JP2008286859A - Optical film and method for manufacturing the same, retardation plate, elliptically polarizing plate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film excellent in property of developing in-plane and thickness-direction retardations and in aptitude for fabricating a polarizing plate. <P>SOLUTION: The optical film comprises a thermoplastic resin composition containing a lactone ring-containing polymer and has a coefficient of linear thermal expansion of ≤80 ppm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical film and a method for producing the same. The present invention also relates to a retardation plate, an elliptically polarizing plate and an image display device using the optical film.

  A liquid crystal display device has various advantages such as low voltage and low power consumption, and can be reduced in size and thickness, and is widely used for monitors of personal computers and portable devices, and for television applications. In such a liquid crystal display device, various modes have been proposed depending on the alignment state of the liquid crystal molecules in the liquid crystal cell. Conventionally, the liquid crystal display device is in an alignment state twisted by about 90 ° from the lower substrate to the upper substrate of the liquid crystal cell. The TN mode is the mainstream.

  In general, a liquid crystal display device includes a liquid crystal cell, an optical compensation sheet, and a polarizer. The optical compensation sheet is used for eliminating image coloring or expanding the viewing angle, and a stretched birefringent film or a film obtained by applying a liquid crystal to a transparent film is used. For example, Patent Document 1 discloses a technique for applying a discotic liquid crystal on a triacetyl cellulose film, aligning and fixing the optical compensation sheet to a TN mode liquid crystal cell, and widening the viewing angle. However, a television-use liquid crystal display device that is expected to be viewed from various angles on a large screen has a strict requirement for viewing angle dependency, and even with the above-described method, the requirement cannot be satisfied. Therefore, liquid crystal display devices different from the TN mode, such as an IPS (In-Plane Switching) mode, an OCB (Optically Compensatory Bend) mode, and a VA (Vertically Aligned) mode, have been studied. In particular, the VA mode is attracting attention as a liquid crystal display device (LCD) for televisions because of its high contrast and relatively high manufacturing yield (Patent Document 1).

  A viewing angle compensation phase difference film is used as a liquid crystal display device that expands the viewing angle of such a liquid crystal display device, maintains high contrast even when viewed from an oblique direction, and does not easily cause gradation inversion. Liquid crystal display devices that have been known are also known. As a retardation film for viewing angle compensation, for example, in-plane retardation (Re) is approximately 0 and a negative uniaxial retardation film having an optical axis in a direction perpendicular to the film surface, Re is 100 nm or less. A biaxial retardation film having a thickness direction retardation (Rth) of 100 nm or more is known. As materials for these retardation films, for example, aromatic polymers such as polycarbonate polymers, polyarylate polymers, and polyester polymers, acrylic polymers, and cyclic polyolefin polymers are known. (Patent Document 2).

  Patent Document 3 discloses a technology that has a viewing angle compensation function and reduces contrast unevenness during high-temperature exposure by using a polymer having a specific photoelastic coefficient and Re and Rth expression. ing.

Patent Document 4 shows a wavelength dispersion characteristic of a quarter-wave plate or a half-wave plate in a visible light region (wavelength range of 400 to 700 nm) with a relatively thin film by having a specific chemical structure. A phase difference plate is disclosed.
Japanese Patent No. 2587398 JP-A-11-95208 JP 2001-27707 A JP 2006-171464 A

  In Patent Document 2, since a retardation film made of an aromatic polymer is used, there is a problem in that unevenness in contrast of the liquid crystal display device is likely to occur when exposed to high temperatures. In addition, in order to obtain high Re and Rth required for liquid crystal display devices, films made of acrylic polymers and cyclic polyolefin polymers need to be used in combination of two or three or more. In the liquid crystal display device industry where the price competition is intense, it is not preferable because it leads to high cost and low productivity. For this reason, there is a demand for a technique for reducing the unevenness of contrast when a single sheet is exposed to a high temperature.

  In Patent Document 3, it has been found that contrast unevenness suppression at the time of high-temperature exposure, which is considered to be improved, is insufficient, and the display performance quality of a liquid crystal display device that has been required in recent years cannot be ensured. Furthermore, in a high-temperature exposure test in the form of a polarizing plate in which a protective film, a polarizer, and a retardation film were laminated in this order, it was found that curling of the polarizing plate occurred and contrast unevenness was further deteriorated. This contrast unevenness is a level that can be visually recognized as unevenness even when the optical film and its polarizing plate are mounted on a liquid crystal display device, and development of an optical film that reduces contrast unevenness when exposed to high temperatures. Is desired.

  An object of the present invention is to provide an optical film that is excellent in in-plane and thickness direction retardation and excellent in polarizing plate processing suitability. Another object of the present invention is to provide a method for producing an optical film having such characteristics at low cost and with high productivity.

The present invention achieves the above object by the following means.
[1] An optical film comprising a thermoplastic resin composition containing a lactone ring-containing polymer and having a linear thermal expansion coefficient of 80 ppm or less.
[2] The optical film according to [1], wherein the linear thermal expansion coefficient is 20 ppm to 80 ppm.
[3] The optical film as described in [1] or [2], wherein the lactone ring-containing polymer has a lactone ring structure represented by the following general formula (1).

（式中、Ｒ¹、Ｒ²、Ｒ³は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を表す。）
［４］ 前記熱可塑性樹脂組成物が、シアン化ビニル単量体と芳香族ビニル単量体を含む単量体組成物を共重合させた構造を有する重合体をさらに含むことを特徴とする、［１］〜［３］のいずれか１項に記載の光学フィルム。
［５］ 前記熱可塑性樹脂組成物が、アクリロニトリルとスチレンを含む単量体組成物を共重合させた構造を有する重合体をさらに含むことを特徴とする［４］に記載の光学フィルム。
［６］ 面内のレターデーションが０〜１５ｎｍであり、膜厚方向のレターデーションが３００ｎｍ以下であることを特徴とする［１］〜［５］のいずれか一項に記載の光学フィルム。

(In the formula, R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms.)
[4] The thermoplastic resin composition further includes a polymer having a structure obtained by copolymerizing a monomer composition containing a vinyl cyanide monomer and an aromatic vinyl monomer. The optical film according to any one of [1] to [3].
[5] The optical film as described in [4], wherein the thermoplastic resin composition further includes a polymer having a structure obtained by copolymerizing a monomer composition containing acrylonitrile and styrene.
[6] The optical film according to any one of [1] to [5], wherein the in-plane retardation is 0 to 15 nm and the retardation in the film thickness direction is 300 nm or less.

[7] A method for producing an optical film having a linear thermal expansion coefficient of 80 ppm or less, comprising a step of press-stretching a film comprising a thermoplastic resin composition containing a lactone ring-containing polymer.
[8] The method for producing an optical film as described in [7], wherein the linear thermal expansion coefficient is 20 ppm to 80 ppm.
[9] The method for producing an optical film as described in [7] or [8], wherein the press stretching is performed at a temperature equal to or higher than a glass transition temperature of the film.
[10] The method for producing an optical film as described in [9], wherein the press stretching is performed at Tg to (Tg + 10) ° C.
[11] The method for producing an optical film according to any one of [7] to [10], wherein an area stretching ratio of the press stretching is 1.5 to 5 times.

[12] A retardation film using the optical film according to any one of [1] to [6].
[13] An elliptically polarizing plate formed by bonding the optical film according to any one of [1] to [6] and a polarizing plate.
[14] At least one or more of the optical film according to any one of [1] to [6], the retardation film according to [12], or the elliptically polarizing plate according to [13] is used. A characteristic image display device.

  The optical film of the present invention is excellent in in-plane and thickness direction retardation, and can reduce manufacturing failures that occur from the cut surface during processing of a polarizing plate. Moreover, according to the manufacturing method of this invention, the optical film of this invention can be manufactured efficiently and cheaply. Furthermore, the phase difference plate, the elliptically polarizing plate and the image display device of the present invention are excellent in optical properties.

  Hereinafter, the optical film of the present invention and the production method thereof will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Lactone ring-containing polymer]
The optical film of the present invention comprises a thermoplastic resin composition containing a lactone ring-containing polymer.
The lactone ring-containing polymer has a lactone ring structure in the polymer, and preferably has a lactone ring structure represented by the following general formula (1).

In the formula, R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue referred to here may contain an oxygen atom. 1-15 are preferable, as for carbon number of an organic residue, 1-12 are more preferable, 1-8 are more preferable, and 1-5 are still more preferable. Examples of the organic residue include a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, and the like, and an alkyl group is preferable. Examples of the substituent include an alkyl group, an aryl group, and an alkoxy group. R ¹ , R ² and R ³ are more preferably a hydrogen atom, a methyl group, an ethyl group or a propyl group, still more preferably a hydrogen atom, a methyl group or an ethyl group, still more preferably a hydrogen atom or a methyl group. It is.

  The content ratio of the lactone ring structure represented by the general formula (1) in the lactone ring-containing polymer structure is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and still more preferably 10 to 60% by mass. Especially preferably, it is 10-50 mass%. If the content of the lactone ring structure represented by the general formula (1) in the lactone ring-containing polymer structure is 5% by mass or more, sufficient heat resistance, solvent resistance, and surface hardness tend to be obtained. . Further, when the content ratio of the lactone ring structure represented by the general formula (1) in the lactone ring-containing polymer structure is 90% by mass or less, higher moldability tends to be easily obtained.

  The lactone ring-containing polymer may have a structure other than the lactone ring structure represented by the general formula (1). The structure other than the lactone ring structure represented by the general formula (1) is not particularly limited, but a (meth) acrylic acid ester and a hydroxyl group-containing monomer as will be described later as a method for producing a lactone ring-containing polymer. A polymer structural unit (repeating structural unit) constructed by polymerizing at least one selected from unsaturated carboxylic acids and monomers represented by the following general formula (2a) is preferable.

(Wherein R ⁴ 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 acetate group, a cyano group, a —CO—R ⁵ group, or —CO—O. represents -R ⁶ group, the organic residue R ⁵ and R ⁶ represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms. having 1 to 20 carbon atoms, the organic residue in the formula (1) Reference can be made to the description.
The content ratio of the structure other than the lactone ring structure represented by the general formula (1) in the lactone ring-containing polymer structure is a polymer structural unit (repeated structural unit) constructed by polymerizing (meth) acrylic acid ester. In this case, it is preferably 10 to 95% by mass, more preferably 10 to 90% by mass, further preferably 40 to 90% by mass, and particularly preferably 50 to 90% by mass, and is constructed by polymerizing a hydroxyl group-containing monomer. In the case of a polymer structural unit (repeating structural unit), preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, particularly preferably 0 to 10% by mass. . In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing an unsaturated carboxylic acid, it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, particularly Preferably it is 0-10 mass%. In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing the monomer represented by the general formula (2a), it is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, and still more preferably. Is 0 to 15% by mass, particularly preferably 0 to 10% by mass.

  The method for producing the lactone ring-containing polymer is not particularly limited, but preferably, after the polymer (a) having a hydroxyl group and an ester group in the molecular chain is obtained by the polymerization step, the obtained polymer ( This is a method of performing a lactone cyclization condensation step in which a lactone ring structure is introduced into a polymer by heat-treating a).

  In the polymerization step, for example, a polymer having a hydroxyl group and an ester group in a molecular chain is obtained by performing a polymerization reaction using a monomer composition containing a monomer represented by the following general formula (1a). Obtainable.

(In the formula, R ⁷ and R ⁸ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. For the organic residue having 1 to 20 carbon atoms, the organic group in the above general formula (1)). (See description of residues.)
Examples of the monomer represented by the general formula (1a) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- ( Hydroxymethyl) n-butyl acrylate, tert-butyl 2- (hydroxymethyl) acrylate, and the like. Among these, methyl 2- (hydroxymethyl) acrylate and 2- (hydroxymethyl) ethyl acrylate are preferable, and methyl 2- (hydroxymethyl) acrylate is particularly preferable in that the effect of improving heat resistance is high. As for the monomer represented by the general formula (1a), only one type may be used, or two or more types may be used in combination.

  The content ratio of the monomer represented by the general formula (1a) in the monomer composition to be subjected to the polymerization step is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and even more preferably 10 to 10% by mass. 60% by mass, particularly preferably 10 to 50% by mass. If the content ratio of the monomer represented by the general formula (1a) in the monomer composition to be subjected to the polymerization step is 5% by mass or more, sufficient heat resistance, solvent resistance, and surface hardness are easily obtained. Tend. If the content of the monomer represented by the general formula (1a) in the monomer composition to be subjected to the polymerization step is 90% by mass or less, it is possible to sufficiently prevent gelation during lactone cyclization. And a polymer having higher moldability tends to be obtained.

  The monomer composition used for the polymerization step may contain a monomer other than the monomer represented by the general formula (1a). Such a monomer is not particularly limited, and for example, (meth) acrylic acid ester, a hydroxyl group-containing monomer, an unsaturated carboxylic acid, and a monomer represented by the general formula (2a) are preferable. It is done. Only one type of monomer other than the monomer represented by the general formula (1a) may be used, or two or more types may be used in combination.

  The (meth) acrylic acid ester is not particularly limited as long as it is a (meth) acrylic acid ester other than the monomer represented by the general formula (1a). For example, methyl acrylate, ethyl acrylate, and acrylic acid n -Acrylic esters such as butyl, isobutyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, benzyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid methacrylic acid esters such as tert-butyl, cyclohexyl methacrylate, benzyl methacrylate; and the like. These may be used alone or in combination of two or more. Among these, methyl methacrylate is particularly preferable from the viewpoint of excellent heat resistance and transparency.

  When a (meth) acrylic acid ester other than the monomer represented by the general formula (1a) is used, the content ratio in the monomer composition to be subjected to the polymerization step is sufficient to exert the effect of the present invention. And preferably 10 to 95% by mass, more preferably 10 to 90% by mass, still more preferably 40 to 90% by mass, and particularly preferably 50 to 90% by mass.

  The hydroxyl group-containing monomer is not particularly limited as long as it is a hydroxyl group-containing monomer other than the monomer represented by the general formula (1a). For example, α-hydroxymethyl styrene, α-hydroxyethyl styrene, 2 -2- (hydroxyalkyl) acrylic acid ester such as methyl (hydroxyethyl) acrylate; 2- (hydroxyalkyl) acrylic acid such as 2- (hydroxyethyl) acrylic acid, and the like. Or two or more of them may be used in combination.

  In the case of using a hydroxyl group-containing monomer other than the monomer represented by the general formula (1a), the content ratio in the monomer composition to be subjected to the polymerization step is sufficient to exert the effect of the present invention. The content is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid and the like. These may be used alone or in combination of two or more. May be. Among these, acrylic acid and methacrylic acid are preferable in that the effects of the present invention are sufficiently exhibited.

  In the case of using an unsaturated carboxylic acid, the content ratio in the monomer composition to be subjected to the polymerization step is preferably 0 to 30% by mass, more preferably 0 to 20%, in order to sufficiently exhibit the effects of the present invention. It is 0 mass%, More preferably, it is 0-15 mass%, Most preferably, it is 0-10 mass%.

  Examples of the monomer represented by the general formula (2a) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. These are used alone. Or two or more of them may be used in combination. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited.

  When using the monomer represented by the general formula (2a), the content ratio in the monomer composition to be subjected to the polymerization step is preferably 0 to 30 mass in order to sufficiently exhibit the effects of the present invention. %, More preferably 0 to 20% by mass, still more preferably 0 to 15% by mass, particularly preferably 0 to 10% by mass.

  The form of the polymerization reaction for polymerizing the monomer composition to obtain a polymer having a hydroxyl group and an ester group in the molecular chain is preferably a polymerization form using a solvent, and solution polymerization is particularly preferred. .

  The polymerization temperature and polymerization time vary depending on the type of monomer used, the ratio of use, etc., but preferably the polymerization temperature is 0 to 150 ° C. and the polymerization time is 0.5 to 20 hours, more preferably polymerization. The temperature is 80 to 140 ° C. and the polymerization time is 1 to 10 hours.

  In the case of a polymerization form using a solvent, the polymerization solvent 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 ketone; ethers such as tetrahydrofuran A solvent; etc. are mentioned, Only 1 type of these may be used and 2 or more types may be used together. Moreover, since the residual volatile matter of the lactone ring containing polymer finally obtained will increase when the boiling point of the solvent to be used is too high, a thing with a boiling point of 50-200 degreeC is preferable.

  During the polymerization reaction, a polymerization initiator may be added as necessary. Although it does not specifically limit as a polymerization initiator, For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-tert-butyl peroxide, lauroyl peroxide, benzoyl peroxide, tert-butylperoxyisopropyl carbonate, tert-amyl Organic peroxides such as peroxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2, Azo compounds such as 4-dimethylvaleronitrile), and the like. These may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of the monomers used and the reaction conditions.

  When performing the polymerization, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 50% by mass or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the produced polymer in the polymerization reaction mixture exceeds 50% by mass, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture and controlled to be 50% by mass or less. . The concentration of the produced polymer in the polymerization reaction mixture is more preferably 45% by mass or less, and further preferably 40% by mass or less. In addition, since productivity will fall when the density | concentration of the polymer in a polymerization reaction mixture is too low, it is preferable that the density | concentration of the polymer in a polymerization reaction mixture is 10 mass% or more, and is 20 mass% or more. It is more preferable.

  The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and the polymerization solvent may be added continuously or intermittently. By controlling the concentration of the produced polymer in the polymerization reaction mixture in this way, the gelation of the reaction solution can be more sufficiently suppressed, and in particular, to increase the lactone ring content and improve the heat resistance. Even when the ratio of the hydroxyl group to the ester group in the molecular chain is increased, gelation can be sufficiently suppressed. The polymerization solvent to be added may be the same type of solvent used during the initial charging of the polymerization reaction or may be a different type of solvent, but is the same as the solvent used during the initial charging of the polymerization reaction. It is preferable to use different types of solvents. Further, the polymerization solvent to be added may be only one type of solvent or a mixed solvent of two or more types.

  The polymerization reaction mixture obtained when the above polymerization step is completed usually contains a solvent in addition to the obtained polymer, but it is necessary to completely remove the solvent and take out the polymer in a solid state. Rather, it is preferably introduced into the subsequent lactone cyclization condensation step in a state containing a solvent. If necessary, after taking out in a solid state, a solvent suitable for the subsequent lactone cyclization condensation step may be added again.

  The polymer obtained in the polymerization step is a polymer (a) having a hydroxyl group and an ester group in the molecular chain, and the weight average molecular weight of the polymer (a) is preferably 1,000 to 2,000,000. 000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000. The polymer (a) obtained in the polymerization step is subjected to heat treatment in the subsequent lactone cyclization condensation step, whereby a lactone ring structure is introduced into the polymer to become a lactone ring-containing polymer.

  The reaction for introducing the lactone ring structure into the polymer (a) is a reaction in which a hydroxyl group and an ester group present in the molecular chain of the polymer (a) are cyclized and condensed to form a lactone ring structure by heating. The cyclized condensation produces alcohol as a by-product. By forming the lactone ring structure in the molecular chain of the polymer (in the main skeleton of the polymer), high heat resistance is imparted. If the reaction rate of the cyclization condensation reaction leading to the lactone ring structure is insufficient, the heat resistance will not be improved sufficiently, or the condensation reaction will occur during the molding process due to the heat treatment during molding, and the resulting alcohol will be contained in the molded product. It is not preferable because it is present as bubbles or silver streaks.

  The lactone ring-containing polymer obtained in the lactone cyclization condensation step preferably has a lactone ring structure represented by the general formula (1).

  The method for heat-treating the polymer (a) is not particularly limited, and a known method can be used. For example, you may heat-process the polymerization reaction mixture containing the solvent obtained by the superposition | polymerization process as it is. Moreover, you may heat-process using a ring-closing catalyst as needed in presence of a solvent. Further, the heat treatment can be performed using a heating furnace or reaction apparatus having a vacuum apparatus or a devolatilizing apparatus for removing volatile components, an extruder having a devolatilizing apparatus, or the like.

  In carrying out the cyclization condensation reaction, in addition to the polymer (a), another thermoplastic resin may coexist. Further, when performing the cyclization condensation reaction, if necessary, an esterification catalyst or a transesterification catalyst such as p-toluenesulfonic acid generally used as a catalyst for the cyclization condensation reaction may be used. Organic carboxylic acids such as propionic acid, benzoic acid, acrylic acid, and methacrylic acid may be used as a catalyst. As disclosed in JP-A-61-254608 and JP-A-61-261303, basic compounds, organic carboxylates, carbonates and the like may be used.

  In carrying out the cyclization condensation reaction, it is preferable to use an organic phosphorus compound as a catalyst as disclosed in JP-A No. 2001-151814. By using an organophosphorus compound as a catalyst, the cyclization condensation reaction rate can be improved, and coloring of the resulting lactone ring-containing polymer can be greatly reduced. Furthermore, by using an organophosphorus compound as a catalyst, it is possible to suppress a decrease in molecular weight that can occur when a devolatilization step described later is used in combination, and to impart excellent mechanical strength.

  Although the usage-amount of the catalyst used in the case of a cyclization condensation reaction is not specifically limited, Preferably it is 0.001-5 mass% with respect to a polymer (a), More preferably, it is 0.01-2.5 mass%. More preferably, it is 0.01-1 mass%, Most preferably, it is 0.05-0.5 mass%. If the amount of the catalyst used is 0.001% by mass or more, the reaction rate of the cyclization condensation reaction tends to be sufficiently improved, whereas if it is 5% by mass or less, coloring and crosslinking are prevented. There is a tendency that good melt formability is easily obtained.

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

  The cyclization condensation reaction is preferably performed in the presence of a solvent, and a devolatilization step is preferably used in combination with the cyclization condensation reaction. In this case, a mode in which the devolatilization step is used throughout the cyclization condensation reaction and a mode in which the devolatilization step is not used over the entire cyclization condensation reaction but only in a part of the process. In the method using the devolatilization step in combination, the alcohol produced as a by-product in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous for the production side.

  The devolatilization step refers to a step of removing volatile components such as a solvent and residual monomers and alcohol produced as a by-product by a cyclocondensation reaction leading to a lactone ring structure, if necessary under reduced pressure heating conditions. If this removal treatment is insufficient, the residual volatile components in the produced resin increase, resulting in problems such as coloration due to alteration during molding, or molding defects such as bubbles or silver streaks.

  In the case of a form in which a devolatilization step is used throughout the cyclization condensation reaction, the apparatus to be used is not particularly limited, but a devolatilization apparatus comprising a heat exchanger and a devolatilization tank in order to perform the present invention more effectively. It is preferable to use an extruder equipped with a vent, or a device in which the devolatilizer and the extruder are arranged in series, and it is more preferable to use a devolatilizer comprising a heat exchanger and a devolatilization tank or an extruder equipped with a vent. preferable.

  In the case of using a devolatilizer comprising the heat exchanger and a devolatilizer, the reaction treatment temperature is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the reaction treatment temperature is 150 ° C. or higher, the cyclization condensation reaction tends to proceed sufficiently and the residual volatile content tends to be suppressed, and if it is 350 ° C. or lower, coloring and decomposition tend to be prevented.

  When using a devolatilizer comprising the heat exchanger and the devolatilization tank, the pressure during the reaction treatment is preferably in the range of 931 to 1.33 hPa (700 to 1 mmHg), and 798 to 66.5 hPa (600 to 50 mmHg). The range of is more preferable. If the pressure is 931 hPa or more, there is a tendency to sufficiently prevent the remaining volatile components including alcohol, and if it is 1.33 hPa or less, industrial implementation tends to be easier.

  When using the extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  The reaction processing temperature in the case of using the vented extruder is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the said temperature is 150 degreeC or more, there exists a tendency for a cyclization condensation reaction to fully advance and it becomes easy to suppress a residual volatile matter amount, and if it is 350 degrees C or less, it exists in the tendency which is easy to prevent coloring and decomposition | disassembly.

  When using the extruder with a vent, the pressure during the reaction treatment is preferably in the range of 931 to 1.33 hPa (700 to 1 mmHg), and more preferably in the range of 798 to 13.3 hPa (600 to 10 mmHg). If the pressure is 931 hPa or more, there is a tendency to sufficiently prevent the remaining volatile components including alcohol, and if it is 1.33 hPa or less, industrial implementation tends to be easier.

  In the case of using the devolatilization step throughout the cyclization condensation reaction, as described later, the physical properties of the lactone ring-containing polymer obtained may be deteriorated under severe heat treatment conditions. It is preferable to use a catalyst for a dealcoholization reaction and under a mild condition as much as possible using an extruder with a vent.

  In the case of using the devolatilization step throughout the entire cyclization condensation reaction, preferably, the polymer (a) obtained in the polymerization step is introduced into the cyclization condensation reactor system together with the solvent. If necessary, it may be passed through the reactor system such as a vented extruder once again.

  You may perform the form used together only in a part of process, without using a devolatilization process over the whole process of cyclization condensation reaction. For example, the apparatus for producing the polymer (a) is further heated, and if necessary, a part of the devolatilization step is used together to advance the cyclization condensation reaction to some extent in advance, followed by the devolatilization step. Is a form in which a cyclization condensation reaction is simultaneously used to complete the reaction.

  In the form in which the devolatilization step is used throughout the cyclization condensation reaction described above, for example, when the polymer (a) is heat-treated at a high temperature close to 250 ° C. or higher using a twin-screw extruder. Depending on the difference in thermal history, partial decomposition or the like may occur before the cyclization condensation reaction occurs, and the physical properties of the resulting lactone ring-containing polymer may be deteriorated. Therefore, if the cyclization condensation reaction is allowed to proceed to some extent before the cyclization condensation reaction using the devolatilization step at the same time, the latter reaction conditions can be relaxed and the physical properties of the resulting lactone ring-containing polymer deteriorated. Is preferable. As a particularly preferred embodiment, the devolatilization step is started after a lapse of time from the start of the cyclization condensation reaction, that is, the hydroxyl group and the ester group present in the molecular chain of the polymer (a) obtained in the polymerization step. A form in which a cyclization condensation reaction is performed in advance to increase the cyclization condensation reaction rate to some extent and then a cyclization condensation reaction using a devolatilization step in combination is performed. Specifically, for example, a cyclization condensation reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle-type reactor, and then a reactor equipped with a devolatilizer, for example, a heat Preferred is a mode in which the cyclization condensation reaction is completed with a devolatilizer comprising an exchanger and a devolatilization tank, an extruder with a vent, or the like. Particularly in this form, it is more preferable that a catalyst for the cyclization condensation reaction is present.

  As described above, the hydroxyl group and ester group present in the molecular chain of the polymer (a) obtained in the polymerization step are preliminarily subjected to a cyclization condensation reaction to increase the cyclization condensation reaction rate to some extent. The method of carrying out the cyclization condensation reaction using the steps at the same time is a preferred form in obtaining a lactone ring-containing polymer in the present invention. With this form, a lactone ring-containing polymer having a higher glass transition temperature, a higher cyclization condensation reaction rate, and excellent heat resistance can be obtained. In this case, as a measure of the cyclization condensation reaction rate, the mass reduction rate between 150 to 300 ° C. in the dynamic TG measurement shown in the examples is preferably 2% or less, more preferably 1.5% or less. More preferably, it is 1% or less.

  The reactor that can be employed in the cyclization condensation reaction that is performed in advance before the cyclization condensation reaction using the devolatilization process at the same time is not particularly limited, but preferably an autoclave, a kettle reactor, a heat exchanger, and a devolatilization tank A vented extruder suitable for a cyclocondensation reaction in which a devolatilization step is simultaneously used can also be used. More preferred are autoclaves and kettle reactors. However, even when using a reactor such as an extruder with a vent, by adjusting the temperature condition, barrel condition, screw shape, screw operating condition, etc. It is possible to carry out the cyclization condensation reaction in the same state as the reaction state in the kettle reactor.

  In the case of the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step at the same time, preferably, a mixture containing the polymer (a) obtained in the polymerization step and the solvent is used as (i). Examples thereof include a method in which a catalyst is added and subjected to a heat reaction, (ii) a method in which a heat reaction is performed without a catalyst, and a method in which the above (i) or (ii) is performed under pressure.

  The “mixture containing the polymer (a) and the solvent” introduced into the cyclization condensation reaction in the lactone cyclization condensation step may be the polymerization reaction mixture obtained in the polymerization step as it is, or once It means that a solvent suitable for the cyclocondensation reaction may be added again after removing the solvent.

  The solvent that can be re-added in the cyclization condensation reaction that is carried out in advance before the cyclization condensation reaction simultaneously used in the devolatilization step is not particularly limited, and examples thereof include aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; Ketones such as methyl ethyl ketone and methyl isobutyl ketone; chloroform, DMSO, tetrahydrofuran and the like may be used, but the same type of solvent that can be used in the polymerization step is preferable.

  Examples of the catalyst added in the above method (i) include esterification catalysts such as p-toluenesulfonic acid or transesterification catalysts, basic compounds, organic carboxylates, carbonates and the like that are generally used. Is preferably the above-described organophosphorus compound. The addition timing of the catalyst is not particularly limited, and it may be added at the beginning of the reaction, during the reaction, or both. The amount of the catalyst to be added is not particularly limited, but is preferably 0.001 to 5% by mass, more preferably 0.01 to 2.5% by mass, and still more preferably 0.01% with respect to the mass of the polymer (a). -1% by mass, particularly preferably 0.05-0.5% by mass. 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 1 to 20 hours, more preferably 2 to 10 hours. If the heating temperature is low or the heating time is short, the cyclization condensation reaction rate is lowered, which is not preferable. Further, if the heating time is too long, the resin may be colored or decomposed, which is not preferable.

  Examples of the method (ii) include a method of directly heating the polymerization reaction mixture obtained in the polymerization step using a pressure-resistant kettle or the like. The heating temperature is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. The heating time is preferably 1 to 20 hours, more preferably 2 to 10 hours. If the heating temperature is low or the heating time is short, the cyclization condensation reaction rate is lowered, which is not preferable. Further, if the heating time is too long, the resin may be colored or decomposed, which is not preferable.

  Both the above methods (i) and (ii) have no problem even under pressure depending on conditions.

  In the case of the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step at the same time, there is no problem even if part of the solvent volatilizes spontaneously during the reaction.

  The mass reduction rate between 150 and 300 ° C. in the dynamic TG measurement at the end of the cyclization condensation reaction performed in advance before the cyclization condensation reaction simultaneously using the devolatilization step, that is, immediately before the start of the devolatilization step is 2% or less is preferable, More preferably, it is 1.5% or less, More preferably, it is 1% or less. If the mass reduction rate is 2% or less, when the cyclization condensation reaction is performed simultaneously with the devolatilization step, the cyclization condensation reaction rate increases to a sufficiently high level, and the resulting lactone ring-containing polymer There is a tendency to improve the physical properties. In addition, when performing said cyclization condensation reaction, in addition to a polymer (a), you may coexist other thermoplastic resins.

  The hydroxyl group and ester group present in the molecular chain of the polymer (a) obtained in the polymerization step were subjected to a cyclization condensation reaction in advance to increase the cyclization condensation reaction rate to some extent, and then the devolatilization step was simultaneously used in combination. In the case of a form in which a cyclization condensation reaction is performed, a polymer obtained by a cyclization condensation reaction performed in advance (a polymer in which at least a part of a hydroxyl group and an ester group present in a molecular chain are subjected to a cyclization condensation reaction) and a solvent, The devolatilization step may be used as it is, and may be introduced into the cyclization condensation reaction. If necessary, the polymer (a polymer obtained by cyclization condensation reaction of at least a part of hydroxyl groups and ester groups present in the molecular chain) may be used. You may introduce | transduce into the cyclocondensation reaction which used the devolatilization process together after passing through other processes, such as adding a solvent again after isolating a compound.

  The devolatilization step is not limited to being completed at the same time as the cyclization condensation reaction, and may be completed after a lapse of time from the completion of the cyclization condensation reaction.

  The lactone ring-containing polymer has a weight average molecular weight of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, and particularly preferably. Is from 50,000 to 500,000.

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

  Since the lactone ring-containing polymer has a high cyclization condensation reaction rate, it is possible to avoid the disadvantage that bubbles and silver streaks enter the molded product after molding. Furthermore, since the lactone ring structure is sufficiently introduced into the polymer due to a high cyclization condensation reaction rate, the obtained lactone ring-containing polymer has sufficiently high heat resistance.

  The lactone ring-containing polymer preferably has a coloring degree (YI) in a 15% by mass chloroform solution of 6 or less, more preferably 3 or less, still more preferably 2 or less, and most preferably 1 or less. If the degree of coloring (YI) is 6 or less, coloring tends to be prevented and higher transparency tends to be obtained.

  The lactone ring-containing polymer preferably has a 5% mass reduction temperature in thermal mass spectrometry (TG) of 280 ° C. or higher, more preferably 290 ° C. or higher, and still more preferably 300 ° C. or higher. The 5% mass loss temperature in thermal mass spectrometry (TG) is an indicator of thermal stability. If this is 280 ° C. or higher, sufficient thermal stability is likely to be exhibited.

  The lactone ring-containing polymer has a glass transition temperature (Tg) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, further preferably 130 ° C. or higher, more preferably 135 ° C. or higher, and most preferably 140 ° C. or higher. .

  The total amount of residual volatile components contained in the lactone ring-containing polymer is preferably 5000 ppm or less, more preferably 2000 ppm or less. If the total amount of residual volatile components is 5000 ppm or less, molding defects such as coloring, foaming, and silver streaking due to deterioration during molding tend to be more effectively prevented.

  The lactone ring-containing polymer preferably has a total light transmittance of 85% or more, more preferably 88% or more, and still more preferably a molded product obtained by injection molding, as measured by a method according to ASTM-D-1003. Is 90% or more. Total light transmittance is a measure of transparency.

[Other thermoplastic resins]
When the other thermoplastic resin according to the present invention is blended with a lactone ring-containing polymer to form a film, the glass transition temperature is 120 ° C. or more, the phase difference per 100 μm in the plane direction is 20 nm or less, The type of the thermoplastic resin is not particularly limited as long as it has a transmittance of 85% or more, but a thermoplastic resin that is thermodynamically compatible is preferable in terms of improving transparency and mechanical strength.

  The content ratio of the lactone ring-containing polymer and the other thermoplastic resin in the optical film according to the present invention is preferably 60 to 99: 1 to 40% by mass, more preferably 70 to 97: 3 to 30% by mass, Preferably it is 80-95: 5-20 mass%. If the content ratio of the lactone ring-containing polymer in the optical film is 60% by mass or more, the effects of the present invention tend to be more sufficiently exhibited.

  Other thermoplastic resins according to the present invention include, for example, olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); vinyl chloride, chlorinated vinyl resin, and the like. Halogen-containing polymer; acrylic polymer such as polymethyl methacrylate; styrene polymer such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene terephthalate , Polyesters such as polybutylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetals; polycarbonates; polyphenylene oxides; I de; polyether ether ketone; polysulfone; polyether sulfone; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as ABS resin or ASA resin containing an acrylic rubber; and the like. The rubbery polymer preferably has a graft portion having a composition compatible with the lactone ring polymer of the present invention on the surface, and the average particle size of the rubbery polymer is transparency when formed into a film. From the viewpoint of improvement, it is preferably 100 nm or less, and more preferably 70 nm or less.

  Thermoplastic resins compatible with lactone ring-containing polymers include copolymers containing vinyl cyanide monomer units and aromatic vinyl monomer units, specifically acrylonitrile-styrene. A polymer containing 50% by mass or more of a copolymer, a polyvinyl chloride resin, or a methacrylic acid ester may be used. Among them, when an acrylonitrile-styrene copolymer is used, an optical film having a glass transition temperature of 120 ° C. or higher, Re of 20 nm or lower, and a total light transmittance of 85% or higher can be easily obtained. Note that the thermodynamic compatibility of the lactone ring-containing polymer and other thermoplastic resins should be confirmed by measuring the glass transition point of the thermoplastic resin composition obtained by mixing them. Can do. Specifically, only one point of the glass transition point measured by the differential scanning calorimeter is observed for the mixture of the lactone ring-containing polymer and the other thermoplastic resin, so that the thermodynamic compatibility is achieved. I can say that.

  When an acrylonitrile-styrene copolymer is used as the other thermoplastic resin, an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, a bulk polymerization method, or the like can be used as the production method. From the viewpoint of the transparency and optical performance of the optical film, it is preferably obtained by a solution polymerization method or a bulk polymerization method.

  The thermoplastic resin composition for molding an optical film according to the present invention may contain other additives. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. UV absorbers such as phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide Flame retardants such as: antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; Inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants;

  The content ratio of the other additives in the optical planar thermoplastic resin molded article is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 0.5% by mass.

[Optical film]
The optical film of the present invention is an optical film that can sufficiently exhibit characteristics according to various optical applications.
The glass transition temperature of the optical film of the present invention is usually 120 ° C. or higher, preferably 125 ° C. or higher, more preferably 130 ° C. or higher.
In the optical film of the present invention, the in-plane retardation (Re) per 100 μm is usually 20 nm or less, preferably 15 nm or less, more preferably 10 nm or less. The retardation (Rth) per 100 μm in the film thickness direction is usually 300 nm or less, preferably 250 nm or less, and more preferably 200 nm or less.
The optical film of the present invention has a total light transmittance of usually 85% or more, preferably 87% or more, and more preferably 90% or more.

The optical film of the present invention has a small incident angle dependency of the phase difference, and the difference (R40−R0) between the phase difference R0 per 100 μm at an incident angle of 0 ° and the phase difference R40 per 100 μm at an incident angle of 40 ° is Preferably it is 20 nm or less, More preferably, it is 10 nm or less.
The film thickness of the optical film of the present invention is preferably 1 μm or more and less than 500 μm, more preferably 10 μm or more and less than 300 μm. An optical film having a thickness of less than 1 μm is not preferable because of its poor strength, and breakage or the like is likely to occur when stretching.

  The optical film of the present invention preferably has a tensile strength measured based on ASTM-D-882-61T of 10 MPa or more and less than 100 MPa, more preferably 30 MPa or more and less than 100 MPa. If it is 10 MPa or more, sufficient mechanical strength tends to be easily obtained. If it is 100 MPa or less, higher workability tends to be obtained.

  In the optical film of the present invention, the elongation measured based on ASTM-D-882-61T is preferably 1% or more, and more preferably 3% or more. Although an upper limit is not specifically limited, Usually, 100% or less is preferable. If it is 1% or more, sufficient toughness tends to be obtained.

  The optical film of the present invention preferably has a tensile modulus measured based on ASTM-D-882-61T of 0.5 GPa or more, more preferably 1 GPa or more, and further preferably 2 GPa or more. Although an upper limit is not specifically limited, Usually, 20 GPa or less is preferable. If it is 0.5 GPa or more, sufficient mechanical strength tends to be easily obtained.

  The method for producing the optical film of the present invention is not particularly limited. For example, a lactone ring-containing polymer, other thermoplastic resin, other additives, and the like are mixed by a conventionally known mixing method, and are thermoplastic in advance. An optical film can be produced from the resin composition. As a method for producing this thermoplastic resin composition, for example, a method of pre-blending with a mixer such as an omni mixer and then extruding and kneading the obtained mixture can be employed. In this case, the kneader used for extrusion kneading is not particularly limited. For example, a conventionally known kneader such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader can be used. .

  Examples of the film forming method include known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable. At this time, a thermoplastic resin composition that has been extruded and kneaded in advance as described above may be used, or a lactone ring-containing polymer and other thermoplastic resins and other additives may be separately dissolved in a solution. After forming a uniform mixed solution, it may be subjected to a film forming process such as a solution casting method (solution casting method) or a melt extrusion method.

  Solvents used in the solution casting method (solution casting method) include, for example, chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, and isopropanol , N-butanol, 2-butanol and the like alcohol solvents; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether, etc. Is mentioned. These solvents may be used alone or in combination of two or more.

  Examples of the apparatus for performing the solution casting method (solution casting method) include a drum casting machine, a band casting machine, and a spin coater.

Examples of the melt extrusion method include a T-die method and an inflation method. In this case, the film forming temperature is preferably 150 to 350 ° C., more preferably 200 to 300 ° C.
When the film is formed by the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, and a film that has been extruded into a film can be obtained as a take-up roll. At this time, it is possible to adjust the temperature of the winding roll as appropriate and apply stretching in the extruding direction so that a uniaxial stretching process can be performed. Moreover, it is also possible to add processes, such as sequential biaxial stretching and simultaneous biaxial stretching, by adding the process of extending | stretching a film in the direction perpendicular | vertical to an extrusion direction.

  The optical film of the present invention may be an unstretched film or a stretched film. When extending | stretching, a uniaxially stretched film may be sufficient and a biaxially stretched film may be sufficient. When a biaxially stretched film is used, it may be biaxially stretched simultaneously or sequentially biaxially stretched. In the case of biaxial stretching, the mechanical strength is improved and the film performance is improved. The optical film of the present invention can suppress an increase in retardation even when stretched by mixing other thermoplastic resins, and can maintain optical isotropy.

  The optical film of the present invention is more preferably produced by a hot press method. The hot press stretching method is a method in which biaxial stretching is simultaneously performed in a die using a press compressive force, and is a method of performing tensile stretching. By press-stretching, the plane orientation of the molecular chain of the film sheet can be promoted, and the linear expansion coefficient can be increased while maintaining transparency.

The linear thermal expansion coefficient of the optical film of the present invention is 80 ppm or less, preferably 70 ppm or less, more preferably 60 ppm or less, and further preferably 50 ppm or less. The lower limit of the linear thermal expansion coefficient of the optical film of the present invention is preferably 20 ppm or more, more preferably 30 ppm or more, still more preferably 35 ppm or more, and even more preferably 40 ppm or more. For example, an optical film having a linear thermal expansion coefficient within the range of 35-80 ppm, 40-70 ppm, 40-60 ppm, or 40-50 ppm can be selected.
When the linear thermal expansion coefficient of the optical film exceeds 80 ppm, the amount of generated chips becomes extremely large, and the productivity is remarkably deteriorated. On the other hand, if the linear thermal expansion coefficient of the optical film is too low, the amount of chips generated can be suppressed, but the degree of cracking tends to be slightly increased.

  As a result of intensive studies, the inventors have reduced the free volume of the protective film of the polarizing plate and increased the interaction between the molecular chains in order to reduce the manufacturing failure that occurs from the cut surface during processing of the polarizing plate. As a result, it was newly found that the shape of the cross section of the polarizing plate is stabilized. In other words, when a polarizing plate is inserted and cut, failure such as chips, chips, cracks, stringing, etc. does not occur, and the polarizing plate can be manufactured stably and can be obtained. It has been found that the rate is dramatically improved and the surface failure of the polarizing plate is drastically reduced. In this way, by reducing the linear thermal expansion coefficient of the film by the hot press method, the resulting free volume decreased and the interaction between the molecular chains was increased, thereby reducing the failure during polarizing plate processing. Conceivable.

  The stretching temperature is preferably performed in the vicinity of the glass transition temperature (Tg) of the thermoplastic resin composition of the film raw material. Specifically, it is preferably performed at (Tg-30) ° C to (Tg + 100) ° C. Preferably, it is (Tg−20) ° C. to (Tg + 80) ° C. If it is (Tg-30) degreeC or more, there exists a tendency for sufficient draw ratio to become easy to be obtained. If it is (Tg + 100) degrees C or less, there exists a tendency which prevents the flow (flow) of resin and performs stable extending | stretching easily.

  The draw ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably in the range of 1.3 to 10 times, and still more preferably in the range of 1.5 to 5 times. If it is 1.1 times or more, it tends to be easy to improve toughness accompanying stretching. If it is 25 times or less, the effect of only increasing the draw ratio tends to be obtained.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. If it is 10% / min or more, the film can be efficiently stretched and the manufacturing cost tends to be kept low. If it is 20000% / min or less, there exists a tendency which becomes easy to prevent the fracture | rupture etc. of a stretched film.

  In order to stabilize the optical isotropy and mechanical properties of the film, heat treatment (annealing) or the like can be performed after the stretching treatment.

  Hereinafter, the features of the present invention will be described more specifically with reference to Examples and Comparative Examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. Hereinafter, for convenience, “mass part” may be simply referred to as “part”, and “liter” may be simply referred to as “L”.

<Polymerization reaction rate, polymer composition analysis>
The reaction rate during the polymerization reaction and the content of the specific monomer unit in the polymer were determined by gas chromatography (manufactured by Shimadzu Corporation, apparatus name: GC17A) based on the amount of unreacted monomer in the obtained polymerization reaction mixture. ) And measured.

<Dynamic TG>
The polymer (or polymer solution or pellet) is once dissolved or diluted in tetrahydrofuran, poured into excess hexane or methanol for reprecipitation, and the taken out precipitate is vacuum dried (1 mmHg (1.33 hPa), 80 ° C. Volatile components and the like were removed by conducting the reaction for 3 hours or more, and the obtained white solid resin was analyzed by the following method (dynamic TG method).
Measuring device: Thermo Plus2 TG-8120 Dynamic TG (manufactured by Rigaku Corporation)
Measurement conditions: Sample amount 5-10 mg
Temperature increase rate: 10 ° C / min
Atmosphere: Nitrogen flow 200ml / min
Method: Step-like isothermal control method (controlled at a mass reduction rate of 0.005% / second or less between 60 ° C and 500 ° C)

<Dealcoholization reaction rate and proportion of lactone ring structure>
The dealcoholization reaction rate was determined based on the amount of mass loss that occurred when all hydroxyl groups were dealcoholated as methanol from the polymer composition obtained by polymerization, and from 150 ° C. before the mass loss began in dynamic TG measurement, It calculated | required from the mass reduction by the dealcoholization reaction to 300 degreeC before decomposition | disassembly started.
That is, in a dynamic TG measurement of a polymer having a lactone ring structure, a mass reduction rate between 150 ° C. and 300 ° C. is measured, and the obtained actual mass reduction rate is defined as (X). On the other hand, from the composition of the polymer, all the hydroxyl groups contained in the polymer composition are involved in the formation of the lactone ring, so that it becomes an alcohol and is dealcoholized. The mass reduction rate calculated on the assumption that% dealcoholization reaction has occurred is defined as (Y). The theoretical mass reduction rate (Y) is more specifically the molar ratio of the raw material monomers having a structure (hydroxyl group) involved in the dealcoholization reaction in the polymer, that is, the raw material unit in the polymer composition. It can be calculated from the content of the monomer. These values (X, Y) are calculated from the dealcoholization formula:
1- (actual mass reduction rate (X) / theoretical mass reduction rate (Y))
Substituting into, the value is obtained and expressed in% to obtain the dealcoholization reaction rate. Then, the content (mass ratio) in the polymer composition of the raw material monomer having a structure (hydroxyl group) involved in lactone cyclization is determined as a result of the predetermined lactone cyclization by this dealcoholization reaction rate. By multiplying the dealcoholization reaction rate, the proportion of the lactone ring structure in the polymer can be calculated.

  As an example, the proportion of the lactone ring structure in the pellets obtained in Example 1 described later is calculated. When the theoretical mass reduction rate (Y) of this polymer was determined, the molecular weight of methanol was 32, the molecular weight of methyl 2- (hydroxymethyl) acrylate was 116, and methyl 2- (hydroxymethyl) acrylate. Since the content (mass ratio) in the polymer is 20.0% by mass in terms of composition, (32/116) × 20.0≈5.52% by mass. On the other hand, the actual mass decrease rate (X) by dynamic TG measurement was 0.17% by mass. When these values are applied to the above-described dealcoholization calculation formula, 1− (0.17 / 5.52) ≈0.969 is obtained, so that the dealcoholization reaction rate is 96.9%. And in the polymer, the content (20.0% by mass) of 2- (hydroxymethyl) methyl acrylate in the polymer, assuming that the predetermined lactone cyclization was performed by this dealcoholization reaction rate, When multiplied by the dealcoholization reaction rate (96.9% = 0.969), the proportion of the lactone ring structure in the polymer is 19.4 (20.0 × 0.969) mass%.

<Weight average molecular weight>
The weight average molecular weight of the polymer was determined by polystyrene conversion of GPC (GPC system manufactured by Tosoh Corporation). Tetrahydrofuran was used as the developing solution.

<Thermal analysis of resin>
Thermal analysis of the resin was performed using DSC (manufactured by Rigaku Corporation, apparatus name: DSC-8230) under the conditions of about 10 mg of sample, a temperature rising rate of 10 ° C./min, and a nitrogen flow of 50 ml / min. The glass transition temperature (Tg) was determined by the midpoint method according to ASTM-D-3418.

<Melt flow rate>
The melt flow rate was measured at a test temperature of 240 ° C. and a load of 10 kg based on JIS-K6874.

<Optical characteristics>
Refractive index anisotropy (retardation: Re) was measured using KOBRA-21ADH manufactured by Oji Scientific Instruments. Visible light transmittance was measured using NDH-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

<Linear thermal expansion coefficient>
Measured with TMA8310 (Thermo Plus series, Thermo Plus series), an average value of 0 to 200 ° C. was calculated and used as the linear thermal expansion coefficient.

<Polarizer processing aptitude>
The film was cut with a Thomson blade under an ambient humidity of 25 ° C. and a relative humidity of 60%, and the shape of the cut surface and the state of chip generation were visually observed.
◎ There is almost no disturbance in the cross-sectional shape of the film and the generation of chips. ○ The cross-sectional shape of the film is almost clean and there is no problem with the generation of chips.
Δ: The cross-sectional shape of the film is rather slight and generation of chips is slightly observed.
X The cross-sectional shape of the film is considerably rough, and the number of chips generated is considerable.

[Production Example 1]
In a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, nitrogen introduction pipe, 8000 g of methyl methacrylate (MMA), 2000 g of methyl 2- (hydroxymethyl) acrylate (MHMA), 10000 g of 4-methyl- 2-Pentanone (methyl isobutyl ketone, MIBK), 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while passing through nitrogen, and when refluxed, 5.0 g of tertiary butyl peroxyisopropyl was used as an initiator. While adding carbonate (manufactured by Akzo Kayaku Co., Ltd., trade name: Kaya-Carbon Bic-75), a solution comprising 10.0 g of tertiary butyl peroxyisopropyl carbonate and 230 g of MIBK was added dropwise over 2 hours under reflux ( Solution polymerization at about 105 to 120 ° C.) The aging was further performed for 4 hours.

  To the obtained polymer solution, 30 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-18) was added and cyclized under reflux (about 90 to 120 ° C.) for 5 hours. A condensation reaction was performed. Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4 It is introduced into a type screw twin screw extruder (φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization are carried out in the extruder. A transparent pellet (1A) was obtained by extrusion.

  When the obtained pellet (1A) was measured for dynamic TG, a mass loss of 0.17% by mass was detected. Moreover, the weight average molecular weight of the pellet was 133,000, the melt flow rate was 6.5 g / 10 min, and the glass transition temperature was 131 ° C.

[Examples 1 to 3, Comparative Examples 1 and 2]
The pellet (1A) obtained in Production Example 1 and acrylonitrile-styrene (AS) resin (manufactured by Toyo Styrene Co., Ltd .; trade name: Toyo AS AS20) are mixed at a weight ratio of 1A / AS resin = 90/10 (φ = 30 mm) to obtain transparent pellets. The obtained pellet had a glass transition temperature of 127 ° C.

  This pellet was dissolved in methyl ethyl ketone, and a 180 μm film (1B) was prepared by a solution casting method. This film was hot press-stretched at a glass transition temperature of + 10 ° C. (137 ° C.) for 10 minutes at an area ratio of 1.5 times, 2 times, and 3 times to obtain (1C), (1D), and (1E). Table 1 shows the results of evaluation of optical properties (Re, Rth), linear thermal expansion coefficient, and polarizing plate processability of the obtained films (1B), (1C), (1D), and (1E).

  Further, this pellet was dissolved in methyl ethyl ketone, and a 60 μm film (1F) was prepared by a solution casting method. The evaluation results are also shown in Table 1.

  A film having a large linear thermal expansion coefficient, such as films 1B and 1F, has poor suitability for polarizing plate processing, but it can be seen that the processing suitability for polarizing plate is improved by lowering the linear thermal expansion coefficient by hot press stretching ( 1C-1E). It is considered that by performing the hot pressing, the polarizing plate processing aptitude was improved by reducing the free volume and increasing the cohesive force between the molecular chains.

[Examples 4 to 6, Comparative Examples 3 and 4]
As in Example 1, transparent pellets were obtained by kneading using a single screw extruder at a mass ratio of 1A / AS resin = 80/20. The obtained pellet had a glass transition temperature of 125 ° C.
Using this pellet, a 180 μm cast film (2B) was prepared in the same manner as in Example 1. This film was subjected to hot press stretching at a glass transition temperature of + 10 ° C. (135 ° C.) for 10 minutes at an area ratio of 1.5 times, 2 times, and 3 times to obtain (2C), (2D), and (2E). Table 2 shows the results of evaluation of optical properties (Re, Rth), linear thermal expansion coefficient, and polarizing plate processing suitability of the obtained films (2B), (2C), (2D), and (2E).
Further, this pellet was dissolved in methyl ethyl ketone, and a 60 μm film (2F) was prepared by a solution casting method. The evaluation results are also shown in Table 2.
Table 2 shows the results of evaluation of the optical properties of the obtained films (2B) and (2C).

  A film having a large linear thermal expansion coefficient, such as films 2B and 2F, has poor suitability for polarizing plate processing, but it can be seen that the suitability for polarizing plate processing improves by reducing the linear thermal expansion coefficient by hot press stretching ( 2C-2E). It is considered that by performing the hot pressing, the polarizing plate processing aptitude was improved by reducing the free volume and increasing the cohesive force between the molecular chains.

  The optical film of the present invention is excellent in in-plane and thickness direction retardation, and can reduce manufacturing failures that occur from the cut surface during processing of a polarizing plate. For this reason, it can use preferably for manufacture of a polarizing plate, and industrial applicability is high. Moreover, according to the manufacturing method of this invention, the optical film of this invention can be manufactured efficiently and cheaply. Furthermore, the phase difference plate, the elliptically polarizing plate and the image display device of the present invention are excellent in optical properties. Therefore, the present invention has high industrial applicability.

Claims (14)

  An optical film comprising a thermoplastic resin composition containing a lactone ring-containing polymer and having a linear thermal expansion coefficient of 80 ppm or less.   The optical film according to claim 1, wherein the linear thermal expansion coefficient is 20 ppm to 80 ppm. The optical film according to claim 1 or 2, wherein the lactone ring-containing polymer has a lactone ring structure represented by the following general formula (1).

(In the formula, R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms.)    The thermoplastic resin composition further comprises a polymer having a structure obtained by copolymerizing a monomer composition containing a vinyl cyanide monomer and an aromatic vinyl monomer. The optical film of any one of -3.   The optical film according to claim 4, wherein the thermoplastic resin composition further includes a polymer having a structure obtained by copolymerizing a monomer composition containing acrylonitrile and styrene.   In-plane retardation is 0-15 nm, Retardation of the film thickness direction is 300 nm or less, The optical film as described in any one of Claims 1-5 characterized by the above-mentioned.   A method for producing an optical film having a linear thermal expansion coefficient of 80 ppm or less, comprising a step of press-stretching a film comprising a thermoplastic resin composition containing a lactone ring-containing polymer.   The method for producing an optical film according to claim 7, wherein the linear thermal expansion coefficient is 20 ppm to 80 ppm.   The method for producing an optical film according to claim 7 or 8, wherein the press stretching is performed at a temperature equal to or higher than a glass transition temperature of the film.   The method for producing an optical film according to claim 9, wherein the press stretching is performed at Tg to (Tg + 10) ° C.   The method for producing an optical film according to any one of claims 7 to 10, wherein an area stretching ratio of the press stretching is 1.5 to 5 times.   A phase difference plate using the optical film according to claim 1.   An elliptically polarizing plate formed by bonding the optical film according to any one of claims 1 to 6 and a polarizing plate.   An image display comprising at least one optical film according to any one of claims 1 to 6, a phase difference plate according to claim 12, or an elliptically polarizing plate according to claim 13. apparatus.