JP7122830B2 - OPTICAL FILM MANUFACTURING METHOD AND OPTICAL FILM - Google Patents

Description

The present invention relates to an optical film manufacturing method and an optical film.

2. Description of the Related Art Conventionally, an optical film is known which is formed by melt-forming a resin containing an ultraviolet absorber (UVA). For example, Patent Document 1 discloses 2,2′-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethyl) represented by the following formula, which is an ultraviolet absorber. butyl)phenol] (hereinafter referred to as "compound a").

It is known that the optical film has a low b ^* value in the L ^* a ^* b ^* color system and is capable of suppressing bleed-out of the compound a even in a high-temperature and high-humidity environment. ing.

By the way, in the production of an optical film, it is generally necessary to raise the extrusion temperature of the resin in order to use a resin with high heat resistance or high melt viscosity, or to increase the extrusion rate of the resin. However, the compound a has a low thermal decomposition temperature, and if the extrusion temperature of the resin is increased, the compound a bleeds out when an optical film is produced by open film formation, resulting in the inconvenience of contamination of the roll. Therefore, the bleed-out of compound a can be suppressed by using a benzotriazine-based ultraviolet absorber with high heat resistance instead of compound a, or by using the ultraviolet absorber and compound a together. It is For example, Patent Document 2 describes an optical film obtained by forming an open film from an acrylic resin containing benzotriazine and benzotriazole. Further, Patent Document 3 describes an optical film obtained by open film formation of a resin composition having a glass transition temperature (Tg) of 110° C. or higher, which is obtained by adding benzotriazine having a molecular weight of 700 or higher to a cyclic acrylic resin. ing.

In addition, (meth)acrylic resins, which have recently been used as raw materials for optical films, sometimes turn yellow and lose transparency when exposed to light including ultraviolet rays. As a method of preventing this phenomenon, a method of adding an ultraviolet absorber (UVA) is known. However, when a general UV absorber is added, the hue, heat resistance, or transparency of the optical film deteriorates, and the UV absorber evaporates during molding, resulting in a decrease in UV absorption capacity and contamination of the molding equipment. There were problems such as

Therefore, a method to solve the above problem is to use a triazine-based ultraviolet absorber that can obtain a high ultraviolet absorption effect even if the amount added is small and has high heat resistance either alone or in combination with other ultraviolet absorbers. It has been proposed (for example, Patent Documents 4 and 5).

Japanese Patent Application Laid-Open No. 2007-108775 (published on April 26, 2007) International Publication No. 2006/112223 pamphlet (published on October 26, 2006) Japanese Patent Application Laid-Open No. 2009-052021 (published on March 12, 2009) Japanese Patent Application Laid-Open No. 2017-088728 (published on May 25, 2017) Special table 2015-535544 (published on December 14, 2015)

However, although the optical films described in Patent Documents 2 and 3 can suppress bleed-out during the production of the optical film, there is room for improvement in terms of the b ^* value.

In addition, the ultraviolet absorbers used in Patent Documents 4 and 5 absorb even visible light having a wavelength of 400 nm or more, and there is a problem that the optical film is colored yellow. In addition, a new problem arises in that color saturation is increased by coloring with an ultraviolet absorber. On the other hand, if the amount of the ultraviolet absorber added is reduced in order to suppress coloration, there is a possibility that sufficient ultraviolet absorbing ability cannot be exhibited.

The present invention has been made in view of the above problems, and provides a method for producing an optical film having a low b ^* value, no transfer of contaminants from a roll during film formation, and excellent optical properties, and an optical film. The main purpose is to

Another object of the present invention is to provide a method for producing an optical film having high transparency, a small hue, and a low saturation and excellent heat resistance, and to provide the optical film.

The present invention includes the following configurations.
<1> A melt made of a thermoplastic resin composition containing 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360 ° C. or less with respect to 100 parts by weight of (meth)acrylic resin, A method for producing an optical film in which touch roll film formation is performed after discharging a film from the A method for producing an optical film that satisfies the following formula.

50≦Td−Tp
<2> The method for producing an optical film according to <1>, wherein the thermoplastic resin composition has a melt viscosity of 500 Pa·S or more at 270°C and a shear rate of 10/sec.
<3> The (meth)acrylic resin has, in its main chain, at least one ring structure selected from a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure. The method for producing an optical film according to <1> or <2>, characterized by:
<4> A method for producing an optical film, comprising forming a melted product comprising a thermoplastic resin composition containing a (meth)acrylic resin and an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less; A method for producing an optical film, wherein the meth)acrylic resin has a glass transition temperature of 108° C. or higher; and the melt is extruded from a die in the form of a film, followed by forming a film with a touch roll.
<5> A roll-shaped optical film made of a thermoplastic resin composition containing 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less with respect to 100 parts by weight of (meth)acrylic resin. When the optical film has a thickness of 80 μm, the b ^* value is less than 0.5; An optical film having a total noise of 5 points or less when 80% of the width direction (TD direction) is projected and inspected.
<6> An optical film made of a thermoplastic resin composition containing 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360° C. or lower with respect to 100 parts by weight of (meth)acrylic resin, an optical film having a b ^* value of less than 0.5 when the optical film has a thickness of 80 μm; and a noise of 5 points or less per 1 m ² when the optical film is subjected to projection inspection.

The present invention provides a method for producing an optical film having a low b ^* value, no transfer of contaminants from a roll during film formation, and good optical properties, even when an ultraviolet absorber having a low thermal decomposition temperature is used. and an optical film can be provided.

In addition, according to the present invention, it is possible to provide a method for producing an optical film having excellent heat resistance, which combines high transparency, a small hue, and a low saturation, and an optical film, and an optical film such as a polarizer protective film. It can be suitably used for films.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to this, and various modifications are possible within the scope described, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the present invention. Included in the technical scope.

In the present specification, "(meth)acrylic acid" means "acrylic acid or methacrylic acid", "main component" means containing 50% by mass or more, and "ppm" unless otherwise specified. As far as possible, it means a value obtained in terms of mass (for example, 10,000 ppm is 1% by mass). In addition, "weight" is treated as a synonym for "mass", "% by weight" is treated as a synonym for "mass%", and unless otherwise specified in this specification, "A to B" indicating a numerical range are " A or more and B or less".

A method for producing an optical film according to an embodiment of the present invention contains 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less with respect to 100 parts by weight of (meth)acrylic resin. , A method for producing an optical film in which a melt made of a thermoplastic resin composition is extruded from a die in the form of a film and then formed into a film by a touch roll, wherein the thermal decomposition temperature Td (° C.) and the temperature at the exit of the die The relationship with the temperature Tp (° C.) of the melt is the following formula: 50 ≤ Td - Tp
is a method that satisfies

A method for producing an optical film according to another embodiment of the present invention comprises producing a melt of a thermoplastic resin composition containing a (meth)acrylic resin and an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less. A method for producing an optical film, wherein the (meth)acrylic resin has a glass transition temperature of 108° C. or higher, and the melt is discharged from a die in the form of a film, followed by film formation with a touch roll. is.

[1. Features of the present invention]
[Use of heat-resistant (meth)acrylic resin]
An optical film according to an embodiment of the present invention contains a heat-resistant (meth)acrylic resin (for example, a (meth)acrylic resin having a glass transition temperature of 108° C. or higher) as a raw material. The optical film is obtained by forming a heat-resistant thermoplastic resin composition into a film, and has heat resistance itself.

Advantages of heat-resistant optical films made from heat-resistant (meth)acrylic resin include, for example, excellent weather resistance and surface hardness, and easy placement near heat-generating parts (light sources, etc.). There is

By the way, when producing an optical film using a heat-resistant (meth)acrylic resin as a raw material, the ultraviolet absorber is usually placed in a high-temperature environment. At this time, when an ultraviolet absorber with a low thermal decomposition temperature is used, the problem that the roll is contaminated due to the bleeding out of the ultraviolet absorber and transferred to the film surface to cause defects is conventionally known. was As one means for solving the above problems, a production method using an ultraviolet absorber having a high thermal decomposition temperature (for example, a benzotriazine-based ultraviolet absorber) has been proposed. However, benzotriazine-based ultraviolet absorbers absorb light even in the visible light region, and thus have the disadvantage of producing hues and saturations in optical films.

These matters are the premises of the present invention. That is, the present invention solves the problem that film defects occur while using a heat-resistant (meth)acrylic resin and an ultraviolet absorber with a low thermal decomposition temperature as raw materials. As a result of using an ultraviolet absorber with a low thermal decomposition temperature, the resulting optical film has excellent optical properties (for example, high transparency, low hue, and low chroma).

[Adoption of touch roll]
In order to solve the above problems, the present invention employs a touch roll as a film forming method. The reason why film defects can be suppressed by forming a film using a touch roll is presumed to be as follows. That is, in touch roll film formation, the film being formed is in close contact with rolls from both sides. For this reason, the ultraviolet absorber cannot volatilize from the film surface and tends to remain inside the film. Moreover, even if a part of the ultraviolet absorber is volatilized, the volatilized ultraviolet absorber will not accumulate on the roll surface in such a large amount as to cause a defect. As a result, a large amount of the ultraviolet absorber is not deposited on the roll surface, and thus the deposited ultraviolet absorber is not transferred to cause defects in the film.

Means for suppressing the occurrence of film defects as described above, however, have been overlooked in the past due to technical difficulties in applying touch rolls to film-making techniques. For example, touch rolls in film forming technology have the following technical difficulties.

(1) Occurrence of Thickness Distribution Touch roll film formation is generally configured such that both ends of a roll are pressed by an air cylinder or the like. Therefore, a bending moment acts on the roll, and the roll may be bent. When a film is formed using such rolls, the thickness distribution of the film is thick at the center and thin at the ends. Such films have the disadvantage that they tend to tear near the gripping area. There are countermeasures against the above-mentioned drawbacks, such as crowning the touch roll and attaching a backup roll.

(2) Uneven force applied to the film The pressure applied to the film affects the orientation of the resin and changes the retardation of the resulting film. It is important to perform pinching with a sufficient pressure. However, if the casting die is widened to obtain a wide optical film, even if an elastic touch roll is used as the touch roll, the touch roll will not uniformly contact the film surface due to roll deflection. If the film thickness of the raw film is made convex toward the center from both ends in the width direction of the film, the uneven pressure caused by the bending can be eliminated. However, custom-made equipment is required to manufacture such a film stock. Further, if the melt is strongly pressed during casting, residual strain will be generated in the film. When such a film is stretched, the residual strain causes a bias in the stretching, and a bias in the thickness of the film. Thus, it is difficult to press the extruded film-like melt with a uniform pressure between the cast roll and the touch roll.

(3) Difficulties associated with high-speed film formation In high-speed touch roll film formation, for example, the following problems may arise. (i) The problem that horizontal steps occur in the molten resin when the molten resin is squeezed. (ii) The problem that the molten resin does not partially contact the touch roll. (iii) Since the narrowing pressure is not uniform, there is a problem that the pressure is biased at the edges and the center in the width direction.

The present invention focuses on touch roll film formation, which has tended to be avoided in the past due to the above-mentioned difficulties, and provides a method for producing an optical film that achieves both suppression of film defects and excellent optical properties. I am trying to provide a film.

[2. (Meth) acrylic resin]
[Structure of (meth)acrylic resin]
An optical film according to one embodiment of the present invention is molded from a thermoplastic resin composition containing a (meth)acrylic resin. The (meth)acrylic resin constituting the thermoplastic resin composition is acrylic acid, methacrylic acid, derivatives of these compounds, or a monomer composition containing a hydroxyl group-containing monomer having a structure represented by the following formula It is a resin and its derivative obtained by polymerizing or copolymerizing a substance. These structures are not particularly limited as long as they do not impair the effects of the present invention. Specifically, a known (meth)acrylic resin can be used.

_CH2 =C( ^COOR1 )-CHR2 ^- OH
(wherein R ¹ and R ² each independently represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms).

Specific examples of (meth)acrylic acid derivatives include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, ( t-butyl meth)acrylate, n-hexyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, (meth)acrylic 2,3,4,5-tetrahydroxypentyl acid and 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, and the like. A plurality of types of these derivatives may be used in combination. Among the above specific examples, methyl (meth)acrylate is most preferable because the obtained (meth)acrylic resin has excellent thermal stability.

In addition, the (meth)acrylic resin may have a ring structure introduced into the molecular chain (also referred to as the main skeleton or main chain of the polymer) in order to improve the heat resistance of the (meth)acrylic resin. . Examples of such ring structures include at least one selected from lactone ring structures, glutaric anhydride structures, glutarimide structures, N-substituted maleimide structures, and maleic anhydride structures. More specifically, the (meth)acrylic resin may be, for example, a copolymer of (meth)acrylic acid or a derivative thereof and an N-substituted maleimide such as phenylmaleimide, cyclohexylmaleimide, and methylmaleimide. good.

The content of the ring structure in the (meth)acrylic resin is, for example, preferably in the range of 1 to 60 mol%, more preferably in the range of 1 to 40 mol%, and 2 to 30 mol. % range is more preferred. Further, the content of the ring structure in the (meth)acrylic resin is, for example, preferably in the range of 1 to 80% by mass, more preferably in the range of 1 to 50% by mass, and 2 to 40% by mass. It is more preferable to be within the mass % range. As a result, the optical film made of the (meth)acrylic resin exhibits excellent transparency and heat resistance, as well as excellent mechanical strength.

The (meth)acrylic resin more preferably has a structure that does not contain nitrogen atoms so that it is difficult to color (yellowing) when made into an optical film.

Moreover, it is more preferable that the (meth)acrylic resin has a lactone ring structure introduced into the main chain so as to easily develop a positive birefringence (positive retardation). The lactone ring structure introduced into the main chain is preferably a 4- to 8-membered ring, more preferably a 5- to 6-membered ring from the viewpoint of structural stability, and particularly preferably a 6-membered ring. Examples of the six-membered lactone ring structure to be introduced into the main chain include the lactone ring structure represented by the general formula (1) described below, the lactone ring structure described in JP-A-2004-168882, and the like. . Among these, (i) the polymerization yield is high when synthesizing a polymer having a hydroxyl group and an ester group before introducing a lactone ring structure into the main chain, and (ii) the content of the lactone ring structure is high. The general formula ( A lactone ring structure represented by 1) is more preferable.

In addition, the (meth)acrylic resin may have structural units obtained by polymerizing other monomers copolymerizable with (meth)acrylic acid or its derivatives within a range that does not impair heat resistance. . Specific examples of other copolymerizable monomers include aromatic vinyl monomers such as styrene and α-methylstyrene, nitrile monomers such as acrylonitrile, and vinyl esters such as vinyl acetate. be done.

The (meth)acrylic resin in the embodiment of the present invention preferably has a styrene-equivalent weight average molecular weight (Mw) of 3,000 to 1,000,000 by GPC measurement. If this weight average molecular weight is 3,000 or more, the strength required as a polymer can be exhibited. Moreover, if it is 1,000,000 or less, it can be made into a molded object by molding processing. The weight average molecular weight of the (meth)acrylic resin is more preferably 4,000 to 800,000, still more preferably 5,000 to 500,000, and even more preferably 100,000 to 500,000. is. A (meth)acrylic resin having a weight-average molecular weight within the above range is preferable because it has good moldability by extrusion melting.

The (meth)acrylic resin in one embodiment of the present invention preferably has a molecular weight distribution (Mw/Mn) of 1-10 by GPC measurement. From the viewpoint of adjusting the resin viscosity suitable for molding, the molecular weight distribution (Mw/Mn) is preferably 1.1 to 7.0, more preferably 1.2 to 5.0, and still more preferably 1.5 to 4.0.

[Method for producing (meth)acrylic resin]
The method for producing the (meth)acrylic resin is not particularly limited, and known methods can be used. Specifically, there is a method of polymerizing a monomer composition containing (meth)acrylic acid or a derivative thereof. When the (meth)acrylic resin is used as an optical material, it is preferable to avoid contamination with minute foreign matter as much as possible. From this point of view, it is desirable to use bulk polymerization, cast polymerization, or solution polymerization without using a suspending agent or an emulsifier. As a polymerization method, for example, both a batch polymerization method and a continuous polymerization method can be used. The batch polymerization method is preferable from the viewpoint of simple polymerization operation, and the continuous polymerization method is preferable from the viewpoint of obtaining a polymer having a more uniform composition.

The polymerization temperature and polymerization time vary depending on the types of monomers used, their usage ratio (composition of the monomer composition), and the like. Generally, however, the polymerization temperature is preferably in the range of 0°C or higher and 150°C or lower, more preferably in the range of 80°C or higher and 140°C or lower. The polymerization time is preferably in the range of 0.5 hours or more and 20 hours or less, more preferably in the range of 1 hour or more and 10 hours or less.

The solvent used in the polymerization mode using a solvent is not particularly limited. Examples thereof include aromatic hydrocarbon solvents such as toluene, xylene and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran; A plurality of types of solvents may be used in combination.

In particular, when producing a (meth)acrylic resin in which a lactone ring structure is introduced into the main chain, if the boiling point of the solvent used is too high, the residual volatile content of the finally obtained (meth)acrylic resin will increase. Therefore, the boiling point of the solvent is more preferably in the range of 50°C or higher and 200°C or lower.

If necessary, a polymerization initiator may be added during the polymerization reaction of the monomer composition. A polymerization initiator is not particularly limited. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, etc. organic peroxide; 2,2'-azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2,4-dimethylvaleronitrile) and other azo compounds ; and the like. A plurality of polymerization initiators may be used in combination. The amount of the polymerization initiator to be used is not particularly limited, and may be appropriately set according to the type of monomers to be used, their usage ratio (composition of the monomer composition), reaction conditions, and the like.

During the polymerization reaction of the monomer composition, it is preferable to control the concentration of the polymer in the reaction liquid to 50 mass % or less in order to suppress gelation of the reaction liquid. Specifically, when the concentration of the polymer in the reaction liquid exceeds 50% by mass, it is preferable to appropriately add a solvent to the reaction liquid so that the concentration is 50% by mass or less. The concentration is more preferably 45% by mass or less, and even more preferably 40% by mass or less. In addition, if the concentration of the polymer is too low, the productivity decreases, so the concentration is preferably 10% by mass or more, more preferably 20% by mass or more.

The method of adding the solvent to the reaction solution during the polymerization reaction is not particularly limited. For example, the solvent may be added continuously or intermittently to the reaction solution. Gelation of the reaction liquid can be suppressed by controlling the concentration of the polymer in the reaction liquid. In order to increase the content of the lactone ring structure and improve the heat resistance of the (meth)acrylic resin, it is possible to increase the proportion of hydroxyl groups and ester groups in the polymer before introducing the lactone ring structure into the main chain. Even if there is, the gelation of the reaction solution can be sufficiently suppressed by controlling the concentration of the polymer in this manner.

The solvent added to the reaction solution may be of the same type (composition) as the solvent used at the start of the polymerization reaction, or may be of a different type (composition), but the same type (composition) as the solvent used at the start of the polymerization reaction. is more preferable. Moreover, the solvent to add may use multiple types together.

The reaction solution obtained when the polymerization reaction is completed usually contains a solvent in addition to the polymer obtained by the polymerization. When the above polymer is used as a polymer containing a lactone ring structure, which will be described later, it is not necessary to remove the solvent from the reaction solution to take out the polymer in a solid state. It can continue to be used as a reaction solution in the polycondensation step. Alternatively, after the polymer is taken out in a solid state, a solvent suitable for the lactone cyclization condensation step may be added to form the reaction solution.

[Characteristics of (meth)acrylic resin]
The hue of the (meth)acrylic resin obtained by the polymerization reaction is not particularly limited. A transparent resin with a low degree of yellowing is preferable for molding into an optical film without impairing the original characteristics of the (meth)acrylic resin. The (meth)acrylic resin preferably has a haze value of 3 or less, more preferably 2 or less, and even more preferably 1 or less when formed into a molded body having a thickness of 3 mm, for example. . The (meth)acrylic resin preferably has a YI (yellow index) value of 10 or less, more preferably 5 or less when formed into a molded body having a thickness of 3 mm, for example.

In the present embodiment, the thermoplastic resin composition containing the (meth)acrylic resin has a melt viscosity at 270° C. and a shear rate of 10/sec. It is more preferable that it is 600 Pa·S or more, and it is particularly preferable that it is 600 Pa·S or more. If the melt viscosity is less than 500 Pa·S, the thermoplastic resin composition may become brittle and may not be a material having sufficient mechanical properties. The upper limit of the melt viscosity is preferably about 3000 Pa·S.

The melt viscosity can be measured using, for example, a twin-bore barrel type capillary rheometer RH10 manufactured by Rosand Co., Ltd. Details such as measurement conditions will be described in Examples.

In the present embodiment, the (meth)acrylic resin constituting the thermoplastic resin composition has a glass transition temperature (Tg) of 108° C. or higher and 160° C. or lower, more preferably 110° C. or higher and 150° C. or higher. °C or less. In a more preferred embodiment, the glass transition temperature range has an upper limit of 140°C or lower and a lower limit of 111°C or higher, 112°C or higher, 113°C or higher, 115°C or higher, and 117°C or higher in this order. In this respect, the thermoplastic composition is different from general (meth)acrylic resins (polymethyl methacrylate (PMMA)).

If the glass transition temperature is less than 108° C., for example, when an optical film made of the (meth)acrylic resin is incorporated as a polarizing plate of an optical device, sufficient durability at high temperatures cannot be exhibited. There is a risk. If the glass transition temperature exceeds 160°C, it is necessary to increase the molding temperature of the (meth)acrylic resin, which may cause foaming during molding or bleeding out of the ultraviolet absorber. be. In addition, if the glass transition temperature of the (meth)acrylic resin is within this range, the glass transition temperature of the thermoplastic resin composition formed into the film can be adjusted without difficulty in film forming or processing such as stretching. can be increased, and thus the glass transition temperature of the optical film can also be increased. An optical film with a high glass transition temperature can reduce the rate of change in retardation in a high-temperature environment.

The glass transition temperature can be measured according to JIS K7121. Details such as measurement conditions will be described in Examples.

The thermal decomposition temperature (thermal decomposition initiation temperature; Td) of the (meth)acrylic resin in one embodiment of the present invention is preferably 310° C. or higher, more preferably 315° C. or higher, and 320° C. or higher. is more preferable. A (meth)acrylic resin having a thermal decomposition temperature of 310° C. or higher can be said to have sufficient heat resistance. Although the upper limit of the thermal decomposition temperature is not particularly limited, it can be about 380°C. By forming a touch roll film from a (meth)acrylic resin having such a thermal decomposition temperature, advantages such as reduction of film defects, reduction of film coloring, and suppression of air bubbles can be obtained.

As shown in Examples, the term "thermal decomposition temperature" used herein refers to the lowest temperature among temperatures at which the rate of mass reduction increases with temperature rise. That is, in this specification, "thermal decomposition temperature" means "thermal decomposition initiation temperature". Hereinafter, the terms "thermal decomposition temperature" and "thermal decomposition initiation temperature" are both used, but have the same meaning.

The glass transition temperature and thermal decomposition temperature of the (meth)acrylic resin may differ from the glass transition temperature and thermal decomposition temperature of the thermoplastic composition. This is because components other than the (meth)acrylic resin may be added when preparing the thermoplastic composition. On the other hand, when the thermoplastic composition is molded into an optical film, the glass transition temperature and thermal decomposition temperature of the thermoplastic composition are considered to be substantially the same as the glass transition temperature and thermal decomposition temperature of the optical film. you can In this regard, preferred glass transition temperature and thermal decomposition temperature of the thermoplastic resin composition in one embodiment of the present invention (that is, preferred glass transition temperature and thermal decomposition temperature of the optical film according to one embodiment of the present invention) will be described later in Section [5].

Further, in the present embodiment, the (meth)acrylic resin constituting the thermoplastic resin composition has an absolute value of the stress optical coefficient (Cr) of the resin within the range of 1.5×10 ⁻¹⁰ Pa ⁻¹ or less. , more preferably 1.0×10 ⁻¹⁰ Pa ⁻¹ or less, more preferably 5.0×10 ⁻¹¹ Pa ⁻¹ or less. Therefore, the (meth)acrylic resin is a so-called zero retardation resin. Such a (meth)acrylic resin can suppress the anisotropy of the refractive index at the time of stretching and reduce the birefringence.

The stress optical coefficient (Cr) is derived from the slope of the approximate straight line obtained by plotting the stress during stretching of the thermoplastic resin composition and the refractive index of the film on a plane. Details of the derivation method will be described in the section of Examples.

[Structure of polymer containing lactone ring structure]
The (meth)acrylic resin is more preferably a so-called lactone ring structure-containing polymer in which a lactone ring structure is introduced into the main chain of the polymer by an intramolecular cyclization reaction. A ring structure-containing polymer is particularly preferred. In this specification, a (meth)acrylic resin having a lactone ring structure introduced into its main chain is referred to as a lactone ring structure-containing polymer. Such a lactone ring structure-containing polymer has high transparency, heat resistance, and optical isotropy, and can sufficiently exhibit properties suitable for various optical applications.

Although the lactone ring structure-containing polymer is not particularly limited, it preferably has a lactone ring structure represented by the following general formula (1).

(In the formula, R ¹¹ , R ¹² and R ¹³ are each independently a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms (the alkyl group may be any may have oxygen atoms in the configuration)).

The content of the lactone ring structure represented by general formula (1) in the lactone ring structure-containing polymer is preferably 5% by mass or more and 90% by mass or less, more preferably 10% by mass or more and 70% by mass or less, It is more preferably 10% by mass or more and 60% by mass or less, and particularly preferably 10% by mass or more and 50% by mass or less. If the content is less than 5% by mass, heat resistance, solvent resistance and surface hardness may be insufficient. Moreover, if the content is more than 90% by mass, moldability may be poor.

The lactone ring structure-containing polymer may have a structure other than the lactone ring structure represented by general formula (1). Structures other than the lactone ring structure represented by general formula (1) are not particularly limited. For example, it is constructed by polymerizing at least one monomer selected from (meth)acrylic acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the following general formula (2). A polymer structural unit (repeating structural unit) is preferred.

CH ₂ =C(X)-R ¹⁴ (2)
(Wherein, R ¹⁴ represents a hydrogen atom or a methyl group. X is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, a —OAc group, a —CN group, a —CO—R ¹⁵ group, or represents a C—O—R ¹⁶ group, Ac represents acetyl, and R ¹⁵ and R ¹⁶ represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms) .

The lactone ring structure-containing polymer has a polymer structural unit (repeating structural unit) constructed by polymerizing a (meth)acrylic acid ester as a structure other than the lactone ring structure represented by general formula (1). If it is, the content is preferably 10% by mass or more and 95% by mass or less, more preferably 10% by mass or more and 90% by mass or less, still more preferably 40% by mass or more, It is within the range of 90% by mass or less, particularly preferably within the range of 50% by mass or more and 90% by mass or less.

In addition, the lactone ring structure-containing polymer has a polymer structural unit (repeating structural unit) constructed by polymerizing a hydroxyl group-containing monomer as a structure other than the lactone ring structure represented by general formula (1). If it is, the content is preferably greater than 0% by mass and within the range of 30% by mass or less, more preferably greater than 0% by mass and within the range of 20% by mass or less, still more preferably 0% by mass % and 15 mass % or less, particularly preferably more than 0 mass % and 10 mass % or less.

Further, the lactone ring structure-containing polymer has a polymer structural unit (repeating structural unit) constructed by polymerizing an unsaturated carboxylic acid as a structure other than the lactone ring structure represented by general formula (1). If it is, the content is preferably more than 0% by mass and 30% by mass or less, more preferably more than 0% by mass and 20% by mass or less, still more preferably 0% by mass and within the range of 15% by mass or less, particularly preferably within the range of greater than 0% by mass and 10% by mass or less.

Further, the lactone ring structure-containing polymer is a polymer structural unit constructed by polymerizing a monomer represented by general formula (2) as a structure other than the lactone ring structure represented by general formula (1). (repeating structural unit), the content is preferably more than 0% by mass and 30% by mass or less, more preferably more than 0% by mass and 20% by mass or less. More preferably, it is in the range of over 0% by mass and 15% by mass or less, and particularly preferably in the range of over 0% by mass and 10% by mass or less.

In the lactone ring structure-containing polymer, the total content of structures other than the lactone ring structure represented by general formula (1) is preferably 10% by mass or more and 95% by mass or less, more preferably 30% by mass. % or more and 90 mass % or less, more preferably 40 mass % or more and 90 mass % or less, particularly preferably 50 mass % or more and 90 mass % or less.

[Method for Producing Lactone Ring Structure-Containing Polymer]
The method for producing the lactone ring structure-containing polymer is not particularly limited. Preferably, after obtaining a polymer having a hydroxyl group and an ester group in the molecular chain, the polymer is heat-treated to perform a cyclization condensation reaction (lactone ring condensation reaction) in which a lactone ring structure is introduced into the polymer. A lactone ring structure-containing polymer can be obtained. That is, the monomer composition becomes a lactone ring structure-containing polymer through the polymerization step and the lactone cyclization condensation step.

The formation of the lactone ring structure in the molecular chain of the polymer (in the main skeleton of the polymer) imparts high heat resistance to the polymer. When the reaction rate of the cyclization condensation reaction for introducing the lactone ring structure into the polymer is low, the heat resistance of the polymer may not be sufficiently improved. In addition, the heat associated with the heat treatment during molding may cause a condensation reaction of the polymer during molding, and the resulting alcohol may appear as bubbles or silver streaks in the molded product.

The method of heat-treating the polymer to carry out the cyclization condensation reaction is not particularly limited, and a known method can be used. For example, the polymerization reaction mixture containing the polymer and the solvent obtained by performing the polymerization step may be heat-treated as it is. Alternatively, the polymer may be heat-treated in the presence of a solvent, optionally using a ring-closing catalyst. Further, heat treatment may be performed using a heating furnace or reaction apparatus equipped with a vacuum device or a devolatilization device for removing volatile components. Furthermore, the heat treatment of the polymer can also be carried out using a devolatilization device, an extruder, or the like.

When performing the cyclization condensation reaction, other acrylic resins may coexist in addition to the above polymer. In addition, when performing the cyclization condensation reaction, if necessary, (i) an organic phosphorus compound, (ii) an esterification catalyst such as p-toluenesulfonic acid, which is generally used as a catalyst for the cyclization condensation reaction, or ( iii) A transesterification catalyst may be used. Alternatively, organic carboxylic acids such as acetic acid, propionic acid, benzoic acid, acrylic acid and methacrylic acid may be used as catalysts. Furthermore, basic compounds, organic carboxylates, carbonates, etc. described in JP-A-61-254608 and JP-A-61-261303 may be used as catalysts.

As a catalyst for the cyclization condensation reaction, which is a dealcoholization reaction, an organic phosphorus compound is more preferable. By using an organic phosphorus compound as a catalyst, the reaction rate of the cyclization condensation reaction can be improved, and the coloring of the obtained lactone ring structure-containing polymer can be greatly reduced. Furthermore, by using an organic phosphorus compound as a catalyst, it is possible to suppress the decrease in the molecular weight of the polymer that can occur when the lactone cyclization condensation step and the devolatilization step described later are used in combination. Excellent mechanical strength can be imparted.

Examples of the organic phosphorus compound that can be used as a catalyst for the cyclization condensation reaction include alkyl (aryl) sulfites such as methyl sulfonate, ethyl sulfonate, and phenyl sulfonate (provided that these tautomeric alkyl (aryl) phosphinic acids) and monoesters or diesters thereof; Dialkyl(aryl)phosphinic acids and esters thereof; Alkyl(aryl)phosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, phenylphosphonic acid and monoesters or diesters thereof; methylphosphinic acid, ethylphosphite acids, alkyl (aryl) phosphites such as phenylphosphite and their esters; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, Phosphite monoesters, diesters or triesters such as trimethyl phosphite, triethyl phosphite and triphenyl phosphite; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, Lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diiso phosphate Phosphate monoesters, diesters or triesters such as stearyl, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, and triphenyl phosphate; mono-, di- or tri-alkyl(aryl)phosphines such as phosphine, ethylphosphine, phenylphosphine, dimethylphosphine, diethylphosphine, diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine; methyldichlorophosphine, ethyldichlorophosphine, Alkyl (aryl) halogen phosphines such as phenyldichlorophosphine, dimethylchlorophosphine, diethylchlorophosphine, diphenylchlorophosphine; methylphosphine oxide, ethyl oxide mono-, di- or tri-alkyl(aryl)phosphine oxides such as phosphine, phenylphosphine oxide, dimethylphosphine oxide, diethylphosphine oxide, diphenylphosphine oxide, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide; tetramethyl chloride; and tetraalkyl(aryl)phosphonium halides such as phosphonium, tetraethylphosphonium chloride, and tetraphenylphosphonium chloride.

Among these organic phosphorus compounds, alkyl (aryl) phosphonous acids, phosphorous diesters or monoesters, phosphoric acid diesters or monoesters, and alkyl (aryl) phosphonic acids are preferred because of their high catalytic activity and low colorability. , alkyl(aryl)phosphonous acids, phosphorous diesters or monoesters, phosphoric acid diesters or monoesters are more preferred, and alkyl(aryl)phosphonous acids, phosphoric acid diesters or monoesters are particularly preferred. A plurality of types of these organic phosphorus compounds may be used in combination.

The amount of the catalyst used in the cyclization condensation reaction is not particularly limited, but is preferably in the range of 0.001 to 5% by mass, more preferably 0.01 to 5% by mass, relative to the polymer. It is in the range of 2.5 mass %, more preferably in the range of 0.01 to 1 mass %, particularly preferably in the range of 0.05 to 0.5 mass %. If the amount of the catalyst used is less than 0.001% by mass, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. On the other hand, if the amount of the catalyst used exceeds 5% by mass, it may cause coloring of the lactone ring structure-containing polymer, or the cross-linking of the polymer may make melt-shaping difficult.

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

As a method for producing a lactone ring structure-containing polymer, it is preferable to carry out the lactone cyclization condensation step in the presence of a solvent, and to use a devolatilization step in combination with the lactone cyclization condensation step. Examples of such a production method include (i) a mode in which the devolatilization step is used throughout the lactone cyclization condensation step, and (ii) a devolatilization step is used only in part of the lactone cyclization condensation step. morphology. In the method using the devolatilization step in combination, the alcohol by-produced in the cyclization condensation reaction is forcibly devolatilized and removed, so the equilibrium of the reaction favors the production side.

The form in which the devolatilization step is used in combination only in part of the lactone cyclization condensation step is, for example, after the polymer is produced, the apparatus in which the polymer is produced is further heated to advance the cyclization condensation reaction to some extent in advance. After that, a cyclization condensation reaction is performed in combination with a devolatilization step to complete the reaction. Here, even in the step of further heating the apparatus in which the polymer is produced to advance the cyclization condensation reaction to some extent in advance, the devolatilization step may be partially used in combination, if necessary. All forms in which the lactone cyclization condensation step and the devolatilization step are used in combination and the degassing step is not used in combination throughout the lactone cyclization condensation step are classified into this embodiment.

Here, the devolatilization step refers to a step of removing volatile matter such as a solvent and residual monomers, and alcohol by-produced by a cyclization condensation reaction leading to a lactone ring structure. The devolatilization step may be performed under reduced pressure heating conditions, if necessary. If this removal treatment is insufficient, the resulting lactone ring structure-containing polymer will have a large amount of residual volatile matter, resulting in coloration of the lactone ring structure-containing polymer due to deterioration during molding, etc., bubbles, silver streaks, and the like. Problems such as defective molding occur.

In the embodiment in which the devolatilization step is used in combination with the lactone cyclization condensation step, the device to be used is not particularly limited. In order to carry out the production method of the present invention more effectively, (i) a devolatilization device consisting of a heat exchanger and a devolatilization tank, (ii) an extruder with a vent, or (iii) a devolatilization device and a vent It is preferable to use an apparatus in which an extruder with a vent is arranged in series, and it is more preferable to use (i) a devolatilizing apparatus comprising a heat exchanger and a devolatilizing tank or (ii) an extruder with a vent.

When the devolatilization device comprising a heat exchanger and a devolatilization tank is used, the temperature during the cyclization condensation reaction is preferably in the range of 150 to 350°C, more preferably in the range of 200 to 300°C. If the temperature is lower than 150°C, the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. If the temperature is higher than 350°C, the lactone ring structure-containing polymer may be colored or decomposed.

When using the devolatilization device consisting of a heat exchanger and a devolatilization tank, the pressure during the cyclization condensation reaction is preferably in the range of 931 to 1.33 hPa (700 to 1 mmHg), 798 to 66.5 hPa (600 ~50 mmHg) is more preferred. If the pressure is higher than 931 hPa, volatile matter including alcohol may easily remain in the lactone ring structure-containing polymer. If the pressure is lower than 1.33 hPa, industrial implementation may become difficult.

When the extruder with vents is used, the number of vents may be one or plural, but plural is more preferable.

When the vented extruder is used, the temperature during the cyclization condensation reaction is preferably in the range of 150 to 350°C, more preferably in the range of 200 to 300°C. If the temperature is lower than 150°C, the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. If the temperature is higher than 350°C, the lactone ring structure-containing polymer may be colored or decomposed.

When using the vented extruder, the pressure during the cyclization condensation reaction is preferably in the range of 931 to 1.33 hPa (700 to 1 mmHg), more preferably in the range of 798 to 13.3 hPa (600 to 10 mmHg). . If the pressure is higher than 931 hPa, volatile matter including alcohol may easily remain in the lactone ring structure-containing polymer. If the pressure is lower than 1.33 hPa, industrial implementation may become difficult.

In addition, in the form in which the devolatilization step is used throughout the lactone cyclization condensation step, the physical properties of the lactone ring structure-containing polymer obtained by heat treatment under severe conditions may deteriorate, as will be described later. Therefore, preferably, the devolatilization step is carried out using a vented extruder or the like under mild conditions as much as possible using the catalyst for the cyclization condensation reaction described above. Here, “heat treatment under severe conditions” refers to heat treatment performed under high temperature conditions of 300° C. or higher, for example. On the other hand, “heat treatment under mild conditions” refers to heat treatment performed at a temperature of 250 to 300° C., for example.

Moreover, in the form in which the devolatilization step is used in combination throughout the lactone cyclization condensation step, preferably the polymer obtained in the polymerization step is introduced into the reactor together with the solvent. In this case, if desired, the polymer removed from the reactor may be passed through the devolatilizer or vented extruder again.

In a form in which a devolatilization step is used in combination throughout the lactone cyclization condensation step (for example, a form in which the polymer is heat-treated at a high temperature of nearly 250 ° C. or higher using a twin-screw extruder), due to differences in heat history A phenomenon such as partial decomposition of the polymer may occur before the cyclization condensation reaction occurs. If such a phenomenon occurs, the physical properties of the obtained lactone ring structure-containing polymer may deteriorate.

Therefore, it is preferable that the lactone ring condensation step is combined with the devolatilization step only in part of the lactone ring condensation step. For example, if the cyclization condensation reaction is allowed to proceed to some extent in advance before performing the lactone cyclization condensation step in which the devolatilization step is also used, the reaction conditions in the latter half can be relaxed, and the resulting lactone ring structure-containing It is preferable because deterioration of the physical properties of the polymer can be suppressed.

A particularly preferred form is a form in which the devolatilization step is started after some time from the start of the lactone cyclization condensation step. Specifically, (i) the hydroxyl group and the ester group present in the molecular chain of the polymer obtained in the polymerization step are previously subjected to a cyclic condensation reaction to increase the reaction rate of the cyclic condensation reaction to some extent. Then, (ii) the lactone cyclization condensation step is performed in combination with the devolatilization step. More specifically, for example, (i) the cyclization condensation reaction is advanced in advance to a certain degree of reaction rate in the presence of a solvent using a pot reactor, and then (ii) a devolatilization device is installed. It is a mode in which the cyclization condensation reaction is completed in a provided reactor (for example, a devolatilization device consisting of a heat exchanger and a devolatilization tank, an extruder with a vent, etc.). In this form, it is particularly preferred that a catalyst for the cyclization condensation reaction is present in the reaction system.

As described above, (i) the hydroxyl group and the ester group present in the molecular chain of the polymer obtained in the polymerization step are previously subjected to a cyclic condensation reaction to increase the reaction rate of the cyclic condensation reaction to some extent. Then, (ii) the method of performing the lactone cyclization condensation step in combination with the devolatilization step is a preferred mode for obtaining a lactone ring structure-containing polymer. This form further increases the reaction rate of the cyclization condensation reaction. In addition, a lactone ring structure-containing polymer having a higher glass transition temperature and excellent heat resistance can be obtained. In this embodiment, as a guideline for the reaction rate of the cyclization condensation reaction, the mass reduction rate between 150 and 300° C. in the dynamic TG measurement shown in Examples is preferably 2% or less, and 1.5. % or less, more preferably 1% or less.

There is no particular limitation on the reactor that can be used in the cyclization-condensation reaction that is performed in advance before the lactone cyclization-condensation step combined with the devolatilization step. Preferable examples include an autoclave, a kettle-type reactor, a devolatilization device consisting of a heat exchanger and a devolatilization tank, a vented extruder, etc. It can also be suitably used in the condensation step). More preferred are autoclaves and pot-type reactors. However, even when using a reactor such as a vented extruder, (i) venting conditions should be mild (e.g., 931 hPa (700 mmHg) or more), (ii) no venting, (iii) temperature conditions By adjusting barrel conditions, screw shape, screw operation conditions, etc., it is possible to carry out the cyclization condensation reaction in the same reaction conditions as in an autoclave or kettle reactor.

As the cyclization condensation reaction to be performed in advance, preferably, the mixture containing the polymer and the solvent obtained in the polymerization step is (i) reacted by heating with the addition of a catalyst, (ii) by heat reaction without a catalyst. and (iii) a method of performing the above (i) or (ii) under pressure.

The "mixture containing a polymer and a solvent" to be introduced into the cyclization condensation reaction in the lactone cyclization condensation step may be the polymerization reaction mixture obtained in the polymerization step as it is, or the polymerization reaction mixture may be used as it is. A mixture in which the solvent is once removed and then another solvent suitable for the cyclization condensation reaction is added may be used. That is, the solvent used in the cyclization-condensation reaction previously performed before the lactone cyclization-condensation step combined with the devolatilization step may be the solvent used in the polymerization step or another solvent.

The other solvent used in the previously performed cyclization condensation reaction is not particularly limited, and examples thereof include aromatic hydrocarbons such as toluene, xylene and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; chloroform, DMSO, tetrahydrofuran; and the like. However, it is more preferred to use the same type of solvent as that used in the polymerization step.

The catalyst added in the above method (i) includes an esterification catalyst or transesterification catalyst such as p-toluenesulfonic acid, which is generally used as a catalyst for a cyclization condensation reaction, a basic compound, an organic carboxylate, and a carbonate. etc. may be used. However, in one embodiment of the present invention, it is preferred to use the organophosphorus compounds described above.

The timing of addition of the catalyst is not particularly limited, and it may be added at the initial stage of the cyclization condensation reaction, during the reaction, or both. The amount of the catalyst to be added is not particularly limited, but is preferably in the range of 0.001 to 5% by mass, more preferably 0.01 to 2.5% by mass, based on the mass of the polymer. within the range, more preferably within the range of 0.01 to 0.1% by mass, and particularly preferably within the range of 0.05 to 0.5% by mass.

The heating temperature and heating time in method (i) are not particularly limited, but the heating temperature is preferably room temperature or higher, more preferably 50° C. or higher, and the heating time is preferably 1 to 20 hours, more preferably 2 to 10 hours. If the heating temperature is low or the heating time is short, the reaction rate of the cyclization condensation reaction may decrease. Also, if the heating temperature is high or the heating time is long, there is a possibility that the lactone ring structure-containing polymer will be colored or decomposed.

The method (ii) includes, for example, a method in which the polymerization reaction mixture obtained in the polymerization step is heated as it is using a pressure-resistant pot-type reactor or the like. The heating temperature is preferably 100° C. or higher, more preferably 150° C. or higher. The heating time is preferably within the range of 1 to 20 hours, more preferably within the range of 2 to 10 hours. If the heating temperature is low or the heating time is short, the reaction rate of the cyclization condensation reaction may decrease. Also, if the heating temperature is high or the heating time is long, there is a possibility that the lactone ring structure-containing polymer will be colored or decomposed.

Depending on the conditions, both methods (i) and (ii) may be carried out under pressure without any problem (method (iii) above). Moreover, in the cyclization-condensation reaction previously performed, there is no problem even if part of the solvent spontaneously evaporates during the reaction.

At the end of the previously performed cyclization condensation reaction, that is, immediately before the start of the devolatilization step, the mass reduction rate between 150 and 300° C. in dynamic TG measurement is preferably 2% or less. It is more preferably 5% or less, even more preferably 1% or less. If the mass reduction rate is higher than 2%, even if the lactone cyclization condensation step in combination with the devolatilization step is continuously performed, the reaction rate of the cyclization condensation reaction does not rise to a sufficiently high level, resulting in a lactone ring structure. The physical properties of the contained polymer may deteriorate.

In addition, in the lactone cyclization condensation step (including both the step of using the devolatilization step together and the step of not using the devolatilization step together), another thermoplastic resin coexists in the mixture containing the polymer and the solvent. You may let As the other thermoplastic resin, a thermoplastic resin that is thermodynamically compatible with the lactone ring structure-containing polymer is preferable. Other thermoplastic resins include, for example, copolymers containing vinyl cyanide-based monomer units and aromatic vinyl-based monomer units. Specific examples include acrylonitrile-styrene copolymers, polyvinyl chloride resins, and polymers containing 50% by mass or more of methacrylic acid esters.

Among these other thermoplastic resins, acrylonitrile-styrene copolymers are more preferable because they have the best compatibility and can give transparent molded articles without impairing heat resistance. Whether or not the lactone ring structure-containing polymer and the other thermoplastic resin are thermodynamically compatible can be confirmed by measuring the glass transition point of the thermoplastic resin composition obtained by mixing the two. can do. Specifically, when only one glass transition point of the thermoplastic resin composition measured by a differential scanning calorimeter is observed, it can be said that both are thermodynamically compatible.

When an acrylonitrile-styrene copolymer is used as another thermoplastic resin, methods for polymerizing the lactone ring structure-containing polymer and the acrylonitrile-styrene copolymer include emulsion polymerization, suspension polymerization, solution A polymerization method, a bulk polymerization method, and the like can be mentioned. Among these polymerization methods, the solution polymerization method and the bulk polymerization method are more preferable from the viewpoint of the transparency and optical performance of the resulting optical film.

(i) The hydroxyl groups and ester groups present in the molecular chain of the polymer obtained in the polymerization step are subjected to a cyclization condensation reaction to raise the reaction rate of the cyclization condensation reaction to some extent in advance, and then ( ii) In a mode in which a lactone cyclization condensation step is performed in combination with a devolatilization step, the polymer obtained by the cyclization condensation reaction previously performed (part of the hydroxyl groups and ester groups present in the molecular chain undergoes the cyclization condensation reaction The lactone cyclization condensation step may be started in combination with the devolatilization step without separating the polymer) and the solvent. In addition, if necessary, other treatment (polymer obtained by previous cyclization condensation reaction (polymer in which part of the hydroxyl group and ester group present in the molecular chain has undergone cyclization condensation reaction) and solvent After separation, another solvent is added, etc.), and then the lactone cyclization condensation step in combination with the devolatilization step may be started.

The devolatilization step does not need to be completed at the same time as the lactone cyclization condensation step, and may be completed after some time from the lactone cyclization condensation step. That is, the devolatilization step may be completed before or after the lactone cyclization condensation step.

As described above, in the lactone cyclization condensation step, hydroxyl groups and ester groups present in the molecular chain of the polymer undergo a cyclization condensation reaction to cause a dealcoholization reaction, which is a type of transesterification. A lactone ring structure is formed in the combined molecular chain (in the main skeleton of the polymer).

As also mentioned above, it is preferred to use a catalyst during the cyclization condensation reaction. However, if the catalyst remains in the lactone ring structure-containing polymer, when the lactone ring structure-containing polymer is heated, unreacted ring-forming units (that is, units that have not yet formed a ring) ) or an active hydrogen such as water present in a small amount in the system and the alkyl ester group may be transesterified. As a result, alcohol is generated and a foaming phenomenon may occur. Therefore, in order to prevent this foaming phenomenon, it is preferable to add a deactivator to the lactone ring structure-containing polymer.

In general, when the catalyst used in the cyclization condensation reaction such as transesterification is an acidic substance, neutralization with a basic substance is sufficient to deactivate the catalyst remaining after the reaction. Therefore, when the catalyst used for the cyclization condensation reaction is an acidic substance, a basic substance is preferably used as the deactivator. The basic substance is not particularly limited as long as it does not generate a substance that inhibits the physical properties of the resin composition during thermal processing. metal compounds of

The metal that constitutes the metal compound is not particularly limited as long as it does not impair the physical properties of the resin composition and does not cause environmental pollution upon disposal. Examples include alkali metals such as lithium, sodium and potassium; alkaline earth metals such as magnesium, calcium, strontium and barium; amphoteric substances such as zinc, aluminum, tin and lead; zirconium; Among these metals, typical metal elements are preferred, alkaline earth metals and amphoteric metals are particularly preferred, and calcium, magnesium and zinc are most preferred, since they cause little coloration of the resin composition.

The metal salt is preferably a metal salt of an organic acid, more preferably a metal salt of an organic carboxylic acid, an organic phosphorus compound, or an acidic organic sulfur compound, in terms of dispersibility in the resin composition and solubility in a solvent. preferable.

The organic carboxylic acid constituting the metal salt of organic carboxylic acid is not particularly limited. For example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, pehenic acid, tridecanoic acid, pentadecanoic acid, heptadecanoic acid, lactic acid, malic acid, citric acid, oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, adipic acid and the like.

Examples of the organophosphorus compound constituting the metal salt of the organophosphorus compound include the organophosphorus compounds described above.

Examples of the acidic organic sulfur compound constituting the metal salt of the acidic organic sulfur compound include p-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, and dodecylbenzenesulfonic acid.

Examples of the organic component in the metal complex include, but are not particularly limited to, acetylacetone.

Examples of metal oxides include, but are not limited to, zinc oxide, calcium oxide, and magnesium oxide.

On the other hand, in general, when the catalyst used in the cyclization condensation reaction such as transesterification is a basic substance, the catalyst remaining after the reaction can be deactivated by neutralization with an acidic substance. Therefore, when the catalyst used for the cyclization condensation reaction is a basic substance, an acidic substance is preferably used as the deactivator. The acidic substance is not particularly limited as long as it does not generate a substance that inhibits the physical properties of the resin composition during thermal processing, and examples thereof include organic phosphorus compounds.

Multiple types of deactivators may be used in combination regardless of whether the catalyst is an acidic substance or a basic substance. The deactivator may be added to the lactone ring structure-containing polymer in any form such as solid, powder, granule, dispersion, suspension, aqueous solution, etc., and is not particularly limited.

The amount of the deactivator to be added may be appropriately adjusted according to the amount of the catalyst used in the cyclization condensation reaction, and is not particularly limited. The amount of the deactivator is, for example, preferably 10 ppm or more and 10,000 ppm or less, more preferably 50 ppm or more and 5000 ppm or less, and still more preferably 100 ppm or more and 3000 ppm or less, based on the mass of the lactone ring structure-containing polymer. be. If the amount is less than 10 ppm, the action of the deactivator may be insufficient and bubbles may be generated during heating. If the content exceeds 10,000 ppm, the action of the deactivator is saturated and the deactivator is used more than necessary, resulting in an increase in manufacturing cost.

The deactivator may be added to the lactone ring structure-containing polymer at any stage after the lactone ring structure is formed. For example, after producing a lactone ring structure-containing polymer, the lactone ring structure-containing polymer, a deactivator, other components, etc. are heated and melted at the same time and kneaded; A method of heating and melting, adding a deactivator thereto and kneading; The "other components" referred to here are, for example, antioxidants, other thermoplastic resins, and the like.

[Characteristics of polymer containing lactone ring structure]
The weight average molecular weight of the lactone ring structure-containing polymer obtained in the present embodiment is preferably 1,000 or more and 2,000,000 or less, more preferably 5,000 or more and 1,000,000 or less, and still more preferably is 10,000 or more and 500,000 or less, particularly preferably 50,000 or more and 500,000 or less.

The lactone ring structure-containing polymer preferably has a mass loss rate of 1% or less, more preferably 0.5% or less, in a dynamic TG measurement between 150 and 300°C. It is more preferably 3% or less.

Since the lactone ring structure-containing polymer obtained in the present embodiment has a high reaction rate of the cyclization condensation reaction, it is possible to avoid defects such as bubbles and silver streaks in the molded article after molding. Furthermore, since the lactone ring structure is sufficiently introduced into the lactone ring structure-containing polymer due to the high reaction rate of the cyclization condensation reaction, the obtained lactone ring structure-containing polymer has sufficiently high heat resistance. is doing.

The lactone ring structure-containing polymer preferably has a 5% mass loss temperature in thermogravimetric analysis (TG) of 280°C or higher, more preferably 290°C or higher, and even more preferably 300°C or higher. . The 5% mass loss temperature in thermogravimetric analysis (TG) is an index of thermal stability, and when the temperature is less than 280°C, the obtained lactone ring structure-containing polymer exhibits sufficient thermal stability. It may not work.

The total amount of residual volatile matter contained in the lactone ring structure-containing polymer is preferably 5,000 ppm or less, more preferably 2,000 ppm or less. If the total amount of residual volatile matter is more than 5,000 ppm, the lactone ring structure-containing polymer may be colored or foamed due to deterioration during molding, or molding defects such as silver streaks may occur.

The lactone ring structure-containing polymer preferably has a total light transmittance of 85% or more, more preferably 88% or more, of a molded article obtained by injection molding, as measured by a method according to ASTM-D-1003. Preferably it is 90% or more. The total light transmittance is a measure of transparency, and if the transmittance is less than 85%, the transparency may deteriorate and the intended use may not be possible.

[Structures of Glutaric Anhydride Structure-Containing Polymer and Glutarimide Structure-Containing Polymer]
The (meth)acrylic resin may be a so-called glutaric anhydride structure-containing polymer or glutarimide structure-containing polymer in which a glutaric anhydride structure or a glutarimide structure is introduced into the main chain of the polymer. In this specification, a (meth)acrylic resin having a glutaric anhydride structure introduced into the main chain is referred to as a glutaric anhydride structure-containing polymer, and a (meth)acrylic resin having a glutarimide structure introduced into the main chain. The resin is called a glutarimide structure-containing polymer.

Although the glutaric anhydride structure-containing polymer and the glutarimide structure-containing polymer are not particularly limited, they preferably have a glutaric anhydride structure or a glutarimide structure represented by the following general formula (3).

(wherein R ¹⁷ and R ¹⁸ each independently represent a hydrogen atom or a methyl group; X ¹ represents an oxygen atom or a nitrogen atom; and when X ¹ is an oxygen atom, R ¹⁹ is present and when X ¹ is a nitrogen atom, R ³ represents a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group or a phenyl group).

That is, when X1 in general formula ( ³ ) is an oxygen atom, the ring structure represented by general formula (3) is a glutaric anhydride structure. The glutaric anhydride structure-containing polymer can be formed, for example, by subjecting a copolymer of (meth)acrylic acid ester and (meth)acrylic acid to an intramolecular dealcoholization cyclization condensation reaction.

The method of intramolecular dealcoholization cyclization condensation reaction is not particularly limited, but can be carried out, for example, by heating the copolymer. The heating temperature is not particularly limited as long as it is a temperature at which dealcoholization causes an intramolecular cyclization reaction. The heating time may be appropriately changed according to the composition of the (meth)acrylic resin, and is preferably within the range of 1 to 2 hours, for example. In the dealcoholization cyclization condensation reaction, a catalyst (for example, an acid catalyst, a basic catalyst, a salt-based catalyst, etc.) may be used as necessary.

When X1 in general formula (3) is ^a nitrogen atom, the ring structure represented by general formula (3) is a glutarimide structure. A glutarimide structure-containing polymer can be formed, for example, by imidating a (meth)acrylic acid ester polymer with an imidizing agent such as methylamine. A known method can be used for the imidization method. Specifically, for example, ammonia, a substituted amine, or the like can be used to imidize a (meth)acrylic acid ester polymer.

[N-Substituted Maleimide Structure-Containing Polymer and Maleic Anhydride Structure-Containing Polymer]
The (meth)acrylic resin may be a so-called N-substituted maleimide structure-containing polymer or maleic anhydride structure-containing polymer in which an N-substituted maleimide structure or maleic anhydride structure is introduced into the main chain of the polymer. good. In this specification, a (meth)acrylic resin in which an N-substituted maleimide structure is introduced into the main chain is referred to as an N-substituted maleimide structure-containing polymer, and a maleic anhydride structure is introduced into the main chain (meth)acrylic resin. ) The acrylic resin is called a maleic anhydride structure-containing polymer.

The above N-substituted maleimide structure-containing polymer and maleic anhydride structure-containing polymer are not particularly limited, but have an N-substituted maleimide structure or maleic anhydride structure represented by the following general formula (4). is more preferred.

(wherein R ²⁰ and R ²¹ each independently represent a hydrogen atom or a methyl group; X ² represents an oxygen atom or a nitrogen atom; and when X ² is an oxygen atom, R ²² is present and when X ² is a nitrogen atom, R ²² represents a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group, a benzyl group or a phenyl group).

That is, when X2 in general formula ( ⁴ ) is an oxygen atom, the ring structure represented by general formula (4) is a maleic anhydride structure. The maleic anhydride structure-containing polymer can be formed, for example, by copolymerizing maleic anhydride and (meth)acrylic acid ester (for example, by radical polymerization, preferably by solution polymerization). When X ² in general formula (4) is a nitrogen atom, the ring structure represented by general formula (4) is an N-substituted maleimide structure. An N-substituted maleimide structure-containing polymer can be formed, for example, by copolymerizing an N-substituted maleimide and a (meth)acrylic acid ester (for example, by radical polymerization, preferably by solution polymerization).

In the glutaric anhydride structure-containing polymer, the glutarimide structure-containing polymer, the N-substituted maleimide structure-containing polymer, and the maleic anhydride structure-containing polymer, all the polymers used to form each ring structure are (meta) It has an acrylic acid ester unit as a structural unit. Therefore, the resin obtained by this method is included in the category of (meth)acrylic resin.

The lactone ring structure-containing polymer, the glutaric anhydride structure-containing polymer, the glutarimide structure-containing polymer, the N-substituted maleimide structure-containing polymer, and the maleic anhydride structure-containing polymer may be used in combination if necessary. good too. That is, the thermoplastic resin composition in the embodiment of the invention may be a mixture of these polymers.

[3. UV absorber]
A thermoplastic resin composition in one embodiment of the present invention contains a (meth)acrylic resin and an ultraviolet absorber having a thermal decomposition temperature of 360° C. or lower.

A thermoplastic resin composition according to another embodiment of the present invention contains a (meth)acrylic resin having a glass transition temperature of 108° C. or higher and an ultraviolet absorber having a thermal decomposition temperature of 360° C. or lower.

Although the lower limit of the thermal decomposition temperature of the ultraviolet absorber is not particularly limited, it should be 250° C. or higher so that the ultraviolet absorber contained in the thermoplastic resin composition does not decompose during the production of the optical film. more preferred. Therefore, the ultraviolet absorber preferably has a thermal decomposition temperature of 250° C. or higher and 360° C. or lower.

The thermal decomposition temperature (Td) of the ultraviolet absorber can be measured using, for example, a differential thermal balance apparatus. A more specific method is described in Examples. In addition, values published by the manufacturer can also be adopted.

The ultraviolet absorber is not particularly limited. Specifically, for example, at least one selected from benzophenone-based compounds, salicicate-based compounds, benzoate-based compounds, cyanoacrylate-based compounds, benzotriazole-based compounds, and triazine-based compounds can be used. Among these UV absorbers, benzotriazole-based compounds and triazine-based compounds are more preferable because of their high UV absorbability.

As the benzotriazole-based compound, an ultraviolet absorber represented by the following general formula (5) is preferable.

(wherein R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms (the alkyl group may optionally have a substituent) (R ³ and R ⁴ each independently represent a hydrogen atom or a halogen atom, and L represents an alkylene group having 1 to 4 carbon atoms).

Among the UV absorbers represented by the general formula (5), 2,2′-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1) represented by the following formula, which is the compound a described above ,3,3-tetramethylbutyl)phenol] (trade name: LA-31, manufactured by ADEKA Corporation) is particularly preferable.

As the triazine-based compound, an ultraviolet absorber represented by the following general formula (6) is preferable.

(In the formula, R ²³ represents a hydrogen atom or a group represented by the formula “—OR ²⁷ ”. R ²⁷ represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an alkyl ester group. R ²⁴ to R ²⁶ each independently represent a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an alkyl ester group, provided that the alkyl ester group is represented by the formula “—CH(—R ²⁸ )C (=O) OR ²⁹ ", R ²⁸ is a hydrogen atom or a methyl group, and R ²⁹ is an alkyl group. R ²⁴ to R ²⁶ and R ²⁷ and R ²⁹ is a linear or branched alkyl group).

The molecular weight of the ultraviolet absorber is preferably 400 or more. If the molecular weight is less than 400, too much ultraviolet absorber is sucked into the vent during production of the thermoplastic resin composition or the optical film, which may clog pipes and the like.

[4. Manufacturing method of optical film]
A method for producing an optical film according to an embodiment of the present invention contains 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less with respect to 100 parts by weight of (meth)acrylic resin. , A method of forming a touch roll film after discharging a melt made of a thermoplastic resin composition from a die in the form of a film, wherein the thermal decomposition temperature Td (° C.) of the ultraviolet absorber and the above at the exit of the die In this method, the relationship with the melt temperature Tp (° C.) satisfies the formula “50≦Td−Tp”.

A method for producing an optical film according to another embodiment of the present invention comprises producing a melt of a thermoplastic resin composition containing a (meth)acrylic resin and an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less. A method for producing an optical film, wherein the (meth)acrylic resin has a glass transition temperature of 108° C. or higher, and the melt is discharged from a die in the form of a film, followed by film formation with a touch roll. is.

[1] As explained in section [1], in the production of optical films, touch roll film formation is usually a film formation method that is not adopted. It has been found that there is an effect of suppressing In order to further enhance this effect, it is preferable to adjust the temperature of the melt at the exit of the die so as to satisfy "50≦Td−Tp".

The temperature of the melt is the highest of the temperatures measured at multiple points by contacting a needle-shaped or rod-shaped thermocouple with the melt immediately after being discharged from a die such as a T die (within 30 mm from the die lip). refers to temperature.

Although the upper limit of "Td-Tp" is not particularly limited, it is more preferably 90°C or less. Therefore, "Td-Tp" is more preferably 50°C or higher and 90°C or lower, further preferably 55°C or higher and 85°C or lower, and particularly 60°C or higher and 80°C or lower. preferable. If "Td-Tp" is less than 50°C, the ultraviolet absorber contained in the thermoplastic resin composition will be thermally decomposed. If "Td-Tp" exceeds 90°C, the viscosity of the melt is high and the flow within the die is poor. As a result, the melt does not flow sufficiently to the edge, and the film thickness profile may deteriorate.

The above-mentioned touch roll film formation is, for example, a film of a predetermined size and thickness by sandwiching a melt of a thermoplastic resin composition continuously discharged from a die in the form of a film between a touch roll and a cast roll. It is a method of continuously forming a film. More specifically, touch roll film formation involves, for example, discharging the melt from a die between a touch roll and a cast roll, sandwiching it between the touch roll and the cast roll and molding it, and then cooling and solidifying it. This is a method of continuously forming a film. Touch roll film formation is an effective film formation method for suppressing bleed out.

[Thermoplastic resin composition]
In one embodiment of the present invention, the thermoplastic resin composition contains 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less with respect to 100 parts by weight of (meth)acrylic resin. more preferably within the range of 0.3 to 4 parts by weight, more preferably within the range of 0.5 to 3.5 parts by weight. If the amount of the ultraviolet absorber is less than 0.1 parts by weight or exceeds 5 parts by weight, an optical film with good optical properties cannot be produced.

The method of adding the ultraviolet absorber to the (meth)acrylic resin is not particularly limited. The thermoplastic resin composition according to one embodiment of the present invention is obtained by uniformly mixing the (meth)acrylic resin and the ultraviolet absorber.

The thermoplastic resin composition according to the embodiment of the present invention may contain other polymers than the (meth)acrylic resin as long as the effects of the present invention are not impaired.

Other polymers include, for example, olefinic polymers such as polyethylene, polypropylene, ethylene-propylene polymers, and poly(4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins. ; acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polymer polyethylene terephthalate, polyesters such as polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyamide-imide; rubber-like polymers such as ABS resin and ASA resin compounded with polybutadiene-based rubber and acrylic-based rubber; and the like.

Further, the thermoplastic resin composition in the embodiment of the present invention contains a solvent, unreacted monomers, and volatile components such as by-products generated during the reaction process, as long as the effects of the present invention are not impaired. , or may contain a diluting solvent or the like. The total content of the volatile matter in 100% by mass of the thermoplastic resin composition in the embodiment of the invention is preferably 5000 mass ppm or less, more preferably 3000 mass ppm or less. If it is 5,000 ppm by mass or more, there is a risk that coloration may occur during molding, and molding defects such as silver streaks may occur.

Here, the content of structural units derived from styrene-based monomers in 100% by mass of the thermoplastic resin composition in the embodiment of the present invention is preferably 0% by mass or more and less than 10% by mass, more preferably 0% by mass. % or more and less than 8 mass %, more preferably 0 mass % or more and less than 5 mass %. If the content of structural units derived from styrene-based monomers in the thermoplastic resin composition is 10% by mass or more, the optical properties may deteriorate due to heat during long-term use.

The thermoplastic resin composition according to the embodiment of the present invention may contain additives other than the ultraviolet absorbent as long as the effects of the present invention are not impaired. Other additives include, for example, antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers. near-infrared absorbers; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; retardation modifiers such as phase difference increasing agents, phase difference reducing agents, and phase difference stabilizers; , antistatic agents including nonionic surfactants; coloring agents such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; organic fillers and inorganic fillers; The content of other additives in 100% by mass of the thermoplastic resin composition in the embodiment of the present invention is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 1% by mass. is within the range of

Examples of the coloring agent include a compound having an anthraquinone skeleton, a compound having a phthalocyanine skeleton, and the like. Among these, compounds having an anthraquinone skeleton are preferred from the viewpoint of heat resistance. The content of the colorant in 100% by mass of the thermoplastic resin composition in the embodiment of the present invention is preferably 0.01 to 5 mass ppm, more preferably 0.05 to 3 mass ppm, and 0.1 to 1 mass ppm is more preferred. A known colorant can be appropriately used. For example, specifically, "Macrolex (registered trademark) Violet B", "Macrolex (registered trademark) Violet 3R" (manufactured by Lanxess Corporation), "Sumiplast (registered trademark) Violet B" and "Sumiplast (registered trademark) Green" G" (manufactured by Sumika Chemtex Co., Ltd.) and the like. The colorant can reduce the hue and saturation of the thermoplastic resin composition according to the embodiment of the invention.

Other polymers and additives may be mixed when mixing the (meth)acrylic resin and the ultraviolet absorber, or may be mixed with the (meth)acrylic resin and/or the ultraviolet absorber in advance. It may be mixed with the other after being set aside. A mixing method is not particularly limited.

Here, in producing the thermoplastic resin composition according to the embodiment of the present invention, metal elements may be mixed in through various routes. For example, metal elements derived from additives such as polymerization initiators, cyclization catalysts, and deactivators during the production of (meth)acrylic resins, and metal elements derived from UVA and other additives during the production of thermoplastic resin compositions. can be considered. The content of the metal element in 100% by mass of the thermoplastic resin composition in the embodiment of the present invention is preferably 0 to 200 mass ppm, more preferably 0 to 100 mass ppm, still more preferably 0 to 60 mass ppm, especially It is preferably within the range of 0 to 10 mass ppm. If the content of the metal element in the thermoplastic resin composition exceeds 200 ppm by mass, the hue and saturation of the thermoplastic resin composition may increase, and the transparency may deteriorate due to the generation of foreign matter. . Metal elements that bring about such undesirable effects are not particularly limited. Examples include alkali metals, alkaline earth metals, and heavy metals, since they may form a complex with an ultraviolet absorber that is a benzotriazole-based compound and increase hue and saturation. Examples include zinc, copper, Iron etc. are mentioned.

The glass transition temperature (Tg) of the thermoplastic resin composition in the embodiment of the present invention is not particularly limited as long as it is 108° C. or higher, preferably 110° C. or higher, hereinafter 111° C. or higher, 113° C. or higher, 115° C. or higher, 117° C. or higher, and 120° C. or higher are preferred in that order. When the Tg of the thermoplastic resin composition is less than 110° C., for example, when an optical film made of the thermoplastic resin composition is incorporated as a polarizing plate of an optical device, sufficient durability at high temperatures is not obtained. You may not be able to perform. However, if the Tg of the thermoplastic resin composition is too high, it is necessary to raise the molding temperature of the thermoplastic resin composition, and therefore, foaming occurs during molding or the ultraviolet absorber bleeds out. Tg of the thermoplastic resin composition is preferably 200° C. or lower, more preferably 180° C. or lower, still more preferably 150° C. or lower, and particularly preferably 140° C. or lower. Incidentally, the glass transition temperature of the thermoplastic resin composition can be regarded as substantially the same as the glass transition temperature of the optical film.

The thermal decomposition temperature (thermal decomposition initiation temperature; Td) of the thermoplastic resin composition in one embodiment of the present invention is preferably 310° C. or higher, more preferably 315° C. or higher, and 320° C. or higher. It is even more preferable to have It can be said that a thermoplastic resin composition having a thermal decomposition temperature of 310° C. or higher has sufficient heat resistance. Although the upper limit of the thermal decomposition temperature is not particularly limited, it can be about 380°C. Incidentally, the thermal decomposition temperature of the thermoplastic resin composition can be regarded as substantially the same as the thermal decomposition temperature of the optical film. By forming a touch roll film from a thermoplastic resin composition having such a thermal decomposition temperature, advantages such as reduction of film defects, reduction of film coloring, and suppression of air bubbles can be obtained.

The thermal decomposition temperature (Td) of a thermoplastic resin composition can be measured using dynamic TG for the thermoplastic resin composition. A specific measuring method is as described in Examples.

(Optical performance when made into an unstretched film with a thickness of 100 μm)
The thermoplastic resin composition in one embodiment of the present invention has a c ^* value of 0.45 or less, measured in accordance with JIS Z 8729, when made into an unstretched film with a thickness of 100 µm. It is preferably 0.35 or less, more preferably 0.30 or less, and still more preferably 0.25 or less. In addition, the absolute value of the a ^* value measured in accordance with JIS Z 8729 when an unstretched film having a thickness of 100 μm is preferably 0.10 or less, more preferably 0.05 or less. preferable. Furthermore, the absolute value of the b ^* value measured in accordance with JIS Z 8729 when an unstretched film having a thickness of 100 μm is preferably 0.45 or less, more preferably 0.35 or less, and 0.30. The following is more preferable, and 0.25 or less is particularly preferable. In addition, the L ^* value measured in accordance with JIS Z 8729 when an unstretched film having a thickness of 100 μm is preferably 95.0% or more, more preferably 98.0% or more. It is preferably 99.0% or more, more preferably 99.5% or more, and particularly preferably 99.5% or more. If the thermoplastic resin composition in one embodiment of the present invention is within the above range, it can be suitably used for optical films such as polarizer protective films.

Here, the a ^* value, b ^* value and L ^* value described above are indices in the L ^* a ^* b ^* color system defined in JIS Z 8729, and the a ^* value and b ^* value indicate the hue. and the L ^* value represents lightness. The c ^* value represents chroma, and is calculated from the above a ^* and b ^* values by the following formula.

c ^* = (a ^*2 +b ^*2 ) ^1/2 .

For the a ^* value, b ^* value and c ^* value, the closer to 0, the closer to achromatic color. The closer the L ^* value is to 100%, the closer it is to white, meaning that all white light is transmitted. Optical films used for polarizer protective films, etc., need to be nearly achromatic in order to improve color reproducibility from the backlight, and must have high brightness to achieve high contrast. be. The thermoplastic resin composition according to one embodiment of the present invention is more nearly achromatic and exhibits high brightness, and therefore can be suitably used for optical films.

The thermoplastic resin composition in one embodiment of the present invention has a light transmittance of 3.0% or less at a wavelength of 380 nm measured in accordance with JIS K7361:1997 when made into an unstretched film with a thickness of 100 μm. is preferably 2.0% or less, more preferably 1.5% or less. If the light transmittance at a wavelength of 380 nm of the unstretched film is within this range, it can exhibit sufficient ultraviolet absorption ability when incorporated as a polarizing plate of an optical device. In addition, the thermoplastic composition preferably has a light transmittance of 95.0% or more at a wavelength of 420 nm as measured in accordance with JIS K7361:1997 when an unstretched film having a thickness of 100 μm is formed. , more preferably 96.0% or more, more preferably 97.0% or more. If the light transmittance of the unstretched film at a wavelength of 420 nm is within this range, the transmittance in the visible light region is high, which is particularly suitable when the thermoplastic resin composition is used for optical applications.

The thermoplastic resin composition in one embodiment of the present invention has a total light transmittance of preferably 95.0% or more, more preferably 97.0% or more, and still more preferably 100 μm thick unstretched film. is 99.0% or more.

The thermoplastic resin composition in one embodiment of the present invention preferably has a haze of 1.0% or less when made into an unstretched film having a thickness of 100 µm. It is more preferably 0.8% or less, still more preferably 0.5% or less. If the haze exceeds 1.0%, the transparency is lowered and the thermoplastic resin composition is not suitable for optical applications.

[Die]
The die is provided at the outlet of the melting device that melts the thermoplastic resin composition. Then, the melt of the thermoplastic resin composition is made into a film and is continuously discharged onto a touch roll or a cast roll. The material of the die is preferably metal, more preferably stainless steel. The size and number of dies may be appropriately set according to the amount of melt to be discharged, and are not particularly limited.

The temperature of the die may be appropriately set according to the temperature of the melt to be discharged, and is not particularly limited. However, the above temperature is determined by the relationship between the thermal decomposition temperature Td (° C.) of the ultraviolet absorber contained in the thermoplastic resin composition and the temperature Tp (° C.) of the melt at the exit of the die. Tp” is set to be satisfied. The melting device is configured to melt the thermoplastic resin composition so as to satisfy the above formula and prepare a melt having a temperature Tp (° C.) or higher.

[Touch Roll and Cast Roll]
The touch roll and cast roll are installed in parallel facing each other. A plurality of touch rolls and cast rolls may be present. It is particularly preferable that the surfaces of the touch roll and the cast roll are mirror-finished.

The touch roll is preferably made of an elastic material. The material of the touch roll and cast roll is preferably SCM steel, stainless steel such as SUS, or the like. Furthermore, as touch rolls and cast rolls, materials obtained by plating the above steel or stainless with chromium, nickel, titanium, etc.; TiN, TiAlN, TiCN, CrN, DLC (diamond It is also suitable to use a material formed with a surface coating such as carbon); a material formed by spraying tungsten carbide or other ceramics; and a material obtained by nitriding the surface of the above steel or stainless steel. be.

The touch pressure, which is the value obtained by dividing the pressing force of the touch roll against the cast roll by the contact area between the film and the touch roll, is preferably in the range of 0.1 MPa to 10 MPa, and in the range of 0.3 MPa to 8 MPa. more preferably, and particularly preferably within the range of 0.5 MPa to 5 MPa.

The touch roll and cast roll preferably have a surface arithmetic mean height (Ra) of 100 nm or less, more preferably 50 nm or less, and even more preferably 25 nm or less. As a result, a film having moderate unevenness on the surface can be formed. If the material of the surfaces of the touch roll and the cast roll is metal, it is easy to make Ra of these rolls 100 nm or less.

The thickness, length, temperature, etc. of the touch roll and cast roll may be appropriately set according to the desired size and thickness of the optical film, and are not particularly limited. However, in order to slowly cool (cool) the melt, it is more preferable to have a plurality of (more specifically, 2 to 6) cast rolls.

Then, for example, when the melt is slowly cooled using two or more cast rolls to form a film, the cast roll adjacent to the downstream side of the cast roll closer to the die (upstream side) The temperature is preferably lower than the temperature of the upstream casting roll in the range of more than 0°C and 20°C or lower, more preferably 1°C to 18°C lower, and 2°C to 15°C lower. is more preferred. Thereby, the physical properties of both surfaces of the obtained optical film can be made more uniform, and the residual strain in the optical film can be easily eliminated. Therefore, the dimensional stability of the optical film against humidity and heat can be improved. The temperature of the cast roll closest to the die (most upstream side) may be appropriately set according to the temperature of the melt.

The temperature of the touch roll is preferably within the range of Tg-80°C to Tg+10°C, based on the glass transition temperature (Tg) of the (meth)acrylic resin, and within the range of Tg-70°C to Tg+5°C. It is more preferable that the temperature is within the range of Tg-60°C to Tg.

The temperature control of the touch roll and cast roll can be performed, for example, by circulating a temperature-controlled heating medium (liquid or gas) inside these rolls.

[Film forming speed]
The film-forming speed of the melt is not particularly limited and may be appropriately set according to the desired size and thickness of the optical film. The film forming speed is preferably within the range of 2 m/min to 50 m/min, more preferably within the range of 2 m/min to 40 m/min, and within the range of 3 m/min to 35 m/min. It is even more preferable to have By setting the film forming speed within the above range, the melt is pulled by the touch roll and the cast roll at the exit of the die, the expansion of the melt is suppressed, and the melt rubs against the exit of the die. Suppressed. Therefore, the unevenness of the surface of the obtained optical film can be controlled within a preferable range. In addition, by setting the film forming speed within the above range, the residence time of the melt in the die can be shortened, so the number of foreign substances (gels and contaminants) contained in the melt can be reduced. . If the film-forming speed exceeds 50 m/min, turbulence may occur in the flow of the melt at the exit of the die, which may reduce the uniformity of the film.

By forming a touch roll film of a (meth)acrylic resin having a heat resistance (glass transition temperature of 108 ° C. or higher) in this way, even when an ultraviolet absorber with a low thermal decomposition temperature is used, the b ^* value is It is possible to produce an optical film with good optical properties, which is low and good, and which does not transfer contaminants from the rolls (touch roll and cast roll) during film formation.

Then, the relationship between the thermal decomposition temperature Td (° C.) of the ultraviolet absorber contained in the thermoplastic resin composition and the temperature Tp (° C.) of the melt at the exit of the die is expressed by the formula “50≦Td−Tp”. Extruding the melt from the die in a filling manner can enhance the above effect.

Both ends of the optical film obtained by touch roll film formation may be trimmed, if necessary. The optical film cut off by trimming can be reused as a raw material if crushed.

[Winding and drawing]
An optical film continuously produced by touch roll film formation is peeled off from a cast roll, passed through a nip roll or the like, and then wound around a core material to form a roll-shaped optical film. Although the winding speed of the optical film is not particularly limited, it is preferably in the range of 1 m/min to 100 m/min, more preferably in the range of 2 m/min to 80 m/min. More preferably, it is in the range of 3 m/min to 70 m/min. In addition, although the winding tension of the optical film is not particularly limited, it is preferably in the range of 1 N/m width to 500 N/width, and in the range of 1 N/m width to 300 N/width. is more preferred.

A protective film made of polyethylene, polypropylene, polyester, or the like may be attached to one side or both sides of the optical film before winding the optical film. Although the thickness of the protective film is not particularly limited, it is preferably in the range of 5 μm to 100 μm, more preferably in the range of 10 μm to 50 μm.

An optical film continuously produced by touch roll film formation is preferably longitudinally stretched and/or transversely stretched (hereinbelow, longitudinal stretching is also referred to as “MD stretching” and lateral stretching is also referred to as “TD stretching”). MD stretching and/or TD stretching may be combined with shrinkage relaxation treatment. The optical film according to the invention is more preferably biaxially stretched (MD stretching and TD stretching). Note that MD is an abbreviation for Machine Direction, and is synonymous with "longitudinal direction" and "longitudinal direction". TD is an abbreviation for Transverse Direction and is synonymous with "width direction" and "horizontal direction".

Specific methods of MD stretching include, but are not limited to, oven longitudinal stretching, roll longitudinal stretching, and the like.

Oven longitudinal stretching is a method of stretching an original film in its longitudinal direction by creating a peripheral speed difference between a transport roll on the inlet side of an oven and a transport roll on the outlet side. The oven is configured to heat the raw film to a stretchable temperature. According to the oven longitudinal stretching, depending on the stretching conditions, the stretched film can be given a heat treatment effect.

The stretching temperature in the oven longitudinal stretching is preferably in the range of Tg-10°C to Tg+50°C, based on the glass transition temperature (Tg) of the original film, and is in the range of Tg-5°C to Tg+40°C. is more preferable, and it is even more preferable to be within the range of Tg°C to Tg+30°C. If the film is stretched at a temperature lower than Tg-10°C, the raw film may be broken. Stretching at a temperature higher than Tg+50° C. increases the slack of the original film, which may result in rubbing between the original film and the apparatus or breakage of the original film.

Roll longitudinal stretching is a method in which an original film is heated to a stretching temperature while being continuously brought into contact with a number of heating rolls, and stretched by nip rolls provided in a stretching section. The stretched film is then cooled by chill rolls. An auxiliary heating device may be provided in the stretching section to stabilize the stretching temperature. Roll longitudinal stretching can be carried out using a roll longitudinal stretching machine.

The temperature of the heating roll in the roll longitudinal stretching machine refers to the set temperature of the heating roll. The stretching temperature and stretching ratio of the original film can be appropriately adjusted using the mechanical strength, surface properties and thickness accuracy of the film obtained after longitudinal stretching as indices. At the time of stretching, it is preferable to heat the original film to within the range of Tg−10° C. to Tg+20° C. with a heating roll based on the glass transition temperature (Tg) of the film. Furthermore, it is more preferable to heat to within the range of Tg° C. to Tg+30° C. by an auxiliary heating device provided in the stretching section. If the heating of the original film by the heating roll is lower than Tg-10°C, problems in the process such as tearing or cracking of the original film are likely to occur. If the heating of the original film by the heating roll is higher than Tg+30° C., it is difficult to improve mechanical properties such as elongation, tensile strength, and flexibility of the finally obtained optical film, resulting in poor secondary workability. It can get worse.

The total number of heating rolls is preferably 5 or more. If the number of heating rolls is less than 5, the heating effect is reduced, and the original film cannot be sufficiently heated. The method of increasing the diameter of the heating rolls to enhance the heating effect instead of reducing the total number of heating rolls to less than 5 cannot sufficiently stretch the original film that has been thermally expanded by heating, and wrinkles occur. It is not preferable because it becomes easy to break and breakage due to wrinkles also tends to occur.

A known device can be used as the auxiliary heating device provided in the stretching section. Specifically, for example, at least one selected from IR heaters, ceramic heaters, and hot air heaters is preferable.

The stretching speed during MD stretching may be appropriately set according to the desired properties of the optical film, and is not particularly limited, but is preferably in the range of 10 to 20,000%/min, and 100 to 10,000%. /min is more preferable. If the stretching speed is slower than 10%/min, it will take time to obtain a sufficient stretching ratio, resulting in high production costs. If the stretching speed is higher than 20000%/min, the film may be broken.

The draw ratio in MD drawing may be appropriately set according to the desired properties of the optical film, and is not particularly limited, but is preferably in the range of 10 to 300%, preferably 15 to 300%. %, more preferably 20 to 200%. The stretch ratio is defined as "stretch ratio (%)=100×{(length after stretching)−(length before stretching)}/(length before stretching)".

The stretching temperature when performing TD stretching is not particularly limited, but is preferably in the range of Tg-5 ° C. to Tg + 30 ° C., based on the glass transition temperature (Tg) of the original film. It is more preferably within the range of Tg+30°C, and even more preferably within the range of Tg to Tg+20°C. If the stretching temperature is lower than Tg-5°C, the film may break before stretching. If the stretching temperature exceeds Tg+30° C., the relaxation of the molecular chains is increased and the orientation of the molecules may become difficult.

The stretching speed during TD stretching may be appropriately set according to the desired properties of the optical film, and is not particularly limited, but is preferably in the range of 10 to 20,000%/min, and 100 to 10,000%. /min is more preferable. If the stretching speed is slower than 10%/min, it will take time to obtain a sufficient stretching ratio, resulting in high production costs. If the stretching speed is higher than 20000%/min, the film may be broken.

The draw ratio for TD stretching may be appropriately set according to the desired properties of the optical film, and is not particularly limited, but is preferably in the range of 10 to 300%, preferably 15 to 300%. %, more preferably 20 to 200%.

The optical film may be heat treated before MD stretching and/or TD stretching, or may be heat treated after MD stretching and/or TD stretching.

Although the optical film according to the present invention is not particularly limited, the ratio of the draw ratio in the longitudinal direction to the draw ratio in the transverse direction (stretch ratio in MD stretch/stretch ratio in TD stretch) is 0.40 to 0.40. It is preferably in the range of 1.50, more preferably in the range of 0.45 to 1.40, even more preferably in the range of 0.50 to 1.30.

[5. Optical film]
The optical film produced by the above method has a b ^* value of less than 0.5 when the optical film is made into a film having a thickness of 80 μm, and has good optical properties. The absolute value of the b ^* value is preferably 0.4 or less and then 0.3 or less. There is no particular lower limit to the absolute value of the b ^* value, and the smaller the value, the better (that is, the closer the b ^* value is to zero, the better). Here, the optical film includes a film manufactured by the method described in Section [4]. More specifically, it includes an unstretched film produced by touch roll film formation, a stretched film after stretching, and the like.

[noise]
When the optical film is a roll-shaped optical film, the total noise is 5 when 80% of the width direction of the optical film is projected and inspected every 12 m over the length of 120 m in the longitudinal direction. It is below the point. Further, when the optical film is a sheet-fed optical film, the noise per 1 m ² is 5 points or less when the optical film is subjected to projection inspection. A film that satisfies these properties is referred to herein as having "no contaminant transfer from the roll."

As used herein, "noise" means a defect caused by transfer of a contaminant (for example, a thermoplastic resin composition or a substance resulting from deterioration of a volatilized ultraviolet absorber) to the surface of an optical film. do. The categories of noise include (i) faults caused by foreign substances such as gels contained in the melt of the thermoplastic resin composition, and (ii) floating substances in the air (lint, dust, dust, etc.) and (iii), dirt (dust, dirt, etc.) adhering to the surfaces of touch rolls and cast rolls. The above noise makes it difficult to detect foreign matter (eg, gel) contained in the melt of the thermoplastic resin composition, which is originally desired to be confirmed. Furthermore, the film with much noise interferes with its function as an optical film.

A method of projecting and inspecting 80% of a roll-shaped optical film in the width direction at intervals of 12 m over a length of 120 m in the longitudinal direction is, for example, by winding an optical film manufactured by touch roll film production on a core material. Sometimes (ie, in-line) there is a method of projection inspection. Specifically, the procedure is as follows.
(1) An automatic defect inspection device is arranged at a position where the continuously transported optical film can be measured.
(2) A measurement interval that can be measured every 12 m is calculated from the conveying speed of the optical film (for example, every minute when the conveying speed is 12 m/min).
(3) A projection inspection is performed by the automatic defect inspection apparatus a total of 11 times at the measurement interval. At this time, projection inspection is performed on 80% of the width direction of the optical film at each measurement point.

80% of the width direction of the optical film may be set anywhere. Preferably, it is set to 40% from the center in the width direction of the optical film toward both ends. In other words, 10% of both ends in the width direction are set to be omitted.

Also, the projection inspection of a sheet of optical film should be performed by converting the number of noises obtained by projection inspection of a plurality of optical films into the number of noises per ^1m2 (that is, off-line). is preferred. It is more preferable that the plurality of optical films have a total area of 1 m ² or more (for example, 17 sheets or more for A4 size). Projection inspection of the optical film can be performed using a commercially available automatic defect inspection device. An example of a specific projection inspection method is as described in Examples.

When noise occurs in the optical film, the magnitude of the noise is preferably 15 μm or less, more preferably 10 μm or less. Noise with a size of 15 μm or less is not detected in projection inspection, and may pose no problem when actually used as an optical film. It should be noted that the smaller the noise, the better, and the smaller the noise, the better.

The optical film according to the present invention is manufactured so that the relationship between the thermal decomposition temperature Td (° C.) and the temperature Tp (° C.) satisfies the formula “50≦Td−Tp”. Therefore, the b ^* value when the optical film has a thickness of 80 μm is less than 0.5, and the optical properties are good. In addition, the amount of foreign matter such as gel contained in the melt of the thermoplastic resin composition is small, and the rolls (touch roll and cast roll) are not contaminated. Therefore, even in a general optical film manufacturing environment, the noise in the projection inspection can be reduced to 5 points or less (that is, there is no transfer of contaminants from the roll).

[Optical Performance]
(Optical performance when made into a film with a thickness of 80 μm)
The optical film according to an embodiment of the present invention preferably has a c ^* value of less than 0.5, more preferably less than 0.5, measured in accordance with JIS Z 8729 when the film has a thickness of 80 μm. less than 0.3. The optical film preferably has an absolute value of a ^* value of 0.10 or less, more preferably 0.05 or less, measured in accordance with JIS Z 8729 when the film has a thickness of 80 μm. More preferred. The above optical film has a b ^* value of less than 0.5 as measured according to JIS Z 8729 when made into a film having a thickness of 80 μm, and has good optical properties. The absolute value of the b ^* value is preferably 0.4 or less and then 0.3 or less. There is no particular lower limit to the absolute value of the b ^* value, and the smaller the value, the better (that is, the closer the b ^* value is to zero, the better). The optical film preferably has an L ^* value of 95.0% or more, more preferably 98.0% or more, measured in accordance with JIS Z 8729 when the film has a thickness of 80 μm. It is more preferably 99.0% or more, and particularly preferably 99.5% or more. If the optical properties of the optical film are within the above range, it can be suitably used as a polarizer protective film or the like.

The optical film according to one embodiment of the present invention has a light transmittance of 5.0% or less at a wavelength of 380 nm, which is measured in accordance with JIS K7361:1997 when the film has a thickness of 80 μm. It is preferably 4.0% or less, more preferably 3.0% or less. If the light transmittance is within this range, the optical film can exhibit sufficient ultraviolet absorption ability when incorporated as a polarizing plate of an optical device. In addition, the optical film preferably has a light transmittance of 95.0% or more at a wavelength of 420 nm measured in accordance with JIS K7361:1997 when the film has a thickness of 80 μm, more preferably. 96.0% or more, more preferably 97.0% or more. If the light transmittance is within this range, the transmittance in the visible light region is high, and the optical film is particularly suitable for optical applications.

The optical film of the present invention preferably has a total light transmittance of 95.0% or more, more preferably 97.0% or more, and still more preferably 99.0% or more when made into a film having a thickness of 80 μm.

The optical film according to one embodiment of the present invention preferably has a haze of 1.0% or less when formed into a film having a thickness of 80 μm. It is more preferably 0.8% or less, still more preferably 0.5% or less. If the haze exceeds 1.0%, the transparency is lowered and the optical film is not suitable for optical applications.

The optical film according to one embodiment of the present invention preferably has a contact angle with pure water of 76° or less. If the contact angle with pure water is 76° or less, the hydrophilic adhesive composition can be applied uniformly to the optical film.

[Use of optical film]
The optical properties of the optical film according to one embodiment of the present invention can be further controlled by laminating the same optical material and/or different optical material. The optical material to be laminated at this time is not particularly limited, but examples thereof include a polarizing plate, a stretched and oriented film made of polycarbonate, and a stretched and oriented film made of cyclic polyolefin. Of course, the optical film may be used alone.

Various functional coating layers may be formed on the surface of the optical film according to an embodiment of the present invention, if necessary. The functional coating layer includes, for example, an antistatic layer, an adhesive layer, an adhesive layer, an easy adhesive layer, an antiglare (non-glare) layer, an antifouling layer such as a photocatalyst layer, an antireflection layer, a hard coat layer, and an ultraviolet shielding layer. layer, heat ray shielding layer, electromagnetic wave shielding layer, and gas barrier layer.

Applications of the optical film according to one embodiment of the present invention are not particularly limited. The optical film according to one embodiment of the present invention has high transparency, small hue, low chroma and high heat resistance, and is suitable for the following uses. The applications include, for example, optical protective films (specifically, protective films for substrates of various optical discs (VD, CD, DVD, MD, LD, etc.)), and polarizing plates provided in image display devices such as LCDs. It is a polarizer protective film. In addition, as optical films such as viewing angle compensation films, light diffusion films, reflective films, antireflection films, antiglare films, brightness enhancement films, conductive films for touch panels, retardation films, and light conversion films, the present invention. An optical film according to one embodiment may be used. An optical film according to one embodiment of the present invention is particularly suitable for use as a polarizer protective film.

[6. Other configurations of the present invention]
The present invention also includes the following configurations.

The (meth)acrylic resin composition (thermoplastic resin composition) of the present invention is a (meth)acrylic resin composition containing a (meth)acrylic polymer ((meth)acrylic resin) and an ultraviolet absorber. (Thermoplastic resin composition) having a glass transition temperature of 110° C. or higher and a c ^* value of 0.45 measured in accordance with JIS Z 8729 as an unstretched film having a thickness of 100 μm. It is characterized by the following.

According to the above configuration, it is possible to provide a (meth)acrylic resin composition (thermoplastic resin composition) excellent in transparency, hue, saturation and heat resistance.

The (meth)acrylic resin composition (thermoplastic resin composition) of the present invention has an a ^* absolute value of 0 measured in accordance with JIS Z 8729 as an unstretched film having a thickness of 100 μm. 0.10 or less is preferred.

According to the above configuration, it is possible to provide a (meth)acrylic resin composition (thermoplastic resin composition) having a more excellent hue.

The ultraviolet absorber is preferably a benzotriazole compound.

Further, the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention has a light transmission at a wavelength of 380 nm measured in accordance with JIS K7361:1997 when made into an unstretched film having a thickness of 100 μm. It is preferable that the ratio is 3.0% or less and the light transmittance at a wavelength of 420 nm is 95.0% or more.

According to the above configuration, for example, when the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention is used for an optical film such as a polarizer protective film, it has sufficient ultraviolet absorption ability and has a hue and a (meth)acrylic resin composition (thermoplastic resin composition) having excellent chroma.

The (meth)acrylic resin composition (thermoplastic resin composition) of the present invention is composed of styrene-based monomers in 100% by mass of the (meth)acrylic resin composition (thermoplastic resin composition). Preferably, the unit content is less than 8% by mass.

Further, the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention has a metal element content of 60 in 100% by mass of the (meth)acrylic resin composition (thermoplastic resin composition). It is preferably mass ppm or less.

According to the above configuration, it is possible to provide a (meth)acrylic resin composition (thermoplastic resin composition) with better hue and saturation.

The (meth)acrylic polymer ((meth)acrylic resin) according to the present invention preferably has a ring structure in its main chain.

Moreover, the ring structure is more preferably at least one selected from a maleic anhydride structure, a glutarimide structure, a glutaric anhydride structure and a lactone ring structure, and more preferably a lactone ring structure.

According to the above configuration, it is possible to provide a (meth)acrylic resin composition (thermoplastic resin composition) having excellent transparency, hue and saturation while maintaining high heat resistance. .

In order to solve the above problems, the molded article and film of the present invention are characterized by being formed from the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention.

According to the above configuration, since it is formed from the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention, it provides a molded article and film excellent in transparency, hue, saturation and heat resistance. It has the effect of being able to

The film of the present invention preferably has a noise number of 5 points or less per 1 m ² when the film is subjected to projection inspection.

According to the above configuration, when the film of the present invention is used as an optical film such as a polarizer protective film, it is possible to provide an optical film having good optical properties.

EXAMPLES The present invention will be described in more detail below using examples and comparative examples. However, the present invention should not be construed as being limited to these examples.

[Example 1]
<Method for measuring physical properties>
[Projection inspection method]
1. Projection inspection method for roll-shaped optical film For inspection, an automatic continuous defect inspection device (manufactured by MEC Co., Ltd.: LSC-6000L, optical system: 45 degree regular transmission, 1/8 edge, rod illumination (with slit on one side)) is used. Using. Specifically, the procedure was as follows.
(1) The automatic continuous defect inspection device was arranged in front of the winding device. The conveying speed of the optical film was 12 m/min.
(2) 11 locations in the longitudinal direction (ie, 120 m in the longitudinal direction) were inspected by inspection at 1 minute intervals. The inspection target was an optical film of 40% from the center in the width direction toward both ends (that is, a portion excluding 10% at both ends in the width direction).
(3) Defects (noise) were detected by image processing on the optical film to be inspected, and the optical film was evaluated.

It should be noted that the larger the amount of noise (that is, the more contaminants adhering to the surface of the roll are transferred to the optical film), the greater the number of defects detected by the automatic continuous defect inspection apparatus. Films with more than 1,000 detected defects cannot be counted.

2. Projection inspection method for sheet-fed optical film For inspection, an automatic defect inspection device (manufactured by MEC Co., Ltd.: MLA-5000, optical system: 45 degree regular transmission, 1/8 edge, rod illumination (with slit on one side)) is used. board. Specifically, the procedure was as follows.
(1) The surface of the sheet of optical film was air-blown to remove dust (dust, dust, etc.) adhering to the surface of the optical film.
(2) Defects (noise) were detected by image processing using 17 sheets of optical films having a size of 200 mm×300 mm (A4) as inspection objects.
(3) The number of defects obtained in (2) was converted to the number of defects per 1 m ² to evaluate the optical film.

It should be noted that the larger the amount of noise (that is, the more contaminants adhering to the surface of the roll are transferred to the optical film), the larger the number of defects detected by the automatic defect inspection apparatus. Films with more than 1,000 detected defects cannot be counted.

[b ^* value]
Using a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd.: Colormeter ZE6000), the b ^* value was determined in accordance with JIS Z 8729.

[Melt viscosity]
It was measured using a twin-bore barrel type capillary rheometer RH10 manufactured by Rosand. Using a long die with a diameter of 1 mm and a length of 16 mm and a short die with a diameter of 1 mm and a length of 0.25 mm, the measurement was performed at a measurement temperature of 270° C. and a shear rate of 10/sec. The melt viscosity was calculated by performing Bergley correction on the value thus obtained.

[Weight average molecular weight (Mw)]
The weight average molecular weight (Mw) of the (meth)acrylic resin was obtained by polystyrene conversion using gel permeation chromatography (GPC). The apparatus and measurement conditions used for the measurement are as follows.

System: Tosoh GPC system HLC-8220
Measurement side column configuration Guard column: TSKguardcolumn SuperHZ-L manufactured by Tosoh
・ Separation column: TSKgel SuperHZM-M, manufactured by Tosoh, 2 columns connected in series Reference side column configuration ・ Reference column: TSKgel SuperH-RC, manufactured by Tosoh
Developing solvent: Chloroform (manufactured by Wako Pure Chemical Industries, special grade)
Flow rate of developing solvent: 0.6 mL / min Standard sample: TSK standard polystyrene (manufactured by Tosoh, PS-oligomer kit)
Column temperature: 40°C.

[Glass transition temperature (Tg)]
It was obtained in accordance with the provisions of JIS K7121. Specifically, using a differential scanning calorimeter (manufactured by Rigaku Co., Ltd.: DSC-8230), a sample of about 10 mg was heated from room temperature to 200 ° C. at a heating rate of 20 ° C./min in a nitrogen gas atmosphere. From the obtained DSC curve, the glass transition temperature was calculated by the starting point method. α-alumina was used as a reference.

[Stress optical coefficient (Cr)]
An unstretched film was cut into a rectangle of 60 mm×20 mm, and a weight was selected so that the stress was 1 N/mm ² or less, and attached to the lower end of the unstretched film. This was set in a constant temperature dryer (manufactured by AS ONE: DOV-450A) set at Tg+3° C. with a chuck distance of 40 mm. After holding the film at Tg+3° C. for about 30 minutes and stretching, the heating was stopped and the film was cooled at a rate of about 1° C./min to Tg−40° C. After that, the obtained stretched film was taken out, and the length and thickness of the stretched film and the weight of the weight were measured. Also, the in-plane retardation Re of the stretched film was measured.

Next, four different weights were selected so that the stress was 1 N/mm ² or less, and the weights were attached to the lower end of the unstretched film and measured in the same manner. ) was calculated. A method for calculating the stress-optical coefficient (Cr) is described in [Polymer Society, "Forefront of Transparent Plastics", NTS, 2006, pp. 37-44]. Specifically, Δn (=nx−ny) was plotted on the y-axis and σ was plotted on the x-axis, and the slope of the straight line obtained by the least squares method was obtained, and the value was taken as Cr. Here, nx is the refractive index in the slow axis direction in the plane of the film (direction showing the maximum refractive index in the plane of the film), ny is the fast axis direction in the plane of the film (the slow axis in the plane of the film direction), σ is the stress on stretching [N/m ² ].

[Thermal decomposition temperature (thermal decomposition initiation temperature; Td)]
A 10 mg sample was heated from room temperature to 500° C. in a nitrogen gas atmosphere using a differential type differential thermal balance apparatus (manufactured by Rigaku Corporation: Thermo Plus2 TG-8120). At this time, when the mass reduction rate of the sample during temperature rise was 0.005% by mass/second or less, the temperature was raised at a temperature elevation rate of 10° C./min. Conversely, when the mass reduction rate of the sample during heating exceeded 0.005% by mass/second, the temperature was raised by stepwise isothermal control so that the rate was maintained at 0.005% by mass/second or less. Then, in order to maintain the mass reduction rate, the temperature (the lowest temperature in the section where the temperature was raised by the stepwise isothermal control) was first set to the stepwise isothermal control to maintain the Td of the thermoplastic resin composition and the ultraviolet absorber. and

<Production example of thermoplastic resin composition>
First, a lactone ring structure-containing polymer was produced as a (meth)acrylic resin by the following method.

229.6 parts of methyl methacrylate (MMA), 33 parts of methyl 2-(hydroxymethyl)acrylate (MHMA) and 248.6 parts of toluene were added to a reaction vessel equipped with a stirrer, temperature sensor, condenser and nitrogen inlet tube. , and 0.19 parts of n-dodecylmercaptan were charged, and the temperature was raised to 105° C. while nitrogen gas was passed through. At the point where reflux with temperature rise begins, 0.25 parts of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd.: Luperox (registered trademark) 570) is added as a polymerization initiator, and t-amyl per is further added. While 0.51 parts of oxyisononanoate and 12.4 parts of styrene were added dropwise over 2 hours, solution polymerization was allowed to proceed under reflux at about 105-110°C. After completion of dropping, aging was further performed at the same temperature for 4 hours.

Next, 0.21 part of stearyl phosphate (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) is added to the obtained polymerization solution as a catalyst for the cyclization condensation reaction (cyclization catalyst), and the temperature is adjusted to about 90 to 110°C. The cyclization condensation reaction to form the lactone ring structure was allowed to proceed for 1.5 hours under reflux of .

Next, the resulting polymerization solution was passed through a shell and tube heat exchanger heated to 240° C. to complete the cyclization condensation reaction. After that, the polymerization solution was introduced into a vent-type screw twin-screw extruder (L/D=52) at a processing rate of 35.1 parts/hour (converted to the amount of resin). The vent-type screw twin-screw extruder has a barrel temperature of 250 ° C., one rear vent, four fore vents (referred to as the first, second, third, and fourth vents from the upstream side), and the A side feeder is provided between the 3rd vent and the 4th vent, and a leaf disk type polymer filter (filtration accuracy of 5 μm) is arranged at the tip. When introducing the polymerization solution, a separately prepared mixed solution of antioxidant/cyclization catalyst deactivator was added at a rate of 0.15 parts/hour, and 0.54 parts of ion-exchanged water was added from the downstream side of the second vent. Charges were made downstream of the first and third vents, respectively, at a charge rate of parts per hour. In the mixed solution of antioxidant / cyclization catalyst deactivator, 4.3 parts of each antioxidant (manufactured by BASF: Irganox 1010, manufactured by ADEKA: Adekastab (registered trademark) LAO-412S) and A solution prepared by dissolving 14 parts of zinc octylate (Nippon Kagaku Sangyo Co., Ltd.: Nikka Octix Zinc) as a deactivator in 144 parts of toluene was used. Further, from the side feeder, an ultraviolet absorber (manufactured by ADEKA Co., Ltd.: Adekastab (registered trademark) LA-31, thermal decomposition temperature Td (° C.) is 345° C.) was added at a rate of 0.79 parts/hour.

Next, after the completion of devolatilization, the hot-melt resin composition remaining in the extruder was discharged from the tip of the extruder while being filtered with a polymer filter. After that, it was passed through a die provided at the tip of the extruder and cooled in a water bath filled with cooling water to obtain a strand of the resin composition. The cooling water was filtered through a filter with a pore size of 1 μm (manufactured by Organo Corporation, product name: Micropore Filter 1EU) and maintained at a temperature within the range of 30±10°C. By introducing the strand after cooling into a cutting machine (pelletizer), pellets made of a thermoplastic resin composition containing a lactone ring structure-containing polymer and an ultraviolet absorber were obtained.

Various physical properties of the obtained lactone ring structure-containing polymer are as follows.
Glass transition temperature (Tg): 120°C
Weight average molecular weight: 149000
Stress optical coefficient (Cr): 0.7×10 ⁻¹¹ Pa ⁻¹
Thermal decomposition temperature (Td): 339°C
5% mass loss temperature in thermogravimetric analysis (TG): 366°C
Total amount of residual volatile matter: 2050 ppm
Total light transmittance: 92.5%.

The melt viscosity of the obtained thermoplastic resin composition at 270° C. and a shear rate of 10/sec was 694 Pa·S or more.

<Example 1-1>
An optical film was produced by applying the thermoplastic resin composition obtained in the above production example to a touch roll film formation. The temperature Tp (°C) of the melt of the thermoplastic resin composition at the exit of the die was 272°C. Therefore, "Td-Tp" was 73°C.

Specifically, the film was formed by the following procedure.
(1) Using a vented single-screw extruder, melt film formation was carried out at a processing rate of 25 kg/hour. The extruder had a barrier flight type screw with a diameter of 65 mm and L/D=32. A polymer filter (filtration accuracy of 5 μm) and a T-die were provided at the tip of the extruder.
(2) The molten resin film after film formation was passed through cooling rolls. The cooling rolls consisted of a first roll (elastic touch roll), a second roll (cast roll), and a third roll, each of which was plated with chromium. The temperature of each cooling roll was set to R1/R2/R3=95/100/85° C. (R1, R2 and R3 mean the first roll, the second roll and the third roll in order, the same applies hereinafter). The angle θ between the molten resin film of the thermoplastic resin composition extruded from the T-die exit and the vertical plane including the gap between R1 and R2 was set at 5°.
(3) The molten resin film was cast on R1 to obtain an unstretched film with a thickness of 215 µm. The obtained unstretched film was continuously supplied to an oven longitudinal stretching machine as it was, and was stretched in the longitudinal direction at a stretching ratio of 1.6 at an oven temperature of 136°C.
(4) The stretched film was wound up by a winding machine to obtain a longitudinally stretched film roll having an average thickness of 160 μm.
(5) The obtained longitudinally stretched film roll was unwound by a unwinding machine, gripped with 2-inch clips at positions 20 mm from both ends, and supplied to a tenter stretching machine. Then, the temperature of the oven was set to 138° C., and transverse stretching was performed at a stretching ratio of 2.0 times in the transverse direction.
(6) The stretched film was wound up by a winding machine to obtain a roll-shaped optical film having an average thickness of 80 μm.
(7) The obtained optical film was cut into a size of 200 mm×300 mm (A4) to produce a plurality of sheet-like optical films.

The b ^* value of the produced optical film was 0.18. When the projection inspection of the sheet-shaped optical film was performed according to the projection inspection method described above, the noise (the number of noises per 1 m ² ) was 0 points. Table 1 shows the results.

In addition, even after long-term operation, adhesion of contaminants was not observed on both the touch roll (R1) and the cast roll (R2).

<Example 1-2>
(i) the processing speed of the vented single-screw extruder is 56 kg/h, (ii) the temperature of each cooling roll is R1/R2/R3=80/80/80°C, and (iii) the melt at the exit of the die A plurality of sheet-like optical films were produced in the same manner as in Example 1-1, except that the object temperature Tp (°C) was set to 277°C (“Td-Tp” was set to 68°C). The b ^* value of the produced optical film was 0.20. When the projection inspection of the sheet-shaped optical film was performed according to the projection inspection method described above, the noise (the number of noises per 1 m ² ) was 0 points. Table 1 shows the results.

In addition, even after long-term operation, adhesion of contaminants was not observed on both the touch roll (R1) and the cast roll (R2).

<Comparative Example 1-1>
An optical film was produced by subjecting the thermoplastic resin composition obtained in the above production example to open film formation. The temperature Tp (°C) of the melt of the thermoplastic resin composition at the exit of the die was 272°C. Therefore, "Td-Tp" was 73°C.

Specifically, the film was formed by the following procedure.
(1) Using a vented single-screw extruder, melt film formation was carried out at a processing rate of 25 kg/hour. The extruder had a barrier flight type screw with a diameter of 65 mm and L/D=32. A polymer filter (filtration accuracy of 5 μm) and a T-die were provided at the tip of the extruder.
(2) The molten resin film after film formation was passed through cooling rolls. The cooling rolls consisted of a second roll (cast roll) and a third roll, each of which was plated with chromium. The temperature of each cooling roll was R2/R3=120/95°C.
(3) A molten resin film of the thermoplastic resin composition extruded from the T-die exit was cast on R2 to obtain an unstretched film having a thickness of 215 µm. The obtained unstretched film was continuously supplied to an oven longitudinal stretching machine as it was, and was stretched in the longitudinal direction at a stretching ratio of 1.6 at an oven temperature of 136°C.
(4) The stretched film was wound up by a winding machine to obtain a longitudinally stretched film roll having an average thickness of 160 µm.
(5) The obtained longitudinally stretched film roll was unwound by a unwinding machine, gripped with 2-inch clips at positions 20 mm from both ends, and supplied to a tenter stretching machine. Then, the temperature of the oven was set to 138° C., and transverse stretching was performed at a stretching ratio of 2.0 times in the transverse direction.
(6) The stretched film was wound up by a winding machine to obtain a roll-shaped optical film having an average thickness of 80 µm.
(7) The obtained optical film was cut into a size of 200 mm×300 mm (A4) to produce a plurality of sheet-like optical films.

The b ^* value of the produced optical film was 0.20. Then, when the projection inspection of the optical film was carried out according to the projection inspection method described above, seven of the 17 films had zero noise. However, the remaining 10 sheets had a lot of noise due to transfer of contaminants adhering to the surface of the cast roll (R2), and the number of defects detected by the automatic defect inspection device exceeded 1000 points, so they could not be counted. . Table 1 shows the results.

Also, after a long period of operation, adhesion of contaminants to the cast roll (R2) was observed.

(result)
As is clear from Table 1, by performing touch roll film formation, even when an ultraviolet absorber with a low thermal decomposition temperature is used, the b ^* value is low and favorable, and the roll (touch roll and It has been found that optical films with good optical properties can be produced without the transfer of contaminants from the cast roll).

[Example 2]
<Method for measuring physical properties>
[Thermal decomposition temperature (Td), glass transition temperature (Tg) and weight average molecular weight (Mw)]
The thermal decomposition temperature (thermal decomposition initiation temperature), glass transition temperature and weight average molecular weight were measured in the same manner as in Example 1.

[Film thickness]
The thickness of the film was measured using a Digimatic micrometer (manufactured by Mitutoyo Corporation). A sample for measuring and evaluating the physical properties of the film, including the physical properties shown in the following evaluation methods, was obtained from the central portion of the film in the width direction.

[a ^* value, b ^* value, c ^* value and L ^* value]
The a ^* value, b ^* value, and L ^* value were measured according to JIS Z 8729 using a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd.: Colormeter ZE6000). Specifically, the following procedure was followed.
(1) The thermoplastic resin composition was melt-press molded at 250° C. for 5 minutes using a manual heat press (manufactured by Imoto Seisakusho, Model IMC-180C) to prepare an unstretched film.
(2) An unstretched film cut into 45 mm × 35 mm was immersed in a quartz cell with an optical path length of 10 mm containing 1,2,3,4-tetrahydronaphthalene (tetralin), and the a ^* value, b ^* value, and L ^* values were measured.
(3) The measurement of (2) was repeated in the same manner while overlapping the second, third and additional unstretched films.
(4) The measured a ^* value, b ^* value, and L ^* value were plotted on the y-axis, respectively, and the thickness of the unstretched film was plotted on the x-axis, and the slope of the straight line of the plot was derived by the least squares method. . From this, the a ^* value, b ^* value, and L ^* value were calculated for an unstretched film having a thickness of 100 μm.
(5) The c ^* value was calculated from the following formula using the a ^* value and b ^* value calculated by the above method.

c ^* = (a ^*2 +b ^*2 ) ^1/2 .

[Light transmittance at 380 nm and 420 nm]
The light transmittance at 380 nm and 420 nm was measured in accordance with JIS K7361:1997 using UV-1600PC manufactured by Shimadzu Corporation. Specifically, the following procedure was followed.
(1) The thermoplastic resin composition was melt-press molded at 250° C. for 5 minutes using a manual heat press (manufactured by Imoto Seisakusho, Model IMC-180C) to prepare an unstretched film.
(2) An unstretched film cut out to 40 mm×10 mm was immersed in a quartz cell having an optical path length of 10 mm containing deionized water, and each light transmittance was measured.
(3) Using the results of the measured light transmittance T and the thickness L of the unstretched film, each light transmittance T (100 μm) when an unstretched film having a thickness of 100 μm is calculated from the following formula. did.

T(100 μm)=10 ^{2−(2−LOG(T))×100/L} .

[Total light transmittance and haze]
Total light transmittance and haze were measured using NDH-1001DP manufactured by Nippon Denshoku Industries Co., Ltd. Specifically, the following procedure was followed.
(1) The thermoplastic resin composition was melt-press molded at 250° C. for 5 minutes using a manual heat press (manufactured by Imoto Seisakusho, Model IMC-180C) to prepare an unstretched film.
(2) The unstretched film cut out to 45 mm × 35 mm was immersed in a quartz cell having an optical path length of 10 mm containing 1,2,3,4-tetrahydronaphthalene (tetralin), and the total light transmittance and haze were measured. .
(3) The measurement of (2) was repeated while overlapping the second, third and additional unstretched films.
(4) The measured total light transmittance and haze were plotted on the y-axis, respectively, and the thickness of the unstretched film was plotted on the x-axis, and the slope of the straight line of the plot was derived by the method of least squares. From this, the total light transmittance and haze were calculated for an unstretched film having a thickness of 100 μm.

[Number of noise per ^m2 of film]
The number of noises per ^square meter of film was measured in the same manner as in Example 1. The results were evaluated as "O" when the number of noise points obtained per 1 ^m2 was 5 points or less, and as "X" when the number of noise points obtained per 1 ^m2 exceeded 5 points.

[Contact angle with pure water]
It was measured according to JIS R3257:1999 using a contact angle measuring instrument ("FACE contact angle meter CA-X" manufactured by Kyowa Interface Science Co., Ltd.). Thirty seconds after dropping, the contact angle with pure water was measured five times, and the average value of the three measurements excluding the highest and lowest values was taken as the "contact angle with pure water."

<Example 2-1>
83.5 parts of methyl methacrylate (MMA), 12 parts of methyl 2-(hydroxymethyl)acrylate (MHMA) and 90.4 parts of toluene were added to a reaction vessel equipped with a stirrer, temperature sensor, cooling tube and nitrogen inlet tube. , and 0.07 part of n-dodecyl mercaptan were charged, and the temperature was raised to 105° C. while passing nitrogen through. When the reflux started with the temperature rise, 0.10 part of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd.: Luperox (registered trademark) 570) was added as a polymerization initiator. Subsequently, 0.20 parts of the above t-amylperoxyisononanoate and 4.5 parts of styrene were added dropwise over 2 hours, and solution polymerization was allowed to proceed under reflux at about 105-110°C. After completion of dropping, aging was further performed at the same temperature for 4 hours.

Next, 0.08 part of stearyl phosphate (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) is added to the obtained polymerization solution as a catalyst for the cyclization condensation reaction (cyclization catalyst), and the amount is about 90 to 110 parts. The cyclization condensation reaction to form the lactone ring structure was allowed to proceed for 2 hours under reflux at °C. Furthermore, the obtained polymerization solution was passed through a shell and tube heat exchanger heated to 240° C. to complete the cyclization condensation reaction.

After that, using a vent-type screw twin-screw extruder (L/D=52), the resulting polymer was introduced at a processing rate of 35.1 parts/hour (converted to the amount of resin). The extruder has a barrel temperature of 250 ° C., one rear vent, four fore vents (hereinafter referred to as the first, second, third, and fourth vents from the upstream side) and the third and third vents. A side feeder was provided between the 4 vents. In addition, the extruder was provided with a leaf disk type polymer filter (filtration accuracy of 5 μm) at the tip.

When introducing the polymer, ion-exchanged water was introduced at a rate of 0.54 parts/hour from upstream of the second and fourth vents, and at a rate of 0.18 parts/hour from upstream of the third vent. put in. Also, from the side feeder, an ultraviolet absorber (manufactured by ADEKA Co., Ltd.: Adekastab (registered trademark) LA-31, weight loss start temperature Td (° C.) is 345° C.) was added at a rate of 0.79 parts/hour. .

After the devolatilization was completed, the hot-melt resin composition remaining in the extruder was discharged from the tip of the extruder while being filtered with a polymer filter. After that, it was passed through a die provided at the tip of the extruder and cooled in a water bath filled with cooling water to obtain a strand of the resin composition. The cooling water was filtered through a filter with a pore size of 1 μm (manufactured by Organo Corporation, product name: Micropore Filter 1EU) and maintained at a temperature within the range of 30±10°C. A thermoplastic resin composition (A-1) was obtained by introducing the strand after cooling into a cutting machine (pelletizer). Table 2 summarizes the physical properties of the obtained thermoplastic resin composition (A-1).

A film was produced from the thermoplastic resin composition (A-1) by touch roll film formation. The temperature Tp of the melt of the thermoplastic resin composition (A-1) at the exit of the die was 272°C. Therefore, "Td-Tp" was 73°C.

Specifically, the film was formed by the following procedure.
(1) Using a vented single-screw extruder, melt film formation was carried out at a processing rate of 25 kg/hour. The extruder had a barrier flight type screw with a diameter of 65 mm and L/D=32. A polymer filter (filtration accuracy of 5 μm) and a T-die were provided at the tip of the extruder.
(2) The molten resin film after film formation was passed through cooling rolls. The cooling rolls consisted of a first roll (elastic touch roll), a second roll (cast roll), and a third roll, each of which was plated with chromium. The temperature of each cooling roll was R1/R2/R3=95/100/85°C. The angle θ between the molten resin film of the thermoplastic resin composition extruded from the T-die exit and the vertical plane including the gap between R1 and R2 was set at 5°.
(3) The molten resin film was cast on R1 to obtain an unstretched film with a thickness of 215 μm. The obtained unstretched film was continuously supplied to an oven longitudinal stretching machine as it was, and was stretched in the longitudinal direction at a stretching ratio of 1.6 at an oven temperature of 136°C.
(4) The stretched film was wound up by a winding machine to obtain a longitudinally stretched film roll having an average thickness of 160 µm.
(5) The obtained longitudinally stretched film roll was unwound by a unwinding machine, gripped with 2-inch clips at positions 20 mm from both ends, and supplied to a tenter stretching machine. Then, the temperature of the oven was set to 138° C., and transverse stretching was performed at a stretching ratio of 2.0 times in the transverse direction.
(6) The stretched film was wound up by a winding machine to obtain a roll-shaped optical film having an average thickness of 80 μm.
(7) The obtained optical film was cut into a size of 200 mm×300 mm (A4) to produce a plurality of sheet-like optical films. The number of noises per ^square meter of the film was 5 points or less. When the contact angle of the film with pure water was measured, it was 76°.

<Example 2-2>
In a glass container, 18 parts by weight of methyl methacrylate (MMA), 2 parts by weight of methyl acrylate (MA), 20 parts by weight of methyl isobutyl ketone (MIBK), 2,2'-azobis (isobutyrate) dimethyl (Wako Pure Chemical Industries, Ltd.) 0.06 part by mass of V-601) manufactured by Co., Ltd. was charged, nitrogen gas was introduced into the flask, and the mixture was sealed and reacted at 60° C. for 4 hours and at 50° C. for 48 hours. Subsequently, the resulting polymerization solution was diluted with MIBK, reprecipitated using hexane, filtered and dried to obtain a (meth)acrylic resin. 20 parts by mass of the obtained polymer was dissolved in 20 parts by mass of toluene, and a thermoplastic resin composition (A-2) was obtained from the resulting polymer solution in the same manner as in Example 2-1. Table 2 summarizes the physical properties of the obtained thermoplastic resin composition (A-2).

From the thermoplastic resin composition (A-2), touch roll film formation and stretching were performed in the same manner as in Example 2-1 to produce a plurality of sheet-like films. The number of noises per ^square meter of the film was 5 points or less.

<Example 2-3>
81 parts of methyl methacrylate (MMA), 8 parts of N-phenylmaleimide (PMI), 11 parts of N-cyclohexylmaleimide (CHMI), and xylene were added to a reaction vessel equipped with a stirrer, temperature sensor, condenser and nitrogen inlet. 67 parts was charged, and the temperature was raised to 130° C. while passing nitrogen through it. At the point where reflux due to temperature rise begins, 0.19 parts of t-butyl peroxy-2-ethylhexanoate (manufactured by NOF Co., Ltd.: Perbutyl (registered trademark) O) as a polymerization initiator is added dropwise over 6 hours. The solution polymerization was allowed to proceed under reflux at about 130 to 145°C.

A thermoplastic resin composition (A-3) was obtained from the resulting polymerization solution in the same manner as in Example 2-1, except that the barrel temperature of the twin-screw extruder was set to 260°C. Table 2 summarizes the physical properties of the obtained thermoplastic resin composition (A-3).

From the thermoplastic resin composition (A-3), touch roll film formation and stretching were performed in the same manner as in Example 2-1 to produce a plurality of sheet-like films. The number of noises per ^square meter of the film was 5 points or less.

<Example 2-4>
Except that a solution of 0.01 part of a coloring agent (Sumiplast (registered trademark) Violet B manufactured by Sumika Chemtex Co., Ltd.) dissolved in 44 parts of toluene was added from the upstream of the third vent at a rate of 0.15 parts/hour. obtained a thermoplastic resin composition (A-4) in the same manner as in Example 2-1. Table 2 summarizes the physical properties of the obtained thermoplastic resin composition (A-4).

From the thermoplastic resin composition (A-4), touch roll film formation and stretching were performed in the same manner as in Example 2-1 to produce a plurality of sheet-like films. The number of noises per ^square meter of the film was 5 points or less.

<Example 2-5>
Except that a solution of 0.01 part of a coloring agent (Sumiplast (registered trademark) Green G, manufactured by Sumika Chemtex Co., Ltd.) dissolved in 44 parts of toluene was added from the upstream of the third vent at a rate of 0.15 parts/hour. obtained a thermoplastic resin composition (A-5) in the same manner as in Example 2-1. Table 2 summarizes the physical properties of the obtained thermoplastic resin composition (A-5).

From the thermoplastic resin composition (A-5), touch roll film formation and stretching were performed in the same manner as in Example 2-1 to produce a plurality of sheet-like films. The number of noises per ^square meter of the film was 5 points or less.

<Comparative Example 2-1>
0.59 parts of a solution obtained by dissolving 0.55 parts of an ultraviolet absorber (manufactured by ADEKA Co., Ltd.: ADEKA STAB (registered trademark) LA-F70, weight loss start temperature Td (° C.) is 379° C.) in 1.13 parts of toluene. A thermoplastic resin composition (A-6) was obtained in the same manner as in Example 2-2, except that the material was charged from the upstream side of the third vent at a charging rate of /hour. Table 2 summarizes the physical properties of the obtained thermoplastic resin composition (A-6).

From the thermoplastic resin composition (A-6), touch roll film formation and stretching were performed in the same manner as in Example 2-1 to produce a plurality of sheet-like films. The number of noises per ^square meter of the film was 5 points or less.

<Reference example 2-1>
320 parts of a commercially available polymethyl methacrylate resin (Sumitomo Chemical Co., Ltd.: Sumipex (registered trademark) EX) and 480 parts of toluene are introduced into an autoclave equipped with a stirrer and dissolved by heating at 100° C. for 30 minutes to obtain a polymerization solution. rice field.

A thermoplastic resin composition (A-7) was obtained from the resulting polymerization solution in the same manner as in Example 2-1. Table 2 summarizes the physical properties of the obtained thermoplastic resin composition (A-7).

From the thermoplastic resin composition (A-7), touch roll film formation and stretching were performed in the same manner as in Example 2-1 to produce a plurality of sheet-like films. The number of noises per ^square meter of the film was 5 points or less.

(result)
In Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-2, films were formed using a touch roll. Therefore, it was possible to produce a good optical film in which noise generation was suppressed. This point is the same as the first embodiment.

Further, in Examples 2-1 to 2-3, by changing the composition of the thermoplastic resin composition, the glass transition temperature was different, but all of them obtained thermoplastic compositions with high heat resistance. Examples 2-4 and 2-5 also used a coloring agent, but also obtained thermoplastic compositions with high heat resistance. As a result, a thermoplastic composition excellent in various optical properties could be obtained.

On the other hand, in Comparative Example 2-1, a thermoplastic composition was obtained using an ultraviolet absorbent having a high thermal decomposition temperature. As a result, the above thermoplastic composition had defects in optical properties. Specifically, the a ^* value, b ^* value, c ^* value and 420 nm light transmittance were out of the preferred range.

Even when a thermoplastic resin composition having a low glass transition temperature (not having high heat resistance) is used as in Reference Example 2-1, a thermoplastic resin composition having excellent optical properties can be obtained. However, as described in Section [1], the optical film obtained from such a thermoplastic resin composition does not have the advantages that high heat resistance optical films have.

From the results of Example 2, it can be seen that the combined use of a highly heat-resistant thermoplastic composition (highly heat-resistant (meth)acrylic resin) and an ultraviolet absorber with a low thermal decomposition temperature produces an optical film with excellent optical properties. suggested that it can be done. At this time, if a touch roll is adopted as a film forming method, noise generation can also be suppressed.

According to the method for producing an optical film according to the present invention, it is possible to produce an optical film which has a good b ^* value, is free from transfer of contaminants from the roll during film formation, and has good optical properties.

Claims (5)

A melt made of a thermoplastic resin composition containing 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360 ° C. or less with respect to 100 parts by weight of (meth)acrylic resin is passed from a die into a film form. A method for producing an optical film in which the film is formed by sandwiching between a touch roll and a cast roll after discharging to
The ultraviolet absorber is 2,2′-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl)phenol],
The (meth)acrylic resin has, in its main chain, at least one ring structure selected from a lactone ring structure and an N-substituted maleimide structure,
The content of structural units derived from a styrene-based monomer in 100% by mass of the thermoplastic resin composition is 0% by mass or more and less than 10% by mass,
The relationship between the thermal decomposition temperature Td (° C.) and the temperature Tp (° C.) of the melt at the exit of the die is expressed by the following formula: 50 ≤ Td - Tp
A method for producing an optical film that satisfies The method for producing an optical film according to claim 1, wherein the thermoplastic resin composition has a melt viscosity of 500 Pa·S or more at 270°C and a shear rate of 10/sec. A method for producing an optical film, comprising forming a melt of a thermoplastic resin composition containing a (meth)acrylic resin and an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less, comprising:
The (meth)acrylic resin has a glass transition temperature of 108° C. or higher,
The ultraviolet absorber is 2,2′-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl)phenol],
The content of the ultraviolet absorber is 0.1 to 5 parts by weight with respect to 100 parts by weight of the (meth)acrylic resin,
The (meth)acrylic resin has, in its main chain, at least one ring structure selected from a lactone ring structure and an N-substituted maleimide structure,
The content of structural units derived from a styrene-based monomer in 100% by mass of the thermoplastic resin composition is 0% by mass or more and less than 10% by mass,
A method for producing an optical film, in which the melt is extruded from a die in the form of a film, and then sandwiched between touch rolls and cast rolls to form a film. A roll-shaped optical film made of a thermoplastic resin composition containing 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less with respect to 100 parts by weight of (meth)acrylic resin, ,
The ultraviolet absorber is 2,2′-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl)phenol],
The (meth)acrylic resin has, in its main chain, at least one ring structure selected from a lactone ring structure and an N-substituted maleimide structure,
The content of structural units derived from a styrene-based monomer in 100% by mass of the thermoplastic resin composition is 0% by mass or more and less than 10% by mass,
The b ^* value when the optical film has a thickness of 80 μm is less than 0.5,
An optical film having a total noise of 5 points or less when 80% of the width direction of the optical film is projected and inspected every 12 m over a length of 120 m in the longitudinal direction. An optical film made of a thermoplastic resin composition containing 0.1 to 5 parts by weight of an ultraviolet absorber having a thermal decomposition temperature of 360° C. or less with respect to 100 parts by weight of a (meth)acrylic resin,
The ultraviolet absorber is 2,2′-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl)phenol],
The (meth)acrylic resin has, in its main chain, at least one ring structure selected from a lactone ring structure and an N-substituted maleimide structure,
The content of structural units derived from a styrene-based monomer in 100% by mass of the thermoplastic resin composition is 0% by mass or more and less than 10% by mass,
The b ^* value when the optical film has a thickness of 80 μm is less than 0.5,
An optical film having a noise of 5 points or less per 1 m ² when the optical film is subjected to projection inspection.