JP2018120919A - Adhesive for solar cell protective sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an adhesive for a solar cell protective sheet, which is excellent in adhesion and adhesion durability with a substrate and an adherend and which allows a coating film to be cut successfully; a solar cell protective sheet and a solar cell module, including a resin layer formed by the adhesive for a solar cell protective sheet.SOLUTION: There is provided an adhesive for a solar cell protective sheet, including: a (meth)acrylic resin containing a hydroxyl group; blocked polyisocianate; and a polyfunctional ethylenically unsaturated double bond-containing compound having a weight average molecular weight of 700-20,000. There are further provided a solar cell protective sheet and a solar cell module, including a resin layer formed by the adhesive for a solar cell protective sheet.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an adhesive for a solar cell protective sheet, and particularly relates to an adhesive for a solar cell protective sheet that is excellent in adhesion to a substrate and an adherend and excellent in cutting properties of a coating film.

  In recent years, solar cells have been attracting attention as a clean energy source free from environmental pollution due to increasing awareness of environmental problems, and their practical application is progressing. 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, a thin film solar cell element represented by an amorphous silicon solar cell element in which silicon is laminated on a conductive metal substrate and a transparent conductive layer is further formed thereon is lightweight, Moreover, since it is rich in impact resistance and flexibility, it is considered promising as a future form in solar cells.

  A simple one of the solar cell modules has a configuration in which a sealing material and a protective material are sequentially laminated on both surfaces of the solar cell element. Typical examples of the protective material include a glass plate and a solar cell protective sheet (hereinafter also referred to as “protective sheet”). The glass plate is very excellent in transparency, weather resistance, and scratch resistance, but there are problems in terms of cost, safety, and workability, while the protective sheet is excellent in cost, safety, and workability. A protective sheet has been proposed. As the sealing material, an ethylene-vinyl acetate copolymer (hereinafter referred to as “EVA”) that is highly transparent and excellent in moisture resistance is often used.

  Among various performances required for the protective sheet, adhesion to the sealing material and adhesion durability are basic and important performance requirements. If the adhesiveness to the sealing material is insufficient, the protective sheet is peeled off and the solar cell cannot be protected from moisture and external factors, leading to deterioration of the output of the solar cell. As a method for ensuring the adhesion between the protective sheet and the sealing material, (1) a layer made of an anchor coating agent (sometimes referred to as a primer or simply an adhesive) is provided on the surface where the protective sheet and the sealing material are in contact with each other. The method and (2) a method of using a film having a high adhesiveness with the sealing material on the surface where the protective sheet and the sealing material are in contact with each other. The method 1) is drawing attention. Various types of anchor coating agents are known to be applied to the surface of the protective sheet in contact with the sealing material. However, as in Patent Document 1, ethylenic unsaturation is contained in the vinyl-based copolymer used in the primer. It is known that when a double bond is contained, the adhesiveness to the sealing material is excellent. However, in order to contain an ethylenically unsaturated double bond in the vinyl copolymer, there is a problem that the copolymer production process tends to be complicated.

  On the other hand, Patent Document 2 discloses a sealing material by blending a specific amount of a compound having a (meth) acryloyl group and a polyisocyanate compound into a (meth) acrylic copolymer having no (meth) acryloyl group. It is described that it is excellent in adhesion and adhesion durability.

  On the other hand, in addition to the adhesiveness to the sealing material and the adhesive durability, the performance required for the protective sheet includes processing suitability of the protective sheet. Examples of suitable processing include "blocking" that prevents the sheets that come into contact with each other when the protective sheet is wound into a roll shape, or the end face that has been cut out when the roll-shaped protective sheet is cut to an optimum size. "Cutting property" that prevents the occurrence of defects (such as film peeling).

  As a method for achieving both adhesiveness and blocking property with a sealing material, for example, Patent Document 3 describes a method in which an easy-adhesion layer contains a crosslinkable main resin, a polyisocyanate compound, and an organometallic coordination compound. ing. However, little is known about the method for achieving both adhesiveness and cutting performance with the sealing material, and provides a protective sheet that combines excellent adhesiveness to the sealing material, adhesion durability and cutting properties. There is a need for an anchor coating agent for this purpose.

JP 2013-071948 A Japanese Patent No. 4924780 International Publication WO2012 / 133748

  The problem to be solved by the present invention is an adhesive for a solar cell protective sheet, which is excellent in adhesion and adhesion durability to a substrate and an adherend, and excellent in the cutting property of a coating film, and a resin layer formed therefrom It is providing the solar cell protection sheet and solar cell module provided with. In particular, the present invention is to provide an adhesive for a solar cell protective sheet excellent in adhesion durability and cutting performance in a high-temperature and high-humidity environment, and a solar cell protective sheet and a solar cell module provided with a resin layer formed therefrom. .

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following adhesive for solar cell protective sheets, and have completed the present invention.
That is, the present invention relates to an adhesive for a solar cell protective sheet comprising a (meth) acrylic resin containing a hydroxyl group, a blocked polyisocyanate, and a polyfunctional ethylenically unsaturated double bond-containing compound having a weight average molecular weight of 700 to 20,000. About.

  Moreover, this invention relates to the said adhesive agent for solar cell protection sheets whose said (meth) acrylic-type resin is a copolymer of the mixture containing an aliphatic ring containing monomer.

  Moreover, this invention relates to the said adhesive agent for solar cell protection sheets in which the said aliphatic ring containing monomer contains the aliphatic hydrocarbon ring containing monomer whose ring member carbon number is 5-7.

  Moreover, this invention relates to the said adhesive agent for solar cell protection sheets which contains an epoxy resin further.

  Moreover, this invention relates to the solar cell protection sheet provided with the resin layer formed from a base material and the said adhesive agent for solar cell protection sheets.

  Moreover, this invention relates to the solar cell module provided with the photovoltaic cell, the sealing material, and the said solar cell protection sheet.

  The adhesive for solar cell protective sheets of this invention has the outstanding effect that it is excellent in the adhesiveness and adhesion durability with a base material or a to-be-adhered body, and is excellent in the cutting property of a coating film. Moreover, the solar cell protective sheet of the present invention has an excellent effect in adhesion durability and cutting performance in a high temperature and high humidity environment.

Hereinafter, the present invention will be described in detail. In the present specification, a numerical range specified using “to” includes numerical values described before and after “to” as a range of a lower limit value and an 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.
In the present specification, “(meth) acrylic resin” means “acrylic resin”, “methacrylic resin”, and “acrylic-methacrylic resin”, and “(meth) acryloyl”. Means “acryloyl” and “methacryloyl”, and “(meth) acryl” means “acryl” and “methacryl”.

  The adhesive for solar cell protective sheets of this invention contains the (meth) acrylic-type resin containing a hydroxyl group, blocked polyisocyanate, and the polyfunctional ethylenically unsaturated double bond containing compound of weight average molecular weight 700-20000.

First, the (meth) acrylic resin containing a hydroxyl group will be described.
A (meth) acrylic resin containing a hydroxyl group can be obtained by polymerizing a radically polymerizable (meth) acrylic monomer. Examples of radically polymerizable (meth) acrylic monomers include (meth) acrylic monomers having an alkyl group, (meth) acrylic monomers having a hydroxyl group, (meth) acrylic monomers having a carboxyl group, and glycidyl groups. (Meth) acrylic monomers and the like can be mentioned, but (meth) acrylic monomers having a hydroxyl group are included as essential components.

  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 (meth) acrylic resin, in addition to these radically polymerizable (meth) acrylic monomers, vinyl monomers such as vinyl acetate, maleic anhydride, vinyl ether, vinyl propionate, and styrene may be used.

  Among these monomers, it is preferable to use a monomer having an aliphatic ring in the monomer structure (sometimes referred to as an aliphatic ring-containing monomer) because an effect of improving durability can be obtained. Furthermore, an aliphatic hydrocarbon ring is preferable among the aliphatic rings, and an aliphatic hydrocarbon ring having 5 to 7 ring carbon atoms is more preferable. The mechanism by which the aliphatic ring structure of the monomer improves the durability of the adhesive is not clear, but the inventors consider as follows. When evaluating a member for solar cell, a durability test under high temperature and high humidity is performed as an accelerated test, but those having poor hydrolysis resistance are affected by moisture and deteriorate. It is considered that when an aliphatic ring is included in the structure of the resin used for the adhesive, it is less susceptible to hydrolysis due to the hydrophobicity of the structure, and durability is improved.

  Examples of the monomer having an aliphatic ring in the monomer structure include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, and the like. Among these monomers having an aliphatic ring, cyclohexyl (meth) acrylate and 1,4-cyclohexanedimethanol mono (meth) acrylate are preferable, and 1,4-cyclohexanedimethanol mono (meth) acrylate is particularly preferable.

  As a method for polymerizing these monomers, a conventional radical polymerization, for example, a known polymerization method such as solution polymerization, bulk polymerization or emulsion polymerization can be performed. The polymerization initiator used in the polymerization reaction includes organic peroxides such as benzoyl peroxide, acetyl peroxide, methyl ethyl ketone peroxide, lauroyl peroxide, and azo initiators such as azobisisobutyronitrile. A well-known thing can be used.

  In the present invention, the (meth) acrylic resin containing a hydroxyl group preferably has a weight average molecular weight of 10,000 to 1,000,000, more preferably 20,000 to 750,000, Furthermore, it is more preferable that it is 30,000-500,000. When the weight average molecular weight is 1,000,000 or less, the coating property is improved or the solvent solubility of the resin is improved. When the weight average molecular weight is 10,000 or more, the durability of the adhesive is further improved. In addition, the weight average molecular weight in this specification is the value of polystyrene conversion by gel permeation chromatography (GPC).

  The glass transition temperature (Tg) of the (meth) acrylic resin containing a hydroxyl group is preferably -20 to 100 ° C, more preferably 0 to 90 ° C, and further 20 to 80 ° C. Is more preferable. When the glass transition temperature is 100 ° C. or lower, the flexibility of the adhesive is increased, and the effect of improving the adhesive force to the substrate can be expected. In the case of −20 ° C. or higher, the durability of the adhesive is further improved.

  The glass transition temperature in this specification means the glass transition temperature measured by differential scanning calorimetry (DSC) for a resin obtained by drying a (meth) acrylic resin containing a hydroxyl group to a solid content of 100%. . Specifically, an aluminum pan containing a sample weighed about 10 mg and an aluminum pan not containing the sample are set in a DSC apparatus, and this is heated to −100 ° C. using liquid nitrogen in a nitrogen stream. After quenching, the temperature is raised to 200 ° 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 hydroxyl value of the (meth) acrylic resin containing a hydroxyl group is preferably from 0.1 to 100 (mgKOH / g), more preferably from 1 to 50 (mgKOH / g), and even more preferably from 2 to 30 (mgKOH / g). . When the hydroxyl value is 100 (mgKOH / g) or less, the adhesion to the substrate is further improved. Moreover, when the hydroxyl value is 0.1 (mgKOH / g) or more, it is easy to suppress a decrease in peel strength after the wet heat test.

  The (meth) acrylic resin containing a hydroxyl group may or may not have an acid value, but if the adhesive of the present invention contains an epoxy resin, the (meth) acrylic resin The acid value of is preferably 3 mgKOH / g or less.

Next, the blocked polyisocyanate used in the adhesive of the present invention will be described.
The blocked polyisocyanate functions as a crosslinking agent for crosslinking the hydroxyl group of the (meth) acrylic resin containing a hydroxyl group, and the durability of the adhesive of the present invention can be improved by crosslinking the hydroxyl group. Accordingly, the number of functional groups of the blocked polyisocyanate (the number of isocyanate groups protected by the blocking agent in the blocked polyisocyanate) is preferably 2 or more.

  The blocked polyisocyanate is formed by applying the adhesive of the present invention to a substrate and drying it to form a solar cell protective sheet, and then integrating the glass, solar cell and sealing material by thermocompression bonding under vacuum. In the process of “vacuum lamination”, the blocking agent is separated by heating and reacts with the hydroxyl group. The temperature in the vacuum laminating process is usually 140 to 160 ° C., and the time is generally about 10 to 40 minutes. Therefore, the dissociation temperature of the blocking agent is preferably 80 to 150 ° C.

  The blocked polyisocyanate can be obtained by reacting a compound containing isocyanate with a blocking agent.

  As the compound containing an isocyanate group, 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6 -Tolylene diisocyanate, 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, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene Isocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), 1 , 3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,4-bis (isocyanatomethyl) cyclohexane and the like can be mentioned.

  In addition to isocyanate compounds, adducts of the above isocyanate compounds and polyol compounds such as trimethylolpropane, burettes and isocyanurates of isocyanate compounds, and also isocyanate compounds and known polyether polyols, polyester polyols, acrylic polyols, Examples thereof include adducts such as polybutadiene polyol and polyisoprene polyol.

  Among these isocyanate compounds, a low yellowing type aliphatic or alicyclic isocyanate compound is preferable from the viewpoint of weather resistance, and isocyanurate is preferable from the viewpoint of durability. 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.

  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.

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

  The blended amount of the blocked polyisocyanate is preferably 1 to 100 parts by weight, more preferably 1 to 70 parts by weight, and 1 to 50 parts by weight with respect to 100 parts by weight of the (meth) acrylic resin. It is particularly preferred.

  Next, the polyfunctional ethylenically unsaturated double bond-containing compound used for the adhesive of the present invention will be described. A polyfunctional ethylenically unsaturated double bond-containing compound refers to a compound having two or more ethylenically unsaturated double bonds in its structure.

  It is important that the weight average molecular weight of the polyfunctional ethylenically unsaturated double bond-containing compound is 700 to 20,000. When the weight average molecular weight is 700 or more, the cutting property of the coating film is improved and the productivity is improved. Moreover, compatibility with the (meth) acrylic-type resin containing a hydroxyl group improves because the weight average molecular weight is 20000 or less, thereby improving the durability of the adhesive.

  Examples of the polyfunctional ethylenically unsaturated double bond-containing compound include EO-modified glycerin triacrylate, EO-modified pentaerythritol tetraacrylate, EO-modified bisphenol A dimethacrylate, isocyanuric acid EO-modified diacrylate and urethane resin at the end and side chain. Examples thereof include urethane acrylate having an ethylenically unsaturated double bond introduced therein. Here, EO modification means a skeleton in which a hydroxyl group such as glycerin or pentaerythritol is chain-extended with an ethylene oxide group (oxyethylene group), and the molecular weight can be controlled by the number of chain extensions of ethylene oxide. Commercially, “KAYARAD” series of Nippon Kayaku Co., Ltd., “NK Ester” series of Shin-Nakamura Chemical Co., Ltd., “Aronix” series of Toagosei Co., Ltd., “ It can be purchased as a “beam set” series.

  In the present specification, the number of functional groups of a compound containing a polyfunctional ethylenically unsaturated double bond (the number of ethylenically unsaturated double bonds in the compound) is 2, such as “bifunctional”. May be indicated depending on

  The compounding amount of the polyfunctional ethylenically unsaturated double bond-containing compound is preferably 1 to 50 parts by mass and more preferably 1 to 40 parts by mass with respect to 100 parts by mass of the (meth) acrylic resin. 1 to 30 parts by mass is particularly preferable.

  Further, by adding an epoxy resin to the adhesive of the present invention, it is possible to expect the effect of improving the adhesion durability and the heat and moisture resistance. 1-70 mass parts is preferable with respect to 100 parts of (meth) acrylic-type resins containing a hydroxyl group, and, as for the addition amount of an epoxy resin, 1-50 mass parts is more preferable.

Examples of the epoxy resin include glycidyl ether compounds and glycidyl ester compounds.
Examples of the glycidyl ether compound include bisphenol-type epoxy resins, novolac-type epoxy resins, biphenol-type epoxy resins, bixylenol-type epoxy resins, trihydroxyphenylmethane-type epoxy resins, and tetraphenylolethane-type epoxy resins. Among these, a biphenol type epoxy resin is preferable.

  Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, brominated bisphenol A type epoxy resin, and hydrogenated bisphenol A type epoxy resin.

  Examples of the novolak type epoxy resin include phenol novolak type epoxy resin, cresol novolak type epoxy resin, brominated phenol novolak type epoxy resin, naphthalene skeleton containing phenol novolak type epoxy resin, dicyclopentadiene skeleton containing phenol novolak type epoxy resin, and the like. .

  Examples of the glycidyl ester compound include terephthalic acid diglycidyl ester. These epoxy resins may be used alone or in combination of two or more.

  You may add a crosslinking accelerator to the adhesive agent of this invention in the range which does not prevent the effect by this invention as needed. The crosslinking accelerator serves as a catalyst for promoting the reaction between the (meth) acrylic resin containing a hydroxyl group and the blocked polyisocyanate. 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, and naphthenic acid. Zinc, triethylamine, triethylenediamine and the like can be mentioned. These can be used alone or in combination.

  Moreover, you may add a pigment to the adhesive agent of this invention in the range which does not prevent the effect by this invention as needed. As the pigment component, achromatic pigments such as carbon black, titanium oxide, calcium carbonate, or chromatic organic pigments can be used.

  In addition, the adhesive of the present invention may have a filler, a thixotropic agent, an anti-aging agent, an antioxidant, an antistatic agent, a flame retardant, a thermal conductivity, as long as it does not interfere with the effects of the present invention. Various additives such as improvers, plasticizers, anti-sagging agents, antifouling agents, antiseptics, bactericides, antifoaming agents, leveling agents, curing agents, thickeners, pigment dispersants, silane coupling agents are added. May be.

The adhesive of the present invention may contain 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. Two or more solvents may be used.

  The adhesive of this invention can produce a solar cell protective sheet by applying to a base material.

  As a method of applying the adhesive of the present invention to a substrate, a conventionally known method can be used. Specific examples include comma coating, gravure coating, reverse coating, roll coating, lip coating, and spray coating. By applying an adhesive by these methods and drying, a solar cell protective sheet having a resin layer made of the adhesive can be formed.

  The type of the substrate is not particularly limited. For example, polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, olefin films such as polyethylene, polypropylene, and polycyclopentadiene, polyvinyl fluoride, and polyvinylidene fluoride films. Fluorine films such as polytetrafluoroethylene film and ethylene-tetrafluoroethylene copolymer film, and plastic films such as acrylic film and triacetyl cellulose film. Alternatively, it may be applied to a rigid base material such as a glass plate. Further, the substrate may have a multilayer structure of two or more layers, and a deposited film in which a metal oxide or a nonmetallic inorganic oxide is deposited may be laminated. Furthermore, the substrate may be transparent or colored. The substrate is preferably a polyester resin film from the viewpoint of film rigidity and cost, and among them, a polyethylene terephthalate film is preferable.

  The solar cell module of the present invention can be produced by integrating a solar cell, a sealing material, and the above solar cell protective sheet through a vacuum thermocompression process called vacuum lamination. As the configuration of the module, for example, a solar cell protective sheet, a sealing material, a solar battery cell, a sealing material, a solar cell protective sheet in order, a glass plate, a sealing material, a solar battery cell, a sealing material, Although the structure etc. which are laminated | stacked in order of a solar cell protective sheet are mentioned, it is not limited to these.

  Examples of the pressure bonding conditions of the vacuum laminate described above include conditions in which vacuum defoaming is performed at 140 ° C. to 170 ° C. for about 3 to 10 minutes, and then pressing is performed at atmospheric pressure for about 10 to 50 minutes while maintaining the temperature. After thermocompression bonding, if necessary, it may be put into an oven at 100 to 200 ° C. and heated for about 5 to 60 minutes.

  Examples of the sealing material include EVA and an olefin film. These sealing materials may contain an ultraviolet absorber for improving the weather resistance, a light stabilizer or a peroxide for crosslinking the sealing material itself.

  Examples of the solar battery cell include an element in which an electrode is provided on a photoelectric conversion layer such as a compound semiconductor typified by single crystal silicon, polycrystalline silicon, amorphous silicon, or copper indium selenide. The element may be formed on a substrate such as glass.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by a following example. In Examples, unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”. The glass transition temperature, weight average molecular weight (Mw), hydroxyl value, and acid value were measured by the following methods. "

<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 measurement used what heated the resin solution to measure at 150 degreeC for about 15 minutes, and was made to dry.

<Weight average molecular weight (Mw)>
The weight average molecular weight was measured by gel permeation chromatography (GPC) under the following conditions.
GPC apparatus: Tosoh Corporation HLC-8220 GPC system column: Showa Denko KF-805L, KF-803L, and KF-802 connected in series Measurement temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 0.2 ml / min Detection: Differential refractometer (RI)
Sample: Polystyrene having a known molecular weight was used as a 0.02% concentration tetrahydrofuran (THF) solution standard substance, and the weight average molecular weight (Mw) was determined by an external standard method.

<Measurement of hydroxyl value (OHV)>
About 1 g of a sample was accurately weighed in a stoppered Erlenmeyer flask and dissolved by adding 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution. 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, a phenolphthalein test solution was added as an indicator and stirred for 30 seconds. Thereafter, the solution was titrated with a 0.5N alcoholic potassium hydroxide solution until the solution turned 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 × 28.05} / S] / (Nonvolatile content concentration / 100) + D
Where S: Amount of sample collected (g)
a: Consumption of 0.5N alcoholic potassium hydroxide solution (ml)
b: Consumption of the 0.5N alcoholic potassium hydroxide solution in the blank experiment (ml)
F: Potency of 0.5N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

<Measurement of acid value (AV)>
About 1 g of a sample was accurately weighed in a stoppered Erlenmeyer flask and dissolved by adding 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution. To this is added phenolphthalein reagent as an indicator and held for 30 seconds. Thereafter, the solution was titrated with a 0.1N alcoholic potassium hydroxide solution until the solution turned 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

<(Meth) acrylic resin A1 solution>
A reaction vessel equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube was charged with 50 parts of toluene and 50 parts of methyl ethyl ketone, and the temperature was raised to 100 ° C. in a nitrogen atmosphere. Next, a monomer mixed solution containing 1 part of methacrylic acid, 45 parts of methyl methacrylate, 1 part of 2-hydroxyethyl methacrylate, 8 parts of n-butyl methacrylate, 45 parts of t-butyl methacrylate, and 0.75 part of azobisisobutyronitrile. The mixture was added dropwise using a dropping funnel over 2 hours. Subsequently, the polymerization reaction was carried out while adding 0.3 parts of azobisisobutyronitrile in 3 portions over 3 hours, and the mixture was further stirred for 1 hour for polymerization to have a weight average molecular weight of 12,000, A (meth) acrylic resin A1 solution having a Tg of 102 ° C., a hydroxyl value of 4.3 (mgKOH / g), an acid value of 6.5 (mgKOH / g), and a solid content of 50% was obtained.

<(Meth) acrylic resin A2-A5 solution>
The (meth) acrylic resin A2-A5 solution was prepared in the same manner as the synthesis of the (meth) acrylic resin A1 solution except that the types and amounts of the monomer and azobisisobutyronitrile were changed as shown in Table 1. Synthesized.

In addition, the symbol in Table 1 shows the following.
MAA: methacrylic acid MMA: methyl methacrylate CHMA: cyclohexyl methacrylate (aliphatic hydrocarbon ring-containing monomer having 6 ring carbon atoms)
HEMA: 2-hydroxyethyl methacrylate CHDMMA: 1,4-cyclohexanedimethanol monoacrylate (aliphatic hydrocarbon ring-containing monomer having 6 hydroxyl group carbon atoms)
BA: butyl acrylate nBMA: n-butyl methacrylate tBMA: t-butyl methacrylate IBMA: isobornyl methacrylate (aliphatic hydrocarbon ring-containing monomer having 7 ring member carbon atoms)
AIBN: Azobisisobutyronitrile

<(Meth) acrylic resin A6 solution>
In a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer and a dropping tube, 90 parts of water was added and the temperature in the reaction vessel was raised to 85 ° C., and then 0.1 part of potassium persulfate was added.
Next, 50 parts of water, 0.8 part of methacrylic acid, 10 parts of methyl methacrylate, 0.2 part of 2-hydroxyethyl methacrylate, 49 parts of butyl acrylate, 40 parts of n-butyl methacrylate, sodium lauryl sulfate (product name: EMAL O [Made by Kao Co., Ltd.]) 20% aqueous solution 1.5 parts and polyoxyethylene lauryl ether (Product name: Emulgen 123P [Kao Co., Ltd.]) 2% mixed solution mixed, It dropped over 2 hours from the dripping layer in the reaction container. During the dropping, the temperature in the reaction vessel was kept at 80 ° C. After completion of dropping, the mixture was kept at 80 ° C. for 2 hours. Finally, it is cooled to 25 ° C., adjusted to pH 8 by adding 25% aqueous ammonia, filtered, weight average molecular weight is 910,000, Tg is −16 ° C., and hydroxyl value is 0.9 (mg KOH / g ), A (meth) acrylic resin A6 solution having an acid value of 5.2 (mgKOH / g) and a solid content of 40% was obtained.

<(Meth) acrylic resin A7 to A9 solution>
(Meth) acrylic resins A7 to A9 were synthesized in the same manner as the synthesis of the (meth) acrylic resin A6 solution except that the types and amounts of the monomer and potassium persulfate were changed as shown in Table 2.
The abbreviations for (meth) acrylic monomers in Table 2 are the same as those in Table 1.

<Blocked polyisocyanate B1 solution>
75% solid content comprising isocyanurate of hexamethylene diisocyanate blocked with methyl ethyl ketone (MEK) oxime and isocyanurate of hexamethylene diisocyanate blocked with 3,5-dimethylpyrazole in a mass ratio of 1: 1. This solution was designated as blocked polyisocyanate solution B1.

<Blocked polyisocyanate B2 solution>
An isocyanurate emulsion solution of hexamethylene diisocyanate blocked with 3,5-dimethylpyrazole was designated as blocked polyisocyanate solution B2.

[Examples 1 to 13]
<Adhesive solution 1-13>
A solution prepared by blending (meth) acrylic resin, a polyfunctional ethylenically unsaturated double bond-containing compound, and a blocked polyisocyanate at a ratio (part) shown in Table 3 as a solid content ratio, and adhesive solutions 1 to 13 did.

In addition, the polyfunctional ethylenically unsaturated double bond containing compound in Table 3 shows the following.
KAYARAD DPCA-20: Nippon Kayaku Co., Ltd., bifunctional, weight average molecular weight 748
KAYARAD DPCA-60: Nippon Kayaku Co., Ltd., 6 functional, weight average molecular weight 1088
KAYARAD DPCA-120: Nippon Kayaku Co., Ltd., 6 functional, weight average molecular weight 1946

[Examples 14 to 21]
<Adhesive Solution Examples 14 to 21>
Adhesive solution containing (meth) acrylic resin, epoxy resin, polyfunctional ethylenically unsaturated double bond-containing compound, and blocked polyisocyanate in proportions (parts) shown in Table 4 in solid content ratio Solutions 14-21 were obtained.

In addition, the epoxy resin in Table 4 shows the following.
jER834: manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin jER1004: manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin jER1009: manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin YDPN-638: Nippon Steel & Sumikin Chemical ( Co., Ltd., phenol novolac type epoxy resin Denacol EX-821: manufactured by Nagase ChemteX Corporation, polyethylene glycol diglycidyl ether

[Examples 22 to 25]
<Adhesive solution 22-25>
A solution prepared by blending a (meth) acrylic resin, a polyfunctional ethylenically unsaturated double bond-containing compound, and a blocked polyisocyanate at a ratio (parts) shown in Table 5 as a solid content ratio is used as adhesive solutions 22 to 25. did.

In addition, the polyfunctional ethylenically unsaturated double bond containing compound in Table 5 shows the following.
UCECOAT 7788: manufactured by Daicel Ornex Co., Ltd., weight average molecular weight 20000
UCECOAT 7200: Daicel Ornex Co., Ltd., weight average molecular weight 1000
Beam set EM-90: Arakawa Chemical Industries, Ltd., weight average molecular weight 2000
UA-W2A: Shin-Nakamura Chemical Co., Ltd., weight average molecular weight 3500

[Examples 26 to 31]
<Adhesive solution 26-31>
An adhesive solution is a solution in which a (meth) acrylic resin, an epoxy resin, a polyfunctional ethylenically unsaturated double bond-containing compound, and a blocked polyisocyanate are blended in proportions (parts) shown in Table 6 as solid content ratios. 26-31.

In addition, the epoxy resin in Table 6 shows the following.
jER W2821R70: manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin jER W3435R67: manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin jER W1155R55: manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin Adeka Resin EM-1- 61L: Made by ADEKA, bisphenol A type epoxy resin

[Comparative Examples 1-3]
<Adhesive solution 32-34>
A solution prepared by blending a (meth) acrylic resin, a polyfunctional ethylenically unsaturated double bond-containing compound, and a blocked polyisocyanate at a ratio (parts) shown in Table 7 as a solid content ratio is used as an adhesive solution 32-34. did.
・ “Adhesive solutions 21 to 23” cannot be distinguished from Examples 21 to 23, so we will correct them to 32 to 34 for the time being.

In addition, the polyfunctional ethylenically unsaturated double bond containing compound in Table 7 shows the following.
TMPTA: trimethylolpropane triacrylate, trifunctional, weight average molecular weight 296
DPHA: dipentaerythritol hexaacrylate, hexafunctional, weight average molecular weight 578
KAYARAD DPCA-20: Nippon Kayaku Co., Ltd., bifunctional, weight average molecular weight 748

  The adhesive solutions 1 to 34 obtained above were evaluated for adhesiveness and cutting property by the methods described below.

<EVA adhesive strength evaluation>
The adhesive solution was applied to the corona-treated surface of a 188 μm thick polyester film (Lumirror X10S, manufactured by Toray Industries, Inc.) with a gravure coater, and dried at 100 ° C. for 1 minute. A layer (resin layer) was produced. Heat of an EVA film (Ultra Pearl PV-45FR00S manufactured by Sanvic Co., Ltd.) and a white plate glass plate on the anchor coat layer, and a laminate laminator PVL0505S (manufactured by Nisshinbo Mechatronics Co., Ltd.) heated to 140 ° C. The glass plate was placed on the plate with the white plate glass facing down, evacuated to 1 Torr, and left for 4 minutes. Next, the sample was pressed at atmospheric pressure while maintaining 140 ° C., and left for 16 minutes to prepare a sample for evaluating adhesive strength. The surface of the polyester film was cut to a width of 15 mm with a cutter, and the adhesive force between the anchor coat layer and the EVA film was immediately measured (this adhesive force is referred to as “initial”). 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 measured values were evaluated based on the following criteria.
S: 50 N / 15 mm or more (very good)
A: 30 N / 15 mm or more to less than 50 N / 15 mm (good)
B: 10N / 15mm or more to less than 30N / 15mm (usable)
C: Less than 10N / 15mm (defect)

  Next, this adhesive strength evaluation sample 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, and then the adhesive strength was evaluated in the same manner as above. This test method is called a dump heat (DH) test, and those after standing for 1000 hours and 2000 hours are referred to as “after DH 1000 h” and “after DH 2000 h”, respectively.

  Tables 3 to 7 show the initial adhesive strength of each adhesive solution to the EVA film and the results after DH1000h and after DH2000h.

<Cutting evaluation>
Each adhesive solution was applied to a corona-treated surface of a 188 μm thick polyester film (manufactured by Toray Industries, Inc., Lumirror X10S) with a gravure coater, and dried at 100 ° C. for 1 minute. Produced. Next, the film coated with the adhesive using a cutting machine was cut into A4 size, and the peeled state of the anchor coat layer from the cut end polyester film was confirmed. This peeled state was confirmed visually and evaluated as follows.
○: No peeling of the anchor coat layer on the cut end face (good)
X: Peeling of the anchor coat layer is observed on the cut end face (defect)

The results of cutting evaluation are shown in Tables 3 to 7.
As is clear from Tables 3 to 7, the adhesives of the present invention (Examples 1 to 31) all had excellent adhesiveness and cutting properties, whereas the comparative adhesives had adhesiveness or cutting properties. It became clear that one of sex was inferior. In the adhesives of Comparative Examples 1 and 2, since the polyfunctional ethylenically unsaturated double bond-containing compound has a small weight average molecular weight, the coating film becomes brittle and the cutting property is deteriorated. It is presumed that durability was deteriorated because it did not contain isocyanate.

Claims (6)

  An adhesive for a solar cell protective sheet, comprising a (meth) acrylic resin containing a hydroxyl group, a blocked polyisocyanate, and a polyfunctional ethylenically unsaturated double bond-containing compound having a weight average molecular weight of 700 to 20,000.   The adhesive for solar cell protection sheets of Claim 1 whose said (meth) acrylic-type resin is a copolymer of the mixture containing an aliphatic ring containing monomer.   The adhesive for solar cell protective sheets according to claim 2, wherein the aliphatic ring-containing monomer includes an aliphatic hydrocarbon ring-containing monomer having 5 to 7 ring carbon atoms.   Furthermore, the adhesive agent for solar cell protection sheets of any one of Claims 1-3 containing an epoxy resin. The solar cell protective sheet provided with the resin layer formed from a base material and the adhesive agent for solar cell protective sheets of any one of Claims 1-4.   The solar cell module provided with the photovoltaic cell, the sealing material, and the solar cell protection sheet of Claim 5.