JP2006303233A - Adhesive sheet for solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sheet for a solar cell of uniform quality, which can be shaped stably and efficiently. <P>SOLUTION: In the adhesive sheet for the solar cell where a resin sheet of three or more layers, each made of an ethylene series copolymer and an organic peroxide, are laminated; 80 wt.% or higher for of organic peroxide of both sides outermost layer has 1-hour half-life temperature is 130°C-160°C, and 20 wt.% or higher for the organic peroxide of an inner layer is in the range of 100°C to 130°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solar cell adhesive sheet that is suitably used to join a solar cell element and a substrate when a solar cell module is produced.

  For solar cell modules consisting of silicon or selenium semiconductor wafers, both sides of these solar cell elements are laminated with an adhesive sheet such as an ethylene copolymer, with the upper protective material on one side and the lower substrate on the other side. A material is used in which protective materials are stacked, degassed in a vacuum, and heated to be bonded together.

  Since the adhesive sheet is required to have transparency, weather resistance, adhesiveness, etc., an adhesive sheet composed of an ethylene copolymer and an organic peroxide has been proposed.

For example, in a protective sheet for a solar cell module made of an ethylene-based copolymer containing an organic peroxide, the organic peroxide is selected from the group consisting of a dialkyl peroxide (A), an alkyl peroxy ester, and a peroxy ketal. Protection for solar cell module using at least one selected peroxide (B) blended at a ratio of (A) / (B) in a ratio of 10/90 to 90/10 A sheet has been proposed, and the one-hour half-life temperature of the dialkyl peroxide (A) is 130 to 160 ° C, and the one-hour half-life temperature of the peroxide (B) is preferably 100 to 135 ° C. (See Patent Document 1). Moreover, as the manufacturing method, an extrusion molding method using a T die is described.
JP 11-26791 A

  However, when the ethylene copolymer is extruded using a T-die, if the ethylene copolymer stays in the extruder or T-die, the cross-linking agent reacts due to a long thermal history and the viscosity increases. Gel formation occurs. In particular, in the T-die, when the ethylene copolymer is developed, the contact area between the ethylene copolymer and the inner surface of the mold is increased, and an ethylene copolymer layer having a slow flow rate and easily staying can be formed.

  When the T die is about 80 to 110 ° C., the ethylene copolymer has a high melt viscosity, so that the resin tends to stay on the inner surface of the T die. In addition, when an organic peroxide having a one-hour half-life temperature of 100 to 135 ° C. is blended, if it stays at such a temperature for a long time, the crosslinking reaction proceeds and the ethylene copolymer is thickened. Furthermore, it becomes easy to stay.

  In addition, when the T die is about 110 to 130 ° C., when an organic peroxide having a one-hour half-life temperature of 100 to 135 ° C. is used, a part thereof reacts to increase the viscosity of the ethylene copolymer. However, it tends to stay even at this temperature.

  As described above, when the ethylene copolymer stays in the T-die, thickening and gelation of the staying portion further proceeds due to the heat history. If the viscosity of the ethylene copolymer becomes non-uniform due to thickening or gelation, the flow of the ethylene copolymer in the T die becomes non-uniform, causing a thickness defect or further gelling. The ethylene copolymer is solidified in a part of the inside.

  The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a uniform quality solar cell adhesive sheet that can be stably and efficiently molded.

  The adhesive sheet for solar cells of the present invention is an adhesive sheet for solar cells composed of an ethylene copolymer and an organic peroxide, in which three or more resin sheets are laminated, and the organic peroxide on both outermost layers. 80% by weight or more of the product has a one-hour half-life temperature of 130 ° C. to 160 ° C., and 20% by weight or more of the organic peroxide in the inner layer has a one-hour half-life temperature of 100 ° C. or more and less than 130 ° C. It is characterized by.

  The ethylene-based copolymer used in the present invention is a copolymer of ethylene and a copolymerizable monomer that can be copolymerized with ethylene, and the copolymerizable monomer is from the viewpoint of adhesiveness and transparency. , Vinyl acetate, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, maleic acid, maleic anhydride, maleic acid ester and the like. These copolymerizable monomers may be copolymerized with ethylene alone. Two or more kinds of copolymerizable monomers may be copolymerized.

  Although content of the copolymerizable monomer contained in an ethylene-type copolymer is not specifically limited, It is preferable that it is 5 to 50 weight%. If the content of the copolymerizable monomer is less than 5% by weight, the transparency after the formation of the solar cell is insufficient, and the power generation performance of the solar cell may not be sufficient. There is a possibility that it is not satisfactory or the strength of the solar cell sheet is insufficient.

  The ethylene copolymer is preferably an ethylene-vinyl acetate copolymer, and the ethylene-vinyl acetate copolymer preferably has a vinyl acetate content of 5 to 50 parts by weight.

  The adhesive sheet for a solar cell of the present invention is formed by laminating three or more resin sheets made of an ethylene copolymer and an organic peroxide, and is 80% by weight of the organic peroxide added to both outermost layers. The above is the organic peroxide having a one-hour half-life temperature of 130 ° C to 160 ° C.

  When the ratio of the organic peroxide having a 1-hour half-life temperature of 130 ° C. to 160 ° C. is less than 80% by weight, the effect of preventing the stay in the T die without reducing the crosslinking rate of the entire solar cell adhesive sheet. Is not enough.

  Examples of the organic peroxide having a one-hour half-life temperature of 130 ° C. to 160 ° C. include di (2-t-butylperoxyisopropyl) benzene (one-hour half-life temperature 138 ° C.), dicumyl peroxide (same as above). 136 ° C), di-t-hexyl peroxide (136 ° C), 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (138 ° C), t-butylcumyl peroxide (same as above) 137 ° C), di-t-butyl peroxide (144 ° C), p-menthane hydroperoxide (151 ° C), 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 (150 degreeC), etc. are mentioned, These organic peroxides may be used independently and 2 or more types may be used together.

  The inner layer of the adhesive sheet for solar cells of the present invention is also composed of an ethylene copolymer and an organic peroxide, and 20% by weight or more of the organic peroxide has a one-hour half-life temperature of 100 ° C. or higher and lower than 130 ° C. .

  When the proportion of organic peroxide having a one-hour half-life temperature of 100 ° C. or more and less than 130 ° C. is less than 20% by weight, the cross-linking reaction of the ethylene copolymer takes time in the bonding step of the solar cell module, and the production efficiency Becomes worse.

  Examples of the organic peroxide having a one-hour half-life temperature of 100 ° C. or more and less than 130 ° C. include 1,1-di (t-butylperoxy) -2-methylcyclohexane (one-hour half-life temperature 102 ° C.), 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane (106 ° C.), 1,1-di (t-hexylperoxy) cyclohexane (107 ° C.), 1,1- Di (t-butylperoxy) cyclohexane (at 111 ° C.), 2,2-di (4,4-di- (t-butylperoxy) cyclohexyl) propane (at 114 ° C.), t-hexylperoxyisopropyl mono Carbonate (115 ° C), t-butylperoxymaleic acid (119 ° C), t-butylperoxy-3,5,5-trimethylhexanoate (119 ° C), t- Tilperoxylaurate (118 ° C), 2,5-dimethyl-2,5-di- (3-methylbenzoylperoxy) hexane (117 ° C), t-butylperoxyisopropyl monocarbonate (118 ° C) ), T-butylperoxy 2-ethylhexyl monocarbonate (119 ° C.), t-hexyl peroxybenzoate (119 ° C.), 2,5-dimethyl-2,5-di (benzoylperoxy) hexane (119) ° C), t-butyl peroxyacetate (121 ° C), 2,2-di (t-butylperoxy) butane (122 ° C), t-butylperoxybenzoate (125 ° C), n-butyl- 4,4-di- (t-butylperoxy) valerate (127 ° C.) and the like, and these organic peroxides may be used alone. And, or two or more of them may be used in combination.

  Further, 80% by weight or more of the organic peroxide added to the inner layer is preferably an organic peroxide having a one-hour half-life temperature of 100 ° C. or more and less than 160 ° C. When the ratio of the organic peroxide having a one-hour half-life temperature of 100 ° C. or more and less than 160 ° C. is less than 80% by weight, the effect of preventing retention in the T die without reducing the crosslinking rate of the entire solar cell adhesive sheet. Is not enough.

  The gel fraction after heat bonding of the solar cell bonding sheet of the present invention is preferably 70% by weight or more in order to impart sufficient heat resistance. In order to make the gel fraction 70% by weight or more, the amount of the organic peroxide added to 100 parts by weight of the ethylene copolymer is preferably 0.3 to 3 parts by weight.

  When the amount of the organic peroxide added is less than 0.3 parts by weight, it is difficult to obtain a gel fraction of 70% by weight or more. In addition, when it is added in an amount of more than 3 parts by weight, the durability is not improved so much, and there is a possibility that bubbles are generated during the production of the solar cell or the sheet is likely to be colored.

  You may add a coupling agent to the adhesive sheet for solar cells of this invention as needed. The coupling agent has an effect of improving the adhesion between the solar cell adhesive sheet, the solar cell element, and the upper and lower protective materials.

  As the coupling agent, a silane coupling agent having one or more functional groups selected from the group consisting of an amino group, a glycidyl group, a methacryloxy group, and a mercapto group is preferably used. Examples thereof include propyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane, and one or more of these are preferably used.

  The coupling agent need only be added to the outermost layers on both sides, and the coupling agent need not be added to the inner layer.

Furthermore, one type or two or more types of additives such as a crosslinking aid, an antioxidant, and an ultraviolet absorber may be added to the solar cell adhesive sheet of the present invention as necessary.
A well-known additive can be used as the additive, and the addition amount may be added within a range that does not impair the achievement of the object of the present invention.

  For forming the solar cell adhesive sheet of the present invention, a general multilayer T-die extruder can be used. For example, two or more extruders are used, and the resin composition for both outermost layers and the inner layer are used. The resin composition is melt-kneaded at a temperature at which the organic peroxide is not substantially decomposed, extruded with a multilayer T-die extruder, and the molten resin sheet extruded from the T-die is cooled and solidified with a cooling roll, Wind up.

  The melt-kneading is preferably carried out at a temperature lower by 10 ° C. or more than the one-hour half-life temperature of the organic peroxide used. When two or more organic peroxides are used, it is preferable to melt knead at a temperature lower by 10 ° C. or more than the lowest one-hour half-life temperature.

  The solar cell bonding sheet of the present invention preferably has an embossed pattern on the surface of the sheet in order to improve the deaeration property in the laminating process of the solar cell module. Examples of the method for shaping the embossed pattern on the surface of the sheet include a method of niping with a cooling roll having an embossed pattern on the surface immediately after the molten resin is extruded from the T die, A known embossing method such as a method of heating and nipping between an embossing roll and a rubber roll can be used.

  Since the configuration of the solar cell adhesive sheet of the present invention is as described above, it can be stably and efficiently molded, and the obtained solar cell adhesive sheet has a uniform quality and is bonded to the solar cell module. Productivity in the process is improved.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Examples 1-3)
100 parts by weight of ethylene-vinyl acetate copolymer (vinyl acetate content 25% by weight, MFR 20 g / 10 min), 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (antioxidant) and 0.3 parts by weight of 2-hydroxy-4-methoxybenzophenone (ultraviolet absorber) and predetermined amounts of organic peroxide, triallyl isocyanurate (crosslinking aid) and 3-glycidoxypropyltrimethoxy shown in Table 1 A resin composition composed of silane (coupling agent) is supplied to a feed block from three extruders, extruded at a resin temperature of 120 ° C. by a T-die method, and has a thickness of 0.6 mm and a width of 1250 mm. A layered solar cell adhesive sheet was obtained. The thickness ratio between the outermost layer on both sides and the inner layer was 1/2/1.

  The gel fraction and the cold / humidity heat cycle test of the obtained adhesive sheet for solar cells were performed, and the results are shown in Table 1. In addition, the gel fraction and the method of the cold and wet heat cycle test were as follows.

  (1) Gel fraction It measured 2 points | pieces (5 cm and center from an edge part) in the width direction of the adhesive sheet for solar cells obtained 1 hour after the extrusion start, and 24 hours after. In addition, the gel fraction after the solar cell adhesive sheet was sandwiched between release sheets and crosslinked by heating at 150 ° C. for 10 minutes was measured. The gel fraction was determined by immersing 0.2 g of the sample in 50 ml of xylene, heating and dissolving at 110 ° C. for 12 hours, filtering off the insoluble matter with a 200 mesh wire net, drying under reduced pressure at 80 ° C. for 4 hours, and then insoluble. It is expressed as% by weight relative to the sample for minutes.

  (2) Cold and wet heat cycle test Between the obtained two solar cell adhesive sheets, a plurality of solar cell silicon semiconductor wafers were arranged in series using an interconnector, and a transparent flat glass was placed on the upper surface of the upper sheet. Then, a polyvinyl fluoride resin sheet was superposed on the lower surface of the lower sheet, and heated and bonded for 10 minutes under a heating temperature of 150 ° C., a reduced pressure of 10 mmHg, and an atmospheric pressure press to produce a solar cell module.

  The obtained solar cell module was allowed to stand at −20 ° C. for 6 hours, then heated from −20 ° C. to + 85 ° C. over 1 hour, left in an atmosphere of + 85 ° C. and 85% RH for 6 hours, and then +85 The process of cooling from 1 ° C. to −20 ° C. for 1 hour was defined as 1 cycle, and the appearance of the solar cell module after 10 cycles was visually observed to determine the presence or absence of abnormalities such as discoloration and peeling.

(Comparative Examples 1 and 2)
100 parts by weight of ethylene-vinyl acetate copolymer (vinyl acetate content 25% by weight, MFR 20 g / 10 min), 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (antioxidant) and 0.3 parts by weight of 2-hydroxy-4-methoxybenzophenone (ultraviolet absorber) and predetermined amounts of organic peroxide, triallyl isocyanurate (crosslinking aid) and 3-glycidoxypropyltrimethoxy shown in Table 1 A single-layer solar cell having a thickness of 0.6 mm and a width of 1250 mm is obtained by extruding a resin composition made of silane (coupling agent) from one extruder and extruding it at a resin temperature of 120 ° C. by a T-die method. An adhesive sheet was obtained.

  The adhesive sheet for solar cells obtained in Comparative Example 1 has a thickness that gradually decreases with the passage of time, and the resin is clogged at both ends of the T die in 3 hours after the start of extrusion, thereby obtaining a stable product. could not. Since a stable sheet was not obtained, a solar cell module could not be produced.

  The gel fraction and the cold / humidity heat cycle test of the obtained solar cell adhesive sheet were carried out in the same manner as in Example 1, and the results are shown in Table 1. In addition, the gel fraction after bridge | crosslinking measured the adhesive sheet center part for solar cells 1 hour after the extrusion start.

(Comparative Examples 3 and 4)
100 parts by weight of ethylene-vinyl acetate copolymer (vinyl acetate content 25% by weight, MFR 20 g / 10 min), 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol (antioxidant) and 0.3 parts by weight of 2-hydroxy-4-methoxybenzophenone (ultraviolet absorber) and predetermined amounts of organic peroxide, triallyl isocyanurate (crosslinking aid) and 3-glycidoxypropyl-methoxy shown in Table 1 A resin composition composed of silane (coupling agent) is supplied to a feed block from three extruders, extruded at a resin temperature of 120 ° C. by a T-die method, and has a thickness of 0.6 mm and a width of 1250 mm. A layered solar cell adhesive sheet was obtained. The thickness ratio between the outermost layer on both sides and the inner layer was 1/2/1. The 1-hour half-life temperature of dibenzoyl peroxide used in Comparative Example 4 was 92 ° C.

  The gel fraction and the cold / humidity heat cycle test of the obtained solar cell adhesive sheet were carried out in the same manner as in Example 1, and the results are shown in Table 1.

  In the solar cell adhesive sheet obtained in Comparative Example 3, the thickness of the end portion gradually decreases with time, and the resin is clogged at both ends of the T die in 5 hours after the start of extrusion, and a stable product can be obtained. There wasn't.

  Although the gel fraction of the obtained adhesive sheet for solar cells was measured in the width direction in the same manner as in Example 1, it was measured only 1 hour after the start of extrusion. Moreover, since the stable solar cell adhesive sheet was not obtained, the solar cell module was not able to be produced. The gel fraction after crosslinking was measured at the center of the sheet 1 hour after the start of extrusion.

Claims (4)

  An adhesive sheet for a solar cell, which is made of an ethylene copolymer and an organic peroxide and is laminated with three or more resin sheets, wherein 80% by weight or more of the organic peroxide on both outermost layers is 1 hour. An adhesive sheet for solar cells, wherein the half-life temperature is 130 ° C to 160 ° C, and 20% by weight or more of the organic peroxide in the inner layer has a one-hour half-life temperature of 100 ° C to less than 130 ° C.   The solar cell adhesive sheet according to claim 1, wherein 80% by weight or more of the organic peroxide in the inner layer has a one-hour half-life temperature of 100 ° C or higher and lower than 160 ° C.   3. The solar cell adhesive sheet according to claim 1, wherein the resin sheet comprises 100 parts by weight of an ethylene copolymer and 0.3 to 3 parts by weight of an organic peroxide, respectively.   4. The solar cell adhesive sheet according to claim 1, wherein a coupling agent is added only to the outermost layers on both sides.