TWI548104B - Adhesive composition for laminating sheet and back protective sheet for solar cell - Google Patents

Description

Adhesive composition for laminated sheets and back protective sheet for solar cells

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

In recent years, multi-layer (composite) membranes used in outdoor industry applications such as barrier materials, roofing materials, solar panel materials, window materials, outdoor flooring materials, lighting protection materials, automotive parts, signs, labels, etc. The multilayer (composite) laminate is put to practical use. The multilayered laminate can be obtained by laminating (laminating) a metal-based raw material or a plastic-based raw material or the like. Examples of the metal-based raw material include metal foils such as aluminum, copper, and steel sheets, metal plates, and metal deposition films. Examples of the plastic material include a plastic film such as polypropylene, polyvinyl chloride, polyester, fluororesin, or acrylic resin, a plastic sheet, a plastic sheet, and a plastic film having an inorganic oxide layer such as a ruthenium dioxide vapor-deposited film formed on the surface. . A binder used for bonding metal-based materials or plastic-based materials is known as a polyepoxy-based adhesive and a polyurethane-based adhesive.

Patent Document 1 describes a sheet for sealing a back surface of a solar cell, which comprises a laminate in which at least two or more substrates are bonded together with a polyurethane-based adhesive. More specifically, a polyurethane-based adhesive that satisfies the following conditions and contains an adhesive having hydrolysis resistance is described. Condition 1: In the high acceleration temperature and humidity as a promotion evaluation device using pressurized steam, In the saturated vapor stress test (HAST) chamber, the laminate strength after storage for 168 hours at 105 ° C and 1.05 atm is at least 1 N / 15 mm. Condition 2: In the HAST chamber which is a promotion evaluation apparatus using pressurized steam, after holding at 105 ° C and 1.05 atm for 168 hours, no bulging between the substrates accompanying delamination occurred. Specifically, various polyurethane-based adhesives in which a cross-linking agent is combined with each of the six types of polyols of the polyol A to the polyol F have been proposed (refer to Patent Application No. 2 items - 11 items).

Patent Document 2 describes a rear sheet for a solar cell module including a laminate in which at least two substrates are bonded together by an acrylic adhesive. More specifically, an acrylic adhesive is proposed as an acrylic adhesive having hydrolysis resistance, insulation resistance, and moisture barrier property, and the acrylic adhesive contains a compound represented by the general formula (I). An acrylic polymer obtained by polymerizing a monomer component of a monomer (refer to Patent Application No. 2 of Patent Document 2).

CH ₂ =C(R ¹ )-CO-OZ (I)

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

Further, as for the patent documents disclosed in the prior application which is the basis of the priority, Patent Document 3 and Patent Document 4 describe an adhesive composition suitable for the following applications: on the untreated side of the plastic film. Other substrates are used in the subsequent sheets.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] International Publication No. 2007-148754

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-246360

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2011-105819

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2011-111519

In order to stably maintain the adhesion force over a long period of time under severe outdoor conditions, it is important that the subsequent strength is stabilized even over time. Recently, an adhesive which can well adhere to an untreated surface of a plastic film such as a polyester film which has not been subjected to surface treatment as well as another substrate as disclosed in Patent Document 3 or Patent Document 4 has been actively developed. Since the surface treatment is not performed, the manufacturing steps can be shortened, so that the cost can be reduced. However, on the other hand, the surface treatment technology previously applied has also been utilized, and the demand for an adhesive composition which further enhances the original performance of the adhesive composition and synergistically has superior adhesive characteristics is also utilized. It also became higher.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive composition for a laminated sheet and a back protective sheet for a solar cell, wherein the laminated sheet adhesive composition is interposed between various sheet members, particularly plastic. The film surface treatment layer exhibits a high adhesion between the layers, and maintains a high adhesion even when exposed to a high temperature and high humidity environment, and is suitable for manufacturing a back surface protective sheet for solar cells.

The present inventors have made intensive studies to solve the above problems, and as a result, have found that the above problems can be solved by the adhesive composition for laminated sheets shown below, and the present invention has been completed.

That is, the adhesive composition for a laminated sheet of the present invention includes acrylic acid a polyol (A) and a polyisocyanate (B) having a number average molecular weight of 10,000 to 100,000, a hydroxyl value of 1 mgKOH/g to 100 mgKOH/g, and a glass transition temperature (Tg) exceeding - 40 ° C and 10 ° C or less, 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 3.

Preferable examples of the polyisocyanate (B) include an example of a polyisocyanate derived from an alicyclic diisocyanate or an aliphatic diisocyanate.

The laminated sheet adhesive composition of the above aspect is used in the manufacture of a back protective sheet for solar cells comprising two or more sheet members, and is suitable for use in the following applications: forming the sheet members to be joined to each other At least a portion of the layer of the agent.

The back surface protective sheet for a solar cell of the present invention comprises: an adhesive layer formed of the adhesive composition for a laminated sheet of the above aspect; and at least two or more sheet members laminated with the adhesive layer.

According to the present invention, it is possible to provide an adhesive composition for a laminated sheet and a back protective sheet for a solar cell, wherein the laminated sheet is composed of an adhesive composition between various sheet members, particularly a plastic film. The surface treatment layer exhibits a high adhesion between the layers, and maintains a high adhesion even when exposed to a high temperature and high humidity environment, and is suitable for manufacturing a back surface protective sheet for solar cells.

Embodiments of the present invention will be described in detail below. Further, other embodiments are also within the scope of the invention as long as they conform to the gist of the invention. Further, in the present specification, the description of "arbitrary number A to any number B" means a range of the number A and the number A, and is a range of the number B and the number B. Further, the description of "(meth) propylene oxime" as described in the specification and the patent application includes any one of a compound referred to as "acryl oxime" and a compound referred to as "methacryl oxime". Further, it is similarly defined in "(meth)acrylyl" and "(meth)acrylate".

<Acrylic polyol (A)>

As the acrylic polyol (A), a copolymer of a hydroxyl group-containing mono(meth)acrylate monomer and a hydroxyl group-free mono(meth)acrylate monomer can be preferably used. The mono(meth)acrylate monomer having a hydroxyl group is a monomer having one (meth)acrylonium group and one or more hydroxyl groups in one molecule. Preferable examples thereof include a mono(meth)acrylate monomer obtained by a reaction of a divalent alcohol and (meth)acrylic acid, and an ε-caprolactone modified (meth)acrylic monomer.

If the number average molecular weight of the acrylic polyol (A) is the same degree, the portion irrelevant to the copolymerization of the mono(meth)acrylate monomer, that is, via the ester bond and (methyl), from the viewpoint of improving the adhesion force The carbon number of the partially bonded portion (alkyl or alkenyl group, hereinafter referred to as "side chain portion") is preferably from 1 to 17, more preferably from 1 to 9, further preferably 1 ~3. The side chain portion forms a side chain of the acrylic polyol (A) after copolymerization. The carbon number of the side chain portion of the mono(meth)acrylate monomer is generally from about 1 to about 30, but if the number average molecular weight of the acrylic polyol (A) is equivalent, the more the side chain portion Short, acrylic plural The more the main chain of the alcohol (A) becomes relatively long. As a result, the mechanical properties (specifically, elongation) of the adhesive layer after hardening are improved, and the force is increased.

Examples of the mono(meth)acrylate monomer obtained from the divalent alcohol include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and 1,4-butanediol mono(methyl). ) acrylate, (poly)ethylene glycol mono (meth) acrylate, and the like.

Further, a mono(meth)acrylate monomer obtained from an alcohol having 3 or more members such as 2,3-dihydroxypropyl (meth)acrylate may also be used as a mono(methyl) group having a hydroxyl group. Acrylate monomer.

The mono(meth)acrylate monomer having no hydroxyl group can be suitably used by selecting a radical polymerizable monomer known from the prior art. Suitable examples are, for example, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (A) Representative of alkyl (meth) acrylate such as n-octyl acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate or stearyl (meth) acrylate Long chain (meth)acrylic monomers, acrylonitrile, and the like.

Further, in addition to the above-mentioned hydroxyl group-containing (meth) acrylate monomer and hydroxyl group-free mono(meth) acrylate monomer, other monomers such as (meth)acrylic acid and maleic acid may be copolymerized. A monomer containing a carboxyl group such as maleic anhydride or an anhydride thereof, or a vinyl monomer such as styrene. Further, the hydroxyl group-containing (meth) acrylate monomer or the hydroxy group-free mono(meth) acrylate monomer may be used singly or in combination of two or more kinds of compounds. The same applies to the case of using other monomers.

In the present invention, the acrylic polyol (A) must have a number average molecular weight of 10,000 to 100,000. Further, preferably 10,000 ~70,000, more preferably 25,000~50,000.

The laminated sheet obtained by laminating two or more sheet-like members, for example, a back protective sheet for a solar cell using the adhesive composition for laminated sheets of the present invention (hereinafter also referred to as "adhesive composition"), for example, can be subjected to the following steps And get. The adhesive composition is applied to the joint surface of one of the sheet members to be dried. Next, the other sheet-like members are superposed on the adhesive layer, and the layer is called "aging" in the environment of 40 ° C to 60 ° C for 2 days to 1 week, and the adhesive layer is hardened to obtain a laminate. sheet.

When the number average molecular weight of the acrylic polyol is less than 10,000, there is a tendency that the cohesive force of the adhesive layer before the aging step is insufficient, and the adhesive force before the aging step becomes small. In the case of industrial production, the laminated body in a state of being wound into a roll is normally aged in the vertical direction of the winding core. If the force before the aging step is small, the winding is easily spread when aging is occurring, and is not suitable for industrial production. In addition, when the amount is less than 10,000, the cohesive force after the aging step tends to be insufficient, and as a result, the moist heat resistance is lowered, and delamination or the like occurs.

Further, when the number average molecular weight of the acrylic polyol exceeds 100,000, the viscosity of the adhesive increases, and there is a problem in coating properties, and the wettability of the sheet member tends to decrease, and as a result, there is an adhesive force before the aging step. Become smaller. Although the initial adhesion force became larger as compared with that before aging due to aging, there was a gradual decrease due to the subsequent heat and humidity resistance test, and it was lower than the lower limit of use after 3,000 hours.

Further, the number average molecular weight in the present invention is determined by a gel permeation chromatography (GPC) and is converted to a value in terms of polystyrene. More specific In other words, the number average molecular weight in the present invention is a value obtained by a measurement method described in Examples described later. Further, the values of the glass transition temperature and the NCO/OH equivalent ratio are also similarly obtained by the method described in the examples described later.

The hydroxyl value of the acrylic polyol (A) is determined by the content of the mono(meth)acrylate monomer having a hydroxyl group. In the present invention, the hydroxyl value is from 1 mgKOH/g to 100 mgKOH/g, preferably 1 mgKOH/g~ 50 mgKOH/g, more preferably 1 mgKOH/g to 15 mgKOH/g. When it is less than 1 mgKOH/g, the crosslinking with the isocyanate curing agent tends to decrease, and the heat and humidity resistance is lowered. Further, when it exceeds 100 mgKOH/g, the adhesion strength before aging may be exhibited, but the crosslinking density tends to be high after aging, and there is a possibility that a sufficient adhesive force cannot be exhibited, and thereafter the moist heat resistance test is performed. The force of the middle and the second is further reduced.

Further, in the present invention, the glass transition point (Tg) of the acrylic polyol (A) is more than -40 ° C and 10 ° C or less, more preferably more than -25 ° C and 10 ° C or less for the reason described below.

<polyisocyanate (B)>

The polyisocyanate (B) is, for example, a compound derived from a well-known diisocyanate, and a known compound can be used without limitation. For example, it can be exemplified by 2,4-toluene diisocyanate (alias: 2,4-TDI), 2,6-toluene diisocyanate (alias: 2,6-TDI), xylene diisocyanate (alias: XDI), two Phenylmethane diisocyanate (alias: MDI), isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate (alias: HDI), bis(4-isocyanate cyclohexyl)methane, or hydrogenation Diphenylmethane diisocyanate a compound derived from a diisocyanate such as an ester, that is, an isocyanate of a diisocyanate, a trimethylolpropane adduct, a biuret type, a prepolymer having an isocyanate residue (obtained from a diisocyanate and a polyhydric alcohol) Low polymer), a uretdione having an isocyanate residue, an allophanate body, or a complex of such compounds, and a blocked isocyanate. The polyisocyanate (B) may be used singly or in combination of two or more.

From the viewpoint of the viscoelasticity of the cured coating film after self-crosslinking, the polyisocyanate (B) is preferably a polyisocyanate derived from an alicyclic diisocyanate or an aliphatic diisocyanate. More specifically, examples of the alicyclic diisocyanate include isophorone diisocyanate and methyl-2,6-cyclohexane diisocyanate. Further, examples of the aliphatic diisocyanate include hexamethylene diisocyanate and pentamethylene diisocyanate. Further, an isocyanate of a diisocyanate, a trimethylolpropane adduct, a biuret type, and a prepolymer having an isocyanate residue, which are derivatives of the above-mentioned alicyclic diisocyanate and an aliphatic diisocyanate compound, may be mentioned. (lower polymer obtained from diisocyanate and polyol), uretdione having isocyanate residue, allophanate body, or a composite thereof.

Further, in the case where the rate of hardening is emphasized, it is preferred to use an isocyanate having an aromatic ring, such as xylene diisocyanate (alias: XDI), having an alkyl group between the NCO and the aromatic ring. If the hardening speed is fast, it is preferable in terms of shortening the aging time.

Further, the isocyanate group concentration in the polyisocyanate (B) is preferably from 5% by weight to 30% by weight. The isocyanate group concentration in the polyisocyanate (B) is set to be in the range of 5 wt% to 30 wt%. In addition, polyisocyanate (B) The isocyanate group concentration in the middle can be determined by titration. The titration was evaluated by n-butylamine/hydrochloric acid titration. Specifically, after dissolving the sample in dry toluene, adding an excess of dibutylamine solution to react, and back-titrating the remaining di-n-butylamine by hydrochloric acid, the titration curve is The inflection point is used as the end point, and the isocyanate group content rate is calculated from the titration to the end point.

The amount of the polyisocyanate (B) used can be determined by the NCO/OH equivalent ratio of the hydroxyl group derived from the acrylic polyol (A) to the isocyanate group derived from the polyisocyanate (B), and the NCO/OH equivalent ratio is set to 0.1 to 3 . More preferably, the NCO/OH equivalent ratio is 1 to 3, and further preferably 1.5 to 3. The NCO/OH equivalent ratio can be obtained by the following mathematical formula (1).

NCO/OH ratio = polyisocyanate required amount (parts by weight) × (561 / OH value) × (NCO% / (42 × 100)) × (100 / polyol amount (solid weight)) Mathematical formula (1)

The inventors of the present invention have found that an adhesive composition for a laminated sheet having surprisingly excellent characteristics can be obtained by satisfying all of the following conditions. That is, it is found that by satisfying all of the following conditions, an adhesive composition can be provided which exhibits high between various sheet members, particularly between layers of a surface treatment layer containing a plastic film. Then, the force can maintain a high adhesion even when exposed to a high temperature and high humidity environment, and is suitable for manufacturing a back protective sheet for solar cells): using the above-mentioned (i) a specific range of the average molecular weight, (ii) a specific range a hydroxyl value, (iii) a specific range of glass transition temperature (Tg) of the acrylic polyol (A), and further (iv) a difference between the hydroxyl group derived from the acrylic polyol (A) and the polyisocyanate (B) The equivalent ratio NCO/OH of the cyanate group is set to the above specific range. Hereinafter, the reason will be explained.

In the case of laminating a plastic film which is treated with a corona discharge or the like as compared with the case where the untreated plastic film is laminated, the added value of the added portion of the manufacturing step is required. In the subsequent force, a higher adhesion force is required in comparison with the case of the untreated plastic film on the laminated surface.

If the Tg of the acrylic polyol is too low, the adhesion of the adhesive layer before aging is not sufficient, so that the adhesive layer formed of the adhesive composition is soft. Moreover, due to the degree of softness, a certain degree of adhesion can be exhibited between the sheet members. However, even if the adhesive layer is sufficiently cured after aging, the Tg of the acrylic polyol as a raw material is low, and the cohesive force of the adhesive layer is insufficient, and it becomes difficult to secure a large adhesive force. Further, when the laminate is placed under high temperature and high humidity for a long period of time, there is a tendency that the adhesion force is gradually lowered due to insufficient 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. Although the adhesion after aging is somewhat larger than before aging, the hardened adhesive layer after crosslinking is too hard, so there is a tendency that the adhesion force after the aging step is deteriorated.

In the present invention, the reason for obtaining the above excellent effect is that the Tg of the acrylic polyol is not too low but not too high (specifically, it exceeds -40 ° C and is 10 ° C or less). And further comprising a specific hydroxyl value, a specific NCO/OH equivalent ratio, and a specific number average molecular weight range, thereby synergistically exciting the molecule The degree of activity of the exercise-grade acrylic polyol increases so that the wettability and anchoring properties of the subsequent objects are improved. In particular, it has been found that by controlling the NCO/OH equivalent ratio to a range of 0.1 to 3, particularly 1 to 3, a moderate degree of crosslinking can be achieved and a high subsequent appearance can be exhibited after the aging step. force. Moreover, it was surprisingly found that even after aging, a high adhesion force was exhibited. It has also been found that after the aging step, a high adhesion force can be maintained after being placed under high temperature and high humidity.

When a metal foil, a metal plate, or a metal deposition film is used as the substrate, it is preferable that the adhesive composition for a laminated sheet of the present invention contains a decane coupling agent from the viewpoint of improving the adhesion strength.

The decane coupling agent is not limited to the following, and examples thereof include vinyl decane such as vinyl tris(β-methoxyethoxy)decane, vinyl ethoxy decane, and vinyl trimethoxy decane; γ-( Methyl)propenyloxypropyltrimethoxydecane, γ-(meth)acryloxypropyltriethoxydecane, and γ-(meth)acryloxypropyldimethoxymethyl (meth) propylene decyl oxane such as decane; β-(3,4-epoxycyclohexyl)ethyltrimethoxydecane, β-(3,4-epoxycyclohexyl)methyltrimethoxy Decane, β-(3,4-epoxycyclohexyl)ethyltriethoxydecane, β-(3,4-epoxycyclohexyl)methyltriethoxydecane, γ-glycidoxypropyl Epoxy decanes such as trimethoxy decane and γ-glycidoxypropyl triethoxy decane; N-β-(aminoethyl)-γ-aminopropyltrimethoxydecane, N- --(Aminoethyl)-γ-aminopropyltriethoxydecane, N-β-(aminoethyl)-γ-aminopropylmethyldiethoxydecane, γ-amino group Propyltriethoxydecane, γ-aminopropyltrimethoxydecane, N-phenyl-γ-aminopropyltrimethoxydecane, And N-phenyl-γ-aminopropyltriethoxyhydrazine An amine-based decane such as an alkane; and a sulfur-containing decane such as γ-mercaptopropyltrimethoxydecane or γ-mercaptopropyltriethoxydecane. These compounds may be used alone or in combination of two or more.

The amount of the decane coupling agent to be added is preferably from 0.1 part by weight to 5 parts by weight, more preferably from 1 part by weight to 3 parts by weight, per 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 of the metal foil due to the addition of the decane coupling agent is inferior; even if it is added in an amount exceeding 5 parts by weight, the performance of the above is not improved.

The adhesive composition for a laminated sheet of the present invention may be a so-called two-liquid mixed type adhesive in which a main component and a curing agent are mixed at the time of use, or a one-liquid type adhesive in which a main component and a curing agent are mixed in advance. . Further, the acrylic polyol (A) or the polyisocyanate (B) may each be used in a plurality of kinds independently. Further, other main agents or curing agents other than the above may be used independently of one or more. In general, the main agent includes an acrylic polyol (A), a decane coupling agent, an organic solvent, and other additives, and the hardener includes a polyisocyanate (B), an organic solvent, and other additives.

As other additives, an adhesion promoter, a reaction accelerator, a leveling agent, a phosphorus-based or phenol-based antioxidant, and an ultraviolet ray may be formulated in the adhesive for laminating sheets of the present invention within the range not departing from the gist of the present invention. Various additives such as stabilizers, metal deactivators, flame retardants, plasticizers, organic pigments, inorganic pigments, and the like.

In the case where a metal layer (metal foil, metal plate, or the like) is used as the sheet member, in order to make the laminated sheet of the present invention use the metal composition of the adhesive composition The connectivity is improved, and a phosphate compound such as phosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid or an ester of the acid may be added.

Further, the adhesive composition of the present invention can be preferably used as a tackifying coating agent for a solar cell laminate sheet, in addition to being preferably used as an adhesive for producing a back surface protective sheet for a solar cell. In this case, it is preferred to incorporate an anti-caking agent.

Further, an additive known as an adhesive agent can be formulated without limitation without departing from the gist of the invention. For example, a reaction accelerator can be used. Specific examples thereof include metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dimaleate; 1,8-diaza-bicyclo[5.4.0] Undecen-7,1,5-diazabicyclo[4.3.0]nonene-5,6-dibutylamino-1,8-diazabicyclo[5.4.0]undecene a tertiary amine such as -7; a reactive tertiary amine such as triethanolamine. One type of the reaction accelerator or two or more types may be used in combination.

Further, in order to improve the appearance of the laminate, a known leveling agent or antifoaming agent may be formulated in the main component.

Examples of the leveling agent include polyether modified polydimethyl siloxane, polyester modified polydimethyl siloxane, aralkyl modified polymethyl alkyl siloxane, and polyester modified hydroxyl group. Polydimethyl methoxy olefin, polyether ester modified hydroxy-containing polydimethyl siloxane, acrylic copolymer, methacryl fluorenyl copolymer, polyether modified polymethyl alkyl decane, A known leveling agent such as an alkyl acrylate copolymer, an alkyl methacrylate copolymer, lecithin, or a mixture thereof.

Examples of antifoaming agents include anthrone resin, anthrone solution, alkyl vinyl ether and A known defoaming agent such as a copolymer of an alkyl acrylate and an alkyl methacrylate, or a mixture thereof. When a leveling agent or an antifoaming agent is added, one type of compound may be used independently, and two or more types of compounds may be used arbitrarily in combination.

Further, as a known additive used in the present invention, in order to further suppress the yellowing of the adhesive which is caused by the ultraviolet rays of the sun or the like, and the yellowing of the adhesive which is caused by heat such as solar heat over time, A known phosphorus-based or phenol-based antioxidant, a UV stabilizer, and a metal deactivator are blended in the main component. These additives may be used singly or in combination of two or more kinds. The phosphorus-based or phenol-based antioxidant, ultraviolet stabilizer, and metal deactivator used in the present invention are preferably 0.05 parts by weight to 5 parts by weight based on 100 parts by weight of the solid content of the acrylic polyol (A). The range is more preferably from 0.1 part by weight to 1 part by weight. When the amount is less than 0.05 part by weight, the effect of suppressing the sufficient yellowing effect may not be obtained, and if it is more than 5 parts by weight, the adhesion of the adhesive may be greatly deteriorated.

As the curing agent, in addition to the above polyisocyanate (B), a well-known oxazoline compound (for example, 2,5-dimethyl-2-oxazoline or the like) may be optionally contained within a range not inhibiting the effects of the present invention. 2,2-(1,4-butylene)-bis(2-oxazoline) or anthraquinone compounds (for example, dioxonium isophthalate, diterpene sebacate, or diammonium adipate)肼) and so on.

Examples of the solvent used in the present invention include esters such as ethyl acetate, butyl acetate, and celecoxime; and ketones such as acetone, methyl ethyl ketone, isobutyl ketone, methyl isobutyl ketone, and cyclohexanone. Ethers such as tetrahydrofuran and dioxane; An aromatic hydrocarbon such as benzene or xylene; a halogenated hydrocarbon such as dichloromethane or 1,2-dichloroethane; dimethyl hydrazine or dimethyl sulfonamide. The solvent to be used may be one type of solvent, or two or more types may be used in combination.

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

Next, a method of manufacturing a back protective sheet for a solar cell using the adhesive composition for a laminated sheet of the present invention, and an example of a back protective sheet for a solar cell will be described. In addition, the manufacturing method or the structure of the back surface protective sheet for solar cells is not limited to the following examples, and various manufacturing methods or structures can be employ|adopted according to an objective or a need.

As a solar cell module, a simple solar cell module has a configuration in which a filler and a glass plate are sequentially laminated on both surfaces of a solar cell unit as a solar cell element. Since the glass plate is excellent in transparency, weather resistance, and scratch resistance, it is now generally used as a sealing sheet on the light-receiving side of a solar cell module. However, in terms of cost, safety, and workability, the company has developed back protective sheets for solar cells other than glass sheets (hereinafter referred to as back protective sheets) on the non-light-receiving side. The protective sheet is replacing the glass sheet.

The back surface protective sheet for solar cells has a back surface protective sheet for solar cells, such as a plastic film such as a polyester film, or a metal with a vapor deposition layer of a metal oxide or a non-metal oxide on a polyester film or the like. A plastic film such as a layer, a metal foil such as aluminum foil, or a plastic film with a tantalum nitride layer. The laminate of the laminated sheet of the present invention can be used for the adhesive composition of the laminate of the present invention. Line bonding. The back surface protective sheet for a solar cell composed of a plurality of layers can impart various properties by the multilayer structure. For example, the insulating property can be imparted by using a polyester film, the weather resistance can be imparted by using a fluorine-based film, and the aluminum foil can be used to impart water vapor barrier properties. As for the type of back surface protection sheet for solar cells, it can be selected according to the product and use of the solar cell module.

Examples of the plastic film include a polyester resin film such as polyethylene terephthalate or polybutylene terephthalate, a polyethylene resin film, a polypropylene resin film, and a polyvinyl chloride resin film. Carbonate-based resin film, polyfluorene-based resin film, poly(meth)acrylic resin film, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, polyethylene tetrafluoroethylene, polytetrafluoroethylene, tetra A fluorine-based resin film such as a fluoroethylene perfluoroalkyl vinyl ether copolymer or a tetrafluoroethylene-hexafluoropropylene copolymer.

A film obtained by coating the acrylic film or the fluorine-based paint with the plastic film as a support, or a multilayer film obtained by laminating polyvinylidene fluoride or an acrylic resin by co-extrusion or the like can be used. Further, a sheet member in which a plurality of the above-mentioned plastic films are laminated, such as a urethane-based adhesive layer, may be used.

The plastic film can be suitably used to form a plastic film which is easy to adhere to by surface treatment by the following treatments: physical treatment such as corona discharge, plasma treatment, flame treatment, etc., and the surface of the film is modified by acid or alkali. In the chemical treatment, fine irregularities are attached to the surface of the film to cause soaking in a so-called pleated state. Of course, the laminate composition of the present invention can also be applied to an untreated raw material.

The metal foil may be an aluminum foil or a copper foil. Evaporated metal oxide As the non-metal inorganic oxide, for example, an oxide of lanthanum, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, hafnium or the like can be used.

Among these, in order to satisfy the weather resistance, water vapor permeability, electrical insulation properties, mechanical properties, packaging workability and the like when used as a solar cell module, it is preferable to laminate a temperature-resistant pair. A back surface protective sheet for a solar cell obtained by using a polyester resin film such as ethylene phthalate or polybutylene terephthalate or a polycarbonate resin film; in order to prevent the solar cell from being affected by water The output is lowered, and it is preferable to laminate a back surface protective sheet for a solar cell formed by laminating a metal foil or a metal foil such as a metal oxide or a non-metallic inorganic oxide having a water vapor barrier property; The appearance of the deterioration is poor, and it is preferable to use a back surface protective sheet for a solar cell in which a fluorine-based resin film having good weather resistance is laminated.

Moreover, in order to protect the solar cell module from damage due to voltage application, the back surface protection sheet for a solar cell uses an electric resistance that requires a partial discharge voltage of 700 V or 1000 V depending on the power generation capacity of the solar cell unit. Insulation or a structure including a foamed layer to increase a partial discharge voltage. The electrical insulation of the method for increasing the partial discharge voltage depends on the thickness of the film or the foam layer, and therefore the film or the foam layer tends to be a film. Recently, a composition using about 100 μm to 300 μm has been widely used.

The formation of the agent layer is performed, for example, by applying a binder composition to one side of a sheet member such as a plastic film by a comma coater or a dry laminator to evaporate the solvent. It is obtained by laminating with another laminated substrate and hardening it at normal temperature or under heating. Alternatively, it may be produced by applying a composition of an adhesive to any one of the sheet members and performing heat curing to form an adhesive layer, and then applying a coating liquid for forming other sheet members by heat or active. The energy lines form other sheet members. Examples of the apparatus for applying the adhesive composition to the sheet member include a knurling wheel coater, a dry laminator, a knife roll coater, a die coater, a roll coater, and a bar coater. A gravure roll coater, a reverse roll coater, a blade coater, a gravure coater, a micro gravure coater, or the like. The amount of the coating applied to the surface of the laminated substrate is preferably from about 0.1 g/m ² to about 50 g/m ^{2 in} terms of dryness. More preferably, it is about 1 g/m ² to 50 g/m ² . As the laminated base material, any base material can be selected in any number depending on the application, and when it is a multilayer structure of three or more layers, the adhesive composition of the present invention can be used in all or a part of the bonding of the respective layers.

Examples of the coating liquid for forming a sheet-like member include a polyester resin solution, a polyethylene resin solution, a polypropylene resin solution, a polyvinyl chloride resin solution, and a polycarbonate resin which can be used for forming a plastic film. A solution, a polyfluorene-based resin solution, a poly(meth)acrylic resin solution, a fluorine-based resin solution, or the like is preferable.

It is conceivable to select various manufacturing methods or to combine these methods in consideration of performance, price, productivity, and the like required as a back protective sheet for solar cells.

"example"

The invention is further illustrated by the following examples, but the following examples are not intended to limit the scope of the invention. In addition, the instance Each evaluation was carried out in accordance with the following method. Further, in the examples, parts represent parts by weight, % means wt%, and hydroxyl number means mgKOH/g. The number average molecular weight, the glass transition temperature, and the hydroxyl value can be determined by the following methods.

<number average molecular weight>

The number average molecular weight was measured by GPC (gel permeation chromatography) "HPC-8020" manufactured by Tosoh Corporation, and the column was used with 2 SHODEX KF-806L, 1 KF-804L, and 1 KF-802. Tetrahydrofuran. The number average molecular weight can be determined by standard polystyrene conversion.

<glass transition temperature (Tg)>

The measurement of the glass transition temperature (Tg) can be carried out using DSC "RDC220" manufactured by Seiko Instruments Inc. A sample of about 10 mg of an acrylic polyol A-1~acrylic polyol A-21 solution synthesized by the following method was weighed in an aluminum pan and placed in a DSC apparatus and cooled with liquid nitrogen to - After 100 ° C, the glass transition temperature was determined from the DSC chart obtained by heating at 10 ° C / min.

<hydroxy value>

The hydroxyl value can be determined by dissolving about 2 g of the sample in about 10 ml of pyridine, and then adding 5 ml of a previously prepared mixed solution of acetic anhydride/pyridine in a volume ratio of 15/85, and allowing to stand for 20 hours. Thereafter, 1 ml of water and 10 ml of ethanol were added, and the mixture was titrated with 0.1 N potassium hydroxide (ethanol solution). The indicator uses phenolphthalein.

<Manufacture of acrylic polyol (A)>

(Synthesis Example 1) 100 parts by weight of ethyl acetate was placed in a 4-necked flask equipped with a condenser, a nitrogen gas introduction tube, a dropping funnel, and a thermometer, and the temperature was raised to 80 ° C. Then, 42.7 parts by weight of butyl acrylate, 51.0 parts by weight of ethyl methacrylate, 1.8 parts by weight of 2-hydroxyethyl acrylate, and 2.0 parts by weight of azobisisobutylonitrile were added dropwise by means of a dropping funnel over 2 hours. Pre-mixed monomer liquid. Thereafter, the reaction was allowed to proceed for 1 hour, and then 0.2 part by weight of azobisisobutylcarbonitrile was added thereto to carry out a reaction for 1 hour, and the above steps were carried out until the conversion of the monomer became 98% or more, followed by cooling. Then, ethyl acetate was added to obtain a solution in which the solid content was 50%.

(Synthesis Example 2 to Synthesis Example 21) Synthesis Example 2 shown in Table 1 was obtained in the same manner as in Synthesis Example 1 except that the molecular weight was adjusted by the addition amount of the polymerization initiator azobisisobutyl nitrile. ~ The acrylic polyol of Synthesis Example 21. Further, the synthesis example 17 is an acrylic polyol which is a composition shown in Synthesis Example 1 in Patent Document 2. In addition, the abbreviation in Table 1 is as follows.

BA: butyl acrylate, EMA: ethyl methacrylate, EA: ethyl acrylate, St: styrene, CHMA: cyclohexyl methacrylate, 2EHA: 2-ethylhexyl acrylate, HEA: acrylic acid-2 -hydroxyethyl ester, 4HBA: 4-hydroxybutyl acrylate, HEMA: hydroxyethyl methacrylate

<Example of preparation of adhesive composition>

(Examples 1 to 17 and Comparative Examples 1 to 6) The acrylic polyol (A) as a main component in terms of solid content was used as the formulation ratio shown in Table 2 A polyisocyanate (B) as a curing agent is blended, and a glycidyl group-containing decane coupling agent ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) as an additive is added in an amount of 3.0 parts by weight, and dioctyltin dilaurate ("NEOSTANN" U-810", manufactured by Nitto Kasei Co., Ltd.) was 0.01 parts by weight, and the solid content was further adjusted to 30% with ethyl acetate.

<Production Example of Laminated Film 1>

Using the respective adhesive compositions of Examples 1 to 17 and Comparative Examples 1 to 6, the amount of the dry coating amount was 4 g/m ² to 5 g/m ² , and the adhesive was composed by a dry laminator. The object was applied to a corona-treated surface of a polyester film [manufactured by Toray Industries, Lumirror X-10S, thickness: 50 μm]. Then, the solvent was volatilized, and then laminated on a corona-treated surface of another polyester film [manufactured by Toray Industries, Lumirror X-10S, thickness: 50 μm]. Thereafter, the hardening treatment (aging) was performed at 40 ° C for 3 days to cure the adhesive to form the laminated film 1 .

<Production Example of Laminated Film 2>

Using the adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 3, a laminate having a structure of [corona treated polyester film/adhesive layer/aluminum foil] was produced in accordance with the method for producing the laminated film 1. Membrane 2.

<Production Example of Laminated Film 3>

Using the adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 3, in accordance with the method for producing the laminated film 1, the vapor deposited layer of the polyester film deposited with ruthenium dioxide was bonded to the adhesive layer. In this manner, the laminated film 3 having a configuration of a corona-treated polyester film/adhesive layer/cerium oxide-deposited polyester film is used.

Tables 2 and 3 show the combination of the main agent and the hardener in Examples 1 to 17, and Comparative Examples 1 to 6, and the initial adhesion force of the laminated film 1 in an environment of 85 ° C and a humidity of 85%. Exposure to 1000 hours, 2000 hours, and 3000 hours after exposure.

Further, Tables 4 and 5 show the initial adhesion of the laminated film 2 and the laminated film 3 of the examples 1 to 4 and the comparative examples 1 to 3, and exposed to an environment of 85 ° C and a humidity of 85% for 1,000 hours. , 2000 hours, and 3000 hours after the end of the force. The specific evaluation method will be described below.

<Adhesion test before aging and after aging>

The laminated film 1, the laminated film 2, and the laminated film 3 before and after aging are cut into a size of 200 mm × 15 mm, and allowed to stand in an environment of 25 ° C and a humidity of 65% for 6 hours, according to ASTM-D1876. In the test method of -61, a T-peel test was carried out using a tensile tester at a load speed of 300 mm/min under an environment of 25 ° C and a humidity of 65%. The peeling strength (N/15 mm width) between the PET film/PET film, the PET film/aluminum foil, and the PET film/cerium oxide vapor-deposited polyester film was represented by the average value of the five test pieces.

<Adhesion test after moisture and heat resistance test>

The laminated body after aging was cut into a size of 200 mm × 15 mm, and allowed to stand in an environment of 85 ° C and a humidity of 85% for 1,000 hours, 2000 hours, and 3000 hours. Thereafter, after standing at 25 ° C and a humidity of 65% for 6 hours, a tensile tester was used according to the test method of ASTM-D1876-61 at a load speed of 25 ° C and a humidity of 65%. A T-peel test was performed at 300 mm/min. The peeling strength (N/15 mm width) between the PET film/PET film, the PET film/aluminum foil, and the PET film/cerium oxide vapor-deposited polyester film was represented by the average value of the five test pieces.

<Evaluation criteria>

[Adhesion test before aging]

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

○ Practical area: 2N/15mm~3N/15mm

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

×Not practical: less than 1N/15mm

[After aging test, adhesion test after moisture and heat resistance test]

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

○ Practical area: 4N/15mm~5N/15mm

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

×Not practical: less than 2N/15mm

As shown in Table 3, it is understood that the adhesive composition of the example is excellent in the adhesion force before the aging, the adhesion after aging, and the heat and humidity resistance test, and the bonding strength can be maintained over a long period of time. Therefore, the adhesive composition of these examples is excellent in long-term heat and humidity resistance for outdoor use.

Further, in JIS C 8917 (Environmental Test Method and Endurance Test Method for Crystalline Solar Cell Module), it is specified as a moisture resistance test B-2 at 85 ° C and a humidity of 85% for 1000 hours, and is known as a special Severe test method. In the present example, the characteristics of the adhesive strength can be maintained for more than 1000 hours and after 3,000 hours, and it can be said that the adhesive composition of the present invention has sufficient long-term heat and humidity resistance.

The solar cell back protective sheet maintains sufficient interlayer adhesion strength (laminate strength) in such long-term moisture resistance test, and does not cause delamination between the sheet layers, thereby contributing to solar cell element protection and power generation efficiency. Maintenance can further contribute to the extended life of the solar cell. The extension of the life of solar cells is related to the popularity of solar cell systems, and it also contributes to environmental protection from the viewpoint of ensuring energy other than fossil fuels.

The adhesive composition of the present invention can be used as a multi-layer laminate material (barrier material, exterior wall material, roofing material, solar cell panel material (back surface protection sheet for solar cells, solar cell surface protection sheet) for outdoor industrial applications such as buildings, Window materials, outdoor flooring materials, lighting protection materials, automotive parts, etc.) provide strong bonding strength with an adhesive. Further, it is possible to suppress the subsequent strength due to hydrolysis or the like from being lowered over time during outdoor exposure, and it is possible to maintain a strong adhesive strength over a long period of time.

Comparative Example 1 is an example in which the glass transition temperature of the acrylic polyol (A) was 55 ° C and higher than 50 ° C. As a result of the evaluation, it was found that substantially no wettability to the substrate was obtained, the initial adhesion was small, and the adhesion was lowered in the heat and humidity resistance test.

Comparative Example 2 is an example in which the number average molecular weight of the acrylic polyol (A) is 6,000 and less than 10,000. It can be seen that the result of the evaluation is that the cohesive force of the adhesive before the aging step is insufficient, and the adhesion force before the aging step is small. In the case of industrial production, the laminated body in a state of being wound into a roll is such that the core is Aging is performed in the vertical direction. If the adhesion force before the aging step is small, the winding is easily spread at the time of aging, and is not suitable for industrial production.

Comparative Example 3 is an example in which the acrylic polyol (A) has a number average molecular weight of 150,000 and more than 100,000. As a result of the evaluation, it was found that the wettability to the PET film was insufficient, and sufficient adhesion could not be obtained before the aging. The same as in Comparative Example 2, the winding was easily spread during the aging process, and it was not suitable for industrial production. Further, since the adhesion was gradually lowered due to the heat and humidity resistance test, and the force was originally low, the result was lower than the practical lower limit after 3000 hours.

Comparative Example 4 is an example in which the glass transition temperature of the acrylic polyol (A) is -50 ° C and lower than -40 ° C. As a result of the evaluation, even in the case of surface-treating the polyester film, even an adhesion force of about 3 (N/15 mm) could not be exhibited.

Comparative Example 5 is an example in which the OH value of the acrylic polyol (A) is 110 and more than 100. As a result of the evaluation, it was found that the cross-linking became excessive and it became a very hard cured coating film, which was a result of poor adhesion.

Comparative Example 6 is an example in which the amount of the polyisocyanate (B) blended was NCO/OH = 12. As a result of the evaluation, it was found that the reaction with the acrylic polyol (A) was carried out before the coating to produce a gel, and thus the coating could not be performed.

The present application claims priority based on Japanese Patent Application No. 2011-078188, filed on Jan. 31, 2011, to the Japan Intellectual Property Office, the disclosure of which is incorporated herein by reference. .

[Industrial availability]

The adhesive composition for laminated sheets of the present invention is an adherend for joining the same or different raw materials, and can be suitably used, for example, in the joining of a multi-layer laminate of a plastic-based raw material and a metal-based raw material. Of course, it is also suitable for the joining of plastic raw materials and metal-based raw materials. The adhesive composition for a laminated sheet of the present invention maintains a high adhesion even when exposed to a high temperature and high humidity environment. Therefore, it is a multi-layer laminate material (barrier material, exterior wall material, roofing material, solar cell panel material (back surface protection sheet for solar cells, solar cell surface protection sheet), window material, outdoor floor material for outdoor industrial applications such as buildings. , lighting protection materials, automotive parts, etc.) are suitable for the adhesive. The bonding strength can be maintained over time for a long period of time, and therefore it is particularly suitable for applications in which environmental resistance is strongly required, for example, formation of a back surface protective sheet for a solar cell. Moreover, it is also suitable for the formation of a surface protection sheet for a solar cell. Further, the adhesive sheet composition for laminated sheets of the present invention exhibits a high adhesion between the layers particularly including the surface treatment layer of the plastic film, and can be suitably applied to the untreated raw material (including the surface uncovered). Processed in plastic film).

Claims (4)

An adhesive composition for a laminate sheet comprising an acrylic polyol (A) and a polyisocyanate (B), the acrylic polyol (A) having a number average molecular weight of 10,000 to 100,000 and a hydroxyl value of 1 mgKOH/g to 100 mgKOH/ g, in addition, the glass transition temperature (Tg) is -15 ° C or more and 10 ° C or less, and the equivalent ratio of the hydroxyl group derived from the acrylic polyol (A) to the isocyanate group derived from the polyisocyanate (B) is NCO / OH is 0.1~3. The adhesive composition for a laminated sheet according to the above aspect of the invention, wherein the polyisocyanate (B) comprises a polyisocyanate derived from an alicyclic diisocyanate or an aliphatic diisocyanate. The adhesive composition for a laminated sheet according to the first or second aspect of the invention, which is used in the manufacture of a back protective sheet for solar cells comprising two or more sheet members, and is used for the following purposes. Medium: forming at least a portion of an adhesive layer for joining the sheet members to each other. A back surface protective sheet for a solar cell, comprising: an adhesive layer formed of an adhesive composition for a laminated sheet according to any one of claims 1 to 3; At least two or more sheet members laminated in layers.