JP5222004B2 - 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, solar cells that directly convert sunlight into electrical energy have been widely used and further developed in terms of effective use of resources and prevention of environmental pollution.

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

  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.

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

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

  Moreover, the sealing film which consists of an ethylene-polar monomer copolymer mentioned above is also used in order to adhere | attach a transparent substrate in a laminated glass. In the laminated glass, laminated glass to which a further high function is added, such as a heat ray shielding laminated glass sandwiched by a heat ray shielding film made of a metal film or a metal oxide film, is employed. Similarly, in such a laminated glass, the moisture that has entered inside may reach the metal film and the metal oxide film to corrode them.

  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 2). ). 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.

JP 2000-174296 A JP 2005-29588 A

  A wide range of research and development has been carried out on solar cells, etc., but in order to promote its spread, it is necessary to prevent the corrosion of metals such as conductors and electrodes even under extremely harsh natural environments outdoors, for a longer period of time. It is desired that it can be used over a wide range.

  Moisture that has entered the inside of the solar cell or the like hydrolyzes the ethylene-polar monomer copolymer to generate carboxylic acid such as acetic acid, and further causes the following deterioration factors.

  That is, moisture that has entered the solar cell may hydrolyze the ethylene-polar monomer copolymer to produce carboxylic acid or alcohol such as acetic acid, and may further produce amine. As described above, the carboxylic acid produced in this way comes 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.

  In addition, the sealing film is required to maintain a high degree of transparency over a long period of time depending on its use, but according to the study of the present inventor, a sealing film using a carbodiimide compound formed from an isocyanate compound in particular. It has been clarified that the sealing film may turn yellow over time depending on use conditions such as irradiation of ultraviolet rays over a long period of time.

  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.

  A carbodiimide compound is generally formed using an isocyanate compound. Therefore, an unreacted isocyanate group may remain in the obtained carbodiimide compound. Such isocyanate groups are considered to cause a chemical reaction with time to form an azo group known as a chromophore such as yellow and yellow the sealing film. That is, an unreacted isocyanate group in the carbodiimide compound is considered as one of the causes of yellowing of the sealing film using the carbodiimide compound.

  Therefore, the present invention has found that the above-mentioned problem can be solved by using a carbodiimide compound formed using an isocyanate compound having an unreacted isocyanate group content of a predetermined value or less.

That is, the present invention includes an ethylene-polar monomer copolymer and a carbodiimide compound having at least one carbodiimide group formed from an isocyanate compound,
The said subject is solved by the sealing film for solar cells whose content of the unreacted isocyanate group in the said carbodiimide compound is 1.0 mass% or less.

  Preferred embodiments of the sealing film of the present invention are listed below.

  (1) The unreacted isocyanate group is modified to a urethane group-containing group and / or a ureylene group-containing group.

  (2) The carbodiimide compound has the following formula (I)

[However, R ¹ and R ² may be the same or different, and —NHCONH ₂ , —NHCONHR ⁴ , —NHCONR ⁴ R ⁵ and —NHCOOR ⁶ (provided that R ⁴ and R ⁵ are the same or different. Each represents an alkyl group, a cycloalkyl group, an aryl group, and a hydroxyalkyl group, each optionally having a substituent, and R ⁶ is a hydrogen atom, and each alkyl group optionally having a substituent. Represents a cycloalkyl group, an aryl group, and a hydroxyalkyl group), and represents at least one group selected from the group consisting of
R ³ represents the aralkylene group interrupted by an alkylene group, a cycloalkylene group, an arylene group or an arylene group, which may be the same or different and may have a substituent,
n represents an integer of 1 or more].

  (3) The weight average molecular weight of the carbodiimide compound is 100 to 10,000.

  (4) 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.

  (5) The content of the polar monomer in the ethylene-polar monomer copolymer is 20 to 35 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer.

  (6) Furthermore, 0.1-2 mass parts of organic peroxide is included with respect to 100 mass parts of ethylene-polar monomer copolymers.

  ADVANTAGE OF THE INVENTION According to this invention, the sealing film which can not only suppress a metal corrosion over a long period of time but can maintain high transparency 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 has at least one carbodiimide group (—N═C═N—) formed from an isocyanate compound in addition to the ethylene-polar monomer copolymer, and the content of unreacted isocyanate groups. Includes a carbodiimide compound having a content of 1.0% by mass or less.

  In the present invention, by using a carbodiimide compound, moisture can be taken into the carbodiimide group and a sealing film having dehydrating properties can be obtained. Furthermore, even if hydrolysis of the ethylene-polar monomer copolymer occurs due to moisture that could not be removed by dehydration, the carboxylic acid, alcohol, and amine generated thereby react with the carbodiimide compound to generate power generation characteristics of the solar cell. In addition, a compound having a carbamoyl group, an isourea group, or the like that does not adversely affect the appearance can be formed. Thus, according to the carbodiimide compound, in addition to being excellent in dehydrating properties, it is possible to highly suppress the occurrence of degradation factors of the solar cell caused by hydrolysis, and the corrosion of the metal contained in the inside of the solar cell is further prolonged. A sealing film that can be suppressed over a period of time can be provided.

  Furthermore, in the sealing film of this invention, content of an unreacted isocyanate group shall be 1.0 mass% or less in the carbodiimide compound formed from the isocyanate compound. Thereby, it is possible to suppress the yellowing of the sealing film due to the reaction of isocyanate groups with time to form azo groups known as chromophores such as yellow. Therefore, according to the said isocyanate compound, high transparency can be maintained in the use over a long period of time, and it becomes possible to provide the sealing film which is excellent in external appearance design property.

  Therefore, according to the present invention, it is possible not only to suppress metal corrosion over a long period of time, but also to provide a sealing film that can maintain high transparency over a long period of time and is excellent in appearance design. can do.

  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-.

  The carbodiimide compound thus formed from the isocyanate compound has an unreacted isocyanate group content of 1.0% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0% by mass. Thereby, yellowing with time can be suppressed and a sealing film excellent in transparency and appearance design can be obtained.

  The isocyanate compound used for forming the carbodiimide compound is not particularly limited as long as it is a conventionally known isocyanate compound. Since a carbodiimide compound having a relatively high molecular weight can be easily synthesized, it is preferable to use a carbodiimide compound obtained by polymerization of a diisocyanate compound. Specific examples of the diisocyanate compound are as described later.

The unreacted isocyanate groups in the carbodiimide compound, for isocyanate groups to each other to present at the end of the molecular structure is likely to react to form an azo group, unreacted isocyanate groups are terminal isocyanate groups, as described above It is preferable that it is 1.0 mass% or less in a carbodiimide compound .

In the present invention, the carbodiimide compound is preferably used in which the unreacted isocyanate group is modified with a urethane group-containing group and / or a ureylene group-containing group. Examples of the urethane group-containing group and / or ureylene group-containing group include a group consisting of —NHCONH ₂ , —NHCONHR ⁴ , —NHCONR ⁴ R ⁵ and —NHCOOR ⁶ in R ¹ and R ² of the following formula (I). Examples include at least one group selected.

  Such a carbodiimide compound is generally obtained by polymerizing an isocyanate compound, particularly a diisocyanate compound, and then modifying an unreacted isocyanate group to a urethane group-containing group and / or a ureylene group-containing group. In the carbodiimide compound thus obtained, it is desirable that all of the unreacted isocyanate group is modified to a urethane group-containing group and / or a ureylene group-containing group, but a part of the unreacted isocyanate group is not modified. It may remain.

  Therefore, the carbodiimide compound may be a mixture of an unreacted isocyanate group modified with a urethane group-containing group and / or a ureylene group-containing group and a group in which the unreacted isocyanate group remains, In this invention, content of the unreacted isocyanate group in each of these carbodiimide compounds shall be 1.0 mass% or less.

  As the carbodiimide compound, a carbodiimide compound represented by the following formula (I) is particularly preferable.

In the formula (I), R ¹ and R ² may be the same or different, and —NHCONH ₂ , —NHCONHR ⁴ , —NHCONR ⁴ R ⁵ and —NHCOOR ⁶ (provided that R ⁴ and R ⁵ are the same) Or an alkyl group, a cycloalkyl group, an aryl group, and a hydroxyalkyl group, which may be different and each may have a substituent, and R ⁶ may be a hydrogen atom, each having a substituent. And represents at least one group selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group and a hydroxyalkyl group.

Examples of the alkyl group in R ⁴ , R ⁵ and R ⁶ include linear or branched alkyl groups having 1 to 14 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group.

Examples of the cycloalkyl group in R ⁴ , R ⁵ and R ⁶ include cycloalkyl groups having 3 to 14 carbon atoms, particularly 3 to 8 carbon atoms. Specifically, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group and the like are preferable.

Examples of the aryl group in R ⁴ , R ⁵ and R ⁶ include aryl groups having 6 to 20 carbon atoms, particularly 6 to 14 carbon atoms. Specifically, a phenyl group, a tolyl group, a naphthyl group, etc. are mentioned preferably.

Examples of the hydroxyalkyl group in R ⁴ , R ⁵ and R ⁶ include a hydroxyalkyl group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms and having one or more hydroxyl groups. Specifically, a hydroxymethyl group 2-hydroxyethyl group, 2-hydroxypropyl group, 3-hydroxypropyl group, 4-hydroxybutyl group, 6-hydroxyhexyl group and the like.

The alkyl group, cycloalkyl group, aryl group and hydroxyalkyl group described above for R ⁴ , R ⁵ and R ⁶ may each preferably have 1 to 4 substituents. Preferred examples of the substituent include a linear or branched alkyl group having 1 to 6 carbon atoms. In addition, as said alkyl group, the thing similar to what was enumerated above is mentioned preferably.

In the formula (I), R ¹ and R ² are preferably —NHCOOR ⁶ (R ⁶ represents a hydroxyalkyl group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms which may have a substituent. ). Thereby, it is possible to obtain a sealing film in which not only the corrosion of the metal but also the yellowing over time is highly suppressed.

In the formula (I), R ³ may be the same or different and each represents an alkylene group, a cycloalkylene group, an arylene group, or an aralkylene group interrupted by an arylene group, which may have a substituent.

The alkylene group for R ³ is preferably a linear or branched alkylene group having 1 to 14 carbon atoms, particularly 1 to 8 carbon atoms. Specifically, methylene group, ethylene group, ethylidene group, trimethylene group, propylene group (1,2-propanediyl group), isopropylidene group, tetramethylene group, ethylethylene group, pentamethylene group, hexamethylene group, hepta Preferred examples include a methylene group and an octamethylene group.

Preferred examples of the cycloalkylene group for R ³ include cycloalkylene groups having 3 to 14 carbon atoms, particularly 3 to 8 carbon atoms. Specifically, 1,2-cyclopropylene group, 1,2-cyclobutylene group, 1,3-cyclobutylene group, 1,2-cyclopentylene group, 1,3-cyclopentylene group, 1,2 -Cyclohexylene group, 1,3-cyclohexylene group, 1,4-cyclohexylene group, 1,2-cyclooctylene group, 1,3-cyclooctylene group, 1,4-cyclooctylene group, 1, A 5-cyclooctylene group is preferred.

Preferred examples of the arylene group for R ³ include an arylene group having 6 to 20 carbon atoms, particularly 6 to 14 carbon atoms. Specifically, o-phenylene group, m-phenylene group, p-phenylene group and the like are preferable.

The aralkylene group interrupted by the arylene group in R ³ includes the following formula (II)

(Wherein, R ⁴ represents a hydrogen atom or an alkyl group, m is 1 to 4, in particular represents an integer of 1 to 3) groups preferably represented by. Preferred examples of the alkyl group for R ⁴ include straight-chain or branched alkyl groups having 1 to 6 carbon atoms. Examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group.

  Examples of the group represented by the formula (II) include an o-xylylene group, m-xylylene group, p-xylylene group, o-diethylenephenylene group, m-diethylenephenylene group, p-diethylenephenylene group and the like. .

The alkylene group, cycloalkylene group, arylene group, and aralkylene group interrupted by the arylene group described above as R ³ may each have 1 to 4 substituents. Preferred examples of the substituent include a linear or branched alkyl group having 1 to 6 carbon atoms. In addition, as said alkyl group, the thing similar to what was enumerated above is mentioned preferably.

Among those described above, R ³ is preferably an arylene group and / or an aralkylene group interrupted by an arylene group. Particularly preferred is an aralkylene group interrupted by an arylene group represented by the above formula (II). Thereby, it is possible to obtain a sealing film in which not only the corrosion of the metal but also the yellowing over time is highly suppressed.

  In the formula (I), n is an integer of 1 or more. The n is preferably an integer of 1 to 1000, more preferably 1 to 100. Within this range, a carbodiimide compound excellent in compatibility with the ethylene-polar monomer copolymer and storage stability can be obtained.

  The weight average molecular weight of the carbodiimide compound is preferably 100 to 10,000, more preferably 100 to 1,000. Thereby, it can be set as the carbodiimide compound excellent in compatibility with an ethylene-polar monomer copolymer, and the sealing film excellent in the suppression performance of metal corrosion and transparency can be formed over a long period of time.

  In the present invention, the weight average molecular weight of the carbodiimide compound is a value measured in terms of polystyrene using gel permeation chromatography (manufactured by Showa Denko KK, Shodex GPC System-21H).

  The carbodiimide compound described above is particularly preferably the following formula (III)

(Wherein, r represents an integer of 1 to 10, and p represents an integer of 2 to 100).

  The synthesis of the carbodiimide compound may be performed in accordance with a conventionally known method. For example, after a diisocyanate compound is carbodiimidized by decarboxylation condensation reaction in the presence of a carbodiimidization catalyst in the absence of a solvent or in a predetermined solvent, an unreacted isocyanate group, particularly a part or all of a terminal isocyanate group is reacted with an active hydrogen compound Or the like.

  Known solvents are used as the solvent. 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.

  The carbodiimidization catalyst may be a known catalyst, and examples thereof include organic phosphorus compounds and organometallic compounds.

  Examples of the organic phosphorus compound include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, and 3-methyl-1- Preferable examples include phospholene oxides such as phenyl-2-phospholene-2-oxide or their 3-phospholene isomers.

As the organometallic compound, a general formula: M- (OR) _l (M represents titanium, sodium, potassium, vanadium, tungsten, hafnium, zirconium, lead, manganese, nickel, calcium, or barium; An alkyl group having 1 to 20 carbon atoms or an aryl group, and 1 represents an integer of 1 to 4 determined according to the valence of M). Preferable examples of the organometallic compound include alkoxides of titanium, hafnium, and zirconium.

  Examples of the diisocyanate compound 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 Etc., and the like.

  Moreover, when setting it as a polycarbodiimide compound, a polymerization reaction can be stopped on the way by cooling etc., and it can control to a suitable polymerization degree. At this time, the terminal is isocyanate.

  Further, in order to adjust the unreacted isocyanate group, particularly the terminal isocyanate group to a predetermined content, all or part of the remaining terminal isocyanate is used by using an active hydrogen compound that reacts with the unreacted isocyanate group of the polycarbodiimide compound. A method of sealing is used. By controlling the degree of polymerization, compatibility with the polymer and storage stability can be improved, which is preferable.

  Examples of such active hydrogen compounds include the following.

(I) an aliphatic, alicyclic, aromatic, or araliphatic compound having an —OH group; specifically, methanol, ethanol, n-propanol, isopropanol, n-butanol, secondary butanol, n-pen Tanol, n-hexanol, 2-ethylhexanol, octanol, 2-ethyloctanol, decanol, dodecanol, cyclohexanol, benzyl alcohol, phenol, N-methylethanolamine, polyethylene glycol monomethyl ether and polypropylene glycol monomethyl ether;
(Ii) alkoxy polyoxyalkylenes such as polyoxybutylene alcohol, polyoxypropylene alcohol, polyoxypropylene-polyoxyethylene alcohol and polyoxyethylene alcohol;
(Iii) = diethylamine, diethylamine, dipropylamine, dibutylamine, methylbutylamine, ethylbutylamine, ethylhexylamine, cyclohexylamine, dicyclohexylamine and benzylamine having an NH group;
(Iv) Methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, 2-ethylhexylamine, octylamine, decylamine, cyclohexylamine, N, N′-bis (2,6) having —NH ₂ group -Diisopropylphenyl) thiourea;
(V) succinic acid, benzoic acid, cyclohexanoic acid having a -COOH group;
(Vi) a compound having an epoxy group;
(Vii) Acetic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride.

  The reaction temperature in the decarboxylation condensation reaction is preferably 70 ° C. or higher. Thereby, the decarboxylation condensation reaction proceeds sufficiently.

  In addition to the above-described method, the synthesis of the carbodiimide compound is performed by reacting a part of the isocyanate group of the diisocyanate compound with the active hydrogen compound, and then in the absence of a solvent or in a predetermined solvent in the presence of a carbodiimidization catalyst. A method of carbodiimidization by a decarboxylation condensation reaction is also used.

  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 due to the carbodiimide compound may not be obtained. May fall.

(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, 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 may contain an ultraviolet absorber, 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. 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 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, the corrosion of the metal contained in the inside of a battery etc. can be suppressed.

  In addition to the sealing film using the carbodiimide compound having an unreacted isocyanate group content of 1.0% by mass or less, the unreacted isocyanate group is a urethane group as a carbodiimide compound formed from the isocyanate compound. Even with a sealing film using a carbodiimide compound that has been modified into a containing group and / or a ureylene group-containing group, the metal corrosion contained in the inside of the solar cell, etc. is excellent in suppressing performance and transparency, and these are made longer. It is possible to provide a sealing film that can be maintained throughout.

  That is, the second sealing film of the present invention includes an ethylene-polar monomer copolymer and a carbodiimide compound having at least one carbodiimide group formed from an isocyanate compound, and an unreacted isocyanate group in the carbodiimide compound. However, the sealing film | membrane modified | denatured by the urethane group containing group and / or the ureylene group containing group is mentioned.

  Even with the second sealing film of the present invention, the carbodiimide compound is excellent in dehydrating property, and can highly suppress the generation of degradation factors of the solar cell caused by hydrolysis. The sealing film which can suppress the corrosion of the metal contained in etc. over a further long period can be provided. Moreover, since a carbodiimide compound does not contain an unreacted isocyanate group, it can maintain high transparency in the use over a long period of time, and it becomes possible to provide the sealing film excellent in external appearance design property.

Examples of the urethane group-containing group and / or ureylene group-containing group include a group consisting of —NHCONH ₂ , —NHCONHR ⁴ , —NHCONR ⁴ R ⁵ and —NHCOOR ⁶ in R ¹ and R ² of the following formula (I). Examples include at least one group selected.

  In the second sealing film of the present invention, the carbodiimide compound is preferably the following formula (I);

[However, R ¹ and R ² may be the same or different, and —NHCONH ₂ , —NHCONHR ⁴ , —NHCONR ⁴ R ⁵ and —NHCOOR ⁶ (provided that R ⁴ and R ⁵ are the same or different. Each represents an alkyl group, a cycloalkyl group, an aryl group, and a hydroxyalkyl group, each optionally having a substituent, and R ⁶ is a hydrogen atom, and each alkyl group optionally having a substituent. Represents a cycloalkyl group, an aryl group, and a hydroxyalkyl group), and represents at least one group selected from the group consisting of
R ³ represents the aralkylene group interrupted by an alkylene group, a cycloalkylene group, an arylene group or an arylene group, which may be the same or different and may have a substituent,
Preferably, n represents an integer of 1 or more.

  Note that the detailed description of the carbodiimide compound and the ethylene-polar monomer copolymer represented by the formula (I) is the same as that of the sealing film described above, and is omitted here.

  In addition to the carbodiimide compound and the ethylene-polar monomer copolymer, the second sealing film of the present invention includes a crosslinking agent, a crosslinking aid, an acid acceptor, a plasticizer, an adhesion improver, if necessary. Various additives such as an acryloxy group-containing compound, a methacryloxy group-containing compound, an epoxy group-containing compound, an ultraviolet absorber, a light stabilizer and an anti-aging agent may be further included. Detailed description thereof is also omitted here because it is similar to the sealing film already described above.

  According to each sealing film of the present invention described above, in addition to hydrolysis of the ethylene-polar monomer copolymer by moisture that has entered the solar cell, degradation factors such as carboxylic acids, alcohols, and amines generated by the hydrolysis Occurrence can be suppressed. Therefore, each sealing film of the present invention described above is preferably used 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, 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.

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. By crosslinking the ethylene-polar monomer copolymer contained in the front side sealing film 13A and the back side sealing film 13B during this heating and pressurization, the front side sealing film 13A and the back side sealing film 13B are interposed. And the surface side transparent protection member 11, the back surface side transparent member 12, and the cell 14 for solar cells can be integrated, and the cell 14 for solar cells can be sealed.

  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.

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

Example 1
The composition shown in Table 1 was supplied to a roll mill, and the composition prepared by kneading at 70 ° C. was calendered at 70 ° C. and allowed to cool, thereby sealing film (thickness 0.6 mm). ) Was produced.

(Examples 2 to 4, Reference Examples 1 to 4 and Comparative Example 1)
A sealing film was produced in the same manner as in Example 1 except that the materials and blending were as shown in Table 1 and Table 2, respectively.

(Evaluation)
About the sealing film produced above, the yellowing degree after the durability test and the acetic acid generation amount were evaluated according to the following procedures.

1. Yellowing degree (1) Production of module for yellowing degree test After each sealing film 26 produced above was sandwiched between two glass plates (thickness 3 mm) 21 as shown in FIG. Sealed to produce a yellowing degree test module. The sealing is performed by heating and pressing a laminated body of a glass plate and a sealing film with a vacuum laminator at 90 ° C. for 10 minutes, and then heating in an oven at 155 ° C. for 20 minutes to form a sealing film gel. This was carried out by heat crosslinking until the fraction (crosslinking degree) reached 90%.

(2) Measurement of yellowing degree (ΔYI) The test module prepared above was irradiated with ultraviolet rays for 200 hours with a radiation intensity of 1000 W / m ² (manufactured by iSuper UV Iwasaki Electric Co., Ltd.). Thereafter, YI ₀ of the test module before being left and YI ₁ of the test module after being left were measured, and ΔYI was calculated by calculating the difference (ΔYI = YI ₁ −YI ₀ ). The YI value was measured using a multiple light source spectrocolorimeter (manufactured by Suga Test Instruments Co., Ltd.) with a C light source and a visual field of 2 °. The results are shown in Table 1.

2. Acetic acid generation amount (1) Production of acetic acid generation amount test module Each sealing film 36 produced above, and PET film on which an Ag film was formed by sputtering (XIR 72-47, South Wall Technologies, Inc., thickness 50 μm) 3) is sandwiched between two glass plates 31 (thickness: 3 mm) 31 that have been washed and dried, put into a rubber bag, vacuum degassed, and pre-pressed at a temperature of 100 ° C. as shown in FIG. . Further, this was put in an autoclave and subjected to pressure and heat treatment for 30 minutes under the conditions of a pressure of 13 × 10 ⁵ Pa and a temperature of 140 ° C. to produce an acetic acid generation amount test module.

(2) Measurement of acetic acid generation amount The test module prepared above was left in an environment of a temperature of 121 ° C. and a humidity of 100% RH for 12 hours, and then the sealing film was taken out and placed in 2.0 ml of acetone at 25 ° C. for 48 hours. It was immersed and the amount of acetic acid (ppm) contained in the acetone extract was measured using a gas chromatograph. The results are shown in Table 1. In Table 1, ◎, ○, × are as follows.

A: The amount of acetic acid is less than 500 ppm. A: The amount of acetic acid is 500 ppm or more and less than 2000 ppm. X: The amount of acetic acid is 2000 ppm or more. In Examples 3 and 4, and Reference Examples 3 and 4, the amount of acetic acid generated was not measured.

備考）
＊１：ＥＶＡ１００質量部に対して酢酸ビニルの含有量は２５質量部である。
＊２：ＥＥＡ１００質量部に対してエチルアクリレートの含有量は２５質量部である。
＊３：１，１−ジ（ｔｅｒｔ−ヘキシルパーオキシ）トリメチルシクロヘキザン
＊４：トリアリルイソシアヌレート
＊５：γ−メタクリロキシプロピルトリメトキシシラン
＊６：上記式（ＩＩＩ）で示されるカルボジイミド化合物（未反応イソシアネート基含有量０質量％：ＢＳＡＦ製 Ｅｌａｓｔｏｓｔａｂ Ｈ０１）
＊７：カルボジイミド化合物（未反応イソシアネート基含有量８質量％：日清紡績株式会社製 カルボジライトＶ−０５）

Remarks)
* 1: The content of vinyl acetate is 25 parts by mass with respect to 100 parts by mass of EVA.
* 2: The content of ethyl acrylate is 25 parts by mass with respect to 100 parts by mass of EEA.
* 3: 1,1-di (tert-hexylperoxy) trimethylcyclohexane * 4: triallyl isocyanurate * 5: γ-methacryloxypropyltrimethoxysilane * 6: carbodiimide compound represented by the above formula (III) ( Unreacted isocyanate group content: 0% by mass: Elastostab H01 manufactured by BSAF)
* 7: Carbodiimide compound (Unreacted isocyanate group content: 8% by mass: Carbodilite V-05 manufactured by Nisshinbo Industries, Inc.)

It is explanatory drawing of a common solar cell. It is sectional drawing of the module for yellowing degree test produced in the Example. It is sectional drawing of the module for acetic acid generation amount tests produced in the Example.

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 cells,
21, 31 glass plate,
26, 36 sealing film,
37 A PET film on which an Ag film is formed.

Claims (20)

An ethylene-polar monomer copolymer and a carbodiimide compound having at least one carbodiimide group formed by an isocyanate compound,
The sealing film for solar cells whose content of the unreacted isocyanate group in the said carbodiimide compound is 1.0 mass% or less.   The sealing film according to claim 1, wherein the content of unreacted isocyanate groups in the carbodiimide compound is 0.5% by mass or less.   The sealing film according to claim 1, wherein the carbodiimide compound is formed by polymerization of a diisocyanate compound.   The sealing film according to claim 1, wherein the unreacted isocyanate group is modified with a urethane group-containing group and / or a ureylene group-containing group. The carbodiimide compound has the following formula (I)

[However, R ¹ and R ² may be the same or different, and —NHCONH ₂ , —NHCONHR ⁴ , —NHCONR ⁴ R ⁵ and —NHCOOR ⁶ (provided that R ⁴ and R ⁵ are the same or different. Each represents an alkyl group, a cycloalkyl group, an aryl group, and a hydroxyalkyl group, each optionally having a substituent, and R ⁶ is a hydrogen atom, and each alkyl group optionally having a substituent. Represents a cycloalkyl group, an aryl group, and a hydroxyalkyl group), and represents at least one group selected from the group consisting of
R ³ represents the aralkylene group interrupted by an alkylene group, a cycloalkylene group, an arylene group or an arylene group, which may be the same or different and may have a substituent,
The sealing film according to any one of claims 1 to 4, wherein n represents an integer of 1 or more. R ¹ and R ² may be the same or different and are represented by —NHCOOR ⁶ (R ⁶ represents an optionally substituted hydroxyalkyl group having 1 to 10 carbon atoms). The sealing film according to claim 5. R ³ represents the following formula (II)

The sealing film according to claim 5, wherein R ⁴ represents a hydrogen atom or an alkyl group, and m represents an integer of 1 to 4.   The sealing film according to claim 1, wherein the carbodiimide compound has a weight average molecular weight of 100 to 10,000.   The sealing film according to any one of claims 1 to 8, wherein a 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.   The content of the polar monomer in the ethylene-polar monomer copolymer is 20 to 35 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Sealing film.   Furthermore, the sealing film of any one of Claims 1-10 which contain 0.1-2 mass parts of organic peroxide with respect to 100 mass parts of ethylene-polar monomer copolymers. An ethylene-polar monomer copolymer and a carbodiimide compound having at least one carbodiimide group formed from an isocyanate compound,
The sealing film for solar cells in which the unreacted isocyanate group in the carbodiimide compound is modified to a urethane group-containing group and / or a ureylene group-containing group. The carbodiimide compound has the following formula (I)

[However, R ¹ and R ² may be the same or different, and —NHCONH ₂ , —NHCONHR ⁴ , —NHCONR ⁴ R ⁵ and —NHCOOR ⁶ (provided that R ⁴ and R ⁵ are the same or different. Each represents an alkyl group, a cycloalkyl group, an aryl group, and a hydroxyalkyl group, each optionally having a substituent, and R ⁶ is a hydrogen atom, and each alkyl group optionally having a substituent. Represents a cycloalkyl group, an aryl group, and a hydroxyalkyl group), and represents at least one group selected from the group consisting of
R ³ represents the aralkylene group interrupted by an alkylene group, a cycloalkylene group, an arylene group or an arylene group, which may be the same or different and may have a substituent,
The sealing film according to claim 12, wherein n represents an integer of 1 or more. R ¹ and R ² may be the same or different and are represented by —NHCOOR ⁶ (R ⁶ represents an optionally substituted hydroxyalkyl group having 1 to 10 carbon atoms). The sealing film according to claim 13. R ³ represents the following formula (II)

The sealing film according to any one of claims 13 and 14, wherein R ⁴ represents a hydrogen atom or an alkyl group, and m represents an integer of 1 to 4.   The sealing film according to claim 12, wherein the carbodiimide compound has a weight average molecular weight of 100 to 10,000.   The sealing film according to any one of claims 12 to 16, wherein a 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.   The content of the polar monomer in the ethylene-polar monomer copolymer is 20 to 35 parts by mass with respect to 100 parts by mass of the ethylene-polar monomer copolymer. Sealing film.   Furthermore, the sealing film of any one of Claims 12-18 which contains an organic peroxide 0.1-2 mass parts with respect to 100 mass parts of ethylene-polar monomer copolymers. 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 sealing film for solar cells of any one of Claims 1-19, The solar cell characterized by the above-mentioned.

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