JP5777292B2 - Solar cell sealing film, solar cell module, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solar cell sealing film, a solar cell module, and a method for producing the same. Specifically, the present invention relates to a resin composition comprising an ethylene / α-olefin / diene copolymer, a polymer component comprising an ethylene / α-olefin copolymer or an ethylene / cyclic olefin copolymer, and a crosslinking agent. The sealing film for solar cells which consists of this, The solar cell module using this sealing film for solar cells, and its manufacturing method.

  A solar cell module is usually formed by laminating solar cells formed of polycrystalline silicon or the like between two sheets of a sealing film for solar cells such as ethylene / vinyl acetate copolymer (EVA). It has a structure in which both surfaces are covered with a solar cell module protective sheet (protective member). Such a solar cell module has a surface side transparent protective member, a solar cell sealing film, a solar cell, a solar cell sealing film, and a back surface side protective member laminated in this order; Then, it is produced by crosslinking and curing an ethylene / vinyl acetate copolymer (EVA).

  In order to perform the crosslinking and curing by heating and pressurization, a crosslinking agent such as an organic peroxide, various additives for imparting adhesiveness and long-term durability with a solar battery cell, etc. Has been proposed (see, for example, Patent Document 1).

  In many crystalline silicon solar cells, a p-type region is formed on one of the front and back surfaces of a single crystal silicon substrate, and an n-type region is formed on the other surface. On the front and back surfaces, there are formed collector electrodes (such as bus bar electrodes and finger electrodes) for collecting current generated on the light receiving surface (or the back surface). Since the collector electrode arranged on the light receiving surface side blocks incident light, power generation efficiency may be reduced.

  As one solution to increase the effective light receiving area, p-doped regions and n-doped regions are alternately provided on the back side opposite to the light receiving surface of the solar cell, and the charge extraction structure is entirely formed on the back side. (See Patent Document 2). The solar cell having such a structure is referred to as a back contact type solar cell.

  Also, a p / n junction is formed on a substrate provided with a through hole (through hole), and a doped layer on the front surface (light receiving surface) side is formed up to the through hole inner wall and the peripheral portion of the through hole on the back surface side. A back contact type solar cell is also proposed in which the current on the light receiving surface is taken out (see Patent Document 3).

JP 2007-281135 A JP 2006-523025 A Japanese Patent Laid-Open No. 2-51282

  According to the present invention, in a solar battery module, the sealing member that seals the solar battery cell affects the power generation characteristics of the solar battery cell, and in particular, a change in temperature may cause a decrease and fluctuation in output. I found it. Then, this invention aims at suppressing the fall and fluctuation | variation of the output by a temperature change in a solar cell module, especially a back contact type solar cell module by adjusting the composition of a sealing member.

  The inventors of the present invention are sealing films for solar cells mainly comprising polymer components such as ethylene / α-olefin / diene copolymer, ethylene / α-olefin copolymer and ethylene / cyclic olefin, The said subject was solved by using the sealing film for solar cells which provided the specific charging characteristic.

That is, the present invention includes the following matters.
[1] A solar cell sealing film comprising a polymer component selected from the group consisting of an ethylene / α-olefin / diene copolymer and an ethylene / α-olefin copolymer, and a crosslinking agent,
A solar cell in which the sheet obtained by heating the solar cell sealing film at 150 ° C. for 10 minutes has a charge decay time of 9000 seconds or more measured at an applied voltage of 500 V and 100 ° C. in accordance with JIS K6911. Sealing film.
[2] The solar cell sealing film according to [1], further including a light stabilizer, wherein the content of the light stabilizer relative to 100 parts by weight of the polymer component is 0 to 1 part by weight.
[3] The solar cell sealing film according to [2], wherein the light stabilizer is bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate.

[4] A front-side transparent protective member, a back-side protective member, a plurality of solar cells sandwiched between the front-side transparent protective member and the back-side protective member, the front-side transparent protective member, and the back-side protective member A solar cell module having a sealing member for sealing solar cells between
The said sealing member is a solar cell module which is a hardened | cured material of the sealing film for solar cells in any one of [1]-[3].
[5] (i) The front surface side transparent protective member, the solar cell sealing film according to any one of [1] to [3], the solar battery cell, the solar battery sealing film, and the back surface side A step of forming a laminate by stacking protective members in this order; and (ii) a step of heating and pressurizing and integrating the laminate obtained in step (i). Manufacturing method of battery module.

  By using the solar cell sealing film of the present invention, in a solar cell module, particularly in a back contact type solar cell module in which a p-type region and an n-type region for taking out electricity are close to each other, power generation of the solar cell module It is possible to suppress the output decrease and fluctuation.

  Hereinafter, the sealing film for solar cells, the solar cell module, and the manufacturing method thereof according to the present invention will be described in detail. In the following description, “to” is used to define a numerical range, but “to” in the present invention includes a boundary value. For example, “10 to 100” is 10 or more and 100 or less.

1. Solar cell sealing film The solar cell sealing film of the present invention is selected from the group consisting of an ethylene / α-olefin / diene copolymer, an ethylene / α-olefin copolymer, and an ethylene / cyclic olefin copolymer. A polymer component, a crosslinking agent, and various additives such as an adhesion-imparting agent, if necessary.

  The charge decay time measured according to JIS K6911 under the conditions of an applied voltage of 500 V and 100 ° C. of the sealing film for solar cell of the present invention is 9000 seconds or more. Charge decay time is the time when a voltage is applied in a state where the solar cell sealing film is incorporated in the solar electronic module (the solar cell sealing film is heated, crosslinked, and cured). This is an index indicating whether or not the bias of the electric field in the film is alleviated.

To determine the charge decay time of the solar cell sealing film of the present invention,
1) A solar cell sealing film cut to a predetermined size is laminated using a solar cell module manufacturing laminator at 150 ° C., a vacuum of 3 minutes, and a pressure of 10 minutes to create a sheet;
2) Place the sheet on an electrode for measuring volume resistance with a volume resistivity measuring device (manufactured by Advantest, product number: TR8601 High Megameter Meter) under a temperature environment of 100 ± 2 ° C .;
3) A voltage of 500 V is applied to the sheet, and when the electric field (V / cm) in the sheet is stabilized, the applied voltage is set to 0 V until the electric field (V / cm) in the film reaches 100 V / cm. Find the time.

  The longer the charging decay time of the solar cell sealing film of the present invention, the better. Specifically, the charging time is preferably 9000 seconds or more, and more preferably 10,000 seconds or more. The solar cell sealing film having a short charge decay time has a characteristic of being easily charged. A portion covered with a member that is easily charged is easily affected by an electric field. In the case of a back contact type solar cell module, the electric charge charged on the cell surface may deactivate the generated electrons or holes. Since the module temperature may be, for example, 70 ° C. or higher in the time zone in which sunlight is irradiated, it is desirable to make it difficult to charge the cell surface under high temperature conditions, that is, to increase the charge decay time.

  In order to lengthen the charge decay time of the solar cell sealing film of the present invention, the composition of the resin composition constituting the solar cell sealing film may be adjusted. For example, 1) increase the proportion of components having no polar group in the polymerization component of the copolymer component, 2) appropriately select various additives, for example, bis (2,2, The charge decay time can be increased by selecting 6,6-tetramethyl-4-piperidyl) sebacate or the like.

  As described above, the solar cell sealing film of the present invention contains a polymer component composed of an ethylene / α-olefin / diene copolymer, an ethylene / α-olefin copolymer, and an ethylene / cyclic olefin copolymer. . The ethylene / α-olefin / diene copolymer, ethylene / α-olefin copolymer, and ethylene / cyclic olefin copolymer, which are polymer components contained in the sealing film for solar cells, are random copolymers. It may be a block copolymer.

  Examples of the ethylene / α-olefin / diene copolymer contained in the solar cell sealing film of the present invention include ethylene / propylene / diene copolymer (EPDM). Examples of the diene component of the ethylene / α-olefin / diene copolymer include 5-ethylidene-2-norbornene, 5-propylidene-5-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, 5-methylene- Cyclic dienes such as 2-norbornene, 5-isopropylidene-2-norbornene, norbornadiene; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 5-methyl-1 , 5-heptadiene, 6-methyl-1,5-heptadiene, 6-methyl-1,7-octadiene, 7-methyl-1,6-octadiene, and the like. A part of the diene component may be a triene such as 2,3-diisopropylidene-5-norbornene and 4-ethylidene-8-methyl-1,7-nonadiene. Of these, 5-ethylidene-2-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene and the like are preferable as the diene component from the viewpoint of moldability of the solar cell sealing film.

  The melt flow rate (MFR) of the ethylene / α-olefin / diene copolymer (typically EPDM) contained in the solar cell sealing film of the present invention at 190 ° C. and a load of 2.16 kg is 0.00. It is preferable that it is 1-50, and it is more preferable that it is 2-30. When the MFR is within the above range, flexibility is increased and workability is improved. For example, the embedding property of the solar cell element in the solar cell sealing film is improved.

  The diene content of the ethylene / α-olefin / diene copolymer (typically EPDM) contained in the solar cell sealing film of the present invention is such that the iodine value of the ethylene / α-olefin / diene copolymer is For example, it is preferably set to 0.5 to 50 (g / 100 g), preferably 10 to 30 (g / 100 g). When the diene content is within the above range, good heat resistance and weather resistance can be obtained.

  Further, the ethylene content of the ethylene / α-olefin / diene copolymer (typically EPDM) contained in the solar cell sealing film of the present invention is, for example, 50 to 75% by weight, preferably 50 to 50%. 55% by weight. When the ethylene content is within the above range, there is an advantage that the compression set at a low temperature is reduced.

  Examples of the ethylene / α-olefin copolymer contained in the solar cell sealing film of the present invention include a copolymer of ethylene and at least one α-olefin having 3 to 20 carbon atoms. Can do. The ethylene / α-olefin copolymer may be a modified ethylene polymer.

  Specific examples of the α-olefin of the ethylene / α-olefin copolymer contained in the solar cell sealing film of the present invention include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1- Penten, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like are included, and α-olefins having 4 to 10 carbon atoms are preferable.

Examples of the cyclic olefin of the ethylene / cyclic olefin copolymer contained in the solar cell sealing film of the present invention include norbornene derivatives, tricyclo-3-decene derivatives, tricyclo-3-undecene derivatives, and tetracyclo-3-dodecene derivatives. Pentacyclo-4-pentadecene derivatives, pentacyclopentadecadiene derivatives, pentacyclo-3-pentadecene derivatives, pentacyclo-4-hexadecene derivatives, pentacyclo-3-hexadecene derivatives, hexacyclo-4-heptadecene derivatives, heptacyclo-5-eicosene derivatives, Heptacyclo-4-eicosene derivatives, heptacyclo-5-heneicosene derivatives, octacyclo-5-docosene derivatives, nonacyclo-5-pentacocene derivatives, nonacyclo-6-hexacocene derivatives, cyclopentadiene-acenaphthylene adducts, 1,4-meta No-1,4,4a, 9a-tetrahydrofluorene derivatives, 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene derivatives, cycloalkylene derivatives having 3 to 20 carbon atoms, etc. . Preferred cyclic olefins, tetracyclo [4.4.0. ^12,5 .1 ^7,10] -3-dodecene derivatives and hexacyclo [6.6.1.1 ^3,6 .1 ^10,13 .0 ^2,7 . ^09,14] -4-heptadecene derivatives, especially tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] -3- dodecene preferred.

  The α-olefin in the ethylene / α-olefin copolymer and the cyclic olefin in the ethylene / cyclic olefin copolymer may be used singly or in combination of two or more.

  The ethylene / α-olefin copolymer or ethylene / cyclic olefin copolymer contained in the solar cell sealing film of the present invention may be a copolymer with an adhesion auxiliary component. The adhesion auxiliary component is a radically polymerizable unsaturated compound having a polar group such as a hydrogen bonding functional group. Such a copolymer can be obtained by copolymerizing ethylene, an α-olefin or a cyclic olefin, and an adhesion auxiliary component by a method such as graft copolymerization. A copolymer having such an adhesive strength auxiliary component as a copolymer component can improve the adhesive strength to the surfaces to be joined.

  Examples of the adhesion auxiliary component to be copolymerized include a hydroxyl group-containing ethylenically unsaturated compound, an amino group-containing ethylenically unsaturated compound, an epoxy group ethylenically unsaturated compound, an aromatic vinyl compound, an unsaturated carboxylic acid or a derivative thereof, Vinyl ester compounds, vinyl chloride, carbodiimide compounds and the like are included, and unsaturated carboxylic acids or derivatives thereof are particularly preferable.

  Specific examples of the co-adhesive auxiliary component to be copolymerized include acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, nadic acid [trademark] And unsaturated carboxylic acids such as bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid).

  The adhesive strength auxiliary component to be copolymerized may be a derivative of the unsaturated carboxylic acid, and may be, for example, an acid halide, amide, imide, anhydride, ester or the like. Specific examples of the unsaturated carboxylic acid derivative include maleenyl chloride, maleimide, maleic anhydride, citraconic anhydride, 2-methylmaleic anhydride, 2-chloromaleic anhydride, and 2,3-dimethylmaleic anhydride. 4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride monomethyl maleate, dimethyl maleate, glycidyl malate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, Butyl methacrylate and the like are included.

  The unsaturated carboxylic acid and / or derivative thereof as an auxiliary component for adhesion to be copolymerized can be used singly or in combination of two or more. Of these, unsaturated dicarboxylic acids or their anhydrides are preferred, and maleic acid, nadic acid or their acid anhydrides are particularly preferred.

  In the ethylene / α-olefin copolymer or the ethylene / cyclic olefin copolymer, the content of the adhesion auxiliary component is usually 0.1 to 5 parts by weight with respect to 100 parts by weight of these olefin copolymers. And preferably 0.1 to 4 parts by weight. When the content of the adhesive strength auxiliary component in these olefin copolymers is in the above range, the adhesive strength of the solar cell sealing film is sufficiently improved, and the transparency, flexibility, etc. of the sealing film are adversely affected. Is preferable.

  When the sealing film for solar cells of the present invention contains an ethylene / α-olefin copolymer or an ethylene / cyclic olefin copolymer as the main component, 1) the ethylene / α-olefin copolymer or ethylene -It is preferable to silane-modify a cyclic olefin copolymer or to add 2) adhesive imparting agents (after-mentioned), such as a silane compound, to the sealing film for solar cells. Of course, the ethylene / α-olefin copolymer or the ethylene / cyclic olefin copolymer may be silane-modified, and an adhesion-imparting agent (described later) may be added.

  The silane-modified ethylene / α-olefin copolymer or ethylene / cyclic olefin copolymer can be obtained by copolymerizing ethylene, α-olefin or cyclic olefin, and a polymerizable silane compound. Specifically, it can be produced by graft copolymerization using an organic peroxide.

  By graft copolymerizing the polymerizable silane compound, a functional group (such as a silyloxy group) of the polymerizable silane compound is used as a side chain of the copolymer. Since the functional group of the polymerizable silane compound improves the adhesive strength of the copolymer, if the degree of freedom of the functional group of the polymerizable silane compound is increased, the adhesive strength is further improved.

  As the polymerizable silane compound for modifying silane, a conventionally known one can be used without particular limitation, and may be, for example, an ethylenically unsaturated silane compound. Specific examples of the ethylenically unsaturated silane compound include vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxy-ethoxysilane), γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane and the like are included.

  The compounding amount of the polymerizable silane compound in the silane-modified ethylene / α-olefin copolymer or ethylene / cyclic olefin copolymer is 100 parts by weight of the main components (total of ethylene, α-olefin and cyclic olefin). The amount is usually 0.1 to 5 parts by weight, preferably 0.1 to 4 parts by weight. This is because when the amount of the polymerizable silane compound is within the above range, the transparency, flexibility and the like of the ethylene resin composition are not adversely affected while the adhesiveness of the ethylene resin composition is sufficiently improved. .

  It is preferable that the silane compound used as the adhesiveness imparting agent that can be added to the solar cell sealing film is a silane coupling agent. Specific examples of the silane coupling agent include γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris- (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and N-β- ( Aminoethyl) -γ-aminopropyltrimethoxysilane and the like. The silane compound used as the adhesion-imparting agent may be a silane-modified resin.

  From the viewpoint of the stability of the adhesion-imparting agent, alkoxysilanes are preferably used. This is because alkoxysilanes are relatively stable at room temperature and in a neutral pH range. On the other hand, when producing a solar cell module, there exists a problem that the adhesive force of the sealing film for solar cells is hard to express from the stability.

  The content of the silane compound used as the adhesion-imparting agent in the solar cell sealing film is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the polymer component. It is more preferable that it is 2-1.5 weight part.

  As described above, the polymerizable silane compound for modifying silane and the silane compound as an adhesion-imparting agent preferably have a reactive group (such as an alkoxy group or a halogen group) bonded to a silicon atom. . The reactive group bonded to the silicon atom is a member in contact with the solar cell sealing film in the solar cell module (that is, a solar cell formed of silicon or the like, or a surface protection member formed of an inorganic substance such as glass). This is because a chemical bond or a physical bond such as a hydrogen bond can be formed by reacting with. This bonding is considered to greatly improve the adhesion between the solar cell sealing film and the protective member.

  The reactive group bonded to the silicon atom in the polymerizable silane compound for modifying the silane and the silane compound as the adhesion-imparting agent has a higher activity and the larger the number of the groups, the more the solar cell sealing film has. Adhesion can be improved. On the other hand, if the activity of the reactive group is too high, the adhesion-imparting agent reacts during storage of the solar cell sealing film, and when the solar cell module is manufactured using the sealing film, the adhesion is imparted. You may not be able to do it.

  The polymer component contained in the solar cell sealing film of the present invention can be produced by a known polymerization method, and its production method is not particularly limited. For example, it is preferable to produce by a gas phase polymerization method or a slurry polymerization method that requires a small amount of polymerization catalyst. When a large amount of a polymerization catalyst containing a metal element remains in the polymer component, the insulating property of the solar cell sealing film is lowered, and when a solar cell module is produced using the sealing film, the power generation efficiency is lowered. Because there is a fear.

  The solar cell sealing film of the present invention may contain a crosslinking agent. A crosslinking agent can improve the heat resistance and weather resistance of the sealing film for solar cells by crosslinking reaction of the polymer component contained in the sealing film for solar cells. In general, the crosslinking agent is preferably an organic peroxide that generates radicals at 100 ° C. or higher. In particular, considering the stability at the time of blending, an organic peroxide having a decomposition temperature of 70 hours or higher with a half-life of 10 hours is more preferable. preferable.

  Examples of organic peroxides as crosslinking agents include 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 3-di-t-butyl peroxide, t-dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne, dicumyl peroxide, α, α'-bis (t-butylperoxyisopropyl) benzene, n-butyl-4,4-bis (T-butylperoxy) butane, 2,2-bis (t-butylperoxy) butane, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) 3 , 3,5-trimethylcyclohexane, t-butyl peroxybenzoate, benzoyl peroxide and the like.

  The content of the crosslinking agent in the solar cell sealing film is preferably 0.1 to 3.0 parts by weight, and preferably 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the polymer component. It is more preferable.

  The solar cell sealing film used in the present invention may further contain various additives such as a crosslinking aid, if necessary.

  The crosslinking aid can increase the crosslinking reactivity of the polymer component contained in the solar cell sealing film and improve the durability of the solar cell sealing film. Examples of the crosslinking aid include polyfunctional polymerizable compounds. Specifically, in addition to trifunctional crosslinking aids such as triallyl isocyanurate, triallyl isocyanate, and trimethylolpropane triacrylate, N, N '-m-phenylene bismaleimide, ethylene glycol dimethacrylate, etc. are included.

  The content of the crosslinking aid in the solar cell sealing film is preferably 0 to 1 part by weight and more preferably 0 to 0.5 part by weight with respect to 100 parts by weight of the polymer component. This is for suppressing the decrease and fluctuation of the output of the solar cell module due to the temperature change during power generation.

  The solar cell sealing film of the present invention may contain other optional additives. Examples of optional additives include colorants, ultraviolet absorbers, anti-aging agents, anti-discoloring agents, heat-resistant stabilizers, ultraviolet absorbers, light stabilizers and the like.

  Examples of colorants include inorganic pigments such as metal oxides and metal powders; organic pigments such as azo, phthalocyanine, azo, and acidic or basic dye lakes.

  Examples of UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 4- Benzophenone series such as dodecyloxy-2-hydroxybenzophenone; 2- (2′-hydroxy-5-methylphenyl) benzotriazole, 2- (3-tertiarybutyl-2-hydroxy-5-methylphenyl) -5-chlorobenzo Benzotriazole systems such as triazole; salicylate systems such as phenyl salicylate and pt-butylphenyl salicylate are included.

  Light stabilizers include amines, phenols, bisphenyls and hindered amines such as di-t-butyl-p-cresol and bis (2,2,6,6-tetramethyl-4 -Piperazil) sebacate and the like. In particular, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate is preferred for increasing the charge decay time at 75 ° C. to 100 ° C. In addition, hydroquinone, hydroquinone monomethyl ether, p-benzoquinone and methylhydroquinone may be included in improving the stability of the ethylene / α-olefin / diene copolymer and / or the ethylene / α-olefin copolymer. Good.

  The sealing film for solar cells of the present invention was obtained by melt-kneading a resin composition containing the above-described components (at least a copolymer component and a crosslinking agent) using a T-die extrusion molding machine as a molten resin sheet. Thereafter, it is obtained by cooling and solidifying. The thickness of the solar cell sealing film is, for example, about 100 μm to 2000 μm. The sealing film for solar cells may be embossed on the surface in terms of improving cushioning properties and deaeration properties in the heat curing step.

2. Solar cell module The solar cell module of the present invention is sealed using the above-described solar cell sealing film, more specifically, the above-described solar cell sealing film or a cured product thereof. A stop member is provided.

  The solar cell module of the present invention includes, for example, a front surface side transparent protective member, a sealing member obtained from a solar cell sealing film, a solar cell sealed by the sealing member, and a back surface side protective member. Have Thus, the photovoltaic cell is sealed by the sealing member between the front surface side transparent protective member and the back surface side protective member. The sealing member can be formed by disposing the above-described solar cell sealing film on the front surface side and the back surface side of the solar battery cell and pressure sealing. Therefore, the basic structure of the solar cell module of the present invention is the front surface side transparent protective member / sealing member / solar cell / sealing member / back surface side protective member.

Surface side transparent protective member There is no restriction | limiting in particular as a surface side transparent protective member of the solar cell module of this invention, The surface side protective member generally used in a solar cell module can be used. Since the surface side transparent protective member is located on the outermost layer of the solar cell module, the performance to ensure long-term reliability in outdoor exposure of the solar cell module including weather resistance, water repellency, contamination resistance and mechanical strength It is preferable to comprise. Moreover, in order to utilize sunlight effectively, it is preferable that it is a highly transparent sheet | seat with a small optical loss.

  Examples of materials for the surface-side transparent protective member of the solar cell module include resin films made of polyester resin, fluorine resin, acrylic resin, ethylene / vinyl acetate copolymer, cyclic olefin (co) polymer, glass, etc. Etc. are included.

  A resin film suitable as the surface-side transparent protective member is a fluorine-based resin film that is excellent in terms of weather resistance and the like. Specifically, tetrafluoroethylene / ethylene / copolymer (ETFE), polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene / resin (TFE), tetrafluoroethylene -It may be a hexafluoropropylene copolymer (FEP), poly (trifluoroethylene chloride) resin (CTFE), or the like. From the viewpoint of weather resistance, polyvinylidene fluoride resin is excellent, but in terms of both weather resistance and mechanical strength, tetrafluoroethylene / ethylene / copolymer is excellent.

  The glass as the surface-side transparent protective member is a glass substrate having a total light transmittance of 80% or more, preferably 90% or more, of light having a wavelength of 350 to 1400 nm. The glass as the surface-side transparent protective member is generally a white plate glass with little absorption in the infrared region; however, it may be blue plate glass as long as the thickness is 3 mm or less, and to the output characteristics of the solar cell module. There is almost no adverse effect.

  Further, the glass as the surface-side transparent protective member may be tempered glass that has been heat-treated in order to increase mechanical strength, but may also be float plate glass that has not been heat-treated. Since the glass as the surface-side transparent protective member needs to withstand wind pressure, it is generally a glass substrate having a thickness of about 3 mm and is reinforced with an aluminum frame.

  Moreover, in order to improve the adhesiveness between the surface-side transparent protective member and other members such as a sealing member, the surface-side transparent protective member is preferably subjected to corona treatment or plasma treatment. Further, the light-receiving surface side of the front surface side transparent protective member is usually subjected to antireflection coating or embossing in order to suppress light reflection.

Back surface side protection member There is no restriction | limiting in particular as a back surface side protection member of the solar cell module of this invention, The back surface side protection member generally used in a solar cell module can be used. You may comprise a back surface side protection member with the material similar to the said surface side transparent protection member.

  The back surface side protection member of the solar cell module needs to have a function of preventing moisture from entering the solar cell module. Since the sealing member of the solar cell module of the present invention may have water absorption and moisture permeability, the function of preventing moisture from entering the back surface side protection member is important. However, since the sealing member of the present invention is a cured product of the above-described sealing film for solar cells, it absorbs water compared to a cured product of an ethylene / vinyl acetate copolymer that is a normal sealing film for solar cells. Low permeability and moisture permeability.

  The back surface side protection member of the solar cell module desirably has light resistance against reflected light from the ground or the like, heat resistance that can withstand a temperature of 60 to 100 ° C., and the like. On the other hand, since the back surface side protection member does not assume the passage of sunlight, the transparency required for the front surface side protection member is not necessarily required.

  As a specific example of the back surface side protection member, a white or black flame retardant PET film is bonded to a PET film on which a moisture-proof film made of silicon oxide or aluminum oxide is vapor-deposited; The thing which bonded the vinyl chloride resin film etc. is mentioned.

  A light reflection function or a scattering function may be imparted to the back surface side protection part. Thereby, the utilization efficiency of light can be improved. There is no particular limitation on the method for imparting the reflection function or the scattering function. For example, a metal layer may be provided in order to impart the reflection function, and in order to impart the scattering function, light scattering fine particles may be provided. What is necessary is just to add.

Solar cell The solar cell in the solar cell module of the present invention is not particularly limited as long as it can generate power using the photovoltaic effect of a semiconductor. Examples of solar cells include silicon (single crystal, polycrystalline, amorphous) solar cells, compound semiconductors (Groups 3-5, 2-6, etc.) solar cells, wet solar cells, Organic semiconductor solar cells and the like are included. Among these, a polycrystalline silicon solar cell is preferable from the viewpoint of balance between power generation performance and cost.

  Both silicon solar cells and compound semiconductor solar cells have excellent characteristics as solar cells, but are easily damaged by external stress and impact. The sealing member obtained from the solar cell sealing film of the present invention is excellent in flexibility, can absorb stress and impact to the solar battery cell, and effectively suppress the damage of the solar battery cell. . Therefore, in the preferable solar cell module of the present invention, the sealing member obtained from the solar cell sealing film of the present invention is directly joined to the solar cell.

  In the solar battery cell, a collecting electrode for taking out the generated electricity is arranged. The collecting electrode refers to a bus bar electrode, a finger electrode, or the like. The current collecting electrode may be arranged on both the front and back surfaces of the solar battery cell; however, if the current collecting electrode is arranged on the light receiving surface, the current collecting electrode blocks light and the power generation efficiency is lowered. Can occur.

  In order to improve the power generation efficiency, it is conceivable to use a back-contact solar cell that does not require a collecting electrode on the light receiving surface. In one aspect of the back contact solar cell, p-doped regions and n-doped regions are alternately provided on the back surface side provided on the opposite side of the light receiving surface of the solar cell. In another aspect of the back contact solar cell, a p / n junction is formed on a substrate provided with a through hole (through hole), and the surface (light-receiving surface) side of the through hole inner wall and the through hole peripheral portion on the back surface side is formed. A doped layer is formed, and the current on the light receiving surface is taken out on the back side.

  In a back contact solar cell (particularly, a solar cell that extracts charges only on the back surface of the light receiving surface), the charge extraction site is biased toward and close to the back surface. Therefore, compared to a solar cell in which a collecting electrode is also arranged on the light receiving surface, the generated electric charge is less likely to flow in the back contact type solar cell, and moreover, the electric charge tends to be biased in the sealing film on the light receiving surface side. it is conceivable that. For this reason, it is considered that the back contact solar cell is easily affected by the surrounding environment, for example, the electrical properties of the sealing member that seals the solar cell.

  Therefore, the solar cell sealing film of the back contact solar cell is required to hardly affect the extraction of the generated charge of the solar cell. In order to make it difficult to affect the extraction of the generated charge, it is preferable to increase the charge decay time (described above) of the solar cell sealing film. As described above, since the charging decay time of the solar cell sealing film of the present invention is long, it is preferably used for back contact solar cells.

  The solar cell module of the present invention may have an arbitrary member as long as the object of the present invention is not impaired. Typically, an adhesive layer, a shock absorbing layer, a coating layer, an antireflection layer, a back surface rereflection layer, a light diffusion layer, and the like can be provided, but not limited thereto. There are no particular limitations on the positions at which these layers are provided, and the layers can be provided at appropriate positions in consideration of the purpose of providing such layers and the characteristics of such layers.

3. Manufacturing method of solar cell module The manufacturing method of the solar cell module of this invention is (i) surface side transparent protective member, the sealing film for solar cells of this invention, a photovoltaic cell, and the sealing film for solar cells, And a step of laminating the back side protection member in this order to form a laminated body, and (ii) a step of pressurizing and heating the obtained laminated body to integrate them.

  In the step (i), it is preferable to dispose the surface on which the uneven shape (embossed shape) of the solar cell sealing film is on the solar cell side.

  In step (ii), the laminate obtained in step (i) is integrated (sealed) by heating and pressurizing using a vacuum laminator according to a conventional method. In sealing, since the sealing film for solar cells of the present invention has high cushioning properties, cell damage can be prevented. Moreover, since the deaeration property is good, there is no air entrainment, and a high-quality product can be manufactured with a high yield.

  When the solar cell module is manufactured, the resin composition constituting the solar cell sealing film is crosslinked and cured. This crosslinking step may be performed simultaneously with step (ii) or after step (ii).

  When the cross-linking step is performed after step (ii), vacuuming and heating is performed for 3 to 6 minutes at a temperature of 125 to 155 ° C. and a vacuum pressure of 10 Torr or less in step (ii); The above laminate is integrated for about one minute. The crosslinking step performed after the step (ii) can be performed by a general method. For example, a tunnel-type continuous crosslinking furnace may be used, or a shelf-type batch-type crosslinking furnace may be used. . Moreover, crosslinking conditions are 140-155 degreeC normally for about 30-40 minutes.

  On the other hand, when the cross-linking step is performed simultaneously with the step (ii), the cross-linking step is performed in the step (ii) except that the heating temperature in the step (ii) is set to 145 to 155 ° C. and the pressurizing time by atmospheric pressure is set to 6 to 15 minutes. It can be carried out in the same manner as in the case after ii).

  In any case, the solar cell module of the present invention can be produced at a temperature at which the crosslinking agent does not substantially decompose and the solar cell sealing film of the present invention melts. A solar cell sealing film may be temporarily bonded, and then heated to sufficiently bond and crosslink the sealing film. What is necessary is just to select the additive prescription which can satisfy various conditions, for example, what is necessary is just to select the kind and impregnation amount, such as the said crosslinking agent and the said crosslinking adjuvant.

  EXAMPLES Next, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.

[Physical property measurement method and evaluation method]
Measurement of charging decay time A solar cell sealing film cut to a predetermined size was laminated at 150 ° C. under a vacuum of 3 minutes and a pressure of 10 minutes using a solar cell module production laminator to obtain a sheet. Volume resistivity in accordance with JIS-K6911 under the conditions of temperature 23 ± 2 ° C., humidity 50 ± 5% RH, 75 ° C. (no humidity control), 100 ° C. (no humidity control) The charge decay time was measured with a measuring device (manufactured by Advantest Corporation, product number: TR8601 High Megameter Meter) using an electrode for measuring volume resistance.

  Specifically, a sample obtained by pre-processing (thermally laminating) a sheet having a thickness of about 0.4 mm was prepared, and the thickness was measured. Using this sample, it was set in a volume resistivity measuring jig according to JIS-K6911 and connected to the apparatus so that a voltage was applied in the thickness direction. The guard electrode was connected to the ground.

  Next, after fully discharging at a predetermined temperature, a voltage of 500 V was applied, and the apparatus was on standby until the flowing current was saturated to a certain level. Thereafter, the voltage was set to 0, and the amount of current flowing through the sample was monitored by the current measurement mode of the measuring apparatus. At this time, the output was measured with a digital multimeter (trade name: Digital Multimeter 2000, manufactured by Keithley) and converted into an amount of current. This current value was multiplied by the volume resistance of the sample to convert it into a voltage, which was used as the voltage due to charging. The voltage due to charging was defined as the charging electric field normalized by the sample thickness. At this time, the resistance value used was a value 60 seconds after voltage application. The time until the charging electric field reached 100 V / cm after the application of the voltage (500 V) was defined as “charging decay time”.

Measurement of Volume Resistivity Similarly to the measurement of the charge decay rate described above, a solar cell sealing film sheet was prepared and cut into 10 × 10 cm and a thickness of about 0.4 mm. The volume resistivity of the cut sheet was measured at an applied voltage of 500 V in accordance with ASTM-D257-93. The measurement environment is a temperature 23 ± 2 ° C., humidity 50 ± 5% RH, 75 ° C. (no humidity control), 100 ° C. (no humidity control), and the measuring machine (trade name: R8340A, manufactured by Advanced) Using.

Evaluation of output of solar cell In order to confirm the effect of the present invention, a module for evaluation of one cell was simply produced and evaluated. Specifically, after cleaning the p-type silicon substrate with an HCl solution, a substrate whose surface was slightly etched using a mixed solution of hydrofluoric acid and nitric acid was prepared in order to remove the damaged layer.

  Next, a silicon oxide thin film was formed as a passivation film on the surface of the silicon substrate that became the light receiving side when the module was formed. Subsequently, a silicon oxide film was formed as a mask layer for impurity diffusion on the back surface side, a portion to be an n + region was removed by etching, and phosphorus was doped by a thermal diffusion method. Similarly, the silicon oxide film was removed by etching, and the p + region was vapor-deposited with aluminum and doped by a thermal diffusion method. Further, aluminum electrodes were formed by vapor deposition in the n + region and the p + region, respectively, and used as extraction electrodes.

  Next, a one-cell evaluation module was produced. Specifically, a ribbon plated with solder having a width of 2 mm and a copper foil thickness of 100 μm is connected to the extraction electrodes in the n + region and the p + region; an epoxy-based Ag paste is applied to the connected ribbon and cured, and then the extraction lead is obtained. Was established. A cell was obtained with the lead taken out from the n + region and the lead taken out from the p + region as a positive electrode and a negative electrode, respectively.

  The laminated body which put the glass plate and mounted the sealing film for solar cells, the said cell, the sealing film for solar cells, and the back sheet in this order on it was prepared. The glass plate was white plate glass (manufactured by Asahi Glass Fabrictech, white plate float glass 3.2 mm thick). The back sheet was a tedla film (manufactured by GH Craft Co., Ltd.). The laminate was sealed with a vacuum heating laminator to form a module.

The obtained module was irradiated with light of 100 W / m ² (1 SUN: AM1.5 filter), and the current at the time of short circuit was measured with an ammeter (trade name: Digital Multimeter 2000, manufactured by Keithley). Evaluation Isc0.

  Next, the plus terminal and the minus terminal were short-circuited, a carbon sheet was placed on the glass surface, and the carbon sheet was connected to the ground. A voltage of 500 V was applied to the terminal and left for 2 hours. Thereafter, the voltage was set to 0, the connection was quickly changed so that the short circuit current (Isc) could be measured, and the short circuit current was measured in the same manner under a 1 SUN light source. The short-circuit current value immediately after this measurement was Isc1.

  Further, after leaving for 2 hours in the absence of light, the Isc value was measured in the same manner as Isc2.

  The value of the short-circuit current (Isc0) before voltage application was set to 1, and the short-circuit current values Isc1 and Isc2 immediately after setting the voltage to 0 after voltage application were normalized. A when the normalized short-circuit current values Isc1 and Isc2 are less than 1% change amount, A when the change amount is 1% or more and less than 5%, and B when the change amount is 5% or more. It was evaluated.

[Example 1]
100 parts by weight of an ethylene / propylene / 5-ethylidene-2-norbornene copolymer having an ethylene content of 73% by mass, a propylene content of 22.9% by mass and a 5-ethylidene-2-norbornene (ENB) of 4.1% by mass, and crosslinking 0.8 parts by weight of organic peroxide t-butylperoxy-2-ethylhexyl carbonate (TBEC) as an agent, 1 part by weight of triallyl isocyanurate (TAIC) as a crosslinking aid, and silane as an adhesion promoter 0.2 part by weight of γ-methacryloxypropyltrimethoxysilane as a coupling agent, 0.1 part by weight of bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate as a light stabilizer, A resin composition containing was prepared. The ethylene / propylene / 5-ethylidene-2-norbornene copolymer had a melt flow rate (MFR) at 190 ° C. and a load of 2.16 kg of 5.0 dg / min.

  A sheet-like molten web of the resin composition was extruded to produce a solar cell sealing film having a thickness of 0.45 mm.

[Example 2]
100 parts by weight of an ethylene / propylene / 5-ethylidene-2-norbornene copolymer having an ethylene content of 73% by mass, a propylene content of 22.9% by mass and a 5-ethylidene-2-norbornene (ENB) of 4.1% by mass, and crosslinking 0.4 parts by weight of organic peroxide t-butylperoxy-2-ethylhexyl carbonate (TBEC) as an agent and 2,5-dimethyl-2,5-bis (t-butylper (Oxy) hexane (DBPH) 0.1 part by weight, triallyl isocyanurate (TAIC) 1 part by weight, and γ-methacryloxypropyltrimethoxysilane 0.2 part by weight as a silane coupling agent as an adhesion promoter , 0.1 parts by weight of bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate as a light stabilizer and 2-hydroxy-4-octoxy as a UV absorber A resin composition containing 0.3 part by weight of benzophenone was prepared. The ethylene / propylene / 5-ethylidene-2-norbornene copolymer had a melt flow rate (MFR) at 190 ° C. and a load of 2.16 kg of 5.0 dg / min.

  A sheet-like molten web of the resin composition was extruded to produce a solar cell sealing film having a thickness of 0.45 mm.

[Example 3]
Preparation of Solid Catalyst Component A solid catalyst containing dimethylsilylene bis (3-methylcyclopentadienyl) zirconium dichloride as a metallocene compound was prepared by the method described in JP-A-9-328520. The zirconium content per gram was 2.3 mg.

Preparation of Prepolymerization Catalyst Using 4 g of the prepared solid catalyst, a prepolymerization catalyst composed of 1-hexene and ethylene was obtained by the method described in JP-A-9-328520. The zirconium content per 1 g of the solid catalyst was 2.2 mg, and a prepolymerized catalyst obtained by prepolymerizing 3 g of polyethylene was obtained.

Production of pellets of ethylene polymer (A1) 800 ml of dehydrated and purified hexane was charged into a 2-liter stainless steel autoclave sufficiently purged with nitrogen, and a mixed gas of ethylene and hydrogen (hydrogen content; 0.7 mol%). Next, the system was brought to 60 ° C., and 1.5 mmol of triisobutylaluminum, 200 ml of 1-hexene, and 0.015 mg atom in terms of zirconium atom were added to the prepolymerized catalyst. Thereafter, a mixed gas of ethylene and hydrogen having the same composition as above was introduced, and polymerization was started at a total pressure of 3 MPaG. Thereafter, only the mixed gas was supplied, the total pressure was kept at 3 MPaG, and polymerization was carried out at 70 ° C. for 1.5 hours. After completion of the polymerization, the polymer was collected by filtration and dried overnight at 80 ° C. to obtain 101 g of an ethylene polymer (A1).

  The ethylene polymer (A1) was pelletized under the condition of a die temperature = 190 ° C. using a single screw extruder (screw diameter 20 mmφ · L / D = 28) manufactured by Thermo Plastic Co., Ltd.

Production of pellets of ethylene polymer (A2) Polymerization example except that the hydrogen content of the mixed gas of ethylene and hydrogen was changed to 0.5 mol%, the amount of hexane was changed to 870 ml, and the amount of 1-hexene was changed to 230 ml. In the same manner as in Example 1, 130 g of an ethylene polymer (A2) was obtained. Furthermore, it pelletized with the single screw extruder similarly to the polymerization example 1.

Production of sealing film for solar cell γ-methacryloxypropyltrimethoxysilane 0.5% was added to a mixture of 90 parts by weight of ethylene polymer (A1) pellets and 10 parts by weight of ethylene polymer (A2) pellets. Parts by weight, 0.05 parts by weight of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 0.4 parts by weight of 2-hydroxy-4-normal-octyloxybenzophenone, bis ( 2,2,6,6-Tetramethyl-4-piperidyl) sebacate 0.1 part by weight and tris (2,4-di-tert-butylphenyl) phosphite 0.1 part by weight were added. The mixture was dry blended to obtain an ethylene polymer blend.

  A coat hanger type T die (lip shape; 270 × 0.8 mm) was mounted on a single screw extruder (screw diameter: 20 mmφ · L / D = 28) manufactured by Thermo Plastic Co., Ltd. Using the obtained molding machine, the ethylene polymer blend was molded under the conditions of a die temperature = 210 ° C., a roll temperature of 30 ° C., and a winding speed of 1.0 m / min. Thus, a solar cell sealing film having a thickness of 0.45 mm made of an ethylene resin composition containing a modified ethylene resin by γ-methacryloxypropyltrimethoxysilane was produced.

  A sheet-like molten web of the resin composition was extruded to produce a solar cell sealing film having a thickness of 0.45 mm.

  Table 1 shows physical property values and evaluation results of the solar cell sealing films of Examples 1 to 3.

  The charging decay time of the solar cell sealing films of Examples 1 to 3 is a long time under any temperature environment. In particular, the charge decay time in a 75 ° C. or 100 ° C. environment is 9000 seconds or more. Therefore, the output fluctuation of the solar cell module produced using each sealing film for solar cells was also small in output fluctuation.

The solar cell sealing film of the present invention has a specific charging characteristic, that is, a property that it is difficult to be charged. For this reason, when used as a sealing member in a solar cell module, it is possible to suppress a decrease in power generation output or output fluctuation of the solar cell due to a change in temperature, without adversely affecting the power generation characteristics of the solar cell.

Claims (3)

A polymer component selected from the group consisting of an ethylene / α-olefin / diene copolymer and an ethylene / α-olefin copolymer, a crosslinking agent, and bis (2,2,6,6-tetramethyl-4- Piperidyl) sebacate, and a solar cell sealing film comprising:
A back contact in which a sheet obtained by heating the solar cell sealing film at 150 ° C. for 10 minutes has a charge decay time of 9000 seconds or more measured at an applied voltage of 500 V and 100 ° C. in accordance with JIS K6911. Solar cell sealing film for a solar cell module . Between the surface side transparent protective member, the back side protective member, the plurality of solar cells sandwiched between the front side transparent protective member and the back side protective member, and between the front side transparent protective member and the back side protective member A back contact type solar cell module having a sealing member for sealing the solar cell,
The back contact solar cell module, wherein the sealing member is a cured product of the solar cell sealing film according to claim 1 . (I) The front surface side transparent protective member, the solar cell sealing film according to claim 1, the solar cell, the solar cell sealing film, and the back surface side protective member are stacked in this order. Forming a body;
(Ii) A step of heating and pressurizing and integrating the laminate obtained in the step (i). A method for producing a back contact solar cell module.