JP7517879B2 - Film with reduced retardation in the thickness direction - Google Patents

Description

The present invention relates to a film with reduced retardation in the thickness direction.

In the field of image display, optical films that utilize birefringence caused by the orientation of polymers have been widely used. One such film is a retardation film that is incorporated into image display devices, and various retardation films that can be used with a variety of optical designs are being investigated.

In image display devices, due to optical characteristics, light leakage occurs when the screen is viewed from an oblique direction, and the contrast of the displayed image may decrease due to the so-called "floating black". In order to avoid this problem and expand the viewing angle of the image display device, a retardation film that has the necessary in-plane retardation and suppresses the retardation in the thickness direction is desired. It is possible to produce a retardation film that has an in-plane retardation and suppresses the retardation in the thickness direction by laminating retardation films together, but in that case, advanced techniques and devices such as lamination and adhesion are required, and a decrease in yield has been observed. For example, Patent Document 1 discloses a laminated retardation film that has a layer with positive birefringence and a layer with negative birefringence as a retardation film that can be produced without using techniques such as lamination and adhesion and suppresses the retardation in the thickness direction.

International Publication No. 2014/034521

However, producing the layered phase difference film of Patent Document 1 requires a complex process of stretching, coating, and then stretching again, which creates the problem of time and cost involved in production.

The present invention was made in light of the above-mentioned circumstances, and its purpose is to provide a film that can reduce the retardation in the thickness direction by appropriately selecting the constituent polymers of the film, even if the film is manufactured using a simple process.

As a result of intensive research by the present inventors to solve the above problems, it has been found that when a resin composition contains a polymer chain (A) having a unit derived from a diene and/or an olefin, and a polymer chain (B) having a unit (b1) derived from a (meth)acrylic monomer, when the resin composition is stretched, the thickness direction retardation caused by the positive form birefringence of the polymer chain (A) and the thickness direction retardation caused by the negative orientation birefringence of the polymer chain (B) cancel each other out, making it possible to complete a film having an NZ coefficient of 0.35 or more and less than 1.0, thereby completing the present invention.
That is, the present invention includes the following inventions.

[1] A film formed from a resin composition containing a polymer chain (A) having a unit derived from a diene and/or olefin, and a polymer chain (B) having a unit (b1) derived from a (meth)acrylic monomer,
NZ coefficient = (Rth / Re) + 0.50
(Here, Re is the in-plane retardation (nm) at a wavelength of 589 nm, and Rth is the thickness direction retardation (nm) at a wavelength of 589 nm.)
The NZ coefficient of the film calculated from the above formula is 0.35 or more and less than 1.0.
[2] The film according to [1], further comprising a (meth)acrylic polymer (Q).
[3] The film according to [1] or [2], further comprising an additive (C).
[4] The film according to any one of [1] to [3], wherein the polymer chain (A) has a polymer block (a1) having a unit derived from a diene and/or an olefin, and a polymer block (a2) having a unit derived from an aromatic vinyl monomer.
[5] The film according to [4], wherein the polymer chain (B) is grafted to the polymer block (a1) of the polymer chain (A).
[6] The film according to any one of [1] to [5], wherein the polymer chain (A) is contained in the film in an amount of 10 to 50% by mass.
[7] The film according to any one of [1] to [6], wherein the polymer chain (B) further has a unit (b2) having a ring structure in the main chain.
[8] The film according to any one of [7], wherein the ring structure is a cyclic imide structure.
[9] The film according to any one of [1] to [8], wherein the polymer chain (B) further has a unit (b3) derived from a vinyl monomer copolymerizable with the (meth)acrylic monomer.
[10] The film according to [9], wherein, per 100 parts by mass of the polymer chain (B), 15 to 50 parts by mass of a unit (b3) derived from a vinyl monomer copolymerizable with the (meth)acrylic monomer is contained.
[11] The film according to any one of [1] to [10], wherein the film is a monolayer film.
[12] The film according to any one of [1] to [11], wherein the film is a uniaxially stretched film.
[13] The film according to [12], wherein the Rth displacement per 100 μm of the thickness of the uniaxially stretched film is 40 μm or more.
[14] The film according to any one of [1] to [13], which has a glass transition temperature of 110° C. or higher.
[15] The film according to any one of [1] to [14], wherein the resin composition has a stress optical coefficient Cr of -25.0 x 10 ^-11 Pa ^-1 or more and -4.0 x 10 ^-11 Pa ^-1 or less.
[16] The film according to any one of [1] to [15], having an internal haze of 5.0% or less per 100 μm thickness.
[17] The film according to any one of [1] to [16], which is an optical film.

The film of the present invention has a polymer chain (A) having a unit derived from a diene and/or olefin, and a polymer chain (B) having a unit (b1) derived from a (meth)acrylic monomer. When a resin film having these is stretched, the thickness direction retardation caused by the respective polymer chains and layer separation structure cancel each other out, so that the magnitude (absolute value) of the thickness direction retardation Rth of the obtained film can be kept small; specifically, a film having an NZ coefficient of 0.35 or more and less than 1.0 can be obtained. When the in-plane retardation Re of such a film is made sufficiently large, a retardation film with excellent color compensation, viewing angle compensation, etc. can be obtained.

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

The magnitude of the thickness direction retardation relative to the in-plane retardation is evaluated by the NZ coefficient shown in the following formula, and in the film of the present invention, the NZ coefficient is 0.35 or more and less than 1.0, the lower limit is preferably 0.40 or more, and the upper limit is preferably 0.80 or less, more preferably 0.60 or less. When the NZ coefficient is close to 0.50, it has the advantage that the decrease in contrast can be suppressed when the film has a large in-plane retardation.
NZ coefficient = (Rth / Re) + 0.50
(Here, Re is the in-plane retardation (nm) at a wavelength of 589 nm, and Rth is the thickness direction retardation (nm) at a wavelength of 589 nm.)
In the above formula, the in-plane retardation Re and the retardation Rth in the thickness direction can be calculated from the following formula: where the refractive index in the slow axis direction in the plane of the film is nx, the refractive index in the fast axis direction in the plane of the film is ny, the refractive index in the thickness direction of the film is nz, and the thickness of the film is d.
In-plane phase difference Re=|nx−ny|×d
Thickness direction retardation Rth = [(nx + ny) / 2 - nz] x d

In order to exhibit the basic properties of a retardation film, it is necessary for the film obtained from the resin composition to have a specified in-plane retardation Re. However, when the film has a specified in-plane retardation Re, the thickness direction retardation Rth also becomes equal to or greater than a specified value, and contrast tends to decrease. In the present invention, however, the magnitude (absolute value) of the thickness direction retardation Rth is also kept small, which is useful in that it can suppress the decrease in contrast and enhance viewing angle compensation.

The in-plane retardation Re of the film of the present invention is preferably 40 nm or more and 400 nm or less, more preferably 50 nm or more and 350 nm or less, even more preferably 60 nm or more and 300 nm or less, and particularly preferably 80 nm or more and 250 nm or less. When the in-plane retardation Re is in the above range, sufficient retardation required for various retardation films such as λ/2 plates and λ/4 plates can be expressed. The film of the present invention is preferably a film having an in-plane retardation Re of 80 to 250 nm and an NZ coefficient of 0.40 to 0.60. When the in-plane retardation Re is a large value of 80 nm or more, the magnitude (absolute value) of the thickness direction retardation Rth also becomes large, and contrast is likely to decrease. However, in a preferred embodiment of the present invention, even if the in-plane retardation Re is a large value of 80 nm or more, the magnitude (absolute value) of the thickness direction retardation Rth is kept small (in other words, the NZ coefficient is close to 0.50), making it possible to suppress the decrease in contrast and improve viewing angle compensation.

The absolute value of the thickness direction retardation Rth of the film of the present invention is preferably 40 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, and particularly preferably 10 nm or less. When the thickness direction retardation Rth is in the above range, excellent viewing angle compensation can be achieved.

In order to reduce the retardation in the thickness direction, in the present invention, a film is formed from a resin composition containing a polymer chain (A) having a unit derived from a diene and/or olefin and a polymer chain (B) having a unit (b1) derived from a (meth)acrylic monomer. The polymer chain (A) having a unit derived from a diene and/or olefin is soft and difficult to be oriented even when stretched, but exists in phase separation from the polymer chain (B), and therefore exhibits positive form birefringence. Form birefringence refers to the birefringence exhibited by a material that has a structure that is much larger than a molecule and smaller than the wavelength of light, either periodically or collectively, and the strength of birefringence is determined according to its size and shape, and is always a positive value.
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 when the main chain of a chain-like polymer (polymer chain) is oriented.
As described above, the positive birefringence is determined by the size and shape of the polymer chain (A), and the negative birefringence is determined by the orientation of the polymer chain (B). In the film of the present invention, these positive and negative birefringences are controlled separately. Therefore, even if the in-plane retardation Re is increased, the thickness direction retardation Rth can be made close to 0, and the NZ coefficient can be made close to 0.50.

When the NZ coefficient is within the above range, the in-plane retardation Re is set to a predetermined value or more, so that the film of the present invention can be suitably used for color compensation and viewing angle compensation for image display devices. The film of the present invention may be a single-layer film (single-layer film). Even a single-layer film can have an NZ coefficient within a desired range. When a plurality of retardation films are produced and then laminated to form a laminated retardation film, problems occur such as the film lamination angle being shifted during lamination, and an adhesive being required, which increases the film thickness and makes the process more complicated. However, since the film of the present invention can have an NZ coefficient within a desired range with a single layer film, there is no need to laminate or attach other films to form a retardation film as in the past. However, the film of the present invention may be a film consisting of multiple layers as long as the NZ coefficient is within the above range.

1. Polymer Chain (A)
The polymer chain (A) has a unit derived from a diene and/or an olefin, and is a portion that exhibits positive birefringence. The polymer chain (A) is contained in the film in an amount of preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and further preferably 20 to 30% by mass.

As the diene forming the diene-derived unit, alkadienes such as 1,3-butadiene (also called butadiene), 2-methyl-1,3-butadiene (also called isoprene), 1,3-pentadiene, 1,4-pentadiene, 1,5-hexadiene, and 2,5-dimethyl-1,5-hexadiene (also called diisobutene) are preferably used, and among these, conjugated dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene, and 1,3-pentadiene are more preferable.
As the olefin forming the olefin-derived unit, monoolefins (also called alkenes) such as ethylene, propylene, 1-butene, isobutene, 2-methyl-1-butene, 3-methyl-1-butene, 1-tetradecene, 1-octadecene, etc. are preferably used, and among them, α-olefins, which are alkenes with a carbon-carbon double bond at the α-position, are more preferred. The number of carbon atoms in these dienes and olefins is preferably 2 or more, more preferably 3 or more, and is preferably 20 or less, more preferably 10 or less, and even more preferably 6 or less.

The diene and/or olefin-derived units are defined as units formed by the polymerization of dienes and/or olefins. As long as the same structure is formed, the olefin-derived units are not limited to those actually formed by homopolymerization or copolymerization of olefins, and may be formed by hydrogenating diene-derived units (Note that in this specification, "homopolymerization or copolymerization" may be expressed as "homo/copolymerization", and "homopolymer or copolymer" may be expressed as "(homo/co)polymer").

The polymer chain (A) preferably contains a polymer block (a1) having units derived from a diene and/or an olefin, and more preferably contains 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. By containing the polymer chain (A) having the polymer block (a1) functioning as a soft component and the polymer block (a2) functioning as a hard component, the mechanical strength is increased, and such a resin composition has high mechanical strength (e.g., impact resistance (dropping ball strength)). In addition, by containing the polymer chain (B), the transparency and heat resistance are increased, and such a resin composition containing the polymer chain (A) and the polymer chain (B) can achieve both high transparency and high mechanical strength (e.g., impact resistance (dropping ball strength)).

In the polymer chain (A), the content of units derived from dienes and/or olefins is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. There is no particular upper limit, and it is preferably, for example, 90% by mass or less.

The diene forming the diene-derived unit of polymer block (a1) and the olefin forming the olefin-derived unit may be any of those listed above. It is preferable that polymer block (a1) contains, as the diene and/or olefin-derived unit, at least one selected from butadiene-derived units, isoprene-derived units, ethylene-derived units, propylene-derived units, 1-butene-derived units, and isobutene-derived units.

Examples of the polymer block (a1) include olefin (homo/co)polymers such as polyethylene, polypropylene, polybutene-1, ethylene-propylene copolymer, and ethylene-butene copolymer; diene (homo/co)polymers such as polyisoprene, polybutadiene, and isoprene-butadiene copolymer; and olefin and diene copolymers such as ethylene-propylene-diene copolymer and isobutene-isoprene copolymer. As the olefin (homo/co)polymer, α-olefin (homo/co)polymer is preferred, as the diene (homo/co)polymer, conjugated diene (homo/co)polymer is preferred, and as the olefin and diene copolymer, a copolymer of α-olefin and conjugated diene is preferred. Among these, copolymers of α-olefin and conjugated diene such as polyisoprene and isobutene-isoprene copolymer, polybutadiene, polyethylene, and polypropylene are more preferred.

The polymer block (a1) may have units derived from other unsaturated monomers in addition to units derived from dienes and/or olefins. The other unsaturated monomers are not particularly limited as long as they are compounds having a polymerizable double bond, and examples thereof include vinyl esters such as vinyl acetate and vinyl propionate; unsaturated carboxylic acids and esters thereof such as (meth)acrylic acid, maleic anhydride, methyl (meth)acrylate, and ethyl (meth)acrylate; vinyl silanes such as vinyltrimethoxysilane and γ-(meth)acryloyloxypropylmethoxysilane; and aromatic vinyl monomers.

The aromatic vinyl monomer is not particularly limited as long as it is a compound in which a vinyl group is bonded to an aromatic ring, and examples thereof include styrene-based monomers such as styrene, vinyltoluene, methoxystyrene, α-methylstyrene, α-hydroxymethylstyrene, and α-hydroxyethylstyrene; polycyclic aromatic hydrocarbon ring vinyl monomers such as 2-vinylnaphthalene; and aromatic heterocyclic vinyl monomers such as N-vinylcarbazole, 2-vinylpyridine, vinylimidazole, and vinylthiophene. Among these, styrene-based monomers are preferred. Styrene-based monomers include not only styrene but also styrene derivatives in which any substituent is bonded to the polymerizable double bond carbon or benzene ring of styrene, and examples of such substituents include alkyl groups, alkoxy groups, hydroxy groups, halogen groups, amino groups, nitro groups, and sulfo groups. The alkyl groups and alkoxy groups bonded to styrene preferably have 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and the alkyl groups and alkoxy groups bonded to styrene may have at least a portion of the hydrogen atoms substituted with hydroxy groups or halogen groups. From the viewpoint of reducing coloration of the resin composition, it is preferable that the styrene-based monomer does not have an amino group. Furthermore, it is preferable that the styrene-based monomer is an unsubstituted styrene in which no substituent is bonded to the polymerizable double bond carbon or benzene ring of styrene.

The polymer block (a1) may be a copolymer of these other unsaturated monomers with a diene and/or an olefin. As the other unsaturated monomer, an aromatic vinyl monomer is preferable. When the copolymer of an aromatic vinyl monomer with a diene and/or an olefin is used as the polymer block (a1), the transparency of the film is easily increased. For example, even when the difference in refractive index between the polymer chain (A) and the polymer chain (B) is large, the transparency of the film is easily increased.

When the polymer block (a1) has units derived from an aromatic vinyl monomer, the content of the units derived from the aromatic vinyl monomer in the polymer block (a1) is preferably 1% by mass or more, more preferably 2% by mass or more, even 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 the units derived from the diene and/or olefin and the units derived from the aromatic vinyl monomer in the polymer block (a1) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The polymer block (a1) may be substantially composed of only the units derived from the diene and/or olefin and the units derived from the aromatic vinyl monomer, and for example, the total content of these units may be 99% by mass or more.

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

The polymer block (a1) preferably contains units derived from dienes and/or olefins as the main component, and the content of the units derived from dienes and/or olefins in 100% by mass of the polymer block (a1) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. The polymer block (a1) may be substantially composed of only units derived from dienes and/or olefins, and may be, for example, 99% by mass or more of units derived from dienes and/or olefins.

The polymer chain (A) may have a polymer block (a2) having units derived from an aromatic vinyl monomer. Examples of the aromatic vinyl monomer that forms the polymer block (a2) include the aromatic vinyl monomers exemplified for the polymer block (a1) above, and among these, 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. The other unsaturated monomers are not particularly limited as long as they are compounds having a polymerizable double bond, and examples thereof include vinyl esters such as vinyl acetate and vinyl propionate; unsaturated carboxylic acids and their esters such as (meth)acrylic acid, maleic anhydride, methyl (meth)acrylate, and ethyl (meth)acrylate; and vinyl silanes 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) preferably does not have any diene and/or olefin-derived units.

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

Examples of the polymer chain (A) composed of the polymer block (a1) and the polymer block (a2) include styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, hydrogenated products of styrene-butadiene-styrene block copolymers (e.g., styrene-ethylene/butylene-styrene block copolymer (SEBS), styrene-butadiene/butylene-styrene block copolymer), styrene-isoprene block copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products of styrene-isoprene-styrene block copolymers (e.g., styrene-ethylene/propylene-styrene block copolymer (SEPS)). In addition, among these block copolymers, those in which the butadiene block becomes a butadiene/styrene block and those in which the isoprene block becomes an isoprene/styrene block are exemplified. In the above notation, each block is divided by "-", and the notation "/" in each block represents the monomer unit constituting the block.

The polymer chain (A) is preferably one in which polymer block (a2) is bonded to both sides of polymer block (a1). This allows the polymer chain (A) to function as an elastomer, and the mechanical strength of the film can be further increased. In this case, the polymer chain (A) may be a triblock copolymer, a multiblock copolymer, or a radial block copolymer, but a triblock copolymer is preferable because it is easy to control the properties of the polymer chain (A). Examples of such copolymers include styrene-butadiene-styrene block copolymers and hydrogenated products thereof, styrene-isoprene-styrene block copolymers and hydrogenated products thereof, etc.

In the polymer chain (A), the content of the polymer block (a2) may be 0% by mass (consisting only of the polymer block (a1)), but it is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. This makes the polymer chain (A) have a good balance of soft and hard components, making it easier to increase 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, even more preferably 55% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less. In addition, the content of units derived from aromatic vinyl monomers 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, even more preferably 15% by mass or more, and is preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. When the polymer chain (A) has multiple different (co)polymers, the weighted average is calculated based on the blending ratio (other parameters are calculated in a similar manner).

The weight average molecular weight of the polymer chain (A) is preferably 1,000 or more, more preferably 5,000 or more, even more preferably 10,000 or more, even more preferably 30,000 or more, and preferably 300,000 or less, more preferably 250,000 or less, and even more preferably 200,000 or less. By setting the weight average molecular weight of the polymer chain (A) within such a range, it is possible to ensure the mechanical strength of the resin composition and to easily improve the moldability of the resin composition.

2. Polymer chain (B)
The polymer chain (B) has a unit (b1) derived from a (meth)acrylic monomer (hereinafter, sometimes referred to as "(meth)acrylic unit (b1)"), which becomes a portion exhibiting negative birefringence. In addition, the presence of the polymer chain (B) can also increase the transparency of the film.

In this specification, the term "(meth)acrylic monomer" refers to a monomer containing an acrylic group to which a hydrogen atom or an alkyl group (preferably an alkyl group having 1 to 4 carbon atoms) is bonded at the α-position and/or β-position, and the alkyl group may have at least a portion of the hydrogen atoms substituted with a hydroxyl group or a halogen group. The term "(meth)acrylic monomer" refers to a monomer preferably having an acrylic group or a methacrylic group. The term "(meth)acrylic monomer" also refers to (meth)acrylic acid (i.e., free acid) and its derivatives, which include esters, salts, acid amides, etc.

As the (meth)acrylic monomer, a (meth)acrylic acid ester is preferred. Examples of the (meth)acrylic acid ester 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.

Examples of (meth)acrylic acid esters having a linear or branched aliphatic hydrocarbon group include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 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, dodecyl (meth)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 even more preferably a C1-6 alkyl group. In this specification, the terms "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 cycloalkyl (meth)acrylates such as cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate; and crosslinked cyclic (meth)acrylates such as isobornyl (meth)acrylate. The cycloalkyl group of the cycloalkyl (meth)acrylate is preferably a C3-20 cycloalkyl group, more preferably a C4-12 cycloalkyl group, and even more preferably a C5-10 cycloalkyl group.

Examples of (meth)acrylic acid esters having an aromatic hydrocarbon group include aryl (meth)acrylates such as phenyl (meth)acrylate, tolyl (meth)acrylate, xylyl (meth)acrylate, naphthyl (meth)acrylate, binaphthyl (meth)acrylate, and anthryl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and aryloxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate. The aryl group of the aryl (meth)acrylate is preferably a C6-20 aryl group, and more preferably a C6-14 aryl group. The aralkyl group of the 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, and 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, or an epoxy group. In particular, in a (meth)acrylic acid ester having a linear or branched aliphatic hydrocarbon group, it is preferable that the aliphatic hydrocarbon group has a hydroxy group, an amino group, a halogen group, an alkoxy group, or an epoxy group. Examples of such (meth)acrylic acid esters include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; alkyl halide (meth)acrylates such as chloromethyl (meth)acrylate and 2-chloroethyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate; and epoxyalkyl (meth)acrylates such as glycidyl (meth)acrylate. The alkyl groups of the hydroxyalkyl (meth)acrylate and epoxyalkyl (meth)acrylate are preferably C1-12 alkyl groups, and more preferably C1-6 alkyl groups. 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.

(Meth)acrylic monomers also include monomers exemplified as (meth)acrylic monomer A and (meth)acrylic monomer B having a protic hydrogen atom-containing group, which will be described later.

It is preferable that the polymer chain (B) has a ring structure in the main chain. That is, it is preferable that the polymer chain (B) has a unit (b2) (hereinafter, sometimes referred to as "ring structure unit (b2)") having a ring structure in the main chain of the polymer chain (B). By having the polymer chain (B) have a ring structure in the main chain, the transparency and heat resistance of the film can be improved. In addition, improvements in solvent resistance, dimensional stability, surface hardness, adhesion, 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 a part or all of the (meth)acrylic monomer in the ring structure, or may be a ring structure introduced separately from the (meth)acrylic monomer. In this way, when a component (also called a ring structure forming monomer) necessary for forming a ring structure in the main chain of the polymer chain is contained in the ring structure as a part or all of the (meth)acrylic monomer, for example, two carboxylic acid groups of adjacent (meth)acrylic units (b1) may be linked by acid anhydride conversion, imidization, etc. In addition, when one of the adjacent (meth)acrylic units (b1) has a hydroxy group and/or an amino group, the hydroxy group and/or amino group of this one (meth)acrylic unit (b1) and the carboxylic acid group of the other (meth)acrylic unit (b1) may be condensed to form a ring structure. 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 may be copolymerized.

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., and is preferably a 5-membered ring structure or a 6-membered ring structure.

From the viewpoint of the heat resistance of the resin composition, preferred examples of the ring structure include a lactone ring structure, a lactam ring structure, a cyclic imide structure (e.g., a succinimide structure, a glutarimide structure, etc.), a cyclic anhydride structure (e.g., a succinic anhydride structure, a glutaric anhydride structure, etc.), etc. The main chain of the polymer chain (B) may contain only one type of these ring structures, or two or more types. Among these, a cyclic imide structure is preferred, and a succinimide structure is more preferred.

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

Examples of lactone ring structures include those disclosed in JP-A-2004-168882, but a structure represented by the following formula (1a) is preferred because it is easy to introduce a lactone ring structure, specifically, because the polymerization yield of the precursor (polymer before lactone cyclization) is high, it is possible to increase the lactone ring content in the cyclization condensation reaction of the precursor, and it is possible to prepare a polymer having a unit derived from (meth)acrylate as the precursor. Furthermore, a structure represented by the following formula (1b) is preferred as the lactam ring structure. In formula (1a) or formula (1b), R ¹ , R ² and R ³ each independently represent a hydrogen atom or a substituent.

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

In the lactone ring structure of formula (1a) or the lactam ring structure of formula (1b), from the viewpoint of facilitating the production of a resin composition having excellent heat resistance, it is preferable that R ¹ and R ² are each independently a hydrogen atom or a C1-20 alkyl group and R ³ is a hydrogen atom or a methyl group, and it is more preferable that 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.

A lactone ring structure and/or lactam ring structure can be introduced into the polymer chain (B) by cyclization condensation of the hydroxy group and/or amino group of the unit derived from (meth)acrylic monomer A with the ester group of the unit derived from (meth)acrylic acid ester adjacent to the unit derived from the (meth)acrylic monomer A. As a polymerization component, the (meth)acrylic monomer A having a hydroxy group and/or amino group is essential, and the (meth)acrylic monomer B includes the monomer A. The monomer B may or may not be the same as the monomer A. When the monomer B is the same as the monomer A, the result is a homopolymerization of the monomer A.

Examples of (meth)acrylic monomer A include (meth)acrylic monomer A1 having a hydroxy group and (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)acrylates (e.g., methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, t-butyl 2-(hydroxymethyl)acrylate), alkyl 2-(hydroxyethyl)acrylates (e.g., methyl 2-(hydroxyethyl)acrylate, ethyl 2-(hydroxyethyl)acrylate), and the like. Preferred are 2-(hydroxymethyl)acrylic acid and alkyl 2-(hydroxymethyl)acrylates, which are monomers having a hydroxyallyl moiety. Particularly preferred are methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate.

An example of the (meth)acrylic monomer A2 having an amino group is a compound in which the hydroxy group of the monomer A1 is replaced with 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 preferred, and examples thereof include (meth)acrylic acid, alkyl (meth)acrylates (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, etc.), aryl (meth)acrylates (e.g., phenyl (meth)acrylate, benzyl (meth)acrylate, etc.), 2-(hydroxyalkyl)alkyl acrylates (e.g., 2-(hydroxymethyl)alkyl acrylates such as methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate, and 2-(hydroxyethyl)alkyl acrylates such as methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate).

The polymer chain (B) may have only one type of lactone ring structure or lactam ring 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 (i.e., a structure derived from a maleic anhydride monomer) or a succinimide structure (i.e., a structure derived from a maleimide monomer) as a ring structure of the main chain, the succinic anhydride structure or the succinimide structure is preferably a structure represented by the following formula (2): In the following formula (2), ^R4 and ^R5 each independently represent a hydrogen atom or a methyl group, ^R6 represents a hydrogen atom or a substituent, ^X1 represents an oxygen atom or a nitrogen atom, n1=0 when ^X1 is an oxygen atom, and n1=1 when ^X1 is a nitrogen atom.

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

When ^X1 is an oxygen atom, the ring structure represented by formula (2) becomes a succinic anhydride structure. The succinic anhydride structure can be introduced into the polymer chain (B) by, for example, copolymerizing maleic anhydride with a (meth)acrylic monomer (e.g., (meth)acrylic acid ester, etc.). When the polymer chain (B) has a succinic anhydride structure, maleic anhydride becomes a ring structure-forming monomer.

When ^X1 is a nitrogen atom, the ring structure represented by formula (2) becomes a succinimide structure. The succinimide structure can be introduced into the polymer chain (B) by, for example, copolymerizing an N-substituted maleimide with a (meth)acrylic monomer (e.g., a (meth)acrylic acid ester). Examples of the succinimide structure include a succinimide structure unsubstituted at the N-position, 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. As the maleimide that gives the succinimide structure, there can be used maleimide unsubstituted at the N-position, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-naphthylmaleimide, N-benzylmaleimide, etc., and at least one selected from the group consisting of N-cyclohexylmaleimide and N-phenylmaleimide is preferable. 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 ^X1 is a nitrogen atom, from the viewpoint of easiness in obtaining a resin composition excellent in heat resistance, it is preferable that ^R4 and ^R5 are hydrogen atoms and ^R6 is a C3-20 cycloalkyl group or a C6-20 aromatic group (an aryl group, an aralkyl group, etc.), and it is more preferable that ^R4 and ^R5 are hydrogen atoms and ^R6 is a cyclohexyl group or a phenyl group.

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

When the polymer chain (B) has a glutarimide structure or a glutaric anhydride structure as a ring structure of the main chain, the glutarimide structure or the glutaric anhydride structure is preferably a structure represented by the following formula (3): In the following formula (3), ^R7 and ^R8 each independently represent a hydrogen atom or an alkyl group, ^R9 represents a hydrogen atom or a substituent, ^X2 represents an oxygen atom or a nitrogen atom, n2=0 when ^X2 is an oxygen atom, and n2=1 when ^X2 is a nitrogen atom.

In formula (3), the alkyl group of R ⁷ and R ⁸ is preferably a linear or branched alkyl group, such as a C1-8 alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, an isohexyl group, an n-heptyl group, an isoheptyl group, an n-octyl group, or a 2-ethylhexyl group. From the viewpoint of easiness in obtaining a resin composition having excellent heat resistance, R ⁷ and R ⁸ are each preferably independently a hydrogen atom or a C1-4 alkyl group, and more preferably a hydrogen atom or a methyl group.

The substituent of R ⁹ in formula (3) may be an organic residue such as a hydrocarbon group, for example a C1-20 hydrocarbon group which may have a substituent. The hydrocarbon group may be a saturated or unsaturated linear, branched or cyclic aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be, for example, a C1-20 alkyl group such as a methyl group, an ethyl group, an n-propyl group, or an isopropyl group (preferably a C1-10 alkyl group, more preferably a C1-6 alkyl group); a C2-20 alkenyl group such as an ethenyl group or a propenyl group (preferably a C2-10 alkenyl group, more preferably a C2-6 alkenyl group); a C3-20 cycloalkyl group such as a cyclopentyl group or a cyclohexyl group (preferably a C4-12 cycloalkyl group, more preferably a C5-8 cycloalkyl group); and the like. Examples of aromatic hydrocarbon groups include C6-20 aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenyl (preferably C6-14 aryl, and more preferably C6-10 aryl); and C7-20 aralkyl groups such as benzyl and phenylethyl (preferably C7-15 aralkyl, and more preferably C7-11 aralkyl). These hydrocarbon groups may have a substituent such as a halogen. Among these, R 9 is preferably an alkyl ^group , a cycloalkyl group, an aryl group, or an aralkyl group, and more preferably a methyl group, a cyclohexyl group, a phenyl group, or a tolyl group, in terms of easiness in obtaining a resin composition having excellent heat resistance.

When ^X2 is an oxygen atom, the ring structure represented by formula (3) becomes a glutaric anhydride structure. The glutaric anhydride structure can be introduced into the polymer chain (B) by, for example, converting two carboxylic acid groups of adjacent units derived from a (meth)acrylic monomer into acid anhydrides.

When ^X2 is a nitrogen atom, the ring structure represented by formula (3) becomes a glutarimide structure. The glutarimide structure can be introduced into the polymer chain (B) by, for example, imidizing two carboxylic acid groups of adjacent units derived from a (meth)acrylic monomer, or by cyclizing and condensing an amide group of adjacent units derived from a (meth)acrylic acid amide and an ester group of adjacent units derived from a (meth)acrylic acid ester. When the polymer chain (B) has a glutarimide structure, the (meth)acrylic monomer becomes a monomer for forming a ring structure.

In the ring structure of formula (3), when the glutarimide structure is one in which ^X2 is a nitrogen atom, it is more preferable that ^R7 and ^R8 are each independently a hydrogen atom or a methyl group, and ^R9 is a methyl group, a cyclohexyl group, a phenyl group, or a tolyl group, in terms of ease of obtaining a resin composition having excellent heat resistance, and it is particularly preferable that ^R7 and ^R8 are each independently a hydrogen atom or a methyl group, and ^R9 is a cyclohexyl group or a phenyl group.

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

Of the ring structures described above, from the viewpoint of imparting good surface hardness, solvent resistance, adhesion, barrier properties, and optical properties to the resin composition, it is preferable that the ring structural unit (b2) of the polymer chain (B) contains a lactone ring structure and/or a succinimide structure (a structure derived from a maleimide monomer), and it is more preferable that it contains a succinimide structure.

The content ratio of the ring structure unit (b2) in the main chain in the polymer chain (B) is not particularly limited, but the content ratio of the ring structure unit (b2) in the polymer chain (B) is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and 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 ratio of the ring structure unit (b2) in the main chain in this way, it is possible to impart a good balance between heat resistance and mechanical strength to the resin composition. In addition, since the ring structure of the main chain in the polymer chain (B) makes it easier to develop positive orientation birefringence, the NZ coefficient may be 1 or more depending on the composition of the polymer chain (B), the amount of the polymer chain (A), and the degree of stretching of the film. The content ratio of the ring structure unit (b2) described here means the content ratio of units having a ring structure contained in the main chain of the polymer chain (B), and means, for example, the content ratio of the structures represented by the above formulas (1) to (3).

The polymer chain (B) may further have a unit (b3) derived from a vinyl monomer 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, and examples thereof include vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, vinyl toluene, methoxystyrene, α-methylstyrene, and 2-vinylpyridine; and vinyl silanes such as vinyl trimethoxysilane and γ-(meth)acryloyloxypropyl methoxysilane. For example, if the polymer chain (B) has a unit derived from an aromatic vinyl monomer, it becomes easy to adjust the refractive index and phase difference characteristics of the resin composition. For details of the aromatic vinyl monomer, see 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 types of monomer components, it is preferable that the polymer chain (B) is a random copolymer.

The amount of the units (b3) derived from the vinyl monomer copolymerizable with the (meth)acrylic monomer is, for example, preferably 15 to 50 parts by mass, more preferably 20 to 40 parts by mass, and even more preferably 20 to 30 parts by mass, per 100 parts by mass of the polymer chain (B).

The resin composition used in the present invention preferably contains a copolymer (P) containing a polymer chain (A) and a polymer chain (B). In addition, it is more preferable that the copolymer (P) has a polymer chain (A) having a polymer block (a1) having a unit derived from a diene and/or olefin and a polymer block (a2) having a unit derived from an aromatic vinyl monomer, and a polymer chain (B) having a unit derived from a (meth)acrylic monomer (b1). In the copolymer (P), it is preferable that the polymer chain (B) is grafted to the polymer chain (A), it is more preferable that the polymer chain (B) is grafted to the polymer block (a1) of the polymer chain (A), and it is most preferable that the polymer chain (B) is bonded to the unit derived from a diene and/or olefin of the polymer block (a1). 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) is preferably a triblock copolymer. According to the glossary of basic terms in polymer science by the International Union of Pure and Applied Chemistry (IUPAC) Polymer Nomenclature Commission, a graft polymer is described as "a polymer having one or more blocks bonded to the main chain as side chains, and these side chains have different constitutional (chemical structure) or arrangement characteristics from the main chain." The graft copolymer can be obtained by known manufacturing methods such as the chain transfer reaction method, the polymer initiator method, the coupling method, the macromonomer method, and the surface graft method. Only one of these methods may be adopted, or a combination of multiple methods may be used. For details of these methods, refer to the 6th edition of the Chemical Handbook (Applied Chemistry Edition) edited by the Chemical Society of Japan.

When the polymer chain (B) is bonded to a diene and/or olefin-derived unit of the polymer block (a1), the polymer chain (B) may be bonded to a carbon atom of the main chain of the diene and/or olefin-derived unit, or 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 of the main chain of the copolymer block (a1), or to an adjacent carbon atom of the double bond. Alternatively, the polymer chain (B) may be bonded to a diene-derived double bond bonded to the main chain of the copolymer block (a1) as a substituent (side chain), or to an adjacent carbon atom of the double bond.

3. Additive (C)
The additive (C) is preferably at least one selected from the group consisting of triazine compounds, triester phosphite compounds (preferably triaryl phosphite compounds), and tri-substituted phenyl compounds, and among these, compounds having _C2 or _C3 symmetry are preferred. The additive (C) may be used alone or in combination of two or more.

<Triazine-based compounds>
The triazine compound preferably has a structural formula represented by the following formula (4).

R ^a1 to R ^a3 are each independently an alicyclic hydrocarbon group, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or one or more hydrogen atoms of these hydrocarbon groups substituted with any substituent. R ^a1 to R ^a3 may be the same structure or different, and it is more preferable that two or three of R ^a1 to R ^a3 have the same structure, and it is even more preferable that three of R ^a1 to R ^a3 have the same structure. It is preferable that at least one of R ^a1 to R ^a3 has an aromatic ring, and it is more preferable that all of R ^a1 to R ^a3 have an aromatic ring. It is also preferable that at least one of R ^a1 to R ^a3 has a hydroxy group.

Examples of triazine compounds include 2,4-diphenyl-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2,4-bis(2-methylphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2,4-bis(2-methoxyphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2,4-bis(2-ethylphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2,4-bis(2-ethoxyphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2,4-diphenyl-6-[2-hydroxy-4-(2- methacryloyloxyethoxy)]-s-triazine, 2,4-bis(2-methylphenyl)-6-[2-hydroxy-4-(2-methacryloyloxyethoxy)]-s-triazine, 2,4-bis(2-methoxyphenyl)-6-[2-hydroxy-4-(2-methacryloyloxyethoxy)]-s-triazine, 2,4-bis(2-ethylphenyl)-6-[2-hydroxy-4-(2-methacryloyloxyethoxy)]-s-triazine, 2,4-bis(2-ethoxyphenyl)-6-[2-hydroxy-4-(2-methacryloyloxyethoxy)]-s-triazine, 2,4-bis(2,4-dimethoxyphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2,4 -Bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)-s-triazine, 2,4-bis(2,4-diethoxyphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2,4-bis(2,4-diethylphenyl)-6-[2-hydroxy-4-(2-acryloyloxyethoxy)]-s-triazine, 2-[2-hydroxy-4-(11-acryloyloxy-undecyloxy)phenyl]-4,6-diphenyl-1,3,5-triazine, 2-[2-hydroxy-4-(11-methacryloyloxy-undecyloxy)phenyl]4,2-[4,6-bis(biphenyl-4-yl)-1,3,5-triazin-2-yl] -5-[(2-ethylhexyl)oxy]phenol, 6-diphenyl-1,3,5-triazine, 2-[2-hydroxy-4-(2-methacryloyloxyethoxy)phenyl]-4,6-diphenyl-1,3,5-triazine, 2-[2-hydroxy-4-(11-acryloyloxy-undecyloxy)phenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(11-methacryloyloxyundecyloxy)phenyl]-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(2-methacryloyloxyethoxy)phenyl]-1,3,5-triazine, etc.

<Phosphite triester compound>
The phosphite triester compound preferably has a structural formula represented by the following formula (2).

R ^b1 to R ^b3 are each independently an alicyclic hydrocarbon group, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or one or more of the hydrogen atoms of these groups substituted with any substituent, but R ^b1 to R ^b3 are preferably an aromatic hydrocarbon group or an aromatic hydrocarbon group in which one or more of the hydrogen atoms have been substituted with any substituent, and R ^b1 to R ^b3 are more preferably an aromatic hydrocarbon group in which one or more of the hydrogen atoms have been substituted with any substituent. R ^b1 to R ^b3 may have the same structure or different structures, and it is more preferable that two or three of R ^b1 to R ^b3 have the same structure, and it is even more preferable that three of R ^b1 to R ^b3 have the same structure.

Examples of compounds represented by formula (5) include triaryl phosphites such as triphenyl phosphite, tricresyl phosphite, tris(ethylphenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite, and tris(hydroxyphenyl)phosphite; trimethyl phosphite, triethyl phosphite, tributyl phosphite, trioctyl phosphite, tris(2-ethylhexyl)phosphite, trinonyl phosphite, tridecyl phosphite, triisodecyl phosphite, and trioctyl phosphite. Examples of such phosphites include trialkyl phosphites such as decyl phosphite, tristearyl phosphite, tris(2-chloroethyl)phosphite, and tris(2,3-dichloropropyl)phosphite; tricycloalkyl phosphites such as tricyclopentyl phosphite and tricyclohexyl phosphite; and arylalkyl phosphites such as phenyl didecyl phosphite, diphenyl decyl phosphite, diphenyl isodecyl phosphite, diphenyl isooctyl phosphite, phenyl isooctyl phosphite, and 2-ethylhexyl diphenyl phosphite. Among these, triaryl phosphites are preferred, and tris(2,4-di-t-butylphenyl)phosphite is more preferred.

<Tri-substituted phenyl compounds>
The tri-substituted phenyl compound preferably has a structural formula represented by the following formula (6).

R ^c1 to R ^c3 are each independently an aromatic hydrocarbon ring or a ring in which one or more hydrogen atoms of an aromatic hydrocarbon ring are substituted with any substituent. R ^c1 to R ^c3 may be the same structure or different, and it is more preferable that two or three of R ^c1 to R ^c3 have the same structure, and it is even more preferable that three of R ^c1 to R ^c3 have the same structure.

At least one of R ^c1 to R ^c3 preferably has a benzene ring or a naphthalene ring, more preferably at least one has a benzene ring, and further preferably R ^c1 , R ^c2 , and R ^c3 each have a benzene ring. The substituent in formula (6) is not particularly limited, and examples thereof include an alkyl group, an alkoxy group, an alkylthiooxy group (alkylthio group), an alkyloxycarbonyl group, an alkylsulfonyl group, an aryl group, an aralkyl group, an aryloxy group, an arylthiooxy group (arylthio group), an aryloxycarbonyl group, an arylsulfonyl group, an arylsulfinyl group, an amide group (-NHCOR), a sulfonamide group (-NHSO ₂ R), a carboxy group (carboxylic acid group), a benzothiazole group, a halogenoalkyl group, a cyano group, a halogeno group, a hydroxyl group, a nitro group, an amino group, and a sulfo group (sulfonic acid group). However, it is preferable that R ^c1 to R ^c3 are an unsubstituted aromatic hydrocarbon ring. It is particularly preferred that the tri-substituted phenyl compound is one in which R ^c1 to R ^c3 are benzene rings that are not substituted with any substituent (the tri-substituted phenyl compound is triphenylbenzene).

The film preferably contains 1 to 15% by mass of additive (C), more preferably 2 to 10% by mass, and even more preferably 2.5 to 7.5% by mass.

4. Method for Producing Polymer Chain (A) and Copolymer (P) The method for producing the polymer chain (A) having units derived from a diene and/or an olefin is not particularly limited, and the polymer chain may be produced by a known method.

As described above, the resin composition used in the present invention preferably contains a copolymer (P) having a polymer chain (A) having a polymer block (a1) having units derived from a diene and/or olefin and a polymer block (a2) having units derived from an aromatic vinyl monomer, and a polymer chain (B) having units (b1) derived from a (meth)acrylic monomer. An example of a method for producing such a copolymer (P) is described below.

The copolymer (P) can be easily produced by addition polymerization of a monomer component forming the polymer chain (B) to the polymer chain (A). Therefore, the copolymer (P) is preferably obtained by polymerizing a monomer component containing a (meth)acrylic monomer in the presence of a copolymer (hereinafter referred to as "raw copolymer (P1)") having a polymer block (a1) having units derived from a diene and/or olefin and a polymer block (a2) having units derived from an aromatic vinyl monomer. In this specification, the "raw copolymer (P1)" may be simply referred to as the "copolymer (P1)". For details of the raw copolymer (P1), see the explanation of the polymer chain (A) above.

In the copolymer (P), it is preferable that the polymer chain (B) is grafted to the polymer block (a1) of the polymer chain (A). In particular, it is preferable that the polymer chain (B) is bonded to the diene and/or olefin-derived unit of the polymer block (a1). In this case, the polymer chain (B) may be bonded to a carbon atom of the main chain of the diene and/or olefin-derived unit, or 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 double bond derived from a diene in the main chain of the copolymer block (a1), or to an adjacent carbon atom of the double bond. Alternatively, the polymer chain (B) may be bonded to a double bond derived from a diene bonded to the main chain of the copolymer block (a1) as a substituent (side chain), or to an adjacent carbon atom of the double bond.

As the raw copolymer (P1), it is preferable to use one having an olefinic double bond amount of 0.030 mmol/g or more and 2.3 mmol/g or less. By using the raw copolymer (P1) having an olefinic double bond amount of 0.030 mmol/g or more, it is easy to obtain a copolymer (P) having high transparency. On the other hand, by using the raw copolymer (P1) having an olefinic double bond amount of 2.3 mmol/g or less, it is easy to obtain a copolymer (P) with less generation of gelling matter. The olefinic double bond amount of the raw copolymer (P1) is more preferably 0.040 mmol/g or more, even more preferably 0.050 mmol/g or more, and more preferably 2.0 mmol/g or less. The olefinic double bond amount of the raw copolymer (P1) can be determined by ¹ H-NMR measurement or iodine titration method.

The copolymer (P) can be obtained by a manufacturing method including a step (polymerization step) of polymerizing a monomer component containing a (meth)acrylic monomer in the presence of the raw copolymer (P1). In the polymerization step, the monomer component containing a (meth)acrylic monomer is polymerized to form a polymer chain (B), and the raw copolymer (P1) gives a polymer chain (A), thereby obtaining a copolymer (P) in which the polymer chain (B) is bonded to the diene and/or olefin-derived unit of the polymer block (a1) of the polymer chain (A). The raw copolymer (P1) can be obtained, for example, by polymerizing the monomer components constituting the polymer block (a1) to form the polymer block (a1), and then polymerizing the monomer components constituting the polymer block (a2) in the presence of the polymer block (a1).

In order to bond the polymer chain (B) to the diene and/or olefin-derived units of the polymer block (a1) in the polymerization step, it is preferable to abstract highly active hydrogen from the vinyl position, allyl position, etc. of the double bond (olefinic double bond) of the diene and/or olefin-derived units of the polymer block (a1) of the raw copolymer (P1) in the polymerization step. This allows radicals to be generated at the relevant positions, and the monomer components that form the polymer chain (B) can be addition polymerized. In this case, as explained above, by adjusting the amount of olefinic double bonds in the raw copolymer (P1), the transparency of the copolymer (P) can be increased and the occurrence of gelation can be easily suppressed.

In the polymerization step, the raw material copolymer (P1) may be used alone or in combination of two or more. In the latter case, it becomes easier to adjust the weight average molecular weight and physical properties of the resin composition.

In addition to the (meth)acrylic monomer, the monomer components used to form the polymer chain (B) may also include a monomer having a polymerizable double bond in a ring structure as a monomer that provides a ring structure unit. For example, when forming a polymer chain (B) having a ring structure in the main chain, a monomer having a polymerizable double bond in a ring structure may be used, or a monomer that can form a ring structure by performing a ring structure formation process after the polymerization process may be used. In addition, other unsaturated monomers may also be used. For details of these monomer components, see the explanations of the (meth)acrylic monomer that forms the polymer chain (B), the monomer that provides the ring structure of the polymer chain (B), and the other unsaturated monomers that form the polymer chain (B).

The polymerization of the monomer components can be carried out using known polymerization methods such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization, but it is preferable to use solution polymerization. If a solution polymerization method is used, it is possible to prevent the inclusion of minute foreign matter in the copolymer (P), making it easier to suitably apply the copolymer (P) to optical material applications and the like. As the polymerization method, for example, either a batch polymerization method or a continuous polymerization method can be used. During polymerization, the monomer components may be charged all at once or may be added in portions.

The amount of raw copolymer (P1) used during polymerization is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, particularly preferably 9 parts by mass or more, most preferably 12 parts by mass or more, and also preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, based on 100 parts by mass of the total of raw copolymer (P1) and monomer components. The amount of monomer components used is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, even more preferably 65 parts by mass or more, and also preferably 99 parts by mass or less, more preferably 97 parts by mass or less, even more preferably 95 parts by mass or less, even more preferably 93 parts by mass or less, particularly preferably 91 parts by mass or less, and most preferably 88 parts by mass or less, based on 100 parts by mass of the total of raw copolymer (P1) and monomer components.

The polymerization solvent can be appropriately selected according to the composition of the monomer components, and organic solvents used in normal 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; ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and anisole; esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; alcohols such as methanol, ethanol, isopropanol, and n-butanol; nitriles such as acetonitrile, propionitrile, butyronitrile, and benzonitrile; chloroform; and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more.

The polymerization reaction between the raw material copolymer (P1) and the monomer components is preferably carried out in the presence of a polymerization catalyst (polymerization initiator). Examples of the polymerization catalyst include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, dimethyl-2,2'-azobis(2-methylpropionate), and 4,4'-azobis(4-cyanopentanoic acid); persulfates such as potassium persulfate; and organic peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropylcarbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyoctoate, t-amylperoxyisononanoate, t-amylperoxyisopropylcarbonate, and t-amylperoxy2-ethylhexylcarbonate. These may be used alone or in combination of two or more. Among these, it is preferable to use an organic peroxide that has a strong hydrogen abstracting power, and it is particularly preferable to use a peroxycarbonate-based peroxide. The amount of the polymerization catalyst used is preferably, for example, 0.01 to 1 part by mass per 100 parts by mass of the monomer component.

The total concentration of the raw copolymer (P1) and the monomer components in the reaction solution is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 80% by mass or less, and more preferably 70% by mass or less. 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, it is also possible to appropriately add the raw copolymer (P1), the monomer components, the polymerization catalyst, the reaction solvent, etc.

The polymerization reaction is preferably carried out in an atmosphere or flow of an inert gas such as nitrogen gas. In order to reduce the amount of residual monomer, an azo compound and a peroxide may be used in combination as a polymerization initiator. The reaction temperature is preferably 50°C to 200°C. The reaction time may be adjusted as appropriate while observing the progress of the copolymerization reaction and the degree of gelation, and is preferably carried out for, for example, 1 hour to 20 hours.

The above polymerization process produces a copolymer (P) in which a polymer chain (B) containing a unit (b1) derived from a (meth)acrylic monomer is bonded to a polymer chain (A). In the polymerization process, when a (meth)acrylic monomer and a monomer having a polymerizable double bond in a ring structure (e.g., maleic anhydride or maleimide) are used as the monomer components, a copolymer (P) in which a unit derived from a (meth)acrylic monomer and a polymer chain (B) having a ring structure unit (succinic anhydride structure, succinimide structure) are bonded to a polymer chain (A) is produced.

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), it is preferable to carry out a ring structure formation process following the polymerization process. In the ring structure formation process, a ring structure is formed in the main chain of the polymer chain (B) having the (meth)acrylic unit formed in the polymerization process. Specifically, the substituents of adjacent (meth)acrylic units of the polymer chain (B) having the (meth)acrylic unit formed in the polymerization process are condensed to form a ring structure in the main chain of the polymer chain (B). The cyclization condensation reaction includes an esterification reaction, an acid anhydride reaction, an amidation reaction, an imidization reaction, and the like. For example, a glutaric anhydride structure can be formed by converting two carboxylic acid groups of adjacent (meth)acrylic units into acid anhydrides, and a glutarimide structure can be formed by imidization. Furthermore, when one of the adjacent (meth)acrylic units has a protic hydrogen atom-containing group such as a hydroxyl group or an amino group, a lactone ring structure and/or a lactam ring structure can be formed by condensing the protic hydrogen atom-containing group of one (meth)acrylic unit with the carboxylic acid group of the other (meth)acrylic unit.

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). As the cyclization catalyst, at least one selected from the group consisting of acids, bases, and salts thereof can be used. The acids, bases, and salts thereof may be organic or inorganic, and are not particularly limited. In particular, it is preferable to use an organic phosphorus compound as the catalyst for the cyclization reaction. By using an organic phosphorus compound as the cyclization catalyst, the cyclization condensation reaction can be carried out efficiently, and coloration of the resulting copolymer (P) can be reduced.

Examples of organic phosphorus compounds that can be used as cyclization catalysts include alkyl (aryl) phosphonic acids and their monoesters or diesters; dialkyl (aryl) phosphinic acids and their esters; alkyl (aryl) phosphonic acids and their monoesters or diesters; alkyl (aryl) phosphinic acids and their esters; monoesters, diesters or triesters of phosphorous acid; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, lysine phosphate, ... Examples of the phosphate monoester, diester, or triester include diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, and triphenyl phosphate; mono-, di-, or tri-alkyl(aryl)phosphine; alkyl(aryl)halogen phosphine; mono-, di-, or tri-alkyl(aryl)phosphine oxide; and tetraalkyl(aryl)phosphonium halide. These may be used alone or in combination of two or more. Among these, phosphate monoester or diester is particularly preferred because of its high catalytic activity and low colorability. The amount of the cyclization catalyst used is preferably 0.001 to 1 part by mass per 100 parts by mass of the copolymer obtained in the polymerization step.

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

The ring structure formation step is preferably carried out under heating. In this case, the polymerization solution containing the polymerization solvent obtained in the polymerization step may be heated as it is, or may be heated after the polymerization solvent is devolatilized, or both may be combined. Examples of reactors used in the cyclization condensation reaction include autoclaves, kettle-type reactors, devices consisting of a heat exchanger and a devolatilization tank, and vented extruders.

In the ring structure formation step, it is preferable to carry out devolatilization. Devolatilization can be carried out by reducing the pressure inside the reactor with a vacuum pump or the like. Devolatilization removes the polymerization solvent used in the polymerization step and brought to the ring structure formation step, and the alcohol by-product of the cyclization condensation reaction, etc., and can reduce the remaining volatile content in the resulting copolymer (P). In addition, since the alcohol by-product of the cyclization condensation reaction is removed, the reaction equilibrium is inclined toward the product side, which is favorable. Furthermore, devolatilization removes low molecular weight compounds, which can suppress the contamination of the cast roll during film molding and the occurrence of silver streaks during injection molding.

When the cyclization condensation reaction is carried out while devolatilization is being performed, it is preferable to carry out the cyclization condensation reaction under reduced pressure in order to carry out the devolatilization efficiently. The reduced pressure in the cyclization condensation reaction is, for example, preferably 90 kPa or less in absolute pressure, more preferably 80 kPa or less, and even more preferably 70 kPa or less. On the other hand, in order to avoid excessive specifications of the equipment for achieving the reduced pressure state and to keep equipment costs low, the absolute pressure during the reduction is preferably 0.1 kPa or more, and more preferably 1 kPa or more. Note that when the cyclization condensation reaction is carried out without devolatilization, the cyclization condensation reaction may be carried out under normal pressure or under pressure.

When using an extruder with a vent, the extruder preferably has a cylinder, a screw provided within the cylinder, and a heating means. The cylinder is provided with one or more vents. The vent is preferably provided at least downstream of the raw material input section with respect to the transport direction within the extruder, and may also be provided upstream of the raw material input section.

The copolymer fed into the extruder undergoes a cyclization condensation reaction while being kneaded by the screw and transported from the upstream side to the downstream side of the extruder, and the copolymer (P) is discharged from the downstream side of the extruder. A die is preferably provided on the downstream side of the extruder, and the copolymer (P) can be molded into a desired shape (film or rod). For example, pellets can be produced by cutting the resin molded into a rod shape into small pieces.

When the cyclization condensation reaction is carried out in the presence of a cyclization catalyst in the ring structure formation step, it is preferable to add a deactivator after or during the cyclization condensation reaction. For example, when a resin composition containing copolymer (P) is pelletized or filmed, if the cyclization catalyst remains in the resin composition, the cyclization condensation reaction may generate alcohol, etc., which may cause undesired foaming. However, by adding a deactivator 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 explained above, an organic phosphorus compound is preferably used as the cyclization catalyst, and since the compound is often an acidic substance, it is preferable to use a basic substance as the deactivator. The basic substance is not particularly limited as long as it has the function of stopping the cyclization condensation reaction, but for example, a metal carboxylate, a metal complex, a metal oxide, etc. can be used. Conversely, when a basic substance is used as the cyclization catalyst, an acidic substance that can be used for the cyclization catalyst explained above can be used as the deactivator.

The timing for adding the deactivator is preferably during the cyclization condensation reaction or after the reaction and before the resin composition containing the copolymer (P) is pelletized or filmed. For example, the deactivator may be added to the resin composition in a molten state, or to the resin composition dissolved in a solvent. When the cyclization condensation reaction is carried out using an extruder as described above, the deactivator may be added at a position after the cyclization condensation reaction has been sufficiently carried out in the extruder.

The conversion rates of the various monomers in the polymerization reaction are preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. If the conversion rate of each monomer is lower than 85%, new equipment for recovering the monomers may be required, or the remaining monomers may cause undesired reactions in the next process, resulting in the generation of foreign matter, which may significantly impair productivity.

The following describes the case where the ring structure formation process is not performed. When the ring structure formation process is not performed, devolatilization may be performed following the polymerization process. Examples of reactors that can be used to perform devolatilization include a kettle-type reactor, a device consisting of a heat exchanger and a devolatilization tank, and a vented extruder.

When the ring structure formation step is not performed, devolatilization can be performed by reducing the pressure inside the reactor with a vacuum pump or the like. Devolatilization can reduce the amount of volatile matter remaining in the resulting copolymer (P). Devolatilization also removes low molecular weight compounds, making it possible to suppress contamination of the casting roll during film molding and the occurrence of silver streaks during injection molding.

When the ring structure formation process is not performed, the pressure reduction during devolatilization is, for example, preferably 90 kPa or less in absolute pressure, more preferably 80 kPa or less, and even more preferably 70 kPa or less. On the other hand, in order to avoid excessive equipment specifications for achieving a reduced pressure state and to keep equipment costs low, the absolute pressure during reduction is preferably 0.1 kPa or more, and more preferably 1 kPa or more.

When using an extruder with a vent, the extruder preferably has a cylinder, a screw provided within the cylinder, and a heating means. The cylinder is provided with one or more vents. The vent is preferably provided at least downstream of the raw material input section with respect to the transport direction within the extruder, and may also be provided upstream of the raw material input section.

It is preferable that a die is provided downstream of the extruder, and the copolymer (P) can be extruded from the die to be molded into a desired shape (film or rod). For example, pellets can be produced by cutting the resin molded into a rod shape into small pieces.

The additive (C) may be added appropriately during the production process of the resin composition. For example, the additive (C) may be added during the polymerization process, or when pelletizing the resin composition by devolatilization using a vented extruder or the like, the additive (C) may be added to the extruder, or the additive may be kneaded separately after pelletization.

The weight average molecular weight of the copolymer (P) is preferably 2,000 or more, more preferably 5,000 or more, even more preferably 30,000 or more, and is preferably 600,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less. 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, even more preferably 1.3 times or more, and preferably 10 times or less, more preferably 7 times or less, and even more preferably 5 times or less, of the weight average molecular weight of the polymer chain (A). This makes it easy to impart a good balance between the properties of transparency and mechanical strength to the resin composition.

The refractive index of the copolymer (P) is preferably close to that of the polymer chain (A), which makes it easier to ensure the transparency of the resin composition. Specifically, the difference between the refractive index of the copolymer (P) and that of the polymer chain (A) is preferably less than 0.1, more preferably 0.05 or less, and even more preferably 0.02 or less. From the same viewpoint, the refractive index of the polymer chain (A) in the copolymer (P) and the refractive index of the polymer chain (B) are preferably close to each other, specifically, the difference between the refractive index of the polymer chain (A) and that of the polymer chain (B) is preferably less than 0.1, more preferably 0.05 or less, and 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. In addition to the copolymer (P) described above, the resin composition may contain other polymers. In this case, the resin composition may contain the copolymer (P) as a resin component (matrix resin), or may contain other polymers as a resin component (matrix resin). As the other polymer, a (meth)acrylic polymer (Q) is preferably used because of its excellent compatibility with the copolymer (P). This makes it easier to improve 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 above polymer chain (B), and preferably has the unit derived from the (meth)acrylic acid ester described in the above polymer chain (B). The (meth)acrylic polymer (Q) may have a unit derived from another unsaturated monomer described in the above polymer chain (B). From the viewpoint of increasing the compatibility with the copolymer (P) in the resin composition, it is more preferable that the (meth)acrylic polymer (Q) has the unit (b1) derived from the (meth)acrylic monomer contained in the polymer chain (B) of the copolymer (P). That is, it is preferable that the unit derived from the (meth)acrylic monomer constituting the (meth)acrylic polymer (Q) is the same as the unit (b1) derived from the (meth)acrylic monomer constituting the polymer chain (B).

The (meth)acrylic polymer (Q) preferably has a ring structure, and more preferably has a ring structure in the main chain. This can improve the heat resistance of the resin composition and the film obtained therefrom. Preferred examples of the ring structure in the main chain of the (meth)acrylic polymer (Q) include a lactone ring structure, a cyclic imide structure (e.g., a succinimide structure, a glutarimide structure, etc.), and a cyclic anhydride structure (e.g., a succinic anhydride structure, a glutaric anhydride structure, etc.), and the like. For details of these ring structures, see the explanation of the ring structure of the polymer chain (B) above. In particular, the (meth)acrylic polymer (Q) preferably has a ring structure in the main chain that is the same as the ring structure of the polymer chain (B) of the copolymer (P).

It is preferable that the (meth)acrylic polymer (Q) has the same (meth)acrylic units as the (meth)acrylic units in the polymer chain (B) of the copolymer (P) and has the same ring structural unit as the ring structural unit in the polymer chain (B). This increases the compatibility between the (meth)acrylic polymer (Q) and the copolymer (P), making it easier to improve the transparency and heat resistance of the resin composition and the film obtained therefrom. From the viewpoint of further increasing the heat resistance of the resin composition, it is preferable that the (meth)acrylic polymer (Q) has a ring structural unit containing a cyclic imide structure.

It is convenient to polymerize such a (meth)acrylic polymer (Q) together with the copolymer (P) when polymerizing the copolymer (P). In the method for producing the copolymer (P) described above, the (meth)acrylic polymer (Q) corresponding to the polymer chain (B) of the copolymer (P) is also produced at the same time as the copolymer (P). In this case, by not separating the copolymer (P) and the (meth)acrylic polymer (Q), a resin composition containing the copolymer (P) and the (meth)acrylic polymer (Q) 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 obtain a resin composition. In the above-mentioned method for producing the copolymer (P), after the graft polymerization reaction to the copolymer (P1) is completed, another monomer may be added and a polymerization reaction may be carried out to obtain a resin composition. Alternatively, a resin composition may be obtained by adding another polymer (e.g., another (meth)acrylic polymer) to the mixture of the copolymer (P) and the (meth)acrylic polymer (Q) obtained by the above-mentioned method for producing the copolymer (P). When the other 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 may be used.

As explained above, the resin composition may contain a polymer other than the (meth)acrylic polymer (Q). Examples of such polymers include olefin polymers such as polyethylene, polypropylene, ethylene-propylene polymer, and poly(4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resin; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 66, and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; polysulfone; polyether sulfone; polyoxybenzene; polyamide imide; cycloolefin polymers; cellulose derivatives; polybutadiene rubber, and rubber-like polymers such as ABS resin and ASA resin blended with (meth)acrylic rubber; and the like.

In the method for producing a resin composition, a filtration step can be performed following the polymerization step or 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 film with high transparency and few surface irregularities or defects. The filtration step can be performed continuously following the polymerization step or ring structure formation step described above.

As the filter used for filtration, any conventionally known filter can be used, and although there are no particular limitations, for example, leaf disc filters, candle filters, pack disc filters, cylindrical filters, etc. can be used. Among them, it is preferable to use leaf disc filters or candle filters, which have 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 for optical materials such as optical films, the filtration accuracy is preferably 10 μm or less, and more preferably 5 μm or less, from the viewpoint of reducing optical defects. There is no particular lower limit for the filtration accuracy, and it is, for example, 0.2 μm or more.

The content of the copolymer (P) in the resin composition is not particularly limited, but the content of the copolymer (P) in 100% by mass of the solid content of the resin composition is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and even more preferably 15% by mass or more. This makes it easier to increase the mechanical strength of the resin composition and to increase the fluidity of the resin composition when it 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), and the content of the copolymer (P) in the resin composition 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.

In 100% by mass of the solid content of the resin composition, the content of the polymer chain (A) of the copolymer (P) is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, even more preferably 12% 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. If the content of the polymer chain (A) in the resin composition is 1% by mass or more, it is easy to increase the mechanical strength of the resin composition and to increase the fluidity when the resin composition is heated and melted. If the content of the polymer chain (A) in the resin composition is 50% by mass or less, it is possible to express the positive form birefringence necessary to cancel the negative orientation birefringence caused by the polymer chain (B) while maintaining transparency.

The content of the ring structural unit in the resin composition is not particularly limited, but the content of the ring structural unit in 100% by mass of the solid content of the resin composition is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and 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 of the ring structural unit in this way, it becomes easy to improve both the heat resistance and mechanical strength of the resin composition in a well-balanced manner. The content of the ring structural unit described here means the total content of the ring structural unit contained in the main chain of the polymer chain (B) of the copolymer (P) and the ring structural unit contained in the main chain of the (meth)acrylic polymer (Q), and means, for example, the content of the structure represented by the above formulas (1) to (3).

When the resin composition contains a (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 preferably 1% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, and preferably 99% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, and even more preferably 85% by mass or less.

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

The resin composition may contain various additives other than additive (C) as long as the effect of the present invention is not impaired. Examples of additives other than additive (C) include ultraviolet absorbers; antioxidants such as phenols, 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, and antimony oxide; retardation adjusters such as retardation increasers, retardation reducers, and retardation stabilizers; antistatic agents including anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic and inorganic fillers; resin modifiers; organic and inorganic fillers; and the like. The content ratio of additives other than additive (C) in 100% by mass of the solid content of the resin composition is preferably within the range of 0 to 5% by mass, more preferably 0 to 2% by mass.

5. 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. This can increase the heat resistance of the resin composition, making it possible to apply the resin composition to applications requiring heat resistance, such as image display devices. The resin composition preferably has a glass transition temperature in a 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, in order to ensure moldability into films, etc.

It is preferable that the resin composition has a glass transition temperature of 110°C or higher and 110°C or lower, and more preferably has a high-temperature glass transition temperature of 110°C or higher and a low-temperature glass transition temperature of 0°C or lower. The glass transition temperature of 110°C or higher is referred to as the "high-temperature glass transition temperature", and the glass transition temperature of 0°C or lower is referred to as the "low-temperature glass transition temperature". The resin composition may have multiple high-temperature glass transition temperatures or multiple low-temperature glass transition temperatures. When there are multiple glass transition temperatures of 110°C or higher, the lowest glass transition temperature among them is the "high-temperature glass transition temperature", and when there are multiple glass transition temperatures of 0°C or lower, the highest glass transition temperature among them is the "low-temperature glass transition temperature". When the resin composition has a high-temperature glass transition temperature, the heat resistance of the resin composition is increased. When the resin composition has a low-temperature glass transition temperature, the mechanical strength and impact resistance of the resin composition can be increased. The preferred range of the high-temperature glass transition temperature of the resin composition is as described above. The low-temperature glass transition temperature of the resin composition is preferably less than 50°C, more preferably less than 30°C, and even more preferably less than 10°C, and is preferably -100°C or higher, more preferably -90°C or higher, and even more preferably -80°C or higher.

The weight average molecular weight of the resin composition is preferably 2,000 or more, more preferably 5,000 or more, even more preferably 30,000 or more, particularly preferably 50,000 or more, most preferably 100,000 or more, and preferably 600,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less. By setting the weight average molecular weight of the resin composition in such a range, the molding processability of the resin composition is improved. The weight average molecular weight of the resin composition means a polystyrene-equivalent value measured by gel permeation chromatography of the resin composition, and when the resin composition contains a copolymer (P) and a (meth)acrylic polymer (Q), 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, even more preferably 10,000 or more, particularly preferably 30,000 or more, most preferably 50,000 or more, and preferably 400,000 or less, more preferably 300,000 or less, even more preferably 200,000 or less, and most preferably 100,000 or less. By setting the number average molecular weight of the resin composition in such a range, the molding processability of the resin composition is improved. The number average molecular weight of the resin composition means a polystyrene-equivalent value measured by gel permeation chromatography of the resin composition, and when the resin composition contains a copolymer (P) and a (meth)acrylic polymer (Q), 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 out 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 a (meth)acrylic monomer is preferably -25.0 x 10 ^-11 Pa ^-1 or more and -4.0 x 10 ^-11 Pa ^-1 or less, more preferably -20.0 x 10 ^-11 Pa ^-1 or more and -6.0 x 10 ^-11 Pa ^-1 or less, even more preferably -15.0 x 10 ^-11 Pa ^-1 or more and -7.0 x 10 ^-11 Pa ^-1 or less, and particularly preferably -12.0 x 10 ^-11 Pa ^-1 or more and -8.0 x 10 ^-11 Pa ^-1 or less. The stress optical coefficient Cr is the slope of the change in the phase difference of the obtained phase difference film with respect to the stress σ when the original film obtained by molding the resin composition is stretched at a temperature equal to or higher than the Tg thereof to form a phase difference film, and the stress σ applied to the original film for stretching is changed. The stretched film is molded and the stress optical coefficient Cr is measured, but the stress optical coefficient Cr is a value specific to the resin composition and is not affected by the stretching ratio of the film, the stretching conditions, etc. The stress optical coefficient Cr is measured at a temperature equal to or higher than the Tg of the resin composition, and is therefore an index of the degree of phase difference that is generated in the film by stretching the original film. When the stress optical coefficient Cr of the resin composition is set within the above range, it is easy to bring the thickness direction phase difference Rth of the film close to 0 by the cancellation between the thickness direction phase difference Rth caused by the polymer chain (A) and the thickness direction phase difference Rth caused by the polymer chain (B). The stress optical coefficient Cr of the resin composition is obtained by the method described in the 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 even more preferably 11.0 g/10 min or more, measured at a temperature of 240 ° C and a load of 98 N (10 kgf). If the resin composition has such a melt flow rate, the melt viscosity when the resin composition is heated and melted can be reduced, and molding processability can be improved. In addition, when removing foreign matter from the melt of the resin composition through a filter prior to molding, the pressure loss of the filter can be kept low, and productivity can be improved. On the other hand, if the melt viscosity is too low, molding processes such as film molding and stretching may be difficult, and the replacement of the resin may be poor when molding another resin with the same machine. Therefore, the melt flow rate is preferably 60.0 g/10 min or less, more preferably 50.0 g/10 min or less, and even more preferably 45.0 g/10 min or less. The melt flow rate of the resin composition is determined in accordance with JIS K 7210 (Method B).

In order to increase the strength of the film of the present invention, the thickness is preferably 5 μm or more, and more preferably 15 μm or more. On the other hand, in order to make the film thinner, 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 digimatic micrometer manufactured by Mitutoyo Corporation.

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

The glass transition temperature, weight average molecular weight, number average molecular weight, stress optical coefficient Cr, and melt flow rate of the film of the present invention are preferably within the numerical ranges described for the glass transition temperature, weight average molecular weight, number average molecular weight, stress optical coefficient Cr, and melt flow rate of the resin composition described above.

6. Film Molding Method The resin composition can be molded into a film by a known method, for example, a solution casting method (solution casting method), a melt extrusion method, a calendar method, a compression molding method, etc. Among these, the solution casting method and the melt extrusion method are preferred. In this case, the resin composition may be directly supplied to an extrusion molding machine or the like without being pelletized after polymerization, or may be solution cast to form a film.

Examples of devices for carrying out the solution casting method include drum-type casting machines, band-type casting machines, spin coaters, etc. The dope liquid for carrying out the solution casting method may be prepared by dissolving pelletized resin, or may be prepared by directly diluting the polymerization liquid.

Examples of the melt extrusion method include the T-die method and the inflation method. When a film is formed by the melt extrusion method, it may be stretched to form a stretched film. By stretching, the mechanical strength of the film can be further improved. As a stretching method for obtaining a stretched film, a conventionally known stretching method can be applied. For example, uniaxial stretching such as free width uniaxial stretching and fixed width uniaxial stretching; biaxial stretching such as sequential biaxial stretching and simultaneous biaxial stretching, etc. can be mentioned. In order to make the NZ coefficient within the above range, it is preferable to make it a uniaxially stretched film, and free end uniaxial stretching is more preferable. When an unstretched film is uniaxially stretched in the x-axis direction, the NZ coefficient can be brought close to 0.50 while expressing the desired phase difference. In addition, the stretching conditions such as the stretching ratio, stretching temperature, and stretching speed can be appropriately set according to the desired mechanical strength and phase difference value as long as the NZ coefficient is within the above range, and are not particularly limited.

When a film exhibiting a normal retardation is stretched uniaxially in the x-axis direction, ny=nz because it is not stretched in the y and z directions, and the thickness direction retardation Rth=[(nx+ny)/2-nz]×d=[(nx+ny)/2-ny]×d=[(nx-ny)/2]×d. As described above, the in-plane retardation Re is |nx-ny|×d, and when a film having negative orientation birefringence is stretched uniaxially in the x-axis direction, nx-ny becomes negative, so Re=-(nx-ny)×d. That is, theoretically, Rth=-Re/2.
In this specification, the difference between the measured Rth and the theoretical Rth (=-Re/2) is defined as the Rth displacement. Since the Rth displacement depends on the thickness of the film, it is converted to the Rth displacement per 100 μm thickness. The Rth displacement per 100 μm thickness is preferably 40 nm or more, more preferably 50 nm or more. By increasing the Rth displacement per 100 μm thickness, the NZ coefficient can be made 0.35 or more. The upper limit of the Rth displacement per 100 μm thickness is not particularly limited, but is, for example, 150 nm or less, preferably 130 nm or less.

Examples of stretching devices include roll stretching machines, tenter type stretching machines, and small experimental stretching devices such as tensile testers and uniaxial stretching machines, and any of these devices can be used.

When the stretched film is applied to an optical film, it may be subjected to heat treatment (annealing) after stretching as necessary to stabilize the optical and mechanical properties of the optical film.

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

The optical film of the present invention can be used as a polarizer protective film by laminating it on one 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 (e.g., retardation film, polarizer protective film, transparent conductive film, light conversion film) can be suitably used in image display devices. 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 components 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 (PDPs), field emission displays (FEDs), QLEDs, microLEDs, etc.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is of course possible to carry out the invention with appropriate modifications within the scope of the above and below-mentioned aims, all of which are included in the technical scope of the present invention. In the following explanation, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

In the following examples, various physical properties were measured and evaluated by the following analytical 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 gel permeation chromatography (GPC) using the following apparatus and conditions:
- Measurement system: Tosoh Corporation, GPC system HLC-8220
- Measurement column configuration Guard column: TSKguardcolumn SuperHZ-L, manufactured by Tosoh Corporation
Separation column: Tosoh Corporation, TSKgel SuperHZM-M, two columns connected in series - Reference column configuration Reference column: Tosoh Corporation, TSKgel SuperH-RC
-Developing solvent: Chloroform (Wako Pure Chemical Industries, Ltd., 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 in accordance with JIS K 7121 (2012). Specifically, a differential scanning calorimeter (Rigaku Thermo plus EVO DSC-8230) was used to evaluate the starting point method from the DSC curve obtained by heating the sample from room temperature to 200 ° C. (heating rate 20 ° C. / min) under a nitrogen gas atmosphere. α-alumina was used as a reference. The glass transition temperature of less than 40 ° C. was evaluated by the starting point method from the DSC curve obtained by heating the sample from -100 ° C. to 60 ° C. (heating rate 10 ° C. / min) under a nitrogen gas atmosphere using a differential scanning calorimeter (Netsch DSC-3500). An empty container was used as a reference.

(3) Monomer Conversion Rate The monomer conversion rate (reaction rate) was determined by measuring the amount of remaining monomer in the polymerization reaction liquid using gas chromatography (GC-2014, manufactured by Shimadzu Corporation).

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

First, the resin composition obtained in the manufacturing example was hot-press molded by a hot press at 250 ° C. to obtain an unstretched film (thickness 190 μm) of the polymer. Next, the unstretched film thus prepared was cut into a size of 20 mm × 60 mm to obtain a test piece for Cr evaluation. Next, a weight having a weight that applies a stress of 1 N / mm ² or less to the test piece during stretching was selected and attached to one short side of the test piece, and then the test piece was placed in a constant temperature dryer (manufactured by AS ONE, DOV-450A) maintained at Tg + 20 ° C. of the polymer to be evaluated, and left for 1 hour. When the test piece was placed in the constant temperature dryer, the other short side of the test piece was fixed by a chuck, and the test piece was stretched uniaxially at its free end in the long side direction (vertical direction) by the stress applied to the test piece by the weight. In addition, when the test piece was placed, the distance between the chuck and the weight in the test piece was 40 mm. After 1 hour of heat stretching, the heater of the dryer was turned off, and the test piece was naturally cooled in the dryer. When the temperature in the oven reached Tg-40°C of the polymer, the test piece (uniaxially stretched film) was 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 were measured to calculate the in-plane birefringence Δn of the test piece. Separately, the cross-sectional area of the test piece after stretching by the load of the weight was obtained, and the stress σ (Pa) applied to the film was calculated from the cross-sectional area and the load of the weight. While changing the weight of the weight, Δn and σ were obtained for each load, and the slope of Δn with respect to the obtained σ was obtained by the least squares method, which was taken as the stress optical coefficient Cr (Pa ^-1 ). When the orientation angle when measuring the in-plane retardation Re is near 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 near 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 polymer's ability to develop birefringence (develop retardation) due to stretching.

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

(6) Foreign matter evaluation (filtration test)
The gelation evaluation of the resin composition was performed by a filter filtration test. For the foreign matter evaluation, the resin composition obtained in the manufacturing example was dissolved in chloroform to prepare a 0.1 mass% chloroform solution, which was filtered using a plastic syringe equipped with a filter (GL Science, Chromatodisk 13N, pore size 0.45 μm) at the tip. If the entire amount of 2 mL of the chloroform solution of the resin composition could be filtered, it was evaluated as ○, and if the filter was clogged during the process and 2 mL of the solution could not be filtered, it was evaluated as ×.

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

(8) Retardation The in-plane retardation Re, thickness direction retardation Rth, and NZ coefficient of the stretched film produced in the examples with respect to light having a wavelength of 589 nm were measured using a fully automatic birefringence meter ("KOBRA-WR" manufactured by Oji Scientific Instruments Co., Ltd.) under the condition of an incident angle of 40°. Specifically, the in-plane retardation Re and thickness direction retardation Rth were calculated from the following formula, where nx is the refractive index in the slow axis direction of the film, ny is the refractive index in the fast axis direction of the film, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film.
In-plane phase difference Re=|nx−ny|×d
Thickness direction retardation Rth = [(nx + ny) / 2 - nz] x d
NZ coefficient = (Rth / Re) + 0.50
The difference between the measured Rth and the theoretical Rth (=-Re/2) was taken as the Rth displacement. Since the Rth displacement depends on the film thickness, it was converted to the Rth displacement per 100 μm thickness.

(9) Internal haze of stretched film (internal haze per 100 μm thickness)
A quartz cell was filled with 1,2,3,4-tetrahydronaphthalene (tetralin), and the stretched film produced in the examples was immersed therein. The haze was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-5000), and the internal haze per 100 μm thickness was calculated according to the following formula: internal haze per 100 μm thickness (%)=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.

<Production Example 1>
Into a reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen inlet tube, 3.5 parts of Asahi Kasei Corporation's Tuftec (registered trademark) P1083 (olefinic double bond amount 2.01 mmol/g, styrene unit content 20 mass%, refractive index 1.500, weight average molecular weight 94,000, number average molecular weight 64,000) as a SEBS triblock copolymer, and 1.0 parts of Asahi Kasei Corporation's Tuftec (registered trademark) H1051 (olefinic double bond amount 0.38 mmol/g, styrene unit content 42 mass%, refractive index 1.524, weight average molecular weight 2 A mixture of 16.2 parts of a copolymer made by Asahi Kasei Corp. (amount of olefinic double bonds: 0.3 mmol/g, styrene unit content: 67 mass%, refractive index: 1.554, weight average molecular weight: 141,000, number average molecular weight: 58,000), 5.3 parts of Tuftec (registered trademark) H1043 (amount of olefinic double bonds: 0.3 mmol/g, styrene unit content: 67 mass%, refractive index: 1.554, weight average molecular weight: 141,000, number average molecular weight: 58,000), 43.5 parts of methyl methacrylate (MMA), 15 parts of styrene (St), 0.03 part of n-dodecyl mercaptan (nDM), and 150 parts of toluene as a polymerization solvent was charged, and the temperature was raised to 105° C. while nitrogen was passed through the mixture. Thereafter, 0.06 parts of t-butylperoxyisopropyl carbonate (manufactured by Kayaku Akzo Co., Ltd., Kayacarvon (registered trademark) Bic75) was added as an initiator, and 0.14 parts of t-butylperoxyisopropyl carbonate diluted with 7.5 parts of styrene (St) and 1 part of toluene was added dropwise at a constant rate over 3 hours to carry out solution polymerization at 105 to 110 ° C., and 9.0 parts of N-cyclohexylmaleimide (CMI) dissolved in 27 parts of toluene was added dropwise over 5 hours, and the mixture was further aged for 2 hours after the completion of both additions. 0.05 parts each of a sulfur-based antioxidant (manufactured by ADEKA Corporation, Adekastab (registered trademark) AO-412S) and a hindered phenol-based antioxidant (manufactured by ADEKA Corporation, Adekastab (registered trademark) AO-60) were added to the resulting reaction solution. As a result, a copolymer was obtained that contained an acrylic copolymer formed by polymerization of MMA, CMI, and St, and a graft copolymer in which the copolymer chain was bonded to the diene/olefin-derived unit of the SEBS triblock copolymer chain. The conversion rate of MMA calculated from the amount of remaining monomer in the polymerization reaction solution was 91.1%, the conversion rate of CMI was 99.0%, and the conversion rate of St was 94.5%. The composition ratio (mass basis) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion rate was MMA:CMI:St=56.8:12.8:30.5, and the content of the ring structural unit of the copolymer was 9.6% by mass.
Next, the obtained polymerization reaction liquid was introduced into a vent-type screw twin-screw extruder (hole diameter: 15 mm, L/D: 45) with one rear vent and two fore vents at a processing rate of 600 g/h in resin equivalent, and devolatilization was performed in this extruder, and the resin was 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 reduced pressure of 13.3 to 400 hPa (10 to 300 mmHg). The weight average molecular weight of the obtained resin composition was 125,000, the number average molecular weight was 57,000, the high-temperature side glass transition temperature was 122° C., the low-temperature side glass transition temperature was −61° C., the MFR was 30 g/10 min, and the refractive index was 1.527. Then, when the gelation evaluation of the obtained resin composition was performed, it was possible to perform filtration suitably.

<Production Examples 2 to 5>
A resin composition was prepared 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.

As shown in Table 1, in Production Examples 2 and 3, Tuftec (registered trademark) H1517 and P2000 manufactured by Asahi Kasei Corporation were used. H1517 has an olefinic double bond amount of 0.10 mmol/g, a styrene unit content of 39 mass%, a refractive index of 1.523, a weight average molecular weight of 99,000, and a number average molecular weight of 75,000, while P2000 has an olefinic double bond amount of 4.5 mmol/g, a styrene unit content of 67 mass%, a refractive index of 1.554, a weight average molecular weight of 74,000, and a number average molecular weight of 58,000. In this specification, the "styrene unit content" of the SEBS triblock copolymer is the catalog value.

In Production Example 2, the conversion of MMA, CMI, and ST calculated from the amount of remaining monomers in the polymerization reaction solution were 90.5%, 99.2%, and 95.6%, respectively. The composition ratio (by mass) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain, calculated from the conversion, was MMA:CMI:St=54.4:12.8:32.8, and the content of ring structural units in the copolymer was 9.6% by mass.
In Production Example 3, the conversion of MMA, CMI, and St calculated from the amount of remaining monomers in the polymerization reaction solution were 93.9%, 99.5%, and 95.2%, respectively. The composition ratio (mass basis) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion was MMA:CMI:St=62.2:15.8:22.0, and the content of ring structural units in the copolymer was 11.8% by mass.
In Production Example 4, the conversion of MMA calculated from the amount of remaining monomer in the polymerization reaction solution was 92.1%, the conversion of CMI was 98.5%, and the conversion of ST was 98.7%. The composition ratio (mass basis) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion was MMA:CMI:St=54.3:12.4:33.3, and the content of ring structural units in the copolymer was 10.0% by mass.
In Production Example 5, the conversion of MMA calculated from the amount of remaining monomer in the polymerization reaction solution was 92.1%, the conversion of CMI was 99.3%, and the conversion of ST was 96.3%. The composition ratio (mass basis) of the acrylic copolymer chain bonded to the SEBS triblock copolymer chain calculated from the conversion was MMA:PMI:St=56.7:12.6:30.7, and the content of the ring structure unit in the copolymer was 12.6% by mass.

Example 1
After dry blending 19.5 parts of the copolymer obtained in Production Example 1 and 0.5 parts of Adeka STAB (registered trademark) 2112 (AD2112) manufactured by ADEKA Corporation, a resin composition was obtained by kneading for 5 minutes at 250 ° C. and 100 rpm using a Labo Plastomill manufactured by Toyo Seiki Co., Ltd. The obtained resin composition was hot-press molded at 250 ° C. to produce an unstretched film having a thickness of 145 μm. The obtained unstretched film was cut into a size of 50 mm x 80 mm to prepare a test piece. Using an autograph with a thermostatic bath (manufactured by Shimadzu Corporation, AG-X 1kN), the test piece was subjected to free-end uniaxial stretching at a stretching rate of 40 mm / min at a chuck distance of 40 mm and a temperature of Tg + 7 ° C. so that the stretch ratio was 2 times, and then annealed for 1 minute and cooled to obtain a stretched film having a thickness of 99 μm. The Rth displacement per 100 μm of the resulting stretched film was 48.5 nm.

<Examples 2 to 11 and Comparative Examples 1 to 8>
A stretched film was produced in the same manner as in Example 1, except that the type of copolymer, the type and content of additives, the thickness of the unstretched film, and the stretching conditions were as shown in Table 2. The retardation of the obtained stretched film was as shown in Table 2. The additives used in the examples and comparative examples are as follows, and are listed by abbreviation in Table 2. Among the additives listed below, Adeka STAB (registered trademark) 2112 and LA-F70 are manufactured by ADEKA Corporation, and Tinuvin (registered trademark) 1600 and Irganox (registered trademark) 1330 and 3114 are manufactured by BASF Corporation.

Claims (9)

A film formed from a resin composition containing: a polymer chain (A) having a unit derived from a diene; a polymer chain (B) having a unit (b1) derived from a (meth)acrylic monomer, a unit (b2) having a cyclic imide structure in the main chain, and a unit (b3) derived from an aromatic vinyl monomer copolymerizable with the (meth)acrylic monomer; and a (meth)acrylic polymer (Q),
the polymer chain (A) has a polymer block (a1) having a unit derived from a diene and a polymer block (a2) having a unit derived from an aromatic vinyl monomer ,
the polymer chain (B) is grafted to the polymer block (a1);
the (meth)acrylic polymer (Q) has only the units (b1), (b2), and (b3) contained in the polymer chain (B),
NZ coefficient = (Rth / Re) + 0.50
(Here, Re is the in-plane retardation (nm) at a wavelength of 589 nm, and Rth is the thickness direction retardation (nm) at a wavelength of 589 nm.)
The NZ coefficient of the film calculated from the above formula is 0.35 or more and 0.60 or less,
The film is characterized in that it is a uniaxially stretched film . The film according to claim 1, further comprising an additive (C). 3. The film according to claim 1, wherein the polymer chain (A) is contained in the film in an amount of 10 to 50% by mass. The film according to any one of claims 1 to 3 , wherein the polymer chain (B) contains 15 to 50 parts by mass of a unit (b3) derived from an aromatic vinyl monomer copolymerizable with the (meth)acrylic monomer, per 100 parts by mass of the polymer chain (B). The film according to any one of claims 1 to 4 , which is a monolayer film. 6. The film according to claim 1, wherein the Rth displacement, which is the difference between the measured Rth and the theoretical Rth, −Re/2, per 100 μm thickness , is 40 nm or more. The film according to any one of claims 1 to 6 , which has a glass transition temperature of 110°C or higher. The film according to any one of claims 1 to 7 , which has an internal haze of 5.0% or less per 100 µm thickness. The film according to any one of claims 1 to 8 , which is an optical film.