KR101847153B1 - Adhesive composition for multilayer sheets, and backside protective sheet for solar cells - Google Patents

Abstract

Provided is an adhesive composition suitable for the production of a backsheet for a solar cell capable of maintaining a high adhesive force even when exposed to a high temperature and high humidity environment showing high adhesive strength between various sheet-like members, in particular, between layers including a surface treatment layer of a plastic film. The adhesive composition for a laminated sheet according to the present invention contains an acrylic polyol (A) and a polyisocyanate (B), wherein the acryl polyol (A) has a number average molecular weight of 10,000 to 100,000, (1) to 100 mgKOH / g, and a glass transition temperature (Tg) of more than 10 DEG C and not more than 50 DEG C, and furthermore, an equivalent ratio NCO / OH of an hydroxyl group derived from the acrylic polyol (A) to an isocyanate group derived from the polyisocyanate Is set to 0.1 to 10.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an adhesive composition for a laminated sheet and a backsheet for a solar battery,

The present invention relates to an adhesive composition for a laminated sheet and a backsheet for a solar cell.

Recently, there has been a demand for an outdoor industrial application such as a barrier film, a roofing material, a solar cell panel material, a window material, an outdoor laminate material, a multilayer (composite) film used for a lighting protection material, A multilayer (composite) laminate has been put to practical use. The multilayer laminate can be obtained by laminating (laminating) a metal material or a plastic material. Examples of metal materials include metal foils such as aluminum, copper, and steel plates, metal plates, and metal evaporated films. Examples of the plastic material include plastic films such as polypropylene, polyvinyl chloride, polyester, fluorine resin and acrylic resin, and plastic films formed on the surface of inorganic oxide layers such as plastic sheet, plastic plate and silica deposition film. BACKGROUND ART Conventionally, polyepoxy-based adhesives and polyurethane-based adhesives have been known as adhesives used for joining metal-related materials and plastic-based materials.

Patent Document 1 discloses a sealing sheet for a solar cell having a laminate in which at least two layers of a base material are fitted with a polyurethane-based adhesive. More specifically, condition 1: the laminate strength after storage at 105 DEG C, 1.05 atm for 168 hours in a HAST chamber, which is an acceleration evaluation device by pressurized steam, is at least 1N / 15 mm or more, and Condition 2: In an HAST chamber at 105 DEG C and 1.05 atm for 168 hours and then satisfying the condition that the substrate is not peeled off by peeling. Specifically, a plurality of polyurethane-based adhesives in which a crosslinking agent is combined with each of the six types of polyols A to F has been proposed (see claims 2 to 11 of Patent Document 1).

Patent Document 2 discloses a back sheet for a solar cell module having a laminate in which at least two substrates are adhered with an acrylic adhesive. More specifically, an acrylic adhesive containing an acrylic polymer obtained by polymerizing a monomer component containing a monomer represented by the general formula (I) as an acrylic adhesive having resistance to decomposition, resistance to moisture and moisture has been proposed (see Patent Document 2 2).

CH ₂ = C (R ¹ ) -CO-OZ (I)

In the formulas, R ¹ represents a hydrogen atom or a methyl group, and Z represents a hydrocarbon group having 4 to 25 carbon atoms.

Patent Documents 3 and 4 disclose an adhesive composition suitable for use in a sheet bonded with a base material different from the plastic film.

Patent Document 1: International Publication No. 2007-148754 Patent Document 2: JP-A-2009-246360 Patent Document 3: JP-A-2011-105819 Patent Document 4: JP-A-2011-111519

It is important that the adhesive strength is stable over time in order to stably maintain the adhesive over a long period of time under harsh outdoor conditions. In recent years, development of adhesives for adhering different substrates and untreated plastic surfaces, such as polyester films, which are not subjected to surface treatment as in Patent Documents 3 and 4, is in full swing. This is because the surface treatment is not performed and the manufacturing process can be shortened, thereby reducing the cost. On the other hand, there is a high demand for an adhesive composition having a synergistically superior adhesive property by further enhancing the original performance of the adhesive composition by utilizing the surface treatment technology that has been used conventionally.

The present invention is based on the above background and aims to maintain high adhesion even when exposed to a high temperature and high humidity environment showing high adhesion between various sheet members, especially between layers including a surface treatment layer of a plastic film An adhesive composition for a laminated sheet suitable for the production of a backsheet for a solar cell and a backsheet for a solar cell.

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following adhesive composition for a laminated sheet, and have completed the present invention.

That is, the adhesive composition for a laminated sheet according to the present invention is an adhesive composition for a laminated sheet containing an acrylic polyol (A) and a polyisocyanate (B), wherein the acryl polyol (A) has a number average molecular weight of 10,000 to 100,000, (Tg) is more than 10 ° C and not more than 50 ° C and the equivalent ratio of the hydroxyl group derived from the acrylic polyol (A) to the isocyanate group derived from the polyisocyanate (B) is in the range of 1 to 100 mg KOH / / OH is from 0.1 to 10.

Preferable examples of the polyisocyanate (B) include aliphatic cyclic diisocyanates or polyisocyanates derived from aliphatic diisocyanates.

The adhesive composition for a laminated sheet of the present invention is used for producing a backsheet for a solar cell having a sheet type member having two or more layers and for forming at least a part of an adhesive layer for bonding the sheet- It is used reasonably.

The backsheet for a solar cell according to the present invention comprises an adhesive layer formed from the adhesive composition for a laminated sheet of the above embodiment and two or more sheet-shaped members laminated through the adhesive layer.

According to the present invention, there is provided a laminated sheet suitable for the production of a backsheet for a solar cell, which can maintain a high adhesive force even when exposed to a high temperature and high humidity environment showing a high adhesive force between various sheet- An adhesive composition for a solar cell and a backsheet for a solar cell.

Hereinafter, embodiments of the present invention will be described in detail. Incidentally, other embodiments are within the scope of the present invention as long as they are consistent with the purpose of the present invention. In the present specification, the expression "any number A to arbitrary number B" means a range larger than the number A and the number A, and a range smaller than the number B and the number B. The notation "(meth) acryloyl" in the present specification and claims includes both compounds that can be read with "acrylo" and compounds that can be read with "methacrylo". Also, "(meth) acrylic" and "(meth) acrylate" are similarly defined.

≪ Acrylic polyol (A) >

The acrylic polyol (A) is preferably an interpolymer of a mono (meth) acrylate monomer containing a hydroxyl group and a mono (meth) acrylate monomer containing no hydroxyl group. The hydroxyl group-containing mono (meth) acrylate monomer is a monomer containing one (meth) acryloyl group and at least one hydroxyl group in one molecule. Preferred examples thereof include mono (meth) acrylic acid ester monomers and ε-caprolactone modified (meth) acrylic monomers which can be obtained by the reaction of a dihydric alcohol and (meth) acrylic acid.

From the viewpoint of improving the adhesive strength, the acrylic polyol (A) has a number average molecular weight of about the same level as that of the acrylic polyol (A) in the portion not involved in copolymerization of the mono (meth) acrylate monomer, Alkenyl group, etc. Hereinafter, the number of carbon atoms in the "side chain portion") is preferably from 1 to 17, more preferably from 1 to 9, still more preferably from 1 to 3. The side chain portion on the upper side forms a side chain of the acrylic polyol (A) after the copolymerization. Mono (meth) acrylate monomer The number of carbon atoms in the side chain moiety is generally about 1 to 30, but if the number average molecular weight of the acrylic polyol (A) is about the same, Is relatively long. As a result, it is considered that the mechanical properties (specifically, the increase rate) of the adhesive layer after curing are improved and the adhesive strength is improved.

Examples of mono (meth) acrylic acid ester monomers obtainable from dihydric alcohols include 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 1,4-butanediol mono (meth) (Poly) ethylene glycol mono (meth) acrylate, and the like.

Furthermore, a mono (meth) acrylic acid ester monomer obtained from a trivalent or higher alcohol such as 2,3-dihydroxypropyl (meth) acrylate can also be used as a mono (meth) acrylate monomer containing a hydroxyl group.

The mono (meth) acrylate monomers not containing a hydroxyl group can be appropriately selected from previously known radically polymerizable monomers. (Meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (Meth) acrylate monomer represented by alkyl (meth) acrylate monomers such as acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate and stearyl (meth) acrylate, acrylonitrile and the like have.

In addition to the above mono (meth) acrylate monomers containing no hydroxyl groups and mono (meth) acrylate monomers containing no hydroxyl groups, other monomers such as (meth) acrylic acid, maleic acid, maleic anhydride, A monomer, an anhydride thereof, or a vinyl monomer such as styrene may be copolymerized. The hydroxyl group-containing (meth) acrylate monomers and the hydroxyl group-free mono (meth) acrylate monomers may be used alone or in combination of two or more compounds. The same applies to the case where other monomers are used.

In the present invention, the number average molecular weight of the acrylic polyol (A) should be 10,000 to 100,000. Further, it is preferably 10,000 to 70,000, more preferably 25,000 to 50,000.

A laminated sheet in which two or more sheet-like members are laminated using the adhesive composition for a laminated sheet of the present invention (hereinafter also referred to as an " adhesive composition "), for example, a backsheet for a solar battery, Loses. The adhesive composition is coated and dried on the bonding surface of one of the sheet-like members. Then, another sheet-like member is superimposed on the adhesive layer, and curing of the adhesive layer is carried out in a process called "aging" in which storage is carried out for about 2 days to 1 week under an environment of 40 ° C to 60 ° C to obtain a laminated sheet.

When the number-average molecular weight of the acrylic polyol is less than 10,000, the cohesive force of the adhesive layer before the aging step tends to be insufficient, and the adhesive force before the aging step can be reduced. In the case of industrial production, the laminate in the rolled state is aged in the direction of the normal direction. If the adhesive strength before the aging step is small, the roll tends to collapse during aging and is unsuitable for industrial production. On the other hand, when it is less than 10,000, the cohesive force after the aging step tends to be insufficient. As a result, the heat and humidity resistance may be lowered and peeling may occur.

When the number-average molecular weight of the acrylic polyol is more than 100,000, the viscosity of the adhesive becomes high, which causes problems in the coating property and the wettability of the sheet-like member to deteriorate. As a result, the adhesive strength before the aging step can be reduced. The initial adhesive force is increased by aging as compared with that before aging. However, the initial adhesive strength is gradually lowered by the after-wet heat resistance test, and may be lower than the lower limit after 3000 hours have elapsed.

The number average molecular weight of the present invention is determined by gel permeation chromatography (GPC) and is a polystyrene reduced value. More specifically, the number average molecular weight of the present invention is a value obtained by the measurement method described in the following examples. Also, the glass transition temperature and the NCO / OH equivalent ratio similarly show values obtained by the methods described in the following examples.

The hydroxyl value of the acrylic polyol (A) is determined according to the content of the hydroxyl group-containing mono (meth) acrylate monomer. In the present invention, the hydroxyl value is 1 to 100 mgKOH / g. And more preferably 4 to 40 mgKOH / g. If it is less than 1 mgKOH / g, the crosslinking with the isocyanate curing agent tends to be lowered, which may lower the heat and humidity resistance. On the other hand, if it exceeds 100 mgKOH / g, the adhesive strength before aging can be expressed, but the crosslinking density after the aging tends to be high, so that sufficient adhesive force can not be exhibited and the adhesion strength may be lowered in the subsequent humidity and humidity test.

In the present invention, the glass transition point (Tg) of the acrylic polyol (A) should be 10 ° C or more and 50 ° C or less for reasons to be described later. And more preferably 10 ° C or higher and 30 ° C or lower.

≪ Polyisocyanate (B) >

The polyisocyanate (B) can be used, for example, without limitation, a known compound which is a compound derived from a known diisocyanate. For example, 2,4-tolylene diisocyanate (aka 2,4-TDI), 2,6-tolylene diisocyanate (aka 2,6-TDI), xylene diisocyanate (aka XDI) Diisocyanates such as diisocyanate (aka MDI), isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexadiisocyanate (aka HDI), bis (4-isocyanatocyclohexyl) methane, or hydrolyzed diphenylmethane diisocyanate , A prepolymer (a diisocyanate and a low polymer obtained from a polyol) having a isocyanate residue, a compound having an isocyanate group, such as a nylate of the diisocyanate, a trimethylolpropane duct, a biuret, , Allophanate groups, or complexes thereof and block isocyanates. The polyisocyanate (B) may be used singly or in combination of two or more.

From the viewpoint of viscoelasticity of the cured coating film after crosslinking, the polyisocyanate (B) is preferably a polyisocyanate derived from aliphatic cyclic diisocyanate or aliphatic diisocyanate. More specifically, examples of the alicyclic diisocyanate include isophorone diisocyanate and methyl-2,6-cyclohexane diisocyanate. Examples of the aliphatic diisocyanate include hexadiisocyanate, pentamethylene diisocyanate, and the like. Also included are a nylate of a diisocyanate, a trimethylolpropane duct, a biuret type, a prepolymer having a isocyanate residue (a low polymer obtained from a diisocyanate and a polyol), which is a derivative of a compound of an aliphatic cyclic diisocyanate and an aliphatic diisocyanate, A uretdione compound having an isocyanate residue, an allophanate compound, or a complex thereof.

When it is important that the curing speed is high, it is preferable to use an isocyanate having an aromatic ring such as xylene diisocyanate (aka XDI), but having an alkylene group between the NCO and the aromatic ring. A faster curing rate is desirable in that the aging time can be reduced.

The isocyanate component concentration in the polyisocyanate (B) is preferably 5 to 30% by weight. The isocyanate component concentration in the polyisocyanate (B) can be determined by an appropriate method. The titration was evaluated by n-butylamine-hydrochloric acid titration. Specifically, the sample is dissolved in dry toluene, and an excess n-dibutylamine solution is added to react. The remaining n-dibutylamine is reversely titrated with hydrochloric acid and the inflection point on the titration curve is used as an end point. And the component content was calculated.

The amount of the polyisocyanate (B) to be used is determined by the NCO / OH equivalent ratio between the hydroxyl group derived from the acrylic polyol (A) and the isocyanate group derived from the polyisocyanate (B). The NCO / OH equivalent ratio is 0.1 to 10. More preferably, the NCO / OH equivalent ratio is 0.5 to 6. When it is less than 0.1, the adhesive strength tends to decrease after the indoor / outdoor exposure. And if it exceeds 10, the adhesive force after aging tends to decrease. The NCO / OH equivalence ratio was obtained using the following equation (1).

NCO / OH ratio = polyisocyanate required amount (parts by weight) x (561 / OH value) x (NCO% / (42 x 100) x 100 / polyol amount (solid content weight)

The present inventors have found that an adhesive composition for a laminated sheet having surprisingly excellent properties can be obtained by satisfying all of the following conditions. That is, the acrylic polyol (A) having the number average molecular weight of (i) the specific range, (ii) the hydroxyl value of the specific range, and (iii) the glass transition temperature (Tg) ) By satisfying all of the conditions that the equivalent ratio NCO / OH of the hydroxyl group derived from the acrylic polyol (A) to the isocyanate group derived from the polyisocyanate (B) is in the above specific range, It is possible to provide an adhesive composition capable of producing a backsheet for a solar cell capable of maintaining a high adhesive force even when exposed to a high temperature and high humidity environment showing high adhesion between layers including layers. Hereinafter, the reason will be described.

Compared with the case where a plastic film having no surface treatment is laminated, a plastic film having a surface treated with a corona discharge or the like is laminated, which requires added value as much as the manufacturing process increases. In the case of the adhesive force, a higher adhesive force is required than in the case of laminating a plastic film having no surface treatment.

If the Tg of the acrylic polyol is lowered, the adhesive layer before aging still has insufficient curing, so that the adhesive layer formed from the adhesive composition is soft. Depending on the softness, a certain degree of adhesive force can be developed between the sheet-like members. However, even after the curing of the adhesive layer sufficiently after aging, since the Tg of the acrylic polyol as the starting material is low, the lack of cohesive force of the adhesive layer is surfaced, which tends to make it difficult to secure a large adhesive force. Furthermore, if the laminate is left under a high temperature and high humidity for a long time, the adhesive force tends to gradually decrease due to the lack of cohesive force of the adhesive layer.

On the other hand, if the Tg of the acrylic polyol is too high, the wettability to the substrate tends to be insufficient. The adhesive strength after aging is somewhat larger than that before aging. However, since the cured adhesive layer after crosslinking is hardened, the adhesive force tends to deteriorate after the aging step. The reason why the above-mentioned excellent effects are obtained in the present invention is that the Tg of the acrylic polyol is not too low and is not too high (more specifically, more than 10 ° C but not more than 50 ° C) It is considered that the wettability and fixability of the adhesive object can be improved by utilizing the activity of the acrylic polyol synergistically at a molecular motion level by making the NCO / OH equivalent ratio and the specific number average molecular weight range. Especially, it is considered that by controlling the equivalent ratio of NCO / OH to the range of 0.1 to 10, particularly in the range of 0.5 to 6, a proper balance of the degree of crosslinking can be realized and a high adhesive force can be exhibited after the aging step. Moreover, surprisingly, it was found that even before aging, high adhesion was exhibited. Further, it has been found that a high adhesive strength can be maintained even after being placed under high temperature and high humidity after the aging step.

The adhesive composition for a laminated sheet of the present invention preferably contains a silane coupling agent from the viewpoint of improving the adhesive strength when a metal foil, a metal plate, a metal vapor deposition film or the like is used as a substrate.

Examples of the silane coupling agent include, but are not limited to, vinylsilanes such as vinyltris (? -Methoxyethoxy) silane, vinylethoxysilane and vinyltrimethoxysilane; (meth) acryloxysilanes such as? - (meth) acryloxypropyltrimethoxysilane,? - (meth) acryloxypropyltriethoxysilane and? - (meth) acryloxypropyldimethoxymethylsilane; ? - (3,4-epoxycyclohexyl) ethyltrimethoxysilane,? - (3,4-epoxycyclohexyl) methyltrimethoxysilane, ,? - (3,4-epoxycyclohexyl) methyltriethoxysilane,? -glycidoxypropyltrimethoxysilane and? -glycidoxypropyltriethoxysilane; Aminoethyl) gamma -aminopropyltrimethoxysilane, N-beta (aminoethyl) gamma -aminopropyltriethoxysilane, N- beta (aminoethyl) Aminosilanes such as aminopropyltriethoxysilane,? -Aminopropyltrimethoxysilane, N-phenyl-? -Aminopropyltrimethoxysilane and N-phenyl-? -Aminopropyltriethoxysilane; And thiosilanes such as? -Mercaptopropyltrimethoxysilane and? -Mercaptopropyltriethoxysilane. These may be used alone or in combination of two or more.

The addition amount of the silane coupling agent is preferably 0.1 to 5 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of the acrylic polyol (A). When the amount is less than 0.1 part by weight, the effect of improving the adhesion strength to the metal foil by adding the silane coupling agent is insufficient, and even if the amount exceeds 5 parts by weight, further improvement in performance may not be recognized.

The adhesive composition for a laminated sheet of the present invention may be a so-called two-liquid mixing type adhesive in which a base and a curing agent are mixed at the time of use, or a one-liquid type adhesive in which a base and a curing agent are mixed in advance. Further, the acrylic polyol (A) or the polyisocyanate (B) according to the present invention may be used independently in various kinds. Further, the subject other than the present development and the curing agent may be used independently or singly or as a plurality of kinds. Usually, the subject includes an acrylic polyol (A), a silane coupling agent, an organic solvent, and other additives, and the curing agent includes a polyisocyanate (B), an organic solvent, and other additives.

As other additives, the adhesive for a laminated sheet of the present invention may contain additives such as a tackifier, a reaction promoter, a leveling agent, a phosphorus-based or phenol-based antioxidant, a UV stabilizer, a metal deactivator, Retardants, plasticizers, organic and inorganic pigments, and the like.

When a metal layer (metal foil, metal plate or the like) is used as the sheet-like member, a phosphate compound such as phosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid or an ester thereof Etc. may be added.

The adhesive composition for a laminated sheet of the present invention is preferably used as an adhesive for producing a backsheet for a solar cell, and can also be used as an anchor coat for a solar cell laminated sheet. In that case, it is preferable to add an anti-blocking agent. In addition, known additives for adhesives can be blended without limitation without departing from the spirit of the present invention. For example, a reaction accelerator may be used. Specifically, metal-based catalysts such as dibutyl tin diacetate, dibutyl tin dilaurate, dioctyl tin dilaurate and dibutyl tin dimaleate; 1,8-diaza-bicyclo (5,4,0) undecene-7,1,5-diazabicyclo (4,3,0) nonene-5,6-dibutylamino- Tertiary amines such as carbacycl (5,4,0) undecene-7; And reactive tertiary amines such as triethanolamine. As the reaction promoter, one or more reaction promoters may be used.

For the purpose of improving the appearance of the laminate, a known leveling agent or antifoaming agent may be added to the subject.

Examples of the leveling agent include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl-containing polydimethylsiloxane, polyetherester-modified hydroxyl-containing polydimethylsiloxane, acrylic copolymer, Based copolymer, a polyether-modified polymethylalkylsiloxane, an acrylic acid alkyl ester copolymer, a methacrylic acid alkyl ester copolymer, lecithin, or a mixture thereof.

Examples of the defoaming agent include silicone resins, silicone solutions, copolymers of alkyl vinyl ethers and alkyl acrylates and methacrylates, and mixtures thereof. When a leveling agent and defoaming agent are added, one compound may be used independently or two or more compounds may be arbitrarily used in combination.

In addition, for the purpose of further suppressing the yellowing of the adhesive due to the heat of yellowing and solar heat over time of the adhesive by the ultraviolet ray such as sun as a known additive used in the present invention, known phosphorus and phenol- Antioxidants, UV stabilizers, and metal deactivators can be incorporated into the subject. These may be used alone or in combination of two or more kinds. The phosphorus-containing and phenol-based antioxidant, ultraviolet stabilizer and metal deactivator used in the present invention are preferably used in an amount of 0.05 to 5 parts by weight, more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the solid content of the acrylic polyol (A) to be. If the addition amount is less than 0.05 parts by weight, a sufficient yellowing inhibiting effect may not be obtained. If the addition amount is more than 5 parts by weight, the adhesive strength of the adhesive may be greatly deteriorated.

The curing agent may be a known oxazoline compound such as 2,5-dimethyl-2-oxazoline or 2,2- (1, 2-dimethyl-2-oxazoline) optionally in addition to the polyisocyanate (B) 4-butylene) bis (2-oxazoline), or hydrazide compounds such as isophthalic acid dihydrazide, sebacic acid dihydrazide, or adipic acid dihydrazide.

Examples of the solvent to be used in the present invention include esters such as ethyl acetate, butyl acetate and cellosolve acetate; Ketones such as acetone, methyl ethyl ketone, isobutyl ketone, methyl isobutyl ketone, and cyclohexanone; Ethers such as tetrahydrofuran and dioxane; Aromatic hydrocarbon such as toluene and xylene; Halogenated hydrocarbons such as methylene chloride and ethylene chloride; Dimethyl sulfoxide, dimethylsulfoamide, and the like. These may be used alone or in combination of two or more.

The nonvolatile matter (solid content) of the adhesive of the present invention is preferably in the range of 10 to 50% by weight. This adhesive can be adjusted in solids content using a solvent as exemplified above.

Next, a method for producing a backsheet for a solar cell using the adhesive composition for a laminated sheet of the present invention and an example of a backsheet for a solar cell will be described. The manufacturing method and construction of the backsheet for a solar cell are not limited to the following examples, and various manufacturing methods and configurations may be employed depending on the purpose and necessity.

The solar cell module has a configuration in which a filler and a glass plate are sequentially stacked on both sides of a solar cell cell, which is a solar cell element. The glass sheet is excellent in transparency, weather resistance, and scratch resistance, and is used as a sealing sheet on the light receiving surface side of the sun. However, on the non-light-emitting side, which does not require transparency, in terms of cost, safety, and workability, glass backing sheets for solar cells other than glass have been developed by each company, replacing glass plates.

BACKGROUND OF THE INVENTION [0002] A backsheet for a solar cell is formed by laminating a plastic film such as a polyester film, a plastic film having a metal layer provided with a deposition layer of a metal oxide and a non-metal oxide on a polyester film, a metal foil such as an aluminum foil, There is one thing. Between the respective sheet-like members to be laminated can be bonded by using the adhesive composition for a laminated sheet of the present invention. The backsheet for a solar cell of a composite structure can impart various performances according to its multilayer structure. For example, waterproofing properties can be imparted by using an aluminum foil by using a polyester film and by using an aluminum foil by using a fluorine film. Which solar cell backsheet to use depends on the products and applications in which the solar cell module is used.

Examples of the plastic film include a polyester resin film such as polyethylene terephthalate and polynaphthalene terephthalate, a polyethylene resin film, a polypropylene resin film, a polyvinyl chloride resin film, a polycarbonate resin film, a polysulfone resin film , Poly (meth) acrylic resin film, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, polyethylene tetrafluoroethylene, Teflon, tetrafluoroethylene, perfluoroalkyl vinyl ether copolymer, tetrafluoro Ethylene-hexafluoropropylene copolymer, and the like.

These plastic films can be used as a support, a film coated with an acrylic or fluorine-based paint, or a multilayered film obtained by co-extruding polyvinylidene fluoride or an acrylic resin or the like. Alternatively, a sheet-like member in which a plurality of the above-described plastic films are laminated through a urethane adhesive layer or the like may be used.

The plastic film can be easily adhered to the surface of the plastic film by physical treatments such as corona discharge, plasma treatment and frame treatment, chemical treatment for improving the film surface by acid or alkali, and matte working by putting fine irregularities on the film surface, It can be used suitably as the surface. Needless to say, the adhesive composition for a laminated sheet of the present invention may be applied to a surface-untreated material.

The metal foil may be an aluminum foil or a copper foil. As the metal oxide or non-metal inorganic oxide to be deposited, oxides such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium and yttrium can be used.

Among them, polyesters such as polyethylene terephthalate and poly naphthalene terephthalate, which have resistance to temperature, in order to satisfy the properties such as weather resistance, water vapor permeability, insulation, mechanical characteristics, and mounting workability when used as a solar cell module Based plastic film and a metal foil such as a plastic film on which a non-metal inorganic oxide is deposited, or a metal foil such as an aluminum foil, or the like, in order to prevent the output power from being affected by water of the solar cell, , And a back protection sheet for a solar cell in which a fluororesin film having good weather resistance is laminated is preferable in order to prevent appearance defect due to light deterioration.

In addition, in order to protect the solar cell module from damage by voltage application, the back protection sheet for the solar cell is required to have a partial discharge voltage of 700 V or 1000 V in accordance with the generating capacity of the solar cell, A configuration for improving the partial discharge voltage is widely adopted. As a method for improving the partial discharge voltage, since the insulation depends on the thickness of the film or the foam layer, the film or the foam layer tends to become a film. In recent years, a configuration using about 100 mu m to 300 mu m has been widely adopted.

The adhesive layer can be formed, for example, by applying an adhesive composition to one side of a sheet-like member such as a plastic film, volatilizing the solvent, sticking it to the other laminate material, and curing at room temperature or under heating . Alternatively, the adhesive composition may be coated on any one of the sheet-like members and heated and cured to form an adhesive layer. After forming an adhesive layer, another sheet-like member forming liquid is coated and heat- Or by forming a member. Examples of the apparatus for coating an adhesive composition on a sheet-like member include a comma coater, a dry laminator, a roll knife coater, a die coater, a roll coater, a bar coater, a gravure roll coater, a reverse roll coater, a blade coater, a gravure coater and a microgravure coater . The discharge amount of the adhesive applied to the surface of the laminate substrate is preferably about 0.1 to 50 g / m 2 on a dry basis. More preferably about 1 to 50 g / m < ^{2 &} gt ;. As the laminate substrate, any desired number of substrates may be selected depending on the application, and when the multilayer substrate is composed of three or more layers, the adhesive composition of the present invention may be used for all or part of the bonding of each layer.

The sheet-form member-forming liquid may be any one of a polyester resin solution, a polyethylene resin solution, a polypropylene resin solution, a polyvinyl chloride resin solution, a polycarbonate resin solution, a polysulfone resin solution , A poly (meth) acrylic resin solution, a fluorine resin solution and the like are preferable.

Various manufacturing methods can be selected or combined in consideration of performance, price, and productivity required in the backsheet for solar cell.

≪ Embodiment >

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples do not limit the scope of the present invention. Incidentally, among the examples, each evaluation was performed according to the following method. In the examples, parts represent parts by weight,% represents weight%, and hydroxyl value represents mgKOH / g. The number average molecular weight, glass transition temperature and hydroxyl value were obtained as follows.

<Number average molecular weight>

GPC (gel permeation chromatography) "HPC-8020" manufactured by TOSOH CORPORATION is used for measurement of the number average molecular weight, and tetrahydrofuran is used as a solvent. The number average molecular weight was measured in terms of standard polystyrene.

&Lt; Glass transition temperature (Tg) >

The glass transition temperature (Tg) was measured using a DSC "RDC220" manufactured by Seiko Instruments Inc. Approximately 10 mg of the dried polyurethane polyol A-1 to A-14 solution synthesized by the following method was quantified in an aluminum pan, set in a DSC apparatus, cooled to -100 ° C with liquid nitrogen, and then heated to 10 ° C / min The glass transition temperature was determined on the obtained DSC chart.

&Lt; Hydroxyl value >

About 2 g of the sample was dissolved in about 10 ml of pyridine, and then 5 ml of a mixed solution having a volume ratio of 15/85 of acetic anhydride / pyridine adjusted in advance was added and left for 20 hours. Thereafter, 1 ml of water and 10 ml of ethanol were added and titrated with 0.1 N potassium hydroxide (ethanol solution). The indicator was phenolphthalein.

&Lt; Preparation of acrylic polyol (A) >

(Synthesis Example A-1) In a four-necked flask equipped with a condenser, a nitrogen introducing tube, a dropping rod, and a thermometer, 100 parts by weight of ethyl acetate was added and the temperature was raised to 80 캜. Then, 42.7 parts by weight of butyl acrylate, , 1.8 parts by weight of 2-hydroxyethyl acrylate and 2.0 parts by weight of azobisisobutyl nitrile were dropped over a dropping rod for 2 hours and reacted for 1 hour, and then azobisisobutyl And 0.2 part by weight of nitrile were added and reacted for 1 hour was continued until the conversion rate of the monomer became 98% or more, followed by cooling. Ethyl acetate was added to obtain a 50% solids solution.

(Synthesis Examples A-2 to A-18) Polymerization initiators The polymerization initiators A-2 to A-18 shown in Table 1 were obtained in the same manner as in Synthesis Example 1 except that the molecular weight was adjusted by the addition amount of azobisisobutylnitrile To obtain an acrylic polyol.

In addition, for Synthesis Example A-15, an acrylic polyol having the composition shown in Synthesis Example 1 in Patent Document 2 is used. The abbreviations in Table 1 are as follows.

Butyl acrylate, EMA: ethyl methacrylate, EA: ethyl acrylate, St: styrene, CHMA: cyclohexyl methacrylate, 2EHA: 2-ethylhexyl acrylate, HEA: 2-hydroxyethyl acrylate, 4HBA: 4-hydroxybutyl acrylate

[Table 1]

&Lt; Blending Example of Adhesive Composition >

(Examples 1 to 13 and Comparative Examples 1 to 6) 100 parts by weight of a polyisocyanate (B) as a curing agent was added to 100 parts by weight of the acrylic polyol (A) in terms of solids in a blending ratio shown in Table 2, , 3.0 parts by weight of a glycidyl group-containing silane coupling agent ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.01 part by weight of dioctyltin dilaurate ("Neostan U-810", manufactured by Nitto Chemical Industry Co., Ltd.) To adjust the solid content to 30%.

[Table 2]

* 1 Mixing ratio = Theme: Hardener (solid content ratio)

* 2 To 100 parts by weight of (A), 3.0 parts by weight of KBM-403 (silane coupling agent) was added.

* 3 To 100 parts by weight of (A), 0.01 parts by weight of U-810 as a reaction accelerator was blended.

* 4 Curing agent A: Takenate D-160N (manufactured by Mitsui Chemicals, Inc., TMP adduct modified product of hexamethylene diisocyanate)

   Curing agent B: Takenate D-178N (manufactured by Mitsui Chemicals, Inc., allophanate-modified product)

   Curing agent C: isocyanurate-modified product of isophorone diisocyanate

   Curing agent D: Sumidule N3300 (manufactured by Sumika Bayer Urethane Co., isocyanurate modified product of hexamethylene hardener diisocyanate)

Curing agent E: Smyrule N3200 (made by Sumika Bayer Urethane, modified buret of hexamethylene hardener diisocyanate)

<Production Example of Laminated Film 1>

Adhesive compositions were applied to the corona-treated surfaces of a polyester film (Lumirra-X-10S, thickness 50 μm) by using the adhesive compositions of Examples 1 to 13 and Comparative Examples 1 to 6 at a dry coating amount of 4 to 5 g / m &lt; ² &gt; by a dry laminator. Then, the solvent was evaporated, and then laminated on the corona-treated surface of one polyester film (Lumirra-X-10S, thickness 50 μm, manufactured by Doreya). Thereafter, the adhesive was cured by curing treatment (aging) at 40 DEG C for 3 days to produce a laminated film 1.

<Production Example of Laminated Film 2>

Laminated film 2 having the constitution of [corona-treated polyester film / adhesive layer / silver foil] was produced by using the adhesive compositions of Examples 1 to 4 and Comparative Examples 2 and 3 according to the method of producing laminated film 1 described above.

<Production Example of Laminated Film 3>

Using the adhesive compositions of Examples 1 to 4 and Comparative Examples 2 and 3, the vapor deposition layer of the silica-deposited polyester film was brought into contact with the adhesive layer in accordance with the production method of the laminated film 1 to obtain [the corona-treated polyester film / adhesive layer / Silica-deposited polyester film].

In Table 3, the initial adhesion of the laminated film 1 with the subject of Examples 1 to 13 and Comparative Examples 1 to 6 and the curing agent and the adhesive strength after 1000 hours, 2000 hours and 3000 hours of exposure at 85 ° C and 85% .

In Table 4 and Table 5, the initial adhesion of laminated films 2 and 3 using Examples 1 to 4 and Comparative Examples 2 and 3 was evaluated after 1000 hours, 2000 hours, and 3000 hours of exposure at 85 ° C and 85% Adhesive strength. A specific evaluation method will be described below.

&Lt; Adhesion test before and after aging >

The laminated films 1, 2 and 3 before and after aging were each cut into a size of 200 mm x 15 mm and allowed to stand at 25 캜 for 65 hours under an environment of 65% humidity and then subjected to a tensile tester according to the test method of ASTM-D1876-61 And subjected to a T-type peel test under an environment of 25 占 폚 and a humidity of 65% at a load rate of 300 mm / min. Peel strength (N / 15 mm width) between PET film / PET film, between PET film / silver foil, and PET film / silica-deposited polyester film is shown by the average value of five specimens.

&Lt; Adhesion Test after Humidity Durability Test >

The aged laminate was cut into a size of 200 mm x 15 mm, and left for 1000 hours, 2000 hours, and 3000 hours in an environment of 85 ° C and 85% humidity. Thereafter, the resultant was subjected to T-type peeling at a load speed of 300 mm / min under an environment of 25 ° C and a humidity of 65% using a tensile tester in accordance with the test method of ASTM-D1876-61, Test was conducted. The peel strength (N / 15 mm width) between PET film / PET film, between PET film / silver foil, and PET film / silica-deposited polyester film is shown by the average value of five specimens.

<Evaluation Criteria>

[Adhesion test before aging]

◎ Excellent in practical use: 3N / 15mm or more

Practical steps: 2 ~ 3N / 15mm

△ Practical lower limit: 1 to 2N / 15mm

× Not practical: Less than 1N / 15mm

[Test after aging and adhesive strength test after heat and humidity resistance test]

◎ Excellent in practical use: 5N / 15mm or more

Practical steps: 4 ~ 5N / 15mm

△ Practical lower limit: 2 to 4N / 15mm

× Not practical: Less than 2N / 15mm

[Table 3]

[Table 4]

[Table 5]

As shown in Table 3, the adhesive compositions of the examples were found to have excellent adhesive strength both before and after aging. It was also found that excellent adhesion can be obtained even after the heat resistance test. Since the adhesive strength over a long period of time can be maintained, the adhesive composition of the examples is particularly suitable for long-term moisture and humidity resistance for outdoor use.

In JIS C 8917 (environmental test method and durability test method for crystalline solar cell module), humidity resistance test B-2 withstanding 85 hours at 85% humidity for 1000 hours is determined and is known as a particularly severe test method. In the present embodiment, it is shown that the adhesive strength can be maintained over a long term of 3000 hours over 1000 hours, and the adhesive composition of the present invention has sufficient long-term moisture resistance.

The backsheet for solar cell has sufficient interlaminar bond strength (laminate strength) in the long-term resistance to heat and humidity test and does not cause interlayer delamination of the sheet, thereby protecting the solar cell element, maintaining the power generation efficiency, . &Lt; / RTI &gt; The extension of the lifetime of the solar cell contributes to environmental preservation in terms of securing energy other than fossil fuel, which is followed by the spread of the solar cell system.

The adhesive composition of the present invention can be applied to various applications such as a multi-layer plywood for use in the outdoor industry (such as a barrier material, an outer wall material, a barrier material, a roof material, a solar panel material (solar cell back protection sheet, solar cell surface protection sheet) , Proof protective material, automobile parts, etc.), it is possible to provide strong adhesive strength. In addition, it is possible to prevent a decrease in the adhesive strength over time due to hydrolysis and the like at the time of outdoor exposure, and to maintain a strong adhesive strength for a long period of time.

In Comparative Example 1, the glass transition temperature of the acrylic polyol (A) is -20 占 폚, which is lower than 10 占 폚. As a result of the evaluation, it was found that even in the case of the surface-treated polyester film, only an adhesive strength of about 3 (N / 15 mm) could be exhibited.

In Comparative Example 2, the glass transition temperature of the acrylic polyol (A) is 55 캜, which is higher than 50 캜. As a result of the evaluation, since the flowability to the substrate was scarcely present, the initial adhesive strength was very small, and the result was further lowered in the heat and humidity resistance test.

Comparative Example 3 is an example in which the number average molecular weight of the acrylic polyol (A) is 6,000 and less than 10,000. As a result of the evaluation, the adhesive force before the aging process was very small because the adhesive force of the adhesive before the aging process was insufficient. In the case of industrial production, the laminate in the rolled state is aged with the wick in the direction of the cloth. If the adhesive strength before the aging step is very small, the rolls tend to collapse during aging and are not suitable for industrial production.

Comparative Example 4 is an example in which the number average molecular weight of the acrylic polyol (A) is 120,000 and greater than 100,000. As a result of the evaluation, it was found that sufficient adhesion force was not obtained before aging due to lack of wettability to PET film. As in comparative 3, rolls are easily broken during aging and are not suitable for industrial production. Also, even after the heat and humidity resistance test, the adhesion strength was not observed due to the heat and humidity test, but the adhesive strength was lower than that of the Examples.

Comparative Example 5 is an example in which the OH value of the acrylic polyol (A) is 110.0 and greater than 100. As a result of the evaluation, excessive crosslinking resulted in a very hard cured film and poor adhesion.

Comparative Example 6 is an example in which the content of polyisocyanate (B) is NCO / OH = 12. As a result of the evaluation, it was found that the acrylic polyol (A) proceeded to react before coating, and the gel could not be formed due to gelation.

This application claims priority based on Japanese patent application No. 2011-030369 filed on February 16, 2011, and inserts all of its contents here.

Since the adhesive composition for a laminated sheet according to the present invention is used for bonding adherends of the same or different materials, it is suitably used for bonding plastic-based materials, metal-related materials and multi-layered laminate materials. Of course, it is preferable for bonding between plastic materials and metal materials. The adhesive composition for a laminated sheet according to the present invention can maintain a high adhesive force even when exposed to a high temperature and high humidity environment. Accordingly, it is possible to provide a multi-layer plywood (barrier material, outer wall material, roofing material, solar panel material (solar back surface protection sheet, solar cell surface protection sheet), window material, outdoor board material, And is preferable as an adhesive for use. It is particularly suitable for forming a backsheet for a solar cell, for example, in which the environmental strength is strongly demanded because the adhesive strength with time can be maintained over a long period of time. It is also preferable to form a surface protective sheet for a solar cell. In addition, the adhesive composition for a laminated sheet according to the present invention exhibits a high adhesive strength particularly in a layer including a surface treatment layer of a plastic film, but can be suitably applied also to an untreated surface material (including a surface untreated plastic film).

Claims (4)

In an adhesive composition for a laminated sheet containing an acrylic polyol (A) and a polyisocyanate (B)
Wherein the acryl polyol (A) has a number average molecular weight of 10,000 to 100,000, a hydroxyl value of 1 to 40 mgKOH / g, a glass transition temperature (Tg) of 10 to 30 占 폚,
Wherein the equivalent ratio NCO / OH of the hydroxyl group derived from the acrylic polyol (A) to the isocyanate group derived from the polyisocyanate (B) is 0.1 to 10. The adhesive composition for a laminated sheet according to claim 1, wherein the polyisocyanate (B) comprises a polyisocyanate derived from an aliphatic cyclic diisocyanate or an aliphatic diisocyanate. The method according to claim 1,
Is used for manufacturing a backsheet for a solar cell having two or more sheet-like members,
To form at least a part of an adhesive layer for bonding the sheet-like members. An undercoat backing sheet for a solar cell, comprising: an adhesive layer formed of the adhesive composition for a laminated sheet according to any one of claims 1 to 3; and at least two or more sheet-like members laminated through the adhesive layer.