JP2011084058A - Film, method for producing the same, polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a film by which a thin film exhibiting ≥45 nm Re (in-plane retardation) can be easily produced with high productivity. <P>SOLUTION: The method for producing the film comprises the steps of: supplying a molten resin containing a thermoplastic resin from a supply means; making the supplied melt pass between a first nip pressing plane and a second nip pressing plane which constitute a nip pressing device, and continuously molding the passing melt into the film; and conveying the molded film. The melt is nip pressed between the first nip pressing plane and the second nip pressing plane under 10-150 MPa and the molded film is conveyed at 10-100 m/minute. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a film. More specifically, the present invention relates to a technique in which a thermoplastic resin in a molten state is supplied from a supply unit and is cooled and solidified into a film with a pinching device. The present invention also relates to a film prepared by the production method, a polarizing plate having the film, and a liquid crystal display device.

  In recent years, various films have been developed along with the rise of the liquid crystal display market. In recent years, as an optical compensation film application, a thin film (more specifically referred to as “Re” hereinafter) having a retardation in the in-plane direction (hereinafter also referred to as “Re”) of 45 nm or more is developed. A film of less than about 100 μm, preferably 20 to 80 μm has been demanded. Moreover, as a simple and low-cost manufacturing method for a film for a liquid crystal display device, for example, in Patent Documents 1 to 7, a thermoplastic resin melt is continuously passed between pressing devices, and between the pressing devices. A film manufacturing method (hereinafter also referred to as touch roll method) is disclosed.

  The general influence when the pressure and line speed which pinch | melt a molten resin in the touch roll method is examined is known conventionally. For example, it is known that when the pressure for sandwiching the molten resin is increased, a large compressive force acts in the thickness direction, and a film in which molecular chains are selectively oriented in the in-plane direction can be produced. On the other hand, in the upper right column on page 62 to the upper left column on page 63 of Patent Document 7, when the film conveyance speed by the clamping surface is increased, the amount of molten resin staying immediately before the clamping unit (so-called bank amount) is reduced. It is disclosed that the birefringence of the resulting film is reduced. Such a relationship between the bank amount and retardation is also disclosed in FIG.

  Here, first, in the touch roll method described in Patent Documents 1 to 3, for example, for the purpose of forming a thin film having a film thickness of 500 μm or less, a touch roll that is an elastic roll and a chill roll that is a metal roll A method is used in which the molten resin is clamped between the clamping devices constituted by: When a metal roll described in Patent Documents 1 to 3 and a rubber roll whose surface is coated with a metal are used for pinching, the elasticity is applied when pressure is applied to the elastic roll to apply a high pinching pressure of 10 MPa or more to the molten resin. The roll is deformed, the contact area with the melt increases, and a pressure of 10 MPa or more cannot be applied.

Patent Document 1 discloses a method for producing a film that uses an elastic roll as a touch roll, has no residual distortion of 140 to 550 μm, and does not have irregular reflection or retardation of light. In addition, the same document discloses that a film in which a large residual strain is generated by increasing the pressure for sandwiching the molten resin in the touch roll method causes irregular reflection of light and the like, so that it cannot be used for optical applications or liquid crystal display devices. ing.
Patent Document 2 discloses a method for producing a film that can reduce the retardation when the film thickness is 120 to 400 μm by using a rubber roll whose surface is coated with a metal as a touch roll and specifying a line speed or the like. Has been.

  However, none of the documents discloses a method for producing a thin film in which Re is expressed at 45 nm or more. There is no suggestion about the change in Re when the film conveyance speed is increased when the film is clamped at a high pressure. That is, in the touch roll method described in Patent Documents 1 to 3 using a metal roll and an elastic roll having low hardness, it has been studied to reduce the retardation of a film obtained by pinching with a low pressure. It has not been studied to produce a thin film having a large thickness by the touch roll method.

  Next, a touch roll method is also known in which a film is formed by applying a certain high pressure to the molten resin between the clamping devices (see Patent Documents 4 to 7). However, it has hardly been studied to increase the film conveying speed when a film is formed by applying a certain high pressure in this way. For example, Patent Documents 4 and 5 do not disclose the film conveying speed. In Patent Document 7, the sheet is conveyed at a low speed of 2.16 m / min. Here, as an example of increasing the film transport speed in the touch roll method in which a film is formed by applying a certain high pressure to the molten resin, the roll peripheral speed in Example 2 of Patent Document 6 was set to 8.8 m / min. An example is the maximum speed. According to the example, it is disclosed that Re can be expressed by 6.2 nm when such a roll peripheral speed is set. However, in the same document, a description suggesting a range of a preferable roll peripheral speed or a film is disclosed. There was no suggestion regarding the relationship between the transport speed and Re.

  As described above, even in the touch roll method in which a large pressure of 10 MPa or more is applied, there are almost no literatures examining the production method of a thin film in which Re is expressed by 45 nm or more, or increasing the film conveyance speed by the nipping surface. The current situation is not known.

Japanese Patent No. 3194904 JP 2000-239409 A Japanese Patent No. 3422798 Japanese Patent No. 4117589 JP-A-4-1010 JP 2007-38646 A JP-A-4-59210 JP-A-10-264238

  The present invention has been made in consideration of the above-mentioned problems, and a first object of the present invention is to provide a film production method capable of producing a thin film having a Re of 45 nm or more expressed easily and with high productivity. There is. The second object of the present invention is to provide a film produced by the method for producing the film, a polarizing plate using the film, and a liquid crystal display device.

In view of the above circumstances and problems, the present inventors have studied to make the roll peripheral speed faster than Example 2 of Patent Document 4 while pinching the molten resin at a pressure of 10 MPa or more between the pinching devices. Surprisingly, contrary to the description that the birefringence decreases when the film conveyance speed of Patent Document 7 is increased, it was found that the Re expression amount is significantly higher than that of the film of Example 2 of Patent Document 6.
That is, the inventors have found that the following production method and a film produced by the method can solve the above problems, and have completed the present invention described below.

[1] A supply step of supplying a molten resin containing a thermoplastic resin from a supply means, and continuously passing a melt supplied between a first clamping surface and a second clamping surface constituting the clamping device. A film forming method and a step of conveying the formed film, wherein the melt is pressed by the first clamping surface and the second clamping surface at a pressure of 10 to 150 MPa. The manufacturing method of the film which narrows by pressure and conveys the said film at 10-100 m / min.
[2] The method for producing a film according to [1], wherein the first clamping surface and the second clamping surface are both made of metal and rigid.
[3] The method for producing a film according to [1] or [2], wherein the temperature of the melt immediately after the discharge port of the supply unit is (Tg + 60 ° C.) to (Tg + 140 ° C.) Tg represents the glass transition temperature of the thermoplastic resin).
[4] The distance from the discharge port of the supply means to the melt landing point of the clamping device is 200 m.
It is m or less, The manufacturing method of the film as described in any one of [1]-[3] characterized by the above-mentioned.
[5] The method for producing a film according to any one of [1] to [4], wherein the moving speed of the first pressing surface is made faster than the moving speed of the second pressing surface.
[6] The moving speed ratio between the first clamping surface and the second clamping surface of the clamping device defined by the following formula (I) is 0.6 to 0.99, [1] to [1] [5] The method for producing a film according to any one of [5].
Movement speed ratio = Speed of the second clamping surface / Speed of the first clamping surface (I)
[7] The method for producing a film according to any one of [1] to [6], wherein the pinching device is two rolls having different peripheral speeds.
[8] The method for producing a film according to any one of [1] to [7], wherein the formed film has a thickness of 20 to 80 μm.
[9] The method for producing a film according to any one of [1] to [8], wherein the thermoplastic resin contains at least one of a cyclic olefin resin or a polycarbonate resin.
[10] including a step of heating the film formed in the first clamping step, and a second narrowing step of constricting the heated film between two narrow pressure surfaces that are opposed to each other and have different moving speeds. The method for producing a film according to claim 1, wherein the first clamping step and the second narrowing step are performed in-line.
[11] The surface temperature of the first clamping surface and the second clamping surface is Tg or less, and the heating temperature in the heating step is Tg−10 ° C. to Tg + 20 ° C. Film production method (however, Tg represents the glass transition temperature (unit: ° C.) of the thermoplastic resin).
[12] A third pinching step that includes a third pinching step that constricts between two confining surfaces that are arranged opposite to each other and have different moving speeds, and the third pinching step is a line different from the line of the first pinching step. The method for producing a film according to any one of [1] to [11], wherein
[13] In the second clamping step or the third clamping step, the two narrow pressure surfaces that are arranged opposite to each other and have different moving speeds are two rolls having different circumferential speeds. ] The manufacturing method of the film of description.
[14] A film produced by the method for producing a film according to any one of [1] to [13].
[15] The film according to [14], having a thickness of 20 to 80 μm and a retardation Re in the in-plane direction of the film at a wavelength of 550 nm of 20 to 400 nm.
[16] A polarizing plate comprising a polarizer and the film according to [14] or [15].
[17] A liquid crystal display device comprising the film according to [14] or [15].

ADVANTAGE OF THE INVENTION According to this invention, the film which can implement | achieve sufficient optical compensation when it uses for a liquid crystal display, and its manufacturing method can be provided. Specifically, the film having the above optical characteristics can realize sufficient optical compensation when used in a TN mode, ECB mode, or OCB mode liquid crystal display. Moreover, the film of this invention can be provided with the manufacturing method of the film of this invention.
Furthermore, according to a more preferable aspect of the present invention, it is possible to improve the touch omission of the film, and it is possible to provide a film having a better surface shape in addition to the above characteristics.

It is a top view showing the absorption axis of the polarizing plate, the orientation direction of a liquid crystal cell, and the slow axis of a film in the transflective ECB mode liquid crystal display device of the present invention. In the manufacturing method of this invention, the schematic diagram of the pinching apparatus of the aspect which drops the melt supplied from die | dye to the center of the part pinched with the chill roll and the touch roll is represented. The preferable aspect of the manufacturing method of this invention WHEREIN: The schematic diagram of the clamping apparatus of the aspect which performs a 1st clamping process, a heating process, and a 2nd clamping process in-line is represented.

Hereinafter, the present invention will be described in more detail. 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. In the present specification, the “film longitudinal direction” means the MD (machine direction) direction.
In addition, “a composition containing a thermoplastic resin” and “a film composed of a thermoplastic resin” means containing 50% or more of a thermoplastic resin that can be melt-formed.
In this specification, that the pinching surface (or roll) of the pinching device is “rigid” means that the ratio of the rigid material outer cylinder thickness / roll diameter is 1/80 or more. Even when a rigid material is used for the portion, the pressing surface or the touch roll is not necessarily “rigid”.
Further, in this specification, the pinching surface (or roll) of the pinching device being “elastic” means that the ratio of rigid material outer cylinder thickness / roll diameter is less than 1/80. The case where a rigid material is used for a part of the case may be included. That is, a roll in which a layer containing no rigid material such as an elastic layer is formed inside the touch roll is elastically deformed as a whole even if a rigid material layer is formed on the surface or inside. Therefore, it is included in the elastic roll. Also, in the case of a roll whose core is rubber and whose surface is a rigid material (a roll having a surface metal ring as an outer cylinder), the metal on the surface is not deformed, but the center of the rotating shaft and the surface metal ring is shifted, Included in elastic roll.
Further, in this specification, the pressure-clamping surface (or roll) of the pressure-clamping device is “metallic and rigid”, and at least all the surfaces are metal, and the pressure-clamping surface (or roll) of the pressure-clamping device. Represents “rigidity”.

[the film]
The film of the present invention can be preferably used as a film for optical applications, and can be particularly preferably used as an optical compensation film. Moreover, it can also be set as a laminated | multilayer film by further providing an optically anisotropic layer to the film of this invention. Hereinafter, the film of the present invention will be described.

(Film thickness)
The film of the present invention preferably has a thickness of 20 to 80 μm. When used for a liquid crystal display or the like, from the viewpoint of thinning, it is more preferably 30 to 70 μm, and particularly preferably 40 to 60 μm or less. In the film manufacturing method of the present invention, even such a thin film can be produced while sufficiently expressing Re. This is one of the differences from the prior art.

(In-plane retardation Re)
The film of the present invention contains a thermoplastic resin, and has a retardation Re (hereinafter also referred to as Re [0 °]) at a wavelength of 550 nm measured from the film normal direction of 45 nm or more.

  The film of the present invention preferably has an in-plane retardation Re of 20 to 400 nm, more preferably 40 to 300 nm, and still more preferably 60 to 200 nm.

  A film having Re in the above preferred range can be produced by the production method of the present invention described later. In addition, when the optical film having the preferable optical characteristics is used for optical compensation of a liquid crystal display such as a TN mode, an ECB mode, and an OCB mode, it contributes to the improvement of the viewing angle characteristics and achieves a wide viewing angle. it can.

Furthermore, the film of the present invention has a retardation Re [+ 40 °] measured from a direction tilted 40 ° toward the tilt direction with respect to the film normal direction, and tilted −40 ° toward the tilt direction with respect to the normal line. It is preferable from the viewpoint of realizing sufficient optical compensation that the retardation Re [−40 °] measured from the other direction satisfies the following formula (II).
0 nm ≦ | Re [+ 40 °] −Re [−40 °] | ≦ 300 nm (II)
The | Re [+ 40 °] −Re [−40 °] | is more preferably 20 to 250 nm, and particularly preferably 40 to 200 nm.

  In this specification, the “direction inclined by θ ° from the film normal” is defined as a direction inclined in the film surface direction by θ ° from the normal direction to the inclination direction. That is, the normal direction of the film surface is a direction with an inclination angle of 0 °, and an arbitrary direction within the film surface is a direction with an inclination angle of 90 ° when the sign of the inclination angle (θ) is not considered. . When considering the sign of the inclination angle (θ), the direction in which Re [+ 40 °] is measured and the direction in which Re [−40 °] are measured are positions symmetrical with respect to the film normal.

The optical characteristic value can be measured by the following method.
In the present invention, Re of the film uses KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.), and includes the film tilt direction (however, if no tilt direction exists, the film transport direction) and the film normal In the figure, the phase difference at an inclination angle of 0 ° is measured.

In the present specification, Re [0 °] represents in-plane retardation (nm) of a film-like measurement object such as an optically anisotropic layer, a film, or a laminate.
Re [0 °] is measured by making light having a wavelength of 550 nm incident in the normal direction of a film-like measurement object in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
Note that the Re [θ °] and refractive index measurement wavelengths are values at a measurement wavelength of 550 nm unless otherwise specified.

In the present specification, Re [0 °], Re [+ 40 °] and Re [−40 °] of the film are retardation values at a wavelength of 550 nm (at an inclination angle of 0 °) measured from the film normal direction, Retardation value (at an inclination angle of 40 degrees) measured from a direction inclined 40 ° toward the tilt azimuth side or temporary tilt azimuth side with respect to the normal line, and toward the tilt azimuth side or temporary tilt azimuth side with respect to the normal line − Retardation value (inclination angle −40 degrees) measured from a direction inclined by 40 ° is represented.
Here, the inclination direction was determined by the following method.
(1) The slow axis direction in the film plane is 0 °, the fast axis direction in the film plane is 90 °, and the temporary tilt direction is set in increments of 0.1 ° between 0 ° and 90 °.
(2) Re [+ 40 °] and Re [−40 °] are measured from the direction inclined by 40 ° or −40 ° toward each temporary inclination direction with respect to the film normal, and | Re [+40 of each temporary inclination direction °] −Re [−40 °] |
(3) The direction in which | Re [+ 40 °] −Re [−40 °] | is maximized is determined as the tilt direction.
That is, in this specification, “having a tilted direction” means that there is an orientation in which | Re [+ 40 °] −Re [−40 °] |
Re [0 °], Re [+ 40 °], and Re [−40 °] are sampled at any 10 or more positions apart from each other by 2 mm or more in the center of the film, and Re [0 °] by the above method. ], Re [+ 40 °] and Re [−40 °] are measured, and the average value of the 10 points is defined as Re [0 °], Re [+ 40 °], and Re [−40 °].

(Thermoplastic resin)
The thermoplastic resin used in the present invention is not particularly limited as long as it has the above-mentioned optical characteristics. However, when it is produced using a melt extrusion method, it is preferable to use a material having good melt extrusion moldability. In, polyolefins such as cyclic olefin resins, cellulose acylate resins, polycarbonate resins, polyesters, transparent polyethylene, transparent polypropylene, polyarylates, polysulfones, polyethersulfones, maleimide copolymers, transparent It is preferable to select nylons, transparent fluororesins, transparent phenoxys, polyetherimides, polystyrenes, acrylic resins, and styrene resins. One kind of the resin may be contained, or two or more kinds of the resins different from each other may be contained. The film of the present invention preferably contains at least one of a cyclic olefin resin, a cellulose acylate resin, a polycarbonate resin, a styrene resin, and an acrylic resin, and contains at least one of a cyclic olefin resin or a polycarbonate resin. More preferably. The cyclic olefins are preferably cyclic olefins obtained by addition polymerization.

In particular, cellulose acylate resins, cyclic olefin resins, polycarbonate resins, and modified polyesters that exhibit positive intrinsic birefringence have a slow axis oriented in a tilt direction when shear deformation is applied by two rolls. For example, when two rolls are arranged in parallel with the die exit, the tilt direction is the same as the film longitudinal direction.
Moreover, when the acrylic resin and styrene resin exhibiting negative intrinsic birefringence are processed as described above, a film having a fast axis oriented in a tilt direction can be produced.

  When the film of the present invention is applied to a liquid crystal display device as a viewing angle compensation film, the positive or negative intrinsic birefringent resin is appropriately used in consideration of the characteristics of the liquid crystal display device and the convenience of polarizing plate processing. You can select and use.

Examples of the cyclic olefin resin that can be used in the present invention include a norbornene resin obtained by polymerization of a norbornene compound. Further, it may be a resin obtained by any polymerization method of ring-opening polymerization and addition polymerization.
Examples of the addition polymerization and the cyclic olefin-based resin obtained thereby include, for example, Japanese Patent No. 3517471, Japanese Patent No. 3559360, Japanese Patent No. 3867178, Japanese Patent No. 3871721, Japanese Patent No. 3907908, Japanese Patent No. 3945598, Special Table 2005 Nos. 527696, 2006-28993, 2006-11361, WO 2006/004376, and WO 2006/0307077. . Among these, those described in Japanese Patent No. 3517471 are particularly preferable.
Examples of the ring-opening polymerization and the cyclic olefin-based resin obtained thereby include International Publication WO 98/98499 pamphlet, Japanese Patent No. 30605532, Japanese Patent No. 3320478, Japanese Patent No. 3273046, Japanese Patent No. 3404027, Japanese Patent No. 3428176. , Japanese Patent No. 3687231, Japanese Patent No. 3873934, and Japanese Patent No. 3912159. Among these, those described in International Publication WO 98/14499 pamphlet and Japanese Patent No. 30605532 are particularly preferable.
Among these cyclic olefin-based resins, those obtained by addition polymerization are preferable from the viewpoint of the expression of birefringence and the melt viscosity. For example, “TOPAS # 6013” (manufactured by Polyplastics) can be used.

  Examples of the cellulose acylate resin that can be used in the present invention include any cellulose acylate in which three hydroxyl groups in a cellulose unit are at least partially substituted with an acyl group. The acyl group (preferably an acyl group having 3 to 22 carbon atoms) may be either an aliphatic acyl group or an aromatic acyl group. Among them, cellulose acylate having an aliphatic acyl group is preferable, those having an aliphatic acyl group having 3 to 7 carbon atoms are more preferable, those having an aliphatic acyl group having 3 to 6 carbon atoms are more preferable, and carbon number More preferably has 3 to 5 aliphatic acyl groups. A plurality of these acyl groups may be present in one molecule. Examples of preferred acyl groups include acetyl, propionyl, butyryl, pentanoyl, hexanoyl and the like. Among these, a cellulose acylate having one or more selected from an acetyl group, a propionyl group and a butyryl group is more preferable, and an even more preferable one has both an acetyl group and a propionyl group. Cellulose acylate (CAP). The CAP is preferable in terms of easy resin synthesis and high stability of extrusion molding.

When producing a film by the melt extrusion method including the production method of the present invention, the cellulose acylate to be used preferably satisfies the following formulas (S-1) and (S-2). Cellulose acylate satisfying the following formula has a low melting temperature and improved meltability, and is therefore excellent in melt extrusion film formation.
Formula (S-1) 2.0 ≦ X + Y ≦ 3.0
Formula (S-2) 0.25 <= Y <= 3.0
In the formulas (S-1) and (S-2), X represents the substitution degree of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the total substitution degree of the acyl group with respect to the hydroxyl group of cellulose. As used herein, “degree of substitution” means the sum of the ratios of substitution of hydrogen atoms of hydroxyl groups at the 2-, 3- and 6-positions of cellulose. When the hydrogen atoms of all hydroxyl groups at the 2nd, 3rd and 6th positions are substituted with acyl groups, the substitution degree is 3.
Furthermore, it is more preferable to use a cellulose acylate that satisfies the following formulas (S-3) and (S-4).
Formula (S-3) 2.3 ≦ X + Y ≦ 2.95
Formula (S-4) 1.0 ≦ Y ≦ 2.95
It is more preferable to use a cellulose acylate that satisfies the following formulas (S-5) and (S-6).
Formula (S-5) 2.7 ≦ X + Y ≦ 2.95
Formula (S-6) 2.0 ≦ Y ≦ 2.9

  There is no restriction | limiting in particular about the mass average polymerization degree and number average molecular weight of a cellulose acylate-type resin. In general, the mass average degree of polymerization is about 350 to 800, and the number average molecular weight is about 70000 to 230,000. The cellulose acylate resin can be synthesized using an acid anhydride or acid chloride as an acylating agent. In the industrially most general synthesis method, cellulose obtained from cotton linter, wood pulp, etc. is converted into organic acids (acetic acid, propionic acid, butyric acid) corresponding to acetyl groups and other acyl groups, or their acid anhydrides (anhydrous anhydride). A cellulose ester is synthesized by esterification with a mixed organic acid component containing acetic acid, propionic anhydride, and butyric anhydride). As a method for synthesizing cellulose acylate satisfying the above formulas (S-1) and (S-2), the technical report of the Japan Society of Invention (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention) 7 Pp. 12 to 12, JP-A-2006-45500, JP-A-2006-241433, JP-A-2007-138141, JP-A-2001-188128, JP-A-2006-142800, JP-A-2007. Reference can be made to the method described in Japanese Patent No. 98917.

  Examples of polycarbonate resins that can be used in the present invention include polycarbonate resins having a bisphenol A skeleton, which are obtained by reacting a dihydroxy component and a carbonate precursor by an interfacial polymerization method or a melt polymerization method. JP-A-2006-277914, JP-A-2006-106386, and JP-A-2006-284703 can be preferably used. For example, “Taflon MD1500” (manufactured by Idemitsu Kosan Co., Ltd.) can be used as a commercial product.

  Examples of the modified polyesters that can be used in the present invention include a polyester resin composed of a polyol skeleton and a diol unit having a cyclic acetal skeleton and a dicarboxylic acid unit. As such modified polyesters, for example, those described in JP 2007-171914 A can be preferably used.

The styrenic resin that can be used in the present invention refers to a resin obtained by polymerizing styrene and derivatives thereof as a main component, and copolymers of other resins, and is not particularly limited as long as the effects of the present invention are not impaired. A known styrene-based thermoplastic resin can be used, and a copolymer resin that can improve birefringence, film strength, and heat resistance is particularly preferable.
Examples of the copolymer resin include styrene-acrylonitrile resins, styrene-acrylic resins, styrene-maleic anhydride resins, and multi-component (binary, ternary, etc.) copolymer polymers thereof. Among these, styrene-acrylic resins and styrene-maleic anhydride resins are preferable from the viewpoints of heat resistance and film strength.
In the styrene-maleic anhydride resin, the mass composition ratio of styrene and maleic anhydride is preferably styrene: maleic anhydride = 95: 5 to 50:50, and styrene: maleic anhydride = 90: 10. More preferably, it is ˜70: 30. In order to adjust the intrinsic birefringence, hydrogenation of a styrene resin can be preferably used.
Examples of the styrene-maleic anhydride resin include “Daylark D332” manufactured by Nova Chemical Co., Ltd.
As the styrene-acrylic resin, “Delpet 980N” manufactured by Asahi Kasei Chemical Co., Ltd., which will be described later, can be used.

前記一般式（１）中、Ｒ¹およびＲ²は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を示す。有機残基とは、具体的には、炭素数１〜２０の直鎖状、分枝鎖状、もしくは環状のアルキル基を示す。 The acrylic resin that can be used in the present invention refers to a resin obtained by polymerizing acrylic acid, methacrylic acid and derivatives thereof as main components, and further derivatives thereof, as long as the effects of the present invention are not impaired. It does not specifically limit, A well-known methacrylic acid type thermoplastic resin etc. can be used.
Examples of the resin obtained by polymerizing acrylic acid, methacrylic acid and derivatives thereof include those having a structure represented by the following general formula (1).

In the general formula (1), R ¹ and R ² each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue specifically represents a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms.

Specific examples of resins obtained by polymerizing the acrylic acid, methacrylic acid and derivatives thereof include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and (meth) acrylic. N-butyl acid, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxy (meth) acrylate Propyl, 2,3,4,5,6-pentahydroxyexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate are preferred, and in terms of excellent thermal stability (meta ) Methyl acrylate (hereinafter also referred to as MMA) is more preferable. Among these, only 1 type may be used and 2 or more types may be used together. Of these, it may be a single polymer, a copolymer of two or more, or a copolymer of other resins, but from the viewpoint of increasing the glass transition temperature, Particularly preferred is a copolymer with a resin.
Among the acrylic copolymer resins, those containing 30 mol% or more of MMA units (monomer) in all monomers constituting the resin are preferable. In addition to MMA, lactone ring units, maleic anhydride units, glutaric anhydrides More preferably, at least one unit of units is included, and for example, the following can be used.

(1) Acrylic resin containing a lactone ring unit JP 2007-297615 A, JP 2007-63541 A, JP 2007-70607 A, JP 2007-100044 A, JP 2007-254726 A, JP 2007-254727 A , JP 2007-261265, JP 2007-293272, JP 2007-297619, JP 2007-316366, JP 2008-9378, and JP 2008-76764. Can be used. Among these, the resin described in JP-A-2008-9378 is more preferable.
(2) Acrylic resin containing maleic anhydride unit JP 2007-113109 A, JP 2003-292714 A, JP 6-279546 A, JP 2007-51233 A (described here), JP JP-A-2001-270905, JP-A-2002-167694, JP-A-2000-302988, JP-A-2007-111110, JP-A-2007-11565 can be used. Of these, the one described in JP-A-2007-113109 is more preferable. A commercially available maleic acid-modified MAS resin (for example, Delpet 980N manufactured by Asahi Kasei Chemicals Corporation) can also be preferably used.
(3) Acrylic resin containing glutaric anhydride unit JP-A-2006-241263, JP-A-2004-70290, JP-A-2004-70296, JP-A-2004-126546, JP-A-2004-163924, JP-A-2004 -291302, JP-A-2004-292812, JP-A-2005-314534, JP-A-2005-326613, JP-A-2005-331728, JP-A-2006-131898, JP-A-2006-134882, JP-A-2006- 206881, JP 2006-241197, JP 2006-283013, JP 2007-118266, JP 2007-176982, JP 2007-178504, JP 2007-197703, JP 2008-74818. No., International Publication WO2005 / 105 Those described in each publication such as 918 can be used. Among these, those described in JP-A-2008-74918 are more preferable.
The glass transition temperature (Tg) of these resins is preferably 106 ° C to 170 ° C, more preferably 110 ° C to 160 ° C, still more preferably 115 ° C to 150 ° C.

Among these, the thermoplastic resin is preferably a cyclic olefin resin, more preferably a norbornene resin from the viewpoints of high transparency, birefringence and heat resistance, and an addition polymerization type norbornene. It is particularly preferable that the resin is a resin.
In addition, when the thermoplastic resin is a copolymer, it may be a random copolymer or a block copolymer.

(Additive)
The film of the present invention may contain a material other than the thermoplastic resin, but contains one or more of the thermoplastic resins as a main component (the highest content ratio among all the materials in the composition). In the aspect which means material and contains 2 or more types of the said resin, it is preferable to contain as the content ratio of those sum total is higher than the content rate of each other material. Examples of materials other than the thermoplastic resin include various additives. Examples thereof include a stabilizer, an ultraviolet absorber, a light stabilizer, a plasticizer, fine particles, and an optical adjusting agent.

Stabilizer:
The film of the present invention may contain at least one stabilizer. The stabilizer is preferably added before or when the thermoplastic resin is heated and melted. The stabilizer has effects such as preventing oxidation of the film constituting material, capturing an acid generated by decomposition, and suppressing or inhibiting a decomposition reaction caused by radical species caused by light or heat. Stabilizers are useful for suppressing the occurrence of alterations such as coloring and molecular weight reduction and the generation of volatile components due to various decomposition reactions including unresolved decomposition reactions. Even at the melting temperature for forming a resin film, the stabilizer itself is required to function without being decomposed. Typical examples of stabilizers include phenol-based stabilizers, phosphorous acid-based stabilizers (phosphite-based), thioether-based stabilizers, amine-based stabilizers, epoxy-based stabilizers, and lactone-based stabilizers. Stabilizers, amine stabilizers, metal deactivators (tin stabilizers) and the like are included. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. Then, it is preferable to use at least one or more of a phenol-based or phosphorous acid-based stabilizer. Among phenolic stabilizers, it is particularly preferable to add a phenolic stabilizer having a molecular weight of 500 or more. Preferable phenolic stabilizers include hindered phenolic stabilizers.

  These materials are readily available as commercial products and are sold by the following manufacturers. From Ciba Specialty Chemicals, Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259, Irganox 565, Irganx 565, Irganx 565, Ir35x10 Moreover, it can obtain from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADK STAB AO-80. Furthermore, from Sumitomo Chemical Co., Ltd., it can obtain as Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80. In addition, it is also possible to obtain as Sinox 326M and Sinox 336B from Sipro Kasei Co., Ltd.

  Moreover, as said phosphorous acid type stabilizer, the compound as described in [0023]-[0039] of Unexamined-Japanese-Patent No. 2004-182979 can be used more preferably. Specific examples of the phosphite ester stabilizer include JP-A-51-70316, JP-A-10-306175, JP-A-57-78431, JP-A-54-157159, Examples thereof include compounds described in Japanese Utility Model Laid-Open No. 55-13765. Furthermore, as other stabilizers, the materials described in detail on pages 17 to 22 of the Japan Institute of Invention Disclosure Bulletin (Public Technical No. 2001-1745, issued March 15, 2001, Japan Society of Invention) are preferably used. be able to.

  The phosphite stabilizer is useful to have a high molecular weight in order to maintain stability at high temperature, has a molecular weight of 500 or more, more preferably a molecular weight of 550 or more, and particularly a molecular weight of 600 or more. Is preferred. Furthermore, at least one substituent is preferably an aromatic ester group. The phosphite ester stabilizer is preferably a triester, and is desirably free of impurities such as phosphoric acid, monoester and diester. When these impurities are present, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly 2% by mass or less. These include compounds described in [0023] to [0039] of JP-A No. 2004-182979, JP-A-51-70316, JP-A-10-306175, JP-A-57. The compounds described in JP-A-78431, JP-A-54-157159, and JP-A-55-13765 can also be mentioned. Preferred specific examples of the phosphite stabilizer include the following compounds, but the phosphite stabilizer that can be used in the present invention is not limited thereto.

  These are commercially available from Asahi Denka Kogyo Co., Ltd. as ADK STAB 1178, 2112, PEP-8, PEP-24G, PEP-36G, and HP-10, and Sandostab P-EPQ from Clariant. Is possible. Furthermore, a stabilizer having phenol and phosphite in the same molecule is also preferably used. These compounds are further described in detail in JP-A-10-273494. Examples of the compounds are included in the examples of the stabilizer, but are not limited thereto. As a typical commercial product, Sumitizer GP is available from Sumitomo Chemical Co., Ltd. These are commercially available from Sumitomo Chemical Co., Ltd. as Sumilizer TPL, TPM, TPS, TDP. Also available from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-412S.

  The stabilizers can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention. Preferably, the addition amount of the stabilizer is preferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, and still more preferably 0.01 to 0% with respect to the mass of the thermoplastic resin. 0.8% by mass.

UV absorber:
The film of the present invention may contain one type or two or more types of ultraviolet absorbers. From the viewpoint of preventing deterioration, the ultraviolet absorbent is preferably excellent in the ability to absorb ultraviolet light having a wavelength of 380 nm or less and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of transparency. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose mixed ester is small. These are disclosed in JP-A-60-235852, JP-A-3-199201, 5-1907073, 5-194789, 5-271471, 6-107854, 6-118233, 6 -148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173.
The addition amount of the ultraviolet absorber is preferably 0.01 to 2% by mass of the thermoplastic resin, and more preferably 0.01 to 1.5% by mass.

Light stabilizer:
The film of the present invention may contain one or more light stabilizers. Light stabilizers include hindered amine light stabilizer (HALS) compounds, more specifically, US Pat. No. 4,619,956, columns 5-11 and US Pat. No. 4,839. 2,405, 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds. These are commercially available from Asahi Denka as ADK STAB LA-57, LA-52, LA-67, LA-62, LA-77, and TINUVIN 765, 144 from Ciba Specialty Chemicals. .

  These hindered amine light stabilizers can be used alone or in combination of two or more. These hindered amine light stabilizers may of course be used in combination with additives such as plasticizers, stabilizers, UV absorbers, etc., or may be introduced into a part of the molecular structure of these additives. Good. The blending amount is determined within a range not impairing the effects of the present invention, and is generally about 0.01 to 20 parts by mass, preferably 0.02 to 15 parts per 100 parts by mass of the thermoplastic resin. About mass parts, and particularly preferably about 0.05 to 10 mass parts. The light stabilizer may be added at any stage of preparing the melt of the thermoplastic resin composition, for example, at the end of the melt preparation process.

Plasticizer:
The film of the present invention may contain a plasticizer. The addition of a plasticizer is preferable from the viewpoint of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. In addition, when the film of the present invention is produced by a melt film-forming method, the purpose is to lower the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the thermoplastic resin to be used, or no addition Will be added for the purpose of lowering the viscosity at the same heating temperature than the other thermoplastic resins. For the film of the present invention, for example, a plasticizer selected from phosphoric acid ester derivatives and carboxylic acid ester derivatives is preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 to 10,000 described in JP-A No. 2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or a cyclohexyl group Acrylic polymers having a side chain are preferably used.

Fine particles:
The film of the present invention may contain fine particles. Examples of the fine particles include fine particles of inorganic compounds and fine particles of organic compounds, and any of them may be used. The average primary particle size of the fine particles contained in the thermoplastic resin in the present invention is preferably 5 nm to 3 μm, more preferably 5 nm to 2.5 μm, more preferably 10 nm to 2.0 μm from the viewpoint of keeping haze low. More preferably. Here, the average primary particle size of the fine particles is determined by observing the thermoplastic resin with a transmission electron microscope (magnification of 500,000 to 1,000,000 times) and determining the average value of the primary particle sizes of 100 particles. The addition amount of the fine particles is preferably 0.005 to 1.0% by mass with respect to the thermoplastic resin, more preferably 0.01 to 0.8% by mass, and further preferably 0.02 to 0%. 4% by mass.

Optical modifier:
The film of the present invention may contain an optical adjusting agent. Examples of the optical adjusting agent include a retardation adjusting agent, for example, those described in JP-A Nos. 2001-166144, 2003-344655, 2003-248117, and 2003-66230. Can be used. By adding an optical adjusting agent, in-plane retardation (Re) and thickness direction retardation (Rth) can be controlled. A preferable addition amount is 0 to 10% by mass, more preferably 0 to 8% by mass, and further preferably 0 to 6% by mass.

[Film Production Method]
In the method for producing a film of the present invention, a supply step of supplying a composition containing a thermoplastic resin from a supply means, and a melt supplied between a first pressing surface and a second pressing surface constituting a pressing device (Hereinafter, also referred to as melt) is a method for producing a film, comprising: a step of continuously forming a film into a film; and a step of conveying the formed film, wherein the first pressing surface and the first The melt is narrowed at a pressure of 10 to 150 MPa by two clamping surfaces, and the film is conveyed at 10 to 100 m / min. Applying such a large pressure is a feature of the present invention that is different from the conventional method. Examples of the clamping device having the first clamping surface and the second clamping surface include a combination of two rolls, a combination of a roll and a touch belt (single-sided belt method) described in Japanese Patent Application Laid-Open No. 2000-219752, And a combination of belts (double-sided belt method). Among these, two rolls are preferable because a high pressure of 10 to 150 MPa can be applied uniformly. The roll pressure can be measured by passing a pressure measuring film (such as a prescale for medium pressure manufactured by Fuji Film) through two rolls.
Hereinafter, the film production method of the present invention (hereinafter also referred to as the production method of the present invention) will be described in detail.

<Supply process>
In the production method of the present invention, first, a composition containing a thermoplastic resin (sometimes referred to as “thermoplastic resin composition”) is supplied from a supply means. Although there is no restriction | limiting in particular as such a supply means, It is preferable to use a die | dye. Moreover, there is no restriction | limiting in particular as a supply method, However, It is preferable to carry out melt extrusion from a die | dye. Prior to melt extrusion, the thermoplastic resin composition is preferably pelletized. Commercially available thermoplastic resins (for example, TOPAS # 6013, Toughlon MD1500, Delpet 980N, DayLark D332, etc.) may be pelletized, but if not pelletized, the raw material of the powder is directly Or put into a twin screw extruder, or the following method can be used.
The thermoplastic resin composition is dried, melted at 150 ° C. to 300 ° C. using a twin-screw kneading extruder, and then extruded into noodles, and solidified in air or water and cut. Further, after melting by an extruder, it can be pelletized by an underwater cutting method in which it is cut while being directly extruded from a die into water. Extruders used for pelletization include single screw extruders, non-meshing different direction rotating twin screw extruders, meshing different direction rotating twin screw extruders, and meshing same direction rotating twin screw extruders. Etc. can be used. The number of revolutions of the extruder is preferably 10 rpm to 1000 rpm, more preferably 20 rpm to 700 rpm. The extrusion residence time is 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes.
No particular limitation is imposed on the size of the pellets is generally about 10mm ³ ~1000mm ^3, more preferably about 30 mm ³ 500 mm ^3.

  It is preferred to reduce the moisture in the pellets prior to melt extrusion. A preferable drying temperature is 40 to 200 ° C, more preferably 60 to 150 ° C. Thereby, the moisture content is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less. Drying may be performed in air, nitrogen, or vacuum.

  Next, the dried pellets are supplied into the cylinder through the supply port of the extruder, and are kneaded and melted. The inside of the cylinder is composed of, for example, a supply unit, a compression unit, and a measurement unit in order from the supply port side. The screw compression ratio of the extruder is preferably 1.5 to 4.5, the ratio of the cylinder length to the cylinder inner diameter (L / D) is preferably 20 to 70, and the cylinder inner diameter is preferably 30 mm to 150 mm. The extrusion temperature of the die (hereinafter also referred to as the discharge temperature) is determined according to the melting temperature of the thermoplastic resin, but generally it is preferably about 190 to 300 ° C. Furthermore, in order to prevent the molten resin from being oxidized by residual oxygen, it is also preferable to carry out the inside of the extruder in an inert (nitrogen or the like) air flow or while evacuating using an extruder with a vent.

  It is preferable to provide a filtration apparatus incorporating a breaker plate type filtration or a leaf type disk filter for filtering foreign matter in the thermoplastic resin composition. Filtration may be performed in one stage or may be performed in multistage filtration. The filtration accuracy is preferably 15 μm to 3 μm, more preferably 10 μm to 3 μm. It is desirable to use stainless steel as the filter medium. As the configuration of the filter medium, a knitted wire, a sintered metal fiber or metal powder (sintered filter medium) can be used, and among them, a sintered filter medium is preferable.

  In order to reduce the fluctuation of the discharge amount and improve the thickness accuracy, it is preferable to provide a gear pump between the extruder and the die. Thereby, the resin pressure fluctuation width in the die can be within ± 1%. In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used.

  The molten resin is melted by the extruder configured as described above, and the molten resin is continuously fed to the die via a filter and a gear pump as necessary. The die may be any of a T die, a fish tail die, and a hanger coat die. It is also preferable to insert a static mixer immediately before the die to increase the uniformity of the resin temperature.

The clearance of the die exit portion is generally 1.0 to 30 times the film thickness, preferably 5.0 to 20 times.
In the manufacturing method of the present invention, the radius of curvature of the tip of the die lip is not particularly limited, and a known die can be used.

It is preferable that the die can be adjusted in thickness at intervals of 5 to 50 mm. An automatic thickness adjustment die that calculates downstream film thickness and thickness deviation and feeds back the results to die thickness adjustment is also effective.
In addition to the single layer film forming apparatus, it is also possible to manufacture using a multilayer film forming apparatus.
Thus, the residence time from when the resin enters the extruder through the supply port until it exits from the die is preferably 3 to 40 minutes, more preferably 4 to 30 minutes.

<Cast>
Next, the melt of the thermoplastic resin is extruded from the die into a film, and the melt-extruded melt is continuously sandwiched between the first sandwiching surface and the second sandwiching surface constituting the sandwiching device, and then cooled and solidified. To obtain a film. At this time, from the viewpoint of stabilization of productivity, one of the first clamping surface and the second clamping surface is peeled off first from the melt, and then the other surface is peeled off from the other surface. preferable.

(pressure)
In the production method of the present invention, in addition to the conventional method of continuously pressing the melt-extruded melt between the first clamping surface and the second clamping surface constituting the clamping device to form a film, A film having a Re of 45 nm or more is produced by narrowing the melt at a pressure of 10 to 150 MPa by the first clamping surface and the second clamping surface. The preferred pressure is 25 to 150 MPa, particularly preferably 30 to 130 MPa.

(Pinch surface)
In the manufacturing method of the present invention, it is preferable that the first clamping surface and the second clamping surface are both made of metal and rigid from the viewpoint of achieving the pressure.

(Movement speed of pinching surface)
In the production method of the present invention, it is preferable that the moving speed of the first pressing surface is faster than the moving speed of the second pressing surface from the viewpoint of increasing the amount of Re expressed and improving the film surface shape.
Further, when there is a difference in the moving speed between the first clamping surface and the second clamping surface, the surface on the side that is first peeled off from the melt may be the first clamping surface or the second clamping surface. From the viewpoint of improving the surface shape by suppressing the peeling dan, it is preferable that the surface to be peeled first is the first clamping surface (a clamping surface having a high moving speed).

In the manufacturing method of the present invention, the moving speed ratio of the first clamping surface and the second clamping surface of the clamping device defined by the following formula (I) is adjusted to 0.6 to 0.99, and the molten resin is sandwiched. It is preferable to apply a larger shear stress when passing through the pressure device from the viewpoint of increasing the amount of Re. The moving speed ratio of the clamping surface is preferably 0.65 to 0.99, and more preferably 0.70 to 0.99. Thus, if the moving speed ratio is 0.70 to 0.99, the surface state of the film can be further improved.
Movement speed ratio = speed of the second clamping surface / speed of the first clamping surface (I)

(Discharge temperature)
In the production method of the present invention, the discharge temperature (the temperature of the melt immediately after the discharge port of the supply means) increases the Re expression level of the obtained film, and improves the moldability of the resin and suppresses deterioration of the film surface. From the viewpoint of improving the shape, Tg + 60 to Tg + 140 ° C. is preferable, Tg + 70 to Tg + 130 ° C. is more preferable, and Tg + 80 to Tg + 120 ° C. is particularly preferable. In particular, when Tg + 60 ° C. or higher, the viscosity of the resin is sufficiently low, so that the moldability is good, and when Tg + 140 ° C. or lower, the resin is hardly deteriorated.
Tg represents the glass transition temperature of the thermoplastic resin contained in the melt, and the glass transition temperature of the thermoplastic resin is measured by placing the resin in a measurement pan using a scanning differential calorimeter (DSC). After raising the temperature from 30 ° C. to 300 ° C. at 10 ° C./min in an air stream (1st-run), cooled to −30 ° C. at −10 ° C./min, and again increased from 30 ° C. to 300 ° C. at 10 ° C./min. Warm (2nd-run). The temperature at which the baseline starts to deviate from the low temperature side in 2nd-run can be obtained as the glass transition temperature (Tg).

(Air gap)
In the manufacturing method of the present invention, the air gap (distance from the discharge port of the supply means to the melt landing point of the pressing device) is as close as possible from the viewpoint of heat retention of the melt between the die and the pressing device. Specifically, it is preferably 200 mm or less, more preferably 20 to 180 mm, and particularly preferably 30 to 160 mm.

(Conveying speed)
The production method of the present invention is characterized in that the transport speed (line speed) is set to 10 to 100 m / min in order to set the Re of the obtained film to 45 nm or more. In this way, by controlling the film conveyance speed and applying a pressure within the range of the present invention between the pressing devices to pinch the film, it is possible to significantly increase the amount of Re in the film. The transport speed is preferably 10 to 80 m / min, more preferably 15 to 60 m / min, and particularly preferably 20 to 40 m / min. When the line speed is increased, cooling of the melt in the air gap can be suppressed, and shearing deformation can be imparted to the melt by the pinching device with the melt temperature being high. Further, by setting the transport speed to 20 to 40 m / min, it is possible to further improve the film touch failure and obtain a film having a good surface shape.
The line speed represents the speed at which the melt passes between the clamping apparatuses and the film conveyance speed in the conveyance apparatus. In addition, in the case of the aspect which forms into a film using two below-mentioned rolls, the speed by which a film is conveyed with a chill roll is represented.

  In the production method of the present invention, the width of the film-like melt is not particularly limited, and can be, for example, 200 to 2000 mm.

(Cast using two rolls)
Among the methods of forming a film by pressing the melt supplied from the supply means continuously between the first pressing surface and the second pressing surface constituting the pressing device, the two rolls (for example, It is preferable to pass between the touch roll (first roll) and the chill roll (second roll). In addition, in this specification, when it has multiple casting rolls which convey the said molten material, the casting roll nearest to the most upstream supply means (die | dye) is also called a chill roll. Hereinafter, the preferable aspect of the manufacturing method of this invention using two rolls is demonstrated.

  In the film production method of the present invention, the landing point of the melt supplied from the supply unit is not particularly limited, and the landing point of the melt supplied from the supply unit, the touch roll, and the cast roll are the most. The distance from the vertical line passing through the midpoint of the gap in the approaching part may be zero or may be shifted. The melt landing point refers to a point where the melt extruded from the supply means (for example, a die) first contacts (landes) the touch roll or chill roll. The midpoint of the gap between the touch roll and the cast roll refers to the midpoint of the touch roll surface and the cast roll surface where the gap between the touch roll and the cast roll is the narrowest.

  The surface of the two rolls (for example, a touch roll or a casting roll) preferably has an arithmetic average height Ra of 100 nm or less, more preferably 50 nm or less, and further preferably 25 nm or less.

  In the production method of the present invention, the width of each of the two rolls is not particularly limited, and can be freely changed and employed according to the width of the film-like melt.

  The roll pressure between the two rolls rotating at different peripheral speeds is 10 to 150 MPa, and the preferable roll pressure range is the same as the preferable range of the pressure between the pressing surfaces of the pressing device.

  In the manufacturing method of the present invention, in order to pressurize the roll pressure in the above range, the cylinder set value is appropriately changed. The cylinder set value varies depending on the resin material used and the material of the two rolls. For example, when the effective width of the film-like melt is 200 mm, it is preferably 3 to 100 KN, and preferably 3 to 50 KN. Is more preferable, and 3 to 25 KN is particularly preferable.

In the production method of the present invention, in order to pressurize the roll pressure in the above range, it is preferable to use a roll having a roll hardness of 45 HS or more. The Shore hardness of the two preferable rolls is preferably 50 HS or more, and more preferably 60 to 90 HS.
The Shore hardness can be determined from the average value of values measured at 5 points in the roll width direction and 5 points in the circumferential direction using the method of JIS Z 2246.

The material of the two rolls is preferably a metal from the viewpoint of achieving the Shore hardness, more preferably stainless steel, and a roll whose surface is plated is also preferred. Moreover, if the material of two rolls is a metal, since the surface unevenness | corrugation is small and the surface of a film is hard to be damaged, it is preferable. On the other hand, a rubber roll or a metal roll lined with rubber can be used if the roll pressure can be achieved.
In the manufacturing method of the present invention, it is preferable that the material of the two rolls is made of metal and is rigid from the viewpoint of achieving the roll pressure.
With respect to the touch roll, for example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, WO97 / 28950, JP-A-2004-216717, JP The thing of 2003-145609 gazette can be utilized.

Furthermore, in the manufacturing method of the present invention, by providing a peripheral speed ratio between two rolls through which the film-like melt passes, a shear stress is applied when the molten resin passes through the two rolls. It is preferable to produce the film. The preferable range of the peripheral speed ratio of the two rolls is the same as the preferable range of the moving speed ratio between the pressing surfaces of the pressing device. Here, the peripheral speed ratio of the two rolls means the peripheral speed of the slow roll / the peripheral speed of the fast roll.
The speed of the two rolls may be higher, but when the touch roll is slow, a bank (residue formed by surplus of the melt staying on the roll) is formed on the touch roll side. Since the touch roll has a short contact time with the melt, the bank formed on the touch roll side cannot be sufficiently cooled, and a peeling dan is generated, which easily causes a surface failure. Therefore, it is preferable that the slow roll is a chill roll (second roll) and the fast roll is a touch roll (first roll).

  Furthermore, in the production method of the present invention, it is preferable to use a roll having a large diameter as each of the two rolls. Specifically, the diameter is 200 to 1500 mm, more preferably 300 mm to 1000 mm, and particularly preferably 350 mm to 800 mm. More preferably, it is preferable to use two rolls of 350 to 600 nm, more preferably 350 to 500 nm. When a roll having a large diameter is used, the contact area between the film-like melt and the roll is increased, and the time required for shearing becomes longer. Therefore, the film of the present invention can be produced while suppressing variations in Re. In the production method of the present invention, the diameters of the two rolls may be the same or different.

  In the manufacturing method of the present invention, the two rolls are driven at different peripheral speeds. The two rolls may be driven or driven independently, but are preferably driven independently in order to suppress Re variation.

  The surface temperatures of the two rolls may be the same or different from the viewpoint of achieving the Re range of the film of the present invention. When giving a temperature difference, a preferable temperature difference is 5 degreeC-80 degreeC, More preferably, it is 20 degreeC-80 degreeC, More preferably, it is 20 degreeC-60 degreeC. At that time, the temperature of the two rolls is Tg−70 ° C. to Tg + 20 ° C., more preferably Tg−50 ° C. to Tg + 10 ° C., more preferably Tg−40 ° C. to Tg + 5 ° C., using the glass transition temperature Tg of the resin. Set to. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through the touch roll.

In the production method of the present invention, the melt is preferably kept warm until the melt is extruded from the die and comes into contact with at least one of the two rolls to reduce the temperature distribution in the width direction. The temperature distribution in the direction is preferably within 5 ° C. In order to reduce the temperature distribution, a member having a heat insulating function or a heat reflecting function is disposed in at least a part of the passage between the melt die and the two rolls to shield the melt from the outside air. Is preferred. Thus, by arranging the heat insulating member in the passage and shielding it from the outside air, it is possible to suppress the influence of the external environment, for example, wind, and to suppress the temperature distribution in the width direction of the film. The temperature distribution in the width direction of the film-like melt is more preferably within ± 3 ° C., and even more preferably within ± 1 ° C.
Furthermore, when the said shielding member is used, since it can pass between rolls in the state with the high temperature of a film-form melt, ie, a state with low melt viscosity, there also exists an effect which is easy to produce the film of this invention.
The temperature distribution of the film-like melt can be measured with a contact thermometer or a non-contact thermometer.

The said shielding member is provided inside the both ends of two rolls, for example, via the width direction side surface of die | dye, and a clearance gap. The shielding plate may be directly fixed to the side surface of the die, or may be supported and fixed by a support member. For example, the width of the shielding member is preferably equal to or greater than the width of the side surface of the die so that the rising airflow due to heat dissipation of the die can be efficiently blocked.
The gap between the shielding member and the end of the film-like melt in the width direction is preferably narrow so as to efficiently shield the rising airflow flowing along the surface of the roll. More preferably, it is about 50 mm from the part. Note that the gap between the side surface of the die and the shielding member is not necessarily provided, but is preferably formed to an extent that allows airflow in the space surrounded by the shielding member to be discharged, for example, 10 mm or less.
In addition, as the material having a heat insulating function and / or a heat reflecting function, a material excellent in wind insulation and heat retention is preferable. For example, a metal plate such as stainless steel can be preferably used.

As a method for eliminating the variation in Re, there is a method of increasing the adhesion when the film-like melt comes into contact with the casting roll. Specifically, the adhesion can be improved by combining electrostatic application method, air knife method, air chamber method, vacuum nozzle method and the like. Such an adhesion improving method may be performed on the entire surface of the film-like melt or may be partially performed.

The surface temperature of the first clamping surface and the second clamping surface is preferably independently Tg-70 ° C. to Tg + 20 ° C. based on the glass transition temperature Tg of the thermoplastic resin used, Tg + 10 ° C. is more preferable, and Tg−40 ° C. to Tg + 5 ° C. is particularly preferable.
On the other hand, when the manufacturing method of the present invention includes a heating step and a second pinching step described later, the surface temperatures of the first pinching surface and the second pinching surface are preferably Tg or less, and Tg-40 ° C. It is more preferably ~ Tg ° C, particularly preferably Tg-30 ° C to Tg ° C. Such temperature control can be achieved by a known method.

<Heating and second clamping step>
In the manufacturing method of the present invention, the step of heating the film formed in the first clamping step and the second step of constricting the heated film between two constricting surfaces arranged opposite to each other and having different moving speeds. The first clamping step and the second narrowing step are preferably performed in-line. By including the heating step and the second clamping step in this way, the value of | Re [40 °] −Re [−40 °] | is not 0 while maintaining the range of Re of the present invention. A retardation film having a structure can be obtained.

In addition, a heating process here means the process of heating a film so that it may become the temperature more than the surface temperature of said 1st clamping surface and said 2nd clamping surface. Moreover, there is no restriction | limiting in particular as a heating method, It can heat using a well-known heating apparatus, for example, can heat a film by applying a warm air with a heater.
In addition, the term “in-line” as used herein means that the pressing step by the first pressing surface and the second pressing surface, the heating step, and the second pressing step are all processes and an integrated film forming step. Say to do.

In the production method of the present invention, the surface temperature of the first clamping surface and the second clamping surface is Tg or less, and the heating temperature in the heating step is Tg-10 ° C to Tg + 20 ° C. It is preferable from the viewpoint.
The heating step is more preferably Tg-10 ° C to Tg + 15 ° C, and particularly preferably Tg-5 ° C to Tg + 10 ° C.

The clamping surface used in the second narrowing step can be independently the same as the first clamping surface or the second clamping surface, and the temperature, moving speed, and clamping pressure are also the same. This is the same as the one clamping surface or the second clamping surface.
The second narrowing step may be performed once or a plurality of times.

  In particular, one of the pressing surfaces used in the second narrowing step may be the same pressing surface as one of the first pressing surface or the second pressing surface. In this case, it is preferable that one of the pressing surfaces used in the second narrowing step is a pressing surface on the side of the first pressing surface or the second pressing surface that will be separated from the film later, for example, a touch roll When chill rolls (cast rolls) are used as the first and second pressing surfaces, respectively, it is preferable that one of the pressing surfaces used in the second narrowing step is a chill roll.

  When one of the clamping surfaces used in the second narrowing step is the same clamping surface as one of the first clamping surface or the second clamping surface, the heating step includes the first clamping surface or the second clamping surface. A step of being heated by one of the clamping surfaces may be included. That is, when the surface temperature of said 1st clamping surface and said 2nd clamping surface and the heating temperature of the said heating process are equal, it is one of the preferable aspects of the manufacturing method of this invention, and a heating and 2nd clamping process It corresponds to the aspect containing.

<Post-processing>
After film formation in this way, it is preferable to cool the film by using one or more casting rolls in addition to two rolls (for example, a casting roll and a touch roll) that allow the film-like melt to pass through. The touch roll is usually arranged so as to touch the first casting roll on the most upstream side (closer to the die). In general, it is relatively common to use three cooling rolls, but this is not a limitation. The interval between the plurality of casting rolls is preferably 0.3 mm to 300 mm, more preferably 1 mm to 100 mm, and even more preferably 3 mm to 30 mm between the surfaces.

  Further, it is preferable to trim both ends of the processed film. The portion cut off by trimming may be crushed and used again as a raw material. Further, it is also preferable to perform a thickness increasing process (knurling process) on one or both ends. The height of the unevenness due to the thickness increasing process is preferably 1 μm to 50 μm, more preferably 3 μm to 20 μm. Thickening processing may be convex on both sides or convex on one side. The width of the thickness increasing process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm. Thickness processing can be performed at room temperature to 300 ° C.

  Prior to winding, it is also preferable to attach a laminated film on one or both sides of the film. The thickness of the laminated film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The material is not particularly limited, such as polyethylene, polyester, and polypropylene.

  The winding tension is preferably 2 kg / m width to 50 kg / m width, more preferably 5 kg / m width to 30 kg / m width.

  The film thickness of the film obtained by the production method of the present invention is preferably 20 to 80 μm. When used for a liquid crystal display or the like, the thickness is more preferably 20 to 70 μm, and particularly preferably 20 to 60 μm from the viewpoint of thinning.

<Third clamping step (nip clamping process after film formation)>
In the production method of the present invention, the obtained film is further subjected to a third pinching step (hereinafter referred to as a pinching step after film formation) in which the film is confined between two narrow pressure surfaces arranged opposite to each other and having different moving speeds. And the third clamping step is preferably performed on a line different from the line of the first clamping step. Thus, by including the nipping treatment step after film formation, the value of | Re [40 °] −Re [−40 °] | is not 0 while maintaining the range of Re of the present invention. A retardation film having a structure can be obtained.
The pressure-clamping surface used in the pressure-clamping treatment step after film formation can be the same as the first pressure-clamped surface or the second pressure-clamped surface, and its temperature, moving speed, and movement between the pressure-clamped surfaces can be used independently. The speed ratio and the clamping pressure are the same as those of the first clamping surface or the second clamping surface.
In the manufacturing method of the present invention, it is preferable that in the second clamping step or the third clamping step, the two narrow pressure surfaces that are arranged opposite to each other and have different moving speeds are two rolls having different circumferential speeds. .
Further, in the third pinching step, for example, a pinching device having a known configuration that is used as a nip roll when performing stretching in the film transport direction in the field of manufacturing an optical film can be used. The manufacturing method of the invention is not limited to such an embodiment.
Further, in this specification, the name “third” clamping step simply means the third type of clamping pressure and does not mean that the order of the steps is the third. In the manufacturing method of the present invention, the third clamping step may be performed after the first clamping step, or after the second clamping step is performed after the first clamping step. Further, the third clamping step may be performed.
In addition, the clamping process step after film formation may be performed once or a plurality of times.

<Stretching and relaxation treatment>
Furthermore, after film formation by the above method, stretching and / or relaxation treatment may be performed. For example, each process can be implemented by the following combinations (a) to (g).
(A) transverse stretching (b) transverse stretching → relaxation treatment (c) longitudinal stretching (d) longitudinal stretching → relaxation treatment (e) longitudinal (transverse) stretching → lateral (longitudinal) stretching (f) longitudinal (transverse) stretching → lateral (Longitudinal) stretching → relaxation treatment (g) Transverse stretching → relaxation treatment → longitudinal stretching → relaxation treatment Among these, the steps (a) to (d) are particularly preferable.

The transverse stretching can be performed using a tenter. That is, the film is stretched by holding both ends in the width direction with clips and widening the film in the lateral direction. At this time, the stretching temperature can be controlled by sending wind at a desired temperature into the tenter. The stretching temperature is preferably Tg-10 ° C to Tg + 60 ° C, more preferably Tg-5 ° C to Tg + 45 ° C, and further preferably Tg-10 ° C to Tg + 20 ° C or less. Moreover, a preferable lateral stretch ratio is 1.2 to 3.0 times, more preferably 1.2 to 2.5 times, and still more preferably 1.2 to 2.0 times.
By performing preheating before stretching and heat setting after stretching, the Re and Rth distribution after stretching can be reduced, and the variation in orientation angle associated with bowing can be reduced. Either preheating or heat setting may be performed, but both are more preferable. These preheating and heat setting are preferably performed by holding with a clip, that is, preferably performed continuously with stretching.
The preheating can be performed at a temperature about 1 ° C to 50 ° C higher than the stretching temperature, preferably 2 ° C to 40 ° C or less, more preferably 3 ° C to 30 ° C. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During preheating, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to ± 10% of the width of the unstretched film.
The heat setting can be performed at a temperature lower by 1 ° C. to 50 ° C. than the stretching temperature, more preferably 2 ° C. to 40 ° C., further preferably 3 ° C. to 30 ° C. More preferably, it is below the stretching temperature and below Tg. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to 0% (the same width as the tenter width after stretching) to −10% (reduced by 10% from the tenter width after stretching = reduced width) of the tenter width after stretching. If the width is wider than the stretched width, residual strain tends to occur in the film, which is not preferable.

Longitudinal stretching can be achieved by making the peripheral speed on the outlet side faster than the peripheral speed on the inlet side while heating between two pairs of rolls. Under the present circumstances, the expression of the retardation of the thickness direction can be changed by changing the space | interval (L) between and the film width (W) before extending | stretching. When L / W (referred to as aspect ratio) is 2 to 50 or less (long span stretching), it is easy to produce a film having a small Rth. When L / W is 0.01 to 0.3 (short span), a film having a large Rth is used. Can be created. In this embodiment, any of long span stretching, short span stretching, and a region between them (intermediate stretching = L / W is more than 0.3 and 2 or less) may be used. Span stretching and short span stretching are preferred. Furthermore, when aiming at high Rth, it is more preferable to use short span stretching, and when aiming at low Rth, it is distinguished from long span stretching.
The stretching temperature is preferably Tg-10 ° C to Tg + 60 ° C, more preferably Tg-5 ° C to Tg + 45 ° C, and further preferably Tg-10 ° C to Tg + 20 ° C or less. Moreover, a preferable longitudinal stretch ratio is 1.2 to 3.0 times, more preferably 1.2 to 2.5 times, and still more preferably 1.2 to 2.0 times.

Furthermore, dimensional stability can be improved by performing relaxation treatment after these stretching. Thermal relaxation is preferably performed either after film formation, after longitudinal stretching, or after lateral stretching, or both. The relaxation treatment may be performed online continuously after stretching, or may be performed offline after winding after stretching.
Thermal relaxation is (Tg-30) ° C to (Tg + 30) ° C, more preferably (Tg-30) ° C to (Tg + 20) ° C, and more preferably (Tg-15) ° C to (Tg + 10) ° C for 1 second to 10 minutes. More preferably 5 seconds to 4 minutes, still more preferably 10 seconds to 2 minutes, 0.1 kg / m to 20 kg / m, more preferably 1 kg / m to 16 kg / m, still more preferably 2 kg / m to 12 kg / m. It is preferable to carry out while conveying with tension.

[Polarizer]
The polarizing plate of the present invention can be obtained by laminating at least a polarizer (hereinafter also referred to as a polarizing film) on the film of the present invention. Hereinafter, the polarizing plate of the present invention will be described. Examples of the polarizing plate of the present invention include a polarizing plate formed on the surface of a polarizing film for the purpose of two functions of a protective film and viewing angle compensation, and a composite polarizing plate laminated on a protective film such as TAC. Can be mentioned.

  If the polarizing plate of this invention uses the film and polarizer of this invention, there will be no restriction | limiting in particular in a structure. For example, when the polarizing plate of the present invention is composed of a polarizer and two polarizing plate protective films (transparent polymer films) that protect both sides of the polarizer, the film of the present invention may be used as at least one polarizing plate protective film. it can. Moreover, the polarizing plate of this invention may have an adhesive layer for sticking with another member in the at least one surface. Moreover, in the polarizing plate of this invention, if the surface of the film of this invention is an uneven | corrugated structure, it will have an anti-glare (anti-glare) function. Further, the polarizing plate of the present invention has an antireflection film of the present invention in which an antireflection layer (low refractive index layer) is further laminated on the surface of the film of the present invention, and further optical anisotropy on the surface of the film of the present invention. It is also preferable to use the optical compensation film of the present invention in which layers are laminated.

  In general, a liquid crystal display device includes four polarizing plate protective films because a liquid crystal cell is provided between two polarizing plates. The film of the present invention may be used for any of the four polarizing plate protective films, but the film of the present invention is particularly advantageous as a protective film disposed between a liquid crystal cell and a polarizing plate in a liquid crystal display device. Can be used.

  The polarizing plate of the present invention more preferably has a configuration in which a cellulose acylate film, a polarizer and a film of the present invention are laminated in this order. Moreover, the structure which the cellulose acylate film, the polarizer, the film of this invention, and the adhesive layer are laminated | stacked in this order is also more preferable.

(Optical film)
The film of the present invention is used for the optical film of the polarizing plate of the present invention. In addition, the film can be surface-treated. Examples of the surface treatment method include methods such as corona discharge, glow discharge, UV irradiation, and flame treatment.

(Cellulose acylate film)
As the cellulose acylate film of the polarizing plate of the present invention, a known cellulose acylate film for a polarizing plate is used. For example, a known triacetyl cellulose (TAC) film (for example, Fujitac T-60 manufactured by Fuji Film Co., Ltd.) can be preferably used. The lurose acylate film may be surface treated. Examples of the surface treatment method include saponification treatment.

(Polarizer)
As the polarizer, for example, a film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution can be used.

  As the polarizer used in the present invention, any appropriate one can be selected as long as the object of the present invention can be achieved. Examples of the polarizer include a uniaxially stretched film obtained by adsorbing a dichroic substance such as iodine or a dichroic dye on a hydrophilic polymer film, a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product. And polyene-based oriented films. Examples of the hydrophilic polymer film include a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene / vinyl acetate copolymer partially saponified film. In the present invention, a polarizer in which iodine is adsorbed on a polyvinyl alcohol film is preferable.

  The polarizer preferably further contains at least one of potassium and boron. When the polarizer contains potassium and boron, a polarizer (polarizing plate) having a composite elastic modulus (Er) in a preferable range and having a high degree of polarization can be obtained. For production of a polarizer containing at least one of potassium and boron, for example, a film which is a material for forming a polarizer may be immersed in a solution of at least one of potassium and boron. The solution may also serve as a solution containing iodine.

  Any appropriate molding method can be adopted as a method for obtaining the polyvinyl alcohol film. A conventionally known method can be applied as the molding method. Moreover, a commercially available film can be used as it is for the polyvinyl alcohol film. Examples of commercially available polyvinyl alcohol films include the product name “Kuraray Vinylon Film” manufactured by Kuraray Co., Ltd., the product name “Tosero Vinylon Film” manufactured by Tosero Co., Ltd., and the product manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Names include “Nippon Vinylon Film”.

  Regarding an example of a method for producing a polarizer, for example, a polymer film (raw film) mainly composed of a polyvinyl alcohol resin is immersed in a swelling bath containing pure water and a dyeing bath containing an aqueous iodine solution. Swelling treatment and dyeing treatment are performed while applying tension in the film longitudinal direction with different rolls. Next, the film subjected to the swelling treatment and the dyeing treatment is immersed in a crosslinking bath containing potassium iodide, and is subjected to crosslinking treatment and final stretching treatment while tension is applied in the longitudinal direction of the film with rolls having different speed ratios. Is given. The film subjected to crosslinking treatment is immersed in a washing bath containing pure water by a roll and subjected to a washing treatment. The film subjected to the water washing treatment is dried and wound up after adjusting the moisture content. Thus, the polarizer can be obtained by stretching the original film, for example, 5 to 7 times the original length.

  The polarizer may be subjected to any surface modification treatment in order to improve the adhesion with the adhesive. Examples of the surface modification treatment include corona treatment, plasma treatment, glow discharge treatment, flame treatment, ozone treatment, UV ozone treatment, and ultraviolet treatment. These treatments may be used alone or in combination of two or more.

(Adhesive layer)
The polarizing plate of the present invention may have an adhesive layer as at least one of the outermost layers (such a polarizing plate may be referred to as an adhesive polarizing plate). As a particularly preferred embodiment, a pressure-sensitive adhesive layer for adhering to another member such as another optical film or a liquid crystal cell can be provided on the side of the optical film where the polarizer is not adhered.

(Production method of polarizing plate)
The manufacturing method of the polarizing plate of this invention is demonstrated.
The polarizing plate of the present invention can be produced by bonding one side of the film of the present invention (a surface-treated surface in the case of surface treatment) to at least one side of the polarizer using an adhesive. When the cellulose acylate film, the polarizer and the film of the present invention are bonded together in this order, the polarizing plate of the present invention can be produced by laminating the polarizer and other films using an adhesive on both sides of the polarizer. . In the manufacturing method of the polarizing plate of this invention, it is preferable that the film of this invention is directly bonded with the polarizer.

  As the adhesive, a known polarizing plate production adhesive can be used. Moreover, the aspect which has an adhesive bond layer between the said polarizer and each film is also preferable. Specific examples of the adhesive include an aqueous solution of polyvinyl alcohol or polyvinyl acetal (eg, polyvinyl butyral) and a latex of a vinyl-based polymer (eg, polybutyl acrylate). A particularly preferred adhesive is an aqueous solution of fully saponified polyvinyl alcohol. The polyvinyl alcohol-based adhesive preferably contains a polyvinyl alcohol-based resin and a crosslinking agent.

  The manufacturing method of the polarizing plate of this invention is not limited to said method, Another method can also be used. For example, JP 2000-171635, JP 2003-215563, JP 2004-70296, JP 2005-189437, JP 2006-199788, JP 2006-215463, JP 2006-227090. JP, 2006-243216, JP 2006-243681, JP 2006-259313, JP 2006-276574, JP 2006-316181, JP 2007-10756, JP 2007-128025, Use methods described in JP 2007-140092, JP 2007-171943, JP 2007-197703, JP 2007-316366, JP 2007-334307, JP 2008-20891, etc. it can. Among these, the methods described in JP2007-316366A and JP2008-20891A are more preferable.

  It is preferable that a protective film is also attached to the other surface of the polarizing film, and the protective film may be the film of the present invention. Moreover, the various films conventionally used as a protective film of a polarizing plate, such as a cellulose acylate film and a cyclic polyolefin polymer film, can be used.

  The polarizing plate of the present invention thus obtained is preferably used in a liquid crystal display device, and may be provided on either the viewing side or the backlight side of the liquid crystal cell, or on both sides. Not. Specific examples of the image display device to which the polarizing plate of the present invention can be applied include a self-luminous display device such as an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED: Field Emission Display). Can be mentioned. The liquid crystal display device is applied to a transmissive liquid crystal display device, a reflective liquid crystal display device, and the like.

[Liquid Crystal Display]
The film and polarizing plate of the present invention can be used for liquid crystal display devices of various modes, and the liquid crystal display device of the present invention can be obtained. Preferably, it can be used for a TN (twisted nematic), OCB (optically compensatory bend), or ECB (electrically controlled birefringence) mode liquid crystal display device, and more preferably for a TN or ECB mode liquid crystal display.

  The present invention will be described more specifically with reference to the following 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 is not limited to the specific examples shown below.

Production Example 1 Production of Cyclic Olefin Copolymer Pellets As the cyclic olefin copolymer (COC), pellets of “TOPAS # 6013” manufactured by Polyplastics were used. “TOPAS # 6013” indicates positive intrinsic birefringence. The glass transition point of the resin was 136 ° C.

[Production Example 2] Manufacture of polycarbonate pellets As polycarbonate (PC), pellets of "Taflon MD1500" manufactured by Idemitsu Kosan Co., Ltd. were used. “Taflon MD1500” exhibits positive intrinsic birefringence. Moreover, the glass transition point of the said resin was 150 degreeC.

[Example 1]
(Production of film)
Using a pellet of the cyclic olefin copolymer TOPAS # 6013 (COC) listed in Table 1 below as a thermoplastic resin, drying at 100 ° C. for 2 hours or more, melting at 260 ° C., and kneading using a single screw kneading extruder And extruded. At this time, a screen filter, a gear pump, and a leaf disk filter were arranged in this order between the extruder and the die, and these were connected by a melt pipe. This was extruded from a die having a width of 450 mm and a lip gap of 0.7 mm at the extrusion temperature (discharge temperature) shown in Table 1 below.
Thereafter, a melt (molten resin) was extruded between the cast roll and the touch roll. At this time, a cylinder was set on the most upstream side cast roll (chill roll) having a width of 1800 mm and a diameter of 300 mm so that the touch pressure described in Table 1 was obtained, and a touch roll having a width of 200 mm and a diameter of 200 mm was brought into contact. The touch pressure was measured by sandwiching a prescale for medium pressure (manufactured by FUJIFILM Corporation) between two rolls at a constant circumferential speed (5 m / min) in the absence of melt, and the value was measured during film formation. Pressure was used. The roll temperature during pressure measurement was 25 ° C. In addition, the melt was dropped on the central part sandwiched between the cast roll and the touch roll. The touch roll and chill roll were made of material S45C with a mirror finish of 0.1S, HCr plating treatment, a rigid material outer cylinder thickness of 20 mm, and a shore hardness of 60 HS. Using these rolls, the peripheral speed ratio between the touch roll and the chill roll (peripheral speed ratio = chill roll speed / touch roll speed) is set to the conditions shown in Table 1 below, and the distance between the die and the melt landing point is shown in Table 1 below. It set to the description distance, and formed into a film with the conveyance speed (chill roll speed) of Table 1 below. The temperature of the touch roll and chill roll was Tg-5 ° C. The film forming atmosphere was 25 ° C. and 60%.
Then, after trimming both ends (5 cm each of the full width) immediately before winding, thicknessing (knurling) with a width of 10 mm and a height of 20 μm was applied to both ends. The film forming width was 200 mm and the film was wound up by 450 m. The thickness of the film after film formation was set to the thickness shown in the following Table 1, and the film of Example 1 was produced.

(Optical properties of the film)
The optical properties of the obtained film of Example 1 are also shown in Table 1. Note that Re was measured based on the method described above.

(Film surface)
The surface condition of the obtained film of Example 1 was evaluated according to the following criteria, and the results are shown in Table 1 below.
As an evaluation of the surface condition of the film, the touch-miss failure area was measured according to the measurement method described below. A film (total width of film formation × 1 m in the flow direction) is placed in parallel with the screen with a space of 10 mm in front of the white screen. Using a point light source, a point light source generator (for example, a slide projector, Color Cabin III manufactured by Cabin Kogyo Co., Ltd.) is used to project light toward the film. At that time, the touch-missing area of the film projected on the screen was determined by dimensional measurement, and converted to a film unit area (1 m ² ) to determine the touch-missing failure rate. In addition, the said touch omission failure part means the part which is in the state of the line along the boundary of the area | region which the touch roll is contacting, and the area | region which is not contacting.
○: Touch failure failure area is less than 0.01%, and the surface shape is very good.
Δ: Touch failure failure area is 0.01% or more and less than 0.1%, and the surface shape is good.
X: Touch failure failure area is 0.1% or more, and the surface shape is poor.

[Examples 2-31, Comparative Examples 1-9]
Films of Examples and Comparative Examples were obtained in the same manner as in Example 1 except that the resin used and the film forming conditions were changed as described in Tables 1 and 2 below. Tables 1 and 2 below show the optical properties and surface states of the films of the examples and comparative examples.

From Table 1 and Table 2, all the films of Examples 1 to 31 obtained by the production method of the present invention have a film thickness of 20 to 80 μm and an in-plane retardation Re of 45 nm or more. There was found. First, Comparative Examples 1 to 5 and Examples 1 to 4 are for examining the conveyance speed, and the films of Comparative Examples 1 to 5 are all sandwiched with a high pressure within the range of the present invention. In either case, Re did not exceed 45 nm. On the other hand, it was found that when the conveyance speed exceeded 10 m / min, the amount of Re was rapidly increased, and this tendency was unexpectedly significant. Next, Comparative Example 6, Examples 2 and 5 to 9 were those in which the touch pressure was examined, and although Comparative Example 6 was formed in the range of the conveyance speed of the present invention, Comparative Example 6 had an Re of 45 nm. Did not exceed. On the other hand, it was found that when the pressure exceeds 10 MPa, the expression amount of Re increases rapidly. In Comparative Example 7 and Example 1, the touch roll method for pinching with two pinching surfaces and the casting method for cooling and solidifying the molten resin without pinching on one casting roll were studied. The method showed that Re does not exceed 45 nm. In Comparative Examples 8 and 9 and Examples 28 to 31, when the polycarbonate resin was used, the conveyance speed was examined, and all of them were clamped at a high pressure within the range of the present invention, but Comparative Example 8 was used. None of the films No. 9 and No. 9 exceeded Re of 45 nm. On the other hand, as in the case of the cyclic olefin resin, it was found that when the conveyance speed exceeded 10 m / min, the amount of Re was rapidly increased, and this tendency was unexpectedly significant.
As described above, according to the manufacturing method of the present invention, the film thickness is 20 to 80 μm and the in-plane direction letter is obtained by setting the clamping pressure within the range of the present invention and the conveyance speed within the range of the present invention. It was found that a film having a foundation Re of 45 nm or more can be produced. If Re is 45 nm or more, it can be suitably used as an optical compensation film for liquid crystal display devices.
Furthermore, in the more preferable aspect of this invention, it turned out that generation | occurrence | production of touch omission failure can be suppressed notably. By improving such touch failure, an optical film with high display visibility and high uniformity of retardation can be obtained.
Further, the CAP resin described in Example 1 of JP-A-2006-348123, “Delpet 980N” which is a styrene-acrylic resin manufactured by Asahi Kasei Chemicals Corporation, and Example 1 of JP-A-2007-171914 As a result of the same examination with the modified polyester resin, the effect of the present application could be obtained similarly.

[Example 201]
(Production of film in a mode including the first clamping step and the second clamping step (1))
The film of Example 201 was manufactured using the pinching apparatus arrange | positioned so that the 1st touch roll and the 2nd touch roll could pinch | melt molten resin in order with respect to the most upstream chill roll, respectively. The angle between the line segment connecting the most upstream chill roll center and the first touch roll center and the line segment connecting the most upstream chill roll center and the second touch roll center is 90 degrees. The second touch roll was a mirror finish 0.1S made of HCr plating on the material S45C, a rigid material outer cylinder thickness of 20 mm, a Shore hardness of 60 HS, a width of 200 mm, and a diameter of 100 mm.
The resin used, the extrusion conditions, and the film forming conditions of the most upstream chill roll and the first touch roll are the same as in Example 3 of Table 1, and are further sandwiched between the most upstream chill roll and the first touch roll. The formed film is heated between the first touch roll and the second touch roll using an infrared heater as a heating device so that the film temperature becomes 141 ° C. (Tg + 5 ° C.), and the heated film is the most upstream The film of Example 201 was obtained by continuously passing between the chill roll and the second touch roll. The pressure applied to the film was adjusted to 100 MPa by the most upstream chill roll and the second touch roll, and the second touch roll was adjusted to a roll speed of 45 m / min and a roll temperature of 145 ° C.
As a result of analyzing the obtained film, a film having an anisotropy of Re [0 °] = 125 nm, Re [40 °] = 180 nm, Re [−40 °] = 26 nm and a thickness of 80 μm was obtained. all right. Re [40 °] and Re [−40 °] were measured by the method described in this specification.

[Example 202]
(Production of film in a mode including the first clamping step and the second clamping step (2))
The resin used, the extrusion conditions, and the film forming conditions of the most upstream chill roll and first touch roll were the same as in Example 10 of Table 1, and the speed of the second touch roll of Example 201 was changed from 45 m / min to 12 m / min. In the same manner except that the film is changed to, the film formed by pressing the uppermost chill roll and the first touch roll is continuously passed between the uppermost chill roll and the second touch roll. Thus, a film of Example 202 was obtained.
As a result of analyzing the obtained film, a film having an anisotropy of Re [0 °] = 49 nm, Re [40 °] = 61 nm, Re [−40 °] = 25 nm and a thickness of 80 μm was obtained. all right.

[Example 301]
(Production of film in an embodiment including a first clamping step and a third clamping step (a clamping treatment step after film formation))
The film prepared in Example 3 was passed between roll 1 (roll speed 2.8 m / min, roll temperature 145 ° C.) and roll 2 (roll speed 1.9 m / min, roll temperature 145 ° C.) arranged opposite to each other. Thus, a film of Example 301 was obtained. The roll 1 was made of a material S45C having a mirror finish of 0.1S and having a mirror finish of 0.1S, a rigid material outer cylinder thickness of 20 mm, a Shore hardness of 60 HS, a width of 200 mm, and a diameter of 200 mm. The roll 2 was made of a material S45C with a mirror finish of HCr plating of 0.1S, a rigid material outer cylinder thickness of 20 mm, a Shore hardness of 60 HS, a width of 200 mm, and a diameter of 200 mm. The force applied to the film by the roll 1 and the roll 2 was adjusted to 100 MPa.
As a result of analyzing the obtained film, it was found that a film having an anisotropy of Re [0 °] = 132 nm, Re [40 °] = 165 nm, Re [−40 °] = 44 nm and a thickness of 80 μm was obtained. all right. Re [40 °] and Re [−40 °] were measured by the method described in this specification.

[Example 401 and comparative example 401]
(Preparation of polarizing plate)
A polarizing plate was produced using the produced film of Example 201 and the film of Comparative Example 1. Specifically, first, iodine was adsorbed to a stretched polyvinyl alcohol film to prepare a polarizing film. Using this polarizing film, an TAC film of 80 μm (manufactured by FUJIFILM), a uniaxially stretched norbornene polymer film, and a λ / 2 plate of Re = 270 nm, the arrangement shown in FIG. Or the film of the comparative example 1 was bonded together. In this manner, two polarizing plates PL1 using the film of Example 201 and two PL2 using the film of Comparative Example 1 were produced.

(Production and evaluation of transflective ECB mode liquid crystal display)
Next, an ECB type transflective liquid crystal display device was manufactured using the polarizing plate. The liquid crystal cell used uses ZLI-1695 (manufactured by Merck) as the liquid crystal material, and the liquid crystal layer thickness is 2.4 μm in the reflective electrode region (reflective display portion) and 4.9 μm in the transmissive electrode region (transmissive display portion). did. The pretilt angle at the substrate interface of the liquid crystal layer was 2 degrees, and Δnd of the liquid crystal cell was about 150 nm for the reflective display portion and about 320 nm for the transmissive display portion.
The two types of polarizing plates prepared above were arranged above and below the liquid crystal cell as shown in FIG. The arrows in the polarizing plates P1 and P2 indicate the respective absorption axes, the arrows in the retardation film indicate the respective slow axes, and the arrows of the ECB cells indicate the rubbing direction of the rubbing treatment applied to the respective facing surfaces. Here, the 12 o'clock direction is 0 ° and the clockwise direction is +.

With respect to the liquid crystal display device LCD1 which is an embodiment of the present invention, a viewing angle with a contrast ratio of 10 or more in monochrome display was obtained, and the LCD 1 achieved a viewing angle of 280 ° or more in any of the left, right, top and bottom directions. On the other hand, in the LCD 2 using the film of the comparative example, the viewing angle with a contrast ratio of 10 or more was less than 260 ° in any of the upper, lower, left and right directions.
Thus, when the film of the present invention is used, a large viewing angle compensation can be performed when incorporated in a liquid crystal display device.

10 Die 11 (First) Touch Roll 12 (First) Chill Roll 13 Lip Adjustment Bolt 14 Cellulose Acylate Resin-Containing Composition 15 Second Touch Roll 16 Heating Device

Claims (17)

A supply step of supplying a molten resin containing a thermoplastic resin from a supply means, and continuously passing the melt supplied between the first clamping surface and the second clamping surface constituting the clamping device into a film form A method for producing a film, comprising: a first clamping step to be molded into a step; and a step of conveying the molded film,
The melt is narrowed at a pressure of 10 to 150 MPa by the first clamping surface and the second clamping surface,
The manufacturing method of the film which conveys the said film at 10-100 m / min.   The method for producing a film according to claim 1, wherein the first clamping surface and the second clamping surface are both made of metal and rigid.   The method for producing a film according to claim 1 or 2, wherein the temperature of the melt immediately after the discharge port of the supply means is (Tg + 60 ° C) to (Tg + 140 ° C). The glass transition temperature of the resin (unit: ° C).   The method for producing a film according to any one of claims 1 to 3, wherein a distance from a discharge port of the supply unit to a melt landing point of the clamping device is 200 mm or less.   The method for producing a film according to any one of claims 1 to 4, wherein the moving speed of the first pressing surface is made faster than the moving speed of the second pressing surface. The moving speed ratio between the first clamping surface and the second clamping surface of the clamping device defined by the following formula (I) is 0.6 to 0.99. The method for producing a film according to one item.
Movement speed ratio = Speed of the second clamping surface / Speed of the first clamping surface (I)   The method for producing a film according to any one of claims 1 to 6, wherein the pressing device is two rolls having different peripheral speeds.   The method for producing a film according to any one of claims 1 to 7, wherein the formed film has a thickness of 20 to 80 µm.   The method for producing a film according to any one of claims 1 to 8, wherein the thermoplastic resin contains at least one of a cyclic olefin resin and a polycarbonate resin. Heating the film formed in the first clamping step;
Including a second constriction step of constricting the heated film between two constricted surfaces opposed to each other and having different moving speeds;
The method for producing a film according to claim 1, wherein the first clamping step and the second narrowing step are performed in-line.   The surface temperature of said 1st clamping surface and said 2nd clamping surface is Tg or less, The heating temperature of the said heating process is Tg-10 degreeC-Tg + 20 degreeC, The manufacture of the film of Claim 10 characterized by the above-mentioned. Method (however, Tg represents the glass transition temperature (unit: ° C.) of the thermoplastic resin). Including a third clamping step of confining between two constricting surfaces arranged opposite to each other and having different moving speeds,
The method for producing a film according to any one of claims 1 to 11, wherein the third clamping step is performed on a line different from the line of the first clamping step.   13. The two narrow pressure surfaces that are arranged opposite to each other and have different moving speeds in the second pressing process or the third clamping process are two rolls having different peripheral speeds. Film manufacturing method.   A film manufactured by the method for manufacturing a film according to claim 1.   The film according to claim 14, wherein the film has a thickness of 20 to 80 μm, and a retardation Re in the in-plane direction of the film at a wavelength of 550 nm is 20 to 400 nm.   A polarizing plate comprising a polarizer and the film according to claim 14 or 15.   A liquid crystal display device comprising the film according to claim 14.

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