JP2009259867A - Rear surface protecting sheet for solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear surface protecting sheet having front surface hardness, wetherability and anti-light performance with good balance, and capable reducing environmental load, and to provide a solar cell module using the rear surface protecting sheet. <P>SOLUTION: The rear surface protecting sheet 6 for a solar cell is formed by laminating a film 7 containing an acrylic polymer having lactone ring structure as a main component, an adhesive layer 8 and a gas barrier film 9. The solar cell module 1 is formed by laminating a front surface protecting sheet 2 for a solar cell, a resin layer 3, a solar cell element 4 having a wiring formed thereon, a resin layer 5, an easily adhering layer 10 and the rear surface protecting sheet 6 for a solar cell. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a back surface protection sheet for solar cells.

  In recent years, global environmental problems such as global warming and acid rain due to the greenhouse effect due to the increase in carbon dioxide have become serious, and the development of clean energy to replace thermal power generation is now anxious.

  One of the energy sources that are currently attracting the most attention and expectation is a solar cell that can directly convert infinite solar energy into electrical energy in terms of cleanliness, safety, and ease of handling.

  A solar cell usually employs a structure called a module in order to obtain a structure in which mechanical strength and weather resistance can be obtained after solar cells are connected in series or in parallel. The solar cell module has a structure in which a glass surface is disposed on the sunlight incident side, and then a resin layer, a solar cell, a resin layer, and a back surface protective sheet are sequentially laminated. The back surface protection sheet is disposed to protect the back surface of the solar cell module (the side opposite to the sunlight incident side). Since solar cells are often installed outdoors, the back surface protection sheet is required to have durability such as mechanical strength, weather resistance, and light resistance.

  Various types of back surface protection sheets for solar cells have been developed in the past. The most widely used is a fluororesin film such as a polyvinyl fluoride film. As a back surface protection sheet using a fluorine resin film, for example, a composite film of a fluorine resin film and a metal foil; a laminate of a fluorine resin film, a silicon oxide thin film layer, and a transparent resin (for example, patent literature) 1).

  However, when a fluororesin film is used as the back surface protective sheet, the adhesion is weak and there is a problem of delamination. In addition, the fluororesin film has a low surface hardness, and there is room for improvement in terms of mechanical strength. Further, in the present situation where the environmental burden is demanded for the fluororesin film depending on the disposal / treatment method, a sheet having a low environmental load is required.

  As a technique for solving the problems of the fluororesin film, Patent Document 2 discloses a back surface comprising a three-layer laminate of a hydrolysis-resistant polyester film, a resin film coated with a metal oxide, and a white resin film. A protective sheet is disclosed. The back surface protective sheet having such a configuration has durability such as hydrolysis resistance, and has improved interlayer adhesion as compared with the fluororesin film.

Moreover, as a film excellent in hydrolysis resistance, as described in Patent Document 3, an acrylic film such as polymethyl methacrylate can also be used as a back surface protective sheet.
JP-A-4-239634 Japanese Patent Laid-Open No. 2002-100788 JP 2007-266382 A

  However, the polyester film has a problem that it easily deteriorates due to ultraviolet rays and easily yellows. In addition, when a general polymethylmethacrylate resin film is used as an acrylic film, it is excellent in hydrolysis resistance and light resistance, but lacks moisture and heat resistance, and produces a solar cell back surface protection sheet excellent in durability. I couldn't.

  Accordingly, there is a need for a back surface protection sheet that balances surface hardness, weather resistance, and light resistance and has reduced environmental burden.

  As a result of intensive studies in view of the above problems, the present inventors have balanced the surface hardness, weather resistance, and light resistance by laminating a film containing an acrylic polymer having a lactone ring structure as a main component, and the environment. It discovered that the back surface protection sheet for solar cells in which the load was reduced was obtained, and completed this invention.

  According to this invention, the back surface protection sheet for solar cells excellent in the weather resistance and the surface hardness is obtained.

  The back surface protection sheet for solar cells of the present invention adopts a structure in which a film containing an acrylic polymer having a lactone ring structure as a main component (hereinafter also referred to as a lactone film) is laminated on a gas barrier film. In the back surface protective sheet, the lactone film is disposed on the side facing the solar battery cell (the barrier film is disposed on the side close to the cell).

  Hereinafter, each component will be described in detail.

(Acrylic polymer)
The acrylic polymer contains a lactone ring structure. Hereinafter, the polymer may be referred to as a “lactone ring-containing polymer”. An acrylic film has a higher surface hardness than a fluorine-based or polyester-based film, but the surface hardness is further improved by the presence of a lactone ring structure. Furthermore, the presence of a lactone ring structure greatly improves the heat and moisture resistance. Therefore, when the lactone film of the present invention is used for a solar cell back surface protective sheet, a solar cell back surface protective sheet excellent in surface hardness and moist heat resistance can be obtained.

  A lactone ring refers to a lactone ring formed by intramolecular dehydration between a hydroxyl group and a carboxyl group of a hydroxy acid to form a cyclic ester. From the viewpoint of polymerizability with the (meth) acrylate monomer, the lactone ring structure is preferably represented by the following general formula (1).

In the formula, each of R ¹ , R ² , and R ³ independently represents a carbon atom having 1 to 20, preferably 1 to 12, more preferably 1 to 8 carbon atoms that may have a hydrogen atom or a substituent. Represents a hydrogen group.

  Specific examples of the hydrocarbon group having 1 to 20 carbon atoms include methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t- Linear, branched or cyclic alkyl groups such as butyl group, n-pentyl group, n-hexyl group, cyclohexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group; vinyl group, 2-propenyl group , And the like; and aromatic hydrocarbon groups having 1 to 20 carbon atoms such as a phenyl group and a naphthyl group. The hydrocarbon group which may have a substituent is preferably one or more of the hydrogen atoms of the hydrocarbon group is a hydroxyl group, a carboxyl group, an alkoxy group having 1 to 8 carbon atoms, or an alkyl group having 1 to 8 carbon atoms. It is a group substituted with an ester group.

Preferably, R ¹ , R ² and R ³ are each independently a hydrogen atom; a linear or branched alkyl group having 1 to 20 carbon atoms; a linear or branched alkyl group having 1 to 20 carbon atoms having a hydroxyl group More preferably, R ¹ and R ² are independently a hydrogen atom, a linear alkyl group having 1 to 20 carbon atoms; R ³ is a hydrogen atom, and one hydrogen is substituted with a hydroxyl group. A linear alkyl group having 1 to 20 carbon atoms, more preferably, R ¹ is a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms; R ² is a methyl group, an ethyl group, an n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, t-butyl group, hexyl group, cyclohexyl group, octyl group, 2-ethylhexyl group; R ³ is a hydrogen atom, hydroxymethyl group, 1 -Hydroxyethyl Group, a methyl group, an ethyl group.

  The content of the lactone ring structure represented by the general formula (1) in the acrylic polymer is preferably 20 to 50% by mass, more preferably 22 to 48% by mass, and further preferably 25 to 45% by mass. . When the content ratio of the lactone ring structure represented by the general formula (1) is within such a range, it is preferable in terms of heat and humidity resistance, moldability, and productivity.

  In addition, the content rate of the said lactone ring structure with respect to the said polymer is calculated by the method of the below-mentioned Example, when the ratio of a lactone ring structure is 70 mass% or less.

  As an example for forming a lactone ring represented by the formula (1) in the polymer, a polymerization reaction of a monomer component including a monomer represented by the following formula (3) is performed in the polymerization step. Thus, after obtaining a polymer having a hydroxyl group and an ester group in the molecular chain, it is obtained by carrying out a cyclization condensation reaction.

In formula (3), R ⁷ and R ⁸ each independently represent a hydrogen atom, or a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms, which may have a substituent. .

Specific examples of the hydrocarbon group having 1 to 20 carbon atoms include methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t- Linear, branched or cyclic alkyl groups such as butyl group, n-pentyl group, n-hexyl group, cyclohexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group; vinyl group, 2-propenyl group , And the like; and aromatic hydrocarbon groups having 1 to 20 carbon atoms such as a phenyl group and a naphthyl group. The hydrocarbon group which may have a substituent is preferably one or more of the hydrogen atoms of the hydrocarbon group is a hydroxyl group, a carboxyl group, an alkoxy group having 1 to 8 carbon atoms, or an alkyl group having 1 to 8 carbon atoms. It is a group substituted with an ester group. Preferably, R ⁷ and R ⁸ are each independently a hydrogen atom; a linear alkyl group having 1 to 20 carbon atoms, and more preferably R ⁷ is a methyl group, an ethyl group, an n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, t-butyl group; R ⁸ is a hydrogen atom or a methyl group.

  Examples of the monomer represented by the formula (3) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- (hydroxy Methyl) normal propyl acrylate, 2- (hydroxymethyl) normal butyl acrylate, 2- (hydroxymethyl) isobutyl acrylate, 2- (hydroxymethyl) secondary butyl acrylate, 2- (hydroxymethyl) tert-butyl acrylate Methyl 2- (1-hydroxyethyl) -2-propenoate, ethyl 2- (1-hydroxyethyl) -2-propenoate, isopropyl 2- (1-hydroxyethyl) -2-propenoate, 2- (1 -Hydroxyethyl) -2-propenoic acid normal propyl, 2- (1-H Roxyethyl) -2-propenoic acid normal butyl, 2- (1-hydroxyethyl) -2-propenoic acid isobutyl, 2- (1-hydroxyethyl) acrylic acid secondary butyl, 2- (1-hydroxyethyl) acrylic acid tertiary Examples include butyl. Among these, methyl 2- (hydroxymethyl) acrylate and 2- (hydroxymethyl) ethyl acrylate are particularly preferable, and methyl 2- (hydroxymethyl) acrylate is particularly preferable in terms of high heat resistance improvement effect. As the monomer represented by the above formula (3), only one type may be used, or two or more types may be used.

  The content ratio of the monomer represented by the above formula (3) in the monomer component used in the polymerization step is preferably 10 to 40% by mass, more preferably 15 to 35% by mass, and still more preferably 15 to 30% by mass. When the content ratio of the monomer represented by the above formula (3) in the monomer component to be used in the polymerization step is within such a range, it is preferable from the viewpoint of heat and humidity resistance, productivity, and moldability.

  The lactone ring-containing polymer preferably has a structure derived from a (meth) acrylate monomer. The structure derived from a (meth) acrylate monomer refers to a structural unit (repeating structural unit) in a polymer constructed by polymerizing a (meth) acrylate monomer.

  A (meth) acrylate monomer refers to a derivative of acrylic acid and methacrylic acid. Preferable specific examples of the (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, (meth) (Meth) acrylic acid such as isobutyl acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate Esters; 2- (hydroxyalkyl) acrylic esters such as methyl 2- (2-hydroxyethyl) -2-propenoate, 2-hydroxyethyl (meth) acrylate (2-hydroxyethyl (meth) acrylate), (meta ) Acrylic acid 3-hydroxypropyl, (meth) acrylic acid 2,3,4,5,6-pentahydride Kishihekishiru and (meth) hydroxyl group-containing monomers such as acrylic acid 2,3,4,5-hydroxypentyl; monomers and the like represented by the above formula (3). These monomers may be used individually by 1 type, and may be used together 2 or more types. Among these, methacrylate is preferable from the viewpoint of availability and heat resistance of the obtained polymer, and methyl methacrylate and benzyl methacrylate are more preferable from the viewpoint that the polymer obtained by polymerization is excellent in thermal stability.

  The content ratio of the structure derived from the (meth) acrylate monomer in the acrylic polymer is preferably 60 to 90% by mass, more preferably 65 to 85% by mass, and further preferably 70 to 85% by mass. When the content ratio of the structure derived from the (meth) acrylate monomer is in such a range, it is preferable in terms of heat and humidity resistance, productivity, and moldability.

  The acrylic polymer may contain a structure other than the structure derived from the lactone ring structure and the (meth) acrylate monomer preferably contained. As other structures, a lactone ring structure and a structure derived from a (meth) acrylate monomer can form a polymer, that is, a monomer for forming a lactone ring structure (preferably the above-mentioned formula (3 The monomer is not particularly limited as long as it is a structure derived from a monomer that can be polymerized with a monomer represented by (II) and a (meth) acrylate monomer. Specific examples of monomers capable of forming a lactone ring structure and monomers that can be polymerized with acrylic acid monomers include hydroxyl group-containing monomers such as α-hydroxymethylstyrene and α-hydroxyethylstyrene. Body; unsaturated carboxylic acid such as acrylic acid, methacrylic acid and crotonic acid; and a structure derived from a monomer represented by the following general formula (2).

In the formula, R ⁴ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or —C—. Represents an O—R ⁶ group, an Ac group represents an acetyl group, R ⁵ and R ⁶ represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms, which may have a substituent. To express. The hydrocarbon group which may have a substituent is the same as that described in the column of the formula (1).

  The content of other structures in the acrylic polymer is preferably 15% by mass or less, and more preferably 10% by mass or less.

  The acrylic polymer preferably has a weight average molecular weight of 20,000 to 1,000,000, more preferably 50,000 to 500,000, and still more preferably 100,000 to 300,000. In the present invention, the weight average molecular weight is calculated by the method described in the following examples.

  The method for producing the acrylic polymer used in the present invention is not particularly limited, and for example, it can be produced by a known production method described in JP-A-2006-96960, JP-A-2007-297619, or the like. it can. Preferably, after obtaining a polymer having a hydroxyl group and an ester group in the molecular chain by a polymerization step, a lactone cyclization condensation reaction in which a lactone ring structure is introduced into the polymer by heat treatment of the obtained polymer It is obtained by carrying out the process.

  In the polymerization step, a polymer having a hydroxyl group and an ester group in the molecular chain is obtained by performing a polymerization reaction of the monomer component including the monomer represented by the above formula (3). Since the monomer represented by the formula (3) has been described above, a detailed description thereof will be omitted.

  For the monomer component used in the polymerization step, a (meth) acrylate monomer other than the monomer represented by the above formula (3) is preferably used. Examples of such monomers include (meth) acrylic acid esters and hydroxyl group-containing (meth) acrylate monomers. Only one type of monomer other than the monomer represented by the above formula (3) may be used, or two or more types may be used in combination.

  The (meth) acrylic acid ester is not particularly limited as long as it is a (meth) acrylic acid ester other than the monomer represented by the formula (3). For example, methyl (meth) acrylate, (meth) acrylic Ethyl acetate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate , Chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more. Among these, methyl (meth) acrylate and benzyl methacrylate are more preferable, and methyl methacrylate is more preferable from the viewpoint of availability and heat resistance of the obtained polymer.

  The hydroxyl group-containing (meth) acrylate monomer is not particularly limited as long as it is a hydroxyl group-containing monomer other than the monomer represented by the above formula (3). For example, 2- (2-hydroxyethyl) ) -2- (hydroxyalkyl) acrylic esters such as methyl 2-propenoate, 2-hydroxyethyl (meth) acrylate (2-hydroxyethyl (meth) acrylate), 3-hydroxypropyl (meth) acrylate, ( (Meth) acrylic acid 2,3,4,5,6-pentahydroxyhexyl and (meth) acrylic acid 2,3,4,5-tetrahydroxypentyl etc. may be mentioned, and these may be used alone. Two or more kinds may be used.

  The content ratio of the (meth) acrylate monomer in the monomer component used in the polymerization step is preferably 60 to 90% by mass, more preferably 65 to 90%, in order to sufficiently exhibit the effects of the present invention. It is 85 mass%, More preferably, it is 70-85 mass%.

  Furthermore, as the monomer component, a polymerizable monomer other than the monomer represented by the formula (3) and the (meth) acrylate monomer suitably contained may be used.

  Examples of other polymerizable monomers include hydroxyl group-containing monomers such as α-hydroxymethylstyrene and α-hydroxyethylstyrene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; The monomer represented by these is mentioned. Examples of the monomer represented by the formula (2) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate, and the like. May be used, or two or more of them may be used in combination. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited. The content ratio of other polymerizable monomers in the monomer component to be subjected to the polymerization step is preferably 15% by mass or less, and more preferably 10% by mass or less.

  The form of the polymerization reaction for polymerizing the monomer component to obtain a polymer having a hydroxyl group and an ester group in the molecular chain (hereinafter sometimes referred to as polymer A) is solution polymerization using a solvent. Is preferred.

  The polymerization temperature and polymerization time vary depending on the type of monomer used, the ratio used, etc., but preferably the polymerization temperature is 50 to 150 ° C. and the polymerization time is 0.5 to 20 hours, more preferably polymerization. The temperature is 80 to 140 ° C. and the polymerization time is 1 to 10 hours.

  In the case of solution polymerization, the solvent used is not particularly limited, and examples thereof include aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran; 1 type of these may be used and 2 or more types may be used together. Moreover, since the residual volatile matter of the lactone ring containing polymer finally obtained will increase when the boiling point of the solvent to be used is too high, a thing with a boiling point of 50-200 degreeC is preferable. The amount of the solvent used can be appropriately set depending on the polymerization conditions, the monomer concentration, the polymer solution concentration, and the like.

  During the polymerization reaction, a polymerization initiator may be added as necessary. The polymerization initiator is not particularly limited. For example, t-amylperoxy-2-ethylhexanoate, t-amylperoxyisononanoate, t-amylperoxyacetate, cumene hydroperoxide, diisopropylbenzene hydroperoxide , Organic peroxides such as di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (Cyclohexanecarbonitrile), azo compounds such as 2,2′-azobis (2,4-dimethylpareronitrile); and the like. These may be used alone or in combination of two or more. May be. The amount of the polymerization initiator used may be appropriately set according to the combination of monomers used and reaction conditions, and is not particularly limited, but is 0.01 to 10% by mass with respect to the total amount of monomers used for polymerization. It is preferable that it is 0.05 to 5% by mass. Further, a chain transfer agent may be used for controlling the molecular weight of the polymer, and examples thereof include alkyl mercaptans such as butyl mercaptan, octyl mercaptan, dodecyl mercaptan, α-styrene dimer, and the like.

  When carrying out the polymerization, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 70% by mass or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the produced polymer in the polymerization reaction mixture exceeds 70% by mass, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture so as to be controlled to 70% by mass or less. . The concentration of the produced polymer in the polymerization reaction mixture is more preferably 60% by mass or less, still more preferably 55% by mass or less. In addition, since productivity will fall when the density | concentration of the polymer in a polymerization reaction mixture is too low, it is preferable that the density | concentration of the polymer in a polymerization reaction mixture is 10 mass% or more, and is 20 mass% or more. It is more preferable.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and the polymerization solvent may be added continuously or intermittently. Thus, by controlling the concentration of the produced polymer in the polymerization reaction mixture, the gelation of the reaction solution can be more sufficiently suppressed. In particular, within the above range, gelation can be sufficiently suppressed even when the proportion of the monomer represented by the formula (3) is increased as the monomer component in order to improve the heat and moisture resistance. The polymerization solvent to be added may be the same type of solvent used during the initial charging of the polymerization reaction or may be a different type of solvent, but is the same as the solvent used during the initial charging of the polymerization reaction. It is preferable to use different types of solvents. Further, the polymerization solvent to be added may be only one type of solvent or a mixed solvent of two or more types.

  The polymerization reaction mixture obtained when the above polymerization step is completed usually contains a solvent in addition to the obtained polymer, but it is necessary to completely remove the solvent and take out the polymer in a solid state. Rather, it is preferably introduced into the subsequent lactone cyclization condensation step in a state containing a solvent. If necessary, after taking out in a solid state, a solvent suitable for the subsequent lactone cyclization condensation step may be added again.

  The polymer obtained in the polymerization step is a polymer (polymer A) having a hydroxyl group and an ester group in the molecular chain, and the weight average molecular weight of the polymer A is preferably 25,000 to 1,500, 000, more preferably 55,000 to 550,000, still more preferably 120,000 to 400,000. The polymer obtained in the polymerization step is subjected to a heat treatment in the subsequent lactone cyclization condensation step, whereby a lactone ring structure is formed in the polymer to become a lactone ring-containing polymer.

  That is, the monomers represented by the formula (3), or the monomer represented by the formula (3) and the (meth) acrylate monomer are polymerized to form the following structural unit in the polymer. Will be included.

  And it becomes a structure represented by a following formula (I) through a cyclization condensation process.

That is, the above structural unit is contained in the polymer. In the structural unit, R ^b represents R ² in formula (3), a hydrogen atom, or an alkyl group which may be substituted in an ester group forming an acrylic monomer.

  The reaction for introducing a lactone ring structure into the polymer A is a reaction in which a hydroxyl group and an ester group present in the molecular chain of the polymer A are cyclized and condensed to form a lactone ring structure by heating or addition of a catalyst. The cyclized condensation produces alcohol as a by-product. By forming a lactone ring structure in the molecular chain of the polymer (in the main skeleton of the polymer), high heat and heat resistance is imparted. If the reaction rate of the cyclization condensation reaction leading to the lactone ring structure is insufficient, the heat and humidity resistance will not be improved sufficiently, or a heat treatment during molding will cause a condensation reaction between molecules during the molding process, resulting in gelation. The generated alcohol is not preferable because bubbles and silver streaks are generated in the molded product.

  The lactone ring-containing polymer obtained in the lactone cyclization condensation step preferably has a lactone ring structure represented by the above formula (1).

  The method for heat-treating the polymer A is not particularly limited. For example, a known method can be used, and the polymerization reaction mixture containing the solvent obtained by the polymerization step may be heat-treated as it is. Moreover, you may heat-process using a ring-closing catalyst as needed in presence of a solvent. Further, the heat treatment can be performed using a heating furnace or reaction apparatus having a vacuum apparatus or a devolatilizing apparatus for removing volatile components, an extruder having a devolatilizing apparatus, or the like.

  When the cyclization condensation reaction is performed, in addition to the polymer A, another thermoplastic resin may coexist. Further, when performing the cyclization condensation reaction, if necessary, an esterification catalyst or a transesterification catalyst such as p-toluenesulfonic acid generally used as a catalyst for the cyclization condensation reaction may be used. Organic carboxylic acids such as propionic acid, benzoic acid, acrylic acid, and methacrylic acid may be used as a catalyst. Moreover, you may use a basic compound, organic carboxylate, carbonate, etc. When a basic compound, organic carboxylate, carbonate, or the like is used, it may be as described in JP-A-61-254608 or JP-A-61-261303.

  In carrying out the cyclization condensation reaction, it is preferable to use an organic phosphorus compound such as stearyl phosphate or distearyl phosphate as a catalyst. When an organophosphorus compound is used as a catalyst, it may be as disclosed in JP-A-2001-151814. By using an organophosphorus compound as a catalyst, the cyclization condensation reaction rate can be improved, and coloring of the resulting lactone ring-containing polymer can be greatly reduced. Furthermore, by using an organophosphorus compound as a catalyst, it is possible to suppress molecular weight reduction and coloration that can occur when a devolatilization step described later is used in combination, and to impart excellent mechanical strength.

  The amount of the catalyst used in the cyclization condensation reaction is not particularly limited, but is preferably 0.001 to 5% by mass, more preferably 0.01 to 2.5% by mass with respect to the polymer A, and further Preferably it is 0.01-1 mass%, Most preferably, it is 0.02-0.5 mass%. If the amount of the catalyst used is less than 0.001% by mass, the reaction rate of the cyclization condensation reaction may not be improved sufficiently. On the other hand, if the amount exceeds 5% by mass, coloring and haze may occur. Or it becomes difficult to melt mold by crosslinking of the polymer, which is not preferable.

  The addition timing of the catalyst is not particularly limited, and it may be added at the beginning of the reaction, during the reaction, or both.

  It is preferable to carry out the cyclization condensation reaction in the presence of a solvent and to use a devolatilization step in combination with the cyclization condensation reaction. In this case, a mode in which the devolatilization step is used throughout the cyclization condensation reaction and a mode in which the devolatilization step is not used throughout the entire cyclization condensation reaction and are used only in a part of the process. In the method using the devolatilization step in combination, the alcohol produced as a by-product in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous for the production side.

  The devolatilization step refers to a step of removing volatile components such as a solvent and residual monomer and alcohol produced as a by-product by a cyclocondensation reaction leading to a lactone ring structure, if necessary under reduced pressure heating conditions. If this removal treatment is insufficient, the residual volatile components in the produced resin increase, resulting in problems such as coloration due to alteration during molding, and molding defects such as bubbles and silver streaks.

  In the case of a form in which a devolatilization step is used throughout the cyclization condensation reaction, the apparatus to be used is not particularly limited, but a devolatilization apparatus comprising a heat exchanger and a devolatilization tank in order to perform the present invention more effectively. It is preferable to use an extruder equipped with a vent or the above-mentioned devolatilizer and the above-mentioned extruder in series, and it is more preferable to use a devolatilizer comprising a heat exchanger and a devolatilizer or a vented pusher. preferable.

  150-350 degreeC is preferable and, as for the reaction processing temperature of the place using the devolatilization apparatus which consists of the said heat exchanger and a devolatilization tank, 200-300 degreeC is more preferable. When the reaction treatment temperature is 150 ° C. or higher, the cyclization condensation reaction proceeds sufficiently to minimize the residual volatile matter, and when it is 350 ° C. or lower, coloring and decomposition can be suppressed.

  In the case of using a devolatilizer comprising the heat exchanger and the devolatilizer, the pressure during the reaction treatment is preferably 1.33 to 931 hPa (1 to 700 mmHg), more preferably 66.5 to 798 hPa (50 to 600 mmHg). preferable. If the pressure is 1.33 hPa or more, volatile components including alcohol hardly remain, and if it is 931 hPa or less, industrial implementation can be easily performed.

  When using the extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  150-350 degreeC is preferable and, as for the reaction processing temperature in the case of using the said extruder with a vent, 200-300 degreeC is more preferable. If the said temperature is 150 degreeC or more, cyclization condensation reaction fully occurs and a residual volatile matter can be suppressed to the minimum, and if it is 350 degrees C or less, coloring and decomposition | disassembly can be suppressed.

  When using the extruder with a vent, the pressure at the time of reaction treatment is preferably 1.33 to 931 hPa (1 to 700 mmHg), more preferably 13.3 to 798 hPa (10 to 600 mmHg). When the pressure is 1.33 hPa or more, volatile components including alcohol hardly remain, and when the pressure is 931 hPa or less, industrial implementation can be easily performed.

  In the case of using the devolatilization step throughout the entire cyclization condensation reaction, the physical properties of the lactone ring-containing polymer obtained may be deteriorated under severe heat treatment conditions, as described later. It is preferable to use a reaction catalyst and use a vented extruder or the like under the mildest conditions possible.

  In the case where the devolatilization step is used throughout the cyclization condensation reaction, preferably, the polymer A obtained in the polymerization step is introduced into the cyclization condensation reaction apparatus system together with a solvent. Depending on the situation, the reactor system such as an extruder with a vent may be passed once again.

  You may perform the form used together only in a part of process, without using a devolatilization process over the whole process of cyclization condensation reaction. For example, the apparatus for producing the polymer A is further heated, and if necessary, a part of the devolatilization step is used together to advance the cyclization condensation reaction to some extent in advance, and then the devolatilization step is performed simultaneously. In this form, the combined cyclization condensation reaction is performed to complete the reaction.

  In the form in which the devolatilization process is used throughout the cyclization condensation reaction described above, for example, when the polymer A is heat-treated at a high temperature of about 250 ° C. or higher using a twin screw extruder, Due to the difference in the history, partial decomposition or the like may occur before the cyclization condensation reaction occurs, and the physical properties of the obtained lactone ring-containing polymer may be deteriorated. Therefore, if the cyclization condensation reaction is allowed to proceed to some extent before the cyclization condensation reaction using the devolatilization step at the same time, the latter reaction conditions can be relaxed and the physical properties of the resulting lactone ring-containing polymer deteriorated. Is preferable. As a particularly preferred embodiment, the devolatilization step is started after a lapse of time from the start of the cyclization condensation reaction, that is, the hydroxyl group and ester group present in the molecular chain of the polymer A obtained in the polymerization step are previously cyclized. A mode in which the cyclization condensation reaction rate obtained by the cyclization condensation reaction is raised to some extent, and then the cyclization condensation reaction using the devolatilization step simultaneously is performed. Specifically, for example, a cyclization condensation reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle-type reactor, and then a reactor equipped with a devolatilizer, for example, a heat The form which completes a cyclization condensation reaction with the devolatilizer which consists of an exchanger and a devolatilization tank, the extruder with a vent, etc. is mentioned. Particularly in this form, it is more preferable that a catalyst for the cyclization condensation reaction is present.

  As described above, the hydroxyl group and ester group present in the molecular chain of the polymer A obtained in the polymerization step are subjected to a cyclization condensation reaction in advance to increase the cyclization condensation reaction rate to some extent, and then the devolatilization step is performed. The method of carrying out the cyclization condensation reaction used at the same time is a preferable mode for obtaining a lactone ring-containing polymer in the present invention. With this form, a lactone ring-containing polymer having a higher glass transition temperature, a higher cyclization condensation reaction rate, and excellent heat resistance can be obtained.

  The reactor that can be employed in the cyclization condensation reaction that is performed in advance before the cyclization condensation reaction using the devolatilization process at the same time is not particularly limited, but preferably an autoclave, a kettle reactor, a heat exchanger, and a devolatilization tank A vented extruder suitable for a cyclocondensation reaction using a devolatilization step at the same time can also be used. More preferred are autoclaves and kettle reactors. However, even when using a reactor such as an extruder with a vent, by adjusting the temperature condition, barrel condition, screw shape, screw operating condition, etc. It is possible to carry out the cyclization condensation reaction in the same state as the reaction state in the kettle reactor.

  The weight reduction rate between 150 and 300 ° C. in the dynamic TG measurement at the end of the cyclization condensation reaction performed in advance before the cyclization condensation reaction simultaneously using the devolatilization step, that is, before the start of the devolatilization step is: It is preferably 2% or less, more preferably 1.5% or less, and still more preferably 1% or less. When the weight reduction rate is higher than 2%, the cyclization condensation reaction rate does not rise to a sufficiently high level even if the cyclization condensation reaction is performed simultaneously with the devolatilization step, and the physical properties of the resulting lactone ring-containing polymer. May decrease. In addition, when performing said cyclization condensation reaction, in addition to the polymer A, you may coexist other thermoplastic resins.

  Cyclization using a hydroxyl group and an ester group present in the molecular chain of the polymer A obtained in the polymerization step in advance by a cyclization condensation reaction to increase the cyclization condensation reaction rate to some extent. In the case of carrying out the condensation reaction, the polymer obtained by the cyclization condensation reaction carried out in advance (a polymer in which at least a part of the hydroxyl groups and ester groups present in the molecular chain have undergone the cyclization condensation reaction) and the solvent are removed as they are. It may be introduced into a cyclocondensation reaction in which the volatilization process is simultaneously used, and, if necessary, the above polymer (a polymer in which at least a part of the hydroxyl group and ester group present in the molecular chain undergoes a cyclocondensation reaction). You may introduce | transduce into the cyclocondensation reaction which used the devolatilization process simultaneously after passing through other processes, such as adding a solvent again after isolating.

  The devolatilization step is not limited to being completed at the same time as the cyclization condensation reaction, and may be completed after a lapse of time from the completion of the cyclization condensation reaction.

  Even after the cyclization catalyst is added and the cyclization condensation reaction is sufficiently performed, a small amount of unreacted reactive groups remain, and problems such as foaming and thickening due to cross-linking between polymers may occur during molding. It is preferable to add a deactivator for the cyclization condensation catalyst. In many cases, an acid catalyst or a basic catalyst is used in the cyclization condensation reaction. In this case, the deactivator deactivates the catalyst by a neutralization reaction. May be a basic substance. Conversely, when the catalyst is a basic substance, an acidic substance may be used as the deactivator. The deactivator is not particularly limited as long as it does not generate a substance that inhibits the physical properties of the resin composition during heat processing, but when a basic substance is used as the deactivator, for example, a metal carboxylate , Metal complexes, metal oxides, and the like, metal carboxylates and metal oxides are preferable, and metal carboxylates are particularly preferable. Here, the metal is not particularly limited as long as it does not inhibit the physical properties of the resin composition and does not cause environmental pollution at the time of disposal. For example, alkali metals such as lithium, sodium, and potassium; magnesium Alkaline earth metals such as calcium, strontium and barium; zinc; zirconium; and the like. The carboxylic acid constituting the metal carboxylate is not particularly limited. For example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, Lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, tridecanoic acid, pentadecanoic acid, heptadecanoic acid, lactic acid, malic acid, citric acid, oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, adipic acid, etc. Is mentioned. The organic component in the metal complex is not particularly limited, and examples thereof include acetylacetone. Examples of the metal oxide include zinc oxide, calcium oxide, magnesium oxide and the like, and zinc oxide is preferable. On the other hand, when an acidic substance is used for the deactivator, for example, an organic phosphoric acid compound or a carboxylic acid can be used. A quencher may be used independently or may use 2 or more types together. The quenching agent may be added in any form such as a solid, powder, dispersion, suspension, aqueous solution, etc., and is not particularly limited.

  The blending amount of the deactivator may be appropriately adjusted according to the catalyst used for the cyclization condensation, and is not particularly limited, but is preferably 10 to 10,000 ppm, more preferably based on the acrylic polymer. Preferably it is 50-5,000 ppm, More preferably, it is 100-3,000 ppm. If the amount of the deactivator is less than 10 ppm, the action of the deactivator is insufficient, and foaming or thickening due to cross-linking between polymers may occur during molding. On the other hand, if the compounding amount of the deactivator exceeds 10,000 ppm, the deactivator is used more than necessary, which may impair the physical properties of the resin composition, such as a decrease in molecular weight.

  The timing of adding the deactivator is in the production of the acrylic polymer, after adding the catalyst and sufficiently performing the cyclization condensation reaction, and before the obtained resin composition is thermally processed, It is not particularly limited. For example, a method in which an inactivator is added at a predetermined stage during production of an acrylic polymer, or after an acrylic polymer has been produced, the inactivator and other components are simultaneously heated and melted and kneaded. A method in which an acrylic polymer and other components are heated and melted, and a deactivator is added thereto and kneaded; an acrylic polymer is heated and melted, and the deactivator and other components are added there. And the like. In this case, it is preferable to provide a devolatilization step after kneading the thermoplastic resin and the quenching agent. This is because the obtained thermoplastic resin hardly causes a foaming phenomenon during heat processing. Examples of the devolatilization step include the devolatilization step described above as the devolatilization step performed in the production of the lactone ring-containing polymer.

  The obtained acrylic polymer preferably has a weight reduction rate of 150% to 300 ° C. in dynamic TG measurement of 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.8%. 3% by mass or less. In addition, dynamic TG is measured by the measuring method as described in the following Example.

  Moreover, you may perform the mixing process which mixes the below-mentioned ultraviolet absorber, other additives, etc. with the obtained acrylic polymer as needed. The mixing method performed in a mixing process can be performed by a conventionally well-known method, For example, the method of mixing with mixers, such as an omni mixer, is mentioned. The mixing of the acrylic polymer with other additives and the like can be performed simultaneously during the above-described deaeration process or the film forming process described later.

<Film containing acrylic polymer as main component>
In a film containing an acrylic polymer as a main component (lactone film), “comprising as a main component” means containing 60% by mass or more of an acrylic polymer, preferably 70% by mass or more, more preferably 80%. Contains at least mass%. If the content of the acrylic polymer in the film is less than 60% by mass, the effects of the present invention may not be sufficiently exhibited.

  The lactone film may contain a polymer (other polymer) other than the acrylic polymer. Other polymers include, for example, ultraviolet absorbing resins described in detail below; olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); vinyl chloride, chlorine Halogen-containing polymers such as vinyl chloride resin; acrylic polymers such as polymethyl methacrylate; styrene such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer Polymers; Polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; Polyamides such as nylon 6, nylon 66 and nylon 610; Polyacetals; Polycarbonates; Polyphenylene oxides; Nirensurufido; polyetheretherketone; polysulfone; polyether sulfone; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as acrylic rubber ABS resin or ASA resin blended with; and the like. The rubbery polymer preferably has a graft portion having a composition compatible with the acrylic polymer on the surface, and the average particle size of the rubbery polymer is improved in transparency when formed into an extruded film. From the viewpoint, it is preferably 100 nm or less, and more preferably 70 nm or less. The content of other polymers is preferably 0 to 40% by mass, more preferably 0 to 30% by mass, and still more preferably 0 to 20% by mass.

  As will be described later, in order to improve light resistance, the lactone film may have an ultraviolet absorbing ability. That is, the lactone film may contain a compound having an ability to absorb ultraviolet rays (ultraviolet absorbing substance). Examples of the ultraviolet absorbing substance include an ultraviolet absorber and an ultraviolet absorbing resin.

  The components constituting the ultraviolet absorber include benzophenone series such as 2-hydroxybenzophenone, benzotriazole series such as (2,2′-hydroxy-5-methylphenyl) benzotriazole, saltylate series such as phenyl salicylate, acrylic Nitrile-based, metal complex-based, hindered amine-based, triazine-based, benzoate-based, oxalic acid anilide-based, and ultrafine titanium oxide (particle diameter, 0.01 to 0.06 μm), ultrafine zinc oxide (0.01 to 0.00). 04 μm) and the like, such as inorganic ultraviolet absorbing compounds. These ultraviolet absorbing compounds can be used alone or in combination of two or more. Among these, benzotriazole-based and triazine-based UV absorbers are preferable because they have excellent UV absorbing ability, good heat resistance, excellent transparency, and little coloring. The blending amount of the ultraviolet absorber may be appropriately determined so that the desired effect is exhibited, but is preferably 0.5 to 30% by mass, and 1 to 20% by mass in the lactone film. Is more preferable.

  UV-absorbing resins include UV-absorbing monomers, optionally (meth) acrylic monomers, and other copolymerizable with UV-absorbing monomers and / or (meth) acrylic monomers UV-absorbing resin obtained by copolymerizing the above monomers. Such an ultraviolet-absorbing resin is more preferably used as an ultraviolet-absorbing material because of its high ultraviolet-absorbing performance and the possibility of bleeding out of the ultraviolet-absorbing material when used for a long time.

  The ultraviolet absorbing resin has a polymer structural unit (repeating structural unit) constructed by polymerizing an ultraviolet absorbing monomer. A conventionally well-known resin can be used as an ultraviolet-absorbing resin, For example, resin described in Unexamined-Japanese-Patent No. 2007-297619 is mentioned.

  As a specific example of the ultraviolet absorbing monomer, preferably, the formula (4):

[Wherein, R ⁹ represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, R ¹⁰ represents an alkylene group having 1 to 6 carbon atoms, R ¹¹ represents a hydrogen atom or a methyl group, and X represents hydrogen. An atom, a halogen atom, a hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group or a nitro group]
A monomer represented by formula (5):

[Wherein, R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or 2 to 2 carbon atoms. 10 represents an alkenyl group or an alkoxy group having 1 to 10 carbon atoms, Y represents a hydrogen atom or a methyl group, and A represents — (CH ₂ CH ₂ O) _n —, —CH ₂ CH (OH) —CH. ₂ O—, — (CH ₂ ) _n —O—, —CH ₂ CH (CH ₂ OR ²⁰ ) —O—, —CH ₂ CH (R ²⁰ ) —O—, or —CH ₂ (CH ₂ ) _p COO—B—O—, R ²⁰ represents an alkyl group having 1 to 10 carbon atoms, B represents a methylene group, an ethylene group, or —CH ₂ CH (OH) CH ₂ —, and n represents 1 to 1 Represents an integer of 20 and p represents 0 or 1]
And a monomer represented by formula (6):

[Wherein R ²¹ represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, or a nitro group, and R ²² represents an element capable of forming a hydrogen bond. R ²³ represents a hydrogen atom or a methyl group, and R ²⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms.]
The monomer shown by these is mentioned. These ultraviolet absorbing monomers may be used alone or in combination of two or more.

The ultraviolet-absorbing monomer represented by the formula (4) is as follows: R ⁹ is a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms; R ¹⁰ is an alkylene group having 1 to 6 carbon atoms; R ¹¹ is a hydrogen atom or methyl X is a benzotriazole composed of a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group, or a nitro group.

In the formula (4), examples of the hydrocarbon group having 1 to 8 carbon atoms represented by R ⁹ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, and pentyl. Group, hexyl group, heptyl group, octyl group and other chain hydrocarbon groups; cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group and other alicyclic hydrocarbon groups; phenyl group, tolyl group, And aromatic hydrocarbon groups such as a xylyl group, a benzyl group, and a phenethyl group.

In formula (4), examples of the alkylene group having 1 to 6 carbon atoms represented by R ¹⁰ include linear alkylene groups such as a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group; And branched chain alkylene groups such as isopropylene group, isobutylene group, sec-butylene, t-butylene group, isopentylene group, and neopentylene group.

  In the formula (4), examples of the halogen atom represented by X include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the hydrocarbon group having 1 to 8 carbon atoms represented by X include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, and a heptyl group. Chain hydrocarbon groups such as octyl group: cycloaliphatic hydrocarbon groups such as cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group; phenyl group, tolyl group, xylyl group, benzyl group, phenethyl group Aromatic hydrocarbon groups such as groups; and the like. As a C1-C6 alkoxy group represented by X, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group etc. are mentioned, for example.

  Although it does not specifically limit as an ultraviolet-absorbing monomer shown by Formula (4), For example, 2- [2'-hydroxy-5 '-(methacryloyloxymethyl) phenyl] -2H-benzotriazole 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-tert-butyl-5 ′-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-t-butyl-3 '-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyl) Oxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2′-hydroxy-5 ′-(methacryloyl) Oxyethyl) phenyl] -5-methoxy -2H- benzotriazole. These monomers may be used alone or in combination of two or more.

The ultraviolet-absorbing monomer represented by the formula (5) has R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ and R ¹⁹ independently of one another, a hydrogen atom, a carbon number An alkyl group having 1 to 10, an alkenyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms; Y is a hydrogen atom or a methyl group; A is — (CH ₂ CH ₂ O) _n —, —CH _{2 CH (OH) -CH 2 O} -, - (CH 2) n -O -, - CH 2 CH (CH 2 oR 20) -O -, - CH 2 CH (R 20) -O-, or - CH ₂ (CH ₂ ) _p COO—B—O—; R ²⁰ is an alkyl group having 1 to 10 carbon atoms; B is a methylene group, an ethylene group, or —CH ₂ CH (OH) CH ₂ —; 2,4,6-triphenyl composed of an integer of ˜20; p is 0 or 1; -1,3,5-triazines.

In the formula (5), examples of the alkyl group having 1 to 10 carbon atoms represented by R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ or R ¹⁹ include, for example, methyl group, ethyl Group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, n-pentyl group, isopentyl group, 2,2-dimethylpropyl group, n-heptyl group, n-octyl group Group, n-nonyl group, n-decyl group, 1,1,3,3, -tetramethylbutyl group, 2-ethylhexyl group or the like linear or branched alkyl group; cyclohexyl group or the like alicyclic alkyl Group; and the like. Examples of the alkenyl group having 2 to 10 carbon atoms represented by R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ or R ¹⁹ include a vinyl group, an allyl group, and a 1-propenyl group. , Isopropenyl group, 1-butenyl group, 2-butenyl group, 2-pentenyl group, 3-pentenyl group, 4-hexenyl group, 5-heptenyl group, 4-methyl-3-pentenyl group, 2,4-dimethyl- A 3-pentenyl group, a 6-methyl-5-heptenyl group, a 2,6-dimethyl-5-heptenyl group and the like can be mentioned. Examples of the alkoxy group having 1 to 10 carbon atoms represented by R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ or R ¹⁹ include, for example, methoxy group, ethoxy group, propoxy group, butoxy Group, pentyloxy group, hexyloxy group, heptyloxy, octyloxy, nonyloxy, decyloxy and the like.

In the formula (5), examples of the alkyl group having 1 to 10 carbon atoms represented by R ²⁰ include those represented by R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ or R ¹⁹ . And the above-mentioned substituents listed as the alkyl group having 1 to 10 carbon atoms.

  Although it does not specifically limit as an ultraviolet absorptive monomer shown by Formula (5), For example, 2, 4- diphenyl-6- [2-hydroxy-4- (2-acryloyloxy) phenyl] -1,3,5-triazine, 2,4-bis (2-methylphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy) phenyl] -1,3,5-triazine, 2, 4-bis (2-methoxyphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2-ethylphenyl) -6 -[2-hydroxy-4- (2-acryloyloxyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2-ethoxyphenyl) -6- [2-hydroxy-4- (2- Acry Yloxyethoxy) phenyl] -1,3,5-triazine, 2,4-diphenyl-6- [2-hydroxy-4- (2-methacryloyloxyethoxy) phenyl] -1,3,5-triazine, 2, 4-bis (2-methylphenyl) -6- [2-hydroxy-4- (2-methacryloyloxyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2-methoxyphenyl) -6 -[2-Hydroxy-4- (2-methacryloyloxyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2-ethylphenyl) -6- [2-hydroxy-4- (2- Methacryloyloxyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2-ethoxyphenyl) -6- [2-hydroxy-4- (2-methacryloylo) Cyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2,4-dimethoxyphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy) phenyl] -1,3 5-triazine, 2,4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2,4-diethoxyphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy) phenyl] -1,3,5-triazine, 2,4-bis (2,4-diethylphenyl) -6- [2-hydroxy-4- (2-acryloyloxyethoxy) phenyl] -1,3,5-triazine, 2- [2-hydroxy-4- (11-acryloyloxy-undec) Ruoxy) phenyl] -4,6-diphenyl-1,3,5-triazine, 2- [2-hydroxy-4- (11-methacryloyloxy-undecyloxy) phenyl] -4,6-diphenyl-1,3 , 5-triazine, 2- [2-hydroxy-4- (2-methacryloyloxyethoxy) phenyl] -4,6-diphenyl-1,3,5-triazine, 2- [2-hydroxy-4- (11- Acryloyloxy-undecyloxy) phenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2,4-bis (2,4-dimethylphenyl) -6- [2 -Hydroxy-4- (11-methacryloyloxyundecyloxy) phenyl] -1,3,5-triazine, 2,4-bis (2,4-dimethylphenyl) -6- [2- , And the like proxy-4- (2-methacryloyloxy) phenyl] -1,3,5-triazine. These monomers may be used alone or in combination of two or more. Of these monomers, the formula (7):

A monomer represented by formula (8):

A monomer represented by the formula (9):

A monomer represented by is preferable.

In the ultraviolet absorbing monomer represented by the formula (6), R ²¹ is a hydrogen atom, a halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, or a nitro group; R ²² Are groups having an element capable of forming a hydrogen bond; R ²³ is a hydrogen atom or a methyl group; R ²⁴ is a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms;

In the formula (6), examples of the halogen atom represented by R ²¹ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group having 1 to 8 carbon atoms represented by R ²¹ include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, n -Linear or branched such as -pentyl group, isopentyl group, 2,2-dimethylpropyl group, n-heptyl group, n-octyl group, 1,1,3,3-tetramethylbutyl group, 2-ethylhexyl group A branched alkyl group; an alicyclic alkyl group such as a cyclohexyl group; and the like. As a C1-C4 alkoxy group represented by R < ²¹ >, a methoxy group, an ethoxy group, a propoxy group, a butoxy group etc. are mentioned, for example.

In the formula (6), examples of the group represented by R ²² and having an element capable of forming a hydrogen bond include —NH—, —CH ₂ NH—, —OCH ₂ CH (OH) CH ₂ O—, _{-CH 2 CH 2 COOCH 2 CH (} OH) CH 2 O- and the like. Among these groups, in that they contain a nitrogen atom having an active hydrogen, -NH _-, - CH 2 NH- are preferred, _-CH 2 NH- is particularly preferred.

In the formula (6), as the hydrocarbon group having 1 to 12 carbon atoms represented by R ²⁴ , for example, in addition to the above-described substituents enumerated as the alkyl group having 1 to 8 carbon atoms represented by R ²¹ Linear or branched alkyl groups such as nonyl group, decyl group, undecyl group, dodecyl group; aromatic hydrocarbon groups such as phenyl group, tolyl group, xylyl group, benzyl group, phenethyl group, etc. . Of these substituents, a linear or branched alkyl group having 4 to 12 carbon atoms is preferable, and a bulky branched alkyl group such as 1,1,3,3-tetramethylbutyl group (or the like). Particularly preferred are groups having The substituent R ²⁴ is preferably a steric hindrance group bonded to the 5-position (para-position to the 2-position hydroxyl group), since the effect of inhibiting the consumption of the 2-position hydroxyl group is further increased.

Although it does not specifically limit as an ultraviolet-absorbing monomer shown by Formula (6), For example, 2- [2'-hydroxy-3 '-(meth) acryloylaminophenyl] -2H-benzotriazole 2- [2′-hydroxy-3 ′-(meth) acryloylaminomethylphenyl] -2H-benzotriazole, 2- [2′-hydroxy-3 ′-(meth) acryloylamino-5 ′-(1,1 , 3,3-tetramethylbutyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3 ′-(meth) acryloylaminomethyl-5 ′-(1,1,3,3-tetramethylbutyl) ) Phenyl] -2H-benzotriazole and the like. These monomers may be used alone or in combination of two or more. Of these monomers, 2- [2′-hydroxy-3 ′-(meth) acryloylamino-5 ′-(1,1,1), which has a bulky substituent R ²⁴ bonded to the 5-position. 3,3-tetramethylbutyl) phenyl] -2H-benzotriazole and 2- [2′-hydroxy-3 ′-(meth) acryloylaminomethyl-5 ′-(1,1,3,3-tetramethyl) Butyl) phenyl] -2H-benzotriazole is preferred.

  The benzotriazole-based monomer represented by the formula (4) or (6) includes, for example, (meth) acrylic acid chloride, N-methylol acrylamide or an alkyl ether thereof in a corresponding benzotriazole (commercially available as an ultraviolet absorber). It can be synthesized by a method such as reaction. For example, 2- [2′-hydroxy-3′-methacryloylamino-5 ′-(1,1,3,3-tetramethylbutyl) phenyl] -2H-benzotriazole is 2- [2′-hydroxy-3 It can be obtained by reacting '-amino-5'-(1,1,3,3-tetramethylbutyl) phenyl] -benzotriazole with methacrylic acid chloride. Further, 2- [2′-hydroxy-3′-methacryloylaminomethyl-5 ′-(1,1,3,3-tetramethylbutyl) phenyl] -2H-benzotriazole is 2- [2′-hydroxy- 5 ′-(1,1,3,3-tetramethylbutyl) phenyl] -benzotriazole (for example, CYASORB UV-5411, manufactured by CYTEC) and N-methylolacrylamide (for example, manufactured by Nitto Chemical Industries, Ltd.) Can be obtained by reacting.

  Among the ultraviolet absorbing monomers represented by the above formulas (4) to (6), the ultraviolet absorbing monomer represented by the formula (6) can be thinned and has high light resistance. Particularly preferred.

  These ultraviolet absorbing monomers may be used alone or in combination of two or more.

  The content of the UV-absorbing monomer unit contained in the UV-absorbing resin is preferably 1 to 80% by mass and preferably 3 to 70% by mass with respect to 100% by mass of the UV-absorbing resin. More preferred. When the content is in such a range, the ultraviolet blocking ability can be sufficiently exerted, and there is little risk of yellowing the film.

  The ultraviolet absorbing monomer represented by the above formulas (4) to (6) may be used in combination with an ultraviolet stable monomer. Examples of UV-stable monomers include 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine. 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4 -(Meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6 -Tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl 4-cyano-4- (meth) acryloyl amino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine and the like. These ultraviolet stable monomers may be used alone or in combination of two or more. Although the usage-amount of a ultraviolet-ray stable monomer is not specifically limited, It is preferable that it is 0-20 mass% with respect to 100 mass% of ultraviolet-absorbing resin, and it is 0-10 mass%. Is more preferable.

  The ultraviolet-absorbing resin preferably includes an acrylic monomer as a structural unit because it is excellent in optical characteristics and thermal stability.

  Acrylic monomers include acrylic unsaturated carboxylic acids such as (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n- Butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryltridecyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) (Meth) acrylic acid esters such as acrylate and cyclododecyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate Hydroxyl group-containing (meth) acrylic acid ester such as (meth) acrylic acid monoester of ester diol obtained from phthalic acid and propylene glycol (for example, Plaxel FM, manufactured by Daicel Chemical Industries, Ltd.); And other acrylic monomers such as acrylonitrile, (meth) acrylamide, N-methylolacrylamide, N-butoxymethylacrylamide, diacetone acrylamide, 2-sulfonic acid ethyl (meth) acrylate and imide (meth) acrylate; . These acrylic monomers may be used alone or in combination of two or more. Among these, (meth) acrylic acid ester is preferable from the viewpoint of compatibility with an acrylic polymer containing a lactone ring structure, and methyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t -Butylcyclohexyl (meth) acrylate is preferable, and methyl (meth) acrylate and cyclohexyl (meth) acrylate are more preferable. The content of the acrylic monomer unit contained in the ultraviolet absorbing resin is preferably 20 to 99% by mass with respect to 100% by mass of the ultraviolet absorbing resin from the viewpoint of thermal stability and the like. More preferably, it is 97 mass%.

  Further, the ultraviolet absorbing resin may contain a monomer other than the ultraviolet absorbing monomer and the acrylic monomer as a constituent unit. Other monomers include, for example, monomers having a crosslinkable functional group described later, acrylonitrile, methacrylonitrile, styrene, butyl vinyl ether, mono- or dialkyl esters of maleic acid and itaconic acid, methyl vinyl ketone, vinyl chloride. , Vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, alkoxysilane having a vinyl group, polyester having an unsaturated bond, and the like. The amount of other monomers used is preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total amount of monomers.

  As the polymerization method of the monomer, for example, a polymerization initiator can be used by a conventionally known polymerization method such as solution polymerization, dispersion polymerization, suspension polymerization, emulsion polymerization or the like. The solvent for performing the solution polymerization is not particularly limited. For example, alcohols such as iso-propanol, n-butanol and diacetone alcohol; cellosolves such as ethyl cellosolve, butyl cellosolve and ethyl cellosolve acetate; propylene glycol monomethyl ether; Propylene glycols such as propylene glycol monoethyl ether and propylene glycol monoethyl ether acetate; Ketones such as acetone, methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; Ethers such as tetrahydrofuran; Ethyl acetate, butyl acetate, ethyl butyrate, butyl butyrate, etc. Esters; halogenated hydrocarbons such as methylene chloride; aromatic hydrocarbons such as toluene and xylene; dimethylacetamide, N-methylpyrrolide It can be used one or more highly polar solvents, etc. and the like. What is necessary is just to set suitably as the usage-amount of a solvent by polymerization conditions, a monomer density | concentration, a polymer solution density | concentration, etc.

Moreover, it does not restrict | limit especially as a polymerization initiator used in the case of superposition | polymerization, For example, a well-known peroxide type | system | group or an azo type | system | group initiator can be used. 2,2′-azobis- (2-methylbutyronitrile), tert-butylperoxy-2-ethylhexanoate, 2,2′-azobisisobutyronitrile, benzoyl peroxide, di-tert-butyl Known radical polymerization initiators such as peroxide and t-amylperoxyisononanoate can be used. These may be used alone or in combination of two or more. The amount of the polymerization initiator to be used should be appropriately determined according to the required characteristics of the polymer, and is not particularly limited, but is 0.01 to 50% by mass with respect to the total amount of monomers used for the polymerization. It is preferable that it is 0.05 to 20% by mass. Further, for example, one or more chain transfer agents such as n-dodecyl mercaptan, n-butyl mercaptan, 3-mercaptopropylmethyldimethoxysilane, (CH ₃ O) ₃ Si—S—S—Si (OCH ₃ ) ₃ are used. It may be added to adjust the molecular weight of the polymer.

  The temperature of the polymerization reaction is not particularly limited, but is preferably in the range of room temperature to 200 ° C, more preferably 40 to 140 ° C. In addition, what is necessary is just to set reaction time suitably so that a polymerization reaction can be completed efficiently according to the composition of the monomer component to be used, the kind of polymerization initiator, etc.

  The weight average molecular weight of the ultraviolet absorbing resin is preferably 2,000 to 500,000, more preferably 3,000 to 300,000, and still more preferably 4,000 to 100,000.

  The blending amount of the UV-absorbing resin may be appropriately determined so that a desired effect is exhibited. However, from the viewpoint of light resistance, it is preferably 1 to 30% by mass in the lactone film. More preferably, it is 20 mass%.

  Moreover, you may use light stabilizers, such as a hindered amine type compound, together with a ultraviolet absorber. Examples of the hindered amine compound include [dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine] polycondensate, bis (1-octyloxy-2,2 , 6,6, -tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6, -pentamethyl-4-piperidinyl) sebacate and the like. Commercially available products include “Tinubin 123”, “Tinubin 144”, “Tinubin 765” (all manufactured by Ciba Specialty Chemicals), “Adekastab LA-52”, “Adekastab LA-57”, “Adekastab LA-62”. And “Adeka Stab LA-77” (all manufactured by Asahi Denka Kogyo Co., Ltd.). When the light stabilizer is contained, the content thereof is preferably 0.5 to 20% by mass with respect to the ultraviolet absorbing substance (in the case of an ultraviolet absorbing resin, the resin non-volatile content), and preferably 1 to 10% by mass. More preferably, it is mass%.

  The lactone film may contain other additives. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. UV absorbers; near infrared absorbers; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents such as anionic, cationic and nonionic surfactants; inorganic pigments, organic Colorants such as pigments and dyes; organic fillers and inorganic fillers; resin modifiers; organic fillers and inorganic fillers; plasticizers; lubricants; antistatic agents; In the lactone film, the content of other additives is preferably 0 to 30% by mass, and more preferably 0 to 20% by mass.

  The thickness of the lactone film is preferably 10 to 200 μm and more preferably 20 to 100 μm because the effects of the present invention are remarkably exhibited.

  Moreover, it is preferable that (DELTA) E as described in the light resistance test method of the following Example is 2 or less, and it is more preferable that it is 1 or less.

  The glass transition temperature (Tg) of a film containing an acrylic polymer as a main component is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint of weather resistance and surface hardness. Although an upper limit is not specifically limited, Usually, Tg is 200 degrees C or less. In addition, the value calculated | required by the midpoint method is employ | adopted for glass transition temperature (Tg) based on ASTM-D-3418.

  In addition, the film as used in the field of this invention is the concept which includes a planar molded object widely, without depending on thickness.

  The lactone film is produced by a conventionally known method. For example, it can be obtained by mixing an acrylic polymer and, if necessary, an ultraviolet absorbing substance and other additives by a conventionally known mixing method, and molding the resulting mixture into a film. Specifically, for example, after pre-blending with a mixer such as an omni mixer, a method of extrusion kneading the obtained mixture can be employed. Moreover, it is good also as a stretched film by extending | stretching. In this case, the kneader used for extrusion kneading is not particularly limited. For example, a conventionally known kneader such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader is used. Can do.

  Examples of the film forming method include known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  Solvents used in the solution casting method (solution casting method) include, for example, chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, and isopropanol And alcohol solvents such as n-butanol and 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, ethyl acetate, and diethyl ether. These solvents may be used alone or in combination of two or more.

  Examples of the apparatus for performing the solution casting method (solution casting method) include a drum casting machine, a band casting machine, and a spin coater.

  Examples of the melt extrusion method include a T-die method and an inflation method, and the molding temperature of the extruded film at that time is preferably 150 to 350 ° C., more preferably 200 to 300 ° C.

  When the extruded film is formed by the T-die method, a T-die is attached to the tip of a known single-screw extruder or biaxial extruder, and a film in the form of a take-up roll can be obtained from the extruded film. . At this time, it is possible to adjust the temperature of the winding roll as appropriate and apply stretching in the extruding direction so that a uniaxial stretching process can be performed. Moreover, it is also possible to add processes, such as sequential biaxial stretching and simultaneous biaxial stretching, by adding the process of extending | stretching a film in the direction perpendicular | vertical to an extrusion direction.

  The extruded film may be an unstretched film or a court stretch film. When stretching, a uniaxially stretched film or a biaxially stretched film may be used. In the case of a biaxially stretched film, it may be a film that has been simultaneously biaxially stretched or a film that has been successively biaxially stretched. In the case of biaxial stretching, the mechanical strength is improved and the film performance is improved.

  The stretching temperature is preferably near the glass transition temperature of the extruded film raw material thermoplastic resin composition, specifically, (glass transition temperature-30) ° C. to (glass transition temperature + 100) ° C. Preferably, it is (glass transition temperature−20) ° C. to (glass transition temperature + 80) ° C. When it is lower than (glass transition temperature-30) ° C., a sufficient draw ratio cannot be obtained, which is not preferable. When the temperature is higher than (glass transition humidity + 100) ° C., resin flow occurs and stable stretching cannot be performed.

  The court stretch ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably in the range of 1.3 to 10 times. When it is less than 1.1 times, it is not preferable because it does not lead to improvement of toughness accompanying stretching. If it is larger than 25 times, the effect of only increasing the draw ratio is not recognized.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. If it is slower than 10% / min, it takes time to obtain a sufficient draw ratio, and the production cost is increased, which is not preferable. If it is faster than 20000% / min, the stretched extruded film may be broken, which is not preferable.

  In order to stabilize the mechanical properties of the extruded film, heat treatment (annealing) or the like can be performed after the stretching treatment.

<Gas barrier film>
The gas barrier film used in the present invention is not particularly limited as long as it can impart moisture resistance to the back protective sheet for protecting a solar cell, and a conventionally known gas barrier film can be used. For example, a laminate of an aluminum foil and a resin film, a film obtained by depositing an inorganic oxide on a resin film, a film obtained by coating an organic thin film on a resin film, and a combination thereof are used. In particular, in the present invention, a film on which an inorganic oxide is deposited is preferably used.

  Specific examples of the material constituting the resin film include, for example, polyethylene resins, polypropylene resins, cyclic polyolefin resins, polystyrene resins such as syndiotactic polystyrene resins, acrylonitrile-styrene copolymers (AS resins), Acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine resin, poly (meth) acrylic polymer, polycarbonate resin, polyethylene terephthalate or polyethylene naphthalate Polyester resins such as nylon, various polyamide resins such as nylon, polyimide resins, polyamideimide resins, polyaryl phthalate resins, silicone resins, polysulfone resins, polyphenylene sulfide resins, polyesters Tersulfone resin Polyurethane resins, acetals - Le resins, cellulose - can be given scan resins. As the constituent material of the film, one or more of the above materials can be used. As the resin film, an unstretched film that has not been stretched, or a stretched film stretched in a uniaxial or biaxial direction can be used. For reasons of mechanical strength, it is preferable to use a biaxially stretched film.

  In the present invention, among the above materials, from the viewpoint of durability and processability, a cyclic polyolefin resin, a polycarbonate resin, a poly (meth) acrylic polymer, a polystyrene resin, a polyamide resin, Alternatively, it is preferable to use a polyester resin.

  Although the thickness of the said resin film should just be determined suitably according to the various physical properties calculated | required by the back surface protection sheet for solar cells of this invention, the inside of the range of 10-200 micrometers is preferable normally.

  For the resin film, if necessary, for example, a lubricant, a crosslinking agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a filler, a lubricant, a reinforcing fiber, a reinforcing agent, an antistatic agent, a flame retardant, and a flame retardant. Additives such as foaming agents, fungicides, pigments and modifying resins can also be used. Such an additive may be appropriately adjusted and contained so that a desired purpose is exhibited, but the content is usually about 0 to 50% by mass.

  Moreover, the vapor deposition film of the inorganic oxide in the film in which the inorganic oxide is vapor deposited on the resin film is not particularly limited as long as it is a thin film in which a metal oxide is vapor deposited. Examples of the metal used for such a deposited film include silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), and boron. (B), titanium (Ti), lead (Pb), zirconium (Zr), yttrium (Y), and the like. These metals may be used alone or in combination of two or more. Especially in this invention, it is preferable to use the vapor deposition film of the metal oxide of silicon (Si) and aluminum (Al) as said vapor deposition film. The vapor deposition film is formed on the base film by using chemical vapor deposition (CVD), thermal chemical vapor deposition, vacuum vapor deposition, sputtering, physical vapor deposition (PVD), or the like. Can do. The thickness of the deposited film is preferably 5 to 500 nm, more preferably 10 to 300 nm, from the viewpoint of weather resistance.

  The organic thin film in the film obtained by coating a resin film with an organic thin film is not particularly limited, and polyvinyl chloride, polyvinylidene chloride, polychlorotrifluoroethylene, ethylene-vinyl alcohol copolymer resin, polyvinyl alcohol, polyacrylic. Examples include acid-based resins. Moreover, the material which added inorganic components, such as a silica particle, can also be used in order to improve barrier property in an organic thin film. The organic thin film can be formed by coating on a resin film using a roll coater, reverse roll coater, gravure coater, knife coater, bar coater or the like. The thickness of the organic thin film is preferably 500 nm to 10 μm, more preferably 1 to 5 μm, from the viewpoint of weather resistance.

  A surface treatment layer may be formed on the resin film in advance in order to improve the close adhesion with a vapor deposition film or the like. Examples of such a surface treatment layer include surface treatment such as corona discharge treatment, ozone treatment, plasma treatment using oxygen gas or nitrogen gas, glow discharge treatment, oxidation treatment using chemicals, and the like. Examples thereof include a corona treatment layer, an ozone treatment layer, a plasma treatment layer, and an oxidation treatment layer.

  In addition to the surface treatment layer, for example, a primer coat agent layer, an undercoat agent layer, an anchor coat agent layer, an adhesive layer in order to improve the tight adhesion with a deposited film or the like. Alternatively, a method of forming a coating agent layer such as a deposition anchor coating agent layer on the surface of the base film can also be used. Examples of the material constituting such a coating agent layer include polyester resins, polyamide resins, polyurethane resins, epoxy resins, phenol resins, (meth) acrylic polymers, polyvinyl acetate. Resin, polyolefin resin such as polyethylene or polypropylene, or a copolymer or modified resin thereof, cellulose resin, or the like can be used.

<Back side protection sheet for solar cells>
The back surface protective sheet for a solar cell of the present invention is formed by laminating a film containing an acrylic polymer having a lactone ring structure as a main component and a gas barrier film.

  An adhesive layer for bonding the lactone film and the gas barrier film is usually present between the lactone film and the gas barrier film. The material constituting the adhesive layer is not particularly limited as long as it is a material capable of adhering the lactone film and the gas barrier film, and polyurethane resin, polyester resin, polyamide resin, epoxy resin, phenol resin, and the like. A resin based on resin, an acrylic resin, a polyvinyl acetate resin, a polyolefin resin such as polyethylene or polypropylene, or a copolymer or modified resin thereof, a cellulose resin, or the like can be used. Among these, from the viewpoint of hydrolysis resistance and adhesiveness, it is preferable to use a polyurethane resin or an acrylic resin, and an acrylic resin is more preferable. The thickness of the adhesive layer is usually about 1 to 50 μm. Further, as will be described later, an ultraviolet absorbing resin may be used for the adhesive layer.

  A preferable example of the acrylic resin used for the adhesive layer is a resin obtained by polymerizing a monomer component containing a monomer represented by the following formula (10).

In the formula, R ³⁰ represents a hydrogen atom or a methyl group. Z represents a hydrocarbon group having 4 to 25 carbon atoms.

  Examples of the hydrocarbon group having 4 to 25 carbon atoms represented by Z include alicyclic hydrocarbon groups such as cyclohexyl group, methylcyclohexyl group, and cyclododecyl group; butyl group, isobutyl group, tert-butyl group, 2 -Linear or branched alkyl groups such as ethylhexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, pentadecyl group and octadecyl group; polycyclic carbonization such as bornyl group and isobornyl group A hydrogen group etc. are mentioned. Among these, an alicyclic hydrocarbon group, a branched alkyl group, and a linear alkyl group having 6 or more carbon atoms are preferable. More preferred are an alicyclic hydrocarbon group having 6 or more carbon atoms and a branched alkyl group having 4 or more carbon atoms, and particularly preferred is an alicyclic hydrocarbon group having 6 or more carbon atoms.

  Examples of the monomer represented by the general formula (10) include cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, and isobutyl (meth) acrylate. , Tert-butyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, stearyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Further, cyclohexyl alkyl esters of (meth) acrylic acid, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meta) as disclosed in JP-A-2002-69130. ) Acrylate, tricyclo [5,2,1,02.6] dec-8-yl (meth) acrylate, terpene (meth) acrylate, and the like.

  Among these, use of cyclohexyl (meth) acrylate and 2-ethylhexyl (meth) acrylate is preferable from the viewpoint of heat and moisture resistance, and use of cyclohexyl (meth) acrylate is more preferable.

  As the usage-amount of the monomer represented by the said General formula (10), when all the monomer components are 100 mass%, it is preferable to set it as 10 to 80 mass%. More preferably, the content is 15% by mass or more and 70% by mass or less. If it is such a range, it will be excellent in heat-and-moisture resistance, and the intensity | strength of an adhesive layer will also become sufficient.

  The acrylic resin used for the adhesive layer may be copolymerized with other copolymerizable monomers in addition to the monomer represented by the formula (10). Other copolymerizable monomers are not particularly limited, and examples thereof include the following monomers. Monomers having a carboxyl group such as (meth) acrylic acid, itaconic acid, maleic anhydride; acidic phosphate ester monomers such as 2- (meth) acryloyloxyethyl acid phosphate; 2-hydroxyethyl (meth) acrylate, hydroxy Monomers having a group having active hydrogen such as propyl (meth) acrylate, hydroxybutyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate (for example, trade name “Placcel FM” manufactured by Daicel Chemical Industries, Ltd.); methyl (meta ) Acrylates, ethyl (meth) acrylates, propyl (meth) acrylates, isopropyl (meth) acrylates, butyl (meth) acrylates and other (meth) acrylates; glycidyl (meth) acrylates and other epoxy groups Ma. Monomers having nitrogen atoms such as (meth) acrylamide, N, N′-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, imide (meth) acrylate; ethylene glycol di (meth) acrylate, Monomers having two or more polymerizable double bonds such as triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate; Monomers having halogen atoms such as vinyl; aromatic monomers such as styrene and α-methylstyrene; vinyl esters such as vinyl acetate; vinyl ethers. These may be used alone or in combination of two or more.

  Furthermore, when improving hydrolysis resistance and insulation resistance, it is preferable to use an acrylate having bisarylfluorene as a basic structure. Specifically, “Ogsol EA-0200”, “Ogsol EA-0200”, “Ogsol EA-0500”, “Ogsol EA-1000” (all trade names, manufactured by Osaka Gas Chemical Co., Ltd.) and the like can be mentioned. These monomers may be used independently and may use 2 or more types together.

  As a polymerization method for producing the acrylic resin, for example, a polymerization initiator can be used by a conventionally known polymerization method such as solution polymerization, dispersion polymerization, suspension polymerization or emulsion polymerization. The solvent for performing the solution polymerization is not particularly limited, and for example, one or more organic solvents as described above can be used. What is necessary is just to set suitably as the usage-amount of a solvent by polymerization conditions, the weight ratio of the polymer component in an acrylic polymer, etc.

  The polymerization initiator is not particularly limited. For example, 2,2′-azobis- (2-methylbutyronitrile), tert-butylperoxy-2-ethylhexanoate, 2,2′-azobisiso Examples include usual radical polymerization initiators such as butyronitrile, benzoyl peroxide, and di-tert-butyl peroxide. These may be used alone or in combination of two or more. The amount to be used may be appropriately set from the desired characteristic value of the polymer. For example, when the monomer component is 100% by mass, it is preferably 0.01 to 50% by mass. More preferably, it is 0.05-20 mass%.

  The polymerization conditions in the polymerization method may be appropriately set depending on the polymerization method, and are not particularly limited. For example, the polymerization temperature is preferably room temperature to 200 ° C. More preferably, it is 40-140 degreeC. What is necessary is just to set reaction time suitably so that a polymerization reaction may be completed according to the composition of a monomer component, the kind of polymerization initiator, etc.

  As a weight average molecular weight of acrylic resin, it is preferable that it is 2000-1 million, for example. More preferably, it is 4000-500,000, More preferably, it is 5000-300,000. The weight average molecular weight is a value measured with polystyrene standard GPC.

  The adhesive layer can be used either cross-linked or non-cross-linked, but is preferably a cross-linked coating film from the viewpoint of improving hydrolysis resistance and insulation resistance. It is preferable to form a cured coating film. Therefore, it is preferable to add a curing agent selected from at least one selected from the group consisting of polyisocyanate compounds or modified products thereof, epoxy resins, and oxazoline group-containing resins to the acrylic resin. Specific examples of the curing agent will be described later.

  Although it does not specifically limit as the usage-amount of a (block) polyisocyanate compound, For example, the isocyanate group in a (block) polyisocyanate compound will be 0.6-1.4 mol with respect to 1 mol of hydroxyl groups in an acrylic polymer. It is preferable to do so. In such a range, the heat and moisture resistance is excellent, and many unreacted isocyanate groups remain in the adhesive layer, which reacts with moisture in the air when the coating is cured, causing the coating to foam or whiten. There are few things. More preferably, it is 0.8-1.2 mol.

  The amount of aminoplast resin used is not particularly limited, and for example, it is preferable that the weight ratio of the acrylic resin and aminoplast resin is 9/1 to 6/4. The acrylic resin has a moderate hardness of the adhesive layer, and is excellent in adhesion and heat-and-moisture resistance.

  Moreover, you may contain the 1 type (s) or 2 or more types of curing catalyst for accelerating the crosslinking reaction with acrylic resin and a hardening | curing agent as needed. Although it does not specifically limit as such a curing catalyst, For example, when using the said (block) polyisocyanate compound, it is preferable to use catalysts, such as a dibutyl tin dilaurate and a tertiary amine, When using an aminoplast resin, it is preferable to use an acidic or basic curing catalyst.

  The adhesive layer may contain, for example, one or more solvents, additives, and the like as a composition other than the adhesive resin and the other additives described above. Examples of such solvents include the same organic solvents as described above, and examples of additives include conventionally known additives that are generally used in resin compositions that form films and coating films. For example, leveling agents; inorganic fine particles such as colloidal silica and alumina sol, polymethyl methacrylate organic fine particles, antifoaming agents, anti-sagging agents, silane coupling agents, titanium white, complex oxide pigments, Pigments such as carbon black, organic pigments and pigment intermediates; pigment dispersants; phosphorous and phenolic antioxidants; viscosity modifiers; ultraviolet light stabilizers; metal deactivators; Flame retardants; Reinforcing agents; Plasticizers; Lubricants; Rust inhibitors; Fluorescent brighteners; Organic and inorganic flameproofing agents; Organic and inorganic antistatic agents; Dehydrating agents such as methyl orthoformate .

  In addition to the resin having adhesive ability, the adhesive layer is blended with an ultraviolet absorbing substance (ultraviolet absorbent, ultraviolet absorbent resin, etc.) in order to make the adhesive layer have ultraviolet absorbing ability as described later. May be.

  It is preferable that the back surface protection sheet for solar cells of this invention has an ultraviolet absorption layer. The light resistance is improved by the presence of the ultraviolet absorbing layer.

  The ultraviolet absorbing layer is not particularly limited as long as it is a layer having ultraviolet absorbing ability, but 1) the lactone film has an ultraviolet absorbing ability, and 2) is formed between the lactone film and the gas barrier film. 3) a form in which the adhesive layer formed has an ultraviolet absorbing ability, 3) a form in which an ultraviolet absorbing layer is provided on the side facing the gas barrier film on the lactone film, and 4) a form in which the resin film of the gas barrier film has an ultraviolet absorbing ability. Can be mentioned. Among them, from the viewpoint of light resistance, 1) a form in which the lactone film has an ultraviolet absorbing ability, 2) a form in which the adhesive layer has an ultraviolet absorbing ability, and 3) an ultraviolet absorption on the side facing the adhesive layer on the lactone film. A form in which a layer is provided is preferred. Moreover, from the viewpoint of the output performance of the solar cell, 2) a mode in which the adhesive layer has an ultraviolet shielding ability is preferable.

  1) The form in which the lactone film has ultraviolet absorbing ability specifically includes the form in which the ultraviolet absorbing substance is contained in the film as described above.

  2) As the form in which the adhesive layer has the ability to absorb ultraviolet rays, specifically, the form in which an ultraviolet absorbing substance is contained in the adhesive layer; (heat, active energy ray) curable ultraviolet absorbing resin as a main component The form which forms an adhesive bond layer is mentioned.

  In the case where the ultraviolet absorbing material is contained in the adhesive layer, the ultraviolet absorbing material and the ultraviolet absorbing resin described in the column of the lactone film can be used as the ultraviolet absorbing material. When using an ultraviolet absorber, the content in the adhesive layer is preferably 1 to 30% by mass and more preferably 2 to 20% by mass from the viewpoint of light resistance. Moreover, when using an ultraviolet absorptive resin, it is preferable that it is 50 mass% or more from a viewpoint of light resistance, and, as for content in an adhesive bond layer, it is more preferable that it is 70 mass% or more. The upper limit of the content of the ultraviolet absorbing resin in the adhesive layer is not particularly limited, and may be 100% by mass, that is, the entire amount may be the ultraviolet absorbing resin.

  (Heat, active energy rays) A mode in which an adhesive layer is formed using a curable ultraviolet absorbing resin as a main component will be described. By using the curable ultraviolet absorbing resin, the adhesive layer can be formed without adding any other curable resin. As the curable ultraviolet absorbing resin, a conventionally known resin can be used, and for example, a resin described in JP-A-2007-331359 can be used. Here, the curable UV-absorbing resin includes not only a resin that is cured solely by the UV-absorbing resin but also a resin that is cured by addition of a curing agent.

  Specifically, the curable ultraviolet absorbing resin includes an ultraviolet absorbing monomer, a (meth) acrylic monomer, a monomer having a crosslinkable functional group described in the section of the lactone film, and a necessity. Accordingly, it is formed by polymerizing UV-stable monomers and other monomers.

  Examples of the crosslinkable functional group in the monomer having a crosslinkable functional group include a carboxyl group, an isocyanate group, an oxazoline group, an amide group, or a methylolated amide group, an amino group (including a substituted amino group), a hydroxyl group, and an epoxy. Groups, acid amide groups, sulfonic acid groups and the like. As monomers having a crosslinkable functional group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, vinyl sulfonic acid, styrene sulfonic acid, acrylamide, methacrylamide, N-methyl methacrylamide, methylol Acrylamide, methylol methacrylate, diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether, dimethylaminoethyl methacrylate, and methylolated amino group, 2-hydroxyethyl acrylate 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxyvinyl ether, 5-hydroxype Nthyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, glycidyl acrylate, glycidyl methacrylate, and the like can be used. In addition, when the acrylic monomer mentioned above contains a crosslinkable functional group, it is set as the monomer which has a crosslinkable functional group here.

  Examples of the other monomers include acrylonitrile, methacrylonitrile, styrene, butyl vinyl ether, mono- or dialkyl esters of maleic acid and itaconic acid, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone. , Alkoxysilane having a vinyl group, polyester having an unsaturated bond, and the like.

  The content of the UV-absorbing monomer unit in the curable UV-absorbing resin is preferably 1 to 80% by mass and 3 to 70% by mass with respect to 100% by mass of the curable UV-absorbing resin. It is more preferable. When the content is in such a range, the ultraviolet blocking ability can be sufficiently exerted, and there is little risk of yellowing the film. Although the usage-amount of a ultraviolet-stable monomer is not specifically limited, It is preferable that it is 0-20 mass% with respect to curable ultraviolet absorption resin, and it is 0-10 mass%. More preferred.

  Further, the content of the (meth) acrylic monomer in the curable ultraviolet absorbing resin is 20 to 99% by mass with respect to 100% by mass of the curable ultraviolet absorbing resin from the viewpoint of thermal stability and the like. It is preferably 30 to 97% by mass.

  The content of the monomer having a crosslinkable functional group in the curable ultraviolet absorbing resin is 1 with respect to 100% by mass of the curable ultraviolet absorbing resin from the viewpoint of adhesion to other films and mechanical strength. It is preferable that it is -30 mass%, and it is more preferable that it is 5-20 mass%.

  The content of other monomers in the curable ultraviolet absorbing resin is preferably 10% by mass or less with respect to 100% by mass of the curable ultraviolet absorbing resin.

  When the curable ultraviolet absorbing resin cannot be cured alone, it is necessary to separately add a curing agent (crosslinking agent) to crosslink. As the curing agent to be used, various known curing agents can be used depending on the functional group. For example, when the functional group is a hydroxyl group, a polyisocyanate compound having two or more isocyanate groups, a modified product thereof, or an aminoplast resin is preferable as the curing agent.

  As the polyisocyanate compound, a compound having a number average molecular weight of about 100 to 2,000 containing 2 or more, preferably 2 to 4 isocyanate groups per molecule, which has been conventionally used for the production of polyurethane resins. Can be preferably used.

  Examples of the polyisocyanate compound include a polyisocyanate compound and / or a block polyisocyanate compound. The polyisocyanate compound is not particularly limited as long as it is a compound having at least two isocyanate groups in the molecule. For example, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, Polyisocyanates such as 4,4′-methylenebis (cyclohexyl isocyanate), lysine diisocyanate, trimethylhexamethylene diisocyanate, 1,3- (isocyanatomethyl) cyclohexane, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate; Polyisocyanate derivatives (modified products) such as isocyanate adducts, burettes, isocyanurates, etc. That.

  The above-mentioned blocked polyisocyanate compound is usually blocked when the adhesive composition is heated and dried, and the isocyanate group of the polyisocyanate compound is usually blocked with a blocking agent in order to improve storage stability at room temperature. Is. The blocking agent is not particularly limited, and examples thereof include compounds such as ε-caprolactam, phenol, cresol, oxime and alcohol. As a commercial item of the above (block) polyisocyanate compound, for example, Death Module N3200, Death Module N3300, Death Module BL3175, Death Module N3400, Death Module N3600, Death Module VPLS2102 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd.), And Duranate E-402-90T (trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.). In order to prevent yellowing of the adhesive layer formed from the adhesive composition, a non-yellowing polyisocyanate compound having no isocyanate group directly bonded to the aromatic ring is preferred.

  Although it does not specifically limit as the usage-amount of a (block) polyisocyanate compound, For example, the isocyanate group in a (block) polyisocyanate compound is 0.6-1. It is preferable to be 4 mol. In such a range, the heat and moisture resistance is excellent, and many unreacted isocyanate groups remain in the adhesive layer, which reacts with moisture in the air when the coating is cured, causing the coating to foam or whiten. There are few things. More preferably, it is 0.8-1.2 mol.

  The aminoplast resin is an addition condensate of a compound having an amino group such as melamine or guanamine with formaldehyde, and is also called an amino resin. The aminoplast resin is not particularly limited. For example, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine, fully alkyl methylated melamine, fully alkyl butylated melamine, fully alkyl type. Melamine resins such as isobutylated melamine, fully alkyl type mixed etherified melamine, methylol group methylated melamine, imino group type methylated melamine, methylol group type mixed etherified melamine, imino group type mixed etherified melamine; butylated benzoguanamine, Examples thereof include guanamine resins such as methyl / ethyl mixed alkylated benzoguanamine, methyl / butyl mixed alkylated benzoguanamine and butylated glycoluril.

  Examples of commercially available aminoplast resins include Cymel 1128, Cymel 303, My Coat 506, Cymel 232, Cymel 235, Cymel 771, Cymel 325, Cymel 272, Cymel 254, Cymel 1170 (all trade names are Mitsui Cytec). Etc.). The amount of the aminoplast resin used is not particularly limited, and for example, it is preferable to blend so that the solid content weight ratio of the ultraviolet absorbing resin and the aminoplast resin is 9/1 to 6/4. The acrylic resin has a moderate hardness of the adhesive layer, and is excellent in adhesion and heat-and-moisture resistance. A hardening | curing agent may be used independently or may use 2 or more types together. Further, a crosslinking catalyst may be added in order to promote the crosslinking reaction. Examples of such a crosslinking catalyst include salts, inorganic substances, organic substances, acid substances, and alkaline substances.

  The blending amount of the curable ultraviolet absorbing resin in the adhesive layer is preferably 50 to 100% by mass, and more preferably 70 to 100% by mass.

  Further, a polymer other than the curable ultraviolet absorbing resin may be contained. Examples of the polymer that can be used in combination with the curable ultraviolet absorbing resin include a thermoplastic polymer or a thermosetting polymer that is crosslinked or cured by itself or with a curing agent. According to the use and required characteristics of the optical laminate of the present invention, the type and amount of such a polymer may be appropriately adjusted, and are not particularly limited. Examples of such polymers include thermoplastic polymers such as vinyl chloride resins, polyester resins, acrylic resins, and silicone resins; thermosetting polymers that are curable alone, such as urethane resins, aminoplast resins, silicone resins, and epoxy resins; And thermosetting polymers that are cured by a curing agent such as polyester resin, acrylic resin, and epoxy resin. The blending amount of the polymer other than the curable ultraviolet absorbing resin in the adhesive layer is preferably 50% by mass or less, and more preferably 30% by mass or less.

  The other additives that can be included in the adhesive layer are as described in the above-mentioned column of the adhesive layer.

  3) As an ultraviolet absorbing layer in a form in which an ultraviolet absorbing layer (hereinafter also referred to as ultraviolet absorbing layer B) is provided on the side facing the adhesive layer on the lactone film, the ultraviolet absorbing material is thermoplastic, thermosetting, active energy. And an ultraviolet absorbing layer contained in a resin component such as a linear curable resin; an ultraviolet absorbing layer containing a curable ultraviolet absorbing resin as a main component.

  In the case of containing an ultraviolet absorbing substance in a resin component such as thermoplastic, thermosetting, or active energy ray curable resin, the resin used is polyurethane resin, polyester resin, polyamide resin, epoxy resin. Resin, phenolic resin, (meth) acrylic polymer, polyvinyl acetate resin, polyolefin resin such as polyethylene or polypropylene, silicone resin, aminoplast resin, cellulose resin, etc. it can. Among these, polyurethane resins and (meth) acrylic resins are preferable from the viewpoint of hydrolysis resistance and adhesiveness. As the ultraviolet absorbing substance, the ultraviolet absorbent and ultraviolet absorbing resin described in the section of the lactone film can be used. The content ratio of the ultraviolet absorbing material and the resin component is not particularly limited, but from the viewpoint of light resistance, when using an ultraviolet absorber, it is preferably 1 to 30% by mass with respect to the resin component, More preferably, it is 5-20 mass%. Moreover, when using an ultraviolet absorptive resin, it is preferable that it is 5-30 mass% with respect to a resin component from a light-resistant viewpoint.

  As the ultraviolet absorbing layer containing the ultraviolet absorbing resin as a main component, an adhesive layer formed using the curable ultraviolet absorbing resin as a main component can be used. Since it is the same as that described in the column of the adhesive layer formed with the curable ultraviolet absorbing resin as a main component, the details of the ultraviolet absorbing layer in this form are omitted.

  The ultraviolet absorbing layer B is preferably 1 to 30 μm and more preferably 2 to 10 μm from the viewpoint of light resistance.

  The ultraviolet absorbing layer B may contain other additives as necessary. For example, hindered phenol, phosphorus, sulfur and other antioxidants; light stabilizers, weather stabilizers, heat stabilizers and other stabilizers; reinforcing materials such as glass fibers and carbon fibers; ultraviolet absorbers; near infrared rays Absorbers; Flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes Organic fillers and inorganic fillers, resin modifiers, organic fillers and inorganic fillers, plasticizers, lubricants, antistatic agents, flame retardants, and the like. In the ultraviolet absorbing layer B, the content of other additives is preferably 0 to 30% by mass, and more preferably 0 to 20% by mass.

  Moreover, in order to improve adhesiveness with the ultraviolet absorption layer B, the surface of the lactone film may be subjected to various discharge treatments, oxidation treatments, roughening treatments, anchor coating treatments, and the like.

  The anchor treatment is not particularly limited as long as it improves the adhesion between the lactone film and the ultraviolet absorbing layer B. For example, the anchor treatment is selected from urea resin, melamine resin, polyurethane resin, polyester resin, acrylic resin, silicon resin, epoxy resin, etc. One or more of these and a thermosetting resin layer containing these resins as a main component and added with a crosslinking agent can be used.

  In consideration of scratch resistance, the solar cell back surface protective sheet preferably has a pencil hardness of H or higher, preferably 2H or higher. At this time, when the pencil hardness is less than H, the surface is easily damaged when the solar cell is assembled or exposed to the outdoors, and the appearance is deteriorated and the light energy absorption efficiency is deteriorated. In addition, the pencil hardness in this invention is the value measured according to the method as described in a following example.

<Solar cell module>
The present invention also relates to a solar cell module including the solar cell back surface protective sheet. The solar cell module which is one Embodiment of this invention is demonstrated using FIG. In addition, this invention is not restrict | limited only to the following embodiment. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  The solar cell module 1 of the present embodiment has a solar cell surface protection sheet 2, a resin layer 3, a solar cell element 4 provided with wiring, a resin layer 5, and a solar cell back surface protection sheet 6 stacked in order. Has the structure. The back surface protective sheet 6 for solar cells includes a lactone film 7, an adhesive layer 8, and a gas barrier film 9. In addition, an easy adhesion layer 10 is formed between the resin layer 5 and the solar cell back surface protective sheet 6.

  As the surface protection sheet for solar cells, generally known ones can be used, and specifically, glass plates, polyamide resins (various nylons), polyester resins, cyclic polyolefin resins, polystyrene resins. , (Meth) acrylic resins, polycarbonate resins, acetal resins, and other various polymers. Among them, it is preferable to use a glass plate from the viewpoints of sunlight permeability, weather resistance, physical strength, and the like.

  The resin layer 3 or the resin layer 5 constituting the solar cell module has a function of maintaining transparency, adhesiveness to the back surface protection sheet and back surface protection sheet, and smoothness of the back surface of the solar cell element. It is necessary to have excellent thermoplasticity, scratch resistance, shock absorption and the like. Specifically, as the resin constituting the resin layer, for example, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid, or acid-modified polyolefin resin, polyvinyl butyral resin, silicone Resin, epoxy resin, (meth) acrylic resin, and mixtures thereof. In consideration of weather resistance such as light resistance, heat resistance and water resistance, an ethylene-vinyl acetate resin is preferable. The resin layer can optionally contain additives such as, for example, a crosslinking agent, a thermal antioxidant, a light stabilizer, an ultraviolet absorbing material, a photoantioxidant, and the like, as long as the transparency is not impaired. In addition, as thickness of a resin layer, it is 200-1,000 micrometers normally, Preferably, it is 350-800 micrometers.

As the solar cell element 4, a conventionally known element, for example, a crystalline silicon solar electronic element such as a single crystal silicon type solar cell element or a polycrystalline silicon type solar cell element, an amorphous silicon solar cell composed of a single junction type or a tandem structure type, etc. Battery elements, III-V compound semiconductor solar electronic elements such as gallium arsenide (GaAs) and indium phosphorus (InP), II-VI compound semiconductor solar electrons such as cadmium tellurium (CdTe) and copper indium selenide (CuInSe ₂ ) An element, an organic solar cell element, etc. can be used. Furthermore, a thin film polycrystalline silicon solar cell element, a thin film microcrystalline silicon solar cell element, a hybrid element of a thin film crystalline silicon solar cell element and an amorphous silicon solar cell element, or the like can also be used.

  The solar cell module can be usually produced by a known method. For example, the solar cell surface protective sheet 2, the resin layer 3, the solar cell element 4, the resin layer 5, and the solar cell back surface protective sheet 6 are sequentially laminated. Arbitrarily stacking the materials, then using a normal molding method such as a lamination method in which these are integrated by vacuum suction or the like, and thermocompression-molded with each of the above layers as an integral molded body, A solar cell module can be manufactured by attaching a frame (spacer).

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

(Example 1)
1. Production of Gas Barrier Film A gas barrier film 20 having the configuration shown in FIG. 2 was produced. The gas barrier film 20 is formed by sequentially laminating a primer layer 12, an inorganic oxide vapor deposition film 13, and a coating layer 14 on a resin film 11.

  A biaxially stretched polyethylene terephthalate (PET) film (trade name: Lumirror S10 manufactured by Toray Industries, Inc.) having a thickness of 12 μm was used as the resin film 11. A primer agent was applied to one side of the resin film by a gravure coating method to form a primer layer (thickness 0.2 μm (dry film thickness)). The primer agent was prepared as follows. In a diluting solvent (ethyl acetate), 5 parts by mass of acrylic polyol is mixed with 1 part by mass of γ-isocyanatopropyltrimethylsilane and stirred. Next, a primer solution was prepared by diluting a mixed solution of triidyl isocyanate (TDI) as an isocyanate compound so that the NCO group was equivalent to the OH group of the acrylic polyol to 2% concentration with ethyl acetate.

  Next, the aluminum vapor is evaporated on the primer layer 12 by an electron beam heating vacuum deposition apparatus, oxygen gas is introduced therein, aluminum oxide (alumina) is deposited, and an inorganic oxide deposited film 13 having a thickness of 20 nm is formed. Formed.

Further, a coating agent was applied thereon with a gravure coater and dried at 100 ° C. for 1 minute with a dryer to obtain a gas barrier film having a coating layer 14 having a thickness of 0.3 μm. The composition of the coating agent used was a mixture of (1) liquid and (2) liquid at a blending ratio (wt%) of 60/40. Here, the liquid (1) is a hydrolyzed solution having a solid content of 3 wt% (converted to SiO ₂ ) obtained by adding 89.6 g of hydrochloric acid (0.1N) to 10.4 g of tetraethoxysilane, and stirring and hydrolyzing for 30 minutes. 2) The solution is a 3 wt% water / isopropyl alcohol solution of polyvinyl alcohol (90:10 by weight ratio of water: isopropyl alcohol).

2. Production of lactone film 8,000 g of methyl methacrylate (MMA) and 2,000 g of 2- (hydroxymethyl) acrylic were added to a 30 L capacity reactor equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction pipe. Methyl acid (MHMA), 10,000 g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), and 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while refluxing nitrogen. As a polymerization initiator, 5.0 g of t-butylperoxyisopropyl carbonate (Kayacarbon BIC-75, manufactured by Kayaku Akzo Co., Ltd.) was added simultaneously with 10.0 g of t-butylperoxyisopropyl carbonate and 230 g of MIBK. A solution consisting of about 105 to 12 under reflux while dropping over 2 hours. Solution polymerization was performed at 0 ° C., and further aging was performed for 4 hours.

  To the obtained polymer solution, 30 g of stearyl phosphate / distearyl phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added and cyclized at about 90-120 ° C. for 5 hours under reflux. A condensation reaction was performed. Next, the obtained polymer solution was a vent type screw twin screw extruder having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4. (Φ = 29.75 mm, L / D = 30), in terms of resin amount, introduced at a processing rate of 2.0 kg / h, cyclized condensation reaction and devolatilization are carried out in this extruder, and extruded. A transparent polymer pellet was obtained. When the obtained polymer was measured for dynamic TG, a mass loss of 0.34% by mass was detected. The lactone ring-containing polymer had a weight average molecular weight of 144,000 and a glass transition temperature of 131 ° C. In addition, the weight average molecular weight was calculated | required by polystyrene conversion using the gel permeation chromatograph (GPC system, Tosoh Corporation make).

  Further, the dynamic TG, glass transition temperature, dealcoholization reaction rate, and proportion of the lactone ring structure were measured by the following methods.

  Polymer pellets were melt-extruded from a coat hanger type T die having a width of 150 mm using a twin-screw extruder having a 20 mmφ screw to prepare a base film having a thickness of 104 μm. Using the biaxial stretching test apparatus (catalog No. 586, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the obtained base film was simultaneously 1.5 times at 150 ° C. and a stretching speed of 0.1 m / min. A lactone film having a thickness of 45 μm was produced by biaxial stretching.

<Dynamic TG>
The polymer (or polymer solution or pellet) is once dissolved or diluted in tetrahydrofuran, poured into excess hexane or methanol for reprecipitation, and the taken out precipitate is vacuum dried (1 mmHg (1.33 hPa), 80 ° C. Volatile components and the like were removed by conducting the reaction for 3 hours or more, and the obtained white solid resin was analyzed by the following method (dynamic TG method).

<Dealcoholization reaction rate and proportion of lactone ring structural unit>
First, based on the amount of mass reduction that occurs when all hydroxyl groups are dealcoholated as methanol from the obtained polymer composition, 300 before the start of decomposition of the polymer from 150 ° C. before the mass reduction starts in dynamic TG measurement. The dealcoholization reaction rate was determined from the mass reduction due to the dealcoholization reaction up to ° C.

  That is, in the dynamic TG measurement of the polymer having a lactone ring structure, the mass reduction rate between 150 ° C. and 300 ° C. is measured, and the obtained actual measurement value is defined as the actual mass reduction rate (X). On the other hand, from the composition of the polymer, the mass reduction rate when assuming that all the hydroxyl groups contained in the polymer composition become alcohol and dealcoholate because they are involved in the formation of the lactone ring (that is, 100 in the composition) % Mass reduction rate calculated assuming that the dealcoholization reaction occurred) is defined as the theoretical mass reduction rate (Y). The theoretical mass reduction rate (Y) is more specifically the molar ratio of raw material monomers having a structure (hydroxyl group) involved in the dealcoholization reaction in the polymer, that is, the raw material single amount in the polymer composition. It can be calculated from the body content. Substituting these values into the dealcoholization calculation formula: 1- (actual mass reduction rate (X) / theoretical mass reduction rate (Y)): to obtain the value and expressing it as a percentage (%), the dealcoholization reaction rate Is obtained. Then, the content (mass ratio) in the polymer composition of the raw material monomer having a structure (hydroxyl group) involved in lactone cyclization, assuming that the predetermined lactone cyclization has been performed by the dealcoholization reaction rate. The content ratio of the lactone ring structure in the polymer can be calculated by multiplying the reaction rate by the dealcoholization reaction rate.

  The content ratio of the lactone ring structural unit represented by the formula (I) in the lactone ring-containing polymer obtained in Example 1 is calculated. When the theoretical mass reduction rate (Y) of this polymer is obtained, the molecular weight of methanol is 32, the molecular weight of methyl 2- (hydroxymethyl) acrylate is 116, and 2- (hydroxymethyl) in the polymer is ) Since the content (mass ratio) of methyl acrylate is 20.0 mass% in terms of composition, (32/116) × 20.0≈5.52 mass%. On the other hand, the actual mass reduction rate (X) by dynamic TG measurement was 0.34% by mass. When these values are applied to the above-described dealcoholization calculation formula, 1− (0.34 / 5.52) ≈0.938 is obtained, and the dealcoholization reaction rate is 93.8%. And the content rate (mass) in the said copolymer composition of the raw material monomer which has a structure (hydroxy group) in connection with lactone cyclization as what was predetermined | prescribed lactone cyclization was performed by this dealcoholization reaction rate The ratio of the lactone ring structure in the copolymer can be calculated by multiplying the ratio) by the dealcoholization reaction rate and converting it to the content (mass ratio) of the lactone ring structure. In the case of the above-mentioned production example, the content of 2- (hydroxymethyl) methyl acrylate in the copolymer is 20.0% by mass, the calculated dealcoholization reaction rate is 93.8%, and the molecular weight is 116- ( Hydroxymethyl) Since the formula amount of the lactone ring structural unit represented by the formula (I) produced when methyl acrylate is condensed with methyl methacrylate is 170, the lactone ring structural unit in the copolymer The content ratio is 27.5 (20.0 × 0.938 × 170/116) mass%.

  In the case of this example, the lactone ring structure is mostly formed by condensation of methyl 2- (hydroxymethyl) acrylate and methyl methacrylate, and the content ratio of the lactone ring is as described above. It can be approximated to a value calculated from the condensation of methyl 2- (hydroxymethyl) acrylate and methyl methacrylate.

<Thermal analysis of polymer>
The thermal analysis of the polymer was performed using a differential scanning calorimeter (DSC-8230, manufactured by Rigaku Corporation) under the conditions of about 10 mg of sample, a heating rate of 10 ° C./min, and a nitrogen flow of 50 mL / min. In addition, the glass transition temperature (Tg) was calculated | required by the midpoint method based on ASTM-D-3418.

3. Production of back surface protection sheet for solar cell On the vapor-deposited surface side of the gas barrier film obtained in the above, a urethane adhesive (main agent “Takelac A310” / curing agent “Takenate A3” = 12/1 manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) is dried to a coating thickness of 4 μm. 1. Apply through the adhesive layer and 2. The lactone film obtained in (1) was laminated and laminated to prepare a back protective sheet for solar cells.

4). Production of solar cell module 3. Using the back surface protective sheet for solar cells of the present invention obtained in 1), a glass with a thickness of 3 mm as a surface protective plate, an ethylene-vinyl acetate resin (EVA) with a thickness of 0.7 mm as a filler, a solar cell element, After sequentially stacking EVA with a thickness of 0.7 mm as a filler, this back surface protection sheet is overlaid and laminated by vacuum heating at 150 ° C. for 30 minutes to 1 torr (133.322 Pa), and the solar cell module is assembled. Produced.

(Example 2)
The following ultraviolet absorbing resin solution was prepared.

(Synthesis of UV-absorbing resin solution)
In a flask equipped with a stirrer, a dripping port, a thermometer, a cooling pipe and a nitrogen gas inlet, 25 parts by mass of ethyl acetate and 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -2H-benzo 10 parts by mass of triazole (trade name “RUVA93”, manufactured by Otsuka Chemical Co., Ltd.) was charged. Separately, 30 parts by mass of cyclohexyl methacrylate, 15 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of RUVA93, 2 parts by mass of UV-stable monomer (trade name “Adeka Stab LA82”, manufactured by ADEKA), 15 parts by mass of 2-hydroxyethyl methacrylate, A monomer solution mixture was prepared by dissolving 18 parts by weight of methyl methacrylate, 75 parts by weight of ethyl acetate, and 6 parts by weight of 2,2′-azobis (2-methylbutyronitrile), and 30% by weight of the mixture was prepared. The flask was charged and nitrogen gas was introduced and the temperature was raised to the reflux temperature while stirring. The mixture of the remaining 70% by mass of the monomer solution was added dropwise over 2 hours. After the addition, the mixture was further heated for 6 hours and then cooled. When diluted with 50 parts by mass of ethyl acetate, an ultraviolet-absorbing resin solution having a nonvolatile content concentration of 40% by mass was obtained. The weight average molecular weight of the ultraviolet absorbing resin was 25,800.

  On the vapor deposition surface side of the gas barrier transparent vapor deposition film used in Example 1, an adhesive (main agent; the above-described ultraviolet absorbing resin solution / curing agent; “Desmodule N3200” manufactured by Sumika Bayer Urethane Co., Ltd. = 5/1 ( The weight ratio)) was applied to a coating thickness of 4 μm after drying, and the lactone film was bonded through the adhesive layer to obtain a solar cell back surface protective sheet, as in Example 1. Thus, a solar cell module was produced.

(Example 3)
1. Production of Gas Barrier Film A gas barrier film was obtained in the same manner as in Example 1.

2. Production of Lactone Film A lactone film was obtained in the same manner as in Example 1. Next, the following ultraviolet absorbing resin was prepared.

(Synthesis of UV-absorbing resin solution)
In a flask equipped with a stirrer, a dripping port, a thermometer, a cooling pipe and a nitrogen gas inlet, 25 parts by mass of ethyl acetate and 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -2H-benzo 10 parts by mass of triazole (trade name “RUVA93”, manufactured by Otsuka Chemical Co., Ltd.) was charged. Separately, 30 parts by mass of cyclohexyl methacrylate, 15 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of RUVA93, 2 parts by mass of UV-stable monomer LA82 (trade name “Adeka Stub LA82”, manufactured by ADEKA), 15 parts by mass of 2-hydroxyethyl methacrylate , 18 parts by mass of methyl methacrylate, 75 parts by mass of ethyl acetate, and 6 parts by mass of 2,2′-azobis (2-methylbutyronitrile) were prepared in advance, and 30% by mass of the mixture was prepared. Was introduced into a flask, and nitrogen gas was introduced and the temperature was raised to the reflux temperature while stirring. The mixture of the remaining 70% by mass of the monomer solution was added dropwise over 2 hours. After the addition, the mixture was further heated for 6 hours and then cooled. When diluted with 50 parts by mass of ethyl acetate, an ultraviolet-absorbing resin solution having a nonvolatile content concentration of 40% by mass was obtained. The weight average molecular weight of the ultraviolet absorbing resin was 25,800.

  Dry the mixture of UV-absorbing resin solution and curing agent on lactone film (main agent; UV-absorbing resin solution / curing agent; “Desmodule N3200” = 5/1 (weight ratio) by Sumika Bayer Urethane Co., Ltd.) The film was applied so as to have a post-coating thickness of 4 μm, and an ultraviolet absorbing layer was formed on the lactone film.

3. Production of back surface protection sheet for solar cell Application of 5 g / m ^{2 of} urethane adhesive (main agent “Takelac A310” / curing agent “Takenate A3” = 12/1 manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) on the vapor deposition surface side of the gas barrier film obtained in the above Then, a lactone film having an ultraviolet absorbing layer formed thereon was laminated through the adhesive layer to produce a back protective sheet for solar cells. The stacking order is a gas barrier film, an adhesive layer, a lactone film, and an ultraviolet absorbing layer.

4). Production of Solar Cell Module A solar cell module was produced in the same manner as in Example 1.

Example 4
1. Production of Gas Barrier Film A gas barrier film was obtained in the same manner as in Example 1.

2. Production of Lactone Film Containing Ultraviolet Absorbing Substance 40 parts of methyl methacrylate (MMA), 10 parts of 2- (hydroxymethyl) acrylic in a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe and nitrogen introduction pipe Methyl acid (MHMA) and 50 parts of toluene were charged, and the temperature was raised to 105 ° C. while refluxing nitrogen. When refluxed, 0.05 part of t-amylperoxyisononanoate (Arkema Yoshitomi ( Co., Ltd., trade name: Luperox 570) and at the same time, 0.10 parts of t-amylperoxyisononanoate was added dropwise over 2 hours while solution polymerization was performed under reflux (about 105 to 110 ° C.). Aged for another 4 hours.

  To the obtained polymer solution, 0.05 part of 2-ethylhexyl phosphate (manufactured by Sakai Chemical Industry Co., Ltd., trade name: Phoslex A-8) was added and refluxed (about 90 to 110 ° C.) for 5 hours. A cyclization condensation reaction was performed. Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4 It is introduced into a type screw twin screw extruder (φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization are carried out in the extruder. A transparent polymer pellet (1) was obtained by extrusion. The weight average molecular weight of the obtained polymer was 144,000.

  The proportion of the lactone ring structural unit represented by the formula (I) in the pellet is calculated. When the theoretical weight loss rate (Y) of this polymer was determined, the molecular weight of methanol was 32, the molecular weight of methyl 2- (hydroxymethyl) acrylate was 116, and methyl 2- (hydroxymethyl) acrylate. Since the content (weight ratio) in the polymer is 20% by weight in terms of composition, (32/116) × 20≈5.52% by weight. On the other hand, the actual weight loss rate (X) by dynamic TG measurement was 0.18% by weight. When these values are applied to the above-described dealcoholization calculation formula, 1− (0.18 / 5.52) ≈0.967, and the dealcoholization reaction rate is 96.7%.

  And the content rate (weight ratio) in the said copolymerization composition of the raw material monomer which has the structure (hydroxy group) which participates in lactone cyclization as what the predetermined | prescribed lactone cyclization was performed by this dealcoholization reaction rate ) Is multiplied by the dealcoholization reaction rate and converted to the content (weight ratio) of the structure of the lactone ring unit, the content of the lactone ring structure in the copolymer can be calculated. In the case of Example 4, the content of 2- (hydroxymethyl) methyl acrylate in the copolymer was 20.0% by weight, the calculated dealcoholization reaction rate was 96.7% by weight, and the molecular weight was 116- ( Hydroxymethyl) Since the formula amount of the lactone cyclized structural unit represented by the formula (I) generated when methyl acrylate is condensed with methyl methacrylate is 170, the lactone ring is contained in the copolymer. The ratio is 28.3 (20.0 × 0.967 × 170/116) wt%.

  Next, an ultraviolet absorbing resin was produced as follows.

  In a 30 L reaction kettle equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe, 15 parts of cyclohexyl methacrylate (CHMA) and 35 parts of the following monomers;

Then, 50 parts of toluene was charged, and the temperature was raised to 105 ° C. while refluxing nitrogen. When refluxed, 0.05 part of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Corp., product) Name: Luperox 570) was added, and at the same time, 0.10 parts of t-amylperoxyisonononanoate was added dropwise over 2 hours, and solution polymerization was performed under reflux (about 105 to 110 ° C.) for another 4 hours. Aged over time.

  The obtained polymer solution was converted into a vent type screw twin screw extruder (φ) having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4. = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin amount, devolatilized in the extruder, and extruded to obtain transparent polymer pellets (2 )

  80 parts by mass of pellet (1) and 20 parts by mass of pellet (2) were melt-extruded from a coat hanger type T die with a width of 150 mm using a twin screw extruder having a 20 mmφ screw to produce an extruded film with a thickness of 50 μm. did. The resulting film had a glass transition temperature of 131 ° C.

3. Production of back surface protection sheet for solar cell On the vapor-deposited surface side of the gas barrier film obtained in the above, an adhesive (main agent “Takelac A310” / curing agent “Takenate A3” = 12/1 manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) is dried to a coating thickness of 4 μm. The back protective sheet for solar cells was produced by coating and laminating an ultraviolet-absorbing substance-containing acrylic resin film through the adhesive layer.

4). Production of Solar Cell Module A solar cell module was produced in the same manner as in Example 1.

(Example 5)
The following polymer solution was prepared.

(Synthesis of polymer solution)
In a flask equipped with a stirrer, a dripping port, a thermometer, a condenser tube and a nitrogen gas inlet, 70 parts by mass of ethyl methacrylate, 15 parts by mass of 2-ethylhexyl acrylate, 15 parts by mass of 2-hydroxyethyl methacrylate, 100 parts by mass of ethyl acetate and A monomer solution mixture in which 6 parts by mass of 2,2′-azobis (2-methylbutyronitrile) was dissolved was prepared, 30% by mass of the mixture was charged into the flask, and nitrogen gas was introduced and stirred. The temperature was raised to the reflux temperature. The mixture of the remaining 70% by mass of the monomer solution was added dropwise over 2 hours. After the addition, the mixture was further heated for 6 hours and then cooled. When diluted with 50 parts by mass of ethyl acetate, a polymer solution having a nonvolatile content concentration of 40% by mass was obtained. The weight average molecular weight of the polymer was 30,200.

  Adhesive (main agent; polymer solution / curing agent; “Desmodule N3200” = 5/1 (weight ratio) manufactured by Sumika Bayer Urethane Co., Ltd.) is applied to the vapor deposition surface side of the gas barrier transparent vapor deposition film used in Example 2. Example 2 except that after drying, a coating thickness of 4 μm was applied, and a film containing an acrylic polymer as a main component was bonded through the adhesive layer to obtain a back protective sheet for solar cells. In the same manner as described above, a solar cell module was produced.

(Example 6)
The following polymer solution was prepared.

(Synthesis of polymer solution)
In a flask equipped with a stirrer, a dripping port, a thermometer, a condenser tube and a nitrogen gas inlet, 18 parts by mass of methyl methacrylate, 22 parts by mass of ethyl methacrylate, 15 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of cyclohexyl methacrylate, 2-hydroxy A monomer solution mixture in which 15 parts by weight of ethyl methacrylate, 100 parts by weight of ethyl acetate and 6 parts by weight of 2,2′-azobis (2-methylbutyronitrile) were dissolved was prepared, and 30% by weight of the mixture was added to the flask. Then, nitrogen gas was introduced and the temperature was raised to the reflux temperature while stirring. The mixture of the remaining 70% by mass of the monomer solution was added dropwise over 2 hours. After the addition, the mixture was further heated for 6 hours and then cooled. When diluted with 50 parts by mass of ethyl acetate, a polymer solution having a nonvolatile content concentration of 40% by mass was obtained. The weight average molecular weight of the polymer was 30,500.

  Urethane adhesive (main agent; polymer solution / curing agent; “Death Module N3200” manufactured by Sumika Bayer Urethane Co., Ltd.) = 5/1 (weight ratio) on the vapor deposition surface side of the gas barrier transparent vapor deposition film used in Example 2 ) Was applied after drying to a coating thickness of 4 μm, and a film containing an acrylic polymer as a main component was bonded through the adhesive layer to obtain a back protective sheet for solar cells. In the same manner as in Example 2, a solar cell module was produced.

(Example 7)
The following ultraviolet absorbing resin solution was prepared.

(Synthesis of UV-absorbing resin solution)
In a flask equipped with a stirrer, a dripping port, a thermometer, a cooling pipe and a nitrogen gas inlet, 25 parts by mass of ethyl acetate and 2- [2′-hydroxy-5 ′-(methacryloyloxyethyl) phenyl] -2H-benzo 10 parts by mass of triazole (trade name “RUVA93”, manufactured by Otsuka Chemical Co., Ltd.) was charged. Separately, 30 parts by weight of ethyl methacrylate, 15 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of RUVA93, 2 parts by weight of UV-stable monomer (trade name “Adeka Stab LA82”, manufactured by ADEKA), 15 parts by weight of 2-hydroxyethyl methacrylate, A monomer solution mixture was prepared by dissolving 18 parts by weight of methyl methacrylate, 75 parts by weight of ethyl acetate, and 6 parts by weight of 2,2′-azobis (2-methylbutyronitrile), and 30% by weight of the mixture was prepared. The flask was charged and nitrogen gas was introduced and the temperature was raised to the reflux temperature while stirring. The mixture of the remaining 70% by mass of the monomer solution was added dropwise over 2 hours. After the addition, the mixture was further heated for 6 hours and then cooled. When diluted with 50 parts by mass of ethyl acetate, an ultraviolet-absorbing resin solution having a nonvolatile content concentration of 40% by mass was obtained. The weight average molecular weight of the ultraviolet absorbing resin was 27,000.

  Adhesive (main agent; UV-absorbing resin solution / curing agent; “Death Module N3200” manufactured by Sumika Bayer Urethane Co., Ltd.) = 5/1 (weight ratio) on the vapor deposition surface side of the gas barrier transparent vapor deposition film used in Example 2 )) Is applied to a coating thickness of 4 μm after drying, and a film containing an acrylic polymer as a main component is bonded through the adhesive layer to obtain a back protective sheet for solar cells. In the same manner as in Example 2, a solar cell module was produced.

(Comparative Example 1)
A solar cell module was produced in the same manner as in Example 2 except that a 38 μm-thick fluorine film (manufactured by DuPont, Tedlar TTR15BG5) was used instead of the lactone film.

(Comparative Example 2)
A solar cell module was produced in the same manner as in Example 2, except that a highly weather-resistant polyethylene terephthalate (PET) film having a thickness of 125 μm (“Lumirror X10S” manufactured by Toray Industries, Inc.) was used instead of the lactone film.

(Comparative Example 3)
A solar cell module was produced in the same manner as in Example 2 except that a 125 μm-thick polymethyl methacrylate (PMMA) film (manufactured by Sumitomo Chemical Co., Ltd., Technoloy, glass transition temperature 103 ° C.) was used instead of the lactone film. did.

(Evaluation)
About the back surface protection sheet for solar cells and solar cell module which were obtained in Examples 1-7 and Comparative Examples 1-3, surface hardness, weather resistance, light resistance, and the output test were implemented based on the following evaluation method. In Table 6, the following three-level evaluation is performed, and environmental measures and costs are also compared and shown.

<Surface hardness test method>
According to JIS-K5400, pencils of various hardnesses were applied to the back protective sheet surface at an angle of 90 degrees, scratched with a load of 1 kg, and displayed as the hardness of the pencil when a scratch occurred.

<Moisture and heat resistance test method>
The back protective sheet was stored for 3000 hours in an environment of 85 ° C.-90% RH, and the elongation at break was measured as the mechanical properties of the film. The retention rate (%) of elongation at break before and after the aging treatment was calculated by the following formula, and judged according to the following criteria.

<Light resistance test method>
The back surface protection sheet is set in an ultraviolet deterioration accelerating tester (“eye super UV tester UV-W131”; manufactured by Iwasaki Electric Co., Ltd.), and an ultraviolet ray of 120 mW / cm ² is applied for 240 hours in an atmosphere of 60 ° C. and 50% RH. Continuous irradiation. L *, a *, and b * before and after the test were measured using a color difference meter (model “SE-2000”; manufactured by Nippon Denshoku). L *, a *, and b * before irradiation are set to L * 0, a * 0, and b * 0, and after irradiation, L * 1, a * 1, and b * 1, and ΔE is calculated from the following formula. Evaluated by.

<Output test method>
The battery output after storing the solar cell module in an 85 ° C.-90% RH environment for 250 hours and 500 hours was evaluated according to the following criteria.

  The results are shown in Table 6.

  From the above results, it is understood that the back surface protection sheet for solar cells of the present invention is a sheet having a balanced surface hardness, weather resistance, and light resistance.

It is a schematic diagram which shows one Embodiment of the solar cell module of this invention. It is a schematic diagram which shows the gas barrier film used in the Example.

Explanation of symbols

1 solar cell module,
2 Surface protection sheet for solar cell,
3 resin layer,
4 solar cell elements,
5 resin layer,
6 Back protection sheet for solar cells,
7 Lactone film,
8 Adhesive layer,
9, 20 Gas barrier film,
10 Easy adhesion layer,
11 Resin film,
12 Primer layer,
13 Inorganic oxide vapor deposition film,
14 Coating layer.

Claims (7)

  A back protective sheet for solar cells, wherein a film containing an acrylic polymer having a lactone ring structure as a main component and a gas barrier film are laminated. The back surface protection sheet for solar cells of Claim 1 whose said lactone ring structure is the following structure.

In the formula, R ¹ , R ² , and R ³ are each independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms that may have a substituent.   The back surface protection sheet for solar cells of Claim 1 or 2 in which the said acrylic polymer has a structure derived from a (meth) acrylate type monomer.   The back surface protection sheet for solar cells of any one of Claims 1-3 which has an ultraviolet-ray absorption layer.   The ultraviolet absorbing layer is a film containing the acrylic polymer as a main component, an adhesive layer formed between the film containing the acrylic polymer as a main component and the gas barrier film, and the gas barrier property. The back surface protection sheet for solar cells of Claim 4 which is at least one selected from the ultraviolet-ray absorption layer formed on the film which contains the said acrylic polymer as a main component on the side facing a film.   The back surface protection sheet for solar cells of any one of Claims 1-5 whose glass transition temperature of the film which contains the said acrylic polymer as a main component is 110 degreeC or more.   The solar cell module containing the back surface protection sheet for solar cells of any one of Claims 1-6.

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