JP5351098B2 - Sealing film and solar cell using the same - Google Patents

Description

  The present invention relates to a sealing film containing an ethylene-polar monomer copolymer as a main component, and in particular, a sealing material containing an ethylene-polar monomer copolymer as a main component used for laminating various plate materials in laminated glass and solar cells. Concerning the stop film.

  In recent years, conventional power generation methods such as thermal power generation have been regarded as problems such as depletion and soaring of fossil fuels such as oil and coal, and generation of greenhouse gases such as carbon dioxide. On the other hand, solar cells that directly convert solar energy into electric power have attracted attention, and demand is expanding.

  Generally, a solar cell is composed of a solar cell such as a silicon power generation element and a panel material on which the cell is mounted. This panel material is comprised from the surface side transparent protection member which consists of the surface side and back surface side sealing film which seals the cell for solar cells, a glass substrate, etc., a back surface side protection member (back cover), etc.

  As a sealing film used on the front side and the back side in a solar cell, a film made of an ethylene-polar monomer copolymer such as an ethylene vinyl acetate copolymer (EVA) or an ethylene ethyl acrylate copolymer (EEA) is used. It has been.

  When a solar cell is used outdoors for a long period of time in an environment where it is exposed to conditions such as 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.

  Furthermore, moisture that has entered the inside of the solar cell or the like may hydrolyze the ethylene-polar monomer copolymer to generate a carboxylic acid such as acetic acid or an alcohol, and may further generate an amine. The carboxylic acid produced in this manner is brought into contact with a metal such as a lead wire or an electrode inside the battery to promote the generation of rust. In addition, alcohol easily foams in a portion having weak adhesive force such as a wiring portion inside the solar cell. Further, the amine may yellow the sealing film when the solar cell is exposed to the outdoors for a long time. These cause a decrease in the power generation characteristics of the solar cell and a poor appearance, resulting in a decrease in the durability of the solar cell.

  Therefore, in order to further improve the durability of solar cells and the like, the hydrolysis of the ethylene-polar monomer copolymer in the sealing film is suppressed, and further the degradation of carboxylic acid, alcohol, amine, etc. caused by the hydrolysis It is necessary to suppress the generation of factors.

  Therefore, in order to prevent corrosion of the conductive wires and electrodes inside the battery and improve the durability of the solar battery, conventionally, measures such as using a glass plate as the surface-side transparent protective member have been taken. However, even if the solar cell is sufficiently sealed in this way, rusting is not prevented and the durability is not sufficiently improved.

  Among ethylene-polar monomer copolymers, for example, an EVA film is preferably used as a sealing film because it is excellent in transparency and water resistance. However, since EVA films contain vinyl acetate as a constituent component, they tend to be hydrolyzed over time due to permeation of moisture or water at high temperatures to easily generate carboxylic acids such as acetic acid. It became clear that such carboxylic acid promotes the generation of rust by contacting with the lead wires and electrodes inside the battery.

In order to solve this, an EVA film containing 0.5% by mass or less of an acid acceptor having an average particle diameter of 5 μm or less has been proposed as a transparent film used for a sealing film of a solar cell (Patent Document 1). ). According to the EVA film containing the acid acceptor, it is possible to suppress the generation of carboxylic acid from the film and improve the durability of the solar cell.
Further, it has been proposed to supplement carboxylic acid generated by adding a carbodiimide compound having an unreacted isocyanate group content of 1.0% by weight or less as an acid acceptor. (Patent Document 2)

JP 2005-29588 A JP 2008-291222 A

However, these proposed acid acceptors are added mainly for the purpose of capturing the carboxylic acid generated, and have a very poor ability to capture the hydroxyl group generated during hydrolysis. Therefore, although the carboxylic acid that induces hydrolysis catalytically can be supplemented by these acid acceptors, alcohols and amines generated at the same time remain. As a result, the sealing film may be foamed or yellowed.
Furthermore, EVA has a hydrophilic hydroxyl group in its molecular structure due to deacetic acid, so that the water vapor transmission rate gradually increases and the water absorption rate of the sealing film composition itself increases, so that moisture can easily enter the solar cell. , May induce hydrolysis.

  Accordingly, the object of the present invention is to provide a sealing film that is excellent in the performance of suppressing metal corrosion contained in the inside of a solar cell and the like, and is transparent, and that can maintain these for a longer period of time. For the purpose.

  Moreover, an object of this invention is to provide the solar cell using the said sealing film.

  As a result of intensive studies in order to achieve the above object, the present inventors have included an ethylene-polar monomer copolymer containing a carbodiimide compound having an isocyanate group at the terminal, thereby suppressing hydrolysis and causing metal corrosion. As a result, it was found that a sealing film excellent in suppression performance and transparency was obtained, and the present invention was completed.

That is, the present invention
1. A sealing film comprising an ethylene-polar monomer copolymer and a carbodiimide compound having an isocyanate group at the end;
2. The sealing film according to 1, wherein the content of the isocyanate group in the carbodiimide compound having an isocyanate group at the terminal is 2.0% by mass or more,
3. The sealing film according to 1 or 2, wherein the carbodiimide compound having an isocyanate group at the terminal is formed by polymerization of a diisocyanate compound,
4). The sealing film according to 1 to 3, wherein the diisocyanate compound is an aliphatic or alicyclic diisocyanate,
5. The sealing film according to 1-4, wherein the polymerization degree of the carbodiimide compound is 2-20.
6). The sealing film according to 1 to 5, wherein the content of the carbodiimide compound is 0.05 to 2 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer,
7). Furthermore, the sealing film of 1-6 which contains an organic peroxide 0.1-2 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers,
8). The sealing film of 1-7 which is a sealing film for solar cells.
9. In the 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, the sealing film is described in 8. A solar cell characterized by being a sealing film for solar cell,
I will provide a.

  According to the present invention, it is possible not only to suppress metal corrosion over a long period of time, but also to maintain high transparency, and further to adhere to glass substrates, back surface protection members and silicon power generation elements. An excellent sealing film can be provided. By using such a sealing film as a sealing film for a solar cell, it is possible to provide a solar cell that prevents corrosion of the metal contained therein and is excellent in appearance design due to high transparency. .

  The sealing film of the present invention contains a carbodiimide compound having an isocyanate group at the terminal in addition to the ethylene-polar monomer copolymer.

  In the present invention, by using a carbodiimide compound having an isocyanate group at the terminal, the generated acid component reacts with the carbodiimide group, the carbamoyl group reacts, the hydroxyl group and the isocyanate group, the urethane group, the amino group, the carbodiimide group, and An isocyanate group reacts to form a compound having a guanidine group and a urea group. Thus, according to the carbodiimide compound having an isocyanate group at the terminal, it is possible to maintain excellent gas barrier properties and low water vapor permeability, and to highly suppress the occurrence of degradation factors of solar cells caused by hydrolysis. The sealing film which can suppress the corrosion of the metal contained in the inside of a battery etc. further for a long period can be provided.

  Hereinafter, the sealing film of the present invention will be described in more detail.

(Carbodiimide compound)
The carbodiimide compound used for the sealing film of the present invention is a compound which is formed using an isocyanate compound and has at least one carbodiimide group, that is, a group represented by -N = C = N-.

  As the carbodiimide compound used in the present invention, those synthesized by a generally well-known method can be used. For example, an organic phosphorus compound or an organometallic compound is used as a catalyst, and various polyisocyanates are used. Examples thereof include those that can be synthesized by subjecting to a decarboxylation condensation reaction in a solvent-free or inert solvent at a temperature of about 70 ° C. or higher.

  As the polycarbodiimide compound contained in the carbodiimide compound, those produced by various methods can be used. Basically, conventional polycarbodiimide production methods [for example, US Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Pat. 0 rg. Chem. 28, 2069-2075 (1963), Chemical Review 981, Vol. 81 no. 4, p619-621] can be used.

Examples of the diisocyanate compound used in the present invention include aliphatic, alicyclic, aromatic, and araliphatic diisocyanate compounds. Specifically, 1,5-naphthalene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diene Isocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate, methylcyclohexane diisocyanate, 1,3,5-triisopropylbenzene-2,4-diisocyanate Such as tetramethylxylylene diisocyanate.
Of these, aliphatic and alicyclic diisocyanates are preferred, and specifically, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate, methylcyclohexane diisocyanate, tetramethyl. Xylylene diisocyanate is preferable, and isophorone diisocyanate, dicyclohexylmethane-4,4-diisocyanate, and tetramethylxylylene diisocyanate are particularly preferable. When an aliphatic or alicyclic diisocyanate is used, yellowing of the sealing film of the present invention over time can be suppressed.

  The deisocyanate condensation reaction of the diisocyanate is carried out in the presence of a suitable carbodiimidization catalyst. Examples of the carbodiimidization catalyst that can be used include organophosphorus compounds, organometallic compounds (general formula M- (OR) 4 [ M is titanium (Ti), sodium (Na), potassium (K), vanadium (V), tungsten (W), hafnium (Hf), zirconium (Zr), lead (Pb), manganese (Mn), nickel ( Ni), calcium (Ca), barium (Ba), and the like, wherein R represents an alkyl group or aryl group having 1 to 20 carbon atoms] are preferable, particularly from the viewpoint of activity. For organic phosphorus compounds, phospholene oxides are preferable, and for organometallic compounds, alkoxides of titanium, hafnium, and zirconium are preferable.

  Specific examples of the phosphorene oxides include 3-methyl-1-phenyl-2-phospholene-1-oxide, 3-methyl-1-ethyl-2-phospholene-1-oxide, 1,3- Dimethyl-2-phospholene-1-oxide, 1-phenyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 1-methyl-2-phospholene-1-oxide or a double of these Examples of the bond isomer can be exemplified, and 3-methyl-1-phenyl-2-phospholene-1-oxide which is easily available industrially is particularly preferable.

  As the inert solvent, known ones are used. Specifically, halogenated hydrocarbons such as tetrachloroethylene, 1,2-dichloroethane and chloroform, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, cyclic ether solvents such as tetrahydrofuran and dioxane, toluene, xylene and the like And aromatic hydrocarbon-based solvents. These solvents can be used alone or in admixture of two or more.

  In the decarboxylation condensation reaction of the diisocyanate, a carbodiimide compound having an isocyanate group at the terminal can be obtained by stopping the reaction halfway by cooling or the like and controlling it to an appropriate degree of polymerization.

  The carbodiimide compound in the present invention has an isocyanate group content of 2.0% by mass or more, preferably 3.0% by mass or more. Thereby, not only can the corrosion of the metal be suppressed for a long period of time, but also a high transparency can be maintained for a long period of time, and a sealing film excellent in appearance design can be provided.

Furthermore, in order to adjust the content within a range where the isocyanate group does not fall below 2.0% by mass, a part of the remaining terminal isocyanate is sealed with a compound that reacts with the terminal isocyanate of the carbodiimide compound. Method can be used.
Examples of the monoisocyanate for sealing the end of such a carbodiimide compound include phenyl isocyanate, tolyl isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, and butyl isocyanate.
Further, the end-capping agent that seals the end of the carbodiimide compound and controls the degree of polymerization thereof is not limited to the above-mentioned monoisocyanate, but is an active hydrogen compound that can react with isocyanate, such as (i) fat Group, aromatic or alicyclic compound, having —OH group, methanol, ethanol, phenol, cyclohexanol, N-methylethanolamine, polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether; (ii) = NH group (Iii) butylamine having a -NH2 group, cyclohexylamine; (iv) succinic acid, benzoic acid, cyclohexane acid having a -COOH group; (v) ethyl mercaptan having an -SH group, allyl mercaptan, Compounds with (vi) an epoxy group; o phenol (vii) acetic anhydride, methyl tetrahydrophthalic anhydride, can be exemplified methylhexahydrophthalic anhydride and the like.

  As for the polymerization degree of the carbodiimide compound in this invention, 2-20 are preferable. A polymerization degree of 2 or more is preferable from the viewpoint of heat resistance, and a polymerization degree of 20 or less is preferable from the viewpoint of compatibility. Moreover, by setting it as this range, it can be set as the carbodiimide compound excellent in compatibility with an ethylene-polar monomer copolymer, and forms the sealing film excellent in the metal corrosion suppression performance and transparency over a long period of time. be able to.

  In the sealing film of the present invention, the content of the carbodiimide compound described above is preferably 0.05 to 2 parts by mass, more preferably 0.1 to 1 part with respect to 100 parts by mass of the ethylene-polar monomer copolymer. It is good to be a mass part. If the content of the carbodiimide compound is less than 0.05 parts by mass, a sufficient effect of the carbodiimide compound may not be obtained, and if it exceeds 2 parts by mass, the transparency of the sealing film may be reduced.

(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 of these unsaturated carboxylic acids, sodium, 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 and sulfur dioxide. 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.

  Among them, the ethylene-polar monomer copolymer is most preferably an ethylene vinyl acetate copolymer (EVA) and / or an ethylene ethyl acrylate copolymer (EEA). Particularly preferred is an ethylene vinyl acetate copolymer (EVA). With these ethylene-polar monomer copolymers, a sealing film having excellent transparency and water resistance can be formed at low cost.

  The content of the polar monomer in the ethylene-polar monomer copolymer is 20 to 35 parts by mass, more preferably 22 to 30 parts by mass, especially 24 to 28 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Is preferred. If the content of the polar monomer is less than 20 parts by mass, the transparency of the sealing film obtained in the case of crosslinking and curing at a high temperature may not be sufficient, and if it exceeds 35 parts by mass, carboxylic acid, alcohol, amine, etc. May be more likely to occur.

(Crosslinking agent)
Furthermore, the sealing film of the present invention preferably contains a crosslinking agent in addition to the ethylene-polar monomer copolymer and the carbodiimide compound. Thereby, durability can be improved, maintaining the high reactivity in the case of bridge | crosslinking.

  As a crosslinking agent used for the sealing film, an organic peroxide or a photopolymerization initiator is preferably used. Among them, it is preferable to use an organic peroxide because a sealing film having improved temperature dependency of adhesive strength, transparency, moisture resistance, and penetration resistance can be obtained.

  Any organic peroxide may be used as long as it decomposes at a temperature of 100 ° C. or higher and generates radicals. The organic peroxide is generally selected in consideration of the film formation temperature, the adjustment conditions of the composition, the curing temperature, the heat resistance of the adherend, and the storage stability. In particular, 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 sealing film, the content of the organic peroxide is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1.5 parts, with respect to 100 parts by mass of the ethylene-polar monomer copolymer. It is preferable that it is a mass part. 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 sealing film, the content of the photopolymerization initiator is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

(Crosslinking aid)
The crosslinking aid can be added to the composition in order to improve the gel fraction of the ethylene-polar monomer copolymer and improve the durability. As a crosslinking aid (compound having a radical polymerizable group as a functional group) provided for this purpose, in addition to a trifunctional crosslinking aid such as triallyl cyanurate and triallyl isocyanurate, (meth) acrylic ester ( Examples thereof include monofunctional or bifunctional crosslinking aids such as NK ester. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable. These crosslinking aids are generally used in an amount of 10 parts by mass or less, preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the ethylene-vinyl acetate copolymer.

(Other)
The sealing film is for improving or adjusting various physical properties of the film (optical properties such as mechanical strength, adhesiveness, transparency, heat resistance, light resistance, crosslinking speed, etc.), in particular for improving mechanical strength. If necessary, it may further contain various additives such as an acid acceptor, a plasticizer, an adhesion improver, an acryloxy group-containing compound, a methacryloxy group-containing compound and / or an epoxy group-containing compound.

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

  In the sealing film, the content of the acid acceptor is preferably 0.01 to 0.15 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

  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 a sealing film having an excellent 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, Mention may be made of phenol (ethyleneoxy) 5 glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, glycidyl methacrylate, 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 may contain an ultraviolet absorber, an antioxidant, a light stabilizer and 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 influence of irradiated light and the like, and yellowing of the sealing film. Although it does not restrict | limit especially as said ultraviolet absorber, At least 1 type of ultraviolet absorber chosen from a benzotriazole type compound, a triazine type compound or a hydroxylamine type compound, and a benzophenone type compound is mentioned.

  Examples of the benzotriazole-based compound include those usually used as organic ultraviolet absorbers and those used in peptide condensation reactions, and may be simply benzotriazole or a derivative thereof. The benzotriazole compound used as the ultraviolet absorber is not particularly limited as long as it is usually used as an ultraviolet absorber. For example, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole 2- (2′-hydroxy-5′-t-butylphenyl) benzotriazole, 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] benzotriazole 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole and the like. Specifically, for example, “TINUVIN 234”, “TINUVIN 320”, “TINUVIN 326”, “TINUVIN 327”, “TINUVIN 328”, “TINUVIN P” manufactured by Ciba Specialty Chemicals, Sumitomo “Sumisorb 340” manufactured by Chemical Co., Ltd., “Adeka Stub LA-31” manufactured by Asahi Denka Kogyo Co., Ltd., and the like. Moreover, as a benzotriazole type compound used in the case of a peptide condensation reaction, N-hydroxy benzotriazole (or 1-hydroxy benzotriazole), its derivative (s), etc. are mentioned.

  Examples of the triazine compound include those usually used as organic ultraviolet absorbers and triazine derivatives having at least one amino group in the molecule. The triazine compound used as the ultraviolet absorber is not particularly limited as long as it is usually used as an ultraviolet absorber. For example, 2- (4,6-diphenyl-1,3,5-triazine-2 -Yl) -5-[(hexyl) oxy] phenol, 2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5-[(octyl) Specific examples include, for example, “TINUVIN 1577” manufactured by Ciba Specialty Chemicals, “Cyasorb UV-1164” manufactured by Cytec Industries, and the like. Is mentioned. Examples of the triazine derivative having at least one amino group in the molecule include 2,4,6-triamino-1,3,5-triazine (or melamine), 2,4-diamino-6-phenyl-1 , 3,5-triazine (or benzoguanamine), 2,4-diamino-6-methyl-1,3,5-triazine, 2,4-diamino-6- (2- (dodecylamino) ethyl) -1, 3,5-triazine, 2,4-diamino-6- (o-methoxyphenyl) -1,3,5-triazine, 4,6-diamino-1,2-dihydro-2,2-dimethyl-1- (2 , 6-Xylyl) -1,3,5-triazine, 2,4-diamino-6- (2-methoxyethyl) -1,3,5-triazine, 2-amino-4-ethyl-1,3,5 -Triazine, 2-amino- -Phenyl-1,3,5-triazine, 2-amino-4-ethyl-6-methyl-1,3,5-triazine, 2-amino-4-ethyl-6-phenyl-1,3,5-triazine 2-amino-4-methyl-6-phenyl-1,3,5-triazine, 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) Examples include -1,3,5-triazine. Specifically, for example, “IRGANOX 565” and “CHIMASSORB 119 FL” manufactured by Ciba Specialty Chemicals are listed. The triazine derivative used in the present invention is not limited to these, and any triazine derivative having at least one amino group in the molecule can be used.

  Examples of the hydroxylamine-based compound include those used in peptide condensation reactions, such as N-hydroxybenzotriazole (1-hydroxybenzotriazole), N-hydroxysuccinimide, and derivatives thereof. N-hydroxybenzotriazole is also exemplified in the benzotriazole-based compound.

  Examples of the benzophenone compounds include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, and 2-hydroxy. Preferred is -4-n-octoxybenzophenone.

When the sealing film of the present invention contains an antioxidant, it is possible to suppress the weakening of the resin due to thermal oxidative degradation. Examples of the antioxidant include hindered phenolic antioxidants and phosphite antioxidants.
Examples of the hindered phenol antioxidant include 4,4′-methylene-bis- (2,6-di-t-butylphenol) (MW = 420) and octadecyl-3- (3,5-di-). t-butyl-4-hydroxyphenyl) propionate (MW = 531) (trade name Irganox 1076 sold by Ciba Specialty Chemicals), pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate] (MW = 1178) (trade name Irganox 1010 sold by Ciba Specialty Chemicals), 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl Oxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] un Examples include decane (MW = 741) (trade name Sumilizer GA-80 sold by Sumitomo Chemical Co., Ltd.).
Examples of the phosphite-based antioxidant include tris- (2,4-di-t-butylphenyl) phosphite (trade name Irgafos 168 sold by Ciba Specialty Chemicals, trade name Adeka Stub 2112 sold by Asahi Denka Kogyo Co., Ltd., etc. ), Bis- (2,4-di-t-butylphenyl) pentaerythritol-diphosphite (trade name Irgaphos 126 sold by Ciba Specialty Chemicals, trade name Adeka Stab PEP-24G sold by Asahi Denka Kogyo Co., Ltd.), bis -(2,6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite (trade name ADK STAB PEP-36 sold by Asahi Denka Kogyo Co., Ltd.), distearyl-pentaerythritol-diphosphite (Asahi Denka) Trade name ADK STAB PEP-8, sold by Johoku Chemical Co., Ltd. Trade name JPP-2000, etc.), [bis (2,4-di-t-butyl-5-methylphenoxy) phosphino] biphenyl (GSY-P101 sold by Osaki Kogyo Co., Ltd.), N, N-bis [2- [[2,4,8,10-tetrakis (1,1dimethylethyl) dibenzo [d, f] [1,3,2] dioxaphosphine-6-yl] oxy] -ethyl] ethanamine (Ciba Specialty) A trade name of Irgaphos 12) sold by Chemical Co.

  Even when the sealing film of the present invention contains a light stabilizer, it is possible to suppress deterioration of the ethylene-polar monomer copolymer and yellowing of the sealing film due to the influence of irradiated light or the like. 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.

  In order to form the above-described sealing film of the present invention, a method of forming a sheet-like material by molding the above-described composition containing various components by ordinary extrusion molding, calendar molding (calendering) or the like is used. Can do. 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. 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.

  The thickness of the sealing film is not particularly limited, but may be in the range of 50 μm to 2 mm.

  According to the sealing film described above, in addition to hydrolysis of the ethylene-polar monomer copolymer by moisture that has penetrated into the solar cell, generation of deterioration factors such as carboxylic acid, alcohol, and amine generated by hydrolysis is suppressed. be able to. Therefore, suppressing the corrosion of the metal contained in the inside of a battery etc. is used preferably as a sealing film for solar cells.

  The structure of the solar cell using the solar cell sealing film according to the present invention is not particularly limited, but is integrated with the solar cell sealing film between the front surface side transparent protective member and the back surface side protective member. The structure etc. which sealed the cell for solar cells by making it form are mentioned.

  In the solar cell, in order to sufficiently seal the solar cell, the front side transparent protective member, the front side sealing film 1, the solar cell, the back side sealing film and the back side protective member are laminated, The sealing film may be cross-linked and cured according to a conventional method such as heat and pressure.

  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 1.5 kg / cm <2> and press time 5-15 minutes. By crosslinking the ethylene-polar monomer copolymer contained in the front surface side sealing film and the back surface side sealing film during this heating and pressurization, the front surface side sealing film and the back surface side sealing film are passed through the front surface side. The solar cell can be sealed by integrating the transparent protective member, the back surface side transparent member, and the solar cell.

  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. A film laminated with is preferable.

  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. .

  Moreover, although the solar cell was mainly demonstrated above as an application of a sealing film, it is not limited to this, It uses for bonding of the various board | plate materials which have a metal. For example, it can be used for heat ray shielding laminated glass having a heat ray shielding film such as a metal film or a metal oxide film. Even in such applications, the sealing film of the present invention can exhibit excellent characteristics in which the occurrence of corrosion and yellowing of metals and metal oxides is suppressed over a long period of time.

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

[Water absorption rate]
In accordance with JIS K7209, three test pieces (50 mm x 50 mm x 3 mm) were prepared, and the water absorption rate (%) was measured by measuring the weight when dried and after immersion for 24 hours in ion-exchanged water before and after the wet heat resistance test. The average of was calculated.

[Moisture and heat resistance test]
Using a constant temperature and humidity tester (manufactured by AGX-225 ADVANTEC), the sample piece was exposed at 80 ° C. and 95% RH.

[Weight reduction rate]
The prepared test piece was dried for 24 hours in a thermostatic bath in which the weight before and after the moisture and heat resistance test was maintained at 50 ± 2 ° C., and after cooling in a desiccator, the weight change rate was calculated.

[Weather resistance test]
The prepared test piece was exposed at 100 W / m ² and a black panel temperature of 63 ° C. using a Super Xenon Weather Meter SC-750 (manufactured by Suga Test Instruments Co., Ltd.).

[Total light transmittance]
The total light transmittance before and after the weather resistance test of the prepared test piece was measured using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.).

[Yellowness test]
The yellowness (YI) before and after the weather resistance test of the prepared test piece was measured using a simple color difference meter NF333 (manufactured by Nippon Denshoku Industries Co., Ltd.) using a C light source at a viewing angle of 2 °.

Each analysis in the synthesis example was performed by the following method.
(1) Infrared absorption (IR) spectrum FTIR-8200PC (manufactured by Shimadzu Corporation) was used.
(2) GPC
RI detector: RID-6A (manufactured by Shimadzu Corporation)
Column: KF-806, KF-804L, KF-804L
Developing solvent: THF 1 ml / min.
Calculated by polystyrene conversion.
(3) NCO%
Hiranuma automatic titrator COM-900 (manufactured by Hiranuma Sangyo Co., Ltd.), Tight Station K-900 (manufactured by Hiranuma Sangyo Co., Ltd.) is used, a dibutylamine / toluene solution of a known concentration is added, and calculation is performed by electric difference titration with an aqueous hydrochloric acid solution did.

<Synthesis Example 1>
Add 1000 g of 4,4′-dicyclohexylmethane diisocyanate and 10.0 g of 3-methyl-1-phenyl-2-phospholene-1-oxide to a flask equipped with a stirring motor, nitrogen gas bubbling tube and cooling tube, and perform nitrogen gas bubbling. While performing, carbodiimidization reaction was performed at 185 ° C. for 18 hours. The degree of polymerization of the obtained carbodiimide was 15, and the NCO group content was 2.38% by mass. Infrared absorption was confirmed absorption peak due to the isocyanate groups of the absorption due to wavelength 2150 cm ^-1 before and after the carbodiimide group by (IR) spectroscopy peak wavelength 2200~2300cm ^-1. The number average molecular weight in terms of polystyrene was 4061 as measured by GPC.

<Synthesis Example 2>
Add 1000 g of 4,4′-dicyclohexylmethane diisocyanate and 10.0 g of 3-methyl-1-phenyl-2-phospholene-1-oxide to a flask equipped with a stirring motor, nitrogen gas bubbling tube and cooling tube, and perform nitrogen gas bubbling. While performing, carbodiimidization reaction was performed at 185 ° C. for 8 hours. The degree of polymerization of the obtained carbodiimide was 3, and the NCO group content was 9.16% by mass. Infrared absorption was confirmed absorption peak due to the isocyanate groups of the absorption due to wavelength 2150 cm ^-1 before and after the carbodiimide group by (IR) spectroscopy peak wavelength 2200~2300cm ^-1. As measured by GPC, the polystyrene-equivalent number average molecular weight was 1,575.

<Synthesis Example 3>
In a flask equipped with a stirring motor, a nitrogen gas bubbling tube and a cooling tube, 576.4 g of 4,4′-dicyclohexylmethane diisocyanate and 50 g of cyclohexyl isocyanate and 3-methyl-1-phenyl-2-phospholene- After adding 6.0 g of 1-oxide and carrying out nitrogen gas bubbling to carry out a carbodiimidization reaction at 185 ° C. for 30 hours, absorption of isocyanate groups of wavelengths 2200 to 2300 cm ⁻¹ disappears by infrared absorption (IR) spectrum measurement After confirming that it was cooled, carbodiimide (polymerization degree = 10) in which the terminal of 4,4′-dicyclohexylmethanecarbodiimide was sealed was obtained. The number average molecular weight in terms of polystyrene was 3474 as measured by GPC.

<Example 1>
50 parts by weight of ethylene vinyl acetate copolymer (hereinafter abbreviated as EVA) containing a peroxide as a curing agent in a roller mixer R60H (manufactured by Toyo Seiki Co., Ltd.) and polycarbodiimide (hereinafter abbreviated as PCD) synthesized in Synthesis Example 1 Each 25 parts by weight was added and kneaded at 80 ° C. for 5 minutes. After that, it was rolled at 80 ° C., formed into a film with a thickness of 10 mm, sandwiched between polyethylene terephthalate (hereinafter abbreviated as “PET”) films on both sides of the prepared test piece, inserted with a 3 mm spacer, and placed in a vacuum press. Then, a test piece having a thickness of 3 mm was prepared by thermocompression bonding at a degassing time of 5 minutes, a pressing pressure of 1.0 kg / cm 2 and a pressing time of 15 minutes at a heating temperature of 150 ° C. and cured with peroxide. Thereafter, the release-treated PET was peeled off, and a product cut out to 50 mm × 50 mm was used as a test piece.

<Example 2>
A test piece was prepared in the same manner as in Example 1 except that the polycarbodiimide was changed to PCD synthesized in Synthesis Example 2.

<Comparative Example 1>
A test piece was prepared in the same manner as in Example 1 except that polycarbodiimide was changed to PCD synthesized in Synthesis Example 3.

<Comparative example 2>
A test piece was prepared in the same manner as in Example 1 except that the polycarbodiimide was changed to 4,4′-dicyclohexylmethane diisocyanate (HMDI).

<Comparative Example 3>
Only 50 parts by weight of EVA was added without adding the additive, and a test piece was prepared in the same manner as in Example 1.

  Each test piece described above was measured for initial water absorption, water absorption after 100 hours of wet heat test, and weight loss after 100 hours of wet heat test. The results are shown in Table 1.

  Examples 1 and 2 are superior to Comparative Examples 1 to 3 in all of the reduction in the initial water absorption rate, the water absorption rate after the wet heat test, and the weight reduction rate, and are suitable as a solar cell sealing film that is exposed to a harsh environment for a long period of time. ing.

Claims (9)

  A sealing film comprising an ethylene-polar monomer copolymer and a carbodiimide compound having an isocyanate group at a terminal.   The sealing film according to claim 1, wherein the content of the isocyanate group in the carbodiimide compound having an isocyanate group at the terminal is 2.0% by mass or more.   The sealing film according to any one of claims 1 and 2, wherein the carbodiimide compound having an isocyanate group at the terminal is formed by polymerization of a diisocyanate compound.   The sealing film according to claim 1, wherein the diisocyanate compound is composed of an aliphatic or alicyclic diisocyanate.   The sealing film according to any one of claims 1 to 4, wherein a polymerization degree of the carbodiimide compound is 2 to 20.   The sealing film according to any one of claims 1 to 5, wherein the content of the carbodiimide compound is 0.05 to 2 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.   Furthermore, the sealing film of any one of Claims 1-6 which contain 0.1-2 mass parts of organic peroxides with respect to 100 mass parts of ethylene-polar monomer copolymers.   It is a sealing film for solar cells, The sealing film of any one of Claims 1-7. 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 Claim 8, The solar cell characterized by the above-mentioned.