JP2014200944A - Laminate film, backsheet for solar cell module and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate film having both light resistance and weather resistance which is used for a backsheet for a solar cell module and has excellent surface properties.SOLUTION: There is provided a laminate film 10 which comprises: a polyester support 2; a first polymer layer 4 laminated on at least one surface of the polyester support; and a second polymer layer 6 laminated on an opposite side to the polyester support through the first polymer layer. The first polymer layer 4 contains an ultraviolet absorber and an acrylic resin. The second polymer layer 6 contains at least one of a silicone-based resin and a fluorine-based resin. The laminate film has an optical density at 350 nm of 2.0 or more. The ultraviolet absorber is inorganic particles and is contained by 20 to 70 mass% with respect to the acrylic acid. The first polymer layer and the second polymer layer contain a crosslinking agent and are formed by coating.

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 weather resistance and light resistance, and also has excellent surface properties.

  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 is incident. 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.

  Conventionally, glass, fluorine resin, or the like has been used for the back sheet for the solar cell module, but in recent years, polyester is often applied from the viewpoint of cost reduction and the like. As a back sheet for a solar cell module using polyester, a sheet formed by a method in which polyethylene terephthalate (PET) is used as a support and another polymer sheet is bonded thereto is used.

The back sheet for solar cell modules is assumed to be placed in a harsh environment for a long period of time, such as being exposed to outdoor wind and rain or direct sunlight. It is demanded to have sex. However, there is a problem that the strength of the polyester film decreases when it is wet with heat for a long time, and the back sheet for a solar cell module having such a polyester film as a support sufficiently exhibits its function for a long time. Therefore, further improvements were required.

  In order to solve such a problem, a polymer layer containing an ultraviolet absorber is laminated on a polyester film (for example, Patent Documents 1 and 2). Patent Document 1 discloses a laminated film in which an acrylic resin layer containing an ultraviolet absorber is laminated on a polyester film. Patent Document 2 discloses a laminated film in which a silicone resin layer, a polyester resin layer, or a polyurethane resin layer containing an ultraviolet absorber is laminated on a polyester film.

JP 2010-92958 A JP 2012-69769 A

As described above, weather resistance and light resistance can be enhanced to some extent by laminating a polymer layer containing an ultraviolet absorber on a polyester film.
However, when the laminated film of Patent Document 1 is used as a back sheet for a solar cell module, the weather resistance of the acrylic layer is insufficient, and the examination by the present inventors reveals that the adhesiveness after aging is lowered. became.
Further, in the laminated film of Patent Document 2, the surface property of the polymer layer is not always good, and the adhesiveness after wet heat aging may be inferior, so further improvement has been demanded.
That is, the conventional back sheet for a solar cell module has been required to have both light resistance and weather resistance in addition to having excellent surface properties.

  Therefore, in order to solve the problems of the prior art, the present inventors aim to provide a laminated film having excellent surface properties and having both light resistance and weather resistance. We proceeded with examination.

As a result of earnest studies to solve the above problems, the present inventors have found that the polyester support, the first polymer layer laminated on at least one surface of the polyester support, and the first polymer layer In the laminated film having the second polymer layer laminated on the side opposite to the polyester support through the first polymer layer, the type of the binder contained in the first polymer layer and the second polymer layer is specified, and the first polymer It has been found that by adjusting the optical density of the layer to a certain value or more, both the weather resistance and light resistance of the laminated film can be improved. Furthermore, the present inventors have found that the surface properties of the polymer layer are improved by adopting the above configuration, and have completed the present invention.
Specifically, the present invention has the following configuration.

[1] A polyester support, a first polymer layer laminated on at least one surface of the polyester support, and a first polymer layer laminated on the opposite side of the polyester support via the first polymer layer. The first polymer layer includes an ultraviolet absorber and an acrylic resin, and the second polymer layer includes at least one of a silicone resin and a fluorine resin, The laminated film, wherein the optical density at 350 nm of one polymer layer is 2.0 or more.
[2] The laminated film according to [1], wherein the acrylic resin contained in the first polymer layer has an elastic modulus of 5 × 10 ⁻⁹ Pa or less.
[3] The ultraviolet absorber contained in the first polymer layer is inorganic particles, and the content of the inorganic particles is 20 to 70% by mass with respect to the acrylic resin. The laminated film according to [1] or [2].
[4] The silicone-based resin contained in the second polymer layer contains 15 to 85% by mass of a — (Si (R ¹ ) (R ² ) —O) _n — moiety in the molecule, and is copolymerized therewith. The laminated film according to any one of [1] to [3], which is a composite polymer containing 15 to 85% by mass of a polymer structure portion to be formed.
(However, R ¹ and R ² each independently represents a monovalent organic group that can be covalently bonded to a hydrogen atom, a halogen atom, or a Si atom, and R ¹ and R ² may be the same or different.)
[5] The laminated film according to any one of [1] to [4], wherein the first polymer layer and the second polymer layer further contain a crosslinking agent.
[6] The laminated film according to [5], wherein the crosslinking agent is an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent.
[7] The laminated film according to any one of [1] to [6], wherein the first polymer layer and the second polymer layer are formed by coating.
[8] The laminated film according to any one of [1] to [7], wherein an average film thickness of the first polymer layer is 0.3 to 18 μm.
[9] The laminated film according to any one of [1] to [8], wherein surface treatment is performed on at least one surface of the polyester support.
[10] A solar cell module backsheet using the laminated film according to any one of [1] to [9].
[11] A solar cell module using the back sheet for a solar cell module according to [10].

  According to the present invention, a laminated film having excellent surface properties and having both weather resistance and light resistance can be obtained. For this reason, the laminated | multilayer film of this invention are preferably used for the back sheet | seat for solar cell modules used in severe environments, such as outdoors.

FIG. 1 is a schematic cross-sectional view 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.

(1. Laminated film)
The present invention relates to a laminated film having a polyester support, a first polymer layer, and a second polymer layer. The first polymer layer is laminated on at least one surface of the polyester support, and the second polymer layer is laminated on the opposite side of the polyester support via the first polymer layer. In the present invention, other layers may be provided between the polyester support, the first polymer layer, and the second polymer layer, but the polyester support, the first polymer layer, and the second polymer layer are It is preferable to laminate adjacently in this order.

  The first polymer layer includes an ultraviolet absorber and an acrylic resin, and the second polymer layer includes at least one of a silicone resin and a fluorine resin. The optical density at 350 nm of the first polymer layer is 2.0 or more. The optical density at 350 nm of the first polymer layer may be 2.0 or more, preferably 2.5 or more, and more preferably 3.0 or more.

The elastic modulus of the acrylic resin contained in the first polymer layer is preferably 5 × 10 ⁻⁹ Pa or less, more preferably 4 × 10 ⁻⁹ Pa or less, and 3 × 10 ⁻⁹ Pa or less. More preferably. By setting the elastic modulus of the acrylic resin contained in the first polymer layer within the above range, the flexibility of the first polymer layer can be increased, and the adhesion between the polyester support and the first polymer layer can be improved. Can be increased. In addition, the adhesion between the first polymer layer and the second polymer layer can be enhanced. Furthermore, by setting the elastic modulus of the acrylic resin contained in the first polymer layer within the above range, the surface properties of the first polymer layer and the second polymer layer can be improved.

By setting the laminated film as described above, the laminated film of the present invention can have both weather resistance and light resistance. Furthermore, the surface properties of the first polymer layer and the second polymer layer can be made in a better state.
For this reason, in the laminated film of the present invention, even when it is exposed to a harsh environment such as outdoors for a long time, the laminated film itself does not become brittle, and the strength of the laminated film can be maintained. it can. Moreover, since the laminated film of this invention is excellent in the adhesiveness between layers, generation | occurrence | production of defects, such as delamination, is few, and it can exhibit the outstanding function as a solar cell module backsheet.

(2. Polyester support)
The laminated film of the present invention includes a polyester support. The polyester support is preferably a polyester film, and the polyester film is excellent in terms of cost and mechanical strength, and is preferably used as a support for a laminated 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 the linear saturated polyester include polyethylene terephthalate (PET), polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), and polyethylene-2,6-naphthalate. Among these, polyethylene terephthalate or polyethylene-2,6-naphthalate 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 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 still 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 adhesion between the layers of the laminated film can be enhanced.
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.

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.

  When the polyester is polymerized, from the viewpoint of keeping the carboxyl group content below a predetermined range, Sb-based, Ge-based, and Ti-based compounds are preferably used as the catalyst, and among these, 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 so that the Ti element-converted value is in the range of 1 to 30 ppm, more preferably 3 to 15 ppm is preferable. When the amount of Ti compound used is within the above range in terms of Ti element, the terminal carboxyl group can be adjusted to the following range, and the hydrolysis resistance of the polyester support can be kept low.

  For the synthesis of polyester using a Ti-based compound, for example, Japanese Patent Publication No. 8-301198, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 397756, Japanese Patent No. 39622626, Japanese Patent No. 39786666 No. 3, Patent No. 3,996,871, Patent No. 4000086, Patent No. 4053837, Patent No. 4,127,119, Patent No. 4,134,710, Patent No. 4,159,154, Patent No. 4,269,704, Patent No. 4,313,538 and the like can be applied.

  The 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 thickness of the polyester support is preferably 25 to 300 μm. If the thickness is 25 μm or more, the mechanical strength is good, and if it is 300 μm or less, it is advantageous in terms of cost. In particular, the polyester support tends to be difficult to withstand long-term use because its hydrolysis resistance deteriorates as the thickness increases.
Especially, the thickness of a polyester support body is 120-300 micrometers, and the case where the carboxylic acid value in polyester is 22 eq / ton or less is preferable at the point from which the improvement effect of wet heat durability is show | played more.

  The support of the present invention is preferably subjected to a surface treatment before the first polymer layer described later is applied. Examples of the surface treatment include corona treatment, flame treatment, low pressure plasma treatment, atmospheric pressure plasma treatment, UV treatment, sand blast treatment, and chromium mixed acid treatment. In addition, as the flame treatment, a method of adding a silane compound described in Japanese Patent No. 3893394 and Japanese Patent Application Laid-Open No. 2007-39508 can also be used. Among these, corona treatment, flame treatment, atmospheric pressure plasma treatment, and UV treatment are preferable from the viewpoint of simplicity and environmental load. By applying these surface treatments, repellency when the first polymer layer is applied can be prevented, and adhesion when exposed to a wet heat environment can be further enhanced.

(3. First polymer layer)
(3-1. Acrylic resin)
The first polymer layer includes an acrylic resin. The acrylic resin that can be used in the present invention is a polymerized acrylic monomer such as methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxymethyl acrylate, hydroxyethyl acrylate, and glycidyl methyl acrylate. It is a polymer that is copolymerized with a carboxylic acid such as acrylic acid, methacrylic acid, itaconic acid or a monomer copolymerizable with an acrylic monomer such as styrene, acrylonitrile, vinyl acetate, acrylamide, divinylbenzene, etc. Also good. The average molecular weight of the acrylic resin of the present invention is preferably about 2000 to 200000, more preferably about 5000 to 150,000.

The elastic modulus of the acrylic resin is preferably 5 × 10 ⁻⁹ Pa or less, more preferably 4 × 10 ⁻⁹ Pa or less, and 3 × 10 ⁻⁹ Pa or less in order to develop sufficient adhesiveness. Further preferred. Examples of such acrylic resins include Bonlon XPS-001 and Bonlon XPS-002 (both manufactured by Mitsui Chemicals, Inc.).
The acrylic resin used in the present invention may be soluble in an organic solvent or in the form of a latex in which a water-insoluble polymer is dispersed in water. However, the latex form is preferred from the viewpoint of reducing the environmental burden during production. In this case, the polymer is preferably copolymerized with a carboxylic acid such as acrylic acid, methacrylic acid or itaconic acid.

  The content of the acrylic resin is preferably 40 to 95% by mass, and more preferably 60 to 90% by mass with respect to the total mass of the binder resin contained in the first polymer layer. When the acrylic resin content is 40% by mass or more, sufficient layer strength is obtained, and when it is 95% by mass or less, an ultraviolet absorber can be sufficiently added, which is advantageous in terms of light resistance.

(3-2. UV absorber)
The first polymer layer includes an ultraviolet absorber. As the ultraviolet absorber that can be used in the present invention, organic and inorganic ultraviolet absorbers can be used.
Examples of the ultraviolet absorber include, as organic ultraviolet absorbers, salicylic acid-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based, triazine-based ultraviolet absorbers, hindered amine-based ultraviolet stabilizers, and the like. Specifically, for example, pt-butylphenyl salicylate, p-octylphenyl salicylate and the like can be cited as salicylic acid-based ultraviolet absorbers.
2,4-Dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone as benzophenone-based UV absorbers , Bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane and the like.
As a benzotriazole-based ultraviolet absorber, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2,2′-methylenebis [ 4- (1,1,3,3-tetramethylbutyl) -6- (2Hbenzotriazol-2-yl) phenol] and the like.
Examples of cyanoacrylate ultraviolet absorbers include ethyl-2-cyano-3,3′-diphenylacrylate).
Examples of the triazine-based ultraviolet absorber include 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol.
As hindered amine UV stabilizers, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6, Examples include 6-tetramethylpiperidine polycondensate.
In addition, nickel bis (octylphenyl) sulfide, 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate, and the like can be given.
Moreover, as an inorganic type ultraviolet absorber, inorganic particles, such as titanium dioxide and a cerium oxide, can be mentioned, for example.
From the viewpoint of durability, an inorganic ultraviolet absorber is preferable, and titanium dioxide is particularly preferably used.

In order to impart light resistance to the first polymer layer of the present invention, it is necessary that the optical density at a wavelength of 350 nm be 2.0 or more by adding the above-described ultraviolet absorber. Here, the optical density can be determined by the following method.
First, for the sample of the entire laminated film (sample with the first polymer layer and the second polymer layer), the optical density obtained by the following formula is calculated, and this is defined as optical density 1. Next, the optical density obtained by the following formula is calculated for the sample from which the first polymer layer and the second polymer layer are peeled from the laminated film, and this is defined as optical density 2.
Optical density = Log {(Intensity of 350 nm light incident on the laminated film from the second polymer layer side) / (Intensity of 350 nm light transmitted to the opposite side of the second polymer layer)}
From the optical density 1 and the optical density 2 calculated as described above, the optical density of the first polymer layer is calculated by the following equation.
Optical density of first polymer layer = optical density 1−optical density 2
Here, the second polymer layer does not affect the optical density.

  The optical density of the first polymer layer of the present invention needs to be 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more. By setting the optical density to 2.0, preferably 2.5, and more preferably 3.0 or more, there is no problem of coloring or strength reduction even when the back sheet is used outdoors for a long period of time.

  It is preferable that the content rate of the ultraviolet absorber contained in a 1st polymer layer is 20-70 mass% with respect to acrylic resin. The content of the ultraviolet absorber is preferably 20% by mass or more, more preferably 25% by mass or more, and further preferably 30% by mass or more. Moreover, it is preferable that the content rate of a ultraviolet absorber is 70 mass% or less, It is more preferable that it is 65 mass% or less, It is further more preferable that it is 60 mass% or less. By setting the content of the ultraviolet absorber in the first polymer layer within the above range, the optical density of the first polymer layer can be within a desired range.

(3-3. Other ingredients)
The first polymer layer may contain other components in addition to those described above. Examples of other components include a crosslinking agent, a surfactant, and a filler. Especially, it is preferable that a 1st polymer layer contains a crosslinking agent.
Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. In these, it is preferable that it is at least 1 or more types of crosslinking agents chosen from a carbodiimide type crosslinking agent and an oxazoline type crosslinking agent, and it is especially preferable that it is an oxazoline type crosslinking agent.
The addition rate of the crosslinking agent is preferably 0.5 to 30% by mass, more preferably 3% by mass or more and less than 15% by mass with respect to the acrylic resin contained in the first polymer layer. When the addition amount of the crosslinking agent is 0.5% by mass or more, a sufficient crosslinking effect is obtained while maintaining the strength and adhesiveness of the first polymer layer, and when it is 30% by mass or less, Long pot life.

As the surfactant, a known surfactant such as an anionic or nonionic surfactant can be used. 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 form a favorable layer while suppressing the occurrence of repelling, and when it is 10 mg / m ² or less, the adhesion to the polyester support is good. Can be done.

  A filler may be further added to the first polymer layer of the present invention. A known filler such as colloidal silica can be used as the filler. The addition amount of the filler is preferably 20% by mass or less, more preferably 15% by mass or less with respect to the binder of the first polymer layer. When the addition amount of the filler is 20% by mass or less, the planar shape of the polymer layer can be kept better.

  The thickness of the first polymer layer of the present invention is preferably from 0.3 μm to 18 μm, more preferably from 0.8 μm to 10 μm, and even more preferably from 1.0 μm to 8 μm. When the thickness of the first polymer layer is 0.3 μm or more, it is difficult for moisture to penetrate from the surface of the polymer layer to the inside when exposed to a humid heat environment, and moisture hardly reaches the interface with the support. As a result, the adhesion is remarkably improved. Further, when the thickness of the first polymer layer is 18 μm or less, the internal stress during coating and drying of the first polymer layer itself can be kept small, and good adhesiveness can be obtained.

(4. Second polymer layer)
The second polymer layer contains at least one of a silicone resin and a fluorine resin. The second polymer layer may include either one of a silicone-based resin or a fluorine-based resin, or may include both.

(4-1. Silicone resin)
The silicone-based resin that can be used in the present invention is a polymer having a (poly) siloxane structure represented by the following general formula (1) in the molecular chain.

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

The “monovalent organic group” represented by R ¹ and R ² is a group that can be covalently bonded to the Si atom, and may be unsubstituted or may have a substituent. Specific examples of monovalent organic groups include alkyl groups (eg, methyl group, ethyl group, etc.), aryl groups (eg: phenyl group, etc.), aralkyl groups (eg: benzyl group, phenylethyl, etc.), alkoxy groups (eg, : Methoxy group, ethoxy group, propoxy group, etc.), aryloxy group (eg, phenoxy group etc.), mercapto group, amino group (eg: amino group, diethylamino group etc.), amide group and the like.
Among the above, R ¹ and R ² are each independently a hydrogen atom, a chlorine atom, a bromine atom, an unsubstituted or substituted alkyl group having 1 to 4 carbon atoms (particularly a methyl group or an ethyl group), or unsubstituted. Or a substituted phenyl group, an unsubstituted or substituted alkoxy group, a mercapto group, an unsubstituted amino group or an amide group is preferred.
Moreover, n is preferably 1 to 50000, and more preferably 1 to 10000.

The ratio of the portion of “— (Si (R ¹ ) (R ² ) —O) _n —” ((poly) siloxane structural unit represented by the general formula (1)) in the silicone resin is the same as that of the silicone resin. It is preferable that it is 15-95 mass% with respect to the total mass, and it is more preferable that it is 25-85 mass%. When the ratio of the (poly) siloxane structural unit is 15% by mass or more, sufficient durability is obtained, and when it is 95% by mass or less, the coating liquid is used when the silicone-containing resin polymer layer is formed by coating. It can be kept stable.

Portions other than “— (Si (R ¹ ) (R ² ) —O) _n —” in the silicone resin can be formed of an acrylic polymer, a polyester polymer, or the like, which is “— (Si (R ^1)”. ) (R ² ) —O) _n — ”. The portion other than “— (Si (R ¹ ) (R ² ) —O) _n —” is preferably an acrylic polymer among the polymers. As the composition and molecular weight of the acrylic polymer, those described for the acrylic resin described above can be used.

(4-2. Fluorine resin)
The fluororesin that can be used in the present invention is not particularly limited as long as it is a polymer having a repeating unit represented by-(CFX ¹ -CX ² X ³ )-(however, X ¹ , X ² and X ³ are hydrogen atoms). , A fluorine atom, a chlorine atom, or a perfluoroalkyl group having 1 to 3 carbon atoms). Specific examples of the polymer include polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), polyvinyl fluoride (hereinafter sometimes referred to as PVF), and polyvinylidene fluoride (hereinafter referred to as PVDF). ), Polychlorotrifluoroethylene (hereinafter sometimes referred to as PCTFE), polytetrafluoropropylene (hereinafter sometimes referred to as HFP), and the like.

The fluorine resin may be a polymer obtained by copolymerizing a fluorine monomer represented by-(CFX ¹ -CX ² X ³ )-and other monomers. Examples of these are copolymers of tetrafluoroethylene and ethylene (abbreviated as P (TFE / E)), copolymers of tetrafluoroethylene and propylene (abbreviated as P (TFE / P)), tetrafluoroethylene and vinyl ether. Copolymer (abbreviated as P (TFE / VE)), copolymer of tetrafluoroethylene and perfluorovinyl ether (abbreviated as P (TFE / FVE)), copolymer of chlorotrifluoroethylene and vinyl ether (P (CTFE) / VE)), a copolymer of chlorotrifluoroethylene and perfluorovinyl ether (abbreviated as P (CTFE / FVE)), and the like.
These fluorine-based polymers may be used by dissolving the polymer in an organic solvent, or may be in the form of a latex in which polymer fine particles are dispersed in water.

(4-3. Other components)
The second polymer layer may contain other components in addition to those described above. Examples of other components include a crosslinking agent, a surfactant, and a filler. Especially, it is preferable that a 2nd polymer layer contains a crosslinking agent.
As the crosslinking agent and other additives, those described for the first polymer layer can be used. Further, the addition rate of each additive is the same as that of the first polymer layer.

A lubricant may be added to the second polymer layer of the present invention. Preferred lubricants include synthetic wax compounds, natural wax compounds, surfactants and the like. Specific examples of preferred lubricants include polyethylene wax, polypropylene wax, esters or amides such as stearic acid and oleic acid, carnauba wax, candelilla wax, paraffin wax, microcrystalline wax, and other petroleum waxes, montan wax, and the like. be able to.
Organic lubricant is preferably contained in the range of 0.2~500mg / m ^2. When the content ratio of the organic lubricant is 0.2 mg / m ² or more, the scratch resistance is sufficiently improved by the effect of reducing the dynamic friction coefficient by containing the organic lubricant. In addition, when the content ratio of the organic lubricant is 500 mg / m ² or less, when the second polymer layer disposed in the outermost layer of the laminated film is applied and formed, coating unevenness and aggregates are less likely to occur. It is difficult for repellency failures to occur.

  The thickness of the second polymer layer of the present invention is preferably from 0.5 to 10 μm, more preferably from 0.8 to 8 μm, particularly preferably from 1.0 to 5 μm. When the thickness of the second polymer layer is 0.5 μm or more, deterioration of the first polymer layer can be suppressed when exposed to a humid heat environment. Further, when the thickness of the second polymer layer is 10 μm or less, the internal stress during coating and drying of the second polymer layer itself can be kept small, and good adhesiveness can be obtained.

(5. Manufacturing method of laminated film)
The method for producing a laminated film of the present invention comprises a step of forming a first polymer layer on at least one surface of a polyester support, and a second polymer layer on the opposite side of the support via the first polymer layer. Forming a step. In addition, before the step of forming the first polymer layer on the polyester support, there is a step of subjecting the surface of the polyester support to the surface on the side where the first polymer layer is to be formed. It is preferable to be provided.

(5-1. Method for forming polyester support)
The polyester support used in the present invention can be formed by a known method. For example, the polyester support can be obtained by melt-extruding polyester into a film and then cooling and solidifying it with a casting drum to form an unstretched film, and stretching the unstretched film. The polyester support is preferably a biaxially stretched film, and the magnification is 1 to 2 times or more in the longitudinal direction at Tg to (Tg + 60) ° C. (when it is 2 times or more, the total magnification) is 3 to 6 times. It is preferable that the film is stretched and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C. Furthermore, you may heat-process for 1 to 60 second at 180-230 degreeC as needed.

(5-2. Method for Forming First Polymer Layer)
The polymer layer of the present invention can be formed by a known method such as coating or pasting. Among these, it is preferable to form a polymer layer on the support by coating.
As a coating method, for example, a known coating method such as a gravure coater or a bar coater can be used.
The coating solution may be an aqueous system using water as an application solvent, or a solvent system using an organic solvent such as toluene or methyl ethyl ketone. Among these, from the viewpoint of environmental burden, it is preferable to use water as a solvent. One type of coating solvent may be used alone, or a water-miscible organic solvent may be mixed with water. Examples of preferable coating solvents include water, water / ethyl alcohol = 95/5 (mass ratio), water / methyl cellosolve = 97/3 (mass ratio), and the like.
When the polyester support is a biaxially stretched film, the first polymer is applied by applying a coating solution for forming an acrylic resin layer on the polyester support after biaxial stretching, and drying the coating film. A layer may be formed, or may be formed by applying a coating solution to a polyester support after uniaxial stretching and drying the coating film, and then stretching in a direction different from the initial stretching. Furthermore, you may extend | stretch to 2 directions, after apply | coating a coating liquid to the polyester support body before extending | stretching and drying a coating film.

(5-3. Method for Forming Second Polymer Layer)
Although the 2nd polymer layer of this invention can be formed by well-known methods, such as application | coating and bonding, the method by application | coating is preferable.
As a coating method, for example, a known coating method such as a gravure coater or a bar coater can be used. As the coating method and the coating solution, those described above can be used.

(5-4. Surface treatment)
Before the step of forming the polymer layer on the support, it is preferable to provide a surface treatment step. As the surface treatment, corona treatment, ultraviolet treatment (UV treatment), flame treatment, low pressure plasma treatment, There are atmospheric pressure plasma treatment, sandblast treatment, chromium mixed acid treatment and the like. As the flame treatment, a method of adding a silane compound described in Japanese Patent No. 3893394 and Japanese Patent Application Laid-Open No. 2007-39508 can also be used. Among these, corona treatment, flame treatment, atmospheric pressure plasma treatment, and ultraviolet treatment (UV treatment) are preferable from the viewpoint of simplicity and environmental load.

(6. 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 is excellent in weather resistance and light resistance, it is preferably used as a back sheet for a solar cell module used in a humid heat environment such as outdoors. Moreover, since the adhesiveness between laminated films is high, delamination or the like does not occur even when used over a long period of time.

  The second polymer 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 polyester support opposite to the surface on which the first polymer 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 polymer 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), thickeners (eg: sodium polyacrylate, methylcellulose, etc.), film-forming aids (eg: butyl carbitol acetate, etc.), etc. May be.

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.

(7. 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, a higher light transmittance is preferable, and as such a substrate, for example, a transparent resin such as a glass substrate or an acrylic resin 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.

  Part of the binder contained in the second polyester in the laminated film of the present invention was synthesized by the following method.

(Synthesis Example 1) Synthesis of Silicone Acrylic Water Dispersion B-12 In a reaction vessel equipped with a stirrer and a dropping funnel and purged with nitrogen gas, 81 parts of propylene glycol mono-n-propyl ether (PNP), isopropyl alcohol (IPA) 360 parts, 110 parts of phenyltrimethoxysilane (PTMS) and 71 parts of dimethyldimethoxysilane (DMDMS) were charged, and the temperature was raised to 80 ° C. with stirring in a nitrogen gas atmosphere.
Next, 260 parts of methyl methacrylate (MMA), 200 parts of n-butyl methacrylate (BMA), 110 parts of n-butyl acrylate (BA), 30 parts of acrylic acid (AA), 3-methacryloyl at the same temperature in the reaction vessel. A mixture consisting of 19 parts of oxypropyltrimethoxysilane (MPTMS), 31.5 parts of tert-butylperoxy-2-ethylhexanoate (TBPO), and 31.5 parts of PNP part was added dropwise over 4 hours. Thereafter, the mixture was heated and stirred at the same temperature for 2.5 hours to obtain an acrylic polymer solution having a weight average molecular weight of 29,300 and containing a carboxyl group and a hydrolyzable silyl group.
Next, 54.8 parts of deionized water was added thereto, and heating and stirring were continued for 16 hours to hydrolyze the alkoxysilane and further condense with an acrylic polymer, so that the non-volatile content (NV) = 56.3 mass%. A solution of a composite polymer having a site derived from a carboxyl group-containing acrylic polymer and a polysiloxane site, with a solution acid value = 22.3 mgKOH / g, was obtained.
Next, 42 parts of triethylamine was added to this solution with stirring at the same temperature, and stirring was performed for 10 minutes. Thereby, 100% of the contained carboxyl groups were neutralized.
Thereafter, 1250.0 parts of deionized water was added dropwise at the same temperature for 1.5 hours for phase inversion emulsification, and then the temperature was raised to 50 ° C. and stirring was performed for 30 minutes. Next, a part of water was removed under reduced pressure together with the organic solvent over 3.5 hours at an internal temperature of 40 ° C. In this manner, an aqueous dispersion B-12 of a composite polymer containing a part derived from a carboxyl group-containing acrylic polymer and a polysiloxane part having a solid content concentration of 42% by mass and an average particle diameter of 110 nm was obtained. Aqueous dispersion B-12 has about 25% polysiloxane sites.

(Synthesis Example 2) Synthesis of Silicone Acrylic Water Dispersion B-13 In the synthesis of Composite Polymer Aqueous Dispersion B-12, a composite polymer was prepared in the same manner as in Synthesis Example 1 except that the amount of monomer used was changed to the following amount. An aqueous dispersion B-13 was synthesized.
The proportions of the monomers used are as follows: phenyltrimethoxysilane (PTMS): 210 parts, dimethyldimethoxysilane (DMDMS): 166 parts, 3-methacryloyloxypropyltrimethoxysilane (MPTMS): 24 parts, methyl methacrylate (MMA): 200 parts , N-butyl methacrylate (BMA): 100 parts, n-butyl acrylate (BA) 70 parts, acrylic acid (AA) 30 parts. Aqueous dispersion B-13 has about 50% polysiloxane sites.

(Synthesis Example 3) Synthesis of Silicone Acrylic Water Dispersion B-14 In the synthesis of Composite Polymer Water Dispersion B-12, a composite polymer was prepared in the same manner as in Synthesis Example 1 except that the amount of monomer used was changed to the following amount. An aqueous dispersion B-14 was synthesized.
The ratio of the monomers used is as follows: phenyltrimethoxysilane (PTMS): 320 parts, dimethyldimethoxysilane (DMDMS): 244 parts, 3-methacryloyloxypropyltrimethoxysilane (MPTMS): 36 parts, methyl methacrylate (MMA): 90 parts N-butyl methacrylate (BMA): 60 parts, n-butyl acrylate (BA): 20 parts, and acrylic acid (AA): 30 parts. Aqueous dispersion B-14 has about 75% polysiloxane sites.

(Synthesis Example 4) Synthesis of Silicone Acrylic Water Dispersion B-15 In the synthesis of Composite Polymer Aqueous Dispersion B-12, a composite polymer was prepared in the same manner as in Synthesis Example 1 except that the amount of monomer used was changed to the following amount. An aqueous dispersion B-15 was synthesized.
The ratio of the monomers used was 60 parts phenyltrimethoxysilane (PTMS), 25 parts dimethyldimethoxysilane (DMDMS), 15 parts 3-methacryloyloxypropyltrimethoxysilane (MPTMS), 300 parts methyl methacrylate (MMA), n-butyl. Methacrylate (BMA) 220 parts, n-butyl acrylate (BA) 150 parts, acrylic acid (AA) 30 parts. Aqueous dispersion B-15 has about 87% polysiloxane sites.

Example 1
<Preparation of laminated film>
-Synthesis of polyester support-
A slurry of 100 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) and 45 kg of ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) is charged with about 123 kg of bis (hydroxyethyl) terephthalate in advance, at a temperature of 250 ° C. and a pressure of 1.2 The esterification reaction tank maintained at × 10 ⁵ Pa was sequentially supplied over 4 hours, and the esterification reaction was further performed over 1 hour after the completion of the supply. Thereafter, 123 kg of the obtained esterification reaction product was transferred to a polycondensation reaction tank.
Subsequently, 0.3% by mass of ethylene glycol was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, based on the resulting polymer. After stirring for 5 minutes after the addition, an ethylene glycol solution of cobalt acetate and manganese acetate was added to the obtained polymer so that the cobalt element conversion value was 30 ppm and the manganese element conversion value was 15 ppm. After further stirring for 5 minutes, a 2% by mass ethylene glycol solution of a titanium alkoxide compound was added to the obtained polymer so that the titanium element equivalent value was 5 ppm. As the titanium alkoxide compound, the titanium alkoxide compound synthesized in Example 1 described in paragraph No. [0083] of JP-A-2005-340616 was used (Ti content = 4.44 mass%). Five minutes later, a 10% by mass ethylene glycol solution of ethyl diethylphosphonoacetate was added so as to be 5 ppm with respect to the resulting polymer.
Thereafter, while stirring the low polymer at 30 rpm, the reaction system was gradually heated from 250 ° C. to 285 ° C. and the pressure was reduced to 40 Pa. The time to reach the final temperature and final pressure was both 60 minutes. The reaction was continued for 3 hours, and then the reaction system was purged with nitrogen, returned to normal pressure, and the polycondensation reaction was stopped. Then, the obtained polymer melt was discharged into cold water in a strand shape and immediately cut to obtain polyethylene terephthalate (PET) pellets (diameter: about 3 mm, length: about 7 mm).

-Solid state polymerization-
The pellets obtained above were held in a vacuum vessel maintained at 40 Pa at a temperature of 220 ° C. for 30 hours for solid phase polymerization.

-Production of support-
The pellets after undergoing solid phase polymerization as described above were melted at 285 ° C. and cast on a metal drum to prepare an unstretched base having a thickness of about 2.5 mm. Thereafter, the film was stretched 3 times in the longitudinal direction at 90 ° C., and further stretched 3.3 times in the transverse direction at 120 ° C. Thus, a biaxially stretched polyethylene terephthalate base material (polyester support; P-1) having a thickness of 250 μm was obtained.

-Preparation of pigment dispersion-
Each component in the following composition was mixed, and the mixture was subjected to a dispersion treatment with a dynomill type dispersing machine for 1 hour to prepare a titanium dioxide dispersion as a pigment dispersion.
<Composition of titanium dioxide dispersion>
・ Titanium dioxide (volume average particle size = 0.42 μm) 40% by mass
(Taipeke R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content: 100% by mass)
・ Polyvinyl alcohol aqueous solution (10% by mass): 8.0% by mass
(PVA-105, manufactured by Kuraray Co., Ltd.)
・ Surfactant ... 0.5% by mass
(Demol EP, manufactured by Kao Corporation, solid content: 25% by mass)
・ Distilled water: 51.5% by mass

-Formation of first polymer layer-
(1) Preparation of 1st coating liquid for polymer layer formation Each component in the following composition was mixed and the coating liquid for 1st polymer layer formation was prepared.
<Composition of coating solution>
Bonron XPS-001 (binder, B-1) 430 parts by mass (acrylic resin, manufactured by DIC Corporation, solid content: 45% by mass)
Oxazoline compound (crosslinking agent) ... 77 parts by mass (Epocross WS700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
・ Surfactant: 19 parts by mass (Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
・ Titanium dioxide dispersion (ultraviolet absorber) 194 parts by mass Distilled water 280 parts by mass

(2) Formation of first polymer layer The obtained coating solution for forming the first polymer layer was coated on one surface of the biaxially stretched polyester support obtained above with a binder amount of 3.0 g in coating amount. / M ^2, and dried at 180 ° C. for 1 minute to form a first polymer layer (first polymer layer) having a dry thickness of about 3 μm. At this time, the ratio of the inorganic fine particles (not including titanium dioxide derived from the titanium dioxide dispersion) contained in the first polymer layer was 11.3% by volume.

-Second polymer layer-
(1) Preparation of 2nd coating liquid for polymer layer formation Each component in the following composition was mixed and the coating liquid for 2nd polymer layer formation was prepared.
<Composition of coating solution>
-Ceranate WSA-1070 (binder, B-11) ... 323 parts by mass (acrylic / silicone binder, manufactured by DIC Corporation, solid content: 40% by mass)
-Oxazoline compound (crosslinking agent) 52 parts by mass (Epocross WS700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
・ Surfactant: 32 parts by mass (Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
・ Organic lubricant: 207 parts by mass (Kemipearl W950, manufactured by Mitsui Chemicals, Ltd., concentration: 5% by mass)
Colloidal silica (mat agent) 30 parts by mass (Snowtex UP, average particle size: 0.5 μm, manufactured by Nissan Chemical Co., Ltd., solid content 20%)
-1% aqueous solution of alkoxysilane compound: 30 parts by mass (TSL8340, manufactured by Toshiba Silicone Co., Ltd.)
・ Distilled water ... 280 parts by mass

(2) Formation of second polymer layer The obtained coating solution for forming the second polymer layer is formed on the first polymer layer provided on one side of the biaxially stretched polyester support. The applied amount was 2.0 g / m ² and dried at 180 ° C. for 1 minute to form a second polymer layer having a dry thickness of about 2 μm.
As described above, a laminated film in which the first polymer layer and the second polymer layer were sequentially laminated on a biaxially stretched polyethylene terephthalate substrate (PET substrate) was produced.

-Evaluation-
Subsequent to the above, the following evaluation was performed on the obtained laminated film. The evaluation results are shown in Table 1 below.

(1) Planar shape A sample piece of 30 cm × 40 cm size is processed so that the coating amount of the first polymer layer is 0.9 g / m ² , three of them are prepared, and the coating solution is applied. Then, the number of repels in the first polymer layer solution was visually counted. Less than 10 is a practically acceptable range.

(2) Adhesion-before wet heat aging-
The surface of the polymer layer (first polymer layer + second polymer layer) of the obtained laminated film was scratched at intervals of 3 mm by 6 razors each with a single blade to form 25 squares. A mylar tape (polyester adhesive tape) was affixed thereon, and then the mylar tape was peeled off manually by pulling it in the 180 ° direction along the polymer sheet surface. At this time, the adhesiveness between the first polymer layer and the polyester support was ranked according to the following evaluation criteria according to the number of peeled cells.
The evaluation ranks 4 to 5 are practically acceptable ranges.
<Evaluation criteria>
5: There was no cell which peeled (0 cell)
4: The peeled cell is 0 to less than 0.5 cell 3: The peeled cell is 0.5 cell or more and less than 2 cell 2: The peeled cell is 2 cell or more and less than 10 cell 1: The peeled cell is 10 squares or more

-After wet heat (Damp heat durability)-
The obtained laminated film was held for 120 hours under an environmental condition of 120 ° C. and 100% RH, and then conditioned for 1 hour under an environment of 25 ° C. and 60% RH. Thereafter, the adhesion between the first polymer layer and the polyester support was evaluated in the same manner as in the evaluation before “wet heat aging”.

-After exposure treatment (light resistance)-
After irradiating the laminated film obtained above with UV light of 700 W / m ² intensity for 48 hours using a super energy irradiation tester (manufactured by Suga Test Instruments Co., Ltd.) In the same way, the adhesion between the first polymer layer and the polyester support was evaluated.

(Examples 2-7 and Comparative Examples 8-11)
As shown in Table 1, a laminated film was produced and a solar cell module was produced and evaluated in the same manner as in Example 1 except that the type of the binder constituting the first polymer layer was changed.

(Examples 8-12 and Comparative Examples 3-7)
As shown in Table 1, a laminated film was produced and a solar cell module was produced and evaluated in the same manner as in Example 1 except that the type of the binder constituting the second polymer layer was changed.

(Example 13)
As shown in Table 1, a laminated film was produced and a solar cell module was produced and evaluated in the same manner as in Example 1 except that the type of polyester was changed.
P-2 was obtained by casting the pellet after undergoing solid-state polymerization at a melting temperature on a metal drum of 285 ° C. to 315 ° C.

(Examples 14 to 18)
As shown in Table 1, a laminated film was produced and a solar cell module was produced and evaluated in the same manner as in Example 1 except that the type and addition rate of the ultraviolet absorber were changed.

(Examples 19 to 23)
As shown in Table 1, a laminated film was produced and a solar cell module was produced and evaluated in the same manner as in Example 1 except that the type and addition rate of the crosslinking agent were changed.

(Examples 24-26 and Comparative Examples 1 and 2)
As shown in Table 1, a laminated film was produced and a solar cell module was produced and evaluated in the same manner as in Example 1 except that the addition rate of the ultraviolet absorber was changed and the optical density was changed.

(Example 27)
As shown in Table 1, a laminated film was produced and a solar cell module was produced and evaluated in the same manner as in Example 1 except that the film thickness of the first polymer layer was changed.

The binders and other additives used in the examples and comparative examples are as follows.
B-1: Bonlon XPS-001 (Mitsui Chemicals Co., Ltd., acrylic binder: elastic modulus 0.1 × 10 ⁻⁹ Pa)
B-2: Bonlon XPS-002 (manufactured by Mitsui Chemicals, acrylic binder: elastic modulus 0.1 × 10 ⁻⁹ Pa)
B-3: AS-563A (manufactured by Daicel Finechem Co., Ltd., acrylic binder: elastic modulus 7.1 × 10 ⁻⁹ Pa)
B-4: Bonron XHS-50 (manufactured by Mitsui Chemicals, acrylic binder: elastic modulus 9.5 × 10 ⁻⁹ Pa)
B-5: Hydran Es650 (manufactured by DIC Corporation, polyester binder)
B-6: Hydran HW340 (DIC Corporation, polyurethane binder)
B-11: Ceranate WSA 1070 (manufactured by DIC Corporation, silicone acrylic binder)
B-12: Synthesis example 1 (polysiloxane part 25%)
B-13: Synthesis example 2 (polysiloxane part 50%)
B-14: Synthesis example 3 (polysiloxane part 75%)
B-15: Synthesis example 4 (polysiloxane part 87%)
B-16: Obligard SW0011F (manufactured by AGC Co-Tech, Inc., fluorine-based binder)

H-1: Epocross WS700 (Oxazoline crosslinker manufactured by Nippon Shokubai Co., Ltd.)
H-2: Carbodilite V-02-L2 (Nisshinbo Co., Ltd., carbodiimide crosslinking agent)
H-3: Dinacol Ex521 (manufactured by Nagase Chemtech Co., Ltd., epoxy crosslinking agent)
∪-1: Taipei R780-2 (Ishihara Sangyo Co., Ltd., titanium dioxide fine particles)
∪-2: Shine Guard TA-04 (Senka Co., Ltd., triazine UV absorber-containing emulsion)

As can be seen from Table 1, in Examples 1 to 27, both the adhesiveness after wet heat aging and the adhesiveness after the light resistance test are high, and it can be seen that it has weather resistance and light resistance. Especially, in Examples 1-4, since the elasticity modulus of acrylic resin is 5 * 10 <^-9> Pa or less, the outstanding adhesiveness is obtained. In particular, in Examples 1 to 3, the elastic modulus of the acrylic resin is as low as 3 × 10 ⁻⁹ Pa or less, and it can be seen that high adhesiveness is obtained even after wet heat aging. Among them, Example 1 is preferable because it has good wet heat aging, adhesion after light resistance, and surface properties.
On the other hand, in Comparative Examples 1 and 2, the adhesion after the light resistance test is weak, and in Comparative Examples 3 to 7, 9 and 10, the adhesion after wet heat aging is weak. These comparative examples have only one of weather resistance and light resistance, and cannot achieve both weather resistance and light resistance. Moreover, in the comparative example 8, since the silicone acrylic binder is used for the 1st polymer layer, it turns out that there are many repellency and the surface property of a polymer layer tends to deteriorate a little.

  According to the present invention, a laminated film having excellent surface properties and having both weather resistance and light resistance can be obtained. For this reason, the laminated | multilayer film of this invention can be preferably utilized as a solar cell module backsheet used in severe environments, such as outdoors, and its industrial applicability is high.

2 Polyester support 4 First polymer layer 6 Second polymer layer 10 Laminated film

Claims (11)

A polyester support, a first polymer layer laminated on at least one surface of the polyester support, and a second polymer laminated on the opposite side of the polyester support via the first polymer layer And having a layer
The first polymer layer includes an ultraviolet absorber and an acrylic resin,
The second polymer layer includes at least one of a silicone resin and a fluorine resin,
An optical density at 350 nm of the first polymer layer is 2.0 or more. 2. The laminated film according to claim 1, wherein an elastic modulus of the acrylic resin contained in the first polymer layer is 5 × 10 ⁻⁹ Pa or less.   The ultraviolet absorber contained in the first polymer layer is inorganic particles, and the content of the inorganic particles is 20 to 70% by mass with respect to the acrylic resin. 2. The laminated film according to 2. The silicone resin contained in the second polymer layer contains a polymer structure containing 15 to 85% by mass of a — (Si (R ¹ ) (R ² ) —O) _n — moiety in the molecule and copolymerizing with the moiety. The laminated film according to any one of claims 1 to 3, which is a composite polymer containing 15 to 85% by mass of a portion.
(However, R ¹ and R ² each independently represents a monovalent organic group that can be covalently bonded to a hydrogen atom, a halogen atom, or a Si atom, and R ¹ and R ² may be the same or different.)   The laminated film according to any one of claims 1 to 4, wherein the first polymer layer and the second polymer layer further contain a crosslinking agent.   The laminated film according to claim 5, wherein the crosslinking agent is an oxazoline-based crosslinking agent or a carbodiimide-based crosslinking agent.   The laminated film according to any one of claims 1 to 6, wherein the first polymer layer and the second polymer layer are formed by coating.   The average film thickness of said 1st polymer layer is 0.3-18 micrometers, The laminated | multilayer film of any one of Claims 1-7 characterized by the above-mentioned.   The laminated film according to any one of claims 1 to 8, wherein at least one surface of the polyester support is subjected to a surface treatment.   The solar cell module backsheet using the laminated | multilayer film of any one of Claims 1-9. The solar cell module using the solar cell module backsheet of Claim 10.

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