JP6215273B2 - Protective sheet for solar cell, method for producing the same, and solar cell module - Google Patents

Description

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

  A solar cell module using crystalline silicon or amorphous silicon as a solar cell element is generally a transparent front substrate on which sunlight is incident, a battery side where a solar cell element as a photovoltaic element is sealed with a sealing material A substrate and a back surface protective material (so-called solar cell backsheet) are sequentially laminated, and are manufactured by using a lamination method or the like in which vacuum suction is performed and thermocompression bonding is performed. Since the solar cell module is placed in an environment (for example, on a roof) exposed to sunlight and wind and rain for a long period of time, the solar cell back sheet forming the solar cell module has durability in a humid heat environment. Various functions such as are required.

  In recent years, resin-made supports (polymer supports) have been used as transparent front substrates or solar cell backsheets used in solar cell modules. The polymer support can be provided with various functions by laminating functional layers, and is also useful from the viewpoint of realizing weight reduction and cost reduction of the solar cell module.

  The protection sheet for solar cells is often used as a laminate in which a functional layer is laminated on a polyester film from the viewpoint of imparting various functions. Typical functional layers include, for example, an adhesive layer for closely adhering to the battery side substrate sealing material, a white layer for improving the power generation efficiency by enhancing the function of reflecting sunlight incident on the module, and a long-term Examples include a weather resistant layer for imparting durability.

  On the other hand, as one of methods for providing the functional layer as described above, a method of forming a layer that exhibits a desired function by coating on a polymer support is known. In this case, in order to improve adhesion between the polymer support and the functional layer, an undercoat layer may be provided on the polymer support in advance. As specific examples, supplying an unstretched sheet containing a polymer constituting the polymer support, stretching the unstretched sheet in the first direction, and at least one surface of the sheet stretched in the first direction A method comprising applying a composition for forming an undercoat layer and stretching a sheet provided with the composition for forming an undercoat layer in a direction perpendicular to the first direction is disclosed ( For example, see Patent Document 1).

  Further, there is an example in which a polymer layer using a composite polymer containing a polysiloxane moiety is provided as a weather resistant layer on one surface of polyethylene terephthalate on which an undercoat layer containing a polyolefin binder is formed by the same method as in Patent Document 1. It is disclosed (for example, see Patent Document 2).

  Furthermore, it has a base film and an olefin-acrylic composite polymer layer disposed on at least one side of the base film, and an undercoat layer containing an olefin resin between the base film and the olefin-acrylic composite polymer layer An easy-adhesive sheet having the above has been disclosed (see, for example, Patent Document 3).

International Publication No. 2013/008945 JP 2013-58747 A JP 2014-74149 A

  A fluororesin or a silicone resin is an effective component in terms of imparting durability to the protective sheet of the solar cell module. When a composite polymer containing a polysiloxane moiety is used to form a weather resistant layer as in Patent Document 2 described above, the dispersion of the composite polymer in an aqueous coating solution tends to be insufficient, so that an undercoat layer is formed. It is difficult to maintain good adhesion between the polyethylene terephthalate and the weathering layer.

  Therefore, in the process of cutting, peeling occurs in the undercoat layer or the weather-resistant layer. As a result, chips may be generated during cutting, and a partial defect may occur in the cut surface. Such a phenomenon significantly impairs product quality.

  The present invention has been made in view of the above, and has excellent adhesion between a polyester film and a weather-resistant layer, and a solar cell protective sheet in which generation of chips during cutting is suppressed, a method for producing the same, and long-term durability. It aims at providing the solar cell module excellent in property, and makes it a subject to achieve this objective.

Specific means for achieving the above object includes the following embodiments.
<1> A biaxially stretched polyester film produced by stretching an unstretched polyester film in a first direction and stretching in a second direction perpendicular to the first direction along the film surface; One side of the stretched polyester film is formed by applying a coating solution before stretching in the second direction and stretching in the second direction, and contains only an acrylic resin as a resin component , or a resin An undercoat layer containing acrylic resin and polyolefin as components and having an acrylic resin content of 25% by mass or more based on the total amount of acrylic resin and polyolefin, and weather resistance including acrylic resin disposed on the undercoat layer And a solar cell protective sheet having a layer.
<2> The weather resistant layer is the protective sheet for solar cells according to <1>, wherein the thickness is 10 μm or more.
<3> On the side opposite to the side having the weather resistant layer of the biaxially stretched polyester film,
Does the polyester film stretched in the first direction contain only acrylic resin as a resin component formed by applying a coating liquid before stretching in the second direction and stretching in the second direction ? Or the sun as described in <1> or <2> which has an undercoat layer which contains an acrylic resin and polyolefin as a resin component, and the content of the acrylic resin with respect to the total amount of an acrylic resin and polyolefin is 25 mass% or more It is a protection sheet for batteries.
<4> The solar cell protective sheet according to any one of <1> to <3>, wherein the biaxially stretched polyester film contains a white pigment.
<5> The solar cell protective sheet according to <4>, wherein the white pigment is titanium dioxide.
<6> The solar cell protection according to any one of <1> to <5>, wherein the weatherable layer includes scattering particles, and the volume ratio of the scattering particles in the weathering layer is 10% to 30%. It is a sheet.
<7> The solar cell protective sheet according to <6>, wherein the scattering particles are titanium dioxide.
<8> The acrylic resin contained in the weather-resistant layer is the solar cell protective sheet according to any one of <1> to <7>, including at least one of a silicone / acrylic composite resin and an acrylic / fluorine composite resin. is there.
<9> A solar cell module including the protective sheet for solar cell according to any one of <1> to <8>.
<10> A step of stretching an unstretched polyester film in the first direction, and one surface of the polyester film stretched in the first direction contains only an acrylic resin as a resin component , or an acrylic resin as a resin component And a step of forming an undercoat layer containing 25% by mass or more of the acrylic resin with respect to the total amount of the acrylic resin and the polyolefin, and a polyester film having the undercoat layer formed in the first direction. And a step of forming a weathering layer containing an acrylic resin on the undercoat layer, and a method for producing a protective sheet for a solar cell.
<11> Between the step of stretching in the first direction and the step of stretching in the second direction, the other surface of the polyester film stretched in the first direction contains only an acrylic resin as a resin component. Or <10> including a step of forming an undercoat layer by coating containing an acrylic resin and a polyolefin as a resin component and having an acrylic resin content of 25% by mass or more based on the total amount of the acrylic resin and the polyolefin. It is a manufacturing method of the solar cell backsheet of description.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in the adhesiveness of a polyester film and a weather resistance layer, the protection sheet for solar cells by which generation | occurrence | production of the chip at the time of cutting was suppressed, its manufacturing method, and the solar cell module excellent in long-term durability. Is provided.

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

<Protective sheet for solar cell>
The protective sheet for solar cell of the present invention is a biaxially stretched polyester produced by stretching an unstretched polyester film in a first direction and stretching in a second direction perpendicular to the first direction along the film surface. An undercoat layer containing an acrylic resin formed by applying a coating liquid on one surface of a film and a polyester film stretched in the first direction before stretching in the second direction and stretching in the second direction And a weathering layer including an acrylic resin, which is disposed on the undercoat layer.
The protective sheet for a solar cell of the present invention may be further provided with a known functional layer such as a colored layer, an ultraviolet absorbing layer, a gas barrier layer, etc., if necessary.

Since the solar cell module is exposed to sunlight and wind and rain by being installed outdoors for a long period of time, long-term durability is required. Therefore, a protective sheet for a solar cell used as a back surface protective material (for example, a so-called back sheet for a solar cell) is also less prone to delamination of a laminated portion in which a plurality of layers are laminated, and even when placed in a humid heat environment It is desirable that it has excellent adhesiveness and is less likely to generate chips during cutting.
On the other hand, in order to improve the long-term durability of the back sheet for solar cells, it is effective to provide a weather resistant layer using a fluororesin or a silicone resin. However, since fluororesins and silicone resins have strong hydrophobic properties, in order to form a weather resistant layer by applying an aqueous coating solution, it is necessary to disperse the resin in water well. Therefore, an acrylic resin such as a composite resin in which a silicone component or a fluorine component and an acrylic component are combined is effective. Such a composite resin has relatively weak interfacial adhesion to, for example, polyethylene terephthalate (PET), and when the solar cell protective sheet is subjected to a cutting process after being exposed to a moist heat environment, chips associated with film peeling are removed. Likely to happen.
On the other hand, even if an undercoat layer using a conventionally used olefin resin is applied to PET as in Patent Document 3, for example, the occurrence of film peeling during cutting is not suppressed. In this respect, the improvement effect is poor even by a method of forming an undercoat layer in the process of stretching in two directions.
In the present invention, an undercoat layer containing an acrylic resin is provided on PET, and further, this undercoat layer is formed by an inline coating method in which biaxially stretched PET is formed between uniaxially stretched and biaxially stretched. Thus, even when the resin component of the weather resistant layer formed on the undercoat layer contains an acrylic resin such as a composite resin containing a silicone component or a fluorine component in the composite component, the adhesion between PET and the weather resistant layer Excellent in properties. As a result, generation of chips during cutting is effectively suppressed.

-Axis stretched polyester film-
The biaxially stretched polyester film in the present invention is a second direction that is an unstretched polyester film that is stretched in a first direction (for example, a film running direction (MD)) and orthogonal to the first direction along the film surface. (For example, it is produced by extending | stretching in the film width direction (TD; Transverse Direction)).
The detail of the extending | stretching method at the time of forming a biaxially stretched polyester film is mentioned later.

  Examples of the polyester that forms the polyester film include linear saturated polyesters synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of the linear saturated polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate, 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.

  The kind of polyester is not limited to the above, and a known polyester may be used. As well-known polyester, you may synthesize | combine using a dicarboxylic acid component and a diol component, and may use commercially available polyester.

  When the polyester is synthesized, for example, it can be obtained by reacting (a) a dicarboxylic acid component and (b) a diol component by at least one of an esterification reaction and a transesterification reaction by a well-known method.

  (A) As the dicarboxylic acid component, for example, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid Aliphatic dicarboxylic acids such as ethylmalonic acid; Alicyclic dicarboxylic acids such as adamantane dicarboxylic acid, norbornene dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dicarboxylic acid; terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-sodium sulfoisophthalic acid, Phenylindanecarbo Acid, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) aromatic dicarboxylic acids such as fluorene acid; dicarboxylic acids or their ester derivatives, and the like.

  (B) Examples of the diol component include fats such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. Group diols; cycloaliphatic diols such as cyclohexanedimethanol, spiroglycol and isosorbide; bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9′-bis (4-hydroxyphenyl) ) Aromatic diols such as fluorene; diol compounds such as;

  (A) It is preferable to use at least one aromatic dicarboxylic acid as the dicarboxylic acid component. More preferably, the dicarboxylic acid component contains an aromatic dicarboxylic acid as a main component. The “main component” means that the proportion of aromatic dicarboxylic acid in the dicarboxylic acid component is 80% by mass or more. A dicarboxylic acid component other than the aromatic dicarboxylic acid may be included. Examples of such a dicarboxylic acid component include ester derivatives such as aromatic dicarboxylic acids.

(B) It is preferable to use at least one aliphatic diol as the diol component. The aliphatic diol can contain ethylene glycol, and preferably contains ethylene glycol as a main component. The main component means that the proportion of ethylene glycol in the diol component is 80% by mass or more.

  The amount of the aliphatic diol (eg, ethylene glycol) used is in the range of 1.015 mol to 1.50 mol with respect to 1 mol of the aromatic dicarboxylic acid (eg, terephthalic acid) and, if necessary, its ester derivative. Is preferred. The amount of the aliphatic diol used is more preferably in the range of 1.02 mol to 1.30 mol, and still more preferably in the range of 1.025 mol to 1.10 mol. When the amount of the aliphatic diol used is in the range of 1.015 mol or more, the esterification reaction proceeds well, and in the range of 1.50 mol or less, for example, a by-product of diethylene glycol by dimerization of ethylene glycol. It is possible to maintain a large number of characteristics such as melting point, glass transition temperature, crystallinity, heat resistance, hydrolysis resistance, and weather resistance.

  A conventionally known reaction catalyst can be used for the esterification reaction or transesterification reaction. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and phosphorus compounds. Usually, it is preferable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst at an arbitrary stage before the polyester production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is.

  For example, in the esterification reaction step, an aromatic dicarboxylic acid and an aliphatic diol are polymerized in the presence of a catalyst containing a titanium compound. In this esterification reaction, an organic chelate titanium complex having an organic acid as a ligand is used as a catalyst titanium compound, and at least an organic chelate titanium complex, a magnesium compound, and an aromatic ring as a substituent are used in the process. It is preferable to provide a process of adding a pentavalent phosphate ester having no sulfite in this order.

  Specifically, in the esterification reaction step, first, an aromatic dicarboxylic acid and an aliphatic diol are added to a catalyst containing an organic chelate titanium complex that is a titanium compound prior to the addition of a phosphorus compound and a magnesium compound. Mix. Titanium compounds such as organic chelate titanium complexes have excellent catalytic activity for the esterification reaction, so that the esterification reaction can be performed satisfactorily. In this case, the titanium compound may be added to the mixture of the aromatic dicarboxylic acid component and the aliphatic diol component, or the aliphatic diol is mixed with the aromatic dicarboxylic acid component (or aliphatic diol component) and the titanium compound. You may mix a component (or aromatic dicarboxylic acid component). Moreover, you may make it mix an aromatic dicarboxylic acid component, an aliphatic diol component, and a titanium compound simultaneously. The mixing is not particularly limited in the method, and can be performed by a conventionally known method.

Here, in the polymerization of the polyester, it is also preferable to add the following compound.
As the pentavalent phosphorus compound, at least one pentavalent phosphate having no aromatic ring as a substituent is used. For example, phosphoric acid ester having a lower alkyl group having 2 or less carbon atoms as a substituent [(OR) ₃ —P═O; R = alkyl group having 1 or 2 carbon atoms], specifically, phosphoric acid Trimethyl and triethyl phosphate are particularly preferable.

  As an addition amount of a phosphorus compound, the quantity from which a phosphorus (P) element conversion value becomes the range of 50 ppm-90 ppm is preferable. The amount of the phosphorus compound is more preferably 60 ppm to 80 ppm, and even more preferably 60 ppm to 75 ppm.

By including a magnesium compound in the polyester, the electrostatic applicability of the polyester is improved.
Examples of the magnesium compound include magnesium salts such as magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. Among these, magnesium acetate is most preferable from the viewpoint of solubility in ethylene glycol.

  The amount of the magnesium compound added is preferably such that the magnesium (Mg) element conversion value is 50 ppm or more, more preferably 50 ppm to 100 ppm in order to impart high electrostatic applicability. The addition amount of the magnesium compound is preferably an amount that is in the range of 60 ppm to 90 ppm, more preferably an amount that is in the range of 70 ppm to 80 ppm, in terms of imparting electrostatic applicability.

In the esterification reaction step, the titanium compound as the catalyst component and the magnesium compound and phosphorus compound as the additive are within a range where the value Z calculated from the following formula (i) satisfies the following relational expression (ii). The case where it is added and melt polymerized is particularly preferred. Here, the P content is the phosphorus amount derived from the entire phosphorus compound including the pentavalent phosphate ester having no aromatic ring, and the titanium (Ti) content is derived from the entire Ti compound including the organic chelate titanium complex. This is the amount of titanium to be used. As described above, by selecting the combined use of the magnesium compound and the phosphorus compound in the catalyst system containing the titanium compound and controlling the addition timing and the addition ratio, while maintaining the catalyst activity of the titanium compound moderately high, yellow A color tone with less taste can be obtained, and heat resistance that hardly causes yellowing can be imparted even when exposed to high temperatures during polymerization reaction or subsequent film formation (during melting).
(I) Z = 5 × (P content [ppm] / P atomic weight) −2 × (Mg content [ppm] / Mg atomic weight) −4 × (Ti content [ppm] / Ti atomic weight)
(Ii) 0 ≦ Z ≦ 5.0

This is an index for quantitatively expressing the balance between the three because the phosphorus compound not only acts on titanium but also interacts with the magnesium compound.
Formula (i) expresses the amount of phosphorus that can act on titanium by excluding the phosphorus content that acts on magnesium from the total amount of phosphorus that can be reacted. When the value Z is positive, it can be said that there is an excess of phosphorus that inhibits titanium, and conversely, when it is negative, there is a shortage of phosphorus necessary to inhibit titanium. In the reaction, since each atom of Ti, Mg, and P is not equivalent, each mole number in the formula is weighted by multiplying by a valence.

  Polyester synthesis does not require special synthesis, etc., and is inexpensive and easily available using titanium compounds, such phosphorus compounds, and magnesium compounds, while having the reaction activity required for the reaction. A polyester excellent in color tone and coloration resistance to heat can be obtained.

  In the formula (ii), it is preferable that 1.0 ≦ Z ≦ 4.0 is satisfied from the viewpoint of further enhancing the color tone and heat resistance with heat while maintaining the polymerization reactivity, and 1.5 ≦ Z ≦ 3. The case where 0 is satisfied is more preferable.

  As a preferred embodiment of the esterification reaction step, before the esterification reaction is completed, a chelate titanium complex having 1 ppm to 30 ppm of citric acid or citrate as a ligand is added to the aromatic dicarboxylic acid and the aliphatic diol. It is good to add. Thereafter, 60 ppm to 90 ppm (more preferably 70 ppm to 80 ppm) of a weak acid magnesium salt is added in the presence of the chelate titanium complex, and after addition, an aromatic ring of 60 ppm to 80 ppm (more preferably 65 ppm to 75 ppm) is further added. It is preferable to add a pentavalent phosphate that does not have a substituent.

  The esterification reaction step should be carried out using a multistage apparatus in which at least two reactors are connected in series under conditions where ethylene glycol is refluxed while removing water or alcohol produced by the reaction out of the system. Can do.

The esterification reaction process may be performed in one stage or may be performed in multiple stages.
When performing an esterification reaction process in one step, the esterification reaction temperature is preferably 230 ° C to 260 ° C, more preferably 240 ° C to 250 ° C.
When the esterification reaction step is performed in multiple stages, the temperature of the esterification reaction in the first reaction tank is preferably 230 ° C to 260 ° C, more preferably 240 ° C to 250 ° C, and the pressure is 1.0 kg / cm. ^{2 ~5.0kg} / cm ^2, and more preferably from ^{2.0kg / cm 2 ~3.0kg / cm 2} . The temperature of the esterification reaction in the second reaction tank is preferably 230 ° C. to 260 ° C., more preferably 245 ° C. to 255 ° C., and the pressure is 0.5 kg / cm ^{2 to} 5.0 kg / cm ² , more preferably 1. 0.0 kg / cm ^{2 to} 3.0 kg / cm ² . Furthermore, when carrying out by dividing into three or more stages, it is preferable to set the conditions for the esterification reaction in the intermediate stage to the conditions between the first reaction tank and the final reaction tank.

  On the other hand, a polycondensation product is produced by subjecting the esterification reaction product produced by the esterification reaction to a polycondensation reaction. The polycondensation reaction may be performed in one stage or may be performed in multiple stages.

  The esterification reaction product such as an oligomer generated by the esterification reaction is subsequently subjected to a polycondensation reaction. This polycondensation reaction can be suitably performed by supplying it to a multistage polycondensation reaction tank.

For example, the polycondensation reaction conditions in the case of performing in a three-stage reaction tank are as follows: the first reaction tank has a reaction temperature of 255 to 280 ° C, more preferably 265 to 275 ° C, and a pressure of 100 to 10 torr (13.3). × 10 ^{−3 to} 1.3 × 10 ⁻³ MPa), more preferably 50 to 20 torr (6.67 × 10 ^{−3 to} 2.67 × 10 ⁻³ MPa), and the second reaction tank is a reaction The temperature is 265 to 285 ° C., more preferably 270 to 280 ° C., and the pressure is 20 to 1 torr (2.67 × 10 ^{−3 to} 1.33 × 10 ⁻⁴ MPa), more preferably 10 to ³ torr (1. 33 × 10 ^{−3 to} 4.0 × 10 ⁻⁴ MPa), and the third reaction vessel in the final reaction vessel has a reaction temperature of 270 to 290 ° C., more preferably 275 to 285 ° C., and a pressure of 10 to 0.1 torr ^{1.33 × 10 -3 ~1.33 × 10 -5} MPa), embodiments are preferred and more preferably ^{5~0.5torr (6.67 × 10 -4 ~6.67 ×} 10 -5 MPa).

  Additives such as light stabilizers, antioxidants, UV absorbers, flame retardants, lubricants (fine particles), nucleating agents (crystallization agents), crystallization inhibitors, etc. to the polyester synthesized as described above May further be included.

In the synthesis of polyester, it is preferable to perform solid phase polymerization after polymerization by esterification reaction. By solid-phase polymerization, it is possible to control the moisture content of the polyester, the crystallinity, the acid value of the polyester, that is, the concentration of the terminal carboxyl group of the polyester, and the intrinsic viscosity.
In particular, the ethylene glycol (EG) gas concentration at the start of solid phase polymerization is preferably higher in the range of 200 ppm to 1000 ppm than the EG gas concentration at the end of solid phase polymerization, more preferably 250 ppm to 800 ppm, and even more preferably 300 ppm. It is preferable to carry out solid phase polymerization by increasing the concentration in the range of ˜700 ppm. In this case, AV (terminal COOH concentration) can be controlled by adding an average EG gas concentration (average gas concentration at the start and end of solid-phase polymerization). That is, AV can be reduced by reaction with terminal COOH by adding EG. EG is preferably 100 ppm to 500 ppm, more preferably 150 ppm to 450 ppm, and still more preferably 200 ppm to 400 ppm.

Moreover, the temperature of solid state polymerization is preferably 180 ° C to 230 ° C, more preferably 190 ° C to 215 ° C, and further preferably 195 ° C to 209 ° C.
The solid phase polymerization time is preferably 10 hours to 40 hours, more preferably 14 hours to 35 hours, and still more preferably 18 hours to 30 hours.

Here, the polyester preferably has excellent hydrolysis resistance. Therefore, the carboxyl group content in the polyester is preferably 50 equivalent / t or less (where t means ton), more preferably 35 equivalent / t or less, and still more preferably 20 equivalent / t or less. It is. When the carboxyl group content is 50 equivalents / t or less, hydrolysis resistance can be maintained, and a decrease in strength when aged with heat and humidity can be suppressed. The lower limit of the carboxyl group content is 2 equivalents / t, more preferably 3 equivalents / t, from the viewpoint of maintaining adhesion between the layer formed on the polyester (for example, a colored layer).
The carboxyl group content in the polyester can be adjusted by polymerization catalyst species, film forming conditions (film forming temperature and time), solid phase polymerization, and additives (end-capping agent, etc.).

(White pigment)
In the production of the polyester film, it is possible to produce a white polyester film in which a white pigment is kneaded by mixing a polyester raw resin and a white pigment, kneading with an extruder or the like to form a film.
Thus, by including a white pigment in a polyester film, interlayer adhesion improves more by reducing the pigment amount contained in a weather-resistant layer etc. Thereby, for example, cross-cut adhesion is suppressed without impairing the reflectance, and generation of chips during cutting can be further reduced.

As the white pigment, those similar to the particles mentioned as the scattering particles that can be used in the weather resistant layer described later can be applied. Specifically, inorganic pigments such as titanium dioxide (TiO ₂ ), barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, colloidal silica can be preferably mentioned, and titanium dioxide is preferred.

  When the white pigment is included in the polyester film, for the same reason as described above, the amount of the white pigment is preferably 0.5% by mass to 20% by mass with respect to the total solid content of the polyester film, and 1% by mass to 10% by mass. % Is more preferable, and 1.5% by mass to 4.5% by mass is more preferable.

(Carbodiimide compound, ketene imine compound)
The polyester film whose raw material resin is polyester may contain at least one of a carbodiimide compound and a ketene imine compound. A carbodiimide compound and a ketene imine compound may be used individually by 1 type, respectively, and may use 2 or more types together. This is effective in suppressing deterioration of the polyester after thermostat and maintaining good insulation even after thermostat.

The carbodiimide compound or ketene imine compound is preferably contained in an amount of 0.1% by mass to 10% by mass, more preferably 0.1% by mass to 4% by mass with respect to the polyester. More preferably, the content is 1% by mass to 2% by mass. By setting the content of the carbodiimide compound or the ketenimine compound within the above range, the adhesion between the support and the adjacent layer can be further enhanced. Moreover, the heat resistance of a support body can be improved.
In addition, when a carbodiimide compound and a ketene imine compound are used together, it is preferable that the sum total of the content rate of two types of compounds exists in the said range.

  Examples of the carbodiimide compound include compounds having one or more carbodiimide groups in the molecule (including polycarbodiimide compounds). Specifically, as the monocarbodiimide compound, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, Examples include dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, N, N′-di-2,6-diisopropylphenylcarbodiimide and the like. As the polycarbodiimide compound, those having a degree of polymerization of usually 2 or more, preferably 4 or more and an upper limit of usually 40 or less, preferably 30 or less, are used, U.S. Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Pat. Org. Chem. 28, p2069-2075 (1963), and Chemical Review 1981, 81, No. 4, p. And those produced by the method described in 619-621 and the like.

  Examples of the organic diisocyanate that is a raw material for producing the polycarbodiimide compound include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and mixtures thereof. Specifically, 1,5-naphthalene diisocyanate, 4 , 4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4 A mixture of tolylene diisocyanate and 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate And 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 2,6-diisopropylphenyl isocyanate, 1,3,5-triisopropylbenzene-2,4-diisocyanate, etc. .

  Specific examples of industrially available polycarbodiimide compounds include Carbodilite (registered trademark) HMV-8CA (manufactured by Nisshinbo), Carbodilite (registered trademark) LA-1 (manufactured by Nisshinbo), and Starvacol (registered trademark) P (Rhein Chemie). Product), Starbazole (registered trademark) P100 (manufactured by Rhein Chemie), Starbaxol (registered trademark) P400 (manufactured by Rhein Chemie), stabilizer 9000 (manufactured by Rashihi Chemi) and the like.

  The carbodiimide compound can be used alone, but a plurality of compounds can also be mixed and used.

  Moreover, as a ketene imine compound, it is preferable to use the ketene imine compound represented by the following general formula (KA).

In the general formula (KA), R ¹ and R ² each independently represents an alkyl group, an aryl group, an alkoxy group, an alkoxycarbonyl group, an aminocarbonyl group, an aryloxy group, an acyl group, or an aryloxycarbonyl group. , R ³ represents an alkyl group or an aryl group.

Here, the molecular weight of the portion excluding the nitrogen atom of the ketene imine compound and the substituent R ³ bonded to the nitrogen atom is preferably 320 or more. That is, in the general formula ^(K-A), preferably has a molecular weight of R 1 -C (= C) -R 2 group is 320 or more. The molecular weight of the portion of the ketene imine compound excluding the nitrogen atom and the substituent R ³ bonded to the nitrogen atom is preferably 320 or more, more preferably 500 to 1500, and even more preferably 600 to 1000. preferable. Thus, the molecular weight of the portion excluding the substituent R ³ that is attached to the nitrogen atom and the nitrogen atom to be in the above range, it is possible to improve the adhesion between the support and the layer in contact with it. This is because the polyester end having a certain bulkiness diffuses into the layer in contact with the support and the anchoring effect because the portion excluding the nitrogen atom and the substituent R ³ bonded to the nitrogen atom has a certain range of molecular weight. It is to demonstrate.

  The biaxially stretched polyester film in the present invention can be produced by sequentially stretching a sheet formed using the above raw material resin in biaxial directions (first direction and second direction) perpendicular to each other. it can. Details of the stretching method will be described later.

-Undercoat layer-
The undercoat layer in the present invention includes an acrylic resin, and is applied to one side of a polyester film stretched in the first direction before applying the coating solution before stretching in the second direction, and then stretched in the second direction ( It is a coating layer (hereinafter also referred to as an inline coat layer) formed by a so-called inline coat described later. By biaxially stretching in a state where an undercoat layer is formed on a uniaxially stretched polyester film, adhesion of the formed undercoat layer to the polyester film is enhanced.
Details of the in-line coating will be described later.

The undercoat layer in the present invention may be formed on the side opposite to the side on which the weather resistant layer of the biaxially stretched polyester film is finally formed (that is, formed on both sides of the biaxially stretched polyester film). Details of the material, thickness, formation method, and the like in this case are the same as those of the undercoat layer provided on the side on which the weather resistant layer is formed.
When it has an undercoat layer on both sides of the biaxially stretched polyester film, the undercoat layer may have the same or different thickness and composition.

  The undercoat layer contains at least an acrylic resin as a resin component, and may contain other resin instead of a part of the acrylic resin. The undercoat layer may further contain various additives as necessary.

  As the acrylic resin, for example, a polymer containing polymethyl methacrylate, polyethyl acrylate, or the like is preferable. Commercially available products may be used as the acrylic resin. For example, AS-563A (manufactured by Daicel Finechem Co., Ltd.), Jurimer (registered trademark) ET-410, SEK-301 (both Nippon Pure Chemical Industries ( Co., Ltd.), Bonron PS-001, Bonlon PS-002 (both manufactured by Mitsui Chemicals, Inc.).

Examples of the other resin include one or more polymers selected from polyolefin, polyester, and polyurethane.
As the polyolefin, for example, a modified polyolefin copolymer is preferable. Commercially available products may be used as the polyolefin. For example, Arrow Base (registered trademark) 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 (registered trademark) S-120, S-75N, V100, EV210H (both manufactured by Mitsui Chemicals, Inc.) and the like. Among them, it is preferable to use Arrowbase (registered trademark) SE-1013N, manufactured by Unitika Co., Ltd., which is a terpolymer of low density polyethylene, acrylic acid ester, and maleic anhydride. .

Polyolefins may be used alone or in combination of two or more. When using 2 or more types together, the combination of an acrylic resin and polyolefin, the combination of polyester and polyolefin, the combination of a urethane resin and polyolefin is preferable, and the combination of an acrylic resin and polyolefin is more preferable.
When the acrylic resin and the polyolefin are used in combination, the content of the acrylic resin relative to the total of the polyolefin and the acrylic resin in the undercoat layer is preferably 25% by mass to 100% by mass, more preferably 50% by mass to 100% by mass, 75 mass%-100 mass% are especially preferable. When the content of the acrylic resin is 25% by mass or more, chip resistance at the time of cutting can be favorably maintained.
On the other hand, for example, when forming an undercoat layer using only polyolefin without containing an acrylic resin, the effect of improving the adhesion between the undercoat layer and the weather resistant layer is poor even when the undercoat layer is formed by the in-line coating method. The effect of improving chip resistance is small.

  Polyester (for example, Vylonal (registered trademark) MD-1245 (manufactured by Toyobo Co., Ltd.)) can be preferably used in combination with polyolefin, and it is also preferable to add polyurethane to polyolefin, for example, carbonate-based polyurethane is preferable. For example, Superflex (registered trademark) 460 (Daiichi Kogyo Seiyaku Co., Ltd.) can be preferably used.

As polyester, for example, polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN) and the like are preferable. As the polyester, a commercially available product may be used. For example, Vylonal (registered trademark) MD-1245 (manufactured by Toyobo Co., Ltd.) can be preferably used.
As the polyurethane, for example, a carbonate-based urethane resin is preferable, and for example, Superflex (registered trademark) 460 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) can be preferably used.

Examples of the crosslinking agent that can be contained in the undercoat layer include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Especially, it is preferable that it is at least 1 or more types of crosslinking agents chosen from a carbodiimide type crosslinking agent, an oxazoline type crosslinking agent, and an isocyanate type crosslinking agent.
As a crosslinking agent, what was demonstrated in the below-mentioned weatherability layer is applicable also to an undercoat layer.

A method for forming the undercoat layer will be described later.
There is no restriction | limiting in particular as thickness of an undercoat layer, The range of 10 nm-1000 nm is preferable, The range of 10 nm-500 nm is more preferable, 100 nm-500 nm are further more preferable.

-Weatherproof layer-
The weather-resistant layer in the present invention is a layer disposed on the undercoat layer, contains at least an acrylic resin, and further contains other components such as a crosslinking agent, a surfactant, a filler, and an ultraviolet absorber as necessary. May be included.

(acrylic resin)
Examples of the acrylic resin include polymers containing polymethyl methacrylate, polyethyl acrylate, etc., and a silicone / acrylic composite resin in which silicone and acrylic are combined in terms of improving weather resistance against sunlight, wind and rain, etc. An acrylic / fluorine composite resin in which acrylic and a fluorine compound are combined is preferable.

Commercially available products may be used as the acrylic resin. For example, AS-563A (manufactured by Daicel Finechem Co., Ltd.), Julimer (registered trademark) ET-410, SEK-301 (both Nippon Pure Chemical Industries ( Co., Ltd.), Bonron PS-001, Bonlon PS-002 (both manufactured by Mitsui Chemicals, Inc.).
Examples of the silicone / acrylic composite resin include Ceranate (registered trademark) WSA 1060 and WSA 1070 (both manufactured by DIC Corporation), and H7620, H7630, and H7650 (both manufactured by Asahi Kasei Chemicals Corporation). Examples of the acrylic / fluorine composite resin include Obligard (registered trademark) SW0011F (manufactured by AGC Co-Tech), SIFCLEAR F101, F102 (manufactured by JSR)), KYNAR AQ.
UQTEC ARC, FMA-12 (both manufactured by Arkema Co., Ltd.) and the like.

The silicone / acrylic composite resin is a polymer having a (poly) siloxane structure and an acrylic structure in the molecular chain. The weather-resistant layer contains a silicone / acrylic composite resin, so that the protective sheet for solar cells adheres to adjacent materials such as polyester film, and is durable in wet and hot environments. Will be better.
The silicone / acrylic composite resin is not particularly limited as long as it has a (poly) siloxane structure and an acrylic structure in the molecular chain, and a homopolymer (homopolymer) of a compound having a (poly) siloxane structural unit and an acrylic structure. Polymer) or a copolymer containing a (poly) siloxane structural unit and an acrylic structural unit.
The silicone / acrylic composite resin preferably has a siloxane structural unit represented by the following general formula (1) as a (poly) siloxane structure.

In the general formula (1), R ¹ and R ² each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group. Here, R ¹ and R ² may be the same or different, and a plurality of R ¹ and R ² may be the same or different from each other. n represents an integer of 1 or more.
The partial structure of “— (Si (R ¹ ) (R ² ) —O) _n —”, which is a siloxane structural unit in the silicone resin, has various (poly) siloxane structures having a linear, branched, or cyclic structure. It is a siloxane segment that can form

Examples of the halogen atom when R ¹ and R ² represent a halogen atom include a fluorine atom, a chlorine atom, and an iodine atom.
In the case where R ¹ and R ² represent a monovalent organic group, the monovalent organic group may be any group that can be covalently bonded to an Si atom, such as an alkyl group (eg, methyl group, ethyl group). Etc.), aryl groups (eg: phenyl groups, etc.), aralkyl groups (eg: benzyl groups, phenylethyl etc.), alkoxy groups (eg: methoxy groups, ethoxy groups, propoxy groups etc.), aryloxy groups (eg: phenoxy groups) Etc.), mercapto group, amino group (eg, amino group, diethylamino group, etc.), amide group and the like. These organic groups may be unsubstituted or may further have a substituent.
n is preferably 1 to 5000, and more preferably 1 to 1000.

Among these, R ¹ and R ² are each independently a hydrogen atom, a chlorine atom, a bromine atom, an unsubstituted or substituted, in terms of adhesion to adjacent materials such as polyester film and durability in a humid heat environment. An alkyl group having 1 to 4 carbon atoms (particularly a methyl group or an ethyl group), an unsubstituted or substituted phenyl group, an unsubstituted or substituted alkoxy group, a mercapto group, an unsubstituted amino group, or an amide group. It is preferably an unsubstituted or substituted alkoxy group (preferably an alkoxy group having 1 to 4 carbon atoms) from the viewpoint of durability in a moist and hot environment.

The ratio of “— (Si (R ¹ ) (R ² ) —O) _n —” in the resin (the (poly) siloxane structural unit represented by the general formula (1)) is based on the total mass of the resin. In particular, it is preferably 15% by mass to 85% by mass. Among them, the strength of the polyester film surface is improved, the occurrence of scratches due to scratching or scratching is prevented, and adhesion to adjacent materials such as a polyester film and the like. From the viewpoint of being more excellent in durability under a humid heat environment, the ratio of the (poly) siloxane structural unit is more preferably in the range of 20% by mass to 80% by mass. When the ratio of the (poly) siloxane structural unit is 15% by mass or more, the strength of the polyester film surface is improved, and scratches caused by scratches, scratches, collisions of flying pebbles, etc. are prevented, and a support is formed. Excellent adhesion to adjacent materials such as polyester film. Suppression of the occurrence of scratches improves weather resistance and effectively enhances peeling resistance, shape stability, and adhesion durability when exposed to a humid heat environment, which are easily deteriorated by heat and moisture. Moreover, a liquid can be kept stable as the ratio of a (poly) siloxane structural unit is 85 mass% or less.

  When the acrylic resin in the present invention is a copolymer polymer having a (poly) siloxane structural unit and an acrylic structural unit, the (poly) siloxane structural unit represented by the general formula (1) in the molecular chain is 15 by mass ratio. The case where it contains 85 mass%-85 mass% and 85 mass%-15 mass% in an acrylic structural unit by mass ratio is preferable. By containing such a copolymer, the film strength of the polyester film is improved, the occurrence of scratches due to scratching and scratching is prevented, and adhesion with the polyester film forming the support, that is, heat and moisture are given. It is possible to drastically improve the peel resistance, shape stability, and durability in a humid heat environment, which are easily deteriorated.

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

A non-siloxane structural unit (derived from an acrylic monomer, a non-siloxane monomer, and a non-siloxane polymer) that is copolymerized with a (poly) siloxane structural unit may have a polymer segment derived from an acrylic polymer. preferable. By having a polymer segment derived from an acrylic polymer, in addition to being easy to prepare, it has excellent hydrolysis resistance, chip prevention during cutting, and excellent adhesion to a polyester film.
About the polymer which forms a non-siloxane type structural unit, 1 type of an acrylic structural unit may be individual, and 2 or more types containing an acrylic structural unit may be used together.

  In the weather resistant layer, an acrylic resin may be used alone or in combination with other resins. When other resins are used in combination, the content ratio of the acrylic resin such as a composite resin containing a (poly) siloxane structure is preferably 30% by mass or more, more preferably 60% by mass or more of the total resin amount. When the content ratio of the acrylic resin is 30% by mass or more, adhesion with the polyester film becomes better, and generation of chips during cutting can be effectively prevented. In addition, it is more excellent in durability under humid heat environment.

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

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

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

In addition, as the acrylic resin having a (poly) siloxane structure, a commercially available product may be used, for example, SERATE series manufactured by DIC Corporation (for example, SERATE (registered trademark) WSA1070, WSA1060, etc.). Asahi Kasei Chemicals Co., Ltd. H7600 series (H7650, H7630, H7620, etc.), JSR Co., Ltd. inorganic-acrylic composite emulsion, etc. can be used.

The acrylic / fluorine composite resin is a polymer having a repeating unit represented by-(CFX ¹ -CX ² X ³ )-and an acrylic repeating unit. In the formula, X ¹ , X ² , and X ³ each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, or a perfluoroalkyl group having 1 to 3 carbon atoms.
Specific examples of the acrylic / fluorine resin include Obligard (registered trademark) SW0011F (manufactured by AGC Cortec Co., Ltd.), SIFCLEAR F101, SIFCLEAR F102 (manufactured by JSR), KYNAR AQUAQTEC ARC, FMA-12 (both Arkema ( Etc.).

  The acrylic resin may be used by being dissolved in an organic solvent, or may be used by dispersing particles in water. The latter is preferable in that the environmental load is small.

  The aqueous dispersion of acrylic resin is described in, for example, Japanese Patent Application Laid-Open Nos. 2003-231722, 2002-20409, and 9-194538, and the polymer described herein is used in the present invention. Applicable.

The content ratio of the acrylic resin in the weather resistant layer is 0.5 g / m ^{2 to} 20.0 g / m in terms of improving the adhesion with the polyester film of the weather resistant layer and suppressing the generation of chips during cutting. ² ranges preferably in ^the range of 8.0g / ^{m 2} ~20.0g / m 2 is more preferable.

  Among them, the weather-resistant layer is preferably in the form of using SER Corporation series manufactured by DIC Corporation and inorganic / acrylic composite emulsion manufactured by JSR Corporation as the polymer.

As the resin for the weather-resistant layer, an acrylic resin may be used alone, or two or more kinds may be used in combination.
Moreover, you may use together resins other than acrylic resin, such as a fluororesin, polyester, a polyurethane, polyolefin, a silicone resin, in the range which does not exceed 50 mass% of all the resins. The target weather resistance improvement effect is acquired because the content rate of resin other than an acrylic resin is 50 mass% or less with respect to the resin component in a weather resistance layer.

(Scattering particles)
The weather resistant layer preferably contains at least one kind of scattering particles. The scattering particles are not particularly limited, and known scattering particles can be used. In the present specification, the scattering particle means a particle that hardly absorbs light in the particle itself, and does not include a colorant described later. In the present invention, white pigments are preferred as the scattering particles.
Examples of white pigments that can be used as scattering particles include titanium dioxide (TiO ₂ ), barium sulfate, silicon dioxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, colloidal silica and other inorganic pigments, and organic pigments such as hollow particles. Is mentioned. Of these, titanium dioxide is preferable.
The crystal system of titanium dioxide includes rutile type, anatase type, and brookite type. The titanium dioxide in the present invention is preferably a rutile type. Titanium dioxide may be surface-treated with aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), alkanolamine compound, silicon compound or the like as necessary.

By adding a white pigment as scattering particles to the weather resistant layer in addition to the acrylic resin, the reflectance of the weather resistant layer can be increased. And yellowing under an ultraviolet (UV) irradiation test (according to the UV test of IEC61215, the total irradiation amount is 45 Kwh / m ² ). Further, by adding a white pigment such as scattering particles to the weather resistant layer, the adhesion with other adjacent layers is further improved.

The content of the case of using the scattering particles weather resistance layer is preferably a weather-resistant layer per layer ^{1.0g / m 2 ~40g / m 2} . When the content of the scattering particles (preferably a white pigment) is 1.0 g / m ² or more, reflectance and UV resistance (weather resistance) can be effectively provided.
Further, when the content of the scattering particles (preferably white pigment) in the weather resistant layer is 40 g / m ² or less, the surface state of the colored layer is easily maintained, and the film strength is excellent. Among them, the content of the scattering particles contained in the weathering ^layer, more preferably in the range of ^{2.5g / m 2 ~30g / m 2} , the range of 5g / ^{m 2} ~20g / m 2 is particularly preferable.

  Further, when the weather resistant layer contains scattering particles, the volume ratio of the scattering particles in the weather resistant layer preferably occupies 10% or more and 30% or less with respect to the total volume of the weather resistant layer, and is 20% or more. More preferably, it occupies 30% or less. When the volume ratio of the scattering particles is 10% or more, the resin amount does not increase excessively, and the content ratio of the scattering particles can be maintained, so that the light reflectance can be favorably maintained. If it is 20% or more, higher light reflectance can be maintained. In addition, when the volume ratio of the scattering particles is 30% or less, the amount of resin is maintained and the layer is not easily brittle, and the cross-cut adhesion and chip resistance during cutting can be further improved.

  The average particle diameter of the scattering particles (particularly white pigment) is preferably 0.03 μm to 0.8 μm, more preferably 0.15 μm to 0.6 μm in terms of volume average particle diameter. When the average particle size is within the above range, the light reflection efficiency is excellent. The average particle diameter is a value measured using Microtrac MT3300EXII (manufactured by Nikkiso Co., Ltd.).

(Coloring agent)
The colorant is not particularly limited except that the scattering particles are excluded, and a known dye or a known pigment can be used. In the present invention, the colorant is preferably a black colorant, a green colorant, a blue colorant, or a red colorant.

The color pigment used for the weather resistant layer is not particularly limited except that it preferably contains at least one selected from carbon black, titanium black, black composite metal oxide, cyanine color and quinacridone color, The selection may be made according to the required optical density.
Here, as the black composite metal oxide, a composite metal oxide containing at least one selected from iron, manganese, cobalt, chromium, copper, and nickel is preferable, and iron, manganese, cobalt, chromium, copper, and A composite metal oxide containing at least two selected from nickel is more preferable. Among them, at least one pigment whose color index is selected from Pigment Black (hereinafter referred to as PBk) 26, PBk 27, and PBk 28, and Pigment Blue (hereinafter referred to as PBr) 34 is more particularly preferable.
Of the above-mentioned pigments, PBk26 is a composite oxide of iron, manganese, and copper, PBk27 is a composite oxide of iron, cobalt, and chromium, and PBk-28 is copper, chromium, and It is a complex oxide of manganese, and PBr34 is a complex oxide of nickel and iron.
Examples of the cyanine color and quinacridone color include cyanine green, cyanine blue, quinacridone red, phthalocyanine blue, and phthalocyanine green.

Among these, carbon black is preferably used as the colorant from the viewpoint of easily controlling the optical density within the above preferable range and from the viewpoint of controlling the optical density with a small amount.
The carbon black is preferably carbon black particles having a particle diameter of 0.1 μm to 0.8 μm. Carbon black is preferably used by dispersing particles in water together with a dispersant.
Carbon black that can be obtained commercially can be used, for example, MF-5630 black (manufactured by Dainichi Seika Co., Ltd.) and paragraph [0035] of JP2009-132877A. ] Etc. can be used.

(Other ingredients)
The weather-resistant layer may contain other components such as a cross-linking agent, a surfactant, a filler, an ultraviolet absorber, and a color pigment as necessary. Among these, from the viewpoint of further improving the strength and durability of the weather resistant layer, the weather resistant layer preferably has a crosslinked structure derived from the crosslinking agent by adding a crosslinking agent to the resin.

[Crosslinking agent]
Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among cross-linking agents, oxazoline-based cross-linking agents are particularly used from the viewpoint of ensuring adhesion after wet heat aging between the weather-resistant layer and the undercoat layer (in-line coat layer) or between the weather-resistant layer and the polyester film. preferable.

  Specific examples of the oxazoline-based crosslinking agent include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline. 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2′-bis- (2-oxazoline), 2,2′-methylene-bis- ( 2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline) 2,2′-hexamethylene-bis- (2-oxazoline), 2,2′-octamethylene-bis- (2-oxazoline), 2,2′-ethylene-bis- ( , 4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'- Examples include m-phenylene-bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinyl norbornane) sulfide, and the like. Furthermore, (co) polymers of these compounds can also be preferably used.

  A commercially available product may be used as the oxazoline-based crosslinking agent, and for example, EPOCROS (registered trademark) K2010E, K2020E, K2030E, WS500, WS700 [all manufactured by Nippon Shokubai Co., Ltd.] and the like can be used.

[Catalyst for cross-linking agent]
In the weather resistant layer, a crosslinking agent catalyst may be used in combination with the crosslinking agent.
By containing the crosslinking agent catalyst, the crosslinking reaction between the binder (resin) and the crosslinking agent is promoted, and the solvent resistance is improved. Moreover, the strength and dimensional stability of the weather resistant layer can be further improved by proceeding with good crosslinking. In particular, when a crosslinking agent having an oxazoline group (oxazoline-based crosslinking agent) is used as the crosslinking agent, it is preferable to use a catalyst for the crosslinking agent in combination.

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, as the onium compound, an ammonium salt, a sulfonium salt, an iodonium salt, and a phosphonium salt are more preferable, and an ammonium salt is more preferable in terms of shortening the curing time. The onium compound is preferably a phosphate-based or benzyl chloride-based compound from the viewpoints of safety, pH, and cost. Of the onium compounds, dibasic ammonium phosphate is particularly preferred.

  When a crosslinking agent is used for the weather resistant layer, the content of the crosslinking agent is preferably 0.5 parts by mass or more and 30 parts by mass or less, more preferably 3 with respect to 100 parts by mass of the resin component contained in the weather resistant layer. More than 15 parts by mass. When the content of the crosslinking agent is 0.5 parts by mass or more, a good crosslinking effect can be obtained while maintaining the strength and adhesiveness of the weather resistant layer. Moreover, the pot life of the coating liquid prepared for weatherproof layer formation can be kept long as content of a crosslinking agent is 30 mass% or less. When the content of the crosslinking agent is less than 15% by mass, the coated surface shape is improved.

[Surfactant]
Examples of the surfactant include known surfactants such as an anionic surfactant and a nonionic surfactant.
If containing a surfactant, the content of the surfactant ^is preferably ^{0.1mg / m 2 ~10mg / m 2} , more preferably ^{0.5mg / m 2 ~3mg / m 2} . When the content of the surfactant is 0.1 mg / m ² or more, it is easy to form a good layer by suppressing the occurrence of repellency in the coating solution. Adhesion with a polyester film etc. can be performed favorably as content of surfactant is 10 mg / m < ² > or less.

[Filler]
As the filler, a known filler such as colloidal silica can be used. The content of the filler is preferably 20% by mass or less, more preferably 15% by mass or less, with respect to the acrylic resin of the weather resistant layer. When the filler content is 20% by mass or less, the surface shape of the weather-resistant layer can be kept better.

[Ultraviolet absorber]
As the ultraviolet absorber, either an organic ultraviolet absorber or an inorganic ultraviolet absorber may be used.
Examples of organic ultraviolet absorbers include benzophenone, benzotriazole, cyanoacrylate, triazine, salicylic acid, oxalic anilide, malonic ester, benzoic acid, cinnamic acid, or dibenzoyl A methane-based ultraviolet absorber can be used. Specifically, for example, Tinuvin 326 is exemplified as a benzotriazole-based ultraviolet absorber. Examples of triazine-based ultraviolet absorbers include Tinuvin 400, Tinuvin 479, Tinuvin 400-DW, and Tinuvin 479-DW (all manufactured by BASF). Examples of the oxalic acid anilide-based ultraviolet absorber include Hostavin 3260HP (manufactured by Clariant). Examples of the malonic ester-based ultraviolet absorber include Hostavin PR25 (manufactured by Clariant). Examples of the benzophenone-based ultraviolet absorber include Siasorb UV531 (manufactured by Cytec Industries).
Further, in addition to the ultraviolet absorber, a light stabilizer may be further contained. As the light stabilizer, hindered phenol or hindered amine may be used.

  Examples of the inorganic ultraviolet absorber include metal oxides such as titanium oxide, zinc oxide, and cerium oxide, and carbon-based components such as carbon, fullerene, carbon fiber, and carbon nanotube.

The content of the ultraviolet absorber in the weather resistant layer varies depending on the type of the ultraviolet absorber, but is preferably in the range of 0.2 g / m ^{2 to} 5 g / m ^2, preferably 0.3 g / m ^{2 to} 3 g / m. A range of ² or less is more preferable.

  The weather resistant layer may contain a color pigment in addition to the scattering particles. By containing a color pigment, a solar cell protective sheet having a weather-resistant layer colored in black, blue, or the like can be produced. The weather resistant layer can also be made transparent without adding a color pigment.

  The thickness of the weather resistant layer is not particularly limited, but is preferably 5 μm or more, and more preferably 10 μm or more. When the thickness of the weathering layer is 5 μm or more, the solvent resistance of the weathering layer can be maintained better, and when the thickness of the weathering layer is 10 μm or more, the solvent resistance of the weathering layer is further improved. be able to.

Next, the easily bonding layer which may be arrange | positioned on the opposite side to the side which has a weather resistance layer of a biaxially stretched polyester film is demonstrated.
The easy-adhesion layer refers to a layer arranged to increase the adhesion of the protective sheet for solar cells to a battery-side substrate (particularly EVA) provided with solar cells when producing a solar cell module. In addition, the easy adhesion layer arrange | positioned in contact with the battery side board | substrate with which the battery cell was sealed by using ethylene vinyl acetate copolymer (EVA) as a sealing material is called "EVA side easy adhesion layer."
The EVA side easy adhesion layer is formed by providing a colored intermediate colored layer, an undercoat layer disposed between the intermediate colored layer and the polyester film, an overcoat layer further disposed on the intermediate colored layer, and the like. Can do.

-Intermediate colored layer-
The protective sheet for a solar cell of the present invention may have an intermediate colored layer on the side opposite to the side having the weather resistant layer on the polyester film.
By having an intermediate colored layer, it reflects the light that has passed through the solar cells and reached the solar cell protective sheet out of the sunlight incident on the solar cell module produced using the solar cell protective sheet. It becomes possible to return to the solar battery cell. Thereby, power generation efficiency can be improved more.

The intermediate colored layer in the present invention can be disposed on the side of the polyester film that does not have a weather-resistant layer, and may be disposed directly on the surface of the polyester film or on the undercoat layer disposed on the polyester film. May be.
The intermediate colored layer can be arranged as a layer containing at least a binder and scattering particles, and further contains other components such as a crosslinking agent, a surfactant, a filler, and an ultraviolet absorber as necessary. Also good.

  Examples of the binder contained in the intermediate colored layer include acrylic resins, polyester resins, polyurethane resins, and polyolefin resins. Among these, acrylic resins and polyolefin resins are preferable.

As the scattering particles contained in the intermediate colored layer, the same scattering particles that can be used for the weather resistant layer can be preferably used.
When the intermediate colored layer contains a white pigment as scattering particles, the volume ratio of the white pigment in the intermediate colored layer preferably occupies 10% or more and 30% or less with respect to the total volume of the weather resistant layer. It is more preferable to occupy from 30% to 30%. When the volume ratio of the white pigment is 10% or more, the resin amount does not increase excessively, and the content ratio of the white pigment can be maintained, so that the light reflectance can be maintained well. Furthermore, when the volume ratio of the white pigment is 20% or more, higher light reflectance can be maintained. Further, when the volume ratio of the white pigment is 30% or less, the resin amount is maintained and the layer is hardly brittle, and the durability of the adhesive force can be further improved.

The crosslinking agent contained in the intermediate colored layer is the same as the crosslinking agent that can be used in the weather resistant layer.
The content of the crosslinking agent in the intermediate colored layer is preferably 5% by mass to 40% by mass, and more preferably 10% by mass to 30% by mass with respect to the binder in the intermediate colored layer. When the content of the crosslinking agent is 5% by mass or more, an intermediate colored layer having an excellent crosslinking effect can be obtained while maintaining strength and adhesiveness. Moreover, the pot life of the coating liquid prepared for intermediate colored layer formation can be kept longer as content of a crosslinking agent is 40 mass% or less.

  As additives other than the above, which are included in the intermediate colored layer, the same additives as those already described in the section of the weather resistant layer can be suitably used. It is the same as the addition amount already described in the section of the property layer.

  The intermediate colored layer can be colored black, blue or the like by adding a coloring pigment in addition to the scattering particles (for example, titanium oxide). Moreover, it can also be made transparent without adding a coloring pigment.

  The thickness of the intermediate colored layer is preferably in the range of 3 μm to 10 μm, and more preferably in the range of 4 μm to 8 μm. By making the thickness of the intermediate colored layer in the range of 3 μm or more and 10 μm or less, it is possible to achieve both necessary reflectance and adhesiveness.

-Overcoat layer-
The protective sheet for solar cells of the present invention may further have an overcoat layer on the intermediate colored layer on the polyester film. The overcoat layer in the present invention contains at least a binder, and a crosslinking agent and other additives can be used as necessary.

  As the binder contained in the overcoat layer, the same binders that can be used for the intermediate colored layer can be preferably used.

The crosslinking agent contained in the overcoat layer is the same as the crosslinking agent that can be used in the weather resistant layer.
The content of the crosslinking agent in the overcoat layer is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less with respect to the binder in the overcoat layer. When the content of the crosslinking agent is 5% by mass or more, a polymer layer excellent in crosslinking effect can be obtained while maintaining strength and adhesiveness. When the content of the crosslinking agent is 40% by mass or less, the pot life of the coating solution prepared for forming the overcoat layer can be kept longer.

  As additives other than the above, which are included in the overcoat layer, those similar to those already described in the section of the weather resistant layer can be preferably used, and the additive amount of other additives is also weather resistant. It is the same as the addition amount already described in the section of the property layer.

  The thickness of the overcoat layer is preferably in the range of 0.1 μm to 1.0 μm, more preferably in the range of 0.2 μm to 0.8 μm. By setting the thickness of the overcoat layer in the range of 0.1 μm or more and 1.0 μm or less, the adhesion between the overcoat layer and the sealing material disposed on the battery-side substrate used for manufacturing the solar cell module becomes strong. .

<Method for producing protective sheet for solar cell>
In the method for producing a protective sheet for a solar cell of the present invention, an unstretched polyester film is applied in a first direction, and an undercoat layer containing an acrylic resin is applied to one surface of the polyester film stretched in the first direction. A step of forming a polyester film on which the undercoat layer is formed, a step of stretching the polyester film in a second direction orthogonal to the first direction, and a step of forming a weather resistant layer containing an acrylic resin on the undercoat layer. Have.

-First stretching step-
The manufacturing method of the protection sheet for solar cells of this invention has the process (henceforth a 1st extending process) of extending | stretching an unstretched polyester film to a 1st direction. By having the first stretching step, the unstretched polyester film is stretched in one direction (uniaxial stretching) to obtain a uniaxially stretched polyester film.

First, an example of a method for producing a polyester film will be described.
For example, the polyester film is made of the above-described polyester as a raw material resin, dried, melted and kneaded, passed through a gear pump or a filter, extruded onto a cooling roll through a die, and cooled and solidified. (Unstretched) sheet.
The melt kneading is performed using an extruder. The extruder may be either a single screw extruder or a twin screw extruder.

  Extrusion is preferably performed in an evacuated or inert gas atmosphere. The temperature of the extruder is preferably from the melting point of the polyester used to a melting point of + 80 ° C. or lower, more preferably a melting point of + 10 ° C. or higher, a melting point of + 70 ° C. or lower, more preferably a melting point of + 20 ° C. or higher and a melting point of + 60 ° C. or lower. Within this range, the resin can be easily melted well, and decomposition of polyester or the like can be suppressed. In addition, it is preferable to dry the polyester masterbatch before extrusion. A preferable moisture content is 10 ppm to 300 ppm, more preferably 20 ppm to 150 ppm.

In terms of improving the hydrolysis resistance of the polyester film, at least one of a ketene imine compound and a carbodiimide compound may be added when the polyester is melted. The carbodiimide compound and the ketene imine compound may be directly added to the extruder, but it is preferable from the viewpoint of extrusion stability that a polyester and a master batch are formed in advance and charged into the extruder. When forming a master batch, it is preferable to vary the supply amount of the master batch containing the ketene imine compound.
The master batch is preferably used as a concentrated ketene imine. From the viewpoint of cost, the ketene imine concentration of the master batch is preferably adjusted to 2 to 100 times, more preferably 5 to 50 times the concentration of ketene imine contained in the polyester after film formation.

The extruded melt is poured on a cast drum through a gear pump, a filter, and a multilayer die. As the multi-layer die system, either a multi-manifold die or a feed block die can be suitably used.
The shape of the die may be a T-die, a hanger coat die, or a fish tail. It is preferable to give the above temperature fluctuations to the tip (die lip) of the die. On the cast drum, the molten resin (melt) can be brought into close contact with the cooling roll using an electrostatic application method. In this case, it is preferable to give the above fluctuations to the driving speed of the cast drum.
The surface temperature of the cast drum can be 10 ° C to 40 ° C.
The diameter of the cast drum is preferably 0.5 m or more and 5 m or less, more preferably 1 m or more and 4 m or less.
The driving speed of the cast drum (linear speed in the outermost week) is preferably 1 m / min or more and 50 m / min or less, and more preferably 3 m / min or more and 30 m / min or less.

In the present invention, the unstretched sheet formed by the above manufacturing method or the like is stretched. In this step, stretching is performed in one of the machine direction (MD) and the transverse direction (TD). The stretching treatment may be either MD stretching or TD stretching.
The stretching treatment is preferably performed at a glass temperature (Tg: unit ° C.) or more and (Tg + 60 ° C.) or less, more preferably (Tg + 3 ° C.) or more (Tg + 40 ° C.), and further preferably (Tg + 5 ° C.) or more (Tg + 30). ° C) or less. At this time, it is preferable to provide a temperature distribution as described above.

A preferable draw ratio is 280% to 500%, more preferably 300% to 480%, and further preferably 320% to 460% on at least one side. The draw ratio here is determined using the following equation.
Stretch ratio (%) = 100 × {(Length after stretching) / (Length before stretching)}

  In the step of stretching in the first direction, the unstretched sheet or stretched film can be subjected to heat treatment before stretching or after stretching (preferably after stretching). By performing heat treatment, microcrystals can be generated, and mechanical properties and durability can be improved. The unstretched sheet or stretched film may be subjected to heat treatment at about 180 ° C. to 240 ° C. (more preferably 200 ° C. to 230 ° C.) for 1 second to 60 seconds (more preferably 2 seconds to 30 seconds).

In the step of stretching in the first direction, a thermal relaxation treatment can be performed after the heat treatment. The thermal relaxation treatment is a treatment for shrinking the film by applying heat to the film for stress relaxation. The thermal relaxation treatment is preferably performed in both the MD and TD directions of the film. The various conditions in the thermal relaxation treatment are preferably a treatment at a temperature lower than the heat treatment temperature, and preferably 130 to 240 ° C. In the thermal relaxation treatment, the thermal shrinkage rate (150 ° C.) of the film is preferably −1% to 12% for MD and TD, and more preferably −0.5% to 10%. For heat shrinkage (150 ° C), a sample with a measurement direction of 350 mm and a width of 50 mm was cut out, marked at 300 mm intervals near both ends in the longitudinal direction of the sample, and fixed at one end to an oven adjusted to a temperature of 150 ° C. The other end is left free for 30 minutes, and then the distance between the gauge points is measured at room temperature. This length is defined as L (mm), and the heat shrinkage rate is obtained by the following formula using the measured value. Can do.
150 ° C. heat shrinkage (%) = 100 × (300−L) / 300
Further, when the thermal shrinkage rate is positive, it indicates shrinkage, and negative indicates elongation.

  Through the above steps, a uniaxially stretched film in which an unstretched polyester film is stretched in one direction is produced.

-Undercoat layer forming step-
The method for producing a protective sheet for a solar cell of the present invention includes a step of forming an undercoat layer containing an acrylic resin on one surface of a polyester film stretched in the first direction (hereinafter also referred to as an undercoat layer forming step). Have.
The coating is preferable in that it can be formed with a simple and 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 solvent of the coating solution used for coating may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.
Application of the coating solution containing the acrylic resin onto the uniaxially stretched film is preferably performed in-line following the step of stretching the polyester film in the first direction.

  It is also preferable to subject the uniaxially stretched film to a surface treatment such as a corona discharge treatment, a glow treatment, an atmospheric pressure plasma treatment, a flame treatment, or a UV treatment before applying a coating solution containing an acrylic resin.

After forming the coating film by applying the coating liquid containing the acrylic resin, it is preferable to provide a step of drying the coating film.
A drying process is a process of supplying dry air to a coating film. The average wind speed of the drying air is preferably 5 m / second to 30 m / second, more preferably 7 m / second to 25 m / second, and further preferably 9 m / second to 20 m / second or less. It is preferable that the drying of the coating film also serves as a heat treatment.

The undercoat layer is preferably formed on the side of the polyester film opposite to the side having the weather resistant layer. That is, it can be set as the aspect which has each undercoat on both sides of a polyester film. In this case, in the undercoat layer forming step, an undercoat layer containing an acrylic resin is formed on one surface of the polyester film stretched in the first direction by coating, and then the polyester film stretched in the first direction. The undercoat layer can be provided on both sides of the polyester film by forming an undercoat layer containing an acrylic resin on the other side opposite to the surface by coating. The composition, coating amount, and the like of the coating solution applied to one side and the other side of the polyester film may be the same or different.
About the undercoat layer formed on the side opposite to the side having the weather-resistant layer of the polyester film (the other side), the details of the material, the forming method, the pretreatment of the film, the drying step, etc. This is the same as described above.

-Second stretching step-
The manufacturing method of the protection sheet for solar cells of this invention has the process (henceforth a 2nd extending | stretching process) of extending | stretching the polyester film in which the undercoat layer was formed to the 2nd direction orthogonal to a 1st direction. The uniaxially stretched film after the undercoat layer is formed is stretched in the second direction so that the uniaxially stretched film is stretched together with the coating liquid, and the undercoat layer containing the acrylic resin is applied. Is produced. The stretching may be performed in either the longitudinal direction (MD) or the transverse direction (TD) as long as the direction is different from the first direction.
Here, the “second direction” means a direction different from the first direction (for example, MD), that is, a direction orthogonal to the first direction (for example, TD).

  The preferable aspect of a 2nd extending process is the same as the process of extending | stretching said polyester film to a 1st direction.

-Weathering layer forming process-
The manufacturing method of the protection sheet for solar cells of this invention has the process (henceforth a weathering layer formation process) which forms the weathering layer containing an acrylic resin on an undercoat layer. The weather-resistant layer can be formed by applying a coating solution containing an acrylic resin to the surface of the undercoat layer of the polyester film as a support to form a coating film and drying the coating film.
In the solar cell protective sheet of the present invention, the weather resistant layer may be a coating layer formed by applying a weather resistant layer coating solution containing at least one of a silicone / acrylic composite resin and an acrylic / fluorine composite resin. preferable.

  In the method for producing a protective sheet for a solar cell of the present invention, an aqueous dispersion containing at least one of a silicone / acrylic composite resin and an acrylic / fluorine composite resin dispersed in water is prepared. As the coating solution, an embodiment in which the coating solution is applied onto a desired biaxially stretched polyester film is preferable.

Moreover, there is no restriction | limiting in particular in the coating method and the solvent of a coating liquid.
Examples of the coating method include known methods using a gravure coater, a bar coater, or the like. The solvent used for the coating solution may be water or an organic solvent such as toluene or methyl ethyl ketone. From the viewpoint of environmental burden, it is preferable to prepare an aqueous coating solution using water as a solvent. In this case, the ratio of water to the total solvent is preferably 60% by mass or more, and more preferably 80% by mass or more. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

After the application, a drying process for drying the coating film under desired conditions may be provided. What is necessary is just to select suitably about the drying temperature at the time of drying according to cases, such as a composition of a coating liquid, a coating amount.
Moreover, in this invention, the coating liquid for forming a weather resistant layer may be apply | coated on the undercoat layer of the polyester film which is a biaxially stretched film, and the coating film formed by application | coating may be dried. A method may be used in which a coating liquid is formed on an undercoat film of a uniaxially stretched polyester film to form a coated film, the coated film is dried, and then stretched in a direction different from the initial stretching.

-Other processes-
In addition to the above-described first stretching step, undercoat layer forming step, second stretching step, and weathering layer forming step, depending on the purpose or case, a step of forming an intermediate colored layer on the polyester film, an intermediate coloring on the polyester film Other steps such as a step of forming an overcoat layer on the layer may be further provided.
In the case of forming the intermediate colored layer, the details of the method for forming the intermediate colored layer, the solvent used in the coating solution, the drying method, and the like are the same as those described in the section of the weather-resistant layer.
When the overcoat layer is formed, details of the method for forming the overcoat layer, the solvent used in the coating solution, the drying method, and the like are the same as those described in the section of the weather-resistant layer.

<Solar cell module>
The solar cell module of the present invention includes the above-described solar cell protective sheet of the present invention. Since the solar cell protective sheet of the present invention is provided, it is excellent in long-term durability and can exhibit stable power generation performance over a long period of time.

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 light energy of sunlight into electric energy is disposed between the transparent front substrate on which sunlight is incident and the above-described solar cell protective sheet of the present invention. The space between the front substrate and the protective sheet is sealed with a sealing material such as ethylene-vinyl acetate copolymer (EVA; hereinafter the same).

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 of the present invention is disposed on a transparent front substrate on which sunlight is incident and on the side of the front substrate opposite to the side on which sunlight is incident, and seals the solar cell element and the solar cell element. An element structure portion including a sealing material to be stopped, and a solar cell backsheet (a solar cell protection sheet of the present invention) disposed on the side opposite to the side where the front substrate of the element structure portion is located. doing.

  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 light transmittance of the front substrate is preferably as high as possible. As the substrate with high transmittance, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used.

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

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “parts” are based on mass. In addition, in a present Example, it shows centering on the case where the solar cell backsheet is produced as an example of the solar cell protective sheet.

Example 1
<Preparation of PET 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 an ethylene glycol solution of manganese acetate were added so as to be 30 ppm and 15 ppm, respectively, with respect to the obtained 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. After 5 minutes, a 10% by mass ethylene glycol solution of ethyl diethylphosphonoacetate was added to 5 ppm with respect to the resulting polymer. Thereafter, while the low polymer was stirred 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 the time to reach the final pressure were 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).
It should be noted that the time from the start of pressure reduction until reaching a 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 a pressure of 40 Pa at a temperature of 220 ° C. for 30 hours to carry out solid phase polymerization.

-Production of PET base film-
The pellets after undergoing solid-phase polymerization as described above are melt-kneaded with a melt extruder having a set temperature of 280 ° C., cast onto a metal drum, and an unstretched polyethylene terephthalate sheet (unstretched PET sheet) having a thickness of about 3 mm. ) Was produced.
Thereafter, the unstretched PET sheet was stretched 3.4 times in the machine direction (MD) at 90 ° C. (MD stretching). Next, after MD stretching, before stretching (TD stretching) in the transverse direction (TD; Transverse Direction) perpendicular to MD, the coating amount for the following undercoat layer is applied to the PET sheet after MD stretching by 5. Application was performed by an in-line coating method so as to be 1 ml / m ² to form an undercoat layer. Next, the PET sheet on which the undercoat layer was formed was stretched 4.5 times to TD at 105 ° C. (TD stretching). The thickness (dry thickness) of the undercoat layer after TD stretching was 80 nm.
Thereafter, heat treatment was performed for 15 seconds at a film surface of 200 ° C. Further, the MD and TD were subjected to thermal relaxation at 190 ° C. with an MD relaxation rate of 5% and a TD relaxation rate of 11%.
As described above, a biaxially stretched polyethylene terephthalate base film (hereinafter referred to as “PET base film”) having a thickness of 250 μm was obtained.

<Composition of coating solution for undercoat layer>
-Acrylic resin aqueous dispersion: 0.3 part [AS-563A, manufactured by Daicel Finechem Co., Ltd., latex with a solid content of 28% by mass]
-Water-soluble oxazoline-based crosslinking agent: 0.85 parts [Epocross (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass]
・ Distilled water: 100 parts

<Preparation of solar cell backsheet>
Using the PET substrate film obtained as described above, a solar cell backsheet is produced as an example of a solar cell protective sheet by forming a weather resistant layer on the PET substrate film as shown below. did.

-Formation of weather resistant layer-
(1) Preparation of titanium dioxide dispersion Titanium dioxide was dispersed using a dynomill disperser to prepare a titanium dioxide dispersion having an average primary particle diameter of titanium dioxide of 0.42 µm. In addition, the average primary particle diameter of titanium dioxide was measured using Microtrac MT3300EXII (made by Nikkiso Co., Ltd.).
<Composition of titanium dioxide dispersion>
・ Titanium dioxide: 455.8 parts (white pigment (scattering particles); average primary particle size: 0.42 μm, Taipei (registered trademark) CR-95, manufactured by Ishihara Sangyo Co., Ltd., powder)
・ Polyvinyl alcohol aqueous solution: 227.9 parts (PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10% by mass)
Surfactant: 5.5 parts (Demol (registered trademark) EP, manufactured by Kao Corporation, solid content: 25% by mass)
・ Distilled water ... 310.8 parts

(2) Preparation of coating solution for weathering layer Each component in the following composition was mixed to prepare a coating solution for weathering layer.
<Composition of coating solution for weather resistant layer>
・ Titanium dioxide dispersion: 494 parts ・ Silicone / acrylic composite resin (acrylic resin): 364 parts (Ceranate (registered trademark) WSA1070, manufactured by DIC Corporation)
・ Surfactant: 20 parts (1% by weight aqueous solution of NAROACTY (registered trademark) CL-95, manufactured by Sanyo Chemical Industries) ・ Crosslinking agent (oxazoline-based compound): 112 parts (Epocross (registered) (Trademark) WS700, solid content 40% by mass, manufactured by Nippon Shokubai Co., Ltd.)
・ Distilled water: Amount of 1000 parts of the entire coating solution

(3) Formation of weathering layer The obtained coating solution for weathering layer was applied on the undercoat layer of the PET base film so that the coating amount of titanium dioxide was 25 g / m ² , Drying for 30 minutes formed a 20 μm thick weathering layer. In addition, content of the white pigment which occupies in the formed weather resistant layer was 24 volume% with respect to the whole volume of a weather resistant layer by a volume ratio.

<Evaluation>
(1) Adhesion (adhesiveness)
The obtained solar cell backsheet was treated for 60 hours in an atmosphere of wet heat with a temperature of 120 ° C. and a relative humidity of 100%. Thereafter, the surface of the weather-resistant layer of the solar cell backsheet was scratched by 6 razors at 1 mm intervals in the vertical and horizontal directions using a razor. On top of that, a 20 mm wide Mylar tape was applied and quickly peeled off in the 90 ° direction. After peeling, the number of squares peeled from the solar cell backsheet was counted and evaluated according to the following evaluation criteria.
The evaluation ranks A to B are practically acceptable ranges.
<Evaluation criteria>
A: No peeling occurred.
B: The peeled squares were zero, but the scratch part was slightly peeled off.
C: The square which peeled was 1 square or more.

(2) Chips Using a processing machine equipped with a feeding device, a winding device, and a cutting mechanism, the obtained solar cell backsheet was cut under the following conditions. The lower blade side end surface of the cut part (the cut surface of the product) was observed with a microscope (50 times), and the maximum length of the chipping (defects) occurring in the undercoat layer and the weathering layer was measured. Based on the measured values, the degree of chip generation was evaluated according to the following evaluation criteria.
<Condition>
・ Blade shape: Round blade (Upper blade angle: 30 °, Lower blade angle: 90 °, Blade material: SKH)
・ Cutting direction: Horizontal ・ Cutting speed: 100 m / min
・ Tension: 40kg / m
<Evaluation conditions>
A: The length of the chip in the cut surface is less than 250 μm.
B: The length of the chip in the cut surface is 250 μm or more and less than 500 μm.
C: The length of the chip in the cut surface is 500 μm or more and less than 750 μm.
D: The length of the chip in the cut surface is 750 μm or more.

(3) Solvent resistance The surface of the weatherproof layer of the obtained solar cell backsheet was rubbed with a cotton swab soaked in ethanol, and the number of rubs that caused the dissolution (peeling) of the weatherproof layer was determined. Evaluation was made according to criteria. Evaluation ranks A to B are practically acceptable ranges.
<Evaluation criteria>
A: The number of rubbing is 100 or more or does not dissolve at all (no peeling occurs).
B: The number of rubbing is 50 times or more and less than 100 times.
C: The number of rubbing is less than 50.

(4) Reflectance With respect to the obtained solar cell backsheet, a spectrophotometer UV-3100 (manufactured by Shimadzu Corporation) was used to make 550 nm light incident from the side having no weathering layer (solar cell) Incidence from the battery cell side in the case of a module), and the reflectance with respect to incident light was measured. Specifically, the reflectance of the barium sulfate standard plate was measured as a reference, and the reflectance of the solar cell backsheet was calculated using this measurement value as a reference (100%). Based on the calculated value of reflectance, evaluation was performed according to the following evaluation criteria.
<Evaluation conditions>
A: The reflectance is 80% or more.
B: The reflectance is 60% or more and less than 80%.
C: The reflectance is less than 60%.

(Examples 2-3)
In Example 1, a solar cell backsheet was prepared and evaluated in the same manner as in Example 1 except that the thickness of the undercoat layer was changed as shown in Table 1 below.

(Examples 4 to 6)
In Example 1, a part of the acrylic resin used in the coating solution for the undercoat layer was replaced with an olefin resin, and the content ratio of the acrylic resin and the olefin resin was changed as shown in Table 1 below. In the same manner as in Example 1, a solar cell backsheet was prepared and evaluated in the same manner.
In addition, the used olefin resin is as follows.
[Olefin resin]
・ Polyolefin aqueous dispersion (content is shown in Table 1)
(Arrowbase (registered trademark) SE-1013N, manufactured by Unitika Ltd., solid content: 20.2% by mass)

(Examples 7 to 8)
In Example 1, a solar cell backsheet was prepared and evaluated in the same manner as in Example 1 except that the thickness of the weathering layer was changed as shown in Table 1 below.

Example 9
In Example 1, when preparing an unstretched PET sheet, a master prepared by kneading pellets after solid-phase polymerization and a white pigment (titanium dioxide (TiO ₂ ), average primary particle size: 0.3 μm) The batch was put into a melt extruder together with pellets after solid phase polymerization, and the content of titanium oxide with respect to the whole PET sheet was adjusted to 4.5% by mass. A back sheet was prepared and evaluated in the same manner.

(Examples 10 to 12)
In Example 9, a solar cell backsheet was prepared and evaluated in the same manner as in Example 9 except that the thickness of the weathering layer was changed as shown in Table 1 below.

(Examples 13 to 16)
In Example 1, a solar cell backsheet was produced in the same manner as in Example 1 except that the volume fraction of titanium dioxide (white pigment) contained in the weather resistant layer was changed as shown in Table 1 below. The same evaluation was performed.

(Example 17)
In Example 1, a solar cell backsheet was prepared in the same manner as in Example 1 except that the silicone / acrylic composite resin used for forming the weather resistant layer was replaced with a fluorine-based polymer. went.
In addition, the used fluorine-type polymer is as follows.
[Fluoropolymer]
・ Acrylic / fluorine composite resin (content is shown in Table 1)
(Obligard (registered trademark) SW0011F, manufactured by AGC Co-Tech)

(Comparative Example 1)
In Example 1, a solar cell backsheet was prepared and evaluated in the same manner as in Example 1 except that an undercoat layer was not formed between MD stretching and TD stretching.

(Comparative Example 2)
A biaxially stretched polyethylene terephthalate substrate film was produced in the same manner as in the production of the PET substrate film of Example 1, except that an undercoat layer was not formed between MD stretching and TD stretching. The undercoat layer coating solution used in Example 1 was applied to the surface of this biaxially stretched polyethylene terephthalate base film so that the coating amount was 5.1 ml / m ² (off-line coating), and an undercoat with a thickness of 80 nm was applied. A layer was formed. In this way, a biaxially stretched polyethylene terephthalate base film with an undercoat layer was obtained.
And in Example 1, the solar cell back sheet was produced like Example 1 except having replaced the PET base film with the biaxially-stretched polyethylene terephthalate base film with the undercoat obtained above. The same evaluation was performed.

(Comparative Example 3)
In Example 1, a solar cell backsheet was prepared in the same manner as in Example 1 except that the acrylic resin (silicone / acrylic composite resin) used in the undercoat layer coating solution was replaced with an olefin resin. Similar evaluations were made.
In addition, the used olefin resin is as follows.
[Olefin resin]
・ Polyolefin aqueous dispersion (content is shown in Table 1)
(Arrowbase (registered trademark) SE-1013N, manufactured by Unitika Ltd., solid content: 20.2% by mass)

As shown in Table 1, in the Examples, the adhesion between the base film and the weather-resistant layer is well maintained even after being placed in a moist heat environment, as compared with the Comparative Example, and during the cutting process The generation of chips was also suppressed.
As is apparent from the comparison of the example with Comparative Example 1, the adhesion is improved by forming the undercoat layer, and the degree of generation of chips during cutting is dramatically improved. Further, even if an undercoat layer is formed as in Comparative Example 2, if the in-line coating method is not applied, the desired effect cannot be expected even if an acrylic resin is used for the undercoat layer and the weather resistant layer. Furthermore, as shown in Comparative Example 3, it can be seen that if the main component of the undercoat layer formed by applying the in-line coating method is an olefin resin, the desired effect cannot be obtained.

(Examples 18 to 24)
In Example 7, the acrylic resin used in the coating solution for the undercoat layer was replaced with another acrylic resin shown in Table 2 below, so that the thickness of the undercoat layer (dry thickness after TD stretching) became the thickness shown in Table 2 below. The undercoat layer was formed by coating and stretching. On the formed undercoat layer can, resistant weather-resistant layer coating solution, the coating amount of titanium oxide was coated to a 12.5 g / m ^2, to form a weather-resistant layer having a thickness of 10μm and dried Except for this, a solar cell backsheet was prepared in the same manner as in Example 7, and the same evaluation was performed.
The details of the acrylic resin used are as follows.
[acrylic resin]
(Aqueous dispersion of acrylic resin A-2)
Julimer (registered trademark) ET-410, manufactured by Nippon Pure Chemical Industries, Ltd., solid content: 30.0% by mass
(Aqueous dispersion of acrylic resin A-3)
Bonron (registered trademark) PS-001, manufactured by Mitsui Chemicals, Inc., solid content: 50.0% by mass
(Aqueous dispersion of acrylic resin A-4)
Bonron (registered trademark) PS-002, manufactured by Mitsui Chemicals, solid content: 45.0 mass%

As shown in Table 2, in Examples 18 to 24, even when acrylic resins A-2, A-3, and A-4 other than Example 1 were used as the material for the undercoat layer, wet heat After being placed in the environment, the adhesion between the PET base film and the weathering layer was maintained well, and the generation of chips during cutting was also suppressed.
Moreover, in Examples 19-23, even if it changed in the range of thickness 40nm -1000nm using acrylic resin A-3, between PET base film after being put in a wet heat environment and a weather resistance layer The adhesion of was maintained well, and the generation of chips during cutting was also suppressed.

(Examples 25 to 48)
In "-Preparation of PET base film-" in Examples 1 to 24, an unstretched PET sheet was stretched in the machine direction (MD) (MD stretch), and after MD stretching, the transverse direction perpendicular to MD Before stretching (TD; Transverse Direction) (TD stretching), the undercoat layer coating solution is applied to one surface of the PET sheet by an inline coating method so that the coating amount is 5.1 ml / m ² . Further, in the same manner as in Example 1, except that the same undercoat layer coating solution was also applied to the other surface of the PET sheet by the in-line coating method so that the coating amount was 5.1 ml / m ^2. A material film was prepared to obtain a solar cell backsheet.

  As a result of evaluating by the method similar to Examples 1-24 with respect to the obtained solar cell backsheet, the same result as Examples 1-24 was obtained.

(Example 49)
In Example 18, the following weather-resistant layer coating solution was used as the weather-resistant layer, except that the coating amount of titanium oxide was 4 g / m ² and the coating amount of carbon black was 1.0 g / m ^2. Produced a solar cell backsheet having a black weather-resistant layer in the same manner as in Example 18, and the same evaluation was performed.

<Composition of coating solution for weather resistant layer>
-Titanium dioxide dispersion obtained above-170 parts-Carbon black dispersion-60 parts (MF Black 5630 (registered trademark), solid content 31.5 mass%, manufactured by Dainichi Seika Co., Ltd.)
Silicone / acrylic composite resin (acrylic resin) 364 parts (Ceranate (registered trademark) WSA1070, manufactured by DIC Corporation)
・ Surfactant: 20 parts (1% by weight aqueous solution of NAROACTY (registered trademark) CL-95, manufactured by Sanyo Chemical Industries) ・ Crosslinking agent (oxazoline-based compound): 112 parts (Epocross (registered) (Trademark) WS700, solid content 40% by mass, manufactured by Nippon Shokubai Co., Ltd.)
・ Distilled water: Amount of 1000 parts of the entire coating solution

(Example 50)
In Example 18, using the following weathering layer coating solution as the weathering layer, the coating amount of titanium oxide was 1.5 g / m ² , the coating amount of carbon black was 0.3 g / m ² , Blue (dark blue) color weather resistance in the same manner as in Example 18, except that the coating amount of phthalocyanine blue pigment was 0.5 g / m ² and the coating amount of quinacridone red pigment was 0.8 g / m ² . A solar cell backsheet having a layer was prepared and evaluated in the same manner.

<Composition of coating solution for weather resistant layer>
-Titanium dioxide dispersion obtained above-75 parts-Carbon black dispersion-15 parts (MF Black 5630 (registered trademark), solid content 31.5 mass%, manufactured by Dainichi Seika Co., Ltd.)
-Phthalocyanine blue pigment dispersion: 30 parts (EP700 blue, manufactured by Dainichi Seika Co., Ltd., solid content: 35% by mass)
Quinacridone red pigment dispersion: 40 parts (NAF 1032, manufactured by Dainichi Seika Co., Ltd., solid content: 45% by mass)
Silicone / acrylic composite resin (acrylic resin) ... 400 parts (Ceranate (registered trademark) WSA1070, manufactured by DIC Corporation)
・ Surfactant: 5 parts (1% by mass aqueous solution of Naroacty (registered trademark) CL-95, manufactured by Sanyo Chemical Industries) ・ Crosslinking agent (oxazoline-based compound): 210 parts (Epocross (registered) (Trademark) WS700, solid content 40% by mass, manufactured by Nippon Shokubai Co., Ltd.)
・ Distilled water: Amount of 1000 parts of the entire coating solution

(Example 51)
In Example 18, the coating amount of the ultraviolet absorber (TINUVIN (registered trademark) 479-DW, manufactured by BASF Corporation, solid content: 40% by mass) was used as the weathering layer using the following coating solution for weathering layer. A solar cell backsheet having a transparent weather-resistant layer was produced in the same manner as in Example 18 except that the amount was 1.0 g / m ^2, and the same evaluation was performed.

<Composition of coating solution for weather resistant layer>
・ Ultraviolet absorber dispersion: 100 parts (TINUVIN479-DW, solid content: 40% by mass, manufactured by BASF)
Silicone / acrylic composite resin (acrylic resin) 550 parts (Ceranate (registered trademark) WSA1070, manufactured by DIC Corporation)
・ Surfactant: 10 parts (1% by weight aqueous solution of Naroacty (registered trademark) CL-95, manufactured by Sanyo Chemical Industries) ・ Crosslinking agent (oxazoline-based compound): 170 parts (Epocross (registered) (Trademark) WS700, solid content 40% by mass, manufactured by Nippon Shokubai Co., Ltd.)
・ Distilled water: Amount of 1000 parts of the entire coating solution

  As shown in Table 3, in Examples 49 to 51, a black pigment or a blue pigment, a red pigment, and a black pigment (dark blue) were contained as the color pigment of the weather-resistant layer, or transparent (pigment-free) was used. Even in this case, after being placed in a moist heat environment, the adhesion between the PET base film and the weathering layer was well maintained, and the generation of chips during cutting was also suppressed. .

(Examples 52 to 102)
<Formation of EVA side easy adhesion layer>
-Preparation of coating solution for intermediate colored layer and coating solution for overcoat layer-
Components in the following composition were mixed to prepare an intermediate colored layer coating solution and an overcoat layer coating solution.

<Composition of coating solution for intermediate colored layer>
-Titanium dioxide dispersion obtained above-305 parts-Polyolefin resin aqueous dispersion-442 parts (Arrowbase (registered trademark) SE-1013N, manufactured by Unitika Ltd., solid content: 20.2 mass%)
-Acrylic resin aqueous dispersion: 35 parts (AS-563A, manufactured by Daicel Finechem Co., Ltd., solid content: 28 mass% latex)
Water-soluble oxazoline compound 99 parts (Epocross (registered trademark) WS700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
・ Distilled water: 106 parts ・ Fluorosurfactant: 4.3 parts (Sodium = bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfoniteoxy Succinate, manufactured by Fujifilm Fine Chemical Co., Ltd., concentration 2% by mass)
・ Secondary ammonium phosphate: 23 parts (secondary ammonium phosphate for food use, manufactured by Nippon Chemical Industry Co., Ltd., 35% aqueous solution)

<Composition of coating solution for overcoat layer>
・ Polyolefin resin: 211 parts (Arrowbase (registered trademark) SE-1013N, manufactured by Unitika Ltd.)
Water-soluble oxazoline compound: 43 parts (Epocross (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
・ Distilled water: 734 parts ・ Fluorosurfactant: 2.4 parts (Sodium = bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfoniteoxy Succinate, manufactured by Fujifilm Fine Chemical Co., Ltd., concentration 2% by mass)
Nonionic surfactant: 9.6 parts (Naroacty (registered trademark) CL95, manufactured by Sanyo Chemical Industries, Ltd., aqueous solution with a solid content of 1% by mass)

-Formation of intermediate colored layer and overcoat layer-
Conveying the back sheet for a solar cell manufactured in Example 1 to 51 at a conveying speed 80 m / min, on the opposite side of the weather-resistant layer-forming surface of the back sheet for a solar cell, a corona discharge treatment under the condition of 730J / m ² went. Thereafter, the coating solution for the intermediate colored layer was applied by a bar coating method so that the coating amount of titanium dioxide as a coloring pigment was 5.5 g / m ² to form a coating film. This coating film was dried at 170 ° C. for 2 minutes to form an intermediate colored layer.
Next, an overcoat layer coating solution is applied onto the intermediate colored layer by a bar coating method so that the coating amount is 0.5 g / m ² to form a coating film, and this coating film is formed at 170 ° C. for 2 minutes. Dried.
As a result, a white intermediate colored layer (olefin-acrylic composite resin layer) having a dry thickness of 6 μm and a dry thickness of 0. A solar cell backsheet having an EVA-side easy-adhesion layer in which a 5 μm overcoat layer (olefin resin layer) was laminated in this order was obtained.

(Example 103)
<Formation of EVA side easy adhesion layer>
-Preparation of coating solution for black intermediate coloring layer-
Components in the following composition were mixed to prepare an intermediate colored layer coating solution.
<Composition of coating solution for intermediate colored layer>
Carbon black dispersion: 6.2 parts (MF Black 5630 (registered trademark), solid content: 31.5% by mass, manufactured by Dainichi Seika Co., Ltd.)
Acrylic resin aqueous dispersion: 100 parts (Bonlon (registered trademark) PS-002, manufactured by Mitsui Chemicals, solid content: 45.0% by mass)
Water-soluble oxazoline compound: 42 parts (Epocross (registered trademark) WS700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
・ Distilled water: 580 parts ・ Fluorosurfactant: 6.7 parts (Sodium = bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfoniteoxy Succinate, manufactured by Fujifilm Fine Chemical Co., Ltd., concentration 2% by mass)
Colloidal silica: 315 parts (Snowtex C (registered trademark), solid content: 20.0% by mass, manufactured by Nissan Chemical Co., Ltd.)

-Formation of intermediate colored layer and overcoat layer-
The black solar cell backsheet produced in Example 49 was transported at a transport speed of 80 m / min, and the condition of 730 J / m ² was placed on the side opposite to the weather resistant layer forming surface of the PET base film in the solar cell backsheet. Then, corona discharge treatment was performed. Thereafter, the coating amount of carbon black was set to 20 mg / m ² and the above-mentioned coating solution for intermediate colored layer was applied by a bar coating method to form a coating film. This coating film was dried at 170 ° C. for 2 minutes to form an intermediate colored layer. Next, the overcoat layer coating solution is applied onto the intermediate colored layer by a bar coating method so that the coating amount is 0.5 g / m ^2, and a coating film is formed. It was dried for 2 minutes to form an overcoat layer.
As a result, a black intermediate colored layer (olefin-acrylic composite resin layer) having a dry thickness of 6 μm and a dry thickness of 0.00 on the opposite side of the weather resistant layer forming surface of the PET base film in the solar cell backsheet. A black solar cell backsheet having an EVA-side easy-adhesion layer in which a 5 μm overcoat layer (olefin-based resin layer) was laminated in this order was obtained.

(Example 104)
<Formation of EVA side easy adhesion layer>
-Preparation of coating solution for blue intermediate colored layer-
Components in the following composition were mixed to prepare an intermediate colored layer coating solution.
<Composition of coating solution for intermediate colored layer>
-Titanium dioxide dispersion obtained above-75 parts-Carbon black dispersion-20 parts (MF Black 5630 (registered trademark), solid content 31.5 mass%, manufactured by Dainichi Seika Co., Ltd. )
-Phthalocyanine blue pigment dispersion: 30 parts (EP700 Blue GA, manufactured by Dainichi Seika Co., Ltd., solid content: 35% by mass)
Quinacridone red pigment dispersion: 40 parts (NAF 1032, manufactured by Dainichi Seika Co., Ltd., solid content: 45% by mass)
Polyolefin resin aqueous dispersion: 400 parts (Arrowbase (registered trademark) SE-1013N, manufactured by Unitika Ltd., solid content: 20.2% by mass)
-Acrylic resin aqueous dispersion: 80 parts (AS-563A, manufactured by Daicel Finechem Co., Ltd., solid content: 28% by mass latex)
Water-soluble oxazoline compound: 205 parts (Epocross (registered trademark) WS700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
・ Distilled water: 140 parts ・ Fluorosurfactant: 5 parts (Sodium = bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfonite oxysucci (NAT, manufactured by FUJIFILM Fine Chemical Co., Ltd., concentration 2% by mass)
・ Secondary ammonium phosphate: 5 parts (secondary ammonium phosphate for food use, manufactured by Nippon Chemical Industry Co., Ltd., 35% by mass aqueous solution)

-Formation of intermediate colored layer and overcoat layer-
The blue solar cell backsheet prepared in Example 50 was transported at a transport speed of 80 m / min, and the condition of 730 J / m ² was placed on the side opposite to the weather resistant layer forming surface of the PET base film in the solar cell backsheet. Then, corona discharge treatment was performed. Thereafter, the coating amount of titanium dioxide, which is a coloring pigment, is 1.5 g / m ² , the coating amount of carbon black is 0.3 g / m ^2, and the coating amount of phthalocyanine blue pigment is 0.5 g / m 2. No. ² , the coating amount of quinacridone red pigment was 0.8 g / m ² , and the coating solution for intermediate colored layer was applied by the bar coating method to form a coating film. This coating film was dried at 170 ° C. for 2 minutes to form an intermediate colored layer. Next, the overcoat layer coating solution is applied onto the intermediate colored layer by a bar coating method so that the coating amount is 0.5 g / m ^2, and a coating film is formed. It was dried for 2 minutes to form an overcoat layer.
Thereby, on the opposite side of the weather resistant layer forming surface of the PET base film in the solar cell backsheet, a blue intermediate colored layer (olefin-acrylic composite resin layer) having a dry thickness of 6 μm, and a dry thickness of 0. A blue solar cell backsheet having an EVA-side easy-adhesion layer in which a 5 μm overcoat layer (olefin-based resin layer) was laminated in this order was obtained.

(Example 105)
<Formation of EVA side easy adhesion layer>
-Preparation of coating solution for transparent intermediate layer-
Components in the following composition were mixed to prepare an intermediate colored layer coating solution.
<Composition of coating solution for intermediate layer>
UV absorber dispersion: 40 parts Polyolefin resin aqueous dispersion: 80 parts (Arrowbase (registered trademark) SE-1013N, manufactured by Unitika Ltd., solid content: 20.2% by mass)
-Acrylic resin aqueous dispersion: 520 parts (AS-563A, manufactured by Daicel Finechem Co., Ltd., solid content: 28 mass% latex)
Water-soluble oxazoline compound: 160 parts (Epocross (registered trademark) WS700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
・ Distilled water: 180 parts ・ Fluorosurfactant: 5.0 parts (Sodium = bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfoniteoxy Succinate, manufactured by Fujifilm Fine Chemical Co., Ltd., concentration 2% by mass)
・ Secondary ammonium phosphate: 15 parts (secondary ammonium phosphate for food use, manufactured by Nippon Chemical Industry Co., Ltd., 35% by mass aqueous solution)

-Formation of intermediate colored layer and overcoat layer-
The transparent solar cell backsheet produced in Example 51 was transported at a transport speed of 80 m / min, and the condition of 730 J / m ² was placed on the side opposite to the weather resistant layer forming surface of the PET base film in the solar cell backsheet. Then, corona discharge treatment was performed. Thereafter, the intermediate layer coating solution was applied by a bar coating method so that the coating amount of the ultraviolet absorbent was 1.0 g / m ² , thereby forming a coating film. This coating film was dried at 170 ° C. for 2 minutes to form an intermediate colored layer. Next, the overcoat layer coating solution is applied onto the intermediate colored layer by a bar coating method so that the coating amount is 0.5 g / m ^2, and a coating film is formed. It was dried for 2 minutes to form an overcoat layer.
As a result, a transparent 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 formed on the side opposite to the weather-resistant layer forming surface of the solar cell backsheet. Obtained the transparent solar cell backsheet which has the EVA side easily bonding layer laminated | stacked in this order.

<Production of solar cell power generation module>
3 mm thick tempered glass, EVA sheet (SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd.), crystalline solar cell, EVA sheet (SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd.), Examples 52 to 105 The EVA-side overcoat layer of the solar cell backsheet is brought into contact with the EVA sheet that is a sealing material for the solar cell element and stacked in this order, and a vacuum laminator ( It was made to adhere to EVA by hot pressing using a Nisshinbo Co., Ltd. vacuum vacuum laminator. The bonding method is as follows.
Using a vacuum laminator, evacuation was performed at 128 ° C. for 3 minutes, and then pressure was applied for 2 minutes to temporarily bond. Thereafter, the main adhesion treatment was performed in a dry oven at 150 ° C. for 30 minutes.
As described above, a solar cell module was manufactured using crystalline solar cells.

  The produced solar cell module was allowed to stand for 60 hours under an environmental condition of 120 ° C. and 100% relative humidity and then operated for power generation. As a result, the solar cell backsheet obtained in Examples 52 to 105 (Examples 1 to 1) 51 (including the back sheet for solar cell) is excellent in weather resistance, and any of the solar cell modules was able to stably obtain power generation performance over a long period of time.

Claims (11)

A biaxially stretched polyester film produced by stretching an unstretched polyester film in a first direction and stretching in a second direction perpendicular to the first direction along the film surface;
On one surface of the polyester film stretched in the first direction, said second coating a coating solution prior to stretching in the direction, which is formed by being stretched in the second direction, and a resin component An undercoat layer containing only an acrylic resin or containing an acrylic resin and a polyolefin as a resin component , and the content of the acrylic resin relative to the total amount of the acrylic resin and the polyolefin is 25% by mass or more ;
A weathering layer comprising an acrylic resin disposed on the undercoat layer;
A protective sheet for a solar cell.   The solar cell protective sheet according to claim 1, wherein the weather resistant layer has a thickness of 10 μm or more. On the opposite side of the biaxially stretched polyester film from the side having the weatherable layer,
An acrylic resin as a resin component formed by applying a coating solution on the other surface of the polyester film stretched in the first direction before stretching in the second direction and stretching in the second direction. Or an undercoat layer having an acrylic resin content of 25% by mass or more based on the total amount of the acrylic resin and the polyolefin. The solar cell protective sheet according to 1.   The solar cell protective sheet according to any one of claims 1 to 3, wherein the biaxially stretched polyester film contains a white pigment.   The solar cell protective sheet according to claim 4, wherein the white pigment is titanium dioxide.   The solar cell protective sheet according to any one of claims 1 to 5, wherein the weather resistant layer includes scattering particles, and a volume ratio of the scattering particles in the weather resistant layer is 10% or more and 30% or less.   The solar cell protective sheet according to claim 6, wherein the scattering particles are titanium dioxide.   The said acrylic resin contained in the said weather resistance layer is a protection sheet for solar cells of any one of Claims 1-7 containing at least one of a silicone / acrylic composite resin and an acrylic / fluorine composite resin.   The solar cell module containing the protection sheet for solar cells of any one of Claims 1-8. Stretching an unstretched polyester film in the first direction;
One side of the polyester film stretched in the first direction contains only an acrylic resin as a resin component, or contains an acrylic resin and a polyolefin as a resin component, and the acrylic resin with respect to the total amount of the acrylic resin and the polyolefin. A step of forming an undercoat layer having a content of 25% by mass or more by coating;
Stretching the polyester film on which the undercoat layer is formed in a second direction perpendicular to the first direction along the film surface;
Forming a weather resistant layer containing an acrylic resin on the undercoat layer;
The manufacturing method of the solar cell backsheet which has this. Between the step of stretching in the first direction and the step of stretching in the second direction,
The other side of the polyester film stretched in the first direction contains only acrylic resin as the resin component, or contains acrylic resin and polyolefin as the resin component, and the acrylic resin with respect to the total amount of acrylic resin and polyolefin. The manufacturing method of the solar cell backsheet of Claim 10 which has the process of forming the undercoat which content is 25 mass% or more by application | coating.