WO2013024892A1

WO2013024892A1 - Solar cell back sheet, method for manufacturing same, and solar cell module

Info

Publication number: WO2013024892A1
Application number: PCT/JP2012/070856
Authority: WO
Inventors: 龍一中山; 畠山　晶; 橋本　斉和; 竜太竹上; 南　一守
Original assignee: 富士フイルム株式会社
Priority date: 2011-08-17
Filing date: 2012-08-16
Publication date: 2013-02-21
Also published as: JP2013058747A

Abstract

The purpose of the present invention is to provide a solar cell back sheet that has an excellent interlayer adhesion over time under a high-temperature high-humidity environment and that is manufactured at low cost. This solar cell back sheet has: a polymer substrate (11); a coloring layer (15) containing a colorant, and a metal-containing layer (13) containing a component selected from the group consisting of a metal and a metal compound, provided on one surface of the polymer substrate (11); and a composite polymer layer (17) provided on the other surface of the polymer substrate, the composite polymer layer containing a composite polymer having, in a molecule, 15-85 mass% of siloxane structural units represented by general formula (1) and 85-15 mass% of non-siloxane structural units.

Description

SOLAR CELL BACK SHEET, MANUFACTURING METHOD THEREOF, AND SOLAR CELL MODULE

The present invention relates to a solar cell backsheet, a manufacturing method thereof, and a solar cell module.

Solar cells are a power generation system that emits no carbon dioxide during power generation and has a low environmental load, and has been rapidly spreading in recent years.

A solar cell module is usually arranged between a front side glass on the side on which sunlight enters and a so-called back sheet disposed as a back protection sheet on the side opposite to the side on which sunlight enters (back side). The solar battery cell (solar battery element) is sandwiched. A sealing material such as EVA (ethylene-vinyl acetate) resin is disposed between the front surface glass and the solar battery cell and between the solar battery cell and the back sheet.

The back sheet has a function of preventing moisture from entering from the back surface of the solar cell module. Conventionally, glass or fluororesin has been used. However, in recent years, various materials such as polyester have been used from the viewpoint of cost. Resin materials have been studied. The back sheet provided as the back surface protection sheet is not limited to a resin sheet as a simple protection application, but also has insulation and barrier properties against moisture, coloring (designability, light reflectivity, etc.), adhesion between layers (adhesion), It is preferable that various functions such as dimensional stability and long-term durability are provided.
There is a case. Among these, as performance that the solar cell module should have, there is a high demand for battery performance, appearance, and long-term durability.

As a function imparted to the back sheet, for example, white inorganic particles such as titanium oxide may be included to give the back sheet a reflection function of reflecting light. This contributes to the improvement of battery performance by increasing the power generation efficiency by irregularly reflecting the light that passes through the battery cell out of the sunlight incident from the front side where the module's sunlight is irradiated and returning it to the cell again. . As an example having such a function, a white polyethylene terephthalate film to which white inorganic fine particles are added is disclosed (see, for example, JP-A Nos. 2003-060218 and 2006-210557). Also, an example of a back surface protection sheet having a white ink layer containing a white pigment is disclosed (for example, see JP-A-2006-210557).

Also, decorativeness (design) may be required for the backsheet. As an example having a decorative function, a solar cell backsheet having improved design by adding a perylene pigment as a black pigment is disclosed (see, for example, JP-A-2007-128943).

Furthermore, it is indispensable to have an adhesive function as the function. In order to provide the above functions, a structure in which a layer having a desired function is laminated on a support base material has been proposed for the back sheet, and a method of bonding sheets having various functions to the support Is widely adopted. For example, a method of forming a back sheet by bonding a plurality of resin films is disclosed (see, for example, JP-A-2002-1000078). When the back sheet is formed in a multi-layer structure, when strong adhesiveness cannot be obtained between the respective layers, the back sheet is easily peeled off due to the influence of moisture and heat, and long-term durability cannot be maintained.

Also disclosed are methods for applying layers having various functions to the support (see, for example, JP-A-2006-210557, JP-A-2007-128943, and JP-A-2010-212296). Furthermore, the white polyester film for reflectors in which a white polyester film is provided with a coating layer containing an antistatic agent and a silicone compound, and an adhesive layer containing an epoxy resin, a phenol resin, a vinyl copolymer, and a siloxane compound are organic. There is also a disclosure relating to a solar cell backsheet laminated on a film (see, for example, Japanese Patent Application Laid-Open Nos. 2008-189828 and 2008-282873).

However, with respect to the adhesiveness (adhesion) of each layer constituting the back sheet, sufficient performance has not always been obtained with the conventional technology alone. That is,
Among the above conventional techniques, the method of forming a back sheet by laminating a plurality of sheets to each other increases the cost, and the adhesive used for laminating tends to deteriorate over time, and gradually decreases the adhesiveness. Tend to invite. This is particularly noticeable when exposed to a high temperature and high humidity environment. On the other hand, the back sheet is generally placed in an environment that is directly exposed to moisture, heat, and light, such as outdoors, and therefore, from the viewpoint of long-term durability, it can be bonded for a long time even under such environmental conditions. The ability to stably maintain the properties is required.

In addition, although a method by coating is conventionally known, it is difficult to maintain good adhesion for a long period of time in a humid heat environment where the temperature and humidity conditions are relatively high with the above-described conventional configuration. Therefore, a back sheet for a solar cell that has been produced at a lower cost than bonding, and that has various functions such as light reflectivity and designability, and long-term adhesiveness independent of temperature and humidity is still provided. It has not reached.

As described above, polyester films and back sheets provided with a layer containing a silicone compound or a siloxane compound have also been proposed, but in the former case, the durability of the cationic polymer contained as an antistatic agent is poor. In the latter case, the durability of the resin or copolymer other than the siloxane compound is poor. Therefore, it is difficult to maintain adhesiveness stably for a long period of time in a humid and hot environment where the temperature and humidity are relatively high.

The present invention has been made in view of the above. That is,
Under the above circumstances, it is excellent in interlayer adhesion (especially the adhesion of the outermost layer exposed to the wet heat environment) when aged in a high temperature and high humidity environment (hereinafter also referred to as a wet heat environment), and is manufactured at a low cost. There is a need for a solar cell backsheet and method for manufacturing the same. There is also a need for a solar cell module that exhibits stable power generation performance over a long period of time.

Specific means for achieving the above-described problems are as follows.
<1> A polymer base, a colored layer containing a colorant on one side of the polymer base, a metal-containing layer containing a component selected from the group consisting of a metal and a metal compound, and the other side of the polymer base In the molecule contains a composite polymer having a siloxane structural unit represented by the following general formula (1) having a mass ratio of 15 to 85 mass% and a non-siloxane structural unit having a mass ratio of 85 to 15 mass%. And a composite polymer layer.

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

<2> A polymer base material containing a colorant, a metal-containing layer containing a component selected from the group consisting of metals and metal compounds on one side of the polymer base, and the other side of the polymer base in the molecule A composite polymer layer containing a composite polymer having a siloxane structural unit represented by the general formula (1) having a mass ratio of 15 to 85 mass% and a non-siloxane structural unit having a mass ratio of 85 to 15 mass%; It is a solar cell backsheet.
<3> The solar cell backsheet according to <1> or <2>, wherein the colorant is a pigment.
<4> The solar cell backsheet according to any one of <1> to <3>, wherein the colorant is a white or black pigment.
<5> The solar cell backsheet according to <1>, <3>, or <4>, wherein a colored layer is formed by coating.
<6> The solar cell backsheet according to any one of <1> to <5>, wherein the component selected from the group consisting of a metal and a metal compound is foil-like aluminum.
<7> The solar cell backsheet according to any one of <1> to <5>, wherein the component selected from the group consisting of metals and metal compounds is aluminum oxide or silicon oxide.
<8> The solar cell backsheet according to any one of <1> to <7>, wherein the metal-containing layer is formed by vapor deposition.
<9> The polymer base material according to any one of <1> to <8>, wherein the end-capping agent is contained in a range of 0.1% by mass to 10% by mass with respect to the total mass of the polymer. It is a solar cell backsheet.

<10> The polymer substrate according to any one of <1> to <9>, wherein the surface of the polymer substrate is treated by a method selected from the group consisting of corona treatment, flame treatment, and glow discharge treatment. It is a solar cell backsheet.
<11> The solar cell backsheet according to any one of <1> to <10>, wherein the composite polymer layer further includes a structural portion derived from a crosslinking agent that crosslinks the composite polymer.
<12> The solar cell backsheet according to <11>, wherein the crosslinking agent is a carbodiimide compound or an oxazoline compound.
<13> The solar cell backsheet according to <11> or <12>, wherein the mass ratio of the structural portion derived from the crosslinking agent to the composite polymer in the composite polymer layer is 1 to 30% by mass.
<14> The solar cell backsheet according to any one of <1> to <13>, wherein the non-polysiloxane structural unit is an acrylic structural unit.
<15> Forming a metal-containing layer containing a component selected from the group consisting of metals and metal compounds on a polymer substrate, and the mass ratio represented by the general formula (1) in the molecule is 15 to 85 mass And forming a composite polymer layer containing a composite polymer having a% siloxane structural unit and a non-siloxane-based structural unit having a mass ratio of 85 to 15% by mass on a polymer substrate, <1> The method for producing a back sheet for a solar cell according to any one of <14>.
<16> Film formation for forming an unstretched resin sheet containing a polymer constituting the polymer base material, first stretching for stretching the resin sheet in the first direction, and stretching in the first direction Forming an undercoat layer to form an undercoat layer on at least one surface of the obtained resin sheet, and extending the resin sheet on which the undercoat layer is formed in a second direction orthogonal to the first direction. It is a manufacturing method as described in said <15> which has.
<17> The solar cell backsheet according to any one of <1> to <14>, or the solar cell backsheet according to <15> or <16>. The solar cell module provided with the back sheet for solar cells.

A solar cell module includes a transparent front substrate on which sunlight is incident, a cell structure portion provided on the front substrate and having a solar cell element and a sealing material for sealing the solar cell element, and a cell structure portion The solar cell backsheet according to any one of <1> to <14>, provided on the side opposite to the side on which the front substrate is located and disposed adjacent to the sealing material, or the <15 > Or a solar cell backsheet produced by the method for producing a solar cell backsheet described in <16>.

According to the present invention, a solar cell backsheet that is excellent in interlayer adhesion (especially the adhesion of the outermost layer that is exposed to a moist heat environment) when aged in a high temperature and high humidity environment, and that is manufactured at low cost. A method is provided. Also,
ADVANTAGE OF THE INVENTION According to this invention, the solar cell module which exhibits the stable electric power generation performance over a long term is provided.

It is sectional drawing which shows schematic structure of the solar cell backsheet which concerns on the 1st aspect of this invention. It is sectional drawing which shows schematic structure of the solar cell backsheet which concerns on the 2nd aspect of this invention.

Hereinafter, the back sheet for a solar cell according to the present invention, a method for producing the back sheet, and a solar cell module using the back sheet will be described in detail.

<Back sheet for solar cell and manufacturing method thereof>
The back sheet for solar cell of the present invention is a back protective sheet for solar cell that is disposed in contact with a battery side substrate (preferably encapsulant) in which solar cell elements (solar cells) are sealed with a sealing material. A functional element using a polymer and a component selected from the group consisting of a colorant, a metal and a metal compound (that is, a functional layer or a polymer substrate containing a colorant or a metal component), and a specific siloxane structural unit And a composite polymer layer including a composite polymer having Specifically, (1) the solar cell backsheet of the first aspect of the present invention comprises:
A polymer substrate;
A colored layer containing a colorant provided on one side of the polymer substrate, a metal-containing layer containing a component selected from the group consisting of metals and metal compounds,
Specific siloxane structural units (15 to 85% by mass based on the total mass of the polymer) represented by the following general formula (1) in the molecule and non-siloxane structural units provided on the other surface of the polymer substrate A composite polymer layer containing a composite polymer having (85-15% by weight based on the total polymer weight);
It consists of
Further, (2) the solar cell backsheet of the second aspect of the present invention comprises:
A polymer substrate comprising a colorant;
A metal-containing layer containing a component selected from the group consisting of a metal and a metal compound provided on one surface of the polymer substrate;
Provided on the other surface of the polymer substrate, a siloxane structural unit having a mass ratio of 15 to 85 mass% represented by the following general formula (1) in the molecule and a non-siloxane structure having a mass ratio of 85 to 15 mass% A composite polymer layer containing a composite polymer having units;
It consists of
These solar cell backsheets may have a configuration in which layers other than the composite polymer layer are further provided as necessary.

Of the various functions required for solar cell backsheets, battery performance, appearance, and long-term durability are particularly important for ensuring the long-term performance of solar cells. A weather-resistant film or a colored film is bonded with an adhesive to impart durability and design. The adhesive used for the bonding may be easily deteriorated in a wet heat environment, and the bonding is difficult to say in terms of cost.
In addition to bonding, a technique for coating and forming a weather-resistant layer with a solvent-based coating solution using a fluorine-containing resin or the like is known. In the application using fluorine-containing resin, etc., the durability improvement effect is expected as long as the coating film itself is resistant, but it is difficult to keep its adhesion stably in a humid heat environment, and within a relatively short period of time Tend to peel off.
Under the circumstances as described above, in the present invention, a colored layer or a metal-containing layer, which is a functional element having a function relating to coloring (light reflectivity, designability (appearance), etc.) and / or a moisture-proof function. In addition, a colored polymer base material and a composite polymer layer having good adhesion (adhesion) and excellent weather resistance are provided. Specifically, the polymer base material supporting the back sheet or the layer provided on one side thereof is provided with functionality including a component selected from the group consisting of a colorant, a metal and a metal compound, and the polymer base material. A composite polymer layer that is a constituent layer of the backsheet is provided on the other side of the substrate, and this composite polymer layer is preferably formed using a specific composite polymer containing a non-siloxane structural unit and a (poly) siloxane structural unit in the molecule. By coating and forming, the amount of adhesive that is inferior in durability under a humid heat environment is reduced, and as a result, deterioration due to heat and moisture is suppressed.
Thereby, while providing various functions, the adhesive strength can be kept high for a long period of time in a humid heat environment exposed to heat and moisture for a long time, and long-term durability can be ensured. Moreover, when a solar cell module is produced, good power generation performance can be obtained, and power generation efficiency can be kept stable over a long period of time.
Here, the above-mentioned various functions include a light reflection function that increases the power generation efficiency by reflecting incident light that has passed through the solar battery cell and returning it to the cell, a design imparting (appearance improving) function, and an installation environment. Includes moisture resistance against moisture. In addition to the above, the solar cell backsheet preferably has functions such as antistatic properties, dimensional stability, and insulating properties.
In the present specification, layers having the above functions are also collectively referred to as “functional layers”.

As shown in FIG. 1, the solar cell backsheet of the present invention (hereinafter also simply referred to as “backsheet”) has a first functional layer (1) (for example, metal) on one surface of a polymer substrate 11. Content layer) 13 and a second functional layer (for example, a colored layer) 15, an aspect having the composite polymer layer 17 on the other side (first aspect), or a colorant as shown in FIG. In an embodiment (second embodiment) having the metal-containing layer 13 as the functional layer (1) on one side of the polymer base material 21 to which the functionality is imparted, and the composite polymer layer 27 on the other side. Can be configured.

Specifically, in the first aspect of the present invention, at least a resin film (or sheet) which is a polymer substrate as a supporting substrate, and a coloring agent-containing coloring disposed as a functional layer thereon You may be comprised by the layer and the moisture-proof layer which shows moisture resistance including a metal and / or a metal compound. In this case, for example, when a white pigment is used as the colorant, a back sheet with light reflectivity is obtained, and when a black pigment is used, for example, the appearance (designability) is improved with the black layer. A back sheet is obtained. The colored layer and the metal-containing layer can further have other functions such as insulating properties, antistatic properties, and dimensional stability. In this case, the insulating property can be imparted by appropriately adjusting the thickness of the polymer substrate. The antistatic property can be imparted by including, for example, antimony-doped tin oxide (TWU-1, manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd.). In addition, since the dimensional stability affects the thermal shrinkage of the polymer, it can be adjusted by a heat treatment after film formation as a polymer substrate.
Thereby, the colored layer and moisture-proof layer which also exhibit other functions are obtained. In this case, the functional layer may be composed of two or more layers by overlapping an antistatic layer or the like together with a colored layer containing a colorant and / or a moisture-proof layer containing a metal or the like.

In the second embodiment of the present invention, a colorant-containing colored film or sheet (plate-shaped colored polymer substrate) in which a colorant (for example, a pigment) is dispersed in the polymer by kneading the colorant into the polymer or the like. ) And a moisture-proof layer provided with moisture-proof properties including a metal and / or a metal compound (for example, metal oxide). For example, when a white pigment is used as the colorant, a polymer substrate having a light reflecting function is obtained. When a black pigment is used, for example, a polymer having improved decorativeness (design) in the appearance of the back sheet A substrate is obtained. In this case, it can be produced by mixing and extruding a pigment or a metal into a molten resin that is melt-kneaded by a melt extruder or the like and forming it into a film (or sheet) shape.

Furthermore, the polymer base material in the present invention may have other functions such as insulation, antistatic properties, and dimensional stability in addition to coloring and moisture resistance.

Colored layers and metal-containing layers
(1) A coating layer formed by coating a coating solution containing a colorant, metal and / or metal compound, or
(2) A film or sheet containing a colorant, a metal and / or a metal compound, or a layer formed by laminating a foil plate (3) A layer formed by vapor phase deposition may be used. Among them, the colored layer containing a colorant is preferably composed of (1) in terms of adhesiveness, and the metal-containing layer containing a metal and / or a metal compound is composed of (3). It is preferable.

In the above (1), when a layer is formed by coating, when providing a colored layer, the back sheet of the present invention is a plate-like polymer substrate such as a resin film (or sheet), and a functional layer. A multi-layer structure including a colored layer containing a colorant such as a pigment applied and formed on the substrate may be used. In this case, it can be produced by forming a colored layer by applying and drying a coating solution containing a colorant such as a pigment in a desired manner on a polymer substrate.

(Colored layer)
The colored layer contains at least a colorant, and is composed of other components such as a binder and a surfactant.

As the colorant, pigments and dyes can be used, and pigments are preferable in terms of weather resistance.
Examples of the pigment include inorganic pigments such as titanium dioxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc, ultramarine blue, bitumen, and carbon black, and organic pigments such as phthalocyanine blue and phthalocyanine green. It can be appropriately selected and contained.

Among the pigments, when the functional layer is configured as a reflective layer that reflects light that has entered the front surface of the solar cell and passed through the solar cell and returned to the solar cell, a white pigment is preferable. As the white pigment, inorganic pigments such as titanium dioxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin and talc are preferable.
Moreover, when giving designability to a functional layer in order to improve an external appearance, a black pigment is preferable as a pigment. As the black pigment, an inorganic pigment such as carbon black is preferable.

The content of the pigment in the functional layer is preferably in the range of 2.5 to 8.5 g / m ² . When the pigment content is 2.5 g / m ² or more, necessary coloring can be obtained, and reflectance and decorative properties can be effectively provided. Further, when the content of the pigment in the functional layer is 8.5 g / m ² or less, the surface shape of the functional layer is easily maintained and the film strength is excellent. In particular, the pigment content is more preferably in the range of 4.5 to 8.0 g / m ² .

The average particle diameter of the pigment is preferably 0.03 to 0.8 μm in volume average particle diameter, more preferably about 0.15 to 0.5 μm. When the average particle size is within the above range, the light reflection efficiency is high in the system using the white pigment, and the design is excellent when the black pigment is used. The average particle diameter is a value measured by a laser analysis / scattering particle size distribution measuring apparatus LA950 (manufactured by Horiba, Ltd.).

The thickness of the colored layer that is the coating layer is not particularly limited, but is preferably in the range of 2 to 30 μm from the viewpoint of effectively imparting reflectance and decorativeness while ensuring the strength of the coating film. More preferably, it is 4 to 20 μm.

When a functional layer imparted with moisture resistance is provided, the backsheet of the present invention is a transparent film obtained by coating a polyethylene terephthalate (PET) film or the like with an inorganic oxide such as silica or alumina, or two transparent films. Are provided with a laminated film formed by bonding the coating surfaces together.

Application can be suitably performed by, for example, an application method using a gravure coater, roll coater, bar coater or the like.

In the above (2), when forming a layer by bonding, when providing a colored functional layer, the back sheet of the present invention comprises a plate-like polymer substrate such as a resin film (or sheet), and a functional layer. As a multilayer structure including a plate-like colored polymer substrate containing a colorant such as a pigment.
The colored polymer substrate here includes a material obtained by kneading a colorant such as a pigment into a polymer and forming it into a plate shape. For example, it may be produced by adding a colorant such as a pigment to a melted polymer melt-kneaded by a melt extruder, melt-extruding, and forming into a film (or sheet) shape. As the colored polymer substrate, commercially available products may be used. For example, Lumirror E20 (white polyethylene terephthalate), Lumirror X20 (black polyethylene terephthalate) manufactured by Toray Industries, Inc. can be used.

The thickness of the plate-like colored polymer substrate is not particularly limited because it depends on the thickness of the polymer substrate to be bonded, but is preferably in the range of 10 to 400 μm.

In addition, when providing moisture resistance by providing a metal-containing layer on a polymer substrate, the backsheet of the present invention has a multi-layer structure including a plate-like polymer substrate and a metal thin plate or a metal layer as a functional layer. can do. The metal thin plate may be configured by providing foil plate-like aluminum (for example, aluminum foil). In addition, the metal layer may be configured by providing a water vapor barrier layer (for example, a metal vapor deposition film or a metal oxide vapor deposition film) formed by vapor deposition (for example, chemical vapor deposition) of a metal and / or a metal compound. it can.

(Metal-containing layer)
The metal is selected from those which can suppress moisture permeation at the time of film formation and have a water vapor transmission rate of 0.005 g / m ² / day or less at 40 ° C. and 90% relative humidity. Examples of the metal include one or more selected from the group consisting of Si, Al, In, Sn, Zn, Ti, Cu, Ce, Ta and the like in terms of moisture resistance. Examples of the metal compound include aluminum oxide such as aluminum oxide (Al ₂ O ₃ ), silicon oxide such as silicon oxide (SiO _x such as SiO and SiO ₂ ), indium oxide (InO ₂ ), and the like. It is done.
The water vapor transmission rate is more preferably 0.001 g / m ² / day or less.

As a method for forming the metal-containing layer, for example, a vapor deposition method such as a sputtering method, a vacuum deposition method, an ion plating method, or a plasma CVD method is suitable. Specifically, the forming methods described in Japanese Patent Nos. 3434344, 2002-322561, 2002-361774, and the like can be employed.

In the case of bonding, the metal-containing layer is provided, for example, by adhering a film (or sheet) having a desired function with an adhesive. The adhesive is not particularly limited. For example, an adhesive obtained by mixing a curing agent with a main agent (eg, LX660 (K) (manufactured by DIC Corporation) as a main agent is used as a curing agent with KW75 (DIC). A two-component thermosetting urethane adhesive) and the like mixed with (made by Co., Ltd.) can be used.

The thickness of the metal-containing layer to be bonded is also not particularly limited because it depends on the thickness of the polymer base material to be bonded, and is appropriately selected depending on the degree of coloring, moisture resistance, and the like. For example, the thickness of the metal-containing layer formed by vapor deposition is preferably 10 nm or more and 500 nm from the viewpoint of moisture resistance against water vapor.

Also in the case of bonding, the polymer base material in the present invention can be further imparted with other functions such as insulation, antistatic properties, and dimensional stability. In this case, as described above, in addition to the use of, for example, an antistatic agent in the polymer base material or the colored layer or the metal-containing layer, in addition to the colored layer or the metal-containing layer in the present invention, for example, the colored layer or the metal-containing layer. A layer containing an antistatic agent or the like may be further laminated on the layer.

One example of the backsheet of the present invention is a multilayer structure of a water vapor barrier layer (metal-containing layer) / reflective layer (white layer) or a design layer (black layer) (both colored layers) as seen from the polymer substrate side. It is the structure which has.

-Polymer substrate-
The back sheet of the present invention is configured by providing a polymer substrate.
Examples of the polymer component forming the polymer substrate include polyesters, polyolefins such as polypropylene and polyethylene, polyphenylene ethers, polystyrenes, and fluorine-based polymers such as polyvinyl fluoride. Among these, polyester, polyphenylene ether, and syndiotactic polystyrene are preferable, and polyester is preferable from the viewpoint of cost and mechanical strength.

The polyester used for the polymer substrate (support substrate) is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate and the like. Of these, polyethylene terephthalate or polyethylene-2,6-naphthalate is 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.

When polymerizing the polyester in the present invention, it is preferable to use an antimony (Sb) -based, germanium (Ge) -based, or titanium (Ti) -based compound as a catalyst from the viewpoint of keeping the carboxyl group content below a predetermined range. Of these, Ti compounds are particularly preferred. In the case of using a Ti-based compound, an embodiment is preferred in which the Ti-based compound is polymerized by using it as a catalyst so that the Ti element conversion value is in the range of 1 ppm to 30 ppm, more preferably 3 ppm to 15 ppm. If the amount of Ti compound used is within the above range in terms of Ti element, it is possible to adjust the terminal carboxyl group present in the polyester to the following range, and to keep the hydrolysis resistance of the polymer substrate low. it can.

Examples of the synthesis of polyester using a Ti compound include Japanese Patent Publication No. 8-301198, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 3897756, Japanese Patent No. 396226, and Japanese Patent No. 39786666. No. 3, Patent No. 3,996,871, Patent No. 40000867, Patent No. 4053837, Patent No. 4,127,119, Patent No. 4,134,710, Patent No. 4,159,154, Patent No. 4,269,704, Patent No. 4,313,538 and the like can be applied.

The carboxyl group content in the polyester is preferably 55 equivalents / t (tons; the same shall apply hereinafter) or less, more preferably 35 equivalents / t or less. The lower limit of the carboxyl group content is preferably 2 equivalents / t in terms of maintaining adhesion between the layer formed on the polyester (for example, a colored layer). When the carboxyl group content is 55 equivalents / t or less, hydrolysis resistance can be maintained, and a decrease in strength when subjected to wet heat aging can be suppressed to be small.
Here, “carboxyl group content” means the amount of the carboxyl group (—COOH) that the polyester has at the end of its molecular structure. “Equivalent / t” represents a molar equivalent per ton.
The carboxyl group content in the polyester can be adjusted by the polymerization catalyst species and the film forming conditions (film forming temperature and time).
The carboxyl group content in this specification is a value measured by a titration method according to the method described in H. A. Pohl, Anal. Chem. 26 (1954) p.2145.

The polyester in the present invention is preferably solid-phase polymerized after polymerization. Thereby, a preferable carboxyl group content can be achieved. Solid-phase polymerization may be a continuous method (a method in which a tower is filled with a resin, which is slowly heated for a predetermined time and then sent out), or a batch method (a resin is charged into a container). , A method of heating for a predetermined time). Specifically, for solid phase polymerization, Japanese Patent No. 2621563, Japanese Patent No. 3121876, Japanese Patent No. 3136774, Japanese Patent No. 3603585, Japanese Patent No. 3616522, Japanese Patent No. 3617340, Japanese Patent No. 3680523, Japanese Patent No. 3717392 are disclosed. The method described in Japanese Patent No. 4167159 can be applied.

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

The polyester base material containing polyester as a polymer component is obtained by, for example, melt-extruding the above polyester into a film and then cooling and solidifying it with a casting drum to form an unstretched film. The unstretched film is Tg to (Tg + 60) ° C. The biaxially stretched so that the total magnification is 3 to 6 times in the longitudinal direction once or twice, and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C. A stretched film is preferred.
Further, heat treatment may be performed at 180 to 230 ° C. for 1 to 60 seconds as necessary.

Specifically, a PET film can be formed as follows.
It is preferable to form a PET film by melt-kneading the polyester after undergoing solid-phase polymerization and extruding it from a die (extrusion die) (melt extrusion).

In the production method of the present invention, the PET resin can be melted using an extruder during melt extrusion.
In melt extrusion, a raw material resin charged in an extruder is melt-kneaded in a cylinder, and the resin is melt-extruded into a sheet shape. The melt kneading by an extruder uses a conventionally known extruder (preferably a twin screw extruder having a biaxial screw) provided with a screw for extruding a molten resin, and a desired resin (preferably a polyester resin). You can set the necessary conditions to obtain. Generally, an extruder is roughly classified into a single axis and a multi-axis depending on the number of screws. As the multi-screw extruder, a twin-screw extruder (a twin-screw extruder) is suitable. Further, the extruder may be any device of small to large size. More preferably, the inside of the extruder is replaced with nitrogen from the viewpoint that generation of terminal COOH due to thermal decomposition can be further suppressed.
The melting temperature is preferably 250 ° C to 320 ° C, more preferably 260 ° C to 310 ° C, and further preferably 270 ° C to 300 ° C.

It is preferable that the molten resin (melt) of the PET resin is formed into a sheet by extruding it from an extrusion die through a gear pump, a filter or the like. At this time, it may be extruded as a single layer or may be extruded as a multilayer. The melt-extruded melt is preferably cooled on a support, solidified and formed into a sheet. There is no restriction | limiting in particular as a support body, The cooling roll used for normal melt film forming can be used.

In film formation, a resin sheet can be formed by cooling the resin melt-extruded during melt extrusion. In film formation, for example, a melt (melt) is passed through a gear pump and a filter, and then extruded from a die onto a cooling (chill) roll. By cooling and solidifying this, an unstretched sheet is obtained. In addition, a melt (melt) can be stuck to a cooling roll using an electrostatic application method.

The temperature of the cooling roll itself is preferably 10 ° C. to 80 ° C., more preferably 15 ° C. to 70 ° C., and further preferably 20 ° C. to 60 ° C. Further, from the viewpoint of improving the adhesion between the molten resin (melt) and the cooling roll and increasing the cooling efficiency, it is preferable to apply static electricity before the melt contacts the cooling roll.

The thickness of the molten resin (melt) discharged in a band after solidification (before stretching) is in the range of 2600 μm to 6000 μm, and a polyester film having a thickness of 260 μm to 400 μm can be obtained through subsequent stretching. The thickness of the melt after solidification is preferably in the range of 3100 μm to 6000 μm, more preferably in the range of 3300 μm to 5000 μm, and still more preferably in the range of 3500 μm to 4500 μm. When the thickness after solidification and before stretching is 6000 μm or less, wrinkles are unlikely to occur during melt extrusion, and unevenness is suppressed. Moreover, it is preferable that the thickness before stretching after solidification is 2600 μm or more suppresses uneven adhesion to the chill roll (cooling roll for solidification) generated due to weak melt, and is preferable from the viewpoint of reducing unevenness of the film.

The production method of the present invention may include stretching the produced extruded film (unstretched film) after the film formation. In the production method of the present invention, the substrate is preferably biaxially stretched from the viewpoint of mechanical strength.

In the production method of the present invention, as the stretching, an embodiment having two stretching processes of first stretching and second stretching before and after forming the undercoat layer is preferable.
In the first stretching, the formed resin sheet is stretched in the first direction. The first direction may be either the sheet longitudinal direction (MD) or the sheet width direction (TD) orthogonal to the direction, but in the first stretching, it is preferably stretched to MD (so-called longitudinal stretching).
Further, after forming an undercoat layer as described later, a second stretching is further provided. In this second stretching, the resin sheet on which the undercoat layer is applied is stretched in a second direction orthogonal to the first direction. The second direction may be either the sheet longitudinal direction (MD) or the sheet width direction (TD) orthogonal to the direction, but in the second stretching, it is preferably stretched to TD (so-called lateral stretching).

Between the first stretching and the second stretching, an undercoat layer is applied and formed on at least one surface of the resin sheet stretched in the first direction.
In the formation of the resin layer, as described above, the undercoat layer can be suitably formed by applying the undercoat layer coating solution to the polymer substrate. The coating method for applying the coating liquid for forming the undercoat layer, the solvent used for the preparation of the coating liquid, and the like are as described above.

Thus, after forming the undercoat layer on the resin sheet that has undergone the first stretching, the adhesion between the undercoat layer and the resin sheet can be improved by further performing the second stretching. .
In the present invention, as described above, it is preferable to form a biaxially stretched film in which polyester molecules are biaxially oriented by stretching in two directions. From the viewpoint of mechanical strength, it is preferably biaxially stretched.

The thickness of the polymer substrate (particularly the polyester substrate) is preferably about 25 to 300 μm. When the thickness is 25 μm or more, the mechanical strength is good, and when the thickness is 300 μm or less, it is advantageous in terms of cost and hydrolysis resistance.
In particular, the polyester base material has a tendency that the hydrolysis resistance deteriorates as the thickness increases, and the durability during long-term use tends to decrease. In the present invention, the thickness is 120 μm or more and 300 μm or less, and When the carboxyl group content in the polyester is 2 to 35 equivalents / t, the wet heat durability can be further improved.

In the present invention, inorganic particles or organic particles (hereinafter also collectively referred to as “fine particles”) can be mixed as a colorant in the polymer resin. Thereby, the reflectance (whiteness) of light can be improved and the electric power generation efficiency of a solar cell can be raised, or designability can be provided.

The average particle size of the fine particles is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, and still more preferably 0.15 to 1 μm. The content of the fine particles is preferably 0 to 50% by mass, more preferably 1 to 10% by mass, and further preferably 2 to 5% by mass with respect to the total mass of the polymer. When the average particle size of the fine particles is 0.1 to 10 μm, the whiteness of the polymer substrate tends to be 50 or more. Further, when the content of the fine particles is 1% by mass or more, the whiteness is easily set to 50 or more. When the content of the fine particles is 50% by mass or less, the weight of the polymer substrate does not become too large, and it is excellent in handling in processing or the like. In addition, the average particle diameter and content here refer to the average value of each layer when the polymer substrate has a multilayer structure. That is, the average particle diameter is calculated by (average value of particle diameter of each layer) × (thickness of each layer / thickness of all layers) for each layer, and the sum is obtained. (Average value of quantity) × (thickness of each layer / thickness of all layers) is calculated for each layer and indicates the sum total.

The average particle size of the fine particles is obtained by an electron microscope method. Specifically, the following method is used.
The fine particles are observed with a scanning electron microscope, and the magnification is appropriately changed according to the size of the particles. Next, the outer circumference of each particle is traced for at least 200 fine particles selected at random. The equivalent circle diameter of the particles is measured from these trace images with an image analyzer. The average value of the measured values is defined as the average particle size.

The fine particles may be either inorganic particles or organic particles, or a combination of both. Thereby, the reflectance of light can be improved and the power generation efficiency of a solar cell can be improved. Suitable inorganic particles include, for example, wet and dry silica, colloidal silica, calcium carbonate, aluminum silicate, calcium phosphate, alumina, magnesium carbonate, zinc carbonate, titanium oxide, zinc oxide (zinc white), antimony oxide, and oxidation. Cerium, zirconium oxide, tin oxide, lanthanum oxide, magnesium oxide, barium carbonate, zinc carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, titanium mica, talc, clay, Examples include kaolin, lithium fluoride, and calcium fluoride. In particular, titanium dioxide and barium sulfate are preferable. The titanium oxide may be either anatase type or rutile type. In addition, the surface of the fine particles may be subjected to an inorganic treatment using alumina, silica, or the like, or may be subjected to an organic treatment using a silicon or alcohol system.

Among these particles, titanium dioxide is preferable. When the polymer substrate contains this, the polymer substrate can exhibit excellent durability even under light irradiation. Specifically, when UV irradiation is performed at 63 ° C., 50% Rh, irradiation intensity of 100 mW / cm ² for 100 hours, the elongation at break is preferably 35% or more, more preferably 40% or more. The polymer base material in the present invention is more suitable as a back surface protective film for solar cells used outdoors because photolysis and deterioration are suppressed.

Titanium dioxide includes those having a rutile crystal structure and those having an anatase crystal structure. It is preferable to add fine particles mainly composed of rutile-type titanium dioxide to the polymer substrate in the present invention. The anatase type has a characteristic that the spectral reflectance of ultraviolet rays is very large, whereas the rutile type has a characteristic that the absorption rate of ultraviolet rays is large (spectral reflectance is small). The present inventor pays attention to the difference in spectral characteristics in the crystal form of titanium dioxide, and can improve the light resistance in the backsheet for protecting the back surface of the solar cell by utilizing the ultraviolet absorption performance of rutile titanium dioxide. it can. Thereby, even if other ultraviolet absorbers are not substantially added, the film durability under light irradiation is excellent. For this reason, problems such as contamination due to bleeding out of the ultraviolet absorber and a decrease in adhesion are unlikely to occur.

In addition, as described above, the titanium dioxide particles in the present invention are mainly composed of rutile type titanium dioxide. Here, “mainly composed of rutile type titanium dioxide” means “rutile type in all titanium dioxide particles”. It means that the amount of titanium dioxide exceeds 50% by mass. Further, the amount of anatase-type titanium dioxide in all titanium dioxide particles is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 0% by mass or less. When the content of the anatase type titanium dioxide is not more than the above upper limit value, the amount of rutile type titanium dioxide in the total titanium dioxide particles can be secured, and the ultraviolet absorption performance can be kept good. Since anatase-type titanium dioxide has a strong photocatalytic action, it is possible to suppress a decrease in light resistance in consideration of this action. Rutile titanium dioxide and anatase titanium dioxide can be distinguished by X-ray structure diffraction and spectral absorption characteristics.

The surface of the rutile titanium dioxide fine particles may be subjected to inorganic treatment such as alumina or silica, or may be subjected to organic treatment such as silicon or alcohol. Before blending rutile titanium dioxide into the polyester composition, the particle size may be adjusted and coarse particles may be removed using a purification process. As industrial means of the purification process, for example, pulverizing means such as a jet mill and a ball mill, for example, classification means such as dry or wet centrifugation can be applied.

The organic particles that can be contained in the polymer substrate are preferably those that can withstand the heat during film formation. For example, fine particles made of a cross-linked resin, specific examples include fine particles made of polystyrene cross-linked with divinylbenzene. The size and amount of fine particles are the same as in the case of inorganic particles.

Various conventionally known methods can be used for adding fine particles into the polymer substrate. The typical method is listed below.
(1) A method in which, when the polymer constituting the polymer substrate is polyester, fine particles are added before the end of the ester exchange reaction or esterification reaction at the time of polyester synthesis such as polyethylene terephthalate, or the fine particles are added before the start of the polycondensation reaction.
(2) When the polymer constituting the polymer substrate is polyester, fine particles are added to polyester such as polyethylene terephthalate and melt kneaded.
(3) In the above methods (1) and (2), master pellets (or master batch (MB)) to which a large amount of fine particles are added are produced, and these and polyesters such as polyethylene terephthalate that do not contain fine particles; In which a predetermined amount of fine particles are contained.
(4) A method of using the master pellet of the above (3) as it is.
In this, the masterbatch method (MB method: said (3)) which mixes polyester resin and microparticles | fine-particles with an extruder beforehand is preferable. In addition, a method can be employed in which MB is prepared while degassing moisture, air, and the like by putting polymer (for example, polyester resin) and fine particles that have not been dried in advance into an extruder. Furthermore, preferably, the increase in the acid value of the polyester is suppressed by preparing the MB using a polyester resin that has been slightly dried in advance. Examples of such a method include a method of extruding while degassing and a method of extruding without sufficiently degassing with a sufficiently dry polyester resin.

For example, when preparing MB, it is preferable to reduce the moisture content of the polymer (for example, polyester resin) to be input by drying in advance. The drying conditions are preferably 100 to 200 ° C., more preferably 120 to 180 ° C., for 1 hour or longer, more preferably 3 hours or longer, and even more preferably 6 hours or longer. Thereby, it is sufficiently dried so that the moisture content of the polyester resin is preferably 50 ppm or less, more preferably 30 ppm or less. The premixing method is not particularly limited, and may be a batch method or a single-screw or biaxial or more kneading extruder. When making MB while degassing, melt the polyester resin at a temperature of 250 ° C to 300 ° C, preferably 270 ° C to 280 ° C, and provide one, preferably two or more degassing ports in the pre-kneader. It is preferable to adopt a method such as performing continuous suction deaeration of 0.05 MPa or more, more preferably 0.1 MPa or more, and maintaining the reduced pressure in the mixer.

The polymer base material may contain many fine cavities (voids) inside. Thereby, higher whiteness can be suitably obtained. In that case, the apparent specific gravity is 0.7 or more and 1.3 or less, preferably 0.9 or more and 1.3 or less, more preferably 1.05 or more and 1.2 or less. When the apparent specific gravity is 0.7 or more, the polymer base material has a waist, and the processing at the time of producing the solar cell module can be performed satisfactorily. When the apparent specific gravity is 1.3 or less, the weight of the polymer base material does not become too large, so that the solar cell can be reduced in weight.

The fine cavities can be formed from fine particles and / or a thermoplastic resin that is incompatible with the polymer constituting the polymer substrate described later. The term “cavity derived from a thermoplastic resin that is incompatible with the fine particles or polymer” means that there are voids around the fine particles or the thermoplastic resin, and is confirmed by, for example, a cross-sectional photograph of the polymer substrate using an electron microscope. be able to.

The resin that can be added to the polymer base material for forming the cavity is preferably a resin that is incompatible with the polymer constituting the polymer base material (incompatible resin). Thereby, light can be scattered and a light reflectance can be raised. Preferred incompatible resins include polyolefin resins such as polyethylene, polypropylene, polybutene, polymethylpentene, polystyrene resins, polyacrylate resins, polycarbonate resins, polyacrylonitrile resins, polyphenylene sulfide resins, polysulfone resins, cellulose resins, And fluorine-based resins are preferred. These incompatible resins may be homopolymers or copolymers, and two or more incompatible resins may be used in combination. Among these, polyolefin resins and polystyrene resins such as polypropylene and polymethylpentene having a low surface tension are preferable, and polymethylpentene is most preferable. Since the polymethylpentene has a relatively large difference in surface tension from the polyester and a high melting point, the polyester film has a low affinity with the polyester and easily forms voids, and is particularly preferable as an incompatible resin. Is.

When the polymer substrate contains an incompatible resin, the amount thereof is 0 to 30% by mass, more preferably 1 to 20% by mass, and further preferably 2 to 15% by mass with respect to the entire polymer substrate. % Range. When the content is 30% by mass or less, the apparent density of the entire polymer base material can be secured, film tearing and the like hardly occur at the time of stretching, and productivity can be kept good.
When fine particles are added, the average particle size of the fine particles is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, and still more preferably 0.15 to 1 μm. When the average particle size is 0.1 μm or more, the reflectance (whiteness) is maintained, and when the average particle size is 10 μm or less, a decrease in mechanical strength due to voids can be avoided. The content of the fine particles is preferably 0 to 50% by mass, more preferably 1 to 10% by mass, and further preferably 2 to 5% by mass with respect to the total mass of the polymer substrate. When the content is 50% by mass or less, the reflectance (whiteness) is kept good, and a decrease in mechanical strength due to voids can be avoided. Preferable fine particles include those having a low affinity with polyester, specifically, barium sulfate and the like.

A white polymer base material, that is, a polymer base material (for example, a polyester film) formed by voids by containing fine particles or the like may have a single layer or a laminated structure including two or more layers. As a laminated structure, it is preferable to combine a high whiteness (a layer with a lot of voids and fine particles) and a low whiteness layer (a layer with a small amount of voids and fine particles). Although the light reflection efficiency can be increased in a layer containing a lot of voids and fine particles, the mechanical strength is easily lowered (brittle) due to the voids and fine particles. In order to compensate for this, it is preferable to combine with a layer having low whiteness. For this reason, it is preferable to use a layer with high whiteness for the outer layer of a polymer base material, and may be used for one side of a polymer base material, and may be used for both surfaces of a polymer base material. In addition, when a high white layer using titanium dioxide as fine particles is used as the outer layer of the polymer base material, titanium dioxide has a UV absorbing ability, so that an effect of improving the light resistance of the polymer base material can be obtained.

When the layer with high whiteness is a layer containing fine particles, the amount of fine particles is preferably 5% by mass or more and 50% by mass or less, more preferably 6% by mass or more and 20% by mass or less. When the layer with high whiteness is a layer in which cavities are formed, the apparent specific gravity of the layer with high whiteness is preferably 0.7 or more and 1.2 or less, more preferably 0.8 or more and 1.1 or less. On the other hand, when the layer with low whiteness is a layer containing fine particles, the amount of fine particles is preferably 0% by mass or more and less than 5% by mass, more preferably 1% by mass or more and 4% by mass or less. When the layer with low whiteness is a layer in which a cavity is formed, the apparent specific gravity of the layer with low whiteness is 0.9 or more and 1.4 or less, and higher density than the high white layer is preferable, and more preferable Has an apparent specific gravity of 1.0 or more and 1.3 or less, and has a higher density than the high white layer. The low white layer may not contain fine particles or cavities.
As a preferable laminated structure of the white polymer base material, high white layer / low white layer, high white layer / low white layer / high white layer, high white layer / low white layer / high white layer / low white layer, high white layer / Low white layer / high white layer / low white layer / high white layer.
The thickness ratio of each layer in the laminated structure is not particularly limited, but the thickness of each layer is preferably 1% or more and 99% or less, more preferably 2% or more and 95% or less of the total layer thickness. Within this range, it is easy to obtain the effects of improving the reflection efficiency and imparting light resistance (UV) resistance. The thickness of all layers of the polymer substrate is not particularly limited as long as it can be formed as a film, but is usually 20 to 500 μm, preferably 25 to 300 μm.
A so-called coextrusion method using two or three or more melt extruders is preferably used as a method for laminating a polymer substrate having a laminated structure.

In order to increase the whiteness of the white polymer substrate, it is also preferable to use a fluorescent whitening agent such as thiofediyl. A preferable addition amount is 0.01% by mass or more and 1% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, and still more preferably, with respect to the total mass of the white polymer substrate. It is 0.1 mass% or more and 0.3 mass% or less. When the addition amount is 0.01% by mass or more, the effect of improving the light reflectivity is easily obtained. Moreover, it can avoid that a reflectance falls by yellowing by the thermal decomposition by extrusion as the addition amount is 1 mass% or less. As such a fluorescent whitening agent, for example, OB-1 (trade name) manufactured by Eastman Kodak Co., Ltd. can be used.

The white polymer base material has an illuminance of 100 mW / cm ² , a temperature of 60 ° C., a relative humidity of 50% RH, an irradiation time of 48 hours, and a yellowish change amount (Δb value) after irradiation with ultraviolet rays of less than 5 Is preferred. The Δb value is more preferably less than 4, and still more preferably less than 3. Thereby, even if it receives irradiation of sunlight for a long time, it is useful at the point which can reduce a color change. Such an effect is prominent in a solar battery module in which a back sheet containing a polymer base material is laminated on a solar battery cell, particularly when receiving light irradiation from the back sheet side.

Also, a black polymer substrate can be obtained by adding a black pigment such as carbon black in the same manner.

(End sealant)
The polymer base material can be configured to contain or not contain an end-capping agent in the range of 0 to 10% by mass relative to the polymer resin. The content of the end-capping agent is preferably in the range of more than 0% by mass to 10% by mass, more preferably 0.2% by mass to 5% by mass, and further preferably 0.3% by mass to 2% by mass. .

Hydrolysis of polymers such as polyester is accelerated by the catalytic effect of hydrogen ions (H ⁺ ) generated from terminal carboxylic acids and the like, so that the hydrolysis resistance (weather resistance) is improved by reacting with terminal carboxyl groups. It is effective to add a terminal blocking agent. Therefore, when the content of the end-capping agent is within the above range, it can be avoided that the end-capping material acts as a plasticizer for the polymer to reduce the mechanical strength and heat resistance of the polymer base material. .

Examples of the end-capping agent include epoxy compounds, carbodiimide compounds, oxazoline compounds, carbonate compounds, and the like. Among these, a carbodiimide compound having high affinity with PET and high end-capping ability is preferable.

When the end-capping agent (particularly carbodiimide compound) has a high molecular weight, volatilization during melt film formation can be reduced. The molecular weight is preferably 200 to 100,000 in terms of weight average molecular weight, more preferably 2000 to 80,000, and still more preferably 10,000 to 50,000. When the weight average molecular weight of the end-capping agent (particularly carbodiimide compound) is 100,000 or less, it is easy to uniformly disperse in the polyester, and the effect of improving weather resistance is exhibited well. On the other hand, when the weight average molecular weight is 200 or more, it is difficult to volatilize during extrusion and film formation, and an effect of improving weather resistance is easily obtained.

-Carbodiimide end-capping agent-
A carbodiimide type terminal blocker is a carbodiimide compound which has a carbodiimide group. This carbodiimide compound includes a monofunctional carbodiimide and a polyfunctional carbodiimide.
Examples of monofunctional carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide and di-β-naphthylcarbodiimide. Particularly preferred are dicyclohexylcarbodiimide and diisopropylcarbodiimide.

As the polyfunctional carbodiimide, carbodiimide having a polymerization degree of 3 to 15 is preferably used. Specifically, 1,5-naphthalene carbodiimide, 4,4′-diphenylmethane carbodiimide, 4,4′-diphenyldimethylmethane carbodiimide, 1,3-phenylene carbodiimide, 1,4-phenylene diisocyanate, 2,4-tolylene Carbodiimide, 2,6-tolylene carbodiimide, mixture of 2,4-tolylene carbodiimide and 2,6-tolylene carbodiimide, hexamethylene carbodiimide, cyclohexane-1,4-carbodiimide, xylylene carbodiimide, isophorone carbodiimide, isophorone carbodiimide, Dicyclohexylmethane-4,4′-carbodiimide, methylcyclohexanecarbodiimide, tetramethylxylylene carbodiimide, 2,6-diisopropylphenylcarbodiimide and 1 3,5-triisopropyl-2,4-carbodiimide can be exemplified.

The carbodiimide compound is preferably a carbodiimide compound having high heat resistance because an isocyanate gas is generated by thermal decomposition. In order to improve heat resistance, the higher the molecular weight (degree of polymerization), the better, and the terminal of the carbodiimide compound preferably has a structure with high heat resistance. Further, since the carbodiimide compound is likely to undergo further thermal decomposition once it is thermally decomposed, it is preferable to devise measures such as setting the extrusion temperature of a polymer such as polyester as low as possible.

The carbodiimide compound used as the end-capping agent preferably has a cyclic structure, and examples thereof include compounds described in JP2011-153209A. These exhibit the same effects as the above-described high molecular weight carbodiimide compounds even at low molecular weights. This is because the terminal carboxyl group of a polymer such as polyester and a cyclic carbodiimide undergo a ring-opening reaction, one of which reacts with this polyester, and the other of the ring-opening reacts with another polyester to increase the molecular weight, thereby generating an isocyanate gas. It is for suppressing doing.

The end-capping agent, which is a carbodiimide compound having a cyclic structure, is preferably a compound having a carbodiimide group and a cyclic structure in which the first nitrogen and the second nitrogen are bonded by a bonding group. Further, the terminal blocking agent has a cyclic structure in which at least one carbodiimide group adjacent to the aromatic ring is present, and the first nitrogen and the second nitrogen of the carbodiimide group adjacent to the aromatic ring are bonded to each other by a bonding group. It is more preferably carbodiimide (also referred to as aromatic cyclic carbodiimide).
The aromatic cyclic carbodiimide may have a plurality of cyclic structures.
The aromatic cyclic carbodiimide is preferably an aromatic carbodiimide having no ring structure in which the first nitrogen and the second nitrogen of two or more carbodiimide groups are bonded by a linking group in the molecule, that is, a monocyclic ring. Can be used.

The cyclic structure has one carbodiimide group (—N═C═N—), and the first nitrogen and the second nitrogen are bonded by a bonding group. One cyclic structure has only one carbodiimide group. For example, when there are a plurality of cyclic structures in the molecule, such as a spiro ring, one cyclic structure bonded to a spiro atom is included in each cyclic structure. As long as it has a carbodiimide group, the compound may have a plurality of carbodiimide groups. The number of atoms in the cyclic structure is preferably 8 to 50, more preferably 10 to 30, further preferably 10 to 20, and particularly preferably 10 to 15.

Here, the number of atoms in the cyclic structure means the number of atoms directly constituting the cyclic structure. For example, the number of atoms is 8 for an 8-membered ring, and the number of atoms is 50 for a 50-membered ring. It is. When the number of atoms in the cyclic structure is 8 or more, the stability of the cyclic carbodiimide compound is maintained, which is suitable for storage and use. Further, from the viewpoint of reactivity, there is no particular restriction on the upper limit of the number of ring members, but a cyclic carbodiimide compound having 50 or less atoms is preferable in terms of suppressing cost increase due to difficulty in synthesis. From this viewpoint, the number of atoms in the cyclic structure is preferably from 10 to 30, more preferably from 10 to 20, and particularly preferably from 10 to 15.

Specific examples of the carbodiimide compound having a cyclic structure include the following compounds. However, the present invention is not limited to the specific examples shown below.

-Epoxy end sealant-
The epoxy-based end-capping agent is selected from epoxy compounds. Preferable examples of the epoxy compound include glycidyl ester compounds and glycidyl ether compounds.

Specific examples of glycidyl ester compounds include benzoic acid glycidyl ester, t-Bu-benzoic acid glycidyl ester, P-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycidyl ester, lauric acid glycidyl ester , Glycidyl palmitate, glycidyl behenate, glycidyl versatate, glycidyl oleate, glycidyl linoleate, glycidyl linolein, glycidyl behenol, glycidyl stearol, diglycidyl terephthalate, isophthalic acid Diglycidyl ester, diglycidyl phthalate, diglycidyl naphthalene dicarboxylate Stell, methyl terephthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diglycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, sebacic acid diglycidyl ester, dodecane Examples thereof include diacid diglycidyl ester, octadecanedicarboxylic acid diglycidyl ester, trimellitic acid triglycidyl ester, and pyromellitic acid tetraglycidyl ester. These can use 1 type (s) or 2 or more types.

Specific examples of the glycidyl ether compound include phenyl glycidyl ether, O-phenyl glycidyl ether, 1,4-bis (β, γ-epoxypropoxy) butane, 1,6-bis (β, γ- Epoxypropoxy) hexane, 1,4-bis (β, γ-epoxypropoxy) benzene, 1- (β, γ-epoxypropoxy) -2-ethoxyethane, 1- (β, γ-epoxypropoxy) -2-benzyl Oxyethane, 2,2-bis- [р- (β, γ-epoxypropoxy) phenyl] propane, 2,2-bis- (4-hydroxyphenyl) propane and 2,2-bis- (4-hydroxyphenyl) Examples thereof include bisglycidyl polyether obtained by the reaction of bisphenol such as methane and epichlorohydrin. These can use 1 type (s) or 2 or more types.

-Oxazoline-based end-capping agent-
The oxazoline-based end capping agent is selected from oxazoline compounds. As the oxazoline compound, a bisoxazoline compound is preferable. Specifically, 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), 2,2′-bis (4,4-dimethyl-2-oxazoline), 2,2′-bis (4-ethyl-2-oxazoline), 2,2′-bis (4,4′-diethyl-2-oxazoline), 2,2 '-Bis (4-propyl-2-oxazoline), 2,2'-bis (4-butyl-2-oxazoline), 2,2'-bis (4-hexyl-2-oxazoline), 2,2'- Bis (4-phenyl-2-oxazoline), 2,2′-bis (4-cyclohexyl-2-oxazoline), 2,2′-bis (4-benzyl-2-oxazoline), 2,2′-p- Phenylenebis (2-oxazoline), 2,2'-m- Enylene bis (2-oxazoline), 2,2'-o-phenylene bis (2-oxazoline), 2,2'-p-phenylene bis (4-methyl-2-oxazoline), 2,2'-p-phenylene bis (4,4-dimethyl-2-oxazoline), 2,2'-m-phenylenebis (4-methyl-2-oxazoline), 2,2'-m-phenylenebis (4,4-dimethyl-2-oxazoline) ), 2,2′-ethylenebis (2-oxazoline), 2,2′-tetramethylenebis (2-oxazoline), 2,2′-hexamethylenebis (2-oxazoline), 2,2′-octamethylene Bis (2-oxazoline), 2,2′-decamethylene bis (2-oxazoline), 2,2′-ethylenebis (4-methyl-2-oxazoline), 2,2′-tetramethylene bis (4,4 -The Methyl-2-oxazoline), 2,2′-9,9′-diphenoxyethanebis (2-oxazoline), 2,2′-cyclohexylenebis (2-oxazoline) and 2,2′-diphenylenebis ( 2-oxazoline) and the like. Of these, 2,2′-bis (2-oxazoline) is most preferably used from the viewpoint of reactivity with polyester. Furthermore, the bisoxazoline compounds listed above may be used alone or in combination of two or more as long as the object of the present invention is achieved.

Such an end-capping agent can be introduced by a method such as kneading into a polymer constituting the polymer substrate. That is, the said effect is acquired by making a terminal blocker and a polymer molecule contact directly, and making it react. Even when the end-capping agent is added to the coating layer on PET, a polymer such as polyester does not react with the end-capping agent.

The surface of the polymer substrate may be subjected to a surface treatment such as a corona treatment, a flame treatment, or a glow discharge treatment as necessary. By applying these surface treatments, it is possible to further improve the adhesiveness when exposed to a humid heat environment. In particular, by performing corona treatment and glow discharge treatment, a more excellent adhesive improvement effect can be obtained.
These surface treatments can increase adhesion by increasing carboxyl groups and hydroxyl groups on the surface of polymer substrates (for example, polyester substrates). However, crosslinking agents (especially oxazoline or carbodiimide compounds that are highly reactive with carboxyl groups) can be used. When the crosslinking agent is used in combination, stronger adhesiveness can be obtained. This is more remarkable in the case of corona treatment and glow discharge treatment.

Corona discharge treatment is usually performed by applying high frequency and high voltage between a metal roll (dielectric roll) coated with a derivative and an insulated electrode to cause dielectric breakdown of the air between the electrodes. Is ionized to generate a corona discharge between the electrodes. And it performs by passing a polymer base material between this corona discharge.
In one embodiment, the conditions for the corona discharge treatment are that the gap clearance between the electrode and the dielectric roll is 1 to 3 mm, the frequency is 1 to 100 kHz, and the applied energy is about 0.2 to 5 kV · A · min / m ^2. preferable.

The glow discharge treatment is a method called vacuum plasma treatment or glow discharge treatment, in which plasma is generated by discharge in a gas (plasma gas) in a low-pressure atmosphere to treat the substrate surface. The low-pressure plasma used here is non-equilibrium plasma generated under a condition where the pressure of the plasma gas is low. Glow discharge treatment can be performed by placing a film to be treated in this low-pressure plasma atmosphere.
In the glow discharge treatment, methods for generating plasma include direct current glow discharge, high frequency discharge, microwave discharge, and the like. The power source used for discharging may be direct current or alternating current. When alternating current is used, a range of about 30 Hz to 20 MHz is preferable. When alternating current is used, a commercial frequency of 50 Hz or 60 Hz may be used, or a high frequency of about 10 Hz to 50 kHz may be used. A method using a high frequency of 13.56 MHz is also preferable.
Examples of the plasma gas used in the glow discharge treatment include inorganic gases such as oxygen gas, nitrogen gas, water vapor gas, argon gas, and helium gas, and oxygen gas or a mixed gas of oxygen gas and argon gas is particularly preferable. Specifically, it is desirable to use a mixed gas of oxygen gas and argon gas. When oxygen gas and argon gas are used, the ratio of the two is preferably about oxygen gas: argon gas = 100: 0 to 30:70, more preferably 90:10 to 70:30, as a partial pressure ratio. In addition, a method is also preferable in which a gas such as the air entering the processing container due to a leak or water vapor coming out of the object to be processed is used as the plasma gas without introducing the gas into the processing container.
As the pressure of the plasma gas, a low pressure at which non-equilibrium plasma conditions are achieved is necessary. The specific plasma gas pressure is preferably in the range of 0.005 to 10 Torr, more preferably about 0.008 to 3 Torr. When the pressure of the plasma gas is 0.005 Torr or more, a good adhesive improvement effect is obtained. Conversely, when the pressure is 10 Torr or less, discharge instability due to an increase in current can be prevented.

The plasma output cannot be generally specified depending on the shape and size of the processing vessel, the shape of the electrode, and the like, but is preferably about 100 to 2500 W, and more preferably about 500 to 1500 W.
The treatment time for the glow discharge treatment is preferably 0.05 to 100 seconds, more preferably about 0.5 to 30 seconds. When the treatment time is 0.05 seconds or longer, a good effect of improving adhesiveness can be obtained. Conversely, when the treatment time is 100 seconds or less, deformation or coloring of the film to be treated can be prevented.
The discharge treatment intensity of the glow discharge treatment is preferably in the range of 0.01 to 10 kV · A · min / m ² , more preferably 0.1 to 7 kV · A · min / m ² , depending on the plasma output and the treatment time.
When the discharge treatment strength is 0.01 kV · A · min / m ² or more, a good adhesion improving effect can be obtained. Moreover, a deformation | transformation, coloring, etc. of a to-be-processed film can be avoided because discharge processing intensity | strength is 10 kV * A * min / m < ² > or less.

In the glow discharge treatment, it is also preferable to heat the polymer substrate in advance. By this method, better adhesiveness can be obtained in a shorter time than when heating is not performed. The heating temperature is preferably in the range of 40 ° C. to the softening temperature of the film to be treated + 20 ° C., more preferably in the range of 70 ° C. to the softening temperature of the film to be processed. By setting the heating temperature to 40 ° C. or higher, a sufficient adhesive improvement effect can be obtained. Moreover, the handleability of a favorable film can be ensured during a process by making heating temperature below into the softening temperature of a to-be-processed film. Specific methods for raising the temperature of the film to be treated in vacuum include heating with an infrared heater, heating by contacting with a hot roll, and the like.

(Composite polymer layer)
The composite polymer layer in the present invention is a layer provided directly or via another layer on the polymer substrate, and is preferably a coating layer formed by a coating method. This composite polymer layer is configured using a specific composite polymer having a (poly) siloxane structural unit represented by the following general formula (1) in the molecule. The composite polymer layer in the present invention is excellent in moisture and heat resistance over a long period of time by including the composite polymer, and also has adhesion to the polymer substrate and adhesion between the other adjacent layers when another adjacent layer is provided. Excellent. The composite polymer layer can be constituted by using other components depending on the application and the case of application.

The composite polymer layer in the present invention is, for example, the outermost layer exposed to the external environment, that is, the outermost layer on the back surface opposite to the front surface on which sunlight directly enters (battery side substrate on which the solar cells of the back sheet are arranged) Is preferably used as the outermost layer on the side opposite to the side on which is disposed. In addition, the composite polymer layer may be configured as a reflective layer that increases power generation efficiency by returning light that is incident from the front surface side and passes through the solar cell (cell structure portion) to the cell again. In this case, a colorant such as a white pigment can be further used.
When two or more composite polymer layers are provided on the polymer base material, the composite polymer layer / light reflective composite polymer layer (white layer) / polymer base material multilayer structure may be used. Excellent in adhesion and adhesion within the back sheet of the reflective layer.

-Composite polymer-
The composite polymer layer in the present invention has a non-siloxane structure having a (poly) siloxane structural unit having a mass ratio of 15 to 85 mass% and a mass ratio of 85 to 15 mass% represented by the following general formula (1) in the molecule. And at least one kind of composite polymer containing units. By containing this composite polymer, the adhesion between the polymer substrate as a support and the interlayer, that is, peeling resistance and shape stability, which are easily deteriorated when given heat and moisture, is dramatically improved compared to conventional products. Can do.

The composite polymer in the present invention is a block copolymer in which (poly) siloxane and at least one polymer are copolymerized. The (poly) siloxane and the copolymerized polymer may be one kind alone, or two or more kinds.
In the present invention, the “siloxane structure” means a structure containing at least one siloxane bond. The “polysiloxane structure” means a structure in which a plurality of siloxane bonds are continuous. The term “(poly) siloxane structure” includes siloxane structures and polysiloxane structures in its scope, “the polymer has a siloxane structure in the molecule” and “the polymer has a (poly) siloxane structure in the molecule”. This means that the polymer contains a siloxane structure or a polysiloxane structure in its molecule.

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

In the part of “— (Si (R ¹ ) (R ² ) —O) _n —” ((poly) siloxane structural unit represented by the general formula (1)), which is the (poly) siloxane segment in the composite polymer, R ¹ and R ² may be the same or different and each represents a hydrogen atom, a halogen atom, or a monovalent organic group.

“— (Si (R ¹ ) (R ² ) —O) _n —” is a (poly) siloxane segment derived from various (poly) siloxanes having a linear, branched or cyclic structure.

Examples of the halogen atom represented by R ¹ and R ² include a fluorine atom, a chlorine atom, and an iodine atom.

The “monovalent organic group” represented by R ¹ and R ² is a group capable of covalent bonding with a Si atom, and may be unsubstituted or have a substituent. The monovalent organic group includes, for example, an alkyl group (eg, methyl group, ethyl group, etc.), an aryl group (eg: phenyl group, etc.), an aralkyl group (eg: benzyl group, phenylethyl etc.), and an alkoxy group (eg: A methoxy group, an ethoxy group, a propoxy group, etc.), an aryloxy group (eg, phenoxy group, etc.), a mercapto group, an amino group (eg, amino group, diethylamino group, etc.), an amide group and the like.

Among them, 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 a polymer substrate and durability in a wet and heat environment. Alkyl groups having 1 to 4 carbon atoms (particularly methyl and ethyl groups), unsubstituted or substituted phenyl groups, unsubstituted or substituted alkoxy groups (eg, methoxy group, ethoxy group, propoxy group, etc.) An alkoxy group having 1 to 4 carbon atoms), a mercapto group, an unsubstituted amino group, or an amide group, and more preferably an unsubstituted or substituted alkoxy group (from the viewpoint of durability in a humid heat environment) Preferred is an alkoxy group having 1 to 4 carbon atoms.

N is preferably from 1 to 5000, and more preferably from 1 to 1000.

Specific examples of the portion of “— (Si (R ¹ ) (R ² ) —O) _n —” ((poly) siloxane structural unit represented by the general formula (1)) in the silicone polymer include dimethyldimethoxysilane Hydrolysis condensate containing a hydrolysis condensate, dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane hydrolysis condensate, dimethyldimethoxysilane / vinyltrimethoxysilane hydrolysis condensate Hydrolysis condensate containing dimethyldimethoxysilane / 2-hydroxyethyltrimethoxysilane hydrolysis condensate, dimethyldimethoxysilane / 3-glycidoxypropyltriethoxysilane hydrolysis condensate Hydrolysis condensate containing dimethyldimethoxysilane / diphenyl / dimethyl It is hydrolyzed condensate containing Kishishiran γ- methacryloxypropyltrimethoxysilane hydrolyzed condensate of trimethoxysilane. Among these, a hydrolysis condensate containing a hydrolysis condensate of dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane, a hydrolysis condensate of dimethyldimethoxysilane / diphenyl / dimethoxysilane γ-methacryloxytrimethoxysilane, and the like. The hydrolyzed condensate contained is preferred.

The content ratio of “— (Si (R ¹ ) (R ² ) —O) _n —” in the composite polymer (the (poly) siloxane structural unit represented by the general formula (1)) is the total content of the composite polymer. The content is 15 to 85% by mass with respect to the mass, and among them, the range of 20 to 80% by mass is preferable from the viewpoint of adhesion to the polymer substrate and durability in a moist heat environment. When the ratio of the polysiloxane moiety is less than 15% by mass, the adhesion to the polymer substrate and the adhesion durability when exposed to a wet heat environment are inferior, and when it exceeds 85% by mass, the liquid becomes unstable.
At this time, the content ratio of the non-siloxane structural unit is 85 to 15% by mass.
By containing such a copolymer, the layer strength is improved, the occurrence of scratches due to scratching or scratching is prevented, and the adhesion to the polymer substrate, that is, the peeling resistance that is easily deteriorated by being given heat or moisture. In addition, the shape stability and the durability in a humid heat environment can be dramatically improved as compared with the conventional case.
When the silicone polymer is a copolymer having a (poly) siloxane structural unit and another structural unit, a moiety of “— (Si (R ¹ ) (R ² ) —O) _n —” in the silicone polymer ( The molecular weight of the (poly) siloxane structural unit represented by the general formula (1) is about 5000 to 300000 in terms of polystyrene-converted weight average molecular weight, and preferably about 10,000 to 150,000.

Further, the non-siloxane structural unit copolymerized with the siloxane structural unit (the structural portion derived from the polymer) is not particularly limited except that it does not have a siloxane structure, and is derived from any polymer. Any of the polymer segments may be used. Examples of the polymer (precursor polymer) that is a precursor of the polymer segment include various polymers such as a vinyl polymer, a polyester polymer, and a polyurethane polymer. From the viewpoint of easy preparation and excellent hydrolysis resistance, vinyl polymers and polyurethane polymers are preferred, and vinyl polymers are particularly preferred.

Typical examples of the vinyl polymer include various polymers such as an acrylic polymer, a carboxylic acid vinyl ester polymer, an aromatic vinyl polymer, and a fluoroolefin polymer. Among these, an acrylic polymer (that is, an acrylic structural unit as a non-siloxane structural unit) is particularly preferable from the viewpoint of design flexibility. Monomers constituting the acrylic polymer include acrylic acid esters (eg, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, etc.) or methacrylic acid esters (eg, methyl methacrylate, butyl methacrylate, hydroxyethyl acrylate). , Glycidyl methacrylate, dimethylaminoethyl methacrylate, etc.). In addition, examples of monomers include carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid, styrene, acrylonitrile, vinyl acetate, acrylamide, and divinylbenzene. Among them, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate methyl methacrylate , Butyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid and the like are preferable.
Specific examples of the acrylic polymer include methyl methacrylate / ethyl acrylate / acrylic acid copolymer, methyl methacrylate / ethyl acrylate / 2-hydroxyethyl methacrylate / methacrylic acid copolymer, methyl methacrylate / butyl acrylate / 2- Examples include bidoxyethyl methacrylate / methacrylic acid / γ-methacryloxytrimethoxysilane copolymer, methyl methacrylate / ethyl acrylate / glycidyl methacrylate / acrylic acid copolymer, and the like.
In addition, the polymer which comprises a non-siloxane type structural unit may be single 1 type, and 2 or more types of combined use may be sufficient as it. Furthermore, the individual polymers may be homopolymers or copolymers.
The molecular weight of the polymer, which is a precursor of the polymer segment constituting the non-siloxane structural unit, is about 5000 to 300000 in terms of polystyrene-equivalent weight average molecular weight, and preferably about 10,000 to 150,000.

In addition, the precursor polymer forming the non-siloxane structural unit is preferably one containing at least one of an acid group and a neutralized acid group and / or a hydrolyzable silyl group. Among such precursor polymers, the vinyl polymer includes, for example, (a) a vinyl monomer containing an acid group and a vinyl monomer containing a hydrolyzable silyl group and / or a silanol group. (2) a method of reacting a polycarboxylic acid anhydride with a vinyl polymer containing a previously prepared hydroxyl group and hydrolyzable silyl group and / or silanol group, 3) Utilizing various methods such as a method in which a vinyl polymer containing an acid anhydride group and a hydrolyzable silyl group and / or silanol group prepared in advance is reacted with a compound having active hydrogen (water, alcohol, amine, etc.). Can be prepared.

Such a precursor polymer can be produced and obtained using, for example, the method described in paragraph Nos. 0021 to 0078 of JP-A-2009-52011.

In the composite polymer layer in the present invention, the composite polymer may be used alone as a binder, or may be used in combination with other polymers. When other polymers are used in combination, the ratio of the composite polymer in the present invention is preferably 30% by mass or more, more preferably 60% by mass or more of the total binder. When the ratio of the composite polymer is 30% by mass or more, the adhesiveness with the polymer base material and the durability under a moist heat environment are more excellent.

The molecular weight of the composite polymer is about 5000 to 300,000, preferably about 10,000 to 150,000.

For the preparation of the composite polymer, (i) a method of reacting a precursor polymer with (poly) siloxane having a structure of the general formula (1) [— (Si (R ¹ ) (R ² ) —O) _n —] (Ii) a silane compound having a structure of “— (Si (R ¹ ) (R ² ) —O) _n —” in which R ¹ and / or R ² is a hydrolyzable group in the presence of a precursor polymer Methods such as hydrolytic condensation 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 composite polymer 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 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.
In the case of preparing a composite polymer by the method (ii), for example, water and a silanol condensation catalyst are added to a mixture of a precursor polymer and an alkoxysilane compound, and the temperature is about 20 to 150 ° C. for 30 minutes to 30 hours. It can be prepared by hydrolytic condensation to a degree (preferably at 50 to 130 ° C. for 1 to 20 hours).

Preferred examples of the composite polymer include a hydrolysis condensate in which the (poly) siloxane structural unit contains a hydrolysis condensate of dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane, dimethyldimethoxysilane / diphenyl / dimethoxysilane γ-methacrylate. It consists of one of the hydrolyzed condensates of loxytrimethoxysilane, and the polymer structure part copolymerized with the (poly) siloxane structural unit is ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate methyl methacrylate, methyl methacrylate, butyl A composite polymer, which is an acrylic polymer composed of a monomer component selected from methacrylate, hydroxyethyl acrylate, acrylic acid, and methacrylic acid, can be mentioned as a more preferred example. (Poly) siloxane structural unit comprises a hydrolysis condensate containing a hydrolysis condensate of dimethyldimethoxysilane / γ-methacryloxytrimethoxysilane and a monomer component selected from methyl methacrylate, ethyl acrylate, acrylic acid and methacrylic acid The composite polymer which is an acrylic polymer is mentioned.

Commercially available products may be used as the polymer having a (poly) siloxane structure. For example, DIC Corporation's Ceranate series (for example, Ceranate WSA1070, WSA1060, etc.), Asahi Kasei Chemicals Corporation H7600 series (H7650, H7630, H7620, etc.) manufactured by JSR Co., Ltd., inorganic / acrylic composite emulsion manufactured by JSR Corporation, and the like can be used.

The content ratio of the polymer having a (poly) siloxane structure in the composite polymer layer is in the range of more than 0.2 g / m ^{2 and} 15 g / m ² or less. When the content ratio of the polymer is 0.2 g / m ² or less, the ratio of the polymer is too small, and scratches generated due to external force cannot be suppressed. On the other hand, when the polymer content ratio exceeds 15 g / m ² , the polymer ratio is too high, and the composite polymer layer is not sufficiently cured.
Among the above range, from the viewpoint of the surface strength of the composite polymer ^layer, the range of ^{0.5g / m 2 ~ 10.0g / m} 2 is preferably in ^the range of ^{1.0g / m 2 ~ 5.0g / m} 2 More preferred.

-Crosslinking agent-
In the present invention, the composite polymer layer preferably has a structural portion derived from a cross-linking agent that cross-links between the composite polymers. That is, the composite polymer layer can be formed using a cross-linking agent that can cross-link between the composite polymers. By crosslinking with a crosslinking agent, adhesion after wet heat aging, specifically adhesion to a polymer substrate when exposed to a wet heat environment, and adhesion between layers can be further improved.

Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among the crosslinking agents, crosslinking agents such as carbodiimide compounds and oxazoline compounds are 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- (4,4'-di Til-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene- Examples thereof include bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, and bis- (2-oxazolinyl norbornane) sulfide. Furthermore, (co) polymers of these compounds are also preferably used.
Further, as a compound having an oxazoline group, Epocros K2010E, K2020E, K2030E, WS-500, WS-700 (all manufactured by Nippon Shokubai Chemical Co., Ltd.) and the like can be used.

Specific examples of the carbodiimide-based crosslinking agent include dicyclohexylmethane carbodiimide, tetramethylxylylene carbodiimide, and dicyclohexylmethane carbodiimide. A carbodiimide compound described in JP-A-2009-235278 is also preferable. Specifically, carbodiimide-based crosslinking agents such as Carbodilite SV-02, Carbodilite V-02, Carbodilite V-02-L2, Carbodilite V-04, Carbodilite E-01, Carbodilite E-02 (all Nisshinbo Chemical Co., Ltd.) (Commercially available) can also be used.

In the composite polymer layer, the mass ratio of the structural part derived from the crosslinking agent to the composite polymer is preferably 1 to 30% by mass, more preferably 5 to 20% by mass. When the content of the crosslinking agent is 1% by mass or more, the strength of the composite polymer layer and the adhesiveness after wet heat aging are excellent, and when it is 30% by mass or less, the pot life of the coating solution can be kept long.

In the backsheet of the present invention, the composite polymer layer contains the composite polymer as described above, so that the adhesion to the polymer substrate is improved and the adhesion between the layers is improved. Furthermore, it is excellent in deterioration resistance (adhesion durability) in a humid heat environment. For this reason, it is also preferable to be provided as the outermost layer disposed at the position farthest from the polymer substrate. Specifically, for example, there is a back layer disposed on the opposite side (back side) to the side (front side) facing the battery side substrate including the solar cell element.

Only one composite polymer layer may be provided, or a plurality of composite polymer layers may be formed.
The thickness of one layer of the composite polymer layer is usually preferably from 0.3 μm to 22 μm, more preferably from 0.5 μm to 15 μm, still more preferably from 0.8 μm to 12 μm, particularly preferably from 1.0 μm to 8 μm. A range of 2 to 6 μm is most preferable. When the composite polymer layer has a thickness of 0.3 μm or more, more preferably 0.8 μm or more, it is difficult for moisture to penetrate from the surface of the composite polymer layer when exposed to a humid heat environment. Adhesiveness is remarkably improved by making it difficult for moisture to reach the interface with the material. Moreover, when the thickness of the composite polymer layer is 22 μm or less, and further 12 μm or less, the composite polymer layer itself is difficult to become brittle, and the composite polymer layer is less likely to be destroyed when exposed to a humid heat environment. Is improved.

The composite polymer layer in the present invention has a cross-linked structure in which the composite polymer and the polymer molecules of the composite polymer are cross-linked with a cross-linking agent, and the ratio of the structural portion derived from the cross-linking agent to the composite polymer is 1 to 30% by mass. In the case where the composite polymer layer has a thickness of 0.8 μm to 12 μm, the effect of improving the adhesion after wet heat aging is particularly excellent.

~ Back layer ~
When the composite polymer layer in the present invention is configured as a back layer, it may be configured to include other components such as various additives as necessary in addition to the composite polymer. In a solar cell having a laminated structure of a battery-side substrate (= transparent substrate on which sunlight is incident (glass substrate, etc.) / Element structure part including a solar cell element) / solar cell backsheet, the back layer is supported. It is a back surface protective layer disposed on the opposite side of the polymer base material that forms the base material and facing the battery side substrate, and may have a single-layer structure or a structure in which two or more layers are laminated. By including the composite polymer, adhesion to the polymer substrate and adhesion between layers in the case where the back layer is composed of two or more layers are improved, and further, resistance to deterioration in a humid heat environment is obtained. Therefore, a form in which the back layer, which is the composite polymer layer in the present invention, is disposed as the outermost layer farthest from the polymer substrate is preferable.

When two or more back layers are provided, both back layers may be a composite polymer or a composite polymer layer containing both the composite polymer and a crosslinking agent, and only one back layer is a composite polymer or a composite polymer. And a composite polymer layer containing both a crosslinking agent and a crosslinking agent.
Among them, from the viewpoint of improving the adhesion durability in a wet heat environment, at least the back layer in contact with the polymer substrate (first back layer) is a composite polymer or a composite polymer layer containing both the composite polymer and a crosslinking agent. It is preferable to be configured. In this case, the second back layer provided further above the first back layer on the polymer substrate includes a (poly) siloxane structural unit and a non-polysiloxane structural unit represented by the general formula (1). It does not need to contain the composite polymer, but in that case, a uniform film without voids of the resin alone is formed to prevent moisture intrusion from the voids between the polymer and the pigment, and adhesion under wet heat environment is improved. From the viewpoint of enhancing, it is preferable not to contain a polysiloxane homopolymer.

As other components that can be contained in the back layer, surfactants, fillers and the like can be mentioned as described later. Moreover, you may include the pigment used for a colored layer. Details of these other components and pigments and preferred embodiments will be described later.

-Colored layer-
When the composite polymer layer in the present invention is configured as a colored layer (preferably a reflective layer), it can further contain a pigment in addition to the composite polymer. The colored layer may further include other components such as various additives as necessary.
When a composite polymer layer is comprised in a colored layer, it can contain at least 1 type of a pigment. As the pigment, the same pigments that can be used for the functional layer constituting the polymer substrate described above can be used, and the details and preferred embodiments such as the type and average particle diameter of the pigment are also the same. . The content in the colored layer of the pigment is 2.5 preferably in the range of ~ 8.5 g / ^{m 2,} and more preferably a range of 4.5 ~ 8.0g / ^{m 2.} When the pigment content is 2.5 g / m ² or more, necessary coloring can be obtained, and reflectance and decorative properties can be effectively provided. When the pigment content is 8.5 g / m ² or less, the surface state of the colored layer is easily maintained, and the film strength is excellent.

When the composite polymer layer is configured as a colored layer, the content of the binder component (including the composite polymer) is preferably in the range of 15 to 200% by mass, more preferably in the range of 17 to 100% by mass with respect to the pigment. When the content of the binder is 15% by mass or more, the strength of the colored layer is sufficiently obtained, and when it is 200% by mass or less, the reflectance and the decorativeness can be kept good.

-Additive-
If necessary, a surfactant, a filler and the like may be added to the composite polymer layer of the present invention. As the surfactant, a known surfactant such as an anionic or nonionic surfactant can be used. When the surfactant is added, the addition amount is preferably 0.1 to 15 mg / m ² , more preferably 0.5 to 5 mg / m ² . When the addition amount of the surfactant is 0.1 mg / m ² or more, it is possible to suppress the occurrence of repelling and to form a favorable layer, and when it is 15 mg / m ² or less, the adhesion can be favorably performed. .

A filler may be further added to the composite polymer layer in the present invention. The addition amount of the filler is preferably 20% by mass or less, more preferably 15% by mass or less per binder of the composite polymer layer. When the added amount of the filler is 20% by mass or less, the planar shape of the composite polymer layer can be kept better.

(Undercoat layer)
In the solar cell backsheet of the present invention, an undercoat layer may be provided between the polymer substrate and the composite polymer layer. The thickness of the undercoat layer is preferably in the range of 2 μm or less, more preferably 0.05 μm to 2 μm, and still more preferably 0.1 μm to 1.5 μm. When the thickness is 2 μm or less, the planar shape can be kept good. Moreover, it is easy to ensure required adhesiveness because thickness is 0.05 micrometer or more.

The undercoat layer is preferably a layer containing one or more kinds of polymers selected from polyolefin resins, acrylic resins, polyester resins, and polyurethane resins.

As the polyolefin resin, for example, a modified polyolefin copolymer is preferable. As the polyolefin resin, commercially available products may be used. For example, Arrow Base (registered trademark) SE-1013N, Arrow Base (registered trademark) SD-1010, Arrow Base (registered trademark) TC-4010, Arrow Base (registered trademark) TD-4010 (both manufactured by Unitika Ltd.), Hitech S3148, Hitech S3121, Hitech S8512 (both manufactured by Toho Chemical Co., Ltd.), Chemipearl (registered trademark) S-120, Chemipearl (registered trademark) S -75N, Chemipearl (registered trademark) V100, Chemipearl (registered trademark) EV210H (both manufactured by Mitsui Chemicals, Inc.), and the like. Among them, in the present invention, it is preferable to use Arrow Base (registered trademark) SE-1013N (manufactured by Unitika Ltd.), which is a terpolymer of low-density polyethylene, acrylic acid ester, and maleic anhydride.

As the acrylic resin, for example, a polymer containing polymethyl methacrylate, polyethyl acrylate, or the like is preferable. As the acrylic resin, a commercially available product may be used. For example, AS-563A (trade name; manufactured by Die Self Einchem Co., Ltd.) can be preferably used.

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

Among these, it is preferable to use a polyolefin resin from the viewpoint of securing adhesiveness with the polymer substrate and the white layer. Moreover, these polymers may be used individually by 1 type, or may use 2 or more types together. When using 2 or more types together, the combination of an acrylic resin and polyolefin resin is preferable.

It is more preferable that the undercoat layer contains a crosslinking agent in that the durability of the undercoat layer can be improved. Examples of the crosslinking agent include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among them, in the polymer base material in the present invention, the crosslinking agent in the undercoat layer is preferably an oxazoline-based crosslinking agent. The oxazoline-based crosslinking agent is a crosslinking agent having an oxazoline group. For example, Epocross (registered trademark) K2010E, Epocross (registered trademark) K2020E, Epocross (registered trademark) K2030E, Epocross (registered trademark) WS-500, Epocross (registered). (Trademark) WS-700 (all manufactured by Nippon Shokubai Chemical Industry Co., Ltd.) can be used.

The addition amount of the crosslinking agent is preferably 0.5% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less, and particularly preferably 5% by mass or more with respect to the binder constituting the undercoat layer. It is less than 15% by mass. In particular, when the addition amount of the crosslinking agent is 0.5% by mass or more, a sufficient crosslinking effect can be obtained while maintaining the strength and adhesiveness of the undercoat layer. Further, when the addition amount of the crosslinking agent is 30% by mass or less, the pot life of the coating solution can be kept long, and when it is less than 15% by mass, the coated surface state can be further improved.

The undercoat layer preferably contains an anionic or nonionic surfactant. The range of the surfactant that can be used for the undercoat layer is the same as the range of the surfactant that can be used for the white layer. Among these, nonionic surfactants are preferable.
When a surfactant is contained, its content is preferably 0.1 to 10 mg / m ² , more preferably 0.5 to 3 mg / m ² . The content of the surfactant is, if it is 0.1 mg / m ² or more, good layer formation by suppressing the occurrence of cissing can be obtained, if it is 10 mg / m ² or less, the polymer substrate and the white layer Adhesion can be performed satisfactorily.

As a method for applying and forming the undercoat layer, a known coating method is appropriately adopted. As the coating method, for example, any method such as a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, a coating method using a spray or a brush can be applied. The undercoat layer may be formed by immersing the polymer base material in an adjustment liquid for forming the undercoat layer. Further, from the viewpoint of cost, the undercoat layer is formed by applying the adjustment liquid for forming the undercoat layer on the resin sheet in the process of manufacturing the resin sheet constituting the polymer base material, by applying the so-called in-line coating method. The aspect in which the made resin film is manufactured is preferable.
Specifically, for example, the raw material resin is melt-kneaded, the resin is melt-extruded, the melt-extruded resin is cooled (for example, by casting on a cooling drum while using an electrostatic contact method), and the resin sheet is cooled. Forming a film, stretching a resin sheet in a first direction (for example, a sheet longitudinal direction (MD: Machine Direction)), and performing a first stretching, and at least a resin sheet stretched in one direction Applying and forming an undercoat layer on one surface, and applying a resin sheet on which the undercoat layer is applied to a second direction orthogonal to the first direction (for example, a width direction orthogonal to the longitudinal direction (TD: Transverse Direction; hereinafter) Similarly, a resin film having an undercoat layer is suitably produced by a method having a second stretching and a second stretching.
In addition, the conditions for drying and heat treatment during coating depend on the thickness of the coating and the conditions of the apparatus, but immediately after coating, the film is sent to stretching in the perpendicular direction and dried in the preheating zone or stretching zone when stretching. preferable. In such a case, drying and heat treatment are usually performed at about 50 ° C. to 250 ° C.
The surface of the polymer substrate on which the undercoat layer is formed may be subjected to corona discharge treatment or other surface activation treatment.

Details of the melt extrusion, film formation, first stretching, second stretching, and formation of the resin layer are as described above.

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

Also, a colored layer can be provided on the side of the polymer substrate opposite to the side on which the first polymer layer is provided.

~ Physical properties ~
When a white pigment is added as a pigment to the colored layer to form a reflective layer, the light reflectance at 550 nm on the surface on which the colored layer is provided is preferably 75% or more. The light reflectivity is the ratio of the amount of light incident from the surface reflected by the reflective layer and emitted from the surface again to the amount of incident light. Here, light having a wavelength of 550 nm is used as the representative wavelength light.
When the light reflectance is 75% or more, the light that passes through the cell and enters the cell can be effectively returned to the cell, and the effect of improving the power generation efficiency is great. The light reflectance can be adjusted to 75% or more by controlling the content of the colorant in the range of 2.5 to 30 g / m ² .

(Other functional layers)
The solar cell backsheet of the present invention may have other functional layers in addition to the polymer substrate and the composite polymer layer. As another functional layer, an easily adhesive layer may be provided.

[Fluorine-containing resin layer]
On the composite polymer layer in the present invention, a fluorine-containing resin layer containing a fluoropolymer may be provided as still another functional layer.
The fluoropolymer used in the fluorine-containing resin layer is not particularly limited as long as it is a polymer having a repeating unit represented by-(CFX ¹ -CX ² X ³ )-(however, X ¹ , X ² , X ³ Represents a hydrogen atom, a fluorine atom, a chlorine atom or a perfluoroalkyl group having 1 to 3 carbon atoms.

Examples of fluoropolymers include polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), polyvinyl fluoride (hereinafter sometimes referred to as PVF), and polyvinylidene fluoride (hereinafter referred to as PVDF). ), Polychloroethylene trifluoride (hereinafter sometimes referred to as PCTFE), polytetrafluoropropylene (hereinafter sometimes referred to as HFP), and the like.

The fluoropolymer may be a homopolymer obtained by polymerizing a single monomer or may be a copolymer obtained by copolymerizing two or more kinds. Examples thereof include a copolymer of tetrafluoroethylene and tetrafluoropropylene (abbreviated as P (TFE / HFP)), a copolymer of tetrafluoroethylene and vinylidene fluoride (abbreviated as P (TFE / VDF)), etc. Can be mentioned.

Furthermore, as a polymer used for the fluorine-containing resin layer, a polymer obtained by copolymerizing a fluorocarbon monomer represented by-(CFX ¹ -CX ² X ³ )-and another monomer (non-fluorine-containing monomer) is used. But you can. Specific examples of fluorocarbon monomers include ethylene tetrafluoride, ethylene trifluoride, vinylidene fluoride, vinyl fluoride, hexafluoropropylene, fluorine-containing alkyl vinyl ethers (eg, perfluoroethyl vinyl ether), fluorine-containing esters. Etc. (perfluorobutyl methacrylate, etc.). Specific examples of the non-fluorine-containing monomer include ethylene, alkyl vinyl ether (eg, ethyl vinyl ether, cyclohexyl vinyl ether), and carboxylic acid (eg, acrylic acid, methacrylic acid, hydroxybutyme vinyl ether, etc.). When the fluoropolymer is a polymer obtained by copolymerizing a fluorocarbon monomer and a non-fluorine-containing monomer), the content of the fluorine-containing monomer with respect to the total mass of the fluoropolymer is preferably 30% by mass to 98% by mass, The amount is preferably 40 to 80% by mass. Sufficient durability can be obtained when the proportion of the fluorine-containing monomer is 30% by mass or more. Further, from the viewpoint of polymerization stability, it is preferably 98% by mass or less.
As an example of a polymer obtained by copolymerizing a fluorocarbon monomer and a non-fluorine-containing monomer, a copolymer obtained by copolymerizing tetrafluoroethylene and ethylene (abbreviated as P (TFE / E)), tetrafluoro A copolymer obtained by copolymerizing ethylene and propylene (abbreviated as P (TFE / P)), a copolymer obtained by copolymerizing tetrafluoroethylene and vinyl ether (abbreviated as P (TFE / VE)), A copolymer obtained by copolymerizing tetrafluoroethylene and perfluorovinyl ether (abbreviated as P (TFE / FVE)), and a copolymer obtained by copolymerizing chlorotrifluoroethylene and vinyl ether (P (CTFE / VE). Abbreviation)), a copolymer obtained by copolymerizing chlorotrifluoroethylene and perfluorovinyl ether (abbreviated as P (CTFE / FVE)), Copolymer made by copolymerizing trifluoroethylene, ethylene and acrylic acid, Copolymer made by copolymerizing hexafluoropropylene and tetrafluoroethylene, Copolymerized hexafluoropropylene, tetrafluoroethylene and ethylene A copolymer formed by copolymerizing chlorotrifluoroethylene and perfluoroethyl vinyl ether, a copolymer formed by copolymerizing chlorotrifluoroethylene, perfluoroethyl vinyl ether and methacrylic acid, A copolymer obtained by copolymerizing chlorotrifluoroethylene and ethyl vinyl ether, a copolymer obtained by copolymerizing chlorotrifluoroethylene, ethyl vinyl ether and methacrylic acid, vinylidene fluoride, methyl methacrylate and methacrylic acid. A copolymer obtained by copolymerization, Copolymerizing a Kka vinyl and ethyl acrylate and acrylic acid comprising a copolymer, and the like.
Among them, a copolymer obtained by copolymerizing chlorotrifluoroethylene and perfluoroethyl vinyl ether, a copolymer obtained by copolymerizing chlorotrifluoroethylene, perfluoroethyl vinyl ether and methacrylic acid, chlorotrifluoro Copolymer made by copolymerizing ethylene and ethyl vinyl ether, Copolymer made by copolymerizing chlorotrifluoroethylene, ethyl vinyl ether and methacrylic acid, Copolymerized vinylidene fluoride, methyl methacrylate and methacrylic acid And a copolymer obtained by copolymerizing vinyl fluoride, ethyl acrylate and acrylic acid.
Among these, a copolymer obtained by copolymerizing chlorotrifluoroethylene and ethyl vinyl ether and a copolymer obtained by copolymerizing chlorotrifluoroethylene, ethyl vinyl ether and methacrylic acid are more preferable.
As the fluorine-based polymer, a commercially available one can be used. Specific examples of commercially available products include Lumiflon (registered trademark) LF200 (manufactured by Asahi Glass Co., Ltd.), Zeffle (registered trademark) GK570 (manufactured by Daikin Industries, Ltd.), Obligard SW0011F (trade name, manufactured by AGC Co-Tech Co., Ltd.) and the like. is there.
The molecular weight of the fluorine-based polymer can be about 2,000 to 1,000,000 in terms of polystyrene equivalent weight average molecular weight, and preferably about 3,000 to 300,000.

The fluoropolymer may be used by dissolving the polymer in an organic solvent, or may be used by dispersing polymer fine particles in water. The latter is preferable from the viewpoint of low environmental load. For example, water dispersions of fluoropolymers are described in, for example, JP-A Nos. 2003-231722, 2002-20409, and No. 9-194538.

[Adhesive layer]
In the back sheet of the present invention, an easy adhesion layer may be further provided on the polymer substrate. The easy-adhesion layer is a layer for firmly bonding the back sheet to a sealing material for sealing a solar cell element (hereinafter also referred to as a power generation element) of the battery side substrate (battery body).

The easy-adhesion layer can be constituted using a binder and inorganic fine particles, and may further comprise other components such as additives as necessary. The easy-adhesion layer is 10 N / cm or more (preferably 20 N / cm or more) with respect to an ethylene-vinyl acetate (EVA: ethylene-vinyl acetate copolymer) -based sealing material that seals the power generation element of the battery side substrate. It is preferable that it is comprised so that it may have the adhesive force of (). When the adhesive force is 10 N / cm or more, it is easy to obtain wet heat resistance capable of maintaining adhesiveness.

The adhesive strength can be adjusted by adjusting the amount of the binder and inorganic fine particles in the easy-adhesive layer, or applying a corona treatment to the surface of the back sheet that is bonded to the sealing material.

-binder-
The easy-adhesion layer can contain at least one binder.
Examples of the binder suitable for the easy-adhesive layer include polyester, polyurethane, acrylic resin, polyolefin, and the like. Among these, acrylic resin and polyolefin are preferable from the viewpoint of durability. As the acrylic resin, a composite resin of acrylic and silicone is also preferable.

Examples of preferred binders include Chemipearl S-120 and S-75N (both manufactured by Mitsui Chemicals, Inc.) as specific examples of polyolefins, and Jurimer ET-410 and SEK-301 (both Nippon Pure Chemicals, Inc.) as specific examples of acrylic resins. As a specific example of a composite resin of acrylic and silicone, Ceranate WSA1060, WSA1070 (both manufactured by DIC Corporation) and H7620, H7630, H7650 (both manufactured by Asahi Kasei Chemicals Corporation) and the like can be given.

The content of the binder in the easy-adhesive layer is preferably in the range of 0.05 to 5 g / m ² . In particular, the range of 0.08 to 3 g / m ² is more preferable. The content of the binder, 0.05 g / m ² or more is desired as easy adhesion obtained to that, better surface state is obtained when the is 5 g / m ² or less.

-Fine particles-
The easily adhesive layer can contain at least one kind of inorganic fine particles.
Examples of the inorganic fine particles include silica, calcium carbonate, magnesium oxide, magnesium carbonate, and tin oxide. Among these, fine particles of tin oxide and silica are preferable in that the decrease in adhesiveness when exposed to a humid heat atmosphere is small.

The particle size of the inorganic fine particles is preferably about 10 to 700 nm, more preferably about 20 to 300 nm in terms of volume average particle size. When the particle size is within this range, better easy adhesion can be obtained. The particle size is a value measured by a laser analysis / scattering particle size distribution measuring apparatus LA950 (manufactured by Horiba, Ltd.).

The shape of the inorganic fine particles is not particularly limited, and any shape such as a spherical shape, an irregular shape, or a needle shape can be used.

The content of the inorganic fine particles is in the range of 5 to 400% by mass with respect to the binder in the easy-adhesive layer. When the content of the inorganic fine particles is less than 5% by mass, good adhesiveness cannot be maintained when exposed to a wet and heat atmosphere, and when it exceeds 400% by mass, the surface state of the easily adhesive layer is deteriorated.
In particular, the content of inorganic fine particles is preferably in the range of 50 to 300% by mass.

-Crosslinking agent-
The easily adhesive layer can contain at least one crosslinking agent.
Examples of the crosslinking agent suitable for the easily adhesive layer include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Among these, an oxazoline-based cross-linking agent is particularly preferable from the viewpoint of ensuring adhesiveness after wet heat aging. Specific examples of the oxazoline-based crosslinking agent include the same specific examples as described in the above-mentioned section of the composite polymer layer.

The content of the crosslinking agent in the easy-adhesive layer is preferably 5 to 50% by mass, more preferably 20 to 40% by mass, based on the binder in the easy-adhesive layer. When the content of the crosslinking agent is 5% by mass or more, a good crosslinking effect can be obtained, and the strength and adhesiveness of the colored layer can be maintained. When the content is 50% by mass or less, the pot life of the coating liquid Can be kept long.

-Additive-
If necessary, the easily adhesive layer in the present invention may further contain a known matting agent such as polystyrene, polymethylmethacrylate, or silica, or a known surfactant such as anionic or nonionic. .

-Method of forming easy-adhesive layer-
The easy-adhesive layer can be formed by a method in which a polymer sheet having easy adhesive properties is bonded to a substrate, or a method by coating. Especially, the method by application | coating is preferable at the point which is easy and can form in a thin film with uniformity. As a coating method, for example, a known coating method such as a gravure coater or a bar coater can be used. The coating solvent used for preparing the coating solution may be water or an organic solvent such as toluene or methyl ethyl ketone. A coating solvent may be used individually by 1 type, and may mix and use 2 or more types.

The thickness of the easy-adhesion layer is not particularly limited, but is usually preferably 0.05 to 8 μm, more preferably 0.1 to 5 μm. When the thickness of the easy-adhesion layer is 0.05 μm or more, necessary easy adhesion can be suitably obtained, and when it is 8 μm or less, the surface shape becomes better.
In addition, the easily adhesive layer of the present invention needs to be transparent so as not to reduce the effect of the colored layer.

~ Physical properties ~
In addition, the back sheet for solar cell of the present invention has an interlayer adhesion after storage for 48 hours in an atmosphere of 120 ° C. and 100% RH of 75% or more with respect to the interlayer adhesion before storage. preferable. As described above, the solar cell backsheet of the present invention has a predetermined composite polymer layer, so that an adhesive strength of 75% or more before storage can be obtained even after the storage. Thereby, as for the produced solar cell module, peeling of a backsheet and the fall of the power generation performance accompanying it are suppressed, and long-term durability improves more.

<Manufacture of solar cell backsheet>
As described above, the solar cell backsheet of the present invention can form a composite polymer layer, a colored layer, a metal-containing layer, and, if necessary, an easily adhesive layer on the polymer substrate. Any method can be used. In the present invention, a metal-containing layer containing a component selected from the group consisting of metals and metal compounds is formed on the polymer substrate, and the mass ratio represented by the general formula (1) described above in the molecule A coating solution containing a composite polymer having a siloxane structural unit of 15 to 85% by mass and a non-siloxane structural unit having a mass ratio of 85 to 15% by mass, and preferably a cross-linking agent (and an easily adhesive layer if necessary) For example, a method for producing a back sheet for a solar cell of the present invention), and forming at least one composite polymer layer on a polymer substrate. be able to.
The coating solution for the composite polymer layer is a coating solution containing at least the composite polymer as described above, and preferably further contains a crosslinking agent selected from carbodiimide compounds and oxazoline compounds. The details of the polymer substrate and the composite polymer, crosslinking agent, colorant, metal and metal compound, and other components constituting each coating liquid are as described in the section of the solar cell backsheet. .

A suitable coating method is also as described above. For example, a coating method using a gravure coater, a roll coater, or a bar coater can be applied. In the coating according to the present invention, a coating solution for a composite polymer layer is applied directly on the surface of the polymer substrate or through an undercoat layer having a thickness of 2 μm or less, and a composite polymer layer (for example, a colored layer ( Preferably, a reflective layer) and a back layer) can be formed.

The formation of the composite polymer layer can be performed by a method of bonding a polymer sheet to a polymer substrate, a method of co-extruding the composite polymer layer when forming the polymer substrate, a method by coating, or the like. Among them, the method by coating is preferable because it is simple and uniform and can be formed as a thin film, and may be an aqueous mixed solvent in which an organic solvent is mixed with water. In the case of coating, as a coating method, for example, a known coating method using a gravure coater, a roll coater, a bar coater or the like can be used.

The coating solution may be an aqueous system using water as an application solvent, or a solvent system using an organic solvent such as toluene or methyl ethyl ketone. Among these, from the viewpoint of environmental burden, it is preferable to use water as a solvent. A coating solvent may be used individually by 1 type, and may mix and use 2 or more types.

The coating solution for the composite polymer layer is preferably an aqueous coating solution in which 50% by mass or more, preferably 60% by mass or more, of the solvent contained therein is water. The aqueous coating solution is preferable in terms of environmental load, and is advantageous in that the environmental load is particularly reduced when the ratio of water is 60% by mass or more. The proportion of water in the coating solution for the composite polymer layer is preferably larger from the viewpoint of environmental load, and more preferably 90% by mass or more of water in the total solvent.

After application, drying may be provided under desired conditions.

<Solar cell module>
The solar cell module of the present invention is configured by providing the solar cell backsheet of the present invention described above or the solar cell backsheet manufactured by the method of manufacturing the solar cell backsheet described above. As a preferred embodiment of the present invention, a solar cell element that converts light energy of sunlight into electrical energy is disposed between a transparent front substrate on which sunlight is incident and the above-described solar cell backsheet of the present invention. The solar cell element is sealed and bonded with a sealing material such as ethylene-vinyl acetate between the front substrate and the back sheet. That is, a cell structure portion having a solar cell element and a sealing material for sealing the solar cell element is provided between the front substrate and the back sheet.

Components other than solar cell modules, solar cells, and backsheets are described in detail in, for example, “Solar Power Generation System Constituent Materials” (supervised by Eiichi Sugimoto, Industrial Research Committee, Inc., issued in 2008).

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

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-arsenic, and II Various known solar cell elements such as a group VI compound semiconductor can be applied.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Unless otherwise specified, “part” is based on mass.

-Fabrication of polymer substrate-
(1) Production of polyethylene terephthalate support (PET) [1] -Esterification-
A slurry of 100 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) and 45 kg of ethylene glycol (manufactured by Nippon Shokubai Kagaku Kogyo 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 . The esterification reaction tank maintained at 2 × 10 ⁵ Pa was sequentially supplied over 4 hours, and the esterification reaction was performed over an additional hour after the completion of the supply. Thereafter, 123 kg of the obtained esterification reaction product was transferred to a polycondensation reaction tank.

[2]-Production of polymer pellets-
Subsequently, 0.3% by mass of ethylene glycol was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, based on the resulting polymer. After stirring for 5 minutes, an ethylene glycol solution of cobalt acetate and manganese acetate was added in the resulting polymer so that the cobalt element equivalent value and the manganese element equivalent value were 30 ppm and 15 ppm, respectively. After further stirring for 5 minutes, a 2% by mass ethylene glycol solution of a titanium alkoxide compound was added so that the titanium element equivalent value was 5 ppm in the obtained polymer. Five minutes later, a 10% by mass ethylene glycol solution of ethyl diethylphosphonoacetate was added so that the phosphorus element equivalent value was 5 ppm in the resulting polymer. Thereafter, while stirring the low polymer at 30 rpm, the reaction system was gradually heated from 250 ° C. to 285 ° C. and the pressure was reduced to 40 Pa. The time to reach the final temperature and final pressure was both 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure, and the polycondensation reaction was stopped. And it discharged to cold water in the shape of a strand, and it cut immediately, and produced the polymer pellet (about 3 mm in diameter, about 7 mm in length). The time from the start of decompression to the arrival of the predetermined stirring torque was 3 hours.
However, as the titanium alkoxide compound, the titanium alkoxide compound (Ti content = 4.44 mass%) synthesized in Example 1 of paragraph No. [0083] of JP-A-2005-340616 was used.

[3]-Production of film-like polymer substrate-
The pellets obtained as described above were melted at 280 ° C. and cast on a metal drum to produce an unstretched PET sheet having a thickness of about 3 mm. Thereafter, the unstretched PET sheet was stretched 3 times in the longitudinal direction at 90 ° C., and further stretched 3.3 times in the lateral direction at 120 ° C. Thus, a biaxially stretched polyethylene terephthalate support (PET) having a thickness of 300 μm was obtained. The carboxyl group content of the obtained PET was 38 equivalent / t.

In addition, about the obtained pellet, the amount of terminal COOH groups was measured by the titration method according to the method described in H. A. Pohl, Anal. Chem. 26 (1954) 2145. Specifically, the pellet was dissolved in benzyl alcohol at 205 ° C., a phenol red indicator was added, titrated with a water / methanol / benzyl alcohol solution of sodium hydroxide, and the amount of terminal carboxylic acid groups (equivalent / t ; = Terminal COOH amount) was calculated.

(2) Production of polyphenylene ether support (PPE) Using a polyphenylene ether resin composition (Noryl N300, manufactured by SABIC Innovation Plastics Co., Ltd.), melt extrusion using an extrusion casting method (cylinder temperature: 270 to 300 ° C.). To form a sheet having a thickness of 240 μm. Thereafter, the sheet was heat-treated in a drier (in-machine temperature: 180 ° C.) using a tenter device. In this way, a polyphenylene ether support (PPE) was produced.

(3) Production of Syndiotactic Polystyrene Support (SPP) Hydrogen of polystyrene-polybutadiene-polystyrene triblock copolymer (SBS) was added to 90 parts of syndiotactic polystyrene resin (Zarek 30A, manufactured by Idemitsu Petrochemical Co., Ltd.). 10 parts of an additive (Tuftec 1052 manufactured by Asahi Kasei Kogyo Co., Ltd.) was added to prepare a master pellet. Using this, it was melt-extruded by extrusion casting (cylinder temperature: 270 to 300 ° C.) and formed into a sheet to produce a sheet having a thickness of 50 μm. Thereafter, the sheet was heat-treated in a drier (in-machine temperature: 180 ° C.) using a tenter device. In this way, a syndiotactic polystyrene support (SPP) was produced.

(4) Production of white polyvinyl fluoride support (white PVF) Polyvinyl fluoride, dimethylformamide, polyethylene glycol, and titanium dioxide were mixed and stirred while heating to 110 ° C. to obtain a uniform solution. This solution was cast on a glass plate to a cast thickness of 0.1 mm in an oven preheated to 80 ° C., and then immediately poured into water at 30 ° C. to obtain white polyvinyl fluoride. A support (white PVF) was prepared.

-Polymer synthesis-
(Synthesis Example 1): Synthesis of Composite Polymer Water Dispersion P-1 A reaction vessel equipped with a stirrer and a dropping funnel and purged with nitrogen gas was charged with 81 parts of propylene glycol mono-n-propyl ether (PNP), isopropyl alcohol ( IPA) 360 parts, phenyltrimethoxysilane (PTMS) 110 parts, and dimethyldimethoxysilane (DMDMS) 71 parts were charged, and the temperature was raised to 80 ° C. with stirring in a nitrogen gas atmosphere.
Then, at the same temperature in this reaction vessel, 260 parts of methyl methacrylate (MMA), 200 parts of n-butyl methacrylate (BMA), 110 parts of n-butyl acrylate (BA), 30 parts of acrylic acid (AA), 3-methacryloyl A mixture of 19 parts of oxypropyltrimethoxysilane (MPTMS), 31.5 parts of tert-butylperoxy-2-ethylhexanoate (TBPO), and 31.5 parts of PNP part was added dropwise over 4 hours. Thereafter, the mixture was heated and stirred at the same temperature for 2.5 hours to obtain an acrylic polymer solution having a weight average molecular weight of 29,300 and containing a carboxyl group and a hydrolyzable silyl group.
Next, 54.8 parts of deionized water was added thereto, and heating and stirring were continued for 16 hours to hydrolyze the alkoxysilane and further condense with an acrylic polymer, so that the nonvolatile content (NV) = 56.3 mass%. A solution of a composite polymer having a site derived from a carboxyl group-containing acrylic polymer and a polysiloxane site, with a solution acid value = 22.3 mgKOH / g, was obtained.
Next, 42 parts of triethylamine was added to this solution while stirring at the same temperature, and stirring was performed for 10 minutes. Thereby, 100% of the contained carboxyl groups were neutralized.
Thereafter, 1250.0 parts of deionized water was added dropwise at the same temperature over 1.5 hours for phase inversion emulsification, and then the mixture was heated to 50 ° C. and stirred for 30 minutes. Next, a part of water was removed under reduced pressure together with the organic solvent over 3.5 hours at an internal temperature of 40 ° C. In this way, a composite polymer aqueous dispersion P-1 having a solid content concentration of 42% by mass and an average particle size of 110 nm and containing a part derived from a carboxyl group-containing acrylic polymer and a polysiloxane part was obtained.
The composite polymer of the aqueous dispersion P-1 had about 25% polysiloxane sites and about 75% acrylic polymer portions.

(Synthesis Example 2): Synthesis of Composite Polymer Water Dispersion P-2 Synthesis Example, except that the amount of monomer used in the synthesis of Composite Polymer Water Dispersion P-1 (Synthesis Example 1) was changed to the following amount: In the same manner as in Example 1, a composite polymer aqueous dispersion P-2 was synthesized. That is,
The ratio of the monomers used is as follows: phenyltrimethoxysilane (PTMS): 210 parts, dimethyldimethoxysilane (DMDMS): 166 parts, 3-methacryloyloxypropyltrimethoxysilane (MPTMS): 24 parts, methyl methacrylate (MMA): 200 parts N-butyl methacrylate (BMA): 100 parts, n-butyl acrylate (BA) 70 parts, acrylic acid (AA) 30 parts.
The composite polymer of the aqueous dispersion P-2 had about 50% of the polysiloxane portion and about 50% of the acrylic polymer portion.

(Synthesis Example 3): Synthesis of Composite Polymer Water Dispersion P-3 Synthesis Example, except that the amount of monomer used in the synthesis of Composite Polymer Water Dispersion P-1 (Synthesis Example 1) was changed to the following amount: In the same manner as in Example 1, a composite polymer aqueous dispersion P-3 was synthesized. That is,
The ratio of the monomers used is as follows: phenyltrimethoxysilane (PTMS): 320 parts, dimethyldimethoxysilane (DMDMS): 244 parts, 3-methacryloyloxypropyltrimethoxysilane (MPTMS): 36 parts, methyl methacrylate (MMA): 90 parts N-butyl methacrylate (BMA): 60 parts, n-butyl acrylate (BA): 20 parts, and acrylic acid (AA): 30 parts.
The composite polymer of the aqueous dispersion P-3 had about 75% polysiloxane sites and about 25% acrylic polymer portions.

(Synthesis Example 4): Synthesis of Composite Polymer Aqueous Dispersion P-4 Synthesis Example except that the amount of monomers used in the synthesis of Synthetic Polymer Water Dispersion P-1 (Synthesis Example 1) was changed to the following amount: In the same manner as in Example 1, a composite polymer aqueous dispersion P-4 was synthesized. That is,
The proportions of the monomers used were as follows: phenyltrimethoxysilane (PTMS): 60 parts, dimethyldimethoxysilane (DMDMS): 25 parts, 3-methacryloyloxypropyltrimethoxysilane (MPTMS): 15 parts, methyl methacrylate (MMA): 300 parts N-butyl methacrylate (BMA): 220 parts, n-butyl acrylate (BA): 150 parts, and acrylic acid (AA): 30 parts.
The composite polymer of the aqueous dispersion P-4 had about 13% polysiloxane sites and about 87% acrylic polymer portions.

(Synthesis Example-5): Synthesis of Composite Polymer Water Dispersion P-5 Synthesis Example, except that the amount of monomer used in the synthesis of Composite Polymer Water Dispersion P-1 (Synthesis Example 1) was changed to the following amount: In the same manner as in Example 1, a composite polymer aqueous dispersion P-5 was synthesized. That is,
The ratio of the monomers used is as follows: phenyltrimethoxysilane (PTMS): 336 parts, dimethyldimethoxysilane (DMDMS): 320 parts, 3-methacryloyloxypropyltrimethoxysilane (MPTMS): 40 parts, methyl methacrylate (MMA): 44 parts N-butyl methacrylate (BMA): 30 parts, n-butyl acrylate (BA): 10 parts, and acrylic acid (AA): 20 parts.
The composite polymer of the aqueous dispersion P-5 had about 87% of the polysiloxane portion and about 87% of the acrylic polymer portion. This aqueous dispersion had a small amount of aggregation after synthesis and was slightly inferior in stability to the aqueous dispersions P-1 to P-4.

(Example 1)
-Formation of polymer layer-
(1) Preparation of coating solution for forming polymer layer Each component in the following composition was mixed to prepare a coating solution for forming a polymer layer.
<Composition of coating solution>
Silicone binder: 362.3 parts (Previously described composite polymer aqueous dispersion P-1, solid content: adjusted to 40% by mass)
Carbodiimide compound (crosslinking agent) 36.2 parts (Carbodilite V-02-L2, manufactured by Nisshinbo Industries, Ltd., solid content: 40% by mass)
・ Surfactant ... 24.2 parts (Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
・ Lubricant (polyethylene wax) ... 3.6 parts (Chemical Pearl W950, manufactured by Mitsui Chemicals, solid content: 40% by mass)
Matting agent (polymethylmethacrylate particles) ... 1.1 parts (MP-1000 (average particle size: 0.4 μm), manufactured by Soken Chemical Co., Ltd.)
・ Distilled water: 572.6 parts

(2) Formation of polymer layer Using PET as a polymer base material, a coating solution for forming a polymer layer is applied on one surface of PET so that a binder coating amount is 2.0 g / m ² , and 1 at 180 ° C. After drying for a minute, a polymer layer having a dry thickness of about 2 μm was formed as a weather-resistant layer.

-Formation of functional layer-
Next, white polyethylene terephthalate (Lumirror E20, manufactured by Toray Industries, Inc .; white PET) having a thickness of 50 μm is formed on the surface of the PET (polymer substrate) where the weather-resistant layer is not formed under the following conditions. The functional layer (light reflection layer) was formed by pasting.

As the adhesive, a two-component thermosetting urethane adhesive obtained by mixing 10 parts of KW75 (manufactured by DIC Corporation; curing agent) with LX660 (K) (manufactured by DIC Corporation; main agent) was used. An adhesive was applied to the side of the PET where the weather-resistant layer was not formed, and white PET was layered thereon, and hot-pressed with a vacuum laminator (vacuum laminator, manufactured by Nisshinbo Co., Ltd.) for adhesion. Adhesion was performed by applying pressure for 2 minutes after evacuation at 80 ° C. for 3 minutes. The thickness of the adhesive layer after bonding was about 5 μm. Thereafter, the obtained sample was held at 40 ° C. for 4 days to complete the reaction, thereby obtaining a back sheet.

-Evaluation 1
About the obtained back sheet, the adhesiveness and reflectance of the weather-resistant layer were evaluated. The evaluation results are shown in Table 1 below.

(1) Adhesiveness (adhesion)
The obtained back sheet was conditioned for 24 hours in an atmosphere of 25 ° C. and 60% RH. After that, the surface of the polymer layer of the backsheet was scratched with 6 razors in the longitudinal and lateral directions at intervals of 3 mm using a razor. On top of that, a 20 mm wide Mylar tape was applied and quickly peeled off in the 180 ° direction. At this time, peeling was performed on the backsheet before and after aging for 90 hours under a wet heat condition of 120 ° C. and 100% RH. After peeling, the number of squares peeled off from the back sheet was counted and evaluated according to the following evaluation criteria. Note that what is practically acceptable is classified into ranks 3 to 5. In Table 1 below, the time before wet heat aging is expressed as “fresh”, and the time after wet heat aging is expressed as “humid heat aging”.
<Evaluation criteria>
5: No peeling occurred.
4: Although the squares which peeled were zero, the crack part had peeled slightly.
3: The square which peeled was less than 1 square.
2: The square which peeled was 1 square or more and less than 5 squares.
1: The square which peeled was 5 squares or more.

(2) Reflectance The reflection spectrum of the obtained back sheet was measured using a spectrophotometer (Sakai V-3100, manufactured by Shimadzu Corporation). The baseline was set using a reference plate in which barium sulfate powder was pressed and hardened. From the obtained spectrum, the reflectance at a wavelength of 550 nm was taken as the representative reflectance of the backsheet.

(Examples 2 to 3)
In Example 1, the composite polymer aqueous dispersion P-1 (silicone-based binder) used for the preparation of the coating solution for forming the weather resistant layer was combined with the composite polymer aqueous dispersion P-2 or P as shown in Table 1 below. A backsheet was prepared and evaluated in the same manner as in Example 1 except that it was changed to -3 (both were adjusted to a solid content of 40% by mass). The evaluation results are shown in Table 1 below.

(Comparative Examples 1 and 2)
In Example 1, the composite polymer aqueous dispersion P-1 (silicone-based binder) used for the preparation of the coating solution for forming the weathering layer was combined with the composite polymer aqueous dispersion P-4 or P as shown in Table 1 below. A backsheet was prepared and evaluated in the same manner as in Example 1 except that it was changed to −5 (both solid contents were adjusted to 40% by mass). The evaluation results are shown in Table 1 below.

(Comparative Example 3)
In Example 1, the weathering layer formed by applying the coating solution for forming the weathering layer was replaced with an ETFE film having a thickness of 50 μm (neoflon EF-0050, manufactured by Daikin Industries, Ltd.). After the corona treatment was performed under the conditions, a back sheet was prepared in the same manner as in Example 1 except that the ETFE film was bonded in the same manner as the method for forming the functional layer in Example 1. The same evaluation was performed. The evaluation results are shown in Table 1 below.
<Corona treatment>
・ Equipment: Solid state corona treatment machine 6KVA model made by Pillar Co. ・ Gap clearance between electrode and dielectric roll: 1.6 mm
・ Processing frequency: 9.6 kHz
Processing speed: 10 m / min Processing intensity: 0.75 kV / A / min / m ²

(Example 4)
In Example 1, in order to impart white color to the weather resistant layer, as shown below, before applying the coating liquid for forming a polymer layer on one surface of PET, the following white color is applied to one surface of the PET: A resin layer forming coating solution was applied and dried to form a white resin layer, thereby forming a weather resistant layer consisting of two layers, a polymer layer and a white resin layer, in the same manner as in Example 1. A back sheet was prepared and subjected to the same evaluation. The evaluation results are shown in Table 1 below.

-Formation of weathering layer-
(1) Formation of white resin layer-Preparation of titanium dioxide dispersion-
Each component in the following composition was mixed, and the mixture was subjected to a dispersion treatment with a dynomill type dispersing machine for 1 hour to prepare a titanium dioxide dispersion.
<Composition of titanium dioxide dispersion>
・ Titanium dioxide (volume average particle size = 0.28 μm) ・・・ 40% by mass
(Taipeke CR95, manufactured by Ishihara Sangyo Co., Ltd., solid content: 100% by mass)
-Polyvinyl alcohol aqueous solution (solid content: 10% by mass) ... 20% by mass
(PVA-105, manufactured by Kuraray Co., Ltd.)
・ Surfactant: 0.5% by mass
(Demol EP, manufactured by Kao Corporation, solid content: 25% by mass)
・ Distilled water ... 39.5 mass%

-Formation of white resin layer-
Components in the following composition were mixed to prepare a coating solution for forming a white resin layer. The obtained white resin layer-forming coating solution was applied on one surface of PET so that the binder coating amount was 4.7 g / m ² and the titanium dioxide coating amount was 5.6 g / m ^2. It was dried for 2 minutes to form a white resin layer having a dry thickness of 5.7 μm.
<Composition of coating solution for white resin layer formation>
-Titanium dioxide dispersion described above ... 298.5 parts-Polyolefin binder ... 568.7 parts (Arrowbase SE-1013N, manufactured by Unitika Ltd., concentration 20 mass%)
Nonionic surfactant: 23.4 parts (Naroacty CL95, manufactured by Sanyo Chemical Industries, Ltd., concentration 1% by mass)
・ Oxazoline-based crosslinking agent: 58.4 parts (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., concentration: 25% by mass)
・ Distilled water: 51.0 parts

(2) Formation of polymer layer Subsequently, on the white resin layer formed on one surface of PET, the polymer layer forming coating solution prepared in Example 1 was applied at a binder coating amount of 2.0 g / m ^2. And dried at 180 ° C. for 1 minute to form a polymer layer having a dry thickness of about 2 μm.

(Example 5)
In Example 4, the white PET (Lumirror E20, manufactured by Toray Industries, Inc.) having a thickness of 50 μm used for forming the functional layer was not used, and the surface on the side where the PET weathering layer was not formed was used. The white resin layer forming coating solution No. 4 was applied so that the binder coating amount was 4.7 g / m ² and the titanium dioxide coating amount was 5.6 g / m ^2, and dried at 170 ° C. for 2 minutes to dry thickness. A backsheet was prepared and evaluated in the same manner as in Example 1 except that a functional resin layer was formed by forming a 5.7 μm white resin layer. The evaluation results are shown in Table 1 below.

(Example 6)
In Example 5, a polymer sheet for a solar cell was produced in the same manner as in Example 1 except that the above-described PET used as the polymer substrate was replaced with a PET with an undercoat layer produced as follows.
<PET with undercoat>
In the above-mentioned “(1) Production of polyethylene terephthalate support (PET)”, the produced unstretched PET sheet was stretched 3.4 times in the MD direction, and then the light-resistant layer side of this PET sheet was The undercoat layer coating solution was applied, and then further stretched 4.5 times in the TD direction. At this time, the thickness of the undercoat layer was 0.1 μm.
<Composition of undercoat layer coating solution>
Polyolefin binder: 24.12 parts (Arrow Base SE-1013N, manufactured by Unitika Ltd., concentration: 20% by mass)
・ Oxazoline-based crosslinking agent: 3.90 parts (Epocross WS-700, manufactured by Nippon Shokubai Co., Ltd., concentration: 25% by mass)
・ Fluorine-based surfactant: 0.19 parts (sodium bis (3,3,4,4,5,5,6,6-nonafluoro) = 2-sulfonite oxysuccinate, Sankyo Chemical ( Co., Ltd., concentration: 1% by mass)
・ Distilled water: 71.80 parts

(Example 7)
In Example 5, a polymer sheet for a solar cell was produced in the same manner as in Example 5 except that the synthesis of PET used as the polymer substrate and the method for producing the polymer substrate were changed to the following methods.

<Synthesis of polyethylene terephthalate>
A transesterification reaction vessel was charged with 100 parts by mass of dimethyl terephthalate, 61 parts by mass of ethylene glycol, and 0.06 parts by mass of magnesium acetate tetrahydrate, heated to 150 ° C., melted and stirred. The reaction was advanced while the temperature in the reaction vessel was slowly raised to 235 ° C., and the produced methanol was distilled out of the reaction vessel. When the distillation of methanol was completed, 0.02 parts by mass of trimethyl phosphoric acid was added. After adding trimethyl phosphoric acid, 0.03 parts by mass of antimony trioxide was added, and the reaction product was transferred to a polymerization apparatus. Subsequently, the temperature in the polymerization apparatus was raised from 235 ° C. to 290 ° C. over 90 minutes, and at the same time, the pressure in the apparatus was reduced from atmospheric pressure to 100 Pa over 90 minutes. When the stirring torque of the contents of the polymerization apparatus reached a predetermined value, the inside of the apparatus was returned to atmospheric pressure with nitrogen gas to complete the polymerization. The valve | bulb of the polymerization apparatus lower part was opened, the inside of the polymerization apparatus was pressurized with nitrogen gas, and the polyethylene terephthalate which superposed | polymerized was made into strand shape, and was discharged in water. The strand was chipped with a cutter. Thus, PET having an intrinsic viscosity IV = 0.58 and an acid value (AV) = 12 was obtained. This was designated as PET-A.

<Polyester solid-state polymerization>
PET-A was pre-dried at 150 to 160 ° C. for 3 hours and then subjected to solid phase polymerization at 205 ° C. for 25 hours in an atmosphere of 100 torr and nitrogen gas to obtain PET-B.

<Manufacture of master pellets containing polyester and end-capping agent>
90 parts by mass of PET-B and 10 parts by mass of the following carbodiimide compound A as a terminal blocking agent were mixed. This mixture was supplied to a biaxial kneader, melted and kneaded at 280 ° C., discharged into water in a strand shape, and then cut into a chip by a cutter. This was designated as PET-C.

<Film formation of polyester film>
PET-B and PET-C were dried at 180 ° C. for 3 hours, then charged into an extruder for mixing so that the end-capping material was 1% by mass with respect to the polymer resin, and kneaded at 280 ° C. Then, after passing through a gear pump and a filter, it was extruded onto a cooling drum of 25 ° C. to which electrostatic application was applied from a T die, and cooled and solidified to obtain an unstretched sheet. Thereafter, the unstretched polymer substrate was stretched 3.4 times in the machine direction at 90 ° C., biaxially stretched 4.5 times in the transverse direction at 120 ° C., and heat-set at 200 ° C. for 30 seconds. The polymer substrate which is a polyethylene terephthalate film (PET film) having a thickness of 240 μm was prepared by relaxing the heat at 190 ° C. for 10 seconds.

(Example 8)
In Example 5, a polymer sheet for a solar cell was produced in the same manner as in Example 5 except that the PET film was subjected to the glow discharge treatment described below.
<Glow discharge treatment>
The polyethylene terephthalate film is heated to 145 ° C. using a heating roller in advance, and then the processing atmosphere pressure is 0.2 Torr, the discharge frequency is 30 kHz, the output is 5000 w, the physical strength is 4.2 kV · A · min / m ² . The surface treatment was performed.

(Comparative Example 4)
In Comparative Example 3, the ETFE film was replaced with the white PVF described above as a weather-resistant layer, and the white PETF was replaced with the white PVF described above. After the corona treatment is performed on the surface that is not bonded under the same conditions as in Comparative Example 3, the functional layer (light reflecting layer) is formed by bonding in the same manner as the method for forming the functional layer in Example 1. Except for the above, a back sheet was produced in the same manner as in Comparative Example 3, and the same evaluation was performed. The evaluation results are shown in Table 1 below.

(Examples 9 to 10)
In Example 1, the PET used as the polymer base material was replaced with PPE or SPP, and both sides of the polymer base material were treated in the same manner as in Example 1 except that the corona treatment was performed under the same conditions as in Comparative Example 3. A back sheet was prepared and evaluated in the same manner. The evaluation results are shown in Table 1 below.

As shown in Table 1, in Examples 1 to 3, the change in the adhesion of the weather resistant layer due to aging with wet heat was suppressed to a small level as compared with Comparative Examples 1 to 3, and all showed good adhesion. . Moreover, favorable reflectivity was obtained by giving white to the functional layer, and no influence on the reflectance was observed in any of the weather resistant layers.

Further, as shown in Table 1, in Examples 4 to 8 in which layers are formed by coating, the adhesion of the weather resistant layer is remarkably higher than that of Comparative Example 4 formed by typical bonding as a back sheet. It improved. In Examples 4 to 8, the reflectance was higher than that in Comparative Example 4.
In Examples 9 to 10 in which the polymer substrate was changed, almost the same results as in Example 1 were obtained, and the adhesion of the weather resistant layer was better than those in Comparative Examples 1 to 3.

(Example 11)
In Example 1, the white PET provided as the functional layer (light reflecting layer) is replaced with black polyethylene terephthalate (Lumorer X20, manufactured by Toray Industries, Inc .; black PET) having a thickness of 50 μm, and the design has been improved. A back sheet was prepared in the same manner as in Example 1 except that the adhesive layer was formed, and the adhesion was evaluated. The optical density (OD) was evaluated by the following method. The evaluation results are shown in Table 2 below.

-Evaluation 2-
(3) Optical Density The optical density (OD) in the visible light region (380-700 nm) was measured with a Macbeth optical densitometer on the obtained backsheet.

Example 12
In Example 1, white PET provided as a functional layer (light reflecting layer) was not used, and a black resin layer-forming coating solution having the following composition was applied to the surface on which the PET weather-resistant layer was not formed. Example 1 except that the coating amount was 1.45 g / m ² and dried at 160 ° C. for 1 minute to form a black resin layer having a dry thickness of 1.3 μm to form a functional layer. Similarly, a back sheet was produced. Further, in the same manner as in Examples 1 and 10, the adhesiveness and optical density (OD) were evaluated. The evaluation results are shown in Table 2 below.

-Preparation of coating solution for black resin layer formation-
Components in the following composition were mixed to prepare a coating solution for forming a black resin layer.
<Composition of coating solution for forming black resin layer>
-Carbon black aqueous dispersion: 159.0 parts (manufactured by Dainichi Seika Co., Ltd. MF-5630 black, solid content: 31.5%)
-Acrylic resin aqueous dispersion A: 333.0 parts (solid content: 30% by mass)
-Oxazoline compound: 100.0 parts (Nippon Shokubai Co., Ltd., Epocros WS700, solid content: 25% by mass)
・ Surfactant: 100.0 parts (manufactured by Sanyo Chemical Industries, Ltd., 1% by mass aqueous solution of NAROACTY CL-95)
・ Distilled water: Add so that the total is 1000 parts

(Comparative Example 5)
In Example 11, the polymer layer formed by applying the coating solution for forming the polymer layer was replaced with hydrolysis-resistant PET, and corona treatment was performed on one surface of PET (polymer substrate) under the same conditions as in Comparative Example 3. A back sheet was prepared in the same manner as in Example 11 except that hydrolysis resistant PET was applied to form a weather resistant layer. Further, in the same manner as in Example 11, the adhesiveness and optical density (OD) were evaluated. The evaluation results are shown in Table 2 below.

The following polyethylene terephthalate support was used as hydrolysis resistant PET. That is,
In the same manner as in “(1) Production of polyethylene terephthalate support (PET)” in Example 1, the above [1] to [2] were carried out to obtain pellets, which were then maintained at 40 Pa. Solid-state polymerization was performed in a vacuum vessel at a temperature of 220 ° C. for 30 hours. And the pellet after passing through solid phase polymerization was melted at 280 ° C. and cast on a metal drum to produce an unstretched base having a thickness of about 3 mm. Thereafter, the film was stretched 3 times in the longitudinal direction at 90 ° C., and further stretched 3.3 times in the transverse direction at 120 ° C. to obtain a biaxially stretched polyethylene terephthalate support having a thickness of 300 μm. The carboxyl group content of the obtained biaxially stretched polyethylene terephthalate support was 30 equivalent / t.

(Example 13)
In Example 1, white PET provided as a functional layer is replaced with a SiO vapor deposition film, and a corona treatment is performed under the same conditions as in Comparative Example 3 on the side of the PET (polymer substrate) on which the weathering layer is not formed. A back sheet was prepared and evaluated for adhesiveness in the same manner as in Example 1 except that a SiO vapor deposition film was applied to form a functional layer. Further, the water vapor transmission rate was evaluated by the following method. The evaluation results are shown in Table 3 below.
In addition, the SiO vapor deposition film is a film in which a silicon oxide (SiO) layer is formed on a PET film having a thickness of 100 μm by a method described in paragraphs 0081 to 0082 of JP-A-2006-297737 (water vapor transmission rate: 0. 0). 005 g / m ² / day or less) was used.

-Evaluation 3-
(4) Water vapor transmission rate After the back sheet was cut into a diameter of 10 cm, the moisture was conditioned for 3 days or more in an auto dry desiccator with a humidity of 1%. Thereafter, the water vapor transmission rate of the back sheet was measured using a water vapor transmission rate measuring device Model 7001 (manufactured by Illinois).

(Examples 14 to 15, Comparative Examples 6 to 7)
In Example 13, the composite polymer aqueous dispersion P-1 (silicone-based binder) used for the preparation of the coating solution for forming the weather resistant layer was combined with the composite polymer aqueous dispersions P-2 to P as shown in Table 3 below. A backsheet was prepared and evaluated in the same manner as in Example 13 except that it was changed to −5 (both solid content was adjusted to 40% by mass). The evaluation results are shown in Table 3 below.

(Comparative Example 8)
In Example 13, the weathering layer formed by coating the coating solution for forming the weathering layer was replaced with an ETFE film having a thickness of 50 μm (neoflon EF-0050, manufactured by Daikin Industries, Ltd.) on one side of the PET. After performing corona treatment under the same conditions as in Comparative Example 3, the same method as in Example 13 was applied except that the ETFE film was bonded in the same manner as the method for forming the functional layer in Example 1. A back sheet was prepared and subjected to the same evaluation. The evaluation results are shown in Table 3 below.

(Examples 16 to 17)
In Example 13, the SiO vapor deposition film provided as the functional layer was replaced with an aluminum oxide (Al ₂ O ₃ ) vapor deposition film or an aluminum foil (Al foil) with a thickness of 30 μm, and was the same as in Example 13. A back sheet was prepared and evaluated in the same manner. The evaluation results are shown in Table 3 below.
For the Al deposited film, aluminum oxide (Al ₂ O ₃ ) is formed on a PET film having a thickness of 100 μm by replacing the target from Si to Al in the method described in paragraphs 0081 to 0082 of JP-A-2006-297737. Was used (water vapor permeability of 0.005 g / m ² / day or less).

(Example 18)
In Example 13, in order to provide light reflectivity in addition to moisture resistance, white polyethylene terephthalate (Lumirror E20, manufactured by Toray Industries, Inc .; white PET) having a thickness of 50 μm was further laminated on the SiO vapor-deposited film. A backsheet was produced and evaluated in the same manner as in Example 13 except that a functional layer composed of layers was formed. The evaluation results are shown in Table 3 below.

(Example 19)
In Example 13, on one surface of PET, a white resin layer-forming coating solution was applied in the same manner as in Example 4 and dried to form a white resin layer. A polymer layer was further formed on the white resin layer. A coating layer is applied and dried to form a polymer layer, thereby providing a two-layer weather-resistant layer, and further on the SiO vapor deposition film formed on the other surface of PET, as in Example 4. A back sheet was prepared in the same manner as in Example 13 except that a white resin layer was formed by applying a white resin layer forming coating solution and drying to form a white resin layer. The same evaluation was performed. The evaluation results are shown in Table 3 below.

(Comparative Example 9)
In Comparative Example 8, a back sheet was produced in the same manner as in Comparative Example 8, except that the ETFE film was replaced with white PVF to form a weather resistant layer, and white PVF was further bonded onto the SiO vapor-deposited film. The same evaluation was performed. The evaluation results are shown in Table 3 below.
In addition, 10 parts of KW75 (made by DIC Corporation; hardening | curing agent) were mixed with LX660 (K) (made by DIC Corporation; main agent) as an adhesive agent for bonding of white PVF on a SiO vapor deposition film. A two-component thermosetting urethane adhesive was used.

As shown in Table 3, in Examples 13 to 19, a layer imparting moisture resistance and light reflectivity was formed on the functional layer, but compared with Comparative Examples 6 to 9 regardless of the provision of the functional layer. Thus, the change in the adhesion of the weather-resistant layer with the passage of time of wet heat was suppressed to a small level, and all showed good adhesion. In addition, it was confirmed that the water vapor permeability in the examples had good performance, and no influence by the weather resistant layer was observed.

(Example 20)
In Example 1, a coating solution for a fluorine-containing resin layer was further applied on the polymer layer formed as the weather resistant layer so that the binder coating amount was 1.3 g / m ² , and the temperature was 170 ° C. for 2 minutes. A backsheet was prepared and evaluated for adhesiveness in the same manner as in Example 1 except that it was dried to form a fluorine-containing resin layer having a dry thickness of about 1.6 μm. The evaluation results are shown in Table 4 below.

-Preparation of coating solution for fluorine-containing resin layer-
Components in the following composition were mixed to prepare a coating solution for a fluorine-containing resin layer.
<Composition of coating solution for fluorine-containing resin layer>
・ Chlorotrifluoroethylene-vinyl ether copolymer: 34.5% by mass
(Obligato SW0011F, AGC Co-Tech, solid content: 39% by mass; fluoropolymer)
・ Polyoxyalkylene alkyl ether: 1.5% by mass
(Naroacty CL-95, Sanyo Chemical Industries, solid content: 1% by mass)
・ Carbodiimide compound: 6.2% by mass
(Carbodilite V-02-L2, Nisshinbo, solid content: 20% by mass)
・ Silica sol: 0.4% by mass
(Snowtex-ΜP, manufactured by Nissan Chemical Industries, Ltd., solid content 20% by mass)
・ Silane coupling agent: 7.6% by mass
(TSL8340, Momentive Performance Material, solid content: 1% by mass)
・ Polyolefin wax dispersion: 20.8% by mass
(Chemical Pearl W950, manufactured by Mitsui Chemicals, solid content: 5% by mass)
・ Distilled water: Added to 100% by mass as a whole

(Comparative Example 10)
In Example 1, except that the coating solution for forming a weather-resistant layer using the composite polymer aqueous dispersion P-1 (silicone-based binder) was replaced with the coating solution for a fluorine-containing resin layer in Example 20, the Example In the same manner as in No. 1, a back sheet was prepared and the adhesion was evaluated. The evaluation results are shown in Table 4 below.

(Examples 21 to 22)
In Example 1, in order to provide anti-static property or adhesion to the battery-side substrate sealing material (EVA) in addition to light reflectivity, white PET provided on the surface on which the weathering layer of PET is not formed Besides, an antistatic film (Espet film T4100, manufactured by Toyobo Co., Ltd.) or an ethylene vinyl acetate (EVA) sheet (thickness: 100 μm) is further bonded to form a functional layer consisting of two layers. A back sheet was produced in the same manner as in Example 1, and the same evaluation was performed. The evaluation results are shown in Table 4 below.
In addition, for bonding of an antistatic film or an EVA sheet, two liquids in which 10 parts of KW75 (manufactured by DIC Corporation; curing agent) are mixed with LX660 (K) (manufactured by DIC Corporation; main agent) as an adhesive A thermosetting urethane adhesive was used.

(Example 23)
In Example 9, the PPE used as the polymer substrate was replaced with a SiO deposited film,
The white resin layer of Example 4 was not used on the surface on which the PET weatherproof layer was not formed without using 50 μm-thick white PET (Lumirror E20, manufactured by Toray Industries, Inc.) used to form the functional layer. The forming coating solution was applied so that the binder coating amount was 4.7 g / m ² and the titanium dioxide coating amount was 5.6 g / m ² , dried at 170 ° C. for 2 minutes, and dried to a white thickness of 5.7 μm. A backsheet was prepared and evaluated in the same manner as in Example 9 except that the resin layer was formed into a functional layer. The evaluation results are shown in Table 4 below.
Note that a SiO vapor deposited film was formed by forming a silicon oxide film on a PET film having a thickness of 100 μm (water vapor transmission rate: 0.005 g / m ² / m) by the method described in paragraphs 0081 to 0082 of JP-A-2006-297737. day or less).

(Example 24)
-Preparation of polymer substrate-
As a polymer substrate, white polyethylene terephthalate containing a white pigment (Lumirror E20, manufactured by Toray Industries, Inc., thickness 50 μm; white PET) was prepared.

-Formation of primer layer-
(1) Preparation of primer layer forming coating solution Components in the following composition were mixed to prepare a primer layer forming coating solution.
<Composition of coating solution>
・ Polyester binder: 47.7 parts (Vylonal MD-1245, manufactured by Toyobo Co., Ltd., solid content concentration: 30% by mass)
・ PMMA fine particles: 10.0 parts (MP-1000, manufactured by Soken Chemical Co., Ltd., solid content concentration: 5% by mass)
Nonionic surfactant: 15.0 parts (Naroacty CL95, manufactured by Sanyo Chemical Industries, solid content concentration: 1% by mass)
・ Distilled water ... 927.3 parts

(2) Formation of primer layer The primer layer-forming coating solution is applied to one surface of white PET prepared as a polymer substrate so that the binder coating amount is 0.12 g / m ^2. The primer treatment was performed after drying for 2 minutes.

-Formation of polymer layer-
On the primer-treated surface of white PET, the polymer layer-forming coating solution of Example 1 was applied so that the binder coating amount was 2.0 g / m ² and dried at 180 ° C. for 1 minute to form a weather resistant layer. A polymer layer having a dry thickness of about 2 μm was formed.
As described above, a back sheet having a multilayer structure of a weather resistant layer / polymer substrate was produced, and the same evaluation was performed. The evaluation results are shown in Table 4 below.

(Example 25)
In Example 1, white PET (Lumirror E20, manufactured by Toray Industries, Inc.) having a thickness of 50 μm used for forming the functional layer was not used, and Example 4 was formed on the surface on which the weathering layer of PET was not formed. The white resin layer-forming coating solution was applied so that the binder coating amount was 4.7 g / m ² and the titanium dioxide coating amount was 5.6 g / m ^2, and dried at 170 ° C. for 2 minutes to obtain a dry thickness of 5 A backsheet was prepared and evaluated in the same manner as in Example 1 except that a white resin layer of .7 μm was formed as a functional layer. The evaluation results are shown in Table 4 below.

As shown in Table 4, in the form of Comparative Example 10 in which the fluorine-containing resin layer was formed alone in the weather resistant layer, the adhesion of the weather resistant layer was not always sufficient. On the other hand, in the form of Example 20 in which a fluorine-containing resin layer was provided together with a composite polymer layer containing a composite polymer to form a multilayer structure, better adhesiveness was obtained.
In addition, as shown in Examples 21 to 25, a form provided with functionality other than moisture resistance and coloring, a form using a colored film having moisture resistance and light reflectivity as a polymer substrate, and a primer as a surface treatment Even when configured in a treated form, the adhesiveness of the weathering layer was not affected, and the change in the adhesiveness of the weathering layer over time with wet heat was suppressed to a small extent, and both showed good adhesiveness. .

(Examples 26 to 50)
3 mm thick tempered glass, EVA sheet (SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd.), crystalline solar cell (polycrystalline 3 bus bar cell, 156 mm × 156 mm, manufactured by Q Cells Co., Ltd.), EVA sheet ( SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd. and any of the backsheets produced in Examples 1 to 25 are superposed in this order and hot-pressed using a vacuum laminator (Nisshinbo Co., Ltd., vacuum laminator). This was adhered to EVA. At this time, the backsheets produced in Examples 1 to 25 were arranged so that the functional layer was in contact with the EVA sheet. Moreover, the adhesion method is as follows.
<Adhesion method>
Using a vacuum laminator, evacuation was performed at 128 ° C. for 3 minutes, followed by pressurization for 2 minutes and temporary adhesion. Thereafter, the main adhesion treatment was performed in a dry oven at 150 ° C. for 30 minutes.
As described above, a crystalline solar cell module was produced.

When the power generation performance of each of the produced solar cell modules was examined by a solar simulator, all showed good power generation performance as a solar cell. Moreover, when these modules were aged for 1000 hours under the condition of 85 ° C./85% RH, and the performance was compared with that before the wet heat aging, the change in the maximum extraction power was within 2%.

The disclosure of Japanese application 2011-178561 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims

A polymer substrate;
On one side of the polymer substrate, a colored layer containing a colorant, and a metal-containing layer containing a component selected from the group consisting of metals and metal compounds,
On the other side of the polymer substrate, a siloxane structural unit having a mass ratio of 15 to 85 mass% and a non-siloxane structural unit having a mass ratio of 85 to 15 mass% represented by the following general formula (1) in the molecule: A composite polymer layer containing a composite polymer having
A solar cell backsheet.

[Wherein, R 1 and R 2 each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group, and R 1 and R 2 may be the same or different. n represents an integer of 1 or more. The plurality of R 1 and R 2 may be the same as or different from each other. ]
A polymer substrate comprising a colorant;
A metal-containing layer containing a component selected from the group consisting of metals and metal compounds on one side of the polymer substrate;
On the other side of the polymer substrate, a siloxane structural unit having a mass ratio of 15 to 85 mass% and a non-siloxane structural unit having a mass ratio of 85 to 15 mass% represented by the following general formula (1) in the molecule: A composite polymer layer containing a composite polymer having
A solar cell backsheet.

[Wherein, R 1 and R 2 each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group, and R 1 and R 2 may be the same or different. n represents an integer of 1 or more. The plurality of R 1 and R 2 may be the same as or different from each other. ]
The solar cell backsheet according to claim 1 or 2, wherein the colorant is a pigment.
The solar cell backsheet according to any one of claims 1 to 3, wherein the colorant is a white or black pigment.
The back sheet for a solar cell according to claim 1, wherein the colored layer is formed by coating.
The solar cell backsheet according to any one of claims 1 to 5, wherein the component selected from the group consisting of the metal and the metal compound is aluminum in the form of a foil plate.
The solar cell backsheet according to any one of claims 1 to 5, wherein the component selected from the group consisting of the metal and the metal compound is aluminum oxide or silicon oxide.
The solar cell backsheet according to any one of claims 1 to 7, wherein the metal-containing layer is formed by vapor deposition.
The solar cell back according to any one of claims 1 to 8, wherein the polymer base material contains an end-capping agent in a range of 0.1% by mass to 10% by mass with respect to the total mass of the polymer. Sheet.
The solar cell back according to any one of claims 1 to 9, wherein a surface of the polymer substrate is treated by a method selected from the group consisting of corona treatment, flame treatment, and glow discharge treatment. Sheet.
The solar cell backsheet according to any one of claims 1 to 10, wherein the composite polymer layer further includes a structural portion derived from a crosslinking agent that crosslinks the composite polymer.
The solar cell backsheet according to claim 11, wherein the crosslinking agent is a carbodiimide compound or an oxazoline compound.
The solar cell backsheet according to claim 11 or 12, wherein a mass ratio of the structural portion derived from the crosslinking agent to the composite polymer in the composite polymer layer is 1 to 30% by mass.
The solar cell backsheet according to any one of claims 1 to 13, wherein the non-polysiloxane structural unit is an acrylic structural unit.
Forming a metal-containing layer containing a component selected from the group consisting of metals and metal compounds on the polymer substrate;
A composite polymer containing a composite polymer having a siloxane structural unit having a mass ratio of 15 to 85% by mass and a non-siloxane structural unit having a mass ratio of 85 to 15% by mass represented by the general formula (1) in the molecule Forming a layer on a polymer substrate by coating;
The method for producing a solar cell backsheet according to any one of claims 1 to 14, comprising:
Forming a non-stretched resin sheet containing a polymer constituting the polymer substrate; and
First stretching to stretch the resin sheet in a first direction;
Forming an undercoat layer by applying an undercoat layer on at least one surface of the resin sheet stretched in the first direction; and
A second stretching for stretching the resin sheet on which the undercoat layer is formed in a second direction orthogonal to the first direction;
The manufacturing method of Claim 15 which has these.
The solar cell backsheet according to any one of claims 1 to 14, or the solar cell backsheet produced by the method for producing a solar cell backsheet according to claim 15 or 16. Solar cell module provided.