JP5465804B2 - Sealing film for solar cell - Google Patents

Description

  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.

  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 as a front surface side transparent protective member 1 and a back surface side protective member (back cover) 2. The solar cells 4 such as silicon power generation elements are sealed 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.

  Patent Documents 1 and 2 propose a benzophenone-based ultraviolet absorber, which shows a stabilizing effect, but has a shorter life of the sealing film than the life of the solar battery cell. As a result, the life of the solar battery is less than that of the sealing film. The situation depends on the lifetime, and further stabilization is required for the spread of solar cells.

  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 studies conducted by the inventors in view of the above problems, it is considered that the use of a hindered amine light stabilizer having a specific structure in a film made of an ethylene-vinyl acetate copolymer is conventionally preferred. The present inventors have found that the light resistance can be remarkably improved as compared with the case where the hindered amine light stabilizer is used, and have completed the present invention.

（式中、Ｒ^５はヒドロキシ基で置換されていてもよい炭素原子数１〜１８の直鎖または分岐鎖アルキル基、炭素原子数５〜８のシクロアルキル基を表し、Ｒ^６は炭素原子数１〜２０のアルキル基を表す。）で表されるヒンダードアミン化合物０．０５〜１０重量部を配合したことを特徴とするものである。 That is, the solar cell sealing film of the present invention is represented by the following general formula (IV) with respect to 100 parts by weight of the ethylene-vinyl acetate copolymer.

(In the formula, R ⁵ represents a linear or branched alkyl group having 1 to 18 carbon atoms which may be substituted with a hydroxy group, or a cycloalkyl group having 5 to 8 carbon atoms, and R ⁶ represents the number of carbon atoms. It represents an alkyl group of 1 to 20. The hindered amine compound represented by (1) to (20) is blended in an amount of 0.05 to 10 parts by weight.

  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.

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

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

  As an ethylene-vinyl acetate copolymer used for this invention, it is good that a vinyl acetate unit is 10-30 mass parts, More preferably, it is 10-28 mass parts, Most preferably, it is 22-28 mass parts. When the vinyl acetate content exceeds 30 parts by mass, the viscosity of the resin is lowered, and there is a possibility that the resin may easily flow out between the glass substrate and the back cover during sealing. Furthermore, it becomes easy to receive deterioration by light or heat. 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.

（式中、Ｒ^１、Ｒ^２、Ｒ^３およびＲ^４は各々独立に炭素原子数１〜４の低級アルキル基を、Ｒは水素原子、ヒドロキシ基で置換されていてもよい炭素原子数１〜１８の直鎖または分岐鎖アルキル基、炭素原子数５〜８のシクロアルキル基を表す。）

（式中、Ｒ^５はヒドロキシ基で置換されていてもよい炭素原子数１〜１８の直鎖または分岐鎖アルキル基、炭素原子数５〜８のシクロアルキル基を表す。）

（式中、Ｒ^５はヒドロキシ基で置換されていてもよい炭素原子数１〜１８の直鎖または分岐鎖アルキル基、炭素原子数５〜８のシクロアルキル基を表す。）

（式中、Ｒ^５はヒドロキシ基で置換されていてもよい炭素原子数１〜１８の直鎖または分岐鎖アルキル基、炭素原子数５〜８のシクロアルキル基を表し、Ｒ^６は炭素原子数１〜２０のアルキル基を表す。） As the hindered amine compound used in the present invention, a hindered amine compound having a structure represented by the following general formula (I) is used, and a compound having a structure represented by the following general formula (II) is excellent in weather resistance. A compound having a structure represented by the following general formula (III) or (IV) is particularly preferable because it exhibits a remarkable stabilizing effect.

(Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a lower alkyl group having 1 to 4 carbon atoms, R is a carbon atom having 1 to 1 carbon atoms optionally substituted with a hydrogen atom or a hydroxy group) 18 represents a linear or branched alkyl group and a cycloalkyl group having 5 to 8 carbon atoms.)

(In the formula, R ⁵ represents a linear or branched alkyl group having 1 to 18 carbon atoms which may be substituted with a hydroxy group, or a cycloalkyl group having 5 to 8 carbon atoms.)

(In the formula, R ⁵ represents a linear or branched alkyl group having 1 to 18 carbon atoms which may be substituted with a hydroxy group, or a cycloalkyl group having 5 to 8 carbon atoms.)

(In the formula, R ⁵ represents a linear or branched alkyl group having 1 to 18 carbon atoms which may be substituted with a hydroxy group, or a cycloalkyl group having 5 to 8 carbon atoms, and R ⁶ represents the number of carbon atoms. Represents an alkyl group of 1 to 20.)

Examples of the lower alkyl group having 1 to 4 carbon atoms represented by R ¹ , R ² , R ³ and R ⁴ include a methyl group, an ethyl group, a propyl group and a butyl group.

Examples of the linear or branched alkyl group having 1 to 18 carbon atoms which may be substituted with a hydroxy group represented by R ⁵ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and secondary butyl. Group, tertiary butyl group, isobutyl group, pentyl group, isopentyl group, tertiary pentyl group, hexyl group, heptyl group, n-octyl group, isooctyl group, tertiary octyl group, nonyl group, isononyl group, decyl group, undecyl Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like. These alkyl groups may be substituted with a cycloalkyl group.

Examples of the cycloalkyl group having 5 to 8 carbon atoms represented by R ⁶ include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. These may be substituted with an alkyl group or the like.

It said R ⁵ is represented as a linear or branched alkyl group optionally having 1 to 20 carbon atoms optionally substituted by hydroxy group include the same as described above R ^5.

  Examples of the compound having a partial structure represented by the general formula (II) used in the present invention include No. 1-No. 6 compounds.

  The hindered amine compound is preferably used in an amount of 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and particularly preferably 0.2 to 3 parts by weight with respect to 100 parts by weight of the ethylene-vinyl acetate copolymer. preferable. If the amount is less than 0.05 part by weight, the stabilizing effect cannot be obtained, and if it is used more than 10 parts by weight, the transparency of the resulting resin composition is lowered or the improvement in the stabilizing effect due to the increase is reduced and only the cost is increased. Evil such as that comes to be recognized.

  In the present invention, it is preferable to use a crosslinking agent in the ethylene-vinyl acetate copolymer, and a peroxide or the like is used as the crosslinking agent. Examples of the peroxide used include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane; 3-di-t- T-Dicumyl peroxide; 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane; 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne Dicumyl peroxide; t-butyl cumyl peroxide; α, α′-bis (tert-butylperoxyisopropyl) benzene; α, α′-bis (tert-butylperoxy) diisopropylbenzene; n-butyl-4 2,2-bis (tert-butylperoxy) butane; 2,2-bis (tert-butylperoxy) butane; 1,1-bis (t-butyl) Peroxy) cyclohexane; 1,1-bis (tert- butylperoxy) -3,3,5-trimethylcyclohexane; tert-butyl peroxybenzoate; and benzoyl peroxide.

  In general, in the production of a sealing film using an ethylene-vinyl acetate copolymer, a crosslinking agent such as the above 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, the content of the organic peroxide used as a crosslinking agent in the hindered amine light stabilizer having a specific structure and the ethylene-vinyl acetate copolymer film is optimal. Is preferable.

  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 peroxide remain in a sealing film. Moreover, when content of an organic peroxide is less than 0.2 mass part, there exists a possibility that the time for bridge | crosslinking hardening of a sealing film may become unnecessarily long.

  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.

  Since the sealing film for solar cells of the present invention improves weather resistance, it is preferable to use the hindered amine light stabilizer and the ultraviolet absorber in combination. As a ultraviolet absorber used, if it is a conventionally well-known thing, it can use together, without being restrict | limited in particular. 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 -T-butyl-5 '-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5'-(2-hydroxyethyl) phenyl] -2H-benzo Triazole, 2- [2′-hydroxy-3′-t-butyl-5 ′-(2-hydroxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2′-hydroxy-3′-t -Butyl-5 '-(3-hydroxypropyl) 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-hydroxypropyl) phenyl] -2H-benzotriazole or the like, or 2,2′-methylenebis [6- (2H-benzotriazoly-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-benzotriazoly-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-benzotriazoly-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-hydro Ci-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-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-bis [6- (2H-benzotriazolyl) 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-benzotriazo 2-yl) -4- (2-hydroxyethyl) phenol] amine.

  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-hexyloxyphenyl) -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4 -(2-ethylhexyloxy) phenyl] -4,6- (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- {2- (2-ethylhexyloxy) ethyl} phenyl]- 4,6-diphenyl-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-hydroxypropyl) phenyl] -4 , 6-Bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2-hydroxy-4-methyl) Phenyl) -s-triazine, 2,4,6-tris (2,4-bis (2-hydroxyethyloxy) phenyl) -s-triazine, 2,4,6-tris [2-hydro Ci-4- {2- (2-ethylhexanoyloxy) ethyloxy} phenyl] -s-triazine, 2,4,6-tris [2-hydroxy-3-methyl-4- {2- (2-ethylhexa) Noyloxy) ethyloxy} phenyl] -s-triazine 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 cyanoacrylate ultraviolet absorbers include 2-ethylhexyl-2-cyano-3,3′-diphenyl acrylate, ethyl-2-cyano-3,3′-diphenyl acrylate, tetrakis (2-cyano-3,3′- And diphenyl acrylate methyl) methane.

  Further, hindered amine light stabilizers other than the hindered amine compound having the partial structure of the general formula (I) can be used without particular limitation as long as they are conventionally known.

  For example, bis (2,2,6,6-tetramethyl-1 (octyloxy) -decanedioate is used as a low molecular weight hindered amine light stabilizer that can be used in combination with the hindered amine light stabilizer used in the present invention. 4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane reaction product (molecular weight 737) 70% by weight and polypropylene 30% by weight; 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); (2,2,6,6-tetramethyl-4-piperidyl) sebacate (molecular weight 481); tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetra Carboxylate (molecular weight 791); tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate (molecular weight 847); 2,2,6,6 A mixture of tetramethyl-4-piperidyl-1,2,3,4-butanetetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate (molecular weight 900); 1,2,2,6 A mixture of 6-pentamethyl-4-piperidyl-1,2,3,4-butanetetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate (molecular 900), and the like.

  As the high molecular weight hindered amine light stabilizer that can be used in combination with the hindered amine light stabilizer used in the present invention, 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); polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (molecular weight 3,100-4,000); N , N ′, N ″, N ′ ″-tetrakis- (4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazine -2-yl) -4,7 A mixture of diazadecane-1,10-diamine (molecular weight 2,286) and the above 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 combination of two or more. May be.

  The content of the hindered amine light stabilizer that can be used in combination with the hindered amine light stabilizer used in the present invention is 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Part, more preferably 0.1 to 1.0 part by mass. 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.

  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. ). As crosslinking aids used for this purpose, known triaryl cyanurates; trifunctional crosslinking aids such as triallyl isocyanurate, as well as (meth) acrylic esters (eg, NK esters, etc.) 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.

  Although the thickness of the sealing film for solar cells of this invention is not specifically limited, Usually, what is necessary is just to be 20 micrometers-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 this invention, generation | occurrence | production of yellowing is suppressed and the sealing film for solar cells excellent in light resistance, heat resistance, and a 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 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 with the solar cell sealing film of 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 together with the solar cell sealing film of the present invention is generally a plastic film (eg, polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE)). A polyethylene film is preferred.

  The members other than the sealing film, such as the front-side transparent protective member, the back-side protective member, and the solar battery cell, are not particularly limited as long as they have the same configuration as a conventionally known solar battery.

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

(Example 1 and Comparative Examples 1-1 to 1-8)
An EVA film was formed by calendering at 80 ° C. using a composition having the following composition. The thickness of the film was 500 μm.
Ethylene vinyl acetate copolymer (vinyl acetate content 25% by mass) 100 parts by mass Organic peroxide ^{* 1} 0.5 part by mass Hindered amine compound (described in Table 1) 0.3 part by mass Ultraviolet absorber (described in Table 1) 0 .3 parts by mass Phenolic antioxidant ^{* 2} 0.1 part by weight Phosphorous antioxidant ^{* 3} 0.1 part by weight Calcium stearate 0.05 part by mass * 1: 2,5-dimethyl-2,5-bis (T-Butylperoxy) hexane * 2: Tetrakis (3- (3,5-ditertiarybutyl-4-hydroxyphenyl) propionyloxymethyl) methane * 3: Tris (2,4-ditertiarybutylphenyl) Phosphite

[Evaluation by break time]
Degradation of the obtained EVA film was accelerated with a sunshine weatherometer (black panel temperature 63 ° C., no water spray), and the time until breakage was measured every 120 hours. The results are shown in Table 1 below.

＊４：トリス（２−ヒドロキシ−３−メチル−４−（２−エチルヘキサノイルオキシ）フェニル−ｓ−トリアジン
＊６：（２，２，６，６−テトラメチル−４−ピペリジル）セバケート
＊７：（１，２，２，６，６−ペンタメチル−４−ピペリジル）セバケート
＊８：１，６−ビス（２，２，６，６−テトラメチル−４−ピペリジルアミノ）ヘキサン／２，４−ジクロロ−６−第三オクチルアミノ−ｓ−トリアジン重縮合物

* 4: Tris (2-hydroxy-3-methyl-4- (2-ethylhexanoyloxy) phenyl-s-triazine * 6: (2,2,6,6-tetramethyl-4-piperidyl) sebacate * 7 : (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate * 8: 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / 2,4- Dichloro-6-tert-octylamino-s-triazine polycondensate

(Example 2 and Comparative Examples 2-1 to 2-8)
A film was obtained in the same manner as in Example 1 except that the ethylene vinyl acetate copolymer (vinyl acetate content 25% by mass) was changed to an ethylene vinyl acetate copolymer (vinyl acetate content 6% by mass). As the hindered amine compound and the ultraviolet absorber, those listed in Table 2 below were blended.

[Evaluation by carbonyl index]
The EVA film (size 50 × 50 mm) obtained in Example 2 was sandwiched between float glass (thickness 3 mm, size 50 × 50 mm), degassed at 100 ° C. for 5 minutes, and 10 kPa. Was preformed by pressing for 10 minutes, and then heated and pressurized at 160 ° C. to prepare a sample for measuring weather resistance. This weather resistance measurement sample was measured with a sunshine weatherometer (black panel temperature 63 ° C., without water spray) every 120 hours until the carbonyl index exceeded 1.0.

＊４：トリス（２−ヒドロキシ−３−メチル−４−（２−エチルヘキサノイルオキシ）フェニル−ｓ−トリアジン
＊６：（２，２，６，６−テトラメチル−４−ピペリジル）セバケート
＊７：（１，２，２，６，６−ペンタメチル−４−ピペリジル）セバケート
＊８：１，６−ビス（２，２，６，６−テトラメチル−４−ピペリジルアミノ）ヘキサン／２，４−ジクロロ−６−第三オクチルアミノ−ｓ−トリアジン重縮合物

* 4: Tris (2-hydroxy-3-methyl-4- (2-ethylhexanoyloxy) phenyl-s-triazine * 6: (2,2,6,6-tetramethyl-4-piperidyl) sebacate * 7 : (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate * 8: 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / 2,4- Dichloro-6-tert-octylamino-s-triazine polycondensate

  In Comparative Example 1-7, although molding was possible, there was a problem in workability at the time of preparation of a weather resistance measurement sample because there was a viscous ejection on the film surface.

DESCRIPTION OF SYMBOLS 1 Front surface side transparent protective member 2 Back surface side protective member 3A Front surface side sealing film 3B Back surface side sealing film 4 Cell for solar cells

Claims (2)

For 100 parts by weight of ethylene-vinyl acetate copolymer, the following general formula (IV):

(In the formula, R ⁵ represents a linear or branched alkyl group having 1 to 18 carbon atoms which may be substituted with a hydroxy group, or a cycloalkyl group having 5 to 8 carbon atoms, and R ⁶ represents the number of carbon atoms. A solar cell encapsulating film comprising 0.05 to 10 parts by weight of a hindered amine compound represented by 1 to 20 alkyl groups).   A solar cell, wherein the solar cell sealing film according to claim 1 is used for either one or both of the front surface side sealing film and the back surface side sealing film.

Images