JP7301534B2 - Optical film with reduced retardation in the thickness direction - Google Patents

Description

TECHNICAL FIELD The present invention relates to a film in which retardation in the thickness direction is suppressed.

2. Description of the Related Art Conventionally, in the field of image display and the like, optical films utilizing birefringence caused by orientation of polymers have been widely used. As one of them, there is a retardation film incorporated in an image display device, and among them, various retardation films that are compatible with various optical designs are being studied.

In the image display device, light leakage occurs when the screen is viewed from an oblique direction due to its optical characteristics, and the contrast of the displayed image may be lowered due to so-called "black floating". In order to avoid this problem and expand the viewing angle of an image display device, a retardation film is desired which has an essentially necessary in-plane retardation and suppresses a retardation in the thickness direction. By laminating retardation films together, it is conceivable to produce a retardation film that has an in-plane retardation and suppresses a retardation in the thickness direction. A reduction in yield was observed in addition to the need for technology and equipment. As a retardation film that suppresses the retardation in the thickness direction that can be produced without using techniques such as bonding and adhesion, for example, Patent Document 1 discloses a layer having positive birefringence and a layer having negative birefringence. A laminated retardation film comprising a layer is disclosed.

WO2014/034521

However, in order to produce the laminated retardation film of Patent Document 1, it is necessary to go through a complicated process of stretching, coating, and stretching, so there is a problem that it takes time and cost to produce.

The present invention has been made in view of the circumstances as described above, and its object is to make the constituent polymer of the film appropriate even if the film is manufactured by a simple process, so that the thickness direction can be reduced. To provide a film capable of reducing the retardation of .

The present inventors have made intensive studies to solve the above problems, and found that a polymer chain (A) having a diene and / or olefin-derived unit in a resin composition and a (meth)acrylic monomer-derived When the polymer chain (B) having the unit (b1) is contained, when the resin composition is stretched, the thickness direction retardation due to the positive form birefringence of the polymer chain (A) and the polymer chain ( The thickness direction retardation caused by the negative orientation birefringence in B) cancels each other out, and a film having an NZ coefficient greater than 0 and less than 1 can be completed, thus completing the present invention.
That is, the present invention includes the following inventions.

[1] Formed from a resin composition containing a polymer chain (A) having a diene and/or olefin-derived unit and a polymer chain (B) having a (meth)acrylic monomer-derived unit (b1) a film produced by
NZ coefficient = (Rth/Re) + 0.5
(Here, Re is an in-plane retardation (nm) at a wavelength of 589 nm, and Rth is a thickness direction retardation (nm) at a wavelength of 589 nm.)
is greater than 0 and less than 1.
[2] The film according to [1], further comprising a (meth)acrylic polymer (Q).
[3] The polymer chain (A) has a polymer block (a1) having a diene and/or olefin-derived unit and a polymer block (a2) having an aromatic vinyl monomer-derived unit [ 1] or the film according to [2].
[4] The film according to [3], wherein the polymer chain (B) is grafted to the polymer block (a1) of the polymer chain (A).
[5] The film according to any one of [1] to [4], wherein the polymer chain (A) is contained in the film in an amount of 10 to 50% by mass.
[6] The film according to any one of [1] to [5], wherein the polymer chain (B) further has a unit (b2) having a ring structure in its main chain.
[7] The film according to [6], wherein the ring structure is a cyclic imide structure.
[8] Any one of [1] to [7], wherein the polymer chain (B) further has a vinyl monomer-derived unit (b3) copolymerizable with the (meth)acrylic monomer. film.
[9] In 100 parts by mass of the polymer chain (B), 15 to 50 parts by mass of units (b3) derived from a vinyl monomer copolymerizable with the (meth)acrylic monomer are included in [8] Film as described.
[10] The film according to any one of [1] to [9], wherein the film is a single layer film.
[11] The film according to any one of [1] to [10], wherein the film is a uniaxially stretched film.
[12] The film according to any one of [1] to [11], which has a folding endurance of 500 times or more in the MIT test based on JIS P 8115.
[13] The film according to any one of [1] to [12], which has a glass transition temperature of 110°C or higher.
[14] Any one of [1] to [13], wherein the resin composition has a stress optical coefficient Cr of −25.0×10 ⁻¹¹ Pa ⁻¹ or more and −4.0×10 ⁻¹¹ Pa ^{−1 or} less. The film described in .
[15] The film according to any one of [1] to [14], which has an internal haze of 5.0% or less per 100 µm of thickness.
[16] The film according to any one of [1] to [15], which is an optical film.

The film of the present invention has a polymer chain (A) having a diene and/or olefin-derived unit and a polymer chain (B) having a (meth)acrylic monomer-derived unit (b1). , When the resin film having these is stretched, the thickness direction retardation due to each polymer chain has a relationship of canceling each other, so the magnitude (absolute value) of the thickness direction retardation Rth of the obtained film can be kept small, and specifically, a film with an NZ coefficient greater than 0 and less than 1 can be obtained. When the in-plane retardation Re of such a film is sufficiently increased, a retardation film excellent in color tone compensation, viewing angle compensation and the like can be obtained.

The present invention relates to a film having a small retardation in the thickness direction, comprising a polymer chain (A) having a diene and/or olefin-derived unit and a (meth)acrylic monomer-derived unit (b1). It is formed from a resin composition containing a polymer chain (B) having

The magnitude of the retardation in the thickness direction with respect to the in-plane retardation is evaluated by the NZ coefficient represented by the following formula. 04 or more and 0.9 or less, more preferably 0.08 or more and 0.7 or less. If the NZ coefficient is brought close to 0.5, there is an advantage that a decrease in contrast can be suppressed when a retardation film having a large in-plane retardation of the film is formed.
NZ coefficient = (Rth/Re) + 0.5
(Here, Re is an in-plane retardation (nm) at a wavelength of 589 nm, and Rth is a thickness direction retardation (nm) at a wavelength of 589 nm.)
In the above formula, the in-plane retardation Re and the thickness direction retardation Rth can be obtained from the following formulas. In addition, nx is the refractive index in the slow axis direction in the plane of the film, ny is the refractive index in the fast axis direction in the plane of the film, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film. do.
In-plane retardation Re=(nx−ny)×d
Thickness direction retardation Rth = [(nx + ny) / 2-nz] × d

In order to exhibit basic characteristics as a retardation film, the film obtained from the resin composition must have a predetermined in-plane retardation Re. However, in the case of having a predetermined in-plane retardation Re, the thickness direction retardation Rth is also a predetermined value or more, and the contrast tends to decrease. It is useful in terms of being kept small, suppressing a decrease in contrast, and enhancing viewing angle compensation.

The in-plane retardation Re of the film of the invention is preferably 40 nm or more and 400 nm or less, more preferably 50 nm or more and 350 nm or less, still more preferably 60 nm or more and 300 nm or less. When the in-plane retardation Re is within the above range, a sufficient retardation required for various retardation films such as a λ/2 plate and a λ/4 plate can be exhibited.

The absolute value of the thickness direction retardation Rth of the film of the invention is preferably 120 nm or less, more preferably 100 nm or less, still more preferably 90 nm or less, and particularly preferably 85 nm or less. When the thickness direction retardation Rth is within the above range, excellent viewing angle compensation can be exhibited.

In order to reduce the retardation in the thickness direction, in the present invention, a polymer chain (A) having a diene and/or olefin-derived unit and a (meth)acrylic monomer-derived unit (b1). A film is formed from the resin composition containing (B). The polymer chain (A) having a diene and/or olefin-derived unit is soft and difficult to orient even when subjected to stretching, etc., but is phase-separated from the polymer chain (B), so it has a positive morphology. It exhibits birefringence. Form birefringence is the birefringence exhibited by materials in which structures much larger than molecules and smaller than the wavelength of light are present periodically or collectively. Determines the strength of refraction and is always positive.
On the other hand, the polymer chain (B) having the unit (b1) derived from the (meth)acrylic monomer exhibits negative orientation birefringence. Orientation birefringence generally refers to birefringence that occurs due to the orientation of the main chain of a chain polymer (polymer chain).
As described above, the positive birefringence is determined by the size and shape of the polymer chains (A), and the negative birefringence is determined by the orientation of the polymer chains (B). , the thickness direction retardation Rth can be brought close to 0 and the NZ coefficient can be brought close to 0.5 even when the in-plane retardation Re is increased.

When the NZ coefficient is within the above range and the in-plane retardation Re is set to a predetermined value or more, the film of the present invention can be suitably used for color tone compensation and viewing angle compensation for image display devices. The film of the present invention may be a one-layer film (monolayer film). Even a single layer film can have the NZ factor within the desired range. When a plurality of retardation films are produced and then laminated to form a laminated retardation film, there are problems such as misalignment of the film lamination angle during lamination and the need for an adhesive, which increases the thickness of the film and complicates the process. occurs. However, since the film of the present invention can have a NZ coefficient within a desired range with a single layer film, it is not necessary to attach or laminate another film to form a retardation film as in the conventional art. . However, the film of the present invention may be a multi-layered film as long as the NZ coefficient is within the above range.

1. Polymer chain (A)
The polymer chain (A) has diene- and/or olefin-derived units and is a portion exhibiting positive birefringence. The polymer chain (A) content in the film is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and preferably 20 to 30% by mass.

Examples of dienes that form a diene-derived unit include 1,3-butadiene (alias: butadiene), 2-methyl-1,3-butadiene (alias: isoprene), 1,3-pentadiene, 1,4-pentadiene, 1 ,5-hexadiene, 2,5-dimethyl-1,5-hexadiene (a.k.a. diisobutene) and the like are preferably used. - conjugated dienes such as pentadiene are more preferred.
Examples of olefins that form olefin-derived units include monoolefins (alkene is 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 homopolymerization or copolymerization of olefins, as long as the same structure is formed, and may be formed by hydrogenation of diene-derived units. , In this specification, "homopolymerization or copolymerization" is expressed as "homo/copolymerization", and "homopolymer or copolymer" is expressed as "(homo/co)polymer". may be indicated).

The polymer chain (A) preferably contains a polymer block (a1) having a diene and/or olefin-derived unit, and the polymer block (a1) having a diene and/or olefin-derived unit and an aromatic vinyl unit. It is more preferable to have a polymer block (a2) having units derived from a mer. The inclusion of the polymer chain (A) having the polymer block (a1) functioning as a soft component and the polymer block (a2) functioning as a hard component enhances the mechanical strength, and such a resin composition exhibits high mechanical strength. It has strength (for example, impact resistance (falling ball strength)). In addition, transparency and heat resistance are enhanced by containing the polymer chain (B), and the resin composition containing such polymer chain (A) and polymer chain (B) has high transparency and high mechanical strength ( For example, impact resistance (falling ball strength) can be compatible.

The content of diene- and/or olefin-derived units in the polymer chain (A) is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. The upper limit is not particularly limited, and is preferably 90% by mass or less, for example.

As the diene forming the diene-derived unit of the polymer block (a1) and the olefin forming the olefin-derived unit, those mentioned above may be used. 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 (homo/co)polymers such as polyethylene, polypropylene, polybutene-1, ethylene-propylene copolymer and ethylene-butene copolymer; polyisoprene, polybutadiene, isoprene- Diene (homo/co)polymers such as butadiene copolymers; copolymers of olefins and dienes such as ethylene-propylene-diene copolymers and isobutene-isoprene copolymers; The olefin (homo/co)polymer is preferably an α-olefin (homo/co)polymer, and the diene (homo/co)polymer is preferably a conjugated diene (homo/co)polymer. A copolymer of an α-olefin and a conjugated diene is preferred as the polymer. 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 their esters; vinylsilanes such as vinyltrimethoxysilane and γ-(meth)acryloyloxypropylmethoxysilane; and aromatic vinyl monomers, etc. mentioned.

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-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethyl Styrenic monomers such as styrene; polycyclic aromatic hydrocarbon ring vinyl monomers such as 2-vinylnaphthalene; aromatic heterocyclic vinyl monomers such as N-vinylcarbazole, 2-vinylpyridine, vinylimidazole, and vinylthiophene and the like. 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, hydroxy 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 resin composition, 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.

Polymer block (a1) may be a copolymer of these other unsaturated monomers with dienes and/or olefins. An aromatic vinyl monomer is preferable as the other unsaturated monomer. When a copolymer of an aromatic vinyl monomer and a diene and/or an olefin is used as the polymer block (a1), the transparency of the film can be easily improved. For example, even when the difference in refractive index between the polymer chain (A) and the polymer chain (B) is large, it becomes easy to increase the transparency of the film.

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 50% by mass or less, more preferably 40% 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

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 chain (A) may have a polymer block (a2) having units derived from aromatic vinyl monomers. Examples of the aromatic vinyl monomer forming the polymer block (a2) include the aromatic vinyl monomers exemplified for the polymer block (a1) above, and styrene-based monomers are preferred.

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. good too.

Examples of the polymer chain (A) composed of the polymer block (a1) and the polymer block (a2) include a styrene-butadiene block copolymer, a styrene-butadiene-styrene block copolymer, a styrene-butadiene- Hydrogenated products of styrene block copolymers (e.g., styrene-ethylene/butylene-styrene block copolymers (SEBS), styrene-butadiene/butylene-styrene block copolymers), styrene-isoprene block copolymers, styrene- Examples include isoprene-styrene block copolymers and hydrogenated styrene-isoprene-styrene block copolymers (eg, styrene-ethylene/propylene-styrene block copolymers (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 film 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. 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) may be 0% by mass (consisting only of the polymer block (a1)), but is preferably 5% by mass or more, and 10% by mass or more. It is more preferably 15% by mass or more, more preferably 55% by mass or less, 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, facilitating the enhancement of the mechanical strength of the resin composition. 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, 90% by mass or less is more preferable, and 85% by mass or less is even more preferable. Further, the content of units derived from the aromatic vinyl monomer in the polymer chain (A) may be 0% by mass, but is preferably 5% by mass or more, more preferably 10% by mass or more, and 15% by mass. % or more, preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less.

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, and 200,000 or less is even more preferable. By setting the weight-average molecular weight of the polymer chain (A) within such a range, it becomes easy to secure the mechanical strength of the resin composition and improve the moldability of the resin composition.

2. Polymer chain (B)
The polymer chain (B) has units (b1) derived from (meth)acrylic monomers (hereinafter sometimes referred to as "(meth)acrylic units (b1)"), and has negative birefringence. This is the part that shows the sex. In addition, the transparency of the film can be enhanced by having the polymer chain (B).

As used herein, the (meth)acrylic monomer is a monomer containing an acrylic group having a hydrogen atom or an alkyl group (preferably an alkyl group having 1 to 4 carbon atoms) bonded to the α-position and/or β-position. and at least part of the hydrogen atoms of the alkyl group may be substituted with a hydroxy group or a halogen group. A (meth)acrylic monomer preferably means a monomer having an acrylic group or a methacrylic group. (Meth)acrylic monomers include (meth)acrylic acid (ie, free acid) and derivatives thereof, including esters, salts, acid amides, and the like.

As the (meth)acrylic monomer, a (meth)acrylic acid ester is preferable. (Meth)acrylic acid esters include (meth)acrylic acid esters in which a linear, branched or cyclic aliphatic hydrocarbon group or aromatic hydrocarbon group is bonded to the oxygen atom of the ester bond of (meth)acrylic acid. is mentioned.

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 hydroxy group, an amino group, a halogen group, an alkoxy group, an epoxy group, and the like. In particular, in (meth)acrylic acid esters having a linear or branched aliphatic hydrocarbon group, the aliphatic hydrocarbon group preferably has a hydroxy group, an amino group, a halogen group, an alkoxy group, an epoxy group, or the like. 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 (meth)acrylic monomer also includes monomers exemplified by (meth)acrylic monomer A and (meth)acrylic monomer B having a protic hydrogen atom-containing group described later. .

The polymer chain (B) preferably has a ring structure in its main chain. That is, the polymer chain (B) preferably has a unit (b2) having a ring structure (hereinafter sometimes referred to as "ring structure unit (b2)") 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.

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. In this way, a component necessary for forming a ring structure in the main chain of the polymer chain (also referred to as a ring structure-forming monomer) is contained in the ring structure of a part or all of the (meth)acrylic monomer. In this case, for example, two carboxylic acid groups of adjacent (meth)acrylic units (b1) may be linked by acid anhydride conversion, imidation, or the like. When one of the adjacent (meth)acrylic units (b1) has a protic hydrogen atom-containing group such as a hydroxy group or an amino group, the protic hydrogen atom of this one (meth)acrylic unit (b1) A ring structure can also be formed by condensing the containing group with the carboxylic acid group of the other (meth)acrylic unit (b1). When the ring structure is introduced separately from the (meth)acrylic unit (b1), for example, a (meth)acrylic monomer and a monomer having a polymerizable double bond in the ring structure are copolymerized. Just do it.

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 resin composition, a lactone ring structure, a lactam 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.) are preferably mentioned. 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, a cyclic imide structure is preferable, and a succinimide structure is more preferable.

When the polymer chain (B) has a lactone ring structure or lactam ring structure as the ring structure of the main chain, the number of ring members of the lactone ring structure or lactam ring structure is not particularly limited, for example, any one of a 4-membered ring to an 8-membered ring. If it is The lactone ring structure or lactam ring structure is preferably a 5-membered ring or a 6-membered ring, more preferably a 6-membered ring, from the viewpoint of excellent stability of the ring structure.

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 (1a) is preferably shown. As the lactam ring structure, a structure represented by the following formula (1b) is preferably shown. In formula (1a) or (1b) 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 formulas (1a) and (1b) include organic residues such as hydrocarbon groups, for example, optionally substituted C1-20 and the like. 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 group are selected from a hydroxy group, a carboxy group, an ether group and an ester group. It may be substituted with at least one group.

In the lactone ring structure of formula (1a) or the lactam ring structure of formula (1b), R ¹ and R ² are each independently a hydrogen atom or a C1 -20 alkyl group, R ³ is preferably a hydrogen atom or a methyl group, R ¹ and R ² are each independently a hydrogen atom or a methyl group, and R ³ is a hydrogen atom or a methyl group is more preferred.

A protic hydrogen atom-containing group of a unit derived from a (meth)acrylic monomer A having a protic hydrogen atom-containing group such as a hydroxy group or an amino group, and a unit derived from the (meth)acrylic monomer A A lactone ring structure and/or a lactam ring structure can be introduced into the polymer chain (B) by cyclocondensation with an ester group of an adjacent (meth)acrylic acid ester-derived unit. As a polymerization component, a (meth)acrylic monomer A having a protic hydrogen atom-containing group such as a hydroxy group or an amino group is essential, and a (meth)acrylic monomer B includes the monomer A. do. 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 protic hydrogen atom-containing group include a (meth)acrylic monomer A1 having a hydroxy group and a (meth)acrylic monomer A2 having an amino group. .

Examples of the (meth)acrylic monomer A1 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.

Examples of the (meth)acrylic monomer A2 having an amino group include compounds in which the hydroxy group of the monomer A1 is changed to an amino group. When the polymer chain (B) has a lactone ring structure and/or a lactam ring structure, the (meth)acrylic monomer A serves as a ring structure-forming monomer.

As the (meth)acrylic monomer B, a monomer having a vinyl group and an ester group or a carboxy 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 or lactam structure represented by formula (1a) or formula (1b), 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 the polymer chain (B) has a succinic anhydride structure, maleic anhydride is the ring structure-forming monomer.

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 an N-substituted 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. It is preferably at least one selected from the group consisting of N-cyclohexylmaleimide and N-phenylmaleimide. When the polymer chain (B) has a succinimide structure, the N-substituted maleimide serves as a ring structure-forming monomer.

When the polymer chain (B) has a succinimide structure in which X ¹ is a nitrogen atom, it is easy to obtain a resin composition having excellent heat resistance, so R ⁴ and R ⁵ are hydrogen atoms, and R ⁶ is It 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 a cyclohexyl group or a phenyl group. more preferred.

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 resin composition having excellent heat resistance, each of R ⁷ and R ⁸ is preferably independently a hydrogen atom or a C1-4 alkyl group, more preferably a hydrogen atom or a methyl group.

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 from the viewpoint that a resin composition having excellent heat resistance can be easily obtained. 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 polymer chain (B) has a glutarimide structure, the (meth)acrylic monomer becomes the ring structure-forming monomer.

When the ring structure of formula (3) has a glutarimide structure in which ^X2 is a nitrogen atom, it is easy to obtain a resin composition having excellent heat resistance, so ^R7 and ^R8 are each independently more preferably a hydrogen atom or a methyl group, R ⁹ is a methyl group, a cyclohexyl group, a phenyl group, or a tolyl group; R ⁷ and R ⁸ are each independently a hydrogen atom or a methyl group; ⁹ is particularly preferably 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 unit (b2) of the polymer chain (B) is , a lactone ring structure and/or a succinimide structure (a structure derived from a maleimide monomer), more preferably a succinimide structure.

The content of the cyclic structural unit (b2) in the main chain in the polymer chain (B) is not particularly limited, but the content of the cyclic structural unit (b2) in the polymer chain (B) is preferably 3% by mass or more. It is more preferably 10% by mass or more, more preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. By adjusting the content of the ring structural unit (b2) in the main chain in this manner, both heat resistance and mechanical strength can be imparted to the resin composition in a well-balanced manner. In addition, due to the ring structure of the main chain in the polymer chain (B), positive orientation birefringence is likely to occur. may have an NZ coefficient of 1 or more. The content ratio of the cyclic structural unit (b2) described here means the content ratio of units having a cyclic structure contained in the main chain of the polymer chain (B). means the content ratio of the structure represented by.

The polymer chain (B) may further have a vinyl monomer-derived unit (b3) copolymerizable with the (meth)acrylic monomer. The vinyl monomer copolymerizable with the (meth)acrylic monomer is not particularly limited as long as it is a compound having a polymerizable double bond. Examples include vinyl esters such as vinyl acetate and vinyl propionate; styrene; aromatic vinyl compounds such as vinyltoluene, methoxystyrene, α-methylstyrene and 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 resin composition. 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 vinyl monomer-derived unit (b3) copolymerizable with the (meth)acrylic monomer is preferably 15 to 50 parts by weight in 100 parts by weight of the polymer chain (B), for example, 20 It is more preferably up to 40 parts by mass, and even more preferably 22 to 35 parts by mass.

The resin composition used in the present invention preferably contains a copolymer (P) containing polymer chains (A) and polymer chains (B). Further, the copolymer (P) includes a polymer chain (A ) and a polymer chain (B) having a (meth)acrylic monomer-derived unit (b1). In the copolymer (P), the polymer chain (B) is preferably grafted to the polymer chain (A), and the polymer chain (B) is grafted to the polymer block (a1) of the polymer chain (A). It is more preferable that the polymer chain (B) is bonded to the diene- and/or olefin-derived units of the polymer block (a1). Further, the polymer chain (A) contained in the copolymer (P) may be a triblock copolymer, a multiblock copolymer, or a radial block copolymer. However, from the viewpoint of ease of introduction of the polymer chain (B) into the copolymer (P), the polymer chain (A) contained in the copolymer (P) should be a triblock copolymer. is preferred. 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.

When the polymer chain (B) is bonded to the diene- and/or olefin-derived units of the polymer block (a1), the polymer chain (B) is bonded to the main chain carbon atoms of the diene- and/or olefin-derived units. may be bonded to a carbon atom of a hydrocarbon group bonded to the main chain as a substituent (side chain). 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

3. Method for Producing Polymer Chain (A) and Copolymer (P) The method for producing the polymer chain (A) having a diene- and/or olefin-derived unit is not particularly limited, and a known method may be used.

As described above, the resin composition used in the present invention has 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. It preferably contains a copolymer (P) having a polymer chain (A) and a polymer chain (B) having a (meth)acrylic monomer-derived unit (b1). An example of a method for producing such a copolymer (P) is described below.

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 to 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 ¹ H-NMR measurement or iodometric titration.

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) is 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 enhanced 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 easy to adjust the weight average molecular weight and physical properties of the resin composition.

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, particularly preferably 7 parts by mass or more, most preferably 9 parts by mass or more, particularly preferably 12 parts by mass or more, preferably 50 parts by mass or less, and more preferably 40 parts by mass or less; 35 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 60 parts by mass or more, and more preferably 65 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, particularly preferably 93 parts by mass or less, most preferably 91 parts by mass or less, and particularly 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; aliphatic hydrocarbons such as hexane and cyclohexane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; tetrahydrofuran, dioxane and ethylene glycol dimethyl ether. , diethylene glycol dimethyl ether, ethers such as anisole; esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve; methanol, ethanol, isopropanol, alcohols such as n-butanol; nitriles such as acetonitrile, propionitrile, butyronitrile and benzonitrile; chloroform; 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, and it is particularly preferable to use a peroxycarbonate-based peroxide. 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 azo 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 (b1) derived from a (meth)acrylic monomer is bonded to the 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 a unit derived from an acrylic monomer 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 main chain of the polymer chain (B). 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 ( Lactone ring structures and/or lactam ring structures can be formed by condensing the meth)acrylic units with the carboxylic acid groups.

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 5 minutes to 6 hours, for example.

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. Furthermore, the devolatilization removes low-molecular-weight compounds, which can suppress staining of cast rolls during film molding and generation of silver streaks during injection molding.

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 resin.

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 and 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, the deactivator can be an acidic substance that can be used for the cyclization catalyst explained above.

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 conversion rates of various monomers in the polymerization reaction are preferably 85% or higher, more preferably 88% or higher, and even more preferably 90% or higher. If the conversion rate of each monomer is lower than 85%, a separate facility for recovering the monomer is required, or the residual monomer causes an unwanted reaction in the next step, resulting in the generation of foreign matter. There is a possibility of significantly impairing productivity.

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, preferably 600,000 or less, and more preferably 400,000 or less. 300,000 or less is more preferable. By setting the weight average molecular weight of the copolymer (P) within such a range, the moldability of the resin composition containing 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. Thereby, it becomes easy to provide the resin composition with well-balanced properties of transparency and mechanical strength.

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

The (meth)acrylic polymer (Q) may have the unit (b1) derived from the (meth)acrylic monomer described in the polymer chain (B) above, preferably the above polymer It has a unit derived from the (meth)acrylic acid ester explained in the chain (B). The (meth)acrylic polymer (Q) may have units derived from other unsaturated monomers described in the polymer chain (B) above. The (meth)acrylic polymer (Q) is contained in the polymer chain (B) of the copolymer (P) from the viewpoint of enhancing compatibility with the copolymer (P) in the resin composition (meth ) It is more preferable to have a unit (b1) derived from an acrylic monomer. That is, the (meth)acrylic monomer-derived unit constituting the (meth)acrylic polymer (Q) is the (meth)acrylic monomer-derived unit (b1) constituting the polymer chain (B). is preferably the same as

The (meth)acrylic polymer (Q) preferably has a ring structure, and more preferably has a ring structure in its main chain. Thereby, the heat resistance of the resin composition and the film obtained therefrom can be improved. The ring structure of the main chain of the (meth)acrylic polymer (Q) 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.), etc., and the details of these ring structures are referred to the above description of the ring structure of the polymer chain (B). Among them, the (meth)acrylic polymer (Q) 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 (Q) has the same (meth)acrylic units as the (meth)acrylic units that the polymer chain (B) of the copolymer (P) has, and the ring that the polymer chain (B) has. It is preferred to have the same ring structural unit as the structural unit. This enhances the compatibility between the (meth)acrylic polymer (Q) and the copolymer (P), and facilitates enhancing the transparency and heat resistance of the resin composition and the film obtained therefrom. From the viewpoint of being able to further improve the heat resistance of the resin composition, the (meth)acrylic polymer (Q) preferably has a cyclic structural unit containing a cyclic imide structure.

Such a (meth)acrylic polymer (Q) is conveniently polymerized together with the (meth)acrylic polymer (Q) when the copolymer (P) is polymerized. In the method for producing the copolymer (P) described above, together with the copolymer (P), the (meth)acrylic polymer (Q) corresponding to the polymer chain (B) of the copolymer (P) is also produced at the same time. However, at this time, by not separating the copolymer (P) and the (meth)acrylic polymer (Q), a resin containing the copolymer (P) and the (meth)acrylic polymer (Q) A composition can be obtained.

The method for producing the resin composition is not limited to the above method, and the copolymer (P) may be isolated and mixed with another polymer to form a resin composition. Further, in the above method for producing the copolymer (P), after completion of the graft polymerization reaction to the copolymer (P1), another monomer may be added and the polymerization reaction may be performed to obtain a resin composition. good. Alternatively, another polymer (for example, another (Meth)acrylic polymer) may be added to form a resin composition. When another polymer is added and mixed, it may be melt-kneaded, and in this case, a general device such as a kneader or a multi-screw extruder can be used.

As described above, the resin composition may contain a polymer other than the (meth)acrylic polymer (Q). Examples of such polymers include polyethylene, polypropylene, ethylene-propylene Polymers, olefin polymers such as poly(4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resin; polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer Polymers, styrene polymers such as acrylonitrile-butadiene-styrene copolymers; polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetals; polyphenylene sulfide; polyetheretherketone; polysulfone; polyethersulfone; polyoxypentylene; polyamideimide; cycloolefin polymer; cellulose derivative; and the like.

In the method for producing a resin composition, a filtration step can also be performed following the polymerization step or the ring structure formation step described above. By performing the filtration step, the amount of foreign matter in the resin composition can be reduced, and the resin composition can be suitably applied to applications such as optical films that require high quality. In addition, when a film is formed from the resin composition, it becomes 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 resin composition is used as an optical material such as an optical film, 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 content of the copolymer (P) in the resin composition is not particularly limited. It is more preferably at least 5% by mass, even more preferably at least 5% by mass, and even more preferably at least 15% by mass. This makes it easier to increase the mechanical strength of the resin composition and to increase the fluidity when the resin composition is heated and melted. The upper limit of the content of the copolymer (P) in the resin composition is not particularly limited, and the resin composition may be composed only of the copolymer (P). The content of P) 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. When the resin composition contains a solvent, the solid content of the resin composition means the amount of the resin composition excluding the solvent.

The content of the polymer chain (A) of the copolymer (P) in the solid content of 100% by mass of the resin composition is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. , 12% by mass or more is even more preferable, 50% by mass or less is preferable, 40% by mass or less is more preferable, and 30% by mass or less is even more preferable. When the content of the polymer chain (A) in the resin composition is 1% by mass or more, the mechanical strength of the resin composition can be increased, and the fluidity of the resin composition when heated and melted can be easily increased. If the content of the polymer chain (A) in the resin composition is 50% by mass or less, the positive form necessary to cancel the negative orientation birefringence caused by the polymer chain (B) while maintaining transparency. It can develop birefringence.

The content of the cyclic structural unit in the resin composition is not particularly limited, but the content of the cyclic structural unit is preferably 3% by mass or more, more preferably 5% by mass or more, based on 100% by mass of the solid content of the resin composition. , more preferably 7% by mass or more, preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. By adjusting the content ratio of the ring structural unit in this way, it becomes easy to improve both the heat resistance and the mechanical strength of the resin composition in a well-balanced manner. In addition, the content ratio of the ring structural unit described here is the same as the ring structural unit contained in the main chain of the polymer chain (B) of the copolymer (P) and the main chain of the (meth)acrylic polymer (Q). It means the total content ratio of the ring structural units contained, for example, it means the content ratio of the structures represented by the above formulas (1) to (3).

When the resin composition contains the (meth)acrylic polymer (Q), the content of the (meth)acrylic polymer (Q) in 100% by mass of the solid content of the resin composition is 1% by mass or more. Preferably, 10% by mass or more is more preferable, 20% by mass or more is more preferable, 30% by mass or more is even more preferable, 99% by mass or less is preferable, 95% by mass or less is more preferable, and 90% by mass or less is even more preferable. , 85% by mass or less is even more preferable.

The total content of the copolymer (P) and the (meth)acrylic polymer (Q) in the solid content of 100% by mass of the resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, and 80% by mass. It is more preferably at least 90% by mass, and even more preferably at least 90% by mass. The upper limit of the content ratio of the copolymer (P) and (meth)acrylic polymer (Q) in the resin composition is not particularly limited, and the resin composition substantially contains the copolymer (P) and (meth) It may be composed only of the acrylic polymer (Q), for example, the total content of the copolymer (P) and the (meth)acrylic polymer (Q) in 100% by mass of the solid content of the resin composition is It may be 99% by mass or more.

The resin composition may contain various additives as long as the effects of the present invention are not impaired. Additives include, for example, ultraviolet absorbers; antioxidants such as phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers. near-infrared absorbers; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; retardation modifiers such as phase difference increasing agents, phase difference reducing agents, and phase difference stabilizers; , antistatic agents including 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 100% by mass of the solid content of the resin composition is preferably in the range of 0 to 5% by mass, more preferably in the range of 0 to 2% by mass.

4. Physical Properties of Resin Composition and Film The resin composition used in the present invention preferably has a glass transition temperature of 110° C. or higher. As a result, the heat resistance of the resin composition can be enhanced, and the resin composition can be applied to applications requiring heat resistance, such as image display devices. The resin composition preferably has a glass transition temperature in the temperature range of 120°C or higher. The upper limit of the glass transition temperature is preferably less than 300°C, more preferably less than 200°C, and even more preferably less than 180°C, from the viewpoint of ensuring moldability into films and the like.

The resin composition preferably has a glass transition temperature of 110° C. or higher and less than 110° C., respectively. A glass transition temperature of 110° C. or higher is referred to as a “high temperature side glass transition temperature”, and a glass transition temperature of less than 110° C. is referred to as a “low temperature side glass transition temperature”. The resin composition may have a plurality of glass transition temperatures on the high temperature side, or may have a plurality of glass transition temperatures on the low temperature side. Since the resin composition has a glass transition temperature on the high temperature side, the heat resistance of the resin composition is enhanced. When the resin composition has a glass transition temperature on the low temperature side, the mechanical strength and impact resistance of the resin composition can be enhanced. The preferred range of the glass transition temperature on the high temperature side of the resin composition is as described above. The glass transition temperature on the low temperature side of the resin composition 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 -80. °C or more is more preferable.

The weight average molecular weight of the resin composition is preferably 2,000 or more, more preferably 5,000 or more, still more preferably 30,000 or more, particularly preferably 50,000 or more, most preferably 100,000 or more, and 600,000. The following is preferable, 400,000 or less is more preferable, and 300,000 or less is even more preferable. By setting the weight average molecular weight of the resin composition within such a range, the moldability of the resin composition is improved. The weight average molecular weight of the resin composition means a polystyrene-equivalent value obtained by measuring the resin composition by gel permeation chromatography, and the resin composition is a copolymer (P) and a (meth)acrylic polymer (Q). is contained, the weight-average molecular weight of the resin composition is the weight-average molecular weight of the entirety of these multiple types of polymers.

The number average molecular weight of the resin composition is preferably 2,000 or more, more preferably 5,000 or more, still more preferably 10,000 or more, particularly preferably 30,000 or more, most preferably 50,000 or more, and 400,000 or less. It is preferably 300,000 or less, more preferably 200,000 or less, and most preferably 100,000 or less. By setting the number average molecular weight of the resin composition within such a range, the moldability of the resin composition is improved. The number average molecular weight of the resin composition means a polystyrene-equivalent value obtained by measuring the resin composition by gel permeation chromatography, and the resin composition contains the copolymer (P) and the (meth)acrylic polymer (Q). In this case, the number average molecular weight of the resin composition is the total number average molecular weight of these multiple types of polymers.

In the resin composition, in order to cancel the thickness direction retardation Rth caused by the polymer chain (A), the stress optical coefficient Cr of the polymer chain (B) having the unit (b1) derived from the (meth)acrylic monomer is , -25.0 × 10 ^-11 Pa ^-1 or more and -4.0 × 10 ^-11 Pa ^-1 or less, preferably -20.0 × 10 ^-11 Pa ^-1 or more -6.0 × 10 ^-1 It is more preferably ¹¹ Pa ^-1 or less, more preferably -15.0 × 10 ^-11 Pa ^-1 or more and -7.0 × 10 ^-11 Pa ^-1 or less, and -12.0 × 10 ^{-1 11} Pa ⁻¹ or more and −8.0×10 ⁻¹¹ Pa ⁻¹ or less is particularly preferable. The stress optical coefficient Cr is obtained by stretching the original film obtained by molding the resin composition at a temperature of Tg or higher to form a retardation film, and at that time, changing the stress σ applied to the original film for stretching. It is the slope of the change in the retardation of the obtained retardation film with respect to the stress σ. A stretched film is formed and the stress optical coefficient Cr is measured. The stress optical coefficient Cr is a value unique to the resin composition and is not affected by the film stretch ratio, stretching conditions, and the like. Since the stress-optical coefficient Cr is measured at a temperature equal to or higher than the Tg of the resin composition, it serves as an index of how much retardation is developed in the film by stretching the original film. When the stress-optical coefficient Cr of the resin composition is within the above range, the thickness direction retardation Rth caused by the polymer chains (A) and the thickness direction retardation Rth caused by the polymer chains (B) cancel each other out, resulting in a film It is easy to make the thickness direction retardation Rth of . The stress optical coefficient Cr of the resin composition is determined by the method described in Examples.

The resin composition preferably has a melt flow rate of 9.0 g/10 min or more, more preferably 10.0 g/10 min or more, and more preferably 11.0 g/10 min or more, measured at a temperature of 240° C. and a load of 98 N (10 kgf). More preferred. If the resin composition has such a melt flow rate, the melt viscosity is lowered when the resin composition is melted by heating, and moldability can be improved. In addition, when the molten resin composition is passed through a filter to remove foreign matter prior to molding, the pressure loss of the filter can be suppressed to increase productivity. On the other hand, even if the melt viscosity is too low, there is a risk that molding such as film molding and stretching will be difficult, and from the viewpoint of poor resin substitution when molding another resin on the same machine, the above-mentioned The melt flow rate is preferably 60.0 g/10 min or less, more preferably 50.0 g/10 min or less, even more preferably 45.0 g/10 min or less. The melt flow rate of the resin composition is determined according to JIS K 7210 (B method).

The film of the present invention is preferably a film with high mechanical strength. Specifically, the film of the present invention preferably has a folding endurance of 500 times or more, more preferably 1000 times or more, according to the MIT test based on JIS P 8115 (2001). 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. . In the case of a uniaxially stretched film, it is more preferable that the number of folding endurances when the film is stretched and the direction orthogonal to the film stretching direction (unstretched direction) are both within the above range. The folding endurance number by the MIT test is determined by the method described in Examples.

The thickness of the film of the present invention is preferably 5 μm or more, more preferably 15 μm or more, from the viewpoint of increasing strength. On the other hand, from the viewpoint of thinning the film, the thickness 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.

The film of the present invention preferably has an internal haze per 100 µm of thickness of 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and 1.0%. The following are particularly preferred.

5. Film Forming Method The resin composition can be formed into a film by forming according to a known technique, for example, a solution casting method (solution casting method), a melt extrusion method, a calendering method, a compression molding method, or the like. be able to. Among these, the solution casting method and the melt extrusion method are preferable. In this case, the polymer may be directly supplied to an extruder or the like to form a film without being pelletized after polymerization.

Apparatus for performing the solution casting method includes, for example, a drum type casting machine, a band type casting machine, a spin coater and the like.

The melt extrusion method includes a T-die method, an inflation method, and the like. When forming a film by a melt extrusion method, it may be made into a stretched film by stretching. Stretching can further improve the mechanical strength of the film. As a stretching method for obtaining a stretched film, a conventionally known stretching method can be applied. Examples include uniaxial stretching such as free width uniaxial stretching and constant width uniaxial stretching; biaxial stretching such as sequential biaxial stretching and simultaneous biaxial stretching; It is preferably formed into a film, and more preferably uniaxially stretched at the free end. When the unstretched film is uniaxially stretched in the x-axis direction, the NZ coefficient can be brought close to 0.5 while exhibiting the desired retardation. The stretching conditions such as the stretching ratio, stretching temperature, and stretching speed are not particularly limited, and may be appropriately set according to the desired mechanical strength and retardation value as long as the NZ coefficient is within the above range.

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 and a uniaxial stretching machine, and any of these apparatuses can be used.

When applying the stretched film to the optical film, in order to stabilize the optical properties and mechanical properties of the optical film, heat treatment (annealing) may be performed after stretching, if necessary.

6. Optical Film Since the film of the present invention is excellent in transparency, it can be suitably used as an optical film. The use of the optical film of the present invention is not particularly limited, but for example, it can be used for optical compensation (color tone compensation, viewing angle compensation) of LCDs of various modes including VA mode and IPS mode liquid crystal display devices (LCDs). In addition to LCD, it can be suitably used for various image display devices and optical devices.

The optical film of the present invention can also be used as a polarizer protective film by laminating it on one side or both sides of a polarizer. It can also be used as a transparent conductive film by forming a transparent conductive layer on the surface.

The optical film of the present invention (for example, retardation film, polarizer protective film, transparent conductive film, light conversion film) can be suitably used in 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 optical 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.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be modified appropriately within the scope that can conform to the gist of the above and later descriptions. It is of course possible to implement them, and all of them are included in the technical scope of the present invention. In the following description, "part" means "mass part" and "%" means "% by mass" unless otherwise specified.

Measurement and evaluation of various physical properties in the following examples were performed by the following analysis methods.
(1) Weight average molecular weight (Mw) and number average molecular weight (Mn)
The weight average molecular weight and number average molecular weight of the resin composition 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)

(2) Glass transition temperature (Tg)
The glass transition temperature of the resin composition was determined 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.

(3) Monomer Conversion Rate The monomer conversion rate (reaction rate) was obtained by measuring the residual monomer amount in the polymerization reaction solution using gas chromatography (Shimadzu Corporation, GC-2014).

(4) Stress optical coefficient Cr
The stress-optical coefficient Cr of the resin composition was obtained as follows using a measurement wavelength of 589 nm.

First, the resin composition obtained in Production Example was hot-press molded at 250° C. to obtain an unstretched film (thickness: 190 μm) of the polymer. Next, the produced unstretched film was cut into a size of 20 mm×60 mm to obtain a test piece for Cr evaluation. Next, on one of the short sides of the test piece, a weight with a weight that applies a stress of 1 N/mm ² or less to the test piece during stretching is selected and attached. It was housed in a constant temperature dryer (DOV-450A manufactured by AS ONE) and left for 1 hour. When the test piece is stored in the constant temperature dryer, the other short side of the test piece is fixed with a chuck, and the stress applied to the test piece by the weight causes the free end of the test piece to uniaxially move in its long side direction (vertical direction). Made to stretch. In addition, the distance between the chuck and the weight of the test piece was set to 40 mm when the test piece was accommodated. After heating and drawing for 1 hour, the heater of the dryer was turned off, and the test piece was naturally cooled in the dryer. When the temperature in the oven reaches Tg-40 ° C. of the polymer, the test piece (uniaxially stretched film) is taken out, and the thickness of the taken out test piece and the in-plane retardation Re for light with a wavelength of 589 nm are measured. The in-plane birefringence Δn of the test piece was calculated. Separately, the cross-sectional area of the test piece after being stretched by the load of the weight was determined, and the stress σ (Pa) applied to the film was calculated from the cross-sectional area and the load of the weight. Δn and σ were obtained for each load while changing the weight of the weight, and the slope of Δn with respect to the obtained σ was obtained by the method of least squares, and this was taken as the stress optical coefficient Cr(Pa ⁻¹ ). When the orientation angle when measuring the in-plane retardation Re is close to 0° with respect to the stretching direction (load application direction), the sign of the stress optical coefficient Cr is positive. In this case, the orientation birefringence of the polymer to be evaluated is positive. On the other hand, when the orientation angle is around 90° with respect to the stretching direction, the sign of the stress optical coefficient Cr is negative. In this case, the orientation birefringence of the polymer to be evaluated is negative. The larger the absolute value of Cr, the higher the birefringence development (retardation development) by stretching.

(5) Melt flow rate (MFR)
The melt flow rate was measured at a temperature of 240° C. and a load of 98 N (10 kgf) according to JIS K 7210 (B method) using a melt indexer (manufactured by Takara Industries Co., Ltd.).

(6) Foreign matter evaluation (filtration test)
Gelation evaluation of the resin composition was performed by a filter filtration test. Foreign matter evaluation was performed by dissolving the resin composition obtained in Production Example in chloroform to prepare a 0.1% by mass chloroform solution, which was applied to the tip of a filter (chromatodisc 13N, manufactured by GL Sciences, pore size 0.45 μm). ) using a plastic syringe attached. If 2 mL of the chloroform solution of the resin composition could be completely filtered, it was evaluated as ◯, and if the filter was clogged on the way and 2 mL of the solution could not be filtered, it was evaluated as x.

(7) Film thickness The film thickness was measured using a Digimatic micrometer (manufactured by Mitutoyo).

(8) Retardation The in-plane retardation Re, the thickness direction retardation Rth, and the NZ coefficient of the stretched film prepared in the example for light with a wavelength of 589 nm were measured by a fully automatic birefringence meter ("KOBRA- WR”) at an incident angle of 40°. Specifically, nx is the refractive index in the slow axis direction in the plane of the film, ny is the refractive index in the fast axis direction in the plane of the film, nz is the refractive index in the thickness direction of the film, and the thickness of the film is d, the in-plane retardation Re and the thickness direction retardation Rth are obtained from the following equations. In the following examples, the thickness d of the film was assumed to be 60 μm, that is, the in-plane retardation Re and the thickness-direction retardation Rth were obtained in terms of a thickness of 60 μm.
In-plane retardation Re=(nx−ny)×d
Thickness direction retardation Rth = [(nx + ny) / 2-nz] × d
NZ coefficient = (Rth/Re) + 0.5

(9) Internal haze of stretched film (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.

(10) Folding number by MIT test (MIT strength)
The stretched film for MIT test prepared in the example was cut into a size of 90 mm × 15 mm to make a test piece, and an MIT folding endurance tester (BE-201 manufactured by Tester Sangyo Co., Ltd.) was used at a temperature of 23 ° C. and relative humidity. A load of 200 gf was applied in a 50% atmosphere, and the number of MIT folding endurance tests was measured according to JIS P 8115 (2001). For the measurement, the number of folding endurances when folded in the film stretching direction was measured using five samples, and the average value of the three points excluding the maximum and minimum values was taken as the folding endurance number when folded in the film stretching direction. . In addition, the number of folding endurances when the film was folded in the direction perpendicular to the film stretching direction (unstretched direction) was calculated in the same manner as the number of folding endurances when the film was folded in the direction of film stretching.

<Production Example 1>
A reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen inlet pipe was charged with Tuftec (registered trademark) P1083 (olefinic double bond content: 2.01 mmol/g, styrene unit) manufactured by Asahi Kasei Corporation as an SEBS triblock copolymer. Content 18.3% by mass, refractive index 1.500, weight average molecular weight 94,000, number average molecular weight 64,000) 3.5 parts, Asahi Kasei Co., Ltd. Tuftec (registered trademark) H1517 (olefinic double bond 0.10 mmol/g, styrene unit content 39% by mass, refractive index 1.523, weight average molecular weight 99,000, number average molecular weight 75,000) 21.5 parts, methyl methacrylate (MMA) 47. 3 parts, 0.03 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 passing nitrogen. After that, 0.04 parts of t-butyl peroxyisopropyl carbonate (manufactured by Kayaku Akzo Co., Ltd., Kayacarbon (registered trademark) Bic75) was added as an initiator, and 0.04 parts of styrene (St) diluted with 18.7 parts of styrene (St) and 1 part of toluene were added. 10 parts of t-butyl peroxyisopropyl carbonate over 3 hours, and 9.0 parts of N-cyclohexylmaleimide (CMI) dissolved in 10 parts of toluene was added dropwise at a constant rate over 5 hours. The solution polymerization was carried out at 0° C., and after the completion of both dropwise additions, the mixture was further aged for 2 hours. This includes an acrylic copolymer polymerized from MMA, CMI, and St, and a graft copolymer in which the copolymer chain is bonded to the diene/olefin-derived units of the SEBS triblock copolymer chain. A resin composition was obtained. The conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 90.1%, the conversion rate of CMI was 96.4%, and the conversion rate of St was 98.2%. The compositional ratio (by mass) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the acrylic copolymer was MMA:CMI:St = 61.1:12. .5:26.4, and the content of the ring structural unit in the resin composition was 9.3% by mass.
Next, the obtained polymerization reaction solution was placed in a vent-type screw twin-screw extruder (hole diameter: 15 mm, L/D: 45) with one rear vent and two fore vents at a rate of 600 g / h in terms of resin. It was introduced at a processing speed, devolatilized in the extruder, and extruded to obtain pellets of a transparent resin composition. 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 had a weight average molecular weight of 129,000, a number average molecular weight of 61,000, a glass transition temperature on the high temperature side of 122°C, a glass transition temperature on the low temperature side of -62.1°C, and an MFR of 34 g/10 min, the refractive index was 1.520, and the stress optical coefficient Cr was -95×10 ⁻¹² Pa ⁻¹ . Then, when the resulting resin composition was evaluated for gelation, it was found that the filtration could be performed favorably.

<Production Examples 2 to 7>
In the same manner as in Production Example 1, except that the contents of the SEBS triblock copolymer, methyl methacrylate (MMA), N-cyclohexylmaleimide (CMI), and styrene (St) were set to the contents shown in Table 1, A resin composition was produced. In Production Example 5, N-phenylmaleimide (PMI) is used instead of N-cyclohexylmaleimide (CMI).

As shown in Table 1, in Production Examples 2, 5, and 6, Tuftec (registered trademark) H1051 and H1043 manufactured by Asahi Kasei Corporation were used. The content is 39.9% by mass, the refractive index is 1.524, the weight average molecular weight is 255,000, and the number average molecular weight is 195,000. It has an amount of 65.6% by mass, a refractive index of 1.554, a weight average molecular weight of 141,000, and a number average molecular weight of 58,000.

In Production Example 2, the conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 90.5%, the conversion rate of CMI was 96.0%, and the conversion rate of St was 98.4%. . The compositional ratio (by mass) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the acrylic copolymer was MMA:CMI:St = 54.1:12. .3:33.6, and the content of the ring structural unit in the resin composition was 9.2% by mass.
In Production Example 3, the conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 93.9%, the conversion rate of CMI was 93.7%, and the conversion rate of St was 99.1%. . The compositional ratio (by mass) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the acrylic copolymer was MMA:CMI:St = 62.2:14. .8:22.9, and the content of the ring structural unit in the resin composition was 11.1% by mass.
In Production Example 4, the conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 92.1%, the conversion rate of CMI was 99.2%, and the conversion rate of St was 96.0%. . The compositional ratio (by mass) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the acrylic copolymer was MMA:CMI:St = 61.8:12. .7:22.5, and the content of the ring structural unit in the resin composition was 10.8% by mass.
In Production Example 5, the conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 91.1%, the conversion rate of PMI was 94.0%, and the conversion rate of St was 98.7%. . The compositional ratio (by mass) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the acrylic copolymer was MMA:PMI:St = 64.5:10. .1:25.4, and the content of the ring structural unit in the resin composition was 7.6% by mass.
In Production Example 6, the conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 93.2%, and the conversion rate of St was 98.9%. The composition ratio (mass basis) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate and the acrylic copolymer was MMA:St = 75.9: 24.1. Met.
In Production Example 7, the conversion rate of MMA calculated from the amount of residual monomers in the polymerization reaction solution was 94.0%, the conversion rate of CMI was 96.8%, and the conversion rate of St was 99.1%. . The composition ratio (by mass) of the acrylic copolymer calculated from the conversion rate was MMA:CMI:St = 62.6:12.1:25.8, and the content of the ring structural unit in the resin composition was 12.1% by mass.

<Example 1-1>
The resin composition obtained in Production Example 1 was hot-press molded at 250° C. to prepare an unstretched film having a thickness of 160 μm. The obtained unstretched film was cut into a size of 50 mm×80 mm to prepare a test piece. Using an autograph with a constant temperature bath (AG-X 1kN, manufactured by Shimadzu Corporation), the distance between chucks was 40 mm, and the temperature was Tg + 4°C, and the stretching speed was 40 mm/min, and the stretching ratio was 2.5 times. The piece was uniaxially stretched at the free end, annealed for 1 minute and then cooled to obtain a stretched film having a thickness of 65 μm.
In addition, as the stretched film for the MIT test, a test piece cut into a size of 100 mm × 110 mm from an unstretched film having a thickness of 80 μm formed by hot pressing is used, and the distance between chucks is set to 80 mm. A stretched film for MIT test with a thickness of 40 μm was obtained by stretching under the same conditions as the free-end uniaxial stretching.

<Examples 1-2 to 6-3, Comparative Examples 1-1 to 1-3>
In the same manner as in Example 1-1, except that the resin composition shown in Table 1 was used, the stretch ratio was changed to the ratio shown in Table 1, and a stretched film having the thickness shown in Table 1 was obtained. to prepare a stretched film.
Further, a stretched film for MIT test with a thickness of 40 μm was obtained by the same manufacturing method as the stretched film for MIT test of Example 1-1. However, the thickness of the unstretched film was adjusted so that the thickness of the stretched film for MIT test obtained by uniaxially stretching the free end was 40 μm.

Claims (15)

A polymer chain (A) containing a polymer block (a1) having a diene-derived unit, a unit (b1) derived from methyl (meth) acrylate , a unit (b2) having a ring structure in the main chain, and styrene and a polymer chain (B) having a unit (b3) derived from An optical film comprising:
The optical film contains 10 to 30% by mass of the polymer chain (A),
The polymer chain (B) contains 5 to 20% by mass of the unit (b2) and 15 to 35% by mass of the unit (b3),
NZ coefficient = (Rth/Re) + 0.5
(Here, Re is an in-plane retardation (nm) at a wavelength of 589 nm, and Rth is a thickness direction retardation (nm) at a wavelength of 589 nm.)
The NZ coefficient of the optical film obtained from is 0.04 or more and less than 0.5 ,
An optical film, wherein the optical film is a stretched film . 2. The polymer chain according to claim 1 , wherein the polymer chain (A) has a polymer block (a1) having a diene-derived unit and a polymer block (a2) having an aromatic vinyl monomer-derived unit. optical film. The polymer chain (A) is a styrene-butadiene-styrene block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a styrene-isoprene-styrene block copolymer. 3. The optical film according to claim 1, which is at least one selected from the group consisting of hydrogenated products of coalescence. 4. The optical film according to any one of 1 to 3, wherein the methyl (meth)acrylate is methyl methacrylate. The optical film according to any one of claims 1 to 4, wherein the ring structure is a cyclic imide structure. 6. The optical film according to any one of claims 1 to 5, comprising a copolymer (P) containing the polymer chain (A) and the polymer chain (B), and a (meth)acrylic polymer (Q). . 7. The optical film according to claim 6, wherein the total content of the copolymer (P) and the (meth)acrylic polymer (Q) is 90% by mass or more. The (meth)acrylic polymer (Q) is a polymer chain having units (b1) derived from methyl (meth)acrylate, units (b2) having a ring structure in the main chain, and units (b3) derived from styrene. The optical film according to claim 6 or 7, comprising (B). 9. Any one of claims 6 to 8, wherein the (meth)acrylic polymer (Q) contains 5 to 20% by mass of the unit (b2) and 15 to 35% by mass of the unit (b3). optical film. The optical film according to any one of claims 1 to 9, wherein the optical film is a single layer film. The optical film according to any one of claims 1 to 10, wherein the optical film is a uniaxially stretched film. 12. The optical film according to claim 11, which has a folding endurance of 500 times or more when folded in a direction orthogonal to the film stretching direction according to the MIT test based on JIS P 8115. The optical film according to any one of claims 1 to 12, which has a glass transition temperature of 110°C or higher. 14. The resin composition according to any one of claims 1 to 13, wherein the stress optical coefficient Cr is −25.0×10 ⁻¹¹ Pa ⁻¹ or more and −4.0×10 ⁻¹¹ Pa ⁻¹ or less. optical film. The optical film according to any one of claims 1 to 14, which has an internal haze of 5.0% or less per 100 µm of thickness.