JP4513204B2 - Sealing film for solar cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solar cell sealing film, in particular, a solar cell sealing film made of an ethylene-vinyl acetate copolymer resin, in which a solar cell is damaged in a sealing step during solar cell production. The present invention relates to a solar cell sealing film to be prevented.
[0002]
[Prior art and prior art]
In recent years, solar cells that directly convert sunlight into electric energy have attracted attention and are being developed from the viewpoint of effective use of resources and prevention of environmental pollution.
[0003]
As shown in FIG. 16, a solar cell generally includes an ethylene-vinyl acetate copolymer resin (EVA) film 13 </ b> A between a glass substrate 11 as a front surface side transparent protective member and a back surface side protective member (back cover) 12. It is set as the structure which sealed the cell for solar cells, such as the silicon power generation element 14, with the sealing film of 13B.
[0004]
In such a solar cell, the glass substrate 11, the sealing film EVA film 13 </ b> A, the silicon power generation element 14, the sealing film EVA film 13 </ b> B and the back cover 12 are laminated in this order, and heated and pressurized to cross-link the EVA. Manufactured by curing and adhesive integration.
[0005]
Note that the sealing film EVA films 13A and 13B are generally formed by a T-die method, a calendar method, or the like in which a molten resin is extruded from a die having a linear slit and rapidly cooled and solidified by a cooling roll or a water tank.
[0006]
By the way, when the solar cell is manufactured, the EVA film is pressed against the solar cell at the time of heating and pressurization in the sealing step, and thus the solar cell is broken by this pressing force. In addition, there has been a problem that the yield of the product is reduced due to the air being entrained due to poor deaeration at the time of sealing, or when the EVA film flows and the resin protrudes when heated and pressurized.
[0007]
Conventionally, in order to improve the deaeration failure at the time of sealing, it has been proposed to emboss an EVA film to form a recess on the film surface (Japanese Patent Publication No. 1-52428).
[0008]
In addition, the applicant firstly increases the depth of the recesses by embossing, thereby improving the solar cell damage, deaeration failure, resin outflow, etc. in the sealing process during solar cell production. A battery sealing film was proposed (Japanese Patent Application No. 2000-227388).
[0009]
[Problems to be solved by the invention]
If it is an embossed film, poor deaeration, damage to solar cell cells, resin flow, etc. are prevented, but it cannot be said that a sufficiently satisfactory effect has been obtained. Improvement is desired.
[0010]
In particular, in recent years, it has been required to reduce the thickness of the solar cell in order to reduce the amount of silicon constituting the solar cell and to reduce the cost. In this case, the solar cell is more likely to be damaged and removed. Development of a sealing film for solar cells that can further alleviate the strain applied to the cells for solar cells at the time of sealing, and can reliably prevent air bubbles from remaining because it is likely to cause illness. Is desired.
[0011]
Accordingly, the present invention can more reliably prevent solar cell damage, degassing failure, resin outflow, etc. in the sealing process during solar cell production, and efficiently produce solar cells with high yield. It aims at providing the sealing film for solar cells which can be performed.
[0012]
[Means for Solving the Problems]
This onset Ming solar cell sealing film, ethylene - by embossing a film obtained by forming a vinyl acetate copolymer resin, by forming a plurality of recesses in the film plane solar cell The sealing film for solar cells is provided with a concave groove as a communication path communicating between the adjacent concave portions, wherein the concave portion has a circular shape in plan view and a diameter R of 0.1. ˜2 mm, and the width W of the groove as the communication path is 0.1 to 1 mm .
[0013]
In the case of a film in which recesses are formed by embossing, when sealing a solar cell, when the local pressing force is concentrated, the stress is absorbed by the cushion effect on the recess forming surface, and the solar cell. Since the concentration of local stress on the solar cell can be prevented, damage to the solar cell can be prevented. In addition, the embossed uneven surface can enhance the deaeration at the time of sealing and prevent the protrusion due to the flow of the resin at the time of heating and pressing.
[0014]
However, in a film in which a recess is simply formed by embossing, air is enclosed in the recess during sealing, and sufficient cushioning and stress absorption performance may not be obtained due to the repulsive force of the enclosed air. . That is, in a film having a recess, when the film surface is brought into surface contact with the object to be sealed at the time of sealing, the recess becomes a sealed space covered with the object to be sealed, and the air escape space Disappears. In addition, degassing may be caused by trapping air in the recess.
[0015]
In the present invention, since the communication path communicating between the recesses by embossing is provided, the air can escape from the communication path to the adjacent recesses, and the containment of the air in the recesses is prevented, and sufficient cushioning properties and stress are provided. Absorbability can reliably prevent cell breakage and poor deaeration. Moreover, the protrusion of the resin due to the flow of the resin is also effectively prevented.
[0016]
In particular, it is preferable to provide a communication path that communicates with the film end face because air can be discharged out of the film. Moreover, it is preferable that two or more communication paths communicating with the film end face are provided.
[0017]
In the present invention, the recesses by embossing may be provided on both sides of the film, and in this case, the communication path is preferably provided on both sides of the film .
[0018]
Et styrene - In the solar cell sealing film consisting of the film obtained by forming a vinyl acetate copolymer resin, if sealing film solar cell formed in a large number of protrusions on the film surface, Since the convex portion is provided instead of the concave portion, there is no problem of the above-described air containment, and the convex and concave surface cushioning property and the stress absorption property by the convex portion can surely prevent cell breakage and poor deaeration. it can. Moreover, the protrusion of the resin due to the flow of the resin is also effectively prevented.
[0019]
In this solar cell sealing film, projections, arbitrary preferable to be formed at regular equidistant to the film surface.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
1 to 6 are views illustrating an embodiment of the sealing film present onset Ming solar cell, each part (a) shows is a plan view, (b) drawing (a) view of the line B-B FIG.
[0022]
The solar cell sealing film 1 </ b> A in FIG. 1 is provided with a large number of concave portions 3 and concave grooves 4 as communication passages that connect adjacent concave portions 3, 3 by embossing on one surface of the EVA film 2. Is.
[0023]
The solar cell sealing film 1A in FIG. 1 has the recesses 3 in a staggered arrangement, whereas the solar cell sealing film 1B in FIG. 2 has the recesses 3 arranged at equal intervals in the horizontal and vertical directions. A concave groove 4 is provided between the concave portions 3 and 3 adjacent in the direction.
[0024]
Thus, by providing the concave groove 4 as a communication path that communicates the adjacent concave portions 3 and 3, the air in the concave portion 3 can move to the adjacent concave portion 3. It is possible to prevent the air from being confined in 3, and to obtain good cushioning and stress absorption.
[0025]
As shown in FIGS. 1 and 2, by providing the groove 4 between the adjacent recesses 3 and 3, the air can move between the recesses 3 and 3, but preferably the air is excluded from the sealing interface. It is desirable.
[0026]
The solar cell sealing films 1C, 1D, 1E, and 1F shown in FIGS. 3 to 6 have a concave groove 4A as a communication path communicating with the film end surface of the concave portion 3A closest to the film edge. It is provided. With such solar cell sealing films 1 </ b> C to 1 </ b> F, the air on the sealing surface can be discharged to the film end surface via the recesses 4 and 4 </ b> A, and a much better effect can be obtained.
[0027]
As shown in the solar cell sealing film 1G in FIG. 7, the concave portions 3 and 3A and the concave grooves 4 and 4A may be provided on both surfaces of the EVA film 2. In this case, the projection position of the concave portion 3 is set to EVA. By shifting between one surface and the other surface of the film 2, good cushioning properties, stress absorption properties, and gas venting properties can be obtained.
[0028]
In the present invention, the depth D of the recess 3 (3A) is also different between the case where when the double-sided to provide a recess on one surface of the film, also varies depending on the size and formation ratio of the recess diameter R Is provided with a recess having a depth D of about 20 to 95% of the thickness T of the film so that the total formation area of the recess with respect to the total area of the film is about 20 to 99%. Is preferred.
[0029]
Further, the groove as the communication passage is 50 to 90% of the thickness T of the depth d in view of transfer efficiency of the air film, the width W is Ru Ah at 0.1 to 1 m m.
[0030]
In addition, the cross-sectional shape of the recess is not limited to a semicircle or a semicircle-like shape as shown in FIGS . Planar shape of the recessed portion is circular.
[0031]
Such recesses are preferably provided regularly at equal intervals on one or both sides of the film.
[0032]
Figure 8-15 is a view showing an embodiment of a solar cell sealing film according to the reference example, (a) drawing a plan view of FIG. 8, (b) drawing of (a) Figure B-B It is sectional drawing which follows a line.
[0033]
The solar cell sealing film 1 </ b> H in FIG. 8 is formed by regularly forming a large number of convex portions 5 at equal intervals on one surface of the EVA film 2.
[0034]
Even in such a solar cell sealing film 1H, since air smoothly flows between the convex portions 5 and 5, good cushioning property, stress absorption property and degassing property by the convex portions 5 and 5 are obtained. be able to.
[0035]
The solar cell sealing film 1H in FIG. 8 is provided with a conical convex portion 5. However, the shape of the convex portion is not particularly limited, and is hemispherical like the solar cell sealing film 1I in FIG. The convex portion 5A may be used. Moreover, as shown in the solar cell sealing film 1J of FIG. 10, the frustum-shaped convex part 5B may be sufficient.
[0036]
Further, the shape and arrangement of the projections in plan view are not particularly limited, and as shown in FIG. 11, a solar cell sealing film 1K in which the projections 5C having a square shape in plan view are arranged regularly at regular intervals in a staggered arrangement. There may be.
[0037]
Furthermore, as shown in FIG. 12, a solar cell sealing film 1 </ b> L in which convex portions 5 </ b> D are provided on both surfaces of the EVA film 2 may be used. Thus, when providing the convex part 5D on both surfaces of the EVA film 2, by shifting the projection position of the convex part 5D between one surface and the other surface of the EVA film 2, good cushioning properties and stress Absorption and degassing properties can be obtained.
[0038]
Moreover , what provided the convex part and the recessed part may be sufficient, for example, as shown in FIG. 13, the convex part 5E is provided in one surface of the EVA film 2, and it corresponds to this convex part 5E in the other surface. It may be a solar cell sealing film 1M provided with a recess 3E at a position. In this case, you may provide the ditch | groove as a communicating path which connects between the recessed parts 3E and 3E.
[0039]
Further, as shown in FIG. 14, a solar cell sealing film 1 </ b> N in which convex portions 5 </ b> E and concave grooves 3 </ b> E are alternately and evenly arranged on one surface of the EVA film 2 may be used. Further, as shown in FIG. 15, the solar cell sealing film 1P in which the convex portions 5E and the concave portions 3E are alternately and alternately arranged on both surfaces of the EVA film 2 may be used. The positions of the convex portions 5E and 3E are shifted between the one surface and the other surface, and the concave portion 3E is located on the opposite surface of the film at the position where the convex portion 5E is formed, opposite to the film where the concave portion 3E is formed. By providing the convex portion 5E on the side surface, it is possible to obtain good cushioning properties, stress absorption properties and gas venting properties .
[0040]
The height H of the projection 5,5A~5E, if provided when the both surfaces of providing a protrusion on one surface of the film, or different in the case of providing the projections and recesses, also Ya size of the convex portion Although it depends on the formation ratio, in general, a convex portion with a base diameter R of about 0.1 to 2 mm and a height H of about 20 to 95% of the thickness T of the film is a convex portion with respect to the total area of the film. It is preferable to provide the total formation area of 1 to 50%.
[0041]
In addition, about the recessed part provided with a convex part, it can be set as the depth and diameter similar to the recessed part concerning the above-mentioned this invention, The formation ratio is the sum total of the formation area of the convex part and a recessed part with respect to the total area of a film. It is preferable to provide so that it may become about 20 to 99%.
[0042]
Such a sealing film for a solar cell of the present invention is formed by forming an EVA resin composition containing a crosslinking agent according to a conventional method, and further forming a recess and a groove having a predetermined depth by embossing, Or it can manufacture easily by forming a convex part.
[0043]
In addition, the thickness T of the sealing film for solar cells of the present invention is usually 50 μm to 2000 μm, preferably 100 to 1000 μm, particularly preferably about 200 to 800 μm.
[0044]
Such a solar cell sealing film of the present invention is used so that a concave-convex surface in which concave portions and concave grooves or convex portions are formed becomes a sealing surface.
[0045]
Next, an EVA resin composition suitable as a film forming raw material according to the present invention will be described.
[0046]
The EVA resin used in the present invention has a vinyl acetate content of 40% by weight or less, preferably 10 to 36% by weight, particularly preferably 10 to 33% by weight, and particularly preferably 10 to 26% by weight.
[0047]
When the content of vinyl acetate in the EVA resin exceeds 40% by weight, the resin is very easy to flow and easily flows out from between the glass substrate and the back cover at the time of heat crosslinking. In addition, the tackiness is increased and it becomes easy to tack, and the handleability is deteriorated.
[0048]
EVA resin having a vinyl acetate content of less than 10% by weight has poor processability, and the film is too hard and the deaeration property is poor, and the cells for solar cells are liable to be damaged.
[0049]
The EVA resin used in the present invention preferably has a melt flow rate of 0.7 to 20, more preferably 1.5 to 10.
[0050]
In order to improve weather resistance, the EVA resin composition used in the present invention has a crosslinking structure by adding a crosslinking agent. Generally, the crosslinking agent is an organic peroxide that generates radicals at 100 ° C. or higher. In particular, if the stability at the time of blending is taken into consideration, it is preferable that the decomposition temperature with a half-life of 10 hours is 70 ° C. or higher. Examples of such an organic peroxide include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; -T-butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; dicumyl peroxide; α, α'-bis (t-butylperoxide Oxyisopropyl) benzene; n-butyl-4,4-bis (t-butylperoxy) butane; 2,2-bis (t-butylperoxy) butane; 1,1-bis (t-butylperoxy) cyclohexane 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane; t-butylperoxybenzoate; benzoyl peroxide, etc. Kill. The compounding amount of these organic peroxides is generally 5 parts by weight or less, preferably 1 to 3 parts by weight with respect to 100 parts by weight of the EVA resin.
[0051]
Moreover, a silane coupling agent can be added to EVA resin as a sealing film of a solar cell for the purpose of improving the adhesive force with a power generating element. Known silane coupling agents for this purpose are, for example, γ-chloropropyltrimethoxysilane; vinyltrichlorosilane; vinyltriethoxysilane; vinyl-tris- (β-methoxyethoxy) silane; γ-methacryloxy. Propyltrimethoxysilane; β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; vinyltriacetoxysilane; γ-mercaptopropyltrimethoxysilane; γ-aminopropyltrimethoxysilane N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and the like can be mentioned. The amount of these silane coupling agents is generally 5 parts by weight or less, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the EVA resin.
[0052]
Furthermore, a crosslinking aid can be added to the EVA resin in order to improve the gel fraction of the EVA resin and improve the durability. Examples of crosslinking aids provided for this purpose include trifunctional crosslinking aids such as triallyl isocyanurate; triallyl isocyanate as well as monofunctional crosslinking aids such as NK esters. it can. The amount of these crosslinking aids is generally 10 parts by weight or less, preferably 1 to 5 parts by weight with respect to 100 parts by weight of the EVA resin.
[0053]
Furthermore, hydroquinone; hydroquinone monomethyl ether; p-benzoquinone; methyl hydroquinone, etc. can be added for the purpose of improving the stability of the EVA resin. The amount of these compounds is generally 5 parts by weight with respect to 100 parts by weight of the EVA resin. It is as follows.
[0054]
Furthermore, if necessary, a colorant, an ultraviolet absorber, an anti-aging agent, a discoloration preventing agent and the like can be added in addition to the above. Examples of the colorant include inorganic pigments such as metal oxides and metal powders, and organic pigments such as azo-based, phthalocyanine-based, additive-based, acidic or basic dye-based lakes. Examples of ultraviolet absorbers include 2-hydroxy-4-octoxybenzophenone; benzophenones such as 2-hydroxy-4-methoxy-5-sulfobenzophenone; 2- (2′-hydroxy-5-methylphenyl) benzotriazole Benzotriazoles; phenyl salsylates; hindered amines such as pt-butylphenyl salsylates. Antiaging agents include amines; phenols; bisphenyls; hindered amines, such as di-t-butyl-p-cresol; bis (2,2,6,6-tetramethyl-4-piperazyl). ) Sebacate.
[0055]
In order to manufacture a solar cell using the EVA film thus formed, a glass substrate 11, an EVA film 13A, a silicon power generation element 14, an EVA film 13B and a back cover 12 are laminated as shown in FIG. According to a conventional method, the laminate may be heated and pressure-bonded with a vacuum laminator at a temperature of 125 to 150 ° C., a degassing time of 5 to 12 minutes, a pressing pressure of 0.5 to 1 kg / cm ² , and a pressing time of 8 to 45 minutes. During the heating and pressurization, the EVA films 13A and 13B can be cross-linked to form a sealing film having excellent weather resistance. In this sealing, since the EVA film of the present invention has a good cushioning property, it is possible to prevent cell damage due to the unmelted film being pressed against the cell, and the deaeration property is good. Therefore, there is no problem of air entrainment, and furthermore, there is no problem of resin outflow and tack, and a high-quality product can be manufactured with a high yield.
[0056]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0057]
Example 1
Using an EVA resin composition having the following composition, an EVA film was formed, and by embossing, on one side, a recess having a diameter R = 0.6 mm and a depth D = 300 μm, and a width W for communicating them, W = 0.5 mm A film having a thickness of T = 600 μm and a ditch having a depth of d = 100 μm was obtained. In addition, the shape and arrangement | positioning of a recessed part and a recessed groove are as showing to Fig.6 (a), (b), and the ratio of the formation area of a recessed part with respect to the area of a film is 50%.
[EVA resin composition blend (parts by weight)]
EVA resin (vinyl acetate content 26% by weight): 100
Cross-linking agent (1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane): 2.0
Silane coupling agent (γ-methacryloxypropyltrimethoxysilane)
: 1.0
Cross-linking aid (triallyl isocyanurate): 3.0
UV adsorbent (2-hydroxy-4-octylbenzophenone): 0.3
[0058]
This film is used as the sealing film EVA films 13A and 13B. As shown in FIG. 16, the silicon power generation element 14 is interposed between the glass plate 11 having a thickness of 3 mm and the back cover 12 made of a fluorinated polyethylene film having a thickness of 38 μm. Was sealed to produce a solar cell. The films 13A and 13B were arranged so that their embossed surfaces were on the element 14 side. Sealing was performed by using a vacuum laminator and hot-pressing the hot plate temperature of 150 ° C., degassing time of 5 minutes, pressing pressure of 1 atm, pressing time of 45 minutes, and crosslinking EVA resin.
[0059]
Thus, when 100 solar cells were produced, damage to the element, poor deaeration, poor tack, and no protrusion of EVA resin were observed.
[0060]
Comparative Example 1
When a solar cell was produced in the same manner as in Example 1 except that only the concave portion was formed by embossing and an EVA film without a concave groove was used, cell damage was observed for two out of 100 solar cells.
[0061]
【The invention's effect】
As described above in detail, according to the sealing film for solar cell of the present invention, the sealing film is pressed against the cell for solar cell in the sealing process at the time of manufacturing the solar cell, and the cell is damaged or detached at the time of sealing. It is possible to reliably prevent the occurrence of badness and tack, and to prevent the EVA resin from protruding, so that a solar cell can be manufactured with a high yield.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a solar cell sealing film of the present invention, in which FIG. 1 (a) is a plan view, and FIG. 1 (b) is a sectional view taken along line BB in FIG. It is.
FIGS. 2A and 2B are diagrams showing another embodiment of the sealing film for solar cell of the present invention, in which FIG. 2A is a plan view, and FIG. 2B is along the line BB in FIG. It is sectional drawing.
FIGS. 3A and 3B are diagrams showing another embodiment of the solar cell sealing film of the present invention, in which FIG. 3A is a plan view, and FIG. 3B is a sectional view taken along line BB in FIG. It is sectional drawing.
4A and 4B are diagrams showing another embodiment of the solar cell sealing film of the present invention, in which FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view along line BB in FIG. It is sectional drawing.
5A and 5B are diagrams showing another embodiment of the solar cell sealing film of the present invention, in which FIG. 5A is a plan view, and FIG. 5B is a sectional view taken along line BB in FIG. 5A. It is sectional drawing.
6A and 6B are diagrams showing another embodiment of the solar cell sealing film of the present invention, in which FIG. 6A is a plan view, and FIG. 6B is a sectional view taken along line BB in FIG. It is sectional drawing.
FIG. 7 is a cross-sectional view showing another embodiment of the solar cell sealing film of the present invention.
8A and 8B are diagrams showing a solar cell sealing film according to a reference example, in which FIG. 8A is a plan view, and FIG. 8B is a cross-sectional view taken along line BB of FIG.
FIG. 9 is a cross-sectional view showing a solar cell sealing film according to a reference example .
FIG. 10 is a cross-sectional view showing a solar cell sealing film according to a reference example .
FIG. 11 is a plan view showing a sealing film for a solar cell according to a reference example .
FIG. 12 is a cross-sectional view showing a solar cell sealing film according to a reference example .
FIG. 13 is a cross-sectional view showing a solar cell sealing film according to a reference example .
FIG. 14 is a cross-sectional view showing a solar cell sealing film according to a reference example .
FIG. 15 is a cross-sectional view showing a solar cell sealing film according to a reference example .
FIG. 16 is a cross-sectional view showing a method for manufacturing a solar cell.
[Explanation of symbols]
1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1P Solar cell sealing film 2 EVA film 3, 3A, 3E Recess 4, 4A Recess 5 , 5A, 5B, 5C, 5D, 5E Convex part 11 Glass substrate 12 Back cover 13A, 13B EVA film 14 Silicon power generation element

Claims (5)

By embossing a film obtained by forming an ethylene-vinyl acetate copolymer resin into a film, a solar cell sealing film in which a large number of recesses are formed on the film surface,
A solar cell sealing film provided with a concave groove as a communication path communicating between adjacent concave portions ,
The sealing film for solar cells, wherein the recess has a circular shape in plan view, a diameter R of 0.1 to 2 mm, and a width W of the recess as a communication path is 0.1 to 1 mm .   2. The solar cell sealing film according to claim 1, wherein a communication passage that communicates at least a part of the recess and the film end surface is provided. 3.   The solar cell sealing film according to claim 2, wherein two or more communication passages are provided to communicate the recess and the film end surface.   4. The solar cell sealing film according to claim 1, wherein the embossed recesses are formed on both surfaces of the film.   The solar cell sealing film according to claim 4, wherein the communication path is provided on both surfaces of the film.

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