JP5416345B2 - Method for producing sealing film for solar cell - Google Patents

Description

  The present invention relates to a method for producing a sealing film containing an ethylene-polar monomer copolymer as a main component in a solar cell.

  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.

  In general, as shown in FIG. 1, a solar cell has a front side sealing film 13 </ b> A and a back side sealing film 13 </ b> B between a front side transparent protective member 11 and a back side protective member (back cover) 12. A plurality of solar battery cells 14 such as silicon power generation elements are sealed.

  A transparent substrate such as a glass substrate is used for a surface-side transparent protective member used in a conventional solar cell in order to make sunlight enter the battery as efficiently as possible and concentrate it on the solar cell. On the other hand, the back side protective member has a plastic film such as polyethylene terephthalate (PET) or a film in which a vapor deposition film made of silver is formed on the surface of the plastic film in order to prevent moisture from entering the battery. It is used.

  As the sealing film used on the front side and the back side, a film made of an ethylene-polar monomer copolymer such as ethylene vinyl acetate copolymer (EVA) or ethylene ethyl acrylate copolymer (EEA) is used. . In conventional solar cells, an ethylene vinyl acetate copolymer is preferably used as the sealing film because it is inexpensive and has high transparency.

  In general, a solar cell is formed by heating and rolling an EVA composition containing EVA and a crosslinking agent to form a sealing film, and then a surface-side transparent protective member, a surface-side sealing film, and a solar cell. The cell, the back-side sealing film, and the back-side protective member are laminated in this order, and are heated and pressed at a temperature of about 135 to 180 ° C. to cross-link and cure the EVA and to be integrated.

  Moreover, in the conventional sealing film for solar cells, in order to improve film strength and durability, the crosslinking density is improved by using a crosslinking agent such as an organic peroxide in addition to the ethylene-polar monomer copolymer. (Patent Document 1). The crosslinking agent activation method includes a thermal decomposition method, a redox decomposition method, and an ion decomposition method, and the thermal decomposition method is generally used.

  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.

  For example, when a sealing film for solar cells made of EVA is used, since vinyl acetate is included as a constituent component, it tends to hydrolyze with time due to permeation of moisture or water at high temperatures, and acetic acid tends to be generated. It was revealed that acetic acid such as this contacted the internal conductors and electrodes to promote the generation of rust. 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.

Japanese Patent No. 3473605 JP 2005-29588 A

Solar cells are desired to exhibit high power generation performance over a long period of time, which is said to be several decades or more, and further improvement in durability is required. The present inventors have found that by using Mg (OH) ₂ as the acid acceptor, better acid acceptability can be obtained and the durability of the solar cell can be improved.

However, in such a sealing film containing an acid acceptor such as Mg (OH) _2, although the durability of the solar cell is improved by the addition of the acid acceptor, the transparency of the seal film may be reduced. . When the transparency of the solar cell sealing film is reduced, the amount of light taken into the solar cell is reduced, leading to a reduction in the power generation performance of the solar cell. Therefore, in order to obtain a solar cell capable of exhibiting high power generation performance over a long period of time, the solar cell sealing film needs to have high transparency even if it contains an acid acceptor.

  Then, an object of this invention is to provide the manufacturing method of the sealing film for solar cells which is excellent in both acid acceptability and transparency.

  As the acid acceptor for imparting acid acceptability to the sealing film for solar cells, one having an extremely small average particle diameter is generally used in order to ensure the transparency of the sealing film. However, such a fine acid acceptor tends to cause aggregation, and it is considered that the acid acceptor aggregates when the composition is kneaded in the sealing film production process, thereby reducing the transparency of the sealing film. .

As a result of various studies focusing on such knowledge, the present inventors have used an acid acceptor composed of Mg (OH) ₂ having excellent acid acceptability, and the acid acceptor is dispersed in the sealing film. In order to improve the properties, among the various components used in the solar cell sealing film, an ethylene vinyl acetate copolymer and an acid acceptor are mixed in advance at a predetermined concentration to prepare a master batch, and then other components It has been found that the above problem can be solved by mixing.

That is, the present invention includes a step (A) of producing a master batch containing 1 to 5 parts by mass of an acid acceptor composed of Mg (OH) _{2 with} respect to 100 parts by mass of an ethylene-polar monomer copolymer, and the master batch Is further mixed with an ethylene-polar monomer copolymer and a crosslinking agent, and the composition obtained thereby is formed into a film (B), wherein the ethylene-polar monomer copolymer is ethylene-vinyl acetate. In the step (A), the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 26 to 33 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. In the step (B), the ethylene-polar monomer copolymer and the acid acceptor are heated and kneaded at a temperature of 40 to 90 ° C. to prepare the master batch . The said subject is solved by the manufacturing method of the sealing film for solar cells which mixes 0.5-4.0 mass parts with respect to 100 mass parts of said ethylene-polar monomer copolymers with said masterbatch .

According to the method of the present invention, even when an acid acceptor having a very fine average particle diameter is used, a solar cell sealing film having excellent dispersibility of the acid acceptor and high transparency is formed. be able to. Furthermore, the solar cell sealing film can exhibit high acid acceptability by including an acid acceptor composed of Mg (OH) ₂ .

  Therefore, according to the sealing film for solar cells obtained by the method of the present invention, it is possible to provide a solar cell that can exhibit high power generation performance over a long period from the beginning of power generation.

  The method of the present invention includes at least steps (A) and (B), that is, first, a step (A) for preparing a masterbatch containing an ethylene-polar monomer copolymer and an acid acceptor, and this masterbatch. A step (B) of forming a composition obtained by mixing with another component such as a crosslinking agent;

  The master batch prepared in the step (A) contains an acid acceptor at a relatively high concentration as an accessory component in the ethylene-polar monomer copolymer as the main component. After preparing such a masterbatch first, by mixing with a crosslinking agent or the like in step (B), each component is uniformly highly dispersed even when using a very fine acid acceptor that easily aggregates during mixing. It becomes possible to produce a solar cell sealing film.

Furthermore, in this invention, it becomes possible to set it as the solar cell sealing film which has high acid acceptability by using Mg (OH) ₂ as an acid acceptor.

Therefore, according to the present invention, there is provided a solar cell sealing film that has high transparency due to high dispersion of an acid acceptor and can exhibit excellent acid acceptability by an acid acceptor composed of Mg (OH) _2. It can be produced.

  Hereinafter, the present invention will be described in more detail in order.

In the method of the present invention, first, the step (A) of producing a master batch containing 1 to 5 parts by mass of an acid acceptor composed of Mg (OH) _{2 with} respect to 100 parts by mass of the ethylene-polar monomer copolymer is performed. .

The masterbatch contains 1 to 5 parts by mass of the acid acceptor with respect to 100 parts by mass of the ethylene-polar monomer copolymer. As a result, a master batch in which the ethylene-polar monomer copolymer and the acid acceptor are uniformly mixed can be obtained.

(Acid acceptor)
As the acid acceptor used in the master batch, generally, an acid acceptor that absorbs and / or neutralizes an acid such as acetic acid can be used.

In general, a metal oxide, a metal hydroxide, a metal carbonate or a composite metal hydroxide is used as the acid acceptor, 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. As the _{hydrotalcite, Mg 4.3 Al l2 (OH)} 12.6 CO 3 · mH 2 O ( manufactured by Kyowa Chemical Industry Co., Ltd. DHT-4A), and the like.

In the method of the present invention, since it is possible to particularly high prevent rusting of the battery internal conductors and electrodes, as the acid acceptor, Ru used as consisting of Mg (OH) _2.

  The average particle diameter of the acid acceptor is preferably 0.01 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.1 to 2.5 μm. If the average particle size of the acid acceptor exceeds 10 μm, the transparency of the resulting solar cell sealing film may be reduced even if the acid acceptor is highly dispersed. If it is less than 01 μm, the acid acceptor tends to aggregate and it may be difficult to achieve high dispersion.

  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.

(Ethylene-polar monomer copolymer)
Moreover, as polar monomers of ethylene-polar monomer copolymers used for the production of masterbatches, it is generally possible to exemplify unsaturated carboxylic acids, salts thereof, esters thereof, amides, vinyl esters, carbon monoxide and the like. it can. More specifically, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, itaconic anhydride, lithium of these unsaturated carboxylic acids, sodium, Salts of monovalent metals such as potassium, salts of polyvalent metals such as magnesium, calcium and zinc, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, methacrylic acid Examples include unsaturated carboxylic acid esters such as methyl, ethyl methacrylate, isobutyl methacrylate, and dimethyl maleate, vinyl esters such as vinyl acetate and vinyl propionate, carbon monoxide, sulfur dioxide, etc. be able to.

The ethylene-polar monomer copolymer is generally an ethylene-acrylic acid copolymer, an ethylene-unsaturated carboxylic acid copolymer such as an ethylene-methacrylic acid copolymer, or the ethylene-unsaturated carboxylic acid copolymer. Ionomers in which some or all of the carboxyl groups of the copolymer are neutralized with the above metal, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-isobutyl acrylate Copolymer, ethylene-unsaturated carboxylic acid ester copolymer such as ethylene-n-butyl acrylate copolymer, ethylene-isobutyl acrylate-methacrylic acid copolymer, ethylene-n-butyl acrylate-methacrylic acid copolymer Ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymer such as coalescence It can be exemplified vinyl ester copolymers and the like as a typical example - some or all of Bisono carboxyl group ionomer neutralized with the metal, ethylene - ethylene such as vinyl acetate copolymer.

In the present invention, ethylene - polar monomer copolymer, et styrene - vinyl acetate copolymer (EVA) is used. Thereby, it can be set as the sealing film for solar cells which is cheap and excellent in transparency.

In the present invention, the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 26 to 33 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer. If the vinyl acetate content exceeds 33 masses, the viscosity of the solar cell encapsulating film may be reduced, making it difficult to handle. If the vinyl acetate content is less than 26 masses, the processability is reduced. The resulting film may be too hard.

  In the method of the present invention, a master batch can be produced by using a known kneader such as a batch-type pressure kneader, open kneader, Banbury mixer, single screw extruder, twin screw kneader, roll kneader. Good. For example, an acid acceptor is added to and mixed with the ethylene-polar monomer copolymer, the obtained composition is supplied to a kneader, and after kneading, it is extruded from a die and processed into a pellet form. Further, the acid-accepting agent may be added after the ethylene-polar monomer copolymer is first supplied to the kneader.

  In addition to this, while supplying the ethylene-polar monomer copolymer to the kneader and kneading it in advance, a predetermined amount of the acid acceptor is supplied in several batches, and after kneading, it is extruded from a die and formed into a pellet. A means for processing is also used.

  In order to improve the dispersibility of the acid acceptor, it is preferable to use pellets or powders of a predetermined size as the ethylene-polar monomer copolymer used for preparing the masterbatch. For example, it is preferable to use an ethylene-polar monomer copolymer having an average diameter of 1 to 10 mm, preferably 2 to 5 mm.

  Therefore, prior to kneading with the acid acceptor, the ethylene-polar monomer copolymer may be supplied to a pulverizer, an extruder, etc. and adjusted to a predetermined size.

  In the present invention, the average diameter of the ethylene-polar monomer copolymer means that 50 arbitrary ethylene-polar monomer copolymers are taken out and the maximum diameter of each ethylene-polar monomer copolymer (in the case of an ellipse) The major axis) and the minimum diameter (minor axis in the case of an ellipse) are measured, and the average value is obtained.

In the method of the present invention, ethylene - polar monomer copolymer and an acid acceptor, 4 0 to 90 ° C., good Mashiku is you produce a master batch by heating and kneading at a temperature of 60-80 ° C.. By kneading while heating, the acid acceptor can be highly dispersed in the ethylene-polar monomer copolymer. However, the heating temperature is too high ethylene - because dispersibility of the polar monomer copolymer is melted acid acceptor may be lowered rather, the heating temperature is set to 90 ° C. or less.

  The time for heating and kneading the ethylene-polar monomer copolymer and the acid acceptor is not particularly limited, but may be 0.5 to 5 minutes, preferably about 0.5 to 2 minutes.

  The master batch is preferably pelletized into a predetermined shape such as a cylindrical shape, a prismatic shape, a spherical shape, or an elliptical spherical shape. Among these, a cylindrical shape and a prismatic shape are preferable, and the average diameter of the circular cross section is 1 to 10 mm, particularly 2 to 5 mm, and the average length is 1 to 10 mm, particularly 2 to 5 mm. Is particularly preferred.

  In the method of the present invention, the master batch prepared as described above is mixed with an ethylene-polar monomer copolymer and a crosslinking agent, and the step (B) for forming a film of the resulting composition is performed.

  The ethylene-vinyl acetate copolymer used in the step (B) is the same as that described above in the preparation of the masterbatch.

In the said process (B), a masterbatch is 0. 0, with respect to 100 mass parts of ethylene-vinyl acetate copolymers. 5 you mixed so that 4.0 parts by weight. Thereby, the high dispersibility of an acid acceptor is acquired.

(Crosslinking agent)
As the crosslinking agent, those having a 10-hour half-life temperature of 80 to 120 ° C, particularly 85 to 95 ° C are preferably used. Thereby, generation | occurrence | production of the gas in a bridge | crosslinking process can be suppressed highly. The time until the residual amount is reduced to half of the initial value when the crosslinking agent is decomposed is called a half-life, and the 10-hour half-life temperature means a temperature at which the half-life is 10 hours.

  As the cross-linking agent, an organic peroxide is preferably used because it can be cross-linked by a simple method such as a thermal decomposition method and can form a sealing film for solar cells with improved adhesion, transparency and moisture resistance.

  Specific examples of the organic peroxide include 2,5-dimethylhexane, 2,5-dihydroperoxide, 3-di-t-butyl peroxide, t-dicumyl peroxide, and 2,5-dimethyl. -2,5-bis (tert-butylperoxy) hexane, 2,5-dimethyl-2,5 di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) Oxy) hexyne, dicumyl peroxide, α, α′-bis (tert-butylperoxysopropyl) benzene, n-butyl-4,4-bis (tert-butylperoxy) butane, tert-butylperoxy 2 -Ethylhexyl monocarbonate, 2,2-bis (tert-butylperoxy) butane, 1,1-bis (tert-butylperoxy) silane Rhohexane, 1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexan, 1,1-di (Tert-hexylperoxy) -3,3,5-trimethylcyclohexane, t-butylperoxybenzoate; benzoyl peroxide and the like.

  The amount of the crosslinking agent added is preferably 0.1 to 5.0 parts by mass, more preferably 0, based on the total amount of the ethylene-polar vinyl monomer copolymer used in the step (A) and the step (B). It is good to set it as 3-3.0 mass parts.

(Crosslinking aid)
In the method of the present invention, in the step (B), the master batch is mixed with the ethylene-polar monomer copolymer and the crosslinking agent, but it is preferable to further mix a crosslinking aid. The crosslinking aid can improve the crosslinking density of the ethylene-polar monomer copolymer and improve the durability of the resulting solar cell sealing film.

  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 / or triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

  The crosslinking aid is preferably 0.1 to 3.0 parts by mass, more preferably 0.1 to the total amount of the ethylene-polar vinyl monomer copolymer used in the steps (A) and (B). Used at ~ 2.5 parts by weight.

(Adhesion improver)
In the step (B), it is preferable that the master batch is further mixed with an adhesion improver in addition to the ethylene-polar monomer copolymer and the crosslinking agent. Thereby, the adhesiveness of the solar cell sealing film obtained can be improved.

  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, and γ-glycidoxypropyltrimethoxy. Silane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β Mention may be made of-(aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Of these, γ-methacryloxypropyltrimethoxysilane is particularly preferred.

  The addition amount of the silane coupling agent is 0.1 to 0.7 parts by mass, particularly 0.3 with respect to the total amount of the ethylene-polar vinyl monomer copolymer used in the steps (A) and (B). It is preferable that it is -0.65 mass part. Thereby, the sealing film for solar cells which has the stable adhesive force is obtained.

(Other additives)
Further, in the step (B), for improving or adjusting various physical properties (optical properties such as mechanical strength and transparency, heat resistance, light resistance, crosslinking speed, etc.) of the resulting solar cell sealing film. If necessary, various additives such as a plasticizer, an acryloxy group-containing compound, a methacryloxy group-containing compound and / or an epoxy group-containing compound may be further mixed with the master batch.

  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 the total amount of the ethylene-polar vinyl monomer copolymer used in the step (A) and the step (B).

  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 0.5% relative to the total amount of the ethylene-polar vinyl monomer copolymer used in the step (A) and the step (B), respectively. It is preferable that -5.0 mass parts, and 1.0-4.0 mass parts are contained especially.

  Moreover, in a process (B), you may mix a ultraviolet absorber, a light stabilizer, and / or an anti-aging agent with a masterbatch further.

  By including the ultraviolet absorber in the solar cell sealing film of the present invention, 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 cell sealing film from yellowing. can do. 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, the compounding quantity of the said benzophenone series ultraviolet absorber is 0.01-5 mass parts with respect to the whole quantity of the ethylene-polar vinyl monomer copolymer used in the process (A) and the process (B). preferable.

  Even when the solar cell sealing film of the present invention contains a light stabilizer, the ethylene-polar monomer copolymer deteriorates due to the influence of irradiated light and the like, and the solar cell sealing film is yellowed. Can be suppressed. 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 the ethylene-polar vinyl monomer copolymer used in the process (A) and the process (B). It is preferable that it is 0.01-5 mass parts with respect to the whole quantity.

  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.

  Furthermore, in the step (B), a colorant may be further mixed with the master batch. Thereby, by coloring the sealing film for solar cells, the utilization efficiency of incident light can be increased and the power generation efficiency of the solar cells can be improved.

  As the colorant, various colorants such as white, black, blue, red, and others can be used. Among them, white colorants such as titanium oxide, calcium carbonate, zinc white, lead white, lithopone, barite, precipitated barium sulfate, and gypsum are preferably used because high utilization efficiency of incident light can be obtained.

  The content of the colorant is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Thereby, a colorant can be highly dispersed.

  In a process (B), the various components mentioned above are mixed, and the solar cell sealing film is produced by forming into a film the composition obtained by this. For this, a method similar to the conventionally known production method is used except that the master batch produced in the step (A) is used. For example, the solar cell sealing film can be produced by heating and rolling the composition by extrusion molding, calendar molding, or the like.

  The heating temperature during film formation is preferably a temperature at which the crosslinking agent does not react or hardly reacts. For example, it is preferable to set it as 40-90 degreeC, especially 50-80 degreeC.

  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.

In the solar cell sealing film obtained by the above-described method of the present invention, an acid acceptor composed of Mg (OH) ₂ that can prevent rusting of the conductive wires and electrodes inside the solar cell is highly dispersed. Therefore, it has high transparency. Therefore, the sealed solar cell using the solar cell sealing film is excellent in both durability and power generation performance.

  The configuration of the solar cell is the same as that of a conventionally known solar cell except that the solar cell sealing film obtained by the method of the present invention is used. For example, the structure etc. which sealed the cell for solar cells by interposing and hardening the said solar cell sealing film between the surface side transparent protection member and the back surface side protection member, etc. are mentioned.

  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”.

  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. At this time, the solar cell sealing film according to the present invention is used for at least one of the front surface side sealing film 13A and the back surface side sealing film 13B, preferably both.

In order to heat and pressurize, for example, the laminate is heated with a vacuum laminator at a temperature of 135 to 180 ° C., further 140 to 180 ° C., particularly 155 to 180 ° C., a degassing time of 0.1 to 5 minutes, and a press pressure of 0.1. What is necessary is just to heat-press in about 1.5 kg / cm < ² > and press time 5-15 minutes.

  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 side protective member is a plastic film such as PET, but in consideration of heat resistance and moist heat resistance, a fluorinated polyethylene film, particularly a fluorinated polyethylene film / Al thin film / fluorinated polyethylene film is laminated in this order. Films are preferred.

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

Example 1
1. Preparation of master batch 100 parts by mass of ethylene vinyl acetate copolymer (vinyl acetate content 26 parts by mass) and 5 parts by mass of acid acceptor (Mg (OH) ₂ , average particle size 0.1 μm) are put in a Henschel mixer. Stir and mix for 3 minutes. The obtained mixture was kneaded and extruded while being heated to the melting point or higher using a biaxial extruder, and pelletized to prepare a master batch (maximum diameter 5 μm).

2. Production of Solar Cell Sealing Film The master batch produced as described above was mixed with the following materials and blends.

(1) Ethylene vinyl acetate copolymer (vinyl acetate content 26 parts by mass) 100 parts by mass (2) Cross-linking agent (1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexan) 2 0.03 parts by mass (3) Cross-linking aid (triallyl isocyanurate) 2.0 parts by mass (4) Additive (γ-methacryloxypropyltrimethoxysilane) 0.5 parts by mass (5) Masterbatch 4 parts by mass A composition obtained by mixing was extruded at 80 ° C. to form a solar cell sealing film (thickness 1 mm).

(Examples 2 to 4 and Comparative Examples 1 to 3)
A solar cell encapsulating film was prepared in the same manner as in Example 1 except that the acid acceptor in the masterbatch was one having the composition and composition shown in Table 1.

(Evaluation)
1. Transparency The haze value (%) of each solar cell sealing film produced above was measured according to the method of JIS K 7105 (1981). Under the present circumstances, fully automatic direct reading haze computer HGM-2DP (made by Suga Test Instruments Co., Ltd.) was used.

2. Total light transmittance The light transmittance spectrum in the thickness direction of each of the solar cell sealing films produced above was measured using a spectrophotometer (U-4000, manufactured by Hitachi, Ltd.), and the light transmittance in the wavelength range of 300 to 1200 nm. Three places were measured and the average value was calculated. The results are shown in Table 1.

3. Acid-acceptance The acetic acid generation amount was measured after accelerating the reaction rate of acetic acid generation by the endurance test for each of the solar cell sealing films prepared above according to the following procedure.

  As shown in FIG. 2, each of the solar cell sealing films 24 produced as described above has a front surface side transparent protective member 21 made of a glass plate (thickness 3 mm) and a back side protective member 22 made of a fluorinated polyethylene film (thickness). And 120 μm) to form a laminate, which was then sealed to prepare a durability test module.

  The sealing was performed by heating the laminate with a vacuum laminator under vacuum at 155 ° C. for 30 minutes to crosslink and cure the sealing film.

  Next, the module for durability test was allowed to stand in an environment of a temperature of 121 ° C. and a humidity of 100% RH for 240 hours, and then the solar cell sealing film was immersed in 2.0 ml of acetone at 25 ° C. for 48 hours. The amount of acetic acid (ppm) contained in the extract was quantified using a gas chromatograph. The results are shown in Table 1. In Table 1, “◎”, “◯”, and “X” are as follows.

A: The amount of acetic acid is less than 600 ppm. A: The amount of acetic acid is 600 ppm or more and less than 2000 ppm. X: The amount of acetic acid is 2000 ppm or more.

It is explanatory drawing for showing the structure of a general solar cell. It is sectional drawing of the module for an endurance test produced in the Example.

Explanation of symbols

11, 21 Surface side transparent protective member,
12, 22 Back side protection member,
13A surface side sealing film,
13B Back side sealing film,
14 solar cells,
24 Solar cell sealing film.

Claims (2)

A step (A) of producing a master batch containing 1 to 5 parts by mass of an acid acceptor composed of Mg (OH) _{2 with} respect to 100 parts by mass of an ethylene-polar monomer copolymer;
(B) further mixing the masterbatch with an ethylene-polar monomer copolymer and a crosslinking agent, and forming a composition obtained thereby.
The ethylene-polar monomer copolymer is an ethylene-vinyl acetate copolymer,
The content of vinyl acetate in the ethylene-vinyl acetate copolymer is 26 to 33 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer,
In the step (A), the ethylene - by a polar monomer copolymer and said acid acceptor is heated and kneaded at a temperature of 40 to 90 ° C., to prepare the master batch,
The manufacturing method of the sealing film for solar cells which mixes 0.5-4.0 mass parts with respect to 100 mass parts of said ethylene-polar monomer copolymers in the said process (B) .   The method for producing a solar cell sealing film according to claim 1, wherein the acid acceptor has an average particle diameter of 0.01 to 10 μm.

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