JP2015146360A - Protective sheet for solar cell, back sheet for solar cell, solar cell module, and method for re-processing solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a protective sheet for a solar cell, which has a high adhesive force to a sealing material at room temperature and is easy to be peeled off from a sealing material at high temperature; a back sheet for a solar cell; a solar cell module in which a protective sheet for a solar cell can be easily peeled off in a re-processing process; and a method for re-processing a solar cell module.SOLUTION: There are provided: a protective sheet 31 for a solar cell, including a base material film 16 and an olefin-based polymer layer 18 which is disposed, as the outermost layer, on one surface side of the base material film, containing an olefin-based resin, and has a melt flow rate of 75 g/10 minutes or more and 300 g/10 minutes or less; a back sheet 32 for a solar battery, including the protective sheet 31 for a solar cell; a solar cell module 10; and a method for re-processing a solar cell module.

Description

  The present invention relates to a solar cell protective sheet, a solar cell backsheet, a solar cell module, and a solar cell module reworking method.

  Generally, a solar cell module using crystalline silicon or amorphous silicon as a solar cell element has a transparent front substrate on the side on which sunlight is incident, and the solar cell element as a photovoltaic element is a sealing material (for example, ethylene- A battery side substrate sealed with a vinyl acetate copolymer (hereinafter may be referred to as “EVA”), a back surface protection sheet layer (back sheet for solar cell), etc. are laminated in that order, and vacuum sucked. Manufactured using a lamination method that uses thermocompression bonding. Since solar cells are placed in an environment where sunlight shines on the roof, etc., and is exposed to rain, the layers that make up the solar cell module have various functionalities that are representative of durability under humid heat environments. Is required.

Conventionally, glass has often been used as a transparent front substrate or solar cell backsheet, but various functionalities can be added by laminating functional layers, reducing the weight of the solar cell module and reducing the cost. From the viewpoint of reduction, etc., it has recently been required to use a solar cell protective sheet using a base material mainly composed of a resin film as a front substrate or a solar cell backsheet.
Such a protective sheet for a solar cell is often a laminate of various functional layers as described above. As a typical functional layer, an adhesive layer for closely adhering to the sealing material and a function of reflecting sunlight transmitted through the transparent front substrate and the battery side substrate are given to increase the expression efficiency of the solar cell element. And a weather-resistant layer that is preferably installed on the outermost layer of the solar cell protective sheet.

  The functionality required for the solar cell protective sheet is various as described above, and among them, durability under a wet heat environment that is directly related to the life of the solar cell module is particularly required. From the viewpoint of durability of the solar cell module in a moist heat environment, it is particularly important that the sealing material and the solar cell protective sheet are peeled off and moisture does not enter the battery side substrate. That is, there is a demand for a solar cell protective sheet that has good adhesion to a sealing material used in a solar cell module in a wet heat environment.

  For example, Patent Documents 1 and 2 disclose a solar cell protective sheet having an outermost layer containing an olefin-based resin as a layer that improves adhesion to a sealing material.

On the other hand, after manufacturing the solar cell module, for example, when a defect of the solar cell element is found in the inspection process, the solar cell protective sheet once bonded to the sealing material is peeled off and reattached in order to repair the inside. So-called rework work is necessary.
For example, in Patent Document 3, as a back surface protection sheet having adhesion to a solar cell module sealing material, handling properties, and reworkability, a core layer made of a polypropylene resin and a sealing material are bonded together. And a skin layer exposed to the outer layer, and the content of ethylene units in the polypropylene resin constituting the skin layer is 1.9% by mass or more and 3.0% by mass or less, and the sealing measured by an adhesion test A back surface protection sheet having a material adhesion strength of 30 N / 15 mm or more and less than 70 N / 15 mm is disclosed.

JP2012-197435A JP 2012-15264 A JP2013-211401A

  When peeling backsheets for solar cells in the rework process, the adhesive strength is strong at room temperature and it is difficult to peel off, so the temperature is raised. At this time, it is convenient to peel easily, but if the adhesion is weak even at room temperature, peeling or the like occurs.

  The present invention provides a solar cell protective sheet and a solar cell backsheet that are easy to peel off from the sealant at high temperatures at high temperatures, and easily peels off the solar cell protective sheet in a rework process. It is an object of the present invention to provide a solar cell module that can be used and a method for reworking the solar cell module.

  In order to achieve the above object, the following invention is provided.

<1> A base film and an olefin polymer layer that is disposed as an outermost layer on one side of the base film, includes an olefin resin, and has a melt flow rate of 75 g / 10 min to 300 g / 10 min. And a solar cell protective sheet.
<2> Adhesive force when the olefin polymer layer and the EVA sealing material at 25 ° C. are peeled in the 180 ° direction is 6 N / mm or more, and the olefin polymer layer and the EVA sealing material at 150 ° C. The solar cell protective sheet according to <1>, wherein the adhesive strength when peeled in the 180 ° direction is 0.25 N / mm or less.
<3> The solar cell protective sheet according to <1> or <2>, wherein the olefin resin is an olefin resin that has been acid-modified.
<4> The protective sheet for solar cells according to any one of <1> to <3>, wherein the olefin polymer layer has a thickness of 0.1 μm or more and 100 μm or less.
<5> The solar cell protective sheet according to <4>, wherein the olefin polymer layer has a thickness of 0.1 μm or more and 10 μm or less.
<6> The solar cell protective sheet according to any one of <1> to <5>, wherein the olefin polymer layer is a layer formed by applying a coating solution.
<7> The solar cell protective sheet according to <6>, wherein the olefin polymer layer is a layer formed by applying an aqueous coating solution.
<8> The solar cell according to any one of <1> to <7>, wherein the base film is a film containing at least one resin selected from the group consisting of polyester, polyolefin, polyamide, and fluorine-containing resin. Protective sheet.
<9> The solar cell protective sheet according to any one of <1> to <8>, having an intermediate layer between the base film and the olefin polymer layer.
<10> The solar cell protective sheet according to <9>, wherein the intermediate layer contains a color pigment.

<11> A solar cell backsheet comprising the solar cell protective sheet according to any one of <1> to <10>.
<12> A first weathering layer containing a silicone-acrylic composite resin and a second weathering containing a fluororesin on the side opposite to the side on which the olefin polymer layer of the solar cell protective sheet is disposed. The solar cell backsheet according to <11>, wherein the layers are laminated in this order.

<13> a transparent front substrate on which sunlight is incident;
A solar cell element;
A sealing material for sealing the solar cell element;
The solar cell backsheet according to <11> or <12>, which is disposed on the side opposite to the front substrate of the encapsulant, and the olefin polymer layer is directly bonded to the encapsulant,
Including solar cell module.

<14> A method for reworking a solar cell module, comprising the step of heating the solar cell module according to <13> to peel the solar cell backsheet from the sealing material.
<15> In the step of peeling the solar cell backsheet from the encapsulant, the solar cell module is heated from two directions on the front substrate side and the solar cell backsheet side. Processing method.

  According to the present invention, the solar cell protective sheet and the solar cell back sheet that have high adhesion to the encapsulant at room temperature and easily peel off from the encapsulant at high temperature, and the solar cell protective sheet easily in the rework process. A solar cell module that can be peeled off and a reprocessing method of the solar cell module are provided.

It is the schematic which shows an example of the laminated constitution of the protection sheet for solar cells of this invention. It is the schematic which shows an example of a structure of the solar cell module of this invention.

Hereinafter, the solar cell protective sheet of the present invention, the solar cell backsheet provided with the solar cell protective sheet, the solar cell module, and the solar cell module reworking method will be described in detail.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Protective sheet for solar cell]
The solar cell protective sheet of the present invention is disposed as a base film and an outermost layer on one side of the base film, includes an olefin resin, and has a melt flow rate (MFR) of 75 g / 10 min or more and 300 g / 10. And a polymer layer that is less than or equal to minutes.
With such a configuration, the solar cell protective sheet of the present invention has high adhesion to the encapsulant at room temperature (for example, 25 ° C.), and the high temperature heating (for example, 150 ° C.) during the reworking process. Adhesion is greatly reduced and easily peeled off.

  Due to the above characteristics of the solar cell protective sheet of the present invention, the solar cell module using the solar cell protective sheet of the present invention is moist heat due to the adhesive force with the good sealing material of the solar cell protective sheet of the present invention. Occurrence of peeling and the like over time in the environment is suppressed, and power generation performance can be stably maintained over a long period of time. In addition, after bonding the solar cell protective sheet of the present invention to the sealing material, for example, when a defect or the like of the solar cell element is found, it is easily peeled off by heating by a heating means such as a hot plate in the rework process. Can be pasted again.

  The solar cell protective sheet of the present invention is not limited to the solar cell backsheet, but can also be suitably used as a solar cell front sheet on which sunlight is incident. The case where the protective sheet is used as a solar cell backsheet for protecting the back side of the solar cell will be mainly described.

FIG. 1 schematically shows an example of the layer configuration of the solar cell protective sheet of the present invention, and FIG. 2 shows an example of the configuration of the solar cell backsheet and solar cell module including the solar cell protective sheet of the present invention. Is shown schematically.
The solar cell protective sheet 31 shown in FIG. 1 is provided with an olefin polymer layer 18 as an outermost layer on one surface side of the base film 16, and between the base film 16 and the olefin polymer layer 18. An intermediate layer 17 is provided as an optional layer.

In the solar cell module of the present invention, as shown in FIG. 2, the olefin polymer layer 18 of the solar cell protective sheet 31 is directly bonded to the sealing material 22.
Moreover, when using the solar cell protective sheet of the present invention as a solar cell backsheet, the surface of the base film 16 opposite to the surface on which the olefin polymer layer 18 is disposed has a weather resistant layer. It is preferable to be provided. For example, as shown in FIG. 2, two surfaces of the first weathering layer 14 and the second weathering layer 12 are provided on the surface of the base film 16 opposite to the surface on which the olefin polymer layer 18 is provided. A weather-resistant layer may be laminated and provided. If it has a weather resistant layer, the solar cell protective sheet of the present invention can be used as it is as the solar cell backsheet 32.
Moreover, it is preferable that the transparent front substrate 24 is arrange | positioned at the solar cell module 10 of this invention on the opposite side to the protective sheet for solar cells of this invention of the sealing material 22. FIG.

  Hereinafter, the base film and each layer which comprise the solar cell protective sheet of this invention are demonstrated concretely. The reference numerals are omitted as appropriate.

(Base film)
-Raw resin-
Polyester, polystyrene, polyphenylene ether, polyphenylene sulfide, polyolefin, polyamide, fluorine-containing resin, etc. can be used as the raw material resin constituting the base film of the solar cell protective sheet of the present invention. From the viewpoint of cost, mechanical stability, durability, etc., the base film preferably contains at least one resin selected from the group consisting of polyester, polyolefin, polyamide, and fluorine-containing resin, and is composed of polyester. It is particularly preferred.

  Examples of the polyester that can be preferably used for the base film include a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate and the like. Of these, polyethylene terephthalate, polyethylene-2,6-naphthalate, and poly (1,4-cyclohexylenedimethylene terephthalate) are particularly preferable from the viewpoint of balance between mechanical properties and cost.

  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.

Additives such as light stabilizers, antioxidants, UV absorbers, flame retardants, lubricants (fine particles), nucleating agents (crystallization agents), crystallization inhibitors, color pigments, end-capping agents, etc. for polyester May further be included.
Furthermore, after extending | stretching to a longitudinal direction, you may apply | coat before extending | stretching of the width direction.

-Manufacturing method of substrate film-
Hereinafter, the preferable aspect of the manufacturing method of a base film is demonstrated taking the case where a base film is polyester as an example.
The base film is obtained by, for example, melt-extruding the above polyester into a film shape and then cooling and solidifying it with a casting drum to form an unstretched film. The unstretched film is once in the longitudinal direction at Tg to (Tg + 60) ° C. Or it may be a biaxially stretched film that is stretched twice or more so that the total magnification is 3 to 6 times, and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C. preferable.
Furthermore, what was heat-processed for 1 to 60 second at 180-230 degreeC as needed may be used.

  The thickness of the base film is preferably 30 μm or more and 350 μm, more preferably 160 μm or more and 300 μm or less, and further preferably 180 μm or more and 280 μm or less from the viewpoint of withstand voltage.

The base film may be subjected to surface treatment such as corona treatment, flame treatment, and glow discharge treatment as necessary. Of these, corona treatment is a preferred surface treatment method that can be performed at low cost.
Corona discharge treatment is usually performed by applying high frequency and high voltage between a metal roll (dielectric roll) coated with a derivative and an insulated electrode to cause dielectric breakdown of the air between the electrodes. Is ionized to generate a corona discharge between the electrodes. And it performs by passing a base film between this corona discharge.
The preferable processing conditions used in the present invention are preferably a gap clearance of 1 to 3 mm between the electrode and the dielectric roll, a frequency of 1 to 100 kHz, and an applied energy of about 0.2 to 5 kV · A · min / m ² .

The glow discharge treatment is a method called vacuum plasma treatment or glow discharge treatment, in which plasma is generated by discharge in a gas (plasma gas) in a low-pressure atmosphere to treat the substrate surface. The low-pressure plasma used in the process of the present invention is a non-equilibrium plasma generated under conditions where the plasma gas pressure is low. The treatment of the present invention is performed by placing a film to be treated in this low-pressure plasma atmosphere.
In the glow discharge treatment, methods such as direct current glow discharge, high frequency discharge, and microwave discharge can be used as a method for generating plasma. The power source used for discharging may be direct current or alternating current. When alternating current is used, a range of about 30 Hz to 20 MHz is preferable.
When alternating current is used, a commercial frequency of 50 or 60 Hz may be used, or a high frequency of about 10 to 50 kHz may be used. A method using a high frequency of 13.56 MHz is also preferable.

  As the plasma gas used in the glow discharge treatment, an inorganic gas such as oxygen gas, nitrogen gas, water vapor gas, argon gas, and helium gas can be used. In particular, oxygen gas or a mixed gas of oxygen gas and argon gas can be used. Is preferred. Specifically, it is desirable to use a mixed gas of oxygen gas and argon gas. When oxygen gas and argon gas are used, the ratio between the two is preferably about oxygen gas: argon gas = 100: 0 to 30:70, more preferably 90:10 to 70:30, as a partial pressure ratio. In addition, a method is also preferable in which a gas such as the air entering the processing container due to a leak or water vapor coming out of the object to be processed is used as the plasma gas without introducing the gas into the processing container.

As the pressure of the plasma gas, a low pressure at which non-equilibrium plasma conditions are achieved is necessary. The specific plasma gas pressure is preferably in the range of about 0.005 to 10 Torr, more preferably about 0.008 to 3 Torr. When the pressure of the plasma gas is less than 0.005 Torr, the effect of improving adhesiveness may be insufficient. Conversely, when the pressure exceeds 10 Torr, the current may increase and the discharge may become unstable.
The plasma output cannot be generally specified depending on the shape and size of the processing vessel, the shape of the electrode, and the like, but is preferably about 100 to 2500 W, more preferably about 500 to 1500 W.
The treatment time of the glow discharge treatment is 0.05 to 100 seconds, more preferably about 0.5 to 30 seconds. If the treatment time is less than 0.05, the adhesion improving effect may be insufficient. Conversely, if the treatment time exceeds 100 seconds, problems such as deformation and coloring of the film to be treated may occur.
Discharge treatment intensity of the glow discharge treatment depends on the plasma power and treatment time, preferably in the range of 0.01~10kV · A · min / m ^2, 0.1~7kV · A · min / m ² is more preferable. Discharge treatment intensity that is sufficient adhesion improving effect of the 0.01 kV · A · min / m ² or more is obtained, and such deformation and coloration of the processed film by a 10 kV · A · min / m ² or less You can avoid problems.
In the glow discharge treatment, it is also preferable to heat the film to be treated in advance. By this method, better adhesiveness can be obtained in a shorter time than when heating is not performed. The heating temperature is preferably in the range of 40 ° C. to the softening temperature of the film to be processed + 20 ° C., more preferably in the range of 70 ° C. to the softening temperature of the film to be processed. By setting the heating temperature to 40 ° C. or higher, a sufficient adhesive improvement effect can be obtained. Moreover, the handleability of a favorable film can be ensured during a process by making heating temperature below into the softening temperature of a to-be-processed film.
Specific methods for raising the temperature of the film to be treated in vacuum include heating with an infrared heater, heating by contacting with a hot roll, and the like.

(Olefin polymer layer)
The solar cell protective sheet of the present invention includes an olefin-based resin as an outermost layer directly bonded to the sealing material on one side of the base film, and has a melt flow rate (MFR) of 75 g / 10 min or more and 300 g / min. An olefin polymer layer that is 10 minutes or less is disposed.
The MFR of the olefin polymer layer is preferably 250 g / 10 min or less, and more preferably 200 g / 10 min or less.

  The MFR of the olefin polymer layer in the present invention is a melt flow rate (MFR) value at 190 ° C. under a load of 2160 g (according to JIS K7210: 1999). MFR can be measured about the constituent material of the whole olefin type polymer layer by peeling an olefin type polymer layer from the protection sheet for solar cells. Moreover, before forming an olefin type polymer layer, it can obtain | require from MFR of raw material resin.

The film thickness of the olefin polymer layer is preferably from 0.1 μm to 100 μm, and more preferably from 0.1 μm to 10 μm.
By setting the film thickness of the olefin-based polymer layer to 0.1 μm or more and 100 μm or less, the adhesiveness with the sealing material can be sufficiently expressed at room temperature, and is easily peeled off at high temperature heating. In particular, if the film thickness of the olefin polymer layer is 10 μm or less, the adhesiveness with the sealing material can be kept high even after the wet heat treatment.

-Resin-
The olefin polymer layer may have an MFR of 75 g / 10 min or more and 300 g / 10 min or less, and an MFR of 75 g / 10 min or more and 300 g / 10 min or less of the whole material constituting the olefin polymer layer. Preferably, the olefin polymer layer may be formed by blending olefin polymers having an MFR of 75 g / 10 min or more and 300 g / 10 min or less.
The single MFR is not 75 g / 10 min or more and 300 g / 10 min or less, but is blended with another olefin polymer to form an olefin polymer layer having an MFR of 75 g / 10 min or more and 300 g / 10 min or less. Also good. For example, an olefin resin having an MFR of less than 75 g / 10 minutes and an olefin resin having an MFR of more than 300 g / 10 minutes are blended, and the MFR of the entire olefin polymer layer is 75 g / 10 minutes or more and 300 g / 10 minutes or less. You may adjust it.

If the MFR of the material (mainly olefin resin) constituting the olefin polymer layer as a whole is 75 g / 10 min or more and 300 g / 10 min or less, the olefin polymer layer includes other resins other than the olefin resin. May be.
Examples of other resins include polyurethane resins and acrylic resins. Examples of polyurethane resins include Superflex 110 and 460, both of which are manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Examples of the acrylic resin include AS-563A, manufactured by Daicel Finechem Co., Ltd., Jonkrill PDX-7341, 7696, all manufactured by BASF Corporation.
The ratio (mass ratio) between the olefin resin and the other resin is preferably 50:50 to 100: 0, and more preferably 80:20 to 100: 0.

  Examples of the olefin used in the olefin resin constituting the olefin-based polymer layer include those obtained by polymerizing ethylene, propylene, isobutylene and the like, and among them, ethylene is preferable. That is, in the solar cell protective sheet of the present invention, the main chain of the olefin resin used in the olefin polymer layer preferably contains an ethylene unit.

In the protective sheet for solar cell of the present invention, the olefin resin used in the olefin polymer layer is preferably a modified olefin resin, and more preferably an acid-modified olefin resin. The protective sheet for solar cell of the present invention preferably includes a (meth) acrylic acid unit, and particularly preferably includes an acrylic acid unit, as an acidic unit used for the polyolefin resin used in the olefin polymer layer. Further, in this specification, the acrylic resin includes an acrylate skeleton resin and a methacrylate skeleton resin. Moreover, (meth) acryl means a generic name of acrylic and methacryl, and (meth) acrylate means a generic name of acrylate and methacrylate.
Part or all of the acidic units of the polyolefin resin are preferably neutralized with cations. The cation is preferably a metal such as sodium ion, zinc ion, magnesium ion, copper ion, lithium ion or potassium ion, an amine, or ammonia. As the metal ion, sodium ion, zinc ion and the like are preferable. As the amines or ammonia, triethylamine, N, N′-dimethylethanolamine, ammonia and the like are preferable.

Examples of the main chain skeleton of the olefin resin include ethylene-acrylic acid ester-maleic anhydride (and / or acrylic acid) copolymer, ethylene-propylene-maleic anhydride (and / or acrylic acid) copolymer Polymer, ethylene-butene-maleic anhydride (and / or acrylic acid) copolymer, propylene-butene-maleic anhydride (and / or acrylic acid) copolymer, ethylene-propylene-butene-maleic anhydride copolymer , Ethylene-propylene-acrylic acid ester-maleic anhydride (and / or acrylic acid) copolymer, ethylene-butene-acrylic acid ester-maleic anhydride (and / or acrylic acid) copolymer, propylene-butene-acrylic Acid ester-maleic anhydride (and / or acrylic acid) Copolymer, ethylene - propylene - butene - acrylic ester - maleic anhydride (and / or acrylic acid) copolymers.
As the polyolefin resin, for example, a polymer composed of ethylene and acrylic acid or ethylene and methacrylic acid is preferable.
The copolymerization ratio (molar ratio) between the olefin unit and the acidic unit in the polyolefin resin is preferably 99.7: 0.3 to 90:10, more preferably 99.5: 0.5 to 97: 3. preferable.

The form of the olefin resin is not particularly limited as long as a polymer layer having an MFR of 75 g / 10 min to 300 g / 10 min can be formed. For example, it may be an olefin resin dispersed in water or an organic solvent, or may be a melt extruded olefin resin. Further, it may be a crystalline olefin resin or a non-crystalline olefin resin.
Among them, in the present invention, it is preferable to use an olefin resin dispersible in a solvent from the viewpoint of being able to form an olefin polymer layer by coating and further improving the adhesion after sealing with a sealing material after wet heat. The olefin resin is more preferably dispersible in water.

  There is no restriction | limiting in particular also about the acquisition method of an olefin resin, You may obtain commercially and may synthesize | combine. Moreover, you may add an additive in the range which does not impair the effect by this invention.

  As commercially available olefin-based resins used in the present invention, for example, Arrow Base SA-1010 (manufactured by Unitika, MFR: 200 g / 10 min), Arrow Base SB-1010 (manufactured by Unitika, MFR: 65 g) / 10 minutes, Bondine HX-8020 (manufactured by Arkema, MFR: 200 g / 10 minutes), Sumikasen G807 (manufactured by Sumitomo Chemical, MFR: 75 g / 10 minutes), and the like.

  For example, when an olefin polymer layer is formed alone, the MFR is not 75 g / 10 min to 300 g / 10 min, but the MFR of the olefin polymer layer is 75 g / 10 min to 300 g / 10 min. As such, it may be blended with other olefin resins. In the case of blending, for example, Nukurel N1050H (Mitsui / DuPont Polychemical Co., Ltd., MFR: 500 g / 10 min, Arrow Base SE-1010 (Unitika Ltd., MFR: 3 g / 10 min)), Arrow Base SD-1010 (Unitika) Company, MFR: 5 g / 10 min), Bondine TX-8030 (manufactured by Arkema, MFR: 3 g / 10 min) and the like can be used.

-Additives-
The olefin-based polymer layer can contain an additive in a range where the MFR is 75 g / 10 min or more and 300 g / 10 min or less.

When the olefin polymer layer contains a cross-linking agent, the adhesion can be improved, which is more preferable. Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among them, in the present invention, the crosslinking agent is preferably an oxazoline-based crosslinking agent. 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.
The addition amount of the crosslinking agent is preferably 0.5 to 50% by mass, more preferably 3 to 40% by mass, and particularly preferably 5% by mass or more and less than 30% by mass with respect to the binder constituting the olefin polymer layer. It is. In particular, 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 olefin polymer layer, and when it is 50% by mass or less, If the pot life is kept long and the amount is less than 40% by mass, the coated surface can be improved.

  A crosslinking agent catalyst can be further added to the olefin polymer layer. The preferred range of the crosslinking agent catalyst that can be used for the olefin polymer layer is the same as the preferred range of the crosslinking agent catalyst that can be used for the olefin-acrylic composite polymer layer, and is a combination of an oxazoline crosslinking agent and an onium compound. Is preferred.

The olefin polymer layer preferably contains an anionic or nonionic surfactant. Of these, anionic surfactants are preferred.
When adding a surfactant, the addition amount is preferably 0.1 to 10 mg / m ² , more preferably 0.5 to 4 mg / m ² . When the addition amount of the surfactant is 0.1 mg / m ² or more, generation of a repellency is suppressed and good layer formation is obtained, and when it is 10 mg / m ² or less, the olefin polymer layer layer, Adhesion with a material film or an intermediate layer described later can be performed satisfactorily.

  The coating solution for forming the olefin polymer layer may further contain an antistatic agent, a colorant, an ultraviolet absorber and the like.

-Solvent-
When the olefin polymer layer is formed by coating, the solvent in the coating solution is not particularly limited as long as each component constituting the olefin polymer layer can be dispersed or dissolved and removed after coating. For example, water or an organic solvent such as toluene or methyl ethyl ketone may be used. As the solvent, one kind may be used alone, or two or more kinds may be mixed and used, but water is preferably used. It is preferable that 60 mass% or more in the solvent contained in the composition for forming an olefin polymer layer is water. Such an aqueous composition (aqueous coating liquid) is preferable in that it is difficult to place a burden on the environment, and is advantageous in terms of safety because the ratio of water is 60% by mass or more. The proportion of water in the composition for forming an olefin-based polymer layer is preferably larger from the viewpoint of environmental load, and more preferably 70% by mass or more of water in the total solvent.
In the protective sheet for a solar cell of the present invention, the solvent residual ratio in the olefin polymer layer is preferably 0.05% by mass or less based on the mass of the olefin polymer layer (mass of the coating film), and 0.025 It is more preferably at most mass%, particularly preferably at most 0.01 mass%.

-Formation method of olefin polymer layer-
The method for forming the olefin polymer layer in the present invention is not particularly limited. For example, a method of applying and forming an olefin polymer layer forming composition directly on one side of a base film or on an intermediate layer formed on one side of a base film, a method of extrusion molding, and the like are mentioned. The method is preferable in that it can be formed with a simple and highly uniform thin film.

  As a coating method, for example, a known method such as a gravure coater or a bar coater can be used.

The coating amount of the olefin polymer layer is preferably 0.1-5 g / m ^2, and more preferably 0.2 to 3 g / m ^2.
Moreover, when forming an olefin type polymer layer by application | coating, it is preferable to serve as the drying and heat processing of an olefin type polymer layer in the drying zone after heat processing. The same applies to the case where a colored layer and other functional layers described later are formed by coating.

  In addition, before applying the olefin polymer layer, the corona treatment, the glow treatment, the atmospheric pressure plasma treatment, the flame treatment, the UV treatment, etc. are performed on one side of the base film or the intermediate layer formed on one side of the base film. It is also preferable to perform a surface treatment.

  After applying the coating solution for forming the olefin polymer layer, it is preferable to provide a step of drying the olefin polymer layer. The drying step is a step of supplying drying air to the olefin polymer layer. The average wind speed of the dry wind is preferably 5 to 30 m / sec, more preferably 7 to 25 m / sec, and further preferably 9 to 20 m / sec.

(Middle layer)
The solar cell protective sheet of the present invention may have an intermediate layer between the base film and the olefin polymer layer. The intermediate layer is configured to include at least a resin, and when the olefin polymer layer and the sealing material are peeled off at a high temperature (for example, 150 ° C.), the intermediate layer is preferably a layer that does not peel off. That is, at high temperatures, the adhesive strength between the intermediate layer and the olefin polymer layer and the adhesive strength between the intermediate layer and the substrate film are higher than the adhesive strength between the sealing material and the olefin polymer layer. Is preferred.

  Examples of the intermediate layer include an olefin-acrylic composite polymer layer containing an olefin resin and an acrylic resin.

  The thickness of the intermediate layer is preferably 30 μm or less, more preferably 1 μm to 20 μm, particularly preferably 1.5 μm to 15 μm, and particularly preferably 2 to 10 μm. By setting the film thickness to 1 μm or more, it is possible to sufficiently exhibit decorativeness and reflectivity, and by setting the film thickness to 30 μm or less, the deterioration of the surface condition is suppressed and the adhesion with the sealing material after aging with wet heat is improved. can do.

-Binder-
In the present invention, as the binder for the intermediate layer, for example, at least one olefin resin having an elastic modulus of 320 MPa or less (in this specification, synonymous with olefin resin binder and polyolefin resin) and an acrylic resin binder are used. The ratio of the acrylic resin to the total olefin resin is in the range of 5 to 55% by mass.

The ratio of the acrylic resin to the total of the acrylic resin and the olefin resin is preferably in the range of 10 to 50% by mass, and more preferably in the range of 15 to 40% by mass.
Examples of the acrylic resin include AS-563A, manufactured by Daicel Finechem Co., Ltd., Jonkrill PDX-7341, 7696, all manufactured by BASF Corporation.

-Other binders-
The binder of the intermediate layer may contain other binders other than the olefin resin and the acrylic resin, as long as not departing from the gist of the present invention.
Examples of other binders include polyurethane binders. Examples of polyurethane binders include Superflex 110 and 460, both manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
The ratio (mass ratio) of the olefin resin binder and the acrylic resin binder to the other binder is preferably 50:50 to 100: 0, and more preferably 80:20 to 100: 0.

-Color pigment-
When the solar cell protective sheet of the present invention is used as a solar cell backsheet, the intermediate layer is preferably a colored layer containing a color pigment (hereinafter sometimes referred to as “intermediate colored layer”).

  The first function of the colored layer is to increase the power generation efficiency of the solar cell module by reflecting the light that reaches the back sheet without being used for power generation by the solar cell in the incident light and returning it to the solar cell. is there. The second function is to improve the decorativeness of the appearance when the solar cell module is viewed from the surface side. In general, when a solar cell module is viewed from the surface side, a back sheet can be seen around the solar cell, and by providing a colored layer on the back sheet, the decorativeness can be improved and the appearance can be improved.

The color pigment used in the intermediate layer is not particularly limited, and may be selected according to required reflectivity, design properties, and the like. For example, titanium oxide which is a white pigment can be preferably used.
Among the colored pigments, at least one selected from titanium oxide, carbon black, titanium black, black composite metal oxide, perylene color pigment, cyanine color pigment, and quinacridone color pigment is preferable, and titanium oxide or carbon black Is more preferable, and titanium oxide is preferable from the viewpoints of reflectivity and cost.
Here, as the black composite metal oxide, a composite metal oxide containing at least one of iron, manganese, cobalt, chromium, copper, and nickel is preferable, and among cobalt, chromium, iron, manganese, copper, and nickel It is more preferable to include two or more types, and at least one pigment selected from PBk26, PBk27, PBk28, and PBr34 is more particularly preferable.
The pigment of PBk26 is a complex oxide of iron, manganese and copper, the pigment of PBk-27 is a complex oxide of iron, cobalt and chromium, and PBk-28 is a complex oxide of copper, chromium and manganese. PBr34 is a composite oxide of nickel and iron.
Examples of the cyanine color and quinacdrine color include cyanine green, cyanine blue, quinacridone red, phthalocyanine blue, and phthalocyanine green.
Examples of perylene color pigments include perylene green and perylene black.

If, for example, a white pigment is used as the coloring pigment, the colored layer has a function of increasing power generation efficiency by irregularly reflecting light that has passed through the cell out of sunlight incident from the front surface of the solar cell module and returning it to the cell. .
The light reflectance at a wavelength of 550 nm of the surface (outermost surface) on which the colored layer is disposed of the base film is controlled by controlling the content and thickness of the colored pigment in the colored layer or within the numerical range described later. It can be adjusted in the direction of increasing the reflectance.

The volume average particle size of the color pigment is preferably 0.03 μm to 0.9 μm, more preferably 0.2 μm to 0.7 μm. By setting the volume average particle diameter of the color pigment within this range, it is possible to suppress a decrease in light reflection efficiency.
The volume average particle diameter of the color pigment is a value (solvent: water, particle shape: non-spherical, particle refractive index: 2.7, ultrasonic treatment: none) measured by Nikkiso Co., Ltd., Microtrac MT3300EX2.

The preferred content of the color pigment in the intermediate layer (colored layer) varies depending on the type and average particle size of the color pigment used, but if the content of the color pigment in the colored layer is not too small, the reflectivity and design will be sufficiently exerted. If it is not too much, it is preferable from the viewpoint of adhesion to an adjacent layer. From the viewpoint of sufficiently exerting these functions, in the protective sheet for a solar cell of the present invention, the content of the color pigment in the colored layer is preferably 2 g / m ^{2 to} 20 g / m ² , more preferably 2 g / m ^{2 to} 15 g. / m ^2, particularly preferably from ^{2g / m 2 ~10g / m 2} .
In the solar cell protective sheet of the present invention, from the same viewpoint, the volume fraction of the colored pigment in the colored layer is preferably 15 to 40%, more preferably 15 to 34%, and particularly preferably 17 to 34%. 25%.

-Crosslinking agent-
The intermediate layer may be formed containing a crosslinking agent. Details of the crosslinking agent will be described in the description of the intermediate layer forming composition described later.

-Other additives-
The intermediate layer can further contain various additives such as surfactants, fine particles other than coloring pigments, ultraviolet absorbers, antioxidants, etc., and in particular, a colored layer forming composition for forming a colored layer. The product is preferably prepared using a surfactant for the dispersion stability of the color pigment.

  As the surfactant, for example, known surfactants such as anionic, cationic, and nonionic surfactants can be used. Specifically, Demole EP (manufactured by Kao Corporation), Naroacty CL95 [Sanyo] Kasei Kogyo Co., Ltd.]. As the surfactant, a single species or a plurality of species may be used.

Examples of the fine particles other than the color pigment include inorganic oxide fillers such as silica, magnesium oxide, and tin oxide. Among these, tin oxide or silica is preferable because the decrease in adhesiveness when exposed to a humid heat atmosphere is small.
The volume average particle diameter of the inorganic oxide filler is preferably 10 nm to 700 nm, and more preferably 20 nm to 300 nm. By using the inorganic oxide filler having an average particle diameter in this range, good easy adhesion between the colored layer and the adjacent layer can be obtained. The volume average particle diameter of the inorganic oxide filler is a value measured by Microtrack FRA manufactured by Nikkiso Co., Ltd.
The shape of the fine particles other than the color pigment is not particularly limited, and a spherical shape, an indefinite shape, a needle shape, or the like can be used.
In addition, as fine particles other than the inorganic oxide filler, for example, calcium carbonate, magnesium carbonate, or the like may be included.

-Formation of intermediate layer-
The intermediate layer can be formed by a known method and is not particularly limited. For example, a base film may be used as a support to form a solution film or a melt film, and the intermediate layer may be laminated with a solution film or a melt film formed on another support in advance. A material film may be laminated via an adhesive or the like. Among them, the solar cell protective sheet of the present invention is preferably formed into a solution by using a base film as a support. There is no particular limitation on the method for forming the solution, and it may be cast film formation or coating. However, in the solar cell protective sheet of the present invention, the intermediate layer is formed by coating. Is preferred.
The intermediate layer may be provided not only on one side of the base film but also on both sides, and in this case, it is preferable to apply to both sides of the base film.
In addition, the intermediate layer has a coating liquid for forming the intermediate layer directly on the base film, or when it has an undercoat layer described later between the base film and the intermediate layer, on the undercoat layer, It can be formed by coating.
The composition for forming an intermediate layer for forming the intermediate layer contains, for example, an olefin-based binder having an elastic modulus of 320 MPa or less, and if necessary, a coloring pigment, other binder resin, an inorganic oxide filler, a crosslinking agent. It can be prepared by mixing an additive or the like with a coating solvent.

〔solvent〕
The coating solvent is not particularly limited as long as each component constituting the intermediate layer can be dispersed or dissolved, and can be removed after coating, but water is preferably used in the solvent contained in the intermediate layer forming composition. It is preferable that 60 mass% or more of is water. Such an aqueous composition is preferable in that it is difficult to place a load on the environment, and the ratio of water is 60% by mass or more, which is advantageous in terms of explosion-proof property and safety. The proportion of water in the composition for forming an intermediate layer is preferably larger from the viewpoint of environmental burden, and more preferably 70% by mass or more of water in the total solvent. In the protective sheet for a solar cell of the present invention, the solvent residual ratio in the intermediate layer is preferably 0.05% by mass or less, and 0.025% by mass or less with respect to the mass of the intermediate layer (mass of the coating film). More preferably, it is particularly preferably 0.01% by mass or less.

[Crosslinking agent]
The intermediate layer forming composition preferably contains a crosslinking agent.
It is preferable that the intermediate layer forming composition contains a crosslinking agent, whereby the binder resin contained in the intermediate layer forming composition can be cross-linked to form a colored layer having adhesiveness and strength.
Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among these, an oxazoline-based cross-linking agent (compound having an oxazoline group) is particularly preferable from the viewpoint of securing the adhesion of the solar cell module after aging with wet heat.

  The oxazoline-based crosslinking agent has two or more oxazoline groups in the molecule and may be a low molecular compound or a polymer, but the polymer has better adhesion. preferable.

Specific examples of the oxazoline-based crosslinking agent include low-molecular-weight oxazoline-based crosslinking agents such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, and 2-vinyl-5-methyl. -2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2′-bis- (2- Oxazoline), 2,2′-methylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2, 2'-tetramethylene-bis- (2-oxazoline), 2,2'-hexamethylene-bis- (2-oxazoline), 2,2'-octamethylene-bis- (2-o Xazoline), 2,2'-ethylene-bis- (4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene -Bis- (2-oxazoline), 2,2'-m-phenylene-bis- (4,4'-dimethyl-2-oxazoline), 2,2 '-(1,3-phenylene) -bis- (2 -Oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinyl norbornane) sulfide, and the like. Furthermore, (co) polymers of these compounds can also be preferably used.
These may be used alone or in combination of two or more.

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

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

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

-Crosslinking agent catalyst-
It is preferable that an intermediate | middle layer contains at least 1 type of the catalyst of a crosslinking agent. By containing the catalyst of the crosslinking agent, the crosslinking reaction between the polymer of the intermediate layer and the crosslinking agent is promoted, and the solvent resistance is improved. Moreover, the adhesiveness between an intermediate | middle layer and a base film can also be improved by bridge | crosslinking progressing favorably.
In particular, when the intermediate layer contains a crosslinking agent having an oxazoline group as a crosslinking agent (also referred to as an oxazoline-based crosslinking agent), it is preferable to further contain a crosslinking agent catalyst.
Examples of the crosslinking agent catalyst include onium compounds.

  Preferred examples of the onium compound include ammonium salts, sulfonium salts, oxonium salts, iodonium salts, phosphonium salts, nitronium salts, nitrosonium salts, diazonium salts and the like.

Specific examples of onium compounds include monoammonium phosphate, diammonium phosphate, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium p-toluenesulfonate, ammonium sulfamate, ammonium imidodisulfonate, tetrabutylammonium chloride, benzyltrimethylammonium chloride. Ammonium salts such as triethylbenzylammonium chloride, tetrabutylammonium tetrafluoride, tetrabutylammonium hexafluoride, tetrabutylammonium perchlorate, tetrabutylammonium sulfate;
Trimethylsulfonium iodide, boron trifluoride trimethylsulfonium, boron tetrafluoride diphenylmethylsulfonium, boron tetrafluoride benzyltetramethylenesulfonium, antimony hexafluoride 2-butenyltetramethylene sulfonium, antimony hexafluoride 3-methyl-2 -Sulfonium salts such as butenyltetramethylenesulfonium;
Oxonium salts such as boron tetrafluoride trimethyloxonium;
Iodonium salts such as diphenyliodonium chloride and boron tetrafluoride diphenyliodonium;
Phosphonium salts such as antimony hexacyanocyanomethyltributylphosphonium, boron tetrafluoride ethoxycarbonylmethyltributylphosphonium;
Nitronium salts such as boron tetrafluoride nitronium; Nitrosonium salts such as boron tetrafluoride nitrosonium;
Diazonium salts such as 4-methoxybenzenediazonium chloride,
Etc.

  Among these, an onium compound is more preferably an ammonium salt, a sulfonium salt, an iodonium salt, or a phosphonium salt from the viewpoint of shortening the curing time, and among these, an ammonium salt is more preferable, and from the viewpoints of safety, pH, and cost. Are preferably phosphoric acid type and benzyl chloride type. More preferably, the onium compound is dibasic ammonium phosphate.

Only one type of crosslinking agent catalyst in the intermediate layer may be used, or two or more types may be used in combination.
The content of the crosslinking agent catalyst in the intermediate layer is preferably in the range of 0.1% by mass to 15% by mass and more preferably in the range of 0.5% by mass to 12% by mass with respect to the crosslinking agent in the intermediate layer. More preferably, the range is 1% by mass or more and 10% by mass or less, and particularly preferably 2% by mass or more and 7% by mass or less. That the content of the crosslinking agent catalyst with respect to the crosslinking agent is 0.1% by mass or more means that the crosslinking agent catalyst is actively contained, and the polymer is crosslinked by the inclusion of the crosslinking agent catalyst. The cross-linking reaction between the agents proceeds better, and better solvent resistance is obtained. Moreover, it is advantageous at the point of solubility, filterability, and contact | adherence because content of the catalyst of a crosslinking agent is 15 mass% or less.

(Application method)
Application | coating on the base film of the composition for intermediate | middle layer formation can utilize well-known methods, such as a gravure coater and a bar coater, for example.

(Other layers)
-Undercoat layer-
In the solar cell backsheet of the present invention, an undercoat layer may be further provided between the base film (support) and the colored layer (intermediate layer).
The undercoat layer is configured to include at least a resin, and is preferably a layer in which peeling does not occur in the undercoat layer when the olefin polymer layer and the sealing material are peeled off at a high temperature (for example, 150 ° C.).

  The thickness of the undercoat layer is preferably in the range of 2 μm or less, more preferably 0.005 μm to 2 μm, and still more preferably 0.01 μm to 1.5 μm. When the thickness is 0.005 μm or more, coating unevenness hardly occurs, and when the thickness is 2 μm or less, a decrease in workability due to stickiness of the film is suppressed.

The undercoat layer preferably contains one or more polymers selected from polyolefin resins, acrylic resins, polyester resins, and polyurethane resins.
As the polyolefin resin, for example, a modified polyolefin copolymer is preferable. Commercially available products may be used as the polyolefin resin. For example, Arrow Base SE-1013N, SD-1010, TC-4010, TD-4010 (both manufactured by Unitika Ltd.), Hitech S3148, S3121, S8512. (Both manufactured by Toho Chemical Co., Ltd.), Chemipearl S-120, S-75N, V100, EV210H (both 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., which is a terpolymer of low density polyethylene, acrylic acid ester, and maleic anhydride.
As the acrylic resin, for example, a polymer containing polymethyl methacrylate, polyethyl acrylate, or the like is preferable. A commercially available product may be used as the acrylic resin, and for example, AS-563A (manufactured by Daicel Einchem Co., Ltd.) can be preferably used.
As the polyester resin, for example, polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN) and the like are preferable. As the polyester resin, a commercially available product may be used. For example, Vylonal MD-1245 (manufactured by Toyobo Co., Ltd.) can be preferably used.
As the polyurethane resin, for example, a carbonate-based urethane resin is preferable, and for example, Superflex 460 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) can be preferably used.
Among these, it is preferable to use polyolefin resin from a viewpoint of ensuring adhesiveness with a base film and an intermediate | middle layer. These polymers may be used alone or in combination of two or more. When two or more of these polymers are used in combination, a combination of an acrylic resin and a polyolefin resin is preferable.

If the undercoat layer contains a crosslinking agent, the durability of the undercoat layer can be improved, which is more preferable. Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among them, in the polymer sheet of the present invention, the crosslinking agent in the undercoat layer is preferably an oxazoline-based crosslinking agent. As a cross-linking agent having an oxazoline group, Epocros K2010E, K2020E, K2030E, WS-500, WS-700 (all manufactured by Nippon Shokubai Co., Ltd.) and the like can be used.
The addition amount of the crosslinking agent is preferably 0.5 to 30% by mass, more preferably 5 to 20% by mass, and particularly preferably 3% by mass or more and less than 15% by mass with respect to the binder constituting the undercoat layer. . In particular, 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 undercoat layer, and when it is 30% by mass or less, the pot life of the coating liquid Can be kept long, and the coating surface shape can be improved if it is less than 15% by mass.

The undercoat layer preferably contains an anionic or nonionic surfactant. The range of the surfactant that can be used for the undercoat layer is the same as the range of the surfactant that can be used for the white layer. Of these, anionic surfactants are preferred.
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, the generation of repellency is suppressed and good layer formation is obtained, and when the addition amount is 10 mg / m ² or less, the base film and the intermediate layer Adhesion can be performed satisfactorily.

As a method for applying the coating liquid for forming the undercoat layer to the substrate film, a known coating method is appropriately adopted. For example, any method such as a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, a coating method using a spray or a brush can be used. Moreover, you may immerse a base film in the aqueous liquid of this invention.
From the viewpoint of cost, it is preferable to apply a coating solution for forming an undercoat layer by a so-called in-line coating method in which a film is coated in a film manufacturing process. Specifically, for example, a resin that forms a base film is extruded, casted on a cooling drum while using an electrostatic adhesion method or the like to obtain a sheet, and then stretched in the longitudinal direction, and then the longitudinal stretching. A method such as stretching in the lateral direction after applying the coating solution for forming the undercoat layer on one side of the subsequent film can be used. The conditions for drying and heat treatment during coating depend on the thickness of the coat and the conditions of the apparatus, but it is preferable that the coating is sent to the stretching step in the perpendicular direction immediately after coating and dried in the preheating zone or stretching zone of the stretching step. In such a case, it is normally performed at about 50 to 250 ° C.
The base film may be subjected to corona discharge treatment or other surface activation treatment.

  The solid concentration in the coating solution for forming the undercoat layer is preferably 30% by mass or less, particularly preferably 10% by mass or less. The lower limit of the solid content concentration is preferably 1% by mass, more preferably 3% by mass, and particularly preferably 5% by mass. An undercoat layer having a good surface shape can be formed within the above range.

-Weatherproof layer-
The protective sheet for a solar cell of the present invention further includes a weather resistance containing at least one of a fluororesin and a silicone-acrylic composite resin on the surface of the base film opposite to the surface on which the olefin polymer layer is disposed. It is preferable to have a conductive layer. As the weather resistant layer, it is more preferable that the first weather resistant layer containing the silicone-acrylic composite resin and the second weather resistant layer containing the fluororesin are laminated in this order from the base film side.
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.

In the portion of “— (Si (R ¹ ) (R ² ) —O) _n —” which is a polysiloxane segment in the composite polymer, R ¹ and R ² may be the same or different and can be covalently bonded to the Si atom. Represents a monovalent organic group.
Examples of the “monovalent organic group that can be covalently bonded to the Si atom” represented by R ¹ and R ² include a substituted or unsubstituted alkyl group (eg, methyl group, ethyl group, etc.), substituted or unsubstituted Aryl groups (eg, phenyl group, etc.), substituted or unsubstituted aralkyl groups (eg, benzyl group, phenylethyl etc.), substituted or unsubstituted alkoxy groups (eg: methoxy group, ethoxy group, propoxy group, etc.), A substituted or unsubstituted aryloxy group (eg, phenoxy group), substituted or unsubstituted amino group (eg, amino group, diethylamino group, etc.), mercapto group, amide group, hydrogen atom, halogen atom (eg, chlorine atom) Etc.).
Among them, R ¹ and R ² are each independently an unsubstituted or substituted alkyl group having 1 to 4 carbon atoms (particularly a methyl group or an ethyl group), an unsubstituted or substituted phenyl group, a mercapto group, An unsubstituted amino group and an amide group are preferable.

Specific examples of the — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer include a hydrolysis condensate of dimethyldimethoxysilane, dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane. Hydrolysis condensate, hydrolysis condensate of dimethyldimethoxysilane / vinyltrimethoxysilane, hydrolysis condensate of dimethyldimethoxysilane / 2-hydroxyethyltrimethoxysilane, dimethyldimethoxysilane / 3-glycidoxypropyltriethoxysilane Hydrolysis condensate of dimethyldimethoxysilane / diphenyl / dimethoxysilane / γ-methacryloxytrimethoxysilane.

The — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer may have a linear structure or a branched structure. Furthermore, a part of the molecular chain may form a ring.
The ratio of the — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer is preferably 15 to 85% by mass with respect to the total mass of the composite polymer. A mass% range is particularly preferred.
If the ratio of the polysiloxane moiety is less than 15% by mass, the adhesiveness may be poor when exposed to a moist heat environment, and if it exceeds 85% by mass, the liquid may become unstable.
The molecular weight of the — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) of the composite polymer is about 30,000 to 1,000,000 in terms of polystyrene-converted weight average molecular weight, but more preferably about 50,000 to 300,000.

There is no restriction | limiting in particular in the preparation method of-(Si (R _< ¹ _> ) (R _< ² _> )-O) _n- part (polysiloxane part) of a composite polymer, A well-known synthesis method can be used. Specifically, there is a method of adding an acid to an aqueous solution of an alkoxysilane compound such as dimethylmethoxysilane or dimethylethoxysilane, followed by hydrolysis and condensation.
The polymer structure portion copolymerized with the polysiloxane portion is not particularly limited, and acrylic polymers, polyurethane polymers, polyester polymers, rubber polymers, and the like can be used. Among these, acrylic polymers are particularly preferable from the viewpoint of durability.

Esters of acrylic acid (eg, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, etc.) or methacrylic acid esters (eg: methyl methacrylate, butyl methacrylate, hydroxyethyl acrylate, glycidyl) as monomers constituting the acrylic polymer And polymers composed of methacrylate, dimethylaminoethyl methacrylate and the like. Furthermore, examples of the monomer include carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, styrene, acrylonitrile, vinyl acetate, acrylamide, and divinylbenzene.
The acrylic polymer is a polymer obtained by polymerizing one or more of these monomers, and may be a homopolymer or a copolymer.
Specific examples of the acrylic polymer include methyl methacrylate / ethyl acrylate / acrylic acid copolymer, methyl methacrylate / ethyl acrylate / 2-bidroxyethyl methacrylate / methacrylic acid copolymer, methyl methacrylate / butyl acrylate / 2-bidoxy Examples include ethyl methacrylate / methacrylic acid / γ-methacryloxytrimethoxysilane copolymer, methyl methacrylate / ethyl acrylate / glycidyl methacrylate / acrylic acid copolymer, and the like.

As the polyurethane polymer, a polyurethane polymer comprising a polyisocyanate such as toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and a polyol such as diethylene glycol, triethylene glycol, or neopentyl glycol can be preferably used. There is no restriction | limiting in particular in the preparation method of a polyurethane-type polymer, A well-known synthesis method can be used.
Specific examples of the polyurethane polymer include urethane obtained from toluene diisocyanate and diethylene glycol, urethane obtained from toluene diisocyanate and diethylene glycol / neopentyl glycol, and urethane obtained from hexamethylene diisocyanate and diethylene glycol.

As the polyester polymer, a polyester polymer comprising a polycarboxylic acid such as terephthalic acid, isophthalic acid, adipic acid or sulfoisophthalic acid and the polyol described in the polyurethane can be preferably used. There is no restriction | limiting in particular in the preparation methods of a polyester-type polymer, A well-known synthesis method can be used.
Specific examples of polyester polymers include polyesters obtained from terephthalic acid / isophthalic acid and diethylene glycol, polyesters obtained from terephthalic acid / isophthalic acid / sulfoisophthalic acid and diethylene glycol, and adipic acid / isophthalic acid / sulfoisophthalic acid and diethylene glycol. There are polyester etc.

As the rubber polymer, a copolymer of a diene monomer such as butadiene, isoprene or chloroprene and a copolymer of these diene monomer and a monomer such as styrene copolymerizable therewith can be preferably used. There is no restriction | limiting in particular also in the preparation methods of a rubber-type polymer, A well-known synthesis method can be used.
Specific examples of the rubber-based polymer include a rubber-based polymer composed of butadiene / styrene / methacrylic acid, a rubber-based polymer composed of butadiene / methyl methacrylate / methacrylic acid, a rubber-based polymer composed of isoprene / methyl methacrylate / methacrylic acid, and chloroprene / acrylonitrile. / There are rubber polymers made of methacrylic acid.

  The polymer constituting the polymer structure portion copolymerized with the polysiloxane portion may be used alone or in combination of two or more. Furthermore, the individual polymers may be homopolymers or copolymers.

  The molecular weight of the polymer structure portion copolymerized with the polysiloxane portion is about 3000 to 1000000 in terms of polystyrene-equivalent weight average molecular weight, and more preferably about 5000 to 300000.

There is no particular limitation on the method of chemically bonding the — (Si (R ¹ ) (R ² ) —O) _n — moiety (polysiloxane moiety) and the polymer structure moiety copolymerized with this moiety. The polymer structure part copolymerized with this part is separately polymerized, each polymer is chemically bonded, the polysiloxane part is prepolymerized and graft polymerized, the copolymerized polymer part is prepolymerized There is a method of graft polymerization of the polysiloxane portion. The latter two methods are preferable because they are easy to create. For example, as a method of copolymerizing an acrylic polymer with a polysiloxane portion, there is a method in which a polysiloxane portion obtained by copolymerizing γ-methacryloxytrimethylsilane or the like is prepared, and this and an acrylic monomer are radically polymerized. Further, as a method of copolymerizing polysiloxane with an acrylic polymer portion, there is a method of causing hydrolysis and polycondensation by adding an alkoxysilane compound to an aqueous dispersion of an acrylic polymer containing γ-methacryloxytrimethylsilane.

When the polymer structure portion copolymerized with the polysiloxane portion is an acrylic polymer, a known polymerization method such as emulsion polymerization or bulk polymerization can be used, but ease of synthesis and aqueous polymer dispersion can be obtained. From the viewpoint, emulsion polymerization is particularly preferable.
Moreover, there is no restriction | limiting in particular in the polymerization initiator used for graft polymerization, Well-known polymerization initiators, such as potassium persulfate, ammonium persulfate, and azobisisobutyronitrile, can be used.

  By using the silicone-based composite polymer described above as the binder for the back surface layer, it becomes possible to make the adhesion between the back surface layer and the base film particularly good, and the adhesiveness is lowered even after a long period of time. It can be kept small.

  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 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 a 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.

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

  Examples of the fluorine resin contained in the composition for forming a weather resistant layer for forming a weather resistant layer include chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, Examples thereof include a fluoroethylene / ethylene copolymer and a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer. Among these, from the viewpoints of solubility and weather resistance, a chlorotrifluoroethylene / vinyl ether copolymer copolymerized with a vinyl compound is preferable.

Examples of the fluororesin contained in the composition for forming a weather-resistant layer include Obligato SW0011F (manufactured by AGC Co-Tech), Lumiflon LF200 (manufactured by Asahi Glass Co., Ltd.), Zaffle GK570 (manufactured by Daikin Industries, Ltd.), and the like. It is done.
From the viewpoint of weather resistance and film strength, the content of the fluororesin relative to the total solid mass of the composition for forming a weather resistant layer is preferably 40% by mass to 90% by mass, and 50% by mass to 80% by mass. It is more preferable that

Examples of the silicone-acrylic composite resin contained in the composition for forming a weather-resistant layer include Ceranate WSA1060 and WSA1070 [both manufactured by DIC Corporation] and H7620, H7630, and H7650 [both manufactured by Asahi Kasei Chemicals Corporation].
From the viewpoint of weather resistance and film strength, the content of the silicone-acrylic composite resin relative to the total solid content mass of the weather resistant layer forming composition is preferably 40% by mass to 90% by mass, and 50% by mass to 80% by mass. % Is more preferable.

The coating amount of the weather-resistant layer forming composition from adhesion standpoint of weatherability and the base film, it is preferable that the ^{0.5g / m 2 ~20g / m 2} , 3g / m 2 ~15g / More preferably, m ² is used.

Although there is no restriction | limiting in particular in the method for forming the composition for weatherproof layer formation, It is preferable to form by application | coating.
As a coating method, for example, a gravure coater or a bar coater can be used.
Water is preferably used as a coating solvent for the weathering layer forming composition, and it is preferable that 60% by mass or more of the solvent contained in the weathering layer forming composition is water. The aqueous composition is preferable in that it is difficult to load the environment, and the ratio of water is 60% by mass or more, which is advantageous in terms of explosion-proof property and safety.
The proportion of water in the composition for forming a weather-resistant layer is preferably larger from the viewpoint of environmental load, and more preferably 70% by mass or more of water in the total solvent.

  The weather resistant layer may contain various additives such as inorganic oxide fillers and fine particles other than inorganic oxide fillers, ultraviolet absorbers, antioxidants, and surfactants.

The layer thickness of the weather resistant layer is preferably 0.5 μm to 15 μm, and more preferably 3 μm to 10 μm. By setting the film thickness to 0.5 μm or more, weather resistance can be sufficiently exhibited, and by setting the film thickness to 15 μm or less, it is possible to suppress deterioration of the surface condition.
Note that the weather-resistant layer may be a single layer or a structure in which two or more layers are laminated. The solar cell protective sheet of the present invention preferably has a structure in which two weathering layers are laminated.

<Use of solar cell protective sheet>
The solar cell protective sheet of the present invention is suitable as a solar cell backsheet or a solar cell backsheet member constituting a part of the solar cell backsheet. It can also be used as a front sheet member for a solar cell that constitutes a part of a front sheet for a solar cell or a front sheet for a solar cell to be bonded to a stopper.

[Back sheet for solar cells]
When the solar cell protective sheet of the present invention is used as a solar cell backsheet, the solar cell protective sheet of the present invention is included, and preferably an intermediate colored layer is provided between the base film and the olefin polymer layer. A weathering layer is provided on the surface of the base film opposite to the side on which the olefin polymer layer is disposed.

  In the solar cell backsheet of the present invention, the surface of the base film on which the olefin polymer layer is disposed can sufficiently return the light passing through the cells of the solar cell to the cells, increasing the power generation efficiency. In the above, the light reflectance at a wavelength of 550 nm is preferably 70% or more, more preferably 75% or more, and further preferably 80% or more.

Since the protective sheet for a solar cell of the present invention has good adhesion between the olefin polymer layer and a sealing material (for example, EVA: ethylene-vinyl acetate copolymer) used for the solar cell module, an adhesive layer, etc. It can be pasted together without using any. In addition, the solar cell laminate in which a sealing material such as EVA is directly bonded to the olefin polymer layer of such a solar cell protective sheet has a long adhesiveness even with aging in a humid heat environment. Good over time.
On the other hand, the protective sheet for solar cell of the present invention is heated to a high temperature in the rework process because the adhesion with the sealing material is greatly reduced when the olefin polymer layer is heated to a high temperature (for example, 150 ° C.). By doing so, it can be easily peeled off from the sealing material and reattached.

[Solar cell module]
The solar cell protective sheet of the present invention is suitable for the production of a solar cell module.
In the solar cell module, for example, a solar cell element that converts sunlight light energy into electric energy is disposed between the transparent substrate on which sunlight is incident and the solar cell backsheet of the present invention described above. The substrate and the back sheet are sealed with a sealing material such as ethylene-vinyl acetate copolymer (EVA).

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 solar cell module 10 of the present invention includes a transparent front substrate 24 on the side on which sunlight is incident, a solar cell element 20, a sealing material 22 that seals the solar cell element 20, and a front surface of the sealing material 22. The solar cell backsheet 32 is disposed on the side opposite to the substrate 24 and adheres to the sealing material 22, the solar cell backsheet 32 includes the solar cell protection sheet 31 of the present invention, and an olefin The system polymer layer 18 is directly bonded to the sealing material 22.

Preferably, the solar cell element, the sealing material that seals the solar cell element, the surface protective member that adheres to the sealing material and protects the light-receiving surface side, and the sealing material that adheres to the light-receiving surface are opposite to each other A back surface protection member that protects the side, the sealing material includes an ethylene-vinyl acetate copolymer (EVA), and the back surface protection member is the back sheet for a solar cell of the present invention, the back surface for the solar cell It can be set as the structure which the olefin polymer layer of the sheet | seat adhered directly with the sealing material.
With the solar cell module having such a configuration, the solar cell backsheet can be adhered to the EVA for a long time even in a moist heat environment, and can be a long-life solar cell module. For example, it can be easily peeled off from the sealing material by heating to 150 ° C. and reattached.

The transparent front substrate may be appropriately selected from base materials that transmit light as long as the transparent front substrate has light transmittance through which sunlight can pass. 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.
In addition, you may use as a front board | substrate, without providing a colored layer in the protective sheet for solar cells of this invention.

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

[Reprocessing method of solar cell module]
For example, when a defect is found in a solar cell element, the solar cell module of the present invention can be easily peeled off from the sealing material by heating and reprocessed. That is, the solar cell module reworking method of the present invention includes a step of heating the solar cell module and peeling the solar cell backsheet from the sealing material.

In the step of peeling the solar cell backsheet from the encapsulant, it is preferable to heat from the solar cell backsheet side. For example, a solar cell module is mounted on a plate-like heating means such as a hot plate with the solar cell backsheet side facing, and heated from 100 ° C to 200 ° C from the solar cell backsheet side. Peel from the sealing material. In addition, if it heats from 2 directions of the front substrate side and the solar cell backsheet side, it can peel more easily.
After peeling, the solar cell element and the sealing material may be exchanged, and the peeled solar cell backsheet may be attached again.

  The solar cell module reworking method of the present invention is not limited to the rework process, and for example, when discarding a solar cell module whose performance has deteriorated due to long-term use, the solar cell backsheet is peeled off and disposed of separately. It can also be applied to recycling.

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

[Example 1]
<Preparation of base film>
-Synthesis of polyester-
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, an ethylene glycol solution of cobalt acetate and manganese acetate was added to 30 ppm and 15 ppm, respectively, with respect to the resulting polymer. After further stirring for 5 minutes, a 2% by mass ethylene glycol solution of a titanium alkoxide compound was added to 5 ppm with respect to the resulting polymer. Five minutes later, a 10% by mass ethylene glycol solution of ethyl diethylphosphonoacetate was added so as to be 5 ppm with respect to the resulting polymer. Thereafter, while stirring the low polymer at 30 rpm, the reaction system was gradually heated from 250 ° C. to 285 ° C. and the pressure was reduced to 40 Pa. The time to reach the final temperature and final pressure was both 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure, and the polycondensation reaction was stopped. And it discharged to cold water in the shape of a strand, and it cut immediately, and produced the polymer pellet (about 3 mm in diameter, about 7 mm in length). The time from the start of decompression to the arrival of the predetermined stirring torque was 3 hours.

  However, the titanium alkoxide compound used was the titanium alkoxide compound (Ti content = 4.44 mass%) synthesized in Example 1 of paragraph No. [0083] of JP-A-2005-340616.

-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.

-Base formation-
The pellets after undergoing solid phase polymerization as described above were melted at 280 ° C. and cast on a metal drum to prepare an unstretched base having a thickness of about 3 mm. Thereafter, the film was stretched 3.4 times in the longitudinal direction at 90 ° C., and then the coating solution for forming the undercoat layer below was applied to the corona-treated surface of the polyethylene terephthalate support so that the coating amount was 5.1 ml / m ^2. After MD stretching, coating was performed by an in-line coating method before TD stretching to form an undercoat layer having a thickness of 0.1 μm. The TD stretching temperature is 105 ° C., stretched 4.5 times in the TD direction, and heat treatment is performed for 15 seconds at a film surface of 200 ° C. The MD relaxation rate is 5% at 190 ° C., and the TD relaxation rate is 11%. Thermal relaxation was performed in the MD and TD directions to obtain a biaxially stretched polyethylene terephthalate support (hereinafter referred to as “PET base film”) having a thickness of 250 μm.

-Preparation of coating solution for forming undercoat layer-
Components in the following composition were mixed to prepare a coating solution for forming an undercoat layer.

(1) Preparation of coating solution for forming undercoat layer Each component in the following composition was mixed to prepare a coating solution for forming an undercoat layer.
<Composition of coating solution>
・ Polyolefin binder: 120 parts by mass
(Arrow Base SE-1013N, manufactured by Unitika Ltd., concentration 20% by mass)
・ Oxazoline-based crosslinking agent: 39 parts by mass
(Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., concentration 25% by mass)
Acrylic resin aqueous dispersion << intermediate colored layer binder resin B >> ... 87 parts by mass [AS-563A, manufactured by Daicel Finechem Co., Ltd.,
Solid content: 28% by weight latex]
・ Fluorosurfactant: 0.9 parts by mass
(Sodium = bis (3, 3, 4, 4, 5, 5, 6, 6-nonafluoro) = 2-sulfonite oxysuccinate, manufactured by Sankyo Chemical Co., Ltd., concentration 1% by mass)
・ Distilled water: 753 parts by mass

(2) Formation of undercoat layer Before forming the undercoat layer, one side of the PET base film was subjected to corona treatment under the following conditions.
・ Electrode and dielectric roll gap clearance: 1.6mm
・ Processing frequency: 9.6 kHz
Processing speed: 20 m / min Processing strength: 0.375 kV / A / min / m ²

-Preparation of white inorganic fine particle dispersion-
Components in the following composition were mixed, and the mixture was subjected to a dispersion treatment with a dynomill type disperser to obtain a white inorganic fine particle dispersion having a volume average particle size of 0.55 μm.
(Composition of white inorganic fine particle dispersion)
・ 1000 parts by weight of titanium dioxide [Taipeku CR-95, manufactured by Ishihara Sangyo Co., Ltd., solid content: 100% by mass; white pigment]
-500% by weight of 10% aqueous solution of polyvinyl alcohol (PVA-105) [PVA-105, manufactured by Kuraray Co., Ltd., solid content: 100% by mass]
-Surfactant 12 parts by mass [Demol EP, manufactured by Kao Corporation, solid content: 25% by mass]
-631 parts by weight of distilled water-6.5 parts by weight of preservative [AF337, manufactured by Daito Chemical Co., Ltd., solid content: 3.5%]

-Preparation of coating solution for forming intermediate colored layer and coating solution for forming olefin polymer layer-
Components in the following composition were mixed to prepare a coating solution for forming an intermediate colored layer and a coating solution for forming an olefin polymer layer.
(Composition of coating solution for forming intermediate colored layer)
-305 parts by mass of the white inorganic fine particle dispersion obtained above-polyolefin resin aqueous dispersion << intermediate colored layer binder resin A >> 442 parts by mass [Arrowbase SE-1013N, manufactured by Unitika Ltd.,
Solid content: 20.2% by mass]
・ Acrylic resin aqueous dispersion << Intermediate colored layer binder resin B >> 35 parts by mass [AS-563A, manufactured by Daicel Finechem Co., Ltd.]
Solid content: 28% by weight latex]
・ 99 parts by mass of water-soluble oxazoline compound [Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass]
・ Distilled water 106 parts by mass ・ Fluorosurfactant 4.3 parts by mass
(Sodium = bis (3, 3, 4, 4, 5, 5, 6, 6-nonafluoro) = 2-sulfonite oxysuccinate, manufactured by Fuji Film Fine Chemical Co., Ltd., concentration 2% by mass)
-23 parts by weight of diammonic phosphate [diammonic phosphate for food use, manufactured by Nippon Chemical Industry Co., Ltd., 35% aqueous solution]

(Composition of coating solution for forming olefin polymer layer)
Polyolefin resin: Arrow Base SA-1010 (manufactured by Unitika) MFR = 200 g / 10 min 211 parts by mass Water-soluble oxazoline compound 43 parts by mass [Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass ]
-734 parts by mass of distilled water-2.4 parts by mass of fluorosurfactant
(Sodium = bis (3, 3, 4, 4, 5, 5, 6, 6-nonafluoro) = 2-sulfonite oxysuccinate, manufactured by Fuji Film Fine Chemical Co., Ltd., concentration 2% by mass)
9.6 parts by weight of nonionic surfactant [Naroacty CL95, Sanyo Chemical Industries, Ltd., solid content: 1% aqueous solution]

-Formation of intermediate colored layer and olefin polymer layer-
One side of the PET substrate film on which the undercoat layer is formed is conveyed at a conveyance speed of 80 m / min and subjected to corona discharge treatment under the condition of 730 J / m ² , and then the color pigment (titanium oxide) is 5.5 g / m ^2. The intermediate colored layer forming coating solution was applied by a bar coating method so as to be dried at 170 ° C. for 2 minutes.
Subsequently, the coating solution for forming an olefin polymer layer was applied to a coating weight of 0.5 g / m ² and dried at 170 ° C. for 2 minutes.
Thereby, white PET in which a white intermediate colored layer (olefin-acrylic composite polymer layer) having a dry thickness of 6 μm and an olefin polymer layer having a dry thickness of 0.5 μm are laminated in this order on one side of the PET base film. A film was obtained.

<Formation of weather-resistant layer>
The following first weathering layer and the following second weathering layer were formed in this order on the surface opposite to the surface on which the white intermediate colored layer and the olefin polymer layer of the white base PET film were formed.

-Preparation of coating solution for forming first weathering layer-
Each component shown in the composition of the following coating solution for forming a first weathering layer was mixed to prepare a coating solution for forming a first weathering layer.

(Composition of coating solution for forming first weathering layer)
Acrylic / silicone binder (silicone resin) 188 parts by mass [Ceranate WSA-1070, manufactured by DIC, solid content: 40%]
-Water-soluble oxazoline compound 58 parts by mass [Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass]
-9.4 parts by mass of fluorosurfactant
(Sodium = bis (3, 3, 4, 4, 5, 5, 6, 6-nonafluoro) = 2-sulfonite oxysuccinate, manufactured by Fuji Film Fine Chemical Co., Ltd., concentration 1% by mass)
-254 parts by weight of the above white inorganic fine particle dispersion-6.2 parts by weight of dibasic ammonium phosphate [diammonic phosphate for food use, manufactured by Nippon Chemical Industry Co., Ltd., 35% aqueous solution]

-Formation of the first weathering layer-
The surface of the white PET film opposite to the surface coated with the white intermediate colored layer was transported at a transport speed of 80 m / min, and a corona discharge treatment was performed under the condition of 730 J / m ² . Thereafter, the first weathering layer forming coating solution is applied to the surface subjected to the corona discharge treatment so that the amount of titanium oxide is 10.5 g / m ² in terms of the coating amount. The film was dried at 0 ° C. for 2 minutes to form a first weather-resistant layer having a dry thickness of 9 μm.

-Preparation of coating solution for forming second weather resistant layer-
Each component shown in the composition of the following coating solution for forming a second weathering layer was mixed to prepare a coating solution for forming a second weathering layer.

(Composition of coating solution for forming second weather resistant layer)
・ 43 parts by mass of fluorine-based binder [Obligato SW0011F, manufactured by AGC Co-Tech, solid content: 36% diluted with water]
Water-soluble oxazoline compound 12 parts by mass [Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass]
-Nonionic surfactant 1.5 parts by mass [Naroacty CL95, Sanyo Chemical Industries, Ltd., solid content: 1% aqueous solution]
-1.3 parts by weight of dimmonium phosphate (dimmonium phosphate for food use, manufactured by Nippon Chemical Industry Co., Ltd., 35% aqueous solution)
-Lubricant 25.7 parts by mass [Chemical Pearl W950, manufactured by Mitsui Chemicals, solid content: 5% water dilution]
-Matting agent 5 parts by weight [Snowtex UP, Nissan Chemical Co., Ltd., diluted with 2% solids in water]
・ Silane coupling agent 5 parts by mass [TSL8340, Momentive Performance Japan, 2% solids hydrolyzate]
・ 114 parts by weight of distilled water

-Formation of second weathering layer-
The obtained coating solution for forming the second weather-resistant layer was applied on the first weather-resistant layer so that the amount of the fluororesin was 1.5 g / m ² in terms of the coating amount, and at 170 ° C. for 2 minutes. By drying, a second weathering layer having a dry thickness of 1.5 μm was formed.

  Thus, an undercoat layer, a white intermediate colored layer (olefin-acrylic composite polymer), and an olefin-based polymer layer are provided on one side of the PET base film, and the first weathering layer and the second layer are provided on the opposite side of the PET base film. A solar cell protective sheet provided with a weather-resistant layer was produced. This solar cell protective sheet was used as the solar cell protective sheet of Example 1.

<Evaluation of solar cell protective sheet>
Evaluation of sealing material adhesion of the solar cell protective sheet of Example 1, sealing material adhesion after aging with wet heat, reflectance, and weather resistance was performed by the following methods. The obtained results are shown in Table 1 below.

-1. Sealant adhesion before wet heat aging-
The protective sheet for solar cell produced as described above was cut into a width of 26 mm × 150 mm to prepare a sample piece. This sample piece is made of glass (Nippon Sheet Glass Co., Ltd. 26 mm × 76 mm), EVA (Hangzhou EVA sheet: F806, cut size: 26 mm × 76 mm), solar cell protective sheet (olefin polymer layer side facing). It laminated | stacked in order and it was made to adhere | attach with EVA by pressing using a vacuum laminator (Nisshinbo Co., Ltd. product). The bonding conditions at this time were as follows.
Vacuuming: 4 minutes at 145 ° C. Pressurization: 10 minutes In this way, the 74 mm portion from the end of the sample piece is not bonded to EVA, and the EVA evaluation sheet is bonded to the remaining 76 mm portion with the EVA sheet. Obtained.

(1) Adhesive force at room temperature (25 ° C.) The EVA non-adhered portion of the obtained adhesion evaluation sample and the glass plate are sandwiched between upper and lower clips of Tensilon (RTC-1210A manufactured by ORIENTEC), a peeling angle of 180 °, and a pulling speed. A tensile test was performed at 100 mm / min, and the adhesive strength was measured.
Based on the measured adhesive strength, ranking was performed according to the following evaluation criteria.

(Evaluation criteria)
A: 6 N / mm or more B: 5 N / mm or more and less than 6 N / mm C: 4 N / mm or more and less than 5 N / mm D: Less than 4 N / mm

(2) Adhesive strength under heating at 150 ° C. (peelability)
The glass side of the sample for adhesion evaluation was placed on the lower side, heated on a laminator at 150 ° C. for 5 minutes, then pulled using a digital force gauge (DPSHII manufactured by Imada Co., Ltd.) at 100 mm / min, and the adhesive strength was measured. . Ranking according to the following evaluation criteria.

(Evaluation criteria)
A: Less than 0.15 N / mm B: 0.15 N / mm or more and less than 0.25 N / mm C: 0.25 N / mm or more and less than 0.35 N / mm D: 0.35 N / mm or more

-2. Sealant adhesion after wet heat aging-
The sample piece produced as described above is held at ambient temperature of 120 ° C. and relative humidity of 100% for 30 hours (wet heat aging), and then the sealing material at room temperature (25 ° C.) before the wet heat aging described above. The adhesive strength with the EVA sheet was measured by the same method as the adhesion, and ranked according to the following evaluation criteria.

(Evaluation criteria)
A: 4 N / mm or more B: 3.0 N / mm or more and less than 4.0 N / mm C: Less than 3.0 N / mm

-3. Reflectance-
About the protective sheet for solar cells produced as mentioned above, the reflectance with respect to light of 550 nm was measured with spectrophotometer UV-3100 (made by Shimadzu Corporation) (incident from the olefin polymer layer). The reflectance of the barium sulfate standard plate was measured as a reference, and the reflectance of the solar cell protective sheet was calculated using this as 100%.
A: 80% or more B: 70% or more and less than 80% C: less than 70%

[Examples 2 to 25, Comparative Examples 1 to 5]
Example 1 except that any of the base film, the resin of the composition for forming an olefin polymer layer, the thickness of the olefin polymer layer, the kind of pigment in the intermediate colored layer, etc. was changed as shown in Table 1 below. In the same manner as described above, protective sheets for solar cells of Examples 2 to 25 and Comparative Examples 1 to 5 were produced and evaluated.

(Base film)
In Table 1, the base films other than the polyester film are as follows.
Polyolefin film: Syndiotactic by a bulk polymerization method of propylene in the presence of hydrogen using a catalyst comprising diphenylmethylene (cyclopentadienyl) fluorenylzirconium dichloride and methylaluminoxane according to JP-A-2-274863. Polypropylene {(The intrinsic viscosity measured in a tetralin solution at 135 ° C. is 1.39 dl / g, the melt flow index is 3.2 g / 10 min, the peak temperature of the crystallization temperature measured by differential scanning calorimetry is 74.6 ° C., ^The syndiotactic pentad fraction measured by ¹³ C-NMR was 78.7%) (H-SPP)}. 80 parts by mass of the syndiotactic polypropylene obtained above and 20 parts by mass of isotactic homopolypropylene (manufactured by Mitsui Toatsu Chemical Co., Ltd., JHH-G: MFI 8 g / 10 min) were blended, and the T- A syndiotactic polypropylene film having a thickness of 240 μm was obtained by forming a film at an extruder temperature of 210 ° C. and a cooling roll temperature of 30 ° C. using an extruder with a die.
Polyamide film: 98% by weight of polycaprolactam and 2% by weight of polycaprolactone having a molecular weight of 10,000 were mixed, melt-kneaded by an extruder set at 250 ° C., and pelletized. Subsequently, this pellet was melt-extruded from a T die at 270 ° C. and cooled on a drum at 30 ° C. to obtain an unstretched film. Subsequently, this film was simultaneously biaxially stretched at 80 ° C. to obtain a biaxially stretched polyamide film having a thickness of 240 μm.
・ Fluorine-containing film: TOYOFLON EL (250 μm), manufactured by Toray Film Processing Co., Ltd., ETFE film

(Olefin polymer layer)
In Table 1, the brand (symbol) of the resin constituting the olefin polymer layer means the following resin.
A-1: Arrow base SA-1010 (manufactured by Unitika) MFR: 200 g / 10 min A-2: Arrow base SE-1010 (manufactured by Unitika) MFR: 3 g / 10 min A-3: Arrow base SD-1010 ( (Made by Unitika) MFR: 5 g / 10 min A-4: Nucleel N1050H (Mitsui / DuPont Polychemical) MFR: 500 g / 10 min A-5: Bondine HX-8020 (Arkema) MFR: 200 g / 10 min A-6: Bondine TX-8030 (manufactured by Arkema) MFR: 3 g / 10 min A-7: Sumikasen G807 (manufactured by Sumitomo Chemical) MFR: 75 g / 10 min A-8: Arrow Base SB-1010 (manufactured by Unitika) ) MFR: 65 g / 10 min A-9: J-226T (manufactured by Prime Polymer Co., Ltd.) MFR: 20 g / 10 min * A-4 aqueous dispersion A-7 aqueous dispersion according manner of Example 8 of JP 2011-184593, to change the resin to be used, it was used by water-dispersed body of.

  In Table 1, the MFR of the olefin polymer layer is a melt flow rate (MFR) value at 190 ° C. under a load of 2160 g (according to JIS K7210: 1999). When the resin was blended to form an olefin polymer layer, the MFR of the blended resin was measured.

In Table 1, the extrusion molding of the olefin polymer layer was performed as follows.
After performing the corona discharge treatment under the condition of 730 J / m ^{2 on} the side where the intermediate layer of the base film is formed, the resin is extruded from the coat hanger die at a molten resin temperature of 320 ° C., and laminated to the base film. A laminate of a base film, an intermediate layer, and an olefin polymer layer was produced.

(Intermediate colored layer)

In Table 1, symbol C-1 of the intermediate colored layer means that two kinds of resins of the following brands are included.
C-1: Intermediate colored layer binder resin A / B (“Arrow Base SE-1013N” / “AS-563A”)

  In Example 25, carbon black (MF5630, manufactured by Dainichi Seika Co., Ltd., solid content: 32% by mass) was used as a coloring pigment in addition to the above-described titanium oxide. The compounding ratio (mass ratio) of titanium oxide and carbon black was set to 5.5: 1.

  The structure and evaluation results of the protective sheet for solar cell prepared in each example and comparative example are shown in Table 1 below.

  From Table 1 above, the solar cell protective sheet of the example is superior to the solar cell protective sheet of the comparative example at the normal temperature and after wet heat aging, and when heated to 150 ° C. It turns out that it is excellent in the peelability of.

[Example 101]
<Production and evaluation of solar cell module>
3 mm thick tempered glass, EVA sheet (RC02B manufactured by Mitsui Chemicals Fabro Co., Ltd.), crystalline solar cell, EVA sheet (RC02B manufactured by Mitsui Chemicals Fabro Co., Ltd.), and each example The thus-prepared solar cell protective sheets were superposed in this order and hot-pressed using a vacuum laminator (Nisshinbo Co., Ltd., vacuum laminating machine) to bond the EVA and each member. At this time, the protective sheet for solar cell of each Example was arrange | positioned so that the olefin type polymer layer might contact with an EVA sheet | seat. Further, as a bonding method, a vacuum laminator was used for vacuuming at 150 ° C. for 3 minutes, and then pressure was applied for 10 minutes for bonding.

  In this way, a crystalline solar cell module was produced. When the power generation operation was performed using the obtained solar cell module, all showed good power generation performance as a solar cell, and stable operation was performed over a long period of time.

DESCRIPTION OF SYMBOLS 10 Solar cell module 12 2nd weather resistant layer layer 14 1st weather resistant layer layer 16 Base film 17 Intermediate layer 18 Olefin containing polymer layer 20 Solar cell element 22 Sealing material 24 Transparent front substrate 31 Protective sheet for solar cell 32 Back sheet for solar cell

Claims (15)

A base film;
An olefin polymer layer that is disposed as an outermost layer on one side of the base film, includes an olefin resin, and has a melt flow rate of 75 g / 10 min to 300 g / 10 min;
A protective sheet for a solar cell.   The adhesion between the olefin polymer layer and the EVA sealing material at 25 ° C. when peeled in the 180 ° direction is 6 N / mm or more, and the olefin polymer layer and the EVA sealing material at 150 ° C. The protective sheet for solar cells according to claim 1, wherein the adhesion when peeled in the 180 ° direction is 0.25 N / mm or less.   The solar cell protective sheet according to claim 1 or 2, wherein the olefin resin is an olefin resin that has been acid-modified.   The thickness of the said olefin type polymer layer is 0.1 micrometer or more and 100 micrometers or less, The protective sheet for solar cells of any one of Claims 1-3.   The solar cell protective sheet according to claim 4, wherein the olefin polymer layer has a thickness of 0.1 μm to 10 μm.   The solar cell protective sheet according to any one of claims 1 to 5, wherein the olefin polymer layer is a layer formed by applying a coating liquid.   The solar cell protective sheet according to claim 6, wherein the olefin polymer layer is a layer formed by applying an aqueous coating solution.   The solar cell according to any one of claims 1 to 7, wherein the base film is a film containing at least one resin selected from the group consisting of polyester, polyolefin, polyamide, and fluorine-containing resin. Protective sheet.   The solar cell protective sheet according to any one of claims 1 to 8, further comprising an intermediate layer between the base film and the olefin polymer layer.   The protective sheet for solar cells according to claim 9, wherein the intermediate layer contains a color pigment.   The solar cell backsheet containing the protective sheet for solar cells of any one of Claims 1-10.   A first weathering layer containing a silicone-acrylic composite resin and a second weathering layer containing a fluororesin on the surface opposite to the side on which the olefin polymer layer of the solar cell protective sheet is disposed. The solar cell backsheet according to claim 11, wherein and are laminated in this order. A transparent front substrate on which sunlight is incident;
A solar cell element;
A sealing material for sealing the solar cell element;
The solar cell backsheet according to claim 11 or 12, wherein the olefin polymer layer is directly bonded to the sealing material, which is disposed on the opposite side of the sealing material to the front substrate.
Including solar cell module.   The solar cell module reworking method including the process of heating the solar cell module of Claim 13, and peeling the said solar cell backsheet from the said sealing material.   The solar cell module according to claim 14, wherein in the step of peeling the solar cell backsheet from the sealing material, the solar cell module is heated from two directions of the front substrate side and the solar cell backsheet side. Rework method.