JP2011119559A - Sealing film for solar cell, and solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell which exhibits high power generation performance, and prevents yellowing of a rear surface protection member. <P>SOLUTION: A pair of two sealing films for solar cell for structuring the solar cell by sealing a cell 14 for the solar cell between a front surface side transparent protection member 11 and a rear surface side protection member 12. The pair of sealing films for solar cell are characterized in that the front surface side sealing film 13A between the cell 14 for the solar cell and the front surface side protection member 11 contains an ethylene-polar monomer copolymer, and a crosslinking agent, and contains ultraviolet absorbent 0.1 pt.mass or less with respect to the ethylene-polar monomer copolymer 100 pts.mass. The rear surface side sealing film 13B between the cell 14 for the solar cell and the rear surface side protection member 12 contains an ethylene-polar monomer copolymer, a crosslinking agent, and colorant. The solar cell uses the sealing films for solar cell. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar cell sealing film mainly composed of an ethylene-polar monomer copolymer and a solar cell using the sealing film, and particularly constitutes a solar cell having high power generation performance and excellent weather resistance. The present invention relates to a solar cell sealing film.

  In recent years, solar cells that directly convert sunlight into electrical energy have been widely used in terms of effective use of resources and prevention of environmental pollution, and further development has been promoted in terms of power generation efficiency and weather resistance. .

  As shown in FIG. 2, the solar cell generally has a surface side transparent protective member 21 made of a glass substrate or the like, a surface side sealing film 23A, a solar cell 24 such as a silicon power generation element, a back side sealing film 23B, And the back-side protection member (back cover) 22 are laminated in this order, deaerated under reduced pressure, and heated and pressurized to cross-link and cure the front-side sealing film 23A and the back-side sealing film 23B to be integrated. It is manufactured by. In the solar battery, a plurality of solar battery cells 24 are connected and used in order to obtain a high electric output. Therefore, in order to ensure insulation between the cells 24 for solar cells, the cells for solar cells are sealed using the sealing films 23A and 23B having insulation properties.

  Conventionally, as a sealing film for solar cells, a film made of an ethylene-polar monomer copolymer such as an ethylene vinyl acetate copolymer (EVA) or an ethylene ethyl acrylate copolymer (EEA) has been used. In particular, an EVA film is preferably used because it is inexpensive and has high transparency. The ethylene-polar monomer copolymer film for the sealing film is crosslinked by using a crosslinking agent such as an organic peroxide in addition to the ethylene-polar monomer copolymer in order to improve the film strength and durability. The density is improved.

  Furthermore, in order to improve the power generation performance of the solar cell, it is necessary to make light enter the solar cell as efficiently as possible and collect it on the solar cell. In general, the organic resin of the surface side sealing film may be deteriorated by sunlight to cause yellowing, and the incident light to the solar battery cell may be reduced. Therefore, for example, the weather resistance can be improved by adding 0.1 to 1.0% by mass of an ultraviolet absorber or 0.05 to 1.0% by mass of a light stabilizer to the organic resin of the surface side sealing film. The reduction of incident light due to yellowing of the organic resin is suppressed (Patent Document 1). Moreover, in patent document 2, the surface side sealing film contains an hindered amine light stabilizer in the organic resin, and the concentration of the ultraviolet absorber in the organic resin is 0.01% by mass or less. Yellowing of the organic resin of the side sealing film is prevented, and a decrease in incident light to the solar battery cell is suppressed.

JP-A-10-112549 JP 2006-66682 A

However, when the ultraviolet light absorber is contained in the organic resin of the surface side sealing film like patent document 1, since the photovoltaic cell is difficult to utilize the light of the ultraviolet region of sunlight, electric power generation performance falls. It will be. On the other hand, when the content of the ultraviolet absorber is reduced as in Patent Document 2, the lower layer member than the surface side sealing film, in particular, the back side protective member made of resin (back cover) is deteriorated by the ultraviolet rays of sunlight. As a result, yellowing causes a problem in appearance.
Accordingly, an object of the present invention is to provide a solar cell that has high power generation performance and in which yellowing of the back surface protection member is prevented.

  The above object is a pair of solar cell sealing films for sealing a solar cell between a front surface side transparent protective member and a back surface side protective member to constitute a solar cell, the solar cell The surface side sealing film between the battery cell and the surface side protective member contains an ethylene-polar monomer copolymer and a crosslinking agent, and the ultraviolet absorber is added to 100 parts by mass of the ethylene-polar monomer copolymer. The backside sealing film between the solar cell and the backside protective member contains an ethylene-polar monomer copolymer, a crosslinking agent, and a colorant. It is achieved by a pair of sealing films for solar cells characterized by including.

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

  By making the content of the ultraviolet absorber in the surface side sealing film as described above, the solar cell can effectively use the light in the ultraviolet region of sunlight incident from the surface side, and has high power generation performance. It can be. Moreover, since the cell for solar cells can use effectively the reflected light of sunlight because the back surface side sealing film contains a coloring agent, it can be set as the solar cell which has higher electric power generation performance. Furthermore, when the back surface side sealing film contains a colorant, it is difficult for ultraviolet rays to reach the back surface side protection member, and yellowing of the back surface side protection member can be prevented.

Preferred embodiments of the pair of solar cell sealing films according to the present invention are as follows.
(1) The surface side sealing film has a light transmittance of 88% or more at a wavelength of 400 nm. (2) The colorant contained in the back side sealing film is titanium dioxide (titanium white). Thereby, the ultraviolet-shielding property can be improved more and the effective utilization of the reflected light of the cell for solar cells can also be improved.
(3) The ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer.
(4) The crosslinking agent is an organic peroxide.

  Further, the object is to provide a solar cell in which a solar cell is sealed by interposing a pair of sealing films between a front surface side transparent protective member and a back surface side protective member. The front-side sealing film between the cell and the front-side protection member, and the back-side sealing film between the solar cell and the back-side protection member are a pair of solar battery seals of the present invention. This is achieved by a solar cell characterized by being a film.

  As described above, by using the front-side sealing film and the back-side sealing film as the pair of solar cell sealing films of the present invention, it has high power generation performance and prevents yellowing of the back-side protection member. Solar cells can be obtained.

  According to the solar cell sealing film of the present invention, since the surface side sealing film easily transmits ultraviolet rays, the solar cell can effectively use the light in the ultraviolet region of sunlight incident from the surface side, and high power generation. A solar cell having performance is obtained. Moreover, since the back surface side sealing film contains the colorant, the solar battery cell can be effectively used for reflected sunlight, and a solar battery having higher power generation performance can be obtained. Furthermore, since the back surface side sealing film contains the colorant, it is difficult for ultraviolet rays to reach the back surface side protection member, and a solar cell in which yellowing of the back surface side protection member is prevented can be obtained.

  Therefore, the solar cell of the present invention is a solar cell that has high power generation performance and prevents yellowing of the back surface protection member.

FIG. 1 is a schematic cross-sectional view for explaining a solar cell sealing film and a solar cell of the present invention. FIG. 2 is a schematic cross-sectional view of a general solar cell.

  Below, the sealing film for solar cells and solar cells of this invention are demonstrated, referring drawings. FIG. 1 is a schematic cross-sectional view for explaining a solar cell sealing film and a solar cell of the present invention. As shown in the drawing, the solar cell sealing film of the present invention is a front side sealing for sealing the solar cell 14 between the front side transparent protective member 11 and the back side protective member (back cover) 12. It is a pair of sealing films composed of a stop film 13A and a back surface side sealing film 13B. The surface side sealing film 13A seals between the solar cell 14 and the surface side transparent protective member 11 (transparent protective member on the light receiving surface side of the solar cell 14), and the back side sealing film 13B is the sun. The space between the battery cell 14 and the back surface side protective member 12 (the protective member on the side opposite to the attending surface of the solar cell 14) is sealed.

In the present invention, among the pair of solar cell sealing films, the surface side sealing film 13A includes an ethylene-polar monomer copolymer and a crosslinking agent, and the content of the ultraviolet absorber is ethylene-polar monomer copolymer. The amount is 0.1 parts by mass or less with respect to 100 parts by mass of the coalescence, and the back side sealing film 13B includes an ethylene-polar monomer copolymer, a crosslinking agent, and a colorant. In some cases, the surface-side sealing film is added with an ultraviolet absorber of 0.1 to 1.0% by mass with respect to the resin as in Patent Document 1. In the present invention, by setting the content of the ultraviolet absorber in the surface side sealing film 13A as described above, the surface side sealing film 13A can easily transmit ultraviolet rays. The solar cell can effectively use the light in the region, and a solar cell having high power generation performance can be obtained. Moreover, since the back surface side sealing film 13B contains colorants, such as a white pigment, since the cell for solar cells can also utilize the reflected light of sunlight effectively, it can be set as the solar cell which has higher electric power generation performance.

  On the other hand, since the content of the ultraviolet absorbent in the surface side sealing film 13A is reduced as described above, if the back side sealing film is a sealing film having the same composition as the surface side sealing film, Yellowing of the back-side protective member made of resin is likely to occur. In the present invention, as described above, since the back surface side sealing film 13B contains a colorant such as a white pigment, it is difficult for ultraviolet rays to reach the back surface side protection member 12, and the back surface side protection member 12 is yellowed. Can be prevented.

Hereinafter, the pair of solar cell sealing films of the present invention will be described in more detail.
[Surface sealing film]
In the present invention, the surface-side sealing film contains an ethylene-polar monomer copolymer and a crosslinking agent, and the ultraviolet absorber content is 0.1 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. It is as follows.

(UV absorber)
The content of the ultraviolet absorber that may be contained in the surface side sealing film may be 0.1 parts by mass or less with respect to 100 parts by mass of the ethylene-polar monomer copolymer as described above, 0.05 mass part or less is preferable.

  There is no restriction | limiting in particular in the kind of ultraviolet absorber, A conventionally well-known thing can be used. 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. Of these ultraviolet absorbers, benzophenone, benzotriazole, and triazine ultraviolet absorbers are preferred.

  Examples of the benzophenone ultraviolet absorber include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2 -Hydroxy-4-n-octoxybenzophenone and the like.

  Examples of the benzotriazole ultraviolet absorber include 2- [2′-hydroxy-5 ′-(hydroxymethyl) phenyl] -2H-benzotriazole and 2- [2′-hydroxy-3′-t-butyl-5. '-(Hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5'-(2-hydroxyethyl) phenyl] -5-chloro-2H-benzotriazole, etc. Is mentioned.

  Examples of triazine ultraviolet absorbers include 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl. ] -4,6-diphenyl-s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -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 and the like.

  As the ultraviolet transmittance of the surface-side sealing film, the light transmittance at a wavelength of 400 nm is preferably 88% or more, and more preferably 90% or more. If the surface-side sealing film has such ultraviolet ray permeability, the solar cell can effectively use the light in the ultraviolet region of sunlight, and high power generation performance can be obtained. Since the light transmittance also affects the thickness of the surface side sealing film, the content of the ultraviolet absorber is preferably adjusted in consideration of the thickness of the sealing film.

[Back side sealing film]
In the present invention, the back side sealing film contains an ethylene-polar monomer copolymer, a crosslinking agent, and a colorant.

(Coloring agent)
The colorant contained in the back side sealing film may be any colorant as long as it reflects sunlight including light in the ultraviolet region. Examples thereof include white with titanium dioxide (titanium white), calcium carbonate, blue with ultramarine, black with carbon black, milky white with glass beads and a light diffusing agent, and the like. In particular, a white colorant is preferable in terms of light reflectivity, and titanium dioxide (titanium white) is particularly preferable in terms of high colorability and high ultraviolet shielding properties. 1-10 mass parts is preferable with respect to 100 mass parts of ethylene-polar monomer copolymers, and, as for content of these coloring agents, 2-5 mass parts is still more preferable.

(Other)
In this invention, the back surface side sealing film may contain the above-mentioned ultraviolet absorber in order to prevent deterioration of the ethylene-polar monomer copolymer. It is preferable that content of a ultraviolet absorber is 0.01-5 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers.
[Ethylene-polar monomer copolymer]
In the present invention, examples of the polar monomer of the ethylene-polar monomer copolymer include unsaturated carboxylic acids, salts thereof, esters thereof, amides, vinyl esters, and carbon monoxide. More specifically, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, itaconic anhydride, lithium of these unsaturated carboxylic acids, sodium, Salts of monovalent metals such as potassium, salts of polyvalent metals such as magnesium, calcium and zinc, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, methacrylic acid Examples include unsaturated carboxylic acid esters such as methyl, ethyl methacrylate, isobutyl methacrylate, and dimethyl maleate, vinyl esters such as vinyl acetate and vinyl propionate, carbon monoxide, sulfur dioxide, etc. be able to.

  More specifically, as the ethylene-polar monomer copolymer, ethylene-acrylic acid copolymer, ethylene-unsaturated carboxylic acid copolymer such as ethylene-methacrylic acid copolymer, the ethylene-unsaturated carboxylic acid Ionomer in which some or all of carboxyl groups of copolymer are neutralized with the above metal, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene- Isobutyl acrylate copolymer, ethylene-unsaturated carboxylic acid ester copolymer such as ethylene-n-butyl acrylate copolymer, ethylene-isobutyl acrylate-methacrylic acid copolymer, ethylene-n-butyl acrylate -Ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid such as methacrylic acid copolymer Some or all of the copolymer and its carboxyl group ionomer neutralized with the metal, ethylene - can be exemplified vinyl ester copolymer as a typical example - ethylene such as vinyl acetate copolymer.

As the ethylene-polar monomer copolymer, it is preferable to use a copolymer having a melt flow rate defined by JIS K7210 of 35 g / 10 min or less, particularly 3 to 6 g / 10 min. According to the sealing film for solar cells using the ethylene-polar monomer copolymer having such a melt flow rate, the sealing film is melted or positioned at the time of heating and pressing in the sealing process at the time of manufacturing the solar battery. It is possible to suppress the occurrence of deviation and the protrusion from the end of the substrate.
In the present invention, the value of the melt flow rate (MFR) is measured based on conditions of 190 ° C. and a load of 21.18 N according to JIS K7210.

  As the ethylene-polar monomer copolymer, an ethylene-vinyl acetate copolymer (also referred to as EVA) is particularly preferable. Thereby, it is cheap and can form the sealing film for solar cells which is excellent in transparency (in the case of the sealing film of the present invention in which the colorant is blended, the reflectivity is affected) and flexibility.

  The content of vinyl acetate in the ethylene-vinyl acetate copolymer is 20 to 35 parts by mass, more preferably 22 to 30 parts by mass, especially 24 to 28 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. Is preferred. If the vinyl acetate content is less than 20 parts by mass, the sealing film obtained when crosslinked and cured at a high temperature may not be sufficiently transparent. If the content exceeds 35 parts by mass, carboxylic acid, alcohol, amine May occur, and foaming may easily occur at the interface between the sealing film and the protective member.

  In addition to the ethylene-polar monomer copolymer, the solar cell encapsulating film of the present invention further comprises a polyvinyl acetal resin (for example, polyvinyl formal, polyvinyl butyral (PVB resin), modified PVB), and a vinyl chloride resin. May be used for In that case, PVB is particularly preferable.

[Crosslinking agent]
In the present invention, the crosslinking agent is capable of forming a crosslinked structure of an ethylene-polar monomer copolymer. As the crosslinking agent, an organic peroxide or a photopolymerization initiator is preferably used. Among them, it is preferable to use an organic peroxide because a sealing film having improved temperature dependency of adhesive strength, transparency, moisture resistance, and penetration resistance can be obtained.

  Any organic peroxide may be used as long as it decomposes at a temperature of 100 ° C. or higher and generates 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, those having a decomposition temperature of 70 hours or more with a half-life of 10 hours are preferred.

  Examples of the organic peroxide include, from the viewpoint of resin processing temperature and storage stability, for example, benzoyl peroxide curing agent, tert-hexyl peroxypivalate, tert-butyl peroxypivalate, 3, 5, 5- Trimethylhexanoyl peroxide, di-n-octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, succinic acid peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethyl Peroxy-2-ethylhexanoate, tert-hexyl par Xyl-2-ethylhexanoate, 4-methylbenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, m-toluoyl + benzoyl peroxide, benzoyl peroxide, 1,1-bis (tert-butyl Peroxy) -2-methylcyclohexanate, 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexanate, 1,1-bis (tert-hexylperoxy) cyclohexanate 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) cyclohexane, 2,2-bis (4,4-di-tert) -Butylperoxycyclohexyl) propane, 1,1-bis (tert-butyl) -Oxy) cyclododecane, tert-hexylperoxyisopropyl monocarbonate, tert-butylperoxymaleic acid, tert-butylperoxy-3,3,5-trimethylhexane, tert-butylperoxylaurate, 2,5- Dimethyl-2,5-di (methylbenzoylperoxy) hexane, tert-butylperoxyisopropyl monocarbonate, tert-butylperoxy-2-ethylhexyl monocarbonate, tert-hexylperoxybenzoate, 2,5-di-methyl -2,5-di (benzoylperoxy) hexane, and the like.

  As the benzoyl peroxide-based curing agent, any can be used as long as it decomposes at a temperature of 70 ° C. or higher to generate radicals, and those having a decomposition temperature of 50 hours or higher with a half-life of 10 hours are preferable, It can be appropriately selected in consideration of preparation conditions, film formation temperature, curing (bonding) temperature, heat resistance of the adherend, and storage stability. Usable benzoyl peroxide curing agents include, for example, benzoyl peroxide, 2,5-dimethylhexyl-2,5-bisperoxybenzoate, p-chlorobenzoyl peroxide, m-toluoyl peroxide, 2, Examples include 4-dichlorobenzoyl peroxide and t-butyl peroxybenzoate. The benzoyl peroxide curing agent may be used alone or in combination of two or more.

  As the organic peroxide, 2,5-dimethyl-2,5di (tert-butylperoxy) hexane and 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexane are particularly preferable. . Thereby, the sealing film for solar cells which has the outstanding insulating property is obtained.

  The content of the organic peroxide is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1.5 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. preferable. If the content of the organic peroxide is small, the insulating properties of the resulting sealing film may be lowered, and if it is increased, the compatibility with the copolymer may be deteriorated.

  As the photopolymerization initiator, any known photopolymerization initiator can be used, but a photopolymerization initiator having good storage stability after blending is desirable. Examples of such a photopolymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1- (4- (methylthio) phenyl). Acetophenones such as 2-morpholinopropane-1, benzoins such as benzyldimethylketal, benzophenones such as benzophenone, 4-phenylbenzophenone and hydroxybenzophenone, thioxanthones such as isopropylthioxanthone and 2-4-diethylthioxanthone, As other special ones, methylphenylglyoxylate can be used. Particularly preferably, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropane-1, Examples include benzophenone. These photopolymerization initiators may contain one or two or more kinds of known and commonly used photopolymerization accelerators such as benzoic acid-based or tertiary amine-based compounds such as 4-dimethylaminobenzoic acid as required. Can be mixed and used. Moreover, it can be used individually by 1 type of only a photoinitiator, or 2 or more types of mixture.

It is preferable that content of the said photoinitiator is 0.5-5.0 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers.
[Others]
(Crosslinking aid)
The solar cell sealing film of the present invention may further contain a crosslinking aid, if necessary. The cross-linking aid can improve the gel fraction of the ethylene-polar monomer copolymer and improve the adhesion and durability of the sealing film.

  The content of the crosslinking aid is generally 10 parts by mass or less, preferably 0.1 to 5 parts by mass, more preferably 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Used in the department. Thereby, the sealing film excellent in adhesiveness is obtained.

  Examples of the crosslinking aid (compound having a radical polymerizable group as a functional group) include trifunctional crosslinking aids such as triallyl cyanurate and triallyl isocyanurate, and (meth) acrylic esters (eg, NK ester) ) Monofunctional or bifunctional crosslinking aids. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

(Adhesion improver)
The sealing film for solar cell of the present invention preferably has excellent adhesive strength in consideration of the sealing performance inside the solar cell. Therefore, an adhesion improver may be further included. As the adhesion improver, a silane coupling agent can be used. Thereby, it becomes possible to form the sealing film for solar cells which has the outstanding adhesive force. Examples of the silane coupling agent include γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, and γ-glycidoxypropyltrimethoxy. Silane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β Mention may be made of-(aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Of these, γ-methacryloxypropyltrimethoxysilane is particularly preferred.
The content of the silane coupling agent is preferably 0.1 to 0.7 parts by mass, and particularly preferably 0.3 to 0.65 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

(Other)
The sealing film for solar cells of the present invention improves or adjusts various physical properties of the film (optical properties such as mechanical strength, adhesiveness, transparency, heat resistance, light resistance, crosslinking speed, etc.), especially mechanical properties. In order to improve the strength, various additives such as a plasticizer, an acryloxy group-containing compound, a methacryloxy group-containing compound and / or an epoxy group-containing compound may be further included as necessary.

  The plasticizer is not particularly limited, but polybasic acid esters and polyhydric alcohol esters are generally used. Examples thereof include dioctyl phthalate, dihexyl adipate, triethylene glycol-di-2-ethylbutyrate, butyl sebacate, tetraethylene glycol diheptanoate, and triethylene glycol dipelargonate. One type of plasticizer may be used, or two or more types may be used in combination. The content of the plasticizer is preferably in the range of 5 parts by mass or less with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

  The acryloxy group-containing compound and the methacryloxy group-containing compound are generally acrylic acid or methacrylic acid derivatives, and examples thereof include acrylic acid or methacrylic acid esters and amides. Examples of ester residues include linear alkyl groups such as methyl, ethyl, dodecyl, stearyl, lauryl, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group. Group, 3-chloro-2-hydroxypropyl group. Examples of amides include diacetone acrylamide. In addition, polyhydric alcohols such as ethylene glycol, triethylene glycol, polypropylene glycol, polyethylene glycol, trimethylolpropane, and pentaerythritol, and esters of acrylic acid or methacrylic acid can also be used.

Examples of the epoxy-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, Phenol (ethyleneoxy) ₅ glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, glycidyl methacrylate, butyl glycidyl ether can be mentioned.

  The acryloxy group-containing compound, the methacryloxy group-containing compound, or the epoxy group-containing compound is generally 0.5 to 5.0 parts by weight, particularly 1.0, respectively, with respect to 100 parts by weight of the ethylene-polar monomer copolymer. It is preferable that -4.0 mass part is contained.

  Furthermore, the solar cell sealing film of the present invention may contain a light stabilizer and / or an anti-aging agent.

  By containing the light stabilizer, it is possible to suppress deterioration of the ethylene-polar monomer copolymer due to the effect of irradiated light and the like, and the yellowing of the solar cell sealing film. As the light stabilizer, a light stabilizer called a hindered amine type is preferably used. For example, LA-52, LA-57, LA-62, LA-63LA-63p, LA-67, LA-68 (all of which are ADEKA) , Tinuvin 744, Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622LD, CHIMASSORB 944LD (all manufactured by Ciba Specialty Chemicals), UV-3034 (manufactured by BF Goodrich), and the like. . In addition, the said light stabilizer may be used individually or may be used in combination of 2 or more types, and the compounding quantity is 0.01-5 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers. It is preferable that

  Examples of the anti-aging agent include lactone heat stabilizers, vitamin E heat stabilizers, sulfur heat stabilizers and the like in addition to the above antioxidants.

  What is necessary is just to perform according to a well-known method in order to form the sealing film for solar cells mentioned above. For example, a composition in which each of the above materials is mixed by a known method using a super mixer (high-speed fluid mixer), a roll mill or the like is molded by ordinary extrusion molding, calendar molding (calendering), or the like, and then a sheet-like material It can manufacture by the method of obtaining. 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 during film formation is preferably a temperature at which the crosslinking agent does not react or hardly reacts. For example, it is preferably 50 to 90 ° C, particularly 40 to 80 ° C. The thickness of the surface side sealing film is not particularly limited, but may be in the range of 50 μm to 2 mm.

[Solar cell]
As shown in FIG. 1, the solar cell of the present invention includes a pair of sealing films (surface-side sealing film 13 </ b> A) between a solar cell 14 between a surface-side transparent protective member 11 and a back-side protective member 12. And the back side sealing film 13B). And 13 A of surface side sealing films (sealing film between the cell 14 for solar cells and the surface side protection member 11) and 13B of back surface side sealing films (cell 14 for solar cells and the back surface side protection member 12) The pair of solar battery sealing films of the present invention is used as the sealing film between them.

  In the solar cell of the present invention, to sufficiently seal the solar cell, as shown in FIG. 1, the front surface side transparent protective member 11, the front surface side sealing film 13A, the solar cell cell 14, the back surface side sealing. The film 13B and the back surface side protection member 12 may be laminated, and the sealing film may be cross-linked and cured according to a conventional method such as heat and pressure.

For the heating and pressurization, for example, the laminate is heated with a vacuum laminator at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., a degassing time of 0.1 to 5 minutes, and a press pressure of 0.1. What is necessary is just to heat-press in about 1.5 kg / cm < ² > and press time 5-15 minutes. At the time of this heating and pressurization, the ethylene-polar monomer copolymer contained in the front surface side sealing film 13A and the back surface side sealing film 13B is cross-linked so that the front surface side sealing film 13A and the back surface side sealing film 13B are interposed. And the surface side transparent protection member 11, the back surface side transparent member 12, and the cell 14 for solar cells can be integrated, and the cell 14 for solar cells can be sealed.

  The surface side transparent protective member 11 used in the solar cell of the present invention is usually a glass substrate such as silicate glass. As for the thickness of a glass substrate, 0.1-10 mm is common, and 0.3-5 mm is preferable. The glass substrate may generally be chemically or thermally strengthened.

  The back side protective member 12 used in the present invention is generally a plastic film such as polyethylene terephthalate (PET). In order to enhance reflectivity, a white pigment such as titanium dioxide (titanium white) may be included.

  In the present invention, since the content of the ultraviolet absorbent in the surface side sealing film 13A is reduced as described above, the surface side sealing film 13A can easily transmit ultraviolet rays. Therefore, the solar cell can effectively use the light in the ultraviolet region of sunlight incident from the front side, and a solar cell having high power generation performance can be obtained. Moreover, since the back surface side sealing film 13B contains colorants, such as a white pigment, since the cell for solar cells can use effectively the reflected light of sunlight, the solar cell which has higher electric power generation performance is obtained. Furthermore, since the back surface side sealing film 13B contains a colorant such as a white pigment, it is difficult for ultraviolet rays to reach the back surface side protection member 12, and the sun in which yellowing due to deterioration of the back surface side protection member 12 is prevented is prevented. A battery is obtained.

  In addition, the solar cell of this invention has the characteristics in a pair of sealing film for solar cells as mentioned above. Therefore, the members other than the solar cell sealing film such as the front surface side transparent protective member, the back surface side protective member, and the solar cell cell may have the same configuration as that of a conventionally known solar cell. Not limited.

Hereinafter, the present invention will be described with reference to examples.
(Examples 1-4, Comparative Examples 1-5)
1. Preparation of Solar Cell Sealing Film Composition Each material was supplied to a roll mill with the formulation shown in Table 1, and kneaded at 70 ° C. The solar cell sealing film compositions of Examples 1 to 4 and Comparative Examples 1 to 5 Product (for front side sealing film) and a colorant-containing solar cell sealing film composition (for back side sealing film) were prepared. Each solar cell sealing film composition was calendered at 70 ° C., allowed to cool, and then solar cell sealing film (surface side sealing film) of Examples 1 to 4 (thickness 0.6 mm) and A colorant-containing solar cell sealing film (back surface side sealing film) was obtained.
2. Preparation of transmittance evaluation sample Each surface-side sealing film (thickness 0.6 mm) was sandwiched between two pieces of white plate glass (length 100 mm, width 100 mm, thickness 3 mm), and temporarily bonded at 90 ° C. with a vacuum laminator. Thereafter, the sample was heated in an oven at 155 ° C. for 30 minutes to crosslink to a gelation fraction of 90% or more to prepare a sample.
3. Back side protective member (back cover) Preparation of sample for yellowing degree evaluation As a back side protective member, polyethylene terephthalate (PET) containing a white pigment (length 100 mm, width 100 mm, thickness 0.2 mm) was used. When the back side sealing film is “present”, the back side sealing film (thickness 0.6 mm), the front side sealing film (thickness 0.6 mm) and the white glass (thickness 3 mm) are arranged in this order. When the back side sealing film was “none”, the front side sealing film (thickness 0.6 mm) and white glass (thickness 3 mm) were laminated in this order on the back side protective member. These laminates were temporarily pressure-bonded at 90 ° C. with a vacuum laminator and then heated in an oven at 155 ° C. for 30 minutes to crosslink to a gelation fraction of 90% or more to prepare samples.

4). Evaluation Method (1) Transmittance For the transmittance evaluation sample prepared in 2 above, the transmittance at a wavelength of 400 nm was measured using a spectrophotometer (U-4000 (manufactured by Hitachi, Ltd.)).
In the evaluation, a transmittance of 88% or more was evaluated as ◯, and a transmittance of less than 88% was evaluated as x.
(2) Yellowing degree of back surface protective member About the sample for back surface protective member yellowing degree evaluation produced in said 3 using a s-UV irradiation tester (eye super UV tester (made by Iwasaki Electric Co., Ltd.)), temperature 63 degreeC In this environment, ultraviolet rays having an ultraviolet intensity of 100 mW / cm ² at 295 to 400 nm were irradiated from the white glass side for 300 hours.
The yellowing degree (YI) of the back surface protection member was evaluated using a color meter (manufactured by Suga Test Instruments Co., Ltd.) after the UV irradiation.
Evaluation made YI less than 5 (circle), YI 5 or more was made x.
In the determination, (1) and (2) were evaluated as ◯ when both evaluations were ◯, and when both were evaluated as ×.

(Evaluation results)
The evaluation results of each sample are shown in Table 1. In Examples 1 to 4, when a back side sealing film containing 0 to 0.08 parts by mass of an ultraviolet absorber and containing a colorant is used for 100 parts by mass of EVA in the front side sealing film. Had a high light transmittance at a wavelength of 400 nm, and yellowing of the back side protective member was prevented. On the other hand, the comparative example 1 which mix | blended 0.15 mass part of ultraviolet absorbers with respect to 100 mass parts of EVA in the surface side sealing film becomes low in the light transmittance of wavelength 400nm, and the back surface sealing which contained the coloring agent. In Comparative Examples 2 to 5 in which no stop film was used, yellowing of the back surface side protective member occurred.
From the above, it was shown that, when the pair of solar cell sealing films of the present invention is used, a solar cell having high power generation performance and preventing the yellowing of the back surface side protection member can be obtained.

  In addition, this invention is not limited to the structure and Example of said embodiment, A various deformation | transformation is possible within the range of the summary of invention.

  According to the present invention, a solar cell having high power generation performance and little change in appearance can be provided.

11, 21 Front side transparent protective member 12, 22 Back side protective member 13A, 23A Front side sealing film 13B, 23B Back side sealing film 14, 24 Solar cell

Claims (6)

A solar cell sealing film for sealing a solar cell between a front surface side transparent protective member and a back surface side protective member to constitute a solar cell,
The surface-side sealing film between the solar cell and the surface-side protective member contains an ethylene-polar monomer copolymer and a crosslinking agent, and the ultraviolet absorber is an ethylene-polar monomer copolymer of 100 mass. 0.1 parts by mass or less with respect to part, and the back side sealing film between the solar cell and the back side protective member is an ethylene-polar monomer copolymer, a crosslinking agent, and a coloring agent. A pair of sealing films for solar cells, comprising an agent.   The pair of solar cell sealing films according to claim 1, wherein the surface-side sealing film has a light transmittance of 88% or more at a wavelength of 400 nm.   The pair of solar cell sealing films according to claim 1, wherein the colorant contained in the back surface side sealing film is titanium dioxide.   The pair of solar cell sealing films according to any one of claims 1 to 3, wherein the ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer.   The pair of solar cell sealing films according to claim 1, wherein the crosslinking agent is an organic peroxide. In a solar cell formed by sealing a solar cell with a pair of sealing films interposed between a front surface side transparent protective member and a back surface side protective member,
The surface side sealing film between the said cell for solar cells and the said surface side protection member, and the back surface side sealing film between the said cell for solar cells and the said back surface side protection member are Claim 1-5. It is a pair of sealing film for solar cells of any one of Claims 1, The solar cell characterized by the above-mentioned.

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