JP2013129751A - Easy adhesive for solar cell back surface protection sheet, solar cell back surface protection sheet, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy adhesive for solar cell back surface protection sheet, whose conventional problem has been overcome, and which is excellent in adhesivity and adhesive durability; and to provide a solar cell back surface protection sheet, and a solar cell module using the solar cell back surface protection sheet.SOLUTION: The easy adhesive for solar cell back surface protection sheet contains: a (meth)acrylic copolymer (A) having a specific glass transition temperature, number-average molecular weight and hydroxide value, and having no (meth)acryloyl group; a compound (B) having a (meth)acryloyl group; and a polyisocyanate compound (C) in specific proportions.

Description

  TECHNICAL FIELD The present invention relates to an easy-adhesive for a solar cell back surface protective sheet, and particularly relates to an easy-adhesive for a solar cell back surface protective sheet that is excellent in adhesion and adhesion durability. Furthermore, this invention relates to the solar cell module which uses the said solar cell back surface protection sheet easy-to-adhesive agent, and also uses this sheet | seat.

In recent years, solar cells have been attracting attention as a clean energy source free from environmental pollution due to an increase in awareness of environmental problems, and earnestly researched and put into practical use from the viewpoint of using solar energy as a useful energy resource.
There are various types of solar cell elements, and typical examples thereof include a crystalline silicon solar cell element, a polycrystalline silicon solar cell element, an amorphous silicon solar cell element, a copper indium selenide solar cell element, and a compound semiconductor solar. Battery elements and the like are known. Among these, polycrystalline silicon solar cell elements, amorphous silicon solar cell elements, and compound semiconductor solar cell elements are relatively low cost and can be increased in area. It has been broken. Among these solar cell elements, thin film solar cell elements represented by amorphous silicon solar cell elements in which silicon is laminated on a conductive metal substrate and a transparent conductive layer is further formed thereon are lightweight. Since it is rich in impact resistance and flexibility, it is considered promising as a future form of solar cells.

  A simple one of the solar cell modules has a configuration in which a sealing agent and a glass plate are sequentially laminated on both surfaces of the solar cell element. A glass plate is still generally used as a protective material on the light receiving surface side of the sun because it is excellent in transparency, weather resistance, and scratch resistance. However, on the non-light-receiving surface side that does not require transparency, various solar cell back surface protection sheets other than glass plates (hereinafter also referred to as “back surface protection sheet”) have been proposed in terms of cost, safety, and workability. (For example, Patent Document 1), a glass plate is being replaced with a back surface protection sheet. As the sealant, an ethylene-vinyl acetate copolymer (hereinafter referred to as “EVA”), which is highly transparent and excellent in moisture resistance, is usually used.

As the back surface protection sheet, (i) a monolayer film such as a polyester film, (ii) a polyester film provided with a vapor deposition layer of a metal oxide or a non-metal oxide, (iii) a polyester film, a fluorine-based film Examples include multilayer films in which films such as films, olefin films, and aluminum foils are laminated.
The back surface protective sheet having a multilayer structure can impart various performances due to the multilayer structure. For example, insulating properties can be imparted by using a polyester film, and water vapor barrier properties can be imparted by using an aluminum foil (see Patent Documents 2 to 4).
What kind of back surface protection sheet is used can be appropriately selected depending on the product and application in which the solar cell module is used.

  Among various performances required for the back surface protection sheet, adhesion to the sealant and adhesion durability are basic and important performance requirements. If the adhesiveness with the sealant is insufficient, the back surface protective sheet is peeled off, and the solar cell cannot be protected from moisture or external factors, leading to deterioration of the output of the solar cell.

  On the other hand, in EVA used as a sealant, solar cell modules using EVA, which is called fast cure type, in which thermal crosslinking reaction efficiency is remarkably improved as compared with conventional standard cure types, are increasing. This is because, in the case of solar cell module manufacturing, in the standard cure type, in addition to the vacuum laminating step (for example, 120 ° C. to 150 ° C. for 60 minutes to 90 minutes), the curing step (for example, 120 ° C. to 150 ° C. for 60 minutes) However, in the fast cure type, the curing process can be omitted, so that the production equipment can be simplified and the productivity can be improved. However, compared with the standard cure type EVA, the fast cure type EVA has a drawback that it is difficult to adhere to the solar cell back surface protective sheet.

  Then, as a method of ensuring the adhesiveness between the solar cell back surface protective sheet and the sealant, (1) a method of performing an easy adhesion treatment on the surface of the back surface protective sheet in contact with the sealant, or (2) the back surface protective sheet The method of using a film with high adhesiveness with a sealing agent is mentioned to the surface which touches a sealing agent.

Examples of the method (1) include surface treatment such as corona treatment, and easy adhesion coating treatment in which an easy adhesive is applied.
However, the former surface treatment such as corona treatment ensures initial adhesion, but has a problem of poor adhesion durability.
Patent Documents 1, 5, and 6 disclose easy adhesives used in the case of the latter easy adhesive coating treatment.

Patent Document 5 includes a crosslinking agent selected from the group consisting of an oxazoline group-containing polymer, a urea resin, a melamine resin, and an epoxy resin, and a crosslinking agent selected from a polyester resin or an acrylic resin having a glass transition point of 20 to 100 ° C. A coating liquid containing a resin component is disclosed (see claims 3 and 4 of the same document). More specifically, an example using a coating liquid containing an epoxy resin and an acrylic resin is described (see Example 5 of the same document).
However, the adhesive strength with the EVA sheet in this example is about 10 to 20 N with a width of 20 mm (that is, 7.5 to 15 N with a width of 15 mm) (see Table 2 of the same document). Since the adhesiveness between the sealant and the back surface protective sheet greatly affects the output deterioration of the solar cell, higher adhesiveness is required in the market, and reliability of adhesive performance under more severe conditions is required. Therefore, an adhesive strength of about 20 N with a width of 20 mm cannot meet such market demands. In Patent Document 1, although the adhesive force is improved, a higher performance easy-adhesive is required in the market.

  Patent Document 6 discloses a back surface of an adhesion improving layer in which at least one resin selected from the group consisting of a polyester-based resin and a polyester polyurethane-based resin is cross-linked with an alkylated melamine or a polyisocyanate cross-linking agent on a polyester film. The structure provided in the surface which contact | connects the sealing agent of a protective sheet is disclosed.

For example, Patent Document 7 discloses polybutylene terephthalate (PBT) as the method of (2) above (a method of using a film having high adhesiveness with the sealant on the surface of the back surface protective sheet that contacts the sealant). How to use is described.
However, since such a film generally has a thickness of several tens of μm, the cost becomes higher than the above easy adhesion treatment.

In addition, although it is the patent document published after the previous application used as the foundation of priority, in patent document 8, the following general formula is attached to the surface bonded with the filler (sealing agent) which comprises a solar cell module. A back sheet for a solar cell module is disclosed in which an adhesive layer made of an acrylic adhesive containing an acrylic polymer obtained by polymerizing a monomer component containing the monomer represented by (I) is formed.
<Of ^{_{1> CH 2 = C (R}} 1) -CO-OZ
However, ^{R 1} is a hydrogen atom or a methyl group, Z is a hydrocarbon group having 4 to 25 carbon atoms.
Patent Document 9 discloses a polymer having a fluorine copolymer, an acrylic copolymer, or a polyurethane copolymer (polymer a) and one or more ethylenically unsaturated groups for photocuring. Solar cell having a primer layer comprising a monomer and / or oligomer (monomer b) and / or a compound (polyisocyanate c) containing one or more ethylenically unsaturated groups and two or more isocyanate groups in the molecule An element back surface protection sheet is disclosed.
However, adhesion to fast cure type EVA is not sufficient.

JP 2009-246360 A Japanese Patent Laid-Open No. 2004-200322 JP 2004-223925 A JP 2001-119051 A JP 2006-152013 A JP 2007-136911 A JP 2010-114154 A JP 2010-263193 A JP 2011-18872 A

  The subject of this invention is providing the solar cell module which uses the easily adhesive agent for solar cell back surface protection sheets which is excellent in adhesiveness and adhesion durability, a solar cell back surface protection sheet, and this solar cell back surface protection sheet. is there.

The present invention has a glass transition temperature exceeding 60 ° C. and not more than 100 ° C., a number average molecular weight of 15,000 to 250,000, a hydroxyl value of 2 to 100 (mgKOH / g), and no (meth) acryloyl group. (Meth) acrylic copolymer (A),
A compound (B) having a (meth) acryloyl group;
Easy adhesive for solar cell back surface protection sheet containing polyisocyanate compound (C) whose isocyanate group is in the range of 0.1 to 5 for one hydroxyl group in the acrylic copolymer (A) About.

The content of the compound (B) having a (meth) acryloyl group is 0.1 to 20 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A) having no (meth) acryloyl group. preferable.

  The polyisocyanate compound (C) is preferably a blocked polyisocyanate (C1). Furthermore, the compound (B) having the (meth) acryloyl group preferably has two or more (meth) acryloyl groups in the molecule.

  Furthermore, this invention relates to the solar cell back surface protection sheet (V ') which comprises the easily adhesive layer (D') formed with the said easily adhesive agent for solar cell back surface protection sheets, and a plastic film (E).

Furthermore, the present invention relates to a solar cell surface protective material (I) located on the light receiving surface side of the solar cell, a sealant (II) located on the light receiving surface side of the solar cell, a solar cell (III), The solar cell back surface protection sheet (V) which is located on the non-light-receiving surface side and is formed from the sealing agent (IV) containing an organic peroxide and the solar cell back surface protection sheet (V ′) according to claim 4. A solar cell module comprising:
The solar cell module is characterized in that the hard adhesive layer (D) of the hard adhesive layer (D ′) is in contact with the non-light-receiving surface side sealing agent (IV).

  Moreover, it is preferable that the sealing agent (IV) on the non-light-receiving surface side contains an organic peroxide. Furthermore, the sealant on the non-light-receiving surface side is preferably a fast cure type ethylene-vinyl acetate copolymer (EVA).

  By using the easy adhesive for solar cell back surface protective sheet of the present invention, the easy adhesive for solar cell back surface protective sheet, the solar cell back surface protective sheet, and the solar cell back surface protective sheet excellent in adhesion and adhesion durability It has the outstanding effect that the solar cell module to be used can be provided. By using the solar cell back surface protective sheet of the present invention, it is possible to provide a solar cell module having a small output drop even when exposed to a high temperature and high humidity environment for a long time.

It is a figure which shows typically the cross section of the module for solar cells of this invention.

  Hereinafter, the present invention will be described in detail. Needless to say, other embodiments are also included in the scope of the present invention as long as they meet the spirit of the present invention. In addition, the numerical value range specified by using “to” in this specification includes numerical values described before and after “to” as ranges of the lower limit value and the upper limit value. In this specification, “film” and “sheet” are not distinguished by thickness. In other words, the “sheet” in this specification includes a thin film-like material, and the “film” in this specification includes a thick sheet-like material.

  FIG. 1 is a schematic cross-sectional view of a solar cell module according to the present invention. The solar cell module 100 includes a solar cell surface protective material (I), a light-receiving surface side sealant (II), a solar cell (III), a non-light-receiving surface side sealant (IV), and a solar cell back surface protection. At least the sheet (V) is included. The light receiving surface side of the solar battery cell (III) is protected by the solar cell surface protecting material (I) through the sealant (II) on the light receiving surface side. On the other hand, the non-light-receiving surface side of the solar battery cell (III) is protected by the solar battery back surface protective sheet (V) through the sealant (IV) on the non-light-receiving surface side. On the surface layer in contact with the solar cell back surface protective sheet (V) on the non-light-receiving surface side, an easy adhesive layer made of an easy adhesive for the solar cell back surface protective sheet is laminated.

  The easy-adhesive layer (D ′) formed by the easy-adhesive for solar cell back surface protective sheet of the present invention undergoes a cross-linking reaction using a thermocompression bonding step when forming the solar cell module 100. In the present invention, the easy-adhesive layer before the thermocompression bonding step is distinguished as the easy-adhesive layer (D ′), and the cross-linked easy-adhesive layer after the thermocompression bonding step is distinguished as the easy-adhesive layer (D). Similarly, the solar cell back surface protection sheet before the thermocompression bonding process is distinguished as a solar cell back surface protection sheet (V ′), and the solar cell back surface protection sheet after the thermocompression bonding process is distinguished as a solar cell back surface protection sheet (V).

The (meth) acrylic copolymer (A) having no (meth) acryloyl group contained in the easy-adhesive for solar cell back surface protective sheet of the present invention will be described.
The (meth) acrylic copolymer (A) has a glass transition temperature exceeding 60 ° C. and not more than 100 ° C., a number average molecular weight of 15,000 to 250,000, and a hydroxyl value of 2 to 100 (mgKOH / g). .

When the glass transition temperature of the (meth) acrylic copolymer (A) exceeds 100 ° C., the coating film of the easy-adhesive agent becomes hard and the adhesive force to the sealing agent decreases. When the glass transition temperature is low, the easy-adhesive layer before the curing treatment is soft, and therefore it is relatively easy to ensure the initial adhesive force against EVA after curing. However, when the glass transition temperature is too low, that is, when the glass transition temperature is less than 60 ° C., the initial adhesive force for fast cure type EVA can be ensured, but the easy-adhesive layer after curing is too soft. It becomes difficult to maintain durability such as heat and moisture resistance and weather resistance.
The glass transition temperature here is a glass transition temperature measured by differential scanning calorimetry (DSC) for a resin obtained by drying the (meth) acrylic copolymer (A) to a solid content of 100%. Indicates. For example, for the glass transition temperature, an aluminum pan containing a sample obtained by weighing about 10 mg of a sample and an aluminum pan containing no sample are set in a DSC apparatus, and this is set to −50 using liquid nitrogen in a nitrogen stream. A rapid cooling treatment is performed until the temperature is increased to 100 ° C. at 20 ° C./min, and a DSC curve is plotted. The slope of the DSC curve on the low temperature side (the DSC curve portion in the temperature region where no transition or reaction occurs in the test piece) is extended to the high temperature side, and the slope of the step change portion of the glass transition is maximized. From the intersection with the tangent drawn at such a point, the extrapolated glass transition start temperature (Tig) can be determined, and this can be determined as the glass transition temperature. The glass transition temperature of this invention has described the value measured by said method.

When the number average molecular weight of the (meth) acrylic copolymer (A) exceeds 250,000, the adhesive force to the sealant is reduced. The wet heat resistance of the film is lowered, and the adhesive force to the sealant is lowered after the wet heat test. The number average molecular weight of the (meth) acrylic copolymer (A) is preferably 25,000 to 150,000, more preferably 25,000 to 100,000, and more preferably 25,000 to More preferably, it is 80,000.
In addition, said number average molecular weight is the value of polystyrene conversion by the gel permeation chromatography (GPC) of a (meth) acrylic-type copolymer (A). For example, the temperature of the columns (KF-805L, KF-803L, and KF-802 manufactured by Showa Denko KK) is 40 ° C., THF is used as the eluent, the flow rate is 0.2 ml / min, and the detection is RI. The sample concentration was 0.02%, and polystyrene was used as a standard sample. The number average molecular weight of the present invention describes the value measured by the above method.

  It is important that the hydroxyl value of the (meth) acrylic copolymer (A) is 2 to 100 mgKOH / g in terms of solid content, preferably 2 to 50 mgKOH / g, and more preferably 2 to 30 mgKOH / g. It is more preferable. When the hydroxyl value of the (meth) acrylic copolymer (A) exceeds 100 mgKOH / g, the cross-linking of the easy-adhesive coating film becomes dense and the adhesive force to the plastic film (E) is reduced. Even if it is initially bonded, the crosslinking reaction may proceed during the moist heat test, and the adhesive strength may decrease after the moist heat test. On the other hand, in the case of less than 2 mgKOH / g, the cross-linking of the easy-adhesive coating film becomes sparse, the wet heat resistance of the coating film decreases, and the adhesive force to the sealant decreases after the wet heat test.

  Such a (meth) acrylic copolymer (A) can be obtained by polymerizing various monomers. Examples of the monomer include a (meth) acrylic monomer having an alkyl group, a (meth) acrylic monomer having a hydroxyl group, a (meth) acrylic monomer having a carboxyl group, and a (meth) acrylic monomer having a glycidyl group. Other examples include vinyl acetate, maleic anhydride, vinyl ether, vinyl propionate, and styrene.

  Examples of the (meth) acrylic monomer having an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, normal butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and octyl (meth) acrylate.

  Examples of the (meth) acrylic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate.

  Examples of the (meth) acrylic monomer having a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, and citraconic acid.

  Examples of the (meth) acrylic monomer having a glycidyl group include glycidyl acrylate, glycidyl methacrylate, and 4-hydroxybutyl acrylate glycidyl ether.

For the polymerization of the above monomers, ordinary radical polymerization can be used. There is no limitation on the reaction method, and it can be carried out by a known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, etc., but solution polymerization is preferable because the control of the reaction is easy and the next operation can be directly performed. . The monomer used may be one type or a mixture of a plurality of types.
The solvent is not particularly limited as long as the resin can be dissolved in the present invention, such as methyl ethyl ketone, methyl isobutyl ketone, toluene, cellosolve, ethyl acetate, butyl acetate, and a single solvent or a plurality of solvents may be mixed. Also known as polymerization initiators used in the polymerization reaction are organic peroxides such as benzoyl peroxide, acetyl peroxide, methyl ethyl ketone peroxide, lauroyl peroxide, and azo initiators such as azobisisobutyronitrile. There is no particular limitation.

Next, the compound (B) having a (meth) acryloyl group will be described.
The compound (B) having a (meth) acryloyl group used in the present invention may be any compound as long as it has at least one (meth) acryloyl group in the molecule, for example, trimethylolpropane. (Meth) acrylates of polyhydric alcohols such as tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, di ( Examples thereof include epoxy (meth) acrylates such as (meth) acrylate and di (meth) acrylate of polyethylene glycol diglycidyl ether.
Among these, from the viewpoint of reactivity, the compound (B) having a (meth) acryloyl group preferably has 2 or more (meth) acryloyl groups in the molecule, and more preferably 3 or more in the molecule. Is preferred.
In addition, as the compound (B) having a (meth) acryloyl group, a hydroxyl group or a group such that the crosslinking between the acrylic copolymer (A) having no (meth) acryloyl group and the polyisocyanate compound (C) is not inhibited. Other functional groups may be included.

The sealing agent (II) located on the light receiving surface side of the solar cell and the sealing agent (IV) located on the non-light receiving surface side are not particularly limited, and known materials can be suitably applied. Suitable materials include EVA (ethylene-vinyl acetate copolymer), polyvinyl butyral, polyurethane, polyolefin and the like. Of these, EVA is mainly used from the viewpoint of cost. As the sealing agents (II) and (IV), a sheet (including a film) is simple, but a paste or the like may be used.
The sealing agent (II) located on the light receiving surface side and the sealing agent (IV) located on the non-light receiving surface side may contain an organic peroxide. By containing the organic peroxide, when the solar battery cell (III) is sandwiched between the sealing agents (II) and (IV) and heated, the sealing agent (II) is crosslinked or sealed by a radical reaction. Crosslinking the agent (II) and the sealant (IV) or crosslinking the sealant (IV) can be performed with high efficiency.
By including an organic peroxide in the sealant (IV) on the non-light-receiving surface side, the (meth) acryloyl group in the easy-adhesive layer (D ′) before the curing treatment is used during heat sealing. In addition, the organic peroxide acts, radical polymerization occurs, and the non-light-receiving surface side sealing agent (IV) and the easy-adhesive layer (D ′) before the curing treatment can be cross-linked or easily cured. Since the adhesive layer (D ′) is cross-linked, it is considered that the adhesive force is improved. The “curing treatment” in the present specification refers to a treatment for bonding the encapsulant (IV) and the solar cell back surface protective sheet (V) after they are overlapped.

The organic peroxide contained in the sealant is preferably used in an amount of 0.05 to 3.0 parts by weight with respect to 100 parts by weight of the resin of the sealant. Specific examples of the organic peroxide include tert-butyl peroxyisopropyl carbonate, tert-butyl peroxy-2-ethylhexyl isopropyl carbonate, tert-butyl peroxyacetate, tert-butylcumyl peroxide, 2,5-dimethyl- 2,5-di (tert-butylperoxy) hexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3,2,5-dimethyl- 2,5-di (tert-butylperoxy) hexane, 1,1-di (tert-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (tert-butylperoxy) cyclohexane, 1,1-di (tert-hexylperoxy) cyclohex 1,1-di (tert-amylperoxy) cyclohexane, 2,2-di (tert-butylperoxy) butane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5-diperoxybenzoate, tert-butyl hydroperoxide, dibenzoyl peroxide, p-chlorobenzoyl peroxide, tert-butyl peroxyisobutyrate, n-butyl-4,4-di (tert-butylperoxy) valerate, ethyl-3, 3-di (tert-butylperoxy) butyrate, hydroxyheptyl peroxide, dichlorohexanone peroxide, 1,1-di (tert-butylperoxy) 3,3,5-trimethylcyclohexane, n-butyl-4,4 -Di (tert-butyl peroxy) ) Valerate, 2,2-di (tert- butylperoxy) butane, and the like. These organic peroxides can be contained in the encapsulant by, for example, adding the encapsulant resin when the sheet is processed, and melt-kneading.

The compound (B) having a (meth) acryloyl group may be contained in a proportion of 0.1 to 20 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A) not having a (meth) acryloyl group. The ratio is preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight. If the proportion is less than 0.1 parts by weight, a sufficient effect of improving the adhesive strength cannot be expected. If the proportion is more than 20 parts by weight, the cross-linking between the compounds (B) having a (meth) acryloyl group becomes dense. Adhesive strength to materials and sealants is reduced.

Next, the polyisocyanate compound (C) will be described.
The polyisocyanate compound (C) reacts with the hydroxyl group of the (meth) acrylic copolymer (A) to crosslink the copolymers, thereby imparting moisture and heat resistance to the coating film and constituting a back protective sheet. It is possible to improve the adhesion with a sealing agent such as EVA which is a sealing agent (IV) on the plastic film (E) or the non-light-receiving surface side. Therefore, it is important that the polyisocyanate compound (C) has two or more isocyanate groups in one molecule, and examples thereof include aromatic polyisocyanates, chain aliphatic polyisocyanates, and alicyclic polyisocyanates. It is done. The polyisocyanate compound (C) may be used alone or in combination of two or more compounds.

  Aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-triisocyanate. Range isocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 " -Triphenylmethane triisocyanate etc. can be mentioned.

  Examples of chain aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and dodeca. Examples include methylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate.

  Examples of alicyclic polyisocyanates include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl- Examples include 2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylene bis (cyclohexyl isocyanate), 1,4-bis (isocyanate methyl) cyclohexane and the like.

  In addition to the polyisocyanate, an adduct of the polyisocyanate and a polyol compound such as trimethylolpropane, a burette or isocyanurate of the polyisocyanate, and further, the polyisocyanate and a known polyether polyol or polyester polyol, Examples thereof include adducts with acrylic polyol, polybutadiene polyol, polyisoprene polyol and the like.

  Among these polyisocyanate compounds (C), a low-yellowing type aliphatic or alicyclic polyisocyanate is preferable from the viewpoint of design, and an isocyanurate is preferable from the viewpoint of heat-and-moisture resistance. More specifically, an isocyanurate form of hexamethylene diisocyanate (HDI) and an isocyanurate form of 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) are preferred.

  Furthermore, the blocked polyisocyanate compound (B1) can be obtained by reacting almost all of the isocyanate groups of the polyisocyanate compound (C) with the blocking agent. Until the solar cell module is manufactured by laminating the easy-adhesive layer (D ′) before the curing treatment obtained by applying the solar cell back sheet protecting easy-adhesive in the present invention with the sealant (IV). It is preferably uncrosslinked, and therefore the polyisocyanate compound (C) is preferably a blocked polyisocyanate compound (C1).

  Examples of the blocking agent include phenols such as phenol, thiophenol, methylthiophenol, xylenol, cresol, resorcinol, nitrophenol, chlorophenol, oximes such as acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime, methanol, ethanol, n- Alcohols such as propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, t-pentanol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol , Pyrazol such as 3,5-dimethylpyrazole, 1,2-pyrazole, etc. , Triazoles such as 1,2,4-triazole, halogen-substituted alcohols such as ethylene chlorohydrin and 1,3-dichloro-2-propanol, ε-caprolactam, δ-valerolactam, γ-butyrolactam, β- Examples include lactams such as propyl lactam, and active methylene compounds such as methyl acetoacetate, ethyl acetoacetate, acetylacetone, methyl malonate, and ethyl malonate. Other examples include amines, imides, mercaptans, imines, ureas, and diaryls. One blocking agent may be used, or two or more blocking agents may be used in combination.

  Among these blocking agents, those having a dissociation temperature of 80 to 150 ° C. are preferable. When the dissociation temperature is less than 80 ° C., when the easy-adhesive is applied and the solvent is volatilized, the curing reaction proceeds and the adhesiveness to the filler may be reduced. When the dissociation temperature exceeds 150 ° C., the curing reaction does not proceed sufficiently in the vacuum thermocompression bonding step when forming the solar cell module, and the adhesion with the filler is lowered.

  Examples of the blocking agent having a dissociation temperature of 80 ° C. to 150 ° C. include methyl ethyl ketone oxime (dissociation temperature: 140 ° C., the same applies hereinafter), 3,5-dimethylpyrazole (120 ° C.), diisopropylamine (120 ° C.), and the like.

  The amount of the polyisocyanate compound (C) in the easy-adhesive of the present invention is such that the isocyanate group exists in the range of 0.1 to 5 for one hydroxyl group in the (meth) acrylic copolymer (A). It is necessary that the amount is such that it is preferably in the range of 0.5 to 4. If it is less than 0.1, the crosslinking density is too low and the heat and moisture resistance is not sufficient, and if it is more than 5, excess isocyanate reacts with moisture in the air during the moist heat test and the coating becomes hard. Moreover, it becomes a cause of the adhesive force fall with sealing agent with the plastic film (E) which comprises a back surface protection sheet, EVA etc. which are sealing agent (IV) by the side of a non-light-receiving surface.

  The easy-adhesive of the present invention can contain 0.01 to 30 parts by weight, more preferably 0.1 to 10 parts by weight, of organic particles or inorganic particles described later with respect to 100 parts by weight of the solid content. Parts can be contained. By containing these particles, tackiness on the surface of the easy-adhesive layer (D ′) before the curing treatment can be reduced. If the content is less than 0.01 parts by weight, the tack on the surface of the easy-adhesive layer (D ′) before the curing treatment cannot be sufficiently reduced. On the other hand, when the amount of the various particles increases, the adhesion between the easy-adhesive layer (D ′) before the curing treatment and the sealant may be hindered, resulting in a decrease in adhesive strength.

  In particular, organic particles having a melting point or softening point of 150 ° C. or higher can be preferably used. If the melting point or softening point of the organic particles is lower than 150 ° C., the particles may be softened in the vacuum thermocompression bonding process when constituting the solar cell module, and the adhesion with the sealant may be hindered.

  Specific examples of the organic particles include polymethyl methacrylate resin, polystyrene resin, nylon (registered trademark) resin, melamine resin, guanamine resin, phenol resin, urea resin, silicon resin, methacrylate resin, acrylate resin and other polymer particles, Alternatively, cellulose powder, nitrocellulose powder, wood powder, waste paper powder, rice husk powder, starch and the like can be mentioned. One type of organic particles may be used, or two or more types may be used in combination.

  The polymer particles can be obtained by a polymerization method such as an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method, a soap-free polymerization method, a seed polymerization method, or a microsuspension polymerization method. The organic particles may contain impurities to the extent that the characteristics are not impaired. The shape of the particles may be any shape such as powder, granule, granule, flat plate, and fiber.

  Specific examples of inorganic particles include magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony, titanium, and other metal oxides, hydroxides, sulfates, carbonates, silicates, etc. Inorganic particles to be used. Further specific examples include silica gel, aluminum oxide, calcium hydroxide, calcium carbonate, magnesium oxide, magnesium hydroxide, magnesium carbonate, zinc oxide, lead oxide, diatomaceous earth, zeolite, aluminosilicate, talc, white carbon, mica Glass fiber, glass powder, glass beads, clay, wollastonite, iron oxide, antimony oxide, titanium oxide, lithopone, pumice powder, aluminum sulfate, zirconium silicate, barium carbonate, dolomite, molybdenum disulfide, iron sand, carbon black, etc. Examples thereof include inorganic particles. One type of inorganic particles may be used, or two or more types may be used in combination.

  Moreover, the said inorganic type particle | grain may contain the impurity to such an extent that the characteristic is not impaired. The shape of the particles may be any shape such as powder, granule, granule, flat plate, and fiber.

  Moreover, you may add a crosslinking accelerator to the easily adhesive in this invention in the range which does not prevent the effect by this invention as needed. The cross-linking accelerator plays a role as a catalyst for promoting the urethane bond reaction by the hydroxyl group of the (meth) acrylic copolymer (A) and the isocyanate of the polyisocyanate compound (C). Examples of the crosslinking accelerator include tin compounds, metal salts, bases and the like. Specifically, tin octylate, dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, tin chloride, iron octylate, cobalt octylate, naphthenic acid. Zinc, triethylamine, triethylenediamine and the like can be mentioned. These can be used alone or in combination.

  In addition, the easy-adhesive in the present invention includes, if necessary, a filler, a thixotropy imparting agent, an anti-aging agent, an antioxidant, an antistatic agent, a flame retardant, and a heat conduction, as long as the effects of the present invention are not hindered. Various additives such as property improvers, plasticizers, anti-sagging agents, antifouling agents, antiseptics, bactericides, antifoaming agents, leveling agents, curing agents, thickeners, pigment dispersants, silane coupling agents It may be added.

The easy-adhesive used in the present invention contains a solvent.
As the solvent, alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether, diethylene glycol methyl ether,
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone,
Ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether,
Hydrocarbons such as hexane, heptane, octane,
Aromatics such as benzene, toluene, xylene, cumene,
Among the esters such as ethyl acetate and butyl acetate, those suitable for the composition of the resin composition can be used, but those having a boiling point of 50 ° C. to 200 ° C. can be preferably used. When the boiling point is lower than 50 ° C., the solvent easily evaporates when applying the easy-adhesive agent, and the solid content becomes high, making it difficult to apply with a uniform film thickness. When the boiling point is higher than 200 ° C., it is difficult to dry the solvent. Two or more solvents may be used.

  The easy-adhesive agent of the present invention is a solar cell back surface protective sheet that has good adhesion to the sealant (IV) by coating the plastic film (E) to form an easy-adhesive layer (D ′). (V ′) can be produced.

As a method of applying the easy-adhesive of the present invention to the plastic film (E), a conventionally known method can be used. Specific examples include comma coating, gravure coating, reverse coating, roll coating, lip coating, and spray coating. The easy-adhesive layer (D ′) before the curing treatment can be formed by applying the easy-adhesive by these methods and volatilizing the solvent by heat drying.
The thickness of the easy-adhesive layer (D ′) before the curing treatment is preferably 0.01 to 30 μm, and more preferably 0.1 to 10 μm.

  Examples of the plastic film (E) include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene terephthalate, olefin films such as polyethylene, polypropylene, and polycyclopentadiene, polyvinyl fluoride, polyvinylidene fluoride film, and polytetra Fluoro-based films such as fluoroethylene films and ethylene-tetrafluoroethylene copolymer films, acrylic films, and triacetyl cellulose films can be used. From the viewpoint of film rigidity and cost, a polyester resin film is preferable, and among these, a polyethylene terephthalate film is preferable. The plastic film (E) may have a single layer or a multilayer structure of two or more layers. Furthermore, the plastic film (E) may be laminated with a deposited film or the like on which a metal oxide or a non-metallic inorganic oxide is deposited.

Examples of the metal oxide or non-metal inorganic oxide to be deposited include oxides such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, and yttrium. Alkali metal and alkaline earth metal fluorides can also be used, and these can be used alone or in combination.
These metal oxides or non-metal inorganic oxides can be deposited using a conventionally known PVD method such as vacuum deposition, ion plating, sputtering, or the like, or a CVD method such as plasma CVD or microwave CVD.

  The plastic film (E) may be colorless or may contain coloring components such as pigments or dyes. Examples of the method of containing the coloring component include a method of kneading the coloring component in advance at the time of film formation, a method of printing the coloring component on a colorless transparent film substrate, and the like. Further, a colored film and a colorless transparent film may be bonded together.

  The solar cell back surface protective sheet (V ′) is formed on the surface of the plastic film (E) where the easy-adhesive layer (D ′) is not formed, such as a metal foil (F) or a weather resistant resin layer (G). A film layer or a coat layer may be provided as a single layer or a plurality of layers.

  As the metal foil (F), aluminum foil, iron foil, zinc plywood and the like can be used, and among these, aluminum foil is preferable from the viewpoint of corrosion resistance. The thickness is preferably 10 μm to 100 μm, more preferably 20 μm to 50 μm. Various conventionally known adhesives can be used for laminating the metal foil (F).

  Examples of the weather resistant resin layer (G) include those obtained by laminating polyester resin films such as polyvinylidene fluoride film, polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene terephthalate using various conventionally known adhesives, Asahi Glass Co., Ltd. ) And a coating layer formed by applying a highly weather-resistant paint such as Lumiflon.

Next, the solar cell module will be described.
The solar cell module 100 seals the solar cell surface protection material (I) positioned on the light receiving surface side of the solar cell with respect to the solar cell (III) before the curing process positioned on the light receiving surface side of the solar cell. The solar cell back surface protection sheet (V ′) before curing treatment is laminated via the sealing agent (IV) before curing treatment positioned on the non-light-receiving surface side of the solar battery cell. It can be obtained by hot pressing under reduced pressure.

  Although it does not specifically limit as solar cell surface protective material (I), A glass plate, a plastic plate of polycarbonate or polyacrylate etc. can be mentioned as a suitable example. In view of transparency, weather resistance, toughness and the like, a glass plate is preferable. Furthermore, white glass with high transparency is preferable among the glass plates.

  Sealants such as EVA used as sealants (II) and (IV) include UV absorbers and light stabilizers for improving weather resistance, organic peroxides for crosslinking EVA itself, etc. The additive may be contained.

  The easy-adhesive layer (D ′) of the present invention seals the (meth) acryloyl group of the compound (B) having a (meth) acryloyl group by a radical reaction in a high-temperature thermocompression bonding step when forming a solar cell module. The adhesive force with the sealing agent (IV) is improved by crosslinking with the agent (IV) or by crosslinking with the compound (B) having a (meth) acryloyl group. In addition, when the organic peroxide is contained in the sealant (IV), this crosslinking reaction is promoted, so that the effect of the present invention is exhibited to the maximum. Therefore, it is preferable that sealing agent (IV) located in the non-light-receiving surface side contains an organic peroxide.

  The sealant on the non-light-receiving surface side is preferably fast cure type EVA. Generally, EVA used as a sealing material for a solar cell module includes standard cure type and fast cure type EVA. The standard cure type requires a curing process (for example, 120 ° C. to 150 ° C. for 60 minutes to 90 minutes) in addition to a vacuum laminating process (for example, 120 ° C. to 150 ° C. for 60 minutes to 90 minutes). On the other hand, the fast cure type EVA has advantages in terms of equipment cost and productivity because it does not require a curing step in addition to shortening the time of the vacuum laminating step.

  Fast cure type EVA is different from the standard cure type in the amount and type of peroxide contained therein, and is improved so that the crosslinking of EVA is completed earlier. However, when the fast cure type EVA and the solar cell back surface protective sheet are bonded, the conventional easy adhesive has a drawback that the laminating time and the curing time are shortened and the adhesiveness and durability are inferior. However, the easy-adhesive of the present invention is excellent in adhesion and durability, and is an extremely good easy-adhesive for fast cure type EVA.

    The fast-cure type EVA referred to in the present invention refers to EVA having a gel fraction of 75% or more when heated at 140 ° C. for 30 minutes under vacuum. The gel fraction is calculated by measuring about 5 g of EVA, refluxing in 200 g of xylene for 3 hours, and then dividing the weight of insoluble matter not dissolved in xylene by the weight of the measured EVA. Refers to the percentage.

  As the solar cell (III), an electrode is provided on a photoelectric conversion layer such as crystalline silicon, amorphous silicon, and a compound semiconductor represented by copper indium selenide, and further, these are laminated on a substrate such as glass. Etc. can be illustrated.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by a following example. In the examples, “part” means “part by weight” and “%” means “% by weight”. Table 1 shows the physical properties of the (meth) acrylic copolymer.

<(Meth) acrylic copolymer A1 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 70 parts of methyl methacrylate, 28 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. with stirring. Subsequently, 0.15 part of azobisisobutyronitrile was added and a polymerization reaction was performed for 2 hours. Subsequently, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours. A (meth) acrylic copolymer A1 solution having an average molecular weight of 40,000, a hydroxyl value of 8.8 (mgKOH / g), a Tg of 76 ° C. and a solid content of 50% was obtained.

  The number average molecular weight, glass transition temperature, acid value, and hydroxyl value were measured as described below.

<Measurement of number average molecular weight (Mn)>
The measurement of Mn was determined by GPC (gel permeation chromatography) described above.

<Measurement of glass transition temperature (Tg)>
The glass transition temperature was measured by the differential scanning calorimetry (DSC) method described above.
In addition, the sample for Tg measurement used what heated said acrylic resin solution at 150 degreeC for about 15 minutes, and was made to dry.

<Measurement of acid value (AV)>
About 1 g of a sample (resin solution: about 50%) is accurately weighed in a stoppered Erlenmeyer flask, and 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution is added and dissolved. To this is added phenolphthalein reagent as an indicator and held for 30 seconds. Thereafter, the solution is titrated with a 0.1N alcoholic potassium hydroxide solution until the solution becomes light red. The acid value was determined by the following formula. The acid value was a numerical value of the dry state of the resin (unit: mgKOH / g).
Acid value (mgKOH / g) = {(5.611 × a × F) / S} / (Nonvolatile content concentration / 100)
Where S: Amount of sample collected (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
F: Potency of 0.1N alcoholic potassium hydroxide solution

<Measurement of hydroxyl value (OHV)>
About 1 g of a sample (resin solution: about 50%) is accurately weighed in a stoppered Erlenmeyer flask, and 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution is added and dissolved. Further, exactly 5 ml of an acetylating agent (a solution in which 25 g of acetic anhydride was dissolved in pyridine to make a volume of 100 ml) was added and stirred for about 1 hour. To this, phenolphthalein reagent is added as an indicator and lasts for 30 seconds. Thereafter, the solution is titrated with a 0.1N alcoholic potassium hydroxide solution until the solution becomes light red.
The hydroxyl value was determined by the following formula. The hydroxyl value was a numerical value in the dry state of the resin (unit: mgKOH / g).
Hydroxyl value (mgKOH / g)
= [{(B−a) × F × 28.25} / S] / (Nonvolatile content concentration / 100) + D
Where S: Amount of sample collected (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
b: Consumption of 0.1N alcoholic potassium hydroxide solution in the empty experiment (ml)
F: Potency of 0.1N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

<(Meth) acrylic copolymer A2 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 70 parts of methyl methacrylate, 28 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. with stirring, and 0.3 part of azobisisobutyronitrile was added to conduct a polymerization reaction for 2 hours. Subsequently, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours. A (meth) acrylic copolymer A2 solution having an average molecular weight of 17,000, a hydroxyl value of 8.0 (mgKOH / g), a Tg of 76 ° C. and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A3 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 70 parts of methyl methacrylate, 28 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The mixture was heated to 80 ° C. with stirring, 0.08 parts of azobisisobutyronitrile was added, and a polymerization reaction was carried out for 2 hours. Subsequently, 0.05 parts of azobisisobutyronitrile was added to conduct a polymerization reaction for another 2 hours, and 0.05 parts of azobisisobutyronitrile was further added to carry out the polymerization reaction for another 2 hours. A (meth) acrylic copolymer A3 solution having an average molecular weight of 75,000, a hydroxyl value of 8.4 (mgKOH / g), a Tg of 76 ° C. and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A4 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 55 parts of methyl methacrylate, 43 parts of n-butyl methacrylate, 2 parts of 2-hydroxylmethacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. with stirring, and 0.08 part of azobisisobutyronitrile was added to conduct a polymerization reaction for 2 hours. Subsequently, 0.05 parts of azobisisobutyronitrile was added to conduct a polymerization reaction for another 2 hours, and 0.05 parts of azobisisobutyronitrile was further added to carry out the polymerization reaction for another 2 hours. A (meth) acrylic copolymer A4 solution having an average molecular weight of 80,000, a hydroxyl value of 8.4 (mgKOH / g), a Tg of 62 ° C. and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A5 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 90 parts of methyl methacrylate, 8 parts of n-butyl methacrylate, 2 parts of 2-hydroxylethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. while stirring, and 0.15 part of azobisisobutyronitrile was added to conduct a polymerization reaction for 2 hours. Subsequently, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours. A (meth) acrylic copolymer A5 solution having an average molecular weight of 40,000, a hydroxyl value of 8.0 (mgKOH / g), a Tg of 95 ° C., and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A6 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen inlet tube was charged with 75 parts of methyl methacrylate, 10 parts of n-butyl methacrylate, 15 parts of 2-hydroxylethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. with stirring, and 0.07 part of azobisisobutyronitrile was added to conduct a polymerization reaction for 2 hours. Subsequently, 0.05 parts of azobisisobutyronitrile was added to conduct a polymerization reaction for another 2 hours, and 0.05 parts of azobisisobutyronitrile was further added to carry out the polymerization reaction for another 2 hours. A (meth) acrylic copolymer A6 solution having an average molecular weight of 120,000, a hydroxyl value of 61.4 (mgKOH / g), a Tg of 86 ° C. and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A7 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 70 parts of methyl methacrylate, 26 parts of n-butyl methacrylate, 4 parts of 2-hydroxylmethacrylate, and 100 parts of ethyl acetate, and a nitrogen atmosphere Under stirring, the temperature was raised to 77 ° C., 0.05 part of azobisisobutyronitrile was added, and a polymerization reaction was carried out for 2 hours. Next, 22 parts of ethyl acetate and 0.05 part of azobisisobutyronitrile were added to conduct a polymerization reaction for 2 hours. Further, 22 parts of ethyl acetate and 0.05 part of azobisisobutyronitrile were added. In addition, a polymerization reaction was carried out for 2 hours. Thereafter, 36 parts of ethyl acetate and 0.05 parts of azobisisobutyronitrile were added to conduct a polymerization reaction for 2 hours, and 0.05 parts of azobisisobutyronitrile was further added to conduct a polymerization reaction for 2 hours. A (meth) acrylic copolymer solution A7 having a number average molecular weight of 244,000, a hydroxyl value of 15.8 (mgKOH / g), a Tg of 77 ° C. and a solid content of 35% was obtained.

<(Meth) acrylic copolymer A8 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 57 parts of methyl methacrylate, 20 parts of n-butyl methacrylate, 23 parts of 2-hydroxylmethacrylate, and 100 parts of toluene, under a nitrogen atmosphere. The temperature was raised to 100 ° C. with stirring at 0.13 parts, 0.13 parts of azobisisobutyronitrile was added and the polymerization reaction was carried out for 2 hours, and then 0.07 parts of azobisisobutyronitrile was added, and another 2 hours. A polymerization reaction was performed. Further, 0.07 part of azobisisobutyronitrile was added and polymerization reaction was further performed for 2 hours. The number average molecular weight was 42,000, the hydroxyl value was 97.9 (mgKOH / g), Tg was 73 ° C., solid content A 50% acrylic resin solution A8 was obtained.

<(Meth) acrylic copolymer A9 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen inlet tube was charged with 70 parts of methyl methacrylate, 30 parts of n-butyl methacrylate and 100 parts of toluene, and the temperature was raised to 100 ° C. while stirring in a nitrogen atmosphere. The mixture was warmed, 0.15 part of azobisisobutyronitrile was added, and the polymerization reaction was carried out for 2 hours. Subsequently, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours. A (meth) acrylic copolymer A9 solution having an average molecular weight of 40,000, a hydroxyl value of 0 (mgKOH / g), a Tg of 75 ° C., and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A10 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 80 parts of methyl methacrylate, 18 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. with stirring, and 0.6 parts of azobisisobutyronitrile was added to conduct a polymerization reaction for 2 hours. Subsequently, 0.05 parts of azobisisobutyronitrile was added to conduct a polymerization reaction for another 2 hours, and 0.05 parts of azobisisobutyronitrile was further added to carry out the polymerization reaction for another 2 hours. A (meth) acrylic copolymer A10 solution having an average molecular weight of 12,000, a hydroxyl value of 8.5 (mgKOH / g), a Tg of 85 ° C. and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A11 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 48 parts of methyl methacrylate, 50 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. while stirring, and 0.15 part of azobisisobutyronitrile was added to conduct a polymerization reaction for 2 hours. Subsequently, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours. A (meth) acrylic copolymer A11 solution having an average molecular weight of 40,000, a hydroxyl value of 9.0 (mgKOH / g), a Tg of 56 ° C., and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A12 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen inlet tube is charged with 98 parts of methyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, and 100 parts of toluene, and is stirred up to 100 ° C. in a nitrogen atmosphere. The temperature was raised, 0.15 part of azobisisobutyronitrile was added, and a polymerization reaction was carried out for 2 hours. Subsequently, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours. A (meth) acrylic copolymer A12 solution having an average molecular weight of 38,000, a hydroxyl value of 8.1 (mgKOH / g), a Tg of 104 ° C. and a solid content of 50% was obtained.

<(Meth) acrylic copolymer A13 solution>
A four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 55 parts of methyl methacrylate, 20 parts of n-butyl methacrylate, 25 parts of 2-hydroxyethyl methacrylate, and 100 parts of toluene under a nitrogen atmosphere. The temperature was raised to 100 ° C. while stirring, and 0.15 part of azobisisobutyronitrile was added to conduct a polymerization reaction for 2 hours. Subsequently, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further performed for 2 hours. A (meth) acrylic copolymer A13 solution having an average molecular weight of 37,000, a hydroxyl value of 108 (mgKOH / g), a Tg of 72 ° C. and a solid content of 50% was obtained.

<Compounds B1 to B6 having (meth) acryloyl group>
As the compounds B1 to B6 having a (meth) acryloyl group, the compounds described in Table 2 were used as they were.

<Allyl group-containing compounds H1 to H4>
As the allyl group-containing compounds H1 to H4, the compounds described in Table 2 were used as they were.

<Polyisocyanate compound (C) solution>
The isocyanurate form of hexamethylene diisocyanate blocked with 3,5-dimethylpyrazole was diluted to 75% with ethyl acetate to obtain a polyisocyanate compound (C) solution.

<Adjustment of easy adhesive solution>
A (meth) acrylic copolymer (A) solution, a compound (B) having a (meth) acryloyl group, an allyl group-containing compound (H), and a polyisocyanate compound (C) solution were mixed in the composition shown in Table 2. Furthermore, 0.01 parts by weight of dioctyl tin laurate as a catalyst was blended with respect to 100 parts by weight of the solid content of the (meth) acrylic copolymer (A) solution to obtain easy adhesive solutions 1 to 31. .

<Preparation of solar cell back surface protection sheet>
A corona treatment was applied to both sides of a polyester film (Teijin DuPont Films, Tetron (registered trademark) S, thickness 188 μm), and a polyester adhesive “Dyna Leo VA-3020 / HD-701” (Toyochem Co., Ltd.) on one side. ), A blending ratio of 100/7, the same applies hereinafter) with a gravure coater, the solvent is dried, an adhesive amount of 10 g / square meter is provided, and the following deposited PET (Mitsubishi resin) is applied to the adhesive layer. The vapor-deposited surfaces manufactured by Co., Ltd., Tech Barrier LX, thickness 12 μm) were superposed. Thereafter, an aging treatment was performed at 50 ° C. for 4 days to cure the adhesive layer, and a polyester film-deposited PET laminate was produced.

  Furthermore, a polyester adhesive “Dyna Leo VA-3020 / HD-701” (manufactured by Toyochem Co., Ltd., blending ratio 100/7, the same applies below) is applied to the surface of the polyester film-deposited PET laminate on the vapor deposition PET side by a gravure coater. It was applied, the solvent was dried, and an adhesive layer having an application amount of 10 g / square meter was provided, and a polyvinyl fluoride film (manufactured by DuPont, Tedlar, thickness 50 μm) was overlaid on the adhesive layer. Thereafter, an aging treatment was performed at 50 ° C. for 4 days to cure the adhesive layer, and a polyester film-deposited PET-polyvinyl fluoride film laminate was produced.

  Furthermore, the easy adhesive solution 1 is applied to the polyester film surface of the polyester film-deposited PET-polyvinyl fluoride film laminate by a gravure coater, the solvent is dried, and an easy adhesive layer having a coating amount of 1 g / square meter is provided. The solar cell back surface protective sheet 1 was produced.

  Similarly to the solar cell back surface protective sheet 1, solar cell back surface protective sheets 2 to 31 were prepared using the easy-adhesive solutions 2 to 31.

  A solar cell back surface protective sheet 32 having a layer structure of polyester film-deposited PET-polyvinyl fluoride film without an easy-adhesive layer was prepared by the same production method as that for the solar cell back surface protective sheet 1.

<Preparation of adhesive strength evaluation sample>
White plate glass, vinyl acetate-ethylene copolymer film (manufactured by Sunvic Co., Ltd., fast cure type, hereinafter referred to as EVA film), solar cell back surface protective sheet 1, and easy adhesive layer of solar cell back surface protective sheet 1 as EVA film It was piled up in order to touch. Then, this laminate was put into a vacuum laminator, evacuated to about 1 Torr, heated at 150 ° C. for 30 minutes at a press pressure of 0.1 MPa, and further heated at 150 ° C. for 30 minutes to evaluate the adhesive strength of 10 cm × 10 cm square. Sample 1 was prepared.

  In the same manner as in Adhesive Strength Evaluation Sample 1, Adhesive Strength Evaluation Samples 2-31 were produced using solar cell back surface protective sheets 2-31.

  The white plate glass, the EVA film, and the solar cell back surface protection sheet 32 are stacked in order so that the polyester film side surface of the solar cell back surface protection sheet 32 is in contact with the EVA film, and the adhesive strength evaluation is performed in the same manner as in the sample 1 for adhesive strength evaluation. Sample 32 was prepared.

[Example 1]
Using the adhesive strength evaluation sample 1, the adhesiveness of the easy-adhesive layer to the EVA film and the wet heat resistance test (1000 hours and 2000 hours) were evaluated by the method described later.

<Adhesion measurement>
One surface of the solar cell back surface protection sheet of the adhesive strength evaluation sample 1 is cut into a width of 15 mm with a cutter, and the adhesive force between the easy-adhesive layer formed on the solar cell back surface protection sheet 1 and the EVA film as a sealant is measured. did. For the measurement, a tensile tester was used, and a 180 degree peel test was performed at a load speed of 100 mm / min. The obtained measurement values were evaluated as follows.
◎: 50 N / 15 mm or more ○: 30 N / 15 mm or more to less than 50 N / 15 mm Δ: 10 N / 15 mm or more to less than 30 N / 15 mm ×: less than 10 N / 15 mm

<Adhesiveness after wet heat resistance test>
After the sample 1 for adhesive strength evaluation was allowed to stand for 1000 hours and 2000 hours under environmental conditions of a temperature of 85 ° C. and a relative humidity of 85% RH, the adhesiveness was evaluated after the wet heat resistance test in the same manner as the adhesiveness measurement. .

[Examples 2 to 19]
In the same manner as in Example 1, samples 2 to 19 for evaluating adhesive strength were used to evaluate the adhesiveness of the easy-adhesive layer to the EVA film and the adhesiveness after the wet heat resistance test.

[Comparative Examples 1 to 12]
In the same manner as in Example 1, the adhesive strength evaluation samples 20 to 31 were used to evaluate the adhesion of the easy-adhesive layer to the EVA film and the adhesiveness after the wet heat resistance test, and Comparative Examples 1 to 12 were obtained.

[Comparative Example 13]
In the same manner as in Example 1, the adhesive strength evaluation sample 32 was used, and the adhesion between the polyester film surface and the EVA film and the adhesion after the wet heat test were evaluated.
The above results are shown in Table 2 or Table 3.

As Table 2 shows, in Examples 1-19, the back surface protection sheet for solar cells using the easily adhesive of this invention has sufficient adhesiveness with respect to an EVA film, and adhesiveness after a moist heat test.

On the other hand, in Comparative Example 1, since the OH value of the (meth) acrylic copolymer (A) is smaller than 2, the crosslinking is not sufficient and the adhesiveness is inferior.
In Comparative Example 2, the molecular weight of the (meth) acrylic copolymer (A) is too low and the adhesiveness after the wet heat resistance test is poor.
Since the Tg of the (meth) acrylic copolymer (A) is low, Comparative Example 3 is difficult in terms of durability when using a fast cure type EVA film. In Comparative Example 4, since the Tg of the (meth) acrylic copolymer (A) is too high and the easy-adhesive layer (D ′) becomes hard, the adhesiveness is inferior.
In Comparative Example 5, the (meth) acrylic copolymer (A) has an OH value greater than 100, so that crosslinking is excessive and the adhesiveness is poor.

  In Comparative Examples 7 to 10, the allyl group-containing compound (H) is added instead of the compound (B) having a (meth) acryloyl group, but the allyl group is less reactive than the (meth) acryloyl group. Therefore, a sufficient effect of improving the adhesive strength cannot be obtained.

  In Comparative Example 11, the polyisocyanate compound (C) was not used, and since the NCO / OH ratio of the curing agent and the acrylic copolymer (A) was 0, the crosslinking reaction did not occur and the adhesiveness after the wet heat resistance test was poor. In Comparative Example 12, since the NCO / OH ratio is 10, crosslinking is excessive, and the adhesiveness and the adhesiveness after the wet heat resistance test are inferior.

[Example 20]
<Production of solar cell module>
White glass ... Solar cell surface sealant (I)
EVA film: Light-receiving surface side sealant (II)
Polycrystalline silicon solar cell element ... Solar cell (III)
EVA film: EVA non-light-receiving surface side sealant (IV)
After the above (I) to (IV) and the solar cell back surface protective sheet 1 are sequentially stacked so that the easy adhesion layer of the solar cell back surface protective sheet 1 is in contact with the sealant (IV) on the EVA non-light-receiving surface side, vacuum is applied. Put into a laminator, evacuate to about 1 Torr, press at atmospheric pressure, heat at 150 ° C. for 30 minutes, then heat at 150 ° C. for 30 minutes, then 10 cm × 10 cm square photoelectric conversion efficiency A solar cell module 1 for evaluation was produced.

<Measurement of photoelectric conversion efficiency>
The solar cell output of the obtained solar cell module 1 was measured, and the photoelectric conversion efficiency was measured using a solar simulator (SS-100XIL, manufactured by Eihiro Seiki Co., Ltd.) according to JIS C8912.
Furthermore, the photoelectric conversion efficiency after the heat and humidity resistance test after standing for 500 hours, 1000 hours, 1500 hours, and 2000 hours under environmental conditions of a temperature of 85 ° C. and a relative humidity of 85% RH was measured in the same manner. The ratio of the decrease in photoelectric conversion efficiency after the wet heat resistance test with respect to the initial photoelectric conversion efficiency was calculated and evaluated as follows.
○: Output decrease is less than 10% Δ: Output decrease is from 10% to less than 15% ×: Output decrease is 20% or more

[Examples 21 to 30], [Comparative Examples 14 to 20]
In the same manner as in Example 20, solar cell modules 2 to 11 (Examples 21 to 30) using solar cell back surface protection sheets 2 to 11 and solar cell modules 12 to 18 using solar cell back surface protection sheets 20 to 26. (Comparative Examples 14 to 20) were prepared, and the photoelectric conversion efficiency (initial, after the wet heat resistance test) was measured.

[Comparative Example 21]
Except for using the solar cell back surface protection sheet 32 instead of the solar cell back surface protection sheet 1 and laminating so that the surface of the polyester film of the solar cell back surface protection sheet 32 is in contact with the sealant (IV) on the non-light-receiving surface side, In the same manner as in Example 20, a solar cell module 19 was produced, and the photoelectric conversion efficiency (initial, after wet heat resistance test) was measured. This was designated as Comparative Example 21.
The results are shown in Table 4.

  As shown in Table 4, Examples 20-30 do not show a decrease in output, but Comparative Examples 14-21 have insufficient adhesiveness between the EVA film and the solar cell back surface protective sheet, so that moisture penetrates. The solar cell element is deteriorated, and the photoelectric conversion efficiency is lowered.

I Solar cell surface protective material located on the light receiving surface side of the solar cell II Sealant located on the light receiving surface side of the solar cell III Solar cell IV Sealant located on the non-light receiving surface side of the solar cell V Solar cell back surface protection sheet

Claims (8)

Acrylic copolymer having a glass transition temperature of more than 60 ° C. and not more than 100 ° C., a number average molecular weight of 15,000 to 250,000, a hydroxyl value of 2 to 100 (mgKOH / g), and no (meth) acryloyl group Coalescence (A),
A compound (B) having a (meth) acryloyl group;
For a solar cell back surface protective sheet containing a polyisocyanate compound (C) having an isocyanate group in the range of 0.1 to 5 with respect to one hydroxyl group in the (meth) acrylic copolymer (A). Easy adhesive.   The amount of the compound (B) having a (meth) acryloyl group is 0.1 to 20 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A) having no (meth) acryloyl group. The adhesive easily for solar cell back surface protection sheets of description.   The easily adhesive agent for solar cell back surface protection sheets of Claim 1 or 2 whose said polyisocyanate compound (C) is blocked polyisocyanate (C1).   The solar cell back surface protective sheet according to any one of claims 1 to 3, wherein the compound (B) having the (meth) acryloyl group has two or more (meth) acryloyl groups in a molecule. Easy-to-use adhesive. The solar cell back surface protection sheet which comprises the easily adhesive layer before the hardening process formed with the easily adhesive agent for solar cell back surface protection sheets of any one of Claims 1-4, and a plastic film. Solar cells,
A solar cell surface protective material that is disposed on the light receiving surface side and protects the solar battery cell via a sealant on the light receiving surface side;
A solar battery back surface protective sheet that is disposed on the non-light receiving surface side and protects the solar battery cell via the non-light receiving surface side sealant;
The said solar cell back surface protection sheet comprises a plastic film and the easily adhesive layer before the hardening process formed from the easy adhesive agent for solar cell back surface protection sheets of any one of Claims 1-4. What was obtained by arranging the solar cell back surface protective sheet such that the easy adhesive layer is in contact with the non-light receiving surface side sealing agent and curing the solar cell back surface protective sheet easy adhesive layer. Is a solar cell module.   The solar cell module according to claim 6, wherein the sealant on the non-light-receiving surface side contains an organic peroxide.   The solar cell module according to claim 6 or 7, wherein the sealant on the non-light-receiving surface side is a fast cure type ethylene-vinyl acetate copolymer (EVA).

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