JP5406408B2 - Adhesive for solar battery backsheet - Google Patents

Description

  The present invention relates to an adhesive for solar battery backsheet. Furthermore, this invention relates to the solar cell backsheet obtained using the adhesive agent, and the solar cell module obtained using the solar cell backsheet.

Solar cells have been put into practical use as useful energy resources. There are various types of solar cells, and typical examples include silicon solar cells, inorganic compound solar cells, and organic solar cells.
These solar cells are generally provided with a surface protective sheet on the side where sunlight enters for the purpose of protecting the surface. A back surface protection sheet (back sheet) is also provided on the surface opposite to the surface on which sunlight enters to protect the solar cells, and the back sheet minimizes long-term performance degradation of the solar cells. Therefore, it is required to be excellent in various physical properties such as weather resistance, water resistance, heat resistance, moisture resistance and gas barrier properties.

In order to obtain a sheet having these physical properties, various films are used, such as metal foils such as aluminum, copper and steel sheets, metal plates and metal vapor-deposited films, polypropylene, polyvinyl chloride, polyester, fluororesin and Examples thereof include a plastic film such as an acrylic resin.
In order to further improve the performance as a solar cell backsheet, a laminate in which these films are laminated is also used.

The example of the laminated body which laminated | stacked the film is illustrated in FIG. The back sheet 10 is a laminate of a plurality of films 11 and 12, and the films 11 and 12 are laminated via an adhesive 13.
A dry lamination method is generally used as a method for laminating the film, and the adhesive 13 is required to have sufficient adhesion to the films 11 and 12.
The back sheet 10 constitutes the solar battery module 1 together with the sealing material 20, the solar battery cell 30, the glass plate 40, and the like (see FIG. 3).

  Since the solar cell module 1 is exposed outdoors for a long period of time, sufficient durability against high temperature, high humidity, and sunlight is required. In particular, when the performance of the adhesive 13 is low, the films 11 and 12 are peeled off, and the appearance of the laminated back sheet 10 is impaired. For this reason, it is requested | required that the film should not peel even if it exposes for a long period of time for the adhesive agent for solar cell backsheets.

There exists a urethane adhesive as an example of the adhesive agent for solar cell backsheets, and patent document 1 and 2 disclose that a urethane type adhesive is used for manufacture of a solar cell backsheet.
Patent Document 1 discloses an outdoor urethane-based adhesive using a specific polyester polyol and having improved durability performance (see Patent Document 1, Claims, Paragraph No. 0014, etc.). It is described that by using a specific polyester polyol as an adhesive raw material, the hydrolysis resistance of a urethane adhesive is improved, and an adhesive effective for solar battery backsheet applications can be obtained (Patent Document 1, paragraph number). 0070-0072 etc.).
Patent Document 2 discloses that an adhesive is prepared by blending an acrylic polyol with an isocyanate curing agent (see Tables 1 and 2 of Patent Document 2), and a solar battery backsheet is manufactured using this adhesive (Patent Document 2). (See 2 paragraph number 0107 etc.).
Patent Documents 1 and 2 disclose that a solar battery back sheet is manufactured using a urethane adhesive, thereby preventing the appearance of the solar battery module from being deteriorated. However, the durability performance required for the adhesive for solar battery backsheet is increasing year by year.

  A solar battery back sheet is generally produced by applying an adhesive to a film, drying it, laminating the film (dry laminating method), and curing the laminate at about 40 to 60 ° C. for several days. Therefore, it is important for the solar cell backsheet adhesive to have sufficient initial adhesion to the film at the time of lamination, adhesive strength to the film after curing, and excellent hydrolysis resistance. The adhesive of 2 does not necessarily satisfy the above performance completely. When a solar battery back sheet is manufactured with the adhesives of Patent Documents 1 and 2, when the outdoor environment is severe, there is a possibility that a plurality of films constituting the back sheet peel from each other.

  Furthermore, in recent years, the development of organic solar cells having a lower manufacturing cost than solar cells using silicon or inorganic compound materials has been promoted. Since the organic solar cell can be colored and can be flexible, a transparent film tends to be employed as a film constituting the solar cell back sheet. Therefore, in addition to maintaining the adhesive strength for a long period of time, the adhesive for solar battery back sheets is required to have a small change in color difference even when exposed to ultraviolet rays for a long period of time and to be extremely excellent in weather resistance.

Japanese Patent No. 4416047 JP 2010-263193 A

  The present invention was made to solve such a problem, the problem is that the initial adhesion to the film at the time of solar cell backsheet production and the adhesive strength to the film after curing is good, further long-term Urethane adhesive for solar battery back sheet having excellent weather resistance and hydrolysis resistance, solar battery back sheet obtained using the adhesive, and solar battery module obtained using the solar battery back sheet It is to be.

  As a result of intensive studies, the inventor surprisingly uses a specific acrylic polyol as a raw material for the urethane resin, so that the initial adhesion to the film during the production of the back sheet and the back sheet film after curing can be obtained. As a result, the present inventors have found that an adhesive for solar battery backsheets having excellent long-term weather resistance and hydrolysis resistance can be obtained, thereby completing the present invention.

That is, the present invention in one aspect,
The urethane polyol obtained by reaction of acrylic polyol (a1) and isocyanate compound (a2) is included, and acrylic polyol (a1) provides the adhesive for solar cell backsheets whose glass transition temperature is 20 degrees C or less.
In one aspect, the present invention provides the adhesive for solar battery backsheet, wherein the acrylic polyol (a1) has a hydroxyl value of 0.5 to 40 mgKOH / g.

In another aspect of the present invention, the acrylic polyol (a1) is obtained by polymerizing a polymerizable monomer, and the polymerizable monomer includes the monomer having a glycidyl group. Providing adhesives.
In a preferred embodiment, the present invention provides the above adhesive for a solar battery back sheet, further comprising a hydroxyphenyltriazine-based compound.

In another aspect, the present invention provides a solar cell backsheet obtained using the adhesive for solar cell backsheet.
In a preferred aspect, the present invention provides a solar cell module obtained by using the solar cell back sheet.

The adhesive for solar battery backsheet according to the present invention is:
Contains urethane resin obtained by reaction of acrylic polyol (a1) and isocyanate compound (a2). Since acrylic polyol (a1) has a glass transition temperature of 20 ° C. or less, it maintains excellent weather resistance and hydrolysis resistance. As it is, the initial adhesion to the film and the adhesive strength to the film after curing are improved.
When the hydroxyl value of the acrylic polyol (a1) is 0.5 to 40 mg KOH / g, an adhesive for a solar battery back sheet with further improved adhesive strength to the film after curing is obtained.

Furthermore, in the adhesive for solar battery backsheet of the present invention, the acrylic polyol (a1) is obtained by polymerizing a polymerizable monomer, and the polymerizable monomer contains a monomer having a glycidyl group. In this case, the adhesive strength to the film after curing is further improved, and a more suitable adhesive is obtained.
When the adhesive for solar battery backsheets of the present invention further contains a hydroxyphenyltriazine-based compound, the weather resistance is remarkably improved, which is more preferable.

Since the solar cell backsheet according to the present invention is obtained using the above-mentioned adhesive for solar cell backsheets, it is superior in productivity, and even when exposed to the outdoors for a long time, the adhesive deteriorates and the film peels off. And discoloration of the film can be prevented.
In recent years, an organic solar cell using an organic compound in a light absorption layer has been developed, and it is required that the organic solar cell has coloring and flexibility. Therefore, since the film which comprises the back sheet | seat of an organic type solar cell tends to be transparent, the solar cell back sheet | seat of this invention with a small color difference change is useful also from this point.
Since the solar cell module according to the present invention is obtained using the above solar cell backsheet, it is excellent in productivity, and is also excellent in appearance and durability.

It is sectional drawing which shows one Embodiment of the solar cell backsheet of this invention. It is sectional drawing which shows another embodiment of the solar cell backsheet of this invention. It is sectional drawing which shows one Embodiment of the solar cell module of this invention.

The adhesive for solar battery backsheets according to the present invention contains (A) urethane resin obtained by reacting acrylic polyol (a1) and isocyanate compound (a2).
The urethane resin (A) according to the present invention is a polymer obtained by a reaction between an acrylic polyol (a1) and an isocyanate compound (a2), and has a urethane bond.
In the present invention, “acrylic polyol” refers to a compound obtained by addition polymerization reaction of (meth) acrylate having a hydroxyl group, and has an ester bond in the “side chain”.

  “Acrylic polyol” may be a homopolymer of (meth) acrylate having a hydroxyl group or a copolymer of (meth) acrylate having a hydroxyl group and “other polymerizable monomer”. From such a viewpoint, a copolymer of (meth) acrylate having a hydroxyl group and “other polymerizable monomer” is preferable. The hydroxyl group of the acrylic polyol reacts with the isocyanate group.

  Examples of the “(meth) acrylate having a hydroxyl group” include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, glycerin mono (meth) acrylate, and 4-hydroxy A butyl acrylate etc. can be illustrated.

  The “other polymerizable monomers” are “radical polymerizable monomers having an ethylenic double bond” other than “(meth) acrylate having a hydroxyl group”. In the present invention, the other polymerizable monomer preferably contains a polymerizable monomer having a glycidyl group. Examples of the “polymerizable monomer having a glycidyl group” include, but are not limited to, glycidyl (meth) acrylate.

  In the present invention, the polymerizable monomer for obtaining the acrylic polyol (a1) preferably contains 0.5 part by weight or more of the polymerizable monomer having a glycidyl group per 100 parts by weight thereof. It is more preferable to contain 10 to 10 parts by weight. When the polymerizable monomer having a glycidyl group is contained in an amount of 0.5 parts by weight or more, the adhesive strength to the film after curing can be improved.

Specific examples of “other polymerizable monomers” include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, and 2-ethylhexyl acrylate. , Dicyclopentanyl (meth) acrylate, glycidyl (meth) acrylate, isobornyl (meth) acrylate, styrene, vinyltoluene and the like.
In this specification, acrylic acid and methacrylic acid are collectively referred to as “(meth) acrylic acid”, and also referred to as “acrylic acid ester and methacrylic acid ester” or “(meth) acrylate”.

  Polymerization of the polymerizable monomer containing a hydroxyl group-containing (meth) acrylate is performed by, for example, using the usual solution polymerization method and appropriately using the above-mentioned polymerizable monomer in an organic solvent using a catalyst or the like. It can be performed by radical polymerization. Here, the “organic solvent” can be used for polymerizing a polymerizable monomer, and particularly if it does not substantially adversely affect the properties as an adhesive for a solar battery backsheet after the polymerization reaction. It is not limited. Examples of such solvents include aromatic solvents such as toluene and xylene, alcohol solvents such as isopropyl alcohol and n-butyl alcohol, ester solvents such as ethyl acetate and butyl acetate, and combinations thereof. it can.

  Polymerization reaction conditions such as reaction temperature, reaction time, type of organic solvent, type and concentration of monomer, stirring speed, type and concentration of catalyst, and the like when polymerizing the polymerizable monomer are the target adhesive. Depending on the characteristics, etc., it can be selected as appropriate.

  The “catalyst” is a compound that can accelerate the polymerization of the polymerizable monomer by addition of a small amount, and preferably usable in an organic solvent. Examples of the catalyst include ammonium persulfate, sodium persulfate, potassium persulfate, t-butyl peroxybenzoate, 2,2-azobisisobutyronitrile (AIBN), and 2,2-azobis (2-aminodipropane) dihydride. And 2,2-azobis (2,4-dimethylvaleronitrile), and 2,2-azobisisobutyronitrile (AIBN) is particularly preferable.

  In the polymerization in the present invention, a chain transfer agent or the like can be appropriately used in order to adjust the molecular weight. As the “chain transfer agent”, compounds well known to those skilled in the art can be used. For example, mercaptans such as n-dodecyl mercaptan (nDM) and laurylmethyl mercaptan can be exemplified.

  The acrylic polyol (a1) is obtained by polymerizing the polymerizable monomer as described above. The weight average molecular weight of the acrylic polyol (a1) is preferably 200,000 or less, and more preferably 5,000 to 100,000, from the viewpoint of application suitability of the adhesive. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) using a polystyrene standard. Specifically, the value can be measured using the following GPC apparatus and measurement method. The GPC apparatus uses HCL-8220 GPC manufactured by Tosoh Corporation and uses RI as a detector. Two TSKgel SuperMultipore HZ-Ms manufactured by Tosoh Corporation are used as GPC columns. Dissolve the sample in tetrahydrofuran, flow at a flow rate of 0.35 ml / min and a column temperature of 40 ° C., convert the molecular weight using a calibration curve using polystyrene with a monodispersed molecular weight as a standard substance, and calculate Mw Ask.

The glass transition temperature of the acrylic polyol (a1) can be set by adjusting the mass fraction of the monomer used. The glass transition temperature of the acrylic polyol (a1) is as follows from the glass transition temperature of the homopolymer (homopolymer) obtained from each monomer and the mass fraction of the homopolymer used in the acrylic polyol (a1): It can obtain | require using the calculation formula (i). It is preferable to determine the monomer composition based on the glass transition temperature obtained by this calculation.
(I): 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + Wn / Tgn
[In the formula (i), Tg represents the glass transition temperature of the acrylic polyol (a1), W1, W2,... Wn represents the mass fraction of each monomer, and Tg1, Tg2,. Indicates the glass transition temperature of the homopolymer of each corresponding monomer. ]

In addition, the value described in literature can be used for Tg of a homopolymer. As such documents, for example, the following documents can be referred to: Mitsubishi Rayon Acrylic Ester Catalog (1997 edition); Kyozo Kitaoka, “New Polymer Library 7, Introduction to Synthetic Resins for Paints”, Polymer Publications 1997, pp. 168-169; and “POLYMER HANDBOOK”, 3rd edition, pages 209-277, John Wiley & Sons, Inc., 1989.
In this specification, the glass transition temperature of the homopolymer of the following monomer shall be as follows.
Methyl methacrylate: 105 ° C
n-butyl acrylate: -54 ° C
2-hydroxyethyl methacrylate: 55 ° C
Cyclohexyl methacrylate: 83 ° C
n-butyl methacrylate: 20 ° C
Glycidyl methacrylate: 41 ° C
2-ethylhexyl acrylate: -70 ° C

  In the present invention, the glass transition temperature of the acrylic polyol (a1) is preferably 20 ° C. or less, more preferably −55 ° C. to 10 ° C., and more preferably −40 ° C. from the viewpoint of adhesion to the film during lamination. To −10 ° C. is particularly preferable.

  The hydroxyl value of the acrylic polyol (a1) is preferably 0.5 to 40 mgKOH / g, more preferably 1 to 35 mgKOH / g, and particularly preferably 3 to 30 mgKOH / g. When the hydroxyl value of the acrylic polyol (a1) is 40 mgKOH / g or more, the adhesion and adhesion to the film may be insufficient, and when it is less than 0.5 mgKOH / g, the urethane resin may be insufficiently cured. The hydrolyzability may be insufficient.

In the present specification, the hydroxyl value indicates the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when acetylating 1 g of the resin.
In the present invention, specifically, it is calculated by the following formula (ii).
(Ii): hydroxyl value = (weight of (meth) acrylate having a hydroxyl group / molecular weight of (meth) acrylate having a hydroxyl group) × number of moles of hydroxyl group contained in 1 mol of a (meth) acrylate monomer having a hydroxyl group × KOH Formula weight x 1000 / weight of acrylic polyol (a1)

  Examples of the isocyanate compound (a2) include aliphatic isocyanates, alicyclic isocyanates, and aromatic isocyanates. The isocyanate compound (a2) is not particularly limited as long as the adhesive for a solar battery backsheet intended by the present invention can be obtained. Absent.

In this specification, “aliphatic isocyanate” is a compound having a chain-like hydrocarbon chain in which an isocyanate group is directly bonded to the hydrocarbon chain, and having no cyclic hydrocarbon chain. Refers to a compound. The “aliphatic isocyanate” may have an aromatic ring, but the aromatic ring and the isocyanate group are not directly bonded.
In the present specification, the aromatic ring is not included in the cyclic hydrocarbon chain.

  The “alicyclic isocyanate” is a compound that has a cyclic hydrocarbon chain and may have a chain hydrocarbon chain. The isocyanate group may be directly bonded to the cyclic hydrocarbon chain or may be directly bonded to the chain hydrocarbon chain that may be included. The “alicyclic isocyanate” may have an aromatic ring, but the aromatic ring and the isocyanate group are not directly bonded.

“Aromatic isocyanate” refers to a compound having an aromatic ring and having an isocyanate group directly bonded to the aromatic ring. Therefore, even if an aromatic ring is present in the molecule, a compound in which the isocyanate group is not directly bonded to the aromatic ring is classified as an aliphatic isocyanate or an alicyclic isocyanate.
Therefore, for example, 4,4′-diphenylmethane diisocyanate (OCN—C ₆ H ₄ —CH ₂ —C ₆ H ₄ —NCO) corresponds to an aromatic isocyanate because the isocyanate group is directly bonded to the aromatic ring. . On the other hand, for example, xylylene diisocyanate (OCN—CH ₂ —C ₆ H ₄ —CH ₂ —NCO) has an aromatic ring, but the isocyanate group is not directly bonded to the aromatic ring, but is bonded to the methylene group. Corresponds to aliphatic isocyanates.
The aromatic ring may be condensed with two or more benzene rings.

  Examples of the aliphatic isocyanate include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (hereinafter referred to as HDI), 1,6-diisocyanato-2,2,4. Examples include -trimethylhexane, methyl 2,6-diisocyanatohexanoate (lysine diisocyanate), 1,3-bis (isocyanatomethyl) benzene (xylylene diisocyanate), and the like.

  Examples of the alicyclic isocyanate include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate), 1,3-bis (isocyanatomethyl) cyclohexane (hydrogenated xylylene diisocyanate). Bis (4-isocyanatocyclohexyl) methane (hydrogenated diphenylmethane diisocyanate), 1,4-diisocyanatocyclohexane and the like.

Examples of the aromatic isocyanate include 4,4′-diphenylmethane diisocyanate, p-phenylene diisocyanate, and m-phenylene diisocyanate.
These isocyanate compounds can be used alone or in combination.

  In the present invention, the isocyanate compound (a2) is not particularly limited as long as the urethane adhesive intended by the present invention can be obtained, but may be selected from aliphatic isocyanates and alicyclic isocyanates from the viewpoint of weather resistance. preferable. In particular, HDI, isophorone diisocyanate and xylylene diisocyanate are preferable, and an HDI trimer is particularly preferable.

  The urethane resin according to the present invention can be obtained by reacting the acrylic polyol (a1) with the isocyanate compound (a2). The reaction can be carried out using a known method, and can usually be carried out by mixing the acrylic polyol (a1) and the isocyanate compound (a2). The mixing method is not particularly limited as long as the urethane resin according to the present invention can be obtained.

In this specification, “(B) hydroxyphenyl triazine-based compound” is a kind of triazine derivative, which is a compound in which a hydroxyphenyl derivative is bonded to a carbon atom of the triazine derivative, and is generally a hydroxyphenyl triazine-based compound. As long as the adhesive for a solar battery back sheet intended by the present invention can be obtained, the present invention is not particularly limited.
Examples of such (B) hydroxyphenyltriazine compounds include compounds represented by the following formulas (1) to (5) and isomers thereof, but are not limited thereto.

In the present invention, the (B) hydroxyphenyltriazine compound represented by the chemical formula (3) is preferable.
The (B) hydroxyphenyltriazine compounds of the chemical formulas (1) to (5) are generally used as UV absorbers, and as long as the adhesive for solar battery backsheets targeted by the present invention can be obtained, Other ultraviolet absorbers can be used in combination. (B) A commercially available hydroxyphenyltriazine compound can be used. For example, Tinuvin 400, Tinuvin 405, Tinuvin 479, Tinuvin 477, Tinuvin 460 (all are trade names) etc. which are marketed from BASF Corporation can be illustrated.

  It is preferable that the adhesive for solar battery backsheets of this invention contains a hindered phenol type compound further. The “hindered phenolic compound” is generally a hindered phenolic compound, and is not particularly limited as long as the solar cell backsheet adhesive targeted by the present invention can be obtained.

  A commercially available hindered phenol compound can be used. As a hindered phenol compound, for example, it is commercially available from BASF. Examples include IRGANOX 1010, IRGANOX 1035, IRGANOX 1076, IRGANOX 1135, IRGANOX 1330, and IRGANOX 1520 (all are trade names). The hindered phenol compound is added to the adhesive as an antioxidant, and may be used in combination with, for example, a phosphite antioxidant, a thioether antioxidant, an amine antioxidant, or the like.

The adhesive for solar battery backsheet of the present invention may further contain a hindered amine compound.
The “hindered amine compound” is generally a hindered amine compound, and is not particularly limited as long as an adhesive for a solar battery backsheet intended by the present invention can be obtained.

  A commercially available hindered amine compound can be used. Examples of hindered amine compounds include Tinuvin 765, Tinuvin 111FDL, Tinuvin 123, Tinuvin 144, Tinuvin 152, Tinuvin 292, and Tinuvin 5100 (all trade names) that are commercially available from BAFS. The hindered amine compound is added to the adhesive as a light stabilizer, and can be used in combination with, for example, a benzotriazole compound, a benzoate compound, a benzotriazole compound, or the like.

The adhesive for solar battery backsheet of the present invention may further contain a silane compound.
Examples of silane compounds include (meth) acryloxyalkyltrialkoxysilanes, (meth) acryloxyalkylalkylalkoxysilanes, vinyltrialkoxysilanes, vinylalkylalkoxysilanes, epoxysilanes, mercaptosilanes, and isocyanurates. Silanes can be used, but are not limited to these silane compounds.

Examples of “(meth) acryloxyalkyltrialkoxysilanes” include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 4- (meth) acryloxyethyltrimethoxy. A silane etc. can be illustrated.
Examples of “(meth) acryloxyalkylalkylalkoxysilanes” include 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, and 3- (meth) acryloxypropylethyl. Examples include diethoxysilane and 3- (meth) acryloxyethylmethyldimethoxysilane.

Examples of the “vinyl trialkoxysilanes” include vinyltrimethoxysilane, vinyltriethoxysilane, vinyldimethoxyethoxysilane, vinyltri (methoxyethoxy) silane, vinyltri (ethoxymethoxy) silane and the like.
Examples of “vinylalkylalkoxysilanes” include vinylmethyldimethoxysilane, vinylethyldi (methoxyethoxy) silane, vinyldimethylmethoxysilane, vinyldiethyl (methoxyethoxy) silane, and the like.

“Epoxysilanes” can be classified into, for example, glycidyl silanes and epoxycyclohexyl silanes. “Glycidyl-based silane” has a glycidoxy group. Specifically, for example, 3-glycidoxypropylmethyldiisopropenoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Examples include triethoxysilane and 3-glycidoxypropyldiethoxysilane.
The “epoxycyclohexyl silane” has a 3,4-epoxycyclohexyl group, and specifically includes, for example, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxy). (Cyclohexyl) ethyltriethoxysilane and the like.

Examples of “mercaptosilanes” include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.
Examples of “isocyanurate silanes” include tris (3- (trimethoxysilyl) propyl) isocyanurate.

The adhesive for solar cell backsheets according to the present invention can further contain other components as long as the intended adhesive for solar cell backsheets can be obtained.
The timing of adding the “other components” to the solar cell backsheet adhesive is not particularly limited as long as the target solar cell backsheet adhesive is obtained. Other components may be added together with, for example, the acrylic polyol (a1) and the isocyanate compound (a2) when synthesizing the urethane resin. First, the acrylic polyol (a1), the isocyanate compound (a2), After synthesizing the urethane resin by adding (B) hydroxyphenyltriazine compound, it may be added together.

Examples of the “other components” include tackifier resins, pigments, plasticizers, flame retardants, catalysts, and waxes.
Examples of the “tackifying resin” include styrene resins, terpene resins, aliphatic petroleum resins, aromatic petroleum resins, rosin esters, acrylic resins, and polyester resins (excluding polyester polyols).
Examples of the “pigment” include titanium oxide and carbon black.

Examples of the “plasticizer” include dioctyl phthalate, dibutyl phthalate, diisononyl adipate, dioctyl adipate, mineral spirit, and the like.
Examples of the “flame retardant” include halogen flame retardants, phosphorus flame retardants, antimony flame retardants, metal hydroxide flame retardants, and the like.

“Catalysts” include metal catalysts such as tin catalysts (trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, dibutyltin maleate, etc.), lead catalysts (lead oleate, lead naphthenate, lead octenoate, etc.) ), Other metal catalysts (such as naphthenic acid metal salts such as cobalt naphthenate), and amine-based catalysts such as triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkenes, dialkylaminoalkylamines, etc. Can be illustrated.
As the “wax”, wax such as paraffin wax and microcrystalline wax is preferable.

  The urethane adhesive for solar battery backsheets of the present invention can be produced by mixing the above-mentioned urethane resin and (B) hydroxyphenyltriazine-based compound, and other components that are optionally added. The mixing method is not particularly limited as long as the urethane adhesive for a solar battery backsheet intended by the present invention can be obtained. The order of mixing the components is not particularly limited. The urethane adhesive for solar battery backsheet according to the present invention can be produced without requiring a special mixing method and a special mixing order. And the obtained urethane adhesive for solar cell backsheets is excellent in productivity, the adhesive strength with respect to a backsheet film, and excellent in weather resistance and hydrolysis resistance.

  Adhesives for producing solar cell modules are required to have particularly high levels of strength and weather resistance as well as excellent productivity. The urethane adhesive for solar battery backsheet of the present invention is suitable as an adhesive for solar battery backsheet because it is suitable for lamination to a film, has excellent adhesion strength to film, and has excellent weather resistance and hydrolysis resistance. It becomes.

  When producing a solar cell backsheet, the adhesive of the present invention is applied to a film. As a coating method, it can be performed by various methods such as gravure coating, wire bar coating, air knife coating, die coating, lip coating, and comma coating. A plurality of films coated with the urethane adhesive for solar cell backsheet of the present invention are bonded together to obtain a solar cell backsheet.

Although one form of the solar cell backsheet of this invention is illustrated in FIGS. 1-3, this invention is not limited to these forms.
FIG. 1 is a cross-sectional view of the solar cell backsheet of the present invention. The solar cell backsheet 10 is formed of two films and a solar cell backsheet adhesive 13 therebetween, and the two films 11 and 12 are bonded together by the solar cell backsheet adhesive 13. . The films 11 and 12 may be the same material or different materials. In FIG. 1, two films 11 and 12 are bonded together, but three or more films may be bonded together.

  Another embodiment of the solar battery backsheet according to the present invention is shown in FIG. In FIG. 2, a foil film 11 a is formed between the film 11 and the solar cell backsheet adhesive 13. For example, when the film 11 is a plastic film, the form in which the metal thin film 11a is formed on the surface of the film 11 is shown. The metal thin film 11a can be formed, for example, by vapor deposition on the surface of the plastic film 11, and the film 11 and the film 12 on which the metal thin film 11a is formed are pasted through an adhesive 13 for solar cell backsheet. A solar battery back sheet according to FIG. 2 can be obtained.

  Examples of the metal deposited on the plastic film include aluminum, steel, and copper. By subjecting the plastic film to vapor deposition, barrier properties can be imparted to the film. As the vapor deposition material, silicon oxide or aluminum oxide is used. The base plastic film 11 may be transparent, or may be colored white or black.

  As the film 12, a plastic film made of polyvinyl chloride, polyester, fluororesin, or acrylic resin is used, but a polyethylene terephthalate film or a polybutylene terephthalate film is used to impart heat resistance, weather resistance, rigidity, insulation, and the like. It is particularly preferred. The films 11 and 12 may be transparent or colored.

  The vapor-deposited thin film 11a and the film 12 of the film 11 are attached by using the solar cell backsheet adhesive 13 of the present invention, and the films 11 and 12 are often laminated by a dry laminating method. Therefore, the solar cell backsheet adhesive 13 is required to have excellent adhesion to the film during lamination and excellent adhesive strength to the film after curing.

  FIG. 3 shows a cross-sectional view of an example of the solar cell module of the present invention. In FIG. 3, the solar cell module 1 of the present invention generates a desired voltage by connecting a glass plate 40, a sealing material 20 such as ethylene vinyl acetate resin (EVA), generally a plurality of solar cells 30, And the back sheet 10 can be overlapped, and then these members 10, 20, 30 and 40 can be fixed with a spacer 50.

  Since the back sheet 10 is a laminate of a plurality of films 11 and 12 as described above, the films 11 and 12 are peeled off from the urethane adhesive 13 even if the back sheet 10 is exposed outdoors for a long period of time. In addition, it is required to have excellent hydrolysis resistance.

  The solar electronic cell 30 is often manufactured using silicon, but may be manufactured using an organic resin containing a pigment. In that case, the solar cell module 1 is an organic (dye-sensitized) solar cell module. Since organic (pigment-sensitized) solar cells are required to be colored, transparent films are often used as the films 11 and 12 constituting the solar cell backsheet 10. Therefore, the solar cell backsheet adhesive 13 is required to have extremely small color difference change and excellent weather resistance even when exposed outdoors for a long period of time.

The main aspects of the present invention will be described below.
1. The adhesive for solar cell backsheets which contains the urethane resin obtained by reaction of an acrylic polyol (a1) and an isocyanate compound (a2), and an acrylic polyol (a1) has a glass transition temperature of 20 degrees C or less.
2. The adhesive for solar battery backsheets according to 1 above, wherein the acrylic polyol (a1) has a hydroxyl value of 0.5 to 40 mgKOH / g.
3. The acrylic polyol (a1) is obtained by polymerization of a polymerizable monomer, and the polymerizable monomer includes the monomer having a glycidyl group, and the adhesive for solar battery backsheet according to 1 or 2 above. .
4). The adhesive for solar battery backsheets according to any one of 1 to 3, further comprising a hydroxyphenyltriazine-based compound.
5. The solar cell backsheet obtained using the adhesive for solar cell backsheets in any one of said 1-4.
6). 6. A solar cell module obtained by using the solar cell back sheet described in 5 above.

  EXAMPLES Hereinafter, although this invention is demonstrated using an Example and a comparative example, these examples are for demonstrating this invention, and do not limit this invention at all.

<Synthesis of acrylic polyol (a1)>
Synthesis Example 1 (acrylic polyol (a1-1))
A four-necked flask equipped with a stirring blade, a thermometer, and a reflux condenser was charged with 150 g of ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) and refluxed at about 80 ° C. The polymerization was started in this flask. 1 g of 2,2-azobisisobutyronitrile was added as an agent, and a mixture of monomers in the amount shown in Table 1 was continuously dropped into the flask over 1 hour and 30 minutes, and after further heating for 2 hours, A solution having a non-volatile content of 39.8% by weight of the acrylic polyol (a1) was obtained.
Table 1 shows the composition of the polymerizable monomer component of the acrylic polyol (a1-1) and the physical properties of the resulting acrylic polyol (a1-1).

Synthesis Examples 7 to 14
Acrylic polyol was synthesized in the same manner as in Synthesis Example 1 except that the composition of monomers and the like used in the synthesis of acrylic polyol (a1) in Synthesis Example 1 was changed as shown in Tables 1 and 2. (a1- 7) to give ~ a (A1-12) and acrylic polymers (a1'-13) and (a1'-14). The physical properties of the resulting acrylic polyol are shown in Tables 1 and 2.
The polymerizable monomers and other components shown in Table 1 and Table 2 are shown below.
・ Methyl methacrylate (MMA): Wako Pure Chemical Industries, Ltd. ・ Butyl acrylate (BA): Wako Pure Chemical Industries, Ltd. ・ Cyclohexyl methacrylate (CHMA): Wako Pure Chemical Industries, Ltd. ・ Butyl methacrylate ( BMA ): Japanese -Koyo Pure Chemical Industries, Ltd.-2-ethylhexyl acrylate (2EHA): Wako Pure Chemical Industries, Ltd.-Glycidyl methacrylate (GMA): Wako Pure Chemical Industries, Ltd.-2-hydroxyethyl methacrylate (HEMA): Wako Jun Yakuhin Co., Ltd. ・ 2,2-Azobisisobutyronitrile (AIBN): Otsuka Chemical Co., Ltd. ・ n-dodecyl mercaptan (nDM): NOF Corporation

<Calculation of glass transition temperature (Tg) of polymer (a1)>
The Tg of the polymers 1, 7 to 14 ((a1) and (a1 ′)) is the above-mentioned value using the glass transition temperature of the homopolymer of the “polymerizable monomer” that is the raw material of each polymer. This was calculated using the formula (i).
Literature values were used for Tg of each homopolymer such as methyl methacrylate.

<Manufacture of adhesive for solar battery back sheet>
The raw materials of the adhesive for solar battery back sheets used in Examples and Comparative Examples are described below.
( A1 ) Acrylic polyol (a1-1) , (a1-7) to (a1-12) correspond to polymer 1 , polymer 7 to polymer 12 described in Tables 1 and 2.
(A1 ′) Polymer (a1′-13) The acrylic polyol corresponds to the polymer 13 described in Table 2.
The (a1′-14) acrylic polymer corresponds to the polymer 14 listed in Table 2.
(A1′-15) Polyester polyol is HS 2N-226P (trade name) manufactured by Toyokuni Oil Co., Ltd .: Polyester polyol obtained from phthalic anhydride, 2,4-dibutyl-1,5-pentanediol (a2) Isocyanate compound (A2-1) Sumidur N3300 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd .: Aliphatic isocyanate (1,6-diisocyanatohexane (HDI))
In addition, (A) urethane resin is obtained by a component (a1) and a component (a2) reacting.

(B) Hydroxyphenyltriazine compound (b-1) Tinuvin 479 (trade name) manufactured by BASF: 2- [4- (octyl-2-methylethanoate) oxy-2-hydroxyphenyl] -4,6- [Bis (2,4-dimethylphenyl)]-1,3,5-triazine (B ′) Benzotriazole compound (b′-1) Tinuvin 328 (trade name) manufactured by BASF: 2- (3,5 -Di-tert-amyl-2-hydroxyphenyl) benzotriazole)
Hindered phenolic compound Irganox 1330 (trade name) manufactured by BASF: 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene The adhesive for solar cell back sheets of Reference Example 1, Examples 8 to 14 and Comparative Examples 1 to 4 was produced using the above components, and the performance of the obtained adhesive for solar cell back sheet was evaluated. A manufacturing method and an evaluation method are shown below.

Reference example 1
<Manufacture of adhesive for solar battery back sheet>
As shown in Table 3,
90.7 g of (a1-1) polymer 1 [228 g of polymer 1 in ethyl acetate solution (solid content: 39.8% by weight)]
9.3 g (a2-1) Sumidur N3300 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.
0.5 g of (b-1) Tinuvin 479 (trade name) manufactured by BASF and 0.2 g of Irganox 1330 (trade name) manufactured by BASF
Were weighed and mixed to prepare an adhesive solution. The following tests were conducted using this preparation solution as an adhesive for solar battery backsheet.

<Manufacture of adhesive-coated PET sheet 1 and film laminate 2>
First, the adhesive for solar battery back sheet of Reference Example 1 was applied to a transparent polyethylene terephthalate (PET) sheet (O300EW36 (trade name) manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) so that the solid content weight would be 10 g / m ^2. And dried at 80 ° C. for 10 minutes to obtain an adhesive-coated PET sheet 1.
Then, the surface of the adhesive-coated PET sheet 1 is coated with a surface-treated transparent polyolefin film (Linear Low Density Polyethylene Film LL-XUMN # 30 (trade name) manufactured by Phutamura Chemical Co., Ltd.), Both films were pressed at a pressing pressure of 1.0 MPa at 50 ° C. for 30 minutes using a flat press machine (ASF-5 (trade name) manufactured by Shindo Metal Industry Co., Ltd.). While pressed, both films were cured at 50 ° C. for 1 week to obtain a film laminate 2.

<Evaluation>
Evaluation of the adhesive for solar battery backsheet was performed by the following method.
1. Evaluation of initial adhesion to film Under a room temperature environment, the adhesive-coated sheet 1 is cut into a 15 mm width, and a surface-treated transparent polyolefin film (Linear Low Density manufactured by Futamura Chemical Co., Ltd.) is applied to the adhesive-coated surface of the adhesive-coated sheet 1. A surface-treated surface of a polyethylene film LL-XUMN # 30 (trade name) was covered and pasted once by a 2 kg roller. Thereafter, using a tensile strength tester (Tensilon RTM-250 (trade name) manufactured by Orientec Co., Ltd.), a peeling test was performed at a tensile speed of 100 mm / min and 180 ° under a room temperature environment. The evaluation criteria are as follows.
A: Peel strength is 1 N / 15 mm or more B: Peel strength is 0.1 N / 15 mm or more and less than 1 N / 15 mm X: Peel strength is less than 0.1 N / 15 mm

2. Measurement of peel strength to film after curing Cut film laminate 2 into 15 mm width, and use tensile strength tester (Tensilon RTM-250 (trade name) manufactured by Orientec Co., Ltd.) under room temperature environment, pulling speed 100 mm / Min, 180 ° peel test was performed. The evaluation criteria are as follows.
A: Peel strength is 8 N / 15 mm or more B: Peel strength is 6 N / 15 mm or more and less than 8 N / 15 mm X: Peel strength is less than 6 N / 15 mm

3. Evaluation of hydrolysis resistance Evaluation was made by an accelerated evaluation method using pressurized steam. The film laminate 2 was cut out to a width of 15 mm, and left for 100 hours under a 120 ° C, 0.1 MPa pressure environment using a high pressure cooker (Autoclave SP300 (trade name) manufactured by Yamato Kagaku Co., Ltd.). I was cured for a day. The sample polyolefin film and PET film were visually observed for floating and peeling. The evaluation criteria are as follows.
◎: No film lifting or peeling ×: Film lifting or peeling

4). As an irradiation surface polyolefin film side of the evaluation film laminate 2 of yellowing due to UV irradiation, and sets the UV irradiation tester (Iwasaki Electric Co. Eye Super UV tester W13 (trade name))), the illuminance 1000W / ^{m 2} Irradiation was performed at 60 ° C. and 50% RH for 15 hours. The color difference (Δb) before and after irradiation was measured with a color difference meter, and the degree of yellowing was evaluated. The evaluation criteria are as follows.
◎: Δb is less than 8 ○: Δb is 8 or more and less than 10 △: Δb is 10 or more and less than 15 ×: Δb is 15 or more

Examples 8-14 and Comparative Examples 1-4
Adhesives for solar battery back sheets having the compositions shown in Tables 4 to 5 were produced in the same manner as in Reference Example 1 .

As shown in Tables 1 to 4, the adhesives for solar cell backsheets of Examples 8 to 14 include a urethane resin obtained by the reaction of acrylic polyol (a1) and isocyanate compound (a2), and acrylic polyol (a1 ) Has a glass transition temperature of 20 ° C. or lower, so it has excellent initial adhesion to the film, adhesive strength after curing (peel strength), and excellent hydrolysis resistance and weather resistance. It is a well-balanced adhesive. Therefore, the adhesive of an Example is suitable as an adhesive for solar cell backsheets.
In particular, the solar cell backsheet adhesives of Examples 10 , 12 and 13 are excellent in all of initial adhesion to the film, adhesion (peeling) strength to the film after curing, hydrolysis resistance, and weather resistance. It is more suitable as an adhesive for a back sheet of an organic (dye sensitized) solar cell.

On the other hand, since the glass transition temperature of acrylic polyol (a'1-13) is higher than 20 degreeC, the comparative example 1 is inferior to the adhesiveness to a film, and peeling strength.
Since Comparative Example 2 is an adhesive using a polymer (a1′-14) consisting only of other polymerizable monomers in place of the acrylic polyol (a1), it is inferior in peel strength and hydrolysis resistance. .
Since Comparative Examples 3 and 4 are adhesives using polyester polyol (a1′-15) instead of acrylic polyol (a1), hydrolysis resistance and weather resistance are inferior. Furthermore, since Comparative Example 4 does not contain (b-1) hydroxyphenyltriazine, the weather resistance is remarkably inferior.

  From these results, an adhesive for a solar battery backsheet comprising a urethane resin obtained by a reaction between an acrylic polyol (a1) and an isocyanate compound (a2), wherein the glass transition temperature of the acrylic polyol (a1) is 20 ° C. or less. It was shown to be excellent.

  The present invention provides an adhesive for solar battery backsheet. The adhesive for solar cell backsheet according to the present invention has productivity, adhesion to a film and long-term weather resistance and durability, and can be suitably used for a solar cell backsheet and a solar cell module. .

DESCRIPTION OF SYMBOLS 1 Solar cell module 10 Back sheet 11 Film 11a Vapor deposition thin film 12 Film 13 Adhesive layer 20 Sealing material (EVA)
30 Solar cell 40 Glass plate 50 Spacer

Claims (4)

A urethane resin obtained by a reaction of an acrylic polyol (a1) and an isocyanate compound (a2), which is a copolymer of a (meth) acrylate having a hydroxyl group and another polymerizable monomer,
The acrylic polyol (a1) has a glass transition temperature of −18 to 8 ° C., a hydroxyl value of 0.5 to 40 mgKOH / g , and a weight average molecular weight of 200,000 or less .
The other polymerizable monomer includes at least one selected from (meth) acrylate having no hydroxyl group, (meth) acrylic acid, styrene, and vinyltoluene,
(Meth) acrylates without hydroxyl groups are methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl acrylate, dicyclopentanyl (meth) acrylate, glycidyl It consists of at least one selected from (meth) acrylate and isobornyl (meth) acrylate,
When the other monomer includes glycidyl (meth) acrylate, 10 parts by weight of glycidyl (meth) acrylate per 100 parts by weight of the total weight of the (meth) acrylate having a hydroxyl group and the other polymerizable monomer Adhesive for solar battery backsheet, including : [However, a solar battery in which the equivalent ratio NCO / OH between the hydroxyl group derived from the acrylic polyol (a1) and the isocyanate group derived from the isocyanate compound (a2) is 3 to 10] Excluding backsheet adhesive].   The adhesive for solar cell backsheets according to claim 1, further comprising a hydroxyphenyltriazine-based compound.   The solar cell backsheet obtained using the adhesive for solar cell backsheets of Claim 1 or 2.   A solar cell module obtained by using the solar cell backsheet according to claim 3.

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