JP2008115344A - Back surface-sealing film for solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing film for a solar cell improving durability by inhibiting the rusting of a conductor wire or an electrode inside a solar cell, without reducing power generating performance. <P>SOLUTION: This back surface-sealing film for the solar cell comprises an ethylene-vinyl acetate copolymer, a crosslinking agent and an acid acceptor, wherein the film includes the acid acceptor of ≥0.5 parts by mass based on 100 parts by mass of the ethylene-vinyl acetate copolymer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a back-side sealing film for a solar cell containing an ethylene vinyl acetate copolymer as a main component.

  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 solar battery cells 4 such as silicon power generation elements 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 viewpoint, the sealing film used in the solar cell has a transparency as high as possible, does not absorb or reflect incident sunlight, and transmits most of sunlight. Since it is preferably used, 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 an EVA film containing vinyl acetate as a constituent component tends to be hydrolyzed with time due to permeation of moisture or water at high temperatures, so that acetic acid tends to be generated. It has become clear that rusting is promoted by contact with the lead wires 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 acid acceptor particles having an average particle diameter of 5 μm or less as a transparent film used for a sealing film of a solar cell or the like. According to the EVA film containing the acid acceptor particles, 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.

  Therefore, an object of the present invention is to provide a solar cell seal capable of further improving durability by suppressing the generation of rust on the conductive wires and electrodes inside the solar cell without degrading the power generation performance. The object is to provide a membrane.

  As described in Patent Document 2, in order to prevent rusting inside the solar cell, it is most effective to include an acid acceptor for supplementing an acid capable of corroding a metal such as acetic acid in the sealing film. Is. However, in order to obtain a higher prevention effect against rusting, when the content of the acid acceptor in the EVA film used as the sealing film is increased, the transparency of the resulting sealing film is lowered, and the power generation performance of the solar cell May decrease.

  As a result of various studies in view of such circumstances, the present inventors have arranged a solar cell sealing film containing a high concentration acid acceptor on the side opposite to the light receiving surface of the solar cell. It has been found that by using it as a sealing film, it is possible to effectively prevent corrosion of the metal inside the battery and further improve durability without reducing the power generation performance of the solar battery.

That is, the present invention includes an ethylene vinyl acetate copolymer, a crosslinking agent and an acid acceptor,
The said objective is achieved by the back surface side sealing film for solar cells which contains the said acid acceptor 0.5 mass part or more with respect to 100 mass parts of said ethylene vinyl acetate copolymers.

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

  (1) The acid acceptor is contained in an amount exceeding 0.5 parts by mass and not more than 5.0 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer.

  (2) In order to obtain an effect of preventing metal corrosion by the acid acceptor, acid acceptor particles having an average particle diameter of 5 μm or less are preferably used as the acid acceptor.

  (3) The acid acceptor is selected from the group consisting of magnesium hydroxide, magnesium oxide, zinc oxide, trilead tetroxide, calcium hydroxide, aluminum hydroxide, iron (II) hydroxide, calcium carbonate and hydrotalcite. Is at least one kind.

  (4) 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.

  (5) It is preferable to further include a colorant in order to improve the power generation performance of the solar cell.

  (6) The colorant contains 2 to 10 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer.

  In the back surface side sealing film for solar cells of the present invention, by optimizing the content of the acid acceptor, corrosion of the metal inside the cell due to an acid such as acetic acid generated by hydrolysis from the EVA film can be highly prevented. Therefore, according to the said solar cell back surface side sealing film, the corrosion of the metal inside a battery is prevented highly, and the outstanding electric power generation performance can be maintained over a long period of time.

  The back surface side sealing film for solar cells of the present invention contains an ethylene vinyl acetate copolymer, a crosslinking agent, and an acid acceptor, and the acid acceptor is added in an amount of 0.0. 5 mass parts or more are included, It is arrange | positioned at the back surface side on the opposite side to the light-receiving surface of the cell for solar cells, It is characterized by the above-mentioned. Specifically, it is used as the back surface side sealing film 3B shown in FIG.

  In order to prevent high rusting in solar cells, it is preferable to increase the content of the acid acceptor in the sealing film, but simply increasing the content of the acid acceptor decreases the transparency of the sealing film. There is a risk of reducing the power generation performance of the solar cell. Therefore, in the present invention, the solar cell sealing film containing a relatively high concentration of the acid acceptor is used as the sealing film disposed on the back surface side of the solar battery cell, so that the back surface side sealing film is transparent. Even if the performance decreases, the light receiving surface side sealing film can sufficiently secure the incident light to the inside of the battery. Thereby, in the back surface side sealing film, it is possible to ensure high resistance to metal corrosion inside the battery without being highly restricted in the use of the acid acceptor such as type and content.

  Although the back surface side sealing film for solar cells of this invention contains an acid acceptor 0.5 mass part or more with respect to 100 mass parts of the said ethylene vinyl acetate copolymers contained in the said back surface side sealing film, More Preferably it is more than 0.5 parts by mass and 5.0 parts by mass or less, particularly preferably more than 0.5 parts by mass and 2 parts by mass or less.

  The shape of the acid acceptor is not particularly limited, but it is preferable to use acid acceptor particles having an average particle diameter of 5 μm or less, particularly 1 to 4 μm, and more preferably 1 to 2.5 μm. Since the acid acceptor particles have a high surface area, a high contact area between the acid acceptor and the acid can be obtained, and rusting of the conductive wires and electrodes inside the battery can be prevented to a higher degree.

  The acid acceptor can be used without particular limitation 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, 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.).

Especially, since the said acid acceptor can prevent the rusting of the conducting wire and electrode inside a battery more highly, magnesium hydroxide (Mg (OH) ₂ ), magnesium oxide (MgO), zinc oxide (ZnO) , Trilead tetraoxide (Pb ₃ O ₄ ), calcium hydroxide (Ca (OH) ₂ ), aluminum hydroxide (Al (OH) ₃ ), iron hydroxide (II) (Fe (OH) ₂ ), calcium carbonate (CaCO ₃ ) and hydrotalcite (Mg ₆ Al ₂ (OH) ₁₆ CO ₃ ) are preferred, and magnesium hydroxide (Mg (OH) ₂ ), magnesium oxide (MgO), and zinc oxide ( ZnO) is preferred.

  The back surface side sealing film for solar cells of this invention contains an ethylene vinyl acetate copolymer. In addition to the ethylene vinyl acetate copolymer, polyvinyl acetal resins such as polyvinyl formal, polyvinyl butyral (PVB resin), and modified PVB, and vinyl chloride resin may be used in combination as the sealing film. However, it is preferable to use only ethylene vinyl acetate copolymer.

  The content of vinyl acetate in the ethylene vinyl acetate copolymer is preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer. If the vinyl acetate content is less than 5 parts by mass, the resin film obtained when crosslinked and cured at a high temperature may not have sufficient transparency, and if it exceeds 50 parts by mass, acetic acid or the like may be easily generated. .

  As a crosslinking agent used for the solar cell sealing film of the present invention, 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 back side sealing film for solar cells, the content of the organic peroxide is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1 with respect to 100 parts by mass of the ethylene vinyl acetate resin. It is preferably 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 back surface side sealing film for solar cells, 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.

  It is preferable that the back surface side sealing film for solar cells of this invention further contains the coloring agent. When using a material containing a colorant as the back surface side sealing film, solar cell cells are reflected by reflection of light at the interface between the back surface side sealing film and the light receiving surface side sealing film inside the solar cell or by irregular reflection by the colorant. The light incident during the period and the light passing 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.

  Examples of the colorant include white colorants such as titanium white and calcium carbonate; blue colorants such as ultramarine; black colorants such as carbon black; milky white colorants such as glass beads and light diffusing agents. it can. Preferably, a white colorant based on titanium white can be used.

  The colorant is preferably contained in an amount of 2 to 10 parts by weight, more preferably 3 to 6 parts by weight with respect to 100 parts by weight of the ethylene vinyl acetate copolymer contained in the back side sealing film.

  The thickness of the solar cell backside sealing film is not particularly limited, and is generally in the range of 50 μm to 2 mm.

  The solar cell backside sealing film is used to improve or adjust 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 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.

  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.

  Furthermore, the solar cell back surface side sealing film of this invention may contain the ultraviolet absorber, the light stabilizer, and 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 back side sealing film for solar cells of the present invention is in accordance with a known method using a resin composition containing an ethylene vinyl acetate copolymer, an acid acceptor, a crosslinking agent, and other additives as required. It is obtained by forming a film. 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 back surface side sealing film by this invention mentioned above is used as a sealing film arrange | positioned in the solar cell at the back surface side opposite to the light-receiving surface of the cell for solar cells. As a configuration of the solar cell using the solar cell back surface side sealing film, the solar cell is sealed between the light receiving surface side transparent protective member and the back surface side protective member via the sealing film. The structure using the back surface side sealing film for solar cells of this invention mentioned above as a sealing film arrange | positioned between the said back surface side transparent protective member and the said cell for solar cells is mentioned. In the solar cell having such a configuration, the backside sealing film contains an acid acceptor at a high concentration, thereby suppressing rusting of the conductors and electrodes inside the battery with the acid acceptor and extending over a long period of time. The deterioration of the power generation performance of the solar cell due to the acid acceptor in use can be suppressed, and it has excellent durability.

  In the solar cell, the light receiving surface side sealing film disposed between the light receiving surface side transparent protective member and the solar cell may contain an acid acceptor as long as the amount is small. The content of the acid acceptor in the light-receiving surface side sealing film is 0.15 parts by mass or less, particularly 0.1 parts by mass or less, and further 0.05 parts by mass or less with respect to 100 parts by mass of the ethylene vinyl acetate copolymer. Is preferable. In this way, by optimizing the content of the acid acceptor in the sealing film disposed on the back surface side and the light receiving surface side inside the solar cell, corrosion of the metal inside the solar cell is ensured while ensuring high power generation performance. Higher can be prevented.

  In addition, as an acid acceptor used for the light-receiving surface side sealing film, the same thing as what was mentioned above in the back surface side sealing film is used.

The solar cell of this invention is obtained by sealing the cell for solar cells through the sealing film containing an ethylene vinyl acetate copolymer between a light-receiving surface side transparent protective member and a back surface side protective member. In the solar cell, in order to sufficiently seal the solar cell, as shown in FIG. 1, the light receiving surface side transparent protective member 1, the light receiving surface side sealing film 3A, the solar cell 4 and the back surface side sealing. The film 3B and the back side protective member 2 are 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, What is necessary is just to heat-press in press pressure 0.1-1.5 kg / cm < ² > and press time 5-15 minutes. During this heating and pressurization, the ethylene vinyl acetate copolymer contained in the light-receiving surface side sealing film 3A and the back surface-side sealing film 3B is cross-linked, and the light-receiving surface side sealing film 3A and the back surface side sealing film 3B are interposed. 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.

  The front 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 surface protection 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 a light-receiving surface side and a back surface side as mentioned above. Accordingly, the members other than the sealing film such as the light-receiving surface side transparent protective member, the back surface side protective member, and the solar battery cell are not particularly limited, and may have the same configuration as a conventionally known solar battery. That's fine.

  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 100 parts by mass of EVA: 26 parts by mass) 100 parts by mass of crosslinking agent (2,5-dimethyl-2,5-bis (t-butylperoxy) hexane) 1 part by mass of crosslinking aid (tri Allyl isocyanurate) 2 parts by mass acid acceptor (Mg (OH) ₂ , average particle size 3 μm) 0.5 parts by mass In the above formulation, these materials are supplied to a roll mill and kneaded at 80 ° C. to obtain a resin composition A product was prepared. 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 Examples 1 and 2)
Sealing films (2) and (3) were prepared in the same manner as in Example 1 except that the amount of the acid acceptor was changed to the value shown in Table 1.

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

1. Acetic acid amount in the sealing film The sealing film was immersed in 2 ml of acetone at room temperature (25 ° C.) and stirred for 50 hours, and then the amount of acetic acid [mg] contained in the acetone extract was quantified using a gas chromatograph. . The results are shown in Table 1.

2. Power generation performance of solar cell The sealing films (1) to (3) produced above were used as the light-receiving surface side and back surface side sealing films 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 was left in an environment of a temperature of 121 ° C. and a humidity of 100% RH for 400 hours, and the nominal maximum output [W] was determined in the same manner as described above for the solar cell after being left. The results are shown in Table 2.

  From the results shown in Table 2, according to the solar cell using the solar cell sealing film of the present invention on the back side, a decrease in the nominal maximum output is suppressed, and a solar cell with further improved durability is obtained. I understand.

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 (7)

An ethylene vinyl acetate copolymer, a crosslinking agent and an acid acceptor,
The back side sealing film for solar cells which contains the said acid acceptor 0.5 mass part or more with respect to 100 mass parts of said ethylene vinyl acetate copolymers.   2. The back side for a solar cell according to claim 1, wherein the acid acceptor is contained in an amount exceeding 0.5 parts by mass and not more than 5.0 parts by mass with respect to 100 parts by mass of the ethylene vinyl acetate copolymer. Sealing film.   The solar cell back surface side sealing film according to claim 1, wherein the acid acceptor is an acid acceptor particle having an average particle diameter of 5 μm or less.   The acid acceptor is selected from the group consisting of magnesium hydroxide, magnesium oxide, zinc oxide, trilead tetraoxide, calcium hydroxide, aluminum hydroxide, iron (II) hydroxide, calcium carbonate, and hydrotalcite. It is at least 1 sort, The back surface side sealing film for solar cells of any one of Claims 1-3 characterized by the above-mentioned.   Content of vinyl acetate in the said ethylene vinyl acetate copolymer is 5-50 mass parts with respect to 100 mass parts of said ethylene vinyl acetate copolymers, The any one of Claims 1-4 characterized by the above-mentioned. The back surface side sealing film for solar cells as described in any one of.   The back surface side sealing film for solar cells of any one of Claims 1-5 which further contains a coloring agent.   The back surface side sealing film for solar cells according to claim 6, wherein the colorant is contained in an amount of 2 to 10 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

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