JP2014221891A - Coating agent composition and backside protective sheet for solar cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating agent composition which is cured to form a coat layer capable of exhibiting excellent antiblocking properties while maintaining good adhesion to a substrate film, and to provide a backside protective sheet for a solar cell using the same.SOLUTION: A backside protective sheet 10 for a solar cell is constituted by providing a coat layer 12 formed of a coating agent composition on a substrate film 11. The coating agent composition forming the coat layer 12 contains as essential components: an acrylic copolymer (A) which has a polymer unit derived from a radically polymerizable acrylic compound (A-1) having a carboxyl group, a hydroxyl group, or an epoxy group as a reactive functional group, and a polymer unit derived from a radically polymerizable acrylic compound (A-2) having no reactive functional group; an isocyanate compound (B) having a plurality of isocyanate groups in one molecule; and an antiblocking agent (C).

Description

  The present invention relates to a coating agent composition suitable for forming a solar cell back surface protective sheet constituting a solar cell module and a solar cell back surface protective sheet using the same.

  Generally, a solar cell module includes a solar cell element, a back surface protection sheet (back surface protection base material) that supports the solar cell element, and a transparent base material (transparent glass plate, transparent resin sheet) provided on the light receiving side of the solar cell element. Etc.). In this solar cell module, in order to protect the solar cell element from the external environment, the solar cell element is sealed between the back surface protection sheet and the transparent substrate. Between the solar cell element and the base material and between the solar cell element and the back surface protection sheet, a sealant sheet made of EVA (ethylene-vinyl acetate copolymer resin) is interposed to form a laminate, A solar cell module is manufactured by vacuum / pressure forming while heating the laminate.

  Conventionally, various configurations have been proposed as back surface protection sheets that constitute solar cell modules. In these backside protection sheets, a coating composition containing a resin component is applied to the backside protection sheet, or films having different characteristics are laminated with adhesives to form multiple layers, thereby providing gas barrier properties such as water vapor and oxygen gas. And weathering resistance.

  Patent Document 1 discloses a highly weather-resistant polyester film used as this type of solar cell back surface protective sheet. That is, the highly weather-resistant polyester film is obtained by forming a coating film (coat layer) of a hydroxyl group-introduced acrylic resin to which an ultraviolet absorber or a hindered amine light stabilizer is added on one side or both sides of a polyester film. An isocyanate compound is added to the hydroxyl group-introduced acrylic resin, and a urethane bond is introduced by the reaction between the isocyanate group of the isocyanate compound and the hydroxyl group of the hydroxyl group-introduced acrylic resin. According to this polyester film, sufficient weather resistance and good coating film adhesion can be obtained.

  Further, Patent Document 2 discloses a solar cell back sheet (solar cell back surface protection sheet). This solar cell backsheet is formed by coating on at least one side of a polymer substrate containing first white inorganic particles and at least one side of the polymer substrate, and also contains a binder and second white inorganic particles. Layer (coat layer). The polymer substrate is polyester, and the binder is, for example, an acrylic resin. According to this solar cell backsheet, it is possible to obtain a solar cell module that has a high reflectance, is lightweight, and has good power generation efficiency.

JP 2005-15557 A JP 2011-165967 A

  By the way, the back surface protection sheet for solar cells in which a coating layer is formed on a base film such as a polyester film is stacked or rolled on the back surface protection sheet for solar cells before producing a solar cell module. Stored. In this case, in the solar cell back surface protection sheet of the conventional configuration described in Patent Documents 1 and 2, since the resin forming the coat layer is an acrylic resin such as a hydroxyl group-introduced acrylic resin, and has good adhesion, There was a problem that the blocking property that the sheets are in close contact with each other during storage of the back protective sheet for solar cells was large.

  In order to solve this problem, it is conceivable to change the resin forming the coating layer to one having low adhesion, but in this case, the adhesion between the coating layer and EVA is lowered, and the solar cell by thermocompression bonding is used. There was a problem that the adhesiveness between the element and the back surface protective sheet for solar cell deteriorated.

  Therefore, an object of the present invention is to provide a coating agent composition capable of exhibiting excellent anti-blocking properties while the coating layer formed by curing retains good adhesion to the base film. And it is providing the back surface protection sheet for solar cells using the same.

  In order to achieve the above object, the coating composition of the invention according to claim 1 is derived from a radical polymerizable acrylic compound (A-1) having a carboxyl group, a hydroxyl group or an epoxy group as a reactive functional group. An acrylic copolymer (A) having a polymer unit derived from the polymer unit and a radically polymerizable acrylic compound (A-2) having no reactive functional group, and a plurality of molecules in one molecule An isocyanate compound (B) having an isocyanate group and an antiblocking agent (C) are contained as essential components.

  The coating agent composition of the invention according to claim 2 is characterized in that, in the invention according to claim 1, the antiblocking agent (C) is stearic acid ester or waxes.

  The coating agent composition according to a third aspect of the present invention is the invention according to the first or second aspect, wherein the anti-blocking agent (C) has a melting point of 90 ° C. or lower.

  The coating agent composition of the invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the content of the antiblocking agent (C) is an acrylic copolymer (A ) 1 to 30 parts by mass with respect to 100 parts by mass.

  The coating agent composition of the invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the content of the isocyanate compound (B) is an acrylic copolymer (A). 10 to 120 parts by mass with respect to 100 parts by mass.

  The back surface protection sheet for solar cells of the invention described in claim 6 has a base film composed of at least one layer and a coat layer composed of at least one layer formed on at least one surface of the base film. It is a back surface protection sheet, Comprising: The said coating layer is a thing formed by hardening | curing the coating agent composition as described in any one of Claims 1-5.

  The back surface protection sheet for solar cells of the invention described in claim 7 is the invention according to claim 6, wherein the substrate film is formed of aluminum or a polyester resin.

According to the present invention, the following effects can be exhibited.
The coating agent composition of the present invention comprises a predetermined acrylic copolymer (A), an isocyanate compound (B) having a plurality of isocyanate groups in one molecule, and an antiblocking agent (C) as essential components. contains. The acrylic copolymer (A) has a polymer unit derived from a radical polymerizable acrylic compound (A-1) having a carboxyl group, a hydroxyl group or an epoxy group as a reactive functional group and a reactive functional group. It has a polymer unit derived from a radically polymerizable acrylic compound (A-2).

  For this reason, the carboxyl group, hydroxyl group or epoxy group of the acrylic copolymer (A) reacts with a plurality of isocyanate groups of the isocyanate compound (B) to form a crosslinked structure in the acrylic copolymer, weather resistance, While exhibiting characteristics such as heat resistance, a urethane bond or the like is formed to exhibit adhesiveness. Further, in the acrylic copolymer (A), a chain bond is formed by copolymerization of the radical polymerizable acrylic compounds (A-1) and (A-2), and the acrylic copolymer is formed by the chain bond. Flexibility is imparted to the polymer. Furthermore, since the anti-blocking agent (C) is contained in the coating agent composition, anti-blocking properties are imparted to the coating layer formed by the coating agent composition.

  Therefore, the coating agent composition of the present invention has an excellent effect that the coating layer formed by curing can exhibit excellent anti-blocking properties while maintaining good adhesion to the base film. Play.

Sectional drawing which shows the structure of the back surface protection sheet for solar cells in one Embodiment of this invention. Sectional drawing which shows the structure of the back surface protection sheet for solar cells in other embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.
As shown in FIG. 1, the back surface protection sheet 10 for solar cells is comprised by providing the coating layer 12 formed by hardening | curing a coating agent composition on the single side | surface of the base film 11. As shown in FIG. This solar cell back surface protection sheet 10 is provided on the back surface side opposite to the light receiving side of the solar cell element so as to support a solar cell element of a solar cell module (not shown).

  The base film 11 is formed of a metal such as aluminum or an aluminum alloy, or a polyester resin such as polyethylene terephthalate (PET), a polyolefin resin such as polypropylene, a synthetic resin such as a polyamide resin, a polystyrene resin, or a polycarbonate resin. Is done. The thickness of the base film 11 is set to about 3 to 300 μm. The base film 11 may be composed of two or more layers. Moreover, the coating layer 12 may be provided on both surfaces of the base film 11, and may be comprised by multiple layers, respectively.

  As shown in FIG. 2, the base film 11 constituting the solar cell back surface protective sheet 10 is a first base film 11 a and the second base film 11 a bonded to the first base film 11 a via an adhesive layer 13. It is comprised by the base film 11b. The back surface protection sheet 10 for solar cells is configured by providing a coat layer 12 on the second base film 11b. The thickness of the coat layer 12 is set to about 5 to 350 μm. When the thickness of the coat layer 12 is less than 5 μm, it is not preferable because the anti-blocking property based on the coat layer 12 cannot be sufficiently exhibited. On the other hand, when the thickness of the coat layer 12 is thicker than 350 μm, characteristics such as adhesion of the coat layer 12 to the base film 11 are not preferable.

  A suitable coating agent composition for forming the solar cell back surface protective sheet 10 includes a specific acrylic copolymer (A), an isocyanate compound (B) having a plurality of isocyanate groups in one molecule, and An antiblocking agent (C) is contained as an essential component. The acrylic copolymer (A) has a polymer unit derived from a radical polymerizable acrylic compound (A-1) having a carboxyl group, a hydroxyl group or an epoxy group as a reactive functional group and a reactive functional group. Not having a polymer unit derived from a radically polymerizable acrylic compound (A-2).

  Examples of the radical polymerizable acrylic compound (A-1) having a reactive functional group include (meth) acrylic acid, itaconic acid, maleic acid, crotonic acid, tiglic acid, cinnamic acid, (meth) acrylic acid- 1-hydroxyethyl, (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-1-hydroxypropyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-1-hydroxybutyl, glycidyl And methacrylate.

  Moreover, 4-hydroxybutyl acrylate glycidyl ether is illustrated as an ester of the glycidyl alcohol which added the epichlorohydrin to the polyhydric alcohol, and radically polymerizable unsaturated carboxylic acid, for example. Furthermore, an adduct of hydroxyethyl (meth) acrylate and ε-caprolactone can also be suitably used. It is also possible to use allyl alcohol or methacryl alcohol. In addition to the hydroxyl group, carboxyl group or epoxy group that reacts with the isocyanate compound (B) described later, the radical polymerizable acrylic compound (A-1), a functional group that does not react with the isocyanate compound (B) described later, For example, it may have an amide group, a carbonyl group, an amino group, or the like. In addition, in this specification, (meth) acryl shall mean the generic name of acryl and methacryl.

  On the other hand, examples of the radical polymerizable acrylic compound (A-2) having no reactive functional group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (n-propyl) (meth) acrylate, ( (Meth) acrylic acid isopropyl, (meth) acrylic acid-n-butyl, (meth) acrylic acid isobutyl, (meth) acrylic acid-t-butyl, (meth) acrylic acid-2-ethylhexyl, lauryl methacrylate, phenyl acrylate , (Meth) acrylic acid isobornyl, methacrylic acid cyclohexyl, (meth) acrylic acid-t-butylcyclohexyl, (meth) acrylic acid dicyclopentadienyl, (meth) acrylic acid dihydrodicyclopentadienyl, and the like. One or two or more of these radically polymerizable acrylic compounds (A-2) are appropriately selected and used.

  As for the acrylic copolymer (A), a radically polymerizable acrylic compound (A-1) having a reactive functional group and a radically polymerizable acrylic compound (A-2) having no reactive functional group are conventionally used. To form a copolymer. The ratio of the polymer unit derived from the radical polymerizable acrylic compound (A-1) constituting the acrylic copolymer (A) is preferably 0.1 to 10% by mass, more preferably 1 to 5% by mass. %. On the other hand, the ratio of the polymer unit derived from the radical polymerizable acrylic compound (A-2) constituting the acrylic copolymer (A) is preferably 90 to 99.9% by mass, more preferably It is 95-99.0 mass%.

  The said isocyanate compound (B) should just have a some isocyanate group in 1 molecule, and aliphatic polyisocyanate or aromatic polyisocyanate is used. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), dicyclohexylmethane diisocyanate (hydrogenated MDI), and the like. Examples of aromatic polyisocyanates include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (monomeric MDI), polymethylene polyphenylene polyisocyanate (polymeric MDI), tolidine diisocyanate (TODI), naphthalene diisocyanate (NDI), and xylylene diisocyanate. (XDI), tetramethyl-m-xylylene diisocyanate (TMXDI) and the like are used.

  The content of the isocyanate compound (B) is preferably 10 to 120 parts by mass and more preferably 15 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). When the content of the isocyanate compound (B) is less than 10 parts by mass, the reactivity between the isocyanate group of the isocyanate compound (B) and the reactive functional group of the radical polymerizable acrylic compound (A-1) becomes poor. The crosslinking density of the acrylic copolymer (A) is lowered, and the properties such as weather resistance and heat resistance of the cured product of the coating agent composition are lowered, which is not preferable. On the other hand, when the content of the isocyanate compound (B) is more than 120 parts by mass, the isocyanate group becomes excessive in the reaction between the isocyanate group and the reactive functional group of the radical polymerizable acrylic compound (A-1), The blocking prevention property of the hardened | cured material of a coating agent composition falls and it is not preferable.

  The anti-blocking agent (C) prevents the sheets from adhering to each other and causing blocking when the sheets formed by applying the coating agent composition to the base film are stacked or rolled. belongs to. Specific examples of the antiblocking agent (C) include stearic acid esters and waxes. Examples of stearic acid esters include stearic acid stearate (melting point 55 ° C.), dodecyl stearate (melting point 41 ° C.), monoglyceryl stearate (melting point 80 ° C.), and the like.

  Examples of waxes include modified polypropylene wax emulsion (melting point 90 ° C.), mixed wax emulsion of synthetic wax and natural wax (melting point 135 ° C.), polyethylene oxide wax emulsion (melting point 135 ° C.) and the like. Examples of the other antiblocking agent (C) include fine powders of modified organic polymers.

  As this antiblocking agent (C), when the base film 11 of the back surface protection sheet 10 for solar cells is a polyester resin especially, a thing with melting | fusing point of 90 degrees C or less is preferable. When the melting point of the anti-blocking agent (C) is higher than 90 ° C., it is not preferable because the adhesion of the coating layer 12 by the coating agent composition to the base film 11 made of polyester resin tends to decrease.

  The content of the anti-blocking agent (C) is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). When content of an antiblocking agent (C) is less than 1 mass part, the antiblocking property of a coating agent composition is not fully expressed but it is unpreferable. On the other hand, when the content of the anti-blocking agent (C) exceeds 30 parts by mass, the adhesion of the coat layer 12 to the base film 11 is lowered, or the coating film performance of the coat layer 12 is lowered. It is not preferable.

  As other components forming the coating agent composition, an antifoaming agent, a wetting agent, a thickening agent, an ultraviolet absorber, a film forming aid, an antifreezing agent and the like are used. As the antifoaming agent, a polyether-based antifoaming agent, a hydrophobic silica-based antifoaming agent, a modified silicone-based antifoaming agent, or the like is used. As the wetting agent, a silicone-containing oligomer, a nonionic surfactant, an anionic surfactant, or the like is used. As the thickener, a modified polyether resin, a urethane-modified polyether resin, or the like is used.

Next, the effect | action of the coating agent composition mentioned above and the back surface protection sheet 10 for solar cells using the same is demonstrated.
Now, as shown in FIG. 1, the back surface protection sheet 10 for solar cells is obtained by apply | coating a coating agent composition on the base film 11, and making it dry and harden | cure, and form the coating layer 12. FIG. The obtained back surface protection sheet 10 for solar cells is piled up and stored in order as it is, or rolled and stored.

  At this time, in addition to the acrylic copolymer and the isocyanate compound, the anti-blocking agent is blended in the coating agent composition used in the present embodiment, so that the solar cell back surface protective sheet 10 is in close contact with each other. Is suppressed. This anti-blocking property is obtained by appropriately selecting the type and blending amount of the anti-blocking agent in accordance with the base film 11, thereby improving the adhesion of the coat layer 12 to the base film 11 and the coating performance of the coat layer 12. Good performance without lowering.

  Further, the reactive functional group of the acrylic copolymer (A) reacts with a plurality of isocyanate groups of the isocyanate compound (B), and a crosslinked structure is formed in the acrylic copolymer so that the weather resistance of the coat layer 12 is improved. At the same time as characteristics such as heat resistance are expressed, urethane bonds and the like are formed, and the adhesion of the coating layer 12 to the base film 11 is enhanced. Furthermore, in the acrylic copolymer (A), a chain bond is formed by copolymerization of the radical polymerizable acrylic compounds (A-1) and (A-2), and the coat layer 12 is formed by the chain bond. Is given flexibility.

  Therefore, after storing the back surface protection sheet 10 for solar cells, the stacked back surface protection sheets 10 for solar cells can be easily peeled off, or the back surface protection sheet 10 for solar cells rolled can be easily rewound. . As a result, the solar cell module can be efficiently manufactured using the solar cell back surface protective sheet 10.

The effect exhibited by the above embodiment is described collectively below.
(1) The coating agent composition of this embodiment comprises a predetermined acrylic copolymer (A), an isocyanate compound (B) having a plurality of isocyanate groups in one molecule, an antiblocking agent (C), Is contained as an essential component. The acrylic copolymer (A) includes a polymer unit derived from a radical polymerizable acrylic compound (A-1) having a reactive functional group and a radical polymerizable acrylic compound having no reactive functional group ( It has a polymer unit derived from A-2).

  For this reason, the reactive functional group of the acrylic copolymer (A) reacts with a plurality of isocyanate groups of the isocyanate compound (B), and the adhesion of the coating layer 12 to the base film 11 is maintained, and acrylic A crosslinked structure is formed in the system copolymer, and properties such as weather resistance and heat resistance are exhibited. Furthermore, since the anti-blocking agent (C) is contained in the coating agent composition, anti-blocking properties are imparted to the coat layer 12.

Therefore, the coating agent composition of the present embodiment can exhibit excellent anti-blocking properties while the coating layer 12 formed by curing retains good adhesion to the base film 11. Excellent effect.
(2) Since the antiblocking agent (C) is a stearic acid ester or wax, the antiblocking agent (C) has improved lubricity and can improve the antiblocking property of the coat layer 12.
(3) Since the anti-blocking agent (C) has a melting point of 90 ° C. or lower, the anti-blocking property of the coat layer 12 can be improved when the base film 11 is particularly a polyester resin. .
(4) The content of the antiblocking agent (C) is set to 1 to 30 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). The anti-blocking property of the coat layer 12 can be satisfactorily exhibited without impairing the adhesion.
(5) The content of the isocyanate compound (B) is 10 to 120 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A), whereby the reactive functionality of the acrylic copolymer (A). The isocyanate group of the isocyanate compound (B) reacts sufficiently with the group, a crosslinked structure is formed in the acrylic copolymer (A), and the coating layer 12 has excellent weather resistance, heat resistance and other characteristics. be able to.
(6) The back surface protection sheet 10 for solar cells is formed by the base film 11 and the coat layer 12 formed by curing the coating agent composition on the base film 11. Therefore, the back surface protection sheet 10 for solar cells can improve antiblocking property, maintaining the adhesiveness of the coating layer 12 with respect to the base film 11. FIG.
(7) The base film 11 is made of aluminum or a polyester resin. For this reason, the adhesiveness of the coat layer 12 with respect to the base film 11 can be improved.

Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples.
The acrylic copolymer emulsion, antiblocking agent, isocyanate compound, antifoaming agent, wetting agent and thickening agent used in the following examples and comparative examples will be described.
(Emulsion of acrylic copolymer)
This acrylic copolymer emulsion (acrylic emulsion) is a radical polymerizable acrylic compound (A-1) having a reactive functional group, 2 parts by mass of acrylic acid, and a radical polymerizable acrylic having no reactive functional group. It is an emulsion (solid content: 13.8% by mass) obtained by copolymerizing 30 parts by mass of cyclohexyl methacrylate, 30 parts by mass of butyl methacrylate and 37 parts by mass of 2-ethylhexyl acrylate as an aqueous compound (A-2).
(Organic inorganic hybrid emulsion)
The organic-inorganic hybrid emulsion is an emulsion of 24-34% by mass of a copolymer of acrylic acid ester and methacrylic acid ester, 10-20% by mass of silica and residual water.
(Anti-blocking agent)
C-1: Stearic acid stearate (melting point 55 ° C.)
C-2: Modified polypropylene wax emulsion (melting point 90 ° C.)
C-3: Mixed wax emulsion of synthetic wax and natural wax (melting point 135 ° C.)
C-4: Polyethylene oxide wax emulsion (melting point 135 ° C.)
C-5: Fine powder of modified organic polymer (melting point 175 ° C.)
(Defoamer)
D-1: Polyether-based antifoaming agent D-2: Hydrophobic silica-based antifoaming agent (wetting agent)
E-1: Silicone-containing oligomer E-2: Nonionic surfactant E-3: Anionic surfactant (thickening agent)
F-1: Modified polyether-based resin F-2: Urethane-modified polyether-based resin (Example 1)
In Example 1, 100 parts by mass of the above acrylic copolymer emulsion (acrylic emulsion) as a solid content, 91.3 parts by mass of an organic-inorganic hybrid emulsion, and stearic acid stearate (C-1) 4 as an antiblocking agent 0.9 parts by mass, 21.7 parts by mass of hexamethylene diisocyanate as an isocyanate compound, 3.6 parts by mass of a polyether antifoaming agent (D-1) as an antifoaming agent, and a silicone-containing oligomer (E-1) as a wetting agent, As a thickener, 1.7 parts by mass of a modified polyether resin (F-1) and 2.6 parts by mass of a urethane-modified polyether resin (F-2) were mixed to prepare a coating agent composition.

  Next, an aluminum film having a length of 10 cm, a width of 10 cm, and a thickness of 0.25 cm (250 μm) was prepared as the base film 11 on which the coating composition was applied. On the aluminum film, the coating agent composition was applied with a bar coater so as to have a dry film thickness of 30 μm, and then heated at 100 ° C. for 10 minutes to cure the coating agent composition. A test piece was formed.

About the produced test piece, blocking prevention property, aluminum adhesiveness, and coating-film performance were evaluated by the method shown below, and those results were shown in Table 1.
(Anti-blocking property)
A polyester (PET) film is bonded onto the coat layer 12 of the test piece, a test body sandwiched between slate plates is clamped with a U-shaped clamp, held in a thermostatic bath at 170 ° C. for 1 hour, taken out, and the polyester film is peeled off. The anti-blocking property was evaluated according to the following criteria.

A: No blocking was observed at all. A: Almost no blocking and good. Δ: Some blocking was observed, but there was no problem. X: Blocking was clearly seen and was bad.
(Aluminum adhesion)
Aluminum adhesion is determined in accordance with JIS K5600-5-6: 1999 [Adhesion (Cross-cut method)], and the evaluation after the test is as follows. did.
(Coating performance)
About the coating film (coat layer 12) as the back surface protection sheet 10 for solar cells by the said coating agent, items, such as repellency, a pinhole, workability | operativity, were evaluated comprehensively and the following reference | standard evaluated.

○: All items were good and the coating film performance was excellent overall. Δ: Although the performance was slightly inferior, the coating film performance was generally good. X: There were items with poor performance, and the coating film performance was poor overall.
(Examples 2 to 14 and Comparative Example 1)
A coating composition as in Example 1 except that the acrylic copolymer emulsion, organic-inorganic hybrid emulsion, isocyanate compound, antifoaming agent, wetting agent and thickener were changed as shown in Table 1. And a test piece was produced using the coating composition. About the produced test piece, it carried out similarly to Example 1, and evaluated antiblocking property, aluminum adhesiveness, and coating-film performance. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 14, the coating agent composition contains a predetermined acrylic copolymer, an isocyanate compound, and an antiblocking agent, so that the aluminum adhesion is maintained. In addition to exhibiting excellent anti-blocking properties, it was possible to exhibit good coating performance. Therefore, it was confirmed that the coat layer 12 formed from the coating agent compositions of Examples 1 to 14 is excellent as the coat layer 12 for the back surface protection sheet 10 for solar cells.

On the other hand, in Comparative Example 1 in which no antiblocking agent was blended, the aluminum adhesion and the coating film performance were good, but the antiblocking property was poor.
(Examples 15 to 25, Comparative Examples 2 and 3)
In Examples 15 to 25, an acrylic copolymer, hexamethylene diisocyanate, and an anti-blocking agent were used in the types and blending amounts shown in Table 2 to prepare coating agent compositions. In Comparative Examples 2 and 3, a coating agent composition containing no antiblocking agent was prepared. And about each coating agent composition, blocking prevention property, aluminum adhesiveness, and coating-film performance were evaluated similarly to Example 1, and those results were shown in Table 2.

As shown in Table 2, in Examples 15 to 25, while being able to exhibit excellent anti-blocking properties while maintaining aluminum adhesion, it was possible to demonstrate good coating performance. Moreover, the result at the time of changing content of an antiblocking agent was shown to Examples 20-25. When the content of the anti-blocking agent is 0.5 parts by mass (Example 20), the anti-blocking property decreases, and when the content of the anti-blocking agent is 35 parts by mass (Example 25). The aluminum adhesion and the coating film performance decreased. On the other hand, in Examples 21-24 which made content of an antiblocking agent 2.2-14.5 mass parts, aluminum adhesiveness, antiblocking property, and coating-film performance were all excellent. Therefore, it was shown that the content of the blocking inhibitor is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the acrylic copolymer.

On the other hand, in Comparative Example 2, since the anti-blocking agent was not blended in the coating agent composition, the anti-blocking property was poor and the coating film performance was also lowered. In Comparative Example 3, since the anti-blocking agent was not blended in the coating agent composition, the anti-blocking property was poor.
(Examples 26 to 33)
In Examples 26 to 33, the acrylic copolymer, hexamethylene diisocyanate, and anti-blocking agent were used in the types and blending amounts shown in Table 3 to prepare coating agent compositions. In this case, the content of hexamethylene diisocyanate was mainly changed. And about each coating agent composition, blocking prevention property, aluminum adhesiveness, and coating-film performance were evaluated similarly to Example 1, and those results were shown in Table 3.

As shown in Table 3, Examples 26 to 33 were able to maintain aluminum adhesion, exhibit excellent anti-blocking properties, and exhibit excellent coating performance. Further, when the content of hexamethylene diisocyanate was 7.2 parts by mass (Example 26), the coating film performance was lowered, and when the content of hexamethylene diisocyanate was 100 parts by mass (Example 30). And when it was 130 mass parts (Example 31), the coating-film performance and the blocking prevention property fell. On the other hand, in Examples 27 to 29 in which the content of hexamethylene diisocyanate was 21.7 to 50.0 parts by mass, all of aluminum adhesion, antiblocking property and coating film performance were good. Therefore, it was shown that the content of hexamethylene diisocyanate is preferably 15 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer.
(Examples 34 to 38 and Comparative Example 4)
In Examples 34 to 38, the acrylic copolymer, hexamethylene diisocyanate, and anti-blocking agent were used in the types and blending amounts shown in Table 4 to prepare coating agent compositions. Moreover, in the comparative example 4, the coating agent composition in which the antiblocking agent was not mix | blended was prepared. Then, a polyester (PET) film having a length of 10 cm, a width of 10 cm, and a thickness of 0.25 cm was used as the base film 11, and a coating composition was applied on the PET film in the same manner as in Example 1 to prepare a test piece did. About this test piece, blocking prevention property, polyester adhesiveness, and coating-film performance were evaluated similarly to Example 1, and those results were shown in Table 4.

As shown in Table 4, in Examples 34 to 38, while maintaining good polyester adhesion, it was possible to demonstrate good anti-blocking properties and to exhibit good coating film performance. On the other hand, in Comparative Example 4, since the antiblocking agent was not blended in the coating composition, the polyester adhesion and the coating film performance were good, but the antiblocking property was poor.

It should be noted that the embodiment described above can be modified and embodied as follows.
-You may comprise at least 1 sort (s) of the acrylic copolymer (A) which is an essential component of the said coating agent composition, an isocyanate compound (B), and an antiblocking agent (C) with multiple types of components, respectively.

  -As the radical polymerizable acrylic compound (A-1) that forms the acrylic copolymer (A), a radical polymerizable acrylic compound having a plurality of types of reactive functional groups may be used. Moreover, you may use one type of radically polymerizable acrylic compound as a radically polymerizable acrylic compound (A-2).

  -A triisocyanate compound having three isocyanate groups may be used as the isocyanate compound (B).

  DESCRIPTION OF SYMBOLS 10 ... Back surface protection sheet for solar cells, 11 ... Base film, 11a ... 1st base film, 11b ... 2nd base film, 12 ... Coat layer.

Claims (7)

Polymer unit derived from radical polymerizable acrylic compound (A-1) having carboxyl group, hydroxyl group or epoxy group as reactive functional group and radical polymerizable acrylic compound having no reactive functional group (A-2) ) An acrylic copolymer having a polymer unit derived from (A), an isocyanate compound having a plurality of isocyanate groups in one molecule (B), and an antiblocking agent (C) as essential components A coating agent composition characterized by comprising: The coating agent composition according to claim 1, wherein the antiblocking agent (C) is a stearic acid ester or a wax. The coating agent composition according to claim 1 or 2, wherein the anti-blocking agent (C) has a melting point of 90 ° C or lower. The content of the anti-blocking agent (C) is 1 to 30 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). The coating agent composition according to item. The content of the isocyanate compound (B) is 10 to 120 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). The coating agent composition described in 1. A back protective sheet for solar cells, comprising a base film comprising at least one layer and a coat layer comprising at least one layer formed on at least one side of the base film,
The said coat layer is a thing formed by hardening | curing the coating agent composition as described in any one of Claims 1-5, The back surface protection sheet for solar cells characterized by the above-mentioned. The said base film is formed with aluminum or the polyester-type resin, The back surface protection sheet for solar cells of Claim 6 characterized by the above-mentioned.