JP5411603B2 - Film, film manufacturing method, polarizing plate and liquid crystal display device - Google Patents

Description

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

  In recent years, with the rise of the liquid crystal display market, various films and manufacturing methods thereof have been developed. For example, as a method for producing a retardation film for a TN mode liquid crystal, when a film is sandwiched by a clamping device composed of two rolls, a peripheral speed difference is given between the two rolls (hereinafter referred to as a peripheral speed difference film formation). In other words, a method is known in which an inclined structure having an optical axis inclined in the film thickness direction is formed and then stretched.

  For example, Patent Document 1 describes a method in which a film is formed in advance by solution casting, and then the optical axis is inclined by passing between two rolls having different peripheral speeds, and then stretched. Yes. On the other hand, Patent Document 1 did not suggest application to a melt.

  Patent Document 2 describes a method in which a metal roll and a metal roll whose surface is covered with rubber are used, and a stretching is performed after giving a peripheral speed difference thereto.

  However, the effect of optical compensation is not sufficient simply by using an optical film having an inclined optical axis for a liquid crystal display. For example, Patent Document 2 discloses an optical film having an optical axis inclined by 11.5 to 18.2 ° in the embodiment, but there is no description about the relationship between the optical axis inclination angle and the optical compensation of the liquid crystal display. Not. In addition, in order to perform optical compensation of a transmissive TN or ECB liquid crystal display or a transflective TN or ECB liquid crystal display, it is necessary to have a large phase difference until the retardation of the liquid crystal cell can be compensated. It was not sufficient that the optical axis was inclined by 11.5 to 18.2 °. Therefore, an optical film having a larger inclined structure has been desired.

  On the other hand, in recent years, the demand for image quality required for liquid crystal display devices has been increasing year by year, and not only does the viewing angle compensation when looking at the liquid crystal display device from an oblique direction, but also the image quality when looking from an oblique direction is good. Development of an optical compensation film is desired.

Japanese Patent Laid-Open No. 7-151915 JP 2007-38646 A

  When the present inventors used a film prepared by the methods described in Patent Documents 1 and 2 in a liquid crystal display device, it was found that display unevenness occurred when viewed from an oblique direction. Moreover, although the method of the said patent document 2 is performing the horizontal extending | stretching process, although the method of heat-processing is disclosed as a processing method of the film after horizontal extending | stretching, when such heat processing is performed, Even if there was, the display unevenness when looking from the same angle was not improved.

  The present invention has been made in consideration of the above-mentioned problems, and a first object of the present invention is to provide a film with little occurrence of display unevenness viewed obliquely when used in a liquid crystal display device, and a method for manufacturing the same. There is to do. A second object of the present invention is to provide a polarizing plate and a liquid crystal display device using the film.

  As a result of intensive studies to solve the above problems, the present inventors found that the display unevenness when looking at the liquid crystal display device from an oblique direction is γ (retardation when measured from the left and right oblique directions) formed by the peripheral speed difference film formation. It was found that the difference in γ varies in the width direction when stretched, and that the variation in γ causes display unevenness when viewed from an oblique direction when incorporated in a liquid crystal display panel. In addition, as a result of further investigation on such a new problem of suppressing the variation of γ, the variation of γ is surprisingly suppressed by curving the film by a specific range after the transverse stretching step, and further, the liquid crystal When used in a display device, it has been found that the occurrence of display unevenness seen from an angle is reduced. That is, the inventors have found that the following production method and a film produced by the method can solve the above problems, and have completed the present invention described below.

[1] A film containing a thermoplastic resin and having a slow axis direction distribution of γ represented by the following formula (I) of 0% to 10.5%.
γ = | Re [+ 40 °] −Re [−40 °] | (I) Formula (In the formula (I), Re [+ 40 °] is measured from a direction inclined by 40 ° toward the tilt direction with respect to the film normal. Represents the retardation in the in-plane direction at a wavelength of 550 nm, and Re [−40 °] represents the retardation in the in-plane direction at a wavelength of 550 nm measured from a direction inclined by −40 ° to the tilt direction with respect to the normal line. .)
[2] The film according to [1], wherein an angle formed by the slow axis and the tilt direction is 30 ° to 150 °.
[3] The film according to [1] or [2], which satisfies the following formulas (II) and (III):
50 nm ≦ Re [0 °] ≦ 300 nm (II) Formula 40 nm ≦ γ ≦ 300 nm (III) Formula (In the formula (II), Re [0 °] is a letter in the in-plane direction at a wavelength of 550 nm measured from the film normal direction. Represents the foundation.)
[4] The film according to any one of [1] to [3], wherein retardation Rth in the thickness direction is 40 nm to 300 nm.
[5] Any one of [1] to [4], wherein the thermoplastic resin is at least one selected from polycarbonate resins, cyclic olefin resins, acrylic resins, and cellulose acylate resins. Film.
[6] A pressing step for forming a film by continuously pressing a melt of a composition containing a thermoplastic resin between a first clamping surface and a second clamping surface constituting the clamping device. (In the clamping step, the moving speed of the first clamping surface is made faster than the moving speed of the second clamping surface), a step of solidifying the film-like melt to obtain a film, and an obtained film A transverse stretching step that stretches in the film width direction, and a center portion in the width direction of the film after the transverse stretching step is curved in the film normal direction with respect to both ends in the width direction, and is represented by the following formula (IV) And a step of controlling the content to 0.1% to 10%.
Formula (IV)
Bending amount (%) = 100 × (the difference in height between the central portion in the width direction of the film and both ends in the width direction) / (total width of the film)
[7] 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. [6] The method for producing a film according to [6].
[8] The lateral stretching step further includes a step of heating the clip to Tg−80 ° C. to Tg, and a step of lateral stretching while gripping both ends of the film with the heated clip. [6] or the method for producing a film according to [7] (wherein Tg represents a glass transition temperature of the thermoplastic resin).
[9] The film according to any one of [6] to [8], wherein the transverse stretching step is performed by controlling the film film surface temperature to be Tg−40 ° C. to Tg + 5 ° C. Manufacturing method.
[10] The method for producing a film according to any one of [6] to [9], wherein in the clamping step, the melt is clamped at a pressure of 5 to 500 MPa.
[11] In the clamping step, control is performed such that the difference in moving speed between the first clamping surface and the second clamping surface of the clamping device defined by the following formula (V) is 0.5 to 20%. The method for producing a film according to any one of [6] to [10].
Formula (V)
Difference in moving speed (%) = 100 × {(moving speed of first pressing surface) − (moving speed of second pressing surface)}
/ (Moving speed of the first clamping surface)
[12] The method for producing a film according to any one of [6] to [11], wherein in the pressing step, the pressing device is two rolls having different peripheral speeds.
[13] The method for producing a film according to [12], wherein a metal touch roll having an outer cylinder thickness of 6 to 45 mm is used for one of the two rolls constituting the pressing device.
[14] A film formed by the method according to any one of [6] to [13].
[15] A polarizing plate comprising at least one film according to any one of [1] to [5] and [14].
[16] A liquid crystal display device using at least one film according to any one of [1] to [5] and [14].

  ADVANTAGE OF THE INVENTION According to this invention, when using for a liquid crystal display, the film with little display nonuniformity at the time of peeping into a liquid crystal display device from the diagonal, and its manufacturing method can be provided. Moreover, in a preferred embodiment of the present invention, it is possible to provide a film with little occurrence of display unevenness viewed obliquely even after roll aging and a method for producing the same. Furthermore, in a more preferred embodiment of the present invention, a film capable of realizing sufficient optical compensation and a method for producing the film can also be provided. Specifically, the film having the above optical characteristics can realize sufficient optical compensation when used in a TN mode, ECB mode, or OCB mode liquid crystal display. For example, in a TN mode liquid crystal display, since the viewing angle is narrow, an optical compensation film provided with an optical compensation layer made of a liquid crystal composition that realizes optical compensation is usually used by being laminated on a polarizer. When the film of the invention is used, the viewing angle is simpler than that using an optical compensation film having an optical compensation layer made of a conventional liquid crystal composition, without using an optical compensation layer made of a liquid crystal composition. Compensation can be performed. Moreover, the film of this invention can be provided with the manufacturing method of the film of this invention.

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. In this specification, the tilt direction represents the direction in which | Re [+ 40 °] −Re [−40 °] |

[the film]
The film of the present invention contains a thermoplastic resin and is characterized in that the distribution in the slow axis direction of γ represented by the following formula (I) is 0% to 10.5%.
γ = | Re [+ 40 °] −Re [−40 °] | (I) Formula (In the formula (I), Re [+ 40 °] is measured from a direction inclined by 40 ° toward the tilt direction with respect to the film normal. Represents the retardation in the in-plane direction at a wavelength of 550 nm, and Re [−40 °] represents the retardation in the in-plane direction at a wavelength of 550 nm measured from a direction inclined by −40 ° to 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 ° when the sign of the inclination angle (θ) is not considered. . When considering the sign of the inclination angle (θ), the direction in which Re [+ 40 °] is measured and the direction in which Re [−40 °] are measured are positions symmetrical with respect to the film normal.

(Distribution of γ in the slow axis direction)
The film of the present invention has a γ slow axis direction distribution of 0% to 10.5%, preferably 0% to 7%, and more preferably 0% to 5%. If the distribution of γ in the slow axis direction is 10.5% or less, it is difficult for practical use to have different γ depending on the location. Display unevenness is difficult to see. Here, among the optical characteristics of the film, γ indicates a difference in birefringence when measured from the left and right, and therefore, display unevenness tends to occur when viewed from the left and right oblique directions.
Such a distribution of γ in the slow axis direction is preferably in the above range wherever it takes, for example, the variation in the slow axis direction 30 cm arbitrarily taken in the slow axis direction is in this range. preferable.

The distribution of γ in the slow axis direction can be measured by the following method. 30 cm of the slow axis direction of an arbitrary part of the stretched film is divided into 10 equal parts, and γ is measured by a measurement method described later. Of the 10 measured values of γ, the difference between the maximum and minimum points divided by the average of 10 points and expressed as a percentage was defined as the distribution (%) of γ in the slow axis direction.
Note that the variations in Re [0 °], slow axis, and Rth are also measured.

(An angle between the slow axis and the tilt direction)
In the film of the present invention, the angle formed between the slow axis and the tilt direction is preferably 30 ° to 150 °, more preferably 40 ° to 140 °, and still more preferably 50 ° to 130 °. In this way, the slow axis is tilted from the tilt orientation, and when the film is wound up on a roll, it is aged, and when it is used for a liquid crystal display panel thereafter, display unevenness when viewed from an angle is difficult to be visually recognized. To preferred. Specifically, the greater the absolute value (length × dimensional change rate) of the dimensional change when the film of the present invention is wound on a roll, the greater the stress, and thus the dimensional change when wound on the roll. If it occurs, even if the distribution in the slow axis direction of γ immediately after stretching is in the above range, the distribution in the slow axis direction of γ after roll aging may increase to a level outside the preferred range. . That is, in the film of the present invention, the distribution of γ in the slow axis direction after such roll aging is preferably 0% to 10.5%, more preferably 0% to 7%, % To 5% is particularly preferable.

  The absolute value of the dimensional change when the film of the present invention is wound on a roll is the largest when the slow axis exists in the tilt direction, and as the slow axis tilts from the tilt direction (this angle is φ ) Will decrease to the length multiplied by cosφ. For example, the case where the angle between the slow axis and the tilt azimuth is 30 ° and 150 ° (= 180 ° −30 °) indicates that the tilt azimuth is symmetrical and the tilt azimuth is the axis. 30 ° and −30 ° are substantially the same.

(In-plane retardation Re, thickness direction retardation Rth)
The film of the present invention preferably satisfies the following formulas (II) and (III).
50 nm ≦ Re [0 °] ≦ 300 nm (II) Formula 40 nm ≦ γ ≦ 300 nm (III) Formula (In the formula (II), Re [0 °] is a letter in the in-plane direction at a wavelength of 550 nm measured from the film normal direction. Represents the foundation.)
More preferably, it is a case where 70 nm ≦ Re [0 °] ≦ 250 nm, 60 nm ≦ γ ≦ 250 nm is satisfied,
More preferably, 100 nm ≦ Re [0 °] ≦ 200 nm and 80 nm ≦ γ ≦ 180 nm.

  When the retardation Re [0 °] in the front direction is in the range of the formula (II), the liquid crystal compensation ability is improved when incorporated in a liquid crystal display device, and slight unevenness is difficult to be visually recognized. The display unevenness when viewed from an oblique angle, where it is difficult to compensate for the optical characteristics, is substantially reduced.

When γ is large, it means that Re measured obliquely is different between, for example, the left side and the right side, and that an inclined structure is formed in the film when viewed from the thickness direction. This tilt structure has the effect of complementing the liquid crystal alignment in the liquid crystal display device and improving the viewing angle.
When γ is in the range of the formula (III), the liquid crystal compensation ability is improved when incorporated in a liquid crystal display device, and slight unevenness is difficult to be seen, particularly from an oblique direction that is difficult to compensate for the optical characteristics of the liquid crystal display panel. Display unevenness when peeping is substantially reduced.

  The film of the present invention preferably has a thickness direction retardation Rth of 40 nm to 300 nm, more preferably 50 nm to 200 nm, and still more preferably 50 nm to 150 nm. Rth is a difference in refractive index between the thickness direction and the in-plane direction, and affects display unevenness when viewed from an oblique direction. If Rth is in the range of 40 nm to 300 nm, display unevenness in an oblique direction is remarkably reduced.

  A film having γ, Re [0 °] and Rth in the above preferred ranges 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 an improvement in viewing angle characteristics and achieves a wide viewing angle. be able to.

  The film thickness of the film of the present invention is preferably 100 μm or less. When used for a liquid crystal display or the like, it is preferably 80 μm or less from the viewpoint of thinning. Such a thin film can be produced by the film production method of the present invention.

  The variation in Re [0 °] appears as display unevenness when used in a liquid crystal display. Therefore, the variation is preferably as small as possible. Specifically, it is preferably within ± 3 nm, and within ± 1 nm. More preferably it is. 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 °.

なお、式中、Ｒｅ［θ］は法線方向から角度θ傾斜した方向におけるレターデーション値を表す。
また、式（Ａ）において、ｎｘは、面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表し、ｄは膜厚を表す。
測定されるフィルム状の測定対象物が１軸、又は２軸の屈折率楕円体で表現できないもの、いわゆる光学軸（ｏｐｔｉｃ ａｘｉｓ）がない測定対象物の場合には、以下の方法により、Ｒｔｈが算出される。
Ｒｔｈは、前記Ｒｅを面内の任意に設定した方位（ＫＯＢＲＡ ２１ＡＤＨ又はＷＲに設定できる）を傾斜軸（回転軸）としてフィルム法線方向に対して−５０°から＋５０°まで１０度ステップで各々その傾斜した方向から波長５５０ｎｍの光を入射させて１１点測定し、その測定されたレターデーション値と、平均屈折率の仮定値、及び入力された膜厚値を基にＫＯＢＲＡ ２１ＡＤＨ又はＷＲが算出する。
上記の測定において、平均屈折率の仮定値は、ポリマーハンドブック（ＪＯＨＮ ＷＩＬＥＹ＆ＳＯＮＳ、ＩＮＣ）、各種光学補償フィルムのカタログの値を使用することができる。平均屈折率の値が既知でないものについては、アッベ屈折計で測定できる。主な光学補償フィルムの平均屈折率の値を以下に例示すると、セルロースアシレート（１．４８）、シクロオレフィンポリマー（１．５２）、ポリカーボネート（１．５９）、ポリメチルメタクリレート（１．４９）、ポリスチレン（１．５９）である。これら平均屈折率の仮定値と膜厚を入力することで、ＫＯＢＲＡ ２１ＡＤＨ又はＷＲは、ｎｘ、ｎｙ、ｎｚを算出する。この算出されたｎｘ、ｎｙ、ｎｚよりＮｚ＝（ｎｘ−ｎｚ）／（ｎｘ−ｎｙ）が更に算出される。
なお、Ｒｅ［θ°］、Ｒｔｈ及び屈折率の測定波長は特別な記述がない限り、測定波長５５０ｎｍでの値である。 The optical characteristic value can be measured by the following method.
In this specification, Re and Rth are the in-plane retardation (nm) and retardation in the thickness direction (nm) of a film-like object to be measured, such as an optically anisotropic layer, a film, or a laminate. Represent.
Re [0 °] is measured by making light having a wavelength of 550 nm incident in the normal direction of a film-like measurement object in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
When the film-like measurement object to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth is calculated by the following method.
Rth is defined by using Re as an in-plane slow axis (determined by KOBRA 21ADH or WR) as an inclination axis (rotation axis) (in the case where there is no slow axis, the in-plane of the film-like object to be measured) The light having a wavelength of 550 nm from the inclined direction in steps of 10 degrees from the normal direction to −50 ° to + 50 ° with respect to the normal direction of the film-like object to be measured. The KOBRA 21ADH or WR is calculated based on the retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
Retardation value from two inclined directions with the slow axis as the rotation axis (in the absence of the slow axis, the in-plane arbitrary direction of the film-like object to be measured is the rotation axis). Rth can also be calculated from the following formula (A) and formula (B) based on the measured value, the assumed value of the average refractive index, and the input film thickness value.

In the formula, Re [θ] represents a retardation value in a direction inclined by an angle θ from the normal direction.
In the formula (A), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz represents the direction orthogonal to nx and ny. Refractive index is represented, d represents a film thickness.
In the case where a film-like measurement object to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a measurement object without a so-called optical axis, Rth is determined by the following method. Calculated.
Rth is an azimuth (respectively set to KOBRA 21ADH or WR) in which Re is set in the plane as a tilt axis (rotation axis) in a step of 10 degrees from −50 ° to + 50 ° with respect to the film normal direction Measured 11 points with light having a wavelength of 550 nm incident from the inclined direction, and KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value. To do.
In the above measurement, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, INC) and catalogs of various optical compensation films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical compensation films are as follows: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49) Polystyrene (1.59). The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.
Note that the measurement wavelengths of Re [θ °], Rth, and refractive index are values at a measurement wavelength of 550 nm unless otherwise specified.

In the present invention, Re [0 °], Re [+ 40 °] and Re [−40 °] of the film were measured from the normal direction of the film using KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) ( The retardation value at a wavelength of 550 nm (at an inclination angle of 0 °), the retardation value measured at an angle of 40 ° toward the inclined azimuth side or temporary inclination azimuth side with respect to the normal line (at an inclination angle of 40 degrees), and the Retardation value (at an inclination angle of −40 degrees) measured from a direction inclined by −40 ° to the tilt direction side or temporary tilt direction side with respect to the normal line is represented. Note that the direction in which Re [+ 40 °] is measured and the direction in which Re [−40 °] are measured are positions that are line-symmetric with respect to the film normal.
Here, the inclination direction was determined by the following method.
(1) The slow axis direction in the film plane is 0 °, the fast axis direction in the film plane is 90 °, and the temporary tilt direction is set in increments of 0.1 ° between 0 ° and 90 °.
(2) Re [+ 40 °] and Re [−40 °] are measured from the direction inclined by 40 ° or −40 ° toward each temporary inclination direction with respect to the film normal, and | Re [+40 of each temporary inclination direction °] −Re [−40 °] |
(3) The direction in which | Re [+ 40 °] −Re [−40 °] | is maximized is determined as the tilt direction.
That is, in this specification, “having a tilted orientation” means that there is an orientation in which | Re [+ 40 °] −Re [−40 °] |
Further, in this specification, Rth of the film is calculated by KOBRA 21ADH or WR using the tilt direction as the tilt axis (rotation axis).
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.
Further, the variation in Re [0 °] can be measured by the following method. Sampling is performed at arbitrary 10 or more positions 2 mm or more apart from each other on the film surface, Re [0 °] is measured by the above method, and the difference between the maximum value and the minimum value is represented by the variation in Re [0 °]. To do.
Further, the slow axis and the variation of Rth described later are 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 polycarbonate resin, the cyclic olefin resin, and the acrylic resin And at least one selected from cellulose acylate resins. The cyclic olefins are preferably cyclic olefins obtained by addition polymerization.

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

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

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

  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.

  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. The total acyl substitution degree of the cellulose acylate resin is preferably 2.1 to 3.0, and the substitution degree of the acetyl group is preferably 0.05 to 2.5, more preferably 0.05 to 0.5 or 1. 5 to 2.5. The degree of propionyl substitution is preferably 0.1 to 2.8, more preferably 0.1 to 1.2 or 2.3 to 2.8.

  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” manufactured by Asahi Kasei Chemical Co., Ltd., which will be described later, 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 2008-74818. No., International Publication WO2005 / 105 Those described in each publication such as 918 can be used. Among these, those described in JP-A-2008-74918 are more preferable.
The glass transition temperature (Tg) of these resins is preferably 106 ° C to 170 ° C, more preferably 110 ° C to 160 ° C, still more preferably 115 ° C to 150 ° C.

Among these, the thermoplastic resin is preferably a cyclic olefin resin, more preferably a norbornene resin from the 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 Co., Ltd.

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

  The phosphite stabilizer is useful to have a high molecular weight in order to maintain stability at high temperature, has a molecular weight of 500 or more, more preferably a molecular weight of 550 or more, and particularly a molecular weight of 600 or more. Is preferred. Furthermore, at least one substituent is preferably an aromatic ester group. The phosphite ester stabilizer is preferably a triester, and is desirably free of impurities such as phosphoric acid, monoester and diester. When these impurities are present, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly 2% by mass or less. These include compounds described in [0023] to [0039] of JP-A No. 2004-182979, JP-A-51-70316, JP-A-10-306175, JP-A-57. The compounds described in JP-A-78431, JP-A-54-157159, and JP-A-55-13765 can also be mentioned. Preferable specific examples of the phosphite ester stabilizer include the following compounds, but the phosphite ester 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, 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. It is 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-2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or a cyclohexyl group An acrylic polymer or the like having 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]
The film production method of the present invention (hereinafter also referred to as the production method of the present invention) is a melt of a composition containing a thermoplastic resin between a first clamping surface and a second clamping surface constituting a clamping device ( Hereinafter, a pressing step of continuously pressing and forming into a film by passing the melt (in the pressing step, the moving speed of the first pressing surface is higher than the moving speed of the second pressing surface). And a step of solidifying the film-like melt to obtain a film, a transverse stretching step of stretching the obtained film in the film width direction, and a widthwise central portion of the film after the transverse stretching step in the width direction. And bending the film in the normal direction with respect to both ends, and controlling the bending amount represented by the following formula (IV) to 0.1% to 10%.
Formula (IV)
Bending amount (%) = 100 × (the difference in height between the central portion in the width direction of the film and both ends in the width direction) / (total width of the film)
It is a feature of the present invention that differs from the conventional method that the film after the transverse stretching step is curved in a specific range as described above. 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 circumferential 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. Among these, it is preferable that the two rolls have different peripheral speeds since the pressure can be applied uniformly by the clamping device.
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 step of forming a film by pressing between the first clamping surface and the second clamping surface constituting the clamping device and continuously clamping (hereinafter also referred to as a clamping step) is performed. However, there is no particular limitation on the means for supplying the melt (melt) of the composition containing the thermoplastic resin in the clamping step. For example, as a specific means for supplying the melt, an embodiment using an extruder for melting a thermoplastic resin composition and extruding it 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 comprises 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 in the first compaction 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. As said thermoplastic resin, what was demonstrated as a thermoplastic resin contained in the film of this invention can be used, and its preferable range is also the same.
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, the dried pellets are then fed into a cylinder via a feed port of the extruder, and are kneaded and melted. The inside of the cylinder is preferably 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.

  The clearance of the die exit portion (hereinafter also referred to as lip gap) is generally 1.0 to 30 times, preferably 5.0 to 20 times the film thickness. 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.
Thus, the residence time from the time when the resin enters the extruder through the supply port to the time when 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.

<Clamping process>
Next, the melt of the thermoplastic resin is supplied from the supply means, and the melt is passed between the first clamping surface and the second clamping surface constituting the clamping device, and continuously pressed into a film shape. Mold 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 from the melt first, and then the melt 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 first surface to be peeled first is the first pinching surface (pressing surface having a high moving speed).

In the production method of the present invention, in addition to the conventional method of continuously pressing the melt of the thermoplastic resin between the first clamping surface and the second clamping surface constituting the clamping device to form a film, In the pinching step, the melt is preferably pinched at a pressure of 5 MPa to 500 MPa in the width direction, more preferably 20 MPa to 300 MPa, and even more preferably 30 MPa to 200 MPa. The pressure of normal touch roll film formation is less than 30 MPa, but if it is 30 MPa or more, Re [0 °] and γ within the preferable ranges of the present invention can be expressed, and a strong inclined structure is formed in the film. Since the orientation becomes more difficult to change due to the shrinkage stress during the transverse stretching process described later, the distribution of γ in the slow axis direction decreases. On the other hand, if the pressure is 500 MPa, the pinching surface is appropriately deformed, so that it can be uniformly deformed in the width direction of the pinching surface, and the distribution of γ in the slow axis direction is not easily revealed after the transverse stretching step.
The roll pressure can be measured by passing a pressure measuring film (such as a prescale for medium pressure manufactured by Fuji Film) through two rolls.

In the manufacturing method of the present invention, in the clamping step, a difference in moving speed between the first clamping surface and the second clamping surface of the clamping device defined by the following formula (V) is 0.5 to 20%. It is preferable to control.
Formula (V)
Difference in moving speed (%) = 100 × {(moving speed of first pressing surface) − (moving speed of second pressing surface)}
/ (Moving speed of the first clamping surface)
The movement speed difference between the clamping surfaces of the clamping device is more preferably 1% to 15%, and further preferably 2% to 10%.
If the moving speed difference is 20% or less, the melt does not cause a slip between the clamping surfaces of the clamping device, and the pressure between the clamping devices is unlikely to occur. If this unevenness does not occur, unevenness is not amplified during the transverse stretching process, and the slow axis direction distribution of γ decreases. On the other hand, if the moving speed difference is 0.5% or more, a strong gradient structure can be formed, and the decline of the gradient structure due to shrinkage stress during the transverse stretching process can be suppressed. The distribution will decrease.

(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 retention of the melt between the air gaps, it is preferable that they are as close as possible, specifically 10 to 300 mm, more preferably 20 to 250 mm, and particularly preferably 30 to 200 mm. .

(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 2 m / min or more, more preferably 5 m / min or more, and 10 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.

(Film forming width)
In the production method of the present invention, the film forming width is preferably 1 m to 3 m, more preferably 1.2 m to 2.5 m, and still more preferably 1.4 m to 2 m.

(Cast using two rolls)
Among the methods of forming a film by continuously passing the melt-extruded melt between the first clamping surface and the second clamping surface constituting the clamping device to form a film, for example, two rolls (for example, It is preferable to pass between the touch roll (first roll) and the chill roll (second roll). In addition, in this specification, when it has two or more casting rolls which convey the said melt, the casting roll nearest to the said thermoplastic resin composition supply means (for example, die | dye) of the most upstream is also called a chill roll. . Hereinafter, the preferable aspect of the manufacturing method of this invention using two rolls is demonstrated.

  In the film production method of the present invention, there is no particular restriction on the landing point of the melt extruded from the supply means, and the landing point of the melt extruded from the supply means, the touch roll and the cast roll are the most. The distance from the vertical line passing through the midpoint of the gap in the approaching part may be zero or may be shifted. The landing point of the melt refers to a point where the melt extruded from the supply means contacts (lands) the touch roll or chill roll for the first time. The midpoint of the gap between the touch roll and the cast roll refers to the midpoint of the touch roll surface and the cast roll surface where the gap between the touch roll and the cast roll is the narrowest.

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

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

  The roll pressure between two rolls rotating at different peripheral speeds is preferably 5 to 500 MPa, more preferably 20 MPa to 300 MPa, particularly preferably 30 MPa to 200 MPa, and still more preferably, 40 to 200 MPa.

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

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

The material of the two rolls is preferably a metal from the viewpoint of achieving the Shore hardness, more preferably stainless steel, and a roll whose surface is plated is also preferred. Moreover, if the material of two rolls is a metal, since the surface unevenness | corrugation is small and the surface of a film is hard to be damaged, it is preferable. On the other hand, a rubber roll or a metal roll lined with rubber can be used without particular limitation as long as the roll pressure can be achieved.
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 present invention, it is preferable to form the inclined structure by sandwiching the melt immediately after coming out of the die between the touch roll and the chill roll, and giving a peripheral speed difference between them. It is preferable to use a metal roll having an outer cylinder thickness of 6 mm to 45 mm for at least one of the two rolls, and it is preferable to use a metal touch roll having an outer cylinder thickness of 6 mm to 45 mm for the touch roll. More preferably, it is a metal roll of 10 mm-40 mm, More preferably, 15 mm-35 mm. In the present invention, it is preferable to use a thicker one than a normal touch roll. If the thickness of the metal outer cylinder is 6 mm or more, the deformation of the touch roll is difficult to increase when it is pressure-bonded to the chill roll, the deformation amount, that is, the uniformity of the pressing pressure in the width direction is sufficient, and the slow axis direction of γ after stretching This is preferable because the distribution is small. On the other hand, if the thickness of the metal outer cylinder is 45 mm or less, the deformation amount of the touch roll is not too small, the contact length between the touch roll and the chill roll is sufficiently long, and a large contact pressure is applied to the film because the contact area can be taken sufficiently. There is no. As a result, even if the pressing is slightly changed in the roll width direction, large unevenness in the width direction is hardly generated in the pressing.
Conventional metal touch rolls are mainly those with a metal outer cylinder thickness as thin as 2 to 5 mm as in JP-A-11-235747, or those with a metal outer cylinder thickness of 50 mm or more like a calendar roll. In the present invention, one feature is that the slow axis direction distribution of γ can be remarkably reduced by using a roll having a novel thickness during this period.

In the production method of the present invention, by controlling the difference in peripheral speed between the two rolls through which the film-like melt passes, a shear stress is applied when the molten resin passes through the two rolls, and the film of the present invention is applied. It is preferable to manufacture. The peripheral speed difference here is expressed by the following equation with respect to the peripheral speed of the touch roll and the cooling (chill) roll.
Peripheral speed difference (%) = 100 x [(peripheral speed of faster roll)-(peripheral speed of slower roll)]
/ (Peripheral speed of faster roll)
The preferable range of the peripheral speed difference between the two rolls is the same as the preferable range of the moving speed difference in the clamping device.

  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).

  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 It is preferred to use two rolls of 800 mm, more particularly preferably 350-600 mm, even more preferably 350-500 nm. When a roll having 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 γ is used, and the variation of Re [0 °] and the delay of γ are slow. It can manufacture, suppressing distribution of a phase-axis direction. 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 °] and distribution of γ in the slow axis direction, the two rolls are preferably driven independently.

Further, in order to increase the expression level of γ, the surface temperature of the two rolls may be differentiated. A preferable temperature difference is 5 ° C to 80 ° C, more preferably 20 ° C to 80 ° C, and further preferably 20 ° C to 60 ° C. At that time, the temperature of the two rolls is Tg−70 ° C. to Tg + 20 ° C., more preferably Tg−50 ° C. to Tg + 10 ° C., more preferably Tg−40 ° C. to Tg + 5 ° C., using the glass transition temperature Tg of the resin. Set to. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through the touch roll.
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).

Further, in the production method of the present invention, the melt of the supplied thermoplastic resin composition is kept warm until just before contacting the at least one of the two rolls to reduce the temperature distribution in the width direction. More specifically, the temperature distribution in the width direction is preferably 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.
Furthermore, when the said shielding member is used, since it can pass between rolls in the state with the high temperature of a film-form melt, ie, a state with low melt viscosity, there also exists an effect which is easy to produce the film of this invention.
The temperature distribution of the film-like melt can be measured with a contact thermometer or a non-contact thermometer.

The said shielding member is provided inside the both ends of two rolls, for example, and the width direction side surface of the supply means (for example, die | dye) of a thermoplastic resin composition, and a clearance gap. 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 effectively 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 die and the shielding member is not necessarily provided, but is preferably formed to an extent that allows airflow in the space surrounded by the shielding member to be discharged, for example, 10 mm or less.
In addition, as the material having a heat insulating function and / or a heat reflecting function, a material excellent in wind insulation and heat retention is preferable. For example, a metal plate such as stainless steel can be preferably used.

  As a method for eliminating the variation of Re [0 °] and the distribution of γ in the slow axis direction, there is a method of increasing the adhesion when the film-like melt comes into contact with the casting roll. Specifically, the adhesion can be improved by combining electrostatic application method, air knife method, air chamber method, vacuum nozzle method and the like. Such an adhesion improving method may be performed on the entire surface of the film-like melt or may be partially performed.

  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. Thickening processing 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 / m width, more preferably 5 kg / m width to 30 kg / m width.

  The film thickness of the film obtained by the production method of the present invention when unstretched is preferably 100 μm or less. When used for a liquid crystal display or the like, from the viewpoint of thinning, it is more preferably 80 μm or less, particularly preferably 60 μm or less, and particularly preferably 40 μm or less.

<Stretching, relaxation treatment, bending>
Furthermore, after forming into a film by the said method, in the manufacturing method of this invention, the horizontal stretch process which extends | stretches the obtained film to a film width direction is performed, and the width direction center part of the film after the said horizontal stretch process is the width direction both ends. The step of bending the film in the normal direction of the film is performed, and the bending amount represented by the formula (IV) is controlled to 0.1% to 10%.
Further, other stretching and / or relaxation treatments may be performed as long as they do not contradict the spirit of the present invention. For example, each process can be implemented by the following combinations (a) to (f).
(A) transverse stretching (b) transverse stretching → relaxation treatment (c) transverse stretching → transverse stretching (d) longitudinal (transverse) stretching → transverse (longitudinal) stretching (e) longitudinal (transverse) stretching → transverse (longitudinal) stretching → Relaxation treatment (f) Transverse stretching → relaxation treatment → longitudinal stretching → relaxation treatment Among these, the step (a) is particularly preferred. Hereinafter, the stretching process will be described.

(Lateral stretching)
A) Ordinary transverse stretching In the production method of the present invention, ordinary transverse stretching can be adopted as the transverse stretching step. That is, normal transverse stretching is a transverse stretching method in which both ends of a film are held with clips and the clips are widened while being heated in an oven using a tenter. For example, the following methods can be used.
Japanese Utility Model Laid-Open Nos. 62-35817, 2001-138394, 10-249934, 6-270246, 4-30922, and 62-152721.

The production method of the present invention preferably includes a step of heating the clip to Tg−80 ° C. to Tg in the transverse stretching step, and a step of transverse stretching while gripping both ends of the film with the heated clip. Tg represents the glass transition temperature of the thermoplastic resin.
In the present invention, the increase in the distribution of γ in the slow axis direction in the tenter is such that the film in the vicinity of the clip is fixed and is less likely to be deformed by the shrinkage stress accompanying lateral stretching than in the central part in the film width direction. I found out that it was caused by. Therefore, in order to reduce the distribution of γ in the slow axis direction, it has been found effective to make the film near the clip soft and easy to deform.
As a specific measure, it is preferable that the film is stretched laterally while gripping both ends of the film with the heated clip after the step of heating the clip to the above temperature. This makes it possible to selectively heat the film in the vicinity of the clip that needs to be particularly easily deformed (fixed by the clip and hardly deformed).

The heating temperature of the clip is preferably Tg-80 ° C to Tg, more preferably Tg-60 ° C to Tg-5 ° C, and still more preferably Tg-50 ° C to Tg-10 ° C.
If the heating temperature of the clip is equal to or lower than Tg, the film of the gripping portion will not be too soft, and will not be easily stretched during stretching, and the distribution of γ in the slow axis direction can be suppressed. On the other hand, if it is Tg-80 degreeC or more, the said effect (effect by the heating of an edge part) will fully appear, and distribution of the follow-up axis direction of (gamma) can fully be suppressed, and it is preferable.

  In the heating process of the clip before gripping, a known heating device can be used without any particular limitation. For example, hot air may be applied to the clip, or the clip may be heated with an IR heater or a halogen heater. Good. Specifically, before the clip once reaches the stretching end point, return to the stretching start point without gripping the film, and install an infrared heater, halogen heater, panel heater, etc. on the upper, lower, and side of the clip. This can be achieved by installing. Examples of the infrared heater include JP-A-5-36469, JP-A-6-84586, JP-A-7-288175, JP-A-8-153572, JP-A-11-86804, JP-A-2001-6850, No. 2006-294337 can be used, and an infrared heater made by Heraeus (for example, BSG500 / 300, BSG1200 / 600, BSG2200 / 1100, BSG3750 / 1500), an infrared heater made by SIGMA (for example, IRK120V, IRK230, IRK350, IRK480) can be used. As the halogen heater, those described in JP-A-7-306604 and JP-A-10-148771 can be used. As the panel heater, those described in Japanese Utility Model Laid-Open Nos. 5-23486, 7-42906, and Japanese Patent Laid-Open Nos. 7-243656 can be used. By installing a clip temperature measuring device in these heating devices and adjusting the output of the heating device based on the measured temperature, the temperature of the clip can be adjusted within a preferred range.

  In addition to the method exemplified above as the heating device, a pipe-shaped cast heater or a tube wound with a band heater may be installed in the passage of the clip, and the heating step of the clip may be performed while adjusting the temperature. Alternatively, a pipe may be installed in the middle of the passage of the clip, and the heating step of the clip may be performed while adjusting the temperature by introducing hot air from the hot air generator into the tube.

In the production method of the present invention, the transverse stretching step is referred to as film film surface temperature (hereinafter also referred to as transverse stretching temperature. Also, in this specification, in each stretching step other than the transverse stretching, the film film surface temperature is each stretched. It is preferable to carry out by controlling so that the stretching temperature in the process is Tg−40 ° C. to Tg + 5 ° C. That is, the transverse stretching temperature in the transverse stretching step is preferably Tg-40 ° C to Tg + 5 ° C, more preferably Tg-30 ° C to Tg ° C, and further preferably Tg-20 ° C to Tg-3 ° C. Here, the transverse stretching temperature in the transverse stretching step represents an average temperature from the stretching start point to the stretching end point. The stretching time in the transverse stretching step is preferably 1 second to 10 minutes, more preferably 2 seconds to 5 minutes, and even more preferably 5 seconds to 3 minutes. By controlling the stretching temperature and the stretching time within the above ranges, it is difficult to relax the tilt structure in the thickness direction in the film formed in the melt clamping step, and the tilt structure of the film after stretching can be largely maintained. And can form γ within the preferred range of the present invention. In addition, by controlling the stretching temperature and the stretching time within the above ranges, the angle formed by the slow axis of the stretched film and the tilt direction can be controlled within the preferred range. The stretching temperature in the transverse stretching step can be controlled by sending wind at a desired temperature into the tenter.
The draw ratio in the transverse drawing step is 1.05 to 3 times, more preferably 1.1 to 2.6 times, and still more preferably 1.2 to 2.3 times.

By such a transverse stretching step, it is possible to control the range of γ slow axis direction distribution (0% to 10.5%) of the present invention.
If the slow axis direction distribution of γ is desired to be 0%, for example, temperature distribution is given to the end and center of the hot air outlet for temperature adjustment of the tenter, and the temperature of the outlets at both ends is set to 15 to 40 ° C. from the center. This can be achieved by increasing the height.
Further, in the production method of the present invention, the transverse stretching step may be performed in one step or in multiple steps, but is preferably performed in one step.

  For such lateral stretching, besides the normal lateral stretching in which the clip is widened in the width direction in the tenter, the following stretching method in which the clip is held and widened in the same manner as these can be applied.

B) Simultaneous biaxial stretching As in normal transverse stretching, the clip is widened in the transverse direction, but at the same time it is stretched and contracted in the longitudinal direction. Specifically, the following methods can be used.
Japanese Utility Model Laid-Open Nos. 55-93520, 63-247021, 6-210726, 6-278204, 2000-334832, 2004-106434, 2004-195712. JP-A-2006-142595, JP-A-2007-210306, JP-A-2005-22087, JP-T-2006-517608, JP-A-2007-210306.

C) Diagonal stretching Like normal transverse stretching, the clip is widened in the transverse direction, but can be stretched in the oblique direction by changing the transport speed of the left and right clips. Thereby, it can be set to 30 degrees-150 degrees from MD direction, More preferably, it is 40 degrees-140 degrees, More preferably, it is 50 degrees-130 degrees, Specifically, the following methods can be used.
JP 2002-22944, JP 2002-86554, JP 2004-325561, JP 2008-23775, JP 2008-110573, JP 2000-9912, JP 2003-342384, JP-A No. 2004-20701, JP-A No. 2004-258508, JP-A No. 2006-224618, JP-A No. 2006-255893, JP-A No. 2008-221434, JP-A No. 2003-342384, and International Publication Nos. WO 2003/102639.

  Thus, the thickness of the film after transverse stretching is 10 μm to 90 μm, more preferably 20 μm to 80 μm, and further preferably 25 μm to 70 μm. If the thickness of the film after transverse stretching is 90 μm or less, a firm gradient structure can be created in the preparation of the gradient structure film. If the thickness is thin to some extent, it is easy to give a shear (shear stress) to the front and back of the film, and the distribution of γ in the slow axis direction can be suppressed. On the other hand, if it is 10 μm or more, the flexural elasticity of the film is sufficiently strong, and the film does not flutter with the wind blown for temperature control by the tenter during the transverse stretching process, and a uniform transverse stretching process can be achieved. The slow axis direction distribution can be suppressed.

(Preheating, heat fixation)
By performing preheating before such a transverse stretching process or heat setting after the transverse stretching process, the Re and Rth distributions of the film after transverse stretching are reduced, and variations in orientation angles associated with bowing are reduced. it can. 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.

(Curvature after transverse stretching)
The production method of the present invention includes a step of bending the central portion in the width direction of the film after the transverse stretching step in the normal direction of the film with respect to both end portions in the width direction, and a bending amount represented by the following formula (IV): Control to 0.1% to 10%. Here, the bending amount is preferably 0.3% to 8%, more preferably 0.5% to 6% of the total width of the film. When the bending amount is 0.1 to 10%, the distribution of γ in the slow axis direction is suppressed, and the display unevenness in the oblique direction when the film is incorporated in a liquid crystal display device is remarkably improved. In addition, it is preferable to implement the process of curving such a film at (lateral stretching temperature) to (lateral stretching temperature −80 ° C.), more preferably (lateral stretching temperature −10 ° C.) to (lateral stretching temperature −50). ° C).
Formula (IV)
Bending amount (%) = 100 × (the difference in height between the central portion in the width direction of the film and both ends in the width direction) / (total width of the film)

Here, specifically, the curve refers to the center in the width direction of the film from a straight line connecting the clips (that is, representing the height of both ends in the width direction) while the film is held by the clip after the transverse stretching step. It shows that a part is curving only the said height. In addition, the film is curved, and the film does not bend in the middle or undulates several times. Represents the state of being. The curvature after the transverse stretching step may also serve as the heat setting.
In the present invention, the curve after the transverse stretching step is not limited as long as the film swells, and may be convex upward or downward.

Without being bound by any theory, in general, a film tends to shrink in the film conveying direction (MD) and in the thickness direction in order to match the mass balance because the film is stretched in the width direction by transverse stretching. For this reason, shrinkage stress works in the thickness direction and MD direction. Among these, the shrinkage stress in the thickness direction acts to crush in the film surface direction, and decreases the orientation in the thickness direction indicated by γ of the present invention. Such shrinkage stress in the thickness direction is particularly likely to appear at the center in the width direction. This is because both ends are fixed by the clip and are not easily contracted, whereas the central part is easily contracted far from the clip and contraction stress is easily generated. Therefore, in the film obtained by carrying out the conventional transverse stretching process, γ is likely to be reduced in the central part of the film width direction due to the shrinkage stress that selectively acts on the central part in the film width direction, and γ is distributed in the width direction of the film. Had. Therefore, the distribution of γ in the slow axis direction occurred.
In the present invention, as a result of studying to reduce the shrinkage stress that acts greatly on the central portion in the film width direction in such a transverse stretching step, it was found that it is effective to curve the film after the transverse stretching step as described above. It was. Although not bound by any theory, the film after the transverse stretching process is strongly directed toward the stretched portions (both ends) due to the shrinkage stress that is greatly generated in the middle portion of the film width direction in the transverse stretching zone. Be pulled. On the other hand, when the film is curved (inflated), a force that causes the center portion to swell further is received from both ends that are physically held. When this film is bent, the force that selectively acts on the central portion and the shrinkage stress generated in the transverse stretching step are towed, and the history of shrinkage stress due to the transverse stretching step can be reduced. That is, the effect of such bending is large at the central portion where the shrinkage stress is large in the transverse stretching step, and is small at both ends where the shrinkage stress is weak. Therefore, by curving the film after transverse stretching while controlling the amount of curvature defined by the production method of the present invention, the shrinkage stress generated in the transverse stretching process over the entire width of the film can be evenly offset, and in the slow axis direction of γ Distribution can be suppressed. As described above, the present invention is characterized in that stress is selectively applied to the central portion by an easy and simple method of curving the film, and a uniform stress is generated in the width direction as compared with a method in which tension is applied and pulled. From the viewpoint of being added, there is a remarkable favorable effect.

  The method of curving the film is not particularly limited as long as it is not contrary to the gist of the present invention, and can be achieved, for example, by adjusting the amount of blowing air introduced for adjusting the temperature of the film up and down.

  As a specific example of the method for adjusting the amount of blowing air, air blowing ports are installed both above and below or below the passage surface of the film after the stretching zone. The outlet may be a perforated plate or a slit. When the outlet is a perforated plate, the diameter of the hole is preferably 1 mm to 100 mm, and when the outlet is a slit, the width of the slit is preferably 1 mm to 100 mm. When the upper and lower outlets are provided, the upper and lower airflows are adjusted, and when only the lower part is provided, the lower airflow is adjusted to achieve the above-described curved amount controlled by the present invention. it can. The adjustment of the air volume of the blown air may be achieved by adjusting the rotational speed of the fan of the blower or by adjusting a damper provided between the blower and the outlet. Furthermore, it can also be achieved by dividing the outlet in the width direction and adjusting the wind speed at the center and the wind speed at the end.

  The temperature of the blowing air is preferably (lateral stretching temperature) to (lateral stretching temperature −80 ° C.), more preferably (lateral stretching temperature −10 ° C.) to (lateral stretching temperature −50 ° C.). It is preferable that the temperature of the blowing air is not more than (transverse stretching temperature −80 ° C.) so that the film does not become too soft and the film does not stretch during bending. On the other hand, when the temperature of the blowing air is equal to or higher than the transverse stretching temperature, the shrinkage amount of the film after the transverse stretching step is hardly increased, and wrinkles derived therefrom are not easily generated, which is preferable.

  Alternatively, the outlet may be installed on the left and right sides of the film passage surface, a baffle plate may be provided at the end and center of the film, and the direction of the wind may be changed upward to curve the film. At this time, the amount of bending can be adjusted by adjusting the angle of the baffle plate other than the adjustment of the air volume as described above.

  Further, the amount of bending can be adjusted by providing a suction duct at the upper or lower part of the central portion of the film and adjusting the suction air volume.

  Such bending after the transverse stretching step is preferably performed continuously immediately after the transverse stretching step.

(Longitudinal stretching)
Further, longitudinal stretching may be performed. The longitudinal stretching may be performed after or before the transverse stretching step.
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-40 ° C to Tg + 5 ° C, more preferably Tg-30 ° C to Tg ° C, and further preferably Tg-20 ° C to Tg-3 ° 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.

(Relaxation treatment)
Furthermore, you may perform a relaxation process after these extending | stretching. The relaxation treatment is preferably performed either after film formation, after longitudinal stretching, after lateral stretching, or both. The relaxation treatment may be performed online continuously after stretching, or may be performed offline after winding after stretching.
The relaxation treatment is (Tg-40) ° C to (Tg + 5) ° C, more preferably (Tg-30) ° C to (Tg) ° C, and more preferably (Tg-20) ° C to (Tg-3) ° C for 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, even more preferably 10 seconds to 2 minutes, 0.1 kg / m to 20 kg / m, more preferably 1 kg / m to 16 kg / m, still more preferably 2 kg / m to 12 kg / m It is preferable to carry out while conveying at a tension of m.

[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 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.

[Optical compensation film]
The film of the present invention can be preferably used as a film for optical applications, and can be particularly preferably used as an optical compensation film.

<Laminated film>
It can also be set as a laminated | multilayer film by further providing an optically anisotropic layer to the film of this invention.

  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>
(1) Re [0 °], γ, Rth
These optical properties were measured according to the method described in the specification.

(2) Distribution of γ in the slow axis direction The film is stretched into 10 equal parts with respect to 30 cm in the slow axis direction of the stretched film, and γ is determined by the above method. Of the 10 measured values, the difference between the maximum and minimum points divided by the average value of 10 points and expressed as a percentage was taken as the slow axis direction distribution (%).

(3) Curvature A camera is installed at the exit of the tenter used in the transverse stretching process, and telephoto shooting is performed where the stretched film is conveyed. Connect the clips on both ends of this photo with a straight line, and from this line, read the height of the highest curved film. This height was divided by the total width of the film, and the percentage (%) was expressed as a percentage.

[Production Example 1] Production of pellets of addition polymerization type norbornene resin As addition polymerization type norbornene resin (COC), pellets of "TOPAS # 6013" manufactured by Polyplastics were used. “TOPAS # 6013” indicates positive intrinsic birefringence. The glass transition point of the resin was 130 ° C.

[Production Example 2] Production of ring-opening polymerization type norbornene resin pellets A ring-opening polymerization type norbornene resin (COP) was produced according to the method described in Example 1 of WO 98/14499, and the pellets were produced according to a conventional method. Turned into. The glass transition point of the resin was 136 ° C.

[Production Example 3] Production of polycarbonate pellets As polycarbonate, "Taflon MD1500" pellets made by Idemitsu Kosan Co., Ltd. were used. “Taflon MD1500” exhibits positive intrinsic birefringence. The glass transition point of the resin was 142 ° C.

[Production Example 4] Production of acrylic resin pellets According to Production Example 1 of JP 2008-9378 A [0222] to [0224], an acrylic resin was methyl methacrylate = 7500 g, 2- (hydroxymethyl) methyl acrylate 2500 g. And an acrylic compound having a lactonization rate of 98% and a glass transition point of 134 ° C. was obtained.

[Production Example 5] Manufacture of pellets of cellulose acylate resin Cellulose acetate propionate (CAP-1) was produced according to the method described in Example 1 of 2008-87398 and pelletized according to a conventional method. . The composition of CAP-1 used was an acetylation degree of 1.95, a propionylation degree of 0.7, and a total acyl substitution degree of 2.65. The glass transition point of the resin was 174 ° C.

[Production Example 6] Manufacture of pellets of cellulose acylate resin Cellulose acetate propionate (CAP-2) was produced according to the method described in Example 101 of 2008-50562 and pelletized according to a conventional method. . The composition of CAP-2 used was an acetylation degree of 0.15, a propionylation degree of 2.55, and a total acyl substitution degree of 2.70. The glass transition point of the resin was 137 ° C.

[Example 1]
(Production of film)
(Film formation)
Using a pellet of the cyclic olefin copolymer TOPAS # 6013 (COC) listed in Table 1 below as a thermoplastic resin, drying at 100 ° C. for 2 hours or more, melting at 260 ° C., and kneading using a single screw kneading extruder And extruded. At this time, a screen filter, a gear pump, and a leaf disk filter were arranged in this order between the extruder and the die, and these were connected by a melt pipe. This was extruded from a die having a width of 1300 mm and a lip gap of 0.8 mm at the extrusion temperature (discharge temperature) shown in Table 1 below.
Thereafter, a melt (molten resin) was extruded at the center of the portion sandwiched between the cast roll and the touch roll. At this time, the cylinder is set to the touch pressure described in the following Table 1 on a hard cast chrome-plated stainless steel cast roll (chill roll) having a width of 1500 mm and a diameter of 300 mm on the most upstream side, and the following table having a width of 1500 mm and a diameter of 200 mm. The touch roll of the material of 1 was made to contact. The outer cylinder thickness of the touch roll is shown in Table 1 below. The touch pressure was measured by sandwiching a pre-scale for medium pressure (manufactured by Fuji Film Co., Ltd.) between two rolls controlled at 25 ° C. at a constant circumferential speed (5 m / min) without melt. The value was taken as the pressure during film formation. Touch rolls and chill rolls having a Shore hardness of 70 HS were used. In addition, the melt was dropped on the central part sandwiched between the cast roll and the touch roll. Using these rolls, the touch roll peripheral speed is made faster than the chill roll peripheral speed, the peripheral speed difference between these rolls is set to the conditions described in Table 1 below, and the distance between the die and the melt landing point is set to 50 mm. Then, a film was formed at a conveyance speed (chill roll speed) of 15 m / min. Note that the temperature of the touch roll was Tg-5 ° C, and the temperature of the chill roll was Tg-10 ° C. The film forming atmosphere was 25 ° C. and 60%.
Then, after trimming both ends (5 cm each of the full width) immediately before winding, thicknessing (knurling) with a width of 10 mm and a height of 20 μm was applied to both ends. Further, the film forming width after trimming was 1 m, and the film of Example 1 was produced by winding up 450 m.

(Stretching)
The film-forming film was stretched under the conditions described in Table 1. Stretching was performed at a magnification described in Table 1 below by setting the blowing temperature at both ends of the tenter to a film surface temperature described in Table 1 below with a setting temperature of Tg + 5 ° C. The thickness after stretching was 80 μm.
At this time, the amount of bending described in Table 1 was adjusted by adjusting the balance of the air volume from the rectangular outlets installed in the stretched tenter. The outlets were installed above and below the tenter, and the air volume was adjusted with a damper. Moreover, the film was curved convexly upward. In addition, the temperature of blowing air was implemented at the blowing temperature -30 degreeC of the both ends of the tenter at the time of extending | stretching.
The temperature of the clip was adjusted to the temperature shown in Table 1 with an infrared heater installed immediately before the stretching start point in the middle of returning to the stretching start point without gripping the film after stretching.
For stretching, in addition to normal transverse stretching as described below, simultaneous biaxial stretching and oblique stretching were performed.
Transverse stretching: The method described in JP-A-10-249934.
Simultaneous biaxial stretching: The method described in JP-T-2006-517608.
Diagonal stretching: The method described in JP-A-2008-110573.

(Optical properties of the film)
By the above method, γ, Re [0 °], Rth, the angle between the slow axis and the tilt direction, and the distribution of γ in the slow axis direction were measured.
The display unevenness in the oblique direction was measured by measuring the uneven region visually recognized when the stretched film was sandwiched between polarizing plates arranged in crossed Nicol and viewed from a direction inclined 45 degrees left and right from the MD direction. This reflects display unevenness in an oblique direction when the liquid crystal display panel is incorporated. Therefore, the “display unevenness in the oblique direction” is preferably as small as possible. For example, if it is less than 20%, there is no practical problem, and it is preferably 5% or less.
Further, the stretched film was slit 5 cm at both ends, knurled, and then wound up by 3000 m with a tension of 20 kg / m and heated at 50 ° C. for 24 hours. Such a process corresponds to the degree of aging for six months at room temperature. Sampling was performed from the winding core portion that was most susceptible to tightening due to the shrinkage stress of the film after 24 hours of humidification, and the display unevenness in the oblique direction was measured by the above method. This was the display unevenness in the oblique direction after roll aging. The display unevenness in the oblique direction after roll aging is preferably as small as possible. For example, if it is less than 20%, it is more practical and more preferably less than 10%.
The measurement results of the optical properties of the film of Example 1 are shown in Table 1 below.

[Examples 2 to 41, Comparative Examples 1 and 2]
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. The optical properties of the films of the examples and comparative examples are shown in Table 1 and Table 2 below. In Example 15, since the blowing temperature at both ends of the tenter was increased by 20 ° C. compared to Example 1, the film film surface temperature during the transverse stretching step was Tg + 6 ° C. Simultaneous biaxial stretching in Example 17 was contracted by 20% in the longitudinal direction simultaneously with transverse stretching at the magnifications shown in Table 1 below. The simultaneous biaxial stretching machine used equipment described in Japanese Patent Application Laid-Open No. 2007-210306. Examples 18 to 21 were obliquely stretched under the conditions described in Table 1 using the apparatus described in Japanese Patent Application Laid-Open No. 2008-110573. In Example 37, the acrylic resin was melted at 230 ° C.

[Example 42, Comparative Example 3]
In Comparative Example 3, a solution was formed in accordance with FS-4 of Example 1 of JP-A-7-151915, dried, wound, and then given a shear stress (slip) between the two rolls. Transverse stretching was performed. Furthermore, the film after transverse stretching was curved by the method of the example of the present invention. Table 2 below shows the conditions and bending amounts of the literature examples.
In Example 42, Comparative Example 3 was carried out according to the production method of the present invention, and after melt film formation, the melt extruded from the die was given a slip by a touch roll and a chill roll having different peripheral speeds. Lateral stretching was performed, and the film after lateral stretching was curved. The conditions of Example 42 are shown in Table 2 below.
The optical properties of the obtained films of Example 42 and Comparative Example 3 are shown in Table 2 below.

[Examples 42 to 49]
A film of each example was obtained in the same manner as in Example 1 except that the film forming conditions and the transverse stretching temperature (film film surface temperature in the transverse stretching step) were changed as described in Table 1 and Table 2 below. In Examples 43 to 47, the transverse stretching temperature was adjusted by adjusting the blowing air temperature from both ends of the tenter to Tg + 22 ° C. in Example 43, Tg + 8 ° C. in Examples 44, 48 and 49, and Tg− in Example 45. The temperature was adjusted to 2 ° C., Tg−32 ° C. in Example 46, and Tg + 38 ° C. in Example 47.

  In Examples 1 to 16, 22 to 49, and Comparative Examples 1 to 3, the slow axis was the width (TD) direction, and the tilt direction was the longitudinal (MD) direction. In Examples 17 to 21, the slow axis was a direction inclined from the longitudinal direction by “an angle formed by the slow axis and the tilt angle” in Table 1, and the tilt direction was the longitudinal direction.

In Tables 1 and 2, Comparative Examples 1 and 2 and Examples 1 to 5 compared the effects of the amount of bending after stretching. In Examples 6 to 12, the effect of the clip temperature before stretching was examined. In Examples 13 to 15, different resins were used and further examined under different conditions. Examples 16-21 compared the effect of the stretching method and the angle of the slow axis. In Examples 22 to 25, the effect of the peripheral speed difference was examined. Examples 26-29 examined the effect of touch roll thickness. Examples 30 to 33 examined the effect of touch pressure. Examples 34-39 examined the effect of resin. In Examples 40 and 41, the effect of the material of the touch roll was examined. Comparative Example 3 and Example 42 show a comparison with Example 1 of JP-A-7-151915, which is a known example. In Examples 43 to 47, the film film surface temperature during transverse stretching was further examined. In Examples 48 and 49, the effect of lowering the touch pressure was further examined. From the above, it was found that according to the production method of the present invention, the film of the present invention in which the distribution of γ in the slow axis direction is within the scope of the present invention can be produced.
Next, it was found that the film of the present invention has little display unevenness in the oblique direction. Further, in a more preferred embodiment of the present invention, there was little display unevenness in the oblique direction after roll aging. Specifically, in Comparative Examples 1 to 3, the distribution of γ in the slow axis direction was outside the scope of the present invention. Further, the display unevenness in the oblique direction and the display unevenness in the oblique direction after the lapse of the roll were also poor.
Further, from Examples 1 to 49, γ, Re [0 °] and Rth were expressed in a favorable range, and the slow axis direction distribution of γ was also small. Therefore, it was found that the film of the present invention is a film suitable for optical use, and can be suitably used as an optical compensation film. In Examples 1 to 14, 16 to 46, 48, and 49 in which the film film surface temperature during transverse stretching was in a more preferable range of Tg−40 ° C. to Tg + 5 ° C. of the present invention, γ may be formed large. I understand.

(Preparation of polarizing plate)
A polarizing plate was produced using the produced films of Examples 1 to 49. Specifically, first, iodine was adsorbed to a stretched polyvinyl alcohol film to prepare each polarizing film. Using these polarizing films, an 80 μm TAC film (manufactured by FUJIFILM Corporation), a uniaxially stretched norbornene polymer film, and a λ / 2 plate with Re = 270 nm, as shown in FIG. 1, Examples 1 to 49 films were laminated. In this manner, two polarizing plates each using the films of Examples 1 to 49 were produced.

(LCD panel)
The films of Examples 1 to 49 were installed as a viewing angle compensation film between a pair of polarizing plates and a liquid crystal cell. Moreover, the polarizing plate using the film of Examples 1-49 was arrange | positioned at the upper and lower sides of the liquid crystal cell. When TN, ECB, OCB, VA, and IPS mode liquid crystal display devices were used, all of them exhibited good viewing angle compensation performance.

Claims (16)

A film comprising a thermoplastic resin, wherein γ represented by the following formula (I) is 17 nm or more, and the distribution of γ in the slow axis direction is 0% to 10.5%.
γ = | Re [+ 40 °] −Re [−40 °] | (I) Formula (In the formula (I), Re [+ 40 °] is measured from a direction inclined by 40 ° toward the tilt direction with respect to the film normal. Represents the retardation in the in-plane direction at a wavelength of 550 nm, and Re [−40 °] represents the retardation in the in-plane direction at a wavelength of 550 nm measured from a direction inclined by −40 ° to the tilt direction with respect to the normal line. The tilt direction here means the direction in which | Re [+ 40 °] −Re [−40 °] | among the in-plane directions in the film is the maximum. Γ is measured by dividing 30 cm in the phase axis direction into 10 equal parts, and the difference between the maximum and minimum points is divided by the average value of 10 points and expressed as a percentage.   The film according to claim 1, wherein an angle formed by the slow axis and the tilt direction is 30 ° to 150 °. The film according to claim 1 or 2, wherein the following formulas (II) and (III) are satisfied.
50 nm ≦ Re [0 °] ≦ 300 nm (II) Formula 40 nm ≦ γ ≦ 300 nm (III) Formula (In the formula (II), Re [0 °] is a letter in the in-plane direction at a wavelength of 550 nm measured from the film normal direction. Represents the foundation.)   The film according to any one of claims 1 to 3, wherein a retardation Rth in the thickness direction is 40 nm to 300 nm.   The film according to any one of claims 1 to 4, wherein the thermoplastic resin is at least one selected from a polycarbonate resin, a cyclic olefin resin, an acrylic resin, and a cellulose acylate resin. A sandwiching step of passing a melt of a composition containing a thermoplastic resin between the first sandwiching surface and the second sandwiching surface constituting the sandwiching device and continuously sandwiching and molding into a film (the sandwiching step) In the pressing step, the moving speed of the first pressing surface is made faster than the moving speed of the second pressing surface),
Solidifying the film-like melt to obtain a film;
A transverse stretching step of stretching the obtained film in the film width direction;
The central part in the width direction of the film after the transverse stretching step is bent in the film normal direction with respect to both ends in the width direction, and the bending amount represented by the following formula (IV) is controlled to 0.1% to 10%. Process,
The manufacturing method of the film containing this.
Formula (IV)
Bending amount (%) = 100 × (the difference in height between the central portion in the width direction of the film and both ends in the width direction) / (total width of the film)   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 film according to claim 6.   The lateral stretching step further includes a step of heating the clip to Tg-80 ° C to Tg, and a step of lateral stretching while gripping both ends of the film with the heated clip. Or the method for producing a film according to 7, wherein Tg represents a glass transition temperature of the thermoplastic resin.   The method for producing a film according to any one of claims 6 to 8, wherein the transverse stretching step is carried out by controlling the film film surface temperature to be Tg-40 ° C to Tg + 5 ° C.   The method for producing a film according to any one of claims 6 to 9, wherein in the pinching step, the melt is pinched at a pressure of 5 to 500 MPa. In the pressing step, the moving speed difference between the first pressing surface and the second pressing surface of the pressing device defined by the following formula (V) is controlled to be 0.5 to 20%. The manufacturing method of the film as described in any one of Claims 6-10 to do.
Formula (V)
Difference in moving speed (%) = 100 × {(moving speed of first pressing surface) − (moving speed of second pressing surface)}
/ (Moving speed of the first clamping surface)   The method for producing a film according to any one of claims 6 to 11, wherein in the clamping step, the clamping device is two rolls having different peripheral speeds.   The method for producing a film according to claim 12, wherein a metal touch roll having an outer cylinder thickness of 6 to 45 mm is used for one of the two rolls constituting the pinching device.   A film formed by the method according to any one of claims 6 to 13.   A polarizing plate comprising at least one film according to any one of claims 1 to 5 and 14. A liquid crystal display device using at least one film according to any one of claims 1 to 5 and 14.

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