JP2013041911A - Adhesive sheet for solar cell and method for producing the same, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet for a solar cell, excellent in adhesive strength and steam barrier property and causing no deterioration in transparency even if exposed to high temperature/high humidity conditions and sun light for a long period of time.SOLUTION: An adhesive sheet for fixing a solar cell element in a solar cell module is obtained by molding a crosslinking composition in a sheet form, the crosslinking composition including a cyclic olefin-based copolymer having a glass transition temperature of 55°C or below and an organic peroxide. The cyclic olefin-based copolymer is suitably a copolymer of ethylene and a cyclic olefin, or a random copolymer of ethylene and norbornene.

Description

  The present invention relates to an adhesive sheet for fixing a solar cell element in a solar cell module, a method for manufacturing the same, and a solar cell module.

  As a typical configuration of the solar cell module, the solar cell element is narrowed by a pair of adhesive sheets from both sides thereof, and a transparent base material such as glass is fixed to the adhesive sheet on the sunlight receiving side, and the back side is bonded. A sheet in which a protective material (back sheet) is fixed is known. In such a configuration, the adhesive sheet is required to have various properties such as adhesiveness and weather resistance. In particular, the sunlight receiving side requires high transparency, and various adhesive sheets that satisfy these requirements are proposed. (For example, see Patent Documents 1 to 5).

  Patent Document 1 describes a protective sheet (adhesive sheet) made of an ethylene copolymer containing an organic peroxide, and Patent Document 2 describes a crosslinkable composition of an ethylene / (meth) acrylate copolymer. An adhesive sheet using a product is described, and Patent Document 3 describes an adhesive sheet made of an ethylene copolymer blended with a predetermined crosslinking agent. In any adhesive sheet, an ethylene-based copolymer is used as the base resin, and sufficient transparency cannot be obtained. In addition, since the water vapor barrier property is low, deterioration of the solar cell element cannot be suppressed. The battery life is shortened.

  On the other hand, Patent Document 4 discloses a sealant containing a norbornene-based ring-opening polymer hydride, and the norbornene-based ring-opening polymer hydride has a melting point of 110 to 145 ° C. Therefore, since it can be defined by the melting point, the crystallinity is high and the transparency is not sufficient.

  Patent Document 5 includes, as an olefin copolymer effective as a material for films and sheets used in solar cell modules, a repeating unit derived from an α-olefin and a repeating unit derived from a cyclic olefin, and an α-olefin. Describes an olefin copolymer in which the content of repeating units derived from is 80 to 99.9 mol%. The olefin copolymer is amorphous, and sufficient transparency can be obtained, but there is a problem that the adhesive strength is poor.

JP 11-26791 A JP-A-6-299125 JP-A-6-322334 JP 2009-79101 A JP-A-5-97933

  The present invention has been made in view of the above-described conventional problems, and the problems are excellent in adhesive strength and water vapor barrier property, and transparency does not deteriorate even when exposed to high temperature and high humidity and sunlight for a long time. The object is to provide a solar cell adhesive sheet, a method for producing the same, and a solar cell module excellent in weather resistance and heat resistance.

Means for solving the above problems are as follows.
(1) An adhesive sheet for fixing a solar cell element in a solar cell module,
An adhesive sheet for solar cells, comprising a crosslinkable composition containing a cyclic olefin copolymer having a glass transition temperature of 55 ° C. or lower and an organic peroxide in a sheet shape.

(2) The solar cell adhesive sheet according to (1), wherein the cyclic olefin copolymer is a copolymer of an α-olefin and a cyclic olefin.

(3) The solar as described in (1) or (2) above, wherein the cyclic olefin copolymer is a random copolymer of α-olefin and norbornene and has a glass transition temperature in the range of −13 to 55 ° C. Battery adhesive sheet.

(4) A manufacturing method for manufacturing the solar cell adhesive sheet according to any one of (1) to (3),
Production of an adhesive sheet for solar cells, comprising a step of forming a crosslinkable resin composition containing a cyclic olefin copolymer and an organic peroxide into a sheet shape while maintaining a kneading temperature of 120 ° C. or lower. Method.

(5) A solar cell module comprising the solar cell adhesive sheet according to any one of (1) to (3).

(6) The solar cell module according to (5), wherein the solar cell adhesive sheet is crosslinked.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in adhesive strength and water vapor | steam barrier property, and even if it exposes to high temperature and high humidity and sunlight for a long time, the adhesive sheet for solar cells, its manufacturing method, and weather resistance and heat resistance It is possible to provide a solar cell module excellent in the above. Moreover, since the adhesive sheet for solar cells of this invention shows the outstanding water vapor | steam barrier property, it has the effect that deterioration of a solar cell element is suppressed and a battery life is extended.

It is a schematic cross section which shows the structural example of the solar cell module of this invention.

<Solar cell adhesive sheet>
The adhesive sheet for a solar cell of the present invention is an adhesive sheet for fixing a solar cell element in a solar cell module, and includes a crosslinkable composition containing an amorphous cyclic olefin copolymer and an organic peroxide. It is characterized by being formed into a sheet shape.
First, the crosslinkable composition according to the present invention will be described in detail below.

[Cyclic olefin copolymer]
The cyclic olefin copolymer is one having a glass transition temperature of 55 ° C. or less, and is a hydrogenated copolymer of an α-olefin and a cyclic olefin, a cyclic olefin ring-opening polymer, or a cyclic olefin ring-opening polymer. It is selected from the group consisting of things. The cyclic olefin copolymer used in the present invention needs to be amorphous in order to ensure transparency. Here, in the present invention, “amorphous” refers to a state in which no crystal melting peak is observed by DSC measurement according to the transition heat measurement method of JIS K 7122 plastic.

  The cyclic olefin-based copolymer further includes those obtained by grafting and / or copolymerizing an unsaturated compound having a polar group.

  Examples of the polar group include a carboxyl group, an acid anhydride group, an epoxy group, an amide group, an ester group, and a hydroxyl group. Examples of the unsaturated compound having a polar group include (meth) acrylic acid and maleic acid. Acid, maleic anhydride, itaconic anhydride, glycidyl (meth) acrylate, alkyl (meth) acrylate (carbon number 1-10) ester, maleic acid alkyl (carbon number 1-10) ester, (meth) acrylamide, (meta ) 2-hydroxyethyl acrylate.

  Further, the cyclic olefin copolymer according to the present invention has a glass transition temperature of 55 ° C. or lower, and a shear viscosity at a shear rate of 100 rad / sec at 200 ° C. is in the range of 500 to 2000 Pa · sec. In order to suppress the decomposition of the organic peroxide, it is preferable in terms of enabling extrusion at a low temperature.

  As the cyclic olefin copolymer according to the present invention, a commercially available resin may be used. Examples of commercially available cyclic olefin resins include TOPAS (registered trademark) (manufactured by Topas Advanced Polymers, Germany), Apel (registered trademark) (manufactured by Mitsui Chemicals), and a metathesis catalyst using a cyclic olefin component as a starting material. Examples of commercially available cyclic olefin-based polymers produced by ring-opening polymerization with hydrogenation and hydrogenation include ZEONEX (registered trademark) (manufactured by ZEON CORPORATION), ZEONOR (registered trademark) (manufactured by ZEON CORPORATION), Arton ( Registered trademark) (manufactured by JSR) and the like.

  The α-olefin of the cyclic olefin copolymer according to the present invention is not particularly limited, but an α-olefin having 2 to 20 carbon atoms is preferable. For example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene and the like. These α-olefin components may be used alone or in combination of two or more. Of these, ethylene is most preferably used alone.

  Suitable examples of the cyclic olefin component in the cyclic olefin copolymer according to the present invention include cyclic olefins represented by the following general formula (A).

（式中、Ｒ^１〜Ｒ^１２は、それぞれ独立に、同一でも異なっていてもよく、水素原子、ハロゲン原子、及び、炭化水素基からなる群より選ばれるものであり、
Ｒ^９とＲ^１０、Ｒ^１１とＲ^１２は、一体化して２価の炭化水素基を形成してもよく、
Ｒ^９又はＲ^１０と、Ｒ^１１又はＲ^１２とは、互いに環を形成していてもよい。
また、ｎは、０又は正の整数を示し、ｎが２以上の場合には、Ｒ^５〜Ｒ^８は、それぞれの繰り返し単位の中で、それぞれ同一でも異なっていてもよい。）

(In the formula, R ^{1 to} R ¹² may be the same or different each independently and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group,
R ⁹ and R ¹⁰ , R ¹¹ and R ¹² may be integrated to form a divalent hydrocarbon group,
R ⁹ or R ¹⁰ and R ¹¹ or R ¹² may form a ring with each other.
N represents 0 or a positive integer, and when n is 2 or more, R ^{5 to} R ⁸ may be the same or different in each repeating unit. )

R ^{1 to} R ¹² in the general formula (A) may be independently the same or different and are selected from the group consisting of a hydrogen atom, a halogen atom, and a hydrocarbon group.

Specific examples of R ^{1 to} R ⁸ include, for example, a hydrogen atom; a halogen atom such as fluorine, chlorine and bromine; a lower alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group. May be different from each other, may be partially different, or all may be the same.

Specific examples of R ^{9 to} R ¹² include, for example, hydrogen atom; halogen atom such as fluorine, chlorine, bromine; methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, hexyl group, stearyl. Alkyl groups such as cycloalkyl groups; cycloalkyl groups such as cyclohexyl groups; substituted or unsubstituted aromatic hydrocarbon groups such as phenyl groups, tolyl groups, ethylphenyl groups, isopropylphenyl groups, naphthyl groups, anthryl groups; benzyl groups, phenethyl groups And an aralkyl group in which an aryl group is substituted with an alkyl group, and the like. These may be different from each other, may be partially different, or all may be the same.

Specific examples of the case where R ⁹ and R ¹⁰ or R ¹¹ and R ¹² are integrated to form a divalent hydrocarbon group include, for example, alkylidene groups such as an ethylidene group, a propylidene group, and an isopropylidene group. Can be mentioned.

When R ⁹ or R ¹⁰ and R ¹¹ or R ¹² form a ring with each other, the formed ring may be monocyclic or polycyclic, or may be a polycyclic ring having a bridge. , A ring having a double bond, or a ring composed of a combination of these rings. Moreover, these rings may have a substituent such as a methyl group.

  Specific examples of the cyclic olefin component represented by the general formula (A) include bicyclo [2.2.1] hept-2-ene (common name: norbornene), 5-methyl-bicyclo [2.2.1] hepta. 2-ene, 5,5-dimethyl-bicyclo [2.2.1] hept-2-ene, 5-ethyl-bicyclo [2.2.1] hept-2-ene, 5-butyl-bicyclo [2 2.1] hept-2-ene, 5-ethylidene-bicyclo [2.2.1] hept-2-ene, 5-hexyl-bicyclo [2.2.1] hept-2-ene, 5-octyl -Bicyclo [2.2.1] hept-2-ene, 5-octadecyl-bicyclo [2.2.1] hept-2-ene, 5-methylidene-bicyclo [2.2.1] hept-2-ene 5-vinyl-bicyclo [2.2.1] hept-2-ene, - propenyl - bicyclo [2.2.1] of the two rings, such as hept-2-ene cyclic olefin;

Tricyclo [4.3.0.1 ^2,5 ] deca-3,7-diene (common name: dicyclopentadiene), tricyclo [4.3.0.1 ^2,5 ] dec-3-ene; tricyclo [ 4.4.0.1 ^2,5 ] undeca-3,7-diene or tricyclo [4.4.0.1 ^2,5 ] undeca-3,8-diene or a partially hydrogenated product thereof (or cyclopentadiene) Tricyclo [4.4.0.1 ^2,5 ] undec-3-ene; 5-cyclopentyl-bicyclo [2.2.1] hept-2-ene, 5-cyclohexyl-bicyclo [2.2.1] hept-2-ene, 5-cyclohexenylbicyclo [2.2.1] hept-2-ene, 5-phenyl-bicyclo [2.2.1] hept-2-ene A cyclic olefin of the ring;

Tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene (also simply referred to as tetracyclododecene), 8-methyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-ethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-methylidenetetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-ethylidenetetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-vinyltetracyclo [4,4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-propenyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] tetracyclic olefins such as dodec-3-ene;

8-cyclopentyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-cyclohexyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-cyclohexenyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene, 8-phenyl-cyclopentyl-tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene; tetracyclo [7.4.1 ^3,6 . 0 ^1,9 . 0 ^2,7 ] tetradeca-4,9,11,13-tetraene (also referred to as 1,4-methano-1,4,4a, 9a-tetrahydrofluorene), tetracyclo [8.4.1 ^4,7 . 0 ^1,10 . 0 ^3,8 ] pentadeca-5,10,12,14-tetraene (also called 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene); pentacyclo [6.6.1]. ^.1,3,6 . 0 ^2,7 . 0 ^9,14 ] -4-hexadecene, pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13] -4-pentadecene, pentacyclo [7.4.0.0 ^2,7. 1 ^3,6 . 1 ^10,13] -4-pentadecene; heptacyclo [8.7.0.1 ^2,9. 1 ^4,7 . 1 ^{11, 17} . 0 ^3,8 . 0 ^12,16 ] -5-eicosene, heptacyclo [8.7.0.1 ^2,9 . 0 ^3,8 . 1 ^4,7 . 0 ^12,17 . 1 ^13,16 ] ^-14-eicosene ; and polycyclic cyclic olefins such as cyclopentadiene tetramer.

  These cyclic olefin components may be used singly or in combination of two or more. Among these, it is preferable to use bicyclo [2.2.1] hept-2-ene (common name: norbornene) alone.

  The polymerization method of the α-olefin component having 2 to 20 carbon atoms and the cyclic olefin component represented by the general formula (A) and the hydrogenation method of the obtained polymer are not particularly limited, and are publicly known. Can be done according to the method. Random copolymerization or block copolymerization may be used, but random copolymerization is preferred.

  The polymerization catalyst used is not particularly limited, and can be obtained by a known method using a conventionally known catalyst such as a Ziegler-Natta, metathesis, or metallocene catalyst. The cyclic olefin and α-olefin addition copolymer or hydrogenated product thereof preferably used in the present invention is preferably produced using a metallocene catalyst.

  Examples of the metathesis catalyst include molybdenum or tungsten-based metathesis catalysts (for example, described in JP-A Nos. 58-127728 and 58-129003) as ring-opening polymerization catalysts for cycloolefins. In addition, the polymer obtained by the metathesis catalyst uses an inorganic carrier-supported transition metal catalyst or the like, and 90% or more of the main chain double bond and 98% or more of the carbon-carbon double bond in the side chain aromatic ring are hydrogenated. It is preferable to add.

  Among the above, the cyclic olefin copolymer according to the present invention is a random copolymer of α-olefin (especially ethylene) and norbornene in that it can form a crosslinked structure effectively with a small amount of peroxide. In this case, it is preferable that the glass transition temperature is −13 to 55 ° C. in that the transparency does not decrease even when exposed to high temperature and high humidity and sunlight for a long time. The glass transition temperature of the copolymer can be adjusted by the ratio of ethylene and norbornene, and the ratio of ethylene and norbornene at which the glass transition temperature is −13 to 55 ° C. is 85:15 (mol%). -70: 30 (mol%), Preferably it is 80: 20-70: 30.

[Organic peroxide]
The organic peroxide is not particularly limited, and a mixture of two or more kinds can be used. However, at least one of the organic peroxides has a one-hour half-life temperature of 130 to 160 ° C, particularly 135 to 150 ° C. It is preferable that The reason for this is that when the crosslinking reaction proceeds during sheet forming, a rugged defect is generated on the sheet surface and transparency is impaired. Specific organic peroxides include dicumyl peroxide (135 ° C.), 1,3-bis (2-tert-butylperoxyisopropyl) benzene (137 ° C.), 2,5-dimethyl-2,5. -Bis (t-butylperoxy) hexane (138 ° C.), t-butylcumyl peroxide (142 ° C.), di-t-butyl peroxide (149 ° C.), etc. ). Moreover, it is also possible to use what diluted these peroxides with the solvent.

  The compounding amount of the organic peroxide is preferably 0.05 to 4 parts by mass and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the cyclic olefin copolymer. If the total amount of organic peroxide used is less than 0.05 parts by mass, it is difficult to sufficiently crosslink the cyclic olefin copolymer, and heat resistance and adhesiveness may be insufficient. Moreover, since it will cause coloring and a swelling of a protective sheet when it uses exceeding 4 mass parts, it is unpreferable.

[Other ingredients]
In addition to the crosslinkable composition used for the adhesive sheet for solar cells of the present invention, for the purpose of improving long-term thermal stability, such as ultraviolet absorbers, hindered amine stabilizers, light stabilizers, etc., for the purpose of improving weather resistance, Lubricants and the like may be blended for the purpose of increasing flexibility, such as antioxidants.

  Although there is no restriction | limiting in particular in the thickness of the adhesive sheet for solar cells of this invention, For example, it can be set as 0.01-10 mm, and it is preferable that it is 0.1-3 mm.

  The solar cell adhesive sheet of the present invention is obtained by molding the above crosslinkable composition into a sheet, and the method will be described in the method for producing the solar cell adhesive sheet of the present invention described later.

  Since the above-mentioned adhesive sheet for solar cells of the present invention uses an amorphous cyclic olefin copolymer, high transparency can be obtained. Moreover, since it has the organic peroxide which functions as a crosslinking agent and heat-crosslinks after producing a predetermined | prescribed laminated structure at the time of preparation of a solar cell module, high adhesive strength and high heat resistance are obtained.

<Method for producing adhesive sheet for solar cell>
The manufacturing method of the adhesive sheet for solar cells of this invention is a manufacturing method which manufactures the above adhesive sheet for solar cells of this invention, Comprising: Crosslinkable resin composition containing a cyclic olefin type copolymer and an organic peroxide The method includes a step of forming the product into a sheet shape while maintaining the kneading temperature at 120 ° C. or lower.

In the production method of the present invention, first, a crosslinkable resin composition containing a cyclic olefin copolymer and an organic peroxide is prepared. For example, a uniaxial or biaxial extruder is used to form a cyclic resin composition. While blending the olefin copolymer and the organic peroxide at the above-mentioned preferred blending ratio, other components can be blended as necessary to produce pellets of the crosslinkable resin composition. Next, the produced pellets are put into an extruder equipped with a T die and formed into a sheet shape, whereby an adhesive sheet for a solar cell can be obtained.
Alternatively, in order to minimize the heat history of the resin until the solar cell adhesive sheet is produced, the raw material of the crosslinkable resin composition is introduced into an extruder equipped with a T die, and kneading and sheet molding are performed at once. It is also possible to do this. The kneading temperature is preferably kept at 120 ° C. or lower in order to suppress the decomposition of the organic peroxide during kneading or sheet forming. More preferably, it is 110 degrees C or less.

<Solar cell module>
The solar cell module of the present invention includes the above-described adhesive sheet for solar cells of the present invention.

  FIG. 1 is a schematic cross-sectional view showing an example of the solar cell module of the present invention. A solar cell module 10 shown in FIG. 1 includes an adhesive sheet 14, a solar cell element 16, an adhesive sheet 18, and a back sheet 20 in order from a transparent glass plate 12 that is a surface substrate on the light receiving side. The adhesive sheets 14 and 18 are the solar cell adhesive sheets of the present invention described above, and the transparent glass plate 12 and the solar cell element 16, the back sheet 20 and the solar cell element 16 are bonded and fixed, respectively. The configuration of the solar cell module shown in FIG. 1 is an example, and the solar cell module of the present invention is not limited to the configuration.

In the present invention, since the adhesive sheet 14 is excellent in transparency, a solar cell module having high photoelectric conversion efficiency can be obtained.
Moreover, in the solar cell module of this invention, the high heat resistance and high adhesive strength which cannot be obtained only with a cyclic olefin type copolymer can be obtained by bridge | crosslinking the adhesive sheets 18 and 20. FIG.
Crosslinking is performed by heat treatment, but the heating temperature varies depending on the organic peroxide used. For example, in the case of dicumyl peroxide, the heating temperature is preferably 120 to 250 ° C.
Moreover, it is preferable to heat-process until all the organic peroxide in an adhesive sheet decomposes | disassembles.

  The solar cell element used in the solar cell module of the present invention is not particularly limited, and silicon-based compounds such as single crystal silicon, polycrystalline silicon, and amorphous silicon, III-V group and II-VI group compounds (gallium-arsenide, Various types of solar cell elements such as semiconductor semiconductors such as copper-indium-selenium, copper-indium-gallium-selenium, and cadmium-tellurium can be used.

  In the solar cell module of the present invention, as the surface substrate on the sunlight receiving side, glass, acrylic resin, polycarbonate, polyester, fluorine-containing resin, or the like can be used as a transparent substrate. The back sheet on the opposite side may be a single or multilayer sheet such as a resin sheet or a metal sheet. Examples of the resin sheet include a fluororesin film, a PET (polyethylene terephthalate) resin film, and a PBT (polybutylene). Terephthalate) resin film and the like, and examples of the metal sheet include aluminum and stainless steel sheets.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Synthesis Example 1] Synthesis of cycloolefin / ethylene copolymer As a cyclic olefin copolymer, a cycloolefin / ethylene copolymer was synthesized as follows.
A 75 l polymerization reactor equipped with a stirrer was flushed with nitrogen and then with ethylene, filled with 12 kg norbornene and 15 l toluene, and 300 ml triisobutylaluminum solution (20% w / w in toluene) was added. The ethylene pressure was then increased to 18 × 10 ⁵ Pa (18 bar) and the reaction temperature was adjusted to 70 ° C. 20 mg of isopropenyl (cyclopentadienyl) (1-indenyl) -zirconium dichloride is dissolved in 500 ml of a toluene solution of methylaluminoxane (10 mass% of methylaluminoxane having a molecular weight of 1300 g / mol as determined by freezing point depression); The solution was weighed into the reactor. By replenishing, the ethylene pressure was kept at 18 × 10 ⁵ Pa (18 bar). After 90 minutes of polymerization reaction, the contents of the reactor were transferred to a 150 l stirring layer. To this, 500 g of celite and 200 ml of water in 50 l of hydrogenated diesel oil fraction (Exxsol, boiling point 100-120 ° C., Exxon) were previously introduced. The mixture was stirred at 60 ° C. for 20 minutes. Celite 500 g of filter cake suspended in 10 l Exxsol was formed on the filter cloth of a 120 l pressure suction filter. The polymer solution was filtered through a pressure suction filter. The nitrogen pressure on the solution was 2.8 × 10 ⁵ Pa (2.8 bar). The mixture was then filtered through 7 filter candles (Fluid Dynamic, Dynaloy XS 64.5 μm 0.1 m ² / candle) and placed in a steel housing. The polymer solution was precipitated by stirring into 500 l acetone with a disperser (Ultraturrax). The suspension was circulated on a 680 l stirring pressure suction filter with the bottom valve open. After closing the bottom valve, the residue was washed three times with 200 l of acetone. After the last wash, the product was pre-dried in a nitrogen stream at 60 ° C. and dried in a drying cabinet for 24 hours at 0.2 × 10 ⁵ Pa (0.2 bar), 80 ° C., 5.37 kg. A cycloolefin / ethylene copolymer (cyclic olefin copolymer) was obtained. The viscosity number was 51 ml / g and the glass transition temperature was 105 ° C.

Various Tg cycloolefin / ethylene copolymers (cyclic olefin copolymers) were synthesized by changing the norbornene content in the above method. Decreasing the norbornene content and increasing ethylene resulted in a corresponding decrease in Tg.
Generally, the Tg of the cyclic olefin copolymer according to the present invention is:
Norbornene content = (Tg + 65) / 4
Follow the relationship. Table 1 below shows the various cyclic olefin copolymers (A-1 to A-4) synthesized as described above, together with the norbornene content and Tg.

[Example 1]
To 100 parts by mass of the cyclic olefin copolymer (A-1) shown in Table 1, 1 part by mass of dicumyl peroxide as an organic peroxide and 0.3% of 2-hydroxy-4-n-octoxybenzophenone as an ultraviolet absorber Mass part, 0.1 parts by mass of bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate as a light-resistant stabilizer, manufactured by Nippon Steel Works, using a twin screw extruder TEX-30α The mixture was kneaded at 105 ° C. to obtain a cyclic olefin-based resin composition pellet. Next, this pellet was put into a single-screw extrusion molding machine equipped with a 300 mm wide T-die, and an adhesive sheet having a thickness of 0.2 mm was produced at a resin temperature of 100 ° C. at the T-die part.

  Furthermore, the prepared adhesive sheet was sandwiched between a 3 mm thick glass plate and a 100 μm thick PET film, bonded together at 125 ° C. for 5 minutes with a vacuum bonding machine, and then heated at 145 ° C. for 30 minutes in a heating oven. A multilayer structure for solar cell evaluation was prepared.

<Crosslinking characteristics (gel fraction)>
Separately from the multilayer structure described above, about 1 g portion is cut out from the adhesive sheet alone, the mass is precisely weighed, heated in a heating oven at 145 ° C. for 30 minutes, dissolved in 100 ml of toluene, and filtered through a 100 mesh wire mesh. The recovered insoluble matter was dried and weighed to determine the gel fraction. The higher the gel fraction, the better the crosslinking properties. The results are shown in Table 2.

<Backsheet adhesive strength>
Adhesive sheet is sandwiched between two 100 μm thick PET films, bonded together at 125 ° C. for 5 minutes with a vacuum bonding machine, and then heated in a heating oven at 145 ° C. for 30 minutes for multilayer sheet for backsheet adhesion evaluation Was made. This multilayer sheet was cut out with a width of 10 mm, and the bonded portion was peeled 180 ° at a tensile rate of 50 mm / min with a tensile tester, and the adhesive force [N] to the back sheet at room temperature was measured. The results are shown in Table 2.

<Transparency>
The haze value of the transparency as a laminate was measured according to JIS-K7106 using a haze meter.
Further, after being exposed for 16 hours in an environment of 70 ° C. and 95% humidity, it was cooled for 1.5 hours in an environment of 23 ° C. and 50% humidity, and the haze value (haze value after wet heat test) was measured again. The results are shown in Table 2.

[Example 2]
A multilayer sheet and a multilayer structure in the same manner as in Example 1 except that the cyclic olefin copolymer (A-1) in Example 1 was changed to the cyclic olefin copolymer (A-2) shown in Table 1. A body was prepared and each evaluation was performed.

[Comparative Example 1]
A multilayer sheet and a multilayer structure in the same manner as in Example 1 except that the cyclic olefin copolymer (A-1) in Example 1 was changed to the cyclic olefin copolymer (A-3) shown in Table 1. A body was prepared and each evaluation was performed.

[Comparative Example 2]
A multilayer sheet and a multilayer structure in the same manner as in Example 1 except that the cyclic olefin copolymer (A-1) in Example 1 was changed to the cyclic olefin copolymer (A-4) shown in Table 1. A body was prepared and each evaluation was performed.

From Table 2, it can be seen that in Examples 1 and 2, the backsheet adhesive strength was high, and no significant change was observed in the transparency before and after the wet heat test. That is, it was shown that the adhesive sheet for solar cells of the present invention has high adhesive strength and does not deteriorate in transparency even when exposed to high temperature and high humidity and sunlight for a long time.
On the other hand, in Comparative Examples 1 and 2, the backsheet adhesive strength was inferior compared with each Example, and the transparency after the wet heat test was remarkably deteriorated.

[Example 3]
With respect to the adhesive sheet for solar cell having a thickness of 0.2 mm in Example 1, the water vapor permeability under conditions of 40 ° C. and 90% RH was examined by the JIS K7126-2 isobaric method (Mocon method), and 0.9 g / m. A value of ² · day was obtained.

[Comparative Example 3]
When a commercially available EVA sheet (0.2 mm) having a vinyl acetate content of 26% was examined for water vapor permeability in the same manner as in Example 3, the value of 48 g / m ² · day was about 50 times that of Example 3. It became.

  From the comparison between Example 3 and Comparative Example 3, it can be seen that the solar cell adhesive sheet of the present invention has extremely low water vapor permeability and excellent water vapor barrier properties.

DESCRIPTION OF SYMBOLS 10 Solar cell module 12 Transparent glass plate 14 18 Adhesive sheet 16 Solar cell element 20 Back sheet

Claims (6)

An adhesive sheet for fixing a solar cell element in a solar cell module,
An adhesive sheet for solar cells, comprising a crosslinkable composition containing a cyclic olefin copolymer having a glass transition temperature of 55 ° C. or lower and an organic peroxide in a sheet shape.   The adhesive sheet for solar cells according to claim 1, wherein the cyclic olefin copolymer is a copolymer of an α-olefin and a cyclic olefin.   The adhesive sheet for solar cells according to claim 1 or 2, wherein the cyclic olefin copolymer is a random copolymer of α-olefin and norbornene, and has a glass transition temperature in the range of -13 to 55 ° C. It is a manufacturing method which manufactures the adhesive sheet for solar cells of any one of Claims 1-3,
Production of an adhesive sheet for solar cells, comprising a step of forming a crosslinkable resin composition containing a cyclic olefin copolymer and an organic peroxide into a sheet shape while maintaining a kneading temperature of 120 ° C. or lower. Method.   A solar cell module comprising the solar cell adhesive sheet according to claim 1.   The solar cell module according to claim 5, wherein the solar cell adhesive sheet is crosslinked.

Images