have completed the present invention.
Specifically, the present invention has the following configuration.

[1] A support, a first adhesive layer laminated on at least one surface of the support, and a second adhesion laminated on the opposite side of the support via the first adhesive layer Each of the first adhesive layer and the second adhesive layer contains a binder and a crosslinking agent, and the sum of the average film thicknesses of the first adhesive layer and the second adhesive layer is , 0.05 to 3 μm, and the ratio of the average film thickness of the first adhesive layer to the total average film thickness of the first adhesive layer and the second adhesive layer is 0.1 The laminated film is characterized in that it is ˜20%, and the first adhesive layer and the second adhesive layer are colorless and transparent.
[2] The laminated film according to [1], wherein the first adhesive layer is formed by applying a first adhesive layer forming coating solution and then stretching.
[3] The laminated film according to [1] or [2], wherein the binder is a polyolefin.
[4] The laminated film according to any one of [1] to [3], wherein the crosslinking agent is an oxazoline-based crosslinking agent.
[5] The laminated film according to any one of [1] to [4], wherein the support is a polyester film, and an average carboxylic acid value (AV) of the polyester film is 22 eq / ton or less. .
[6] A step of applying a first adhesive layer-forming coating solution containing a binder and a crosslinking agent to at least one surface of a support and stretching to form a first adhesive layer, and the first adhesion Applying a second adhesive layer-forming coating solution containing a binder and a crosslinking agent on the layer to form a second adhesive layer, the first adhesive layer and the second adhesive layer The total of the average film thickness is 0.05 to 3 μm.
[7] A laminated film produced by the method according to [6].
[8] A solar cell backsheet using the laminated film according to any one of [1] to [5] and [7].
[9] A solar cell module using the solar cell back sheet according to [8].

  According to the present invention, a laminated film having both adhesion and reworkability can be obtained. For this reason, the laminated film of the present invention is preferably used as a back sheet for a solar cell module.

FIG. 1 is a schematic cross-sectional view showing an example of the laminated film of the present invention.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Laminated film)
The present invention includes a support, a first adhesive layer laminated on at least one surface of the support, and a second adhesive layer laminated on the opposite side of the support via the first adhesive layer. It is related with the laminated film which has. The first adhesive layer and the second adhesive layer each contain a binder and a cross-linking agent, and the total average film thickness of the first adhesive layer and the second adhesive layer is 0.05 to 3 μm. The ratio of the average film thickness of the first adhesive layer to the total of the average film thickness of the first adhesive layer and the second adhesive layer is 0.1 to 20%. Furthermore, in the present invention, the first adhesive layer and the second adhesive layer are colorless and transparent layers.

  FIG. 1 shows a schematic cross-sectional view of a laminated film 10 of the present invention. As shown in FIG. 1, the laminated film 10 of the present invention further comprises a support 2, a first adhesive layer 4 laminated on the support 2, and a first adhesive layer 4. It has the 2nd adhesion layer 6 laminated. The laminated film 10 may include other layers in addition to these three layers, but the first adhesive layer 4 and the support 2 are preferably adjacent to each other, and the second adhesive layer 6 and the EVA film. It is preferable that the adherend such as the above can be directly bonded.

  The total average film thickness of the first adhesive layer and the second adhesive layer is 0.05 to 3 μm. The total average film thickness of the first adhesive layer and the second adhesive layer may be 0.05 μm or more, preferably 0.1 μm or more, and more preferably 0.5 μm or more. Moreover, the sum total of the average film thickness of a 1st contact bonding layer and a 2nd contact bonding layer should just be 3 micrometers or less, It is more preferable that it is 2.5 micrometers or less, It is further more preferable that it is 2.0 micrometers or less. In this invention, even if it is a case where the average film thickness of the sum total of a 1st contact bonding layer and a 2nd contact bonding layer is restrained small in this way, the outstanding adhesiveness can be exhibited. Moreover, since the total average film thickness of the first adhesive layer and the second adhesive layer can be kept small, the solar cell module backsheet itself can be thinned.

  In the present invention, the ratio of the average film thickness of the first adhesive layer to the total average film thickness of the first adhesive layer and the second adhesive layer is 0.1 to 20%. The ratio of the average film thickness of the first adhesive layer may be 0.1% or more, preferably 0.5% or more, and more preferably 1.0% or more. Moreover, the ratio for which the average film thickness of a 1st contact bonding layer should just be 20% or less, it is preferable that it is 15% or less, and it is more preferable that it is 10% or less. In the present invention, the laminate workability of the laminated film can be improved by suppressing the ratio of the first adhesive layer to be small. That is, the peelability when the laminated film is peeled off from an adherend such as an EVA film can be improved.

Such a first adhesive layer can be obtained by an in-line coating method. That is, the first adhesive layer can be obtained by stretching the first adhesive layer forming coating solution after coating.
The in-line coating method is a production method in which the above steps are continuously performed without winding the film in a series of film forming steps such as a resin extrusion step, a stretching step, a coating step, and a stretching step. 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 off-line coating method, a step of winding up the film is included, so that a stretching step is not provided after the adhesive layer forming coating solution is applied. On the other hand, in the inline 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 coating 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 this invention, the laminated film which has adhesiveness and rework property can be formed by forming a 1st contact bonding layer by an in-line coating method. The following reasons can be considered as a reason why a laminated film having both adhesion and reworkability can be formed in the present invention.
In this invention, since the 1st contact bonding layer is thinned and the extending process is provided after application | coating, the intensity | strength of a 1st contact bonding layer is increasing. Thereby, when peeling a laminated | multilayer film from an EVA film, an interlayer is destroyed in a 1st contact bonding layer, and it is suppressed that peeling arises in the layer of a 1st contact bonding layer. Moreover, in this invention, the adhesiveness between a support body and a 1st adhesion layer is increasing by forming a 1st contact bonding layer by an in-line coating method, Thereby, when peeling a laminated | multilayer film from an EVA film. Instead of peeling between the support and the first adhesive layer, it becomes possible to cause peeling within the surface layer at the surface layer portion of the support. Thus, in this invention, since it can cause peeling in a surface layer in the surface layer part of a support body, the peelability at the time of rework can be improved.

  In the present invention, the first adhesive layer and the second adhesive layer are colorless and transparent layers. The colorless transparent layer is a layer in which the content of a coloring substance (inorganic particles) such as a pigment is 5% by mass or less with respect to the mass of the binder, and the total light transmittance showing transparency is 70% or more. It is a layer that is. In addition, it is preferable that it is 3 mass% or less, and, as for the content rate of the coloring substance (inorganic particle) contained in a colorless and transparent layer, it is more preferable that it is 1 mass% or less. The total light transmittance is preferably 80% or more. Thus, the first adhesive layer and the second adhesive layer are colorless and transparent layers, whereby the average film thickness of the first adhesive layer and the second adhesive layer can be further reduced.

<Binder>
Examples of the binder contained in the first adhesive layer and the second adhesive layer include polyolefin resins, acrylic resins, polyester resins, urethane resins, and polyamide resins. Among these, it is preferable to use a polyolefin resin.

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

  The shape and usage of the polyolefin resin that can be used in the present invention are not particularly limited as long as an adhesive layer can be formed. For example, a water-dispersible olefin resin or a meltable olefin resin may be used. Further, it may be a crystalline olefin resin or a non-crystalline olefin resin.

  The polyolefin resin is preferably contained in an amount of 10 to 95% by mass, more preferably 15 to 90% by mass, and more preferably 20 to 85% by mass with respect to the total mass of the binder resin contained in each adhesive layer. Is more preferable. By containing the polyolefin resin so as to be within the above range, the adhesion between the first adhesive layer and the support can be enhanced, and further the adhesion between the second adhesive layer and the adherend such as the EVA film. Can be increased.

  In the present invention, an acid-modified polyolefin resin may be used as the polyolefin resin. The acid-modified polyolefin is a modified product in which a carboxylic acid or a carboxylic anhydride is bonded to a homopolymer or copolymer of an olefin component.

In the present invention, the acid-modified polyolefin resin is a resin that has been 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).

  Content of unsaturated carboxylic acid or its anhydride in acid-modified polyolefin resin is 0.1-10 mass%, 0.5-8 mass% is preferable, 1-5 mass% is more preferable, 2-4 More preferred is mass%. When the content is less than 0.1% by mass, it is difficult to obtain an aqueous dispersion, and when it exceeds 10% by mass, the weather resistance tends to decrease.

  In the present invention, the acid-modified polyolefin resin preferably contains an unsaturated carboxylic acid ester or (meth) acrylic acid ester component so that the adhesive layer can exhibit sufficient adhesiveness.

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, octyl (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 unsaturated carboxylic acid ester or (meth) acrylic acid ester component in the acid-modified polyolefin resin is preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, It is more preferable that it is 18 mass%, and it is especially preferable that it is 3-15 mass%. If the content of the unsaturated carboxylic acid ester or (meth) acrylic acid ester component is less than 0.1% by mass, the adhesiveness tends to decrease, and if it exceeds 25% by mass, the weather resistance and acid resistance decrease. It tends to end up.
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 these, 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 is an ethylene-acrylic acid ester- A ternary copolymer of acrylic acid or its anhydride, or ethylene-methacrylic acid ester-acrylic acid or its anhydride is preferable.

  Specific examples of the acid-modified polyolefin resin include ethylene- (meth) acrylic acid ester-maleic anhydride copolymer, ethylene-propylene- (meth) acrylic acid ester-maleic anhydride copolymer, ethylene-butene- (meta ) Acrylic ester-maleic anhydride copolymer, propylene-butene- (meth) acrylic ester-maleic anhydride copolymer, ethylene-propylene-butene- (meth) acrylic ester-maleic anhydride copolymer, Ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-maleic anhydride copolymer, ethylene-propylene-maleic anhydride copolymer, ethylene-butene-maleic anhydride copolymer, propylene-butene -Maleic anhydride copolymer, ethylene-propylene-butene- anhydride And in-acid copolymer, and among them ethylene - (meth) acrylic acid ester - maleic anhydride copolymer is most preferable. 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.

In the present invention, the acid-modified polyolefin resin is preferably an aqueous dispersion in order to improve the weather resistance and acid resistance and to make the adhesive layer easy to thin.
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 uniform thickness when coating, etc., and preferably 0.5 μm or less. Is more preferably 0.2 μm or less, and particularly preferably 0.1 μm or less.

  A commercially available resin may be used as the polyolefin resin as described above. Commercially available polyolefin resins include, for example, Arrow Base SE-1010, SE-1013N, SD-1010, TC-4010, TD-4010 (manufactured by Unitika Ltd.), Hitech S3148, S3121, S8512 (and above). Toho Chemical Co., Ltd.), Chemipearl S-120, S-75N, V100, EV210H (manufactured by Mitsui Chemicals, Inc.), and the like. Among them, in the present invention, it is preferable to use Arrow Base SE-1013N manufactured by Unitika Ltd.

<Crosslinking agent>
Examples of the crosslinking agent contained in the first adhesive layer and the second adhesive layer include epoxy-based, isocyanate-based, oxazoline-based, and carbodiimide-based crosslinking agents. Of these, oxazoline-based crosslinking agents are preferably used. As the cross-linking agent having an oxazoline group, Epocros K2010E, K2020E, K2030E, WS-500, WS-700 (all manufactured by Nippon Shokubai Chemical Co., Ltd.) and the like can be used. By using such an oxazoline-based cross-linking agent, it is possible to maintain good adhesiveness even after time.

  As a content rate of a crosslinking agent, 0.5-35 mass% is preferable with respect to the binder which comprises each contact bonding layer, 1-30 mass% is more preferable, 2-25 mass% is more preferable. When the content of the crosslinking agent is 0.5% by mass or more, a sufficient crosslinking effect is obtained while maintaining adhesiveness, and when it is 35% by mass or less, the pot life of the coating solution can be kept longer, The coated surface can be improved.

<Other additives>
In addition to the crosslinking agent, the first adhesive layer and / or the second adhesive layer may contain other compounds having an epoxy group. Examples of these compounds include sorbitol tol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, Polyepoxy compounds such as methylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether , Polypropylene glycol diglycidyl ether, polytetramethylene Diepoxy compounds such as recall diglycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and monoepoxy compounds such as phenyl glycidyl ether.

  When these epoxy compounds are used in combination with a crosslinking agent, the total amount of the crosslinking agent and these epoxy compounds is preferably 0.5 to 35% by mass, and 1 to 30% by mass with respect to the binder constituting each adhesive layer. % Is more preferable, and 2 to 25% by mass is more preferable.

Furthermore, the first adhesive layer and / or the second adhesive layer may contain an anionic or nonionic surfactant. When adding a surfactant, it is preferable to use a nonionic surfactant.
When adding a surfactant, the addition amount is preferably 0.1 to 10 mg / m ² , more preferably 0.5 to 3 mg / m ² . When the addition amount of the surfactant is 0.1 mg / m ² or more, it is possible to suppress the generation of repellency and to form a favorable layer, and when the addition amount is 10 mg / m ² or less, the adhesion between the layers is performed well. Can do.

(Support)
The laminated film of the present invention includes a support, and various polymer films can be used as the support. Among them, it is preferable to use a polyester film.

  The polyester constituting the polyester film is preferably a saturated polyester. Thus, 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.

Polyester has a —COO— bond or —OCO— bond in the middle of the polymer. The terminal group of the polyester is an OH group, a COOH group, or a group in which they are protected (OR ^X group, COOR ^X group (R ^X is an arbitrary substituent such as an alkyl group)), and an aromatic dibasic acid Alternatively, a linear saturated polyester synthesized from an ester-forming derivative thereof and a diol or an ester-forming derivative thereof is preferable, for example, Japanese Patent Application Laid-Open No. 2009-155479 and Japanese Patent Application Laid-Open No. 2010-. No. 235824 can be used as appropriate.

  Specific examples of linear saturated polyesters include polyethylene terephthalate (PET), polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate, of which polyethylene terephthalate or Polyethylene-2,6-naphthalate is particularly preferable from the viewpoint of the 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 resins such as polyimide. Moreover, as polyester, you may use crystalline polyester which can form anisotropy at the time of a fusion | melting.

The average carboxylic acid value (AV) of the polyester film is preferably 22 eq / ton or less. The average carboxylic acid value (AV) of the polyester film is preferably 22 eq / ton or less, more preferably 18 eq / ton or less, and even more preferably 16 eq / ton or less. Moreover, although a lower limit is not specifically limited, It is preferable that it is 1 eq / ton or more. By setting the carboxylic acid value (AV) of the polyester film within the above range, the crystallinity and heat resistance of the polyester can be maintained, and the reworkability of the laminated film can be improved.
The carboxylic acid value (AV) of the polyester film can be adjusted by the solid phase polymerization time described later. Increasing the solid phase polymerization time decreases the carboxylic acid value, and shortening the solid phase polymerization time increases the carboxylic acid value.

  Moreover, the polyester film may contain a terminal sealing agent. Examples of the terminal blocking agent include carbodiimide compounds and ketenimine compounds. In the polyester film, the carbodiimide compound or the ketene imine compound functions as a terminal sealing agent that reacts with the terminal carboxyl group of the polyester and suppresses hydrolysis of the polyester. In particular, a cyclic carbodiimide compound and a ketenimine compound are preferably used because they can not only suppress hydrolysis but also suppress generation of volatilized gas in the production process.

  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 thickness of the polyester film is preferably 30 to 400 μm, and more preferably 50 to 250 μm. The polyester film in the present invention may be a single-layer polyester film or a laminate of two or more polyester films (for example, a co-flow film or a co-extruded film). When the polyester film in this invention consists of two or more layers, it is preferable that the total thickness becomes in the said range.

  The polyester film may be subjected to a surface treatment. Examples of the surface treatment in this case include corona treatment, flame treatment, vacuum plasma treatment, atmospheric pressure plasma treatment, and glow discharge treatment. By performing the surface treatment of the polyester film, the adhesion with the first adhesive layer can be further enhanced.

From the viewpoint of transparency, the polyester film preferably has a refractive index of 1.63 to 1.71, more preferably 1.62 to 1.68.
Further, the polyester film may contain other additives without departing from the gist of the present invention, and examples thereof include antioxidants and ultraviolet inhibitors.

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 preferably used from the viewpoint of suppressing the carboxyl group content to a predetermined range or less, and Ti-based compounds are particularly preferable. In the case of using a Ti-based compound, an embodiment in which polymerization is performed by using the Ti-based compound as a catalyst in a range of 1 ppm to 30 ppm, more preferably 3 ppm to 15 ppm is preferable. When the proportion of the Ti-based compound is within the above range, the terminal carboxyl group can be adjusted to the following range, and the hydrolysis resistance of the polymer substrate can be kept low.

  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.

(Laminated film manufacturing method)
The method for producing a laminated film of the present invention is a process in which a first adhesive layer forming coating solution containing a binder and a crosslinking agent is applied to at least one surface of a support and stretched to form a first adhesive layer. And applying a second adhesive layer forming coating solution containing a binder and a crosslinking agent on the first adhesive layer to form a second adhesive layer. The total average film thickness of the first adhesive layer and the second adhesive layer is formed to be 0.05 to 3 μm.

  The support used in the present invention is preferably a polyester film, and in the production process of the polyester film, it is preferable to prepare master pellets in which a polyester resin and other additives are mixed. The polyester resin used for the preparation of the master pellet is processed into a pellet after polycondensation of diol and dicarboxylic acid according to a conventional method.

  In the step of preparing the master pellets, it is preferable to provide a drying step, and the composition such as the fine particles or the end capping agent and the polyester resin is dried in a vacuum or hot air. In the drying step, the water content in these compositions is preferably 100 ppm or less, more preferably 80 ppm or less, and even more preferably 60 ppm or less. The drying temperature at this time is preferably 80 to 200 ° C, more preferably 100 to 180 ° C, and still more preferably 110 to 170 ° C. The drying time can be appropriately adjusted so as to achieve the above moisture content.

  Thereafter, the master pellet 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. 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 any of air, vacuum, and inert airflow.

  The kneaded resin mixture 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 molten resin mixture is discharged from the die into a soft sheet.

  The resin mixture sheet (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.

  Prior to the application of the first adhesive layer described below, it is preferable to perform a surface treatment on the polyester film substrate. For example, corona treatment, flame treatment, ultraviolet treatment, glow treatment, atmospheric pressure plasma treatment and the like can be mentioned.

  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.

A 1st contact bonding layer is formed in the surface of a polyester film by application | coating in the process before such an extending process, or the process between extending processes. 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 a coating process is provided before stretching in the vertical and horizontal directions, it may be performed sequentially as coating → longitudinal → horizontal, coating → horizontal → vertical, or may be stretched in two directions simultaneously after the coating process. good. Further, it is also preferable to stretch in multiple stages such as coating → vertical → vertical (horizontal) → horizontal, vertical → application → vertical (horizontal) → horizontal, vertical → vertical (horizontal) → application → horizontal.

  When applying the first adhesive layer, it is preferable to apply an aqueous solution or an aqueous dispersion (latex). 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 first adhesive layer is formed by applying a coating solution on a polyester film and then curing it by drying. The second adhesive layer may be formed by applying a second adhesive layer forming coating solution on the first adhesive layer after the first adhesive layer is cured. You may apply | coat and form the 2nd coating liquid for contact bonding layer formation before a drying process. In this case, a drying process is provided after apply | coating a 2nd contact bonding layer. In addition, although the extending | stretching process may be provided after apply | coating a 2nd contact bonding layer, it is preferable not to provide.

  The longitudinal stretching is preferably performed at Tg−10 to Tg + 50 ° C., more preferably Tg to Tg + 40 ° C., and further preferably Tg + 10 to Tg + 35 ° C. The 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 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 heater, halogen heater, etc.) may be used, or hot air may be blown.

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). In the heat setting and relaxation step provided after the stretching step, a part of the volatile basic compound having a boiling point of 200 ° C. or less may be volatilized.
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% in both length and width (ratio to the width after transverse stretching), more preferably 2 to 10%, and still more preferably. 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 breaking 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 . 0N / mm ² can be carried out by providing two or more pairs of nip rolls during transportation and slacking them in a suspended manner (in a suspended form).

(Back sheet for solar cell module)
Although the laminated | multilayer film of this invention are used for various uses, it is used suitably as a solar cell module backsheet (protective sheet of a solar cell module). Since the laminated film of the present invention has excellent adhesion and reworkability with respect to an adherend such as an EVA film, when used as a back sheet for a solar cell module, the yield of cells of the solar cell module can be improved. it can. That is, the production cost of the solar cell module can be suppressed.

  The second adhesive layer of the laminated film of the present invention is preferably directly adhered to the EVA film, but the following functional layer can be further laminated on the support side. When laminating the functional layer, it is preferable to provide an easy adhesion layer on the surface of the support opposite to the surface on which the first adhesive layer is provided.

<Reflective layer (colored layer)>
The back sheet of the present invention may be provided with a light reflection layer on the surface of the support opposite to the surface on which the first adhesive layer is provided. 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.

  As the binder for the reflective layer of the present invention, acrylic, polyester, polyurethane, and polyolefin polymers can be used. Of these, polyolefin polymers are preferred.

  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.

  You may add well-known additives, such as surfactant and antiseptic | preservative, to the reflective layer of this invention 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.

The thickness of the reflective layer of the present invention 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.

There is no restriction | limiting in particular in the method of apply | coating the reflective layer of this invention, Well-known coating methods, such as a roll coat method, the bar-coater method slide die method, and the gravure coater method, can be used.
There is no restriction | limiting also in a coating solvent, You may use organic solvent type | system | group solvents like methyl ethyl ketone, toluene, and xylene, or you may use water as a solvent. However, considering that the environmental load is small, application using water as a solvent is particularly preferable. The coating solvent may be used alone or in combination. In particular, in the case of an aqueous coating solvent, a mixed solvent obtained by adding a small amount of a water-miscible organic solvent to water may be used.
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 less than 120 ° C., the drying time becomes long, which is disadvantageous in production. Conversely, if it exceeds 200 ° C., the flatness of the resulting backsheet may be impaired.

<Overcoat layer>
In the solar cell module backsheet of the present invention, an overcoat layer may be provided on the reflective layer.
As the binder for the overcoat layer, those described for the reflective layer can be preferably used. Further, as the type of crosslinking agent for the overcoat layer, those described for the reflective layer can be preferably used. As content of the crosslinking agent of an overcoat layer, 5 mass%-40 mass% are preferable with respect to the binder which comprises an overcoat layer, and 10 mass%-30 mass% are more preferable. When the content of the crosslinking agent is 5% by mass or more, a sufficient crosslinking effect is obtained while maintaining the strength and adhesiveness of the polymer layer. When the content is 40% by mass or less, the pot life of the coating solution is kept longer. Can do.

  As the types and addition amounts of other additives in the overcoat layer, those described in the reflective layer can be preferably used.

  The film thickness of the overcoat layer is preferably 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.

  As the overcoat layer coating method, coating solvent, and drying method, those described in the reflective layer can be preferably used.

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

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”) has a polymer structure that is copolymerized with a — (Si (R ¹ ) (R ² ) —O) _n — moiety in the molecule. A polymer containing a moiety.

  By using a silicone-based composite polymer as a binder for the back surface layer, it becomes possible to make the adhesion between the back surface layer and the support particularly good, and it is possible to keep the decrease in adhesion small even after a long period of time. It becomes possible.

The silicone composite polymer is preferably in the form of an aqueous polymer dispersion (so-called latex). The preferable particle size of the latex of the silicone composite polymer is about 50 to 500 nm, and the preferable concentration is about 15 to 50% by mass.
The silicone composite polymer of the present invention preferably has a water-affinity functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group or an amide group when the aqueous polymer is in the form of latex. When the silicone-based composite polymer of the present invention has a carboxyl group, the carboxyl group may be neutralized with sodium, ammonium, amine or the like. In addition, when used in the form of latex, an emulsion stabilizer such as a surfactant (eg, anionic or nonionic surfactant) or a polymer (eg: polyvinyl alcohol) may be added to improve the stability. Good. Further, if necessary, a pH adjuster (eg, ammonia, triethylamine, sodium hydrogen carbonate, etc.), preservative (eg: 1,3,5-hexahydro- (2-hydroxyethyl) -s-triazine, 2- (4 -Thiazolyl) benzimidazole, etc.), thickeners (eg: sodium polyacrylate, methylcellulose, etc.), film-forming aids (eg: butyl carbitol acetate, etc.), etc. Also good.

In order to improve the adhesion to the support, it is preferable to add a crosslinking agent to the back layer of the present invention. As the kind of the cross-linking agent, those described for the reflective layer can be used.
As content of a crosslinking agent, 5 mass%-40 mass% are preferable with respect to the binder which comprises a back surface layer, and 10 mass%-30 mass% are more preferable. When the content of the crosslinking agent is 5% by mass or more, a sufficient crosslinking effect can be obtained while maintaining the adhesion to the support, and when the content is 40% by mass or less, the pot life of the coating solution can be maintained longer. it can.

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. .
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 ultraviolet absorber added to the back layer varies depending on the type of the ultraviolet absorber, but is preferably in the range of 0.2 to 5 g / m ² , more preferably 0.3 to 3 g / m ² .

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 amount of the white pigment added to the back layer is 0.3 to 10 g / m ² , more preferably 4 to 9 g / m ² . When the addition amount is 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 and addition amounts of other additives in the back layer, those described in the reflective layer can be preferably used.

The thickness of the reflective layer 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.

  As the back layer coating method, coating solvent, and drying method, those described in the reflective layer can be preferably used.

<Back side protective layer>
In the back sheet of this invention, you may provide a back surface protective layer on a back surface layer in order to further improve durability.

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.

  When the fluoropolymer of the present invention is used in a latex form, the particle size is preferably about 50 to 500 nm, and the solid content concentration is preferably about 15 to 50% by mass. The fluoropolymer of the present invention preferably has a water-affinity functional group such as a carboxyl group, a sulfonic acid group, a hydroxyl group or an amide group when the aqueous polymer is in the form of latex.

  In order to improve the adhesion to the support, 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.

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, from the viewpoint of the surface strength of the polymer layer, a compound selected from synthetic wax compounds, natural wax compounds, and surfactant compounds is preferable.

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.

  As the types and addition amounts of other additives for the back surface protective layer, those described for the reflective layer can be preferably used.

  The thickness of the back protective layer is preferably 0.5 to 6 μm, more preferably 1 to 5 μm. If the thickness of the back surface protective layer is less than 0.5, durability may be insufficient, and if it exceeds 6 μm, it is disadvantageous in terms of cost.

  As the coating method, coating solvent, and drying method for the back surface protective layer, those described in the reflective layer can be preferably used.

[Solar cell module]
The solar cell module of the present invention includes the laminated film of the present invention or the back sheet for the solar cell module of the present invention.
The solar cell module of the present invention comprises a solar cell element that converts light energy of sunlight into electric energy, a transparent substrate on which sunlight is incident, and the polyester film (back sheet for solar cell) of the present invention described above. It is arranged and arranged between. Between a board | substrate and a polyester film, it can seal and comprise with resin (what is called sealing agent), such as an ethylene-vinyl acetate copolymer, for example.

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

  The transparent substrate only needs to have a light-transmitting property through which sunlight can pass, and can be appropriately selected from base materials that transmit light. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. For such a substrate, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used.

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

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

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 first adhesive layer)
・ Olefin aqueous dispersion: 24.12 parts by mass
(Arrow Base SE-1013N, manufactured by Unitika Ltd., concentration 20% by mass)
・ Fluorine surfactant: 0.19 parts by mass
(W-AHE, manufactured by FUJIFILM Fine Chemicals Co., Ltd., concentration 1% by mass)
・ Oxazoline-based crosslinking agent: 3.90 parts by mass
(Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., concentration 25% by mass)
・ Distilled water: 71.80 parts by mass

(Preparation of aqueous coating solution for forming second adhesive layer)
・ Olefin aqueous dispersion: 21.09 parts by mass
(Arrow Base SE-1013N, manufactured by Unitika Ltd., concentration 20% by mass)
・ Fluorosurfactant: 0.48 parts by mass
(W-AHE, manufactured by FUJIFILM Fine Chemicals Co., Ltd., concentration 1% by mass)
・ Nonionic surfactant: 0.96 parts by mass
(Naroacty CL95, manufactured by Sanyo Chemical Co., Ltd., concentration 1% by mass)
・ Oxazoline-based crosslinking agent: 4.33 parts by mass
(Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., concentration 25% by mass)
・ Distilled water: 73.13 parts by mass

(Formation of laminated film)
The laminated film is formed by applying an aqueous coating solution for forming a first adhesive layer on at least one surface of the polyester film, and stretching to form a first adhesive layer, and then on the first adhesive layer. Obtained by laminating a second adhesive 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 20 ° C. cooling roll to obtain an amorphous sheet. 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 successively biaxially stretched by the following method to obtain a 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) Application of first adhesive layer-forming coating solution An aqueous coating solution for forming the first adhesive layer is applied on the longitudinally stretched base with a bar coater so as to be 0.65 g / m ^2. did.
(C) Transverse stretching The above-mentioned film subjected to longitudinal stretching and coating was subjected to transverse stretching under the following conditions using a tenter.
<Conditions>
Preheating temperature: 110 ° C
Stretching temperature: 120 ° C
Stretch ratio: 4.2 times Stretch speed: 70% / second

-Heat fixation / thermal relaxation-
Then, the 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 process 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.

-Application of second adhesive layer forming coating solution-
On the base prepared above, an aqueous coating solution for forming the second adhesive layer is applied with a bar coater so as to be 1.10 g / m ² , dried at 170 ° C. for 2 minutes, The adhesive layer was formed.

(Examples 2 to 7)
Except for the configuration shown in Table 1, the first adhesive layer and the second adhesive layer were laminated on the support in the same manner as in Example 1 to produce laminated films of Examples 2 to 5. did. In Example 5, a support having a carboxylic acid value (AV) of 22 eq / ton was obtained by setting the solid phase polymerization time of the polyester film to 25 hours. In Example 6, a support having a carboxylic acid value (AV) of 24 eq / ton was obtained. Moreover, in Example 7, it produced similarly to Example 3 except having used AS-563A (acrylic resin) by Daicel FineChem.

(Comparative Examples 1 and 2)
In Comparative Examples 1 and 2, the first adhesive layer was formed by an off-line coating method to obtain a laminated film. The configuration of each layer was as shown in Table 1.

(Comparative Example 3)
In Comparative Example 3, the first adhesive layer was formed by in-line coating, and the adhesive layer was formed so that the total thickness of the first adhesive layer and the second adhesive layer was 7 μm.

(Comparative Example 4)
In Comparative Example 4, it was produced in the same manner as in Example 3 except that 11% by mass of Type CR-95 manufactured by Ishihara Sangyo Co., Ltd. was used as the inorganic particles (color pigment).

(Evaluation method)
<Adhesion>
Two sample films (MD 20 cm, TD 3 cm) of laminated films obtained as examples and comparative examples were prepared, and EVA films having a thickness of 2 mm, a width of 3 cm, and a length of 10 cm were sandwiched on the adhesive layer application side of each film. At this time, a polyester film was prepared, and an EVA film was placed on one end of both films. That is, the polyester film protrudes from the EVA film by 10 cm on the same side.
The EVA film was heat-treated at 140 ° C. for 5 minutes while applying a pressure of 1 atm of both polyester films, and then allowed to stand at room temperature for one day. Then, the polyester film at both ends was put on a tensile tester, both ends were pulled in the direction of 180 degrees at 30 mm / min, the maximum stress was measured, and it was corrected per unit width (divided by 30 because the sample was 3 cm, to the force per 1 mm Conversion is shown in Table 1.

<Reworkability>
Operation (rework) which peels a back sheet from a solar cell from a solar cell module was performed. When peeling the backsheet from the solar cell, heat was applied from the backsheet side so that the heating temperature was 150 ° C. Thereafter, an operation of peeling by hand was performed. Along with peeling, the adhesive and colored adhesive layer left on the module are considered as defective peels, and the number of those expressed as a percentage is taken as the "peeling defective rate" and evaluated according to the following evaluation criteria. It was. Here, A to C are practical levels.
A: Peeling failure rate is 0%, or peeling resistance is very light B: Peeling failure rate is 0-20%, or peeling resistance is light C: Peeling failure rate is 20-40%, or peeling resistance is slightly light D: Peeling failure rate is 40 to 60% or peeling resistance is slightly heavy E: Peeling failure rate exceeds 60% or peeling resistance is heavy

In Examples 1 to 7, the ratio of the film thickness of the first adhesive layer (total film thickness of the adhesive layer) is in the range of 0.1 to 20%, and the first adhesive layer and the second adhesive Since the total film thickness of the layers is within a predetermined range, it can be seen that excellent reworkability is exhibited in addition to good adhesion. Among them, in Examples 1 to 4, the support has a carboxylic acid value (AV) of 22 eq / ton or less, uses polyolefin as a binder for the first adhesive layer and the second adhesive layer, and contains a coloring pigment. Therefore, it can be seen that better reworkability is obtained.
On the other hand, in Comparative Examples 1 and 2, since the first adhesive layer is formed by the off-line coating method, the ratio of the thickness of the first adhesive layer (total film thickness of the adhesive layer) exceeds 20% by mass. The adhesion is remarkably deteriorated. Moreover, in the comparative example 3, it turns out that the total film thickness of a support 1st contact bonding layer and a 2nd contact bonding layer exceeds 3 micrometers, and rework property is inferior. In the comparative example 4, it turns out that the 2nd contact bonding layer contains an inorganic particle (coloring pigment), and rework property is inferior.

  A laminated film having both adhesion and reworkability can be obtained. For this reason, the laminated | multilayer film of this invention can be used as a solar cell module backsheet, and its industrial applicability is high.

2 Support 4 First adhesive layer 6 Third adhesive layer 10 Laminated film

Claims (8)

A support, a first adhesive layer laminated on at least one surface of the support, and a second adhesive layer laminated on the opposite side of the support via the first adhesive layer. Have
Each of the first adhesive layer and the second adhesive layer contains a binder and a crosslinking agent, and the total average film thickness of the first adhesive layer and the second adhesive layer is 0.05 to 3 μm. And
The ratio of the average film thickness of the first adhesive layer to the total average film thickness of the first adhesive layer and the second adhesive layer is 0.1 to 20%,
The laminated film, wherein the first adhesive layer and the second adhesive layer are colorless and transparent. The laminated film according to claim 1, wherein the first adhesive layer is a stretched thin film layer .   The laminated film according to claim 1 or 2, wherein the binder is a polyolefin.   The laminated film according to any one of claims 1 to 3, wherein the crosslinking agent is an oxazoline-based crosslinking agent.   The laminated film according to any one of claims 1 to 4, wherein the support is a polyester film, and an average carboxylic acid value (AV) of the polyester film is 22 eq / ton or less. Applying a first adhesive layer-forming coating solution containing a binder and a crosslinking agent to at least one surface of the support and stretching to form a first adhesive layer;
Applying a second adhesive layer forming coating solution containing a binder and a crosslinking agent on the first adhesive layer, and forming a second adhesive layer,
The first sum of the average thickness of the the adhesive layer second adhesive layer, Ri 0.05~3μm der,
The method for producing a laminated film, wherein the first adhesive layer and the second adhesive layer are colorless and transparent layers .   The solar cell backsheet using the laminated film of any one of Claims 1-5. The module for solar cells using the solar cell backsheet of Claim 7 .

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