JP5705769B2 - Protective sheet for solar cell and method for manufacturing the same, back sheet for solar cell, and solar cell module - Google Patents

Description

  The present invention relates to a solar cell protective sheet and a method for producing the same, a solar cell backsheet, 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 have been rapidly spreading in recent years. A solar cell module generally includes a front base material disposed on the front surface side on which sunlight is incident and a back surface protection sheet (so-called back surface) disposed on the opposite side (rear surface side) to the front surface side on which sunlight is incident. A solar battery cell in which a solar cell element is sealed with a sealing agent is sandwiched between the sheet and a sheet. In the solar cell module, the space between the front substrate and the solar cell element (cell) and the space between the solar cell element (cell) and the back sheet are respectively sealed with ethylene-vinyl acetate (EVA) resin or the like. .

  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, but in recent years, polyester is applied from the viewpoint of cost reduction and the like. Has reached. In addition, a glass substrate is generally used for the front substrate from the viewpoint of high light transmittance and maintaining a certain level of strength, but attempts have been made to use polyester instead of the glass substrate. Yes.

  Thus, polyester has been widely studied for various uses such as electrical insulation use and optical use as well as solar battery use such as a back sheet.

  Polyester usually has many carboxyl groups and hydroxyl groups on its surface, and tends to undergo a hydrolysis reaction under environmental conditions where moisture exists, and tends to deteriorate over time. Solar cell modules are often used in environments that are constantly exposed to wind and rain, such as outdoors, and are exposed to conditions where hydrolysis reactions are likely to proceed over a long period of time. Therefore, when applying polyester to a solar cell use, it is important that the hydrolyzability of polyester is suppressed. However, in an installation environment such as outdoors, pebbles and the like are affected by wind or the like and collide with the module surface, for example, scratches or the like enter the backsheet surface. When scratches or the like are formed, hydrolysis proceeds from that portion, and the weather resistance of the entire module can be lowered.

  As a technique related to the above situation, a laminate for a solar battery backsheet in which a silicone-modified acrylic resin layer is provided on a vinylidene chloride resin layer is disclosed (for example, see Patent Document 1), and has a water vapor barrier property. It is said that it exhibits and maintains excellent weather resistance and moisture resistance.

  Moreover, the back surface protection sheet for solar cell modules provided with the weatherproof outermost layer by the curable resin composition using an acrylate-type copolymer and organohydro diene polysiloxane is disclosed (for example, refer patent document 2). It is said to be excellent in weather resistance. Furthermore, a technique using organic fine powder such as wax as an antiblocking agent is also disclosed (for example, see Patent Document 3).

JP 2009-290201 A JP 2002-83988 A JP 2010-287762 A

  However, among the above conventional techniques, in the back sheet provided with the silicone-modified acrylic resin layer and the back surface protection sheet using the curable resin composition using the acrylate copolymer and the organohydrodiene polysiloxane, Although an improvement effect with respect to heat resistance and moisture resistance is expected, merely using a silicone-based resin may impair surface slipperiness. In this case, since the dynamic friction coefficient of the layer surface is high, the strength against external force such as scratching is weak, and as a result, the light resistance can be significantly impaired.

  Silicone resins often contain a low molecular silicone component in the resin. Although the low molecular silicone component is advantageous in terms of slipperiness, in the production mode in which a layer is formed by coating, the low molecular silicone component in the coating film is unwound on the reverse side (that is, in the process of winding after coating) It may be transferred to the surface on the side opposite to the side on which the coating film of the polymer substrate is applied and adversely affected in the subsequent process.

  The present invention has been made in view of the above, and has no adverse effects on the manufacturing process by transferring the components to the non-coated surface after coating, etc., and against external forces such as scratching, rubbing, and collision of flying objects (pebbles, etc.). It is possible to provide a solar cell protective sheet excellent in scratch resistance, a method for producing the same, a solar cell backsheet, and a solar cell module that exhibits stable power generation performance over a long period of time.

Specific means for achieving the above object are as follows.
<1> A solar cell protective sheet comprising a polymer substrate and a polymer layer that is an outermost layer disposed on one surface of the polymer substrate,
The polymer layer contains a polymer and a lubricant;
The polymer molecule has a structure containing a siloxane bond,
The polymer content in the polymer layer is more than 0.2 g and 15 g or less per 1 m ^{2 of the} polymer layer,
The content of the lubricant in the polymer layer is 0.2 mg or more and 200 mg or less per 1 m ^{2 of the} polymer layer, and the polymer is a (poly) siloxane structural unit represented by the following general formula (1) and non-siloxane It is a copolymer having a structural unit, and the (poly) siloxane structural unit represented by the general formula (1) is 30 to 75 % by mass and the non-siloxane structural unit is 70 to 25 % by mass. viewing including the door,
The lubricant is the protective sheet that is at least one selected from the group consisting of a synthetic wax compound, a natural wax compound, and a surfactant compound .
<2> before Symbol polymer layer is a protective sheet for a solar cell according to the dynamic friction coefficient of the surface is 0.4 or less <1>.
< 3 > The polymer layer according to <1> or < 2>, wherein the polymer layer contains a matting agent having an average secondary particle size of 0.3 μm to 10 μm in a range of 0.3 mg to 30 mg per 1 m ^{2 of the} polymer layer. It is a protection sheet for solar cells.
< 4 > The solar cell protective sheet according to any one of <1> to < 3 >, wherein the polymer layer further contains colloidal silica and an alkoxysilane compound.
< 5 > The solar cell protective sheet according to any one of <1> to < 4 >, wherein the polymer base is subjected to corona treatment on the surface on which the polymer layer is disposed.

< 6 > The lubricant is selected from the group consisting of polyolefin wax, fatty acid metal salt, natural fatty acid ester compound, synthetic fatty acid ester compound, alkyl sulfate surfactant, and polyoxyethylene alkyl sulfate surfactant. The protective sheet according to any one of <1> to < 5 >, wherein the protective sheet is at least one.
< 7 > On the polymer base material, a polymer having a structure containing a siloxane bond in the molecule, a lubricant, and an aqueous coating solution containing water are applied, and more than 0.2 g and 15 g or less of the polymer per m ² Forming a polymer layer containing 0.2 to 200 mg of the lubricant, and the polymer has a (poly) siloxane structural unit and a non-siloxane structural unit represented by the following general formula (1) a copolymer represented by general formula (1) (poly) viewed contains 30 to 75 wt% in mass ratio of the siloxane structural unit, a 70 to 25% by weight of the non-siloxane structural unit weight ratio, the lubricant, synthetic wax-based compound, natural wax-based compound, and at least is one method for producing a solar cell protective sheet is selected from the group consisting of surfactant compounds That.
< 8 > The polymer layer is formed by mixing at least an aqueous dispersion of the polymer and an aqueous dispersion of the lubricant to prepare the aqueous coating liquid, and using the prepared aqueous coating liquid as the polymer. It is a manufacturing method of the protection sheet for solar cells as described in said < 7 > including apply | coating on a base material.
< 9 > The solar cell protective sheet according to any one of <1> to < 6 >, or the solar cell protective sheet according to < 7 > or < 8 >. It is the solar cell backsheet containing the protective sheet for solar cells.
<1 0 > a transparent substrate on which sunlight is incident;
An element structure portion provided on the base material and including a solar cell element and a sealing material for sealing the solar cell element;
It is a solar cell module provided with the solar cell backsheet as described in said < 9 > arrange | positioned on the opposite side to the side in which the said base material is located of the said element structure part.

According to the present invention, a solar cell having excellent scratch resistance against external forces such as scratching, rubbing, and collision of flying objects (pebbles, etc.) without adversely affecting the manufacturing process by transferring components to a non-coated surface after coating. Protective sheet, method for producing the same, and back sheet for solar cell can be 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 can be provided.

Hereinafter, a solar cell protective sheet and a method for producing the same, and a solar cell backsheet and a solar cell module using the same will be described in detail.
In the present disclosure, the “step” is not limited to an independent step, and even a step that cannot be clearly distinguished from other steps is included in the scope as long as the intended effect of the step is achieved. .
The numerical range display ("m or more and n or less" or "m to n") includes the numerical value (m) displayed as the lower limit value of the numerical range as the minimum value and is displayed as the upper limit value of the numerical range. The range including the numerical value (n) as the maximum value is shown.
When referring to the amount of a certain component in the composition, when there are a plurality of substances corresponding to the component in the composition, the amount is the plural present in the composition unless otherwise defined. Means the total amount of substances.

The protective sheet of the present disclosure is formed as a polymer substrate and an outermost layer on one surface of the polymer substrate, and at least a polymer having a (poly) siloxane structure in a molecule is more than 0.2 g / m ^{2 and} more than 15 g / m ^2. m ² or less and, with a polymer layer containing a 0.2 mg / ^{m 2} or more 200 mg / ^{m 2} or less lubricants, provided, wherein the polymer is represented by the general formula below (1) (poly) siloxane structure It is a copolymer having a unit and a non-siloxane structural unit, and the (poly) siloxane structural unit represented by the general formula (1) in the molecule is 30 to 75 % by mass, and the non-siloxane structural unit is look contains a 70 to 25 wt% in mass ratio, the lubricant is a synthetic wax compound, Ru least 1 Tsudea selected from the group consisting of natural wax-based compound, and a surfactant compound If necessary, the protective sheet may further include a colored layer colored with a colorant (including a light reflecting layer that reflects sunlight) and a constituent substrate of the battery side substrate (for example, a sealing material such as EVA). Other layers such as an easy-adhesive layer that increases the adhesion between the two and the like (for example, the adhesive force to the sealing material is 10 N / cm or more) may or may not be provided.

The protective sheet includes a transparent base material (a front base material such as a glass substrate) disposed on the side on which sunlight is incident, and an element structure part (including a solar cell element and a sealant that seals it). And a solar cell having a laminated structure of “transparent front substrate / element structure portion / back sheet”, which is applied to either the front substrate or the back sheet. Good. Here, the back sheet is a back surface protection sheet disposed on the side where the front base material is not located when viewed from the element structure portion of the battery side substrate.
In the following, a battery part having a laminated structure of “transparent front base material / element structure part” in which an element structure part is arranged on a transparent base material arranged on the side where sunlight enters is referred to as “battery”. It is called “side substrate”.

  By containing a lubricant and a polymer having a (poly) siloxane structure in the molecule so as to satisfy a predetermined quantitative range, the polymer layer formed by coating has high film strength, and scratches, scratches, flying objects ( It can exhibit excellent scratch resistance against external forces such as collisions of pebbles, etc., and can stably maintain light resistance, heat resistance, and moisture resistance for a long period when arranged as the outermost layer. Thereby, the said protection sheet can exhibit the outstanding weather resistance performance as a protection sheet of a solar cell, and can acquire the electric power generation performance stable for a long period of time.

  The polymer layer can be applied to any layer constituting the backsheet as the outermost layer farthest from the polymer substrate. From the point that the polymer layer is excellent in durability under a moist heat environment such as heat and moisture, the protective sheet is the outermost layer exposed to the external environment when used in a solar cell module as a back sheet, that is, on the back side. It is particularly preferable to function as the outermost layer (back layer).

(Polymer substrate)
Examples of the polymer substrate material include polyester, polyolefin such as polypropylene and polyethylene, or fluorocarbon polymer such as polyvinyl fluoride. The substrate may be a film or a sheet. Among these, a polyester base material is preferable from the viewpoint of cost and mechanical strength.

  Examples of the polyester substrate used as the polymer substrate (support) include a linear saturated polyester substrate 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. Among these, polyethylene terephthalate or polyethylene-2,6-naphthalate is preferable from the viewpoint of balance between mechanical properties and cost.

  The polyester base material may be a homopolymer or a copolymer. Furthermore, the polyester base material may be made of only polyester, or may be made of a mixture obtained by blending a small amount of other types of resins, such as polyimide, with the polyester.

  When the polyester is polymerized, from the viewpoint of keeping the carboxyl group content below a predetermined range, Sb-based, Ge-based, and Ti-based compounds are preferably used as the catalyst, and among these, Ti-based compounds are particularly preferable. In the case of using a Ti-based compound, an embodiment 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. When the amount of Ti compound used is within the above range in terms of Ti element, the terminal carboxyl group of the polyester can be adjusted to the following range, and the hydrolysis resistance of the polymer substrate can be kept high.

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

The carboxyl group content in the polyester is preferably 55 equivalents / t (tons; hereinafter the same) or less, more preferably 35 equivalents / t or less. 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 small. The lower limit of the carboxyl group content is preferably 2 equivalents / t in that the adhesion between the layer formed on the polyester film (for example, a colored layer) can be maintained.
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 (AV) is obtained by completely dissolving the target polyester base material in a mixed solution of benzyl alcohol and chloroform (volume ratio [benzyl alcohol] / [chloroform] = 2/3), and phenol red as an indicator. It is a value calculated from the appropriate amount by titrating with a reference solution (0.025N KOH-methanol mixed solution).

  The polyester is preferably subjected to solid phase polymerization 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.

For example, after the polyester base is melt-extruded in the form of a film, the polyester base material is cooled and solidified by a casting drum to form an unstretched film. This unstretched film is once in the longitudinal direction at Tg to (Tg + 60) ° C. Or the biaxially stretched film formed by extending | stretching so that a magnification may be 3 to 6 times in the width direction at Tg- (Tg + 60) degreeC after that, and extending | stretching so that a magnification may be 3 times to 6 times after 2 times or more. It is preferable that
Further, heat treatment may be performed at 180 to 230 ° C. for 1 to 60 seconds as necessary, or may not be performed.
Tg represents a glass transition temperature and can be measured based on JIS K7121 or ASTM D3418-82. For example, it can be measured using a differential scanning calorimeter (DSC) manufactured by Shimadzu Corporation.
Specifically, 10 mg of a polymer such as polyester is weighed as a sample, set in an aluminum pan, and heated at a rate of temperature increase of 10 ° C./min from room temperature to a final temperature of 300 ° C., with a DSC device, the amount of heat relative to temperature Was measured as the glass transition temperature.

As for the thickness of a polymer base material (especially polyester base material), about 25-300 micrometers is preferable. If the thickness is 25 μm or more, the mechanical strength can be good, and if it is 300 μm or less, it can be advantageous in terms of cost.
In particular, the polyester base material tends to have poor hydrolysis resistance as the thickness increases, and durability during long-term use tends to decrease. In a certain embodiment, when thickness is 120 micrometers or more and 300 micrometers or less, and the carboxyl group content in polyester is 2 equivalent / t-35 equivalent / t, the improvement effect of wet heat durability can be show | played more.

The polymer substrate is preferably in a form in which surface treatment is performed by corona treatment, flame treatment, low-pressure plasma treatment, atmospheric pressure plasma treatment, or ultraviolet treatment. By applying these surface treatments, the adhesiveness when exposed to a humid heat environment can be further enhanced. In particular, by performing the corona treatment, a better adhesive improvement effect can be obtained.
By these surface treatments, adhesion can be enhanced by increasing carboxyl groups and hydroxyl groups on the surface of a polymer substrate (for example, polyester substrate), and a crosslinking agent (particularly an oxazoline-based or carbodiimide having a high reactivity with a carboxyl group). When a cross-linking agent) is used in combination, stronger adhesiveness can be obtained. This can be more pronounced with corona treatment. Therefore, it is particularly preferable that the surface of the polymer substrate on which the polymer layer is formed is corona-treated.

(Polymer layer)
The polymer layer is disposed in contact with the surface of the polymer substrate or through another layer. The polymer layer includes at least a polymer having a (poly) siloxane structure in a molecule and a lubricant. The polymer is contained in 0.2 g / ^{m 2} Ultra 15 g / ^{m 2} or less in the range in the polymer layer, wherein the lubricant is contained in the 0.2 mg / ^{m 2} or more 200 mg / ^{m 2} or less in the range in the polymer layer Yes.

  The polymer layer contains a polymer having a (poly) siloxane structure in the molecule as a polymer component, and also contains a lubricant. With this configuration, the film strength of the polymer layer can be increased, while the decrease in slipperiness (that is, increase in the dynamic friction coefficient) that is likely to occur when a siloxane-based polymer having a (poly) siloxane structure is used. For this reason, the susceptibility to scratches caused by external forces such as scratches, scratches, and collisions with pebbles is drastically reduced, and the desired properties are stably maintained over a long period of use.

  By providing the polymer layer, adhesion between adjacent materials such as a polymer substrate can be improved. In certain embodiments, it is preferred that the polymer layer be disposed in direct contact with the polymer substrate.

  This polymer layer may or may not contain other components depending on the case, and its constituent components differ depending on the application to be applied. Since the polymer layer is provided as the outermost layer farthest from the polymer base material, it is preferable to constitute a back layer disposed on the side opposite to the side on which sunlight is incident, and the solar light reflecting function and appearance design The structure which serves also as the colored layer etc. which bear | provide property etc. may be sufficient.

  For example, when the polymer layer is configured as a light reflecting layer that reflects sunlight toward the incident side, the polymer layer may further include a colorant such as a white pigment in addition to the polymer component and the lubricant.

Hereinafter, each component which comprises a polymer layer is explained in full detail.
-Polymer-
The polymer layer contains at least one polymer having a (poly) siloxane structure in the molecule.
By containing this polymer, the polymer layer can improve the strength of the surface of the polymer layer, and can reduce scratches that are likely to occur due to scratches, scratches, collisions of flying objects such as pebbles and sand, etc. It can be more excellent in adhesion to adjacent materials and durability in wet heat environment.

The polymer is not particularly limited as long as it has a (poly) siloxane structure in the molecule. Here, the “siloxane structure” means a structure containing at least one siloxane bond. “Polysiloxane structure” means a structure in which a plurality of siloxane bonds are continuous. The term “(poly) siloxane structure” encompasses siloxane structures and polysiloxane structures within its scope. The expressions “the polymer has a siloxane structure in the molecule” and “the polymer has a (poly) siloxane structure in the molecule” mean that the polymer contains a siloxane structure or a polysiloxane structure in the molecule.
In one embodiment, a homopolymer (monopolymer) of a compound having a (poly) siloxane structural unit, or a copolymer of a compound having a (poly) siloxane structural unit and another compound, that is, a (poly) siloxane structure Copolymers having units and other structural units are preferred. The other compound is a non-siloxane monomer or polymer, and the other structural unit is a non-siloxane structural unit.

  In one embodiment, it may be preferable that the polymer has a (poly) siloxane structural unit represented by the following general formula (1) in a 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. n represents an integer of 1 or more. Here, R ¹ and R ² may be the same or different, and a plurality of R ¹ and R ² existing when n is 2 or more may be the same or different from each other. * Represents a position linked to an adjacent structural unit.

“— (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 that can be covalently bonded to an Si atom, and may be unsubstituted or may have a substituent. Examples of the monovalent organic group include an alkyl group (e.g., methyl group, ethyl group), an aryl group (e.g., phenyl group), an aralkyl group (e.g., benzyl group, phenylethyl group), an alkoxy group (e.g. Examples: methoxy group, ethoxy group, propoxy group, etc.), aryloxy group (eg, phenoxy group, etc.), mercapto group, amino group (eg, amino group, diethylamino group, etc.), amide group and the like.

Among 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. C1-C4 alkyl group (especially methyl group, ethyl group), unsubstituted or substituted phenyl group, unsubstituted or substituted alkoxy group, mercapto group, unsubstituted amino group, amide group And more preferably an unsubstituted or substituted alkoxy group (preferably an alkoxy group having 1 to 4 carbon atoms) from the viewpoint of durability in a humid heat environment.

  The n is preferably 1 to 5000, and more preferably 1 to 1000.

The content of “— (Si (R ¹ ) (R ² ) —O) _n —” in the polymer (the (poly) siloxane structural unit represented by the general formula (1)) depends on the total mass of the polymer. On the other hand, it is preferably 15 to 85% by mass, and among them, it is possible to improve the strength of the surface of the polymer layer, to prevent the occurrence of scratches due to scratching, scratching, etc., and to adhere to adjacent materials such as a polymer substrate and The range of 20 to 80% by mass is more preferable from the viewpoint that it can be more excellent in durability under a humid heat environment. When the ratio of the (poly) siloxane structural unit is 15% by mass or more, the strength of the polymer layer surface is improved, and scratches caused by scratches, scratches, collisions of flying pebbles, etc. can be prevented, and the support It can be excellent in adhesiveness with adjacent materials such as a polymer substrate. The weather resistance can be improved by suppressing the occurrence of scratches, and the peel resistance, shape stability, and adhesion durability when exposed to a wet and heat environment, which are likely to deteriorate when heat and moisture are applied, can be effectively enhanced. Moreover, the coating liquid for polymer layer formation can be kept stable as the ratio of the (poly) siloxane structural unit is 85% by mass or less.

  When the polymer is a copolymer having a (poly) siloxane structural unit and other structural units, in one embodiment, the mass of the (poly) siloxane structural unit represented by the general formula (1) in the molecule is The ratio may include 15 to 85% by mass, and the non-siloxane structural unit may include 85 to 15% by mass. When such a copolymer is contained, the film strength of the polymer layer can be improved, the occurrence of scratches due to scratching or scratching, etc. can be prevented, and adhesion with the polymer substrate forming the support, that is, heat and moisture can be given. If this is done, the peel resistance, shape stability, and durability in a humid heat environment, which are likely to deteriorate, can be drastically improved as compared with the prior art.

  The copolymer is represented by the general formula (1) obtained by copolymerization of a siloxane compound (including polysiloxane) and a compound selected from a non-siloxane monomer or a non-siloxane polymer. ) A block copolymer having a siloxane structural unit and a non-siloxane structural unit is preferred. In this case, each of the siloxane compound and the non-siloxane monomer or non-siloxane polymer to be copolymerized may be one kind or two or more kinds.

The non-siloxane structural unit (derived from the non-siloxane monomer or non-siloxane polymer) copolymerized with the (poly) siloxane structural unit is not particularly limited except that it does not have a siloxane structure, and is arbitrary. Any of the polymer segments derived from the polymer 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.
Among these, vinyl polymers and polyurethane polymers are preferable, and vinyl polymers are particularly preferable because they are easy to prepare and have excellent hydrolysis resistance.

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, acrylic polymers are particularly preferable from the viewpoint of design freedom.
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.

  Further, the precursor polymer constituting 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.

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

  The polymer layer may be used alone or in combination with another polymer as a binder. When other polymers are used in combination, the content of the polymer containing the (poly) siloxane structure is preferably 30% by mass or more, more preferably 60% by mass or more, based on the total amount of binder in the polymer layer. The content of the polymer containing the (poly) siloxane structure is 30% by mass or more, so that the strength of the surface of the layer can be improved and the occurrence of scratches due to scratching or scratching can be prevented, and the adhesion to the polymer substrate In addition, it can be more excellent in durability under humid heat environment.

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

For the preparation of the polymer, (i) a method of reacting the precursor polymer with (poly) siloxane having the structural unit represented by the general formula (1), (ii) the R ^{1 in} the presence of the precursor polymer. A method such as a method of hydrolyzing and condensing a silane compound having the structural unit represented by the general formula (1) in which R ² is a hydrolyzable group can be used.
Examples of the silane compound used in the method (ii) include various silane compounds, and alkoxysilane compounds are particularly preferable.

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

  Moreover, as a polymer which has a (poly) siloxane structure, you may use a commercial item, for example, SERATEN (registered trademark) series (For example, SERANAT (registered trademark) WSA-1070, SELANAATE (registered trademark) manufactured by DIC Corporation. (Trademark) WSA-1060, etc.), Polydurex (registered trademark) H7600 series (H7650, H7630, H7620, etc.) manufactured by Asahi Kasei Chemicals Co., Ltd., inorganic / acrylic composite emulsion manufactured by JSR Corporation, etc. can be used. .

The content of the polymer having the (poly) siloxane structure in the polymer layer may be 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 by external force may not be suppressed. On the other hand, when the polymer content ratio exceeds 15 g / m ² , the polymer ratio is too large, and the curing of the polymer layer may be insufficient.
Among the above range, from the viewpoint of the surface strength of the polymer ^layer, preferably in the range of ^{0.5g / m 2 ~10.0g / m 2} , more in the range of 1.0g / ^{m 2} ~5.0g / m 2 preferable.

-Lubricant-
The polymer layer contains at least one lubricant. By containing a lubricant, it is possible to suppress a decrease in slipperiness (that is, an increase in the dynamic friction coefficient) that is likely to occur when using a siloxane polymer having a siloxane structure as described above, so scratches, scratches, collisions with pebbles, etc. The susceptibility to damage caused by the external force can be drastically reduced. As a result, the weather resistance, particularly the hydrolysis resistance that tends to deteriorate with the occurrence of scratches, can be dramatically improved while increasing the coating film strength using a siloxane-based polymer.

Lubricant is contained in the range of 0.2mg ^{/ m 2} ~200mg ^/ m 2 in the polymer layer. If the content ratio of the lubricant is less than 0.2 mg / m ² , the amount of the lubricant is too small, and the effect of reducing the dynamic friction coefficient due to the inclusion of the lubricant can be reduced. On the other hand, if the content ratio of the lubricant exceeds 200 mg / m ² and increases too much, uneven coating or aggregates may occur or repelling failure may easily occur when the polymer layer is formed by coating.
Among the above range, in view of the dynamic friction coefficient reduction effect and coating ^suitability, preferably in the range of ^{1.0mg / m 2 ~1150mg / m 2} , and more preferably in a range of from ^{5.0mg / m 2 ~100mg / m 2} .

  Examples of the lubricant include synthetic wax compounds, natural wax compounds, surfactant compounds, inorganic compounds, organic resin compounds, and the like. Among these, from the viewpoint of the surface strength of the polymer layer, a compound selected from synthetic wax compounds, natural wax compounds, and surfactant compounds is preferable.

  Examples of the synthetic wax compounds include polyolefin waxes such as polyethylene wax and polypropylene wax, esters of fatty acids such as stearic acid, oleic acid, erucic acid, lauric acid, behenic acid, palmitic acid, and adipic acid, amides, and bisamides. , Ketones, metal salts and derivatives thereof, synthetic hydrocarbon waxes such as Fischer-Tropsch wax, phosphate esters, hydrogenated castor oil, hydrogenated waxes of hydrogenated castor oil derivatives, among which fatty acid ester compounds and fatty acid metal salts preferable.

  The natural wax compound typically includes a natural fatty acid ester compound, for example, a plant wax such as carnauba wax, candelilla wax or wood wax, a petroleum wax such as paraffin wax or microcrystalline wax, or a montan wax. Examples include animal waxes such as mineral wax, beeswax, and lanolin.

Examples of the surfactant compound include cationic surfactants such as alkylamine salts, alkyl sulfates (eg, alkyl sulfate salts), polyoxyethylene alkyl sulfates (eg, polyoxyethylene alkyl sulfate salts), and the like. Anionic surfactants, nonionic surfactants such as polyoxyethylene alkyl ethers, amphoteric surfactants such as alkylbetaines, and fluorosurfactants.
Among the above, the lubricant is selected from the group consisting of polyolefin wax, fatty acid metal salt, natural fatty acid ester compound, synthetic fatty acid ester compound, alkyl sulfate surfactant, and polyoxyethylene alkyl sulfate surfactant. At least one selected from the group. In some embodiments, one lubricant selected from the group. Here, the fatty acid ester compound means a compound having in its molecule an ester bond formed between a hydroxyl group and a carboxyl group of a fatty acid.

A commercially available product may be used as the lubricant.
Synthetic wax-based lubricants include, for example, Chemipearl (registered trademark) series (for example, Chemipearl (registered trademark) W700, W900, and W950) manufactured by Mitsui Chemicals, Inc., Polylon P- manufactured by Chukyo Yushi Co., Ltd. 502, Hymicron L-271, Hydrin L-536 (all trade names), etc.
Examples of the natural wax-based lubricant include Hydrin L-703-35 (trade name), Cellozol (registered trademark) 524, Cellozol (registered trademark) R-586 manufactured by Chukyo Yushi Co., Ltd.
Examples of surfactant-based lubricants include the NIKKOL series (for example, NIKKOL SCS (registered trademark), etc.) manufactured by Nikko Chemicals Co., Ltd., and the Emar (registered trademark) series (for example, EMAL 40 (registered trademark), manufactured by Kao Corporation). Trademark)).

  Among the above-mentioned polymers, the polymer layer is composed of the SERATEN (registered trademark) series manufactured by DIC Corporation, the inorganic / acrylic composite emulsion manufactured by JSR Corporation as the polymer, and Chemipearl manufactured by Mitsui Chemicals, Inc. as the lubricant. The form comprised using the (trademark) series is preferable.

-Matting agent-
The polymer layer may or may not contain a matting agent. When the matting agent is contained, a decrease in the slipperiness (that is, an increase in the dynamic friction coefficient) of the polymer layer can be further reduced. As a result, scratches caused by external forces such as scratches, scratches, and collisions with pebbles can be further alleviated, and hydrolysis resistance and, in turn, weather resistance can be improved.

  The matting agent is preferably a particulate material, and may be either an inorganic material or an organic material. For example, inorganic particles or organic particles can be used. Specifically, examples of the inorganic particles include metal oxides such as titanium oxide, silica, alumina, zirconia, and magnesia, and particles such as talc, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, kaolin, and clay. Preferably mentioned. Moreover, as said organic particle, particles, such as an acrylic resin, a polystyrene resin, a polyurethane resin, a polyethylene resin, a benzoguanamine resin, an epoxy resin, are mentioned suitably, for example.

  The average particle size of the matting agent is preferably 0.3 μm to 10 μm, more preferably 1 μm to 8 μm in terms of secondary particle size. When the average secondary particle diameter of the matting agent is 0.3 μm or more, the effect of preventing scratches due to scratching or abrasion due to the matting agent can be increased, and when the average secondary particle size is 10 μm or less, the polymer layer is applied and formed. It may be advantageous in that it is difficult to cause agglomerates and play failure, and it is easy to obtain a good coated surface.

  The average particle diameter is an average of secondary particle diameters measured by a laser analysis / scattering particle size distribution measuring apparatus LA950 [trade name, manufactured by Horiba, Ltd.].

The content in the polymer layer of the matting ^{agent, 0.3mg / m 2 ~30mg / m} 2 range is preferably in ^the range of 10mg / ^{m 2} ~25mg / m 2, more ^preferably, 15mg / m 2 ^~25mg / m A range of ² is more preferred. When the content of the matting agent is 0.3 mg / m ² or more, the effect of reducing the dynamic friction coefficient of the polymer layer is large, and the occurrence of scratches due to external forces such as scratches, scratches, and collisions with pebbles can be further alleviated. When it is less than / m ² , it may be advantageous in that it is difficult to cause agglomerates and play failure when the polymer layer is applied and formed, and a good coated surface state can be easily obtained.

-Crosslinking agent-
In a certain embodiment, it is preferable that the polymer layer contains the structure part derived from the crosslinking agent which bridge | crosslinks between the said polymers. That is, the polymer layer can be formed using a crosslinking agent capable of crosslinking between polymer molecules. By cross-linking between polymer molecules with a cross-linking agent, adhesion after wet heat aging, specifically adhesion to adjacent materials such as a polymer substrate when exposed to a wet heat environment can be further improved.

  Examples of the crosslinking agent include crosslinking agents such as an epoxy compound, an isocyanate compound, a melamine compound, a carbodiimide compound, and an oxazoline compound. 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 ′) Dimethyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene- Bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinylnorbornane) sulfide and the like can be mentioned. 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 (registered trademark, 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, dicyclohexylmethane carbodiimide, and the like. Also preferred are carbodiimide compounds described in JP-A-2009-235278. Specifically, as carbodiimide-based crosslinking agents, carbodilite SV-02, carbodilite V-02, carbodilite V-02-L2, carbodilite V-04, carbodilite E-01, carbodilite E-02 (all trade names, Nisshinbo Chemical Co., Ltd.) (Commercially available) and the like can also be used.

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

  In the protective sheet, the polymer layer includes a polymer having a (poly) siloxane structure and a lubricant as described above, so that the strength of the polymer layer surface is improved, and scratches, scratches, collisions of flying pebbles, etc. Can be prevented, and can be excellent in adhesion to adjacent materials such as a polymer substrate forming a support. Suppressing the occurrence of scratches can improve the weather resistance, and can be excellent in peeling resistance, shape stability, and adhesion durability when exposed to a humid heat environment, which easily deteriorate when given heat and moisture. For this reason, the protective sheet is arranged as the outermost layer arranged at the position farthest from the polymer base material, so that it does not easily cause a phenomenon of peeling from an adjacent material, and has excellent weather resistance, so that it can be stably stably for a long time. The desired properties can be maintained.

Only one polymer layer may be provided, or a plurality of polymer layers may be laminated in some cases.
The thickness of one layer of the polymer layer is usually preferably 0.3 μm to 22 μm, more preferably 0.5 μm to 15 μm, still more preferably 0.8 μm to 12 μm, particularly preferably 1.0 μm to 8 μm, The range of 2 μm to 6 μm is most preferable. When the thickness of the polymer layer is 0.3 μm, it is difficult for moisture to penetrate from the surface of the polymer layer to the inside when exposed to a humid heat environment, and moisture hardly reaches the interface between the polymer layer and the polymer substrate. Thus, the adhesiveness can be remarkably improved, and these effects can be particularly remarkable when the thickness of the polymer layer is 0.8 μm or more. In addition, when the thickness of the polymer layer is 22 μm or less, the polymer layer itself is not easily fragile, and the adhesiveness can be improved because the polymer layer is not easily broken when exposed to a wet heat environment. Can be particularly prominent when the thickness of the polymer layer is 12 μm or less.

  The polymer layer has a crosslinked structure in which the polymer and the polymer molecules of the polymer are crosslinked with a crosslinking agent, and the ratio of the structural portion derived from the crosslinking agent to the polymer is 1 to 30% by mass, and the polymer layer When the thickness is 0.8 μm to 12 μm, the effect of improving the adhesiveness after wet heat aging can be particularly excellent.

  The polymer layer preferably has a dynamic friction coefficient of 0.4 or less on the surface of the layer. When the coefficient of dynamic friction is 0.4 or less, the generation of scratches caused by external forces such as scratching, scratching, and collision with pebbles is mitigated, which can be effective in maintaining weather resistance. The dynamic coefficient of friction is preferably as small as possible from the viewpoint of preventing scratches due to scratches and the like, but is preferably in the range of 0.1 to 0.3 from the viewpoint of handleability.

Although the said dynamic friction coefficient can be measured using arbitrary well-known methods, specifically, it is a value measured by the following method. That is, after conditioning the polymer layer in an atmosphere of 25 ° C. and 60% RH for 24 hours, the surface was scratched with a sapphire needle having a tip diameter of 1 mm at a speed of 1 cm / second and a load of 20 g. taking measurement. Then, using the obtained measured value, the friction coefficient (μ) is calculated from the following formula to obtain the dynamic friction coefficient.
μ = F / 20

~ Polymer layer as back layer ~
When the polymer layer is used as a back layer in a solar cell, the polymer layer may further contain other components such as various additives, if necessary, in addition to the polymer and the lubricant. A structure in which a battery-side substrate and a back sheet are laminated, that is, a transparent base material (such as a glass substrate) on the side where sunlight enters, an element structure portion including a solar cell element, and a back sheet are laminated in this order. In the solar cell having a structure including the back layer, the back layer is a back surface protective layer disposed on the side opposite to the side facing the battery side substrate of the polymer base material which is a support, and may have a single layer structure. The structure which laminated | stacked the layer or more may be sufficient. By including the polymer, the adhesion to the polymer substrate and the adhesion between layers when the back layer is composed of two or more layers is the polymer layer can be improved, and further, the deterioration resistance in a humid heat environment Can be obtained. For this reason, the polymer layer is preferably disposed in the outermost layer farthest from the polymer base material as a back layer located on the back surface side when viewed from the solar cell element.

When the back layer is composed of two or more layers, both layers may be a polymer layer and a lubricant having the (poly) siloxane structure, or a polymer layer containing the polymer and the lubricant and the crosslinking agent. Alternatively, only one of the layers may be the polymer and the lubricant, or the polymer layer containing the polymer and the lubricant and the crosslinking agent.
Among them, from the viewpoint of improving the adhesion durability in a moist heat environment, at least the back layer (second back layer) on the side farther from the polymer substrate that does not contact the polymer substrate is the polymer and the lubricant, or the It is preferable to be composed of a polymer layer containing a polymer and a lubricant and the crosslinking agent. In this case, the first back layer close to the polymer substrate provided as the lower layer of the second back layer on the polymer substrate has a (poly) siloxane structure (preferably, the general formula (1) The polymer having (poly) siloxane structural unit and non- (poly) siloxane structural unit represented by the following formula may not be included. From the viewpoint of preventing moisture from entering between the gaps and improving the adhesion in a moist heat environment, it is preferable not to contain a (poly) siloxane homopolymer.

  Examples of other components that can be included in the back layer include surfactants and fillers as described later. Moreover, you may include the pigment used for a colored layer.

~ Polymer layer as colored layer ~
The polymer layer may be substantially uncolored or a colored layer. When the polymer layer also serves as a colored layer (preferably a light reflecting layer), it further contains a pigment in addition to the polymer and the lubricant. The colored layer may further contain other components such as various additives as necessary.

  As a function of the colored layer, first, by reflecting the light that has passed through the solar cells and reaches the back sheet without being used for power generation out of the incident light, and returns the solar cells to the solar cells, Increasing the power generation efficiency, secondly, improving the decorativeness of the appearance when the solar cell module is viewed from the side on which sunlight enters (front side), and the like. In general, when the solar cell module is viewed from the front side, a back sheet can be seen around the solar cell, and by providing a colored layer on the back sheet, the decorativeness can be improved and the appearance can be improved.

-Pigment-
The colored layer can contain at least one pigment.
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.

  Of the pigments, a white pigment is preferred when the polymer layer is a light reflecting layer that reflects light that has entered the solar cell and passed through the solar cell and returns it to the solar cell. As the white pigment, titanium dioxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc and the like are preferable.

The content in the colored layer of the pigment is in ^the range of 2.5g / ^{m 2} ~8.5g / m 2 is preferred. 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 colored layer is 8.5 g / m ² or less, the surface state of the colored layer can be easily maintained and the film strength can be improved. Among them, the content of the pigment is in ^the range of 4.5g / ^{m 2} ~8.0g / m 2 is more preferable.

  The average particle diameter of the pigment is preferably 0.03 μm to 0.8 μm, more preferably about 0.15 μm to 0.5 μm in terms of volume average particle diameter. When the average particle size is within the above range, the light reflection efficiency can be increased. The average particle diameter is a value measured by a laser analysis / scattering particle size distribution measuring apparatus LA950 [trade name, manufactured by Horiba, Ltd.].

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

-Additives-
You may add surfactant, a filler, etc. to a polymer layer as needed.
As the surfactant, a known surfactant such as an anionic surfactant or a nonionic surfactant can be used. If a surfactant is added, the addition amount thereof is preferably from ^{0.1mg / m 2 ~15mg / m 2} , more preferably ^{0.5mg / m 2 ~5mg / m 2} . When the addition amount of the surfactant is 0.1 mg / m ² or more, generation of repellency can be suppressed and good layer formation can be obtained, and when it is 15 mg / m ² or less, adhesion can be performed satisfactorily. .

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

  As the filler, an inorganic filler is preferable, and examples thereof include talc, silica, alumina, aluminum hydroxide, magnesia, titania, zirconia, aluminum nitride, boron nitride, and barium sulfate. Among these, silica is preferable, and colloidal silica is particularly preferable. Furthermore, you may add an alkoxysilane compound as needed. Examples of the alkoxysilane compound include tetraalkoxysilane and trialkoxysilane. Among these, trialkoxysilane is preferable, and an alkoxysilane compound having an amino group is particularly preferable.

When a white pigment is added as a pigment to the polymer layer to form a light reflection layer, the light reflectance of 550 nm wavelength light on the surface on which the light reflection layer and the easy-adhesion layer are provided is 75% or more. Is preferred. The light reflectance is the ratio of the amount of light incident from the surface of the easy-adhesion layer to the amount of incident light reflected from the light-reflection layer and emitted from the easy-adhesion layer again. 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 content of the coloring agent by controlling the range of ^{2.5g / m 2 ~30g / m 2} , it is possible to adjust the optical reflectance over 75%.

  The protective sheet may have other functional layers in addition to the polymer substrate and the polymer layer. As other functional layers, an undercoat layer and an easily adhesive layer can be provided.

(Other functional layers)
[Undercoat layer]
In the protective sheet, an undercoat layer may be provided between the polymer substrate (support) and the 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 further 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 can contain a binder. As the binder, for example, polyester, polyurethane, acrylic resin, polyolefin, or the like can be used. In addition to the binder, the undercoat layer includes an epoxy crosslinking agent, an isocyanate crosslinking agent, a melamine crosslinking agent, a carbodiimide crosslinking agent, a crosslinking agent such as an oxazoline crosslinking agent, an anionic surfactant, and a nonionic surfactant. A surfactant such as an agent and a filler such as silica may be added.

There is no particular limitation on the method for applying the undercoat layer and the solvent of the coating solution used.
As a coating method, for example, a gravure coater or a bar coater can be used.
The solvent used for the coating solution may be water or an organic solvent such as toluene or methyl ethyl ketone. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.
When the substrate is a biaxially stretched film, the coating solution may be applied to the polymer substrate after biaxial stretching, or the first stretching is performed after the coating solution is applied to the polymer substrate after uniaxial stretching. Alternatively, the base material may be stretched in a different direction. Further, the substrate may be stretched in two directions after the coating solution is applied to the substrate before stretching.

  The protective sheet is represented by the specific polymer described above (non-siloxane structural unit and general formula (1)) by bringing the solar cell element into contact with the sealing agent of the battery side substrate sealed with the sealing material. Any polymer can be appropriately selected and produced as long as it can dispose a polymer layer containing (poly) siloxane structural unit). Especially, formation of a polymer layer can be most suitably performed with the manufacturing method of the protective sheet shown below.

[Colored layer]
In addition to the polymer layer, the backsheet may or may not be provided with a colored layer (preferably a light reflecting layer) substantially free of a polymer having a (poly) siloxane structure. In the case of providing such a colored layer, for example, a colored layer (especially a light reflecting layer) is sandwiched between the polymer substrate and the polymer layer described above, or on the side where the polymer layer of the polymer substrate is not provided. A colored layer may be provided. The colored layer in this case includes at least a polymer component other than the polymer having a (poly) siloxane structure and a pigment, and may further include other components such as various additives as necessary. In addition, about the detail of a pigment and various additives, it is the same as that of the case where the said polymer layer serves as a colored layer. There is no restriction | limiting in particular about polymer components other than the polymer which has a (poly) siloxane structure, According to the objective etc., it can select suitably.

  The term “substantially free” means that the polymer is not actively contained in the colored layer. Specifically, the polymer content in the colored layer is 15% relative to the total mass of the colored layer. It is said that it is below mass%, Preferably a colored layer does not contain a polymer (content is 0 (zero) mass%).

[Adhesive layer]
The protective sheet (especially the back sheet) has a polymer base on the side where the polymer layer is not provided (further, the colored layer (particularly the light reflecting layer) substantially not containing a polymer having a (poly) siloxane structure). On top of this, an easy-adhesive layer may or may not be provided.
The easy-adhesive layer seals a solar cell element (hereinafter also referred to as a power generation element) of a battery side substrate (battery body) when the protective sheet is used as a back sheet constituting a solar cell module, for example. It functions as a layer to adhere firmly to the material.

  The easy-adhesion layer can be formed using a binder and inorganic fine particles, and may further contain other components such as additives as necessary. The easy-adhesive layer is for a sealing material (for example, ethylene-vinyl acetate (EVA), polyvinyl butyral (PVB), epoxy resin, etc.) that seals the power generation element of the battery side substrate. The adhesive strength is preferably 10 N / cm or more, and more preferably 20 N / cm or more. 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, and applying a corona treatment to the surface of the back sheet that adheres 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 (registered trademark) S-120 and S-75N (both manufactured by Mitsui Chemicals) as specific examples of polyolefin, and Julimer (registered trademark) ET-410 and SEK as specific examples of acrylic resin. -301 (both manufactured by Nippon Pure Chemicals Co., Ltd.), as specific examples of composite resins of acrylic and silicone, Ceranate (registered trademark) WSA-1060, WSA-1070 (both manufactured by DIC Corporation) and Polydurex (registered trademark) ) H7620, H7630, H7650 (both manufactured by Asahi Kasei Chemicals Corporation) and the like.

The content of the binder in the easy adhesion layer is preferably in the range of ^{0.05g / m 2 ~5g / m 2} , the range of 0.08g ^{/ m 2} ~3g ^/ m 2 is more preferable. The content of the binder, 0.05 g / m ² or more is desired as easy adhesion obtained for that may give a better surface If it 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 nm to 700 nm, more preferably about 20 nm 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 [trade name, manufactured by Horiba, Ltd.].

  There is no restriction | limiting in particular in the shape of an inorganic fine particle, Any things, such as a spherical form, an indeterminate form, and a needle shape, can be used.

  The content of the inorganic fine particles is in the range of 5% by mass to 400% by mass with respect to the total mass of the binder in the easy-adhesive layer. When the content of the inorganic fine particles is 5% by mass or more, good adhesiveness can be maintained when exposed to a moist heat atmosphere, and when it is 400% by mass or less, the surface shape of a good easy-adhesive layer is obtained. It can be obtained. The content of the inorganic fine particles is more preferably in the range of 50% by mass to 300% by mass with respect to the total mass of the binder in the easy-adhesive layer.

-Crosslinking agent-
The easily adhesive layer can contain at least one crosslinking agent.
Suitable crosslinking agents for the easily adhesive layer include crosslinking agents such as epoxy crosslinking agents, isocyanate crosslinking agents, melamine crosslinking agents, carbodiimide crosslinking agents, and oxazoline 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 polymer layer section.

  5 mass%-50 mass% are preferable with respect to the total mass of the binder in an easily bonding layer, and, as for content in the easily bonding layer of a crosslinking agent, 20 mass%-40 mass% are more preferable. 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 is increased. Can keep.

-Additives-
If necessary, the easily adhesive layer may further contain a known matting agent such as polystyrene, polymethylmethacrylate and silica, and a known surfactant such as an anionic surfactant and a nonionic surfactant. May be.

-Method of forming easy-adhesive layer-
Examples of the method for forming the easy-adhesion layer include a method of bonding a polymer sheet having easy adhesion to a substrate, and a method by application of a coating solution for forming an easy-adhesion layer. Among these, the method by coating is preferable because it is simple and can form a uniform and thin film. 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.

Although there is no restriction | limiting in particular in the thickness of an easily bonding layer, Usually, 0.05 micrometer-8 micrometers are preferable, More preferably, it is the range of 0.1 micrometer-5 micrometers. 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 can be improved.
The easy-adhesive layer is substantially transparent so as not to affect the effect of the colored layer.

  When the protective sheet is used as a back sheet for a solar cell, the protective sheet is sealed for 48 hours in an atmosphere of 120 ° C. and 100% RH with the protective sheet adhered to the sealing material. The adhesive strength is preferably 75% or more with respect to the adhesive strength of the protective sheet to the sealing material before storage. As described above, the protective sheet includes a predetermined amount of binder and a predetermined amount of inorganic fine particles with respect to the binder, and an easy-adhesive layer having an adhesive force of 10 N / cm or more with respect to the EVA-based sealing material. By being provided, an adhesive strength of 75% or more can be obtained after the storage as compared with the adhesive strength before the storage. Thereby, as for a solar cell module provided with the said protection sheet, peeling of a back sheet | seat and the fall of the power generation performance accompanying it can be suppressed, and long-term durability can improve more.

<Manufacture of solar cell protective sheet>
As described above, the protective sheet may be produced by any method as long as it can form a polymer layer and, if necessary, a colored layer, an easy-adhesive layer, and the like on the polymer substrate. .
Among the above, the present invention applies a water-based coating solution containing a polymer having a structure containing a siloxane bond in a molecule, a lubricant, and water on a polymer substrate, and more than 0.2 g per m ² is 15 g. Forming a polymer layer containing the following polymer and 0.2 to 200 mg of the lubricant, wherein the polymer is a (poly) siloxane structural unit represented by the general formula (1) and a non-siloxane It is a copolymer having a structural unit, the (poly) siloxane structural unit represented by the general formula (1) in the molecule is 30 to 75 % by mass, and the non-siloxane structural unit is 70 by mass. look including a ~ 25 wt%, the lubricant is a synthetic wax compounds, natural wax-based compound, and at least one selected from the group consisting of surfactant compounds solar It is a manufacturing method of the pond for the protective sheet.

  The polymer layer can be formed by a method in which a polymer sheet is bonded to a polymer substrate, a method in which the polymer layer is coextruded when the polymer substrate is formed, a method by coating, or the like. Among these, the method by coating is preferable because it is simple and can form a uniform and thin film. In the case of coating, as a coating method, for example, a known coating method such as a gravure coater or a bar coater can be used.

  In the case of coating, the coating solvent for the coating solution may be either an aqueous system using water or a solvent system using an organic solvent such as toluene or methyl ethyl ketone. From the viewpoint of reducing environmental burden, it is preferable to prepare an aqueous coating solution using water as a coating solvent. A coating solvent may be used individually by 1 type, and may mix and use 2 or more types.

On one surface of the polymer substrate, a water-based coating solution containing a polymer having a (poly) siloxane structure in the molecule, a lubricant, water, and preferably a cross-linking agent (and, if necessary, a coating solution for an easily adhesive layer) ) To form at least one polymer layer containing 0.2 g / m ^{2 to} 15 g / m ² or less polymer and 0.1 mg / m ^{2 to} 50 mg / m ² lubricant as the outermost layer. A protective sheet can be suitably produced by a method including the layer forming step (a method for producing the protective sheet).

In the method for producing a protective sheet, polymer particles having a (poly) siloxane structure and a lubricant are prepared by mixing an aqueous dispersion of a polymer having a (poly) siloxane structure in a molecule with an aqueous dispersion of a lubricant (for example, wax). An embodiment is preferred in which an aqueous dispersion in which particles are dispersed and contained in water is prepared, and this aqueous dispersion is applied onto a desired polymer substrate as an aqueous coating liquid in the polymer layer forming step.
The details of the polymer substrate and the polymer, lubricant, and other components constituting each coating solution are as described above.

  In the polymer layer forming step, an aqueous coating solution for forming a 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 the polymer layer is formed as the outermost layer on the polymer substrate. Can be formed.

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

  After the application, a drying process for drying the coating film under desired conditions may be provided. What is necessary is just to select suitably about the drying temperature at the time of drying according to the case of the composition of a coating liquid, a coating amount, etc.

<Solar cell module>
The solar cell module is configured by providing the above-described protective sheet as a back sheet. The solar cell module which is one Embodiment of this invention is equipped with the said protection sheet. The polymer layer formed by coating has high film strength, excellent scratch resistance against scratching and scratching, and good light resistance, heat resistance, and moisture resistance. Thereby, the solar cell module exhibits excellent weather resistance and exhibits stable power generation performance over a long period of time.

  Specifically, the solar cell module is provided on a transparent base material (a front base material such as a glass substrate) on which sunlight enters and the base material, and the solar cell element and the solar cell element are sealed. An element structure portion having an encapsulant to be sealed, and the above-described back sheet (including the protective sheet) disposed on the side of the element structure portion opposite to the side on which the substrate is located. A front substrate / element structure portion / back sheet ”. Specifically, an element structure portion in which a solar cell element that converts light energy of sunlight into electrical energy is disposed, and a transparent front base material that is disposed on a side where sunlight directly enters, Between the front substrate and the back sheet, an element structure portion including a solar cell element (for example, a solar cell) is used with a sealing material such as an ethylene-vinyl acetate (EVA) system between the back sheet and the back sheet. The structure is sealed and bonded.

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

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

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

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

(Example 1)
-Production of polymer substrate-
<1> Synthesis of Polyester A slurry of 100 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) and 45 kg of ethylene glycol (manufactured by Nippon Shokubai Co., Ltd.) was previously charged with about 123 kg of bis (hydroxyethyl) terephthalate at a temperature of 250 kg. The esterification reaction vessel maintained at ° C. and a pressure of 1.2 × 10 ⁵ Pa was sequentially supplied over 4 hours. After completion of the supply, the esterification reaction was further performed for 1 hour. Thereafter, 123 kg of the obtained esterification reaction product was transferred to a polycondensation reaction tank.

  Subsequently, ethylene glycol was added to the polycondensation reaction tank to which the esterification reaction product had been transferred so that the amount was 0.3% by mass with respect to the obtained polymer. After stirring for 5 minutes, an ethylene glycol solution of cobalt acetate and manganese acetate was added in the obtained 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 mass% ethylene glycol solution of a titanium alkoxide compound was added so that the titanium element conversion 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 conversion value was 5 ppm in the obtained polymer. Thereafter, while stirring the obtained low polymerization degree 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. After continuing the reaction for 3 hours as it was, the reaction system was purged with nitrogen, returned to normal pressure, and the polycondensation reaction was stopped. Then, the obtained polymer melt was discharged into cold water in a strand form and immediately cut to produce polymer pellets (diameter: about 3 mm, length: about 7 mm).

  The titanium alkoxide compound is a titanium alkoxide compound (Ti content = 4.44 mass%) synthesized in Example 1 of paragraph No. [0083] of JP-A-2005-340616.

<2> Solid Phase Polymerization The pellets obtained above were held in a vacuum vessel maintained at 40 Pa at a temperature of 220 ° C. for 36 hours to perform solid phase polymerization.

<3> Production of film-like polymer substrate The pellets after solid-phase polymerization as described above are melt-extruded at 280 ° C. by a melt extruder and cast onto a metal drum. A stretched base was prepared. Then, it extended | stretched 3 times in MD direction (vertical direction; Machine Direction) at 90 degreeC, and also extended | stretched 3.3 times in TD direction (transverse direction; Transverse Direction) at 120 degreeC. Thus, a biaxially stretched polyethylene terephthalate substrate S-1 having a thickness of 250 μm (hereinafter sometimes referred to as “polymer substrate S-1”) was obtained.

  About this polymer base material S-1, the thermal contraction rate, breaking elongation retention, and the carboxyl group content were measured with the following method. As a result, the heat shrinkage rate was 0.4%, the elongation at break was 73%, and the carboxyl group content was 17 equivalents / ton.

-Measurement of physical properties of polymer substrate-
(1. Thermal contraction rate)
The obtained polymer substrate S-1 was conditioned for 24 hours in an atmosphere of 25 ° C. and 60% RH. Using a sample after moisture conditioning, with a two scratches parallel at about 30cm intervals on the sample surface with a razor, and measuring the distance L ^0. The scratched sample was heat treated by holding at 150 ° C. for 15 minutes. After heat-treating the sample after heat treatment in an atmosphere of 25 ° C. and 60% RH for 24 hours, an interval L ¹ between two scratches was measured.
The thermal contraction rate was calculated from the obtained L ⁰ and L ¹ using the following formula.
Thermal contraction rate [%] = {(L ⁰ −L ¹ ) / L ⁰ } × 100
The heat shrinkage rate was measured and calculated for each of the MD direction (longitudinal direction) and the TD direction (width direction) of the polymer base material, and the average value thereof was taken as the heat shrinkage rate of the polymer sheet. The unit of heat shrinkage is [%]. When the numerical value is positive, it indicates shrinkage, and when it is negative, it indicates elongation.

(2. Breaking elongation retention)
With respect to the obtained polymer substrate S-1, the elongation at break (%) was calculated from the following formula based on the measured values L ⁰ and L ¹ of the elongation at break obtained by the following measurement method. A practically acceptable range is one in which the elongation at break is 50% or more.
Elongation at break (%) = (L ¹ / L ⁰ ) × 100
<Measurement of elongation at break>
Sample pieces A and B for measurement were prepared by cutting the polymer substrate into a size of width 10 mm × length 200 mm. The sample piece A was conditioned in an atmosphere of 25 ° C. and 60% RH for 24 hours, and then subjected to a tensile test using a Tensilon universal material testing machine (trade name: RTC-1210A, manufactured by ORIENTEC). The measurement was performed by chucking each region from the end to 50 mm at both ends of the sample and setting the length of the stretched portion to 10 cm. The pulling speed was 20 mm / min. The elongation at break of the sample piece A obtained by this operation and L ^0.
Separately, the sample piece B was subjected to a wet heat treatment in an atmosphere of 120 ° C. and 100% RH for 50 hours, and then a tensile test was performed in the same manner as the sample piece A. The elongation at break of the sample piece B at this time is L ^1.

(3. Carboxyl group content)
The carboxyl group content (AV) was determined by completely dissolving the polymer substrate S-1 in a mixed solution of benzyl alcohol / chloroform (= 2/3; volume ratio), using phenol red as an indicator, and a standard solution (0.025N KOH -Methanol mixed solution) and calculated from the appropriate amount.

-Formation of undercoat layer-
(1) Preparation of coating solution for forming undercoat layer Each component in the following composition was mixed to prepare a coating solution for forming an undercoat layer.
<Composition of coating solution>
・ Polyester binder: 48.0 parts
(Byronal DM1245 (manufactured by Toyobo Co., Ltd., solid content: 30% by mass))
Carbodiimide compound (crosslinking agent) 10.0 parts (trade name: Carbodilite V-02-L2, manufactured by Nisshinbo Industries, Inc., solid content: 10% by mass)
Oxazoline compound (crosslinking agent) 3.0 parts (Epocross (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25% by mass)
-Surfactant ... 15.0 parts (Brand name: NAROACTY CL-95, manufactured by Sanyo Chemical Industries, Ltd., solid content: 1% by mass)
・ Distilled water ... 924.0 parts

(2) Formation of undercoat layer Corona treatment was performed on one surface of the polymer substrate S-1 using a corona treatment device (trade name: Solid State Corona Treatment Machine 6KVA model, manufactured by Pillar) under the following conditions. It was.
<Condition>
・ Electrode and dielectric roll gap clearance: 1.6mm
・ Processing frequency: 9.6 kHz
Processing speed: 20 m / min Processing intensity: 0.375 kV / A / min / m ²

Next, the coating solution for forming the undercoat layer was applied to the corona-treated surface of the polymer substrate S-1 so that the binder amount was 0.1 g / m ² in terms of the coating amount, dried at 180 ° C. for 1 minute, and dried. An undercoat layer having a thickness of about 0.1 μm was formed.

-Formation of light reflection layer-
(1) Preparation of Titanium Dioxide Dispersion Titanium dioxide dispersion was prepared by mixing components in the following composition and subjecting the mixture to a dispersion treatment for 1 hour using a dynomill type disperser.
<Composition of titanium dioxide dispersion>
・ Titanium dioxide (volume average particle size = 0.42 μm) 40.0 mass%
[Product name: Taipei R-780-2, manufactured by Ishihara Sangyo Co., Ltd., solid content: 100% by mass]
・ Polyvinyl alcohol: 28.0% by mass
[Product name: PVA-105, manufactured by Kuraray Co., Ltd., solid content: 10% by mass]
・ Surfactant ... 0.5% by mass
[Product name: Demall EP, manufactured by Kao Corporation, solid content: 10% by mass]
・ Distilled water ... 31.5 mass%

(2) Preparation of coating solution for light reflection layer The components in the following composition were mixed to prepare a coating solution for a light reflection layer.
<Composition of coating solution>
・ Titanium dioxide dispersion: 800.0 parts ・ Polyolefin binder: 108.0 parts [Product name: Arrow Base SE1010, manufactured by Unitika Ltd., solid content: 20 mass%]
-Polyoxyalkylene alkyl ether 30.0 parts [Brand name: NAROACTY CL-95, manufactured by Sanyo Chemical Industries, Ltd., solid content: 1% by mass]
Oxazoline compound: 20.0 parts [Epocross (registered trademark) WS-700, manufactured by Nippon Shokubai Co., Ltd., solid content: 25%; crosslinking agent]
・ Distilled water ... 42.0 parts

(3) Formation of light reflection layer The obtained coating solution was applied on the undercoat layer of the polymer substrate S-1 and dried at 180 ° C. for 1 minute, and the amount of titanium dioxide was 8.0 g as a colored layer. / ^{m 2,} the amount of binder to form a light reflective layer of 1.5 g / ^{m 2.}

-Formation of polymer layer 1-
(1) Preparation of coating solution for forming polymer layer 1 Each component in the following composition was mixed to prepare a coating solution for forming polymer layer 1.
<Composition of coating solution>
Acrylic / silicone binder (Binder B-1) 362.3 parts (Ceranate (registered trademark) WSA-1070 (polysiloxane structural unit content ratio: 30 mass%, non-polysiloxane structural unit content ratio: 70 mass%), manufactured by DIC Corporation, solid content: 40 mass%)
Carbodiimide compound (crosslinking agent) 36.2 parts (trade name: Carbodilite V-02-L2, manufactured by Nisshinbo Industries, Inc., solid content: 40% by mass)
-Surfactant 9.7 parts (Brand name: NAROACTY CL-95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
-Titanium dioxide dispersion ... 157.0 parts-Distilled water ... 434.8 parts

(2) Formation of polymer layer 1 The side opposite to the side where the light reflecting layer of the polymer substrate S-1 was formed (hereinafter also referred to as the back side) was subjected to corona treatment under the same conditions as described above. . Next, the coating solution for forming the polymer layer 1 is applied to the corona-treated surface on the back side of the polymer substrate S-1 so that the binder coating amount is 3.0 g / m ² and dried at 180 ° C. for 1 minute. A polymer layer 1 having a dry thickness of about 3 μm was formed.

-Formation of polymer layer 2-
(1) Preparation of coating solution for forming polymer layer 2 Each component in the following composition was mixed to prepare a coating solution for forming polymer layer 2.
<Composition of coating solution>
Acrylic / silicone binder (Binder B-1) 362.3 parts (Ceranate (registered trademark) WSA-1070 (polysiloxane structural unit: 30% by mass, non-polysiloxane structural unit: 70% by mass), DIC (Product made, solid content: 40 mass%)
Carbodiimide compound (crosslinking agent) 36.2 parts (trade name: Carbodilite V-02-L2, manufactured by Nisshinbo Industries, Inc., solid content: 40% by mass)
-Surfactant ... 24.2 parts (Brand name: NAROACTY CL-95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
・ Lubricant (polyethylene wax): 3.6 parts (Chemical (registered trademark) W950, manufactured by Mitsui Chemicals, solid content: 40% by mass)
-Matting agent (polymethyl methacrylate particles) ... 1.1 parts (trade name: MP-1000 (average particle size: 0.4 µm), manufactured by Soken Chemical Co., Ltd.)
・ Distilled water ... 575.5 parts

(2) Formation of polymer layer 2 The obtained coating solution for forming the polymer layer 2 was applied onto the polymer layer 1 so that the binder coating amount was 2.0 g / m ² and dried at 180 ° C. for 1 minute. Thus, a polymer layer 2 having a dry thickness of about 2 μm was formed.

  As described above, a back sheet having a coating layer formed on both sides of the polymer substrate S-1 was produced.

(Examples 2-6, Comparative Examples 1-2)
In Example 1, a back sheet was produced in the same manner as in Example 1 except that the amount of lubricant contained in the polymer layer 2 was changed as shown in Table 1 below.

(Examples 7-9, Comparative Examples 3-4)
In Example 1, a back sheet was produced in the same manner as in Example 1 except that the coating amount of the binder contained in the polymer layer 2 was changed as shown in Table 1 below.

(Examples 10 to 13)
In Example 1, a back sheet was produced in the same manner as in Example 1 except that the type of lubricant contained in the polymer layer 2 was changed as shown in Table 1 below.

(Example 14)
In Example 1, a back sheet was produced in the same manner as in Example 1 except that the corona treatment applied to the back side of the polymer substrate was not performed.

(Example 15)
In Example 1, as shown in Table 1 below, a back sheet was prepared in the same manner as in Example 1 except that the polymer layer 1 contained a matting agent and the polymer layer 2 contained no matting agent. Was made.

(Example 16)
In Example 1, a back sheet was produced in the same manner as in Example 1 except that the polymer layer 2 did not contain a matting agent.

(Examples 17-22, Comparative Examples 5-6)
In Example 1, the lubricant in the polymer layer 1 was changed as shown in Table 1 below, and the polymer layer 2 was not provided on the polymer layer 1 but a single polymer layer was formed on the back side. Produced a backsheet in the same manner as in Example 1.

(Examples 23 to 25, Comparative Examples 7 to 8)
A back sheet was produced in the same manner as in Example 1, except that the coating amounts of the binder and matting agent contained in the polymer layer 1 were changed as shown in Table 1 below.

(Example 26)
In the formation of the polymer layer 2 of Example 1, 362.3 parts of the acrylic / silicone binder used for the preparation of the coating solution for forming the polymer layer 2 was replaced with the following acrylic / silicone binder (binder B-2) 414.1. A back sheet was prepared in the same manner as in Example 1 except that 575.5 parts of distilled water was replaced with 523.7 parts instead of the parts.
・ Acrylic / silicone binder (Binder B-2)
(Ceranate (registered trademark) WSA-1060 (polysiloxane structural unit: 75 mass%, non-polysiloxane structural unit: 25 mass%), manufactured by DIC Corporation, solid content: 35 mass%)

(Example 27)
In the formation of the polymer layer 2 of Example 1, a back sheet was produced in the same manner as in Example 1 except that the coating liquid for forming the polymer layer 2 was prepared as follows.

The coating liquid for forming the polymer layer 2 was prepared by mixing each component in the following composition.
<Composition of coating solution>
Acrylic / silicone binder (Binder B-1) 362.3 parts (Ceranate (registered trademark) WSA-1070 (polysiloxane structural unit: 30% by mass, non-polysiloxane structural unit: 70% by mass), DIC (Made by Co., Ltd., solid content: 40% by mass)
Carbodiimide compound (crosslinking agent) 36.2 parts (trade name: Carbodilite V-02-L2, manufactured by Nisshinbo Industries, Inc., solid content: 40% by mass)
-Surfactant ... 24.2 parts (Brand name: NAROACTY CL-95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
・ Lubricant (polyethylene wax): 3.6 parts (Chemical (registered trademark) W950, manufactured by Mitsui Chemicals, solid content: 40% by mass)
Colloidal silica: 4.5 parts (Product name: Snowtex UP, manufactured by Nissan Chemical Co., Ltd., solid content: 20% by mass)
-1% aqueous solution of alkoxysilane compound 90.6 parts (trade name: TSL8430, manufactured by Toshiba Silicone Co., Ltd.)
・ Distilled water ... 481.2 parts

(Evaluation)
The following evaluation was performed about the backsheet produced by the Example and the comparative example. The evaluation results are shown in Table 1 below.

-1. Scratch resistance
The back sheet was conditioned for 24 hours in an atmosphere of 25 ° C. and 60% RH, and then the surface of the sheet was scratched with a sapphire needle having a tip diameter of 0.1 mm while changing the load at a speed of 1 cm / second. The surface of the sheet after scratching was observed with an optical microscope, and the lowest load at which scratches were observed was taken as a measure of scratch resistance. Larger values indicate better scratch resistance, and practically acceptable is 30 g or more.

-2. Dynamic friction coefficient
The back sheet was conditioned for 24 hours in an atmosphere of 25 ° C. and 60% RH. Thereafter, the surface of the sheet was scratched with a sapphire needle having a tip diameter of 1 mm at a speed of 1 cm / second and a load of 20 g, the drag F at this time was measured, and the friction coefficient μ was calculated from the following formula to calculate the dynamic friction coefficient.
μ = F / 20

-3. Plane-
The surface state of the back sheet was visually observed and evaluated according to the following evaluation criteria. Among these, ranks 4 and 5 are practically acceptable ranges.
<Evaluation criteria>
5: No unevenness, aggregates or repellency were observed.
4: Very weak unevenness and / or agglomerates were observed slightly (less than 3 / m ² ), but no repelling was observed.
3: Weak unevenness and / or aggregates were observed (less than 10 aggregates / m ² ), but no repelling was observed.
2: Slightly strong unevenness and / or aggregates were observed (aggregates of 10 / m ² or more and less than 20 / m ² ), and repelling was observed in part (less than 10 / m ² ).
1: Strong unevenness and / or agglomerates were observed (aggregates of 20 / m ² or more), and repelling was observed of 10 / m ² or more.

(Example 28)
3 mm thick tempered glass, EVA sheet 1 (trade name: SC50B, manufactured by Mitsui Chemicals Fabro Co., Ltd.), crystalline solar cell, and EVA sheet 2 (trade name: SC50B, manufactured by Mitsui Chemicals Fabro Co., Ltd.) ) And the back sheet of Example 1 in this order, and hot-pressing using a vacuum laminator (Nisshinbo Co., Ltd., vacuum laminating machine), tempered glass, EVA sheet 1, EVA sheet 2, and The back sheet was adhered. At this time, the back sheet produced in Example 1 was disposed so that the easy-adhesive layer was in contact with the EVA sheet 2. Moreover, the adhesion method is as follows.
<Adhesion method>
Using a vacuum laminator, evacuation was performed at 128 ° C. for 3 minutes, and then pressure was applied for 2 minutes to temporarily bond. Thereafter, the main adhesion treatment was performed in a dry oven at 150 ° C. for 30 minutes.
As described above, a crystalline solar cell module was produced. The produced solar cell module was allowed to stand for 70 hours under an environmental condition of 120 ° C. and 100% RH and then subjected to a power generation operation.

(Examples 29 to 54)
In Example 28, a solar cell module was produced in the same manner as in Example 28 except that the back sheet was replaced with the back sheet produced in Examples 2 to 27.
When the obtained solar cell module was subjected to power generation operation in the same manner as in Example 26, all showed good power generation performance as a solar cell.

Claims (10)

A solar cell protective sheet comprising a polymer substrate and a polymer layer that is an outermost layer disposed on one surface of the polymer substrate,
The polymer layer contains a polymer and a lubricant;
The polymer molecule has a structure containing a siloxane bond,
The polymer content in the polymer layer is more than 0.2 g and 15 g or less per 1 m ^{2 of the} polymer layer,
The content of the lubricant in the polymer layer is 0.2 mg or more and 200 mg or less per 1 m ^{2 of the} polymer layer, and the polymer is represented by the following general formula (1) (poly) siloxane structural unit and non-siloxane structure A (poly) siloxane structural unit represented by the general formula (1) in the molecule in a mass ratio of 30 to 75 % by mass, and a non-siloxane structural unit in a mass ratio of 70 to 75 % by mass. look including a 25% by weight,
The lubricant is at least one selected from the group consisting of synthetic wax compounds, natural wax compounds, and surfactant compounds.
The protective sheet.


[In the general formula (1), R ¹ and R ² each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group. n represents an integer of 1 or more. Here, R ¹ and R ² may be the same or different, and a plurality of R ¹ and R ² existing when n is 2 or more may be the same or different from each other. * Represents a position linked to an adjacent structural unit. ] The protective sheet according to claim 1, wherein the dynamic friction coefficient of the surface of the polymer layer is 0.4 or less. The polymer layer, a protective sheet according to claim 1 or claim 2 average secondary particle diameter contains a matting agent 0.3μm~10μm range of the polymer layer 1 m ² per 0.3Mg～30mg. The protective sheet according to any one of claims 1 to 3 , wherein the polymer layer further contains colloidal silica and an alkoxysilane compound. The protective sheet according to any one of claims 1 to 4 , wherein a surface of the polymer substrate on which the polymer layer is disposed is corona-treated. The lubricant is at least one selected from the group consisting of polyolefin wax, fatty acid metal salt, natural fatty acid ester compound, synthetic fatty acid ester compound, alkyl sulfate surfactant, and polyoxyethylene alkyl sulfate surfactant. The protective sheet according to any one of claims 1 to 5 , wherein the protective sheet is one. An aqueous coating solution containing a polymer having a structure containing a siloxane bond in the molecule, a lubricant, and water is applied onto a polymer substrate, and 0.2 g and 0.2 g of the above polymer is added in an amount of more than 0.2 g per 1 m ^2. Forming a polymer layer containing 200 mg or less of the lubricant, wherein the polymer has a (poly) siloxane structural unit and a non-siloxane structural unit represented by the following general formula (1): There, viewed contains 30 to 75% by weight represented by the above general formula (1) in the molecule (poly) siloxane structural unit weight ratio, a 70 to 25% by weight of the non-siloxane structural unit weight ratio, the lubricant, synthetic wax-based compound, natural wax-based compound, and at least is one method for producing a solar cell protective sheet is selected from the group consisting of surfactant compounds


[In the general formula (1), R ¹ and R ² each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group. n represents an integer of 1 or more. Here, R ¹ and R ² may be the same or different, and a plurality of R ¹ and R ² existing when n is 2 or more may be the same or different from each other. * Represents a position linked to an adjacent structural unit. ] The polymer layer is formed by mixing at least the aqueous dispersion of the polymer and the aqueous dispersion of the lubricant to prepare the aqueous coating liquid, and applying the prepared aqueous coating liquid on the polymer substrate. The manufacturing method of the protection sheet for solar cells of Claim 7 including apply | coating to. The back sheet for solar cells containing the protective sheet manufactured by the manufacturing method of the protective sheet of any one of Claims 1-6 , or the protective sheet for solar cells of Claim 7 or Claim 8. . A transparent substrate on which sunlight is incident;
An element structure portion provided on the base material and including a solar cell element and a sealing material for sealing the solar cell element;
The backsheet according to claim 9 , which is disposed on the side opposite to the side on which the base material of the element structure portion is located,
Including solar cell module.