JP2010234747A - Film and method for manufacturing the same, optical compensation film for liquid crystal display panel, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermoplastic film which has large retardation development and an inclined structure, has an inclined azimuth in one direction of the slow phase axis direction and the fast phase axis direction on a film surface, and has an excellent plane shape. <P>SOLUTION: The method for manufacturing a thermoplastic film includes the process for forming in a film shape by passing and continuously clamping a molten material of a composition containing a thermoplastic resin between a first clamping surface and a second clamping surface constituting a clamping device, wherein at least one of the first clamping surface and the second clamping surface is elastic, a moving speed of the first clamping surface is made higher than that of the second clamping surface, and in a releasing point of a clamping surface which is released from the molten material earlier among the first clamping surface and the second clamping surface, slipperiness of the molten material from the clamping surface is reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a film. The present invention also relates to a film produced by the production method, a polarizing plate having the film, and a liquid crystal display device.

  In recent years, various films have been developed with the rise of the liquid crystal display market. For example, Patent Documents 1 to 4 disclose tilted retardation films.

For example, in Patent Document 1 (Japanese Patent Laid-Open No. 6-222213), by passing a film between two rolls having different peripheral speeds, a shearing force is applied to the film, and a film with an inclined optical axis is created. A method and application to a TN liquid crystal display is described. However, the method described in this document has problems such as large variations in optical properties of the film and easy contact scratches on the film surface. On the other hand, in patent documents 2-4, the above-mentioned problem can be solved by giving a shearing force to a thermoplastic resin melt (hereinafter also referred to as a melt) using a touch belt or an elastic touch roll. Is described.
However, merely using an optical film having an inclined optical axis for a liquid crystal display does not provide an effect of optical compensation when incorporated in a liquid crystal display device. That is, it is necessary for the optical compensation film that the retardation of the film is large and that the inclined structure is large. From such a viewpoint, the methods described in Patent Documents 2 to 4 are not satisfactory in practical use because the touch pressure applied to the melt is low, and the expression of the retardation of the film and the gradient structure are both small. .

JP-A-6-222213 JP 2002-365428 A JP 2007-38646 A JP 2003-25414 A

  The present inventors examined applying high linear pressure and high shearing force to the melt in order to develop a higher retardation and inclined structure. As a result, it has been found that both the expression of retardation and the inclined structure of the obtained film can be improved, and further studies have been made. As a result, it has been found that a problem of frequent scratches on the film surface occurs when a high linear pressure and a high shear force are applied. Furthermore, when high linear pressure and high shear force were applied and a thin film (for example, 100 μm or less) was formed, it was found that scratches occur more frequently. In particular, in the method of using the touch belt or the elastic touch roll described in Patent Documents 2 to 4 as one clamping surface of the clamping device, the melt is long to be clamped by the touch belt or the elastic touch roll. It has been found that the thin film is easily cooled, the melt shrinks, the adhesion with the clamping device is weakened, and local slip is likely to occur. For example, in the methods described in Patent Documents 2 to 4, when the pressure is controlled so that a large shear stress is simply applied, the melt surface is rubbed at the time of pinching, and scratches are generated, resulting in a film obtained. Was found to have no optical performance satisfactory for practical use. That is, when a film having a large retardation and a large inclined structure is produced using a touch belt or an elastic touch roll as a pinching device, it is desired to improve the surface state of the obtained film.

  The present invention has been made in consideration of such problems, and the first object of the present invention is that the retardation development and the tilt structure are large, and the slow axis direction or the fast axis direction in the film plane. Another object of the present invention is to provide a method for producing a thermoplastic film having an inclined orientation in any one direction and having a good surface shape. A second object of the present invention is to provide a film capable of realizing sufficient optical compensation when used in a liquid crystal display, a polarizing plate using the thermoplastic film, and a liquid crystal display device.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that, in the film forming method in which high linear pressure and high shear force are applied to the melt, when at least one pressing surface is elastic, the pressing surface and the melt By using a pinching device that can reduce the slipperiness between the two, it becomes possible to suppress the occurrence of scratches on the melt surface even when high linear pressure and high shearing force are applied, and there is a large phase difference. The present inventors have found that a film having a large inclined structure and an excellent film surface shape can be obtained. 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] The method includes a step of passing a melt of a composition containing a thermoplastic resin between a first clamping surface and a second clamping surface constituting the clamping device, and continuously pressing to form a film. A method for producing a film, wherein at least one of the first clamping surface or the second clamping surface is elastic, and the moving speed of the first clamping surface is faster than the moving speed of the second clamping surface, A method for producing a thermoplastic film, wherein the slipping property of the melt from the pressing surface is reduced at the peeling point of the pressing surface of the first pressing surface and the second pressing surface that is peeled off first from the melt.
[2] including a step of melt-extruding a composition containing the thermoplastic resin from a die and a step of passing the melt-extruded melt between the first pressing surface and the second pressing surface. The method for producing a thermoplastic film according to [1], wherein:
[3] The method for producing a thermoplastic film according to [1] or [2], wherein the slipperiness at the peeling point is reduced using at least one of a pressure adjusting unit and a heating unit.
[4] The first clamping surface of the clamping device is a metal belt, the belt is driven by at least two driving rolls, and the driving roll closest to the peeling point is heated among the at least two driving rolls. The method for producing a thermoplastic film according to any one of [1] to [3].
[5] The method for producing a thermoplastic film according to [4], wherein the at least two drive rolls press the melt through the belt.
[6] The first clamping surface of the clamping device is a metal belt, the belt is driven by at least two driving rolls, and the at least two driving rolls press the melt via the belt, Any one of [1] to [5], wherein a pressure at which the driving roll near the peeling point clamps the melt is made smaller than a pressure at which the other driving roll clamps the melt. The manufacturing method of the thermoplastic film as described in any one of.
[7] The thermoplasticity according to any one of [1] to [3], wherein the pinching device is two rolls having different peripheral speeds and locally heats the peeling point. A method for producing a film.
[8] The method for producing a thermoplastic film according to [7], wherein the peeling point is locally heated by warm air from a heater or a heating contact roll.
[9] The first clamping surface is an elastic roll, and the clamping device has a backup roll arranged adjacent to the elastic roll, and the backup roll has a center of clamping (the melting point) [1] to [3], [7], characterized in that they are arranged so as to be shifted in the direction of the peeling point from the connecting line between the pinching start point of the object and the peeling point) and the center of gravity of the elastic roll. And the manufacturing method of the thermoplastic film as described in any one of [8].
[10] The surface roughness Ra of each of the first clamping surface and the second clamping surface is 0.01 μm to 0.5 μm, according to any one of [1] to [9]. A method for producing a thermoplastic film.
[11] The composition according to any one of [1] to [10], wherein a thickness of the composition containing the thermoplastic resin formed into a film is 10 μm to 90 μm. A method for producing a thermoplastic film.
[12] The thermoplastic resin according to any one of [1] to [11], comprising a step of stretching the composition containing the thermoplastic resin formed into the film shape in at least one direction. A method for producing a film.
[13] The heat according to any one of [1] to [12], wherein the thermoplastic film is a cyclic olefin resin, a polycarbonate resin, an acrylic resin, or a cellulose acylate resin. A method for producing a plastic film.
[14] A thermoplastic film formed by the production method according to any one of [1] to [13].
[15] A thermoplastic film having a surface haze of 0.5% or less and having a tilt orientation in either the slow axis direction or the fast axis direction in the film plane.
[16] The thermoplastic film according to [14] or [15], which satisfies the following formulas (I) and (II):
30 nm ≦ Re [0 °] ≦ 250 nm (I) Formula (In the formula (I), Re [0 °] is a front surface at a wavelength of 550 nm measured from the normal direction in the plane including the film tilt direction and the film normal. Represents direction retardation.)
30 nm ≦ γ ≦ 350 nm (II) Formula γ = | Re [+ 40 °] −Re [−40 °] | Formula (II ′)
(In the formulas (II) and (II ′), Re [+ 40 °] is a wavelength measured from a direction tilted 40 ° toward the tilt azimuth side with respect to the normal in the plane including the film tilt azimuth and film normal. Represents the retardation in the front direction at 550 nm, and Re [−40 °] represents the retardation in the front direction at a wavelength of 550 nm measured from a direction inclined 40 ° to the opposite side of the tilt direction with respect to the normal.
[17] A polarizing plate using at least one thermoplastic film according to any one of [14] to [16].
[18] An optical compensation film using at least one thermoplastic film according to any one of [14] to [16].
[19] A liquid crystal display device using at least one thermoplastic film according to any one of [14] to [16].

  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, a film having a large phase difference, a large optical axis tilt structure, a tilt direction in either the slow axis direction or the fast axis direction in the film plane, and a good surface shape. Obtainable. The film having the above optical characteristics can realize sufficient optical compensation when used in a liquid crystal display of a TN mode, an ECB mode, and an OCB mode. Moreover, the film of this invention can be provided with the manufacturing method of the film of this invention.

It is the schematic of the pinching apparatus used for the manufacturing method of the thermoplastic film of Examples 1-8 and 10-13. It is the schematic of the clamping apparatus used for the manufacturing method of the thermoplastic film of Example 9. FIG. 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.

  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 width direction” means a direction orthogonal to the MD (machine direction) direction. The backup roll preferably has a function of reducing the deflection of the touch roll and realizing a uniform high linear pressure, and the touch roll is disposed at a position where the roll is sandwiched between the roll and the cast roll. It represents a roll that presses the touch roll from behind.

[the film]
The film of the present invention can be preferably used as a film for optical applications, more preferably used as an optical compensation film, and more preferably used as an optical compensation film for a liquid crystal display panel. In addition, the film of the present invention can have a laminated structure.

  The film of the present invention has a surface haze of 0.5% or less, and has a tilt azimuth in one of the slow axis direction and the fast axis direction in the film plane. Hereinafter, detailed features of the film of the present invention will be described.

(Haze)
The surface haze of the film of the present invention is 0.5% or less, preferably 0.3% or less, and more preferably 0.15% or less. When the film surface haze is 0.5% or less, it is preferable because image blur can be reduced and contrast can be improved when the film is incorporated into a liquid crystal display device.

  The film of the present invention has a tilt azimuth, and has a tilt azimuth in either one of the slow axis direction and the fast axis direction in the film plane. The tilt azimuth represents an azimuth in which | Re [+ 40 °] −Re [−40 °] | Having a tilt azimuth in either the slow axis direction or the fast axis direction in the film plane means that Re is different on the left and right when viewed from an oblique direction, that is, when viewed from the thickness direction in the film. This means that an inclined structure is formed. Such a film is preferable because, when a liquid crystal display device is incorporated, the inclined structure complements the liquid crystal alignment in the liquid crystal display device and has an effect of improving the viewing angle.

(In-plane retardation Re)
The film of the present invention preferably satisfies the following formulas (I) and (II).
30 nm ≦ Re [0 °] ≦ 250 nm (I) Formula (In the formula (I), Re [0 °] is a front surface at a wavelength of 550 nm measured from the normal direction in the plane including the film tilt direction and the film normal. Represents direction retardation.)
30 nm ≦ γ ≦ 350 nm (II) Formula γ = | Re [+ 40 °] −Re [−40 °] | Formula (II ′)
(In the formulas (II) and (II ′), Re [+ 40 °] is a wavelength measured from a direction tilted 40 ° toward the tilt azimuth side with respect to the normal in a plane including the film tilt azimuth and film normal. The retardation in the front direction at 550 nm is represented, and Re [−40 °] represents the retardation in the front direction at a wavelength of 550 nm measured from a direction inclined 40 ° to the opposite side of the tilt direction with respect to the normal line.

  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 °.

  The γ is preferably 30 to 350 nm, more preferably 40 to 300 nm, and still more preferably 60 to 250 nm. In the film of the present invention, the in-plane retardation Re [0 °] is preferably 40 to 250 nm, more preferably Re [0 °] is 60 to 250 nm, and still more preferably 80 ~ 200 nm.

Furthermore, the film of the present invention preferably satisfies the following formulas (III) and (IV) simultaneously.
40 nm ≦ Re [0 °] ≦ 250 nm (III)
30 nm ≦ γ ≦ 350 nm (IV)

  The film in which the γ and the Re [0 °] are in the 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.

  The film thickness is preferably 10 μm to 90 μm. When used for a liquid crystal display or the like, the thickness is more preferably 20 to 80 μm and particularly preferably 30 to 60 μm from the viewpoint of thinning. Such a thin film can be produced by the film production method of the present invention.

  The film preferably has both Re [0 °] unevenness and γ unevenness within 3 nm. Such unevenness in the optical properties of the film will appear as display unevenness when used in a liquid crystal display, so it is preferably as small as possible. Specifically, both are preferably within 2.5 nm, both within 2 nm. More preferably, both are within 1 nm.

  Similarly, the variation in the angle of the slow axis also causes display unevenness. Therefore, the variation is preferably as small as possible, specifically within ± 1 °, preferably within ± 0.5 °. It is more preferable that the angle is within ± 0.25 °.

The optical characteristic value can be measured by the following method.
In the present invention, Re [0 °], Re [+ 40 °] and Re [−40 °] of the film are measured using KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.). , The phase difference at an inclination angle of 0 °, the phase difference at an inclination angle of 40 degrees, and the phase difference at an inclination angle of −40 degrees were measured.
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 in the plane including each provisional tilt direction and film normal, and | Re [+ 40 °] −Re [−40 °] | Ask for.
(3) The direction in which γ is maximized is determined as the tilt direction.
The measurement wavelength is 550 nm. Note that a film made of a general thermoplastic resin by a melt film-forming method has γ≈0 nm regardless of the orientation. That is, it is a feature of the film of the present invention that when γ is measured in the tilt direction, a phase difference of 0 nm or more is expressed.
The unevenness of Re [0 °] and the unevenness of γ can be measured by the following method. Sampling is performed at 10 or more positions at 2 mm or more apart from each other on the film surface, and Re [0 °], Re [+ 40 °], and Re [−40 °] are measured at 10 mm intervals by the above method. The difference between the value and the minimum value is the unevenness of Re [0 °], Re [+ 40 °], and Re [−40 °]. In addition, the unevenness of γ is calculated by | Re [+ 40 °] −Re [−40 °] | at each sampled point to obtain γ, and the difference between the maximum value and the minimum value among γ obtained at each point. Is the unevenness of γ.
Further, the variation of the slow axis is measured in the same manner.

(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. The cyclic olefin resin, the cellulose acylate resin, and the polycarbonate It is more preferable that at least one of a resin and an acrylic resin is included. The cyclic olefins are preferably cyclic olefins obtained by addition polymerization.

In particular, when a cellulose acylate resin, a cyclic olefin resin, and a polycarbonate resin exhibiting positive intrinsic birefringence are subjected to shear deformation with two rolls, the slow axis faces the tilt direction, and | Re [ + 40 °] −Re [−40 °] |> 0 film can be produced. For example, when two rolls are arranged in parallel to the die exit, the tilt direction is the same as the film longitudinal direction.
In addition, when the acrylic resin and styrene resin exhibiting negative intrinsic birefringence are processed as described above, the fast axis is directed to the tilt direction, and | Re [+ 40 °] −Re [−40 °] | > 0 films can be created.

  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 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 degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the sum of the degree of substitution of the acyl group with respect to the hydroxyl group of cellulose. The “degree of substitution” in the present specification means the total of the ratio of substitution of hydrogen atoms of hydroxyl groups at the 2-position, 3-position and 6-position of cellulose. When the hydrogen atoms of all hydroxyl groups at the 2nd, 3rd and 6th positions are substituted with acyl groups, the degree of substitution 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.

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”, “XSR9251” manufactured by Asahi Kasei Chemical Co., Ltd., which will be described later, and the like can be used.

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).

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。

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. Further, among 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. Among these, the one described in JP 2007-113109 A 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 2008-74918. 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 viewpoint of high transparency, birefringence and heat resistance, and an addition polymerization type norbornene. It is particularly preferable that the resin is a series 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 being higher than the content rate of each other material. Examples of materials other than the thermoplastic resin include various additives, and 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 Corporation.

  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 this invention may contain the 1 type (s) or 2 or more types of ultraviolet absorber. 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, for the purpose of lowering the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the thermoplastic resin used, or without 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 cyclohexyl An acrylic polymer having a group in the side chain is also 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 adjusting agent:
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 film production method of the present invention, a melt of a composition containing a thermoplastic resin is passed between a first clamping surface and a second clamping surface constituting a clamping device, and the film is continuously pressed. A method for producing a film including a step of forming the first pressing surface, wherein at least one of the first pressing surface and the second pressing surface is elastic, and the moving speed of the first pressing surface is set to the moving speed of the second pressing surface. The slipping property of the melt from the pressing surface is reduced at a peeling point of the pressing surface of the first pressing surface and the second pressing surface that is peeled off first from the melt. And At such a peeling point, it is a feature of the present invention that is different from the conventional method to reduce the slipping property of the melt from the pressing surface.
Examples of the clamping device having different speeds on the first clamping surface and the second clamping surface include, for example, a combination of two rolls having different peripheral speeds, and rolls having different speeds described in Japanese Patent Application Laid-Open No. 2000-219752. Examples include a combination of touch belts (single-sided belt method), a combination of belts and belts (double-sided belt method), and the like. The touch pressure can be measured by passing a pressure measurement 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 of melt of thermoplastic resin composition>
In the production method of the present invention, a composition containing a thermoplastic resin (sometimes referred to as a “thermoplastic resin composition”) is passed between a first clamping surface and a second clamping surface constituting the clamping device. Although it includes a step of continuously pressing and forming into a film (hereinafter also referred to as a pressing step), a molten resin containing a thermoplastic resin can be supplied from any supply means to the pressing step. At that time, there is no particular limitation on the means for supplying the melt (melt) of the composition containing the thermoplastic resin. For example, as a specific means for supplying the melt, an embodiment using an extruder that melts and extrudes a thermoplastic resin composition into a film may be used, or an embodiment using an extruder and a die may be used. The thermoplastic resin is solidified once. Alternatively, the film may be formed into a film and then melted by a heating means to form a melt and supplied to the film forming process.
The method for producing a film of the present invention includes a step of melt-extruding a composition containing the thermoplastic resin (hereinafter also referred to as a thermoplastic resin composition) from a die, and the melt-extruded melt with the first nipping surface. And a step of passing between the second pinching surfaces is preferable from the viewpoint of suppressing unevenness in the optical properties of the obtained film.
When the thermoplastic resin composition is melt-extruded, it is preferable to pelletize the thermoplastic resin composition before melt-extruding. Commercially available thermoplastic resins (for example, TOPAS # 6013, Toughlon MD1500, Delpet 980N, DayLark D332, etc.) may be pelletized, but if not pelletized, the following method may be used. it can.
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.

  When melt extrusion is performed using an extruder, it is preferable that the dried pellets are then fed into a cylinder via a feed port of the extruder, 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 (hereinafter also referred to as discharge temperature) of a supply means (for example, a die) for supplying the thermoplastic resin composition is determined according to the melting temperature of the thermoplastic resin, but is generally 190 to 300. A temperature of about ° C is preferred. 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 variation in the discharge amount and improve the thickness accuracy, it is preferable to provide a gear pump between the extruder and the supply means (for example, die) for supplying the thermoplastic resin composition. Thereby, the resin pressure fluctuation width in the supply means (for example, die | dye) which supplies the said thermoplastic resin composition can be made into less than +/- 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 sent to a supply means (for example, a die) for supplying the thermoplastic resin composition 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 supply means (for example, die) for supplying the thermoplastic resin composition in order to increase the uniformity of the resin temperature.

When the supply means is a die, the clearance at the die exit portion (hereinafter also referred to as lip gap) is generally 1.0 to 30 times the film thickness, preferably 5.0 to 20 times. Specifically, it is preferably 0.04 to 3 mm, more preferably 0.2 to 2 mm, and particularly preferably 0.4 to 1.5 mm.
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.
In this way, the residence time from when the resin enters the extruder through the supply port until it exits from the supply means (for example, die) for supplying the thermoplastic resin composition is preferably 3 to 40 minutes, more preferably 4 Minutes to 30 minutes.

<Cast>
Next, the melt of the thermoplastic resin composition supplied from an arbitrary supply means is passed between the first clamping surface and the second clamping surface constituting the clamping device to continuously clamp and cool and solidify. 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. In the manufacturing method of the present invention, the moving speed of the first pressing surface is faster than the moving speed of the second pressing surface, but the surface to be peeled first is the second pressing surface even if it is the first pressing surface. However, from the viewpoint of suppressing the peeling dan, it is preferable that the surface to be peeled first is the first pressing surface (the pressing surface having a high moving speed).

  In the production method of the present invention, in addition to the conventional method of continuously forming a film into a film by passing the melt-extruded melt between the first and second clamping surfaces constituting the clamping device, The pressure is preferably 5 to 500 MPa, more preferably 10 to 500 MPa, particularly preferably 15 to 500 MPa, particularly preferably 20 to 300 MPa, and more preferably 25 to 200 MPa. More preferably, it is 30-150 MPa.

(Moving speed ratio of pinching surface)
In the manufacturing method of the present invention, the moving speed of the first pressing surface is made faster than the moving speed of the second pressing surface. Furthermore, the moving speed ratio of the first clamping surface and the second clamping surface of the clamping device defined by the following formula (V) is adjusted to 0.60 to 0.99, and the molten resin passes through the clamping device. It is preferable to apply a shear stress to produce the film of the present invention. The moving speed ratio of the clamping device is preferably 0.60 to 0.99, and more preferably 0.75 to 0.98.
Movement speed ratio = speed of second clamping surface / speed of first clamping surface (V)

(Discharge temperature)
In the production method of the present invention, the discharge temperature (resin temperature at the outlet of the supply means) is preferably Tg + 50 to Tg + 200 ° C., and preferably Tg + 70 to Tg + 180 ° C. from the viewpoint of improving the moldability of the resin and suppressing deterioration. More preferably, it is Tg + 90-Tg + 150 degreeC. That is, if Tg + 50 ° C. or higher, the viscosity of the resin is sufficiently low and the moldability is good, and if Tg + 200 ° C. or lower, the resin is less likely to deteriorate.

(Air gap)
In the production method of the present invention, for example, when the thermoplastic resin composition is supplied from a supply means such as a die to the clamping device, the air gap (distance from the outlet of the supply device to the melt landing point of the clamping device) is: From the viewpoint of heat insulation of the melt between the air gaps, it is preferable to be as close as possible, specifically 10 to 300 mm is preferable, more preferably 20 to 250 mm, and particularly preferably 30 to 200 mm. .

  In the production method of the present invention, the landing point of the melt extruded from the supply unit is not particularly limited, and the landing point of the melt extruded from the supply unit, the first compression surface, and the second compression surface The distance from the vertical line passing through the midpoint of the gap in the closest part may be zero or may be shifted. The landing point of the melt refers to a point where the melt pushed out from the supply means first contacts (lands) on the first pressing surface or the second pressing surface. The midpoint of the gap between the first clamping surface and the second clamping surface is the first point where the gap between the first clamping surface and the second clamping surface is narrowest in the vicinity of the clamping start portion. It refers to the midpoint of the pinching surface and the second pinching surface.

(Line speed)
In the production method of the present invention, from the viewpoint of heat retention of the melt in the air gap, the line speed (film forming speed) is preferably 5 m / min or more, more preferably 7 m / min or more, and 8 m / min. The above is particularly preferable. When the line speed is increased, cooling of the melt in the air gap can be suppressed, and more uniform shear deformation can be imparted by the pinching device while the melt temperature is high. 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 the production method of the present invention, the width of the melt is not particularly limited, and can be, for example, 200 to 2000 mm.

(Pinch surface)
In the manufacturing method of the present invention, at least one of the first clamping surface and the second clamping surface is elastic. It is one of the features of the present invention to use a pinching surface having such features.
By using the elastic pinching surface as at least one pinching surface in this way, optical retardation unevenness can be improved.
In the present specification, the fact that the pinching surface is “elastic” is not determined only by the material of the pinching surface, but the thickness of the rigid material used for the surface portion of the pinching surface and the thickness of the structure that supports the pinching surface. For example, when the pinching surface is driven by a spherical support roll, the ratio of rigid material outer cylinder thickness / support roll diameter is less than 1/80. For example, a case where a rigid material is used for a part of the touch roll may be included. That is, a roll in which a layer that does not contain any rigid material such as an elastic layer is formed inside the touch roll will elastically deform 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, the case where the pinching surface is supported and driven by another mechanism is the same as the case where the pinching surface is driven by a spherical support roll.

  In the production method of the present invention, the surface roughness Ra of each of the first clamping surface and the second clamping surface is from 0.01 μm to 0.5 μm, which can reduce slippage with the melt and suppress scratches. From the viewpoint, it is preferable. Specifically, by reducing the surface roughness, fine unevenness at the interface between the melt and the pressure-pressing surface is reduced, and the contact area between the melt and the pressure-pressing surface is increased. When the contact area between the melt and the pressing surface is increased, the slipping property is reduced, and the generation of scratches can be suppressed. In order to achieve the surface roughness, it is preferable to provide a metal layer on at least the surface of the pinching surface. In particular, when the surface of the elastic roll is coated with a metal, both rolls have a metal surface, which is preferable because the surface irregularities are small as in the case of the metal roll and the film surface is hardly damaged. It is preferable to employ a metal sleeve material or a thin metal belt as the elastic pressing surface. The metal coat may be a metal thin film such as a plating layer as long as it can prevent the surface from being damaged when the film passes between rolls by utilizing the smooth surface characteristics of the metal layer. Specific examples of the pressure-clamping surface in which the elastic roll surface is coated with a metal include those in which a metal belt is mounted on the surface of a roll made of silicon rubber, or those in which the elastic roll surface is subjected to metal plating.

  The surface roughness Ra of each of the first clamping surface and the second clamping surface is more preferably 0.01 μm to 0.4 μm, and particularly preferably 0.01 to 0.3 μm.

(Shear stress)
In the manufacturing method of this invention, it is preferable to include the process of giving 3000-30000N shear stress per 1m width of a melt with the said clamping apparatus. Thus, by giving a shear stress to a melt, the film of the present invention with good expression of optical properties and good uniformity can be obtained.
The shear stress is more preferably 5000 to 28000 N per 1 m width of the melt, and particularly preferably 8000 to 25000 N per 1 m width of the melt.

(Clamping length)
In the manufacturing method of the present invention, the length of the melt that is clamped between the first clamping surface and the second clamping surface in the clamping device passing direction (hereinafter also referred to as the clamping length) is: It is preferable that it is 3-80 mm. In the manufacturing method of the present invention, the pinching length is increased by using an elastic pinching surface. By increasing the pinching length as described above, there is an advantage of improving optical retardation unevenness.
The pinching length is more preferably 4 to 60 mm, and particularly preferably 5 to 50 mm.

<Method to reduce slipperiness>
The manufacturing method of the present invention reduces the slip property of the melt from the pressing surface at the peeling point of the pressing surface of the first pressing surface and the second pressing surface that is peeled off first from the melt. It is characterized by. The slipping property of the present invention is a phenomenon caused by a minute relative position change between the pressure-carrying surface and the melt at the peeling point. When the slipping property is increased, the shear stress that gives the melt surface between the pressure-carrying surfaces of different peripheral speeds is increased. As a result, scratches frequently occur on the melt surface. When the generated scratch becomes uneven and is incorporated in the liquid crystal display panel, a slight gap is generated between the glass on both sides of the liquid crystal layer, and this causes uneven interference. It is characterized in that it has been found that such scratches are particularly prominent when passing through rolls having different peripheral speed differences.
Thus, at the peeling point of the melt, in the present invention, the occurrence of scratches on the obtained film is suppressed by reducing the slipperiness by locally heating or reducing the pressure applied to the peeling point. In addition, the surface haze can be reduced.
As a method for reducing the slipperiness at such a peeling point, a method of reducing the energy applied to the melt surface by reducing the pressure applied to the peeling point to weaken the stress by which the pressing surface rubs the film surface is preferable. A method of increasing the temperature at the peeling point to reduce the shrinkage of the melt at the peeling point and reducing the slipperiness with the clamping surface is also preferable. When the pressure applied to the peeling point is decreased, the ratio of the linear pressure at the peeling point to the average linear pressure at the pinching portion, that is, the value of the peeling point pinching pressure / the pinching portion average linear pressure is 0. It is preferably 1 to 0.9, more preferably 0.1 to 0.8, and particularly preferably 0.2 to 0.6.
When the temperature of the peeling point is increased, the range of increase in the temperature of the peeling point relative to the case where no means for increasing the temperature of the peeling point is used is preferably 1 to 30 ° C, and preferably 2 to 25 ° C. Is more preferable, and it is especially preferable that it is 3-23 degreeC.
In the production method of the present invention, it is preferable to reduce the slipperiness at the peeling point using at least one of a pressure adjusting means and a heating means.
Hereinafter, the slippage reducing means in the present invention will be described in more detail with respect to a specific control method of the clamping device and a specific configuration of the clamping device, that is, details of the pressure adjusting means and the heating means.

(1) A mode in which the melt is clamped using a roll and a belt As a slip reduction means in the present invention, the melt is continuously clamped between the first clamping surface and the second clamping surface constituting the clamping device. Among the methods for forming into a film shape, the first clamping surface of the clamping device is an endless belt, and the second clamping surface of the clamping device is a cast roll, that is, at least one roll An embodiment in which the melt is passed between belts (for example, a metal touch belt and a chill roll) can be preferably exemplified. In addition, in this specification, when it has multiple cast rolls which convey the said melt, the cast roll nearest to the said thermoplastic resin composition supply means (for example, die | dye) of the most upstream is called chill roll. Hereinafter, preferred embodiments of the production method of the present invention using at least one roll and belt will be described.

  The belt driving method is not particularly limited, but for example, it is preferable that the belt held by two holding rolls is driven by rotating the holding rolls. Moreover, it is preferable from a viewpoint of making a belt and a roll a peripheral speed difference that it is independent drive with a cast roll.

In the manufacturing method of the present invention, the first clamping surface of the clamping device is a metal belt, the belt is driven by at least two driving rolls, and the driving roll closest to the peeling point among the at least two driving rolls. Is preferable from the viewpoint of efficiently heating the peeling point and reducing the slipperiness at the peeling point.
As the set temperature difference between the two drive rolls, it is preferable that the set temperature of the roll closest to the peeling point is 1 to 30 ° C. higher than the first holding roll (the roll closer to the melt landing point). More preferably, it is higher by 25 ° C., particularly preferably 3-20 ° C. higher.

Moreover, even if the at least two drive rolls press the melt through the metal belt, the at least two drive rolls are disposed at positions away from the vicinity of the melt clamping portion. The aspect which is pressing the said melt only with a metal belt may be sufficient.
In the manufacturing method of the present invention, it is more easily applied that the at least two drive rolls press the melt via the metal belt, and a high linear pressure can be applied, and the pressure and temperature at the peeling point can be easily set. It is preferable from the viewpoint of control.

In the manufacturing method of the present invention, the first clamping surface of the clamping device is a metal belt, the belt is driven by at least two driving rolls, and the at least two driving rolls pass the melt through the belt. Pressing and making the pressure at which the driving roll closest to the peeling point pinches the melt to be smaller than the pressure at which the other driving rolls pinch the melt reduces the shearing force applied to the melt and peels It is preferable from the viewpoint that the slipperiness at a point can be easily reduced.
In this case, the preferable pressure reduction ratio is the same as the preferable range of the peeling point linear pressure / clamping portion average linear pressure.

  The surface of the belt (for example, touch belt) preferably has a small surface roughness Ra, and the range thereof is the same as the range described as the surface roughness of the pressing surface.

  The width of the belt is not particularly limited, and can be freely changed according to the melt width.

The belt is preferably made of metal, more preferably stainless steel with a mirror-plated surface. Further, it is preferable that the belt is made of a metal because the surface has small irregularities and the film surface is hardly damaged. On the other hand, a belt lining with a rubber roll or rubber can also be used. Moreover, the surface of the film is hardly damaged by using a belt having no seam.
As the belt, for example, a belt described in JP-A-2007-237495 can be used.
In the manufacturing method of the present invention, the average metal thickness of the belt (that is, the thickness of the metal outer cylinder) is 15 mm or less. When the metal belt is put on the elastic holding roll, the entire pressing surface is It is preferable from the viewpoint of maintaining elasticity. Further, if the elasticity of the entire pressing surface is maintained, there is an advantage that the obtained film is reduced in surface unevenness, and display unevenness is reduced when incorporated in a liquid crystal display device, which is preferable.
The average metal thickness of the belt is more preferably 0.3 to 15 mm, and particularly preferably 0.5 to 10 mm.

  Furthermore, in the production method of the present invention, the shear stress is applied when the melt passes through the roll and the belt by adjusting the peripheral speed ratio between the roll through which the melt passes and the belt. A preferable range of the peripheral speed ratio between the roll and the belt is the same as the moving speed ratio of the pressing surface.

  Further, in order to increase the difference between Re [40 °] and Re [−40 °], the surface temperature of the chill roll may be different from the surface temperature of the belt. A preferable temperature difference is 0.1 ° C to 50 ° C, more preferably 1 ° C to 40 ° C, and further preferably 2 ° C to 30 ° C. Further, the surface temperature of the roll and the surface temperature of the belt preferably employed in the present invention are the same as the surface temperature of the first clamping surface and the second clamping surface of the clamping device described in the temperature of the clamping device, The preferable range is also the same.

(2) A mode in which the melt is clamped by using two rolls As a slip reduction means in the present invention, the melt of the supplied thermoplastic resin is formed between the first clamping surface and the second clamping surface constituting the clamping device. Among the methods of forming a film by continuously pressing between them, it is also preferable to pass between two rolls (for example, a touch roll (first roll) and a chill roll (second roll)).
Hereinafter, the preferable aspect of the manufacturing method of this invention using two rolls is demonstrated.

  In the manufacturing method of this invention, it is preferable that the said clamping apparatus is two rolls from which circumferential speed differs mutually, and heats the said peeling point locally. The method for locally heating the peeling point is not particularly limited, and has a mechanism that allows the temperature to be adjusted in accordance with the position of the roll surface inside the roll even if the heating means is installed outside and heated. You may heat using the roll which is. As such a special roll, there can be mentioned a roll described in JP-A-2006-256159 capable of controlling the surface temperature distribution according to the position.

  In the manufacturing method of this invention, it is more preferable to heat the said peeling point locally with the warm air by a heater, or a heating contact roll. Such a heater or heating contact roll is preferably installed in the vicinity of the peeling point. Specifically, it is preferable to install the heating means 9 in the vicinity of the peeling point as shown in FIG.

In the production method of the present invention, the surface material of the two rolls is preferably a metal from the viewpoint of preventing scratches, preferably stainless steel, and a roll whose surface is plated is also preferred.
As for 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.

In the manufacturing method of the present invention, the elastic roll of the two rolls has at least a core part and an outer cylinder, and the average thickness of the outer cylinder of the elastic roll is 15 mm or less. It is preferable from the viewpoint of holding.
The average wall thickness of the outer cylinder of the elastic roll is more preferably 0.3 to 15 mm, and particularly preferably 0.5 to 10 mm.

  The two rolls (for example, a touch roll and a cast roll) preferably have a small surface roughness Ra, and a preferable range thereof is the same as the preferable surface roughness of the pressure-clamping surface.

  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.

  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 Shore hardness of 45 HS or more as at least one roll. A preferable Shore hardness of the roll is 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.

  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 mm, more preferably 350 to 500 mm. When a roll with a large diameter is used, the contact area between the film-like melt and the roll becomes wide, and the time for shearing becomes longer. Therefore, a film with a large difference between Re [+ 40 °] and Re [−40 °] is used. Moreover, it can be manufactured while suppressing variations in Re [0 °], Re [+ 40 °] and Re [−40 °]. 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. However, in order to suppress variations in Re [0 °], Re [+ 40 °] and Re [−40 °], the two rolls are preferably driven independently. .

Furthermore, in the production method of the present invention, by adjusting the peripheral speed ratio of the 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 a film. The peripheral speed ratio of the two rolls is preferably 0.60 to 0.99, and more preferably 0.75 to 0.98. Here, the peripheral speed ratio of the two rolls means the peripheral speed of the slow roll / the peripheral speed of the fast roll.
If the peripheral speed ratio of the two rolls is 0.60 or more, the absolute value of the difference between Re [+ 40 °] and Re [−40 °] of the obtained film becomes large and satisfies the above formula (II). This is preferable. If the peripheral speed ratio is 0.60 or more, it is preferable that the surface of the obtained film is hardly damaged. It is preferable to set the peripheral speed ratio of the two rolls to 0.60 to 0.99, since it is difficult to scratch the film surface and a film with good smoothness can be stably produced.
In order to obtain the film of the present invention, whichever speed of the two rolls may be high, when the touch roll is slow, a bank (excess of melt stays on the roll and forms on the roll side). Formed residue) is formed. 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).

Further, in order to increase the difference between Re [40 °] and Re [−40 °], the surface temperature of the two rolls may be made different. A preferable temperature difference is 0.1 ° C to 50 ° C, more preferably 1 ° C to 40 ° C, and further preferably 2 ° C to 30 ° C. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through the touch roll.
The glass transition temperature of the thermoplastic resin is measured by adding a resin to a measurement pan using a scanning differential calorimeter (DSC) and raising the temperature from 30 ° C. to 300 ° C. at 10 ° C./min in a nitrogen stream. (1st-run), and then cooled to 30 ° C. at −10 ° C./min, and again heated from 30 ° C. to 300 ° C. at 10 ° C./min (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).

(3) A mode using a backup roll As the slippage reducing means in the present invention, in the manufacturing method of the present invention, the first clamping surface is an elastic roll, and the clamping device is disposed adjacent to the elastic roll. A backup roll, and the center of gravity of the backup roll is shifted in the direction of the peeling point from the connecting line between the pinching center point (the intermediate point between the pinching start point of the melt and the peeling point) and the gravity center of the elastic roll. It is preferable from the viewpoint that the slipperiness at the peeling point can be reduced. Specifically, for example, as shown in FIG. 2, it is preferable to arrange a backup roll.
That is, in the production method of the present invention, the pressure applied to the pinching part melt by the elastic roll can be adjusted by the backup roll so that the pressure at the peeling point is smaller than the average pressure of the pinching part. preferable.

  The deviation of the back-up roll center of gravity from the connecting line between the pinching center point and the center of gravity of the elastic roll is preferably 0.1 to 50%, and preferably 0.5 to 40% of the radius of the elastic roll. More preferred is 1 to 20%.

  In addition, by using the backup roll in this way, the touch roll can be bent uniformly, and further, the chill roll can be bent evenly, and as a result, the linear pressure applied to the melt can be made uniform. Can do. When sandwiching the melt passing between the rolls using two rolls, if the high linear pressure is applied, the touch roll and the chill roll may bend unevenly, and the gap between the touch roll and the chill roll must be kept at a certain distance. Is difficult. In that case, unevenness in the width direction occurs in the linear pressure. On the other hand, by pressing the touch roll in the direction of the chill roll using the backup roll, the touch roll and the chill roll can be deformed so that the deflection amounts of both are equal.

When the backup roll is covered with rubber, it is preferable because an area where the backup roll and the touch roll are in contact with each other can be adjusted to a preferable level. Specifically, it is preferable that the backup roll is covered with rubber because the linear pressure can be applied more uniformly than when the backup roll surface is made of metal.
The rubber that can be used for the backup roll is not particularly limited. For example, fluorine-based rubber, heat-resistant NBR-based rubber, and silicon-based rubber are preferable. Among them, fluorine-based rubber is preferable from the viewpoint of durability and exudation of additives. More preferred.

The means for pushing the touch roll toward the chill roll by the backup roll is not particularly limited. In particular, when the members holding the axis of the backup roll are at both ends of the backup roll, it is possible to press the members holding the axes of the backup roll at both ends simultaneously and with the same amount of force at the center in the width direction of the touch roll. It is preferable from the viewpoint of applying pressure to bend the touch roll uniformly.
Further, the pressure applied when the touch roll is pressed by the backup roll is not particularly limited as long as it satisfies the range of the linear pressure between the touch roll and the chill roll of the present invention, but is preferably 20 to 500 MPa, for example. More preferably, the pressure is 25 to 400 MPa, and particularly preferably 30 to 250 MPa. By pressing the touch roll with such pressure, the touch roll can be sufficiently bent evenly, and the chill roll can also be bent uniformly in the same manner as the touch roll.

  In the manufacturing method of this invention, it is preferable from a viewpoint of adjustment of the deflection amount of a touch roll that the width of the said backup roll is shorter than the width of the said touch roll.

(Heat insulation and heating in the air gap)
In the production method of the present invention, the step of heating the melt until the melt of the thermoplastic resin composition supplied from the supply means reaches the pinching surface of the pinching device from the supply means. Or it is preferable to include at least one of the steps of keeping the temperature. In this way, it is preferable to reduce the temperature distribution (temperature unevenness) in the melt width direction. Specifically, it is preferable that the temperature distribution in the width direction is within 5 ° C. In order to reduce the temperature distribution, it is preferable to dispose a member having a heat insulating function or a heat reflecting function in at least a part of the air gap to shield the melt from the outside air. 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.
Further, when the shielding member is used, the film-like melt can be passed between rolls in a high temperature state, that is, in a state where the melt viscosity is low, so that the expression amount of the optical property is satisfied and the optical property is satisfied. There exists an effect which is easy to produce the film of this invention with few unevenness.
Moreover, when heating a melt, there is no restriction | limiting in particular in a heating means, For example, a well-known heater etc. can be used.
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 and the width direction side surface and clearance gap of the supply means (for example, die | dye) of a thermoplastic resin composition, for example. The shielding plate may be directly fixed to the side surface of the supply means, 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 supply means so that the rising airflow due to the heat radiation of the supply means can be efficiently blocked.
The gap between the shielding member and the end in the width direction of the film-like melt 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 supply unit and the shielding member is not necessarily provided, but is preferably formed to a degree 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 reducing the unevenness of Re [0 °] and the unevenness of γ, there is a method of increasing the adhesion when the 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.

  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 (the one closer to the thermoplastic resin composition supply means, for example, the die). In general, it is relatively common to use three cooling rolls, but this is not a limitation. The distance between the plurality of casting rolls is preferably 0.3 mm to 300 mm, more preferably 1 mm to 100 mm, and still 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. Extrusion can be performed at room temperature to 300 ° C.

  It is also preferable to attach a lami film on one side or both sides before winding. 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 / width, more preferably 5 kg / m width to 30 kg / width.

  In the manufacturing method of this invention, it is preferable that the thickness at the time of film forming of the composition containing the thermoplastic resin shape | molded in the said film form is 10 micrometers-90 micrometers. When used for a liquid crystal display or the like, the thickness is more preferably 20 to 80 μm and particularly preferably 30 to 60 μm from the viewpoint of thinning.

<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 The production method of the present invention stretches the composition containing the thermoplastic resin formed into a film shape in at least one direction. Including a process is preferable from the viewpoint of reducing the generated scratches and further improving the surface state of the resulting film.
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-20 ° C to Tg + 30 ° C, more preferably Tg-15 ° C to Tg + 20 ° C, and further preferably Tg-10 ° C to Tg + 10 ° 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.
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 less than the stretching temperature and less than 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% (shrinking 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 property 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, and 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 exceeds 0.3 and 2 or less) may be used. Span stretching and short span stretching are preferred. Further, 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-20 ° C to Tg + 30 ° C, more preferably Tg-15 ° C to Tg + 20 ° C, and further preferably Tg-10 ° C to Tg + 10 ° C or less. Moreover, a preferable longitudinal draw 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 + 10) ° C, more preferably (Tg-20) ° C to (Tg + 5) ° C, more preferably (Tg-10) ° C to (Tg + 3) ° C for 1 second to 10 minutes. More preferably 5 seconds to 4 minutes, further 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 carrying 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. 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, TD80UL 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. Preferably, it can be used for TN (Twisted Nematic), OCB (Optically Compensatory Bend), ECB (Electrically Controlled Birefringence) mode liquid crystal display devices, and more preferably for TN and ECB mode liquid crystal displays.

  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.

[Measurement method]
(Surface haze)
The total haze (H), internal haze (Hi), and surface haze (Hs) of the obtained film were measured by the following measurements.
[1] The total haze value (H) of the film obtained according to JIS-K7136 is measured.
[2] A few drops of silicone oil were added to both sides of the obtained film, and two glass plates (micro slide glass product number S 9111, manufactured by MATSANAMI) with a thickness of 1 mm were sandwiched from the front and back sides, A value obtained by measuring the haze in a state where the glass plate and the obtained film are optically adhered and the surface haze is removed, and subtracting the haze measured by sandwiching only silicone oil between two separately measured glass plates. Was calculated as the internal haze (Hi) of the film.
[3] A value obtained by subtracting the internal haze (Hi) calculated in [2] from the total haze (H) measured in [1] above was calculated as the surface haze (Hs) of the film.

[Production Example 1] Manufacture of polycarbonate pellets As polycarbonate (resin A-1), pellets of "Taflon MD1500" manufactured by Idemitsu Kosan Co., Ltd. were used. “Taflon MD1500” exhibits positive intrinsic birefringence. The glass transition temperature of the resin was 142 ° C.

[Production Example 2] Manufacture of pellets of ring-opening polymerization type norbornene resin As ring-opening polymerization type norbornene resin (COP, resin A-2), ring-opening polymerization type norbornene resin COP-1 was carried out according to International Publication WO98 / 14499. Prepared according to Example 1 and pelletized according to conventional methods. The resin exhibits positive intrinsic birefringence. The glass transition temperature of the resin was 136 ° C.

Production Example 3 Production of Cyclic Olefin Copolymer Pellets As the addition polymerization type norbornene resin (COC, resin A-3), pellets of “TOPAS # 6013” manufactured by Polyplastics were used. “TOPAS # 6013” indicates positive intrinsic birefringence. The glass transition temperature of the resin was 136 ° C.

[Production Example 4] Manufacture of pellets of cellulose acylate resin Example 101 described in Table 3 of JP-A-2008-50562 is described as the cellulose acetate propionate resin (resin A-4). Manufactured according to the method and pelletized. The composition of the obtained resin has a degree of acetylation of 0.15, a degree of propionylation of 2.55, a total degree of acyl substitution of 2.7, and exhibits positive intrinsic birefringence. The glass transition temperature of the resin was 137 ° C.

[Production Example 5] Production of pellets of styrene-maleic anhydride resin As pellets of styrene-maleic anhydride resin (resin A-5), pellets of "Dylark D332" manufactured by Nova Chemical Co. were used. “Dylark D332” indicates negative intrinsic birefringence. The glass transition temperature of the resin was 130 ° C.

[Example 1]
(Production of film)
Using pellets shown in Table 1 below, drying at 100 ° C. for 2 hours or more, and adding 0.4 parts by weight of stabilizer IRGANOX-1010 (manufactured by Ciba Specialty Chemicals) to 100 parts by weight of resin. It melted at 265 ° C., kneaded and extruded using a single screw kneading extruder. 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 an extrusion temperature (discharge temperature) of 265 ° C. and a width of 1000 mm and a lip gap of 1 mm.
Thereafter, the melt (molten resin) was extruded to an intermediate point between the cast roll and the first holding roll of the metal touch belt using the clamping apparatus having the configuration shown in FIG. At this time, a cylinder with a material having a width of 2000 mm on the most upstream side and a diameter of 400 mm made of hard chrome-plated carbon steel and a cast roll (chill roll) with a shore hardness of 65 HS so that the touch pressure shown in Table 1 below is obtained. A metal touch belt, which was set and made of carbon steel having a width of 800 mm and a material subjected to hard chrome plating surface treatment, was brought into contact. Moreover, the metal outer cylinder thickness and surface roughness of the metal touch belt used were as described in Table 1, and the diameters of the first holding roll and the second holding roll holding the metal touch belt were 150 mm. Using these, the film was formed by setting the peripheral speed ratio of the metal touch belt and the chill roll, the pinching length, the average linear pressure of the pinching portion, and the conditions shown in Table 1 below. The average linear pressure of the pinching part is measured by sandwiching a prescale for medium pressure (manufactured by Fuji Film Co., Ltd.) between the pinching surfaces controlled at 25 ° C. at a constant peripheral speed (5 m / min) in the absence of melt. The average value of the pressure in the pinching length was defined as the average linear pressure of the pinching portion during film formation, and the value in the peeling region of the latter half 20% of the pinching length was defined as the peeling point linear pressure during film formation. The peeling point line pressure is the value of the peeling point line pressure / average line pressure of the pinching part shown in Table 1 by independently controlling the second holding roll of the metal touch belt shown in FIG. It adjusted so that it might become. Moreover, the temperature of the 1st holding roll was set to Tg-10 degreeC, and the temperature of the 2nd holding roll was set to Tg-5 degreeC. The temperature of the touch belt at the peeling point (peeling point temperature) was adjusted to the temperature shown in Table 1 by heating only the second holding roll independently. The temperature of the chill roll was Tg-5 ° C., and the distance between the die and the melt landing point was set to 90 mm. Moreover, although the film-forming atmosphere was 25 ° C. and 60%, a wind shielding plate was disposed between the die and each pressing surface to form a film while keeping the melt warm.
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 formation width was 700 mm, and the film formation speed was 450 m at a speed (chill roll speed) described in Table 1 below. The thickness of the film after film formation was the value described in Table 2 below, and the film of Example 1 was produced.

(Optical properties of the film)
The optical properties of the obtained film of Example 1 are shown together in Table 1. In addition, the inclination direction which measured Re [+40 degrees] and Re [-40 degrees] of the film of this invention is all the longitudinal direction (slow axis) direction of a film.

(Film scratch)
The scratch was evaluated by the following method. One tungsten lamp (Iwasaki Electric Co., Ltd. eye lamp 150W) is installed per 50 cm width, and the film is conveyed under this at 20 m / min. If there is a scratch, light is scattered and becomes a bright spot, and this is visually observed to mark the bright spot. This is observed with a microscope, and those having a scratch size (minimum side size) of 10 μm to 1 mm are extracted and measured. This was converted into the number of generated per 1 m ² and used as the number of scratches. The scratch of the obtained film of Example 1 was evaluated according to the following criteria, and the results are shown in Table 1.
A: The number of scratches generated per 1 m ^{2 on} the film surface is less than 3 by visual observation.
○: The number of scratches generated per 1 m ^{2 on} the film surface is 3 or more and less than 10 by visual observation.
Δ: The number of scratches generated per 1 m ^{2 on} the film surface is 10 or more and less than 30 by visual observation, but there is no practical problem.
X: The number of scratches generated per 1 m ^{2 on the} film surface is 30 or more, which is problematic in practical use.

[Examples 2-8, 10-13, Comparative Example 1]
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. In Table 1 and Table 2 below, “no heating” means that the temperature of the second holding roll of the metal touch belt was adjusted to Tg−20 ° C. and manufactured. Examples 10 to 13 are manufactured by adjusting the temperature of the second holding roll to be Tg + 3 ° C. Tables 1 and 2 below show the various optical properties and film scratch evaluation results of the films of the examples and comparative examples.

[Example 9, Comparative Examples 2 and 3]
In Example 9 and Comparative Examples 2 and 3, instead of the metal belt, using a touch roll having a shore hardness of 50 HS made of carbon steel having a material hard chrome plating surface treatment with a width of 800 mm and a diameter of 350 mm, The melt was sandwiched between and pressed. The touch roll has a rubber roll surface coated with a metal outer cylinder (metal sleeve), and the thickness of the metal sleeve is shown in Table 1 below. Furthermore, in Example 9 and Comparative Example 2, a roll made of silicon rubber having a width of 800 mm and a diameter of 10 mm and a Shore A hardness of 70 ° was used as a backup roll, and the roll linear pressure was adjusted using pressure-sensitive paper. While adjusting the finger pressure, the touch roll was pressed. At that time, in Comparative Example 2, the center of gravity of the backup roll is arranged so as to be on the connecting line between the center of pressure pinching and the center of gravity of the touch roll. In Example 9, the center of gravity of the backup roll is centered on the pressure pin as shown in FIG. It was arranged so as to be vertically downward by 5% of the radius of the touch roll from the connecting line between the point and the center of gravity of the touch roll.
Furthermore, in Example 9, an infrared heater was used to apply heat to the peeling point of the touch roll and heated, and in Comparative Examples 2 and 3, the temperature of the roll was adjusted to Tg-20 without locally heating the peeling point. It was manufactured by setting it to ° C. Tables 1 and 2 below show the various optical properties and film scratch evaluation results of the films of the examples and comparative examples.

From Table 1 and Table 2, all of the films of Examples 1 to 13 of the present invention have a surface haze of 0.5% or less, good expression of optical properties, and good surface condition of the film surface. I found out.
On the other hand, the film of Comparative Example 1 is obtained by pressing the first holding roll and the second holding roll of the metal touch belt at the same pressure, and the surface of the film obtained in comparison with Examples 4-7. The haze was high and the film surface was poor. The film of Comparative Example 2 uses a back roll in a general form, that is, a form in which the center of gravity of the backup roll is on the connecting line between the pinching center point and the center of gravity of the touch roll. The film obtained had a high haze and the film surface was poor. In Comparative Example 3, only the metal elastic touch roll and the chill roll were used for clamping without using the backup roll, and the obtained film had a poor surface shape and a high surface haze.
Moreover, when the inclination structure of the film of Examples 1-13 was confirmed, it turned out that the inclination azimuth | direction of Examples 1-12 is the slow axis direction in a film surface, and has a slow axis in MD direction. Moreover, it turned out that the inclination direction of Example 13 is the fast axis direction in the film plane, the fast axis is in the MD direction, and the slow axis is in the TD direction. As described above, according to the production method of the present invention, the expression of the retardation and the tilt structure are large, the film has a tilt direction in either the slow axis direction or the fast axis direction in the film plane, and It was found that a thermoplastic film having a good surface shape can be obtained.

(Preparation of polarizing plate)
A polarizing plate was produced using the produced films of Examples 1 to 13 and Comparative Examples 1 to 3. Specifically, first, iodine was adsorbed to a stretched polyvinyl alcohol film to prepare a polarizing film. Using this polarizing film, a Re = 270 nm λ / 2 plate composed of a 60 μm TAC film (manufactured by Fuji Film Co., Ltd.) and a uniaxially stretched norbornene polymer film in the arrangement shown in FIG. 3, Invention 1 Or the film of the comparative example 1 was bonded together. In this way, two polarizing plates PL1 using the film of Example 1 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 as shown in FIG. 3 above and below the liquid crystal cell. 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 obtained liquid crystal display device, a region where display unevenness such as oblique stripes and fine haze is generated is visually detected from the front, and the area of this region is divided by the total area of the liquid crystal display plate as a percentage. Indicated. Further, display unevenness during black display in the azimuth angle direction 45 degrees and the polar angle direction 60 degrees from the front of the liquid crystal display device was similarly observed. Evaluation was made according to the following criteria.
(Double-circle): It is not worried at all and there is no display nonuniformity from the front and diagonal.
○: Slight display unevenness was seen, and display unevenness from the front and oblique directions was less than 3%.
(Triangle | delta): Although change is worrisome, it is a grade which is permissible, and the display nonuniformity from the front and diagonal was 3% or more and less than 10%.
X: The change was worrisome, and the display unevenness from the front and diagonal was 10% or more.
Further, regarding the liquid crystal display device LCD1 which is an embodiment of the present invention, when a viewing angle with a contrast ratio of 10 or more in monochrome display was obtained, the LCD 1 achieved a viewing angle of 55 ° or more in any of the left, right, top and bottom directions. It was. 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.

(Stretching)
The unstretched film after film formation of Example 4 was stretched 1.4 times while being heated at a temperature of Tg + 2 ° C. using a transverse stretch tenter. The obtained stretched film has a thickness of 51 μm, the slow axis is in the TD direction, the tilt direction is the MD direction, Re [0 °] = 107 nm, Re [40 °] = 148 nm, Re [−40 °] = 33 nm Γ = 115 nm, surface haze was 0.1%, and scratches were “◎”. It was found that haze was reduced and scratches were improved as compared to unstretched films.

1 die 2 melt 3 first holding roll of metal touch belt 4 second holding roll of metal touch belt 5 metal touch belt 6 chill roll 7 touch roll 7 'touch roll shaft 8 backup roll 8' backup roll shaft 9 heating means 10 clamping pressure The distance between the center line and the center of gravity of the touch roll and the center of gravity of the backup roll

Claims (19)

Production of a film comprising a step of passing a melt of a composition containing a thermoplastic resin between a first clamping surface and a second clamping surface constituting a clamping device and continuously pressing to form a film. A method,
At least one of the first clamping surface or the second clamping surface is elastic,
The moving speed of the first clamping surface is made faster than the moving speed of the second clamping surface,
A method for producing a thermoplastic film, wherein the slipping property of the melt from the pressing surface is reduced at the peeling point of the pressing surface of the first pressing surface and the second pressing surface that is peeled off first from the melt.   A step of melt-extruding a composition containing the thermoplastic resin from a die, and a step of passing the melt-extruded melt between the first and second pressing surfaces. The method for producing a thermoplastic film according to claim 1.   The method for producing a thermoplastic film according to claim 1 or 2, wherein the slipperiness at the peeling point is reduced by using at least one of pressure adjusting means and heating means.   The first clamping surface of the clamping device is a metal belt, the belt is driven by at least two driving rolls, and the driving roll closest to the peeling point is heated among the at least two driving rolls. The manufacturing method of the thermoplastic film as described in any one of Claims 1-3.   The method for producing a thermoplastic film according to claim 4, wherein the at least two driving rolls press the melt through the belt.   The first clamping surface of the clamping device is a metal belt, the belt is driven by at least two driving rolls, the at least two driving rolls press the melt through the belt, and the peeling point is the most. The thermoplastic resin according to any one of claims 1 to 5, wherein a pressure at which the driving roll close to the pressure sandwiches the melt is made smaller than a pressure at which the other driving roll sandwiches the melt. A method for producing a film.   The method for producing a thermoplastic film according to any one of claims 1 to 3, wherein the pinching device is two rolls having different peripheral speeds and locally heats the peeling point.   The method for producing a thermoplastic film according to claim 7, wherein the peeling point is locally heated by warm air by a heater or a heating contact roll. The first clamping surface is an elastic roll;
The clamping device has a backup roll disposed adjacent to the elastic roll;
The backup roll is arranged such that its center of gravity is shifted in the direction of the peeling point from the connecting line between the center of pinching (the intermediate point between the pinching start point of the melt and the peeling point) and the center of gravity of the elastic roll. The method for producing a thermoplastic film according to any one of claims 1 to 3, 7 and 8.   The surface roughness Ra of each said 1st clamping surface and said 2nd clamping surface is 0.01 micrometer-0.5 micrometer, The manufacture of the thermoplastic film as described in any one of Claims 1-9 characterized by the above-mentioned. Method.   The thickness at the time of film-forming of the composition containing the thermoplastic resin shape | molded in the said film form shall be 10 micrometers-90 micrometers, The manufacture of the thermoplastic film as described in any one of Claims 1-10 characterized by the above-mentioned. Method.   The method for producing a thermoplastic film according to any one of claims 1 to 11, further comprising a step of stretching the composition containing the thermoplastic resin formed into a film shape in at least one direction.   The method for producing a thermoplastic film according to any one of claims 1 to 12, wherein the thermoplastic film is a cyclic olefin resin, a polycarbonate resin, an acrylic resin, or a cellulose acylate resin. .   A thermoplastic film formed by the production method according to claim 1.   A thermoplastic film having a surface haze of 0.5% or less and having a tilt orientation in either the slow axis direction or the fast axis direction in the film plane. The thermoplastic film according to claim 14 or 15, wherein the following formulas (I) and (II) are satisfied.
30 nm ≦ Re [0 °] ≦ 250 nm (I) Formula (In the formula (I), Re [0 °] is a front surface at a wavelength of 550 nm measured from the normal direction in the plane including the film tilt direction and the film normal. Represents direction retardation.)
30 nm ≦ γ ≦ 350 nm (II) Formula γ = | Re [+ 40 °] −Re [−40 °] | Formula (II ′)
(In the formulas (II) and (II ′), Re [+ 40 °] is a wavelength measured from a direction tilted 40 ° toward the tilt azimuth side with respect to the normal in the plane including the film tilt azimuth and film normal. Represents the retardation in the front direction at 550 nm, and Re [−40 °] represents the retardation in the front direction at a wavelength of 550 nm measured from a direction inclined 40 ° to the opposite side of the tilt direction with respect to the normal.   A polarizing plate using at least one thermoplastic film according to any one of claims 14 to 16.   An optical compensation film comprising at least one thermoplastic film according to any one of claims 14 to 16.   A liquid crystal display device comprising at least one thermoplastic film according to any one of claims 14 to 16.

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