Optical film manufacturing method and optical film manufacturing apparatus

Abstract

To provide a manufacturing method of an optical film, which is capable of obtaining an optical film having a highly uniform thickness in a transport direction.SOLUTION: There is provided a manufacturing method of an optical film, comprising: a film forming step of continuously forming an extruded film by extruding a resin fluid containing resin from a die provided above a cooling roll; a cooling step of cooling the extruded film while conveying the extruded film by the rotating cooling roll; and a decompression step of decompressing a gap between the cooling roll and a chamber that is provided along a peripheral surface of the cooling roll and above the cooling roll, and that is also provided adjacent to the die and ahead of the die in a rotation direction of the cooling roll. A first opening of a first room faces the peripheral surface of the cooling roll and extends in an axial direction of the cooling roll. A second opening of a second room faces the peripheral surface of the cooling roll and extends in the axial direction of the cooling roll, and is provided at a position closer to the die than the first opening in the rotation direction of the cooling roll. The first room is de-pressurized and the second room is non-pressurized or pressurized.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for producing an optical film. [Background technology]

[0002] A known method for forming a thermoplastic resin into a film is to obtain a resin fluid by melting the thermoplastic resin or by mixing it with an appropriate solvent, and then extruding the resin fluid through a die. The extruded film of the thermoplastic resin formed by extrusion through the die is cooled while being transported by a rotating cooling roll.

[0003] The gas flow accompanied by the rotating chill roll prevents the extruded film being transported by the chill roll from coming into close contact with the chill roll, so the space between the extruded film extruded from the die and the peripheral surface of the chill roll is reduced in pressure using a vacuum chamber (see Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3349388 [Patent Document 2] JP 2020-37235 A [Patent Document 3] Patent No. 6006904 [Patent Document 4] U.S. Pat. No. 5,618,568 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it may be difficult to obtain an extruded film having a uniform thickness in the transport direction simply by reducing the pressure in the space between the extruded film and the circumferential surface of the cooling roll using a vacuum chamber. In particular, when attempting to increase the rotation speed of the cooling roll in order to increase the line speed, the uniformity of the thickness of the extruded film in the transport direction tends to decrease. As described above, in the conventional methods, it may be difficult to produce an optical film having a high uniformity in thickness in the machine direction by extrusion.

[0006] Therefore, there is a need for a method for producing an optical film that can obtain an optical film having a high uniformity in thickness in the transport direction; and an apparatus for producing an optical film that can obtain an optical film having a high uniformity in thickness in the transport direction. [Means for solving the problem]

[0007] As a result of intensive research into solving the above-mentioned problems, the inventors discovered that the above-mentioned problems could be solved by carrying out a decompression process using a specified chamber whose interior is divided into a first chamber and a second chamber, reducing the pressure in the first chamber and leaving the second chamber unpressurized or pressurized, and thus completed the present invention. That is, the present invention provides the following.

[0008] [1] A film forming process in which a resin fluid containing a resin is extruded through a die provided above a cooling roll to continuously form an extruded film; a cooling step of cooling the extruded film while transporting the extruded film by the rotating cooling roll; and a depressurizing step of reducing the pressure of a gap between the chamber and the chill roll by a chamber provided above the chill roll along the peripheral surface of the chill roll, adjacent to the die and before the die in the rotation direction of the chill roll; the chamber includes a first chamber having a first opening defined by a first aperture and a second chamber having a second opening defined by a second aperture; the first opening faces a peripheral surface of the chill roll and extends in an axial direction of the chill roll; the second opening faces a peripheral surface of the chill roll, extends in an axial direction of the chill roll, and is provided at a position closer to the die than the first opening in a rotation direction of the chill roll; and The first chamber is depressurized, and the second chamber is unpressurized or pressurized. A method for producing an optical film. [2] The method for producing an optical film according to [1], wherein the gauge pressure of the second chamber is adjusted to 0.1 Pa or more and 30 Pa or less. [3] The method for producing an optical film according to [1] or [2], wherein a gas having a temperature of 100° C. or more and 300° C. or less is supplied to the second chamber. [4] The method for producing an optical film according to any one of [1] to [3], wherein the gas is discharged from the second opening at a flow rate that is changed in the longitudinal direction of the second opening. [5] A die for extruding a resin fluid containing a resin, a cooling roll for cooling the extruded film continuously formed by extrusion through the die while conveying it by rotation, and a chamber; The die is provided above the cooling roll, the chamber is provided above the chill roll along a peripheral surface of the chill roll, adjacent to the die and ahead of the die in a rotation direction of the chill roll; the chamber includes a first chamber having a first opening defined by the first opening and connected to a pressure reducing device, and a second chamber having a second opening defined by the second opening and connected to a gas pumping device; the first opening faces a peripheral surface of the chill roll and extends in an axial direction of the chill roll; the second opening faces a peripheral surface of the cooling roll, extends in an axial direction of the cooling roll, and is provided at a position closer to the die than the first opening in a rotation direction of the cooling roll. Optical film manufacturing equipment. Effect of the Invention

[0009] According to the present invention, it is possible to provide an optical film manufacturing method capable of obtaining an optical film having a high uniformity in thickness in the transport direction; and an optical film manufacturing apparatus capable of obtaining an optical film having a high uniformity in thickness in the transport direction. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a production apparatus capable of carrying out the method for producing an optical film according to the first embodiment of the present invention. [Diagram 2] FIG. 2 is a partial schematic view showing an example of an optical film production apparatus. [Diagram 3] FIG. 3 is a perspective view that typically shows a chamber used in the manufacturing method according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a partial cross-sectional view that illustrates a schematic view of a part of an optical film manufacturing apparatus including the chamber shown in FIG. [Diagram 5] FIG. 5 is a schematic diagram showing an example of a production apparatus capable of carrying out the method for producing an optical film according to the second embodiment of the present invention. [Figure 6] FIG. 6 is a partial cross-sectional view that illustrates a part of an optical film manufacturing apparatus used in a manufacturing method according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be modified and implemented as desired without departing from the scope of the claims of the present invention and their equivalents.

[0012] In the following description, unless otherwise specified, the directions of elements as "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effect of the present invention, for example, within a range of ±3°, ±2°, or ±1°.

[0013] In the following description, "upper" and "lower" are defined relative to the vertical direction unless otherwise specified.

[0014] In the following description, when an element is provided "above" the chill roll, it means that when the element and the chill roll are viewed in a direction parallel to the axis of the chill roll, a perpendicular line can be drawn from the element to the circumference of the upper part of the chill roll. Here, the upper part of the chill roll refers to the part of the chill roll that is on the upper side in the vertical direction when the chill roll is divided by a horizontal plane including the axis of the chill roll.

[0015] In the drawings, the same elements are given the same reference numerals and their explanation may be omitted.

[0016] The manufacturing method of the present invention may be a method in which the conditions described below are arbitrarily selected and combined, and the manufacturing method of the present invention may use an apparatus in which the components described below are arbitrarily selected and combined.

[0017] In the following description, a "long" film refers to a film having a length of 5 times or more its width, preferably 10 times or more its width, specifically a film having a length sufficient to be wound into a roll for storage or transportation. There is no particular upper limit to the length of the film, and it may be, for example, 100,000 times or less its width.

[0018] In the following description, unless otherwise specified, the width direction of the film means a direction perpendicular to the longitudinal direction of the film, which is usually parallel to the conveying direction of the film during production.

[0019] In the following description, the term "(meth)acrylic" includes "acrylic", "methacrylic" and combinations thereof. In the following description, the term "(meth)acrylate" encompasses "acrylate", "methacrylate" and combinations thereof. In the following description, the term "(meth)acrylonitrile" includes "acrylonitrile", "methacrylonitrile" and combinations thereof.

[0020] [1. Overview of manufacturing method for optical film] A method for manufacturing an optical film according to one embodiment of the present invention includes a film forming process in which a resin fluid containing a resin is extruded from a die provided above a cooling roll to continuously form an extruded film, a cooling process in which the extruded film is cooled while being transported by the rotating cooling roll, and a depressurizing process in which a chamber is used to reduce the pressure in the gap between the chamber and the cooling roll. The extruded film is continuously formed and continuously transported by the chill roll, and the pressure in the gap between the chamber and the chill roll is continuously reduced. Therefore, the film forming step, the cooling step, and the reduction in pressure are usually performed simultaneously.

[0021] In the optical film manufacturing method according to this embodiment, the conveying speed (line speed) of the extruded film is not particularly limited, but is preferably 40 m / min or more, more preferably 50 m / min or more, even more preferably 60 m / min or more, and preferably 120 m / min or less. According to the manufacturing method according to this embodiment, even if the extruded film is conveyed at a speed equal to or higher than the lower limit, an optical film having a high uniformity in thickness in the conveying direction can be obtained. Here, the conveying speed of the extruded film refers to the conveying speed of the extruded film when the extruded film finishes the cooling process by the cooling roll and is separated from the cooling roll.

[0022] The optical film manufacturing method of the present invention can be applied to either a method in which a film-shaped resin fluid extruded from a die is cast onto the peripheral surface of a rotating cooling roll, cooled, and molded (open molding method); or a method in which a film-shaped resin fluid extruded from a die is sandwiched between two rotating cooling rolls, cooled, and molded (touch molding method, see, for example, JP 2011-126184 A).

[0023] [2. First embodiment] The manufacturing method according to the first embodiment of the present invention will be described in detail below. Fig. 1 is a schematic diagram showing an example of a manufacturing apparatus capable of carrying out the optical film manufacturing method according to the first embodiment of the present invention. Fig. 1 is a schematic diagram showing the optical film manufacturing apparatus as viewed from a direction parallel to the axial direction of a cooling roll provided in the optical film manufacturing apparatus. Fig. 2 is a partial schematic diagram showing an example of the optical film manufacturing apparatus.

[0024] The manufacturing apparatus 1000 includes a die 100, a cooling roll 200, and a chamber 300. The die 100 is connected to an extruder 110, a polymer filter 120, and a gear pump 130. A material containing a resin is heated and fluidized in the extruder 110 to become a resin fluid, and is sent to the gear pump 130 via the polymer filter 120. The resin fluid sent to the gear pump 130 is metered and supplied to the die 100 at a predetermined flow rate. The resin fluid is continuously extruded from a slit 101 of the die 100 to form a long extruded film 10.

[0025] The temperatures of the extruder 110, the polymer filter 120, the gear pump 130, and the die 100 are each configured to be appropriately adjusted, so that the resin fluid can be extruded from the die 100 at a desired temperature.

[0026] The die 100 is provided above the cooling roll 200. That is, as shown in Fig. 2, when a perpendicular line is dropped from the die 100 to the circumference of the cooling roll 200, an intersection 100P between the perpendicular line and the circumference of the cooling roll 200 exists in an upper portion 200U of the cooling roll 200. Here, the upper portion 200U of the cooling roll 200 is a portion of the cooling roll 200 that is on the upper side in the vertical direction when the cooling roll 200 is divided by a horizontal plane 200PL shown by a dashed line in Fig. 2, which includes the axis 200R of the cooling roll 200.

[0027] As described above, the film forming process is carried out in which a resin fluid containing a resin is extruded through a die to continuously form an extruded film.

[0028] As shown in Fig. 1, the extruded film 10 extruded from the die 100 is continuously guided to the circumferential surface of the cooling roll 200. The cooling roll 200 rotates in the direction 200D indicated by the arrow around an axis 200R, and transports the extruded film along its circumferential surface. The temperature of the circumferential surface of the cooling roll 200 is adjusted to a temperature lower than the temperature of the resin fluid in the die 100 by a temperature regulator (not shown). As a result, the extruded film extruded from the die 100 is cooled by the cooling roll 200.

[0029] The temperature of the cooling roll 200 may be appropriately adjusted depending on the glass transition temperature of the resin, the rotation speed of the cooling roll 200, etc., and may be, for example, 80°C or higher, such as 90°C or higher, and may be, for example, 150°C or lower, such as 140°C or lower.

[0030] In this manner, a cooling step is carried out in which the extruded film is cooled while being transported by the rotating cooling roll.

[0031] The chamber 300 is provided above the cooling roll 200. That is, as shown in Fig. 2, when the chamber 300 and the cooling roll 200 are viewed from the direction of the axis 200R of the cooling roll 200, if a perpendicular line is drawn from an end 304E of the chamber 300 to the circumference of the cooling roll 200, which will be described in detail later, an intersection 300P between the perpendicular line and the circumference of the cooling roll 200 exists in the upper part 200U of the cooling roll 200.

[0032] The chamber 300 is provided next to the die 100. The chamber 300 and the die 100 are provided next to each other in this order in the rotation direction 200D of the cooling roll 200. Therefore, the chamber 300 is provided before the die 100 in the rotation direction 200D of the cooling roll 200.

[0033] Being provided before the die 100 in the rotation direction 200D means that the intersection 300P exists upstream in the rotation direction 200D of the intersection 101P shown in Fig. 2. Here, the intersection 101P is the intersection of the cooling roll 200 and a vertical line drawn vertically from the slit 101 of the die 100 when the die 100, the cooling roll 200, and the chamber 300 are viewed from the direction of the axis 200R of the cooling roll 200. A point B on the circumference of the cooling roll 200 is located upstream of a point A on the circumference of the cooling roll 200 in the rotation direction 200D when, when point B is moved along the circumference of the cooling roll 200 in the rotation direction 200D to the position of point A, point B does not move away from point A but continues to approach it. On the other hand, point B is located downstream of point A in the rotation direction 200D when, as point B is moved in the rotation direction 200D along the circumference of the cooling roll 200 to the position of point A, it moves away from point A and then approaches it.

[0034] As shown in FIG. 2, an intersection 101P between a vertical line drawn vertically from the slit 101 of the die 100 and the cooling roll 200 exists in an upper portion 200U of the cooling roll 200.

[0035] Furthermore, the angle θ between the line passing through intersection point 300P and axis 200R and the line passing through intersection point 101P and axis 200R is preferably 10° or more, more preferably 15° or more, and is preferably 50° or less, more preferably 35° or less.

[0036] The distance between the die 100 and the chamber 300 is arbitrary. As shown in Fig. 2, a blocking member 1001 such as a seal member is provided between the die 100 and the chamber 300 to prevent airflow from being generated in the gap between the die 100 and the chamber 300 toward the circumferential surface of the cooling roll 200. The chamber 300 is fixed at an arbitrary location. For example, the chamber 300 may be attached to the die 100, or may be fixed to a support table (not shown) that supports the cooling roll 200.

[0037] The chamber 300 is provided so that its longitudinal direction is parallel to the axis 200 R of the cooling roll 200 .

[0038] The chamber 300 is provided along the circumferential surface of the cooling roll 200. Here, as shown in Fig. 2, a gap 300C is provided between the chamber 300 and the circumferential surface of the cooling roll 200 so that the chamber 300 does not interfere with the rotation of the cooling roll 200. As shown in Fig. 1, a pressure reducing device 400 is connected to the chamber 300 to reduce the pressure in the gap 300C.

[0039] The depressurization step is carried out by depressurizing a first chamber of chamber 300 described below and applying no pressure or pressure to a second chamber of chamber 300. This reduces the flow of gas accompanying the rotating cooling roll 200, suppressing gas from being entrained between the extruded film 10 and the circumferential surface of the cooling roll 200, and improving the thickness uniformity of the extruded film 10 in the transport direction.

[0040] In this manner, a depressurization step is carried out in which the pressure in the gap between the chamber and the cooling roll is reduced by the chamber.

[0041] By the method for producing an optical film according to this embodiment, which includes a film forming step, a cooling step, and a decompression step, an optical film having a high uniformity in thickness in the transport direction can be obtained.

[0042] The extruded film is usually cooled to below the glass transition temperature Tg of the resin contained in the extruded film and conveyed in the direction of arrow A1. The cooled extruded film is wound up by a winding machine after its properties are measured by a thickness meter 500 as necessary, to form the finished optical film roll 20.

[0043] Fig. 3 is a perspective view showing a chamber used in the manufacturing method according to the first embodiment of the present invention, and Fig. 4 is a partial cross-sectional view showing a part of an optical film manufacturing apparatus including the chamber shown in Fig. 3.

[0044] 3, the chamber 300 includes a side wall 301, an upper wall 302, a rear wall 303, and a front wall 304. The side walls 301 are provided at two longitudinal ends of the upper wall 302, and the front wall 304 is provided at one of the two lateral ends of the upper wall 302, and the rear wall 303 is provided at the other end. The side walls 301, the upper wall 302, the rear wall 303, and the front wall 304 form a box-shaped chamber 300 separated from the outside.

[0045] 4, a partition wall 305 extending in the longitudinal direction of the chamber 300 is provided inside the chamber 300, and divides the interior of the chamber 300 into a first chamber 306 and a second chamber 307. The partition wall 305 rises vertically from the upper wall 302, but bends toward the front wall 304 near the middle. Since the longitudinal direction of the chamber 300 is provided parallel to the axis 200R of the cooling roll 200, the longitudinal direction of the first chamber 306 and the second chamber 307 divided by the partition wall 305 extending in the longitudinal direction of the chamber 300 is parallel to the axis 200R of the cooling roll 200. The partition wall 305 divides the opening of the chamber 300 into two, forming a first opening 308 and a second opening 309. A first opening 310 defining the first opening 308 includes an end of the rear wall 303, an end of the partition wall 305, and a part of an end of the side wall 301. A second opening 311 defining the second opening 309 includes an end of the front wall 304, an end of the partition wall 305, and a part of an end of the side wall 301. The ends of the partition wall 305 included in the first opening 310 and the second opening 311 are common, and therefore the first opening 310 and the second opening 311 are adjacent to each other in the circumferential direction of the cooling roll 200.

[0046] A distance 303D from an end 303E of the rear wall 303 included in the first opening 310 to the peripheral surface of the cooling roll 200 is preferably 2 mm or more, preferably 20 mm or less, and more preferably 6 mm or less.

[0047] A distance 305D from an end 305E of the partition 305 included in the first opening 310 and the second opening 311 to the peripheral surface of the cooling roll 200 is preferably 2 mm or more, preferably 20 mm or less, and more preferably 6 mm or less.

[0048] A distance 304D from an end 304E of the front wall 304 included in the second opening 311 to the peripheral surface of the cooling roll 200 is preferably 2 mm or more, more preferably 5 mm or more, and is preferably 100 mm or less, more preferably 30 mm or less.

[0049] Both the first opening 308 and the second opening 309 face the peripheral surface of the cooling roll 200 and extend in the direction of the axis 200R of the cooling roll 200. The second opening 309 is provided at a position closer to the die 100 than the first opening 308 in the rotation direction 200D of the cooling roll 200. Therefore, the first opening 308, the second opening 309, and the die 100 are provided in this order in the rotation direction 200D of the cooling roll 200.

[0050] The longitudinal size of each of the first opening 308 and the second opening 309 is preferably 80% or more, more preferably 95% or more, and preferably 120% or less, more preferably 105% or less, of the width of the die 100.

[0051] 4, the circumferential surface of the cooling roll 200 facing the first opening 308 is an arcuate surface having a central angle of θ1. The circumferential surface of the cooling roll 200 facing the second opening 309 is an arcuate surface having a central angle of θ2. Here, θ2 is preferably 15° or more, and preferably 50° or less, more preferably 30° or less, and even more preferably 20° or less. The sum of θ1 and θ2 (θ1+θ2) is preferably 40° or more, preferably 50° or more, and preferably 100° or less, more preferably 80° or less.

[0052] The side wall 301 is provided parallel to the end face of the cooling roll 200, and defines the side in the longitudinal direction of the chamber 300. A distance 301D from an end 301E of the side wall 301 on the cooling roll 200 side to the peripheral surface of the cooling roll 200 is preferably 2 mm or more, preferably 20 mm or less, and more preferably 6 mm or less.

[0053] 3 and 4, a plurality of cylindrical intake pipes 1002 that communicate with the first chamber 306 are provided in the upper wall 302 that defines the first chamber 306, lined up in the longitudinal direction of the chamber 300. The pitch of the intake pipes 1002 in the longitudinal direction of the chamber 300, as the distance between the centers of the intake pipes 1002, is preferably 100 mm or more, more preferably 200 mm or more, and is preferably 500 mm or less, more preferably 350 mm or less. Furthermore, a plurality of cylindrical vent pipes 1003 that communicate with the second chamber 307 are provided in the upper wall 302 that defines the second chamber 307 and are aligned in the longitudinal direction of the chamber 300 .

[0054] 1, a pressure reducing device 400 such as a pressure reducing pump is connected to an intake pipe 1002. A gas compression device 600 such as a gas compressor or a blower is connected to an air vent pipe 1003. A flow rate regulator 1004 such as a flow control valve is connected to a connection path between the intake pipe 1002 and the pressure reducing device 400 and a connection path between the air vent pipe 1003 and the gas compression device 600. A temperature regulator 1005 for adjusting the temperature of the gas to be compressed is further provided to the connection path between the air vent pipe 1003 and the gas compression device 600.

[0055] The second chamber can be pressurized because the gas compression device 600 is connected to the vent pipe 1003. When the vent pipe 1003 is opened without connecting the gas compression device 600 to the vent pipe 1003, the second chamber can be in an unpressurized state.

[0056] The gas pumping device 600 can pump any gas such as air, nitrogen gas, argon gas, or other inert gas. From the viewpoint of suppressing deterioration of the resin fluid extruded from the die 100, it is preferable to pump nitrogen gas or argon gas from the gas pumping device 600.

[0057] The flow regulator 1004 connected to the multiple ventilation pipes 1003 has a mechanism for independently adjusting the flow rate of gas delivered to the multiple ventilation pipes 1003, thereby enabling gas to be delivered from the second opening 309 at a flow rate that varies in the longitudinal direction of the second opening 309.

[0058] A pressure sensor (not shown) is provided inside first chamber 306 near intake pipe 1002, preferably at the boundary between first chamber 306 and intake pipe 1002, to measure the internal pressure of first chamber 306. A pressure sensor (not shown) is also provided inside second chamber 307 near vent pipe 1003, preferably at the boundary between second chamber 307 and vent pipe 1003, to measure the internal pressure of second chamber 307.

[0059] The internal pressure of the first chamber 306 can be adjusted to a desired degree of pressure reduction by the pressure reducing device 400 described above. The internal pressure of the first chamber 306 is preferably −300 Pa or more, more preferably −100 Pa or more, and is preferably −10 Pa or less, more preferably −20 Pa or less, in terms of gauge pressure.

[0060] The internal pressure of the second chamber 307 can be adjusted to any pressure by the gas pumping device 600. In addition, by disconnecting the gas pumping device 600 from the vent pipe 1003 and releasing it, the internal pressure of the second chamber 307 can be set to atmospheric pressure. The internal pressure of second chamber 307 is preferably 0.0 Pa or more, more preferably 0.1 Pa or more, and is preferably 30 Pa or less, more preferably 5 Pa or less, in terms of gauge pressure.

[0061] When gas is supplied to second chamber 307, the temperature of the gas supplied can be adjusted to a desired temperature by temperature regulator 1005 described above. When gas is supplied to second chamber 307, the temperature of the gas supplied is preferably 100° C. or higher, more preferably 150° C. or higher, and preferably 300° C. or lower, more preferably 230° C. or lower.

[0062] The internal temperature of the second compartment 307 may be adjusted to a desired temperature by a heating device (not shown) surrounding the exterior of the chamber 300 .

[0063] 4, a first porous plate 312 is provided inside the first chamber 306 between the first opening 308 and the upper wall 302. This straightens the flow of gas from the first opening 308, making the intake air from the first opening 308 uniform along the longitudinal direction of the first opening 308. Furthermore, a second porous plate 313 is provided inside the second chamber 307 between the second opening 309 and the upper wall 302. This straightens the flow of gas to the second opening 309, making the supply air from the second opening 309 uniform along the longitudinal direction of the second opening 309.

[0064] A first dew tray 314 extending in the longitudinal direction of the chamber 300 is provided at the lower part on the inside of the rear wall 303. The first dew tray 314 has a dish-like structure with an open upper side. The first dew tray 314 can reduce liquid such as water or solvent that has condensed on the inside of the rear wall 303 running down the inside of the rear wall 303 and dripping onto the cooling roll 200.

[0065] A second dew tray 315 extending in the longitudinal direction of the chamber 300 is provided at the lower part of the partition 305 on the second chamber 307 side. The second dew tray 315 has a dish-like structure with an open upper side. The second dew tray 315 can reduce liquid such as water or solvent that has condensed on the second chamber 307 side of the partition 305 from running down the partition 305 and dripping onto the cooling roll 200.

[0066] [3. Second embodiment] The manufacturing method according to the second embodiment of the present invention will be described in detail below. In the manufacturing method of the second embodiment, an optical film is manufactured using a manufacturing apparatus including a chamber having a different configuration from the chamber 300 instead of the above-mentioned chamber 300. Fig. 5 is a schematic diagram showing an example of a production apparatus capable of carrying out the optical film production method according to the second embodiment of the present invention, as viewed from a direction parallel to the axial direction of a cooling roll provided in the optical film production apparatus.

[0067] The manufacturing apparatus 2000 includes a die 100, a cooling roll 200, and a chamber 800. The manufacturing apparatus 2000 is obtained by replacing the chamber 300 in the manufacturing apparatus 1000 with the chamber 800 described below. The manufacturing apparatus 2000 has the same configuration as the manufacturing apparatus 1000 except that the chamber 300 is replaced with the chamber 800, and therefore a description of the components other than the chamber 800 will be omitted.

[0068] FIG. 6 is a partial cross-sectional view that illustrates a part of an optical film manufacturing apparatus used in a manufacturing method according to a second embodiment of the present invention. As shown in FIG. 6, the chamber 800 includes a side wall 801 , a top wall 802 , a rear wall 803 , and a front wall 804 . The side wall 801, the upper wall 802, and the rear wall 803 have the same configurations as the side wall 301, the upper wall 302, the rear wall 303, and the front wall 304 in the chamber 300, respectively, and therefore their explanation will be omitted.

[0069] 6, a partition wall 805 extending in the longitudinal direction of the chamber 800 is provided inside the chamber 800, dividing the interior of the chamber 800 into a first chamber 806 and a second chamber 807. The partition wall 805 rises vertically from the upper wall 802. The chamber 800 is provided with a longitudinal direction parallel to the axis 200R of the cooling roll 200, and therefore the longitudinal direction of the first chamber 806 and the second chamber 807 divided by the partition wall 805 extending in the longitudinal direction of the chamber 800 is parallel to the axis 200R of the cooling roll 200. The opening of the chamber 300 is divided into two by the partition wall 805, and a first opening 808 and a second opening 809 are formed.

[0070] A first opening 810 defining the first opening 808 includes an end of the rear wall 803, an end of the partition wall 805, and a part of an end of the side wall 801. A second opening 811 defining the second opening 809 includes an end of the front wall 804, an end of the partition wall 805, and a part of an end of the side wall. The ends of the partition wall 805 included in the first opening 810 and the second opening 811 are common, and therefore the first opening 810 and the second opening 811 are adjacent to each other in the circumferential direction of the cooling roll 200.

[0071] A partition plate 816 is provided so as to protrude toward the front wall 804 from near the midpoint between the position where the partition wall 805 contacts the upper wall 802 and the end of the partition wall 805. The partition plate 816 extends in the longitudinal direction of the chamber 800. The partition plate 816 causes the gas passing through the second chamber 807 to bend along the plate surface of the partition plate 816 and to be rectified.

[0072] A first porous plate 812 is provided inside the first chamber 806 between the first opening 808 and the upper wall 802. This straightens the gas from the first opening 808, making the intake air from the first opening 808 uniform along the longitudinal direction of the first opening 808.

[0073] A second porous plate 813 is provided between a tip 816T of the partition plate 816 and the front wall 804 so as to connect them. This straightens the flow of gas to the second opening 809, and makes the gas sent from the second opening 809 uniform along the longitudinal direction of the second opening 809.

[0074] A distance 803D from an end 803E of the rear wall 803 included in the first opening 810 to the peripheral surface of the cooling roll 200 can preferably be in the same range as the distance 303D described above.

[0075] A distance 805D from an end 805E of the partition wall 805 included in the first opening 810 and the second opening 811 to the peripheral surface of the cooling roll 200 can preferably be in the same range as the distance 305D described above.

[0076] A distance 804D from an end 804E of the front wall 804 included in the second opening 811 to the circumferential surface of the cooling roll 200 can preferably be in the same range as the distance 304D described above.

[0077] The first opening 808, the second opening 809, the first opening 810, and the second opening 811 have the same configuration as the first opening 308, the second opening 309, the first opening 310, and the second opening 311 in the chamber 300, respectively, and therefore will not be described.

[0078] A distance 801D from an end 801E of the side wall 801 on the cooling roll 200 side to the circumferential surface of the cooling roll 200 can preferably be in the same range as the distance 301D.

[0079] The upper wall 802 defining the first chamber 806 is provided with a plurality of cylindrical intake pipes 1002 which communicate with the first chamber 806. Furthermore, the upper wall 802 defining the second chamber 807 is provided with a plurality of cylindrical vent pipes 1003 which communicate with the second chamber 807.

[0080] 6, the circumferential surface of the cooling roll 200 facing the first opening 808 is an arcuate surface having a central angle of θ1. The circumferential surface of the cooling roll 200 facing the second opening 809 is an arcuate surface having a central angle of θ2. Here, θ2 is preferably 30° or more, preferably 60° or less, and more preferably 50° or less. The sum of θ1 and θ2 (θ1+θ2) is preferably 40° or more, more preferably 50° or more, and is preferably 100° or less, more preferably 80° or less.

[0081] [4. Resins used] In the method for producing an optical film according to the embodiment, a thermoplastic resin is preferably used. The resin usually contains a polymer and optional components that are added as necessary. Examples of the polymer include, but are not limited to, alicyclic structure-containing polymers, polyesters such as polyethylene terephthalate (PET), acrylic polymers such as poly(meth)acrylate (e.g., polymethyl methacrylate (PMMA)), poly(meth)acrylic acid, and poly(meth)acrylonitrile, and cellulose polymers such as triacetyl cellulose (TAC). One type of polymer may be used alone, or two or more types may be used in combination at any ratio.

[0082] Among these, the alicyclic structure-containing polymer is preferred because it has excellent properties such as transparency and mechanical strength. The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the structural unit of the polymer, and either a polymer having an alicyclic structure in the main chain or a polymer having an alicyclic structure in the side chain may be used. Among these, the polymer containing an alicyclic structure in the main chain is preferred from the viewpoint of mechanical strength, heat resistance, etc.

[0083] Examples of the alicyclic structure include saturated alicyclic hydrocarbon (cycloalkane) structures, unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structures, etc. Among these, from the viewpoints of mechanical strength, heat resistance, etc., cycloalkane structures and cycloalkene structures are preferred, and among these, cycloalkane structures are particularly preferred.

[0084] The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, and is preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less, per one alicyclic structure. This provides a high balance between the mechanical strength, heat resistance, and moldability of the resin layer, which is preferable.

[0085] The ratio of the structural unit having an alicyclic structure in the alicyclic structure-containing polymer may be appropriately selected depending on the purpose of use, and is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. If the ratio of the structural unit having an alicyclic structure in the alicyclic structure-containing polymer is within this range, it is preferable from the viewpoint of transparency and heat resistance of the resin layer.

[0086] Examples of the polymer containing an alicyclic structure include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrogenated products thereof. Among these, norbornene polymers are preferred because of their good transparency and moldability.

[0087] Examples of norbornene polymers include ring-opening polymers of monomers having a norbornene structure and hydrogenated products thereof; addition polymers of monomers having a norbornene structure and hydrogenated products thereof. Examples of ring-opening polymers of monomers having a norbornene structure include ring-opening homopolymers of one type of monomer having a norbornene structure, ring-opening copolymers of two or more types of monomers having a norbornene structure, and ring-opening copolymers of a monomer having a norbornene structure and any monomer that can be copolymerized therewith. Examples of addition polymers of monomers having a norbornene structure include addition homopolymers of one type of monomer having a norbornene structure, addition copolymers of two or more types of monomers having a norbornene structure, and addition copolymers of a monomer having a norbornene structure and any monomer that can be copolymerized therewith. Among these, hydrogenated products of ring-opening polymers of monomers having a norbornene structure are particularly suitable from the viewpoints of transparency, moldability, heat resistance, low moisture absorption, dimensional stability, light weight, etc.

[0088] Specific examples of norbornene polymers and hydrogenated products thereof include "ZEONOR" manufactured by Zeon Corporation; "ARTON" manufactured by JSR Corporation; and "TOPAS" manufactured by TOPAS ADVANCED POLYMERS.

[0089] Examples of optional components that the resin may contain as necessary include antioxidants, plasticizers, ultraviolet absorbers, and lubricants. The optional components may be used alone or in combination of two or more in any ratio.

[0090] The resin fluid to be extruded from the die may be a fluid obtained by melting the resin, or a fluid in the form of a solution or dispersion obtained by adding a solvent to the resin. The solvent to be added to the resin is not particularly limited, and may be a conventionally known solvent used in the solution casting method. Specific examples of the solvent to be added to the resin include halogenated hydrocarbon solvents such as dichloromethane; aliphatic or alicyclic hydrocarbon solvents such as hexane and cyclohexane; aromatic hydrocarbon solvents such as xylene and toluene; ether solvents such as tetrahydrofuran; and ester solvents such as ethyl acetate. The solvent may be used alone or in combination of two or more in any ratio.

[0091] [5. Optional process] The method for producing the optical film according to the embodiment may include any step in addition to the film forming step, the cooling step, and the decompression step. Examples of optional steps include a stretching step in which the extruded film is stretched to form a stretched film; a heating step in which the extruded film (which may be stretched; the same applies below) is heated; a cutting step in which the extruded film is cut; a step in which a protective film is laminated to the extruded film; a slippery treatment step in which slip properties are imparted to the surface of the extruded film; a winding step of the extruded film; and a step in which the properties of the extruded film are inspected.

[0092] [6. Optical film manufacturing equipment] The method for producing an optical film according to the present invention can be carried out by any production apparatus. An example of the manufacturing apparatus includes a die that extrudes a resin fluid containing a resin, a cooling roll that cools an extruded film continuously formed by extrusion from the die while conveying it by rotation, and a chamber, wherein the die is provided above the cooling roll, the chamber is provided above the cooling roll along the circumferential surface of the cooling roll and is provided next to the die and before the die in the rotation direction of the cooling roll, the chamber includes a first chamber having a first opening defined by a first opening and to which a pressure reducing device is connected, and a second chamber having a second opening defined by a second opening and to which a gas pressure-feeding device is connected, the first opening faces the circumferential surface of the cooling roll and extends in the axial direction of the cooling roll, and the second opening faces the circumferential surface of the cooling roll and extends in the axial direction of the cooling roll and is provided at a position closer to the die than the first opening in the rotation direction of the cooling roll.

[0093] According to the above-mentioned manufacturing apparatus, the first chamber can be depressurized and the second chamber can be unpressurized or pressurized, thereby reducing the flow of gas accompanying the rotating chill roll, suppressing entrapment of gas between the extruded film and the circumferential surface of the chill roll, and improving the thickness uniformity of the extruded film in the transport direction.

[0094] Specific examples of such a manufacturing apparatus include the above-mentioned manufacturing apparatus 1000 and manufacturing apparatus 2000.

[0095] [7.Applications] According to the optical film manufacturing method and the optical film manufacturing apparatus, an optical film having a high uniformity in thickness in the transport direction can be obtained. The optical film having a high uniformity in thickness is useful as a high-quality optical film with little unevenness in optical properties. EXAMPLES

[0096] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below, and can be modified and carried out as desired without departing from the scope of the claims of the present invention and the scope of equivalents thereto.

[0097] In the following description, the units "%" and "parts" are by weight unless otherwise specified. Furthermore, the operations described below were carried out at room temperature and pressure unless otherwise specified.

[0098] [Evaluation method] (Thickness variation in the conveying direction) Under the conditions of each Example and Comparative Example, a film thickness gauge (in-line infrared film thickness gauge (manufactured by MEC)) was moved back and forth in the width direction of the extruded film as an optical film while being transported, and thickness data of the optical film was obtained for every 5 mm width of the optical film. The film thickness gauge was moved across the optical film for 30 seconds each way. The data acquisition time was 1 hour. The standard deviation σ of the thickness data obtained at points with the same coordinate in the width direction that are aligned in a row in the transport direction of the optical film was MD The standard deviation σ obtained for every 5 mm of the extruded film width was calculated. MD The arithmetic average value Ave was calculated for each of the thicknesses. The smaller the average value Ave, the higher the uniformity of the thickness of the optical film in the transport direction.

[0099] [Example 1] As the resin, a cycloolefin polymer (ZEONOR (registered trademark) ZNR1600, manufactured by Zeon Corporation, glass transition temperature Tg = 160 ° C.), which is an alicyclic structure-containing polymer, was prepared, and an optical film was produced under the following production conditions using the following production apparatus.

[0100] (Production equipment and conditions) The manufacturing apparatus used was the manufacturing apparatus 1000 shown in Fig. 1. The chamber 300 used was the chamber shown in Fig. 4 in which θ1 was 40° and θ2 was 20°. A single screw extruder having an inner diameter of 130 mm was used as the extruder 110. The extrusion rate was set to 230 kg / h. The film take-up speed was adjusted so that the thickness of the extruded film was 40 μm. The set temperatures of the polymer filter 120, the gear pump 130, and the die 100 were set to 280°C. The die 100 used had a slit 101 with a width of 1200 mm. The line speed was set at 80 m / min. A cooling roll having a diameter of 400 mm was used as the cooling roll 200. The surface temperature of the cooling roll 200 was set to 140°C. The chamber 300 was installed so as to maintain the following clearance with respect to the cooling roll 200. Distance 303D from end 303E of rear wall 303 to the circumferential surface of cooling roll 200: 4 mm Distance 305D from the end 305E of the partition 305 to the circumferential surface of the cooling roll 200: 4 mm Distance 304D from the end 304E of the front wall 304 to the circumferential surface of the cooling roll 200: 13 mm Distance 301D from end 301E of side wall 301 on the cooling roll 200 side to the circumferential surface of cooling roll 200: 4 mm

[0101] Perforated plates having a plurality of circular holes with a diameter of 10 mm and an aperture ratio of 35% were used as the first perforated plate 312 and the second perforated plate 313 of the chamber 300. The plurality of holes were provided so that their centers were located at the vertices of an equilateral triangle with one side measuring 15 mm. The pitch of the intake pipes 1002, as the center-to-center distance, was 250 mm. As the thickness meter 500, an in-line infrared thickness meter (manufactured by MEC Corporation) was used. The internal pressures of the first chamber 306 and the second chamber 307 were measured by a pressure sensor installed near the intake pipe 1002 and a pressure sensor installed near the ventilation pipe 1003, respectively. As the pressure sensors, Manostar gauges (manufactured by Yamamoto Electric Works, Ltd.) were used. The temperature of the air supplied to the second chamber 307 was measured by installing a sensor portion of a wall-mounted remote-type thermometer (manufactured by Sato Keiryoki Seisakusho Co., Ltd.) inside the ventilation pipe 1003 in the vicinity of the second chamber 307 .

[0102] The pressure in first chamber 306 was reduced by pressure reducing device 400. Flow rate regulator 1004 connected to pressure reducing device 400 was adjusted so that the pressure in first chamber 306 became the value shown in the table. Air was pressurized as the gas into second chamber 307 by gas compression device 600. Flow rate regulator 1004 connected to gas compression device 600 was adjusted so that the pressure in second chamber 307 became the value shown in the table. Temperature regulator 1005 was also adjusted so that the temperature of the air supplied to second chamber 307 became the value shown in Table 1.

[0103] [Example 2] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. The temperature of the air supplied to the second chamber was adjusted to the value shown in the table.

[0104] [Example 3] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. The temperature of the air supplied to the second chamber was adjusted to the value shown in the table.

[0105] [Example 4] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. As the chamber 300, the chamber shown in FIG. 4 in which θ1 is 20° and θ2 is 40° was used.

[0106] [Example 5] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. No air was supplied from the gas pumping device 600 to the second chamber 307, and the vent pipe 1003 was opened to not pressurize the second chamber 307.

[0107] [Comparative Example 1] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. The gas compression device 600 was not connected to the second chamber 307, but a pressure reducing device was connected to reduce the pressure in the second chamber 307. The flow regulator connected to the pressure reducing device was adjusted so that the pressure in the second chamber 307 became the value shown in the table.

[0108] [Comparative Example 2] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. Instead of chamber 300, a chamber was used that did not have partition wall 305 and was not divided into a first chamber and a second chamber. A pressure reducing device was connected to the chamber to reduce the pressure inside the chamber. A flow regulator connected to the pressure reducing device was adjusted so that the pressure inside the chamber reached the value shown in the table.

[0109] [Comparative Example 3] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. The manufacturing apparatus used was the manufacturing apparatus 1000 shown in Fig. 1, which was not provided with the chamber 300. Therefore, the decompression step was not performed.

[0110] [Reference example 1] An optical film was obtained in the same manner as in Example 1, except for the following changes, and the thickness variation in the machine direction was evaluated. The manufacturing apparatus used was the manufacturing apparatus 1000 shown in Fig. 1, which was not provided with the chamber 300. Therefore, the decompression step was not performed. The line speed was set to 20 m / min.

[0111] [result] The results are shown in the table below. In the section on chamber shape, "dual" means a chamber shape in which the interior is divided into a first chamber and a second chamber, and "single" means a chamber shape in which the interior is not divided into a first chamber and a second chamber. In Example 5 and Comparative Example 1, air was not supplied to the second chamber, so the temperature of the gas supplied to the second chamber is not recorded. In Comparative Example 2, the chamber was a single chamber having no partition separating the first chamber and the second chamber, and therefore θ1 was recorded as the central angle of the arcuate surface of the cooling roll facing the opening of the chamber.

[0112] [Table 1]

[0113] [Table 2]

[0114] From the above results, the following can be seen: According to the optical film manufacturing method of Examples 1 to 5, in which a chamber having a first chamber and a second chamber is used and the first chamber is depressurized and the second chamber is unpressurized or pressurized, the thickness variation in the transport direction of the optical film is small, being 1.0 or less, despite the line speed being high, being 70 m / min or more. On the other hand, the manufacturing method of Comparative Example 3, which does not use a chamber and does not perform a decompression step, the manufacturing method of Comparative Example 2, which uses a chamber not equipped with a first chamber and a second chamber, and the manufacturing method of Comparative Example 1, which uses a chamber equipped with a first chamber and a second chamber but reduces the pressure in the second chamber, show large variations in thickness of the optical film in the transport direction.

[0115] It is also seen that the manufacturing method according to Example 1 improves the variation in thickness in the transport direction of the optical film compared to the manufacturing method according to Example 4. The chamber used in Example 1 has θ1 larger than that used in Example 4, at 40° or more, and θ2 smaller than that, at 20° or less, and it is seen that θ1 has a preferred lower limit and θ2 has a preferred upper limit.

[0116] The above results show that the method for producing an optical film according to the present invention makes it possible to produce an optical film having a high uniformity in thickness in the machine direction. [Explanation of symbols]

[0117] 1000: Manufacturing equipment 10: Extrusion film 20: Roll 100: Die 101: Slit 110: Extruder 120: Polymer filter 130: Gear pump 200: Cooling roll 200R: Axis 300: Chamber 301: Side wall 302: Upper wall 303: Rear wall 304: Front wall 305: Bulkhead 306: First room 307:Second room 308: First opening 309: Second opening 310: First opening 311: Second opening 312: First perforated plate 313: Second perforated plate 314: First Dew Tray 315: Second Dew Tray 400: Pressure reducing device 500: Film thickness gauge 600: Gas pumping device 800: Chamber 801: Side wall 802: Upper wall 803: Rear wall 804: Front wall 805: Bulkhead 806: First room 807:Second room 808: First opening 809: Second opening 810: First opening 811: Second opening 812: First perforated plate 813: Second perforated plate 816: Partition board 816T: Tip 1001: Closure member 1002: Intake pipe 1003: Ventilation pipe 1004:Flow rate regulator 1005: Temperature regulator

Claims

1. a film forming step of extruding a resin fluid containing a resin through a die provided above a cooling roll to continuously form an extruded film; a cooling step of cooling the extruded film while transporting the extruded film by the rotating cooling roll; and a depressurizing step of reducing the pressure of a gap between the chamber and the chill roll by a chamber provided above the chill roll along the peripheral surface of the chill roll, adjacent to the die and before the die in the rotation direction of the chill roll; the chamber includes a first chamber having a first opening defined by a first aperture and a second chamber having a second opening defined by a second aperture; the first opening faces a peripheral surface of the chill roll and extends in an axial direction of the chill roll; the second opening faces the circumferential surface of the chill roll, extends in the axial direction of the chill roll, and is provided at a position closer to the die than the first opening in the rotation direction of the chill roll, the circumferential surface of the chill roll facing the second opening is an arc-shaped surface with a central angle of θ2 in cross section, θ2 being 15° or more and 30° or less, and The first chamber is depressurized, and the second chamber is unpressurized or pressurized. A method for producing an optical film.

2. A method for manufacturing an optical film as described in claim 1, wherein the peripheral surface of the cooling roll facing the first opening is an arc-shaped surface with a central angle of θ1 in cross section, and the sum of θ1 and θ2 (θ1 + θ2) is greater than or equal to 40° and less than 100°.

3. A method for manufacturing an optical film as described in claim 1 or 2, wherein a first porous plate is provided inside the first chamber, and a second porous plate is provided inside the second chamber.

4. The method for producing an optical film according to any one of claims 1 to 3, wherein the second chamber is adjusted to a gauge pressure of 0.1 Pa or more and 30 Pa or less.

5. The method for producing an optical film according to any one of claims 1 to 4, wherein a gas having a temperature of 100°C or more and 300°C or less is supplied to the second chamber.

6. The method for producing an optical film according to any one of claims 1 to 5, wherein the gas is discharged from the second opening at a flow rate that is changed in the longitudinal direction of the second opening.

7. The extrusion apparatus includes a die for extruding a resin fluid containing a resin, a cooling roll for cooling the extruded film continuously formed by extrusion through the die while conveying the film by rotation, and a chamber, The die is provided above the cooling roll, the chamber is provided above the chill roll along a peripheral surface of the chill roll, adjacent to the die and ahead of the die in a rotation direction of the chill roll; the chamber includes a first chamber having a first opening defined by the first opening and connected to a pressure reducing device, and a second chamber having a second opening defined by the second opening and connected to a gas pumping device; the first opening faces a peripheral surface of the chill roll and extends in an axial direction of the chill roll; the second opening faces the circumferential surface of the chill roll, extends in the axial direction of the chill roll, and is provided at a position closer to the die than the first opening in the rotation direction of the chill roll, and the circumferential surface of the chill roll that faces the second opening is an arc-shaped surface with a central angle of θ2 in cross section, θ2 being 15° or more and 30° or less; Optical film manufacturing equipment.

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