JP2008108948A - Solar cell back surface sealing sheet and solar cell module - Google Patents

Abstract

【Task】
A solar cell module using an ethylene-vinyl acetate copolymer as a filler, and to provide a solar cell back surface sealing sheet and a solar cell module excellent in adhesion to a filler after an accelerated test under high temperature and high humidity. With the goal.
[Means for Solving the Problems]
An ethylene- (meth) acrylic acid ester copolymer, ethylene-vinyl acetate copolymer containing at least one of an epoxy compound, an oxazoline compound, or a carbodiimide compound as a protective sheet composed of a heat-resistant film It solved by sealing through the heat-fusible layer which has as a main component any one of a combination or these mixtures.
[Selection] Figure 1

Description

  The present invention relates to a solar cell back surface sealing sheet and a solar cell module using the sealing sheet, and more specifically, adhesion to an ethylene-vinyl acetate copolymer used as a filler of the solar cell module. Solar cell module that can maintain barrier characteristics as a sheet for backside sealing and electrical output characteristics as a solar cell, without being defective in appearance due to delamination even in accelerated evaluation in a hot and humid environment And a solar cell back surface sealing sheet.

  In recent years, various efforts have been made to suppress carbon dioxide emissions while interest from various countries both inside and outside Japan has increased.

  Increasing fossil fuel consumption leads to an increase in atmospheric carbon dioxide, and the greenhouse effect raises the Earth's temperature, significantly affecting the global environment. Various studies have been carried out to solve this global problem, and in particular, solar power generation is highly expected in terms of cleanliness and non-pollution.

  A solar cell constitutes the heart of a photovoltaic power generation system that directly converts sunlight energy into electricity, and is made of a single crystal, polycrystalline, or amorphous silicon semiconductor.

  The structure does not use a single solar cell element (cell) (A-1) as it is, and generally several to several tens of solar cell elements are wired in series and in parallel for a long time. Various packaging has been done and unitized to protect the cells (about 20 years).

  The unit incorporated in this package is called a solar cell module (A), and the surface that is generally exposed to sunlight is covered with a glass plate (A-3), and from a thermoplastic (particularly, ethylene-vinyl acetate copolymer). The filling material (A-2) is used to fill the gap, and the back surface is protected by the sealing sheet (B) (see FIG. 1).

  Since these solar cell modules are mainly used outdoors, sufficient durability and weather resistance are required in the configuration, material structure, and the like.

  In particular, the back surface sealing sheet (B) is required to have weather resistance and a low water vapor transmission rate (excellent in moisture barrier properties). This is because if the filler is peeled off, discolored, or the wiring is corroded due to moisture permeation, the module output itself may be affected.

  Conventionally, this solar cell backside sealing sheet is excellent in weather resistance and flame retardancy, and has a good adhesiveness with an ethylene-vinyl acetate copolymer used as a filler for solar cell modules. "Is proposed (see Patent Documents 1 and 2).

  In addition, a solar cell back surface sealing sheet using a polyester film such as polyethylene terephthalate having excellent electrical insulation has been proposed.

When this polyester film is a solar cell back surface sealing sheet, it is necessary to use a sheet that defines the amount of cyclic oligomer in polyester or a sheet that defines the molecular weight of polyester in order to improve weather resistance. It has been proposed (see Patent Documents 3, 4, and 5).

  Further, as described above, the solar cell needs to maintain its performance for about 20 years, and its durability and weather resistance are evaluated by an accelerated test under high temperature and high humidity (85 ° C.-85% relative humidity). It is.

  At this time, for example, in the case of a solar cell module used as a filler made of an ethylene-vinyl acetate copolymer using a solar cell back surface sealing sheet made of a polyester film, Adhesion immediately after production of the solar cell module is excellent because it is only adhesion by wetting utilizing intermolecular interactions such as hydrogen bonding, but when the accelerated test is performed in the above environment, the adhesion is significantly reduced. .

  Here, it has been proposed to improve the adhesion by performing corona treatment on the surface to be bonded to the filler of the solar cell back surface protective sheet (see Patent Document 6).

  However, even when a sheet having a corona-treated surface is used as the sealing sheet as described above, the problem of adhesion with the filler cannot be sufficiently solved.

  In order to improve this problem, a heat-fusible film having good adhesion to a filler such as an ethylene-vinyl acetate copolymer is further laminated on the sealing surface of the solar cell back surface sealing sheet. An improved technique has been proposed (see Patent Document 7).

  Moreover, in providing the thermal adhesive film on the sealing surface of the solar cell sealing sheet, it is necessary to interpose an adhesive such as a polyurethane adhesive in order to improve the adhesion to the sealing sheet. .

  When a polyurethane-based adhesive mainly composed of polyester polyol is used as the adhesive, the adhesive undergoes hydrolysis and seals with the heat-fusible film when subjected to an accelerated test under high temperature and high humidity. The laminate strength between sheets for use was greatly reduced.

  On the other hand, a resin composition used as a filler generally includes an ethylene-vinyl acetate copolymer as a main component and various additives such as a peroxide and a crosslinking agent.

  When this resin composition is used as a filler, the ethylene-vinyl acetate copolymer undergoes a deacetic acid reaction due to the influence of various additives in the accelerated test environment, and the adhesive is affected by the effect of acetic acid due to this deacetic acid reaction. There was a problem of promoting hydrolysis.

  Currently, solar cell modules are manufactured by batch-bonding thermocompression bonding using a laminator device.

  In order to simplify this module manufacturing process, the use of an ethylene-vinyl acetate copolymer, which is said to be a fast cure type, in which the thermal crosslinking reaction efficiency is improved at each stage, is increasing as a filler.

  This fast cure type filler is obtained by further blending an additive sensitive to heat in order to promote the thermal crosslinking reaction.

For this reason, compared with the standard type filler used until now, there existed a tendency for the adhesiveness with respect to the sheet | seat for solar cell backside sealing to be inferior. Furthermore, the influence of acetic acid by the above-mentioned deacetic acid reaction is also remarkable.

Thus, regardless of the type of ethylene-vinyl acetate copolymer used for the filler, there is no influence of deacetic acid on the filler, and the solar cell module has excellent adhesion to the filler, and the solar There is a need for a battery back surface sealing sheet.
JP-T 8-500214 Japanese translation of PCT publication No. 2002-520820 Japanese Patent Laid-Open No. 2002-100788 JP 2002-134771 A JP 2002-26354 A JP 2000-243999 A Japanese Patent Laid-Open No. 10-25357

  The present invention has been made in consideration of the above-mentioned background, and an object thereof is to provide a solar cell back surface sealing sheet and a solar cell module excellent in adhesion with a filler after an accelerated test under high temperature and high humidity. And

  The invention according to claim 1 is a solar cell module using an ethylene-vinyl acetate copolymer as a filler, and a protective sheet for sealing composed of a heat-resistant film on one surface of the filler, The main component is at least one of an ethylene- (meth) acrylate copolymer, an ethylene-vinyl acetate copolymer, or a mixture thereof containing at least one of an epoxy compound, an oxazoline compound, or a carbodiimide compound. The solar cell module is sealed through a heat-fusible layer.

  According to a second aspect of the present invention, in the heat-fusible layer, any one of an epoxy compound, an oxazoline compound, and a carbodiimide compound is used as the ethylene- (meth) acrylate copolymer, ethylene-vinyl acetate. 2. The solar cell module according to claim 1, wherein 0.1 to 30 parts by weight is blended with 100 parts by weight of any one of a copolymer or a mixture thereof.

  The invention according to claim 3 is characterized in that the heat-fusible layer is laminated on a sealing surface to be bonded to the filler of the back surface sealing sheet. It is a solar cell module.

  The invention according to claim 4 is characterized in that the heat-fusible layer is laminated on a sealing surface to be bonded to the filler of the back surface sealing sheet via a urethane adhesive layer. The solar cell module according to claim 3.

  The invention according to claim 5 is a back surface sealing sheet for sealing one surface of the filler in a solar cell module using an ethylene-vinyl acetate copolymer as a filler, and is a heat resistant film. An ethylene- (meth) acrylate copolymer, an ethylene-vinyl acetate copolymer, in which at least one of an epoxy compound, an oxazoline compound, or a carbodiimide compound is blended on the sealing surface of the substrate composed of Or it is the sheet | seat for solar cell backside sealing characterized by laminating | stacking the heat-fusible layer which has any 1 type of these mixtures as a main component.

The invention according to claim 6 is characterized in that the heat-fusible layer is an epoxy compound, an oxazoline compound,
Alternatively, one kind of carbodiimide compound is added in an amount of 0.1 to 30 weights per 100 weight parts of any one of the ethylene- (meth) acrylate copolymer, the ethylene-vinyl acetate copolymer, or a mixture thereof. It is the sheet | seat for solar cell backside sealing of Claim 5 characterized by including in the range of the part.

  The invention according to claim 7 is the solar cell back surface sealing sheet according to claim 5 or 6, wherein the heat-fusible layer is laminated via a urethane-based adhesive. .

  The solar cell module of the present invention has a peel strength of 10 N / 15 mm or more when the filler and the solar cell back surface sealing sheet are heat-pressed and sealed, and is stored at 85 ° C. to 85% RH. In addition, it was possible to obtain a good laminate strength having a laminate strength retention of 30% or more after 2000 hours, preferably 3000 hours.

  In addition, since it does not involve a decrease in the adhesion between the heat-fusible layer and the solar cell back surface sealing sheet even under high temperature and high humidity, not only the poor appearance due to delamination, but also as a back surface sealing sheet It has become possible to provide a solar cell back surface sealing sheet capable of maintaining the barrier characteristics and the electrical output characteristics of a solar cell.

  Hereinafter, embodiments of the present invention will be described in detail.

The solar cell back surface sealing sheet of the present invention has the following constitution, so that the adhesiveness with the ethylene-vinyl acetate copolymer that is the filler is increased. It is a solar cell module adhered through a fusible layer.
Moreover, it is a solar cell back surface sealing sheet | seat which laminated | stacked the heat-fusible layer on the sealing surface of the back surface sealing sheet.

  By adopting the above configuration, delamination occurs even when the heat sealing layer is laminated on the sealing surface of the solar cell back surface sealing sheet via an adhesive such as urethane adhesive. Can be prevented.

  The heat-fusible layer used in the present invention is specifically composed of a resin composition containing as a main component an ethylene- (meth) acrylate copolymer, an ethylene-vinyl acetate copolymer, or a mixture thereof. Specifically, as the ethylene- (meth) acrylate ester copolymer, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, i-propyl (meth) acrylate, ( N-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, or a multi-component copolymer thereof can be used.

  Here, the solar cell back surface sealing sheet is laminated using a urethane adhesive, that is, the adhesiveness between the heat-fusible layer / adhesive / solar cell back surface sealing sheet base material is improved. Moreover, in order to maintain the adhesion under high temperature and high humidity, the problem has been solved by the following means.

  The thermal fusion layer is added with a compound having reactivity with acetic acid, specifically, an epoxy compound, an oxazoline compound, or a carbodiimide compound.

  By setting it as the said structure, it became possible to use the urethane adhesive for the solar cell back surface sealing sheet, and to improve the adhesiveness between a heat-fusible layer / solar cell back surface sealing sheet.

  Specific examples of the compound used for the heat fusion layer include epoxy compounds such as 1,6-hexanediol, neopentyl glycol, diglycidyl ether of aliphatic diol such as polyalkylene glycol, sorbitol, sorbitan, Polyglycidyl ethers of aliphatic polyols such as polyglycerol, pentaerythritol, diglycerol, glycerol, trimethylolpropane, polyglycidyl ethers of alicyclic polyols such as cyclohexanedimethanol, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellit Diglycidyl esters of aliphatic and aromatic polycarboxylic acids such as acids, adipic acid and sebacic acid, or polyglycidyl esters, resorcinol, bis- (p-hydroxyphenyl) methane Diglycidyl ethers of polyhydric phenols such as 2,2-bis- (p-hydroxyphenyl) propane, tris- (p-hydroxyphenyl) methane, 1,1,2,2-tetrakis (p-hydroxyphenyl) ethane Or, such as polyglycidyl ether, N, N′-diglycidylaniline, N, N, N-diglycidyltoluidine, N, N, N ′, N′-tetraglycidyl-bis- (p-aminophenyl) methane Examples thereof include N-glycidyl derivatives of amines, triglycidyl derivatives of aminofails, triglycidyl tris (2-hydroxyethyl) isocyanurate, triglycidyl isocyanurate, orthocresol type epoxy, and phenol novolac type epoxy.

  As the oxazoline compound, monooxazoline compounds such as 2-oxazoline, 2-methyl-2-oxazoline, 2-phenyl-2-oxazoline, 2,5-dimethyl-2-oxazoline, 2,4-diphenyl-2-oxazoline, 2,2 '-(1,3-phenylene) -bis (2-oxazoline), 2,2'-(1,2-ethylene) -bis (2-oxazoline), 2,2 '-(1,4- And dioxazoline compounds such as butylene) -bis (2-oxazoline) and 2,2 ′-(1,4-phenylene) -bis (2-oxazoline).

  As the carbodiimide compound, N, N′-di-o-toluylcarbodiimide, N, N′-diphenylcarbodiimide, N, N′-di-2,6-dimethylphenylcarbodiimide, N, N′-bis (2 , 6-Diisopropylphenyl) carbodiimide, N, N′-dioctyldecylcarbodiimide, N-triyl-N′-cyclohexylcarbodiimide, N, N′-di-2,2-di-t-butylphenylcarbodiimide, N-triyl- N'-phenylcarbodiimide, N, N'-di-p-nitrophenylcarbodiimide, N, N'-di-p-aminophenylcarbodiimide, N, N'-di-p-hydroxyphenylcarbodiimide, N, N'- Examples include di-cyclohexylcarbodiimide and N, N′-di-p-toluylcarbodiimide.

  The heat-fusible layer suppresses hydrolysis of the urethane-based adhesive by acetic acid by blending these compounds in the range of 0.1 to 300 parts by weight with respect to 100 parts by weight of the heat-fusible resin. It is possible to suppress a decrease in the laminate strength between the heat-fusible layer and the solar cell back surface sealing sheet base material.

  As described above, the heat-resistant base material used for the sealing sheet is not particularly limited, and the sealing sheet is appropriately selected according to the purpose by using a laminated structure in which an adhesive is interposed. It is possible.

  The heat-fusible layer having the above-described composition has a thickness in the range of 5 to 100 μm, and may be formed into a film and provided on the sheet base material for solar cell back surface sealing. Here, if the thickness of the heat-sealing layer is thinner than 5 μm, it cannot be used as a heat-fusible film, and the adhesive force is inferior and cannot be used. Moreover, when exceeding 100 micrometers, it does not adapt to film shaping | molding, but an adhesive improvement is not recognized.

Next, the peel strength when the solar cell back surface sealing sheet having this configuration is thermocompression bonded with a filler made of an ethylene-vinyl acetate copolymer is 10 N / 15 m as the initial strength before storage evaluation.
It is required that the strength retention is 30% or more after 2000 hours, preferably 3000 hours after storage by accelerated evaluation in an environment of 85 ° C.-85% RH.

  In particular, when the strength retention ratio is less than 30%, the appearance strength, the gas barrier property, and the electrical characteristics of the solar cell may be decreased due to the decrease in the peel strength described above.

  As the peel strength at this time, it is not necessary that the initial strength and the peel strength after the acceleration evaluation are peeled at the same site, and a simple strength comparison may be used. For example, even in the case where the initial peel strength is between the filler and the heat-sealed layer, there is a possibility that the accelerated evaluation changes to peel between the heat-sealed film / the solar cell backside sealing sheet base material.

  At this time, since it is a fact that the strength of the solar cell module is lowered even if the peeled portions are different, the strength is purely compared. Further, the above-described accelerated evaluation method is merely a reference example, and as long as the evaluation criteria are unified, for example, a PCT test (corresponding to 105 ° C.-100% RH by the accelerated evaluation method using pressurized steam) may be used.

  The solar cell back surface sealing sheet of the present invention has a multilayer structure composed of at least two heat-resistant substrates.

  What is necessary is just to select this heat-resistant base material suitably according to the various function and use calculated | required. Specifically, polyester base materials selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN)), polybutylene terephthalate (PBT), polycyclohexanedimethanol-terephthalate (PCT), polycarbonate base materials, or acrylics A system base material is mentioned.

  In addition to the base material, a polyolefin resin, a polyamide resin, a polyarylate resin, and the like can be appropriately selected in consideration of heat resistance, strength physical properties, electrical insulation, and the like.

  The base material is preferably a polyester base material, which is obtained by using a polybasic acid or an ester-forming derivative thereof and a polyol or an ester-forming derivative thereof.

  Here, the polybasic acid component is terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyro Acid components such as merit acid, dimer acid, maleic acid and itaconic acid are composed of two or more kinds.

  The polyol component includes ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, trimethylolpropane, pentaerythritol, xylene glycol, diethylene glycol, Methylolpropane, poly (ethylene oxide) glycol, poly (tetramethylene oxide) glycol, and a polyol component containing a carboxylic acid group, a sulfonic acid group, an amino group, or a salt thereof are composed of one or more kinds.

  Specific examples of the polyester base material include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polycyclohexanedimethanol-terephthalate (PCT).

However, the polyester base material is a material that may be hydrolyzed with long-term use. Therefore, particularly when using a polyester base material such as polyethylene terephthalate, the number average molecular weight is in the range of 18,000 to 40,000, and the cyclic oligomer content is 1.5.
It is preferable to use a polyester base material having a hydrolysis resistance of not more than wt% and an intrinsic viscosity of 0.5 dl / g or more.

  Such a polyester base material, when the molecular terminal is a carboxylic acid group, works as heat, water, and further as an acid catalyst and is most affected by hydrolysis, so without increasing the amount of the terminal carboxylic acid A solid state polymerization method capable of increasing the number average molecular weight is used.

  Alternatively, the terminal carboxylic acid group may be sealed with a carbodiimide compound, an epoxy compound, or an oxazoline compound. If there is a concern about the effect of shrinkage due to heat when manufacturing the solar cell module, a polyester base material having a heat shrinkage rate of 1% or less, preferably 0.5% or less, by annealing is used. It is possible to use.

  In addition, when a fluororesin is used as the heat-resistant substrate, specifically, as the resin, polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), polyethylene tetrafluoroethylene (ETFE) , Polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and the like.

  Not only the base material made of the resin alone, but also a resin composition obtained by blending these various fluorine-based resins with an acrylic resin, or a fluorine-based base material provided with an acrylic coat layer may be used. None (these are referred to as acrylic modified products of fluorine-based substrates).

  The heat-resistant substrate may be a resin containing various additives as required.

  For example, when weather resistance is required, ultraviolet absorbers such as benzophenone, benzotriazole, and triazine, hindered phenol-based, phosphorus-based, sulfur-based, tocopherol-based antioxidants, and hindered amine-based light stabilizers are also appropriately used. It is possible to mix.

  Moreover, although the film base material used for the sheet | seat for solar cell backside sealing may be transparent, it is preferable to use a white film from the point of improving the electric power generation efficiency of a solar cell element.

  In particular, when the solar cell back surface sealing sheet has a multilayer structure, it is possible to provide a white film on at least the base material bonded to the filler.

  As the white film, it is possible to use a “pigment dispersion type” in which a white additive such as titanium oxide, silica, alumina, calcium carbonate, barium sulfate or the like is added, but there is no limitation on the method relating to whitening.

  When the urethane-based adhesive is used, a polyurethane resin obtained by allowing a bifunctional or higher functional isocyanate compound to act on a main agent such as polyester polyol, polyether polyol, acrylic polyol, and carbonate polyol can be used.

  Specifically, polyester polyols are aliphatic such as succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, and brassic acid, and aromatics such as isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid. One or more of the dibasic acids of the family, and aliphatic systems such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol, It can be obtained using one or more of alicyclic systems such as cyclohexanediol and hydrogenated xylylene glycol, and aromatic diols such as xylylene glycol.

  Further, the hydroxyl groups at both ends of this polyester polyol are, for example, 2,4- or 2,6-tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, 2 , 2,4- or 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4'- An isocyanate compound selected from diisocyanates and the like, or an adduct, a burette, and an isocyanate comprising the above isocyanate compound selected from at least one or more. Examples thereof include polyester urethane polyols that are chain-extended using an anurate. As the polyether polyol, it is possible to use an ether-based polyol such as polyethylene glycol or polypropylene glycol, or a polyether urethane polyol in which the above-described isocyanate compound is allowed to act as a chain extender. As the acrylic polyol, it is possible to use an acrylic resin polymerized using the above-mentioned acrylic monomer.

  The carbonate polyol can be obtained by reacting a carbonate compound and a diol. As the carbonate compound, dimethyl carbonate, diphenyl carbonate, ethylene carbonate and the like can be used. Diols include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methylpentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, dodecanediol, and other aliphatic diols, cyclohexanediol, hydrogenated xylylene It is possible to use carbonate polyol using a mixture of one or more aromatic diols such as alicyclic diols such as reels, xylylene glycol, etc., or polycarbonate urethane polyols subjected to chain extension with the above-mentioned isocyanate compounds It is.

  These various polyols may be used alone or in the form of a blend of two or more depending on the required function and performance.

  It is possible to use it as a polyurethane-type adhesive by using the isocyanate compound mentioned above as a hardening | curing agent for these main ingredients.

  The polyurethane adhesive mentioned above may be accompanied by deterioration in an accelerated environment under weather resistance or high temperature and high humidity, so a carbodiimide compound, an oxazoline compound, an epoxy compound, etc. should be blended as a compound that suppresses the acceleration of deterioration. Is also possible.

  When performing various laminating processes using these urethane adhesives, in the case of using a fluororesin as the heat-resistant substrate, there may be a case where the adhesion failure of the urethane adhesive is accompanied.

  In that case, for example, various acrylic coating agents such as an acrylic coating agent in which a primary amine is introduced into the structure are provided by a wet process, or surface treatment is performed by a dry process such as corona, flame, or plasma. Thus, it is possible to improve the adhesion. This content is included in the acrylic-modified fluorine-based substrate described above.

  By the way, the heat-resistant base material mentioned above has a subject in terms of gas barrier property, especially water vapor barrier property and oxygen barrier property.

  That is, when there is no water vapor or oxygen gas barrier property, it is difficult to maintain the electrical output characteristics as a solar cell.

  In order to solve such a problem, a metal foil base material, a metal vapor deposition film base material aluminum foil base material, or an inorganic compound vapor deposition film base material is used as a gas barrier base material. The metal foil is typically an aluminum foil, and the metal vapor deposition film is typically an aluminum vapor deposition film obtained by depositing aluminum on a polyester or polyolefin stretched film.

  Here, as the inorganic compound vapor-deposited film base material, a film base material obtained by vapor-depositing aluminum oxide, silicon oxide, tin oxide, magnesium oxide, indium oxide, or a composite oxide thereof on a polyester base material can be cited. And what is necessary is just to have gas barrier properties, such as oxygen and water vapor | steam. Among them, aluminum oxide and silicon oxide are particularly preferable.

  The optimum conditions for the thickness vary depending on the type and configuration of the inorganic oxide used, but generally the thickness is preferably in the range of 5 to 300 nm, and the value is appropriately selected. If the film thickness is less than 5 nm, a uniform film cannot be obtained, and the film thickness is not sufficient for exhibiting the barrier function. When the film thickness is larger than 300 nm, the film is subjected to flexibility, and there is a possibility that a crack is easily generated due to external stress. Preferably, it exists in the range of 10-150 nm. These vapor deposition layers can be formed by the usual vacuum vapor deposition method, but other thin film formation methods such as sputtering, ion plating, and plasma vapor deposition (CVD) are used. Is also possible.

  In addition, if necessary, an overcoat layer composed of a part of ethylene-vinyl acetate copolymer or a completely saponified product and a silane compound is provided on the vapor deposition layer of the inorganic compound in order to further improve the gas barrier property. It doesn't matter. Although the gas barrier substrate as described above can be used, it is preferable to use an inorganic compound vapor-deposited film substrate rather than an aluminum foil substrate or an aluminum vapor-deposited film substrate from the viewpoint of electrical insulation.

  The typical structural example combined from the structural component of the sheet | seat for solar cell backside sealing mentioned above below is shown in FIG.

(Outermost layer) Heat resistant substrate (a) / urethane adhesive layer (c) / gas barrier substrate (b) / urethane adhesive (c) / heat resistant substrate (a) / urethane adhesive (c) / Heat-fusible layer (d) (innermost layer)
A solar cell module is manufactured using the laminate thus obtained as a solar cell back surface sealing sheet. This step is manufactured according to the following steps (1) to (4) as shown in FIG.
(1) A glass plate (A-3), a filler (A-2), a cell (A-1), a filler (A-) on a heated top plate (C-1) (approximately 120 to 160 ° C.) 2) Set the back surface sealing sheet (B).
(2) The chamber 1 (C-2) and the chamber 2 (C-3) are evacuated.
(3) The chamber 1 (C-2) is opened to the atmosphere, and a heat-resistant rubber sheet (C-4) is brought into close contact with the module.
(4) Melting ethylene-vinyl acetate copolymer as a filler with the heat / pressure, embedding cells,
Adhesion with glass plate / cell / back surface sealing sheet, and crosslinking / solidification of filler.

  At this time, the step (4) is classified into a case where a crosslinking reaction is performed in an oven provided in a separate line after lamination and a case where a crosslinking reaction is performed inside the laminator.

The former is a type called standard cure, and the latter is a type called fast cure. Usually, the material used as the filler for the solar cell module is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 40% by weight in order to ensure the heat resistance and physical strength of the solar cell. The ethylene-vinyl acetate copolymer is crosslinked by heat or light.

  In the case of performing thermal crosslinking, an organic peroxide is usually used, and one that decomposes at a temperature of 70 ° C. or higher to generate radicals is used. Usually, those having a decomposition temperature of 50 ° C. or more with a half-life of 10 hours are used, and 2,5-dimethylhexane-2,5-dihydroxyperoxide, 2,5-dimethyl-2,5-di (t-butyl) Peroxy) hexyne-3, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, α, α '-Bis (t-butylperoxyisopropyl) benzene, n-butyl-4,4-bis- (t-butylperoxy) valerate, t-butylperoxybenzoate, benzoyl peroxide and the like are used.

  When performing photocuring, a photosensitizer is used, and hydrogen abstraction type (bimolecular reaction type) such as benzophenone, methyl orthobenzoylbenzoate, 4-benzoyl-4'-methyldiphenyl sulfide, isopropylthioxanthone, etc. As the internal cleavage type initiator, benzoin ether, benzyldimethyl ketal, etc., α-hydroxyalkylphenone type, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl, etc. Phenyl ketone, alkylphenyl glyoxylate, diethoxyacetophenone and the like can be used.

  Further, as α-aminoalkylphenone type, 2-methyl-1- [4 (methylthio) phenyl] -2-morpholinopropane-1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -Butanone-1 and the like, and acylphosphine oxide and the like are also used.

  In addition, a silane coupling agent is also blended in consideration of adhesion with the glass plate constituting the solar cell module, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, Vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane , Γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, and the like.

  Further, there are cases where an epoxy group-containing compound is blended for the purpose of promoting adhesiveness and curing. Examples of the epoxy group-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, acrylic glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, phenol glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, glycidyl In some cases, a compound such as methacrylate or butyl glycidyl ether, an oligomer containing an epoxy group having a molecular weight of several hundred to several thousand, or a polymer having a weight average molecular weight of several thousand to several hundred thousand is blended.

In addition, an acryloxy group, methacryloxy group or allyl group-containing compound is added for the purpose of improving the crosslinking, adhesiveness, mechanical strength, heat resistance, moist heat resistance, weather resistance, etc. of the filler, and (meth) acrylic Acid derivatives such as their alkyl esters and amides are most common. In this case, as the alkyl group, in addition to an alkyl group such as methyl, ethyl, dodecyl, stearyl, lauryl, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group, Examples include 3-chloro-2-hydroxypropyl group.

  Further, esters of (meth) acrylic acid and polyfunctional alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, pentaerythritol and the like are also used.

  A typical amide is acrylamide. Further, as the allyl group-containing compound, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, diallyl maleate and the like are blended.

  Furthermore, an inorganic compound for imparting flame retardancy, an ultraviolet absorber for imparting weather resistance, and an antioxidant for preventing oxidative degradation are variously blended. That is, it can be mentioned that the ethylene-vinyl acetate copolymer constituting the solar cell module is a resin composition in which various additives are blended in order to satisfy the functions required for the solar cell module.

  A solar cell module is manufactured by using the material having the above contents, and the solar cell back surface sealing sheet described above is used not only in an environment actually used as a solar cell module but also when evaluating the solar cell module. Even in the accelerated evaluation under the high temperature and high humidity to be examined, it has a good laminate strength, and it is possible to maintain not only the appearance defect accompanying delamination but also the electric output characteristics as a solar cell.

  Examples of the present invention are shown below, but the present invention is not limited to these examples.

The following two resins were used as the heat-fusible layer.
a-1: Ethylene-ethyl acrylate copolymer a-2: Ethylene-ethyl acrylate copolymer blended with 20 parts by weight of carbodiimide compound The following four types of films were used as heat-resistant substrates.
b-1: An annealed polyethylene terephthalate film having a thickness of 50 μm was used. This polyethylene terephthalate is a polyester film excellent in weather resistance having an oligomer content of 0.5 wt%, a number average molecular weight of 19,500, and an intrinsic viscosity of 0.7 dl / g.
b-2: A polyethylene naphthalate film having a thickness of 25 μm was used.
b-3: Vinyl fluoride (PVF) 25 μm in which a primary amine graft-modified acrylic resin was provided on both sides by a wet coating method was used.
b-4: A 40 μm two-type two-layer film composed of polyvinylidene fluoride (PVDF) and polymethyl methacrylate acrylic resin (PMMA) was used.

  The outer layer side is PVDF / PMMA = 80/20, and the inner layer (bonding surface) side is PVDF / PMMA = 20/80. Similarly, a primary amine graft-modified acrylic resin was provided on both sides by a wet coating method.

The following adhesives were used as polyurethane adhesives.
c-1: The adhesive used when the base materials are bonded together by a dry laminating method is a polyester urethane adhesive, and is composed of a mixture of isophorone diisocyanate (IPDI adduct body) and xylylene diisocyanate (XDI adduct body). A curing agent was used and blended so that the main agent / curing agent (solid content ratio) = 3/1.

The following films were used as gas barrier substrates. ]
d-1: A coating layer comprising a normal biaxially stretched polyethylene terephthalate film having a thickness of 12 μm with an alumina vapor deposition layer of 20 nm by the PVD method, and a saponified saponified ethylene-vinyl acetate copolymer as an overcoat layer. 1 μm was provided. This substrate was used as a gas barrier substrate.
(Sample creation method)
Configuration Example-1: A gas barrier base material is laminated on one side of the heat resistant base material using the above-mentioned adhesive using a dry laminating method, and then the above heat resistant material is used on the gas barrier base material using the above adhesive. The substrate was laminated using a dry lamination method.

  Thereafter, a heat-fusible layer was laminated on the heat-resistant substrate surface of the laminated material.

  Regarding this lamination, an extrusion laminating machine was used to laminate by using an adhesive (AC layer), and the sealing sheet shown in FIG. 3 was created.

  Regarding the adhesive used for laminating the heat-fusible layer, it was applied using an AC unit of an extrusion laminator and laminated in-line.

  Moreover, as shown in FIG. 2, the sealing sheet laminated | stacked without using the said adhesive agent simultaneously was created.

  Aging of the polyurethane adhesive in the dry lamination and extrusion lamination was performed at 50 ° C. for 4 days.

  The solar cell back surface sealing sheet thus obtained was used to prepare a module using a fast cure type ethylene-vinyl acetate copolymer resin composition as a solar cell module filler. The solar cell used was polycrystalline silicon. A cell sandwiched between the ethylene-vinyl acetate copolymer sheets having the same size and a thickness of 600 μm was stacked on an A4 size tempered glass, and a solar cell back surface sealing sheet was further provided thereon.

  The laminating conditions at this time were preheating at 40 ° C. for 3 minutes in advance, and then laminating was performed at 150 ° C. under vacuum for 6 minutes and pressure bonding for 8 minutes under a pressure of 1 atm.

For the fast cure type, this laminate sample was used for evaluation.
(Sample evaluation method)
It was stored in an environment of 85 ° C.-85% RH, and the transition of the laminate strength over time was measured with Tensilon under the condition of 90 ° peeling at 300 mm / min.
<Examples 1 to 16>
Table 1 shows the composition of the samples used in the examples and the evaluation results.

The contents described in Examples 1 to 8 show the results in the case where the heat-fusible layer is a general-purpose material. In the configuration with the AC layers shown in Examples 3, 4, 7, and 8, 3000 hours have elapsed. Although it is a decrease in strength within a range where there is no practical problem afterwards, the strength decrease in the accelerated storage environment is remarkably confirmed, and the strength decrease due to the deterioration of the AC layer is clearly confirmed. X.

  On the other hand, it was confirmed that the initial adhesion strength itself was not obtained in the configurations in which the AC layer was not provided as shown in Examples 1, 2, 5, and 6, and the evaluation was not possible.

  Examples 11, 12, 15 and 16 show the results of no practical problems even after 3000 hours.

  In addition, it was confirmed that the structures in which the AC layers of Examples 9, 10, 13 and 14 were not provided had no initial adhesion strength per se, and thus were not usable.

  The above contents were confirmed to have an effect of trapping acetic acid generated with the deterioration of the filler.

  From the contents of the above examples, the solar cell back surface sealing sheet of the present invention is a heat-fusible layer without selecting the type of ethylene-vinyl acetate copolymer as a filler, and even under high temperature and high humidity. And the lowering of the adhesion of the solar cell back surface sealing sheet is not accompanied.

  As described above, it is possible to provide a solar cell back surface sealing sheet capable of maintaining not only the appearance defect accompanying delamination but also the barrier characteristics as the back surface sealing sheet and the electric output characteristics as the solar cell.

It is a schematic cross section which shows an example of a solar cell module. It is a schematic cross section which shows an example of a solar cell back surface sealing sheet. It is a schematic cross section which shows an example of a solar cell back surface sealing sheet. It is a schematic explanatory drawing which shows an example of the manufacturing process of a solar cell module.

Explanation of symbols

A: Solar cell module A-1: Solar cell A-2: Filler A-3: Glass plate B: Back surface sealing sheet
a: Heat-resistant substrate
b: Gas barrier substrate
c: Polyurethane adhesive
d: Heat-sealable layer C: Laminator C-1: Top plate C-2: Chamber 1
C-3: Chamber 2
C-4: Rubber sheet

Claims (7)

  In a solar cell module using an ethylene-vinyl acetate copolymer as a filler, at least one epoxy compound, an oxazoline compound, or a carbodiimide is provided on one surface of the filler with a protective sheet for sealing composed of a heat resistant film. Through a heat-fusible layer mainly comprising any one of an ethylene- (meth) acrylic acid ester copolymer, an ethylene-vinyl acetate copolymer, or a mixture thereof containing one of the compounds. A solar cell module which is sealed.   The heat-fusible layer is made of any one of an epoxy compound, an oxazoline compound, and a carbodiimide compound, the ethylene- (meth) acrylate copolymer, the ethylene-vinyl acetate copolymer, or a mixture thereof. The solar cell module according to claim 1, wherein the solar cell module is blended in the range of 0.1 to 30 parts by weight with respect to 100 parts by weight of any one kind.   The solar cell module according to claim 1 or 2, wherein the heat-fusible layer is laminated on a sealing surface to be bonded to a filler of the back surface sealing sheet.   The solar cell module according to claim 3, wherein the heat-fusible layer is laminated on a sealing surface to be bonded to the filler of the back surface sealing sheet via a urethane-based adhesive layer. .   In a solar cell module using an ethylene-vinyl acetate copolymer as a filler, a back surface sealing sheet for sealing one surface of the filler, sealing a substrate composed of a heat resistant film Any one of ethylene- (meth) acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, or a mixture thereof containing at least one of an epoxy compound, an oxazoline compound, and a carbodiimide compound on the surface A sheet for sealing the back surface of a solar cell, wherein a heat-fusible layer containing as a main component is laminated.   The heat-fusible layer is one of an epoxy compound, an oxazoline compound, or a carbodiimide compound, any of the ethylene- (meth) acrylate copolymer, the ethylene-vinyl acetate copolymer, or a mixture thereof. The solar cell back surface sealing sheet according to claim 5, which is blended in a range of 0.1 to 30 parts by weight with respect to 100 parts by weight of one kind.   The solar cell back surface sealing sheet according to claim 4 or 5, wherein the heat-fusible layer is laminated via a urethane-based adhesive.