JP7211726B2 - the film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a film, and more particularly to a film that can be suitably used for optical applications.

(Meth)acrylic resins have high transparency and have been conventionally used as materials for optical films. Among them, a (meth)acrylic resin having a ring structure in its main chain can improve heat resistance while maintaining transparency (Patent Document 1, etc.). However, by increasing the heat resistance, the resin itself tends to become hard and brittle and crack easily, and mechanical strength such as folding endurance tends to decrease during film processing. For example, Patent Document 2 discloses a film formed from a (meth)acrylic resin having a ring structure in its main chain. We are evaluating the folding strength. Patent Document 3 discloses a film formed from a resin composition in which a (meth)acrylic resin having a ring structure in the main chain is blended with a flexible resin having a low glass transition temperature. As a standard, folding endurance is evaluated based on the presence or absence of cracks when folded. However, from the viewpoint of increasing the durability of the film and expanding the range of application, it is desirable to have a higher folding endurance.

JP 2006-171464 A JP 2008-191426 A JP 2007-100044 A

The present invention has been made in view of the above circumstances, and an object thereof is to provide a film having high folding endurance.

The present invention includes the following inventions.
[1] A polymer chain (A) having a polymer block (a1) having a diene and/or olefin-derived unit and a polymer block (a2) having an aromatic vinyl monomer-derived unit, and (meth)acrylic A film containing a copolymer (P) having a polymer chain (B) having a unit derived from a system monomer, and having a folding endurance of 1000 times or more according to the MIT test based on JIS P 8115. film to be.
[2] The film according to [1], which has an absolute value of dimensional change of 1.2% or less when left in an atmosphere of 85° C. and 85% RH for 120 hours.
[3] The film according to [1] or [2], which has an internal haze of 2.0% or less per 100 µm of thickness.
[4] The film according to any one of [1] to [3], wherein the polymer chain (B) has a ring structure in its main chain.
[5] The film according to any one of [1] to [4], which has a glass transition temperature in the temperature range of 110°C or higher.
[6] The film according to any one of [1] to [5], wherein the polymer chain (B) is grafted to the polymer block (a1) of the polymer chain (A).
[7] The film according to any one of [1] to [6], wherein the polymer chain (A) has polymer blocks (a2) bound to both sides of the polymer block (a1).
[8] The film according to any one of [1] to [7], further containing a (meth)acrylic polymer.
[9] The (meth)acrylic monomer-derived unit constituting the (meth)acrylic polymer is the same as the (meth)acrylic monomer-derived unit constituting the polymer chain (B) [ 8].
[10] containing at least one antioxidant selected from the group consisting of hindered phenol-based antioxidants, hindered amine-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants [1] to [9] A film according to any one of the preceding claims.
[11] The film according to any one of [1] to [10], wherein the film is an optical film.

The film of the present invention comprises a polymer chain (A) having a polymer block (a1) having a diene and/or olefin-derived unit and a polymer block (a2) having an aromatic vinyl monomer-derived unit, ( Since it contains a copolymer (P) having a polymer chain (B) having a unit derived from a meth)acrylic monomer, it exhibits high folding endurance when formed into a film.

The film of the present invention comprises a polymer chain (A) having a polymer block (a1) having a diene and/or olefin-derived unit and a polymer block (a2) having an aromatic vinyl monomer-derived unit, ( It contains a copolymer (P) having a polymer chain (B) having a unit derived from a meth)acrylic monomer. The film of the present invention is formed from a resin composition essentially containing such a copolymer (P) and has high mechanical strength (for example, folding endurance). Hereinafter, the copolymer (P) constituting the film of the present invention will be described first.

The copolymer (P) comprises a polymer chain (A) having a polymer block (a1) having units derived from a diene and/or an olefin and a polymer block (a2) having units derived from an aromatic vinyl monomer. , and a polymer chain (B) having a unit derived from a (meth)acrylic monomer. In the polymer chain (A), the polymer block (a1) basically functions as a soft component and the polymer block (a2) functions as a hard component. The polymer chain (A) can reduce the hardness and brittleness of the copolymer (P), and a film having excellent mechanical strength can be obtained. In addition, the dimensional stability and shape stability of the film under high temperature and high humidity conditions can be enhanced.

Examples of the diene forming the diene-derived unit of the polymer block (a1) include 1,3-butadiene (alias: butadiene), 2-methyl-1,3-butadiene (alias: isoprene), 1,3-pentadiene, Alkadienes such as 1,4-pentadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene (also known as diisobutene) are preferably used, and among these, 1,3-butadiene, 2-methyl-1, Conjugated dienes such as 3-butadiene and 1,3-pentadiene are more preferred. The olefins forming the olefin-derived units of the polymer block (a1) include ethylene, propylene, 1-butene, isobutene, 2-methyl-1-butene, 3-methyl-1-butene, 1-tetradecene, 1- Monoolefins such as octadecene are preferably used, and α-olefins, which are alkenes having a carbon-carbon double bond at the α-position, are more preferable. The number of carbon atoms in these dienes and olefins is preferably 2 or more, more preferably 3 or more, and preferably 20 or less, more preferably 10 or less, and even more preferably 6 or less.

Diene and/or olefin derived units are defined as units formed by polymerizing dienes and/or olefins. The olefin-derived units are not limited to those actually formed by (co)polymerization of olefins, but may also be formed by hydrogenation of diene-derived units, as long as the same structure is formed. The polymer block (a1) contains, as diene and/or olefin-derived units, butadiene-derived units, isoprene-derived units, ethylene-derived units, propylene-derived units, 1-butene-derived units, and isobutene-derived units. At least one selected from units is preferably included.

Examples of the polymer block (a1) include olefin (co)polymers such as polyethylene, polypropylene, polybutene-1, ethylene-propylene copolymer and ethylene-butene copolymer; polyisoprene, polybutadiene, isoprene-butadiene copolymer Diene (co)polymers such as polymers; copolymers of olefins and dienes such as ethylene-propylene-diene copolymers and isobutene-isoprene copolymers. The olefin (co)polymer is preferably an α-olefin (co)polymer, the diene (co)polymer is preferably a conjugated diene (co)polymer, and the copolymer of an olefin and a diene is α-olefin and Copolymers of conjugated dienes are preferred. Among these, copolymers of α-olefins and conjugated dienes such as polyisoprene and isobutene-isoprene copolymers, and polyethylene and polypropylene are more preferable.

The polymer block (a1) may have units derived from other unsaturated monomers in addition to units derived from dienes and/or olefins. Other unsaturated monomers are not particularly limited as long as they are compounds having a polymerizable double bond. Examples include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic acid, maleic anhydride, (meth) ) unsaturated carboxylic acids such as methyl acrylate and ethyl (meth)acrylate and esters thereof; aromatic vinyl compounds such as styrene, vinyltoluene, methoxystyrene, α-methylstyrene, and 2-vinylpyridine; vinyltrimethoxysilane, Examples include vinylsilanes such as γ-(meth)acryloyloxypropylmethoxysilane. Polymer block (a1) may be a copolymer of these other unsaturated monomers with dienes and/or olefins. In addition, the polymer block (a1) preferably contains diene and/or olefin-derived units as a main component. It is preferably at least 60% by mass, more preferably at least 70% by mass. The polymer block (a1) may consist essentially of diene- and/or olefin-derived units, for example, the diene- and/or olefin-derived units may be 99% by mass or more.

The polymer block (a1) may have units derived from aromatic vinyl monomers, for example, as units derived from other unsaturated monomers as described above. When the polymer block (a1) has an aromatic vinyl monomer-derived unit, it becomes easier to increase the transparency of the copolymer (P). For example, even when the difference in refractive index between the polymer chains (A) and the polymer chains (B) of the copolymer (P) is large, it is easy to increase the transparency of the copolymer (P).

Aromatic vinyl monomers forming units derived from aromatic vinyl monomers are not particularly limited as long as they are compounds in which a vinyl group is bonded to an aromatic ring. Examples include styrene, vinyltoluene, methoxystyrene, α-methyl Styrenic monomers such as styrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene; polycyclic aromatic hydrocarbon ring vinyl monomers such as 2-vinylnaphthalene; N-vinylcarbazole, 2-vinylpyridine, vinyl Examples include aromatic heterocyclic vinyl monomers such as imidazole and vinylthiophene. Among these, styrenic monomers are preferred. Styrenic monomers include not only styrene but also styrene derivatives in which any substituent is attached to the polymerizable double-bond carbon of styrene or the benzene ring, and the substituents include alkyl groups, alkoxy groups, hydroxyl group, halogen group, amino group, nitro group, sulfo group and the like. The alkyl group and alkoxy group bonded to styrene preferably have 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms. may be substituted with a group. From the viewpoint of reducing coloring of the copolymer (P), the styrene-based monomer preferably does not have an amino group. Furthermore, the styrenic monomer is preferably unsubstituted styrene in which no substituent is attached to the polymerizable double-bond carbon of styrene or the benzene ring.

When the polymer block (a1) has an aromatic vinyl monomer-derived unit, the content of the aromatic vinyl monomer-derived unit is preferably 1% by mass or more in the polymer block (a1). It is preferably 2% by mass or more, more preferably 3% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. In this case, the total content of diene and/or olefin-derived units and aromatic vinyl monomer-derived units in the polymer block (a1) is preferably 70% by mass or more, and 80% by mass or more. is more preferable, and 90% by mass or more is even more preferable. The polymer block (a1) may consist essentially only of diene and/or olefin-derived units and aromatic vinyl monomer-derived units, for example, the total content of these units is 99% by mass. or more.

When the polymer block (a1) has units derived from other unsaturated monomers in addition to units derived from dienes and/or olefins, the polymer block (a1) contains these monomers is preferably a random copolymer of

The polymer block (a2) has units derived from aromatic vinyl monomers. For the description of the aromatic vinyl monomer forming the polymer block (a2), refer to the description of the aromatic vinyl monomer of the polymer block (a1) above.

The polymer block (a2) may have units derived from other unsaturated monomers in addition to the units derived from the aromatic vinyl monomer. Other unsaturated monomers are not particularly limited as long as they are compounds having a polymerizable double bond. Examples include vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic acid, maleic anhydride, (meth) ) unsaturated carboxylic acids such as methyl acrylate and ethyl (meth)acrylate and their esters; and vinylsilanes such as vinyltrimethoxysilane and γ-(meth)acryloyloxypropylmethoxysilane. The polymer block (a2) may be a copolymer (particularly a random copolymer) of these other unsaturated monomers and aromatic vinyl monomers. The content of diene- and/or olefin-derived units in the polymer block (a2) is preferably 1% by mass or less, and the polymer block (a2) contains diene- and/or olefin-derived units. preferably not.

The polymer block (a2) preferably contains units derived from an aromatic vinyl monomer as a main component. Specifically, the content of units derived from the aromatic vinyl monomer in the polymer block (a2) is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. preferable. The polymer block (a2) may be substantially composed only of units derived from aromatic vinyl monomers, for example, the content of units derived from aromatic vinyl monomers is 99% by mass or more. good too.

Examples of the polymer chain (A) include styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, hydrogenated styrene-butadiene-styrene block copolymers (e.g., styrene-ethylene/butylene- Styrene block copolymer (SEBS), styrene-butadiene/butylene-styrene block copolymer), styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, styrene-isoprene-styrene block copolymer hydrogenated products (eg, styrene-ethylene/propylene-styrene block copolymer (SEPS)); Moreover, in these block copolymers, those in which a butadiene block has become a butadiene/styrene block, and those in which an isoprene block has become an isoprene/styrene block can be mentioned. In the notation, each block is separated by "-", and the notation of "/" in each block represents a monomer unit constituting the block.

The polymer chain (A) is preferably a polymer block (a1) having polymer blocks (a2) bound to both sides thereof. Thereby, the polymer chain (A) functions as an elastomer, and the mechanical strength of the copolymer (P) can be further enhanced. In this case, the polymer chain (A) may be a triblock copolymer, a multiblock copolymer, or a radial block copolymer. A triblock copolymer is preferred because it is easy to control properties and easy to introduce the polymer chain (B) into the copolymer (P). Such copolymers include styrene-butadiene-styrene block copolymers and hydrogenated products thereof, styrene-isoprene-styrene block copolymers and hydrogenated products thereof, and the like.

The content of the polymer block (a2) in the polymer chain (A) is preferably 5% by mass or more, more preferably 7% by mass or more, still more preferably 9% by mass or more, and preferably 55% by mass or less. , is more preferably 50% by mass or less, and even more preferably 45% by mass or less. As a result, the polymer chain (A) has a well-balanced soft component and hard component, which facilitates increasing the mechanical strength of the copolymer (P). From the same viewpoint, the content of the polymer block (a1) in the polymer chain (A) is preferably 45% by mass or more, more preferably 50% by mass or more, further preferably 55% by mass or more, and 95% by mass or more. % by mass or less is preferable, 93% by mass or less is more preferable, and 91% by mass or less is even more preferable. In the polymer chain (A), the content of units derived from the aromatic vinyl monomer is preferably 8% by mass or more, more preferably 10% by mass or more, further preferably 12% by mass or more, and 60% by mass or more. % by mass or less is preferable, 55% by mass or less is more preferable, and 50% by mass or less is even more preferable.

The weight average molecular weight of the polymer chain (A) is preferably 10,000 or more, more preferably 50,000 or more, still more preferably 10,000 or more, even more preferably 30,000 or more, and preferably 300,000 or less, 250,000 or less is more preferable, 200,000 or less is still more preferable, and 150,000 or less is even more preferable. By setting the weight average molecular weight of the polymer chain (A) to such a range, it becomes easy to secure the mechanical strength of the copolymer (P) and improve the molding processability of the copolymer (P). .

The polymer chain (B) contained in the copolymer (P) will be explained. The polymer chain (B) has at least units derived from (meth)acrylic monomers. The polymer chain (B) can enhance the transparency of the copolymer (P).

The (meth)acrylic monomer-derived units of the polymer chain (B) (hereinafter sometimes referred to as "(meth)acrylic units") are polymerized into the polymer chain by polymerizing the (meth)acrylic monomers. (B) can be introduced. (Meth)acrylic monomers include (meth)acrylic acid and derivatives thereof, and the α- or β-position of the (meth)acrylic monomer is an alkyl group (preferably, a alkyl group) may be bonded, and at least part of the hydrogen atoms of the alkyl group may be substituted with a hydroxyl group or a halogen group. The form of the carboxylic acid contained in the unit derived from the (meth)acrylic monomer is not particularly limited, and examples thereof include forms such as free acid, ester, salt and acid amide.

The polymer chain (B) preferably has a (meth)acrylic acid ester-derived unit as the (meth)acrylic unit. (Meth)acrylic acid esters that give units derived from (meth)acrylic acid esters include linear, branched or cyclic aliphatic hydrocarbon groups and aromatic hydrocarbon groups attached to the oxygen atoms of the ester bonds of (meth)acrylic acid. Examples include (meth)acrylic acid esters with a hydrogen group bonded thereto.

Examples of (meth)acrylic acid esters having a linear or branched aliphatic hydrocarbon group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, (meth)acryl isopropyl acid, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, amyl (meth)acrylate , isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, (meth) ) alkyl (meth)acrylates such as dodecyl acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate and octadecyl (meth)acrylate. The alkyl group of the alkyl (meth)acrylate is preferably a C1-18 alkyl group, more preferably a C1-12 alkyl group, and still more preferably a C1-6 alkyl group. In this specification, the descriptions "C1-18" and "C1-12" mean "1 to 18 carbon atoms" and "1 to 12 carbon atoms", respectively.

Examples of (meth)acrylic acid esters having a cyclic aliphatic hydrocarbon group include (meth)acrylates such as cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate. ) cycloalkyl acrylate; bridged cyclic (meth)acrylates such as isobornyl (meth)acrylate; The cycloalkyl group of cycloalkyl (meth)acrylate is preferably a C3-20 cycloalkyl group, more preferably a C4-12 cycloalkyl group, and still more preferably a C5-10 cycloalkyl group.

Examples of (meth)acrylic acid esters having an aromatic hydrocarbon group include phenyl (meth)acrylate, tolyl (meth)acrylate, xylyl (meth)acrylate, naphthyl (meth)acrylate, and binaphthyl (meth)acrylate. , aryl (meth)acrylates such as anthryl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; aryloxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate; mentioned. The aryl group of the aryl (meth)acrylate is preferably a C6-20 aryl group, more preferably a C6-14 aryl group. The aralkyl group of aralkyl (meth)acrylate is preferably a C6-10 aryl C1-4 alkyl group. The aryloxyalkyl group of the aryloxyalkyl (meth)acrylate is preferably a C6-10 aryloxy C1-4 alkyl group, more preferably a phenoxy C1-4 alkyl group.

The (meth)acrylic acid ester may have a substituent such as a hydroxyl group, a halogen group, an alkoxy group and an epoxy group. Such (meth)acrylic acid esters include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate and the like ( alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate; epoxyalkyl (meth)acrylates such as glycidyl (meth)acrylate; and the like. The alkyl group of hydroxyalkyl (meth)acrylate and epoxyalkyl (meth)acrylate is preferably a C1-12 alkyl group, more preferably a C1-6 alkyl group. The alkoxyalkyl group of the alkoxyalkyl (meth)acrylate is preferably a C1-12 alkoxy C1-12 alkyl group, more preferably a C1-6 alkoxy group, and more preferably a C1-6 alkyl group.

The polymer chain (B) preferably has a ring structure in its main chain. That is, the polymer chain (B) preferably has a unit having a ring structure (hereinafter sometimes referred to as a "ring structure unit") in the main chain of the polymer chain (B). Having a ring structure in the main chain of the polymer chain (B) can improve the transparency and heat resistance of the film. Improvements in solvent resistance, dimensional stability, surface hardness, adhesiveness, barrier properties against oxygen and water vapor, and various optical properties can also be expected. Further, in the case of a stretched film, depending on the stretching conditions, it is also possible to develop a retardation derived from the ring structure of the polymer chain (B).

The ring structure of the main chain of the polymer chain (B) may contain part or all of the (meth)acrylic monomer in the ring structure, and is introduced separately from the (meth)acrylic monomer. may be a ring structure. When part or all of the (meth)acrylic monomer is included in the ring structure, for example, two carboxylic acid groups of adjacent (meth)acrylic monomer-derived units are anhydrided , imidization or the like. In addition, when one of the adjacent (meth)acrylic monomer-derived units has a protic hydrogen atom-containing group such as a hydroxyl group or an amino group, this one (meth)acrylic monomer-derived unit A ring structure can also be formed by condensing the protic hydrogen atom-containing group of the unit with the carboxylic acid group of the other (meth)acrylic monomer-derived unit. When introducing a ring structure separately from a unit derived from a (meth)acrylic monomer, for example, a (meth)acrylic monomer and a monomer having a polymerizable double bond in the ring structure Copolymerization is sufficient.

The ring structure may be any of a 4-membered ring structure, a 5-membered ring structure, a 6-membered ring structure, a 7-membered ring structure, an 8-membered ring structure, etc., preferably a 5-membered ring structure or a 6-membered ring structure.

As the ring structure, from the viewpoint of heat resistance of the copolymer (P), a lactone ring structure, a cyclic imide structure (e.g., succinimide structure, glutarimide structure, etc.), a cyclic anhydride structure (e.g., succinic anhydride structure, anhydride glutaric acid structure, etc.) are preferred. One type of these ring structures may be contained in the main chain of the polymer chain (B), or two or more types thereof may be contained. Among these, at least one selected from a lactone ring structure, a succinimide structure, a succinic anhydride structure, a glutarimide structure, and a glutaric anhydride structure is preferred.

When the polymer chain (B) has a lactone ring structure as the ring structure of the main chain, the number of ring members of the lactone ring structure is not particularly limited, and may be, for example, a 4-membered ring to an 8-membered ring. From the viewpoint of excellent stability of the ring structure, the lactone ring structure is preferably a 5- or 6-membered ring, more preferably a 6-membered ring.

Examples of the lactone ring structure include structures disclosed in JP-A-2004-168882. coalescence), the lactone ring content in the cyclization condensation reaction of the precursor can be increased, and a polymer having a (meth)acrylate-derived unit can be used as a precursor. A structure represented by formula (1) is preferably shown. In formula (1) below, R ¹ , R ² and R ³ each independently represent a hydrogen atom or a substituent.

Examples of substituents for R ¹ , R ² and R ³ in formula (1) include organic residues such as hydrocarbon groups, such as C1-20 hydrocarbon groups optionally having substituents. is mentioned. Examples of the hydrocarbon group include saturated or unsaturated linear, branched or cyclic aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Examples of aliphatic hydrocarbon groups include C1-20 alkyl groups (preferably C1-10 alkyl groups, more preferably C1-6 alkyl groups such as methyl group, ethyl group, n-propyl group and isopropyl group). group); C2-20 alkenyl groups (preferably C2-10 alkenyl groups, more preferably C2-6 alkenyl groups) such as ethenyl group and propenyl group; C3-20 cycloalkyl groups such as cyclopentyl group and cyclohexyl group groups (preferably C4-12 cycloalkyl groups, more preferably C5-8 cycloalkyl groups), and the like. Examples of the aromatic hydrocarbon group include C6-20 aryl groups (preferably C6-14 aryl groups, more preferably C6-10 aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenyl groups). aryl group); C7-20 aralkyl groups (preferably C7-15 aralkyl groups, more preferably C7-11 aralkyl groups) such as benzyl group and phenylethyl group; These hydrocarbon groups may contain an oxygen atom or a halogen atom, and specifically, one or more of the hydrogen atoms possessed by the hydrocarbon groups are selected from hydroxyl groups, carboxyl groups, ether groups and ester groups. It may be substituted with at least one group.

The lactone ring structure is, for example, an ester group of an adjacent (meth)acrylic acid ester-derived unit and a (meth)acrylic monomer-derived unit having a protic hydrogen atom-containing group such as a hydroxyl group or an amino group. It can be introduced into the polymer chain (B) by cyclic condensation with a protic hydrogen atom-containing group.

In the lactone ring structure of formula (1), R ¹ and R ² are each independently a hydrogen atom or C1- 20 alkyl group ^, R3 is preferably a hydrogen atom or a methyl group, ^R1 and ^R2 are each independently a hydrogen atom or a methyl group ^, and R3 is a hydrogen atom or a methyl group. more preferred.

The lactone ring structure is obtained, for example, by polymerizing (preferably copolymerizing) a (meth)acrylic monomer A having a hydroxy group and a (meth)acrylic monomer B to form a hydroxy group and an ester group in the molecular chain. Alternatively, it can be formed by introducing a carboxyl group and then causing dealcoholization or dehydration cyclocondensation between the hydroxy group and an ester group or a carboxyl group. As a polymerizable component, a (meth)acrylic monomer A having a hydroxy group is essential, and a (meth)acrylic monomer B includes the monomer A described above. Monomer B may or may not be identical to monomer A. When monomer B matches monomer A, it results in homopolymerization of monomer A.

Examples of the (meth)acrylic monomer A having a hydroxy group include 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, alkyl 2-(hydroxymethyl)acrylate (e.g., 2-(hydroxy methyl)methyl acrylate, 2-(hydroxymethyl)ethyl acrylate, 2-(hydroxymethyl)isopropyl acrylate, 2-(hydroxymethyl)n-butyl acrylate, 2-(hydroxymethyl)t-butyl acrylate) , 2-(hydroxyethyl)alkyl acrylate (e.g., methyl 2-(hydroxyethyl)acrylate, ethyl 2-(hydroxyethyl)acrylate), etc., preferably a monomer having a hydroxyallyl moiety 2-(hydroxymethyl)acrylic acid and alkyl 2-(hydroxymethyl)acrylates. Particularly preferred are methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate.

As the (meth)acrylic monomer B, a monomer having a vinyl group and an ester group or a carboxyl group is preferable. methyl acid, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, etc.), aryl (meth)acrylate (e.g., phenyl (meth)acrylate, benzyl (meth)acrylate, etc.), alkyl 2-(hydroxyalkyl)acrylates (e.g., methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate) 2-(hydroxymethyl)alkyl acrylate such as, 2-(hydroxyethyl)alkyl acrylate such as methyl 2-(hydroxyethyl)acrylate), and the like.

The polymer chain (B) may have only one type of lactone ring structure represented by formula (1), or may have two or more types.

When the polymer chain (B) has a succinic anhydride structure (that is, a structure derived from a maleic anhydride monomer) or a succinimide structure (that is, a structure derived from a maleimide monomer) as the ring structure of the main chain, succinic anhydride As the structure or succinimide structure, the structure represented by the following formula (2) is preferably shown. In the following formula (2), R ⁴ and R ⁵ each independently represent a hydrogen atom or a methyl group, R ⁶ represents a hydrogen atom or a substituent, X ¹ represents an oxygen atom or a nitrogen atom, and X ¹ is an oxygen atom, n1=0, and when X1 is a nitrogen atom, n1= ¹ .

Examples of the substituent for R ⁶ in formula (2) include organic residues such as hydrocarbon groups, such as C1-20 hydrocarbon groups optionally having substituents. Examples of the hydrocarbon group include saturated or unsaturated linear, branched or cyclic aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Examples of aliphatic hydrocarbon groups include C1-20 alkyl groups (preferably C1-10 alkyl groups, more preferably C1-6 alkyl groups such as methyl group, ethyl group, n-propyl group and isopropyl group). group); C2-20 alkenyl groups (preferably C2-10 alkenyl groups, more preferably C2-6 alkenyl groups) such as ethenyl group and propenyl group; C3-20 cycloalkyl groups such as cyclopentyl group and cyclohexyl group groups (preferably C4-12 cycloalkyl groups, more preferably C5-8 cycloalkyl groups), and the like. Examples of the aromatic hydrocarbon group include C6-20 aryl groups (preferably C6-14 aryl groups, more preferably C6-10 aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenyl groups). aryl group); C7-20 aralkyl groups (preferably C7-15 aralkyl groups, more preferably C7-11 aralkyl groups) such as benzyl group and phenylethyl group; These hydrocarbon groups may have a substituent such as halogen.

When X ¹ is an oxygen atom, the ring structure represented by formula (2) is a succinic anhydride structure. A succinic anhydride structure can be introduced into the polymer chain (B) by, for example, copolymerizing maleic anhydride and a (meth)acrylic monomer (e.g., (meth)acrylic acid ester, etc.). .

When X ¹ is a nitrogen atom, the ring structure represented by formula (2) is a succinimide structure. A succinimide structure can be introduced into the polymer chain (B), for example, by copolymerizing maleimide and a (meth)acrylic monomer (eg, (meth)acrylate). The succinimide structure includes, for example, a succinimide structure in which the N-position is unsubstituted, an N-methylsuccinimide structure, an N-ethylsuccinimide structure, an N-cyclohexylsuccinimide structure, an N-phenylsuccinimide structure, an N-naphthylsuccinimide structure, and an N-benzylsuccinimide structure. structure and the like. As the maleimide giving a succinimide structure, N-unsubstituted maleimide, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-naphthylmaleimide, N-benzylmaleimide and the like are used. be able to.

^When the polymer chain ⁽ B) has a succinimide structure in which X ¹ is a nitrogen atom, it is easy to obtain a copolymer (P) having excellent heat resistance and a small birefringence. is a hydrogen atom, R ⁶ is preferably a C3-20 cycloalkyl group or a C6-20 aromatic group (aryl group, aralkyl group, etc.), R ⁴ and R ⁵ are hydrogen atoms, and R ⁶ is cyclohexyl more preferably a group or a phenyl group.

The polymer chain (B) may have only one type of ring structure represented by formula (2), or may have two or more types.

When the polymer chain (B) has a glutarimide structure or glutaric anhydride structure as the ring structure of the main chain, the glutarimide structure or glutaric anhydride structure is preferably represented by the following formula (3). In the following formula (3), R ⁷ and R ⁸ each independently represent a hydrogen atom or an alkyl group, R ⁹ represents a hydrogen atom or a substituent, X ² represents an oxygen atom or a nitrogen atom, and X ² is an oxygen atom, n2= ⁰ , and when X2 is a nitrogen atom, n2=1.

In formula (3), the alkyl group for R ⁷ and R ⁸ is preferably a linear or branched alkyl group, such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl C1-8 group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, n-hexyl group, isohexyl group, n-heptyl group, isoheptyl group, n-octyl group, 2-ethylhexyl group, etc. An alkyl group and the like can be mentioned. From the viewpoint of facilitating the production of a copolymer (P) having excellent heat resistance and a small birefringence index, each of R ⁷ and R ⁸ is preferably independently a hydrogen atom or a C1-4 alkyl group. Atoms or methyl groups are more preferred.

Examples of the substituent for R ⁹ in formula (3) include organic residues such as hydrocarbon groups, such as C1-20 hydrocarbon groups optionally having substituents. Examples of the hydrocarbon group include saturated or unsaturated linear, branched or cyclic aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Examples of aliphatic hydrocarbon groups include C1-20 alkyl groups (preferably C1-10 alkyl groups, more preferably C1-6 alkyl groups such as methyl group, ethyl group, n-propyl group and isopropyl group). group); C2-20 alkenyl groups (preferably C2-10 alkenyl groups, more preferably C2-6 alkenyl groups) such as ethenyl group and propenyl group; C3-20 cycloalkyl groups such as cyclopentyl group and cyclohexyl group groups (preferably C4-12 cycloalkyl groups, more preferably C5-8 cycloalkyl groups), and the like. Examples of the aromatic hydrocarbon group include C6-20 aryl groups (preferably C6-14 aryl groups, more preferably C6-10 aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenyl groups). aryl group); C7-20 aralkyl groups (preferably C7-15 aralkyl groups, more preferably C7-11 aralkyl groups) such as benzyl group and phenylethyl group; These hydrocarbon groups may have a substituent such as halogen. Among these, R ⁹ is preferably an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group because it is easy to obtain a copolymer (P) having excellent heat resistance and a small birefringence. A methyl group, a cyclohexyl group, a phenyl group, or a tolyl group is more preferred.

When X ² is an oxygen atom, the ring structure represented by formula (3) is a glutaric anhydride structure. The glutaric anhydride structure can be introduced into the polymer chain (B) by, for example, anhydrideizing two carboxylic acid groups of adjacent (meth)acrylic monomer-derived units.

When X ² is a nitrogen atom, the ring structure represented by formula (3) is a glutarimide structure. The glutarimide structure, for example, imidizes two carboxylic acid groups of adjacent (meth)acrylic monomer-derived units, or amide groups and (meth) It can be introduced into the polymer chain (B) by cyclic condensation with an ester group of a unit derived from an acrylic acid ester.

When the ring structure of formula (3) has a ^glutarimide structure in which X ² is a nitrogen atom, it is easy to obtain a copolymer (P) having excellent heat resistance and a small birefringence. and R ⁸ are each independently a hydrogen atom or a methyl group, R ⁹ is more preferably a methyl group, a cyclohexyl group, a phenyl group, or a tolyl group, and R ⁷ and R ⁸ are each independently hydrogen It is particularly preferred that R 9 is an atom or a methyl group and that R ⁹ is a cyclohexyl group or a phenyl group.

The polymer chain (B) may have only one type of ring structure represented by formula (3), or may have two or more types.

Among the cyclic structures described above, the cyclic structural units of the polymer chain (B) are lactone ring structures and / Or it preferably contains a succinimide structure (a structure derived from a maleimide monomer). When the film of the present invention is applied to a retardation film, a positive retardation can be imparted depending on the stretching conditions, and from the viewpoint of excellent stability of retardation properties, the ring structural unit of the polymer chain (B) is More preferably, it contains a lactone ring structure.

The content of the cyclic structural unit in the polymer chain (B) is not particularly limited, but the content of the cyclic structural unit in the polymer chain (B) is preferably 3% by mass or more, more preferably 4% by mass or more, and 5% by mass. % or more, preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. By adjusting the content of the ring structural unit in this manner, both heat resistance and mechanical strength can be imparted to the film in a well-balanced manner. When imparting higher heat resistance and mechanical strength to the film, the content of the structural unit in the polymer chain (B) is 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more. can also The content ratio of the cyclic structural unit described here means the content ratio of units having a cyclic structure contained in the main chain of the polymer chain (B), and is represented by the above formulas (1) to (3), for example. means the content ratio of the structure

The polymer chain (B) may further have units derived from other unsaturated monomers. Other unsaturated monomers are not particularly limited as long as they are compounds having a polymerizable double bond. Examples include vinyl esters such as vinyl acetate and vinyl propionate; styrene, vinyl toluene, methoxystyrene, α-methylstyrene. , 2-vinylpyridine; and vinylsilanes such as vinyltrimethoxysilane and γ-(meth)acryloyloxypropylmethoxysilane. For example, if the polymer chain (B) has an aromatic vinyl monomer-derived unit, it becomes easy to adjust the refractive index and retardation properties of the copolymer (P). For details of the aromatic vinyl monomer, refer to the description of the aromatic vinyl monomer of the polymer chain (A). In addition, when the polymer chain (B) is formed from two or more monomer components, the polymer chain (B) is preferably a random copolymer.

The total content of (meth)acrylic units and ring structural units in the polymer chain (B) is preferably 85% by mass or more, more preferably 88% by mass or more, and even more preferably 90% by mass or more. This facilitates enhancing the transparency and heat resistance of the copolymer (P). Moreover, it is preferable that the total content ratio of the (meth)acrylic acid ester-derived unit and the ring structural unit is within such a range.

The polymer chain (B) is preferably grafted onto the polymer chain (A). Therefore, the copolymer (P) is preferably a graft copolymer having the polymer chain (B) as a graft chain. According to the glossary of basic terms in polymer science by the International Union of Pure and Applied Chemistry (IUPAC) Committee on Polymer Nomenclature, a graft polymer is defined as "a If there is one or several blocks and these side chains have structural (chemical structure) or configurational features different from the main chain, the polymer is called a graft polymer.” there is The graft copolymer can be obtained by known production methods such as chain transfer reaction method, polymer initiator method, coupling method, macromonomer method and surface graft method, and only one of these methods is adopted. may be used, or a plurality of them may be used in combination. For details of these methods, reference can be made to Kagaku Binran (Applied Chemistry), 6th edition, edited by the Chemical Society of Japan.

The copolymer (P) is conveniently produced by addition-polymerizing the polymer chain (A) with a monomer component forming the polymer chain (B). Therefore, the copolymer (P) is a copolymer ( Hereinafter, it is preferably obtained by polymerizing a monomer component containing a (meth)acrylic monomer in the presence of a "raw material copolymer (P1)"). In this specification, the "raw material copolymer (P1)" may be simply referred to as "copolymer (P1)". For the details of the starting copolymer (P1), refer to the description of the polymer chain (A) above.

In the copolymer (P), the polymer chain (B) is preferably grafted onto the polymer block (a1) of the polymer chain (A). Specifically, the polymer chain (B) preferably bonds to the diene- and/or olefin-derived units of the polymer block (a1). In this case, the polymer chain (B) may be bonded to the carbon atoms of the main chain of the diene- and/or olefin-derived units, and the carbon atoms of the hydrocarbon groups bonded to the main chain as substituents (side chains). It may be attached to an atom. The polymer chain (B) may be bonded, for example, to a diene-derived double bond in the main chain of the copolymer block (a1), or may be bonded to a carbon atom adjacent to the double bond. Alternatively, the polymer chain (B) is bonded to a diene-derived double bond bonded as a substituent (side chain) to the main chain of the copolymer block (a1), or bonded to the carbon atom adjacent to the double bond. You may have

As the starting copolymer (P1), it is preferable to use one having an olefinic double bond content of 0.030 mmol/g or more and 2.3 mmol/g or less. By using the starting copolymer (P1) having an olefinic double bond content of 0.030 mmol/g or more, it becomes easier to obtain the copolymer (P) with high transparency. On the other hand, by using the starting copolymer (P1) having an olefinic double bond content of 2.3 mmol/g or less, it becomes easier to obtain the copolymer (P) with less occurrence of gelation. The olefinic double bond content of the copolymer (P1) is more preferably 0.040 mmol/g or more, still more preferably 0.050 mmol/g or more, and more preferably 2.0 mmol/g or less. The olefinic double bond content of the copolymer (P1) can be determined by an iodine titration method.

The copolymer (P) can be obtained by a production method including a step (polymerization step) of polymerizing a monomer component containing a (meth)acrylic monomer in the presence of the starting copolymer (P1). can. A polymer chain (B) is formed by polymerizing a monomer component containing a (meth)acrylic monomer in the polymerization step, and the raw material copolymer (P1) gives the polymer chain (A), thereby A copolymer (P) is obtained in which the polymer chain (B) is bonded to the diene- and/or olefin-derived units of the polymer block (a1) of the polymer chain (A). In addition, the raw material copolymer (P1) can be prepared, for example, by polymerizing the monomer components constituting the polymer block (a1) to form the polymer block (a1), and then in the presence of the polymer block (a1). It can be obtained by polymerizing the monomer components that constitute the polymer block (a2).

In the polymerization step, the polymer block (a1 ) of the diene- and/or olefin-derived unit (olefinic double bond) of the vinyl position, allyl position, etc. of the double bond is preferably abstracted. As a result, a radical is generated at the site, and the monomer component forming the polymer chain (B) can be subjected to addition polymerization. At this time, as described above, by adjusting the amount of olefinic double bonds possessed by the raw material copolymer (P1), the transparency of the copolymer (P) can be increased and the occurrence of gelation can be suppressed. easier.

Polymerization step WHEREIN: Only 1 type may be used for the raw material copolymer (P1), and 2 or more types may be used together. In the latter case, it becomes easier to adjust the physical properties of the film.

The monomer components used to form the polymer chain (B) include, in addition to the (meth)acrylic monomer, a monomer having a polymerizable double bond in the ring structure as a monomer giving a ring structure unit. Ammers and the like can also be used. For example, when forming a polymer chain (B) having a ring structure in the main chain, a monomer having a polymerizable double bond in the ring structure may be used, and the ring structure forming step is performed after the polymerization step. You may use the monomer which can form a ring structure by carrying out. Other unsaturated monomers can also be used. Details of these monomer components include the above-described (meth)acrylic monomer forming the polymer chain (B), the monomer providing the ring structure of the polymer chain (B), and the Reference is made to the description of other unsaturated monomers.

Polymerization of the monomer component can be carried out using known polymerization methods such as bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization, but solution polymerization is preferred. If the solution polymerization method is used, it is possible to suppress contamination of the copolymer (P) with minute foreign matter, and the copolymer (P) can be suitably applied to optical material applications and the like. As a polymerization method, for example, both a batch polymerization method and a continuous polymerization method can be used. At the time of polymerization, the monomer components may be charged all at once or may be added in portions.

The amount of the raw material copolymer (P1) used during polymerization is preferably 1 part by mass or more, more preferably 3 parts by mass or more, with respect to a total of 100 parts by mass of the raw material copolymer (P1) and the monomer component. Preferably, 5 parts by mass or more is more preferable, 7 parts by mass or more is even more preferable, 9 parts by mass or more is even more preferable, 12 parts by mass or more is particularly preferable, 50 parts by mass or less is preferable, and 30 parts by mass or less is more preferable. Preferably, 25 parts by mass or less is more preferable. The amount of the monomer component used is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and more preferably 75 parts by mass or more with respect to a total of 100 parts by mass of the starting copolymer (P1) and the monomer component. It is more preferably 99 parts by mass or less, more preferably 97 parts by mass or less, still more preferably 95 parts by mass or less, and even more preferably 88 parts by mass or less.

The polymerization solvent can be appropriately selected according to the composition of the monomer components, and organic solvents used in ordinary radical polymerization reactions can be used. Specifically, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and anisole; esters such as ethyl, butyl acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve; alcohols such as methanol, ethanol, isopropanol, n-butanol; Nitriles such as pionitrile, butyronitrile and benzonitrile; chloroform; dimethylsulfoxide and the like. These solvents may be used alone or in combination of two or more.

The polymerization reaction between the starting copolymer (P1) and the monomer component is preferably carried out in the presence of a polymerization catalyst (polymerization initiator). Examples of the polymerization catalyst include 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, dimethyl-2,2′-azobis(2-methylpropio azo compounds such as 4,4′-azobis (4-cyanopentanoic acid); persulfates such as potassium persulfate; cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl Peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyoctoate, t-amylperoxyisononanoate, t-amylperoxy Organic peroxides such as isopropyl carbonate and t-amylperoxy 2-ethylhexyl carbonate can be used. These may use only 1 type and may use 2 or more types together. Among these, it is preferable to use an organic peroxide having a strong hydrogen abstraction power. The amount of the polymerization catalyst to be used is preferably 0.01 to 1 part by weight per 100 parts by weight of the monomer component.

The total concentration of the raw material copolymer (P1) and the monomer component in the reaction solution is preferably 3% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, and 80% by mass or less. Preferably, 70% by mass or less is more preferable. The polymerization solvent concentration in the reaction solution is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less. During the polymerization reaction, the starting copolymer (P1), monomer components, polymerization catalyst, reaction solvent, etc. can be added as appropriate.

The polymerization reaction is preferably carried out in an atmosphere of an inert gas such as nitrogen gas or under a stream of air. In order to reduce residual monomers, an azobis-based compound and a peroxide may be used in combination as polymerization initiators. The reaction temperature is preferably 50°C to 200°C. The reaction time may be appropriately adjusted while observing the degree of progress of the copolymerization reaction and the degree of formation of the gelled product.

Through the above polymerization step, a copolymer (P) in which a polymer chain (B) containing units derived from a (meth)acrylic monomer is bonded to a polymer chain (A) is obtained. In the polymerization step, when using a (meth)acrylic monomer and a monomer having a polymerizable double bond in the ring structure (e.g., maleic anhydride or maleimide) as a monomer component, (meth) A copolymer (P) is obtained in which a polymer chain (B) having an acrylic unit and a ring structural unit (succinic anhydride structure, succinimide structure) is bonded to the polymer chain (A).

On the other hand, when obtaining a copolymer (P) having a lactone ring structure, a glutaric anhydride structure, or a glutarimide structure as the ring structure unit of the polymer chain (B), the polymerization step is followed by the ring structure formation step. is preferred. In the ring structure forming step, a ring structure is formed in the main chain of the polymer chain (B) having (meth)acrylic units formed in the polymerization step. Specifically, the substituents of adjacent (meth)acrylic units of the polymer chain (B) having (meth)acrylic units formed in the polymerization step are subjected to a condensation reaction to form a ring on the (B) main chain of the polymer chain. form a structure. Cyclocondensation reactions include esterification reactions, acid anhydride reactions, amidation reactions, imidization reactions, and the like. For example, a glutaric anhydride structure can be formed by acid anhydride conversion of two carboxylic acid groups of adjacent (meth)acrylic units, and a glutarimide structure can be formed by imidization. When one of the adjacent (meth)acrylic units has a protic hydrogen atom-containing group such as a hydroxyl group or an amino group, the protic hydrogen atom-containing group of one (meth)acrylic unit and the other ( A lactone ring structure can be formed by condensing the meth)acrylic unit with the carboxylic acid group.

In the ring structure forming step, the condensation reaction of adjacent (meth)acrylic units is preferably carried out in the presence of a catalyst (cyclization catalyst). At least one selected from the group consisting of acids, bases and salts thereof can be used as the cyclization catalyst. Acids, bases and salts thereof may be organic or inorganic and are not particularly limited. Among them, it is preferable to use an organic phosphorus compound as a catalyst for the cyclization reaction. By using an organic phosphorus compound as a cyclization catalyst, the cyclization condensation reaction can be efficiently performed, and the resulting copolymer (P) can be less colored.

Organic phosphorus compounds that can be used as cyclization catalysts include, for example, alkyl(aryl)phosphonous acids and their monoesters or diesters; dialkyl(aryl)phosphinic acids and their esters; alkyl(aryl)phosphonic acids and their monoesters or diesters of; , lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, di Phosphate monoesters, diesters or triesters such as isostearyl, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; mono-, di- or tri-alkyl(aryl)phosphine; alkyl(aryl)halogenphosphine; mono-, di- or tri-alkyl(aryl)phosphine oxide; tetraalkyl(aryl)phosphonium halide and the like. These may use only 1 type and may use 2 or more types together. Among these, phosphoric acid monoesters and diesters are particularly preferred because of their high catalytic activity and low colorability. The amount of the cyclization catalyst used is preferably, for example, 0.001 to 1 part by mass with respect to 100 parts by mass of the copolymer obtained in the polymerization step.

The reaction temperature in the ring structure forming step is preferably 50°C to 300°C. The reaction time may be appropriately adjusted while observing the degree of progress of the cyclization condensation reaction, and is preferably carried out for, for example, 5 minutes to 6 hours.

The ring structure-forming step is preferably performed under heating. At this time, the polymerization solution containing the polymerization solvent obtained in the polymerization step may be heated as it is, the polymerization solvent may be devolatilized and then heated, or both of these may be combined. Reactors used for the cyclization condensation reaction include, for example, autoclaves, kettle-type reactors, devices comprising a heat exchanger and a devolatilization tank, extruders with vents, and the like.

Volatilization is preferably performed in the ring structure forming step. Volatilization can be performed by reducing the pressure in the reactor with a vacuum pump or the like. The devolatilization removes the polymerization solvent used in the polymerization step and brought into the ring structure formation step, alcohol by-produced in the cyclization condensation reaction, etc., and reduces the residual volatile content in the resulting copolymer (P). can do. In addition, since the alcohol and the like by-produced in the cyclization condensation reaction are removed, the reaction equilibrium is inclined toward the production side, which is advantageous.

When the cyclization condensation reaction is performed while devolatilizing, the cyclization condensation reaction is preferably performed under reduced pressure from the viewpoint of efficient devolatilization. The pressure reduction in the cyclization condensation reaction is, for example, preferably 90 kPa or less, more preferably 80 kPa or less, and even more preferably 70 kPa or less, as an absolute pressure. On the other hand, the absolute pressure when reducing the pressure is preferably 0.1 kPa or more, more preferably 1 kPa or more, from the viewpoint that the equipment for realizing the reduced pressure state does not have excessive specifications and the equipment cost is kept low. When the cyclization condensation reaction is performed without devolatilization, the cyclization condensation reaction may be performed under normal pressure or under pressure.

When a vented extruder is used, the extruder preferably has a cylinder, a screw provided in the cylinder, and heating means. The cylinder is provided with one or more vents. The vent is preferably provided at least on the downstream side of the raw material charging section with respect to the transfer direction in the extruder, and may also be provided on the upstream side of the raw material charging section.

The copolymer fed into the extruder is kneaded by a screw while being transported from the upstream side to the downstream side of the extruder while the cyclization condensation reaction progresses, and the copolymer (P) is released from the downstream side of the extruder. Ejected. A die is preferably provided on the downstream side of the extruder, and by discharging the copolymer (P) from the die, it can be formed into a predetermined shape (film or rod). For example, pellets can be produced by finely cutting a rod-shaped copolymer.

When the cyclization-condensation reaction is performed in the presence of a cyclization catalyst in the ring structure-forming step, it is preferable to add a deactivator after or during the cyclization-condensation reaction. For example, when a resin composition containing a copolymer (P) is pelletized or formed into a film, if a cyclization catalyst remains in the resin composition, a cyclization condensation reaction occurs to generate alcohol or the like. As a result, undesirable foaming can occur. However, by adding a quenching agent after or during the cyclization condensation reaction, such foaming can be prevented.

As the deactivator, a substance capable of neutralizing the cyclization catalyst is preferably used. For example, when the cyclization catalyst is an acidic substance, a basic substance can be used as the deactivator, and conversely, when the cyclization catalyst is a basic substance, an acidic substance can be used as the deactivator. . As described above, an organic phosphorus compound is preferably used as the cyclization catalyst, and the compound is often an acidic substance. Therefore, it is preferable to use a basic substance as the deactivator. The basic substance is not particularly limited as long as it can stop the cyclization condensation reaction, and for example, metal carboxylates, metal complexes, metal oxides and the like are used. Conversely, when a basic substance is used as the cyclization catalyst, an acidic substance that can be used for the cyclization catalyst described above can be used as the deactivator.

The timing of adding the deactivator is preferably during the cyclization condensation reaction or after the reaction and before pelletizing or filming the resin composition containing the copolymer (P). For example, the deactivator may be added to the resin composition in a molten state, or the deactivator may be added to the resin composition dissolved in a solvent. When the cyclization condensation reaction is performed using an extruder as described above, the deactivator may be added to a position after the cyclization condensation reaction has sufficiently occurred in the extruder.

The weight average molecular weight of the copolymer (P) is preferably 2,000 or more, more preferably 5,000 or more, still more preferably 30,000 or more, even more preferably 50,000 or more, and preferably 600,000 or less. , is more preferably 400,000 or less, more preferably 300,000 or less, and even more preferably 200,000 or less. By setting the weight average molecular weight of the copolymer (P) to such a range, the moldability of the copolymer (P) is improved.

The weight average molecular weight of the copolymer (P) is preferably 1.1 times or more, more preferably 1.2 times or more, still more preferably 1.3 times or more, and 10 times the weight average molecular weight of the polymer chain (A). It is preferably twice or less, more preferably seven times or less, and even more preferably five times or less. This makes it easy to give the copolymer (P) properties of transparency and mechanical strength in a well-balanced manner.

The refractive index of the copolymer (P) is preferably close to the refractive index of the polymer chain (A), which facilitates ensuring the transparency of the copolymer (P). Specifically, the difference between the refractive index of the copolymer (P) and the refractive index of the polymer chain (A) is preferably less than 0.1, more preferably 0.05 or less, and 0.02 or less. More preferred. From the same point of view, it is preferable that the refractive index of the polymer chain (A) in the copolymer (P) and the refractive index of the polymer chain (B) are close to each other. The difference between the refractive index and the refractive index of the polymer chain (B) is preferably less than 0.1, more preferably 0.05 or less, even more preferably 0.02 or less.

The film of the present invention may contain only one copolymer (P), or may contain two or more copolymers (P). Moreover, in addition to the copolymer (P) explained above, other polymers may be contained. In this case, the film of the present invention may contain the copolymer (P) as a resin component (matrix resin), or may contain another polymer as a resin component (matrix resin). . As the other polymer, a (meth)acrylic polymer is preferably used because of its excellent compatibility with the copolymer (P). This facilitates enhancing the transparency and heat resistance of the film.

The (meth)acrylic polymer may have a unit derived from the (meth)acrylic monomer described in the polymer chain (B) above, and is preferably described in the polymer chain (B) above. It has a unit derived from a (meth)acrylic acid ester. The (meth)acrylic polymer may have units derived from other unsaturated monomers described in the polymer chain (B) above. From the viewpoint of enhancing compatibility with the copolymer (P), the (meth)acrylic polymer is a unit derived from a (meth)acrylic monomer contained in the polymer chain (B) of the copolymer (P). It is more preferable to have That is, the unit derived from the (meth)acrylic monomer constituting the (meth)acrylic polymer is the same as the unit derived from the (meth)acrylic monomer constituting the polymer chain (B). preferable.

The (meth)acrylic polymer preferably has a ring structure, and more preferably has a ring structure in its main chain. Thereby, the transparency and heat resistance of the film can be enhanced. The ring structure of the main chain of the (meth)acrylic polymer includes a lactone ring structure, a cyclic imide structure (e.g., succinimide structure, glutarimide structure, etc.), a cyclic anhydride structure (e.g., succinic anhydride structure, glutaric anhydride structure, etc.). structure, etc.) and the like are preferably mentioned, and for the details of these ring structures, refer to the above description of the ring structure of the polymer chain (B). Among them, the (meth)acrylic polymer preferably has, in its main chain, the same ring structure as that of the polymer chain (B) of the copolymer (P).

The (meth)acrylic polymer has the same (meth)acrylic unit as the (meth)acrylic unit possessed by the polymer chain (B) of the copolymer (P), and the ring structural unit possessed by the polymer chain (B). It is preferred to have the same ring structural unit. This enhances the compatibility between the (meth)acrylic polymer and the copolymer (P), making it easier to enhance the transparency and heat resistance of the film.

Such a (meth)acrylic polymer is conveniently polymerized together with the (meth)acrylic polymer when the copolymer (P) is polymerized. In the method for producing the copolymer (P) described above, a (meth)acrylic polymer corresponding to the polymer chain (B) of the copolymer (P) is simultaneously produced together with the copolymer (P). At this time, by not separating the copolymer (P) and the (meth)acrylic polymer, a resin composition containing the copolymer (P) and the (meth)acrylic polymer can be obtained. In the case where the film contains a polymer other than the (meth)acrylic polymer, the copolymer (P) may be isolated, or may be mixed with another polymer without isolation to form a film-forming polymer. can be prepared.

The content of the copolymer (P) in the film is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and even more preferably 15% by mass or more. It becomes easier to increase the mechanical strength. The upper limit of the content of the copolymer (P) in the film is not particularly limited, and the film may be composed only of the copolymer (P), and the content of the copolymer (P) in the film is It may be 90% by mass or less, 70% by mass or less, 50% by mass or less, 40% by mass or less, or 30% by mass or less.

The content of the polymer chain (A) of the copolymer (P) in the film is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and even more preferably 12% by mass or more. It is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. If the content of the polymer chain (A) in the film is 1% by mass or more, the mechanical strength of the film can be easily increased. If the content of the polymer chain (A) in the film is 50% by mass or less, the transparency and heat resistance of the film can be easily improved.

When the film contains a (meth)acrylic polymer, the content of the (meth)acrylic polymer in the film is preferably 1% by mass or more, more preferably 10% by mass or more, and further 20% by mass or more. It is preferably 30% by mass or more, still more preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

The total content of the copolymer (P) and (meth)acrylic polymer in the film is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and 90% by mass or more. is even more preferred. The upper limit of the content ratio of the copolymer (P) and (meth)acrylic polymer in the film is not particularly limited, and the film is substantially composed only of the copolymer (P) and (meth)acrylic polymer. may have been

The film of the present invention may contain a polymer other than the (meth)acrylic polymer described above. Such polymers include, for example, polyethylene, polypropylene, ethylene-propylene polymer, poly Olefin polymers such as (4-methyl-1-pentene); Halogen-containing polymers such as vinyl chloride and chlorinated vinyl resin; Polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile -Styrenic polymers such as butadiene-styrene copolymers; polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetal; polyether ether ketone; polysulfone; polyether sulfone; polyoxypentylene; polyamideimide; cycloolefin polymer; cellulose derivative; union; and the like.

From the viewpoint of ease of production, the film of the present invention preferably contains a copolymer (P) and a (meth)acrylic polymer as polymers. Therefore, the film of the present invention is preferably formed from a resin composition containing a copolymer (P) and a (meth)acrylic polymer.

The weight average molecular weight of the film-forming resin composition is preferably 2,000 or more, more preferably 5,000 or more, still more preferably 30,000 or more, even more preferably 50,000 or more, and 600,000 or less. It is preferably 400,000 or less, more preferably 300,000 or less, and even more preferably 200,000 or less. If the weight-average molecular weight of the polymer constituting the film is within this range, the moldability of the film is improved. In addition, the weight average molecular weight described here means a polystyrene-equivalent value obtained by measuring the film by gel permeation chromatography, for example, when the film contains a copolymer (P) and a (meth)acrylic polymer is the total weight-average molecular weight of these multiple types of polymers.

The weight average molecular weight of the film-forming resin composition is preferably 1.1 times or more, more preferably 1.2 times or more, more preferably 1.3 times the weight average molecular weight of the polymer chain (A) of the copolymer (P). It is more preferably 10 times or less, more preferably 7 times or less, and even more preferably 5 times or less. This facilitates enhancing the transparency and mechanical strength of the film.

The refractive index of the resin composition forming the film is preferably close to the refractive index of the polymer chain (A) of the copolymer (P), which facilitates ensuring the transparency of the film. Specifically, the difference between the refractive index of the film and the refractive index of the polymer chain (A) of the copolymer (P) is preferably less than 0.1, more preferably 0.05 or less, and 0.02. More preferred are:

The film may contain various additives. Additives include, for example, ultraviolet absorbers; antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; Reinforcing material; Near-infrared absorber; Flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents including cationic and nonionic surfactants; coloring agents such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; organic fillers and inorganic fillers; . The content of each additive in the film is preferably in the range of 0 to 5% by mass, more preferably 0 to 2% by mass.

Examples of UV absorbers include benzophenone compounds, salicylate compounds, benzoate compounds, triazole compounds, and triazine compounds, and known UV absorbers can be used. Benzophenone compounds include 2,4-dihydroxybenzophenone, 4-n-octyloxy-2-hydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and the like. Examples of salicylate-based compounds include pt-butylphenyl salicicate and the like. Benzoate compounds include 2,4-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate and the like. Triazole compounds include 2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3,5 -di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4 ,6-bis(1-methyl-1-phenylethyl)phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2-[5-chloro(2H)-benzotriazole-2- yl]-4-methyl-6-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4 -(1,1,3,3-tetramethylbutyl)phenol and the like. Triazine compounds include 2-[4,6-bis(biphenyl-4-yl)-1,3,6-triazi-2-yl]-5-[(2-ethylhexyl)oxy]phenol, 2-mono (Hydroxyphenyl)-1,3,5-triazine compound, 2,4-bis(hydroxyphenyl)-1,3,5-triazine compound, 2,4,6-tris(hydroxyphenyl)-1,3,5 - triazine compounds and the like. Commercially available UV absorbers include, for example, triazine-based UV absorbers Tinuvin (registered trademark) 1577, Tinuvin (registered trademark) 460, Tinuvin (registered trademark) 477 (manufactured by BASF Japan), Adekastab (registered trademark) LA. -F70 (manufactured by ADEKA), Adekastab (registered trademark) LA-31 (manufactured by ADEKA), which is a triazole-based UV absorber, and the like. Only one type of ultraviolet absorber may be used, or two or more types may be used in combination.

As the antioxidant, a compound having a radical scavenging function or a peroxide decomposition function can be used, and known antioxidants can be used. Examples of antioxidants include hindered phenol-based antioxidants, hindered amine-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, benzotriazole-based antioxidants, benzophenone-based antioxidants, and hydroxylamine-based antioxidants. Antioxidants, salicylic acid ester-based antioxidants, triazine-based antioxidants, and the like are included. Among these antioxidants, the film of the present invention contains at least one selected from the group consisting of hindered phenol-based antioxidants, hindered amine-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. preferably. This suppresses oxidation deterioration and discoloration of the film.

Hindered phenol antioxidants include 2,4-bis[(laurylthio)methyl]-o-cresol, 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl), 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl), pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] etc.

Hindered amine antioxidants include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(N-methyl-2,2,6,6-tetramethyl-4-piperidyl) sebacate, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexamethylenediamine, 2-methyl-2-(2,2,6,6-tetramethyl-4 -piperidyl)amino-N-(2,2,6,6-tetramethyl-4-piperidyl)propionamide, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)(1,2,3, 4-butanetetracarboxylate, poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)((2,2,6,6 -tetramethyl-4-piperidyl)imino)hexamethyl((2,2,6,6-tetramethyl-4-piperidyl)imino)] and the like can be used.

Phosphorus antioxidants include tris(isodecyl)phosphite, tris(tridecyl)phosphite, phenylisooctylphosphite, phenylisodecylphosphite, phenyldi(tridecyl)phosphite, diphenylisooctylphosphite, diphenylisodecyl Phosphite, diphenyltridecylphosphite, triphenylphosphite, tris(nonylphenyl)phosphite, 4,4' isopropylidenediphenol alkylphosphite, trisnonylphenylphosphite, trisdinonylphenylphosphite, other phosphites Structured oligomeric and polymeric type compounds and the like can also be used.

Sulfur antioxidants include 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis[(octylthio)methyl]- o-cresol, 2,4-bis[(laurylthio)methyl]-o-cresol, tetrakis[methylene-3-(dodecylthio)propionate]methane and the like. In addition, oligomer type or polymer type compounds having a thioether structure can also be used.

The film of the present invention can be formed by forming a film from a resin composition essentially containing the copolymer (P) as described above, and the resin composition further comprises a (meth)acrylic Other components such as polymers and additives may be further included. The film of the present invention may be a stretched film or an unstretched film, but is preferably a stretched film from the viewpoint of exhibiting high mechanical strength. Therefore, the film of the present invention is preferably formed by stretching the resin composition containing the copolymer (P). The stretched film may be either a uniaxially stretched film or a biaxially stretched film, but a biaxially stretched film is more preferable. When the film is biaxially stretched, the film is stretched in two directions perpendicular to each other, so that the mechanical strength can be improved in any direction in the plane of the film. In addition, the in-plane retardation of the film is reduced, making it easier to obtain a film with high optical isotropy.

The draw ratio of the stretched film is preferably 1.2 times or more, more preferably 1.4 times or more, still more preferably 1.6 times or more, and preferably 3.5 times or less, and 3.0 times or less. More preferably, 2.8 times or less is even more preferable. In the case of biaxial stretching, it is preferable that the stretching ratios in the two stretching directions are within such ranges. The draw ratio defined by the area ratio is preferably 1.2 times or more, more preferably 1.4 times or more, still more preferably 1.6 times or more, preferably 12 times or less, and more preferably 10 times or less. More preferably less than twice. By setting the draw ratio in this way, it becomes easier to obtain effects such as an improvement in the mechanical strength of the film accompanying the drawing.

A stretched film can be obtained, for example, by forming a film by a melt extrusion method and stretching the film. As the stretching method, conventionally known stretching methods can be applied, for example, uniaxial stretching such as free width uniaxial stretching and constant width uniaxial stretching; biaxial stretching such as sequential biaxial stretching and simultaneous biaxial stretching; A laminate is formed by adhering a shrinkable film on one or both sides, and the laminate is heated and stretched to apply a shrinkage force in a direction perpendicular to the stretching direction to the film, thereby stretching the film in both the stretching direction and the thickness direction. Examples include stretching for obtaining a birefringent film in which molecular groups oriented in each direction are mixed. From the viewpoint of improving mechanical strength such as folding endurance of the film, biaxial stretching is preferably used.

The stretching apparatus includes, for example, a roll stretching machine, a tenter type stretching machine, and a small experimental stretching apparatus such as a tensile tester, a uniaxial stretching machine, a sequential biaxial stretching machine, a simultaneous biaxial stretching machine, and the like. equipment can be used.

The stretching temperature is preferably around the highest glass transition temperature of the resin composition to be stretched. The stretching temperature is, for example, preferably the highest glass transition temperature −30° C. or higher, more preferably the highest glass transition temperature −15° C. or higher, further preferably the highest glass transition temperature or higher, and the highest glass transition temperature +60 ° C. or less is preferable, the highest glass transition temperature +50° C. or less is more preferable, and the highest glass transition temperature +45° C. or less is even more preferable. The stretching temperature can be appropriately set according to the desired physical properties of the film. For example, if a film with higher mechanical strength is to be obtained, the stretching temperature may be set lower, for example below the highest glass transition temperature plus 20°C. On the other hand, when obtaining a film with a small dimensional change rate or a film with a small in-plane retardation, the stretching temperature is set higher, for example, the highest glass transition temperature + 20 ° C. or higher, or the highest glass transition temperature + 24 ° C. or higher. do it. This makes it easier to obtain a film having both high mechanical strength and small dimensional change in good balance. Normally, when a stretched film is produced at such a high stretching temperature, the mechanical strength of the film is reduced and folding endurance may hardly be exhibited. By containing, it is possible to obtain a film having high mechanical strength even if the stretching temperature is set high.

The stretching speed (one direction) is preferably in the range of 10 to 20,000%/min, more preferably in the range of 100 to 10,000%/min. When it is slower than 10%/min, it takes time to obtain a sufficient draw ratio, which tends to increase the production cost. If the rate is faster than 20,000%/min, the stretched film may break.

In order to stabilize optical properties and mechanical properties, the stretched film may be subjected to heat treatment (annealing) after stretching, if necessary. In this case, by performing heat treatment at a glass transition temperature of +20° C. or higher, it becomes easier to obtain a film having both high mechanical strength and small dimensional change rate in good balance. Note that heat treatment (annealing) after stretching may not be performed.

A step of filtering the resin composition (filtration step) may be provided prior to forming the resin composition into a film. By carrying out the filtration step, the amount of foreign matter in the resin composition can be reduced, thereby making it easier to obtain a highly transparent film with few surface irregularities and defects. The filtration step can be carried out continuously after the polymerization step or ring structure formation step explained above.

As a filter used for filtration, conventionally known filters can be used, and there is no particular limitation. For example, leaf disc filters, candle filters, pack disc filters, cylindrical filters and the like can be used. Among them, it is preferable to use a leaf disk filter or a candle filter, which has a large effective filtration area.

The filtration accuracy (pore size) of the filter is usually, for example, 15 μm or less. When the film of the present invention is used for optical applications, the filtration accuracy is preferably 10 μm or less, more preferably 5 μm or less, from the viewpoint of reducing optical defects. The lower limit of filtration accuracy is not particularly limited, and is, for example, 0.2 μm or more.

The film of the present invention is constructed as described above and has high mechanical strength. Specifically, the film of the present invention has a folding endurance of 1000 times or more according to the MIT test based on JIS P 8115 (2001). For example, in the case of a (meth)acrylic polymer having a lactone ring structure in the main chain as disclosed in polymethyl methacrylate or JP-A-2008-191426, even if it is made into a stretched film, such a high mechanical It is difficult to impart sufficient strength, and the folding endurance in the MIT test is at most several hundred times. However, since the film of the present invention contains the copolymer (P) described above, it has high mechanical strength and can be folded 1000 times or more. The film of the present invention preferably has a folding endurance of 1500 times or more, more preferably 1800 times or more, and even more preferably 2200 times or more. The folding endurance may be 4000 times or more, 6000 times or more, or 8000 times or more. The upper limit of the folding endurance is not particularly limited. A film having such high mechanical strength can be easily obtained by stretching a resin composition containing the copolymer (P) into a film. The folding endurance number by the MIT test is determined by the method described in Examples. The number of folding endurances is preferably within the above range when folded in either direction, and more preferably within the above range when folded in two arbitrary orthogonal directions. .

The absolute value of the dimensional change rate of the film of the present invention is preferably 1.2% or less, more preferably 1.0% or less, when placed in an atmosphere of 85° C. and 85% RH for 120 hours. , is more preferably 0.7% or less. When the resin composition is stretched to form a film, the polymer contained in the resin composition is oriented along the stretching direction, and residual stress tends to occur. Such residual stress causes a dimensional change due to orientation relaxation when the film is placed under high temperature and high humidity. However, the film of the present invention can be formed at a relatively high temperature, which weakens the orientation of the polymer within the film and reduces the rate of dimensional change that accompanies the relaxation of the orientation. Moreover, the film of the present invention can be imparted with high mechanical strength even when molded at a relatively high temperature. The dimensional change rate of the film is determined by the method described in Examples.

The film of the present invention preferably has a water absorption rate of 1.8% by mass or less, more preferably 1.5% by mass or less when placed in an atmosphere of 85° C. temperature and 85% RH for 120 hours. 0.3 mass % or less is more preferable. For example, a film formed from polymethyl methacrylate tends to be plasticized by absorbing water, whereas the film of the present invention has a low water absorption rate and is less likely to be plasticized under high humidity. The water absorption is determined by the method described in Examples.

The film of the present invention preferably has an in-plane retardation Re of 10 nm or less, more preferably 5 nm or less, still more preferably 2 nm or less, and even more preferably 0.8 nm or less with respect to light having a wavelength of 590 nm. By molding the film of the present invention at a relatively high temperature, the in-plane retardation Re derived from orientation birefringence can be made low, so that it can be suitably applied to optical applications that require a low retardation. can be done. A film having a high in-plane retardation Re can be obtained by setting the stretching temperature to a lower value. In-plane retardation Re is defined as Re = (nx-ny) × d, nx is the refractive index in the slow axis direction in the film plane (the direction in which the refractive index is maximized in the film plane), ny is the film In-plane nx and perpendicular refractive index, d represents the thickness (nm) of the film. The lower limit of the in-plane retardation Re is 0 nm.

The thickness direction retardation Rth of the film of the present invention is not particularly limited, but the thickness direction retardation Rth for light with a wavelength of 590 nm is preferably −100 nm or more and 100 nm or less, more preferably −30 nm or more and 30 nm or less, and −10 nm. 10 nm or less is more preferable. As a result, good viewing angle characteristics and contrast characteristics are exhibited. The thickness direction retardation Rth is defined by Rth=d×{(nx+ny)/2−nz}, where nz represents the refractive index in the film thickness direction.

The film of the present invention preferably has an internal haze of 2.0% or less, more preferably 1.0% or less, even more preferably 0.5% or less per 100 µm of thickness. Thereby, it can be set as the film excellent in transparency.

The film of the present invention preferably has a glass transition temperature in the temperature range of 110° C. or higher from the viewpoint of enhancing heat resistance. The glass transition temperature is preferably 115° C. or higher, more preferably 120° C. or higher. In addition, from the viewpoint of enhancing workability during film formation, the glass transition temperature is preferably less than 300°C, more preferably less than 200°C, and even more preferably less than 180°C.

When the glass transition temperature described above is taken as the glass transition temperature on the high-temperature side, the film of the present invention preferably has a glass transition temperature on the low-temperature side within a temperature range of less than 110°C. If the film has such a glass transition temperature on the low temperature side, the mechanical strength and impact resistance of the film can be enhanced. The glass transition temperature on the low temperature side is preferably less than 50°C, more preferably less than 30°C, still more preferably less than 10°C, preferably -100°C or higher, more preferably -90°C or higher, and further -80°C or higher. preferable.

The thickness of the film cannot be unconditionally determined because the suitable range differs depending on the application, but from the viewpoint of ensuring the strength of the film, it is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 20 μm or more. On the other hand, from the viewpoint of thinning the film, the thickness of the film is preferably 350 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less. The thickness of the film can be measured, for example, using a Mitutoyo Digimatic Micrometer.

Since the film of the present invention is excellent in transparency, it can be suitably used as an optical film. Examples of optical films include optical protective films (specifically, protective films for substrates of various optical discs (VD, CD, DVD, MD, LD, etc.)), and polarized light provided in image display devices such as liquid crystal displays. Examples include polarizer protective films, viewing angle compensation films, light diffusion films, reflective films, antireflection films, antiglare films, brightness enhancement films, conductive films for touch panels, retardation films, and light conversion films used for plates.

The optical film may be configured by laminating other optical materials. Further optical properties can be imparted to the film by laminating other optical materials. Other optical materials include, for example, polarizing plates, stretched and oriented films made of polycarbonate, and stretched and oriented films made of cyclic polyolefin.

Various functional coating layers may be provided on the surface of the optical film, if necessary. Functional coating layers include, for example, an antistatic layer, an adhesive layer, an adhesive layer, an easy adhesive layer, an antiglare (non-glare) layer, an antifouling layer such as a photocatalyst layer, an antireflection layer, a hard coat layer, an ultraviolet A shielding layer, a heat ray shielding layer, an electromagnetic wave shielding layer, a gas barrier layer and the like can be mentioned. Further, an optical adjustment layer for appropriately adjusting the transmittance or reflectance of incident light may be provided on the surface of the optical film.

The film of the present invention is particularly suitable for use as a polarizer protective film. In this case, the polarizing plate may be constructed by providing an optical film (polarizer protective film) on one or both sides of the polarizer. The optical film (polarizer protective film) is preferably fixed directly to the polarizer or indirectly via another layer with an adhesive or adhesive.

The type of polarizer is not particularly limited, for example, a polarizer obtained by dyeing and stretching a polyvinyl alcohol film; a reflective polarizer; and a polarizer made of a thin crystal film. As an example of the structure of the polarizing plate, polyvinyl alcohol is dyed with iodine or a dichroic substance such as a dichroic dye, and then uniaxially stretched to obtain a polarizer, and a polarizer protective film is provided on one or both sides of the polarizer. (Optical film) is provided.

The optical film can also be used as a transparent conductive film by forming a transparent conductive layer on the surface. As the material constituting the transparent conductive layer, any of those conventionally used as a conductive material in the relevant field can be used. Specifically, organic conductive compounds; organic conductive polymers; indium oxide; Metal oxides such as tin oxide, zinc oxide, indium-tin oxide (ITO), antimony-tin oxide (ATO), zinc-aluminum oxide, indium-zinc oxide (IZO); gold, silver, copper, Metals such as palladium and aluminum are included.

An optical film (for example, a polarizer protective film, a transparent conductive film) can be suitably used for an image display device. Examples of image display devices include liquid crystal display devices. For example, in the case of a liquid crystal display device, the image display section can be configured to have the film of the present invention together with members such as a liquid crystal cell, a polarizing plate and a backlight. Examples of image display devices other than liquid crystal display devices include electroluminescence (EL) display panels, plasma display panels (PDP), field emission displays (FED), QLEDs, and micro LEDs.

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to these. In the following description, "part" means "mass part" and "%" means "% by mass" unless otherwise specified.

(1) Analysis method (1-1) Weight average molecular weight (Mw) and number average molecular weight (Mn)
The weight average molecular weight and number average molecular weight were determined by polystyrene conversion using gel permeation chromatography (GPC). The apparatus and measurement conditions used for the measurement are as follows.
-Measurement system: GPC system HLC-8220 manufactured by Tosoh Corporation
- Column configuration on the measurement side Guard column: TSKguardcolumn SuperHZ-L manufactured by Tosoh Corporation
Separation column: TSKgel SuperHZM-M, manufactured by Tosoh Corporation 2 columns connected in series - reference side column configuration Reference column: TSKgel SuperH-RC, manufactured by Tosoh Corporation
- Developing solvent: chloroform (manufactured by Wako Pure Chemical Industries, special grade)
- Solvent flow rate: 0.6 mL / min - Standard sample: TSK standard polystyrene (manufactured by Tosoh Corporation, PS-oligomer kit)

(1-2) glass transition temperature (Tg)
The glass transition temperature was obtained according to JIS K 7121 (2012). Specifically, using a differential scanning calorimeter (Thermo plus EVO DSC-8230 manufactured by Rigaku), a sample was heated from normal temperature to 200 ° C. (heating rate 20 ° C./min) in a nitrogen gas atmosphere. From the obtained DSC curve, it was evaluated by the starting point method. α-alumina was used as a reference. A glass transition temperature of less than 40°C was measured by using a differential scanning calorimeter (DSC-3500, manufactured by Netsch Co.) and heating the sample from -100°C to 60°C in a nitrogen gas atmosphere (heating rate: 10°C/min). It was evaluated by the starting point method from the DSC curve obtained by the method. An empty container was used as a reference.

(1-3) Monomer conversion rate Monomer conversion rate (reaction rate) is obtained by measuring the amount of residual monomer in the polymerization reaction solution using gas chromatography (manufactured by Shimadzu Corporation, GC-2014). rice field.

(1-4) Amount of Olefinic Double Bonds The amount of olefinic double bonds was obtained by iodometric titration. After weighing 0.1 to 3 g of the sample and dissolving it in 20 g of toluene, add 12.5 mL of Wiiss' test solution (0.1 mol/L iodine chloride/acetic acid solution, manufactured by Wako Pure Chemical Industries, Ltd.) and stir for 1 hour. left undisturbed. 10 mL of 10 w/v % potassium iodide solution (manufactured by Kishida Chemical Co., Ltd.) and 50 mL of deionized water were added thereto and stirred well, and then several drops of starch solution (manufactured by Kishida Chemical Co., Ltd.) were added and further stirred. Titration was performed with a 0.1 mol/L sodium thiosulfate solution (manufactured by Wako Pure Chemical Industries, Ltd.) while stirring the liquid well, and the end point was when the iodine coloration disappeared. A blank test was also conducted without using any sample. The amount of olefinic double bonds in the sample was determined by the following formula.
Olefinic double bond amount (mmol/g) = (AB) x F x x/(2 x C x d)
A: Amount of sodium thiosulfate in blank test (g)
B: Sodium thiosulfate amount (g) in this test
F: sodium thiosulfate factor x: sodium thiosulfate concentration (0.1 mol / L)
C: sample amount (g)
d: sodium thiosulfate density (1.01 g/mL)

(1-5) Internal haze (internal haze per 100 μm thickness)
A quartz cell is filled with 1,2,3,4-tetrahydronaphthalene (tetralin), the stretched film prepared in the example is immersed therein, and a haze meter (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.) is used. The haze was measured and the internal haze per 100 μm thickness was calculated according to the following formula: internal haze (%) per 100 μm thickness = obtained measured value (%) × (100 μm/film thickness (μm)). . The measurement was performed using three films, and the internal haze per 100 μm thickness was calculated from the average value.

(1-6) Folding endurance number by MIT test The stretched film prepared in the example was cut into a size of 90 mm × 15 mm and used as a test piece, and an MIT folding endurance tester (manufactured by Tester Sangyo Co., Ltd., BE-201) was used. Then, a load of 200 g was applied in an atmosphere with a temperature of 23° C. and a relative humidity of 50%, and an MIT folding endurance test was performed based on JIS P 8115 (2001) to measure the number of folding endurances. The test piece is cut out so that the MD or TD direction during stretching is the longitudinal direction, and the test result when using a test piece whose longitudinal direction is the MD direction is the number of folds in the MD direction, and the TD direction is The test result when using a test piece in the longitudinal direction was obtained as the number of folding endurances in the TD direction. In the case of an unstretched film, the number of folding endurances in two arbitrary orthogonal directions was determined.

(1-7) Water Absorption Rate The stretched film prepared in the example was cut into a size of 100 mm × 100 mm, and subjected to absolute drying treatment overnight under vacuum at a temperature of 40 ° C. using a vacuum dryer to obtain a test piece. . The mass of the specimen before testing was measured in mg (1 decimal place). Place the test piece in a thermo-hygrostat (THE051FA manufactured by ADVANTEC), place it in an atmosphere of 85°C and 85% relative humidity for 120 hours, and then measure the mass of the test piece immediately after taking it out of the thermo-hygrostat. bottom. The water absorption was obtained from the mass change of the test piece before and after the test.

(1-8) Dimensional change rate The stretched film prepared in the example was cut into a size of 100 mm × 100 mm, and was dried overnight under vacuum at a temperature of 40 ° C. using a vacuum dryer. bottom. Before the test, 80 mm × 80 mm square inside the test piece was marked at 40 mm intervals, 3 points in the vertical direction (MD direction) and 3 points in the horizontal direction (TD direction), and the distance between the marks in the vertical direction and the distance between the marks in the horizontal direction Measured with a digital vernier caliper. Place the test piece in a constant temperature and humidity chamber (THE051FA manufactured by ADVANTEC) and place it in an atmosphere of 85 ° C. temperature and 85% relative humidity for 120 hours. The distance between marks and the distance between marks in the horizontal direction were measured with digital calipers. The dimensional change rate was obtained from the change in the distance between the marks of the test piece before and after the test.

(1-9) Retardation Using a fully automatic birefringence meter (KOBRA-WR, manufactured by Oji Scientific Instruments Co., Ltd.), the stretched film prepared in the example was subjected to a light with a wavelength of 590 nm under the condition of an incident angle of 40 °. The internal retardation Re and the thickness direction retardation Rth were measured. The refractive index in the slow axis direction in the plane of the film is nx, the refractive index in the fast axis direction in the plane of the film is ny, the refractive index in the thickness direction of the film is nz, and the thickness of the film is d. The in-plane retardation Re and the thickness direction retardation Rth were obtained from the equations.
In-plane retardation Re=(nx−ny)×d
Thickness direction retardation Rth = [(nx + ny) / 2-nz] × d

(2) Production of Resin Composition (2-1) Preparation Example 1: Preparation of Resin Composition R1 Into a reactor equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction pipe, SEBS triblock copolymer, 6 parts of Tuftec (registered trademark) P1083 (manufactured by Asahi Kasei Corporation, olefinic double bond content 2.01 mmol / g, styrene unit content 20% by mass, refractive index 1.500) and Tuftec (registered trademark) H1052 (Asahi Kasei Corporation 4 parts of olefinic double bond content 0.27 mmol / g, styrene unit content 20 mass%, refractive index 1.500), 73.8 parts of methyl methacrylate (MMA), 2-(hydroxymethyl) acrylic 10.8 parts of methyl acid (MHMA), 0.025 parts of n-dodecyl mercaptan (nDM), and 100 parts of toluene as a polymerization solvent were charged, and the temperature was raised to 105°C while nitrogen was passed therethrough. 0.06 part of oxyisopropyl carbonate (manufactured by Kayaku Akzo Co., Ltd., Kayacarbon (registered trademark) Bic75) was added. After confirming the start of the polymerization reaction, 5.4 parts of styrene (St) was added at a constant rate over 3 hours. solution polymerization was carried out at 105° C. to 110° C. while dropping at a constant rate over 4 hours. 0.07 part of stearyl phosphate as a cyclization catalyst is added thereto, and the cyclization reaction is carried out under reflux at 90° C. to 110° C. for 2 hours. -412S and ADEKA STAB (registered trademark) AO-60 (both manufactured by ADEKA) were each added in an amount of 0.05 part. As a result, a (meth)acrylic copolymer polymerized from MMA, MHMA and St and having a lactone ring structure in the main chain, and a diene/olefin-derived copolymer chain in which the copolymer chain is a SEBS triblock copolymer chain A resin composition comprising the graft copolymer attached to the units was obtained. The conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 94%, the conversion rate of MHMA was 94%, and the conversion rate of St was 99%. The composition ratio (by mass) of the (meth)acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the (meth)acrylic copolymer is MMA:MHMA:St = 82.6:11.9:5.5, and the content of the ring structural unit was 22.0% by mass.
Next, the obtained polymerization reaction solution was placed in an autoclave and heat-treated at 240 ° C. for 1 hour, and then a vent type screw twin screw extruder (L / D: 45) at a processing rate of 600 g/h in terms of resin, devolatilized in this extruder, and extruded to obtain pellets of transparent resin composition R1. The operating conditions of the twin-screw extruder were a barrel temperature of 260° C., a rotation speed of 300 rpm, and a degree of pressure reduction of 13.3 to 400 hPa (10 to 300 mmHg). The resulting resin composition R1 had a weight average molecular weight of 155,000, a number average molecular weight of 55,000, a glass transition temperature of 122° C. on the high temperature side, a glass transition temperature of −54° C. on the low temperature side, and a refractive index of was 1.501.

(2-2) Preparation Example 2: Preparation of Resin Composition R2 In a reactor equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction pipe, 3 Tuftec (registered trademark) P1083 was added as an SEBS triblock copolymer. .5 parts and 5.2 parts of Tuftec (registered trademark) H1052 and Tuftec (registered trademark) H1041 (manufactured by Asahi Kasei Corporation, olefinic double bond content 0.45 mmol / g, styrene unit content 30% by mass, refractive index 1 .513), 66.3 parts of MMA, 12.8 parts of MHMA, 0.01 part of nDM, and 100 parts of toluene as a polymerization solvent were charged, and the temperature was raised to 105° C. while nitrogen was passed through. 0.115 parts of ® Bic 75 were added. After confirming the start of the polymerization reaction, 5.95 parts of St and 0.252 parts of Kayacarvone (registered trademark) Bic75 diluted with 1 part of toluene were added dropwise at a constant rate over 3 hours at 105°C. Solution polymerization was carried out at ~110°C, followed by aging for 4 hours. 0.07 part of stearyl phosphate as a cyclization catalyst is added thereto, and the cyclization reaction is carried out under reflux at 90° C. to 110° C. for 2 hours. -412S, ADEKA STAB (registered trademark) AO-60 and ADEKA STAB (registered trademark) 2112 (both manufactured by ADEKA) were each added in an amount of 0.05 part. As a result, a (meth)acrylic copolymer polymerized from MMA, MHMA and St and having a lactone ring structure in the main chain, and a diene/olefin-derived copolymer chain in which the copolymer chain is a SEBS triblock copolymer chain A resin composition comprising the graft copolymer attached to the units was obtained. The conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 95%, the conversion rate of MHMA was 96%, and the conversion rate of St was 99%. The composition ratio (by mass) of the (meth)acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the (meth)acrylic copolymer is MMA:MHMA:St =79.3:14.8:5.9, and the content of ring structural units was 29.7% by mass.
Next, the obtained polymerization reaction solution was placed in an autoclave and heat-treated at 240 ° C. for 1 hour, and then a vent type screw twin screw extruder (L / D: 45) at a processing rate of 600 g/h in terms of resin, devolatilized in this extruder, and extruded to obtain pellets of transparent resin composition R2. The operating conditions of the twin-screw extruder were a barrel temperature of 260° C., a rotation speed of 300 rpm, and a degree of pressure reduction of 13.3 to 400 hPa (10 to 300 mmHg). The resulting resin composition R2 had a weight average molecular weight of 137,000, a number average molecular weight of 51,000, a glass transition temperature of 124° C. on the high temperature side, a glass transition temperature of −54° C. on the low temperature side, and a refractive index of was 1.501.

(2-3) Preparation Example 3: Preparation of Resin Composition R3 A reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen inlet pipe was charged with A1536 (olefinic Double bond amount 0.10 mmol / g, styrene unit content 39% by mass, refractive index 1.519) 10 parts, MMA 79.8 parts, phenylmaleimide (PMI) 8.4 parts, nDM 0.05 parts, polymerization solvent 100 parts of toluene was charged as a solution, and the temperature was raised to 105° C. while passing nitrogen through it, and 0.07 part of Kayacarvone (registered trademark) Bic 75 was added as an initiator. After confirming the start of the polymerization reaction, 1.8 parts of St and 0.144 parts of Kayacarbon (registered trademark) Bic75 diluted with 1 part of toluene were added dropwise at a constant rate over 3 hours to 105°C. Solution polymerization was carried out at ~110°C, followed by aging for 4 hours. After aging, 0.05 parts of each of ADEKA STAB (registered trademark) AO-412S and ADEKA STAB (registered trademark) AO-60 (both manufactured by ADEKA) were added as antioxidants to the obtained reaction solution. As a result, a (meth)acrylic copolymer polymerized from MMA, PMI, and St, and a graft copolymer in which the copolymer chain is bonded to the diene/olefin-derived unit of the SEBS triblock copolymer chain A resin composition containing was obtained. The conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 95%, the conversion rate of PMI was 99%, and the conversion rate of St was 100%. The composition ratio (by mass) of the (meth)acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the (meth)acrylic copolymer is MMA:PMI:St = 88.2:9.7:2.1, and the content of ring structural units was 9.7% by mass.
Next, the obtained polymerization reaction solution was introduced into a vent-type screw twin-screw extruder (L/D: 45) having one rear vent and two fore vents at a processing rate of 600 g/h in terms of resin. Then, devolatilization was performed in this extruder and extrusion was performed to obtain pellets of transparent resin composition R3. The operating conditions of the twin-screw extruder were a barrel temperature of 260° C., a rotation speed of 300 rpm, and a degree of pressure reduction of 13.3 to 400 hPa (10 to 300 mmHg). The resulting resin composition R3 had a weight average molecular weight of 154,000, a number average molecular weight of 62,000, a glass transition temperature of 128° C. on the high temperature side, a glass transition temperature of −68° C. on the low temperature side, and a refractive index of was 1.515.

(2-4) Preparation Example 4: Preparation of Resin Composition R4 In a reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe, DYNARON (registered trademark) manufactured by JSR Co., Ltd. was added as an SEBS triblock copolymer. ) 2324 (olefinic double bond content 0.10 mmol / g, styrene unit content 39% by mass, refractive index 1.519) 10 parts, MMA 85.5 parts, methyl acrylate (MA) 4.5 parts, nDM0 0.05 part and 100 parts of toluene as a polymerization solvent were charged, heated to 105° C. while passing nitrogen, and 0.06 part of Kayacarvone (registered trademark) Bic 75 as an initiator was added. After confirming the initiation of the polymerization reaction, 0.185 parts of Kayacarvone (registered trademark) Bic75 diluted with 1 part of toluene was added dropwise at a constant rate over 3 hours to carry out solution polymerization at 105°C to 110°C. was further aged for 4 hours. After aging, 0.05 parts of each of ADEKA STAB (registered trademark) AO-412S and ADEKA STAB (registered trademark) AO-60 (both manufactured by ADEKA) were added as antioxidants to the obtained reaction solution. As a result, a (meth)acrylic copolymer polymerized from MMA and MA and a graft copolymer in which the copolymer chain is bonded to the diene/olefin-derived unit of the SEBS triblock copolymer chain are formed. A resin composition containing The conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 95%, and the conversion rate of MA was 96%. The composition ratio (by mass) of the (meth)acrylic copolymer chains bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the (meth)acrylic copolymer was MMA:MA=94. 0.5:5.5.
Next, the obtained polymerization reaction solution was introduced into a vent-type screw twin-screw extruder (L/D: 45) having one rear vent and two fore vents at a processing rate of 600 g/h in terms of resin. Then, devolatilization was performed in this extruder and extrusion was performed to obtain pellets of transparent resin composition R4. The operating conditions of the twin-screw extruder were a barrel temperature of 260° C., a rotation speed of 300 rpm, and a degree of pressure reduction of 13.3 to 400 hPa (10 to 300 mmHg). The resulting resin composition R4 had a weight average molecular weight of 127,000, a number average molecular weight of 52,000, a glass transition temperature of 107° C. on the high temperature side, a glass transition temperature of −68° C. on the low temperature side, and a refractive index of was 1.490.

(2-5) Preparation Example 5: Preparation of Resin Composition R5 83.5 parts of MMA, 12 parts of MHMA, 0.07 parts of n-DM, and polymerization were added to a reactor equipped with a stirring device, temperature sensor, cooling tube, and nitrogen inlet tube. 90.9 parts of toluene was charged as a solvent, and the temperature was raised to 105° C. while passing nitrogen through it. At the point where reflux with the temperature rise started, 0.07 parts of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd., Luperox (registered trademark) 570) was added as a polymerization initiator, and 4.5 parts of St and t- While adding 0.145 parts of amyl peroxyisononanoate dropwise over 2 hours, solution polymerization was carried out under reflux at about 105° C. to 110° C., followed by aging for 4 hours. To this, 0.07 part of stearyl phosphate (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added as a cyclization catalyst, and a cyclization reaction was carried out under reflux at about 90°C to 110°C for 2 hours. As a result, a (meth)acrylic copolymer polymerized from MMA, MHMA and St and having a lactone ring structure in the main chain was obtained. The conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 94%, the conversion rate of MHMA was 94%, and the conversion rate of St was 99%.
Next, the resulting polymerization reaction solution is passed through a shell-and-tube heat exchanger heated to 240° C. to complete the cyclization condensation reaction. It is introduced into a vent-type screw twin-screw extruder (L/D: 52) equipped with a leaf disk-type polymer filter (filtration accuracy: 5 μm), devolatilized in this extruder, and extruded to obtain a transparent resin. Pellets of composition R5 were obtained. The barrel temperature of the twin-screw extruder was 250°C. Resin composition R5 had a weight average molecular weight of 130,000, a number average molecular weight of 58,000, a glass transition temperature of 122° C., and a refractive index of 1.500.

(2-6) Preparation Example 6: Preparation of Resin Composition R6 In Preparation Example 4, 79.5 parts of MMA, 15.0 parts of MHMA, and 100 parts of toluene were used, and 0.5 parts of t-amylperoxyisonanoate was used as a polymerization initiator. A polymerization reaction and a ring reaction were carried out in the same manner as in Preparation Example 4, except that 5.5 parts of St and 0.24 parts of t-amyl peroxyisonanoate diluted in 1.4 parts of toluene were added. reaction was carried out. As a result, a (meth)acrylic copolymer polymerized from MMA, MHMA and St and having a lactone ring structure in the main chain was obtained. The MMA conversion was 94%, the MHMA conversion was 95%, and the St conversion was 99%. Subsequently, by extruding from a twin-screw extruder in the same manner as in Preparation Example 4, pellets of resin composition R6 were obtained. Resin composition R6 had a weight average molecular weight of 130,000, a number average molecular weight of 50,000, a glass transition temperature of 125° C., and a refractive index of 1.501.

(3) Film Production Examples (3-1) Example 1: Production of Film F1 Resin composition R1 was heat-press molded at 250° C. to obtain an unstretched film having a thickness of about 160 μm. The obtained unstretched film was cut into a size of 96 mm × 96 mm, and a sequential biaxial stretching machine (X6-S manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used at a temperature of 156 ° C. (Tg + 34 ° C.) at 300% / min. A stretched film F1 having a thickness of 40 μm was obtained by sequentially biaxially stretching at a stretching rate of 2.0 times in the order of the longitudinal direction (MD direction) and the transverse direction (TD direction) and cooling. Obtained. The MIT folding endurance of the film F1 was 3500 times in the MD direction and 3800 times in the TD direction, the dimensional change rate was -0.2%, the water absorption rate was 1.2%, and the internal haze (converted to 100 µm) was 0.2%. 22, the in-plane retardation Re was 0.1 nm, and the thickness direction retardation Rth was 3.8 nm.

(3-2) Example 2: Production of film F2 A stretched film F2 was obtained in the same manner as in Example 1, except that the stretching temperature was changed to 148°C (Tg + 26°C). The MIT folding endurance of film F2 was 4500 times in the MD direction and 4500 times in the TD direction. 24, the in-plane retardation Re was 0.2 nm, and the thickness direction retardation Rth was 5.0 nm.

(3-3) Example 3: Production of Film F3 A stretched film F3 was obtained in the same manner as in Example 1, except that the stretching temperature was changed to 138° C. (Tg+16° C.). The MIT folding endurance of film F3 was 5000 times in the MD direction and 5200 times in the TD direction. 23, the in-plane retardation Re was 1.0 nm, and the thickness direction retardation Rth was 4.0 nm.

(3-4) Example 4: Production of film F4 In Example 1, the resin composition R2 was used instead of the resin composition R1, and the stretching temperature was 158 ° C. (Tg + 34 ° C.). A stretched film F4 was obtained by performing the same operation. The MIT folding endurance of the film F4 exceeded 10000 in both the MD direction and the TD direction, so the measurement was discontinued. Film F4 had a dimensional change of −0.1%, a water absorption of 0.9%, an internal haze (converted to 100 μm) of 0.18, an in-plane retardation Re of 0.3 nm, and a thickness direction retardation Rth of 9.0. was 7 nm.

(3-5) Example 5: Production of film F5 In Example 1, the resin composition R3 was used instead of the resin composition R1, and the stretching temperature was 162 ° C. (Tg + 34 ° C.). A stretched film F5 was obtained by performing the same operation. The MIT folding endurance of film F5 was 3000 times in the MD direction and 2500 times in the TD direction. 19, the in-plane retardation Re was 0.5 nm, and the thickness direction retardation Rth was 4.0 nm.

(3-6) Example 6: Production of film F6 In Example 1, the resin composition R4 was used instead of the resin composition R1, and the stretching temperature was 137 ° C. (Tg + 30 ° C.). A stretched film F6 was obtained by performing the same operation. The MIT folding endurance of film F6 was 4000 times in the MD direction and 4000 times in the TD direction. 70, the in-plane retardation Re was 0.1 nm, and the thickness direction retardation Rth was -3.0 nm.

(3-7) Comparative Example 1: Production of Film F7 In Example 1, the resin composition R5 was used instead of the resin composition R1, and the stretching temperature was 138 ° C. (Tg + 16 ° C.). A stretched film F7 was obtained by performing the same operation. The MIT folding endurance of the film F7 was 600 times in the MD direction and 600 times in the TD direction, the dimensional change rate was -1.3%, the water absorption rate was 2.0%, and the internal haze (converted to 100 µm) was 0.3%. 08, the in-plane retardation Re was 0.1 nm, and the thickness direction retardation Rth was 0.3 nm.

(3-8) Comparative Example 2: Production of Film F8 In Example 1, the resin composition R6 was used instead of the resin composition R1, and the stretching temperature was 141 ° C. (Tg + 16 ° C.). A stretched film F87 was obtained by performing the same operation. The MIT folding endurance of film F8 was 500 times in the MD direction and 500 times in the TD direction. 07, the in-plane retardation Re was 0.1 nm, and the thickness direction retardation Rth was -0.4 nm.

(3-9) Comparative Example 3: Production of Film F9 A stretched film F9 was obtained in the same manner as in Comparative Example 2, except that the stretching temperature was changed to 159° C. (Tg+34° C.). The MIT folding endurance of film F9 was 1 in the MD direction and 1 in the TD direction. 08, the in-plane retardation Re was 0.1 nm, and the thickness direction retardation Rth was 0.0 nm.

(3-10) Comparative Example 4 Production of Film F10 The resin composition R1 was heat-press molded at 260° C. to obtain an unstretched film F10 having a thickness of about 40 μm. The MIT folding endurance of the film F10 is 3 times in the MD direction and 2 times in the TD direction, the dimensional change rate is -0.1%, the water absorption rate is 1.2%, and the internal haze (converted to 100 µm) is 0.1%. 22, the in-plane retardation Re was 0.1 nm, and the thickness direction retardation Rth was 0.1 nm.

The films of Comparative Examples 1 to 3 were produced by stretching a resin composition containing a (meth)acrylic polymer. The films of Comparative Examples 1 and 2 were stretched at a relatively low temperature of Tg+16° C., but the folding endurance was only 500 to 600 times in the MIT test. The film of Comparative Example 3 stretch formed at a temperature of Tg+34° C., which was higher, broke after one bend. On the other hand, the films produced in Examples 1 to 6 are resin compositions containing a copolymer in which the polymer chain (B) of the (meth)acrylic polymer is grafted onto the polymer chain (A) of the SEBS block copolymer. was stretched and formed, and the number of folding endurance in the MIT test was 1000 times or more, showing excellent mechanical strength (folding endurance). Although the films of Examples 1 and 4 to 6 were stretched at a high temperature of Tg + 30 to 34°C, they exhibited excellent folding endurance and also excellent dimensional stability. The unstretched film of Comparative Example 4 formed from the same resin composition as in Example 1 had almost no folding endurance.

The film of the present invention is used for optical protective films, polarizer protective films, viewing angle compensation films, light diffusion films, reflective films, antireflection films, antiglare films, brightness enhancement films, conductive films for touch panels, retardation films, etc. can be used.

Claims (12)

A polymer chain (A) having a polymer block (a1) having a diene and/or olefin-derived unit and a polymer block (a2) having an aromatic vinyl monomer-derived unit, and a (meth)acrylic monomer A film comprising a copolymer (P) having a polymer chain (B) having units derived from a polymer,
The film is a stretched film,
The folding endurance is 1000 times or more in the MIT test based on JIS P 8115 ,
The in-plane retardation Re for light with a wavelength of 590 nm is 10 nm or less,
An optical film having a thickness direction retardation Rth of −100 nm or more and 100 nm or less with respect to light having a wavelength of 590 nm . 2. The optical film according to claim 1, wherein the absolute value of the dimensional change is 1.2% or less when placed in an atmosphere of 85° C. and 85% RH for 120 hours. 3. The optical film according to claim 1, which has an internal haze of 2.0% or less per 100 [mu]m of thickness. 4. The optical film according to claim 1, wherein the polymer chain (B) has a ring structure in its main chain. The optical film according to any one of claims 1 to 4, which has a glass transition temperature in the temperature range of 110°C or higher. 6. The optical film according to any one of claims 1 to 5, wherein the polymer chain (B) is grafted to the polymer block (a1) of the polymer chain (A). 7. The optical film according to any one of claims 1 to 6, wherein the polymer chain (A) is formed by bonding polymer blocks (a2) to both sides of the polymer block (a1). 8. The optical film according to any one of claims 1 to 7, further comprising a (meth)acrylic polymer. The unit derived from the (meth)acrylic monomer constituting the (meth)acrylic polymer is the same as the unit derived from the (meth)acrylic monomer constituting the polymer chain (B). 9. The optical film according to 8. The antioxidant according to any one of claims 1 to 9, comprising at least one antioxidant selected from the group consisting of hindered phenol antioxidants, hindered amine antioxidants, phosphorus antioxidants, and sulfur antioxidants. Optical film. The optical film according to any one of claims 1 to 10, wherein the polymer chain (B) has a total content of (meth)acrylic units and cyclic structural units of 85% by mass or more. 12. The optical film according to any one of claims 1 to 11, which has a water absorption rate of 1.8% by mass or less when placed in an atmosphere of 85°C temperature and 85% RH for 120 hours.