JP6371403B2 - Sealing sheet, solar cell module, and method for manufacturing sealing sheet - Google Patents

Description

  The present invention relates to a sealing sheet, a solar cell module, and a method for manufacturing the sealing sheet.

  As global environmental problems and energy problems become more serious, solar cells are attracting attention as a means of generating energy that is clean and free from depletion. When a solar cell is used outdoors such as a roof portion of a building, it is generally used in the form of a solar cell module.

Said solar cell module is manufactured by the following procedures, for example.
First, protective sheet for solar cell module (front surface side transparent protective member) / sealing layer (sealing sheet) / solar cell element / sealing layer (sealing sheet) / protective sheet for solar cell module (back side protective member) Are laminated in this order to form a laminate.
Next, the obtained laminate is pressed and heated to be integrated. Thereafter, the solar cell module is manufactured by crosslinking and curing the sealing sheet.
The solar cell element further includes an electrode for taking out the generated electric power. Since an increase in resistance or short circuit of the electrode leads to a decrease in the amount of power generation, the electrode is required to have durability that does not deteriorate even after long-term use.

  As a sealing sheet for solar cells, for example, an ethylene / vinyl acetate copolymer (EVA) film is widely used since it is excellent in transparency, flexibility, adhesiveness, and the like (Patent Document 1). reference).

JP 2010-53298 A

According to the study by the present inventors, when a voltage is applied to the solar cell module in an outdoor environment for a long time, for example, a metal contained in the electrode (hereinafter also referred to as an electrode metal) diffuses and moves in the sealing layer. (Hereinafter also referred to as migration) has revealed that the power generation efficiency of the solar cell module may be reduced.
Therefore, the sealing sheet for forming the sealing layer is required to have a performance that hardly causes the metal contained in the electrode to move even when a voltage is applied for a long time in an outdoor environment.

  The present inventors diligently studied to provide a sealing sheet with excellent long-term reliability. As a result, the inventors have found that by reducing the amount of copper element contained in the sealing sheet, it is possible to realize a sealing layer in which migration of electrode metal hardly occurs even in long-term use.

  That is, according to this invention, the manufacturing method of the sealing sheet shown below, a solar cell module, and a sealing sheet is provided.

[1]
A sealing sheet used for sealing a solar cell element,
It consists of a resin composition containing a crosslinkable resin and copper element,
The sealing sheet whose content of the said copper element in the said sealing sheet measured by ICP emission analysis is 1.0 ppb or less with respect to the said sealing sheet whole.
[2]
In the sealing sheet according to the above [1],
The sealing sheet in which the said crosslinkable resin contains at least 1 type selected from an ethylene-alpha-olefin copolymer and an ethylene-vinyl acetate copolymer.
[3]
In the sealing sheet according to the above [1] or [2],
Further comprising a crosslinking aid,
The sealing sheet whose content of the said crosslinking adjuvant is 0.05 to 5 mass parts with respect to 100 mass parts of said crosslinkable resin.
[4]
In the sealing sheet according to the above [3],
The sealing sheet in which the said crosslinking adjuvant contains triallyl isocyanurate.
[5]
In the sealing sheet according to any one of the above [1] to [4],
Further comprising a cross-linking agent;
The sealing sheet whose content of the said crosslinking agent is 0.1 to 3 mass parts with respect to 100 mass parts of said crosslinkable resin.
[6]
In the sealing sheet according to the above [5],
The sealing sheet in which the said crosslinking agent contains an organic peroxide.
[7]
In the sealing sheet according to any one of [1] to [6] above,
The content of the said crosslinkable resin in the said sealing sheet is a sealing sheet which is 80 mass% or more when the whole resin component contained in the said sealing sheet is 100 mass%.
[8]
In the sealing sheet according to any one of [1] to [7] above,
Further comprising a silane coupling agent,
The sealing sheet whose content of the said silane coupling agent is 0.1 to 2 mass parts with respect to 100 mass parts of said crosslinkable resin.
[9]
In the sealing sheet according to any one of [1] to [8] above,
The sealing sheet which further contains the 1 type, or 2 or more types of additive selected from the group which consists of a ultraviolet absorber, a light stabilizer, and a heat stabilizer.
[10]
A surface-side transparent protective member;
A back side protection member;
A solar cell element;
The said solar cell element formed by bridge | crosslinking the sealing sheet as described in any one of said [1] thru | or [9] is sealed between the said surface side transparent protection member and the said back surface side protection member. A sealing layer;
A solar cell module comprising:
[11]
In the solar cell module according to [10] above,
A solar cell module, wherein the solar cell element includes a silver electrode.
[12]
A manufacturing method for manufacturing the sealing sheet according to any one of [1] to [9],
Preparing a crosslinkable resin and one or more additives selected from a silane coupling agent, a crosslinking agent, a crosslinking aid, an ultraviolet absorber, a light stabilizer, and a heat stabilizer, and
Reducing the content of the copper element contained in one or more selected from the crosslinkable resin and the additive, and
A step of melt-kneading the crosslinkable resin and the additive and then forming the sheet,
The manufacturing method of the sealing sheet containing this.

  According to the present invention, it is possible to realize a sealing sheet in which migration of an electrode metal hardly occurs even after long-term use.

  The above-described object and other objects, features, and advantages will become more apparent from the preferred embodiments described below and the accompanying drawings.

It is sectional drawing which showed typically embodiment of the solar cell module of this invention typically. It is a figure which shows the enlarged photograph of the electrode by which resistance fall was seen.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, “A to B” in the numerical range represents A or more and B or less unless otherwise specified.

1. About a sealing sheet The sealing sheet in this embodiment is used in order to seal a solar cell element, and consists of a resin composition containing a crosslinkable resin and a copper element. And the content of the said copper element in the said sealing sheet measured by ICP emission analysis is 1.0 ppb or less with respect to the said whole sealing sheet, Preferably it is 0.8 ppb or less, Especially Preferably it is 0.5 ppb or less.
When the content of the copper element in the sealing sheet is not more than the above upper limit value, migration of the electrode metal can be suppressed even during long-term use.

Moreover, content of the copper element in the said sealing sheet is 0.001 ppb or more, for example.
The content of the copper element in the encapsulating sheet can be measured by, for example, wet-decomposing the encapsulating sheet, followed by constant volume with pure water, and ICP emission analysis using an ICP emission analyzer.

The inventors of the present invention have intensively studied the factors that cause the metal contained in the electrode to migrate in the sealing sheet. As a result, the following knowledge was obtained.
The sealing layer formed by the sealing sheet is in contact with the electrode and is generally molded from a resin composition containing a crosslinkable resin. This resin composition may contain several ppm of a metal element derived from a crosslinkable resin synthesis catalyst and various additives, for example, an aluminum element. Conventionally, such a metal element has been considered to have a small effect on the electrode metal.
However, the present inventor has found that the migration of the electrode metal is caused even in a small amount of copper element among metal elements.
That is, the present inventors have found for the first time that the copper element mixed in the sealing sheet has an influence on the migration of the electrode metal, and have reached the present invention.

(Crosslinkable resin)
Examples of the crosslinkable resin contained in the encapsulating sheet in the present embodiment include an ethylene / α-olefin copolymer containing ethylene and an α-olefin having 3 to 20 carbon atoms, a high-density ethylene resin, and a low-density ethylene. Resin, medium density ethylene resin, ultra low density ethylene resin, propylene (co) polymer, 1-butene (co) polymer, 4-methylpentene-1 (co) polymer, ethylene / cyclic olefin copolymer Polymer, ethylene / α-olefin / cyclic olefin copolymer, ethylene / α-olefin / non-conjugated polyene copolymer, ethylene / α-olefin / conjugated polyene copolymer, ethylene / aromatic vinyl copolymer, ethylene / Olefin resins such as α-olefin / aromatic vinyl copolymer; ethylene / unsaturated carboxylic anhydride copolymer, ethylene / α-olefin -Ethylene / carboxylic anhydride copolymer such as unsaturated carboxylic anhydride copolymer; ethylene / epoxy-containing unsaturated compound copolymer, ethylene / α-olefin / epoxy-containing unsaturated compound copolymer, etc. Epoxy copolymer: Ethylene / (meth) ethyl acrylate copolymer, ethylene / (meth) methyl acrylate copolymer, ethylene / (meth) propyl propyl copolymer, ethylene / butyl (meth) acrylate Copolymer, ethylene / (meth) acrylic acid hexyl copolymer, ethylene / (meth) acrylic acid-2-hydroxyethyl copolymer, ethylene / (meth) acrylic acid-2-hydroxypropyl copolymer, ethylene / Ethylene / (meth) acrylic acid ester copolymers such as (meth) acrylic acid glycidyl copolymer; ethylene / (meth) Ethylene / ethylenic unsaturated copolymer such as crylic acid copolymer, ethylene / maleic acid copolymer, ethylene / fumaric acid copolymer, ethylene / crotonic acid copolymer; ethylene / vinyl acetate copolymer, Ethylene / vinyl ester copolymers such as ethylene / vinyl propionate copolymer, ethylene / vinyl butyrate copolymer, ethylene / vinyl stearate copolymer; ethylene / styrene copolymer, etc .; (meth) acrylic acid ester ( Unsaturated carboxylic acid ester (co) polymers such as co) polymers; ionomer resins such as ethylene / acrylic acid metal salt copolymers, ethylene / methacrylic acid metal salt copolymers; urethane resins; silicone resins; Acrylic acid resin; methacrylic acid resin; cyclic olefin (co) polymer; α-olefin, aromatic vinyl compound, aroma Ethylene / α-olefin / aromatic vinyl compound; aromatic polyene copolymer; ethylene / aromatic vinyl compound / aromatic polyene copolymer; styrenic resin; acrylonitrile / butadiene / styrene copolymer Styrene / conjugated diene copolymer; acrylonitrile / styrene copolymer; acrylonitrile / ethylene / α-olefin / non-conjugated polyene / styrene copolymer; acrylonitrile / ethylene / α-olefin / conjugated polyene / styrene copolymer; Acrylic acid / styrene copolymer; Ethylene terephthalate resin; Fluororesin; Polyester carbonate; Polyvinyl chloride; Polyvinylidene chloride; Polyolefin thermoplastic elastomer; Polystyrene thermoplastic elastomer; Polyurethane thermoplastic elastomer Chromatography; 1,2-polybutadiene-based thermoplastic elastomer; can be used one or more selected from polylactic acid, trans-polyisoprene-based thermoplastic elastomer, chlorinated polyethylene-based thermoplastic elastomers; liquid crystalline polyester.

Among these, an ethylene / α-olefin copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms, which can be crosslinked by a crosslinking agent such as an organic peroxide, a low density ethylene resin, and a medium density ethylene Resin, ultra-low density ethylene resin, ethylene / cycloolefin copolymer, ethylene / α-olefin / cycloolefin copolymer, ethylene / α-olefin / non-conjugated polyene copolymer, ethylene / α-olefin / conjugated polyene Copolymers, ethylene / aromatic vinyl copolymers, olefin resins such as ethylene / α-olefin / aromatic vinyl copolymers, ethylene / unsaturated carboxylic anhydride copolymers, ethylene / α-olefin / unsaturated Carboxylic anhydride copolymer, ethylene / epoxy-containing unsaturated compound copolymer, ethylene / α-olefin / epoxy-containing Unsaturated compound copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / unsaturated carboxylic acid copolymer such as ethylene / methacrylic acid copolymer, 1,2-polybutadiene type It is preferable to use one or more selected from thermoplastic elastomers.
An ethylene / α-olefin copolymer comprising ethylene and an α-olefin having 3 to 20 carbon atoms, a low density ethylene resin, an ultra low density ethylene resin, an ethylene / α-olefin / non-conjugated polyene copolymer, ethylene / α-olefin / conjugated polyene copolymer, ethylene / unsaturated carboxylic anhydride copolymer, ethylene / α-olefin / unsaturated carboxylic anhydride copolymer, ethylene / epoxy-containing unsaturated compound copolymer, ethylene / α -Selected from ethylene / unsaturated carboxylic acid copolymers such as olefin / epoxy-containing unsaturated compound copolymers, ethylene / vinyl acetate copolymers, ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, etc. It is more preferable to use one kind or two or more kinds.

An ethylene / α-olefin copolymer comprising ethylene and an α-olefin having 3 to 20 carbon atoms, a low density ethylene resin, an ultra low density ethylene resin, an ethylene / α-olefin / non-conjugated polyene copolymer, ethylene / One type selected from ethylene / unsaturated carboxylic acid copolymer such as α-olefin / conjugated polyene copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer Or it is more preferable to use 2 or more types.
Among these, at least one selected from an ethylene / α-olefin copolymer and an ethylene / vinyl acetate copolymer is particularly preferably used. In the present embodiment, the above-described resins may be used alone or blended.

  The content of the crosslinkable resin in the encapsulating sheet in the present embodiment is preferably 80% by mass or more, more preferably 90% by mass when the entire resin component contained in the encapsulating sheet is 100% by mass. More preferably, it is 95% by mass or more, and preferably 100% by mass. Thereby, the sealing sheet excellent in balance of various characteristics, such as transparency, adhesiveness, heat resistance, a softness | flexibility, a bridge | crosslinking characteristic, and an electrical property, can be obtained.

(Ethylene / α-olefin copolymer)
As an α-olefin of an ethylene / α-olefin copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms used as a crosslinkable resin in the present embodiment, usually an α-olefin having 3 to 20 carbon atoms. Can be used singly or in combination of two or more. Among these, α-olefins having 10 or less carbon atoms are preferable, and α-olefins having 3 to 8 carbon atoms are particularly preferable. Examples of such α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, and 4-methyl-1-pentene. , 1-octene, 1-decene, 1-dodecene and the like. Among these, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene are preferable because of their availability. The ethylene / α-olefin copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred from the viewpoint of flexibility.

  The ethylene / α-olefin copolymer is an aromatic vinyl compound such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o, p-dimethylstyrene, methoxystyrene, vinylbenzoic acid, vinyl. Styrenes such as methyl benzoate, vinyl benzyl acetate, hydroxystyrene, p-chlorostyrene, divinylbenzene; 3-phenylpropylene, 4-phenylpropylene, α-methylstyrene, cyclic olefins having 3 to 20 carbon atoms, such as , Cyclopentene, cycloheptene, norbornene, 5-methyl-2-norbornene and the like may be used in combination.

  The polymerization of the ethylene / α-olefin copolymer can be carried out by any of the conventionally known gas phase polymerization methods, liquid phase polymerization methods such as slurry polymerization methods, solution polymerization methods, metallocene catalysts, Ziegler-Natta catalysts, Polymerization can be performed using a conventionally known olefin polymerization catalyst such as a vanadium catalyst.

Furthermore, the ethylene / α-olefin copolymer may be a copolymer composed of ethylene, an α-olefin having 3 to 20 carbon atoms, and a non-conjugated polyene. The α-olefin is the same as described above, and examples of the non-conjugated polyene include 5-ethylidene-2-norbornene (ENB), 5-vinyl-2-norbornene (VNB), and dicyclopentadiene (DCPD). These non-conjugated polyenes can be used alone or in combination of two or more.
The ethylene / α-olefin copolymer preferably satisfies the following requirements a1 and a2.

Requirement a1: The density of the ethylene / α-olefin copolymer measured in accordance with ASTM D1505 is preferably 0.865 g / cm ³ or more and 0.884 g / cm ³ or less, more preferably 0.866 g / cm. ³ or more and 0.883 g / cm ³ or less, more preferably 0.866 g / cm ³ or more and 0.880 g / cm ³ or less, and particularly preferably 0.867 g / cm ³ or more and 0.880 g / cm ³ or less.
The density of the ethylene / α-olefin copolymer can be adjusted by a balance between the content ratio of ethylene units and the content ratio of α-olefin units. That is, when the content ratio of the ethylene unit is increased, the crystallinity is increased, and a high-density ethylene / α-olefin copolymer can be obtained. On the other hand, when the content ratio of the ethylene unit is lowered, the crystallinity is lowered and an ethylene / α-olefin copolymer having a low density can be obtained.

  When the density of the ethylene / α-olefin copolymer is not more than the above upper limit, the crystallinity is lowered and the transparency can be increased. Furthermore, extrusion molding at low temperature becomes easy, and for example, extrusion molding can be performed at 130 ° C. or lower. For this reason, even if a cross-linking agent is kneaded into the ethylene / α-olefin copolymer, the cross-linking reaction in the extruder is prevented from progressing, the generation of gel-like foreign matters on the sealing sheet is suppressed, and the appearance of the sheet is reduced. Deterioration can also be suppressed.

  On the other hand, if the density of the ethylene / α-olefin copolymer is not less than the above lower limit value, the crystallization speed of the ethylene / α-olefin copolymer can be increased, so that the sheet extruded from the extruder is not sticky and is cooled. Peeling with a roll becomes easy and a sealing sheet can be obtained easily. Further, since stickiness is less likely to occur in the sheet, the occurrence of blocking can be suppressed, and the sheet feedability can be improved. Moreover, since it is fully bridge | crosslinked, the fall of the heat resistance of a sheet | seat can be suppressed.

Requirement a2: The melt flow rate (MFR) of the ethylene / α-olefin copolymer measured in accordance with ASTM D1238 and at a temperature of 190 ° C. and a load of 2.16 kg is usually 0.1 g / 10 min or more and 50 g / 10 g or less, preferably 2 g / 10 min or more and 40 g / 10 min or less, more preferably 2 g / 10 min or more and 30 g / 10 min or less, further preferably 5 g / 10 min or more and 10 g / 10 min or less. It is.
The MFR of the ethylene / α-olefin copolymer is adjusted by adjusting the polymerization temperature, the polymerization pressure, the molar ratio of the ethylene and α-olefin monomer concentrations and the hydrogen concentration in the polymerization system, etc. can do.

  When the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, a sheet can be produced by calendar molding. When the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, the flowability of the resin composition containing the ethylene / α-olefin copolymer is low, so that the melted out when laminating the sheet and the battery element This is preferable in that the laminating apparatus can be prevented from being soiled by the resin.

Further, when the MFR is 2 g / 10 min or more, preferably the MFR is 10 g / 10 min or more, the fluidity of the resin composition containing the ethylene / α-olefin copolymer is improved, and the productivity at the time of sheet extrusion molding is improved. Can be improved. When the MFR is 50 g / 10 min or less, the molecular weight increases, and therefore, adhesion to a roll surface such as a chill roll can be suppressed. Therefore, peeling is unnecessary, and a sheet having a uniform thickness can be formed. Furthermore, since it becomes a resin composition with “koshi”, a thick sheet of 0.1 mm or more can be easily formed. Moreover, since the crosslinking characteristic at the time of laminate molding of the solar cell module is improved, it is possible to sufficiently crosslink and suppress a decrease in heat resistance. When the MFR is 27 g / 10 min or less, the draw-down during sheet forming can be further suppressed, a wide sheet can be formed, the cross-linking characteristics and heat resistance are further improved, and the best sealing sheet is obtained. Can do.
When the crosslinking treatment of the resin composition is not performed in the laminating step of the solar cell module, the influence of the decomposition of the crosslinking agent is small in the melt extrusion step, so that the MFR is 0.1 g / 10 min or more and less than 10 g / 10 min, preferably A sheet can also be obtained by extrusion molding using a resin composition of 0.5 g / 10 min or more and less than 8.5 g / 10 min. When the content of the cross-linking agent in the resin composition is 0.15 parts by mass or less, a resin composition having an MFR of 0.1 g / 10 min or more and less than 10 g / 10 min is used. A sheet can also be produced by extrusion molding at a molding temperature of 170 to 250 ° C. while performing a crosslinking treatment. When the MFR is within this range, it is preferable in that the laminating apparatus can be prevented from being soiled by the molten resin that protrudes when the sheet is laminated on the solar cell element.

  The ethylene / α-olefin copolymer preferably further satisfies the following requirement a3.

  Requirement a3: The content ratio of the structural unit derived from ethylene contained in the ethylene / α-olefin copolymer is from 80 mol% to 90 mol%, preferably from 80 mol% to 88 mol%, more preferably from 82 mol% to 88 mol. % Or less, more preferably 82 mol% or more and 87 mol% or less. The proportion of structural units derived from an α-olefin having 3 to 20 carbon atoms (hereinafter also referred to as “α-olefin unit”) contained in the ethylene / α-olefin copolymer is 10 mol% or more and 20 mol% or less, Preferably they are 12 mol% or more and 20 mol% or less, More preferably, they are 12 mol% or more and 18 mol% or less, More preferably, they are 13 mol% or more and 18 mol% or less.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is not less than the above lower limit value, the transparency of the obtained sealing sheet is excellent. Further, extrusion molding at a low temperature can be easily performed, and for example, extrusion molding at 130 ° C. or lower is possible. For this reason, even when a cross-linking agent is kneaded into the ethylene / α-olefin copolymer, it is possible to suppress the progress of the cross-linking reaction in the extruder, and a gel-like foreign matter is generated in the sealing sheet. The appearance can be prevented from deteriorating. Moreover, since moderate softness | flexibility is acquired, generation | occurrence | production of the crack of a solar cell element, the crack of a thin film electrode, etc. can be prevented at the time of lamination molding of a solar cell module.

  When the content ratio of the α-olefin unit contained in the ethylene / α-olefin copolymer is not more than the above upper limit value, the crystallization speed of the ethylene / α-olefin copolymer becomes appropriate, so that it is extruded from the extruder. The sheet is not sticky, can be easily peeled off by a cooling roll, and a sealing sheet can be obtained efficiently. Further, since no stickiness is generated on the sheet, blocking can be prevented, and the sheet feeding property is good. In addition, a decrease in heat resistance can be prevented.

(Method for producing ethylene / α-olefin copolymer)
The ethylene / α-olefin copolymer can be produced using a Ziegler compound, a vanadium compound, a metallocene compound or the like as a catalyst. Among them, it is preferable to produce using various metallocene compounds shown below as catalysts. As the metallocene compound, for example, the metallocene compounds described in JP-A-2006-077261, JP-A-2008-231265, JP-A-2005-314680 and the like can be used. However, a metallocene compound having a structure different from the metallocene compounds described in these patent documents may be used, or two or more metallocene compounds may be used in combination.

  The polymerization of the ethylene / α-olefin copolymer can be carried out by any of the conventionally known gas phase polymerization methods and liquid phase polymerization methods such as slurry polymerization methods and solution polymerization methods. Preferably, it is carried out by a liquid phase polymerization method such as a solution polymerization method.

(Ethylene / vinyl acetate copolymer)
The melt flow rate (MFR) of the ethylene / vinyl acetate copolymer is preferably 5 g / 10 min to 50 g / 10 min, more preferably 5 g / 10 min to 30 g / 10 min, and still more preferably It is 5 g / 10 min or more and 25 g / 10 min or less. When the MFR of the ethylene / vinyl acetate copolymer is within the above range, the extrusion moldability is excellent. The MFR of the ethylene / vinyl acetate copolymer can be adjusted by adjusting the polymerization temperature during the polymerization reaction, the polymerization pressure, and the molar ratio between the monomer concentration and the hydrogen concentration of the polar monomer in the polymerization system. . In the present embodiment, the MFR of the ethylene / vinyl acetate copolymer is measured under conditions of 190 ° C. and a load of 2.16 kg in accordance with ASTM D1238.

  The content of vinyl acetate in the ethylene / vinyl acetate copolymer is preferably 10% by mass to 47% by mass, and more preferably 13% by mass to 35% by mass. When the content of vinyl acetate is in this range, the balance of adhesion, weather resistance, transparency, and mechanical properties of the sealing sheet is further improved. In addition, when the sealing sheet is formed, the film forming property is improved. The vinyl acetate content can be measured according to JIS K7192: 1999. Specifically, the vinyl acetate content was determined by dissolving the sample in xylene, hydrolyzing the acetate group with an alcohol solution of potassium hydroxide, adding excess sulfuric acid or hydrochloric acid, and adding dropwise with a standard sodium hydroxide solution. It can be measured by quantification.

  The ethylene / vinyl acetate copolymer is preferably a binary copolymer consisting only of ethylene and vinyl acetate. In addition to ethylene and vinyl acetate, for example, vinyl formate, vinyl glycolate, vinyl propionate, vinyl benzoate. A vinyl ester monomer such as acrylic acid, methacrylic acid, or an acrylic monomer such as a salt or alkyl ester thereof; When a copolymer component other than ethylene and vinyl acetate is included, the amount of the copolymer component other than ethylene and vinyl acetate in the ethylene / vinyl acetate copolymer may be 0.5 mass% or more and 5 mass% or less. preferable.

  The manufacturing method of the said ethylene-vinyl acetate copolymer is not specifically limited, It can manufacture by a well-known method. For example, in the presence of a radical generator, at 500 to 4000 atm and 100 to 300 ° C., in the presence or absence of a solvent or a chain transfer agent, ethylene, vinyl acetate, and other copolymerization components as necessary are copolymerized. It can be produced by polymerization.

  In the present embodiment, as the sealing sheet, an ethylene / α-olefin copolymer or an ethylene / vinyl acetate copolymer may be used alone, or may be blended. When blending ethylene / α-olefin copolymer and ethylene / vinyl acetate copolymer, the total amount of ethylene / α-olefin copolymer and ethylene / vinyl acetate copolymer is 100 parts by mass. The ethylene / α-olefin copolymer is preferably 50 to 99 parts by mass, the ethylene / vinyl acetate copolymer is preferably 1 to 50 parts by mass, and the ethylene / α-olefin copolymer is More preferably, it is 50 to 98 parts by mass, more preferably 2 to 50 parts by mass of ethylene / vinyl acetate copolymer, and still more preferably 50 to 95 parts by mass of ethylene / α-olefin copolymer. More preferably, the ethylene / vinyl acetate copolymer is 5 parts by mass or more and 50 parts by mass or less, and the ethylene / α-olefin copolymer is 5 parts by mass or more 95 parts by mass or less, and particularly preferably an ethylene-vinyl acetate copolymer is less than 25 parts by mass 5 parts by mass or more.

(Silane coupling agent)
The sealing sheet in this embodiment may contain a silane coupling agent. The content of the silane coupling agent in the sealing sheet is preferably 0.1 parts by mass or more and 2 parts by mass or less, more preferably 0.1 parts by mass or more and 1. 8 parts by mass or less, more preferably 0.1 parts by mass or more and 1.5 parts by mass or less. It can suppress that a bubble generate | occur | produces in a sealing sheet more reliably, improving the adhesiveness of a sealing sheet as content of a silane coupling agent exists in the said range.

  When the content of the silane coupling agent is not less than the above lower limit value, the adhesive strength between the sealing sheet and the other member can be further improved. On the other hand, when the silane coupling agent is below the above upper limit, methanol and ethanol generated by hydrolysis derived from the methoxy group and ethoxy group of the silane coupling agent are reduced, and bubbles are more reliably generated in the sealing sheet. Can be suppressed.

Examples of the silane coupling agent include vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxysilane), 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxypropylmethyl. Dimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethylditriethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-aminopropyltriethoxysilane, 3 -Aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N- ( 1,3-di Til-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyl One or more selected from dimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane, etc. Can be used.
Among these, from the viewpoint of improving adhesiveness, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3- It is preferable to use one or more selected from methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and vinyltriethoxysilane.

(Crosslinking agent)
The sealing sheet in this embodiment may contain a crosslinking agent. The cross-linking agent preferably used for the sealing sheet in the present embodiment is an organic material having a one-minute half-life temperature of 100 to 170 ° C. from the balance of productivity in extrusion sheet molding and cross-linking speed at the time of laminating a solar cell module. Peroxides are preferred. When the one-minute half-life temperature of the organic peroxide is 100 ° C. or higher, sheet molding can be facilitated and the appearance of the sheet can be improved. In addition, the dielectric breakdown voltage can be prevented from being lowered, moisture permeability can be prevented from being lowered, and adhesiveness is further improved. When the one-minute half-life temperature of the organic peroxide is 170 ° C. or lower, it is possible to suppress a decrease in the crosslinking rate when the solar cell module is laminated, and thus it is possible to prevent a decrease in the productivity of the solar cell module. Moreover, the heat resistance of a sealing sheet and the fall of adhesiveness can also be prevented.

Known organic peroxides can be used. Examples of the organic peroxide having a one-minute half-life temperature in the range of 100 to 170 ° C. include dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, and dibenzoylperoxide. Oxide, t-amylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, 1,1-di- (T-amylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-amylperoxy) cyclohexane, t-amylperoxyisononanoate, t-amylperoxynormal octoate, 1 , 1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylpero C) Cyclohexane, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-amyl-peroxybenzoate, t One or more selected from -butyl peroxyacetate, t-butyl peroxyisononanoate, 2,2-di (t-butylperoxy) butane, t-butyl peroxybenzoate, and the like can be used. .
Among these, dilauroyl peroxide, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, t-butyl peroxyisononanoate, t-butyl peroxy-2-ethylhexyl carbonate, t-butyl peroxybenzoate It is preferable to use 1 type, or 2 or more types selected from.

  Since the sealing sheet in the present embodiment has an excellent crosslinking property by containing a crosslinking agent, it is not necessary to go through a two-step bonding process of a vacuum laminator and a crosslinking furnace, and at a high temperature in a short time. Can be completed.

  The content of the crosslinking agent in the sealing sheet is preferably 0.1 parts by mass or more and 3 parts by mass or less, more preferably 0.2 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the crosslinkable resin. Yes, more preferably 0.2 parts by mass or more and 1.5 parts by mass or less. When the content of the cross-linking agent is not less than the above lower limit value, the deterioration of the cross-linking properties of the sealing sheet is suppressed, the graft reaction of the silane coupling agent to the main chain of the cross-linkable resin is improved, and the heat resistance and adhesion Deterioration can be suppressed. Further, when the content of the cross-linking agent is not more than the above upper limit value, the generation amount of the decomposition product of the cross-linking agent is further reduced, and generation of bubbles in the sealing sheet can be suppressed more reliably. .

(UV absorber, light stabilizer, heat stabilizer)
The resin composition constituting the encapsulating sheet in this embodiment may contain one or more additives selected from the group consisting of an ultraviolet absorber, a light stabilizer, and a heat stabilizer. preferable. The content of these additives is preferably 0.005 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the crosslinkable resin. By making it within this range, the effect of improving the resistance to constant temperature and humidity, heat cycle resistance, weather resistance stability, and heat resistance stability is sufficiently secured, and the transparency and adhesiveness of the sealing sheet are lowered. Can be prevented. Furthermore, it is preferable to contain at least two kinds of additives selected from the above three kinds, and it is particularly preferred that all of the above three kinds are contained.

  Examples of the ultraviolet absorber include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-4- Benzophenone ultraviolet absorbers such as carboxybenzophenone and 2-hydroxy-4-N-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2-hydroxy- Benzotriazole ultraviolet absorbers such as 5-methylphenyl) benzotriazole; one or more selected from salicylic acid ester ultraviolet absorbers such as phenyl salicylate and p-octylphenyl salicylate it can.

  Examples of the light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1, 3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) One or more selected from hindered amine compounds such as imino}], hindered piperidine compounds, and the like can be used.

  Examples of the heat stabilizer include tris (2,4-di-tert-butylphenyl) phosphite, bis [2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid Tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, bis (2,4-di-tert-butylphenyl) pentaerythritol diphos Phosphite heat stabilizer such as phyto; Lactone heat stabilizer such as a reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene; 3,3 ′ , 3 ", 5,5 ', 5" -hexa-tert-butyl-a, a', a "-(methylene-2,4,6-triyl) tri-p-cresol, 1,3,5-trimethyl -2, 4, 6 -Tris (3,5-di-tert-butyl-4-hydroxyphenyl) benzylbenzene, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- Hindered phenol heat resistance stability such as (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] 1 type or 2 types or more selected from an agent; sulfur type heat stabilizer; amine type heat stabilizer etc. Among these, a phosphite type heat stabilizer and a hindered phenol type heat stabilizer are preferable. .

(Crosslinking aid)
It is preferable that the sealing sheet in this embodiment contains a crosslinking aid. The content of the crosslinking aid in the sealing sheet is preferably 0.05 parts by mass or more and 5 parts by mass or less, and 0.1 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the crosslinkable resin. More preferably, it is more preferably 0.2 parts by mass or more and 2 parts by mass or less. Thereby, it can be set as a moderate crosslinked structure and can improve the heat resistance of a sealing sheet, a mechanical physical property, and adhesiveness.

As the crosslinking aid, a compound having two or more double bonds in the molecule can be used. For example, t-butyl acrylate, lauryl acrylate, cetyl acrylate, stearyl acrylate, 2-methoxyethyl acrylate, ethyl carbitol acrylate Monoacrylates such as methoxytripropylene glycol acrylate; monomethacrylates such as t-butyl methacrylate, lauryl methacrylate, cetyl methacrylate, stearyl methacrylate, methoxyethylene glycol methacrylate, methoxypolyethylene glycol methacrylate; 1,4-butanediol diacrylate, 1, 6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, Diacrylates such as ethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate; 1,3-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1 , 9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and the like; trimethylolpropane triacrylate, tetramethylolmethane triacrylate, Pentaerythritol triacrylate etc. Triacrylate; trimethacrylate such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate; tetraacrylate such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; divinyl aromatic compound such as divinylbenzene and di-i-propenylbenzene; Cyanurates such as triallyl cyanurate and triallyl isocyanurate; diallyl compounds such as diallyl phthalate; triallyl compounds; oximes such as p-quinonedioxime and pp′-dibenzoylquinonedioxime; One kind or two or more kinds selected can be used.
Among these crosslinking aids, triacrylates such as diacrylate, dimethacrylate, divinyl aromatic compound, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, pentaerythritol triacrylate; trimethylolpropane trimethacrylate, trimethylolethanetri Trimethacrylates such as methacrylate; tetraacrylates such as pentaerythritol tetraacrylate and tetramethylolmethane tetraacrylate; cyanurates such as triallyl cyanurate and triallyl isocyanurate; diallyl compounds such as diallyl phthalate; triallyl compounds; p-quinonedioxime; selected from oximes such as pp'-dibenzoylquinone dioxime; maleimides such as phenylmaleimide It is preferable to use one kind or two or more kinds. Further, among these, triallyl isocyanurate is particularly preferable from the viewpoint that generation of bubbles in the encapsulating sheet can be further suppressed and the crosslinking property is excellent.

  The crosslinking aid may contain a copper element resulting from the raw material or the manufacturing process, and may increase the copper element in the encapsulating sheet. For example, some triallyl isocyanurates contain a copper element exceeding 0.1 ppm, and when added to a sealing sheet, the copper element content may exceed 1.0 ppb. Accordingly, the triallyl isocyanurate is preferably one having an amount of copper element of 0.01 ppm or less. The amount of elemental copper in triallyl isocyanurate can be measured by ICP emission analysis.

(Other additives)
The sealing sheet in the present embodiment may appropriately contain various components other than the components detailed above in a range not impairing the object of the present invention. Examples include various polyolefins other than the crosslinkable resin, styrene-based, ethylene-based block copolymers, and propylene-based polymers. These may be contained in an amount of 0.0001 to 50 parts by mass, preferably 0.001 to 40 parts by mass with respect to 100 parts by mass of the crosslinkable resin. One kind selected from various resins other than polyolefins and / or various rubbers, plasticizers, fillers, pigments, dyes, antistatic agents, antibacterial agents, antifungal agents, flame retardants, crosslinking aids, dispersants, etc. The above additives can be appropriately contained.

  As for the thickness of the sealing sheet in this embodiment, 0.01 mm or more and 2 mm or less are preferable, More preferably, it is 0.05 mm or more and 1.5 mm or less, More preferably, it is 0.1 mm or more and 1.2 mm or less, More preferably, it is 0.00. 2 mm or more and 1 mm or less, particularly preferably 0.3 mm or more and 0.9 mm or less, and particularly preferably 0.3 mm or more and 0.8 mm or less. When the thickness is within this range, damage to the light-receiving surface side protective member, solar cell element, thin film electrode, etc. in the laminating step can be suppressed, and a high amount of photovoltaic power can be obtained by ensuring sufficient light transmittance. be able to. Furthermore, it is preferable because the solar cell module can be laminated at a low temperature.

  The sealing sheet in this embodiment may have layers, such as a hard-coat layer for surface or back surface protection, an adhesive layer, an antireflection layer, a gas barrier layer, and an antifouling layer, for example. If classified by material, layer made of UV curable resin, layer made of thermosetting resin, layer made of polyolefin resin, layer made of carboxylic acid modified polyolefin resin, layer made of fluorine-containing resin, cyclic olefin (co) Examples thereof include a layer made of a polymer and a layer made of an inorganic compound.

(Method for producing sealing sheet)
Although the manufacturing method of the sealing sheet in this embodiment is not particularly limited, various known molding methods (cast molding, extrusion sheet molding, inflation molding, injection molding, compression molding, calendar molding, etc.) can be employed. is there. In particular, extrusion sheet molding and calendar molding are preferred.

Although the manufacturing method of the sealing sheet in this embodiment is not specifically limited, For example, the following method is mentioned. First, a crosslinkable resin and, if necessary, one or more additives selected from a silane coupling agent, a crosslinking agent, a crosslinking aid, an ultraviolet absorber, a light stabilizer, and a heat stabilizer. prepare.
Here, as for the sealing sheet in this embodiment, content of a copper element is 1.0 ppb or less.
The content of the copper element contained in one or more selected from the crosslinkable resin and the additive is reduced. Preferably, the content of copper element contained in the crosslinking aid is reduced. More preferably, the content of copper element contained in triallyl isocyanurate is reduced. Thereby, content of the copper element in the sealing sheet in this embodiment can be 1.0 ppb or less.
As a method of reducing the content of copper element contained in a crosslinking aid such as triallyl isocyanurate, a method of removing with a ligand (EDTA etc.) that forms a chelate complex with copper, a method of removing with an ion exchange resin Etc.
The content of the copper element in the crosslinkable resin can be measured, for example, by wet decomposition of the crosslinkable resin, then constant volume with pure water, and ICP emission analysis using an ICP emission analyzer. The content of copper element in each additive can be measured, for example, by ICP emission analysis using an ICP emission analyzer.

Ethylene / α-olefin copolymers and ethylene-vinyl acetate copolymers, which are crosslinkable resins, are often polymerized using a high-pressure radical method or a titanium catalyst / metallocene catalyst, and rarely contain copper elements. However, when the content of copper element is large, for example, purification such as deashing operation with acid or alkali, reprecipitation operation with poor solvent, etc., to reduce the content of copper element in the crosslinkable resin. Is preferred.
Moreover, various additives may contain the metal element resulting from the raw material and manufacturing process, and increase the quantity of the copper element in a sealing sheet. For this reason, it is preferable that various additives are purified by, for example, a deashing operation with an acid or an alkali or a reprecipitation operation with a poor solvent to reduce the content of copper element in the various additives.
The decalcification operation with an acid or alkali and the reprecipitation operation with a poor solvent can be generally performed according to a known method.

Next, a crosslinkable resin and, if necessary, one or more additives selected from silane coupling agents, crosslinking agents, crosslinking assistants, ultraviolet absorbers, light stabilizers, and heat stabilizers. Dry blend. Next, the obtained mixture is supplied from the hopper to the extruder and melt-kneaded at a temperature lower than the one-hour half-life temperature of the crosslinking agent as necessary. Thereafter, a sealing sheet is produced by extrusion from the tip of the extruder into a sheet. The molding can be performed by a known method using a T-die extruder, a calendar molding machine, an inflation molding machine or the like.
Moreover, the sheet | seat which does not contain a crosslinking agent may be produced by the said method, and a crosslinking agent may be added to the produced sheet | seat by the impregnation method. In the case where two or more kinds of crosslinking agents are contained, melt kneading may be performed at a temperature lower than the one-hour half-life temperature of the lowest crosslinking agent.

  The extrusion temperature range is preferably 100 ° C. or higher and 130 ° C. or lower. When the extrusion temperature is 100 ° C. or higher, the productivity of the sealing sheet can be improved. When the extrusion temperature is 130 ° C. or lower, gelation is unlikely to occur when the resin composition is formed into a sheet with an extruder to obtain a sealing sheet. Therefore, an increase in the torque of the extruder can be prevented and sheet forming can be facilitated. Moreover, since it becomes difficult for unevenness | corrugation to generate | occur | produce on the surface of a sheet, the fall of an external appearance can be prevented. Moreover, since generation | occurrence | production of the crack inside a sheet | seat can be suppressed when a voltage is applied, the fall of a dielectric breakdown voltage can be prevented. Furthermore, a decrease in moisture permeability can be suppressed. Moreover, since it becomes difficult to generate | occur | produce an unevenness | corrugation on the sheet | seat surface, the adhesiveness with glass, a cell, an electrode, and a back sheet becomes favorable at the time of the lamination process of a solar cell module, and it is excellent in adhesiveness.

2. About solar cell module The sealing sheet in this embodiment is used in order to seal a solar cell element in a solar cell module.
As the configuration of the solar cell module, for example, a front surface side transparent protective member / light receiving surface side sealing sheet (light receiving surface side sealing layer) / solar cell element / back surface side sealing sheet (back surface side sealing layer) / back surface side protection Although the structure which laminated | stacked the member (back sheet | seat) in this order is mentioned, it is not specifically limited.
The sealing sheet in this embodiment is used for either one or both of the light receiving surface side sealing sheet and the back surface side sealing sheet.

In FIG. 1, an example of sectional drawing of the solar cell module of this embodiment is shown.
The solar cell module 10 includes a plurality of solar cell elements 13, a pair of light-receiving surface side sealing sheet 11 and back surface side sealing sheet 12 that are sealed with the solar cell element 13 interposed therebetween, and a front surface side transparent protective member 14 and a back surface. A side protection member (back sheet) 15.

(Solar cell element)
Examples of the solar cell element 13 include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and III-V and II-VI compound semiconductors such as gallium-arsenic, copper-indium-selenium, and cadmium-tellurium. Various solar cell elements such as a system can be used.
In the solar cell module 10, the plurality of solar cell elements 13 are electrically connected in series via an interconnector 16 having a conducting wire and a solder joint.

(Front side transparent protective member)
Examples of the surface-side transparent protective member 14 include a glass plate; a resin plate formed of acrylic resin, polycarbonate, polyester, fluorine-containing resin, and the like.

(Back side protection member)
Examples of the back surface side protection member (back sheet) 15 include single or multilayer sheets such as metals and various thermoplastic resin films. Examples thereof include metals such as tin, aluminum, and stainless steel; inorganic materials such as glass; various thermoplastic resin films formed of polyester, inorganic material-deposited polyester, fluorine-containing resin, polyolefin, and the like.
The back surface side protection member 15 may be a single layer or a multilayer.

(electrode)
Although the structure and material of the electrode used for a solar cell module are not specifically limited, In a specific example, it has a laminated structure of a transparent conductive film and a metal film. The transparent conductive film is made of SnO ₂ , ITO, ZnO or the like. The metal film is made of a metal such as silver, gold, copper, tin, aluminum, cadmium, zinc, mercury, chromium, molybdenum, tungsten, nickel, and vanadium. These metal films may be used alone or as a composite alloy. The transparent conductive film and the metal film are formed by a method such as CVD, sputtering, or vapor deposition.
When the metal contained in the electrode is silver, that is, when the electrode is a silver electrode, a phenomenon that silver migrates in the sealing sheet is particularly likely to occur. Therefore, when an electrode is a silver electrode, the effect of the sealing sheet in this embodiment can be acquired especially effectively.

(Method for manufacturing solar cell module)
Although the manufacturing method of the solar cell module in this embodiment is not specifically limited, For example, the following method is mentioned.
First, a plurality of solar cell elements 13 electrically connected using the interconnector 16 are sandwiched between a pair of light receiving surface side sealing sheets 11 and a back surface side sealing sheet 12, and further, these light receiving surface side sealing sheet sheets 11 and The back side sealing sheet 12 is sandwiched between the front side transparent protective member 14 and the back side protective member 15 to produce a laminate. Next, the laminate is heated to receive the light-receiving surface side sealing sheet 11 and the back surface side sealing sheet 12, the light receiving surface side sealing sheet 11 and the front surface side transparent protective member 14, and the back surface side sealing sheet 12 and the back surface side protective member. 15 is bonded.
In manufacturing the solar cell module, a sealing sheet is prepared in advance, and is subjected to pressure bonding at a temperature at which the sealing sheet melts. For example, at a lamination temperature of 145 to 170 ° C. and a vacuum pressure of 10 Torr or less. Heat for 0.5-10 minutes under vacuum. Subsequently, pressurization by atmospheric pressure is performed for about 2 to 30 minutes, and a module having the configuration as described above can be formed. In this case, the encapsulating sheet has excellent cross-linking properties by containing a specific cross-linking agent, and it is not necessary to go through a two-step bonding process in forming the module, and it can be completed at a high temperature in a short time. And the productivity of the module can be greatly improved. It is also possible to go through a two-step bonding process using an oven or the like. When the two-step bonding process is performed, for example, the module is heated by heating at 120 to 170 ° C. for 1 to 120 minutes. It is also possible.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

(1) Measuring method [content of copper element]
Content of the copper element in various additives was calculated | required with the ICP emission spectrometer (ICPS-8100 by Shimadzu Corporation Corp.).

(2) Evaluation of sealing sheet [Ion migration evaluation]
Silver comb-tooth electrodes opposed to each other alternately were formed on a ceramic substrate having a thickness of 0.5 mm. The thickness of the silver electrode was 10-15 μm, and electrode width / space = 100 μm / 100 μm.
Subsequently, the board | substrate which formed the silver comb-tooth electrode was set between two sealing sheets, and the test piece was created by pinching | interposing the upper and lower sides with the glass plate. The test specimen was evaluated for the occurrence of ion migration by applying a voltage of 100 VDC under a wet heat condition of 85 ° C./85% RH and measuring the leakage current.
Specifically, the resistance change until 500 hours elapsed was monitored to observe whether or not the resistance value changed due to conduction. The experiment was performed with N = 4.

(3) Production of sealing sheet [Example 1]
To 100 parts by mass of an ethylene / vinyl acetate copolymer (vinyl acetate content: 28% by mass, MFR: 15 g / 10 min) which is a crosslinkable resin, 0% of t-butylperoxy-2-ethylhexyl carbonate is used as a crosslinking agent. .6 parts by mass, 0.3 parts by mass of 3-methacryloxypropyltrimethoxysilane as a silane coupling agent, 0.2 parts by mass of 2-hydroxy-4-normal-octyloxybenzophenone as an ultraviolet absorber, light stabilization 0.2 parts by mass of bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate as an agent, and octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) as a heat-resistant stabilizer ) 0.04 parts by weight of propionate and 1.2 parts by weight of triallyl isocyanurate as a crosslinking aid The combined resin compositions were prepared and formed into sheets under the following conditions.
The copper element content of triallyl isocyanurate was 0.01 ppm or less. The copper element content of other additives was also 0.01 ppm or less.
Triallyl isocyanurate was purified before use, and the copper element content was reduced to 0.01 ppm or less.

After melt-kneading with a single screw extruder (screw diameter of 30 mmφ) manufactured by Ikegai Co., Ltd., extrusion molding is performed from a coat hanger type T die under the condition of a die temperature of 110 ° C., cooling at a roll temperature of 25 ° C., and a winding speed. Molding was performed at 0.7 m / min. The maximum thickness tmax of the sheet was 450 μm.
Content of the copper element in the obtained sealing sheet was 1.0 ppb or less.

  The ion migration evaluation was performed using the obtained sealing sheet. As a result, no decrease in resistance was observed in the four obtained sealing sheets. That is, it was confirmed that no electrode migration occurred.

[Example 2]
Ethylene / α-olefin copolymer which is a crosslinkable resin (α-olefin: 1-butene, density: 0.870 g / cm ³ , MFR: 20 g / 10 min, content ratio of structural unit derived from ethylene: 86 mol% , Ratio of structural unit derived from α-olefin: 14 mol%, synthesized according to Synthesis Example 1 described in paragraph 0178 of WO2012 / 046456.) T-Butylperoxy-2 as a crosslinking agent with respect to 100 parts by mass -0.7 parts by mass of ethylhexyl carbonate, 0.4 parts by mass of 3-methacryloxypropyltrimethoxysilane as a silane coupling agent, 0.2 parts by mass of 2-hydroxy-4-normal-octyloxybenzophenone as an ultraviolet absorber Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate as a light stabilizer 0.2 parts by weight, 0.1 parts by weight of octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate as a heat stabilizer and tris (2,4-di-tert-butyl) A resin composition was prepared by blending 0.1 part by weight of phenyl) phosphite and 1.2 parts by weight of the same crosslinking aid triallyl isocyanurate as in Example 1, and the same conditions as in Example 1 To form a sheet.
Content of the copper element in the obtained sealing sheet was 1.0 ppb or less.

  The ion migration evaluation was performed using the obtained sealing sheet. As a result, no decrease in resistance was observed in the four obtained sealing sheets. That is, it was confirmed that no electrode migration occurred.

[Comparative Example 1]
A sealing sheet was produced in the same manner as in Example 1 except that triallyl isocyanurate (copper element content 0.63 ppm, unrefined product) was used as a crosslinking aid.
Content of the copper element in the obtained sealing sheet was 7.6 ppb.

The ion migration evaluation was performed using the obtained sealing sheet. As a result, the resistance of the obtained sealing sheet was greatly reduced by conduction at 3 out of 4 points. That is, it was confirmed that electrode migration occurred.
FIG. 2 shows an enlarged photograph of the electrode in which the resistance was reduced. Aggregation called dendrites was observed between the electrodes, confirming that conduction was occurring.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2014-200212 for which it applied on September 30, 2014, and takes in those the indications of all here.

Claims (12)

A sealing sheet used for sealing a solar cell element,
It consists of a resin composition containing a crosslinkable resin and copper element,
The sealing sheet whose content of the said copper element in the said sealing sheet measured by ICP emission analysis is 0.001 ppb or more and 1.0 ppb or less with respect to the said sealing sheet whole. In the sealing sheet according to claim 1,
The sealing sheet in which the said crosslinkable resin contains at least 1 type selected from an ethylene-alpha-olefin copolymer and an ethylene-vinyl acetate copolymer. In the sealing sheet according to claim 1 or 2,
Further comprising a crosslinking aid,
The sealing sheet whose content of the said crosslinking adjuvant is 0.05 to 5 mass parts with respect to 100 mass parts of said crosslinkable resin. In the sealing sheet according to claim 3,
The sealing sheet in which the said crosslinking adjuvant contains triallyl isocyanurate. In the sealing sheet according to any one of claims 1 to 4,
Further comprising a cross-linking agent;
The sealing sheet whose content of the said crosslinking agent is 0.1 to 3 mass parts with respect to 100 mass parts of said crosslinkable resin. In the sealing sheet according to claim 5,
The sealing sheet in which the said crosslinking agent contains an organic peroxide. In the sealing sheet according to any one of claims 1 to 6,
Content of the said crosslinkable resin in the said sealing sheet is a sealing sheet which is 80 mass% or more when the whole resin component contained in the said sealing sheet is 100 mass%. In the sealing sheet according to any one of claims 1 to 7,
Further comprising a silane coupling agent,
The sealing sheet whose content of the said silane coupling agent is 0.1 to 2 mass parts with respect to 100 mass parts of said crosslinkable resin. In the sealing sheet according to any one of claims 1 to 8,
The sealing sheet which further contains the 1 type, or 2 or more types of additive selected from the group which consists of a ultraviolet absorber, a light stabilizer, and a heat stabilizer. A surface-side transparent protective member;
A back side protection member;
A solar cell element;
A sealing layer formed by crosslinking the sealing sheet according to claim 1 and sealing the solar cell element between the front surface side transparent protective member and the back surface side protective member. When,
A solar cell module comprising: In the solar cell module according to claim 10,
A solar cell module, wherein the solar cell element includes a silver electrode. A manufacturing method for manufacturing the sealing sheet according to any one of claims 1 to 9,
Preparing a crosslinkable resin and one or more additives selected from a silane coupling agent, a crosslinking agent, a crosslinking aid, an ultraviolet absorber, a light stabilizer, and a heat stabilizer, and
Reducing the content of the copper element contained in one or more selected from the crosslinkable resin and the additive; and
A step of melt-kneading the crosslinkable resin and the additive and then forming the sheet,
The manufacturing method of the sealing sheet containing this.

Images