JP2009256459A - Sealing film for solar battery and solar battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing film for solar batteries, having an imparted black color degree excellent in designability and excellent in an electric insulating property. <P>SOLUTION: Provided is the sealing film for solar batteries, comprising an ethylene-polar monomer copolymer, a cross-linking agent and a black pigment, characterized by having an L<SP>*</SP>a<SP>*</SP>b<SP>*</SP>color system L<SP>*</SP>value of ≤0.1 as a black color degree and a volume resistivity value of 1.0×10<SP>14</SP>to 1.0×10<SP>15</SP>Ωcm after cross-linked. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solar cell sealing film containing an ethylene-polar monomer copolymer as a main component, and more particularly to a solar cell sealing film excellent in electrical insulation even when colored in black.

  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, the solar cell generally has a surface-side transparent protective member 11 made of a glass substrate or the like, a surface-side sealing film 13A, a solar battery cell 14 such as a silicon power generation element, a back-side sealing film 13B, And the back-side protection member (back cover) 12 are laminated in this order, deaerated under reduced pressure, and heated and pressurized to cross-link and cure the front-side sealing film 13A and the back-side sealing film 13B to be integrated. It is manufactured by. In a conventional solar battery, a plurality of solar battery cells 14 are connected and used in order to obtain a high electric output. Therefore, in order to ensure electrical insulation between the solar battery cells 14, the solar battery cells are sealed using the sealing films 13A and 13B having electrical insulation.

  As a sealing film used for a solar cell, a film made of an ethylene-polar monomer copolymer such as an ethylene-vinyl acetate copolymer (EVA) film or an ethylene-ethyl acrylate copolymer (EEA) film is used. (Patent Document 1). A film made of an ethylene-polar monomer copolymer is produced by film-forming a composition containing an ethylene-polar monomer copolymer, a cross-linking agent, and the like by, for example, heat rolling by extrusion or the like.

  On the other hand, in solar cells, light incident between solar cells or light that has passed through cells can be diffusely reflected and re-entered into the cells. A back side protective member (back cover) colored in black, blue, red, or the like is used.

  In a solar cell using such a colored back side protective member, when a conventional transparent ethylene-polar monomer copolymer film is used as the back side sealing film, the solar cell is due to the presence of the back side sealing film. The cell appears to be floating from the back surface side protection member, causing a sense of incongruity and lowering the design. Since the solar cell is generally attached outdoors such as on the roof of a building and the structure inside the cell can be visually recognized from the light receiving surface, such a design deterioration is not desirable.

  Therefore, in the conventional solar cell, a back side sealing film colored with a pigment or the like according to the back side protective member is also used. As the pigment used for the back surface side sealing film, various inorganic or organic pigments such as white, black, blue, red and others are generally used. Examples include white pigments such as titanium oxide and calcium carbonate; blue pigments such as ultramarine; black pigments such as carbon black; milky white pigments such as glass beads and light diffusing agents.

Japanese Patent Laid-Open No. 06-177412

  The black back-side protective member is particularly preferably used for solar cells because the solar cells can be seen to be tightened, so that an excellent design can be obtained and the incident light can be reflected well. However, when black is imparted to the back surface side sealing film in accordance with the black back surface side protective member, the power generation performance of the resulting solar cell may be reduced. Thus, it is not desirable that the power generation performance is lowered in order to impart design properties to the solar cell.

  One cause of the above problem is that a conductive material such as carbon black is used as a colorant in the sealing film. That is, when a black pigment is simply added to the back side sealing film in order to give sufficient blackness in accordance with the black back side protective member, the electrical insulation of the sealing film is caused by the conductivity of the pigment such as carbon black. As a result, the power generation performance of the solar cell may be reduced.

  However, if the addition amount of the black pigment is reduced in order to ensure the electrical insulation of the sealing film, sufficient blackness may not be imparted. Therefore, in order to suppress a decrease in the power generation performance of the solar cell using the black back surface side protection member, it is necessary to use a solar cell sealing film in which the blackness and the electrically incompatible properties are compatible. is there.

  Then, the objective of this invention aims at providing the sealing film for solar cells which is excellent also in electrical insulation, while providing the blackness excellent in the designability.

  The present inventor has made various studies on the electrical insulation properties of the solar cell encapsulating film provided with a high blackness by including a black pigment, and the blackness and electrical properties are satisfied if specific parameters are satisfied from the obtained results. It discovered that the sealing film for solar cells excellent in both insulation was obtained.

That is, the present invention is a solar cell sealing film comprising an ethylene-polar monomer copolymer, a crosslinking agent, and a black pigment,
The L ^* a ^* b ^* color system has an L ^* value of 0.1 or less and a volume resistivity value after crosslinking of 1.0 × 10 ^{14 to} 1.0 × 10 ¹⁵ Ωcm. The said subject is solved by the sealing film for solar cells to perform.

  The sealing film for solar cells of the present invention satisfies the specific blackness and volume specific resistance value, and is excellent in electrical insulation while being blackness suitable for a black back side protective member. Therefore, according to the solar cell sealing film, it is possible to provide a solar cell that is excellent in design by providing a dark color tone such as black, and that does not have a decrease in power generation performance.

  As described above, the solar cell sealing film of the present invention contains an ethylene-polar monomer copolymer, a crosslinking agent, and a black pigment as basic components. Thus, even if it is a sealing film containing a black pigment, by having predetermined blackness and volume specific resistance value, it is set as the sealing film in which the property which blackness and electrical insulation contradict are compatible. Can do.

Specifically, as the blackness of the sealing film, an L ^* value (brightness), which is an index representing the brightness of the L ^* a ^* b ^* color system, is 0.1 or less, particularly 0.05 or less. . Thereby, it can be set as the black sealing film excellent in the designability. At this time, in order to give the sealing film an excellent black color tone, the a ^* value of the L ^* a ^* b ^* color system is −0.1 to 0.1, and the b ^* value is −0.1. It is more preferable to set it to -0.1. The L ^* value of the L ^* a ^* b ^* color system of the sealing film can be measured by the method described in the examples described later.

On the other hand, the volume resistivity value after crosslinking of the sealing film is specifically 1.0 × 10 ^{14 to} 1.0 × 10 ¹⁵ Ωcm, preferably 1.5 × 10 ^{14 to} 5.0 × 10 ^14. Ωcm, particularly preferably 1.5 × 10 ^{14 to} 3.5 × 10 ¹⁴ Ωcm. If the volume resistivity value is less than 1.0 × 10 ¹⁴ Ωcm, high blackness can be imparted, but sufficient electrical insulation may not be obtained, and the volume resistivity value is 1.0 × 10 6. ^If it exceeds ¹⁵ Ωcm, high electrical insulation can be ensured, but sufficient blackness may not be imparted.

  The crosslinked sealing film is a sealing film having a gel fraction of 90% by mass or more by heat curing. The volume specific resistance value and gel fraction after crosslinking of the sealing film can be measured by the method described in the examples described later.

  In the solar cell sealing film of the present invention, the total light transmittance is 0.1% or less, particularly 0.05% or less, in order to suppress a high decrease in the power generation performance of the solar cell due to the addition of the black pigment. It is preferable to do this. Thereby, the light which entered between the cells for solar cells and the light which passed the cells can be diffusely reflected, and can be made to enter into a cell again, and the power generation performance of a solar cell can be improved. In addition, the total light transmittance of the said sealing film can be measured by the method as described in the Example mentioned later.

(Black pigment)
The sealing film for solar cells of the present invention is imparted with a high black color by including a black pigment. A conventionally well-known thing can be used as a black pigment. For example, carbon black, graphitized carbon black, fine particle graphite, chromium oxide, viridian, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindolinone pigment, dioxazine pigment, selenium pigment, perylene pigment, perinone Examples thereof include pigments, thioindigo pigments, quinophthalone pigments, and metal complex pigments.

  Among these, as the black pigment, it is preferable to use carbon black because a black color tone having excellent design can be imparted. Examples of carbon black include acetylene black, channel black, and furnace black. Of these, furnace black is preferable.

  The average primary particle diameter of the carbon black is preferably 20 to 80 nm, more preferably 30 to 75 nm, and particularly preferably 35 to 50 nm. If the average primary particle diameter of the carbon black is less than 20 nm, the primary particles are likely to aggregate together, which may lead to a decrease in blackness. Further, if the average primary particle diameter of the carbon black exceeds 80 nm, the surface area of the carbon black is reduced, so that sufficient blackness may not be obtained.

DBP oil absorption amount of the carbon black is preferably 30~200cm ³ / 100g, more preferably 30 to 150 ^3/100 g, particularly preferably preferably set to 30~130cm ³ / 100g. With carbon black having such DBP oil absorption amount, it is difficult to form a structure (a chain structure in which primary particles are connected), and a desired volume resistivity can be obtained, and carbon black is highly dispersed. Thus, a sealing film having a high blackness can be obtained.

BET specific surface area of the carbon black is preferably 10 to 200 m ² / g, more preferably 30 to 150 m ² / g, particularly preferably preferably set to 50 to 100 m ² / g. Thereby, carbon black can be highly dispersed while suppressing formation of a structure, and the sealing film having the above-described blackness and volume resistivity can be obtained.

  In addition, let the average primary particle diameter of carbon black, DBP oil absorption, and BET specific surface area be the value measured by the method as described in the Example mentioned later.

  In the solar cell sealing film of the present invention, the content of the black pigment is preferably 0.15 to 5.0 parts by mass, more preferably 0.4 to 100 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. It is good to set it as 1.0 mass part. Thereby, carbon black can be highly dispersed while suppressing formation of the structure, and the sealing film having the above-described blackness and volume resistivity can be obtained.

(Ethylene-polar monomer copolymer)
Examples of the polar monomer of the ethylene-polar monomer copolymer used in the sealing film of the present invention include unsaturated carboxylic acid, its salt, its ester, its amide, vinyl ester, carbon monoxide and the like. More specifically, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, itaconic anhydride, lithium, sodium of these unsaturated carboxylic acids, Monovalent metal salts such as potassium, polyvalent metal salts such as magnesium, calcium and zinc, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, nbutyl acrylate, isooctyl acrylate, methyl methacrylate Illustrative examples of unsaturated carboxylic acid esters such as ethyl methacrylate, isobutyl methacrylate and dimethyl maleate, vinyl esters such as vinyl acetate and vinyl propionate, carbon monoxide, sulfur dioxide, etc. Can do.

  More specific examples of the ethylene-polar monomer copolymer include ethylene-acrylic acid copolymers, ethylene-unsaturated carboxylic acid copolymers such as ethylene-methacrylic acid copolymers, and ethylene-unsaturated carboxylic acid copolymers. Ionomer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acrylic, wherein some or all of the carboxyl groups of the polymer are neutralized with the above metals Acid isobutyl copolymer, ethylene-unsaturated carboxylic acid ester copolymer such as ethylene-n-butyl acrylate copolymer, ethylene-isobutyl acrylate-methacrylic acid copolymer, ethylene-n-butyl acrylate-methacrylic acid Ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymer such as copolymer It can be exemplified vinyl ester copolymers and the like as a typical example - some or all of the body and its carboxyl group ionomer neutralized with the metal, ethylene - ethylene such as vinyl acetate copolymer.

  Most preferably, the ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer (EVA). Thereby, the sealing film excellent in transparency and adhesiveness is obtained.

  The content of vinyl acetate in the ethylene-vinyl acetate copolymer is preferably 20 to 30 parts by mass, more preferably 24 to 28 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. If the content of vinyl acetate is less than 20 parts by mass, the sealing film obtained when crosslinked and cured at a high temperature may not have sufficient transparency. If the content exceeds 30 parts by mass, the sealing film and the protective member in a solar cell There is a risk that foaming is likely to occur at the interface.

(Crosslinking agent)
As a crosslinking agent used for the sealing film of the present invention, an organic peroxide or a photopolymerization initiator is preferably used. By the crosslinking agent, a crosslinked cured film of an ethylene-polar monomer copolymer can be obtained, and the sealing performance of the solar cell can be improved. 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 to generate radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability. In particular, the one having a decomposition temperature of 70 ° C. or more with a half-life of 10 hours is preferable.

  Examples of the organic peroxide include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (tert) from the viewpoint of processing temperature and storage stability of the resin. 3-butyl-peroxy) hexane; 3-di-tert-butyl peroxide; tert-dicumyl peroxide; 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane; Dimethyl-2,5-bis (tert-butylperoxy) hexane; 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne; dicumyl peroxide; tert-butylcumyl peroxide; α, α′-bis (tert-butylperoxyisopropyl) benzene; α, α′-bis (tert-butylperoxy) diisopropyl N-butyl-4,4-bis (tert-butylperoxy) butane; 2,2-bis (tert-butylperoxy) butane; 1,1-bis (tert-butylperoxy) cyclohexane; 1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane; 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexane; tert-butylperoxybenzoate; benzoylper Preferable examples include oxide. These may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  As the organic peroxide, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1,1-bis (tert-hexylperoxy) -3,3,5 is particularly preferable. -Trimethylcyclohexane. If it is this organic peroxide, the sealing film for solar cells which has the outstanding sealing property and transparency will be obtained, without reducing the characteristic of an aziridine compound.

  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 sealing film, the content of the crosslinking agent is preferably 0.1 to 5 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. is there. If the content of the cross-linking agent is small, the transparency of the resulting sealing film may decrease, and foaming may easily occur due to the reaction gas of the cross-linking agent.

(Crosslinking aid)
The sealing film of the present invention preferably further contains a crosslinking aid. 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 with respect to 100 parts by mass of the ethylene-polar monomer copolymer. 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.

(Other)
The sealing film of the present invention improves or adjusts various physical properties of the film (optical properties such as mechanical strength, adhesiveness and transparency, heat resistance, light resistance, crosslinking speed, etc.), especially improvement of mechanical strength. Therefore, if necessary, various additives 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.

  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.

  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. 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 ethylene-polar monomer copolymers.

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

  By including the ultraviolet absorber in the sealing film of the present invention, it is possible to suppress deterioration of the ethylene-polar monomer copolymer due to the effect of irradiated light and the like, and the solar battery sealing film from being yellowed. it can. 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-polar monomer copolymers.

  Even if the sealing film of the present invention contains a light stabilizer, it is possible to suppress deterioration of the ethylene-polar monomer copolymer due to the influence of irradiated light and the like, and the solar battery sealing film to be yellowed. Can do. 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 ( ADEKA), Tinuvin 744, Tinuvin 770, Tinuvin 765, Tinuvin 144, Tinuvin 622LD, CHIMASORB 944LD (all manufactured by Ciba Specialty Chemicals), UV-3034 (BF Goodrich) Can be mentioned. 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 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.

  Although the thickness in particular of the sealing film for solar cells is not restrict | limited, What is necessary is just the range of 50 micrometers-2 mm.

  What is necessary is just to perform according to a well-known method in order to form the sealing film for solar cells of this invention mentioned above. For example, the composition containing each of the above-described components can be produced by a method of obtaining a sheet-like material by molding by ordinary extrusion molding, calendar molding (calendering) or the like. When a film is formed by heat rolling using extrusion molding or the like, heating is generally in the range of 50 to 90 ° C.

  At this time, since high dispersibility of the black pigment can be obtained, a master batch is prepared by previously mixing a high concentration black pigment with an ethylene-polar monomer copolymer, and the various components described above are further mixed with this master batch. Thus, it is preferable to obtain the composition.

  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 structure of the solar cell using the solar cell sealing film according to the present invention is not particularly limited. However, the solar cell sealing film is interposed between the front surface side transparent protective member and the back surface side protective member to crosslink. Examples include a structure in which cells for solar cells are sealed by integration.

  In the solar cell, in order to sufficiently seal the solar cell, as shown in FIG. 1, the surface side transparent protective member 11, the surface side sealing film 13A, the solar cell 14 and the back surface side sealing film 13B. And the back surface side protection member 12 may be laminated | stacked, and the sealing film should just be bridge | crosslinked and hardened | cured according to conventional methods, such as heating and pressurization.

The cross-linking curing is preferably performed until the gel fraction of the sealing film is 90% by mass or more in order to obtain high sealing properties. In order to crosslink and cure the sealing film to such a gel fraction, for example, the laminate is heated at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., and a degassing time of 0. What is necessary is just to heat-press in 1-5 minutes, press pressure 0.1-1.5 kg / cm < ² >, and press time 5-15 minutes. Thereby, by cross-linking the ethylene-polar monomer copolymer contained in the surface side sealing film 13A and the back surface side sealing film 13B, the surface side sealing film 13A and the back surface side sealing film 13B are passed through the surface. The solar cell 14 can be sealed by integrating the side transparent protective member 11, the back surface transparent member 12, and the solar cell 14.

  Since the sealing film for solar cells of this invention contains a black pigment, it is especially preferable to use as a back surface side sealing film arrange | positioned between the cell for solar cells, and a back surface side protection member.

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

  The 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 surface side protective member used in the present invention is a plastic film such as PET. In consideration of heat resistance and moist heat resistance, a fluorinated polyethylene film, particularly a fluorinated polyethylene film / Al / fluorinated polyethylene film, in this order. The film laminated | stacked by may be sufficient.

  The back surface side protection member is preferably colored in a dark color such as black with a black pigment such as carbon black. By using the above-described sealing film of the present invention for a solar cell having such a back surface side protective member, it is possible to provide a solar cell with excellent design properties to which black color is imparted without reducing the power generation performance.

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

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

(Example 1)
Ethylene-vinyl acetate copolymer (content of 25 parts by weight of vinyl acetate with respect EVA100 parts by mass), black pigment (carbon black; average primary particle diameter 40 nm, DBP oil absorption of 50 cm ^3/100 g, BET specific surface area of 75 m ² / g) was placed in a Henschel mixer and stirred and mixed for 3 minutes. The obtained mixture was kneaded and extruded at 150 ° C. using a twin-screw extruder and pelletized to prepare a master batch (average particle size 5 mm).

  The mixture obtained after further adding each material (EVA, crosslinking agent and crosslinking aid) to the masterbatch prepared as described above so that the finally obtained sealing film has the formulation shown in Table 1. Was fed to a roll mill and kneaded at 70 ° C. to obtain a composition, which was calendered at 70 ° C., allowed to cool, and then a solar cell sealing film (thickness 0.6 mm) was produced.

(Examples 2-4, Comparative Examples 1-5)
A solar cell sealing film was prepared in the same manner as in Example 1 except that the amount of the black pigment was as shown in Table 1.

(Measuring method)
In addition, the measurement of each physical property value in this invention was performed using the following method.

1. Blackness of the sealing film The blackness of the sealing film can be determined by using a color difference meter (SM Color Computer Suga Test Instruments Co., Ltd.) and the value of L ^* a ^* b ^* color system in JIS-Z-8729. (1994) and the L ^* value was evaluated as an index of blackness.

2. Volume Specific Resistance of Cross-Linked Sealing Film The sealing film was preheated by being placed in a 90 ° C. atmosphere for 10 minutes, and then further cross-linked by heating at 155 ° C. for 45 minutes. This crosslinked sealing film (gel fraction 95 mass%) was punched into a size of 100 mm × 100 mm and placed on a ring type electrode (UR-100 probe manufactured by Mitsubishi Chemical Corporation). A voltage was applied, the resistance value after 1 minute was measured with a high resistance meter (High Lester UPMCP-HT450 manufactured by Mitsubishi Chemical Corporation), and the volume resistivity was calculated based on the measured value.

3. Gel fraction of the sealing film after crosslinking 1 g of the sealing film crosslinked above is weighed and put into an 80 mesh wire mesh bag. The sample with the wire mesh is put into the Soxhlet extractor, and xylene is refluxed at the boiling point. After 24 hours of continuous extraction, the entire wire mesh and the sample are taken out, dried, weighed, and compared with the weight before and after extraction to measure the mass% of the remaining insoluble matter, which is taken as the gel fraction.

4). Total light transmittance of sealing film Using a fully automatic direct reading haze computer HGM-2DP (manufactured by Suga Test Instruments Co., Ltd.), the total light transmittance in the thickness direction of the sealing film was measured.

5. Average primary particle diameter of carbon black The sealing film was observed with a transmission electron microscope at a magnification of about 1,000,000 times, and the number average value of the area equivalent circle diameters of at least 100 primary particles of carbon black was calculated.

6). DBP oil absorption of carbon black JIS K6221 (1982) Measured according to method A in Section 6.1.2.

7). BET specific surface area of carbon black According to JIS K6217 (2004), the nitrogen adsorption amount was measured by the S-BET method.

It is sectional drawing of a common solar cell.

Explanation of symbols

11, surface side transparent protective member,
12, back side protection member,
13A surface side sealing film,
13B Back side sealing film,
14 Solar cell.

Claims (12)

A solar cell encapsulating film comprising an ethylene-polar monomer copolymer, a crosslinking agent, and a black pigment,
The L ^* a ^* b ^* color system has an L ^* value of 0.1 or less and a volume resistivity value after crosslinking of 1.0 × 10 ^{14 to} 1.0 × 10 ¹⁵ Ωcm. A sealing film for solar cells.   The solar cell sealing film according to claim 1, wherein the total light transmittance is 0.1% or less.   The solar cell sealing film according to claim 1, wherein the black pigment is carbon black.   The solar cell sealing film according to claim 3, wherein the carbon black has an average primary particle diameter of 20 to 80 nm. The solar cell sealing film according to claim 3 or 4 DBP oil absorption amount of the carbon black is characterized in that it is a 30~200cm ³ / 100g. 6. The solar cell sealing film according to claim 3, wherein the carbon black has a BET specific surface area of 10 to 200 m ² / g.   The solar cell according to claim 1, wherein the black pigment is contained in an amount of 0.15 to 5.0 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Sealing film.   The solar cell sealing film according to claim 1, wherein the ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer.   The said crosslinking agent is contained 0.1-5 mass parts with respect to 100 mass parts of said ethylene-polar monomer copolymers, The sealing for solar cells of any one of Claims 1-8 characterized by the above-mentioned. Stop film.   Furthermore, a crosslinking adjuvant is included, The sealing film for solar cells of any one of Claims 1-9 characterized by the above-mentioned.   11. The solar cell sealing film according to claim 10, comprising 0.1 to 5 parts by mass of the crosslinking aid with respect to 100 parts by mass of the ethylene-polar monomer copolymer. In a solar cell formed by sealing a solar cell by interposing a sealing film between the front surface side transparent protective member and the back surface side protective member and integrating them with each other,
The said sealing film is a solar cell sealing film of Claims 1-11, The solar cell characterized by the above-mentioned.

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