JP3972482B2 - Method for producing thermoplastic resin film for sealing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a sealing thermoplastic resin film, in particular, low shrinkage upon heating, for a suitable sealing as a sealing film for solar cell EVA (ethylene - vinyl acetate copolymer) tree fat film It relates to a method of manufacturing.
[0002]
[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. 2, the solar cell is generally configured such that the silicon power generation element 4 is sealed between the glass substrate 1 and the back cover 2 by sealing films of EVA films 3 </ b> A and 3 </ b> B.
[0004]
In such a solar cell, the glass substrate 1, the sealing film EVA film 3A, the silicon power generation element 4, the sealing film EVA film 3B, and the back cover 2 are laminated in this order, and the EVA is heated and melted to be crosslinked and cured. It is manufactured by bonding and integrating.
[0005]
In the production of such a solar cell, if the shrinkage at the time of heat crosslinking of the sealing film EVA films 3A and 3B is large, the silicon power generation element 4 is damaged by the shrinkage. Therefore, the sealing EVA films 3A and 3B In addition, it is required that the shrinkage during heat crosslinking is small.
[0006]
The EVA film as a sealing film of this solar cell is formed by a T-die method in which a molten resin is extruded from a die having a linear slit and rapidly cooled and solidified with a cooling roll or a water tank.
[0007]
[Problems to be solved by the invention]
However, the EVA film manufactured by the conventional T-die method cannot be said to have a sufficiently small shrinkage at the time of heat crosslinking, and there is a problem of damage to the silicon power generation element, and a high-quality solar cell is manufactured with a high yield. It was difficult.
[0008]
The present invention solves the above conventional problems, shrinkage during heating is small, and an object thereof is to provide a manufacturing method of a preferred EVA fill arm for sealing in particular as a sealing film for solar cell.
[0009]
The method for producing a thermoplastic resin film for sealing according to the present invention is a method for producing a thermoplastic resin film for sealing by forming a molten resin into a film and then cooling, wherein the temperature of the resin film is the thermoplastic resin. A method for producing a sealing thermoplastic resin film in which the resin film is annealed before lowering below the softening point of the resin, wherein the thermoplastic resin raw material is an EVA resin composition containing a crosslinking agent, Annealing treatment is started while the resin film is in the range of 70 to 75 ° C. , and this annealing treatment is performed by maintaining the resin film at 60 to 80 ° C. for 1.0 to 2.0 minutes. and wherein the Rigyo Ukoto.
[0010]
In accordance with the present invention, the annealing process is performed before the temperature of the thermoplastic resin film falls below the softening point of the thermoplastic resin, thereby slowing the rate of temperature reduction of the resin film, and the subsequent heat melting and curing. The amount of shrinkage can be reduced.
[0012]
Specifically, the annealing treatment in the present invention can be performed by heating a resin film conveyed by a conveyor having a plurality of rollers by a heating means. In this case, the roller on the entrance side of the conveyor By making the peripheral speed higher than the peripheral speed of the roller on the outlet side so that a large tension is not applied to the resin film during the annealing process, a good annealing effect can be obtained.
[0013]
The sealing thermoplastic resin film formed in the present invention is particularly suitable as a sealing film for solar cells.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0015]
In the present invention, for example, a molten resin is formed into a film according to a conventional method by a T-die method or the like, and then cooled in a cooling roll or a cooling tank to produce a sealing thermoplastic resin film. Prior to this, when the resin film is at a temperature higher than its softening point, the resin film is annealed as necessary, for example.
[0017]
An annealing method suitable for the present invention will be described below with reference to the drawings.
[0018]
FIG. 1 is a schematic diagram showing an annealing method suitable for the present invention. A resin film 10 is transported by a transport conveyor 12 that transports a film by a plurality of rollers 11, and the resin film 10 being transported is added by a heater 13. Warm and anneal.
[0019]
In such an annealing process, it is preferable that a large tension is not applied to the resin film 10 during the annealing process, and the resin film 10 is heated in a relaxed state. In order to make the resin film 10 slack, it is advantageous to make the peripheral speed of the rollers 11 of the transport conveyor 12 faster on the inlet side and slower on the outlet side.
[0020]
For example, in the conveyor 12 shown in FIG. 1, the peripheral speed of the roller 11A on the inlet side is set to about 1.05 to 1.15 times the peripheral speed of the roller 11B on the outlet side, and the roller between these rollers 11A and 11B It is preferable that the peripheral speed becomes an intermediate peripheral speed, and the peripheral speed of the roller gradually decreases from the inlet side toward the outlet side.
[0021]
In addition, when manufacturing an EVA film according to this invention, while the formed EVA film is in the range of 70 to 75 ° C, the EVA film is heated to 60 to 80 ° C over 1.0 to 2.0 minutes. It intends line annealing by holding.
[0022]
Next, an EVA resin composition suitable as a film-forming raw material when producing an EVA film according to the present invention will be described.
[0023]
The EVA resin according to the present invention preferably has a vinyl acetate content of 25% by weight or less. If the vinyl acetate content is less than 25% by weight, the water vapor transmission rate is too large, and it is difficult to obtain sufficient moisture resistance as a sealing film for solar cells. However, EVA resin with an excessively low vinyl acetate content has poor processability and viscosity becomes too high, and the followability to silicon power generation elements becomes poor when manufacturing solar cells. Therefore, the vinyl acetate content of EVA resin is It is preferably 10% by weight or more.
[0024]
The EVA resin used in the present invention preferably has a melt flow rate of 0.7 to 20, particularly 1.5 to 10.
[0025]
In order to improve durability, the EVA resin composition used in the present invention has a cross-linking structure by adding a cross-linking agent. Generally, as the cross-linking agent, an organic peroxide that generates radicals at 100 ° C. or higher is used. 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.
[0026]
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.
[0027]
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.
[0028]
Furthermore, hydroquinone; hydroquinone monomethyl ether; p-benzoquinone; methyl hydroquinone, etc. can be added for the purpose of improving the stability of the EVA resin, and the blending amount thereof is generally 5 parts by weight with respect to 100 parts by weight of the EVA resin. It is as follows.
[0029]
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.
[0030]
In order to manufacture a solar cell using the EVA film formed according to the present invention, as shown in FIG. 2, a glass substrate 1, an EVA film 3A, a silicon power generation element 4, an EVA film 3B and a back cover 2 are laminated, What is necessary is just to heat-press for about 3-10 minutes at 100-150 degreeC and 1 atmosphere, and EVA film 3A, 3B can bridge | crosslink at the time of this heat pressurization, and the sealing film excellent in the weather resistance can be formed. In this sealing, the EVA film formed according to the present invention has a small shrinkage at the time of heat crosslinking, so that the power generation element can be prevented from being damaged and a high quality product can be manufactured with a high yield.
[0031]
In order to reliably prevent damage to the power generation element in the production of the solar cell, the shrinkage rate of the EVA film when heated at about 140 to 160 ° C., which is the heating crosslinking temperature at the time of ordinary solar cell production ( The shrinkage rate in the flow direction) is preferably 1.5% or less, but according to the present invention, an EVA film having this shrinkage rate of 1.0% or less and extremely low shrinkage during heat crosslinking is formed. be able to.
[0032]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0033]
Example 1
An EVA film was formed using an EVA resin composition having the following composition.
[0034]
[EVA resin composition blend (parts by weight)]
EVA resin (vinyl acetate content 25% by weight, melt flow rate 2.0): 100
Cross-linking agent: 1.5
Silane coupling agent: 0.2
Crosslinking aid: 2.0
While the EVA film formed by the normal T-die method was 75 ° C. or higher, annealing was performed according to the method shown in FIG.
[0035]
As the conveyor 12, a roller having 12 rollers 11 arranged in parallel is used. When the peripheral speed of the roller 11B on the outlet side is 100, the peripheral speed of the roller 11A on the inlet side is 110. The peripheral speed of 2 to 3 rollers following 11A is set to 106 to 107, and the peripheral speed of 3 to 4 rollers following these rollers is set to 102 to 103. The peripheral speed of the roller 11 is changed from the inlet side to the outlet side. The peripheral speed was set so that it gradually decreased toward. Then, the EVA film 10 being transported by the transport conveyor 12 was heated by the heater 13 to be kept at 70 ° C. or higher. This annealing treatment was performed for 1.0 minute.
[0036]
The EVA film after the annealing treatment was cooled with a cooling roll and wound up with a winder.
[0037]
The obtained EVA film was examined for the shrinkage rate (shrinkage rate in the flow direction) when heated to 155 ° C., which is the heating crosslinking temperature at the time of ordinary solar cell production, and found to be 0.3%.
[0038]
Comparative Example 1
In Example 1, an EVA film was formed in the same manner except that the annealing treatment was not performed, and the shrinkage rate was examined in the same manner. As a result, the shrinkage rate was 10%, which was larger than that in Example 1.
[0039]
From the results of the above examples and comparative examples, since the EVA film formed in the present invention has a small shrinkage at the time of heat crosslinking, a high-quality solar cell is produced with a high yield by using this EVA film as a sealing film. You can see that you can.
[0040]
【The invention's effect】
As described above in detail, according to the method for producing a sealing thermoplastic resin film of the present invention, a thermoplastic resin film for sealing that is small in shrinkage at the time of heat curing and that is particularly suitable as a sealing film for solar cells is produced. Can be membrane.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment of an annealing process according to the present invention.
FIG. 2 is a cross-sectional view showing a general solar cell.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Back cover 3A, 3B EVA film 4 Silicon power generation element 10 Resin film 11 Roller 12 Conveyor 13 Heater

Claims (4)

In the method for producing a thermoplastic resin film for sealing by cooling the molten resin into a film shape,
Before the temperature of the resin film drops below the softening point of the thermoplastic resin, a method for producing a sealing thermoplastic resin film for annealing the resin film,
The thermoplastic resin raw material is an EVA resin composition containing a crosslinking agent, and the annealing treatment is started while the resin film is in the range of 70 to 75 ° C. , and this annealing treatment is performed for 1.0 to 2.0 minutes. over the method of sealing a thermoplastic resin film characterized in Rigyo Ukoto by to hold the resin film to 60-80 ° C..   The method for producing a sealing thermoplastic resin film according to claim 1, wherein the annealing treatment is performed by heating a resin film conveyed by a conveyor having a plurality of rollers by a heating means.   3. The method for producing a thermoplastic resin film for sealing according to claim 2, wherein the peripheral speed of the roller on the inlet side of the conveyor is faster than the peripheral speed of the roller on the outlet side.   The method for producing a sealing thermoplastic resin film according to any one of claims 1 to 3, wherein the sealing thermoplastic resin film is a thermoplastic resin for a sealing film of a solar cell.

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