JP2008159856A - Sealing film for solar battery and solar battery using same sealing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing film for a solar battery which has superior light stability and thermal resistance by suppressing yellowing caused by an influence of light and heat. <P>SOLUTION: Disclosed is the sealing film for the solar battery which contains an ethylene-vinylacetate copolymer, an organic peroxide, an ultraviolet absorber, and a hindered amine stabilizer, the sealing film for the solar battery containing 0.2 to 1.8 parts by mass of the organic peroxide for 100 parts by mass of the ethylene-vinylacetate copolymer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a solar cell sealing film mainly composed of an ethylene-vinyl acetate copolymer and a solar cell using the sealing film, and more particularly to a solar cell sealing film excellent in yellowing prevention and a solar cell. It relates to batteries.

  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.

  As shown in FIG. 1, a solar cell generally has an EVA (ethylene-vinyl acetate copolymer) film sealed between a glass substrate 1 as a front surface side transparent protective member and a back surface side protective member (back cover) 2. It is set as the structure which sealed the cells 4 for solar cells, such as a silicon power generation element, by the stop films 3A and 3B. In the following, the sealing film disposed on the light receiving surface side with respect to the cell is referred to as “front surface side sealing film”, and the sealing film disposed on the rear side of the cell is referred to as “back surface side sealing film”.

  In such a solar cell, the front surface side transparent protective member 1, the front surface side sealing film 3A, the solar cell cell 4, the back surface side sealing film 3B, and the back surface side protective member 2 are laminated in this order, and heated and pressurized. The EVA is manufactured by cross-linking and curing and integrating the EVA.

  In the solar cell, it is strongly desired from the viewpoint of improving power generation efficiency that light incident on the solar cell can be taken into the solar cell as efficiently as possible. Therefore, it is desirable that the sealing EVA film has transparency as high as possible, does not absorb or reflect incident sunlight, and transmits most of sunlight.

  However, when a solar cell is used for a long time, the phenomenon that the EVA film for sealing is yellowed due to the influence of light and heat, and the transmittance of sunlight is reduced, and the appearance due to the yellowing Defects are a problem.

  Due to these problems, means for using various additives such as various organic peroxides and ultraviolet absorbers in the EVA film for sealing have been disclosed. For example, in Patent Document 1, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, which is a peroxyester peroxide, is used as the organic peroxide (crosslinking agent). As a UV absorber, monohydroxyalkoxybenzophenone-based 2-hydroxy-4-n-octoxybenzophenone is used. In Patent Document 2, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane is used as an organic peroxide, and 2-hydroxy-4-same as described above as an ultraviolet absorber. n-Octoxybenzophenone is used.

Japanese Patent Laid-Open No. 08-139347 JP 2000-183381 A

  However, in the conventional solar cell using the sealing EVA film, there has been a problem that the sealing EVA film is still yellowed when used for a long period of time, resulting in a decrease in power generation performance.

  Therefore, an object of the present invention is to provide a solar cell sealing film having excellent light resistance and heat resistance by preventing yellowing due to the influence of light and heat.

  As a result of various investigations in view of the above-mentioned problems, the present invention, as a result of using a film composed of an ethylene-vinyl acetate copolymer, in combination with a hindered amine light stabilizer in addition to an ultraviolet absorber, It has been found that light resistance and heat resistance can be improved by a synergistic effect. Furthermore, in the present invention, as a result of conducting various studies on the type and content of each component in the film, it was found that the light resistance and heat resistance can be further improved by optimizing the content of the crosslinking agent. .

That is, the present invention is a solar cell encapsulating film comprising an ethylene-vinyl acetate copolymer, an organic peroxide, an ultraviolet absorber, and a hindered amine light stabilizer,
The content of the organic peroxide is 0.2 to 1.8 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Solve the problem.

  The preferable aspect of the sealing film for solar cells of this invention is listed below.

  (1) Since the organic peroxide provides a solar cell sealing film having excellent light resistance and heat resistance, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexyne, α, α'-bis (tert-butylperoxy) diisopropylbenzene, dicumyl peroxide, t-butylcumyl peroxide, and At least one selected from the group consisting of 3-di-t-butyl peroxide is used.

  (2) The maximum absorption wavelength of the ultraviolet absorber is 320 to 350 nm.

  (3) The ultraviolet absorber is a benzophenone ultraviolet absorber. Thereby, the photodegradation of the ethylene-vinyl acetate copolymer can be highly prevented.

  (4) The said benzophenone type ultraviolet absorber contains 2 or less hydroxyl groups in 1 molecule.

  (5) Content of the said ultraviolet absorber is 0.1-0.7 mass part with respect to 100 mass parts of said ethylene-vinyl acetate copolymers.

  (6) The mass ratio (P: U) of the organic peroxide (P) and the ultraviolet absorber (U) is 1: 0.1 to 1: 3.5.

  (7) The content of the hindered amine light stabilizer is 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

  (8) The mass ratio (P: H) of the organic peroxide (P) and the hindered amine light stabilizer (H) is 1: 0.1 to 1:10.

  (9) The vinyl acetate unit of the ethylene-vinyl acetate copolymer is 10 to 30 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Thereby, it can be set as the sealing film for solar cells which has the workability desired and the deterioration by light and a heat | fever was highly prevented.

  According to the present invention, even when used for a long period of time, the occurrence of yellowing or the like is remarkably suppressed, and a solar cell sealing film having excellent light resistance and heat resistance can be provided. Furthermore, the solar cell sealing film can maintain high ultraviolet absorptivity for a long period of time, and can suppress deterioration of cells contained in the solar cell. Therefore, the solar cell using such a sealing film for solar cells is also excellent in light resistance and heat resistance.

  The sealing film for solar cells of the present invention contains an ethylene-vinyl acetate copolymer, an organic peroxide, an ultraviolet absorber, and a hindered amine light stabilizer, and the content of the organic peroxide is It is 0.2-1.8 mass parts with respect to 100 mass parts of said ethylene-vinyl acetate copolymers.

  In general, in the production of a sealing film using an ethylene-vinyl acetate copolymer, a crosslinking agent such as an organic peroxide is used in order to improve the crosslinking density of the monomer. However, the use of the organic peroxide can improve the crosslink density and improve the light resistance and the like, while leaving a reaction residue and an unreacted substance in the sealing film. Since such a residue is unstable, when the sealing film containing the residue is irradiated with light containing ultraviolet rays or heated for a long period of time, the residue easily decomposes and radicals are removed. Once generated, once a radical is generated, a new radical is generated in a chain, leading to oxidative degradation of the polymer and yellowing due to the formation of a conjugated double bond.

  Therefore, in the solar cell sealing film of the present invention, an ultraviolet absorber and a hindered amine light stabilizer are used, and further, an organic peroxide used as a crosslinking agent in the ethylene-vinyl acetate copolymer film is used. It has been found that the occurrence of yellowing in the sealing film can be remarkably suppressed by optimizing the content.

  In the solar cell sealing film of the present invention, the organic peroxide content is preferably 0.2 to 1.8 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Is 0.25 to 1.7 parts by mass, more preferably 0.3 to 1.5 parts by mass. Thereby, it can suppress that the reaction residue and unreacted substance of an organic oxide remain in a sealing film. Moreover, there exists a possibility that the time for bridge | crosslinking hardening of a sealing film may become unnecessarily long as content of an organic-ized oxide is less than 0.2 mass part.

  As the organic peroxide used for the solar cell sealing film of the present invention, any organic peroxide can be used as long as it decomposes at a temperature of 100 ° C. or higher to generate radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability. In particular, the one having a decomposition temperature of 70 ° C. or more with a half-life of 10 hours is preferable.

  Examples of the organic peroxide include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5 from the viewpoint of compatibility with the ethylene-vinyl acetate copolymer. -Di (tert-butylperoxy) hexane; 3-di-tert-butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane; 5-dimethyl-2,5-di (tert-butylperoxy) hexyne; dicumyl peroxide; t-butylcumyl peroxide; α, α′-bis (tert-butylperoxyisopropyl) benzene; α, α ′ -Bis (tert-butylperoxy) diisopropylbenzene; n-butyl-4,4-bis (t-butylperoxy) butane; 2,2-bis (t rt-butylperoxy) butane; 1,1-bis (t-butylperoxy) cyclohexane; 1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane; tert-butylperoxybenzoate; Preferred examples include benzoyl peroxide. These may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  Among the organic peroxides, since a solar cell sealing film having excellent light resistance and heat resistance is obtained, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexyne, α, α′-bis (tert-butylperoxy) diisopropylbenzene, dicumyl peroxide, t-butylcumyl peroxide, and 3 It is particularly preferred to use -di-t-butyl peroxide.

  Next, the ultraviolet absorber used in the solar cell sealing film of the present invention absorbs harmful ultraviolet rays in the irradiated light, converts them into innocuous heat energy in the molecule, and photodegradation in the polymer It prevents the starting active species from being excited.

  The ultraviolet absorber can be used without particular limitation as long as it is a conventionally known one. For example, benzophenone series, benzotriazole series, triazine series, salicylic acid series, cyanoacrylate series, etc. can be used. One of these may be used, or two or more may be used in combination.

  Examples of the benzophenone ultraviolet absorber include 2,2′-dihydroxy-4,4′-di (hydroxymethyl) benzophenone, 2,2′-dihydroxy-4,4′-di (2-hydroxyethyl) benzophenone, 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-di (hydroxymethyl) benzophenone, 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-di (2-hydroxy) Ethyl) benzophenone, 2,2′-dihydroxy-3,3′-di (hydroxymethyl) -5,5′-dimethoxybenzophenone, 2,2′-dihydroxy-3,3′-di (2-hydroxyethyl)- 5,5′-dimethoxybenzophenone, 2,2-dihydroxy-4,4-dimethoxybenzophenone and the like can be mentioned.

  Examples of the benzotriazole ultraviolet absorber include 2- [2′-hydroxy-5 ′-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(2-hydroxyethyl). ) Phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5 '-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-methyl-5'- (Hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-methyl-5 ′-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy- 3′-methyl-5 ′-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-tert-butyl-5 ′-( Droxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-t-butyl-5 ′-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy- 3'-t-butyl-5 '-(2-hydroxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5'-(3-hydroxy Propyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-octyl-5 '-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3' -T-octyl-5 '-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-octyl-5'-(3-hydroxypro ) Phenyl] -2H-benzotriazole or the like, or 2,2′-methylenebis [6- (2H-benzotriazoli-2-yl) -4- (hydroxymethyl) phenol], 2,2′-methylenebis [6- ( 2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-methylenebis [6- (5-chloro-2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) ) Phenol], 2,2'-methylenebis [6- (5-bromo-2H-benzotriazoli-2-yl) -4- (2-hydroxyethyl) phenol], 2,2'-methylenebis [6- (2H- Benzotriazoly-2-yl) -4- (3-hydroxypropyl) phenol], 2,2′-methylenebis [6- (5-chloro-2H-benzotria] Zol-2-yl) -4- (3-hydroxypropyl) phenol], 2,2′-methylenebis [6- (5-bromo-2H-benzotriazoly-2-yl) -4- (3-hydroxypropyl) phenol ], 2,2'-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (4-hydroxybutyl) phenol], 2,2'-methylenebis [6- (5-chloro-2H-benzotriazoly- 2-yl) -4- (4-hydroxybutyl) phenol], 2,2′-methylenebis [6- (5-bromo-2H-benzotriazoly-2-yl) -4- (4-hydroxybutyl) phenol], 3,3- {2,2′-bis [6- (2H-benzotriazoly-2-yl) -1-hydroxy-4- (2-hydroxyethyl) phenyl]} propane, 2,2 {2,2′-bis [6- (2H-benzotriazoly-2-yl) -1-hydroxy-4- (2-hydroxyethyl) phenyl]} butane, 2,2′-oxybis [6- (2H-benzotriazolyl -2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] sulfide, 2, 2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] sulfoxide, 2,2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] sulfone, 2,2′-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] amine and the like. It is.

  Examples of the triazine-based ultraviolet absorber include 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-diphenyl-s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4, 6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy -4- (2-hydroxyethyl) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4, 6-diphenyl-s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) s-triazine, 2- [2-hydroxy-4- (3-hydroxypropyl) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (3-hydroxypropyl) phenyl]- 4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2 -Hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl]- 4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl] -4,6-bis (2,4-dimethylphenyl) s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl]- 4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-bis (2-hydroxy-4-methylphenyl) -s- Triazine, 2- [2-hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- ( 2-hydroxyethoxy) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxyl) (Lopyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2 -Hydroxy-4-methylphenyl) -s-triazine, 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol and the like.

  Examples of the salicylic acid-based ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate and the like.

  Examples of the cyanoacrylate ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3′-diphenyl acrylate, ethyl-2-cyano-3,3′-diphenyl acrylate, and the like.

  Further, as the ultraviolet absorber, those having a maximum absorption wavelength in the range of 320 to 350 nm, particularly 325 to 340 nm are preferably used. If it is such an ultraviolet absorber, it can absorb highly the ultraviolet-ray which may cause the photodegradation of an ethylene-vinyl acetate copolymer especially among the ultraviolet rays contained in irradiated light. In addition, the maximum absorption wavelength of an ultraviolet absorber can be measured using the method etc. which are described in the Example mentioned later.

  Of the above-mentioned ultraviolet absorbers, it is preferable to use a benzophenone-based ultraviolet absorber because the photodegradation of the ethylene-vinyl acetate copolymer can be prevented to a high level, and a benzophenone containing two or less hydroxyl groups in one molecule. It is particularly preferable to use a UV absorber. Such ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, and 2-hydroxy-4-n-octoxy-benzophenone. These have a maximum absorption wavelength in the range of 320 to 350 nm, and can highly prevent the photodegradation of the tylene-vinyl acetate copolymer.

  In the solar cell sealing film of the present invention, the content of the ultraviolet absorber described above is 0.1 to 0.7 parts by mass, preferably 0.15 with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. It is good to set it as -0.6 mass part, Most preferably, it is 0.2-0.5 mass part. Thereby, an ultraviolet absorber can exist more stably with respect to irradiation light in a sealing film, and it becomes possible to suppress yellowing of the sealing film for solar cells highly. Furthermore, it is possible to maintain excellent ultraviolet absorption over a long period of time.

  Moreover, in the solar cell sealing film of this invention, mass ratio (P: U) of the said organic peroxide (P) and the said ultraviolet absorber (U) is 1: 0.1-1: 3. 5, more preferably 1: 0.1 to 1: 2. Thereby, yellowing of the solar cell sealing film can be remarkably suppressed.

  Next, the hindered amine light stabilizer used in the solar cell sealing film of the present invention captures radical species harmful to the polymer so as not to generate new radicals. The hindered amine light stabilizer can be used without particular limitation as long as it is a conventionally known one.

  Low molecular weight hindered amine light stabilizers include decanedioic acid bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and Consists of 70% by weight of a reaction product of octane (molecular weight 737) and 30% by weight of polypropylene; bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1 -Dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate (molecular weight 685); bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6 6-pentamethyl-4-piperidyl sebacate mixture (molecular weight 509); bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate ( 481); tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 791); tetrakis (1,2,2,6, 6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 847); 2,2,6,6-tetramethyl-4-piperidyl-1,2,3,4-butane Mixture of tetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate (molecular weight 900); 1,2,2,6,6-pentamethyl-4-piperidyl-1,2,3,4-butane Examples thereof include a mixture (molecular weight 900) of tetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate.

  As the high molecular weight hindered amine light stabilizer, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2, 2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}] (molecular weight 2,000-3,100); succinic acid Polymer of dimethyl and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (molecular weight 3,100 to 4,000); N, N ′, N ″, N ″ ′-tetrakis- ( 4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10- Diamine (molecular weight 2,286) and above A mixture of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol; dibutylamine, 1,3,5-triazine, N, N′-bis (2,2 , 6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate (molecular weight 2,600-3) 400), etc. The above-mentioned hindered amine light stabilizers may be used alone or in a combination of two or more.

  Among these, as hindered amine light stabilizers, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidyl It is preferred to use a mixture of sebacates, as well as methyl-4-piperidyl sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate. Moreover, it is preferable to use a hindered amine light stabilizer having a melting point of 60 ° C. or higher.

  In the solar cell sealing film of the present invention, the content of the hindered amine light stabilizer is 0.1 to 2.5 parts by mass, more preferably 100 parts by mass of the ethylene-vinyl acetate copolymer. It is good to set it as 0.1-1.0 mass part. When the content is 0.1 parts by mass or more, the effect of stabilization is sufficiently obtained, and when the content is 2.5 parts by mass or less, a sealing film by excessive addition of a hindered amine light stabilizer High yellowing can be prevented.

  Moreover, in the solar cell sealing film of this invention, mass ratio (P: H) of the said organic peroxide (P) and the said hindered amine light stabilizer (H) is 1: 0.1-1. : 10, more preferably 1: 0.2 to 1: 6.5. Thereby, yellowing of the solar cell sealing film can be remarkably suppressed.

  In the solar cell sealing film of the present invention, an ethylene-vinyl acetate copolymer (EVA) is used as an organic resin. Furthermore, polyvinyl acetal resins (for example, polyvinyl formal, polyvinyl butyral (PVB resin), modified PVB), and vinyl chloride resins can be used as secondary agents. In that case, PVB is particularly preferable.

  The ethylene-vinyl acetate copolymer may have a vinyl acetate unit of 10 to 30 parts by mass, more preferably 10 to 28 parts by mass, and particularly preferably 22 to 28 parts by mass. When the vinyl acetate content exceeds 30 parts by mass, the viscosity of the resin decreases, and there is a possibility that the resin may easily flow out from between the glass substrate and the back cover during sealing. Furthermore, deterioration due to light or heat can be prevented to a high degree. When the vinyl acetate content is less than 10 parts by mass, the processability is lowered, and the resulting film becomes too hard, so that the deaeration property is lowered, and the cell may be easily damaged during solar cell production.

  The solar cell sealing film of the present invention may further contain a silane coupling agent for the purpose of improving the adhesive force with the power generation element. Known silane coupling agents used 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. These silane coupling agents are used in an amount of 5 parts by mass or less, preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

  Furthermore, the sealing film for solar cells of the present invention is a crosslinking aid (compound having a radical polymerizable group as a functional group) in order to improve the gel fraction of the ethylene-vinyl acetate copolymer and improve the durability. ). Examples of the crosslinking aid provided for this purpose include trifunctional crosslinking aids such as triallyl cyanurate; triallyl isocyanurate, and (meth) acrylic esters (eg, NK ester). A functional or bifunctional crosslinking aid may also be mentioned. These crosslinking aids are generally used in an amount of 10 parts by mass or less, preferably 0.1 to 5 parts by mass, more preferably 0.5 to 3.5 parts by mass with respect to 100 parts by mass of EVA.

  Hydroquinone; hydroquinone monomethyl ether; p-benzoquinone; methyl hydroquinone, etc. can be added for the purpose of improving the stability of the ethylene-vinyl acetate copolymer. These are 100 parts by weight of the ethylene-vinyl acetate copolymer. Generally, it is used at 5 parts by mass or less.

  In the present invention, a colorant, an antiaging agent, a discoloration preventing agent and the like can be further added as necessary. 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 the anti-aging agent include amines, phenols, and bisphenyls.

  The thickness of the solar cell sealing film of the present invention is usually 20 μm to 2 mm.

  The sealing film for solar cells of the present invention can be produced according to a conventional method such as forming a film by heating and rolling the above-described composition containing various components by, for example, extrusion molding or calendering. Alternatively, a sheet-like material can be obtained by dissolving the composition in a solvent and coating the solution on a suitable support with a suitable coating machine (coater) and drying to form a coating film. The heating temperature is generally 50 to 90 ° C.

  According to the present invention described above, the occurrence of yellowing is suppressed, and a solar cell sealing film excellent in light resistance, heat resistance, and weather resistance can be formed. Therefore, by using such a sealing film for a solar cell, even if it is installed over a long period of time in a harsh environment such as an outdoor room that is easily affected by light and heat, the incident light can be efficiently used. It is possible to realize a solar cell that can be taken in and has excellent power generation efficiency.

In order to manufacture a solar cell using the solar cell sealing film of the present invention, as shown in FIG. 1, the front surface side transparent protective member 1, the front surface side sealing film 3A, the solar cell 4 and the back surface side sealing. In laminating the film 3B and the back surface side protective member 2, the surface layer sealing film and the back surface side sealing film are stacked using the sealing film of the present invention, and the stacked body is vacuum laminator according to a conventional method. And pressurizing and pressing at a temperature of 120 to 150 ° C., a degassing time of 2 to 15 minutes, a pressing pressure of 0.5 to 1 kg / cm ² and a pressing time of 8 to 45 minutes.

  By crosslinking the ethylene-vinyl acetate copolymer contained in the front surface side sealing film and the rear surface side sealing film during this heating and pressurization, the front surface side sealing film and the back surface side sealing film are interposed through the front surface side. The solar cell can be sealed by integrating the transparent protective member, the back surface side protective member, and the solar cell.

  In the present invention, the light receiving surface side with respect to the solar battery cell is referred to as “front surface side”, and the surface opposite to the light receiving surface of the solar battery cell is referred to as “back surface side”.

  In the solar cell, the sealing film of the present invention is used for at least one of the front surface side sealing film and the back surface side sealing film, and yellowing based on deterioration due to light or heat can be highly suppressed over a long period of time. Therefore, it is preferably used at least as the front surface side sealing film, and more preferably used as both the front surface side sealing film and the back surface side sealing film.

  The surface side transparent protective member used in the present invention is usually silicate glass. The glass plate thickness is generally 0.1 to 10 mm, preferably 0.3 to 5 mm. The glass substrate is generally chemically or thermally strengthened.

  The back side protective member used in the present invention is generally a plastic film (eg, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE)), but a fluorinated polyethylene film is preferred in consideration of heat resistance.

  In addition, the solar cell of this invention has the characteristics in the sealing film used for the surface side and / or back surface side as above-mentioned. Therefore, the members other than the sealing film such as the front-side transparent protective member, the back-side protective member, and the solar cell need only have the same configuration as the conventionally known solar cell, and are not particularly limited. .

  Hereinafter, the present invention will be described with reference to examples. The present invention is not limited by the following examples.

(Example 1)
100 parts by mass of ethylene vinyl acetate copolymer (vinyl acetate content 26% by mass),
Organic peroxide (2,5-dimethyl-2,5-bis (t-butylperoxy) hexane)
0.5 parts by mass,
UV absorber 1 (2,4-dihydroxybenzophenone, maximum absorption wavelength 327 nm)
0.25 parts by mass,
Light stabilizer (mixture of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidylsebacate)
0.25 parts by mass.

  An EVA film was formed by calendering at 80 ° C. using the composition having the above composition. The thickness of the film was 500 μm.

(Example 2)
An EVA film was formed in the same manner as in Example 1 except that the blending amount of the light stabilizer was 0.1 parts by mass.

(Example 3)
An EVA film was formed in the same manner as in Example 1 except that the amount of the crosslinking agent was 0.3 parts by mass.

Example 4
An EVA film was formed in the same manner as in Example 1 except that the amount of the crosslinking agent was 1.5 parts by mass.

(Comparative Example 1)
An EVA film was formed in the same manner as in Example 1 except that the light stabilizer was not used.

(Comparative Example 2)
An EVA film was formed in the same manner as in Example 1 except that the amount of the crosslinking agent was 2.0 parts by mass.

(Evaluation)
Evaluation of each EVA film produced in Examples and Comparative Examples was performed according to the following procedure.

1. Measurement of maximum absorption wavelength of ultraviolet absorber The ultraviolet absorber was dissolved in toluene, and measured according to JIS-K7361 using a spectrophotometer UV-3100PC (manufactured by Shimadzu Corporation).

2. Durability evaluation EVA film (size 50 x 50 mm) is sandwiched between float glass (thickness 3 mm, size 50 x 50 mm), degassed at 100 ° C for 5 minutes, after degassing, 10 kPa for 10 minutes, Preliminary molding was performed by pressing, followed by heating and pressurizing at 160 ° C. to prepare a sample for measuring yellowing degree. This sample for measuring yellowing degree was irradiated with ultraviolet rays (1000 mW / cm ² ) for 100 hours in an environment of 63 ° C. and 50% RH.

(1) Light resistance The difference (ΔYI) in yellowing degree of the samples for measuring yellowing degree before and after UV irradiation was measured according to JIS-K-7105-6 (1981). The results are summarized in Table 1.

(2) Light transmittance The light transmittance at a wavelength of 330 nm of the sample for measuring yellowing after ultraviolet irradiation was measured using a spectrophotometer (MPC3100, manufactured by Shimadzu Corporation). The results are summarized in Table 1.

It is a schematic explanatory drawing of a general solar cell.

Explanation of symbols

1 surface side transparent protective member,
2 Back side protection member,
3A surface side sealing film,
3B Back side sealing film,
4 Solar cell.

Claims (11)

A sealing film for solar cells comprising an ethylene-vinyl acetate copolymer, an organic peroxide, an ultraviolet absorber, and a hindered amine light stabilizer,
Content of the said organic peroxide is 0.2-1.8 mass parts with respect to 100 mass parts of said ethylene-vinyl acetate copolymers, The sealing film for solar cells characterized by the above-mentioned.   The organic peroxide is 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexyne, α, α It is at least one selected from the group consisting of '-bis (tert-butylperoxy) diisopropylbenzene, dicumyl peroxide, t-butylcumyl peroxide, and 3-di-t-butyl peroxide. The solar cell sealing film according to claim 1.   3. The solar cell sealing film according to claim 1, wherein the ultraviolet absorber has a maximum absorption wavelength of 320 to 350 nm. 4.   The said ultraviolet absorber is a benzophenone series ultraviolet absorber, The sealing film for solar cells of any one of Claims 1-3 characterized by the above-mentioned.   The solar cell sealing film according to claim 4, wherein the benzophenone-based ultraviolet absorber contains 2 or less hydroxyl groups in one molecule.   Content of the said ultraviolet absorber is 0.1-0.7 mass part with respect to 100 mass parts of said ethylene-vinyl acetate copolymers, The any one of Claims 1-5 characterized by the above-mentioned. The sealing film for solar cells as described in any one of.   The mass ratio (P: U) between the organic peroxide (P) and the ultraviolet absorber (U) is 1: 0.1 to 1: 3.5. The sealing film for solar cells of any one of these.   The content of the hindered amine light stabilizer is 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. The sealing film for solar cells of Claim 1.   The mass ratio (P: H) of the organic peroxide (P) and the hindered amine light stabilizer (H) is 1: 0.1 to 1:10. 9. The solar cell sealing film according to any one of 8 above.   The vinyl acetate unit of the ethylene-vinyl acetate copolymer is 10 to 30 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. The solar cell sealing film according to Item. In a solar cell formed by sealing a solar cell by interposing a sealing film between the front surface side transparent protective member and the back surface side protective member and integrating them with each other,
The said sealing film is a sealing film for solar cells of any one of Claims 1-10, The solar cell characterized by the above-mentioned.

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