KR102465700B1 - Method for producing optical film and optical film - Google Patents

Abstract

An object of the present invention is to provide 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. will be.
A method for producing an optical film according to one embodiment of the present invention is a melt containing 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 based on 100 parts by weight of a (meth)acrylic resin. , A method for producing an optical film in which touch roll film formation is performed after being discharged from a die into a film form, wherein 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 expression “ 50≤Td-Tp” is satisfied.

Description

Optical film manufacturing method and optical film {METHOD FOR PRODUCING OPTICAL FILM AND OPTICAL FILM}

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

BACKGROUND OF THE INVENTION [0002] Conventionally, an optical film formed by melt forming a resin containing an ultraviolet absorber (UVA) into a film is known. For example, in Patent Document 1, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl represented by the following formula as an ultraviolet absorber )phenol] (hereinafter referred to as "compound a") is described.

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

By the way, in general, in the case of manufacturing an optical film, it is necessary to increase the extrusion temperature of the resin in order to use a resin having high heat resistance or melt viscosity or to increase the amount of extrusion of the resin. However, the compound a has a low thermal decomposition temperature, and when the extrusion temperature of the resin is increased, the compound a bleeds out when an optical film is produced by open film forming, causing a problem that the roll is contaminated. Therefore, bleed-out of compound a is suppressed by using a benzotriazine-based ultraviolet absorber having high heat resistance instead of compound a or by using the ultraviolet absorber and compound a in combination. For example, Patent Document 2 describes an optical film formed by open film formation of an acrylic resin containing benzotriazine and benzotriazole. Further, Patent Literature 3 describes an optical film obtained by adding a benzotriazine having a molecular weight of 700 or higher to a ring acrylic resin and forming a resin composition having a glass transition temperature (Tg) of 110°C or higher through open film formation.

Further, (meth)acrylic resins, which have been used in recent years as raw materials for optical films, may turn yellow when exposed to light including ultraviolet rays, resulting in reduced transparency. As a method of preventing this phenomenon, a method of adding an ultraviolet absorber (UVA) is known. However, when a general ultraviolet absorber is added, there are problems such as deterioration of the color, heat resistance or transparency of the optical film, or the evaporation of the ultraviolet absorber during molding, resulting in a decrease in ultraviolet absorbency or contamination of the molding apparatus. .

Therefore, a method for solving the above problem has been proposed by using a triazine-based ultraviolet absorber that can obtain a high ultraviolet ray absorption effect even with a small amount of addition and has high heat resistance, alone or in combination with other ultraviolet absorbers (for example, For example, Patent Documents 4 and 5).

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

However, although the optical films described in Patent Literatures 2 and 3 can suppress bleed-out in the case of manufacturing optical films, they have room for improvement regarding the b ^* value.

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

The main object of the present invention is to provide 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 having been made in view of the above problems. to be

Another object of the present invention is to provide a manufacturing method and an optical film having excellent heat resistance and having high transparency, small color and low chroma.

The present invention includes the following structures.

<1> After discharging a melt containing 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, from a die into a film form, touch roll It is a manufacturing method of the optical film which performs film forming; A method for producing an optical film, wherein a relationship between the thermal decomposition temperature Td (°C) and the temperature Tp (°C) of the melt at the exit of the die satisfies the following expression.

50≤Td-Tp

<2> The manufacturing method of the optical film as described in <1> whose melt viscosity in 270 degreeC and a shear rate of 10/sec of the said thermoplastic resin composition is 500 Pa*S or more.

<3> The (meth)acrylic resin has at least one ring structure selected from a lactone ring structure, a glutaric acid anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure in the main chain. The manufacturing method of the optical film as described in <1> or <2> characterized by the above-mentioned.

<4> A method for producing an optical film in which a melt containing a thermoplastic resin composition containing a (meth)acrylic resin and an ultraviolet absorber having a thermal decomposition temperature of 360° C. or lower is formed into a film; The (meth)acrylic resin has a glass transition temperature of 108° C. or higher; The manufacturing method of the optical film which performs touch-roll film formation, after discharging the said molten material from die to a film form.

<5> A roll-shaped optical film comprising 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 based on 100 parts by weight of a (meth)acrylic resin; a b ^* value when the optical film is made into a film having a thickness of 80 μm is less than 0.5; The optical film, wherein the total noise is 5 points or less when the optical film is subjected to projection inspection of 80% of the width direction (TD direction) at intervals of 12 m over a length of 120 m in its longitudinal direction (MD direction).

<6> An optical film comprising 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 based on 100 parts by weight of a (meth)acrylic resin; a b ^* value when the optical film is made into a film having a thickness of 80 μm is less than 0.5; The optical film whose noise per 1 m 2 is 5 points or less when the optical film is subjected to projection inspection.

<7> An optical film containing a (meth)acrylic resin and an ultraviolet absorber; the glass transition temperature of the optical film is 108° C. or higher; An optical film having a c ^* value of 0.45 or less when the optical film is used as an unstretched film having a thickness of 100 µm and measured according to JIS Z 8729.

<8> The optical film according to <7>, wherein the absolute value of a ^* value measured according to JIS Z 8729 when the optical film is an unstretched film having a thickness of 100 µm is 0.10 or less.

<9> when the said optical film is made into an unstretched film with a thickness of 100 micrometers; a light transmittance at a wavelength of 380 nm measured in accordance with JIS K7361:1997 is 3.0% or less; Moreover, the optical film as described in <7> or <8> whose light transmittance in wavelength 420nm is 95.0% or more.

<10> The optical film according to <7> or <8>, wherein the (meth)acrylic resin has a ring structure in the main chain.

<11> The optical film according to <7> or <8>, wherein the thermal decomposition temperature of the (meth)acrylic resin is 310°C or higher.

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

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

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail. However, the present invention is not limited to this, and various changes are possible within the described range, and embodiments obtained by appropriately combining technical means disclosed in other embodiments are also included in the technical scope of the present invention.

In addition, in this specification, "(meth)acrylic acid" means "acrylic acid or methacrylic acid", "main component" means containing 50 mass % or more, and "ppm" is mass conversion unless otherwise specified A calculated value (for example, 10,000 ppm is 1% by mass). In addition, "weight" is treated as a synonym for "mass", and "weight%" is treated as a synonym for "mass%", and unless otherwise specified in the present specification, "A to B" representing a numerical range is " A or more and B or less”.

A method for manufacturing an optical film according to an embodiment of the present invention is a melt containing 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 based on 100 parts by weight of a (meth)acrylic resin. A method for producing an optical film in which a film is formed by touch roll after discharging from a die into a film, wherein the relationship between the thermal decomposition temperature Td (° C.) and the temperature Tp (° C.) of the melt at the exit of the die is as follows ceremony

50≤Td-Tp

a way to satisfy

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

〔One. Features of the present invention]

[Use of heat-resistant (meth)acrylic resin]

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

A heat-resistant optical film made of a heat-resistant (meth)acrylic resin as a raw material has advantages such as excellent weather resistance and surface hardness and ease of placement close to a heating part (light source, etc.).

By the way, when manufacturing an optical film using heat-resistant (meth)acrylic-type resin as a raw material, a ultraviolet absorber is normally put under a high-temperature environment. At this time, when a UV absorber having a low thermal decomposition temperature is used, the problem that the bleed-out UV absorber causes the roll to be contaminated and transferred to the film surface to generate defects has been conventionally known. As one of the means for solving the above problems, a production method using a UV absorber having a high thermal decomposition temperature (for example, a benzotriazine-based UV absorber) has been proposed. However, since benzotriazine-based ultraviolet absorbers absorb even light rays in the visible light region, there was a difficulty in that color and saturation occur in the optical film produced.

These matters become the premise of this 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 having a low thermal decomposition temperature, the obtained optical film has excellent optical properties (for example, high transparency, low color, and low saturation).

[Adoption of touch roll]

In order to solve the said subject, this invention employ|adopted the touch roll for the film forming method. The reason why generation|occurrence|production of a film defect can be suppressed by forming into a film with a touch roll is estimated as follows. That is, in touch roll film forming, the film during molding adheres to the roll from both sides. For this reason, the ultraviolet absorber cannot volatilize from the surface of the film and tends to stay inside the film. In addition, even if a part of the ultraviolet absorber is volatilized, the volatilized ultraviolet absorber does not accumulate on the roll surface in a large amount as it becomes a defect. As a result, a large amount of ultraviolet absorber is not deposited on the surface of the roll, and therefore, the deposited ultraviolet absorber is not transferred to cause defects in the film.

Means for suppressing the occurrence of the above-described film defects have conventionally been overlooked in view of the technical difficulty of applying a touch roll to film forming technology. For example, the following technical difficulties exist in the touch roll in film forming technology.

(1) Occurrence of thickness distribution

The touch roll film formation is normally configured so that both ends of the roll are suppressed by an air cylinder or the like. For this reason, a bending moment acts on the roll, and deflection may occur in the roll. When formed into a film with such a roll, the thickness distribution of the film becomes thick at the center part and thin at the end part. Such a film has a drawback that it is easy to break in the vicinity of the holding portion. Although there are countermeasures, such as giving a crown process to a touch roll and installing a back-up roll about the said defect, both tend to complicate the structure of a processing method and a manufacturing apparatus.

(2) bias in force applied to the film

Since the pressure applied to the film affects the alignment state of the resin and the retardation of the obtained film changes, it is important to apply pressure with a sufficiently uniform pressure in order to obtain an optical film with high retardation uniformity. However, when 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 does not uniformly touch the film surface due to roll bending. When the film thickness of the original fabric of the film is convex from both ends in the width direction of the film toward the center, the unevenness of the pressure resulting from the warpage can be eliminated. However, in order to manufacture such a film raw material, special equipment is required. In addition, if the molten material is strongly pressed during casting, residual strain will occur in the film. And, when such a film is stretched, bias occurs in the stretching due to the residual strain, and bias also occurs in the film thickness. Thus, it is difficult to pressurize the extruded film-like melt with a uniform pressure with a cast roll and a touch roll.

(3) Difficulties associated with high-speed film formation

When forming a touch roll into a film at high speed, the following problems may arise, for example. (i) The problem that traversal occurs in the molten resin when the molten resin is clamped. (ii) The problem that the molten resin does not partially contact the touch roll. (iii) A problem in which bias in pressure occurs at the end or in the center in the width direction because the clamping pressure is not uniform.

The present invention focuses on touch roll film formation, which conventionally tends to be abandoned due to the above difficulties, and aims to provide an optical film manufacturing method and optical film that achieve both suppression of film defects and excellent optical properties.

〔2. (meth)acrylic resin]

[Structure of (meth)acrylic resin]

An optical film according to an 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 a resin obtained by polymerization or copolymerization of a monomer composition containing acrylic acid, methacrylic acid, a derivative of these compounds, or a hydroxyl group-containing monomer having a structure represented by the following formula. and derivatives thereof. These structures are not particularly limited as long as the effects of the present invention are not impaired. Specifically, known (meth)acrylic resins can be used.

CH ₂ =C(COOR ¹ )-CHR ² -OH

(In the formula, 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).

Specifically as a derivative of (meth)acrylic acid, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate , (meth)acrylic acid n-hexyl, (meth)acrylic acid 2-chloroethyl, (meth)acrylic acid 2-hydroxyethyl, (meth)acrylic acid 3-hydroxypropyl, (meth)acrylic acid 2,3,4,5- tetrahydroxypentyl and (meth)acrylic acid 2,3,4,5,6-pentahydroxyhexyl; and the like. As for these derivatives, multiple types may be used together. Among the above specific examples, methyl (meth)acrylate is most preferable in terms of excellent thermal stability of the obtained (meth)acrylic resin.

In addition, a ring structure may be introduced into the molecular chain (also referred to as the main skeleton or main chain of the polymer) of the (meth)acrylic resin to improve the heat resistance of the (meth)acrylic resin. Examples of such a ring structure include at least one selected from a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure. 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 phenyl maleimide, cyclohexyl maleimide, and methyl maleimide.

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

It is more preferable that (meth)acrylic-type resin has a structure which does not contain a nitrogen atom so that it may be hard to be colored (yellowing) when it is set as an optical film.

Moreover, it is more preferable that the lactone ring structure is introduce|transduced into the main chain so that a (meth)acrylic-type resin may express positive birefringence (positive retardation) easily. 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 in terms of structural stability, and particularly preferably a 6-membered ring. Examples of the 6-membered ring lactone ring structure introduced into the main chain include a lactone ring structure represented by general formula (1) described later, a lactone ring structure described in Japanese Unexamined Patent Publication No. 2004-168882, and the like. Among these, (i) those having a high polymerization yield when synthesizing a polymer having a hydroxyl group and an ester group before introducing a lactone ring structure into the main chain, and (ii) synthesizing a (meth)acrylic resin having a high content of a lactone ring structure. The lactone ring structure represented by General formula (1) is more preferable from the point which the polymerization yield at the time of doing is high and copolymerizability with (meth)acrylic acid esters, such as (iii) methyl methacrylate, is good.

Further, the (meth)acrylic resin may have a structural unit obtained by polymerizing other monomers copolymerizable with (meth)acrylic acid or a derivative thereof within a range not impairing heat resistance. Specific examples of other monomers that can be copolymerized include aromatic vinyl monomers such as styrene and α-methylstyrene, nitrile monomers such as acrylonitrile, and vinyl esters such as vinyl acetate.

It is preferable that the weight average molecular weight (Mw) of styrene conversion by the GPC measurement method of (meth)acrylic-type resin in embodiment of this invention is 3,000-1,000,000. If this weight average molecular weight is 3,000 or more, strength required as a polymer can be expressed. Moreover, if it is 1,000,000 or less, it can be set as a molded body by molding process. 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, still more preferably 100,000 to 500,000. A (meth)acrylic resin having a weight average molecular weight within the above range is preferable because of good moldability by extrusion and melting.

It is preferable that the molecular weight distribution (Mw/Mn) of the (meth)acrylic-type resin in one embodiment of the present invention according to the GPC measurement method is 1 to 10. From the viewpoint of adjusting the resin viscosity suitable for molding processing, the molecular weight distribution (Mw/Mn) is preferably 1.1 to 7.0, more preferably 1.2 to 5.0, still more preferably 1.5 to 4.0.

[Method for producing (meth)acrylic resin]

The manufacturing method of the said (meth)acrylic-type resin is not specifically limited, A well-known method can be used. Specifically, a method of polymerizing a monomer composition containing (meth)acrylic acid or a derivative thereof is exemplified. When using a (meth)acrylic resin for an optical material application, it is preferable to avoid incorporation of minute foreign matter as much as possible. From this point of view, it is preferable to use bulk polymerization, cast polymerization or solution polymerization without using a suspending agent or emulsifying agent. As the polymerization format, for example, both batch polymerization and continuous polymerization can be used. A batch polymerization method is preferred from the viewpoint of simple polymerization operation, and a continuous polymerization method is preferred from the viewpoint of obtaining a polymer product having a more uniform composition.

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

In the case of a polymerization form using a solvent, the solvent used is not particularly limited. For example, 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; etc. can be mentioned. A solvent may use multiple types together.

In particular, when producing a (meth)acrylic resin having a lactone ring structure introduced into the main chain, if the boiling point of the solvent to be used is too high, the residual volatile content of the finally obtained (meth)acrylic resin increases. Therefore, as for the boiling point of a solvent, it is more preferable that it exists in the range of 50 degreeC or more and 200 degrees C or less.

During the polymerization reaction of the monomer composition, a polymerization initiator may be added as needed. The polymerization initiator is not particularly limited. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropylcarbonate, t-amylperoxy organic peroxides such as -2-ethylhexanoate; azo compounds such as 2,2'-azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), and 2,2'-azobis (2,4-dimethylvaleronitrile); etc. can be mentioned. A polymerization initiator may use multiple types together. The usage amount of the polymerization initiator may be appropriately set depending on the type of monomer used, its usage ratio (composition of the monomer composition), or reaction conditions, and is not particularly limited.

In the polymerization reaction of the monomer composition, in order to suppress gelation of the reaction solution, it is preferable to control the concentration of the polymer in the reaction solution to 50% by mass or less. Specifically, when the concentration of the polymer in the reaction solution exceeds 50% by mass, it is preferable to appropriately add a solvent to the reaction solution so that the concentration becomes 50% by mass or less. As for the said concentration, it is more preferable that it is 45 mass % or less, and it is still more preferable that it is 40 mass % or less. Moreover, since productivity will fall when the density|concentration of a polymer is too low, it is preferable that the said density|concentration is 10 mass % or more, and it is more preferable that it is 20 mass % or more.

The method of adding a solvent to the reaction solution during the polymerization reaction is not particularly limited. For example, the solvent may be continuously added to the reaction solution, or the solvent may be added intermittently. Gelation of the reaction liquid can be suppressed by controlling the concentration of the polymer in the reaction liquid. Since the heat resistance of (meth)acrylic resin is improved by increasing the content of the lactone ring structure, the concentration of the polymer is controlled in this way even when the ratio of hydroxyl groups and ester groups of the polymer before introduction of the lactone ring structure to the main chain is increased. If so, gelation of the reaction solution can be sufficiently suppressed.

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

The reaction solution obtained at the time of completion of the polymerization reaction usually contains a solvent in addition to the polymer obtained by polymerization. When the polymer is used as a lactone ring structure-containing polymer described later, it is not necessary to remove the solvent from the reaction solution to take out the polymer in a solid state, and the reaction solution containing the solvent is used in the lactone ring condensation step following the polymerization reaction. It can be continuously used as a reaction solution in Alternatively, after taking out the polymer in a solid state, a solvent suitable for the lactone ring condensation step may be added to form a reaction solution.

[Characteristics of (meth)acrylic resin]

The color of the (meth)acrylic resin obtained by polymerization is not particularly limited. Transparent and low yellowing are preferable for molding into an optical film without damaging the original characteristics of (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, for example, 3 mm. Further, the (meth)acrylic resin preferably has a YI (yellow index) value of, for example, 10 or less, more preferably 5 or less, when formed into a molded body having a thickness of 3 mm.

In this embodiment, the melt viscosity of the thermoplastic resin composition containing the (meth)acrylic resin at 270°C and a shear rate of 10/sec is more preferably 500 Pa·S or more, and still more preferably 550 Pa·S or more. It is preferable, and it is especially 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 fail to produce a material having sufficient mechanical properties. In addition, as for the upper limit of the said melt viscosity, about 3000 Pa*S is suitable.

The said melt viscosity can be measured, for example using the capillary rheometer RH10 of a twin-bore barrel type by Rosende Corporation. Details of measurement conditions and the like are described in the section of Examples.

In the present embodiment, the (meth)acrylic resin constituting the thermoplastic resin composition has a glass transition temperature (Tg) within the range of 108°C or higher and 160°C or lower, more preferably within the range of 110°C or higher and 150°C or lower. to be. In a more preferred aspect, the upper limit of the glass transition temperature range is 140°C or lower, and the lower limit is 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 common (meth)acrylic resins (polymethyl methacrylate (PMMA)).

When the glass transition temperature is less than 108°C, for example, when an optical film containing the (meth)acrylic resin is incorporated as a polarizing plate of an optical device, sufficient durability at high temperatures may not be exhibited. When 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 bleed-out of the ultraviolet absorber. 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 on the film can be increased without making molding processes such as film molding or stretching difficult. The glass transition temperature of the film can also be increased. An optical film having a high glass transition temperature can reduce the rate of change of phase difference in a high-temperature environment.

The said glass transition temperature can be measured based on the rule of JIS K7121. Details of measurement conditions and the like are described in the section of Examples.

The thermal decomposition temperature (thermal decomposition start 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 still more preferably 320°C or higher. It can be said that a (meth)acrylic resin having a thermal decomposition temperature of 310°C or higher has sufficient heat resistance. The upper limit of the thermal decomposition temperature is not particularly limited, but may be about 380°C. By forming a (meth)acrylic-type resin having such a thermal decomposition temperature into a film with a touch roll, advantages such as reduction of film defects, reduction of film discoloration, and suppression of bubble mixing are obtained.

In addition, as shown in Examples, in this specification, "thermal decomposition temperature" refers to the lowest temperature among the temperatures at which the rate of mass decrease accompanying temperature increase increases. That is, in this specification, "thermal decomposition temperature" means "thermal decomposition start temperature". Hereinafter, either notation of "thermal decomposition temperature" and "thermal decomposition start temperature" is used, but the meaning is the same.

In addition, the glass transition temperature and thermal decomposition temperature of (meth)acrylic-type resin may differ from the glass transition temperature and thermal decomposition temperature of a 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 may be regarded as substantially the same as those of the optical film. In this regard, the preferred glass transition temperature and thermal decomposition temperature of the thermoplastic resin composition in one embodiment of the present invention (that is, the preferred glass transition temperature and thermal decomposition temperature of the optical film according to one embodiment of the present invention) are [5 It is described later in section ].

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 a range of 1.5 × 10 ^-10 Pa ^-1 or less, more preferably 1.0 × Within the range of 10 ^-10 Pa ^-1 or less, more preferably within the range of 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 during the stretching process and reduce the birefringence.

The stress optical coefficient (Cr) is derived from the slope of an 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 the embodiment.

[Structure of lactone ring structure-containing polymer]

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, and is particularly a lactone ring structure-containing polymer containing a lactone ring structure as a main component. desirable. In this specification, a (meth)acrylic resin in which a lactone ring structure is introduced into the 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 characteristics suitable for various optical applications.

Although the said lactone ring structure containing polymer is not specifically limited, What has a lactone ring structure represented by the following general formula (1) is more preferable.

(In the formula, R ¹¹ , R ¹² , 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 optionally have an oxygen atom) represents).

The content ratio of the lactone ring structure represented by the 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. Preferably they are 10 mass % or more and 60 mass % or less, Especially preferably, they are 10 mass % or more and 50 mass % or less. When the said content rate is less than 5 mass %, heat resistance, solvent resistance, and surface hardness may become inadequate. Moreover, when the said content ratio is more than 90 mass %, molding processability may become insufficient.

The lactone ring structure containing polymer may have structures 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, a polymer structural unit (repeating structural unit) 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) is preferable

CH ₂ = C(X)-R ¹⁴ . . . (2)

(In the formula, R ¹⁴ represents a hydrogen atom or a methyl group. X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an -OAc group, a -CN group, a -CO-R ¹⁵ group, or a COR ¹⁶ group. Ac represents acetyl, R ¹⁵ and R ¹⁶ represent a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms).

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

In addition, when 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 the general formula (1), the content ratio thereof 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 greater than 0% by mass, and 15 It is within the range of mass % or less, and particularly preferably exceeds 0 mass % and is within the range of 10 mass % or less.

In addition, when 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 the general formula (1), it is contained. The ratio 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 greater than 0% by mass, Within the range of 15 mass % or less, It exists in the range of more than 0 mass % and 10 mass % or less especially preferably.

Further, the lactone ring structure-containing polymer has a polymer structural unit (repeating structural unit) constructed by polymerizing the monomer represented by the general formula (2) as a structure other than the lactone ring structure represented by the general formula (1). In this case, the content ratio 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. It exceeds % and is within the range of 15 mass % or less, Especially preferably exceeds 0 mass % and exists in the range of 10 mass % or less.

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

[Method for Producing Polymers Containing Lactone Ring Structure]

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 subjected to heat treatment to cause a cyclization condensation reaction (lactone ring condensation reaction) to introduce a lactone ring structure into the polymer, thereby obtaining a polymer containing a lactone ring structure. can That is, the monomer composition becomes a lactone ring structure-containing polymer by passing through a polymerization step and a lactone ring condensation step.

When the lactone ring structure is formed in the molecular chain of the polymer (in the main skeleton of the polymer), high heat resistance is imparted to the polymer. When the reaction rate of the cyclization condensation reaction in which the lactone ring structure is introduced into the polymer is low, the heat resistance of the polymer may not be sufficiently improved. In addition, heat accompanying heat treatment during molding is a cause, and a condensation reaction of the polymer occurs during molding, and the generated alcohol may appear as bubbles or silver streaks in the molded article.

The method of heat-treating the polymer for carrying out the cyclization condensation reaction is not particularly limited, and a known method can be used. For example, you may heat-process the polymerization reaction mixture containing a polymer and a solvent obtained by performing a polymerization process as it is. Moreover, you may heat-process a polymer using a ring closure catalyst as needed in presence of a solvent. Furthermore, you may heat-process using the heating furnace or reaction apparatus provided with the vacuum apparatus or devolatilization apparatus for removing volatile components. Alternatively, heat treatment of the polymer may be performed using a devolatilizing device, an extruder, or the like.

When performing a cyclization condensation reaction, in addition to the said polymer, you may make another acrylic resin coexist. In addition, when performing a cyclization condensation reaction, if necessary, generally used as a catalyst for a cyclization condensation reaction, (i) an organic phosphorus compound, (ii) an esterification catalyst such as p-toluenesulfonic acid, or (iii) a transesterification catalyst You can also use Alternatively, organic carboxylic acids such as acetic acid, propionic acid, benzoic acid, acrylic acid, and methacrylic acid may be used as a catalyst. Furthermore, you may use a basic compound, organic carboxylate, carbonate, etc. which are described in Unexamined-Japanese-Patent No. 61-254608 or Unexamined-Japanese-Patent No. 61-261303 as a catalyst.

As a catalyst for the cyclization condensation reaction, which is a dealcoholization reaction, an organic phosphorus compound is more preferable. While being able to improve the reaction rate of a cyclization condensation reaction by using an organic phosphorus compound as a catalyst, coloring of the lactone ring structure containing polymer obtained can be reduced significantly. In addition, by using an organophosphorus compound as a catalyst, it is possible to suppress a decrease in the molecular weight of the polymer, which may occur when the lactone cyclization condensation step and the devolatilization step described later are used together, and to impart excellent mechanical strength to the polymer. can do.

Examples of organic phosphorus compounds that can be used as catalysts in the cyclization condensation reaction include alkyl (aryl) asulfonic acids such as methyl asulfonic acid, ethyl asulfonic acid, and phenyl asulfonic acid (however, these are tautomers, such as alkyl (aryl) phosphines) acids) and their monoesters or diesters; dialkyl(aryl)phosphinic acids and their esters, such as dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid and phenylethylphosphinic acid; alkyl(aryl)phosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, and phenylphosphonic acid, and monoesters or diesters thereof; alkyl (aryl) aphosphinic acids such as methylaphosphinic acid, ethylaphosphinic acid, and phenylaphosphinic acid and their esters; phosphorous acid monoesters, diesters or triesters such as methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, trimethyl phosphite, triethyl phosphite, 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, diisostearyl phosphate, diphenyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisoste phosphate phosphoric acid monoesters, diesters, or triesters such as aryl and triphenyl phosphate; Mono-, di- or tri-alkyl such as methylphosphine, ethylphosphine, phenylphosphine, dimethylphosphine, diethylphosphine, diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine, etc. (aryl)phosphine; alkyl (aryl) halogen phosphines such as methyldichlorophosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine, diethylchlorophosphine and diphenylchlorophosphine; Methylphosphine oxide, ethylphosphine oxide, phenylphosphine oxide, dimethylphosphine oxide, diethylphosphine oxide, diphenylphosphine oxide, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide, etc. mono-, di- or tri-alkyl(aryl)phosphine oxides; halogenated tetraalkyl(aryl)phosphoniums such as tetramethylphosphonium chloride, tetraethylphosphonium chloride, and tetraphenylphosphonium chloride; etc. can be mentioned.

Among these organic phosphorus compounds, alkyl (aryl) phosphonic acid, phosphorous acid diester or monoester, phosphoric acid diester or monoester, and alkyl (aryl) phosphonic acid are preferred because of their high catalytic activity and low colorability. (Aryl) phosphonic acid, phosphorous acid diester or monoester, phosphoric acid diester or monoester is more preferable, and alkyl (aryl) phosphoric acid, phosphoric acid diester or monoester is particularly preferable. As for these organic phosphorus compounds, multiple types may be used together.

The amount of the catalyst used in the cyclization condensation reaction is not particularly limited, but is preferably within the range of 0.001 to 5% by mass, more preferably within the range of 0.01 to 2.5% by mass, and still more preferably, based on the polymer. is within the range of 0.01 to 1% by mass, particularly preferably within the range of 0.05 to 0.5% by mass. If the usage-amount of the catalyst is less than 0.001% by mass, there is a possibility that the improvement in the reaction rate of the cyclization condensation reaction may become insufficient. On the other hand, if the amount of the catalyst used exceeds 5% by mass, there is a possibility that the polymer having a lactone ring structure may be colored or that melt shaping may be difficult due to crosslinking of the polymer.

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

As a method for producing the lactone ring structure-containing polymer, it is preferable to perform the lactone ring condensation step in the presence of a solvent, and also to use a devolatilization step together during the lactone ring condensation step. Examples of such a manufacturing method include (i) a form in which a devolatilization step is used in combination throughout the entire lactone cyclization condensation step, and (ii) a form in which a devolatilization step is used in combination only in a part of the lactone cyclization condensation step. In the method using the devolatilization step together, since the alcohol by-produced in the cyclization condensation reaction is forcibly devolatilized and removed, the equilibrium of the reaction becomes advantageous to the production side.

The form in which the devolatilization process is used together only in a part of the lactone cyclization condensation process is, for example, after production of a polymer, further heating the apparatus that produced the polymer to advance the cyclization condensation reaction to some extent in advance, and then continuing It is the form which completes the said reaction by performing the cyclization condensation reaction which used the devolatilization process together. Here, also in the step of further heating the apparatus which produced the polymer and advancing the cyclization condensation reaction to some extent in advance, you may use a devolatilization process partly together as needed. It is the form which uses the lactone cyclization condensation process and the devolatilization process together, and all the forms in which the degassing process is not used together through the whole lactone cyclization condensation process are classified into this form.

Here, the said devolatilization process refers to the process of removing volatile components, such as a solvent and a residual monomer, and alcohol by-produced by the cyclization condensation reaction which induces a lactone ring structure. You may perform a devolatilization process under reduced-pressure heating conditions as needed. If this removal treatment is insufficient, residual volatile matter in the resulting lactone ring structure-containing polymer increases, and the lactone ring structure-containing polymer is colored due to deterioration during molding, or molding defects such as bubbles and silver streaks occur. problem arises.

In the aspect of concurrently using the devolatilization step through the entire lactone ring condensation step, the device to be used is not particularly limited. In order to more effectively carry out the production method of the present invention, (i) a devolatilization device including a heat exchanger and a devolatilization tank, (ii) an extruder with a vent, or (iii) a device in which a devolatilizer and an extruder with a vent are arranged in series. It is preferable to use, and it is more preferable to use (i) a devolatilization device that combines a heat exchanger and a devolatilization tank or (ii) an extruder with a vent.

When using the devolatilization apparatus including a heat exchanger and a devolatilization tank, 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. When the said temperature is lower than 150 degreeC, there exists a possibility that a cyclization condensation reaction may become insufficient and the residual volatile matter may increase. If the temperature is higher than 350°C, there is a possibility that the lactone ring structure-containing polymer may be colored or decomposed.

When using the devolatilization apparatus including 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), and 798 to 66.5 hPa (600 to 50 mm Hg) within the range is more preferable. If the pressure is higher than 931 hPa, there is a risk that volatile components including alcohol tend to remain in the lactone ring structure-containing polymer. If the pressure is lower than 1.33hPa, there is a possibility that industrial implementation may become difficult.

In the case of using the extruder having the above vent, one or more vents may be used, but a plurality of vents is more preferable.

When using the extruder with the said vent, the inside of the range of 150-350 degreeC is preferable, and, as for the temperature at the time of a cyclization condensation reaction, the inside of the range of 200-300 degreeC is more preferable. When the said temperature is lower than 150 degreeC, there exists a possibility that a cyclization condensation reaction may become insufficient and the residual volatile matter may increase. If the temperature is higher than 350°C, there is a possibility that the lactone ring structure-containing polymer may be colored or decomposed.

When using the extruder with the above vent, the pressure during the cyclization condensation reaction is preferably within the range of 931 to 1.33 hPa (700 to 1 mmHg), and within the range of 798 to 13.3 hPa (600 to 10 mmHg). more preferable If the pressure is higher than 931 hPa, there is a risk that volatile components including alcohol tend to remain in the lactone ring structure-containing polymer. If the pressure is lower than 1.33hPa, there is a possibility that industrial implementation may become difficult.

Further, in the case of concurrently using the devolatilization step throughout the entire lactone ring condensation step, as will be described later, there is a risk that the physical properties of the lactone ring structure-containing polymer obtained in the heat treatment under severe conditions may deteriorate. Therefore, the devolatilization step is preferably performed using the catalyst for the cyclization condensation reaction described above and under as mild conditions as possible using an extruder with a vent or the like. Here, "heat treatment under severe conditions" refers to heat treatment performed under high-temperature conditions of, for example, 300°C or higher. On the other hand, "heat treatment under mild conditions" refers to heat treatment performed under temperature conditions of, for example, 250 to 300°C.

Moreover, in the aspect which uses the devolatilization process together through the whole lactone cyclization condensation process, Preferably, the polymer obtained in the polymerization process is introduce|transduced into the reaction apparatus together with a solvent. In this case, if necessary, the polymer taken out from the reaction apparatus may be once again passed through a devolatilizing apparatus or an extruder having a vent.

In the form of concurrently using the devolatilization step throughout the lactone cyclization condensation step (for example, in the form of heat-treating the polymer at a high temperature close to 250 ° C. or higher using a twin screw extruder), due to differences in thermal history A phenomenon such as decomposition of a part of the polymer may occur before the cyclization condensation reaction occurs. When such a phenomenon occurs, there is a possibility that the physical properties of the lactone ring structure-containing polymer obtained may be deteriorated.

Therefore, it is preferable to make the lactone ring condensation step into a form in which a devolatilization step is used together only in a part of the lactone ring condensation step. For example, if the cyclization condensation reaction is carried out to some extent before performing the lactone cyclization condensation step in combination with the devolatilization step, the reaction conditions in the latter half can be relaxed and the physical properties of the resulting lactone ring structure-containing polymer can be reduced. It is preferable because it can be suppressed.

As an especially preferable form, the form which starts a devolatilization process over time from the start of a lactone ring condensation process is mentioned. Specifically, (i) the hydroxyl group and the ester group present in the molecular chain of the polymer obtained in the polymerization step are subjected to a cyclization condensation reaction in advance to increase the reaction rate of the cyclization condensation reaction to some extent, and then (ii) a devolatilization step is used in combination. It is the form which performs a lactone ring condensation process. More specifically, for example, (i) the cyclization condensation reaction is advanced to a certain reaction rate in advance in the presence of a solvent using a bookcase reactor, and then (ii) a reactor equipped with a devolatilization device (eg For example, in a devolatilization apparatus including a heat exchanger and a devolatilization tank, an extruder having a vent, etc.), the cyclization condensation reaction is completed. In this aspect, it is particularly preferable that the catalyst for the cyclization condensation reaction is present in the reaction system.

As described above, (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 in advance to increase the reaction rate of the cyclization condensation reaction to some extent, and then (ii) devolatilization step is used in combination. A method of performing a lactone ring condensation step is a preferable mode for obtaining a lactone ring structure-containing polymer. With this form, the reaction rate of a cyclization condensation reaction becomes higher. In addition, a lactone ring structure-containing polymer having a higher glass transition temperature and excellent heat resistance is obtained. In this embodiment, as a target for the reaction rate of the cyclization condensation reaction, the mass loss rate between 150 and 300 ° C. in the dynamic TG measurement shown in the examples is preferably 2% or less, more preferably 1.5% or less, It is more preferable that it is 1 % or less.

In the cyclization condensation reaction previously performed before performing the lactone cyclization condensation step using the devolatilization step together, the reactor which can be employed is not particularly limited. Preferably, an autoclave, a bobbin reactor, a devolatilization device including a heat exchanger and a devolatilization tank, an extruder with a vent, and the like are exemplified (among them, an extruder with a vent is also suitable for a lactone ring condensation step using a devolatilization step together). can be used appropriately). More preferably, it is an autoclave and a bobbin type reactor. However, even when using a reactor such as an extruder having a vent, (i) the vent conditions are made mild (for example, 931 hPa (700 mmHg) or more), (ii) no vent is performed, (iii) It is possible to carry out the cyclization condensation reaction in the same reaction state as in an autoclave or a bobbin-type reactor by measures such as adjusting temperature conditions, barrel conditions, screw shape, screw operating conditions, and the like.

As the cyclization condensation reaction to be carried out in advance, preferably, a mixture containing a polymer obtained in the polymerization step and a solvent is subjected to a heating reaction by adding (i) a catalyst, (ii) a method to perform a heating reaction without a catalyst, and (iii) A method of performing the above (i) or (ii) under pressure can be employed.

In the lactone cyclization condensation step, the polymerization reaction mixture obtained in the polymerization step may be used as the "mixture containing the polymer and the solvent" introduced into the cyclization condensation reaction, or the solvent is once removed from the polymerization reaction mixture, and then the cyclization condensation reaction You may use a mixture formed by adding another suitable solvent. That is, the solvent used in the cyclization condensation reaction performed in advance before the lactone cyclization condensation step using the devolatilization step together may be the solvent used in the polymerization step, or may be 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; etc. can be mentioned. However, it is more preferable to use the same kind of solvent as the solvent used in the polymerization step.

As the catalyst added in the method (i), an esterification catalyst such as p-toluenesulfonic acid or a transesterification catalyst, a basic compound, an organic carboxylate, a carbonate, or the like generally used as a catalyst for a cyclization condensation reaction may be used. However, in one embodiment of the present invention, it is preferable to use the organic phosphorus compound described above.

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

The heating temperature and heating time of 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 within the range of 1 to 20 hours. , more preferably within the range of 2 to 10 hours. When the heating temperature is low or the heating time is short, the reaction rate of the cyclization condensation reaction may decrease. In addition, when the heating temperature is high or the heating time is long, there is a possibility that the lactone ring structure-containing polymer may be colored or decomposed.

As said method (ii), the method etc. which heat the polymerization reaction mixture obtained in the polymerization process as it is are mentioned, for example using a pressure-resistant bookcase type reactor etc. The heating temperature is preferably 100°C or higher, more preferably 150°C or higher. The heating time is preferably in the range of 1 to 20 hours, more preferably in the range of 2 to 10 hours. When the heating temperature is low or the heating time is short, the reaction rate of the cyclization condensation reaction may decrease. In addition, when the heating temperature is high or the heating time is long, there is a possibility that the lactone ring structure-containing polymer may be colored or decomposed.

In both methods (i) and (ii), there is no problem at all even if it is performed under pressure depending on conditions (method (iii)). In addition, in the cyclization condensation reaction previously performed, there is no problem at all even if a part of the solvent volatilizes naturally during the reaction.

At the end of the cyclization condensation reaction performed in advance, 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, more preferably 1.5% or less and more preferably 1% or less. If the mass reduction rate is higher than 2%, even if the lactone cyclization condensation step using the devolatilization step is subsequently performed, the reaction rate of the cyclization condensation reaction does not rise to a sufficiently high level, and the physical properties of the obtained lactone ring structure-containing polymer may deteriorate. .

Further, in the lactone ring 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 may be made to coexist with the mixture containing the polymer and the solvent. As the other thermoplastic resin, a thermoplastic resin that is thermodynamically compatible with the lactone ring structure-containing polymer is preferable. Examples of other thermoplastic resins include copolymers containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit. Specifically, an acrylonitrile-styrene-based copolymer, a polyvinyl chloride resin, or a polymer containing 50% by mass or more of methacrylic acid esters is exemplified.

Among these other thermoplastic resins, acrylonitrile-styrene-based copolymers are more preferable because they have the most compatibility and can obtain transparent molded articles without impairing heat resistance. In addition, whether or not the lactone ring structure-containing polymer and other thermoplastic resins are thermodynamically compatible can be confirmed by measuring the glass transition point of a thermoplastic resin composition obtained by mixing both. 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.

In the case of using an acrylonitrile-styrene-based copolymer as another thermoplastic resin, as a method of polymerizing the lactone ring structure-containing polymer and the acrylonitrile-styrene-based copolymer, emulsion polymerization, suspension polymerization, or solution polymerization , bulk polymerization method, etc. are mentioned. Among these polymerization methods, the solution polymerization method and the bulk polymerization method are more preferable from the viewpoint of transparency and optical performance of the resulting optical film.

(i) Lactone cyclization condensation step in which 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 increase the reaction rate of the cyclization condensation reaction to some extent, and then (ii) a devolatilization step is used in combination. In the form of carrying out the lactone cyclization condensation step using the devolatilization step together without separating the polymer (a polymer in which a part of the hydroxyl groups and ester groups present in the molecular chain have undergone a cyclization condensation reaction) and the solvent obtained in the previously performed cyclization condensation reaction, the lactone cyclization condensation step is initiated. You can do it. In addition, if necessary, other treatment (a polymer obtained in a previously performed cyclization condensation reaction (a polymer in which a part of the hydroxyl groups and ester groups present in the molecular chain have undergone a cyclization condensation reaction) and the solvent are separated, and then another solvent is added. etc.), you may start the lactone ring condensation process which used the devolatilization process together.

The devolatilization step does not need to be completed simultaneously with the lactone cyclization condensation step, and may be terminated over time from the end of the lactone cyclization condensation step. That is, the devolatilization step may be completed earlier or later than the lactone ring condensation step.

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

As described above, it is preferable to use a catalyst in the case of 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, the hydroxyl groups of unreacted ring-forming units (ie, units that have not yet formed rings) or in the system In some cases, transesterification of an active hydrogen such as water present in a small amount with an alkyl ester group is promoted. As a result, alcohol is generated and foaming may occur. Therefore, in order to prevent this foaming phenomenon, it is preferable to mix|blend a deactivator with the lactone ring structure containing polymer.

In general, when the catalyst used for cyclization condensation reactions such as transesterification is an acidic substance, in order to deactivate the catalyst remaining after the reaction, it may be neutralized using a basic substance. Therefore, when the catalyst used for the cyclization condensation reaction is an acidic substance, a basic substance is preferably used as a deactivator. The basic substance is not particularly limited as long as no substance or the like that impairs the physical properties of the resin composition is generated during thermal processing, and examples include metal compounds such as metal salts such as metal carboxylates, metal complexes, and metal oxides. can be heard

The metal constituting 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 at the time of disposal. alkali metals such as, for example, lithium, sodium and potassium; alkaline earth metals such as magnesium, calcium, strontium and barium; benign substances such as zinc, aluminum, tin, and lead; zirconium; etc. can be mentioned. Among these metals, typical metal elements are preferable, alkaline earth metals and amphoteric metals are particularly preferable, and calcium, magnesium, and zinc are most preferable in terms of less coloring of the resin composition.

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

The organic carboxylic acid constituting the metal salt of the 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, behenic acid, tridecane acids, 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.

As an organophosphorus compound which comprises the metal salt of an organophosphorus compound, the organophosphorus compound mentioned above is mentioned, for example.

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.

Although it does not specifically limit as an organic component in a metal complex, Acetylacetone etc. are mentioned.

Although it does not specifically limit as a metal oxide, For example, zinc oxide, calcium oxide, magnesium oxide etc. are mentioned.

On the other hand, in general, when the catalyst used for cyclization condensation reactions such as transesterification is a basic substance, in order to deactivate the catalyst remaining after the reaction, what is necessary is just to neutralize it using an acidic substance. Therefore, when the catalyst used for the cyclization condensation reaction is a basic substance, an acidic substance is preferably used as a deactivator. The acidic substance is not particularly limited as long as no substance or the like that impairs the physical properties of the resin composition is generated during thermal processing, and examples thereof include organic phosphorus compounds.

Any of an acidic substance and a basic substance may be sufficient as a catalyst, and multiple types may be used together as a deactivator. In addition, the deactivator may be added to the lactone ring structure-containing polymer in any form such as solid form, powder form, granular form, dispersion, suspension, aqueous solution, etc., and is not particularly limited.

What is necessary is just to adjust the compounding quantity of a quencher suitably according to the usage-amount of the catalyst used for the cyclization condensation reaction, and is not specifically limited. The compounding amount of the deactivator is, for example, based on the mass of the lactone ring structure-containing polymer, and is preferably 10 ppm or more and 10,000 ppm or less, more preferably 50 ppm or more and 5000 ppm or less, still more preferably 100 ppm or more and 3000 ppm or less. When the blending amount is less than 10 ppm, the action of the deactivator becomes insufficient, and bubbles may be generated during heating. When the said compounding quantity exceeds 10,000 ppm, while the effect|action of a quencher is saturated, a quencher will be used more than necessary, and manufacturing cost will rise.

The deactivator may be added to the lactone ring structure-containing polymer at any stage after the lactone ring structure is formed. For example, a method in which, after producing a lactone ring structure-containing polymer, the lactone ring structure-containing polymer, a deactivator, and other components are simultaneously heated and melted and kneaded; a method in which a lactone ring structure-containing polymer and other components are heated and melted, and a deactivator is added thereto and kneaded; etc. can be mentioned. "Other components" as used herein are, for example, antioxidants and other thermoplastic resins.

[Characteristics of polymers 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, still more preferably 10,000 or more and 500,000 or less, particularly preferably 50,000 or more and 500,000 or less. to be.

The lactone ring structure-containing polymer preferably has a mass loss rate between 150 and 300°C of 1% or less, more preferably 0.5% or less, and even more preferably 0.3% or less in dynamic TG measurement.

Since the reaction rate of the cyclization condensation reaction is high in the lactone ring structure-containing polymer obtained in the present embodiment, it is possible to avoid the drawback that air bubbles and silver streaks enter the molded article after molding. Further, 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.

The lactone ring structure-containing polymer has a 5% mass reduction temperature in thermogravimetric analysis (TG) of preferably 280°C or higher, more preferably 290°C or higher, and still more preferably 300°C or higher. The 5% mass reduction temperature in thermogravimetric analysis (TG) is an index of thermal stability, and when the temperature is lower than 280°C, there is a possibility that the resulting lactone ring structure-containing polymer may not exhibit sufficient thermal stability.

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

The lactone ring structure-containing polymer has a total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 of preferably 85% or more, more preferably 88% or more, still more preferably 90% or more. more than 1% The total light transmittance is the target for transparency, and if the transmittance is less than 85%, the transparency is lowered, and there is a risk that the product cannot be used for its intended purpose.

[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 glutarimide structure is introduced into the main chain of the polymer. In the present 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 is referred to as a glutarimide structure. They are called containment polymers.

Although the above glutaric anhydride structure-containing polymer and glutarimide structure-containing polymer are not particularly limited, those having a glutaric anhydride structure or glutarimide structure represented by the following general formula (3) are more preferable.

(In the formula, 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 does not exist, and X ¹ is a nitrogen atom, R ³ represents a hydrogen atom, a straight-chain alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group or a phenyl group).

That is, when X ¹ in General Formula (3) is an oxygen atom, the ring structure represented by General Formula (3) becomes 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 the 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 an intramolecular cyclization reaction occurs by dealcoholization, but is suitably within the range of 180 to 350°C, for example. Although the heating time may be appropriately changed according to the composition of the (meth)acrylic resin, for example, within the range of 1 to 2 hours is suitable. In addition, in the above dealcoholization cyclization condensation reaction, you may use a catalyst (for example, an acid catalyst, a basic catalyst, a salt catalyst, etc.) as needed.

When X ¹ in General Formula (3) is a nitrogen atom, the ring structure represented by General Formula (3) becomes a glutarimide structure. The glutarimide structure-containing polymer can be formed, for example, by imidizing a polymer of (meth)acrylic acid ester using an imidation agent such as methylamine. As the method of imidation, a known method can be used. Specifically, the polymer of (meth)acrylic acid ester can be imidized using, for example, ammonia or a substituted amine.

[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. In the present specification, a (meth)acrylic resin having an N-substituted maleimide structure introduced into the main chain is referred to as an N-substituted maleimide structure-containing polymer, and a (meth)acrylic resin having a maleic anhydride structure introduced into the main chain is referred to as maleic anhydride. They are called acid structure-containing polymers.

Although the above N-substituted maleimide structure-containing polymer and maleic anhydride structure-containing polymer are not particularly limited, those having an N-substituted maleimide structure or maleic anhydride structure represented by the following general formula (4) are more preferable.

(In the formula, 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 does not exist, and X ² is a nitrogen atom, R ²² represents a hydrogen atom, a straight-chain alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group, a benzyl group or a phenyl group).

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

In addition, the polymers used for forming the ring structure of 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 are all (meth)acrylic acid esters units as constituent units. Therefore, the resin obtained by the method is included in the category of (meth)acrylic resin.

A lactone ring structure containing polymer, a glutaric anhydride structure containing polymer, a glutarimide structure containing polymer, an N-substituted maleimide structure containing polymer, and a maleic anhydride structure containing polymer may use several types together as needed. That is, the thermoplastic resin composition in the embodiment of the present invention may be a mixture of these polymers.

[3. UV absorber]

The 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.

The thermoplastic resin composition in 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.

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

The thermal decomposition temperature (Td) of the ultraviolet absorber can be measured, for example, using a differential type differential thermobalance. More specific methods are described in Examples. In addition, a value announced by the manufacturer may be employed.

The ultraviolet absorber is not particularly limited. Specifically, for example, at least one selected from benzophenone-based compounds, salicylate-based compounds, benzoate-based compounds, cyanoacrylate-based compounds, benzotriazole-based compounds and triazine-based compounds can be used. Among these ultraviolet absorbers, a benzotriazole-based compound and a triazine-based compound are more preferable in terms of high ultraviolet absorbing power.

As a benzotriazole type compound, the ultraviolet absorber represented by the following general formula (5) is preferable.

(In the formula, 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 are each independently represents a hydrogen atom or a halogen atom, and L represents an alkylene group having 1 to 4 carbon atoms).

Among the ultraviolet absorbers represented by the general formula (5), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3, 3-tetramethylbutyl)phenol] (trade name: LA-31, manufactured by ADEKA Co., Ltd.) is particularly preferred.

As a triazine type compound, the ultraviolet absorber represented by 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 or an alkyl group or an alkyl ester group having 1 to 18 carbon atoms. R ²⁴ to R ²⁶ are each independently , represents a hydrogen atom, or an alkyl group or an alkyl ester group having 1 to 18 carbon atoms. However, the alkyl ester group is preferably a group represented by the formula "-CH(-R ²⁸ )C(=O)OR ²⁹ ", and R ²⁸ is a hydrogen atom or a methyl group, R ²⁹ is an alkyl group, R ²⁴ to R ²⁶ and R ²⁷ , and R ²⁹ are linear or branched alkyl groups).

The molecular weight of the ultraviolet absorber is preferably 400 or more. If the molecular weight is less than 400, there is a possibility that the ultraviolet absorber absorbed by the vent will be excessively increased and the piping or the like may be clogged during production of the thermoplastic resin composition or the optical film.

〔4. Manufacturing method of optical film]

A method for manufacturing an optical film according to an embodiment of the present invention is a melt containing 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 based on 100 parts by weight of a (meth)acrylic resin. is a method of performing touch roll film formation after discharging a film from a die, and the relationship between the thermal decomposition temperature Td (° C.) of the ultraviolet absorber and the temperature Tp (° C.) of the melt at the exit of the die is expressed by the expression “50 ≤Td-Tp”.

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

As described in section [1], in the production of an optical film, touch roll film formation is usually not employed, but the present inventors found that performing touch roll film formation itself has an effect of suppressing bleed-out. Found out. 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 refers to the highest temperature among the temperatures measured at a plurality of locations by contacting a needle-shaped or bar-shaped thermocouple with the melt immediately after being discharged from a die such as a T die (within 30 mm from the die lip).

The upper limit of "Td-Tp" is not particularly limited, but is more preferably 90°C or less. Therefore, "Td-Tp" is more preferably 50°C or more and 90°C or less, still more preferably 55°C or more and 85°C or less, and particularly preferably 60°C or more and 80°C or less. When "Td-Tp" is less than 50 degreeC, the ultraviolet absorber contained in a thermoplastic resin composition will thermally decompose. When "Td-Tp" exceeds 90°C, the viscosity of the melt is high and the flow in the die deteriorates. Therefore, there is a possibility that the melt does not sufficiently flow to the end and the film thickness profile deteriorates.

The touch roll film formation is, for example, a method of continuously forming a film of a predetermined size and thickness by sandwiching the melt of the thermoplastic resin composition continuously discharged from a die into a film between a touch roll and a cast roll. More specifically, with touch roll film formation, for example, the melt is discharged from a die between a touch roll and a cast roll, molded by being sandwiched between the touch roll and cast roll, and then cooled and solidified to continuously form a film into a film way. The touch roll film formation is an effective film formation method for suppressing bleed-out.

[Thermoplastic resin composition]

The thermoplastic resin composition in one embodiment of the present invention contains a UV absorber having a thermal decomposition temperature of 360°C or less in an amount of 0.1 to 5 parts by weight, more preferably 0.3 to 4 parts by weight, based on 100 parts by weight of the (meth)acrylic resin. Within the range, 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 having 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 in one embodiment of the present invention is obtained by uniformly mixing the (meth)acrylic resin and the ultraviolet absorber.

The thermoplastic resin composition in the embodiment of the present invention may contain other polymers other than the (meth)acrylic resin as long as the effect of the present invention is not impaired.

Examples of other polymers include olefin polymers such as polyethylene, polypropylene, ethylene-propylene polymer, and poly(4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and vinyl chloride resin; acrylic polymers such as polymethyl methacrylate; styrenic polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, and acrylonitrile-butadiene-styrene block copolymer; polyesters such as polymer polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 66, and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; polysulfone; polyethersulfone; polyoxybenzylene; polyamideimide; rubbery polymers such as ABS resins and ASA resins blended with polybutadiene rubber and acrylic rubber; etc. can be mentioned.

Further, as long as the effects of the present invention are not impaired, the thermoplastic resin composition in the embodiment of the present invention may contain solvents, unreacted monomers and volatile components such as by-products generated during the reaction step, or diluting solvents. do. 5000 mass ppm or less is preferable, and, as for total content of the said volatile matter in 100 mass % of thermoplastic resin compositions in embodiment of this invention, 3000 mass ppm or less is more preferable. In the case of 5000 mass ppm or more, there is a possibility that coloration may occur during molding or molding defects such as silver streaks may occur.

Here, the content of the structural unit derived from the styrenic monomer in 100 mass% of the thermoplastic resin composition in the embodiment of the present invention is preferably 0 mass% or more and less than 10 mass%, more preferably 0 mass% or more and 8 mass% less than %, more preferably 0% by mass or more and less than 5% by mass. When the content of the structural unit derived from the styrenic monomer of the thermoplastic resin composition is 10% by mass or more, deterioration of optical properties due to heat during long-term use may occur.

The thermoplastic resin composition in the embodiment of the present invention may contain other additives other than the ultraviolet absorber as long as the effect of the present invention is not impaired. Examples of other additives include hindered phenol-based, phosphorus-based, and sulfur-based antioxidants; stabilizers such as light stabilizers, weathering stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; near-infrared absorbers; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; Phase difference adjusting agents, such as a phase difference increasing agent, a phase difference reducing agent, and a phase difference stabilizer; antistatic agents including anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic or inorganic fillers; resin modifier; organic or inorganic fillers; etc. can be mentioned. The content ratio of the 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, still more preferably 0 to 1 It is within the range of mass %.

As said coloring agent, the compound which has an anthraquinone skeleton, the compound which has a phthalocyanine skeleton, etc. are mentioned. Among these, compounds having an anthraquinone skeleton are preferable from the viewpoint of heat resistance. 0.01-5 mass ppm is preferable, as for content of the said coloring agent in 100 mass % of thermoplastic resin compositions in embodiment of this invention, 0.05-3 mass ppm is more preferable, and its 0.1-1 mass ppm is still more preferable. A well-known colorant can be used suitably. For example, specifically, "Macrolex (registered trademark) Violet B", "Macrolex (registered trademark) Violet 3R" (manufactured by LANXESS Corporation), "Smiplast (registered trademark) Violet B" and "Smifla ST (registered trademark) Green G” (manufactured by Sumika ChemteX Co., Ltd.); and the like. The coloring agent can reduce the hue and saturation of the thermoplastic resin composition in the embodiment of the present invention.

In addition, 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 and then mixed with the other. The mixing method is not particularly limited.

Here, in manufacturing the thermoplastic resin composition in the embodiment of the present invention, there is a possibility that the metal element is mixed in various routes. For example, in the production of (meth)acrylic resin, metal elements derived from additives such as polymerization initiators, cyclization catalysts and deactivators, and in the production of thermoplastic resin compositions, metal elements derived from UVA and other additives may be mixed. The content of the metal element in 100 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, particularly Preferably it exists in the range of 0-10 mass ppm. When the content of the metal element in the thermoplastic resin composition exceeds 200 mass ppm, there is a risk that the hue and chroma of the thermoplastic resin composition increase and the transparency deteriorates due to generation of foreign matter. Metal elements that cause such undesirable effects are not particularly limited. As an example, alkali metals, alkaline earth metals, and heavy metals are exemplified in that they form complexes with ultraviolet absorbers, which are benzotriazole-based compounds, and increase color and saturation. Examples include zinc, copper, iron, and the like. can be heard

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, but is preferably 110°C or higher, and then 111°C or higher, 113°C or higher, or 115°C or higher. , preferably in the order of 117 ° C. or higher and 120 ° C. or higher. When the Tg of the thermoplastic resin composition is less than 110 ° C., when an optical film containing the thermoplastic resin composition is assembled as a polarizing plate of an optical device, for example, there is a risk that sufficient durability at high temperatures cannot be exhibited. However, if the Tg of the thermoplastic resin composition is too high, it is necessary to increase the molding temperature of the thermoplastic resin composition, so there is a possibility of foaming during molding or bleed-out of the ultraviolet absorber. The 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. In addition, the glass transition temperature of the thermoplastic resin composition can be regarded as substantially equal to the glass transition temperature of the optical film.

The thermal decomposition temperature (thermal decomposition start 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 even more preferably 320°C or higher. It can be said that a thermoplastic resin composition having a thermal decomposition temperature of 310°C or higher has sufficient heat resistance. The upper limit of the thermal decomposition temperature is not particularly limited, but may be about 380°C. In addition, the thermal decomposition temperature of the thermoplastic resin composition can be regarded as substantially equal to the thermal decomposition temperature of the optical film. By forming a thermoplastic resin composition having such a thermal decomposition temperature into a film with a touch roll, advantages such as reduction of film defects, reduction of film discoloration, and suppression of bubble mixing are obtained.

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

(Optical performance when using 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 when measured in accordance with JIS Z 8729 as an unstretched film having a thickness of 100 µm. Preferably it is 0.35 or less, More preferably, it is 0.30 or less, More preferably, it is 0.25 or less. In addition, the absolute value of the a ^* value measured in accordance with JIS Z 8729 when used as an unstretched film having a thickness of 100 µm is preferably 0.10 or less, and more preferably 0.05 or less. Further, the absolute value of the b ^* value measured in accordance with the provisions of 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, still more preferably 0.30 or less, and 0.25 The following are particularly preferred. In addition, the L ^* value measured in accordance with the provisions of 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, and still more preferably 99.0% or more, It is especially preferable that it is 99.5% or more. If the thermoplastic resin composition in one Embodiment of this invention is in the said range, it can use suitably for the optical film used for a polarizer protective film etc.

Here, the above-described a ^* value, b ^* value, and L ^* value are indices in the L ^* a ^* b ^* colorimetric system specified in JIS Z 8729, and the a ^* value and b ^* value represent hues, and L ^* The value represents lightness. In addition, the c ^* value represents saturation, and is calculated from the above a ^* value and b ^* value by the following equation.

c ^* ＝ (a ^{* 2} + b ^{* 2} ) ^{1 /2}

Values of a ^* , b ^* , and c ^* mean that the closer to 0, the closer to achromatic. The closer the value of L ^* is to 100%, the closer it is to white, that is, all white light is transmitted. An optical film used for a polarizer protective film or the like needs to be close to an achromatic color in order to improve color reproducibility from a backlight, and it is necessary to have high brightness in order to realize high contrast. Since the thermoplastic resin composition in one Embodiment of this invention is more achromatic and shows high brightness, it can be used suitably for an optical film.

The thermoplastic resin composition in one embodiment of the present invention preferably has a light transmittance of 3.0% or less at a wavelength of 380 nm measured in accordance with the provisions of JIS K7361: 1997 when a film having a thickness of 100 μm is unstretched, and is 2.0 It is more preferable that it is % or less, and it is still more preferable that it is 1.5% or less. If the light transmittance in the wavelength of 380 nm of the said unstretched film is within this range, when assembled as a polarizing plate of an optical device, sufficient ultraviolet-ray absorbing ability can be exhibited. Further, the thermoplastic composition preferably has a light transmittance of 95.0% or more at a wavelength of 420 nm, more preferably 96.0% or more, as measured in accordance with the provisions of JIS K7361: 1997 when the thermoplastic composition is used as an unstretched film having a thickness of 100 μm. It is more preferable that it is 97.0% or more. When the light transmittance of the unstretched film at a wavelength of 420 nm is within this range, the transmittance in the visible region becomes high, and the thermoplastic resin composition is particularly suitable 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, still more preferably 99.0% or more when used as an unstretched film having a thickness of 100 μm. to be.

It is preferable that the haze when the thermoplastic resin composition in one Embodiment of this invention is set as an unstretched film with a thickness of 100 micrometers is 1.0% or less. More preferably, it is 0.8% or less, and still more preferably 0.5% or less. When a haze exceeds 1.0%, transparency will fall and it is not suitable when using the said thermoplastic resin composition for an optical use.

[die]

The die is installed at the outlet of a melting device that melts the thermoplastic resin composition. And it is comprised so that the molten material of a thermoplastic resin composition may be made into a film form, and discharged continuously on the top of a touch roll or on a cast roll. The material of the die is preferably metal, and more preferably stainless steel. The size and number of dies may be appropriately set according to the amount of the 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 temperature is such that 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 satisfies the expression “50≤Td-Tp”. is set so that In addition, the melting device is configured to melt the thermoplastic resin composition so as to satisfy the above expression, and to produce a melt having a temperature Tp (° C.) or higher.

[Touch Roll and Cast Roll]

The touch roll and the cast roll are opposite to each other and installed in parallel. Two or more touch rolls and cast rolls may exist, respectively. It is particularly preferable that the surfaces of the touch roll and the cast roll are mirror-finished.

It is preferable that the touch roll is formed of a material having elasticity. As for the material of a touch roll and a cast roll, stainless steel, such as SCM steel and SUS, etc. are preferable. Moreover, as a touch roll and a cast roll, material formed by plating the said steel or stainless steel with chromium, nickel, titanium, etc.; material formed by forming a surface film of TiN, TiAlN, TiCN, CrN, DLC (diamond-like carbon) or the like by a PVD (Physical Vapor Deposition) method or the like; ash formed by thermal spraying of tungsten carbide or other ceramics; It is also suitable to use; and material obtained by nitriding the surface of the steel or stainless steel.

The touch pressure, which is a 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, more preferably in the range of 0.3 MPa to 8 MPa, and 0.5 MPa. It is particularly preferably within the range of 5 MPa to 5 MPa.

It is preferable that the arithmetic mean height (Ra) of the surface of a touch roll and a cast roll is 100 nm or less, it is more preferable that it is 50 nm or less, and it is still more preferable that it is 25 nm or less. Thereby, a film having appropriate irregularities on the surface can be formed into a film. If the material of the surface of a touch roll and a cast roll is metal, it is easy to make Ra of these rolls 100 nm or less.

The thickness, length, temperature, and the like 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 slowly cooling (cooling) the molten material, it is more preferable that a plurality of (more specifically, 2 to 6) existing cast rolls are present.

And, for example, in the case of forming a film by slowly cooling the melt using two or more cast rolls, the temperature of the cast roll adjacent to the downstream side of the cast roll on the near side (upstream side) of the die is the above-mentioned upstream side Compared to the temperature of the cast roll of , it is preferably lower than 0 ° C and lower than 20 ° C, more preferably 1 ° C to 18 ° C lower, and still more preferably 2 ° C to 15 ° C lower. As a result, physical properties of both surfaces of the obtained optical film can be made more uniform, and 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. In addition, the temperature of the cast roll on the side closest to the die (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 more preferably within the range of Tg-70 ° C to Tg + 5 ° C. , Tg - 60 ° C. to Tg is particularly preferred.

Temperature control of a touch roll and a cast roll can be performed, for example by passing the heat medium (liquid or gas) whose temperature was adjusted inside these rolls.

[Unveiling speed]

The film forming rate of the melt may be appropriately set according to the desired size and thickness of the optical film, and is not particularly limited. The film forming speed is preferably in the range of 2 m/min to 50 m/min, more preferably in the range of 2 m/min to 40 m/min, and still more preferably in the range of 3 m/min to 35 m/min. When the film forming speed is within the above range, the melt is pulled by the touch roll and the cast roll at the exit of the die, and expansion of the melt is suppressed, and rubbing against the exit of the die is suppressed. Therefore, irregularities on 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 in the die of the melt can be suppressed to be short, so the number of foreign substances (gels and contaminants) contained in the melt can be reduced. When the film forming speed exceeds 50 m/min, there is a possibility that the flow of the molten material at the exit of the die may be disturbed and the uniformity of the film may deteriorate.

Thus, by forming a heat-resistant (glass transition temperature of 108 ° C. or higher) (meth)acrylic resin into a touch roll film, even when an ultraviolet absorber having a low thermal decomposition temperature is used, the b ^* value is low and good, and the roll (touch It is possible to produce an optical film having good optical properties without transfer of contaminants from rolls and cast rolls).

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 satisfies the expression “50≤Td-Tp”. If the melt is discharged from the above, the effect described above can be further increased.

In addition, the optical film obtained by touch roll film formation may have both ends trimmed as needed. The optical film cut off by trimming can be reused as a raw material if crushed.

[winding and stretching]

The optical film continuously manufactured by touch roll film formation is peeled off from the cast roll and passed through a nip roll or the like, then wound around a core material to become a roll-shaped optical film. The winding speed of the optical film is not particularly limited, but 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, and in the range of 3 m/min to 70 m/min. It is more preferable to be mine. In addition, the winding tension of the optical film is not particularly limited, but is preferably within the range of 1 N/m width to 500 N/width, more preferably within the range of 1 N/m width to 300 N/width.

Before winding up the optical film, a protective film made of polyethylene, polypropylene, polyester, or the like may be adhered to one or both surfaces of the optical film. The thickness of the protective film is not particularly limited, but is preferably in the range of 5 µm to 100 µm, and more preferably in the range of 10 µm to 50 µm.

It is preferable to perform longitudinal stretching and/or transverse stretching of the optical film continuously manufactured by touch roll film formation (hereafter, "MD stretching" for longitudinal stretching and "TD stretching" for lateral stretching are also described). MD stretching and/or TD stretching may be combined with shrinkage relaxation treatment. The optical film according to the present invention is more preferably biaxially stretched (MD stretching and TD stretching). In addition, MD is an abbreviation of Machine Direction, and is synonymous with "longitudinal direction" and "longitudinal direction". TD is an abbreviation of Transverse Direction, and is synonymous with "width direction" and "lateral direction".

Although it does not specifically limit as a specific method of MD extending|stretching, For example, methods, such as oven longitudinal stretching and roll longitudinal stretching, are mentioned.

Oven longitudinal stretching is a method of stretching an original film in its longitudinal direction by creating a difference in circumferential speed between a conveyance roll at the entrance side of the oven and a conveyance roll at the exit side. The oven is configured to heat the original film to a temperature at which it can be stretched. According to oven longitudinal stretching, depending on stretching conditions, a heat treatment effect can be imparted to the film after stretching.

The stretching temperature in oven longitudinal stretching is preferably within the range of Tg-10°C to Tg+50°C, more preferably within the range of Tg-5°C to Tg+40°C, based on the glass transition temperature (Tg) of the original film. And, more preferably within the range of Tg ℃ to Tg + 30 ℃. Stretching at a temperature lower than Tg - 10°C may cause the original film to break. Stretching at a temperature higher than Tg + 50°C increases the sagging of the original film, so there is a risk of friction between the original film and the device or breakage of the original film.

Longitudinal roll stretching is a method in which an original film is heated to a stretching temperature while being in continuous contact with a plurality of heating rolls, and then stretched by nip rolls installed in the stretching section. After that, the stretched film is cooled by a cooling roll. An auxiliary heating device may be installed in the stretching section to stabilize the stretching temperature. Longitudinal roll stretching can be performed using a longitudinal roll 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 indicators. In the case of stretching, it is preferable to heat the original film within the range of Tg-10°C to Tg+20°C with a heating roll on the basis of the glass transition temperature (Tg) of the film. Moreover, it is more preferable to heat within the range of Tg°C to Tg+30°C with 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, it is easy to cause process problems such as tearing or cracking of the original film. When the heating of the original film with the heating roll is higher than Tg + 30 ° C., it is difficult to improve the mechanical properties such as elongation, tensile strength, and flexibility of the finally obtained optical film, so secondary processability may deteriorate.

Moreover, the total number of heating rolls is preferably 5 or more. When the number of heating rolls is less than five, the original film cannot be sufficiently heated because the heating effect is reduced. The method of increasing the roll diameter of the heating rolls to enhance the heating effect instead of reducing the total number of heating rolls to less than 5 is that the original film thermally expanded by heating cannot be sufficiently stretched, and wrinkles are likely to occur. At the same time, since breakage caused by wrinkles also tends to occur, this is not preferable.

A well-known device is mentioned as an auxiliary heating device installed in an extending|stretching area. Specifically, at least one selected from IR heaters, ceramic heaters, and hot air heaters is preferable.

The stretching speed at the time of performing MD stretching may be appropriately set according to the characteristics of the desired optical film, and is not particularly limited, but is preferably in the range of 10 to 20000%/min, and more preferably in the range of 100 to 10000%/min. do. When the stretching speed is slower than 10%/min, it takes time to obtain a sufficient stretching ratio and the manufacturing cost increases. When the stretching speed is faster than 20000%/min, there is a possibility that the film may be broken or the like.

The draw ratio when performing MD stretching may be appropriately set according to the characteristics of the desired optical film, and is not particularly limited, but is preferably in the range of 10 to 300%, more preferably in the range of 15 to 300%, It is more preferably within the range of 20 to 200%. In addition, a draw ratio is defined as "stretch ratio (%) = 100 x {(length after stretching) - (length before stretching)}/(length before stretching)".

The stretching temperature during TD stretching is not particularly limited, but is preferably within the range of Tg -5 ° C. to Tg + 30 ° C., based on the glass transition temperature (Tg) of the original film, and within the range of Tg to Tg + 30 ° C. It is more preferable, and it is still more preferable that it is 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. When the stretching temperature exceeds Tg+30°C, there is a risk that the relaxation of the molecular chains becomes large, making it difficult for the molecules to orient.

The stretching speed at the time of TD stretching may be appropriately set according to the characteristics of the desired optical film, and is not particularly limited, but is preferably in the range of 10 to 20000%/min, more preferably in the range of 100 to 10000%/min. do. When the stretching speed is slower than 10%/min, it takes time to obtain a sufficient stretching ratio and the manufacturing cost increases. When the stretching speed is faster than 20000%/min, there is a possibility that the film may be broken or the like.

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

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

The optical film according to the present invention is not particularly limited, but the ratio of the draw ratio in the machine direction to the draw ratio in the transverse direction (draw ratio in MD stretching/stretch ratio in TD stretching) is preferably within the range of 0.40 to 1.50. , It is more preferably within the range of 0.45 to 1.40, and more preferably within 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 has a thickness of 80 µm and has good optical properties. The absolute value of the b ^* value is preferably 0.4 or less and 0.3 or less in this order. There is no particular lower limit to the absolute value of the b ^* value, and a smaller value is preferable (that is, the closer the b ^* value is to zero, the more preferable it is). Here, the optical film includes a film manufactured by the method described in Section [4]. More specifically, an unstretched film manufactured by touch roll film formation, a stretched film subjected to stretching after that, and the like are included.

[noise]

When the optical film is a roll-shaped optical film, the total amount of noise when projection inspection is performed on 80% of the optical film in the width direction at intervals of 12 m over a length of 120 m in its longitudinal direction is 5 points or less. In addition, when the optical film is a sheet optical film, the noise per 1 m 2 when the projection inspection of the optical film is performed is 5 points or less. A film satisfying such a property is expressed as "no transfer of contaminants from a roll" in the present specification.

In this specification, “noise” means a defect caused by transfer of a contaminant (for example, a material in which a thermoplastic resin composition or a volatilized ultraviolet absorber has deteriorated) to the surface of an optical film. The category of the noise includes (i) defects caused by foreign substances such as gel contained in the melt of the thermoplastic resin composition, (ii) floating matter in the air (thread, dirt, dust, etc.) attached to the surface of the optical film. and (iii) contaminants (dust, dust, etc.) adhering to the surface of the touch roll and cast roll are not included. Due to the noise, it becomes difficult to detect a foreign material (gel or the like) contained in the melt of the thermoplastic resin composition, which is to be confirmed in the first place. In addition, the film with a lot of noise interferes with the function as an optical film.

A method of projecting and inspecting 80% of the optical film in the width direction at intervals of 12 m over a length of 120 m in the longitudinal direction of the roll-shaped optical film is, for example, when winding an optical film manufactured by touch roll film formation around a core material (that is, , inline), there is a way to check the projection. Specifically, it is based on the following procedure.

(1) An automatic defect inspection device is placed in a position where an optical film continuously transported can be measured.

(2) The measurement interval which can be measured every 12 m is computed from the conveyance speed of an optical film (for example, when conveyance speed is 12 m/min, it is 1 minute interval).

(3) The projection inspection by the said automatic defect inspection apparatus is performed 11 times in total at the said measurement interval. At this time, 80% of the width direction of the optical film in each measurement location is projected and inspected.

80% of the width direction of the optical film may be set anywhere. Preferably, it is set to 40% each toward both ends from the center of the width direction of an optical film. That is, it sets so as to omit 10% of each of both ends in the width direction.

In addition, it is preferable to carry out the projection inspection of the sheet optical film by converting the number of noises obtained by projection inspection of a plurality of optical films into the number of noises per 1 m2 (that is, off-line). It is more preferable that the plurality of optical films have a total area of 1 m 2 or more (for example, 17 or more sheets in 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 the embodiment.

When noise is generated in the optical film, the size of the noise is preferably 15 μm or less, and more preferably 10 μm or less. Noise with a size of 15 μm or less is not detected in projection inspection, and there are cases in which it does not cause a problem even when actually used as an optical film. In addition, the smaller the noise is, the better it is, and the smaller it is, the better it is.

The optical film according to the present invention is manufactured such that the relationship between the thermal decomposition temperature Td (°C) and the temperature Tp (°C) described above satisfies the expression "50≤Td-Tp". Therefore, the b ^* value when the said optical film is made into a film with a thickness of 80 micrometers is less than 0.5, and optical characteristics are favorable. In addition, there are few foreign substances such as gel contained in the melt of the thermoplastic resin composition, and the rolls (touch rolls and cast rolls) 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 using a film with a thickness of 80 μm)

The optical film according to one embodiment of the present invention preferably has a c ^* value of less than 0.5, more preferably less than 0.3, as measured in accordance with JIS Z 8729 when the optical film has a thickness of 80 µm. ^The optical film preferably has an absolute value of 0.10 or less, more preferably 0.05 or less, as measured in accordance with JIS Z 8729 when the optical film has a thickness of 80 µm. The optical film has a b ^* value of less than 0.5 measured in accordance with JIS Z 8729 when a film having a thickness of 80 µm is used, and has good optical properties. The absolute value of the b ^* value is preferably 0.4 or less and 0.3 or less in this order. There is no particular lower limit to the absolute value of the b ^* value, and a smaller value is preferable (that is, the closer the b ^* value is to zero, the more preferable it is). The optical film has an L ^* value of 95.0% or more, more preferably 98.0% or more, and more preferably 99.0% or more, as measured in accordance with JIS Z 8729 when the film has a thickness of 80 μm. It is especially preferable that it is 99.5% or more. If the optical properties of the optical film are within the above range, it can be suitably used for 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 measured in accordance with the provisions of JIS K7361: 1997 when a film having a thickness of 80 μm is preferably 5.0% or less, and more preferably 4.0% or less. It is preferable, and it is more preferable that it is 3.0 % or less. If the light transmittance is within this range, when the optical film is incorporated as a polarizing plate of an optical device, sufficient ultraviolet absorbing power can be exhibited. Further, the optical film preferably has a light transmittance of 95.0% or more at a wavelength of 420 nm, more preferably 96.0% or more, and still more preferably 96.0% or more, as measured in accordance with the provisions of JIS K7361: 1997 when the optical film has a thickness of 80 μm. It is 97.0% or more. When the light transmittance is within this range, the transmittance in the visible light region is high, and it is particularly suitable when the optical film is used for optical applications.

The optical film of the present invention has a total light transmittance of preferably 95.0% or more, more preferably 97.0% or more, still more preferably 99.0% or more when it is 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 it is made into a film having a thickness of 80 μm. More preferably, it is 0.8% or less, and still more preferably 0.5% or less. When a haze exceeds 1.0 %, transparency will fall and it is unsuitable when using the said optical film for an optical use.

The optical film according to one embodiment of the present invention preferably has a contact angle with pure water of 76° or less. When the contact angle with pure water is 76° or less, when applying the hydrophilic adhesion-facilitating agent composition to the optical film, it can be applied uniformly.

[Use of optical film]

The optical properties of the optical film according to one embodiment of the present invention can be further controlled by using a laminate of the same type of optical material and/or a different type of optical material. Although it does not specifically limit as an optical material laminated|stacked at this time, For example, a polarizing plate, a stretched oriented film made from polycarbonate, a stretched oriented film made from cyclic polyolefin, etc. are mentioned. Of course, you may use the said optical film independently.

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 is, for example, an antistatic layer, an adhesive layer, an adhesive layer, an easy bonding layer, an antifouling layer such as an antiglare (non-glare) layer, a photocatalyst layer, an antireflection layer, a hard coat layer, an ultraviolet ray shielding layer, a heat ray shielding layer, and an electromagnetic wave. It is a shielding layer and a gas barrier layer.

The use of the optical film according to one embodiment of the present invention is not particularly limited. Since the optical film according to one embodiment of the present invention has high transparency, small color, low chroma and high heat resistance, it is suitable for the following applications. The application is, for example, a protective film for optics (specifically, a protective film for substrates of various optical disks (VD, CD, DVD, MD, LD, etc.)), used for polarizing plates equipped with image display devices such as LCDs It is a polarizer protective film that In addition, optical films such as a viewing angle compensation film, a light diffusing film, a reflective film, an antireflection film, an antiglare film, a luminance enhancing film, a conductive film for a touch panel, and a retardation film, the optical film according to one embodiment of the present invention can be used. can be used The 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 (thermoplastic resin composition) containing a (meth)acrylic polymer ((meth)acrylic resin) and a UV absorber, and has a glass transition temperature. It is characterized by a c ^* value of 0.45 or less as measured in accordance with the provisions of JIS Z 8729 when the film is 110°C or higher and has a thickness of 100 µm as an unstretched film.

According to the above structure, there is an effect that a (meth)acrylic resin composition (thermoplastic resin composition) excellent in transparency, color, chroma and heat resistance can be provided.

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

According to the above configuration, there is an effect that a (meth)acrylic resin composition (thermoplastic resin composition) having a more excellent color can be provided.

The ultraviolet absorber is preferably a benzotriazole-based compound.

In addition, the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention has a light transmittance of 3.0% at a wavelength of 380 nm measured in accordance with the provisions of JIS K7361: 1997 when used as an unstretched film having a thickness of 100 μm. Hereinafter, it is preferable that the light transmittance in wavelength 420nm is 95.0% or more.

According to the above structure, 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 ray absorbing power and has a better color and chroma (meth)acrylic type. The effect that a resin composition (thermoplastic resin composition) can be provided is exhibited.

In the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention, the content of structural units derived from styrenic monomers in 100% by mass of the (meth)acrylic resin composition (thermoplastic resin composition) is preferably less than 8% by mass.

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

According to the above configuration, there is an effect that a (meth)acrylic resin composition (thermoplastic resin composition) having more excellent color and chroma can be provided.

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

Moreover, as for the said ring structure, it is more preferable that it is at least 1 sort(s) chosen from a maleic anhydride structure, a glutarimide structure, a glutaric acid anhydride structure, and a lactone ring structure, and it is still more preferable that it is a lactone ring structure.

According to the above configuration, it is possible to provide a (meth)acrylic resin composition (thermoplastic resin composition) having higher transparency, color 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 in that they are formed of the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention.

According to the above configuration, since it is formed by the (meth)acrylic resin composition (thermoplastic resin composition) of the present invention, it is possible to provide molded articles and films excellent in transparency, color, chroma, and heat resistance.

The film of the present invention preferably has a noise count of 5 points or less per 1 m 2 when the film is projected.

According to the said structure, when the film of this invention is used as an optical film, such as a polarizer protective film, the effect that an optical film with favorable optical characteristics can be provided is exhibited.

[Example]

Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples. However, the present invention should not be construed as being limited to these examples.

[Example 1]

<Measurement method of physical properties, etc.>

[Projection inspection method]

1. Projection inspection method of optical film on a roll

For the inspection, an automatic continuous defect inspection apparatus (manufactured by Mack Corporation: LSC-6000L, optical system: 45 degree forward transmission, 1/8 edge, rod illumination (single side slit part)) was used. Specifically, it was based on the following procedure.

(1) The automatic continuous defect inspection device was placed in front of the winding device. The transport speed of the optical film was 12 m/min.

(2) 11 locations in the longitudinal direction (namely, 120 m in the longitudinal direction) were inspected by inspecting at intervals of 1 minute. The inspection object was an optical film of 40% each from the center in the width direction toward both ends (that is, a portion omitting 10% of both ends in the width direction).

(3) About the optical film of the said inspection target, defect (noise) was detected by image processing, and the optical film was evaluated.

Also, the greater the amount of noise (ie, the greater the transfer of contaminants adhering to the surface of the roll onto the optical film), the greater the number of defects detected by the automatic continuous defect inspection device. A film in which the number of detected defects exceeds 1000 points becomes uncountable.

2. Projection inspection method of sheet-fed optical film

For the inspection, an automatic defect inspection apparatus (manufactured by Mack Corporation: MLA-5000, optical system: 45 degree direct transmission, 1/8 edge, rod illumination (single side slit part)) was used. Specifically, it was based on the following procedure.

(1) The surface of each sheet of optical film was air-blown, and contaminants (dust, dust, etc.) adhering to the surface of the optical film were removed.

(2) 17 optical films with a size of 200 mm x 300 mm (A4) were set as objects of inspection, and defects (noise) were detected by image processing.

(3) The number of defects obtained in (2) was converted into the number of defects per 1 m 2 , and the optical film was evaluated.

Further, the greater the amount of noise (i.e., the greater the transfer of contaminants adhering to the surface of the roll onto the optical film), the greater the number of defects detected by the automatic defect inspection device. A film in which the number of detected defects exceeds 1000 points becomes uncountable.

[b ^* value]

Using a spectroscopic color difference meter (Nippon Denshoku Kogyo Co., Ltd.: Colormeter ZE6000), the b ^* value was determined in accordance with JIS Z 8729.

[Melt Viscosity]

The measurement was performed using a capillary rheometer RH10 of a twin-bore barrel type manufactured by Lausand Co., Ltd. Using dice with a diameter of 1 mm and a length of 16 mm as a long die and dice with a diameter of 1 mm and a length of 0.25 mm as a short die, measurement was performed at a measurement temperature of 270°C and a shear rate of 10/sec. The melt viscosity was calculated by carrying out bar gray correction of the value thus obtained.

[Weight Average Molecular Weight (Mw)]

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

System: Tosoje GPC system HLC-8220

Measurement-side column configuration

ㆍ Guard Column: Tosoje, TSKguardcolumn SuperHZ-L

ㆍ Separation column: Dosohje, 2 TSKgel SuperHZM-M connected in series

Reference-side column configuration

ㆍ Reference column: Dosohje, TSKgel SuperH-RC

Developing solvent: chloroform (manufactured by Wako Pure Chemical Industries, Limited)

Flow rate of developing solvent: 0.6 mL/min

Standard sample: TSK standard polystyrene (Dosoh, PS-oligomer kit)

Column temperature: 40°C

[Glass Transition Temperature (Tg)]

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

[Stress Optical Coefficient (Cr)]

The unstretched film was cut into a rectangle of 60 mm × 20 mm, and 1 N / mm 2 A weight was selected so as to have the following stress, and was installed at the lower end of the unstretched film. This was set at 40 mm between chucks in a constant temperature dryer (manufactured by As One Co., Ltd.: DOV-450A) set to Tg+3°C. After extending|stretching by holding|maintaining at Tg+3 degreeC for about 30 minutes, heating was stopped and it cooled at about 1 degreeC/min until Tg-40 degreeC. Then, the obtained stretched film was taken out, and the length and thickness of the film after stretching and the weight of the weight were measured. In addition, the in-plane retardation Re of the stretched film was measured.

Next, weights of four different weights were selected again so as to achieve a stress of 1 N/mm or less, installed on the lower end of the unstretched film, and measurements were performed in the same manner, and the stress optical coefficient (Cr) was calculated from the results. The calculation method of the stress optical coefficient (Cr) is described in [Polymer Society Edition "The Front Line of Transparent Plastics" NTS, 2006, pp. 37 to 44]. Specifically, Δn (= nx-ny) was plotted on the y-axis and σ was plotted on the x-axis, the slope of a 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 within the film plane (direction showing the maximum refractive index within the film plane), and ny is the refractive index in the fast axis direction within the film plane (perpendicular to the slow axis direction within the film plane) direction) is the refractive index, σ is the stress for stretching [N/m 2 ].

[Thermal decomposition temperature (pyrolysis initiation temperature; Td)]

A 10 mg sample was heated from normal temperature to 500°C in a nitrogen gas atmosphere using a differential type differential thermobalance (manufactured by Rigac Co., Ltd.: Thermo Plus2 TG-8120). At this time, when the mass reduction rate of the sample during temperature increase was 0.005 mass%/sec or less, the temperature was raised at a temperature increase rate of 10°C/min. Conversely, when the rate of mass reduction of the sample during temperature increase exceeded 0.005% by mass/sec, the temperature was raised by stepwise isothermal control so that the rate was maintained at 0.005% by mass/sec or less. Then, in order to maintain the mass reduction rate, the temperature at which the stepwise isothermal control was first performed (the lowest temperature among the sections heated by the stepwise isothermal control) was taken as the Td of the thermoplastic resin composition and the ultraviolet absorber.

<Manufacture example of thermoplastic resin composition>

First, a lactone ring structure-containing polymer was prepared as a (meth)acrylic resin by the following method.

To a reaction vessel equipped with a stirring device, a temperature sensor, a cooling tube and a nitrogen inlet tube, 229.6 parts of methyl methacrylate (MMA), 33 parts of 2-(hydroxymethyl)methyl acrylate (MHMA), 248.6 parts of toluene and n- 0.19 part of dodecylmercaptan was introduced, and the temperature was raised to 105°C while nitrogen gas was passed therethrough. At the place where the reflux accompanying the temperature rise began, 0.25 part of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd.: Luperox (registered trademark) 570) was added as a polymerization initiator, and further t-amyl While 0.51 part of peroxyisononanoate and 12.4 parts of styrene were added dropwise over 2 hours, solution polymerization was carried out under reflux at about 105 to 110°C. After completion of dropping, aging was further performed at the same temperature for 4 hours.

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

Then, the obtained polymerization solution was passed through a shell and tube heat exchanger heated to 240°C to complete the cyclization condensation reaction. Thereafter, 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 (resin amount conversion). 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 a third vent and a fourth A side feeder is provided between the vents, and a leaf disc-shaped polymer filter (filtration accuracy: 5 μm) is disposed at the front end. At the time of introduction of the polymerization solution, a mixed solution of the antioxidant/cyclization catalyst deactivator prepared separately is introduced from the downstream of the second vent at an input rate of 0.15 part/hour, and ion-exchanged water is introduced into the first vent at an input rate of 0.54 part/hour. and from the downstream of the third vent, respectively. In the mixed solution of antioxidant / cyclization catalyst deactivator, 4.3 parts of each antioxidant (manufactured by BASF: Irganox 1010, manufactured by ADEKA Co., Ltd.: LAO-412S) and 14 parts of jade as a deactivator A solution in which zinc titrate (manufactured by Nippon Chemical Industry Co., Ltd.: Nikka Octix Zinc) was dissolved 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.) of 345° C.) was charged at a feeding rate of 0.79 parts/hour.

Subsequently, after completion of devolatilization, the resin composition remaining in the extruder in a heat-melted state was discharged while filtering with a polymer filter from the tip of the extruder. After that, strands of the resin composition were obtained by passing through dies provided at the front end of the extruder and cooling in a water tank filled with cooling water. The cooling water was filtered with a filter (manufactured by Organo Co., Ltd., product name: Micropore Filter 1EU) with a pore diameter of 1 μm, and maintained at a temperature within the range of 30±10°C. By introducing the strands after cooling into a cutting machine (pelletizer), pellets containing a thermoplastic resin composition containing a lactone ring structure-containing polymer and an ultraviolet absorber were obtained.

Physical properties of the resulting 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 remaining volatile matter: 2050 ppm

Total light transmittance: 92.5%

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

<Example 1-1>

The thermoplastic resin composition obtained in the said manufacture example was formed into a touch roll film, and the optical film was manufactured. 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 degreeC.

Specifically, it formed into a film in the following procedure.

(1) Melt film forming was performed at a processing speed of 25 kg/hour using a single screw extruder equipped with a vent. The extruder had a barrier flight type screw having a diameter of 65 mm and L/D = 32. In addition, a polymer filter (filtration accuracy of 5 µm) and a T-die were provided at the front end of the extruder.

(2) The molten resin film after film formation was passed through a cooling roll. The cooling roll is composed of a first roll (elastic touch roll), a second roll (cast roll), and a third roll, and chrome plating is applied to each roll. 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 below). The angle θ formed by 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 to 5°.

(3) A molten resin film was cast on R1 to obtain an unstretched film having a thickness of 215 µm. The obtained unstretched film was continuously supplied as it was to an oven longitudinal stretching machine, and the temperature of the oven was set to 136° C., and stretching was performed at a stretching ratio of 1.6 times in the machine direction.

(4) The film after stretching was wound up with a winder to obtain a longitudinally stretched film roll having an average thickness of 160 µm.

(5) The obtained longitudinally stretched film roll was drawn out with a feeder, held at a position of 20 mm from both ends with a 2-inch clip, and supplied to a tenter stretcher. Then, the temperature of the oven was set to 138°C, and transverse stretching was performed at a draw ratio of 2.0 times in the transverse direction.

(6) The film after stretching was wound up with a winder 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 x 300 mm (A4) to prepare a plurality of sheet-shaped optical films.

The b ^* value of the prepared optical film was 0.18. Then, when the projection inspection of the sheet-shaped optical film was carried out according to the projection inspection method described above, the noise (the number of noises per 1 m 2 ) was 0 points. The results are shown in Table 1.

In addition, no contaminants adhered to either the touch roll R1 or the cast roll R2 after driving for a long time.

<Example 1-2>

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

In addition, no contaminants adhered to either the touch roll R1 or the cast roll R2 after driving for a long time.

<Comparative Example 1-1>

The optical film was manufactured by performing open film forming of the thermoplastic resin composition obtained in the said manufacture example. 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 degreeC.

Specifically, it formed into a film in the following procedure.

(1) Melt film forming was performed at a processing speed of 25 kg/hour using a single screw extruder equipped with a vent. The extruder had a barrier flight type screw having a diameter of 65 mm and L/D = 32. In addition, a polymer filter (filtration accuracy of 5 µm) and a T-die were provided at the front end of the extruder.

(2) The molten resin film after film formation was passed through a cooling roll. The said cooling roll was comprised from the 2nd roll (cast roll) and the 3rd roll, and chrome plating was given to each roll. The temperature of each cooling roll was set to R2/R3=120/95°C.

(3) The molten resin film of the thermoplastic resin composition extruded from the exit of the T-die was cast on R2 to obtain an unstretched film having a thickness of 215 µm. The obtained unstretched film was continuously supplied as it was to an oven longitudinal stretching machine, and the temperature of the oven was set to 136° C., and stretching was performed at a stretching ratio of 1.6 times in the machine direction.

(4) The film after stretching was wound up with a winder to obtain a longitudinally stretched film roll having an average thickness of 160 µm.

(5) The obtained longitudinally stretched film roll was drawn out with a feeder, held at a position of 20 mm from both ends with a 2-inch clip, and supplied to a tenter stretcher. Then, the temperature of the oven was set to 138°C, and transverse stretching was performed at a draw ratio of 2.0 times in the transverse direction.

(6) The film after stretching was wound up with a winder 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 x 300 mm (A4) to prepare a plurality of sheet-shaped optical films.

The b ^* value of the prepared optical film was 0.20. And, when the projection inspection of the said optical film was performed according to the projection inspection method mentioned above, the noise of 7 out of 17 films was 0. However, the remaining 10 sheets were unable to be counted because there was a lot of noise due to the 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. The results are shown in Table 1.

In addition, adhesion of contaminants to the cast roll R2 was observed after long-time operation.

(result)

As is clear from Table 1, by performing touch roll film formation, even when an ultraviolet absorber having a low thermal decomposition temperature is used, the b ^* value is low and good, and the contamination from the rolls (touch roll and cast roll) during film formation is reduced. It was found that an optical film having good optical properties without transfer can be produced.

[Example 2]

<Measurement method of physical properties, etc.>

[Thermal decomposition temperature (Td), glass transition temperature (Tg) and weight average molecular weight (Mw)]

Thermal decomposition temperature (thermal decomposition start 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 Co., Ltd.). A sample for measuring and evaluating the physical properties of the film, including the physical properties indicating the evaluation method thereafter, was obtained from the central portion in the width direction of the film.

[a ^* value, b ^* value, c ^* value, and L ^* value]

The a ^* value, the b ^* value, and the L ^* value were measured in accordance with JIS Z 8729 using a spectroscopic color difference meter (Nippon Denshoku Kogyo Co., Ltd.: Colormeter ZE6000). Specifically, the following procedure was followed.

(1) The thermoplastic resin composition was subjected to melt press molding at 250° C. for 5 minutes using a manual hot press machine (manufactured by Imoto Seisakusho Co., Ltd., Model IMC-180C) to prepare an unstretched film.

(2) An unstretched film cut out to 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 a ^* value, b ^* value and L ^* value were measured.

(3) The measurement of (2) was similarly repeated while overlapping the second and third sheets 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. As a result, the a ^* value, b ^* value, and L ^* value when the thickness was set to an unstretched film of 100 µm were calculated.

(5) The c ^* value was calculated from the following formula from the a ^* value and the 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 subjected to melt press molding at 250° C. for 5 minutes using a manual hot press machine (manufactured by Imoto Seisakusho Co., Ltd., Model IMC-180C) to prepare an unstretched film.

(2) The unstretched film cut out to 40 mm x 10 mm was immersed in a quartz cell with an optical path length of 10 mm filled with ion-exchanged water, and each light transmittance was measured.

(3) Using the result of each measured light transmittance T and the thickness L of the unstretched film, each light transmittance T (100 μm) when the thickness was an unstretched film of 100 μm was calculated from the following formula.

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 by Nippon Denshoku Kogyo Co., Ltd. Specifically, the following procedure was followed.

(1) The thermoplastic resin composition was subjected to melt press molding at 250° C. for 5 minutes using a manual hot press machine (manufactured by Imoto Seisakusho Co., Ltd., Model IMC-180C) to prepare an unstretched film.

(2) An unstretched film cut out to 45 mm x 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 total light transmittance and haze were measured. Measured.

(3) The measurement of (2) was repeated while overlapping the second and third sheets and additional unstretched films.

(4) The measured total light transmittance and haze were plotted on the y-axis, and the thickness of the unstretched film was plotted on the x-axis, respectively, and the linear inclination of the plot was derived by the least squares method. Thereby, the total light transmittance and haze when the thickness was made into an unstretched film of 100 micrometers were computed.

[Number of noises per 1 m2 of film]

The number of noises per 1 m 2 of the film was measured in the same manner as in Example 1. As for the result, the case where the obtained number of noises per 1 m2 was 5 points or less was rated as "○", and the case where the obtained number of noises per 1 m2 was more than 5 points was rated as "x".

[Contact angle with pure water]

It measured based on JISR3257:1999 using the contact angle measuring instrument ("FACE contact angle meter CA-X" by Kyowa Science and Technology Co., Ltd.). The contact angle with pure water 30 seconds after dropping was measured 5 times, and the average value of the three times excluding the highest value and the lowest value was taken as "contact angle with pure water".

<Example 2-1>

To a reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe and a nitrogen inlet pipe, 83.5 parts of methyl methacrylate (MMA), 12 parts of 2-(hydroxymethyl)methyl acrylate (MHMA), 90.4 parts of toluene and n- 0.07 part of dodecylmercaptan was introduced, and the temperature was raised to 105°C while passing nitrogen through this. When the reflux accompanying the temperature rise started, 0.10 part of t-amylperoxyisononanoate (Luperox (registered trademark) 570, manufactured by Arkema Yoshitomi Co., Ltd.) was added as a polymerization initiator. Then, while 0.20 parts of t-amylperoxyisononanoate and 4.5 parts of styrene were added dropwise over 2 hours, solution polymerization was performed under reflux at about 105 to 110°C. After completion of dropping, aging was further performed at the same temperature for 4 hours.

Next, to the obtained polymerization solution, 0.08 part of stearyl phosphate (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added as a catalyst for a cyclization condensation reaction (cyclization catalyst), and 2 Over time, the cyclization condensation reaction for forming a lactone ring structure was advanced. Further, the obtained polymerization solution was passed through a shell and tube heat exchanger heated to 240°C to complete the cyclization condensation reaction.

Thereafter, the obtained polymer was introduced at a processing rate of 35.1 parts/hour (in terms of resin amount) using a vent type screw twin screw extruder (L/D = 52). The extruder has a barrel temperature of 250 ° C, one rear vent, four fore vents (hereinafter referred to as first, second, third, and fourth vents from the upstream side) and between the third and fourth vents. It was equipped with a side feeder. Further, in the extruder, a leaf disc-shaped polymer filter (filtration accuracy: 5 µm) was disposed at the front end.

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

After completion of devolatilization, the resin composition in a heat-melted state remaining in the extruder was discharged while filtering with a polymer filter from the tip of the extruder. After that, strands of the resin composition were obtained by passing through dies provided at the front end of the extruder and cooling in a water tank filled with cooling water. The cooling water was filtered with a filter (manufactured by Organo Co., Ltd., product name: Micropore Filter 1EU) with a pore diameter of 1 μm, and maintained at a temperature within the range of 30±10°C. The thermoplastic resin composition (A-1) was obtained by introducing the strand after cooling into a cutting machine (pelletizer). The physical property values of the obtained thermoplastic resin composition (A-1) are collectively shown in Table 2.

A film was manufactured from the thermoplastic resin composition (A-1) by forming a film with a touch roll. 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 degreeC.

Specifically, it formed into a film in the following procedure.

(1) Melt film forming was performed at a processing speed of 25 kg/hour using a single screw extruder equipped with a vent. The extruder had a barrier flight type screw having a diameter of 65 mm and L/D = 32. In addition, a polymer filter (filtration accuracy of 5 µm) and a T-die were provided at the front end of the extruder.

(2) The molten resin film after film formation was passed through a cooling roll. The cooling roll is composed of a first roll (elastic touch roll), a second roll (cast roll), and a third roll, and chrome plating is applied to each roll. The temperature of each cooling roll was set to R1/R2/R3=95/100/85°C. The angle θ formed by 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 to 5°.

(3) R1 the molten resin film It was cast on top to obtain an unstretched film having a thickness of 215 μm. The obtained unstretched film was continuously supplied as it was to an oven longitudinal stretching machine, and the temperature of the oven was set to 136° C., and stretching was performed at a stretching ratio of 1.6 times in the machine direction.

(4) The film after stretching was wound up with a winder to obtain a longitudinally stretched film roll having an average thickness of 160 µm.

(5) The obtained longitudinally stretched film roll was drawn out with a feeder, held at a position of 20 mm from both ends with a 2-inch clip, and supplied to a tenter stretcher. Then, the temperature of the oven was set to 138°C, and transverse stretching was performed at a draw ratio of 2.0 times in the transverse direction.

(6) The film after stretching was wound up with a winder 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 x 300 mm (A4) to prepare a plurality of sheet-shaped optical films. The number of noises per 1 m 2 of the film was 5 points or less. The contact angle of the film with pure water was measured and found to be 76°.

<Example 2-2>

In a glass container, 18 parts by mass of methyl methacrylate (MMA), 2 parts by mass of methyl acrylate (MA), 20 parts by mass of methyl isobutyl ketone (MIBK), and 2,2'-azobis(isobutyric acid)dimethyl (Junya Wako) Kukogyo Co., Ltd. make: V-601) 0.06 mass part was thrown in, nitrogen gas was introduce|transduced into this, it sealed, and it was made to react at 60 degreeC for 4 hours and 50 degreeC for 48 hours. Subsequently, the obtained polymerization solution was diluted with MIBK, and (meth)acrylic resin was obtained by reprecipitation using hexane, filtration and drying. 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 in the same manner as in Example 2-1 from the obtained polymerization solution. The physical property values of the obtained thermoplastic resin composition (A-2) are collectively shown in Table 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 prepare a plurality of sheet-like films. The number of noises per 1 m 2 of the film was 5 points or less.

<Example 2-3>

To a reaction vessel equipped with a stirring device, a temperature sensor, a cooling tube and a nitrogen inlet tube, 81 parts of methyl methacrylate (MMA), 8 parts of N-phenylmaleimide (PMI), and 11 parts of N-cyclohexylmaleimide (CHMI) part and 67 parts of xylene were introduced, and the temperature was raised to 130°C while passing nitrogen through this. At the place where the reflux accompanying the temperature rise began, 0.19 part of t-butylperoxy-2-ethylhexanoate (manufactured by Nihon Yushi Co., Ltd.: Perbutyl (registered trademark) O) as a polymerization initiator was added dropwise over 6 hours, Solution polymerization was performed under reflux at about 130 to 145°C.

A thermoplastic resin composition (A-3) was obtained from the obtained 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. The physical property values of the obtained thermoplastic resin composition (A-3) are collectively shown in Table 2.

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 prepare a plurality of sheet-like films. The number of noises per 1 m 2 of the film was 5 points or less.

<Example 2-4>

A solution obtained by dissolving 0.01 part of colorant (manufactured by Sumika Chemtex Co., Ltd.: Sumiplast (registered trademark) Violet B) in 44 parts of toluene was introduced from the upstream of the third vent at an input rate of 0.15 part/hour. A thermoplastic resin composition (A-4) was obtained in the same manner as in Example 2-1. Table 2 shows the physical property values 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 prepare a plurality of sheet-shaped films. The number of noises per 1 m 2 of the film was 5 points or less.

<Example 2-5>

Carried out except that a solution in which 0.01 part of colorant (manufactured by Sumika Chemtex Co., Ltd.: Sumiplast (registered trademark) GreenG) was dissolved in 44 parts of toluene was introduced from the upstream of the third vent at an input rate of 0.15 part/hour. A thermoplastic resin composition (A-5) was obtained in the same manner as in Example 2-1. Table 2 shows the physical property values 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 prepare a plurality of sheet-like films. The number of noises per 1 m 2 of the film was 5 points or less.

<Comparative Example 2-1>

A solution obtained by dissolving 0.55 part of an ultraviolet absorber (manufactured by ADEKA Co., Ltd.: Adeka Staff (registered trademark) LA-F70, weight loss start temperature Td (° C.) is 379 ° C.) in 1.13 parts of toluene at an injection rate of 0.59 part/hour A thermoplastic resin composition (A-6) was obtained in the same manner as in Example 2-2 except that it was introduced from the upstream of the third vent. The physical property values of the obtained thermoplastic resin composition (A-6) are collectively shown in Table 2.

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 prepare a plurality of sheet-like films. The number of noises per 1 m 2 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 were introduced into an autoclave equipped with a stirrer, heated at 100° C. for 30 minutes to dissolve, and a polymerization solution was obtained. Got it.

From the resulting polymerization solution, a thermoplastic resin composition (A-7) was obtained in the same manner as in Example 2-1. The physical property values of the obtained thermoplastic resin composition (A-7) are shown collectively in Table 2.

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

(result)

In all of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-2, film formation was performed with a touch roll. For this reason, it was possible to manufacture a good optical film in which noise generation was suppressed. This point is the same as Example 1.

In Examples 2-1 to 2-3, the glass transition temperature was different by changing the composition of the thermoplastic resin composition, but all obtained highly heat-resistant thermoplastic compositions. Examples 2-4 to 2-5 also used a colorant, but thermoplastic compositions with high heat resistance were also obtained. 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 a UV absorber having a high thermal decomposition temperature. As a result, the thermoplastic composition had defects in optical properties. Specifically, the a ^* value, the b ^* value, the c ^* value, and the 420 nm light passage were out of the suitable range.

Further, even if a thermoplastic resin composition having a low glass transition temperature (not high heat resistance) is used as in Reference Example 2-1, a thermoplastic resin composition excellent in optical properties can be obtained. However, as described in section [1], an optical film obtained from such a thermoplastic resin composition does not have the advantages of a highly heat-resistant optical film.

The results of Example 2 suggest that an optical film having excellent optical properties can be produced by using a combination of a highly heat-resistant thermoplastic composition (high heat-resistant (meth)acrylic resin) and an ultraviolet absorber having a low thermal decomposition temperature. At this time, if a touch roll is employed as a film forming method, generation of noise can also be suppressed.

According to the method for producing an optical film according to the present invention, an optical film having a low b ^* value, no transfer of contaminants from a roll during film formation, and good optical properties can be produced.

Claims (12)

A melt containing 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 based on 100 parts by weight of (meth) acrylic resin is discharged from a die into a film form, and then a touch roll and a cast roll It is a method for producing an optical film formed by being inserted into a film,
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 manufacturing 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. The (meth)acrylic resin according to claim 1 or 2, wherein the (meth)acrylic resin is at least one member selected from a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure. A method for producing an optical film characterized in that it has a ring structure of in the main chain. A method for producing an optical film in which a melt containing a thermoplastic resin composition containing a (meth)acrylic resin and an ultraviolet absorber having a thermal decomposition temperature of 360 ° C. or less is formed into a film,
The glass transition temperature of the (meth)acrylic resin is 108 ° C. or higher,
The manufacturing method of the optical film which comprises discharging the said molten material from a die in the form of a film, and then inserting it into a touch roll and a cast roll to form a film. A roll-shaped optical film comprising 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 based on 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 b ^* value when the optical film is made into a film having a thickness of 80 μm is less than 0.5,
The optical film, wherein the total noise is 5 points or less when the optical film is subjected to projection inspection of 80% of the width direction at intervals of 12 m over a length of 120 m in its longitudinal direction. An optical film comprising 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 based on 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 b ^* value when the optical film is made into a film having a thickness of 80 μm is less than 0.5,
The optical film whose noise per 1 m 2 is 5 points or less when the optical film is subjected to projection inspection. An optical film containing a (meth)acrylic resin and an ultraviolet absorber,
The ultraviolet absorber is 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl)phenol],
The glass transition temperature of the optical film is 108 ° C. or higher,
An optical film having a c ^* value of 0.45 or less when the optical film is used as an unstretched film having a thickness of 100 µm and measured in accordance with JIS Z 8729. The optical film according to claim 7, wherein an absolute value of a ^* value measured according to JIS Z 8729 when the optical film is an unstretched film having a thickness of 100 µm is 0.10 or less. The method according to claim 7 or 8, when the optical film is an unstretched film having a thickness of 100 μm,
The light transmittance at a wavelength of 380 nm measured in accordance with the provisions of JIS K7361: 1997 is 3.0% or less, and
An optical film having a light transmittance of 95.0% or more at a wavelength of 420 nm. The optical film according to claim 7 or 8, wherein the (meth)acrylic resin has a ring structure in its main chain. The optical film according to claim 7 or 8, wherein the thermal decomposition temperature of the (meth)acrylic resin is 310°C or higher. The method according to claim 1 or 4, wherein the ultraviolet absorber is 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl) phenol], a method for producing an optical film.