JP2000183388A - Sealing film for solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the damage to a cell of a solar cell in a sealing process in manufacturing a solar battery by using, for a sealing film for a solar cell, a film made by forming a film of a transparent soft resin composition including a cross linking agent and then giving an emboss finish with an uneven face of a specified depth to the film. SOLUTION: A sealing film 1 for a solar cell is provided with an unevenness by an emboss finish. If the depth D of the unevenness on the surface of the film 1 formed by an emboss finish is less than 15 μm, enough cushioning effect cannot be obtained and thereby the damage to a cell cannot be prevented in a sealing process. Therefore, the depth D should be at least 15 μm. However, if the depth D is excessively large, the air is involved at the time of sealing and the air easily stays in an obtained solar cell and therefore the depth D is preferably 50 μm at most. The depth of the uneven face made by an emboss finish is a difference D in height between the top 2A of a projecting section 2 of the uneven face of the film 1 and the bottom 3A of a recessed section 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sealing film for a solar cell, and more particularly to a sealing film for a solar cell obtained by embossing a film obtained by forming a transparent soft resin composition containing a crosslinking agent. The present invention relates to a sealing film for a solar cell, which does not have a problem of damage to a cell for a solar cell in a sealing step at the time of manufacturing a solar cell.

[0002]

2. Description of the Related Art In recent years, solar cells which directly convert sunlight into electric energy have been attracting attention from the viewpoints of effective use of resources and prevention of environmental pollution, and their development has been promoted.

As shown in FIG. 2, a solar cell generally has an EVA film 13 between a glass substrate 11 as a front-side transparent protective member and a back-side protective member (back cover) 12.
The solar cell such as the silicon power generation element 14 is sealed with the sealing films A and 13B.

[0004] Such a solar cell comprises a glass substrate 11,
EVA film 13A for sealing film, silicon power generation element 1
4. EVA film 13B for sealing film and back cover 1
2 are laminated in this order, and heated and pressurized to crosslink and cure the EVA to bond and integrate it.

[0005] The EVA film 13A, 1
3B is 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.

In addition, in various types of adhesive films,
In some cases, a film formed for the purpose of improving the welding property and the pressure-sensitive adhesive property is subjected to embossing to impart unevenness to the surface.

Conventionally, EVA films for sealing films have not been embossed, or even when embossing is performed, the depth of the uneven surface formed is at most about 5 μm. .

[0008]

At the time of manufacturing a solar cell, the unmelted EVA film is pressed against the solar cell at the time of heating and pressing in the sealing step. There was a problem that the solar cell cracked.

The present invention solves the above-mentioned conventional problems and prevents a solar cell from being damaged in a sealing step during the production of the solar cell, thereby enabling a solar cell to be efficiently produced with high yield. It is intended to provide a sealing film for use.

[0010]

Means for Solving the Problems A sealing film for a solar cell according to the present invention is obtained by embossing a film obtained by forming a transparent soft resin composition containing a crosslinking agent. Wherein the depth of the uneven surface formed by the embossing is 15 μm or more.

By forming the uneven surface having a depth of 15 μm or more in this manner, a good cushioning property is imparted to the film. Therefore, even if the unmelted film is pressed in the sealing step, the solar cell The pressure applied to the cell is reduced, and the cell is prevented from being damaged.

In the present invention, the depth of the embossed surface (hereinafter, simply referred to as "depth") refers to the convex portion 2 of the embossed surface of the film 1 in FIG.
Is the height difference D between the top 2A and the deepest portion 3A of the recess 3.

In the present invention, the transparent soft resin constituting the film is preferably an EVA resin.

In particular, in the present invention, embossing
The depth of the uneven surface to be formed is preferably 15 to 50 μm, and in particular, when embossing is performed only on one side of the film, the depth is preferably 15 to 50 μm. When processing is performed on both surfaces of the film, it is preferable that the depth of the one surface is 15 to 50 μm and the total depth of both surfaces is 30 to 100 μm.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a solar cell sealing film of the present invention.

As shown in the figure, the sealing film (film) 1 for a solar cell of the present invention is obtained by embossing a film to have irregularities. In the present invention, when the depth D of the film 1 by embossing is less than 15 μm,
Sufficient cushioning properties cannot be obtained, and damage to cells in the sealing step cannot be prevented. Therefore, the depth D is set to 15 μm or more. However, if the depth D is excessively large, air is entrapped at the time of sealing and air tends to remain in the obtained solar cell. Therefore, the depth D is preferably set to 50 μm or less.

The embossing may be performed only on one side of the film or on both sides. When embossing is performed only on one side of the film, the depth D is 15 to 5
When embossing is performed on both sides of the film, the embossing depth on one side is 15 to 50 μm, and the total of both sides is 30 to 100 μm.
It is preferred that

The sealing film for a solar cell according to the present invention as described above,
Easily manufactured by forming a transparent soft resin composition containing a crosslinking agent, preferably an EVA resin composition, into a film according to a conventional method, and then embossing the film so as to form an uneven surface having a predetermined depth. can do.

The thickness of the solar cell sealing film of the present invention is usually about 50 μm to 2 mm.

Next, an EVA resin composition suitable as a film forming raw material according to the present invention will be described.

The EVA resin used in the present invention preferably has a melt flow rate of 0.7 to 40, particularly preferably 1.5 to 20.

The EVA resin composition used in the present invention has a cross-linking structure by blending a cross-linking agent for improving weather resistance. The cross-linking agent generally generates radicals at 100 ° C. or higher. Organic peroxides are used, and those having a half-life of 10 hours and a decomposition temperature of 70 ° C. or more are particularly preferable in consideration of stability at the time of compounding. Such organic peroxides include, for example, 2,5-dimethylhexane;
2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; 3-
Di-t-butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; dicumyl peroxide;
α'-bis (t-butylperoxyisopropyl) 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 and the like can be used. The compounding amount of these organic peroxides is generally 5 parts by weight or less, preferably 1 to 3 parts by weight, based on 100 parts by weight of the EVA resin.

In addition, a silane coupling agent can be added to the EVA resin as a sealing film of the solar cell for the purpose of improving the adhesive strength with the power generating element. Known silane coupling agents for this purpose, for example, γ-chloropropyltrimethoxysilane; vinyltrichlorosilane; vinyltriethoxysilane; vinyl-tris-
(Β-methoxyethoxy) silane; γ-methacryloxypropyltrimethoxysilane; β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; vinyltriacetoxysilane; γ-mercapto Propyltrimethoxysilane; γ-aminopropyltrimethoxysilane; N-β
-(Aminoethyl) -γ-aminopropyltrimethoxysilane and the like. The amount of the silane coupling agent 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.

Further, the gel fraction of the EVA resin is improved,
A crosslinking aid can be added to the EVA resin to improve durability. Examples of the crosslinking auxiliary used for this purpose include known triaryl isocyanurate; trifunctional crosslinking auxiliary such as triallyl isocyanate;
Monofunctional crosslinking assistants such as K ester can also be mentioned. The amount of these crosslinking aids is generally equal to the amount of EVA resin 1
10 parts by weight or less, preferably 1 to 5 parts by weight with respect to 00 parts by weight
Parts by weight.

Further, for the purpose of improving the stability of the EVA resin, hydroquinone; hydroquinone monomethyl ether; p-benzoquinone; methylhydroquinone and the like can be added. 5 parts by weight or less.

Further, if necessary, a coloring agent, an ultraviolet absorber, an antioxidant, a discoloration inhibitor and the like can be added in addition to the above. Examples of the coloring agent include inorganic pigments such as metal oxides and metal powders, and organic pigments such as azo-based, phthalocyanine-based, azo-based, acidic or basic dye-based lakes. UV absorbers include 2-hydroxy-4-octoxybenzophenone; benzophenones such as 2-hydroxy-4-methoxy-5-sulfobenzophenone; 2- (2'-hydroxy-5-methylphenyl) benzotriazole; Benzotriazoles; phenyl salicylate; pt-
There are hindered amines such as butylphenyl salicylate. As anti-aging agents, amines; phenols;
Bisphenyl type; hindered amine type, for example, di-t-butyl-p-cresol; bis (2,2,6,6
-Tetramethyl-4-piperazyl) sebacate.

To manufacture a solar cell using the EVA film formed as described above, as shown in FIG. 2, a glass substrate 11, an EVA film 13A, a silicon power generation element 14, an EVA film 13B and a back cover 12 are formed. According to a conventional method, the laminate is heated and pressed by a vacuum laminator at a temperature of 100 to 150 ° C., a deaeration time of 5 to 12 minutes, a press pressure of 0.5 to 1 kg / cm ² , and a press time of 8 to 45 minutes. At this time, the EVA films 13A and 13B are crosslinked at the time of heating and pressurization, so that a sealing film having excellent weather resistance can be formed. In this sealing, the EVA of the present invention is used.
Since the film has a good cushioning property, it is possible to prevent the cell from being damaged due to the unmelted film being pressed against the cell, and to produce a high-quality product with good yield.

[0029]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 to 4, Comparative Examples 1 and 2
Using the VA resin composition, an EVA film was formed into a film, and an embossing process was performed to obtain a film on one side of which a D-shaped unevenness having a depth shown in Table 1 was formed. The thickness of the film is 60
0 μm.

[EVA resin composition formulation (parts by weight)] EVA resin (vinyl acetate content 26% by weight, melt flow rate 4.0): 100 Crosslinking agent (1,1-bis (t-butylperoxy) 3) , 3,5-trimethylcyclohexane): 2.0 Silane coupling agent (γ-methacryloxypropyltrimethoxysilane): 1.0 Crosslinking aid (triallyl isocyanurate): 3.0 Ultraviolet adsorbent (2 -Hydroxy-4-octylbenzophenone): 0.3 This film is used as an EVA film for sealing film 13A, 13B.
2 and a glass plate 1 having a thickness of 3 mm as shown in FIG.
1. The silicon power generation element 14 was sealed between the back guard 12 made of a fluorinated polyethylene film having a thickness of 38 μm to manufacture a solar cell. The films 13A, 1
3B was arranged such that the embossed surface was on the element 14 side. The sealing was performed by using a vacuum laminator to heat and press the hot plate at 100 ° C., a deaeration time of 5 minutes, a press pressure of 1 atm, and a press time of 45 minutes to crosslink the EVA resin.

In this way, when 100 solar cells were manufactured, the number of damaged elements and the number of remaining air in the solar cells were examined. The results are shown in Table 1.

[0033]

[Table 1]

According to Table 1, according to the solar cell sealing film of the present invention, cell damage due to the sealing film being pressed against the solar cell in the sealing step at the time of manufacturing the solar cell is effectively prevented. We can see that we can do it.

[0035]

As described in detail above, according to the solar cell sealing film of the present invention, the damage of the cell due to the sealing film being pressed against the solar cell in the sealing step at the time of manufacturing the solar cell. It can be effectively prevented, and a solar cell can be manufactured with a high yield.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of a solar cell sealing film of the present invention.

FIG. 2 is a cross-sectional view illustrating a general solar cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealing film (film) 2 Convex part 2A Top part 3 Concave part 3A Deepest part 11 Glass substrate 12 Back cover 13A, 13B EVA film 14 Silicon power generation element

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) // C08L 31/04 (72) Inventor Susumu Susumu Kadano 4-5-1-1, Maruyamadai, Konan-ku, Yokohama, Kanagawa No. 103 F-term (reference) 4F209 AA10E AH33 PA09 PB01 PC06 PN09 4F213 AA10E AH33 WA12 WA87 WB01 4J002 BB061 EK006 FD146 FD200 GQ00 4M109 AA02 BA03 CA22 EA12 EB02 EB06 EB08 EB18 GA03 EA18 EC05

Claims (5)

[Claims] 1. A solar cell sealing film obtained by embossing a film obtained by forming a transparent soft resin composition containing a cross-linking agent, wherein the depth of the uneven surface formed by the embossing is reduced. 15μ
m or more. 2. The solar cell sealing film according to claim 1, wherein the transparent soft resin is an ethylene-vinyl acetate copolymer resin. 3. The solar cell sealing film according to claim 1, wherein the depth of the uneven surface formed by the embossing is 15 to 50 μm. 4. The method according to claim 3, wherein the embossing is performed.
It is applied only to one side of the film, and the depth of the unevenness is 1
A solar cell sealing film having a thickness of 5 to 50 μm. 5. The method according to claim 3, wherein the embossing is performed.
It is applied to both sides of the film, the depth of the irregularities on one side is 15 to 50 μm, and the total depth of both sides is 30 to 50 μm.
A solar cell sealing film having a thickness of 100 μm.