JP2008118073A - Sealing film on light-receiving surface side for photovoltaic cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing film for a photovoltaic cell that can prevent rust on lead wires and electrodes and can maintain the high power generation of the photovoltaic cell for a further longer period of time. <P>SOLUTION: This photovoltaic cell includes a plurality of cells for a silicon power generation element for the photovoltaic cell which are sealed through a sealing film on the side of a light-receiving surface and a sealing film on the side of a rear surface between a transparent protection member on the side of the light-receiving surface and a protection member on the rear side that are composed of a glass substrate and the like. The sealing film on the side of the light-receiving surface contains an ethylene vinyl acetate copolymer, a cross-flow linking agent and Mg(OH)<SB>2</SB>as an oxygen accepting agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sealing film used on the light-receiving surface side of a solar cell mainly composed of an ethylene vinyl acetate copolymer.

  In recent years, solar cells that directly convert sunlight into electrical energy have been widely used and further developed in terms of effective use of resources and prevention of environmental pollution.

  As shown in FIG. 1, a solar cell generally includes an EVA (ethylene vinyl acetate copolymer) film between a light-receiving surface side transparent protective member 1 made of a glass substrate or the like and a back surface side protective member (back cover) 2. A plurality of silicon power generation element solar cell cells 4 are sealed through the light-receiving surface side sealing film 3A and the back surface side sealing film 3B.

  Such a solar cell is formed by laminating the light-receiving surface side transparent protective member 1, the light-receiving surface side sealing film 3A, the solar cell 4, the back surface side sealing film 3B, and the back surface side protective member 2 in this order, And EVA is crosslinked and cured to be bonded and integrated.

  When a solar cell is used over a long period of time in an environment such as an outdoor room exposed to high temperature and high humidity or wind and rain, moisture or water may permeate inside the cell. Thus, the water | moisture content which entered the inside of a battery reaches | attains the conducting wire and electrode inside a solar cell, and corrodes these, As a result, durability of a solar cell is reduced.

  Therefore, in order to prevent rusting of the conductive wires and electrodes inside the battery and improve the durability of the solar battery, conventionally, measures such as the use of a glass plate as the light-receiving surface side transparent protective member have been taken. (For example, patent document 1). However, even if the solar cell is sufficiently sealed in this way, rusting is not prevented and the durability is not sufficiently improved.

  On the other hand, in order to improve the power generation performance of the solar battery, it is strongly desired to make light enter the battery as efficiently as possible and collect it on the solar battery cell. From such a point of view, the sealing film used in the solar cell has as high transparency as possible, does not absorb or reflect incident sunlight, and transmits most of sunlight. Since it is preferable, an EVA film which is colorless and transparent and excellent in water resistance is usually used as a sealing film in a solar cell.

  However, even such an EVA film contains vinyl acetate as a constituent component, and therefore tends to be hydrolyzed with time due to permeation of moisture or water at a high temperature to easily generate acetic acid. It has become clear that rust generation is promoted by contact with internal conductors and electrodes. Therefore, in order to prevent the occurrence of rusting inside the solar cell to a higher level, it is most effective to prevent contact between acetic acid and the conductive wire and the electrode inside the solar cell.

  Therefore, Patent Document 2 discloses an EVA film containing 0.5% by mass or less of an acid acceptor having an average particle size of 5 μm or less as a transparent film used for a sealing film of a solar cell. According to the EVA film containing the acid acceptor, it is possible to suppress the generation of acetic acid from the film and improve the durability of the solar cell.

JP 2000-174296 A JP 2005-29588 A

  A wide range of research and development has been conducted on solar cells, but in order to promote the spread of solar cells, it is necessary to be able to demonstrate high power generation performance for a longer period even in extremely harsh natural environments outdoors. ing.

  Accordingly, an object of the present invention is to provide a solar cell sealing film capable of suppressing the generation of rust on conductive wires and electrodes and maintaining the high power generation performance of the solar cell over a longer period of time. And

  As a result of various studies to further improve the durability of the solar cell, the present inventors have used a solar cell using a sealing film containing an acid acceptor over a long period of time. It has been found that the power generation performance of the solar cell may be reduced due to the acid acceptor itself contained. Although the cause of such a decrease in power generation performance is not clear, it is considered that ions generated from the acid acceptor affect the movement of the battery in the back electrode of the solar battery cell. Therefore, in order to further improve the durability of the solar cell, it is effective to prevent a decrease in the power generation performance of the solar cell due to the acid acceptor itself.

  Therefore, in the present invention, a solar cell sealing film containing an acid acceptor is used as a sealing film disposed on the light receiving surface side of the solar cell, thereby effectively preventing metal corrosion. It has been found that the durability of can be further improved.

  That is, this invention achieves the said objective with the light-receiving surface side sealing film for solar cells containing an ethylene vinyl acetate copolymer, a crosslinking agent, and an acid acceptor.

  Preferred embodiments of the solar cell of the present invention are listed below.

  (1) In order to exhibit high power generation performance from the beginning of power generation, the average particle diameter of the acid acceptor is preferably 0.1 to 4.0 μm, particularly preferably 0.1 to 0.9 μm.

(2) The acid acceptor comprises Mg (OH) ₂ . Thereby, the rusting inside a solar cell can be prevented highly.

  (3) In order to obtain high rust prevention properties, the acid acceptor is preferably contained in an amount of 0.01 to 0.15% by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer.

  In the present invention, by using a solar cell sealing film containing an acid acceptor on the light receiving surface side of the solar cell, it is possible to prevent a decrease in power generation performance of the solar cell due to the acid acceptor itself, It is possible to improve the durability by preventing the corrosion of the metal inside the battery due to the acid. In particular, in the solar cell light-receiving surface side sealing film, by optimizing the particle size, composition, content, and the like of the acid acceptor, durability can be improved while maintaining high power generation performance of the solar cell.

  The solar cell light-receiving surface side sealing film of the present invention is a film containing an ethylene-vinyl acetate copolymer, a crosslinking agent, and an acid-accepting agent, and is disposed on the light-receiving surface side of the solar cell. Features. Specifically, it is used as the light receiving surface side sealing film 3A shown in FIG.

  The acid acceptor contained in the solar cell light-receiving surface side sealing film of the present invention has an average particle size of 0.1 to 4.0 μm, further 0.1 to 0.9 μm, particularly 0.1 to 0.5 μm. Is preferable. The sealing film preferably has high transparency (low haze) so that a large amount of incident light is incident on the solar cell, and is particularly high for the light-receiving surface side sealing film disposed on the light-receiving surface side. It is required to have transparency. Therefore, in order to improve the high transparency of the sealing film to ensure high power generation performance from the beginning of power generation for a long period of time and to obtain high acid receiving performance by the acid acceptor, the receiving film included in the light receiving surface side sealing film is used. It is particularly effective to set the average particle diameter of the acid agent within the above-mentioned range.

  By setting the average particle size of the acid acceptor to 4.0 μm or less, it has a high light receiving product, so that a high acid accepting performance by the acid acceptor is obtained, and the acid acceptor is highly dispersed in the light receiving surface. High transparency of the side sealing film can be ensured. Further, by setting the average particle diameter of the acid acceptor to 0.1 μm or more, aggregation of the acid acceptor can be suppressed and the acid acceptor can be highly dispersed in the light receiving surface side sealing film. .

  In the present invention, the average particle diameter of the acid acceptor is determined by observing the solar cell sealing film with an electron microscope (preferably a transmission electron microscope) at a magnification of about 1,000,000 times. The number average value obtained for the area circle equivalent diameter.

  In the present invention, the composition of the acid acceptor contained in the light-receiving surface side sealing film is not particularly limited as long as it has a function of absorbing and / or neutralizing an acid such as acetic acid.

  As the acid acceptor, a metal oxide, a metal hydroxide, a metal carbonate or a composite metal hydroxide is used, and can be appropriately selected according to the amount of acetic acid generated and the application. Specific examples of the acid acceptor include magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium carbonate, barium carbonate, calcium carbonate, calcium borate, zinc stearate, calcium phthalate, Periodic table Group 2 metal oxides such as calcium phosphate, zinc oxide, calcium silicate, magnesium silicate, magnesium borate, magnesium metaborate, calcium metaborate, barium metaborate, hydroxide, carbonate, carvone Acid salts, silicates, borates, phosphites, metaborate, etc .; tin oxide, basic tin carbonate, tin stearate, basic tin phosphite, basic tin sulfite, trilead tetraoxide, silicon oxide, stearin Group 14 metal oxides such as silicon acid, basic carbonate, basic carboxylate, base Phosphites, and basic sulfite salt; zinc oxide, aluminum oxide, aluminum hydroxide, iron hydroxide; composite metal hydroxide such as hydrotalcite; aluminum hydroxide gel compound; and the like. These may be used individually by 1 type, and may mix and use 2 or more types.

Examples of the magnesium oxide include Kamijima Chemical Industries, Ltd., Starmag U, U-2, CX-150, M, M-2, L, P, C, CX, G, and L-10. Starmag L is preferred. Examples of the hydrotalcites include Mg _{4.3 Al 2} (OH) _12.6 CO ₃ .mH ₂ O (DHT-4A manufactured by Kyowa Chemical Industry Co., Ltd.).

Among them, it is most preferable to use a material made of Mg (OH) ₂ as the acid-accepting agent because rusting of the conductive wires and electrodes inside the battery can be particularly prevented.

  The content of the acid acceptor in the light receiving surface side sealing film is preferably 0.01 to 0.15 with respect to 100 parts by mass of the ethylene vinyl acetate copolymer contained in the light receiving surface side sealing film. It is good to set it as a mass part, More preferably, it is 0.01-0.12 mass part, Most preferably, it is 0.01-0.1 mass part. If the content of the acid acceptor exceeds 0.15 parts by mass, the transparency of the light-receiving surface side sealing film obtained may be reduced. If the content is less than 0.01 parts by mass, sufficient acceptance by the acid acceptor is achieved. The acid performance may not be obtained.

  The sealing film of the present invention contains an ethylene vinyl acetate copolymer, but if necessary, in addition to the ethylene vinyl acetate copolymer, polyvinyl acetal resins such as polyvinyl formal, polyvinyl butyral (PVB resin), and modified PVB. A vinyl chloride resin may be used in combination. However, it is preferable to use only an ethylene vinyl acetate copolymer for the sealing film.

  In the light-receiving surface side sealing film, the content of vinyl acetate in the ethylene vinyl acetate copolymer is 5 to 50 parts by mass, particularly 10 to 40 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer. It is preferable to do this. If the vinyl acetate content is less than 5 parts by mass, the transparency of the resin film obtained when crosslinked and cured at high temperatures may not be sufficient, and if it exceeds 50 parts by mass, acetic acid or the like may be easily generated. There is.

  The thickness of the light-receiving surface side sealing film is not particularly limited, and is generally in the range of 50 μm to 2 mm.

  The light-receiving surface side sealing film contains a crosslinking agent in addition to the acid acceptor and the ethylene vinyl acetate copolymer. As the crosslinking agent, an organic peroxide or a photopolymerization initiator is preferably used. Among these, it is preferable to use an organic peroxide because an intermediate 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, 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, 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 (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, tert-hexylperoxy-2-ethylhexa Noate, 4-methylbenzoyl peroxide tert-butylperoxy-2-ethylhexanoate, m-toluoyl + benzoyl peroxide, benzoyl peroxide, 1,1-bis (tert-butylperoxy) -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-trimethylcyclohexanate, 1,1-bis (tert-butylperoxy) cyclohexanate, 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane, 1,1 -Bis (tert-butylperoxy) cyclododecane, tert-hexylperoxy Propyl monocarbonate, tert-butylperoxymaleic acid, tert-butylperoxy-3,3,5-trimethylhexanoate, 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 (benzoyl) Peroxy) hexane and the like.

  As the benzoyl peroxide-based curing agent, any one can be used as long as it decomposes at a temperature of 70 ° C. or higher to generate a radical, but preferably has a decomposition temperature of 50 ° C. or higher with a half-life of 10 hours. The temperature can be appropriately selected in consideration of the preparation conditions, the film formation temperature, the curing (bonding) temperature, the heat resistance of the adherend, and the 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.

  In the solar cell light-receiving surface side sealing film, the content of the organic peroxide is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 100 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate resin. The amount is preferably 1.5 parts by mass. If the content of the organic peroxide is small, the transparency 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.

  In the solar cell light-receiving surface side sealing film, the content of the photopolymerization initiator is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate resin.

  The solar cell light-receiving surface side sealing film improves or adjusts various physical properties of the film (optical properties such as mechanical strength, adhesion, transparency, heat resistance, light resistance, crosslinking speed, etc.). Various additives such as a crosslinking aid such as a plasticizer, an adhesion improver, an acryloxy group-containing compound, a methacryloxy group-containing compound and / or an epoxy group-containing compound may be further included as necessary for improving the mechanical strength. .

  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 EVA.

  As the adhesion improver, a silane coupling agent can be used. Examples of the silane coupling agent include γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltri Methoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- Mention may be made of β- (aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Moreover, it is preferable that content of the said adhesive improvement agent is 5 mass parts or less with respect to 100 mass parts of EVA.

  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, Examples include phenol (ethyleneoxy) ₅ glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, glycidyl methacrylate, and butyl glycidyl ether.

  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 mass, particularly 1.0 to 4.0 parts by mass, respectively, with respect to 100 parts by mass of EVA. It is preferable.

  Further, the solar cell light-receiving surface side sealing film may contain an ultraviolet absorber, a light stabilizer and an anti-aging agent.

  The ultraviolet absorber is not particularly limited, but 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4- Preferred examples include benzophenone-based ultraviolet absorbers such as methoxybenzophenone and 2-hydroxy-4-n-octoxybenzophenone. In addition, it is preferable that the compounding quantity of the said benzophenone series ultraviolet absorber is 0.01-5 mass parts with respect to 100 mass parts of ethylene vinyl acetate resin.

  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 Asahi Denchu Co., Ltd.), Tinuvin 744, Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622LD, CHIMASSORB 944LD (all manufactured by Ciba-Geigy), UV-3034 (manufactured by BF Goodrich), and the like. it can. In addition, the said light stabilizer may be used independently or may be used in combination of 2 or more types, and the compounding quantity shall be 0.01-5 mass parts with respect to 100 mass parts of ethylene vinyl acetate resin. Is preferred.

  Examples of the antioxidant include hindered phenol antioxidants such as N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide]. , Phosphorus heat stabilizers, lactone heat stabilizers, vitamin E heat stabilizers, sulfur heat stabilizers, and the like.

  The light-receiving surface side sealing film of the present invention is formed according to a known method using a resin composition containing an ethylene vinyl acetate copolymer, an acid acceptor, a crosslinking agent, and other additives as required. Can be obtained. For example, a method of forming a film by heating and rolling the resin composition using extrusion molding or the like can be used. Heating is preferably performed to such an extent that the crosslinking agent does not decompose, and is generally in the range of 50 to 90 ° C.

  The solar cell light-receiving surface side sealing film according to the present invention described above is used as a sealing film disposed on the light-receiving surface side of a solar cell in a solar battery. As a configuration of the solar cell using the solar cell light-receiving surface side sealing film, a solar cell is sealed through a sealing film between the light-receiving surface side transparent protective member and the back surface side protective member. The structure using the light-receiving surface side sealing film for solar cells of this invention mentioned above as a sealing film arrange | positioned between the said light-receiving surface side transparent protective member and the said cell for solar cells is mentioned. In the solar cell, the back surface side sealing film disposed between the back surface side protective member and the solar cell cell does not contain an acid acceptor. In the solar cell having such a configuration, only the light-receiving surface side sealing film contains an acid acceptor, and the back surface side sealing film does not contain an acid acceptor, thereby preventing rusting of the conductive wires and electrodes inside the battery. While suppressing with an acid acceptor, the fall of the power generation performance of the solar cell by the acid acceptor in the use over a long period of time can be suppressed, and it has excellent durability.

  In the present invention, the “back side” means a surface opposite to the light receiving surface of the solar cell.

In order to manufacture the solar cell, for example, as shown in FIG. 1, the light-receiving surface side transparent protective member 1, the light-receiving surface side sealing film 3 </ b> A, the solar cell 4, the back surface side sealing film 3 </ b> B, and the back surface side protection The member 2 is laminated, and the laminate is subjected to 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, a press pressure of 0.1 to What is necessary is just to heat-press in 1.5 kg / cm < ² > and press time for 5 to 15 minutes. At the time of heating and pressing, the light-receiving surface side sealing film 3A and the back surface side sealing film 3B are cross-linked by crosslinking the ethylene vinyl acetate copolymer contained in the light receiving surface side sealing film 3A and the back surface side sealing film 3B. The solar cell 4 can be sealed by integrating the light receiving surface side transparent protective member 1, the back surface side transparent member 2, and the solar cell 4.

  In the present invention, the backside sealing film may be a conventionally known film as long as it does not contain an acid acceptor. Moreover, it is preferable that the said back surface side sealing film further contains the coloring agent. If a back side sealing film containing a colorant is used, light is reflected at the interface between the back side sealing film and the light receiving side sealing film or diffusely reflected by the colorant, and is incident between solar cells. The light that has passed through the cell or the light that has passed through the cell can be diffusely reflected and incident again on the cell, so that the utilization efficiency of the light incident on the solar cell is increased and the power generation efficiency can be improved.

  The light-receiving surface side transparent protective member used for 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 used in the present invention is a plastic film such as PET, but a fluorinated polyethylene film is preferable in consideration of heat resistance.

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

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

(Example 1)
EVA (content of vinyl acetate with respect to EVA 100 parts by mass: 26 parts by mass) 100 parts by mass,
1 part by weight of a crosslinking agent (2,5-dimethyl-2,5-bis (t-butylperoxy) hexane),
2 parts by mass of a crosslinking aid (triallyl isocyanurate),
Acid acceptor (Mg (OH) ₂ , average particle size 0.4 μm) 0.05 parts by mass,
With the above formulation, these materials were supplied to a roll mill and kneaded at 80 ° C. to prepare a resin composition. The obtained resin composition was calendered at 100 ° C., allowed to cool, and then a sealing film (1) having a thickness of 0.6 mm was obtained.

(Comparative Example 1)
A sealing film (2) was produced in the same manner as in Example 1 except that the acid acceptor was not used.

(Evaluation)
The sealing film and the solar cell produced above were evaluated according to the following procedure.

1. Transparency of sealing film The haze value (%) of the sealing film was measured according to JIS K 7136 (2000). At that time, a turbidimeter (NDH 2000 type, manufactured by Nippon Denshoku Industries Co., Ltd.) was used. The results are shown in Table 1.

2. Total light transmittance of sealing film Using a turbidimeter (NDH 2000 type, manufactured by Nippon Denshoku Industries Co., Ltd.), the total light transmittance in the thickness direction of the sealing film was measured. The said measurement was implemented 3 places in the sealing film, and the average value was made into the total light transmittance (%) of a sealing film. The results are shown in Table 1.

3. Power generation performance of solar cell The sealing films (1) and (2) produced above were used as the sealing films for the light-receiving surface side and the back surface side as shown in Table 2, respectively, and as shown in FIG. A solar cell 4 made of a silicon power generation element is sealed between a light receiving surface side transparent protective member 1 made of (thickness 0.3 mm) and a back surface side protective member 2 made of a fluorinated polyethylene film (thickness 50 μm). A solar cell was manufactured. The sealing was performed by cross-linking EVA with a vacuum laminator by thermocompression bonding under vacuum at a temperature of 150 ° C.

The solar cell produced above was irradiated with pseudo-sunlight with an irradiation intensity of 1000 mW / cm ² by a solar simulator whose spectrum was adjusted to AM 1.5, and the open voltage [V] of the solar cell and per 1 cm ² . The nominal maximum output operating current [A] and the nominal maximum output operating voltage [V] were measured, and the nominal maximum output [W] (JIS C8911 1998) was determined from these products.

  Next, the solar cell is left in an environment of a temperature of 121 ° C. and a humidity of 100% RH for 240 hours, and the open-circuit voltage [V] and the nominal maximum output [W] are obtained for the solar cell after being left in the same manner as described above. It was. The results are shown in Table 2.

  From the results shown in Table 2, it can be seen that according to the solar cell using the solar cell sealing film of the present invention on the light receiving surface side, both the open-circuit voltage and the nominal maximum output are suppressed from decreasing. Thereby, according to this invention, it turns out that high electric power generation performance can be maintained over a long period of time, and the solar cell whose durability was further improved is obtained.

A sectional view of a general solar cell is shown.

Explanation of symbols

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

Claims (6)

  The light-receiving surface side sealing film for solar cells containing an ethylene vinyl acetate copolymer, a crosslinking agent, and an acid acceptor.   2. The solar cell light-receiving surface side sealing film according to claim 1, wherein an average particle diameter of the acid acceptor is 0.1 to 4.0 μm.   3. The solar cell light-receiving surface side sealing film according to claim 1, wherein an average particle diameter of the acid acceptor is 0.1 to 0.9 μm. The light-receiving surface side sealing film for a solar cell according to claim 1, wherein the acid acceptor is made of Mg (OH) ₂ .   The light-receiving surface side sealing film for solar cells according to claim 1, wherein the acid-accepting agent is contained in an amount of 0.01 to 0.15 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer.   The content of vinyl acetate in the ethylene vinyl acetate copolymer is 5 to 50 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer. Surface side sealing film.

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