JP5010240B2 - Adhesive sheet for solar cell - Google Patents

Description

  The present invention relates to an adhesive sheet for a solar cell that is suitably used for joining a solar cell element and a protective material when producing a solar cell module.

  For solar cell modules consisting of silicon or selenium semiconductor wafers, a laminated body is prepared in which an upper transparent protective material is stacked on the upper surface of the solar cell element with the upper and lower surfaces laminated with an adhesive sheet for solar cells, and a lower substrate protective material is stacked on the lower surface. The laminated body is manufactured by thermocompression bonding under reduced pressure to laminate and integrate a protective material on the upper and lower surfaces of the solar cell element via a solar cell adhesive sheet.

  As such an adhesive sheet for a solar cell, one made of an ethylene copolymer is often used because of its excellent transparency and adhesiveness. However, the solar cell adhesive sheet made of the above-mentioned ethylene-based copolymer is inferior in heat resistance, so that the obtained solar cell module is used under high temperature conditions such as summertime or in the manufacturing process of the solar cell module. When doing so, there was a problem of deformation.

  Therefore, an organic peroxide is contained in the solar cell adhesive sheet made of the ethylene copolymer, and the ethylene copolymer is crosslinked by heat applied during the production of the solar cell adhesive sheet. The heat resistance of the adhesive sheet was improved.

  And as an organic peroxide contained in the said adhesive sheet for solar cells, a half-life temperature is low in order to shorten the heating time at the time of manufacture of a solar cell module, and to improve the production efficiency of a solar cell module. Things are starting to be used.

  As such an adhesive sheet for a solar cell containing an organic peroxide having a low half-life temperature, for example, Patent Document 1 discloses protection for a solar cell module made of an ethylene copolymer containing an organic peroxide. In the sheet, as the organic peroxide, a protective sheet for a solar cell module characterized by using a dialkyl peroxide and an alkyl peroxy ester and / or a peroxy ketal blended in a specific ratio has been proposed, The one-hour half-life temperature of the dialkyl peroxide is preferably 130 to 160 ° C, and the one-hour half-life temperatures of the alkyl peroxyester and peroxyketal are preferably 100 to 135 ° C. The use of a machine is disclosed.

  When the solar cell adhesive sheet containing an organic peroxide having a low half-life temperature, such as the above solar cell module protective sheet, is formed at a high temperature when the film is formed by an extruder, an ethylene copolymer is formed. Since crosslinking proceeds, it was necessary to form a film at a low temperature. And when extruding a solar cell adhesive sheet at such a low temperature, the viscosity of the ethylene-based copolymer in the extruder and in the T-die becomes high and difficult to flow, so the sheet is formed. Tended to be difficult. Therefore, when an organic peroxide having a low half-life temperature is contained in the solar cell adhesive sheet, an ethylene copolymer having a high melt flow rate (MFR) is used to improve the film forming property.

  However, the solar cell adhesive sheet made of an ethylene-based copolymer having a high melt flow rate as described above has a resin component that protrudes from the end of the solar cell module in the heating step during the production of the solar cell module. The problem of contaminating the module body and the solar cell module manufacturing apparatus occurred.

JP 11-26791 A

  INDUSTRIAL APPLICABILITY In the heating process at the time of manufacturing a solar cell module, the present invention hardly causes the ethylene-based copolymer constituting the solar cell adhesive sheet to protrude, and can be suitably used for manufacturing a solar cell module. An adhesive sheet for solar cells is provided.

  The adhesive sheet for solar cells of the present invention is formed by laminating and integrating three or more sheet layers containing an ethylene-based copolymer and an organic peroxide formed from a T die connected to an extruder. A high melt flow rate in which the melt flow rate (MFR) of the ethylene copolymer constituting these sheet layers exceeds 20 g / 10 min. And at least one of the remaining sheet layers excluding the outermost sheet layers on both sides has an ethylene copolymer melt flow rate (MFR) constituting the sheet layer of 20 g / 10 min. It is the following low melt flow rate layer, Furthermore, the total thickness of the said low melt flow rate layer is 50% or more of the thickness of the said adhesive sheet for solar cells, It is characterized by the above-mentioned.

  In the solar cell adhesive sheet, the outermost sheet layer is laminated and integrated on both surfaces of the intermediate sheet layer, the intermediate sheet layer is a low melt flow rate layer, and the both outermost sheet layers are high. It is a melt flow rate layer.

  The adhesive sheet for solar cells of the present invention is formed by laminating and integrating three or more sheet layers containing an ethylene-based copolymer and an organic peroxide formed from a T die connected to an extruder. A high melt flow rate in which the melt flow rate (MFR) of the ethylene copolymer constituting these sheet layers exceeds 20 g / 10 min. And at least one of the remaining sheet layers excluding the outermost sheet layers on both sides has an ethylene copolymer melt flow rate (MFR) constituting the sheet layer of 20 g / 10 min. The low melt flow rate layer is characterized in that the total thickness of the low melt flow rate layer is 50% or more of the thickness of the adhesive sheet for solar cells. The layer has a high viscosity at the time of melting and excellent shape retention, and the low melt flow rate layer occupies 50% or more of the thickness of the solar cell adhesive sheet. The sheet is not deformed by heat applied in the thermocompression bonding process at the time of manufacturing the solar cell module, and does not protrude from the end portion of the obtained solar cell module and contaminate the solar cell module or the manufacturing apparatus.

  Also, since the outermost sheet layers on both sides are high melt flow rate layers and at least one of the remaining sheet layers excluding the outermost sheet layers on both sides is a low melt flow rate layer, an adhesive sheet for solar cells In manufacturing, the high melt flow rate layer with high fluidity can be brought into contact with the inner surface of the T die to reduce the fluid friction force against the inner surface of the T die, thereby improving the extrudability. In addition, the solar cell element and the protective material can be firmly and securely bonded and integrated over the entire surface in the production of the solar cell module.

  Furthermore, in the solar cell adhesive sheet, the outermost sheet layer is laminated and integrated on both surfaces of the intermediate sheet layer, the intermediate sheet layer is a low melt flow rate layer, and the both outermost sheet layers are high. In the case of the melt flow rate layer, in the thermocompression bonding process at the time of manufacturing the solar cell module, the low melt flow rate layer reliably retains the shape because of its low melt viscosity, while the high melt flow rate layer Although the layer has fluidity by heat applied in the thermocompression bonding process, it is in contact with the low melt flow rate layer, and the low melt flow rate layer suppresses the protrusion, and the layer in the adhesive sheet for solar cells Since the thickness ratio of the melt flow rate layer is also small, the low melt flow rate in the thermocompression bonding process at the time of manufacturing the solar cell module is low. It is possible to prevent the protrusion of the coat layer to prevent contamination of the resulting solar cell module and manufacturing apparatus, it is possible to manufacture a solar cell module excellent quality.

  An example of the adhesive sheet for solar cells of the present invention will be described with reference to the drawings. As shown in FIG. 1, the solar cell adhesive sheet A is formed by laminating and integrating the outermost sheet layers 1a and 1b on both sides of the intermediate sheet layer 1c, and the both side outermost sheet layers 1a and 1b and the intermediate sheet. Each layer 1c contains an ethylene copolymer and an organic peroxide.

  The ethylene-based copolymer constituting the outermost sheet layers 1a, 1b and the intermediate sheet layer 1c on both sides is a copolymer of ethylene and a copolymerizable monomer that can be copolymerized with ethylene. The monomer is not particularly limited, and examples thereof include vinyl acetate, acrylic acid, acrylic ester, methacrylic acid, methacrylic ester, maleic acid, maleic anhydride, maleic ester and the like, and vinyl acetate is preferable. In addition, the said copolymerizable monomer may be copolymerized with ethylene independently, or 2 or more types may be copolymerized with ethylene.

  And if content of the copolymerizable monomer in the said ethylene-type copolymer is small, the transparency of the adhesive sheet for solar cells will fall, the electric power generation efficiency of the solar cell module obtained will fall, or it will adhere for solar cells On the other hand, the adhesiveness of the sheet may be lowered. On the other hand, if it is too much, the film forming property and the mechanical strength of the adhesive sheet for solar cells may be lowered.

  In the adhesive sheet A for solar cells of the present invention, the intermediate sheet layer 1c is a low melt flow rate layer in which the melt flow rate (MFR) of the ethylene copolymer is 20 g / 10 min or less, while the outermost sheets on both sides The layers 1a and 1b are high melt flow rate layers in which the melt flow rate (MFR) of the ethylene-based copolymer exceeds 20 g / 10 minutes.

  In this way, by using the intermediate sheet layer 1c of the solar cell adhesive sheet A as a low melt flow rate layer, the viscosity at the time of melting is increased, and when the solar cell module is heated and pressure-bonded, The adhesive sheet A for solar cells is prevented from protruding from the end, and the resulting solar cell module and manufacturing apparatus are prevented from being accidentally contaminated, and the outermost sheet layers 1a and 1b on both sides are subjected to high melt flow. By making it a late layer, the viscosity at the time of melting is lowered, the flow friction resistance between the inner surface of the T die connected to the extruder is reduced and the extrudability is improved. The surface property and the uniformity are excellent, and the solar cell element and the protective material can be bonded and integrated well.

  Specifically, when the melt flow rate of the ethylene copolymer constituting the outermost sheet layers 1a and 1b on both sides of the solar cell adhesive sheet A is low, the solar cell adhesive sheet is formed at a low temperature. Since the film forming property is reduced, the value is limited to a value exceeding 20 g / 10 minutes. However, if it is too high, the adhesive sheet for solar cell may protrude when the solar cell module is produced. 250 g / 10 min is preferred.

  Further, when the melt flow rate of the ethylene copolymer constituting the intermediate sheet layer 1c of the solar cell adhesive sheet A is high, the solar cell adhesive sheet is heated during the solar cell module manufacturing and pressure bonding. This is limited to 20 g / 10 minutes or less because it cannot prevent the outermost sheet layer from protruding or the protrusion of both outermost sheet layers, but if it is too low, the film-forming property of the adhesive sheet for solar cells will deteriorate. Therefore, it is preferably 1 to 18 g / 10 minutes, and more preferably 5 to 15 g / 10 minutes.

  The melt flow rate of the ethylene copolymer can be adjusted in a known manner. For example, the degree of polymerization of the ethylene copolymer can be adjusted, or the type and content of the copolymeric monomer can be adjusted. Can be done.

  In addition, the melt flow rate of the ethylene-type copolymer in this invention says the value measured at 190 degreeC based on JISK6922-2. When a plurality of types of ethylene copolymers are mixed and used, the melt flow rate of the ethylene copolymer refers to the apparent melt flow rate of the entire mixed ethylene copolymer.

  The organic peroxide contained in the outermost sheet layers 1a and 1b and the intermediate sheet layer 1c on both sides of the solar cell adhesive sheet A is not particularly limited. For example, bis (2-t-butylperoxy) Isopropyl) benzene (138 ° C.), dicumyl peroxide (136 ° C.), di-t-hexyl peroxide (136 ° C.), 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane (138) ° C), t-butylcumyl peroxide (137 ° C), di-t-butyl peroxide (144 ° C), p-menthane hydroperoxide (151 ° C), 2,5-dimethyl-2,5-bis (t -Butylperoxy) hexyne-3 (150 ° C.), 1,1-bis (t-butylperoxy) -2-methylcyclohexane (102 ° C.), 1,1-bis (t-hex) Luperoxy) -3,3,5-trimethylcyclohexane (106 ° C.), 1,1-bis (t-hexylperoxy) cyclohexane (107 ° C.), 1,1-bis (t-butylperoxy) cyclohexane (111 ° C.) ), 2,2-bis (4,4-bis (t-butylperoxy) cyclohexyl) propane (114 ° C.), t-hexyl peroxyisopropyl monocarbonate (115 ° C.), t-butyl peroxymaleic acid (119 ° C), t-butylperoxy-3,5,5-trimethylhexanoate (119 ° C), t-butylperoxylaurate (118 ° C), t-butylperoxyisopropyl monocarbonate (118 ° C), t -Butylperoxy-2-ethylhexyl monocarbonate (119 ° C), t-hexylperoxybe Zoate (119 ° C.), 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane (119 ° C.), t-butyl peroxyacetate (121 ° C.), 2,2-bis (t-butyl peroxy) ) Butane (122 ° C.), t-butyl peroxybenzoate (125 ° C.), n-butyl-4,4-bis (t-butyl peroxy) valerate (127 ° C.), etc., and 2,5-dimethyl- 2,5-bis (t-butylperoxy) hexane is preferred. These organic peroxides may be used alone or in combination of two or more. The temperature in the parenthesis represents a 1 hour half-life temperature.

  Further, if the content of the organic peroxide in the outermost sheet layers 1a, 1b and the intermediate sheet layer 1c on both sides of the adhesive sheet A for solar cells is small, the crosslinking of the ethylene-based copolymer becomes insufficient, On the other hand, the heat resistance of the solar cell adhesive sheet may be insufficient. On the other hand, when the solar cell adhesive sheet is formed, crosslinking of the ethylene copolymer proceeds, and the solar cell adhesive sheet having a uniform thickness is formed. Since it may become impossible to obtain, 0.05 to 3 parts by weight is preferable and 0.1 to 1 part by weight is more preferable with respect to 100 parts by weight of the ethylene copolymer.

  Furthermore, if the ratio of the thickness of the intermediate sheet layer 1c to the total thickness of the solar cell adhesive sheet A is low, it is possible to prevent the solar cell adhesive sheet from protruding in the heating and pressure-bonding steps during the production of the solar cell module. On the other hand, if it is high, the film-forming property at the time of forming the solar cell adhesive sheet at a low temperature is lowered, so it is limited to 50% or more, and preferably 60 to 85%.

  In the solar cell adhesive sheet A, the case where the intermediate sheet layer is a single layer has been described. However, the intermediate sheet layer 1c may be formed by laminating and integrating a plurality of low melt flow rate layers, Further, the intermediate sheet layer 1c may be obtained by laminating and integrating one or more low melt flow rate layers and one or more high melt flow rate layers in any order.

  Note that the outermost sheet layers 1a, 1b and the intermediate sheet layer 1c on both sides of the solar cell adhesive sheet, if necessary, within a range not impairing the effects of the present invention, a crosslinking aid, a scorch inhibitor, if necessary. Additives such as coupling agents, antioxidants such as 2,6-di-t-butyl-4-methylphenol, and ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone may be added.

  Examples of the crosslinking aid include polyfunctional monomers having two or more allyl groups, vinyl groups, acryloyl groups, or methacryloyl groups, which stabilize polymer radicals to increase crosslinking efficiency and concentrate crosslinking points. To promote gel formation. Examples of the polyfunctional monomer include diallyl phthalate, diallyl itaconate, diallyl maleate, triallyl isocyanurate, triallyl cyanurate, triallyl phosphate, divinylbenzene; 1,6-hexanediol di (meth) acrylate , Ethylene oxide modified bisphenol A di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, (meth) acrylate of ε-caprolactone modified dipentaerythritol And (meth) acrylates of alkyl-modified dipentaerythritol, and the like may be used alone or in combination of two or more.

  If the amount of the crosslinking aid contained in the intermediate sheet layer 1c is small, the heat resistance of the adhesive sheet for solar cells is reduced during the production of the solar cell module due to insufficient crosslinking of the ethylene copolymer, As a result, the durability of the solar cell module obtained by using the solar cell adhesive sheet may be lowered. On the other hand, if the amount is large, the ethylene copolymer is cross-linked in the T-die and the viscosity is increased. For the solar cell, the copolymer is retained in the T-die and it becomes impossible to obtain an adhesive sheet for a solar cell with a uniform thickness, or the ethylene-based copolymer is cross-linked and solidified in the T-die. Since it becomes impossible to extrude an adhesive sheet from T-die, 0.1-3 weight part is preferable with respect to 100 weight part of ethylene-type copolymers, and 0.2-2.5 weight part is more preferable.

  And it is preferable to adjust so that the gel fraction after bridge | crosslinking of the intermediate | middle sheet layer 1c may be 70 weight% or more. This is because when the gel fraction after crosslinking of the intermediate sheet layer 1c is low, the crosslinking of the ethylene copolymer is insufficient during the production of the solar cell module, and the heat resistance of the solar cell adhesive sheet is reduced, As a result, the durability of the solar cell module obtained using the solar cell adhesive sheet may decrease.

  Further, if the amount of the crosslinking aid contained in the outermost sheet layers 1a and 1b on both sides is large, the ethylene copolymer is crosslinked in the T die and the viscosity is increased. It stays in the die and it becomes impossible to obtain a solar cell adhesive sheet having a uniform thickness, or the ethylene copolymer is cross-linked and solidified in the T die, and the solar cell adhesive sheet is removed from the T die. Since it becomes impossible to extrude, less than 0.4 weight part is preferable with respect to 100 weight part of ethylene-type copolymer.

  Furthermore, the scorch inhibitor is not particularly limited, and 2,4-diphenyl-4-methyl-1-pentene, 2,6-di-t-butyl-p-cresol, hydroquinone, 2-mercaptobenzothiazole, Examples include octyl methacrylate and N-nitrosodiphenylamine, which may be used alone or in combination of two or more.

  If the amount of the scorch inhibitor contained in the outermost sheet layers 1a and 1b on both sides is small, the crosslinking of the ethylene copolymer proceeds during the formation of the solar cell adhesive sheet, and the inside of the T-die In the meantime, it becomes impossible to obtain a solar cell adhesive sheet having a uniform thickness, or it becomes impossible to extrude the solar cell adhesive sheet because the ethylene copolymer is solidified in the T-die. If the amount is too large, crosslinking of the ethylene-based copolymer becomes insufficient during the production of the solar cell module, the heat resistance of the solar cell adhesive sheet is insufficient, and the durability of the resulting solar cell module is reduced. The amount is preferably 0.01 to 2 parts by weight with respect to 100 parts by weight of the ethylene copolymer.

  In addition, an anti-scorch agent may be added to the intermediate sheet layer 1c as long as the crosslinking of the ethylene copolymer is not inhibited, but it is preferable that no anti-scorch agent is contained.

  The coupling agent is added for the purpose of enhancing the adhesiveness of the adhesive sheet for solar cells, and the coupling agent is one or two selected from the group consisting of an amino group, a glycidyl group, a methacryloxy group, and a mercapto group. A silane coupling agent having the above functional group is preferably used. For example, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltri A methoxysilane etc. are mentioned, and it may be used independently or 2 or more types may be used together.

  Next, the manufacturing method of the said adhesive sheet A for solar cells is demonstrated. The adhesive sheet A for solar cells of the present invention can be produced using a multilayer coextrusion apparatus in which two or more extruders are connected to the same T die via the same feed block. Prepare a three-layer coextrusion machine with two extruders connected to the same T die via the same feed block, and two of these extruders are used for the outermost sheet layers 1a and 1b. One of the above is used for the intermediate sheet layer 1c, and two extruders for the outermost sheet layers 1a and 1b are mixed with an ethylene copolymer, an organic polymer having a melt flow rate (MFR) exceeding 20 g / 10 min. While supplying a resin composition comprising an oxide and an additive that is added if necessary, an ethylene-based copolymer having a melt flow rate (MFR) of 20 g / 10 min or less is fed to an extruder for the intermediate sheet layer 1c. Coalescence, organic peroxides, and additives added as needed After supplying the resin composition consisting of the agent and melt-kneading the resin composition in each extruder, the resin composition is supplied to the feed block, and the outermost sheet layer 1a from the T die disposed at the tip of the feed block The intermediate sheet layer 1c and the outermost sheet layer 1b are in this order and are laminated and integrated so that the thickness of the intermediate sheet layer 1c is 50% or more of the total thickness of the adhesive sheet A for solar cells. The film can be formed by extrusion film formation, and the extruded molten sheet is cooled with a cooling roll, solidified and wound up. In addition, when there are a plurality of sheet layers made of the same resin composition, melt-kneading is performed with one extruder, and the resin composition extruded from the extruder is branched into a predetermined number of layers, and then the feed block The film may be supplied to the film.

  Moreover, as a method for forming a solar cell adhesive sheet when the intermediate sheet layer is composed of a plurality of low melt flow rate layers, for example, the number of sheet layers constituting the solar cell adhesive sheet A multi-layer coextrusion device is prepared in which the extruder is connected to the same T-die via the same feed block, and the two extruders of this multi-layer co-extrusion device are used as extruders for both outermost sheet layers 1a and 1b. Then, the remaining extruder may be used as an extruder for the low melt flow rate layer to perform extrusion film formation in the same manner as described above.

  In the production process of the adhesive sheet A for solar cells, if the temperature at which the resin composition is melted and kneaded in the extruder is high, the organic peroxide in the resin composition is decomposed and the ethylene-based copolymer is decomposed. Since the crosslinking of the polymer proceeds, the temperature is preferably 10 ° C. or more lower than the one-hour half-life temperature of the organic peroxide used, and when two or more organic peroxides are used, Of the organic peroxides used, the temperature is preferably 10 ° C. or more lower than the one-hour half-life temperature of the lowest organic peroxide.

  Further, the solar cell adhesive sheet A is preferably subjected to embossing on the surface in order to improve the deaeration in the heating and pressure-bonding steps at the time of manufacturing the solar cell module. In addition, as a method of embossing the surface of the adhesive sheet A for solar cells, a known method is used. For example, the adhesive sheet for solar cells immediately after being extruded from a T die is embossed on the surface. The embossing roll is supplied between the embossing roll and the rubber roll disposed opposite to the embossing roll, and the embossing roll is pressed against the molten solar cell adhesive sheet to emboss the surface of the solar cell adhesive sheet. The method of giving is mentioned. The solar cell adhesive sheet A once manufactured may be heated again to be in a softened state and embossed as described above.

  And as a method of manufacturing a solar cell module using the solar cell adhesive sheet A of the present invention, an upper transparent protective material is laminated on the upper surface of the solar cell element via the solar cell adhesive sheet A, and a solar cell. A laminated body in which the lower substrate protective material is laminated on the lower surface of the element via the solar cell adhesive sheet A, and this laminated body is heated and pressure-bonded under reduced pressure, so that the upper and lower surfaces of the solar cell element are applied to the solar cell. A solar cell module in which protective materials are laminated and integrated via the adhesive sheet A can be obtained.

  In addition, as a heating condition at the time of thermocompression bonding the above laminated body under reduced pressure, in order to reliably decompose the organic peroxide in the adhesive sheet for solar cells and to sufficiently crosslink the ethylene-based copolymer The organic peroxide used is preferably heated at a temperature 10 ° C. or more higher than the one-hour half-life temperature of the organic peroxide used for 5 to 10 minutes, and in the case of using two or more organic peroxides, the organic peroxide used is It is preferable to heat for 5 to 10 minutes at a temperature higher by 10 ° C. or more than the one-hour half-life temperature of the highest organic peroxide.

(Examples 1 to 3, Comparative Examples 1 and 2)
A three-layer coextrusion device is prepared in which three extruders are connected to the same T-die via the same feed block, and two of these extruders are connected to the outermost sheet layers 1a and 1b on both sides. The remaining one machine is for the intermediate sheet layer 1c, and the two outermost sheet layers 1a and 1b are used in two extruders, and the vinyl acetate content and melt flow rate (MFR) shown in Table 1 are used. ) Ethylene-vinyl acetate copolymer having 100 parts by weight, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane (1 hour half-life temperature: 138 ° C.) 1 part by weight, triallyl isocyan 0.3 part by weight of nurate, 0.1 part by weight of 3-glycidoxypropyltrimethoxysilane, 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol and 2-hydroxy-4-methoxybenzophenone Resin composition consisting of 0.3 parts by weight While the product is fed, 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content and a melt flow rate as shown in Table 1, and 2,5-dimethyl-2 are fed to an extruder for the intermediate sheet layer 1c. , 5-bis (t-butylperoxy) hexane (1 hour half-life temperature: 138 ° C.) 1 part by weight, triallyl isocyanurate 0.3 part by weight, 3-glycidoxypropyltrimethoxysilane 0.1 part by weight A resin composition comprising 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol and 0.3 part by weight of 2-hydroxy-4-methoxybenzophenone was supplied.

  Next, in each of the three extruders, the resin composition is melt-kneaded at 90 ° C., the molten resin composition is supplied to the feed block, and from the T die disposed at the tip of the feed block, The outermost sheet layer 1a, the intermediate sheet layer 1c, and the outermost sheet layer 1b are laminated and integrated in this order, and the thickness ratio (the thickness of the outermost sheet layer 1a / the thickness of the intermediate sheet layer 1c / the outermost sheet layer 1c). Extrusion was performed so that the thickness ratio of the outer sheet layer 1b was the thickness ratio shown in Table 1 to form a solar cell adhesive sheet A. Then, the molten solar cell adhesive sheet A immediately after being extruded from the T-die is supplied between an embossing roll and a rubber roll disposed opposite to the embossing roll, and the embossing roll is in a molten state. After pressing the solar cell adhesive sheet A and embossing the surface of the solar cell adhesive sheet A to a depth of 0.2 mm, the film is wound while being cooled by a cooling roll, thereby forming a low melt flow rate layer. A solar cell adhesive sheet A having a thickness of 0.5 mm was obtained by laminating and integrating outermost sheet layers 1a and 1b, which are high melt flow rate layers, on both surfaces of a certain intermediate sheet layer 1c.

(Comparative Example 3)
A single layer extrusion apparatus in which a T die is disposed at the tip of the extruder is prepared, and the extruder of this single layer extrusion apparatus has a vinyl acetate content of 33% by weight and a melt flow rate of 30 g / 10 minutes. 100 parts by weight of ethylene-vinyl acetate copolymer, 1 part by weight of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane (1 hour half-life temperature: 138 ° C.), triallyl isocyanurate 3 parts by weight, 0.1 part by weight of 3-glycidoxypropyltrimethoxysilane, 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol and 0.3 part of 2-hydroxy-4-methoxybenzophenone A resin composition consisting of parts by weight was supplied, melted and kneaded at 90 ° C., and then extruded into a sheet form from a T-die disposed at the tip of the extruder to form a solar cell adhesive sheet. Then, the molten solar cell adhesive sheet immediately after being extruded from the T-die is supplied between the embossing roll and a rubber roll disposed opposite to the embossing roll, and the embossing roll is melted into the sun. After pressing the adhesive sheet for a battery and embossing a depth of 0.2 mm on the surface of the adhesive sheet for a solar cell, the single-layer having a thickness of 0.5 mm is wound while being cooled by a cooling roll. A solar cell adhesive sheet was obtained.

  Next, for the solar cell adhesive sheet obtained as described above, the evaluation of the anti-extrusion performance and the temperature and humidity cycle test were performed as follows, and the results are shown in Table 1.

(Protruding prevention performance)
Two flat square-shaped test pieces having a side of 150 mm are cut out from the obtained adhesive sheet for solar cells and overlapped with each other, and a flat square polyvinyl fluoride sheet having a side of 150 mm on the lower surface of the stacked test pieces. A laminate was prepared by laminating a plane square transparent flat glass having a side of 150 mm on the upper surface.

Next, the laminate was heated at 150 ° C. for 10 minutes under a reduced pressure of 1.3 kPa, and then the distance of the ethylene copolymer protruding from the end of the laminate was measured. It was evaluated by.
◯: The maximum value of the protruding distance of the ethylene copolymer was less than 3 mm.
(Triangle | delta): The maximum value of the protrusion distance of an ethylene-type copolymer was 3 mm or more and less than 10 mm.
X: The maximum value of the protruding distance of the ethylene copolymer was 10 mm or more.

(Temperature and humidity cycle test)
A plurality of silicon semiconductor wafers for solar cells connected through an interconnector are arranged in a row, and transparent flat glass is placed on the upper surface of these silicon semiconductor wafers for solar cells via the obtained adhesive sheet for solar cells. It laminated | stacked and the polyvinyl fluoride sheet was laminated | stacked on the lower surface of the silicon semiconductor wafer for solar cells through the obtained adhesive sheet for solar cells, and the laminated body was produced.

  This laminated body is heated at 150 ° C. for 10 minutes under a reduced pressure of 1.3 kPa, and a transparent flat glass is laminated and integrated on the upper surface of the silicon semiconductor wafer for solar cells via an adhesive sheet for solar cells, and silicon for solar cells. A solar cell module was produced in which a polyvinyl fluoride sheet was laminated and integrated on the lower surface of a semiconductor wafer via a solar cell adhesive sheet.

  The solar cell module thus obtained was allowed to stand for 6 hours under the condition of −20 ° C., and then the temperature was raised from −20 ° C. to 85 ° C. at a humidity of 85% RH over 1 hour. The solar cell module after having been left again for 6 hours and further cooled for 10 hours at a humidity of 85% RH from 85 ° C. to −20 ° C. was repeated 10 times. The appearance was visually observed, and the presence or absence of appearance abnormality such as discoloration of the adhesive sheet for solar cells and peeling between the transparent flat glass and the polyvinyl fluoride sheet and the silicon semiconductor wafer for solar cells was evaluated.

It is the longitudinal cross-sectional view which showed an example of the adhesive sheet for solar cells of this invention.

Explanation of symbols

1 Sheet layer
1a, 1b Outermost sheet layer
1c Intermediate sheet layer A Solar cell adhesive sheet

Claims (2)

It is an adhesive sheet for a solar cell in which three or more sheet layers containing an ethylene copolymer and an organic peroxide, which are formed from a T die connected to an extruder, are laminated and integrated. The outermost sheet layers on both sides are high melt flow rate layers in which the melt flow rate (MFR) of the ethylene copolymer constituting these sheet layers exceeds 20 g / 10 min, At least one of the remaining sheet layers excluding the layer is a low melt flow rate layer in which the melt flow rate (MFR) of the ethylene-based copolymer constituting the sheet layer is 20 g / 10 min or less, Furthermore, the total thickness of the said low melt flow rate layer is 50% or more of the thickness of the said adhesive sheet for solar cells, The adhesive sheet for solar cells characterized by the above-mentioned. The outermost sheet layer is laminated and integrated on both surfaces of the intermediate sheet layer, the intermediate sheet layer is a low melt flow rate layer, and the both outermost sheet layers are high melt flow rate layers. The adhesive sheet for solar cells according to claim 1.

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