JP2006134970A - Sheet for solar cell sealing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet for solar cell sealing with favorable workability capable of eliminating the crack of a solar cell in the periphery of the solar cell in the case of sealing the solar cell element by a laminating method while, in the future further thinning thickness, prolonging the lifetime of the solar cell element enlarged in the tendency and achieving the capability of the cost reduction. <P>SOLUTION: A sealing sheet 1 for a solar cell has an emboss pattern 10 on the ethylene system copolymerization resin sheet surface with cross-linking ability whose ethylene content is from 62 wt% to 85 wt%; a depth of the valley 11a of the emboss pattern 10 is characteristically made 100 μm or more; the top of the peak 11b of the emboss pattern 10 is characteristically made into curved surface structure (curvature radius of R=0.3-5 mm is preferred), so as to serve as a cushion for a solar cell element and to reduce the abutting pressure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a solar cell sealing sheet suitable for sealing a solar cell between front and back materials made of a plate-like material or sheet-like material such as glass and plastic, in particular, a crosslinking agent and a stabilizer. The present invention relates to a solar cell sealing sheet made of a blended crosslinkable ethylene copolymer resin.

  When sealing a solar cell element by a laminator method, a bimetallic warp (a heating unevenness of the glass plate caused by this) may occur in the glass plate itself. That is, when the glass plate is placed on the laminator hot plate, the laminator method is used to cause a bimetallic warp in the glass plate due to thermal expansion due to a temperature difference between the side in contact with the hot plate and the side not in contact with the hot plate. This is unavoidable. As a result of this warpage, a temperature difference of 50 ° C. was confirmed on the upper surface of the glass plate between the central portion and the peripheral portion (measured by our company). This means that the peripheral part does not melt or is in a high viscosity state even if it melts compared to the center part of the sheet, and stress is applied to the solar cell element due to the pressure of the ethylene-based copolymer resin in the peripheral part. Therefore, there was a problem that the solar cell element was cracked.

  In order to solve the above problems, conventionally developed solar cell sealing sheets include Japanese Patent Publication Nos. 1-52428, 2000-183388, and 2003-51605. Of these, Japanese Patent Publication No. 1-52428 is composed of an organic peroxide-containing EVA (ethylene vinyl acetate copolymer resin) having an embossed pattern with a depth of 30 μm or more on both sides of the sheet, and a solar cell element between the front and back surfaces. When heat-sealing, it is mentioned that it is not charged, does not block, does not generate bubbles, and does not cause abnormalities such as cracking of solar cell elements.

  In addition, the invention of JP 2000-183388 is composed of an organic peroxide-containing EVA having an embossed pattern with a depth of 15 to 50 μm on one side of a sheet, and heat-seals solar cell elements between front and back materials. Occasionally, the solar cell element is not damaged, and bubbles are not generated.

  Further, the invention of Japanese Patent Application Laid-Open No. 2003-51605 comprises an organic peroxide-containing EVA having an embossed pattern with a compression rate at 65 ° C. of 10% or more, and heat-seal the solar cell element between the front and back materials. When it stops, it has mentioned as a characteristic that the crack of a solar cell element can be wiped off.

Furthermore, the invention of Japanese Patent Application Laid-Open No. 2003-204074 uses a sealing film for solar cells in which a groove having a depth of 100 μm or more reaching the end surface is formed on the surface of a specific soft resin film, thereby generating bubbles and sun. The feature is that damage to the battery can be prevented.
Japanese Patent Publication No. 1-52428 JP 2000-183388 A JP 2003-51605 A JP 2003-204074 A

  However, the above conventional solar cell encapsulating sheet (particularly, Japanese Patent Publication No. 1-52428, Japanese Patent Application Laid-Open No. 2000-183388) has a shallow embossed groove depth, or the continuity of the embossed groove. Since the solar cell element is sealed between the front and back surface materials (glass plates) by a laminator method because of insufficient consideration (for example, a diamond lattice as shown in FIG. 7) Gas or ambient air remains between the solar cell element and the solar cell sealing sheet, between the glass plate and the solar cell sealing sheet, and between the back sheet and the solar cell sealing sheet. Therefore, when the created solar cell module is used for a long period of time, the solar cell sealing sheet and the solar cell element or the glass plate or the back sheet are peeled off due to the residual gas or air bubbles. There progresses, as a result, water, allow the penetration of dust or the like, corrosion of the solar cell element, an output drop, it was often a generating various problems such as lowering of the insulation resistance. Therefore, how to reduce the generation of bubbles has been a problem for many years.

  Japanese Patent Application Laid-Open No. 2003-51605 discloses that the depth of the embossed groove is sufficient for cracking of the solar cell element, but the shape of the groove is still sufficient for escape of the generated gas. There was a problem that was not.

  Further, in 2003-204074, the groove of the embossed pattern has a zigzag shape, but the zigzag shape has a V-shaped inflection point, so when considering the escape of gas such as acetic acid gas generated from EVA as described above, There is a problem that gas tends to stay at the V-shaped inflection point and the gas releasing property is insufficient.

  In consideration of gas release properties, it is most desirable that the embossed pattern has a straight line as shown in FIG. 6, but the embossed pattern of the groove on the solar cell sealing sheet is not formed in the solar cell element during laminator molding. There was a problem that the peripheral edge portion was bitten and it was very difficult to adjust delicate positioning.

  The present invention is intended to solve the above-mentioned various problems all at once, and the object of the present invention is to further increase the life and cost of solar cell elements that tend to be thinner and larger in the future. In addition, it is possible to wipe off the cracks of the solar cell element at the periphery when the solar cell element is sealed by the laminator method, and the solar cell seal with good workability by a laminator or the like. It is to provide a stop sheet.

  In order to achieve the above object, the solar cell sealing sheet according to the present invention has an embossed pattern on the surface of a crosslinkable ethylene copolymer resin sheet having an ethylene content of 62% to 85% by weight. In the solar cell sealing sheet, the embossed pattern has a valley depth of 100 μm or more, and the top cross section of the embossed pattern peak has a curved surface structure (preferably a radius of curvature R = 0.3 to 5 mm). And a sufficient cushioning property for the solar cell element and a reduction in the contact pressure.

  Further, the solar cell sealing sheet according to the invention of claim 2 is characterized in that the embossed valley is formed in an S-shaped meandering path from which bubbles generated at the time of lamination can be eliminated, And the embossed pattern is configured not to bite into the peripheral edge of the solar cell element.

  Furthermore, the solar cell sealing sheet according to the invention of claim 3 is characterized in that the crosslinkable ethylene-based copolymer resin sheet is made of an ethylene / vinyl acetate copolymer resin, and the solar cell element is cracked. The sheet not to be generated was configured to be realized by EVA having weather resistance, transparency, flexibility and adhesiveness.

  The present invention provides a solar cell sealing sheet obtained by embossing a surface of a crosslinkable ethylene copolymer resin sheet having an ethylene content of 62% by weight to 85% by weight. And the embossed pattern peak cross section has a curved surface structure. Even if there is a temperature difference between the central part and the peripheral part that occurs during lamination, the depth of the embossed pattern valley There is a height of the peak, sufficient cushioning for the solar cell element is obtained, the contact pressure against the solar cell element is soft, and cracking of the element can be reliably prevented from this surface, and the laminating workability is also good It has various excellent effects.

  The invention according to claim 2 is characterized in that the embossed valley is formed in an S-shaped meandering path from which bubbles generated at the time of laminating can be removed. There is no bite into the peripheral edge of the solar cell, and the laminate workability is further improved.

  Furthermore, since the invention according to claim 3 is characterized in that the ethylene copolymer resin is an ethylene / vinyl acetate copolymer resin, an embossed pattern having sufficient cushioning properties and soft contact pressure is provided. It has an excellent effect that the solar cell sealing sheet can be realized by EVA having weather resistance, transparency, flexibility and adhesiveness.

  Next, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an exploded cross-sectional view showing the usage state of the sealing sheet of the present application, FIG. 2 is a plan view of solar cell elements arranged on the sealing sheet of the present application laid on the back material, and FIG. FIG. 4 is an enlarged sectional view showing a continuous state of valleys and peaks of an embossed pattern, and FIG. 5 is a partially enlarged view showing a curved surface structure of the top of one peak. It is sectional drawing.

  In the figure, 1 is a sealing sheet for the present application. The sealing sheet 1 of the present application is for sealing between a solar cell element 4 and a surface material 2 and a back material (back sheet) 3 made of a plate-like material or sheet-like material such as a glass plate or a plastic plate. It is what is used. That is, as shown in FIG. 1, the surface material (glass plate) 2 / the sealing sheet 1 / solar cell element 4 / the sealing sheet 1 / back surface material (glass plate) 3 are stacked in this order from the top, heated, etc. Thus, the solar cell element 4 is sealed between the front and back surface materials and the back surface material by melting the sealing sheet 1 of the present application. The solar cell elements 4 are arranged in a matrix form on the upper surface of the sealing sheet 1 laid on the back material 3 with appropriate gaps a and b as shown in FIG. A double vacuum laminator is used for sealing the solar cell element 4. Needless to say, the crosslinkable ethylene copolymer resin used here contains an organic peroxide, a silane coupling agent, or a necessary stabilizer.

  The sealing sheet 1 of the present application uses a crosslinkable ethylene-based copolymer resin having a cushioning ethylene content of 62% to 85% by weight, and an embossed pattern 10 is applied to the surface of the sheet. . The embossed pattern 10 may have a stripe shape with a straight path in consideration of the ability to remove bubbles generated during lamination, but in FIG. 3, an S-shaped meander path through which bubbles generated during lamination can be removed. 11 are arranged.

  As shown in FIG. 3, the S-shaped meandering path 11 has a ratio of A: B = 1: 5 to 5: 1 when the meandering pitch is A and the meandering height is B (in FIG. 3, A: B = 3: 1)). That is, the S-shaped meandering path 11 within the above ratio can improve the gas releasing property of the bubbles generated at the time of lamination, and at the same time, can eliminate the catching of the solar cell element 4 on the peripheral edge. In addition, when the ratio of A: B is out of the above range, for example, when the S-shaped curve becomes too loose and close to a linear shape, the solar cell element 4 is caught on the periphery. If the S-shaped curve becomes too steep and becomes a hairpin curve shape, the outgassing property is deteriorated. The width D of the S-shaped meandering path 11 is preferably about 1 to 3 mm.

  As shown in FIG. 4, the valley 11 a constituting the path 11 of the embossed pattern 10 may be defined with a depth C of 100 μm or more, specifically 300 to 700 μm. That is, when the thickness is less than 100 μm, the cushioning property is deteriorated, and the solar cell element 4 is easily cracked. However, since the depth C of the valley 11a corresponds to the height of the peak 11b, it is preferable not to exceed 700 μm. This is because when the sealing sheet 1 of the present application is produced by the T-die sheet extrusion molding method or the calender molding method, the embossing roll is likely to be blocked and the workability of sheet molding may be hindered. Of course, the continuous state of the valleys and peaks of the embossed pattern is not limited to that shown in FIG.

  The cross section of the top portion T of the peak 11b constituting the path 11 has a curved surface structure. This is effective to soften the contact pressure with respect to the solar cell element and reliably prevent element cracking from this surface. The curved surface is not specifically limited, but a curved surface structure having a curvature radius R of 0.3 to 5 mm is preferable. That is, if the curvature radius R of the top portion T is less than 0.3 mm, the effect of reducing the contact pressure of the top portion is not sufficient, and if the curvature radius R of the top portion T exceeds 5 mm, the solar cell sealing sheet This is because there are too many contact surfaces of the solar cell element, and the embossing effect cannot be expected substantially.

  The crosslinkable ethylene copolymer resin used for the sealing sheet 1 of the present application is a copolymer of ethylene as a main component and a monomer copolymerizable therewith, and ethylene, vinyl acetate, propionic acid Copolymers of vinyl esters such as vinyl, copolymers of unsaturated carboxylic esters such as ethylene and methyl acrylate, ethyl acrylate, isobutyl acrylate, nbutyl acrylate, methyl methacrylate, ethylene and acrylic acid, methacryl Copolymers of unsaturated carboxylic acids such as acids or their ionomers, copolymers of α-olefins such as ethylene and propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, Or the mixture of these 2 or more types can be illustrated.

  The crosslinkable ethylene copolymer resin preferably has an ethylene content of 62% to 85% by weight. If the ethylene content is 62% by weight or less, a large amount of gas such as acetic acid is generated during lamination. Thus, not only is not preferable for the above-described reason, but also the softening temperature of the copolymer resin is lowered, a problem of blocking between the solar cell sealing sheets occurs, and the workability is remarkably hindered. On the other hand, when the ethylene content is 85% by weight or more, the amount of gas generated at the time of lamination is reduced, but the solar cell sealing sheet becomes too hard, and the problem of cracking of the solar cell element 4 occurs, which is not preferable. .

  Among these crosslinkable ethylene-based copolymer resins, ethylene / vinyl acetate copolymer resin (EVA) is a sheet for solar cell sealing such as easy availability, moldability, transparency, flexibility, adhesion, and light resistance. Desirable because of its conformity to the required physical properties.

  The organic peroxide contained in the sealing sheet of the present application is used as a crosslinking agent. Specifically, it is preferable to use an organic peroxide having a decomposition temperature (temperature at which the half-life is 1 hour) of 90 to 180 ° C, particularly 120 to 160 ° C. Examples of such an organic peroxide include tertiary butyl peroxyisopropyl carbonate, tertiary butyl peroxyacetate, tertiary butyl peroxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-bis ( Tert-butylperoxy) hexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexyne-3, 1,1-bis (tert-butylperoxy)- 3,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5-bisperoxybenzoate, tert-butyl hydroperoxide, p-menthane hydroperoxide, benzoyl peroxide, p-cloben Peroxide, tert-butylperoxy isobutyrate, hydroxyheptyl peroxide, such as dicyclohexanone peroxide.

  Although such an organic peroxide varies depending on the type, it is preferably blended in an amount of about 1 to 5 parts by weight, preferably about 0.5 to 3 parts by weight with respect to 100 parts by weight of the copolymer resin.

  Moreover, in order to advance such a crosslinking reaction easily, you may use a crosslinking adjuvant. Examples of the crosslinking aid include triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate divinylbenzene, diallyl phthalate and the like. The crosslinking aid is preferably blended in an amount of about 0.5 to 3 parts by weight with respect to 100 parts by weight of the copolymer resin.

  Furthermore, the silane coupling agent contained in the sealing sheet of the present application is used as an adhesion promoter. Specifically, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, γ-glycidoxypropyl-tripyltri-methoxysilane, γ-aminopropyltripyrtrioxysilane, and the like can be used. The amount of the silane coupling agent is preferably about 0.1 to 0.5 parts by weight with respect to 100 parts by weight.

  Furthermore, other various additives are blended in the sealing sheet of the present application. Examples of such additives include ultraviolet absorbers, light stabilizers, antioxidants and the like for preventing deterioration due to ultraviolet rays in sunlight. Specific examples of the UV absorber include 2-hydroxy-4-methoxybenzophenone, 2-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2-carboxybenzophenone, 2-hydroxy-4-n- Benzophenone series such as octoxybenzophenone, 2- (2-hydroxy-3,5-ditert-butylphenyl) benzotriazole, 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy- Benzotriazoles such as 5-tertiary octylphenyl) benzotriazole, and salicylic acid esters such as phenyl salicylate and p-octylphenyl salicylate are used.

  As the light stabilizer, a hindered amine type is used. In addition, as the antioxidant, a hindered phenol type or a phosphite type is used.

  Solar cell (polycrystalline silicon) 160 mm × 160 mm, thickness 200 μm, as shown in FIG. 1, 6 rows × 7 rows = 42 sheets at 2 mm intervals, glass / sheet for sealing this application / solar cell element / sheet for sealing this application / Laminated in order of backsheet. The sealing sheet of the present application uses an ethylene vinyl acetate copolymer resin (EVA, ethylene content 72 wt%, vinyl acetate 28 wt%, MFR 15 g / 10 min, 190 ° C.) as an ethylene copolymer resin, and is described in Table 1. Using a T-die sheet molding machine, a straight embossed pattern was formed on the surface having a thickness of 600 μm, and a curved surface structure having a trough depth of 190 μm and a peak radius of curvature R = 0.7 mm was applied. A sheet was produced. Using the solar cell module laminator (LM110 × 160 manufactured by NPC) using the sheet for sealing of the present application, the glass plate and the back sheet produced in this way, a hot plate temperature of 128 ° C., a vacuum time of 3 minutes, Lamination was performed at a pressure time of 2 minutes, and the number of cracks in the solar cell element was examined. The results shown in Table 2 were obtained.

  In addition, the sheet is sandwiched between two 20 cm square 50 μm thick PET films using a heating press, contact pressure is 0.98 MPa for 1 minute under a temperature condition of 150 ° C., deaeration is performed 10 times, and a pressure state is applied for 15 minutes ( (9.8 MPa) After holding, the number of bubbles generated after taking out and naturally cooling was observed. The results are shown in Table 2.

  Furthermore, in order to confirm the ease of catching of the sheet as confirmation of workability, the embossed pattern surface and the back surface of the sealing sheet described in Example 1 are overlapped with each other by a method based on JISK7125, and the static friction coefficient is measured. Went. The results are shown in Table 2.

  Furthermore, the workability during the laminating work was evaluated. In other words, in the operation of stacking the solar cell sealing sheets at the time of laminating, “○” indicates that the embossed pattern does not get caught on the periphery of the solar cell element and the sheet can be positioned without any problem. An embossed pattern peak was caught at the peripheral edge and the problem that the position of the solar cell element was shifted was determined as “×”, and the middle of both was determined as “Δ”. These results are shown in Table 2.

  Example 1 except that ethylene ethyl acrylate resin (EEA, ethylene content 75% by weight, ethyl acrylate content 25% by weight, MFR 20 g / 10 min, 190 ° C.) was used instead of EVA used in Example 1 above. Evaluation was performed in the same manner. The results are shown in Table 2.

  Evaluation was carried out in the same manner as in Example 1 except that the embossed pattern had a depth of 420 μm and a curved surface structure with a radius of curvature R = 1.7 mm at the top of the peak. These results are shown in Table 2.

  An embossed valley is used as an S-shaped meandering path through which bubbles generated during laminating can be removed, and the valley has a depth of 420 μm and a curved surface structure with a radius of curvature R = 1.7 mm at the top of the peak. Other than that, the evaluation was performed in the same manner as in Example 1. These results are shown in Table 2.

Comparative Example 1

  The number of cracks in the solar cell element, the number of bubbles generated, and the laminate were the same as in Example 1 except that a sheet having a curved surface structure with a radius of curvature R = 0.1 mm at the top of the embossed peak was used. When the workability and the static friction coefficient were examined, the results shown in Table 2 were obtained.

Comparative Example 2

  The number of cracks in the solar cell element, the number of bubbles generated, the laminating workability, and the static friction coefficient were examined in the same manner as in Example 1 except that a sheet having no embossed pattern on the surface was used. Got.

Table 1
Mixing ratio (parts by weight)
EVA 100
Crosslinker 1.2
Silane coupling agent 0.5
Light stabilizer 0.1
Antioxidant 0.05
UV absorber 0.03

Table 2
Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2
Resin EVA EEA EVA EVA EVA EVA
Ethylene% 72 75 72 72 72 72 72
R (mm) 0.7 0.7 1.7 1.7 0.1-
Valley depth μm 190 190 420 420 450 450 −
Valley shape Straight line Straight line S-shaped straight line −
Element crack 0/42 0/42 0/42 0/42 0/42 15/42
Number of bubbles 0 0 0 0 0 0 0
Coefficient of static friction gf 280 250 330 340 600 980
Workability ○ ○ ○ ○ × ×

  From Table 2 above, Example 1 (EVA, ethylene 72%, VA 28%, R = 0.7, straight line) and Example 2 (EEA, ethylene 75%, EA 25%, R = 0.7, straight line), Example 3 (EVA, ethylene 72%, VA 28%, R = 1.7, straight line), Example 4 (EVA, ethylene 72%, VA 28%, R = 1.7, S-shape), solar cell element cracks, bubbles There was no occurrence, the coefficient of static friction was low, and there was no problem in laminating work.

  In Comparative Example 1 (EVA, ethylene 72%, VA 28%, R = 0.1 mm, straight line), the solar cell element cracked and the number of bubbles generated was 0, but the static friction coefficient was high and the laminating workability was poor. It was the result.

  Further, Comparative Example 2 without an embossed pattern had 15 solar cell element cracks. In addition, the coefficient of static friction was high and the laminating workability was poor. From these results, it was possible to solve the problem by deepening the valley of the embossed pattern to prevent cracking of the solar cell element. It was confirmed that the workability was inferior when the top of the was too sharp. On the other hand, it was confirmed that the work could be further facilitated by adding a curved surface structure to the top of the embossed pattern peak.

  The sealing sheet of the present application can achieve further longer life and cost reduction of solar cell elements that tend to be thinner and larger in the future. In addition to the use as a sealing sheet for solar cell elements shown in the above embodiment, it is extremely effective as a measure for preventing bubbles in an intermediate resin film of a laminated glass for crime prevention.

It is a decomposition | disassembly sectional drawing which shows the use condition of the sheet | seat for application sealing. It is a top view of the state which arranged the solar cell element. It is a top view of the sheet | seat for this application sealing which gave the S-shaped meander path | route. It is an expanded sectional view which shows the continuous state of the embossed pattern valley and peak. It is a partial expanded sectional view which shows the curved surface structure of the top part of one peak. It is a top view of the sheet | seat for sealing whose trough of an embossed pattern is a straight line. It is a top view of the sheet | seat for sealing whose trough of an embossed pattern is a diamond lattice.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sheet | seat for sealing this application 2 Surface material 3 Back surface material (back sheet)
4 Battery element 10 Embossed pattern 11 S-shaped meander path (valley)
11a Valley 11b Peak a, b Clearance between solar cell elements A Meander pitch B Meander height C Meander path groove depth D Meander path width

Claims (3)

  In a solar cell sealing sheet obtained by embossing a crosslinkable ethylene-based copolymer resin sheet surface having an ethylene content of 62% by weight to 85% by weight, the embossed pattern has a valley depth of 100 μm or more. In addition, a sheet for sealing a solar cell, characterized in that the top cross-section of the embossed pattern has a curved surface structure.   The solar cell sealing sheet according to claim 1, wherein the embossed valley is formed in an S-shaped meandering path from which bubbles generated during lamination can be detached.   The solar cell sealing sheet according to claim 1 or 2, wherein the crosslinkable ethylene copolymer resin sheet comprises an ethylene / vinyl acetate copolymer resin.

Images