KR20140022811A - Adhesive agent composition for laminate sheet, and back surface protecting sheet for solar cell - Google Patents

Abstract

Provided is an adhesive composition suitable for the production of a back protective sheet for solar cells capable of maintaining high adhesion even when exposed to high temperature, high humidity environments exhibiting high adhesion between various sheet-shaped members, particularly interlayers including surface treated layers of plastic films. The adhesive composition for laminated sheets which concerns on this invention is an adhesive composition for laminated sheets containing an acrylic polyol (A) and a polyisocyanate (B), The number average molecular weight of an acrylic polyol (A) is 10,000-100,000, and a hydroxyl value is It is 1-100 mgKOH / g, and glass transition temperature (Tg) is more than -40 degreeC and 10 degrees C or less. Moreover, equivalence ratio NCO / OH of the hydroxyl group derived from acrylic polyol (A) and the isocyanate group derived from polyisocyanate (B) is made into 0.1-3.

Description

Adhesive composition for laminated sheets and back protective sheet for solar cells {ADHESIVE AGENT COMPOSITION FOR LAMINATE SHEET, AND BACK SURFACE PROTECTING SHEET FOR SOLAR CELL}

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

Recently, multi-layer (composite) films used for outdoor industrial use, for example, barrier materials, roofing materials, solar panels, window materials, outdoor flooring materials, lighting protection materials, automotive parts materials, signs, stickers, etc. (Composite) The laminate has been put to practical use. The multilayer laminate can be obtained by laminating (laminating) a metal-related material, a plastic-based material, or the like. Examples of metal-related materials include metal foils such as aluminum, copper, and steel sheets, metal plates, and metal deposition films. Plastic materials include plastic films such as polypropylene, polyvinyl chloride, polyester, fluorine resins, acrylic resins, and the like, plastic films, plastic sheets, plastic plates, and silica films formed on the surface thereof with inorganic oxide layers. Background Art Conventionally, polyepoxy adhesives and polyurethane adhesives are known as adhesives used for joining metal-related materials and plastic-based materials.

Patent Literature 1 describes a solar cell backside sealing sheet comprising a laminate in which at least two or more substrates are bonded together with a polyurethane adhesive. More specifically, condition 1: HAST chamber 105 ° C., 1.05 atm, which is an accelerated evaluation device using pressurized steam, at least 1 N / 15 mm or more after storing for 168 hours. Condition 2: HAST, which is an accelerated evaluation device using pressurized steam. A polyurethane-based adhesive is described which contains an adhesive with hydrolysis resistance that satisfies the condition that the chamber is kept at 105 DEG C, 1.05 atm, and 168 hours, and does not float between the substrates upon peeling. Specifically, a plurality of polyurethane adhesives have been proposed in which a crosslinking agent is combined for each of six types of polyols of polyol A to polyol F (see claims 2 to 11 of Patent Document 1).

Patent document 2 describes the solar cell module back sheet provided with the laminated body which matched at least 2 base materials with the acrylic adhesive agent. 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 hydrolysis resistance, insulation resistance and water barrier property has been proposed (patent document). 2, claim 2).

CH ₂ = C (R ¹ ) -CO-OZ (I)

In formula, R <^1> is a hydrogen atom or a methyl group, Z represents a C4-C25 hydrocarbon group.

Moreover, although it is a patent document published after the application as a basis of priority, patent document 3,4 describes the adhesive composition suitable for the use used for the sheet | seat which adhered the unprocessed surface of a plastic film and another base material.

International Publication No. 2007-148754 Japanese Patent Laid-Open No. 2009-246360 Japanese Patent Laid-Open No. 2011-105819 Japanese Patent Laid-Open No. 2011-111519

In order to maintain the adhesive stably for a long time under severe outdoor conditions, it is important that the adhesive strength is stable even with time (over time). Recently, as in Patent Documents 3 and 4, development of an adhesive that adheres well to an untreated plastic surface such as a polyester film that does not undergo surface treatment and another substrate is in full swing. This is because the manufacturing process can be shortened by not performing the surface treatment, thereby reducing the cost. However, on the other hand, by utilizing the surface treatment technology that has been conventionally used to further enhance the original performance of the adhesive composition, there is also a high demand for an adhesive composition having synergistically superior adhesive properties.

The present invention has been made in accordance with the above-mentioned background, and an object thereof is to show a high adhesion between various sheet-shaped members, in particular between layers including surface treatment layers of plastic films, and for solar cells capable of maintaining high adhesion even when exposed to high temperature and high humidity environments. It is providing the adhesive composition for laminated sheets suitable for manufacture of a back surface protection sheet, and the back surface protection sheet for solar cells.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, the present inventors discovered that the said subject can be solved by the adhesive composition for laminated sheets shown below, and came to complete this invention.

That is, the adhesive composition for laminated sheets which concerns on this invention WHEREIN: The adhesive composition for laminated sheets containing an acrylic polyol (A) and a polyisocyanate (B) WHEREIN: The number average molecular weight of the said acrylic polyol (A) is 10,000-100,000, and The hydroxyl value is 1-100 mgKOH / g, the glass transition temperature (Tg) is more than -40 degreeC and 10 degrees C or less, and the equivalent ratio of the hydroxyl group derived from the said acrylic polyol (A), and the isocyanate group derived from the said polyisocyanate (B) NCO / OH is 0.1-3.

Preferred examples of the polyisocyanate (B) include those containing polyisocyanates derived from aliphatic ring diisocyanates or aliphatic diisocyanates.

The adhesive composition for the laminated sheet of the above form is used in the manufacture of the back protective sheet for solar cells having two or more sheet-like members, and is suitably used for forming at least a part of the adhesive layer for bonding the sheet-like members.

The solar cell back protection sheet which concerns on this invention is equipped with the adhesive bond layer formed from the adhesive composition for laminated sheets of the said aspect, and the at least 2 layer or more sheet-like member laminated | stacked through the said adhesive bond layer.

According to the present invention, lamination is preferred between various sheet-shaped members, in particular, between layers including surface treatment layers of plastic films, and is suitable for the manufacture of solar cell back protective sheets capable of maintaining high adhesion even when exposed to high temperature and high humidity environments. An excellent effect of providing the adhesive composition for a sheet and the back protective sheet for a solar cell is obtained.

In addition, in this specification, description "random number A-arbitrary number B" means the range larger than the number A and the number A, and means the range smaller than the number B and the number B. In addition, the description "(meth) acrylo" described in this specification and a claim includes both the compound read as "acrylo" and the compound read as "methacrylo". Moreover, it defines similarly in "(meth) acryl" and "(meth) acrylate".

<Acrylic polyol (A)>

As the acrylic polyol (A), a hybrid polymer of a hydroxyl group-containing mono (meth) acrylate monomer and a mono (meth) acrylate monomer not containing a hydroxyl group is preferably used. The hydroxyl group-containing mono (meth) acrylate monomer is a monomer containing one (meth) acryloyl group and one or more hydroxyl groups in one molecule. As a preferable example, there exist a mono (meth) acrylic acid ester monomer obtained by reaction of a dihydric alcohol and (meth) acrylic acid, (epsilon) -caprolactone modified (meth) acryl monomer, etc.

If the number average molecular weight of the acrylic polyol (A) is about the same, the part which does not participate in copolymerization of a mono (meth) acrylate monomer from a viewpoint of an adhesive improvement, ie, the part which couple | bonds with an ester bond to the (meth) acrylic acid part (alkyl group or Part of an alkenyl group etc. Hereinafter, it is preferable that carbon number of the "side chain part" is 1-17, It is more preferable that it is 1-9, and 1-3 are more preferable. The side chain portion from above will form side chains of the acrylic polyol (A) after copolymerization. The carbon number of the side chain portion on the mono (meth) acrylate monomer is generally about 1 to 30, but as long as the number average molecular weight of the acrylic polyol (A) is about the same, the shorter the side chain portion is, the main chain of the acrylic polyol (A) Becomes relatively long. As a result, it is considered that the mechanical properties (specifically, increase rate) of the adhesive layer after curing will be improved and the adhesive strength will be improved.

As a mono (meth) acrylic acid ester monomer obtained from a dihydric alcohol, it is (meth) acrylic acid 2-hydroxyethyl, (meth) acrylic-acid hydroxypropyl, 1, 4- butanediol mono (meth) acrylate, for example. , (Poly) ethylene glycol mono (meth) acrylate, and the like.

In addition, mono (meth) acrylic acid ester monomers obtainable from trihydric or higher alcohols such as (meth) acrylic acid 2,3-dihydroxy propyl can also be used as the hydroxyl group-containing mono (meth) acrylate monomers.

Mono (meth) acrylate monomers that do not contain a hydroxyl group can be used by appropriately selecting a radical polymerizable monomer well known from the past. As a preferred example, for example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethyl hexyl (meth) acrylate, n-octyl (meth) Long-chain (meth) acryl monomers and acrylonitrile represented by alkyl (meth) acrylate monomers, such as acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, and stearyl (meth) acrylate, etc. There is this.

Moreover, in addition to the said hydroxyl-containing (meth) acrylate monomer and the mono (meth) acrylate monomer which does not contain a hydroxyl group, other monomers, for example, carboxyl group-containing monomers, such as (meth) acrylic acid, maleic acid, and maleic anhydride Or anhydrides thereof or vinyl monomers such as styrene may be copolymerized, and the hydroxyl group-containing (meth) acrylate monomers and the mono (meth) acrylate monomers containing no hydroxyl group may each independently use one compound or two or more kinds. You may use it in combination. 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. Moreover, it is preferable that it is 10,000-70,000, and 25,000-50,000 are more preferable.

The laminated sheet obtained by laminating | stacking two or more sheet-like members using the adhesive composition for laminated sheets (henceforth "adhesive composition") of this invention, for example, the solar cell back surface protective sheet is obtained through the following process, for example. Lose. The adhesive composition is coated and dried on the bonding surface of the sheet-like member. Subsequently, another sheet-like member is superposed on the adhesive layer, and the adhesive layer is cured by a process called "aging" in which the preservation is performed for two days to one week in 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 process tends to be insufficient, and the adhesive force before the aging process may be small. In the case of industrial production, a laminate in a rolled-up state is usually aged with the rolling core in the celestial direction. If the adhesive force before the aging process is small, the roll is liable to collapse during aging and is unsuitable for industrial production. Moreover, less than 10,000 tends to lack cohesion force after an aging process, and moisture-heat resistance is low by this, and peeling etc. may arise.

Moreover, when the number average molecular weight of an acryl polyol exceeds 100,000, there exists a tendency for adhesive viscosity to become high, a problem in coating property, or wettability with respect to a sheet-like member tends to fall, and as a result, the adhesive force before an aging process may become small. According to aging, although the initial adhesive force becomes large compared with before aging, it declines gradually by the subsequent heat-and-moisture resistance test, and may be below the use limit after 3000 hours.

In addition, the number average molecular weight of this invention is the value calculated | required by gel permeation chromatography (GPC), and polystyrene conversion. More specifically, the number average molecular weight of this invention has shown the value calculated | required by the measuring method described in the Example mentioned later. In addition, the value calculated | required by the method as described in the Example mentioned later about glass transition temperature and NCO / OH equivalence ratio is shown similarly.

The hydroxyl value of the acrylic polyol (A) is determined according to the hydroxyl-containing mono (meth) acrylate monomer content. In the present invention, the hydroxyl value is 1-100 mgKOH / g, preferably 1-50 mgKOH / g, and 1-15 mgKOH / g is more preferred. If it is less than 1 mgKOH / g, there exists a tendency for crosslinking with an isocyanate hardening | curing agent to fall, and there exists a possibility that moisture-heat resistance may fall. If it exceeds 100 mgKOH / g, the adhesive force before aging is expressed, but the crosslinking density tends to increase after aging, and thus sufficient adhesive force may not be expressed, and there is a possibility that the adhesive force may be further lowered in the subsequent moist heat resistance test.

Moreover, in this invention, the glass transition temperature (Tg) of acryl polyol (A) is more than -40 degreeC and 10 degrees C or less for the reason mentioned later, and more preferably more than -25 degreeC and 10 degrees C or less.

<Polyisocyanate (B)>

The polyisocyanate (B) can be used without limitation, for example, known compounds which are compounds derived from known diisocyanates. For example, 2,4-trilene diisocyanate (aka 2,4-TDI), 2,6-triylene diisocyanate (aka 2,6-TDI), xylene diisocyanate (aka XDI), diphenyl methane Diisocyanates such as diisocyanate (aka MDI), isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexa diisocyanate (aka HDI), bis (4-isocyanatecyclohexyl) methane, or hydrogenated diphenyl methane diisocyanate Compounds derived from, i.e., nurates of the diisocyanates, trimethylol propane adducts, biurets, prepolymers with isocyanate residues (low polymers obtained from diisocyanates and polyols), urates with isocyanate residues Diones, allophanate alone, or composites thereof and blocked isocyanates. Polyisocyanate (B) can be used individually by a single compound or in combination of 2 or more type.

It is preferable to use polyisocyanate derived from aliphatic cyclic diisocyanate or aliphatic diisocyanate from a viewpoint of the viscoelasticity of the cured coating film after crosslinking as polyisocyanate (B). More specifically, as alicyclic diisocyanate, isophorone diisocyanate, methyl-2, 6-cyclohexane diisocyanate, etc. are mentioned. Moreover, hexa diisocyanate, pentamethylene diisocyanate, etc. are mentioned as aliphatic diisocyanate. In addition, the prepolymer (low polymer obtained from diisocyanate and polyol) which has a nurate of the diisocyanate which is a derivative of the compound of the said aliphatic ring diisocyanate and an aliphatic diisocyanate, a trimethylolpropane adduct, a biuret type, and an isocyanate residue, Urate diones having isocyanate residues, allophanate alone, or complexes thereof are cited.

Moreover, when it is important to emphasize 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 NCO and the aromatic ring. Fast curing speed is preferable in that aging time can be reduced.

Moreover, it is preferable that the isocyanate group concentration in polyisocyanate (B) is 5-30 weight%. Isocyanate group concentration in a polyisocyanate (B) is taken as the range of 5 weight%-30 weight%. In addition, the isocyanate group concentration in a polyisocyanate (B) can be calculated | required by the titration method. The titration was evaluated by the n-butyl amine hydrochloric acid titration method. Specifically, after dissolving the sample in dry toluene, an excess n-dibutyl amine solution is added and reacted, and the remaining n-dibutyl amine is titrated against with hydrochloric acid, the inflection point on the titration curve is set as the end point, and isocyanate at a proper amount up to the end point. The group content rate was calculated.

The amount of polyisocyanate (B) used is determined by the NCO / OH equivalent ratio of the hydroxyl group derived from the acrylic polyol (A) and the isocyanate group derived from the polyisocyanate (B), and the NCO / OH equivalent ratio is 0.1 to 3. More preferably, NCO / OH equivalence ratio is 1-3, and 1.5-3 are more preferable. NCO / OH equivalent ratio was calculated | required using the following formula (1).

NCO / OH ratio = polyisocinate required amount (weight part) x (561 / OH value) x (NCO% / (42 x 100) x (100 / polyol amount (solid content weight)) Formula (1)

The present inventors found that an adhesive composition for laminated sheets having surprisingly excellent properties can be obtained by satisfying all of the following conditions. That is, using the acrylic polyol (A) having (i) a number average molecular weight in a specific range, (ii) a hydroxyl value in a specific range and (iii) a glass transition temperature (Tg) in a specific range, and (iv) Surface treatment of various sheet members, in particular plastic films, by satisfying all of the conditions that the equivalent ratio NCO / OH of the hydroxyl group derived from the acrylic polyol (A) and the isocyanate group derived from the polyisocyanate (B) falls within the above specific range It has been found that an adhesive composition suitable for the production of a back protective sheet for solar cells, which exhibits high adhesion between layers and layers, and which can maintain high adhesion even when exposed to high temperature, high humidity environment, has been found. The reason for this is as follows.

When laminating a plastic film whose surface has been treated by corona discharge or the like, compared to laminating a plastic film having no surface treatment, an added value as the manufacturing process is increased is required. In the adhesive force, a higher adhesive force is required than in the case of laminating the untreated plastic film.

If the Tg of the acrylic polyol is too low, the adhesive layer before aging is still insufficient in curing, so the adhesive layer formed of the adhesive composition is soft. And the softness to some extent can express between sheet-like members. However, even if the adhesive layer is sufficiently cured after aging, the Tg of the acrylic polyol of the raw material is low, so that the lack of cohesion of the adhesive layer is surfaced, which tends to make it difficult to secure large adhesive force. Moreover, when a laminated body is put under high temperature, high humidity for a long time, it exists in the tendency for adhesive force to fall gradually because of lack of cohesion force of an adhesive bond layer.

On the other hand, when the Tg of the acrylic polyol is too high, the wettability to the substrate tends to be insufficient. Although the adhesive force after aging becomes rather large compared with before aging, since the hardened adhesive layer after crosslinking hardens, there exists a tendency for the adhesive force after an aging process to deteriorate.

In the present invention, the reason for obtaining the above excellent effect is that the Tg of the acrylic polyol is not too low and at the same time not too high (specifically, more than -40 ° C. up to 10 ° C.), and a specific hydroxyl value, specific NCO It is considered that by setting the / OH equivalent ratio and the specific number average molecular weight in a range, the wettability and fixability to the adhesive object can be improved by utilizing the activity of the acrylic polyol movement at the molecular motion level synergistically. In particular, it is considered that by controlling the NCO / OH equivalence ratio in the range of 0.1 to 3, particularly in the range of 1 to 3, high adhesive strength could be exhibited after the aging step of achieving proper crosslinking degree balance. Surprisingly, it has also been found to exhibit high adhesion even before aging. In addition, it was found that even after being placed under high temperature and high humidity after the aging process, high adhesive force can be maintained.

It is preferable that the adhesive composition for laminated sheets of this invention contains a silane coupling agent from a viewpoint of improving adhesive strength, when using a metal foil, a metal plate, a metal vapor deposition film, etc. as a base material.

Although a silane coupling agent is not limited to the following, For example, vinyl silanes, such as vinyl tris ((beta) -methoxy ethoxy) silane, vinyl ethoxy silane, and vinyl trimethoxy silane; (gamma)-(meth) acryl (Meth) acryloxy silanes such as oxypropyl trimethoxy silane, γ- (meth) acryloxy propyl triethoxysilane and γ- (meth) acryloxy propyl dimethoxy methyl silane; β- (3,4-epoxy Cyclohexyl) ethyl trimethoxy silane, β- (3,4-epoxycyclohexyl) methyl trimethoxy silane, β- (3,4-epoxycyclohexyl) ethyl triethoxy silane, β- (3,4- Epoxy silanes such as epoxycyclohexyl) methyl triethoxy silane, γ-glycidoxy propyl trimethoxy silane and γ-glycidoxy propyl triethoxy silane; N-β (aminoethyl) γ-aminopropyl trimethoxy silane, N-β (amino ethyl) γ-aminopropyl triethoxy silane, N-β (amino ethyl) γ-aminopropyl methyl diethoxy silane, γ- Amino silanes such as aminopropyl triethoxy silane, γ-amino propyl trimethoxy silane, N-phenyl-γ-aminopropyl trimethoxy silane, and N-phenyl-γ-aminopropyl triethoxysilane; And thio silanes such as γ-mercaptopropyl trimethoxy silane and γ-mercaptopropyl triethoxy silane. These can be used individually or in combination of 2 or more types, respectively. It is preferable that it is 0.1-5 weight part with respect to 100 weight part of acrylic polyols (A), and, as for the addition amount of a silane coupling agent, it is more preferable that it is 1-3 weight parts. If it is less than 0.1 weight part, the effect of improving the adhesive strength with respect to metal foil is inadequate by adding a silane coupling agent, and even if it adds beyond 5 weight part, the further performance improvement may not be recognized.

The adhesive composition for laminated sheets of the present invention may be a so-called two-liquid mixed adhesive that mixes the main body and the curing agent when used, or may be a one-liquid type adhesive agent in which the main body and the curing agent are mixed in advance. Moreover, you may use acryl polyol (A) and polyisocyanate (B) by several types each independently. Moreover, you may use other subjects and hardening | curing agents other than the above by single or multiple types each independently. Commonly, the subject includes an acrylic polyol (A), a silane coupling agent, an organic solvent, and other curing agents including a polyisocyanate (B), an organic solvent, and other additives.

Other additives include tackifiers, reaction accelerators, leveling agents, phosphorus- and phenol-based antioxidants, ultraviolet stabilizers, metal deactivators, and flame retardants within the range not departing from the gist of the present invention to the adhesive for laminated sheets of the present invention. Various additives, such as a plasticizer and an organic and inorganic pigment, can be mix | blended.

When using a metal layer (metal foil, metal plate etc.) as a sheet-like member, in order to improve the metal adhesiveness of the adhesive composition for laminated sheets of this invention, a phosphoric acid type compound, for example, phosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, The ester etc. can be added. Moreover, the adhesive composition of this invention can be used also as an anchor coat agent for solar cell laminated sheets besides being used suitably as an adhesive agent for solar back surface protection sheet manufacture. In that case, it is preferable to add an anti blocking agent.

In addition, a well-known additive can be mix | blended without a restriction | limiting in the range which does not deviate from the meaning of this invention. For example, a reaction accelerator can be used. Specific examples thereof include metal 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-1,8- Tertiary amines such as diazabicyclo (5,4,0) undecene-7; Reactive tertiary amines such as triethanolamine and the like. A reaction promoter can be used 1 type or in combination or 2 or more types.

Moreover, a well-known leveling agent or defoaming agent can also be mix | blended with a subject for the purpose of improving a laminate appearance.

As the leveling agent, for example, polyether-based modified polydimethyl siloxane, polyester-modified polydimethyl siloxane, aralkyl-modified polymethyl alkyl siloxane, polyester-modified hydroxyl group-containing polydimethyl siloxane, polyether ester-modified hydroxyl group-containing polydimethyl siloxane, acrylic type A well-known thing, such as a copolymer, a methacryl type copolymer, a polyether modified poly methyl alkyl siloxane, an acrylic acid alkyl ester copolymer, a methacrylic acid alkyl ester copolymer, lecithin, or a mixture thereof, is mentioned.

Antifoaming agents include known resins such as silicone resins, silicone solutions, copolymers of alkyl vinyl ethers, acrylic acid alkyl esters and methacrylic acid alkyl esters, or mixtures thereof. When adding a leveling agent and an antifoamer, each independently, 1 type of compounds may be used and 2 or more types of compounds may be combined arbitrarily.

In addition, known additives used in the present invention are known phosphorus and phenol-based compounds for the purpose of further suppressing the yellowing over time of the adhesive due to heat such as the sun, the heat of the adhesive such as solar heat, such as the sun. Antioxidants, ultraviolet stabilizers and metal deactivators can be blended into the subject. These may be used independently or may be used in combination of 2 or more type arbitrarily. Phosphorus- and phenol-based antioxidants, ultraviolet stabilizers, and metal deactivators used in the present invention have a range of 0.05 to 5 parts by weight and more preferably 0.1 to 1 part by weight based on 100 parts by weight of the solid of the acrylic polyol (A). . If the added amount is less than 0.05 weight, there is a fear that a sufficient yellowing inhibiting effect may not be obtained, and if it is more than 5 parts by weight, the adhesive strength of the adhesive may be greatly deteriorated.

A hardening | curing agent is a well-known oxazoline compound, for example, 2, 5- dimethyl- 2-oxazoline, or 2, 2- (1) within the range which does not impair the effect of this invention other than the said polyisocyanate (B). , 4-butylene) bis (2-oxazoline), or a hydrazide compound such as isophthalic acid dihydrazide, sebacic acid dihydrazide, adipic acid dihydrazide, and the like.

As a solvent used by this invention, Ester, such as ethyl acetate, butyl acetate, and cellosolve acetate; Ketones such as acetone, methyl ethyl ketone, isobutyl ketone, methyl isobutyl ketone and cyclo hexanone; Ethers such as tetrahydrofuran and dioxane; Aromatic hydrocarbons such as toluene and xylene; Halogenated hydrocarbons such as methylene chloride and ethylene chloride; Dimethyl sulfoxide and dimethyl formamide are mentioned. The solvent to be used may use 1 type of solvents, and may mix and use 2 or more types arbitrarily.

The nonvolatile matter (solid content) of the adhesive agent of this invention has the preferable range of 10-50 weight%. This adhesive agent can adjust solid content using the solvent illustrated above.

Next, the method of manufacturing the back surface protective sheet for solar cells using the adhesive composition for laminated sheets of this invention, and an example of the back surface protective sheet for solar cells are demonstrated. The manufacturing method and structure of a solar cell back surface protective sheet are not limited to the following examples, Various manufacturing methods and structures can be employ | adopted according to the objective and necessity.

The simple solar cell module has a configuration form in which fillers and glass plates are sequentially stacked on both surfaces of a solar cell which is a solar cell element. A glass plate is excellent in transparency, weather resistance, and abrasion resistance, and is currently generally used as a sealing sheet on the light-receiving surface side of the sun. However, on the non-light-receiving side that does not require transparency, solar cell back protective sheets (hereinafter, referred to as back protective sheets) other than glass panels have been developed by the companies in terms of cost, safety, and workability, and these have replaced glass plates.

Solar cell back protective sheet is plastic film such as polyester film, plastic film with metal layer provided with deposition layer of metal oxide and nonmetal oxide on polyester film, metal foil such as aluminum foil, plastic film with silicon nitride layer, etc. There is a laminated. Between each sheet-like member laminated | stacked, it can bond together using the adhesive composition for laminated sheets of this invention. The solar cell back protective sheet of a composite structure can provide various performances according to the multilayer structure. For example, insulation can be provided by using a polyester film, and weather resistance can be provided by using an aluminum foil by using a fluorine-based film, and water vapor barrier can be imparted. Which solar cell back protective sheet to use is selected suitably according to the product and application to which a solar cell module is used.

Examples of the plastic film include polyester resin films such as polyethylene terephthalate and polynaphthalene terephthalate, polyethylene resin films, polypropylene resin films, polyvinyl chloride resin films, polycarbonate resin films, polysulfone resin films, Poly (meth) acrylic resin film, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, polyethylene ethylene tetrafluoroethylene, Teflon, tetrafluoroethylene, perfluoroalkyl vinyl ether copolymer, tetrafluoro Fluorine resin films, such as an ethylene-hexafluoro propylene copolymer, are mentioned.

Using these plastic films as a support, a film coated with acrylic or fluorine paint, a multilayer film in which polyvinylidene fluoride, an acrylic resin, or the like is laminated by co-extrusion may be used. Moreover, you may use the sheet-like member in which two or more said plastic films were laminated | stacked through the urethane type adhesive bond layer.

The above plastic film is adhered by physical treatment such as corona discharge, plasma treatment, frame treatment, chemical treatment to improve the surface of the film with acid or alkali, and matt processing to make fine embossing on the film surface. It is easy to use what is easy to do. Of course, you may apply the adhesive composition for laminated sheets of this invention to a surface untreated material.

Examples of the metal foil include aluminum foil and copper foil. As the metal oxide or nonmetal inorganic oxide to be deposited, an oxide such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, yttrium or the like may be used.

Among these, polyesters such as polyethylene terephthalate and polynaphthalene terephthalate having temperature resistance in order to satisfy the performance of weather resistance, water vapor permeability, electrical insulation, mechanical properties, and mounting workability when used as a solar cell module Metal foil such as a plastic film or aluminum foil having a metal oxide having a vapor barrier property or a non-metal inorganic oxide deposited thereon in order to prevent a decrease in output caused by the influence of water of the solar cell, In order to prevent appearance defects due to light deterioration, a solar cell back protective sheet having a good weather resistance fluororesin film laminated thereon is preferred.

In addition, in order to protect the solar cell module from damage due to voltage application, the solar cell back protective sheet is required to have a resistance of a partial discharge voltage of 700 V or 1000 V in accordance with the power generation capacity of the solar cell, and includes the insulation or the foam layer. Many configurations have been adopted to improve the partial discharge voltage. As a method of improving the partial discharge voltage, since the said insulation property depends on the thickness of a film or a foaming layer, a film and a foaming layer tend to become a pressure film. In recent years, many structures using 100 micrometers to 300 micrometers are employ | adopted.

Formation of an adhesive bond layer apply | coats an adhesive composition to one surface of sheet-like members, such as a plastic film, for example with a comma coater or a dry laminator, volatilizes a solvent, and sticks it with the other laminate base material, and room temperature Or it is obtained by hardening at heating. Or by coating and heat-curing the adhesive composition to any one sheet-like member to form an adhesive layer, forming the adhesive layer, and then coating the coating liquid for forming another sheet-shaped member to form another sheet by thermal or active energy rays. It can manufacture by forming a shaped member. Examples of the device for coating the adhesive composition on the 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. . It is preferable that the adhesive amount apply | coated to the surface of a laminate base material is about 0.1-50 g / m <2> in dry conversion. More preferably, it is about 1-50 g / m <2>. As a laminate base material, arbitrary base materials can be selected by arbitrary numbers according to a use, and when comprised by the multilayer of three or more layers, the adhesive composition of this invention can be used for all or one part of each layer.

As the coating liquid for forming a sheet-like member, a polyester-based resin solution, a polyethylene-based resin solution, a polypropylene-based resin solution, a polyvinyl chloride-based resin solution, a polycarbonate-based resin solution, and a polysulfone system, which can be used for forming a plastic film Resin solutions, poly (meth) acrylic resin solutions, fluorine resin solutions and the like are considered to be preferable cases.

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

&Lt; Embodiment &gt;

Hereinafter, the present invention will be described in more detail with reference to the following examples, which do not limit the scope of the present invention. In addition, each evaluation in the Example followed the following method. In addition, in an Example, a part shows a weight part, a% shows a weight%, and a hydroxyl value shows mgKOH / g, respectively. The number average molecular weight, glass transition temperature, and hydroxyl value were obtained as follows.

<Number average molecular weight>

The number average molecular weight was measured using GPC (Gel Permeation Chromatography) "HPC-8020" manufactured by Tosoh Corp., and the solvent was tetrahydro using two SHODEX KF-806L, one KF-804L, and one KF-802. Furan was used. The number average molecular weight was carried out in terms of standard polystyrene.

&Lt; Glass transition temperature (Tg) >

The glass transition temperature (Tg) was measured using DSC "RDC220" manufactured by Seiko Instruments. A sample of the polycarbonate urethane polyol A-1 to A-21 solution synthesized by the following method, and about 10 mg of the dried sample 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 calculated | required from the DSC chart obtained by this.

<Hydroxyl value>

The hydroxyl value is about 2 g of the sample dissolved in about 10 ml of pyridine, and 5 ml of a mixed solution having an adjusted volume ratio of anhydrous acetic acid / pyridine of 15/85 is added thereto and left for 20 hours. Then, 1 ml of water and 10 ml of ethanol are added to add 0.1 N of potassium hydroxide ( Ethanol solution) and titrated. The indicator used phenolphthalein.

<Production of Acrylic Polyol (A)>

(Synthesis example 1) 100 weight part of ethyl acetate was put into the four neck flask provided with the condenser, the nitrogen introduction tube, the dropping rod, and the thermometer, and it heated up at 80 degreeC. Subsequently, the monomer liquid which mixed 47.2 weight part of butyl acrylates, 51.0 weight part of ethyl methacrylates, 1.8 weight part of 2-hydroxy ethyl acrylate, and 2.0 weight part of azobis isobutyl nitrile was dripped over 2 hours by the dropping load. After stirring, the mixture was allowed to react for 1 hour, and 0.2 parts by weight of azobis isobutyl nitrile was added for reaction for 1 hour until the conversion rate of the monomer was 98% or more, followed by cooling. Ethyl acetate was added to obtain a solid content 50% solution.

(Synthesis examples 2-21) Except having adjusted the molecular weight by the addition amount of the polymerization initiator azobis isobutyl nitrile, the acryl polyol of the synthesis examples 2-21 shown in Table 1 was obtained similarly to the synthesis example 1. About synthesis example 17, it is an acryl polyol of the composition shown as synthesis example 1 in patent document 2. As shown in FIG. 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-ethyl hexyl acrylate, HEA: 2-hydroxy ethyl acrylate, 4HBA: 4-hydroxy butyl acrylate, HEMA: hydroxy ethyl methacrylate

[Table 1]

<Synthesis example of adhesive composition>

(Examples 1-17, Comparative Examples 1-6) It contains the polyisocyanate (B) which is a hardening | curing agent with respect to the acrylic polyol (A) which is 100 weight part main subject in conversion of solid substance in the compounding ratio shown in Table 2, and is glycish as an additive. 3.0 parts by weight of a dimethyl group-containing silane coupling agent ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.01 parts by weight of dioctyltindilaurate ("Neostan U-810", manufactured by Nitto Kasei Chemical Co., Ltd.) were further mixed with ethyl acetate. It adjusted so that solid content might be 30%.

[Table 2]

<Production example of laminated film 1>

Using the adhesive compositions of Examples 1 to 17 and Comparative Examples 1 to 6, the adhesive composition was dried on the corona treated side of the polyester film [Toray Corporation, Lumira X-10S, 50 μm in thickness] Coating amount: 4 to 5 g / m ² in an amount that was applied to a dry laminator. And after volatilizing a solvent, it laminated | stacked on the corona treatment surface of one polyester film (Toray Corporation make, Lumira X-10S, thickness 50 micrometers) again. Thereafter, the adhesive was cured by performing curing treatment (aging) at 40 ° C. for 3 days to produce laminated film 1.

<Production example of laminated film 2>

According to the manufacturing method of the laminated | multilayer film 1 mentioned above using the adhesive composition of Examples 1-4 and Comparative Examples 1-3, the laminated | multilayer film 2 of the structure used as a [corona treated polyester film / adhesive layer / aluminum foil] was produced. .

<Production example of laminated film 3>

Using the adhesive composition of Examples 1-4 and Comparative Examples 1-3, the vapor deposition layer of a silica vapor-deposited polyester film contact | connected an adhesive layer according to the manufacturing method of the above-mentioned laminated | multilayer film 1, and [The corona treated polyester film / adhesive layer / Silica vapor deposition polyester film] was produced laminated film 3 of the configuration.

In Tables 2 and 3, the combinations of the main materials of Examples 1 to 17 and Comparative Examples 1 to 6 and the curing agent, and the initial adhesive strength of the laminated film 1, and 1000 hours, 2000 hours and 3000 hours under 85 ° C and 85% humidity. The adhesive force after exposure is shown.

In addition, in Table 4, Table 5, after the initial adhesive force of the laminated films 2 and 3 using Examples 1-4 and Comparative Examples 1-3, exposure at 1000 degreeC, humidity 85% atmosphere for 1000 hours, 2000 hours, and 3000 hours, Adhesion is shown. An evaluation method is demonstrated concretely below.

<Adhesion test before and after aging>

After aging and after aging, the laminated films 1, 2, and 3 were cut into 200 mm × 15 mm sizes, respectively, and allowed to stand for 6 hours in an environment of 25 ° C. and 65% humidity, followed by a tensile tester according to the test method of ASTM-D 1876-61. T-type peeling test was implemented at the load speed of 300 mm / min in 25 degreeC, and the environment of 65% of humidity using. Peel strength (N / 15 mm width) between PET film / PET film, between PET film / aluminum foil, and PET film / silica deposited polyester film is expressed as an average of five specimens.

<Adhesion test after moist heat resistance test>

After aging, the above laminates were cut into 200 mm × 15 mm sizes, respectively, and left standing for 1000 hours, 2000 hours, and 3000 hours in an environment of 85 ° C. and 85% humidity. After standing for 6 hours at 25 ° C and 65% humidity, T-type at 300mm / min load speed under 25 ° C and 65% humidity using a tensile tester according to the test method of ASTM-D 1876-61. Peeling test was performed. Peel strength (N / 15 mm width) between PET film / PET film, between PET film / aluminum foil, and PET film / silica deposited polyester film is shown as the average of five specimens.

<Evaluation Criteria>

[Adhesion test before aging]

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

○ practical stage: 2-3 N / 15 mm

△ practical lower limit: 1-2 N / 15mm

× impractical: less than 1 N / 15 mm

[Adhesion Test after Testing after Aging and Moisture and Heat Resistance Test]

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

○ practical stage: 4-5 N / 15 mm

△ practical lower limit: 2-4N / 15mm

× impractical: less than 2 N / 15 mm

[Table 3]

[Table 4]

[Table 5]

As shown in Table 3, it was shown that the adhesive composition of the example is excellent in adhesion before and after aging and after heat-and-moisture resistance test, and can maintain long-term adhesion strength. Therefore, it is thought that the adhesive composition of these Examples is excellent in long-term moisture heat resistance dedicated to outdoor use.

In addition, JIS C 8917 (environmental test method and endurance test method for crystalline solar cell modules) defines a moisture resistance test B-2 that can withstand 1000 hours at 85 ° C and 85% humidity, and is known as a particularly harsh test method. In this embodiment, it is suggested that the adhesive strength can be maintained over a long period of 3000 hours over 1000 hours, and the adhesive composition of the present invention has sufficient long-term moisture heat resistance.

The solar protective backing sheet has sufficient interlaminar adhesive strength (laminate strength) in such a long-term moisture and heat test and does not cause delamination between the sheet layers, thereby protecting the solar cell element, maintaining power generation efficiency, and extending the life of the solar cell. Can contribute to The extension of the life of a solar cell contributes to environmental conservation from the point of view of securing energy other than fossil fuel, which leads to the spread of the solar cell system.

The adhesive composition according to the present invention is a multilayer plywood (barrier material, outer wall material, roof material, solar panel material (solar cell back protective sheet, solar cell surface protective sheet), window material, outdoor flooring plate, proof protective material for outdoor industrial use such as a dry matter) , Adhesives for automobile parts, etc.) can provide strong adhesive strength. In addition, it is possible to prevent a decrease in adhesive strength over time due to hydrolysis at the time of outdoor exposure and to maintain a strong adhesive strength over a long period of time.

Comparative Example 1 is an example where the glass transition temperature of the acrylic polyol (A) is 55 ° C., which is higher than 50 ° C. As a result of evaluation, there was little wettability with respect to a base material, the initial adhesive force was small, and the adhesive force fell in the damp-heat resistance test.

Comparative Example 2 is an example of 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 cohesion force of the adhesive before the aging process was insufficient, indicating that the adhesive force before the aging process was small. In the case of industrial production, the laminate in a state of being rolled out in a roll shape is aged with the rolling core in the celestial direction. If the adhesive force before the aging process is small, the roll is liable to collapse during aging and is not suitable for industrial production.

Comparative Example 3 is an example in which the number average molecular weight of the acrylic polyol (A) is 150,000 and larger than 100,000. The evaluation resulted in the lack of wettability to the PET film, so that sufficient adhesion cannot be obtained before aging. As in Comparative Example 2, the roll is likely to collapse during aging and is not suitable for industrial production. Moreover, since the adhesive force by the heat-and-moisture resistance test gradually fell and the original adhesive force was low, the result below the practical minimum was obtained after 3000 hours.

Comparative Example 4 is an example where the glass transition temperature of the acrylic polyol (A) is -50 ° C, which is lower than -40 ° C. As a result of the evaluation, even in the case of the surface-treated polyester film, only an adhesive force of about 3 (N / 15 mm) can be expressed.

Comparative Example 5 is an example where the OH value of the acrylic polyol (A) is 110 and greater than 100. As a result of evaluation, crosslinking became excess and it became a very hard hardened coating film, and the adhesiveness was inferior.

In Comparative Example 6, the content of polyisocyanate (B) is an example of NCO / OH = 12. As a result of the evaluation, the reaction with the acrylic polyol (A) proceeded before coating, indicating that it could not be coated because it gelled.

This application claims the priority based on Japanese application patent application 2011-078188 for which it applied on March 31, 2011, and inserts all of the publication here.

Industrial availability

Since the adhesive composition for laminated sheets which concerns on this invention is used for bonding the adhere | attachment of the same or another material, it is used suitably for the joining of the multilayer laminated body of a plastic type material and a metal-related material. Of course, it is also preferable for bonding between plastic materials and metal materials. The adhesive composition for laminated sheets according to the present invention can maintain high adhesion even when exposed to a high temperature, high humidity environment. Therefore, multi-layer plywood (barrier, exterior wall material, roof material, solar panel material (solar backside protection sheet, solar cell surface protection sheet), window material, outdoor flooring material, lighting protection material, automotive parts, etc.) It is suitable as an adhesive agent for. Since the adhesive strength can be maintained over a long period of time, it is particularly suitable for the formation of a back protective sheet for solar cells, for example, for applications in which environmental resistance has been strongly demanded. Moreover, it is also suitable for formation of the surface protection sheet for solar cells. Moreover, although the adhesive composition for laminated sheets which concerns on this invention shows especially high adhesive force between layers, including the surface treatment layer of a plastic film, it can be suitably applied also to a surface untreated material (including the surface untreated plastic film).

Claims (4)

In the adhesive composition for laminated sheets containing an acrylic polyol (A) and a polyisocyanate (B),
The number average molecular weight of the said acrylic polyol (A) is 10,000-100,000, a hydroxyl value is 1-100 mgKOH / g, glass transition temperature (Tg) is more than -40 degreeC and 10 degrees C or less,
Adhesive composition for laminated sheets whose equivalent ratio NCO / OH of the hydroxyl group derived from the said acrylic polyol (A) and the isocyanate group derived from the said polyisocyanate (B) is 0.1-3. The adhesive composition for laminated sheets according to claim 1, wherein the polyisocyanate (B) comprises a polyisocyanate derived from an aliphatic ring diisocyanate or an aliphatic diisocyanate. The method for producing a back protective sheet for solar cells according to claim 1 or 2, comprising two or more layers of sheet-like members,
Adhesive composition for laminated sheets used for forming at least one part of an adhesive bond layer for bonding the said sheet-like members. The back surface protective sheet for solar cells provided with the adhesive bond layer formed from the adhesive composition for laminated sheets in any one of Claims 1-3, and the at least 2 layer or more sheet-like member laminated | stacked through the said adhesive bond layer.