JP5329590B2 - Casting film forming method and apparatus, and solution casting method - Google Patents

Abstract

The invention provides a forming method of a curtain coating film and a device thereof and a solution film preparing method. The curtain coating film forming procedure includes a condensed solution flowing procedure, a curtain coating procedure, a film heating procedure, a surface layer forming procedure, a film drying procedure, a film cooling procedure, a ripping procedure and a support body heating procedure repeatedly and successively. In the condensed solution flowing procedure, the condensed liquid flows to an annular band. In the film heating procedure, a curtain coating film is formed from the condensed liquid. The surface of the film is made smooth through the heating the curtain coating film in the film heating procedure. The surface layer is formed on the film surface of the surface forming procedure. The curtain coating film is dried in the film drying procedure. The curtain coating film is cooled into a state capable of conveying independently in the film cooling procedure. The curtain coating film is ripped from the annular band in the ripping procedure. The annular band is heated in the support body heating procedure after the ripping procedure.

Description

  The present invention relates to a casting film forming method and apparatus, and a solution casting method.

  Polymer films (hereinafter referred to as “films”) are widely used as optical films because of their features such as excellent light transmission, flexibility, and reduction in weight. Among them, cellulose ester films using cellulose acylate and the like are optical films such as a protective film for a polarizing plate and a retardation film, which are constituent members of liquid crystal display devices whose market is expanding in recent years, including photographic photosensitive films. Used in film.

  There exists a solution casting method as a manufacturing method of a film. The solution casting method includes a casting film forming process, a film self-supporting process, a peeling process, and a wet film drying process. In the cast film forming step, the dope in which the polymer is dissolved in the solvent is flowed down, and a cast film made of the dope is formed on the support. In the film self-supporting step, the solvent is evaporated from the cast film until it becomes self-supporting and can be transported, that is, until solidification has progressed beyond a certain level. In the peeling step, the cast film is peeled from the support to form a wet film. In the wet film drying step, the solvent is evaporated from the wet film to form a film.

  Patent Document 1 discloses a method of sequentially performing a film drying process for evaporating a solvent from a cast film and a film cooling process for cooling the cast film until it can be independently conveyed in the film self-supporting process. (Patent Document 1). According to the method of Patent Document 1, since the film cooling process in which the time required for solidification of the cast film is shorter than that in the film drying process is performed immediately before the peeling process, the peeling failure due to insufficient drying of the cast film ( It is possible to avoid a tearing failure in which the peeled cast film is torn off, and a peeling failure in which a part of the cast film remains on the support. As a result, the support speed can be improved, so that the production efficiency of the film can be improved as compared with the conventional case.

JP 2006-306059 A

  However, although the production efficiency of the film could be improved by using the method of Patent Document 1, the optical characteristics (in-plane retardation Re and thickness direction retardation Rth due to thickness unevenness of the obtained film). Etc.) has become a problem. The reason why such unevenness in optical characteristics has become apparent is that the required specifications of the optical film have been improved and that the optical film has been made thinner as the liquid crystal display device has been made thinner.

  Therefore, the present invention provides a solution casting method capable of efficiently producing a film while suppressing the thickness unevenness as described above, and a casting membrane drying method and apparatus used in this solution casting method. Objective.

  The present invention relates to a dope flow step for flowing a dope containing a polymer and a solvent to a moving support, and film drying for evaporating the solvent from a cast film formed of the flowed dope and formed on the surface of the moving support. And a peeling film peeling process for peeling the cast film that has undergone the film drying process from the movable support, in the method for forming a cast film, after the film drying process and before the peeling process, A film cooling process for cooling the cast film until it can be conveyed, a support heating process for heating the moving support after the peeling process and before the next film drying process, and the film A film heating step that is performed before the drying step and heats the cast film using heat applied to the moving support in the support heating step.

  In the support heating process, it is preferable to heat the moving support before the dope flowing process. Moreover, the said support body heating process may heat the said moving support body after the said dope flow-down process.

  In the support heating step, a casting area for forming a casting film from the flowed dope set on the surface of the moving support is non-casting except for the casting area on the surface of the moving support. The moving support is preferably heated so that the temperature is higher than that of the area.

  It is preferable to perform the film heating step until the temperature of the moving support in the peeling step is 5 ° C. or higher and 15 ° C. or lower and the temperature of the moving support is 8 ° C. or higher and lower than the boiling point of the solvent.

  A skin layer forming step that is performed between the membrane heating step and the membrane drying step, and that applies a skin layer forming wind to the surface of the casting membrane to form a skin layer on the surface side of the casting membrane. It is preferable.

  The solution casting method of the present invention includes a film drying step of obtaining a film by evaporating the solvent from the casting film peeled from the moving support after performing the casting film forming method. It is characterized by that.

  The casting film forming apparatus of the present invention includes a reaching part where a flowing dope containing a polymer and a solvent reaches, a casting part for forming a casting film from the flowing dope, and a casting film composed of the flowing dope. A membrane drying section that evaporates the solvent, a moving support that sequentially circulates and passes through the peeling section from which the casting film is peeled, and a reaching section support means that supports the moving support positioned in the reaching section And a peeling part supporting means for supporting the moving support located in the peeling part, and a state in which the moving support can leave the film drying part and reach the peeling part in a self-supporting state. A film cooling means for cooling the cast film until it reaches, a support heating means for heating the moving support until it leaves the peeling section and reaches the film drying section, and a support heating means. Using the generated heat to reach the membrane drying section. And having a film heating means for heating the casting film before.

  It is preferable that the support heating means heats the moving support until it leaves the peeling portion and reaches the reaching portion. Moreover, the said support body heating means may heat the said moving support body until it reaches | attains the said film | membrane drying part from the said attainment part.

  In the support heating means, the casting area for forming the casting film set on the surface of the moving support is more than the non-casting area of the surface of the moving support except the casting area. The moving support is preferably heated so that the temperature becomes high.

  Skin layer forming means is provided between the support heating means and the film drying section, and applies a skin layer forming air to the surface of the casting film and forms a skin layer on the surface side of the casting film. It is preferable.

  The casting part support means includes a casting part support roller, the peeling part support means includes a peeling part support roller, and the movable support is stretched over the casting part support roller and the peeling part support roller. An endless band is preferred.

  It is preferable that the support heating means includes a heating air duct that applies heating air to the movable support. Moreover, it is preferable that the said film | membrane cooling means cools the said peeling part support means. Further, the film cooling means adjusts the temperature of the moving support in the peeling part to 5 ° C. or more and 15 ° C. or less, and the support heating means has a temperature of the moving support in the casting part of 8 ° C. or more. It is preferable to heat the moving support so as to be equal to or lower than the boiling point of the solvent.

  According to the present invention, the dope flow process, the film drying process, and the peeling process are performed, and the time required from the film drying process to the peeling process is reduced by the film cooling process performed between the film drying process and the peeling process. Can be shortened. And in this period from the peeling process to the next film drying process, in order to perform the support heating process for heating the moving support, the film heating process for heating the casting film formed by the next dope flowing process from the back side. It can be performed. The surface of the cast film can be smoothed by the film heating process. Thus, according to the present invention, cast films and films can be efficiently produced while suppressing thickness unevenness.

It is explanatory drawing which shows the outline | summary of solution casting apparatus. It is a side view which shows the outline | summary of a 1st casting unit. It is a perspective view which shows the outline | summary of a skin layer forming apparatus. It is IV-IV sectional view taken on the line which shows the outline | summary of a skin layer forming apparatus. It is a VV line sectional view showing an outline of skin layer forming equipment. It is a perspective view which shows the outline | summary of a 1st support body heating apparatus. It is a VII-VII line sectional view showing the outline of the 1st support heating device. It is process drawing which shows the outline | summary of a 1st cast film formation process and a solution casting method. It is sectional drawing which shows the outline | summary of the cast film immediately after formation. It is sectional drawing which shows the outline | summary of the cast film after a film | membrane heating process. It is sectional drawing which shows the outline | summary of the cast film after a skin layer formation process. It is sectional drawing which shows the outline | summary of the cast film after a film | membrane drying process. It is a side view which shows the outline | summary of the principal part of a 2nd casting unit. It is a side view which shows the outline | summary of a 3rd casting unit. It is a side view which shows the outline | summary of the principal part of a 4th casting unit. It is a side view which shows the outline | summary of the principal part of a 5th casting unit. It is a side view which shows the outline | summary of a 6th casting unit. It is a side view which shows the outline | summary of a 7th casting unit. It is sectional drawing which shows the outline | summary of a 2nd support body heating apparatus. It is process drawing which shows the outline | summary of the 2nd cast film formation process and the 2nd solution casting method. It is a side view which shows the outline | summary of the principal part of an 8th casting unit.

(Solution casting equipment)
As shown in FIG. 1, the solution casting apparatus 10 includes a casting unit 12, a drying unit 13, and a winding unit 14.

(Casting unit)
The casting unit 12 creates a wet film 25 from a dope 24 including a polymer (referred to as a raw material polymer) 22 that is a raw material of the film 21 and a solvent 23 of the polymer 22. Details of the casting unit 12 will be described later.

(Drying unit)
The drying unit 13 evaporates the solvent 23 from the wet film 25 to obtain the film 21 from the wet film 25. The clip tenter 35 is sequentially arranged from the casting unit 12 toward the winding unit 14, A slitter 36, a drying chamber 37, and a cooling chamber 38 are provided. In the transition portion 40 between the casting unit 12 and the clip tenter 35, the belt-like wet film 25 fed from the casting unit 12 is conveyed to the clip tenter 35 using a plurality of rollers 41.

  The clip tenter 35 includes a casing 35a, a pair of rails, a clip 35b, and a drying air supply machine 35c. A moving path 66r for the wet film 25 is provided in the casing 35a. The rails accommodated in the casing 35a are provided on both sides of the moving path 66r of the wet film 25. The plurality of clips 35b arranged along the rail can freely transition between a gripping state in which the both lateral edges of the wet film 25 are gripped and a release state in which the gripping of the both lateral edges is released. It can be mounted freely. The plurality of clips 35b are connected in an annular shape by a chain (not shown). When the clip 35b passes the grip start position on the rail, the clip 35b transitions from the release state to the grip state. Thus, the clip 35b grips both side edges of the wet film 25 in the width direction. Further, when the clip 35b passes the grip release position on the rail, the clip 35b transits from the grip state to the release state. In this way, the clip 35b releases the grip on both side edges of the wet film 25 in the width direction.

  The distance between the pair of rails gradually increases from the grip start position toward the grip release position. When the width of the wet film 25 at the grip start position is Wf1, and the maximum width of the wet film 25 is Wf2 between the grip start position and the grip release position, Wf2 / Wf1 is 1.05 or more and 1.5 or less. It is preferable that The drying air supply unit 35c that applies the drying air to the wet film 25 is provided above and below the moving path 66r of the wet film 25.

  The slitter 36 cuts off the ear portion of the wet film 25. The separated ears are sent to a crusher (not shown) by air blowing, cut into small pieces, and reused as a raw material for dopes and the like.

  A large number of rollers 45 are provided in the drying chamber 37. The wet film 25 is conveyed while being wound around the roller 45. An adsorption recovery device 46 is connected to the drying chamber 37. The adsorption recovery device 46 recovers the solvent 23 evaporated from the wet film 25 by adsorption. By collecting the solvent 23 in the drying chamber 37, the condensation point of the solvent 23 in the drying chamber 37 is adjusted within a certain range. Evaporates. As a result, the film 21 is obtained from the wet film 25. In the cooling chamber 38, the film 21 is cooled until the temperature reaches substantially room temperature.

(Winding unit)
The winding unit 14 includes a winding chamber 54 having a winding core 51, a winding core drive unit (not shown), and a press roller 52. By the control unit (not shown), the core driving unit rotates the core 51 at a predetermined speed. As a result, the film 21 is wound on the winding core 51 with a predetermined winding tension, and becomes a film roll 55. The press roller 52 presses the film 21 wound around the winding core 51 toward the winding core 51 or the film roll 55 wound around the winding core 51. Accordingly, the film 21 can be wound while preventing air from being mixed between the films 21.

  It is preferable that a knurling application device 57 for forming knurling at both edges in the width direction of the film 21 is provided between the winding chamber 54 and the cooling chamber 38.

(Details of casting unit)
As shown in FIG. 2, the casting unit 12 that creates the wet film 25 from the dope 24 includes a casting casing 75. In the casting casing 75, a casting die 60 that flows out the dope 24, an endless band 62 that is a moving support that supports the flowing dope 24 and forms a casting film 61 made of the dope 24, and a casting film A skin layer forming device 63 for forming a skin layer on the surface 61a of the 61, a film drying device 64 for evaporating the solvent 23 (see FIG. 1) from the casting film 61, and a peeling for peeling the casting film 61 from the endless band 62 A roller 65, a band moving mechanism 66 that circulates and moves the endless band 62 in a predetermined direction, and first to fourth seal members 71 to 74 are provided.

(Endless band moving mechanism)
The band moving mechanism 66 is for guiding in a predetermined direction while supporting the endless band 62, and includes rollers 66a to 66c and a motor 66m that drives the roller 66c.

  The rollers 66a to 66c are arranged so as to be parallel to each other. The roller 66b and the roller 66c are disposed on substantially the same plane (for example, a horizontal plane), and the roller 66a is disposed between the roller 66b and the roller 66c and above the plane. An annular endless band 62 formed by connecting both ends of the sheet material is wound around the rollers 66a to 66c. The band back surface 62b of the endless band 62 is supported by rollers 66a to 66c. When the roller 66c is rotated by the drive of the motor 66m, the endless band 62 circulates and moves through the rollers 66a, 66b, 66c, 66a,. Thus, the moving path 66r of the endless band 62 is formed by the rollers 66a to 66c.

  Each of the rollers 66x to 66z is for supporting the band back surface 62b of the endless band 62, and is disposed along the moving path 66r of the endless band 62. The roller 66x is disposed between the roller 66c and the roller 66a. The roller 66y is disposed between the rollers 66a and 66b, and the roller 66z is disposed between the rollers 66b and 66c.

  The endless band 62 obtained by connecting both ends of the sheet material is preferably made of stainless steel, and more preferably made of SUS316 having sufficient corrosion resistance and strength. The width of the endless band 62 is preferably not less than 1.1 times and not more than 2.0 times the casting width CW of the dope 24, for example. The length of the endless band 62 is preferably 20 m or more and 200 m or less, for example, and the thickness of the endless band 62 is preferably 0.5 mm or more and 2.5 mm or less, for example. The thickness unevenness of the endless band 62 is preferably 0.5% or less with respect to the total thickness. The band surface 62a is preferably polished, and the surface roughness of the band surface 62a is preferably 0.05 μm or less.

(Seal member)
The first to fourth seal members 71 to 74 are provided on the moving path 66 r of the endless band 62. The first seal member 71 is disposed so as to face the roller 66x via the moving path 66r of the endless band 62. The second seal member 72 is disposed so as to face the roller 66y via the moving path 66r of the endless band 62. The third to fourth seal members 73 to 74 move from the upstream side to the downstream side in the moving direction of the endless band 62 (hereinafter referred to as the X direction) so as to face the roller 66c through the moving path 66r of the endless band 62. Are arranged sequentially.

  The first seal member 71 includes a wind shield 71a attached to the casting chamber 75a and a labyrinth seal 72b attached to the wind shield 71a. The wind shielding plate 71 a has a wind shielding surface that blocks the flow of gas in the casting casing 75. The wind shield 71 a protrudes from the inner wall surface of the casting casing 75 and extends toward the band surface 62 a of the endless band 62. The labyrinth seal 71b is provided at the tip of the wind shielding plate 71a so as to be close to the band surface 62a. The second seal member 72 to the fourth seal member 74 have the same structure as the first seal member 71.

  By each roller and each seal member, the casting casing 75 is partitioned into a casting chamber 75a, a film drying chamber 75b, a peeling chamber 75c, and a support heating chamber 75d from the upstream side in the X direction toward the downstream side. The casting chamber 75a is formed by the first seal member 71, the second seal member 72, the roller 66x, and the roller 66y. Similarly, the film drying chamber 75b is formed by the second seal member 72, the third seal member 73, the roller 66y, and the roller 66c, and the peeling chamber 75c is formed by the third seal member 73, the fourth seal member 74, and the roller 66c. The support heating chamber 75d is formed by the first seal member 71, the fourth seal member 74, the roller 66c, and the roller 66x.

(Casting room)
A casting die 60 is provided in the casting chamber 75a. The casting die 60 is disposed so as to face the roller 66a through the moving path 66r of the endless band 62. A reaching portion is formed between the casting die 60 and the roller 66a. The casting die 60 has a slit outlet through which the dope 24 flows out at the tip. The casting die 60 is arranged so that the slit exit is close to the portion of the endless band 62 supported by the roller 66a. The dope 24 that has flowed out of the casting die 60 is spread on the band surface 62 a, resulting in a belt-shaped casting film 61.

  It is preferable that a decompression chamber 77 is provided in the casting chamber 75a. The decompression chamber 77 is provided upstream of the casting die 60 in the X direction and adjacent to the casting die 60. Under the control of a control unit (not shown), the decompression chamber 77 decompresses the upstream side of the bead in the X direction so that the pressure on the upstream side of the bead in the X direction is lower than that on the downstream side of the bead in the X direction. Here, the bead means that formed by the dope 24 that flows out from the casting die 60 and reaches the endless band 62.

(Membrane drying room)
In the film drying chamber 75b, a skin layer forming device 63 for supplying the skin layer forming air 80 to the casting film 61 and a film drying device 64 for evaporating the solvent from the casting film 61 are arranged from the upstream side to the downstream side in the X direction. It is provided along the movement path 66r sequentially.

(Skin layer forming device)
The skin layer forming device 63 is preferably arranged on the most upstream side in the X direction of the film drying chamber 75b. As shown in FIGS. 3 and 4, the skin layer forming device 63 arranged so as to be close to the membrane surface 61 a includes an air supply duct 81, a cover 82, a pre-air supply nozzle 83, and an air conditioner 84. The air supply duct 81 and the cover 82 are sequentially provided from the upstream side in the X direction toward the downstream side.

  The air supply duct 81 circulates the skin layer forming air 80, and is arranged close to the second seal member 72 in the X direction and separated from the membrane surface 61a. A pre-air supply nozzle 83 is provided on the surface 81 a on the membrane surface 61 a side of the air supply duct 81. The pre-air supply nozzle 83 extends from the upstream side in the X direction toward the downstream side in the X direction as it approaches the membrane surface 61a. At the tip of the pre-air supply nozzle 83, a pre-air supply port 83a that opens toward the band surface 62a is provided. As shown in FIG. 5, the pre-air inlet 83a extends from one end of the endless band 62 to the other end of the endless band 62 in the width direction of the moving path 66r (hereinafter referred to as the Y direction). . Note that the pre-supply port 83a is preferably flush with the surface 81a.

  As shown in FIGS. 3 and 4, the cover 82 guides the skin layer forming air 80 delivered from the pre-air inlet 83 a to the downstream side in the X direction, and flows in a state of being separated from the casting film 61. Covering the membrane 61. The cover 82 is formed in a plate shape, from the air supply duct 81 to the vicinity of the membrane drying device 64 (for example, a front membrane drying device described later) in the X direction, and from one end of the endless band 62 in the Y direction to endless. It extends to the other end of the band 62. The cover 82 has a guide surface 82a substantially parallel to the film surface 61a on the film surface 61a side. The guide surface 82a is preferably flush with the surface 81a.

  From the pre-air supply port 83a to the downstream end portion in the X direction of the cover 82, between the guide surface 82a and the surface 81a and the band surface 62a, the air path of the skin layer forming air 80 sent from the pre-air supply port 83a 86 is formed. The distance from the surface 81a to the band surface 62a is preferably 20 mm or more and 150 mm or less, for example. The width of the air path 86 in the Y direction may be, for example, 0.8 times to 1 time the width of the endless band 62 in the Y direction. The length of the air passage 86 in the X direction may be determined according to manufacturing conditions (such as the moving speed V of the surface 62a of the endless band 62), and is preferably 1000 mm or more and 5000 mm or less, for example.

  The air conditioner 84 is a temperature controller (not shown) that adjusts the temperature of the skin layer forming air 80 within a predetermined range, and a blower fan (not shown) that sends the skin layer forming air 80 to the air supply duct 81 with a predetermined air volume. Not).

  A side wind shielding plate 85 may be provided in the skin layer forming device 63. The side wind shielding plates 85 are arranged in the Y direction and extend from the upstream end in the X direction of the air supply duct 81 to the downstream end in the X direction of the cover 82. The side wind shielding plate 85 extends from the surface 81a and the guide surface 82a toward the band surface 62a. As shown in FIG. 5, the surface 85 a on the inner side in the Y direction of the side wind shielding plate 85 is preferably flush with the inner surface 83 b of the pre-air supply nozzle 83.

(Membrane dryer)
As shown in FIG. 2, the membrane drying device 64 includes a front membrane dryer 88 and a rear membrane dryer 89 that are sequentially provided from the upstream side in the X direction toward the downstream side.

(Pre-film dryer)
The pre-film dryer 88 is disposed along a portion of the moving path 66r of the endless band 62 from the roller 66y to the roller 66b. The front membrane dryer 88 is arranged on the band surface 62a side and sends a pre-drying air 90, a back-side air blower 92 that is arranged on the band back surface 62b side and sends out the pre-drying air 90, and a pre-drying air And a regulator (not shown).

(Front side blower)
The front-side blower 91 includes an air supply duct (not shown) and an exhaust duct (not shown). The air supply port of the air supply duct and the exhaust port of the exhaust duct face the band surface 62a. Further, the air supply port of the air supply duct and the exhaust port of the exhaust duct extend from one end of the casting film 61 to the other end. Note that the air supply port of the air supply duct and the exhaust port of the exhaust duct are preferably arranged alternately in the X direction.

(Back side blower)
Similar to the front side blower 91, the back side blower 92 includes an air supply duct (not shown) and an exhaust duct (not shown). The air supply port of the air supply duct and the exhaust port of the exhaust duct face the band back surface 62b. Further, the air supply port of the air supply duct and the exhaust port of the exhaust duct extend from one end of the casting film 61 to the other end. It is preferable that the air supply port of the air supply duct and the exhaust port of the exhaust duct are alternately arranged in the X direction.

  The pre-drying air regulator is a temperature controller (not shown) that adjusts the temperature of the pre-drying air 90 within a predetermined range, and a blower fan (not shown) that sends the pre-drying air 90 to the air supply duct with a predetermined air volume. And have.

  The front-side blower 91 sends the pre-drying air 90 from the air supply port toward the membrane surface 61a, and sucks the pre-drying air 90 from the exhaust port. Similarly, the back surface side blower 92 sends the pre-drying air 90 from the air supply port toward the band back surface 62b, and sucks the pre-drying air 90 from the exhaust port.

  Note that the front-side blower 91 may apply the pre-drying air 90 in a direction perpendicular to the film surface 61a. Similarly, the back surface side blower 92 may apply the pre-drying air 90 in a direction perpendicular to the band back surface 62b.

(Back membrane dryer)
As shown in FIG. 2, the post-film dryer 89 is disposed along a portion of the moving path 66r of the endless band 62 from the roller 66b to the roller 66c. The rear membrane dryer 89 is arranged on the band surface 62a side, and sends out a post-drying air 94, a parallel blower 95, a back-side blower 96 arranged on the band backside 62b, and a post-drying air regulator (not shown). ). The parallel blower 95 includes a parallel exhaust duct 95a and a parallel air supply duct 95b that are sequentially provided from the upstream side in the X direction toward the downstream side.

  The parallel exhaust duct 95a and the parallel air supply duct 95b are respectively arranged on the band surface 62a side. The parallel exhaust duct 95a is provided with an exhaust port for exhausting the post-drying air 94. The exhaust port that opens toward the downstream side in the X direction extends from one end of the endless band 62 to the other end in the Y direction. The parallel air supply duct 95b is provided with an air supply port through which the post-drying air 94 is sent out. The air supply opening that opens toward the upstream side in the X direction extends from one end of the casting film 61 to the other end.

  The back side blower 96 has the same configuration as the back side blower 92 except that the post-drying air 94 is sent out. The post-drying air regulator (not shown) supplies a temperature controller (not shown) that adjusts the temperature of the post-drying air 94 within a predetermined range, and supplies the post-drying air 94 to the back side blower 96 with a predetermined air volume. And a blower fan (not shown) for sending to the air duct and the parallel air supply duct 95b.

(Peeling chamber)
A peeling roller 65 is provided in the peeling chamber 75c. A peeling portion is formed between the peeling roller 65 and the roller 66c. The peeling roller 65 is connected to the motor 99. Further, an outlet 75o of the casting casing 75 opens in the peeling chamber 75c. The casting film 61 can be peeled from the endless band 62 by making the peripheral speed of the peeling roller 65 larger than that of the roller 66c. The cast film 61 peeled off from the endless band 62 becomes the wet film 25 and is sent out from the outlet 75o to the drying unit 13 (see FIG. 1).

(Support heating room)
The support heating chamber 75d is provided with a support heating device 111 for sending the heating air 110 to the endless band 62. The support body heating device 111 includes a front surface side heater 112 disposed on the band surface 62a side, a back surface side heater 113 disposed on the band back surface 62b side, and a heating air regulator 114. Note that either one of the front surface side heater 112 and the back surface side heater 113 may be omitted.

(Surface heater)
As shown in FIGS. 6 and 7, the surface-side heater 112 includes an air supply duct 112a and an exhaust duct (not shown). The air supply port 112o of the air supply duct 112a and the exhaust port of the exhaust duct face the band surface 62a. The air supply port 112o and the exhaust port are each extended from one end of the endless band 62 to the other end. That is, in the Y direction, the width of the air supply port 112o and the exhaust port is wider than the casting width CW. Note that the air supply port 112o and the exhaust port are preferably arranged alternately in the X direction.

(Back side blower)
The back surface side heater 113 has an air supply duct 113a and an exhaust duct (not shown). The supply port 113o of the supply duct and the exhaust port 113i of the exhaust duct face the band back surface 62b. The supply port 113o and the exhaust port 113i extend from one end of the endless band 62 to the other end, respectively. That is, in the Y direction, the width of the air supply port 113o and the exhaust port 113i is wider than the casting width CW. Note that the air supply port 113o and the exhaust port 113i are preferably arranged alternately in the X direction.

  The heating air adjuster 114 is a temperature controller (not shown) that adjusts the temperature of the heating air 110 within a predetermined range, and the heating air 110 is supplied to the front side heater 112 and the back side heater 113 with a predetermined air volume. It has a ventilation fan (not shown) sent to the air supply ducts 112a and 113a.

  The front surface side heater 112 sends the heating air 110 from the air supply port 112o toward the band surface 62a, and sucks the heating air 110 from the exhaust port. The back surface side heater 113 sends the heating air 110 from the air supply port 113o toward the band back surface 62b, and sucks the heating air 110 from the exhaust port 113i.

  Returning to FIG. 1, a roller temperature controller 121 for adjusting the temperature of the roller 66a is connected to the roller 66a. A roller temperature controller 122 that adjusts the temperature of the roller 66b is connected to the roller 66b. Thereby, the roller 66 b evaporates the solvent from the casting film 61 by heating the casting film 61. In this case, the roller 66b may be included in the film drying device 64. A roller temperature controller 123 that cools the roller 66c is connected to the roller 66c. When the roller temperature controller 123 cools the roller 66 c, the roller 66 c functions as a film cooling unit that cools the casting film 61 via the endless band 62.

  Although not shown in the figure, a condensing device that condenses the solvent contained in the atmosphere in the casting casing 75 and a recovery device that collects the condensed solvent provide a gas in the casting casing 75. The temperature at which the solvent liquefies (condensation point) can be maintained within a predetermined range.

  Next, as shown in FIG. 8, in the solution casting method 125, a cast film forming step 126 and a wet film drying step 127 are sequentially performed.

(Outline of casting film forming process)
A casting film forming step 126 for obtaining the wet film 25 from the dope 24 is performed in the casting unit 12 shown in FIG. Details of the cast film forming step 126 will be described later.

(Wet film drying process)
The wet film drying step 127 for evaporating the solvent from the wet film 25 to form the film 21 is performed by the drying unit 13 shown in FIG.

  The wet film 25 introduced into the clip tenter 35 is conveyed in a state where both ends in the width direction are gripped by the clip 35b. The drying air supply unit 35c applies a predetermined drying air to each of the front surface and the back surface of the wet film 25 between the grip start position and the grip release position. Thus, the solvent can be evaporated from the wet film 25. In addition, since the rail interval gradually increases from the grip start position toward the grip release position, the wet film 25 can be stretched by being conveyed by the clip 35b. By the stretching treatment, the in-plane retardation Re and the thickness direction retardation Rth can be adjusted.

  The wet film 25 introduced into the drying chamber 37 is conveyed while being wound around a plurality of rollers 45. By adjusting the temperature and humidity of the atmosphere in the casing 106a, the solvent evaporates from the wet film 25 conveyed in the casing 106a. Thus, the wet film 25 becomes the film 21.

(Details of casting film forming process)
As shown in FIG. 8, in the casting film forming process 126, the dope flowing process 131, the casting process 132, the film heating process 133, the skin layer forming process 134, the film drying process 135, and the film cooling process 136. Then, the peeling step 137 and the support heating step 138 are sequentially performed.

  As shown in FIG. 2, when the roller 66c is rotated by driving the motor 66m, the endless band 62 sequentially circulates and moves through the chambers 75a to 75d in the casting casing 75. The roller temperature controllers 121 to 123 adjust the temperatures of the rollers 66a to 66c within a predetermined range. In a stock tank (not shown), the temperature of the dope 24 is adjusted to be substantially constant within a predetermined range. The dope 24 is sent from the stock tank to the casting die 60 by a pump (not shown). The temperature of the casting die 60 is adjusted to be substantially constant within a predetermined range by a temperature controller provided in the casting die 60.

(Casting room)
In the casting chamber 75a, a dope flowing process 131 (see FIG. 8) in which the dope 24 flowing out from the casting die 60 reaches the band surface 62a, and a casting film 61 made of the dope 24 is formed on the band surface 62a. The casting process 132 (see FIG. 8) and the film heating process 133 (see FIG. 8) for heating the casting film 61 are performed.

(Dope flow down process)
The casting die 60 continuously flows out the dope 24 from the slit outlet toward the band surface 62a. The dope 24 flowing out from the slit exit reaches a portion of the endless band 62 supported by the roller 66a, that is, a reaching position DP on the band surface 62a.

(Casting process)
Since the endless band 62 is in the moving state, the dope 24 that has reached the arrival position DP is flowed and extended in the moving direction on the band surface 62a. Thus, a casting film 61 made of the dope 24 and having a casting width CW (see FIG. 6) is formed in a band shape on the band surface 62a.

  The moving speed V of the endless band 62 is preferably 200 m / min or less. If the moving speed V exceeds 200 m / min, it becomes difficult to stably form the beads. The lower limit value of the moving speed V may be determined in consideration of the target film productivity. The lower limit value of the moving speed V may be, for example, 20 m / min or more, or 60 m / min or more.

  The content of the solvent in the dope 24 flowing out from the casting die 60 is preferably 300% by mass or more and 450% by mass or less. This is because when the content of the solvent in the dope 24 flowing out from the casting die 60 is less than 300% by mass, the viscosity of the dope 24 becomes high and stable casting cannot be performed. If the content of the solvent in the dope 24 flowing out from the casting die 60 exceeds 450% by mass, the drying load in the film drying chamber 75b increases, resulting in a decrease in production efficiency.

  Here, the content of the solvent indicates the amount of the solvent contained in the dope, cast film and each film on a dry basis, a sample is taken from the target film, and the weight of this sample is expressed as x When the weight after drying the sample is y, {(xy) / y} × 100.

  The temperature of the dope 24 flowing out from the casting die 60 is preferably 20 ° C. or higher and lower than the boiling point of the solvent. This is because when the temperature of the dope 24 flowing out from the casting die 60 is less than 20 ° C., the viscosity of the dope 24 becomes high and stable casting cannot be performed. Further, when the temperature of the dope 24 flowing out from the casting die 60 exceeds the boiling point of the solvent, foaming of the dope 24 occurs, which is not preferable. The boiling point of the solvent represents the boiling point of the compound when the solvent is composed of a single compound, and represents the lowest boiling point among the boiling points of the plurality of compounds when the solvent is composed of a plurality of compounds. .

(Film heating process)
Since the second seal member 72 and the roller 66y are separated by a predetermined distance from the reaching portion toward the downstream side in the X direction, the casting zone CZ (casting) having a predetermined length from the reaching portion toward the downstream side in the X direction. Part) is formed. In the casting zone CZ, a film heating process 133 for heating the casting film 61 is performed using the endless band 62 heated by the support heating process 138 described later as a film heating means.

  Here, the film surface 61a of the casting film 61 immediately after the formation, that is, immediately after the casting step 132 is not smooth (see FIG. 9). Therefore, the thickness unevenness occurs in the casting film 61 immediately after the casting step 132. This uneven thickness is considered to be caused by the vibration of the bead. Further, the dope 24 forming the casting film 61 immediately after the casting step 132 contains a large amount of solvent, and is easy to show fluidity. Therefore, in the present invention, the film heating step 133 is performed using the heated endless band 62 to heat the casting film 61 immediately after the casting step 132. By heating the casting film 61 immediately after the casting step 132, the fluidity of the dope 24 forming the casting film 61 immediately after the formation is increased. As a result, the film surface 61a of the casting film 61 immediately after the formation is smooth and smooth. (See FIG. 10).

  The length of the casting zone CZ in the X direction is not particularly limited as long as the time required for the film surface 61a of the casting film 61 immediately after formation to be smooth can be ensured. It is preferable to perform the film | membrane heating process 133 with respect to the cast film 61 whose content of a solvent is 300 mass% or more and 450 mass% or less.

  By the roller temperature controller 121, the temperature of the roller 66a falls within the range from the temperature of the band surface 62a at the peeling position PP to the boiling point of the solvent.

(Membrane drying room)
In the film drying chamber 75b, until the skin layer 61x (see FIG. 11) is formed on the film surface 61a side of the cast film 61, the skin layer forming step 134 (see FIG. 8) is applied to the film surface 61a. Then, a film drying step 135 (see FIG. 8) for evaporating the solvent from the casting film 61 is performed.

(Skin layer forming process)
As shown in FIG. 4, in the skin layer forming apparatus 63, the air supply nozzle 83 sends out the skin layer forming air 80 from the intake port 83a. Each angle θ1 formed by the direction of the skin layer forming air 80 delivered from the intake port 83a (the extending direction of the pre-air supply nozzle 83) and the X direction is preferably 30 ° or more and 60 ° or less, and 45 More preferably. The skin 68 from the intake port 83a is guided by the cover 68 from the upstream side toward the downstream side in the X direction. Due to the cover 82 close to the casting film 61, a spiral flow of the skin layer forming air 80 is likely to occur near the film surface 61 a of the casting film 61. Since the thermal energy of the skin layer forming wind 80 is easily transmitted to the casting film 61 at the location where the spiral flow is generated, the evaporation of the solvent is caused on the film surface 61 a of the casting film 61 by the vortex flow of the skin layer forming wind 80. Promoted.

  By the skin layer forming step 134, the casting film 61 has a skin layer 61x and a wet layer 61y (see FIG. 11). The skin layer 61x is a portion that is formed on the film surface 61a side of the casting film 61 and is more dried than the wet layer 61y located on the endless band 62 side than the skin layer 61x. Therefore, the solvent content of the skin layer 61x is lower than that of the wet layer 61y.

  Further, the surface of the skin layer 61x is formed smoothly. When the film drying step 135 is performed on the cast film 61 having the skin layer 61x, the surface of the skin layer 61x becomes the film surface 61a of the obtained cast film 61. Therefore, the cast film 61 having a smooth film surface 61 a can be obtained by performing the skin layer forming process 134 on the cast film 61 that has undergone the film heating process 133.

  The skin layer forming step 134 is preferably performed on the cast film 61 having a solvent content of 250% by mass or more and 400% by mass or less. The temperature of the skin layer forming air 80 is preferably 30 ° C. or higher and 80 ° C. or lower, for example. Further, the wind speed of the skin layer forming wind 80 is preferably 5 m / sec or more and 25 m / sec or less.

(Film drying process)
In the film drying process 135, a pre-film drying process 135a and a post-film drying process 135b are sequentially performed (see FIG. 8).

(Pre-membrane drying process)
As shown in FIG. 2, the pre-film dryer 88 performs a pre-film drying step 135 a for evaporating the solvent from the cast film 61. The surface-side blower 91 applies pre-drying air 90 to the film surface 61 a to evaporate the solvent from the casting film 61. Further, the back surface side blower 92 applies the pre-drying air 90 to the band back surface 62 b and heats the casting film 61 through the endless band 62. The solvent is evaporated from the casting film 61 by heating the casting film 61.

(Post-film drying process)
The post-film dryer 89 performs a post-film drying step 135b for evaporating the solvent from the cast film 61. The parallel blower 95 applies post-drying air 94 to the film surface 61 a of the casting film 61 to evaporate the solvent from the casting film 61. Further, the back surface side blower 96 applies the post-drying air 94 to the band back surface 62 b and heats the casting film 61 through the endless band 62. The solvent is evaporated from the casting film 61 by heating the casting film 61. The post-film drying step 135b is preferably performed until the content of the solvent in the cast film 61 becomes 110% by mass or more and 210% by mass or less.

  The post-film drying step 135b may be performed using the heat of the roller 66b. The roller temperature controller 122 is preferably adjusted so that the temperature of the roller 66b is in the range of 20 ° C. or higher and 40 ° C. or lower.

  By performing each process 131-135 (refer FIG. 8), the cast film 61 with the smooth film surface 61a can be obtained (refer FIG. 12).

(Peeling chamber)
In the peeling chamber 75c, a film cooling process 136 (see FIG. 8) for cooling the endless band 62 and a peeling process 137 (see FIG. 8) for peeling the casting film 61 from the endless band 62 are performed.

(Film cooling process)
The roller temperature controller 123 causes the temperature of the roller 66c to fall within the range of −10 ° C. to 15 ° C. In addition, it is preferable that the temperature of the roller 66c exists in the range of -10 degreeC or more and 10 degrees C or less. The endless band 62 that has been brought to a high temperature state by the film drying step 135 is cooled by contact with the roller 66c. Then, the casting film 61 is cooled through the cooled endless band 62. The film cooling process 136 is performed until the film can be conveyed independently.

(Peeling process)
In the peeling chamber 75c, a peeling process 137 (see FIG. 8) is performed using the peeling roller 65 to peel off the cast film 61 that has been peeled off from the endless band 62. At the portion of the endless band 62 supported by the roller 66 c (peeling position PP), the cast film 61 that has been peeled off is peeled from the endless band 62. The cast film 61 peeled from the endless band 62 is sent out from the outlet 75o as the wet film 25. In order to suppress variation in the orientation angle, the peeling step 137 is preferably performed on the cast film 61 having a solvent content of 200% by mass or less. From the viewpoint of production efficiency, the peeling step 137 is preferably performed on the cast film 61 having a solvent content of 100% by mass or more.

(Support heating process)
The endless band 62 after the casting film 61 is peeled off returns to the casting chamber 75a through the support heating chamber 75d. When the dope flowing step 131, the casting step 132, and the skin layer forming step 134 are successively performed on the endless band 62 cooled by the film cooling step 136, the film surface 61a is not smooth (see FIG. 9). ) Drying will continue. As a result, the thickness unevenness occurs in the casting film 27. Since the thickness unevenness generated in the casting film 27 cannot be removed in a later process, the thickness 21 eventually becomes uneven.

  Therefore, in the present invention, in order to perform the film heating step 133 between the (n + 1) th casting step 132 and the (n + 1) th skin layer forming step 134, the nth peeling step 137 and the (n + 1) th time are performed. A support heating step 138 for heating the endless band 62 is performed with the dope flowing step 131.

  In the support heating chamber 75d, a support heating process 138 in which the endless band 62 is heated is performed by the support heating device 111. As shown in FIG. 6, the surface-side heater 112 applies the heating air 110 to the band surface 62a and heats the endless band 62 until the temperature of the band surface 62a falls within a predetermined range. Similarly, the back surface side heater 113 applies the heating air 110 to the band back surface 62b and heats the endless band 62 until the temperature of the band surface 62a falls within a predetermined range.

  In the support heating step 138, it is preferable to heat the band surface 62a so that the temperature of the band surface 62a in the casting zone CZ is in the range T1. Here, the range T1 is 8 ° C. or more and the boiling point of the solvent or less, and the lower limit value of the range T1 is preferably 10 ° C., more preferably 15 ° C. The upper limit of the range T1 is preferably (the boiling point of the solvent−5 ° C.). In addition, it is preferable that the temperature of components (rollers 66a, 66x, etc.) functioning with the support heating device is also in the range T1.

  In the present invention, the film heating step 133 for applying heat to the casting film 61 formed on the endless band 62 in the next casting step 132 using the heat given to the endless band 62 in the support heating step 138 is performed. Do. Therefore, according to this invention, a film can be manufactured efficiently, suppressing thickness nonuniformity.

  The film heating step 133 may be performed between the peeling position PP and the arrival position DP.

  Next, another embodiment of the present invention will be described. Parts and members that are the same as those in the above-described embodiment will be denoted by the same reference numerals, detailed description thereof will be omitted, and details of parts different from those in the above-described embodiment will be described.

  As the support heating means, the support heating device 111 that applies the heated air 110 to at least one of the band surface 62a and the band back surface 62b is used. However, the present invention is not limited to this, and at least one of the band surface 62a and the band back surface 62b is used. You may use the support body heating apparatus 141 provided with the heating roller which contacts. As shown in FIG. 13, the support heating device 141 sets the temperatures of the surface heating roller 142 in contact with the band surface 62 a, the back surface heating roller 143 in contact with the band back surface 62 b, the surface heating roller 142, and the back surface heating roller 143. And a roller temperature controller 144 for adjusting. By the roller temperature adjuster 144, the support heating device 141 heats the band surface 62a so that the temperature when passing through the casting zone CZ (see FIG. 2) is in the range T1.

  As shown in FIG. 2, the roller temperature controller 123 may cool the roller 66 z disposed on the downstream side in the X direction from the rear film dryer 89. The roller 66z cooled by the roller temperature controller 123 serves as a film cooling means. Therefore, the film cooling process 136 may be performed in the film drying chamber 75 b as long as it is after the film drying process 135.

  In the above embodiment, the roller 66c cooled by the roller temperature controller 123 is used as the film cooling means, but the present invention is not limited to this. As shown in FIG. 14, a cooling unit 148 that cools the endless band 62 up to the peeling position PP may be used as the film cooling means. The cooling unit 148 disposed between the rear film dryer 89 and the cooling roller 66c in the film drying chamber 75b applies a liquid supply device 149 for supplying a liquid to the band back surface 62b and a drying air 150 to the band back surface 62b. And an evaporation device 151 for evaporating the liquid. The liquid supply method by the liquid supply device 149 may be any of application, spraying, a method of ejecting droplets, and the like. The liquid supply device 149 and the evaporation device 151 are sequentially arranged along the moving path 66r of the endless band 62 on the band back surface 62b side from the upstream side in the X direction toward the downstream side. The liquid supply device 149 supplies liquid to the band back surface 62b. When the evaporator 151 applies the drying air 150 to the band back surface 62b, the liquid on the band back surface 62b evaporates. When the liquid on the band back surface 62b evaporates, the temperature of the band back surface 62b decreases due to the heat of vaporization of the liquid. Thus, the endless band 62 can be cooled using the cooling unit 148.

  The liquid may be any liquid that evaporates before the endless band 62 reaches the peeling position PP. For example, dichloromethane can be used.

  As the film cooling means, at least one of the rollers 66c and 66z and the cooling unit 148 may be used. Two of the rollers 66c and 66z and the cooling unit 148 may be combined, or all of the three may be used. May be.

  In order to keep the band surface 62a horizontal in the casting zone CZ, it is preferable to arrange the roller 66a and the roller 66x in the same horizontal plane. As shown in FIG. 15, a support roller 66d that is disposed on the same horizontal plane as the roller 66a and supports the band back surface 62b may be provided between the roller 66a and the roller 66y.

Further, as shown in FIG. 16, a support roller 66e that is disposed on the same horizontal plane as the roller 66a and supports the band back surface 62b may be provided between the roller 66a and the roller 66x.
The temperature of the support roller 66e may be adjusted by the roller temperature controller 121 so as to be in the range T1. Thereby, the support roller 66e functions as a support heating means.

  Note that the roller temperature controller 121 may adjust the temperature of the roller 66a to be in the range T1. Thereby, the roller 66a functions as a support heating means.

  In the above embodiment, the roller 66a is disposed above the rollers 66x to 66y, but the present invention is not limited to this. For example, as shown in FIG. 17, a roller 66a and a roller 66b are provided on the same plane (for example, a horizontal plane), and a roller 66c disposed between the rollers 66a and 66b is provided below the plane. May be. The roller 66z may be provided between the roller 66a and the roller 66b.

  The roller 66c shown in FIG. 2 has a function of supporting the endless band 62 at the peeling position PP and a sealing function by the third to fourth seal members 73 to 74. However, these may be separated into functions. For example, the rollers 66c, 66f, and 66g in FIG. 18 correspond to the roller 66c shown in FIG. 18 has a function of supporting the endless band 62 at the peeling position PP, and the support roller 66f of FIG. 18 exhibits a sealing function with the third seal member 73, and the support roller of FIG. 66 g exhibits a sealing function by the fourth seal member 74. The roller temperature controller 123 cools the roller 66c. The roller temperature controller 123 may cool the roller 66f.

  The roller 66g may be heated by the roller temperature controller 123. Thereby, the roller 66g functions as a support heating means.

  Note that the roller 66a shown in FIG. 17 corresponds to the roller 66a, 66x, 66y shown in FIG.

  As shown in FIG. 18, the roller 66a and the roller 66c may be provided on the same plane (for example, a horizontal plane), and the roller 66b may be provided between the roller 66a and the roller 66c. The roller 66b that supports the band back surface 62b is arranged so that the endless band 62 that moves from the roller 66a toward the roller 66c is substantially horizontal. The roller 66b may be provided above the rollers 66a and 66c. The roller 66a shown in FIG. 18 corresponds to the roller 66a, 66x, 66y shown in FIG.

  In the above embodiment, in the support heating step 138, the endless band 62 is heated in the entire Y direction, but only the central portion in the Y direction of the endless band 62 may be heated. Moreover, you may heat only the part of casting area CA (refer FIG. 6) of the casting width CW (refer FIG. 19). As a result, the non-casting area of the endless band 62 excluding the casting area CA (see FIG. 6) is not heated more than necessary. Foaming can be reliably suppressed. In the casting area CA, the central portion in the Y direction may be a heated portion, and both end portions in the Y direction of the casting area CA may be non-heated portions. In this case, the width of the non-heated part in the Y direction is, for example, 10 mm.

  Note that a support surface cleaning process for cleaning the band surface 62a may be performed between the peeling process 137 and the support heating process 138. A peeling failure can be reliably suppressed by the support surface cleaning step. Further, the foreign substance remaining on the band surface 62a (for example, a part of the cast film remaining unremoved) can be removed by the support surface cleaning step. This foreign matter causes bead vibration. Therefore, the vibration of the bead can be prevented by the support surface cleaning step. In order to clean the band surface 62a, for example, it is preferable to use a dry ice cleaning machine that sprays dry ice onto the band surface 62a.

  Further, a contact angle lowering step for reducing the contact angle of the band surface 62a with respect to the dope 24 may be performed between the support heating step 138 and the next dope flowing-down step 131. Due to the contact angle lowering step, the accompanying air hardly flows between the bead and the band surface 62a. Therefore, it is possible to prevent the cast film from being shaken due to the inflow of the accompanying air by the contact angle lowering step. Here, the accompanying wind refers to a wind that is generated near the band surface 62a due to the movement of the endless band 62 and flows in the X direction. In order to reduce the contact angle of the band surface 62a with the dope 24, it is preferable to apply a solvent to the band surface 62a. The solvent used in the contact angle lowering step may be the same component as the solvent 23 or may contain a component common to the solvent 23.

  In the above embodiment, the timing of performing the support heating process 138 is between the peeling process 137 and the dope flowing process 131, but it may be between the casting process 132 and the film heating process 133. FIG. 20 shows a casting film forming process 161 in which the support heating process 138 is performed between the casting process 132 and the film heating process 133 and a solution casting method 162 having the casting film forming process 161.

  A casting unit 165 that performs the casting film forming step 161 is shown in FIG. The casting unit 165 has a support heating device 168 as a support heating means on the band back surface 62b side of the casting zone CZ. The support heating device 168 includes a back surface side heater 113 and a heating air regulator 114. Since the support heating device 168 heats the endless band 62 from the band back surface 62b side, the casting film 61 is heated from the endless band 62 side. Therefore, according to the support body heating device 168, it is possible to heat the casting film 61 while suppressing the formation of the skin layer on the casting film 61. When the support heating process is performed in the casting zone CZ, it is necessary to heat the endless band 62 from the band back surface 62b side. This is because when the endless band 62 is heated from the band surface 62 a side, the skin layer forming step 134 is performed prior to the film heating step 133. The roller temperature controller 121 may cause the roller 66y to function as a support heating means by setting the temperature of the roller 66y within the range T1.

  In order to prevent evaporation of the solvent from the casting film 61 in the film heating process 133, the gas concentration of the solvent in the atmosphere in the vicinity of the casting film 61 in the film heating process 133 is the casting film 61 in the skin layer forming process 134. It is preferable that it is higher than the gas concentration of the solvent in the atmosphere in the vicinity of. Here, “the gas concentration of the solvent in the atmosphere of the temperature Ta” is “(mass of the gaseous solvent contained in the atmosphere of the temperature Ta) / (mass of the gaseous solvent that is saturated in the atmosphere of the temperature Ta)”. ".

  In the cast film forming step 161, the timing for performing the support surface cleaning step and the contact angle reducing step may be between the peeling step 137 and the next dope flowing step 131. When performing both processes, it is preferable to perform in order of a support surface cleaning process and a contact angle reduction process.

  Further, a contact angle lowering step for reducing the contact angle of the band surface 62a with respect to the dope 24 may be performed between the support heating step 138 and the next dope flowing-down step 131. Due to the contact angle lowering step, the accompanying air hardly flows between the bead and the band surface 62a. Therefore, it is possible to prevent the cast film from being shaken due to the inflow of the accompanying air by the contact angle lowering step. Here, the accompanying wind refers to a wind that is generated near the band surface 62a due to the movement of the endless band 62 and flows in the X direction. In order to reduce the contact angle of the band surface 62a with the dope 24, it is preferable to apply a solvent to the band surface 62a. The solvent used in the contact angle lowering step may be the same component as the solvent 23 or may contain a component common to the solvent 23.

  The film 21 obtained by the present invention can be used particularly for a retardation film and a polarizing plate protective film.

  The width of the film 21 is preferably 600 mm or greater and 3000 mm or less, and preferably 2000 mm or greater and 3000 mm or less. Further, the present invention can be applied even when the width of the film 21 exceeds 3000 mm. The thickness of the film 21 is preferably 20 μm or more and 120 μm or less, and more preferably 30 μm or more and 80 μm or less.

  The in-plane retardation Re of the film 21 is preferably 10 nm or more and 300 nm or less, and the thickness direction retardation Rth of the film 21 is preferably −100 nm or more and 300 nm or less.

The method for measuring the in-plane retardation Re is as follows. In-plane retardation Re is a letter obtained by conditioning a sample film at a temperature of 25 ° C. and a humidity of 60% RH for 2 hours, and measuring it from the vertical direction at 632.8 nm with an automatic birefringence meter (KOBRA21DH Oji Scientific Co., Ltd.). Use the foundation value. Re is expressed by the following equation.
Re = | n1-n2 | × d
n1 is the refractive index of the slow axis, n2 is the refractive index of the fast axis 2, and d is the thickness (film thickness) of the film.

The measuring method of the thickness direction retardation Rth is as follows. The sample film was conditioned at a temperature of 25 ° C. and a humidity of 60% RH for 2 hours, and measured in the same manner while tilting the film surface with an ellipsometer (M150 manufactured by JASCO Corporation) measuring 632.8 nm from the vertical direction. It calculates according to the following formula from the extrapolated value of the retardation value.
Rth = {(n1 + n2) / 2−n3} × d
n3 represents the refractive index in the thickness direction.

(polymer)
In the said embodiment, the polymer used as the raw material of a polymer film is not specifically limited. When performing the solution casting method, examples of the polymer include cellulose acylate and cyclic polyolefin. On the other hand, when the melt film-forming method is performed, examples of the raw material polymer include cellulose acylate, lactone ring-containing polymer, cyclic polyolefin, and polycarbonate. Among them, cellulose acylate and cyclic polyolefin are preferable, and cellulose acylate containing acetate group and propionate group and cyclic polyolefin obtained by addition polymerization are more preferable, and cyclic polyolefin obtained by addition polymerization is more preferable. It is.

(Cellulose acylate)
As the cellulose acylate, triacetyl cellulose (TAC) is particularly preferable. Of the cellulose acylates, those in which the hydroxyl group of cellulose is esterified with a carboxylic acid, that is, the substitution degree of the acyl group satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group, A is the substitution degree of the acetyl group, and B is the substitution degree of the acyl group having 3 to 22 carbon atoms. It is. In addition, it is preferable that 90 weight% or more of TAC is a particle | grain of 0.1 mm-4 mm.
(I) 2.0 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio of the hydroxyl group of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1).

  The total acylation substitution degree, that is, DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS3 is the degree of substitution of the hydroxyl group at the 3-position with an acyl group (hereinafter, DS6 is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. When the sum of the substitution degrees by the hydroxyl groups at the 2nd, 3rd and 6th positions is DSA, and the sum of the substitution degree by an acyl group other than the acetyl group at the 2nd, 3rd and 6th hydroxyl groups is DSB, the value of DSA + DSB is More preferably, it is 2.22 to 2.90, and particularly preferably 2.40 to 2.88. The DSB is 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is a substituent at the 6-position hydroxyl group, more preferably 25% or more is a substituent at the 6-position hydroxyl group, more preferably 30% or more, and particularly 33% or more is a 6-position hydroxyl group. It is preferable that it is a substituent. Furthermore, the cellulose acylate having a substitution degree of 6-position of cellulose acylate of 0.75 or more, further 0.80 or more, and particularly 0.85 or more can be mentioned. With these cellulose acylates, a solution having a preferable solubility (dope) can be produced. In particular, a good solution can be prepared in a non-chlorine organic solvent. Furthermore, it is possible to produce a solution having a low viscosity and good filterability.

  Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter or pulp.

  The acyl group having 2 or more carbon atoms of the cellulose acylate of the present invention may be an aliphatic group or an aryl group and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these include propionyl, butanoyl, pentanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl , Naphthylcarbonyl, cinnamoyl group and the like. Among these, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are more preferable, and propionyl and butanoyl are particularly preferable.

(solvent)
Solvents 23 for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, n -Butanol, diethylene glycol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). In the present invention, the dope means a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  Among these, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. One kind of alcohol having 1 to 5 carbon atoms in addition to dichloromethane from the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength of the film, and optical properties of the film It is preferable to mix several kinds. The content of the alcohol is preferably 2% by weight to 25% by weight and more preferably 5% by weight to 20% by weight with respect to the whole solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, but methanol, ethanol, n-butanol or a mixture thereof is preferably used.

  By the way, recently, for the purpose of minimizing the influence on the environment, studies have been conducted on the solvent composition when dichloromethane is not used. For this purpose, ethers having 4 to 12 carbon atoms, carbon atoms A ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferably used. These may be used in combination as appropriate. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester, and alcohol (that is, —O—, —CO—, —COO—, and —OH) can also be used as the solvent.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148. These descriptions are also applicable to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, and release accelerators. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516].

  The present invention can perform simultaneous lamination co-casting in which a merged dope is formed by merging two or more types of dopes, or sequential lamination co-casting in which a plurality of dopes are sequentially co-cast and laminated. . In addition, you may combine both casting. When simultaneous lamination and co-casting is performed, a casting die to which a feed block is attached may be used, or a multi-pocket casting die may be used.

  By performing simultaneous lamination co-casting or sequential lamination co-casting using a first dope containing a first polymer and a second dope containing a second polymer different from the first polymer, Forming a laminated cast film comprising a layer (support surface layer), a layer on the surface side of the cast film (air surface layer), and a layer (base layer) between the support surface layer and the air surface layer; it can. The base layer is composed of the first dope, and the air surface layer and the support surface layer are composed of the second dope.

When the first polymer and the second polymer are cellulose acylates, the total acyl substitution degree Z1 of the acyl groups in the first polymer is preferably lower than the total acyl substitution degree Z2 of the acyl groups in the second polymer. In particular, the total acyl substitution degree Z1 of the acyl group in the first polymer satisfies the formula (1), and the total acyl substitution degree Z2 of the acyl group in the second polymer satisfies the formula (2).
Formula (1) 2.0 <Z1 <2.7
Formula (2) 2.7 <Z2

From the viewpoint of retardation wavelength dispersion, the substitution degree X1 of the acetyl group of the cellulose acylate used in the first polymer and the total substitution degree Y1 of the acyl group having 3 or more carbon atoms are represented by the following formulas (3) and (4 ) Is preferable. Note that the relationship X1 + Y1 = Z1 is established between X1 and Y1 and Z1 in the formula (1).
Formula (3) 1.0 <X1 <2.7
Formula (4) 0 <= Y1 <1.5

From the viewpoint of retardation wavelength dispersion, the substitution degree X2 of the acetyl group of the cellulose acylate used in the second polymer and the total substitution degree Y2 of the acyl group having 3 or more carbon atoms are represented by the following formulas (5) and (6 ) Is preferably satisfied. Note that the relationship of X2 + Y2 = Z2 holds between X2 and Y2 and Z2 in the above formula (2).
Formula (5) 1.2 <X2 <3.0
Formula (6) 0 <= Y2 <1.5

  The second dope has a lower viscosity than the first dope. The viscosity of each dope can be determined based on JIS K 7117.

  The second polymer may be cellulose acylate, and the first polymer may be a polymer other than cellulose acylate. As the first polymer, an acrylic resin is preferably used.

(acrylic resin)
Acrylic resins include methacrylic resins, and acrylate / methacrylate derivatives, in particular, acrylate ester / methacrylate ester (co) polymers are well known. Although it does not restrict | limit especially as an acrylic resin, What consists of 50-99 mass% of methylmethacrylate units and 1-50 mass% of other monomer units copolymerizable with this has a small photoelastic coefficient. Preferred for obtaining a film.

  In the acrylic resin, the other copolymerizable monomer includes alkyl methacrylate having 2 to 18 carbon atoms in the alkyl group, alkyl acrylate having 1 to 18 carbon atoms in the alkyl number, acrylic acid, methacrylic acid, and the like. α, β-unsaturated acids, maleic acids, fumaric acids, dicarboxylic acids containing unsaturated groups such as itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β such as acrylonitrile and methacrylonitrile -Unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned, and these can be used alone or in combination of two or more monomers as a copolymerization component. .

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  As a resin that can form a highly transparent optical film with little performance change even in high temperature and high humidity environments, acrylic resins contain alicyclic alkyl groups as copolymerization components, or have molecular mains by intramolecular cyclization. An acrylic resin in which a cyclic structure is formed in the chain is preferable. As an example of the acrylic resin in which a cyclic structure is formed in the molecular main chain, an acrylic thermoplastic resin containing a lactone ring-containing polymer can be cited as one preferred embodiment. No. 171464. Another preferred embodiment is a resin containing glutaric anhydride as a copolymerization component, and the copolymerization component and a specific synthesis method are described in JP-A-2004-070296.

  The weight average molecular weight of the acrylic resin is 600,000 to 4,000,000, preferably 800,000 to 3,000,000, and particularly preferably 1,000,000 to 1,800,000. The weight average molecular weight of the acrylic resin can be measured by gel permeation chromatography.

  There is no restriction | limiting in particular as a manufacturing method of an acrylic resin, Well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization, can be used. In the present invention, a plurality of acrylic resins can be used in combination.

  The acrylic resin can further contain another thermoplastic resin. In the present invention, the thermoplastic resin having a glass transition temperature of 100 ° C. or higher and a total light transmittance of 85% or higher is mixed with the acrylic resin to form a film. It is preferable in terms of improving the strength.

  The content ratio of the acrylic resin and other thermoplastic resin components in the acrylic resin layer is a mass ratio of [acrylic resin / (total thermoplastic resin)] × 100, preferably 30 to 99 mass%, more preferably 50. It is -97 mass%, More preferably, it is 60-95 mass%. A content ratio of the acrylic resin in the acrylic resin layer of 30% by mass or more is preferable because heat resistance can be sufficiently exhibited.

  Examples of the other thermoplastic resins include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins. Polymer; Styrenic polymer such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; Polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; Nylon 6, polyamides such as nylon 66, nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; Terusaruhon; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as acrylic rubber ABS resin or ASA resin blended with; and the like. The rubbery polymer preferably has a graft portion having a composition compatible with the ring polymer in the present invention on the surface, and the average particle size of the rubbery polymer is improved in transparency when formed into a film. In view of the above, it is preferably 100 nm or less, and more preferably 70 nm or less.

  As the other thermoplastic resin, a resin that is thermodynamically compatible with an acrylic resin is preferably used. Preferred examples of such other thermoplastic resins include acrylonitrile-styrene copolymers having a vinyl cyanide monomer unit and an aromatic vinyl monomer unit, and a polyvinyl chloride resin. Among them, an acrylonitrile-styrene copolymer can easily provide an optical film having a glass transition temperature of 120 ° C. or more, a phase difference per 100 μm in the plane direction of 20 nm or less, and a total light transmittance of 85% or more. Therefore, it is preferable. Specifically, as the acrylonitrile-styrene copolymer, those having a copolymerization ratio in a molar unit of 1:10 to 10: 1 are usefully used.

  In the case where the first polymer is an acrylic resin, if simultaneous lamination co-casting or sequential lamination co-casting is performed using the first dope and the second dope, thickness unevenness frequently occurs in the laminated cast film. This uneven thickness is caused by destabilization of the interface between the base layer made of the first dope and the layer made of the second dope (support surface layer or air surface layer). The destabilization of the interface refers to a phenomenon in which a part of the first dope forming the base layer enters an adjacent support surface layer or air surface layer. In order to avoid this destabilization of the interface, using the combined dope composed of the first dope, the second dope, and a buffer solution flowing between the first dope and the second dope, It is preferable to perform sequential lamination co-casting.

  The buffer solution has a lower viscosity than the first dope and the second dope. Moreover, it is preferable that a buffer solution consists of a solvent compatible with the solvent contained in each dope. The viscosity of the buffer is preferably 1 Pa · second to 15 Pa · second, and more preferably 1 Pa · second to 10 Pa · second. The viscosity of the buffer solution can be determined based on JIS K 7117.

  The buffer solution is preferably the same as the solvent contained in each dope. The buffer may contain a polymer. Examples of the polymer contained in the buffer include a first polymer and a second polymer, and any one of these is preferably contained. The content concentration of the polymer in the buffer is preferably less than 5% by mass.

  By using an acrylic resin as the first polymer, it is possible to efficiently produce an optical film in which the optical characteristics are hardly changed due to generation of stress or change in humidity while suppressing thickness unevenness.

(Experiments 1-8)
Experiments 1 to 8 were performed by the following method. The details of each experiment will be described in detail with respect to Experiment 1, and with respect to Experiments 2 to 8, the description of the same parts as in Experiment 1 will be omitted, and different parts will be described.

(Experiment 1)
The prescription of the compound used for the preparation of the dope 24 is shown below.
Cellulose triacetate (degree of substitution 2.86) 100 parts by weight Triphenyl phosphate (TPP) 10 parts by weight Matting agent (AEROSIL R972) Solid content of 0.03 parts by weight of dichloromethane was 80 parts by weight methanol 13.5 parts by weight The dope 24 was prepared by appropriately adding to a mixed solvent consisting of 6.5 parts by mass of n-butanol and dissolving by stirring.

  The dope 24 was filtered with a filter paper (Toyo Filter Paper Co., Ltd., # 63LB) and further filtered with a sintered metal filter (Nihon Seisen Co., Ltd. 06N, nominal pore size 10 μm), and further filtered with a mesh filter. I put it in the tank.

[Cellulose triacetate]
The cellulose triacetate (TAC) used here has a residual acetic acid content of 0.1% by mass or less, a Ca content of 58 ppm, a Mg content of 42 ppm, and a Fe content of 0.5 ppm. It contained 40 ppm and 15 ppm sulfate ions. The degree of substitution of the acetyl group with respect to the hydrogen at the 6-position hydroxyl group was 0.91. Further, 32.5% of all acetyl groups were acetyl groups in which the hydrogen of the hydroxyl group at the 6-position was substituted. Moreover, the acetone extraction part which extracted this TAC with acetone was 8 mass%, and the mass average molecular weight / number average molecular weight ratio was 2.5. The obtained TAC had a yellow index of 1.7, a haze of 0.08, and a transparency of 93.5%. This TAC is synthesized using cellulose collected from cotton as a raw material.

Using the obtained dope 24, the film 21 (width 1950 mm) was manufactured in the solution casting apparatus 10 shown in FIG. The casting unit 12 shown in FIG. 2 was used. In the casting unit 12, the dope flowing process 131, casting process 132, film heating process 133, skin layer forming process 134, film drying process 135, film cooling process 136, peeling process 137, support heating process shown in FIG. The cast film forming step 126 for sequentially performing 138 was repeated. The moving speed V of the endless band was 100 m / min. In the peeling step 137 in the n-th cast film forming step 126, the temperature of the band surface 62a at the peeling position PP was T _PP (see Table 1). The content of the solvent in the casting film at that time was ZY PP _(see Table 1). When the temperature of the band surface 62a at the arrival position DP in the (n + 1) -th cast film forming step 126 was measured, the temperature at the center in the Y direction was T _DPc (see Table 1), and the temperatures at both ends in the Y direction were T _DPe (see Table 1). Note that both ends in the Y direction are portions 10 mm inside from both ends in the Y direction of the endless band 62.

(Experiments 2-8)
Presence / absence of film cooling step 136, presence / absence of film heating step 133, presence / absence of support heating step 138, temperature T _PP of band surface 62a at peeling position PP, solvent content ZY _PP in casting film at peeling position _PP , reach A film 21 was produced from the dope 24 in the same manner as in Experiment 1 except that the temperatures T _DPc and T _Dpe of the band surface 62 a at the position DP were as shown in Table 1.

(Evaluation)
In the solution casting methods of Experiments 1 to 8, evaluation was performed from the following viewpoints. The number of the evaluation result in Table 1 represents the number assigned to each evaluation item.

1. Stripping evaluation The presence or absence of a peeling failure was examined.
○: No peeling failure occurred in the peeling process.
X: A peeling failure occurred in the peeling process.

2. Thickness nonuniformity evaluation The presence or absence of the thickness nonuniformity of the film 21 was evaluated in the following procedures. The film 21 was measured for thickness unevenness. The procedure for measuring the thickness unevenness is as follows. First, a sample film approximately 6 cm square was cut out from the film 21. Second, the refractive index difference of the sample film was measured using an apparatus that can convert the refractive index difference of the sample film into a thickness difference. As this device, FX-03 FRINGEANALYZER (manufactured by FUJINON Co., Ltd.) was used. Third, this refractive index difference was measured over the entire area of the sample film, and this average value was taken as the thickness unevenness of the laminated film. The thickness unevenness thus obtained was evaluated according to the following criteria. In addition, the thickness of a laminated film is an average value of the thickness of six places of the sample film measured with the micrometer.
○: The thickness unevenness was less than 1.5% with respect to the thickness of the film.
Δ: The thickness unevenness was 1.5% or more and less than 1.8% with respect to the thickness of the film.
X: The thickness unevenness was 1.8% or more with respect to the thickness of the film.

3. Foaming evaluation The cast film obtained was visually observed to check for foaming.
(Double-circle): Foaming in the ear | edge part was not able to be confirmed.
○: Foaming was confirmed in the ear part, but it was limited to the part cut off by the slitter 36, and there was no problem as a film for a product.
X: Foaming was confirmed up to the part to be a film for a product.

DESCRIPTION OF SYMBOLS 10 Solution casting apparatus 12 Casting unit 24 Dope 25 Wet film 61 Casting film 62 Endless band 65 Peeling rollers 66a-66z Roller 111 Support body heating apparatus

Claims (16)

A dope flow-down step of flowing a dope containing a polymer and a solvent onto a moving support;
A film drying step of evaporating the solvent from a cast film formed of the flowed dope and formed on the surface of the moving support;
In the casting film forming method for performing the peeling process of peeling the cast film that has undergone the film drying process from the moving support,
A film cooling step that is performed after the film drying step and before the peeling step, and cools the cast film until it is in a state where it can be independently carried; and
A support heating step for heating the moving support after the peeling step and before the next film drying step;
A film heating step that is performed before the film drying step and heats the cast film using heat applied to the moving support in the support heating step. Forming method.   The casting film forming method according to claim 1, wherein, in the support heating step, the moving support before the dope flowing step is heated.   The method for forming a cast film according to claim 1 or 2, wherein the support heating step heats the movable support after the dope flowing-down step.   In the support heating step, a casting area for forming a casting film from the flowed dope set on the surface of the moving support is non-casting except for the casting area on the surface of the moving support. The method for forming a cast film according to any one of claims 1 to 3, wherein the movable support is heated so that the temperature is higher than that of the area. The temperature of the moving support in the peeling step is 5 ° C. or more and 15 ° C. or less,
The method for forming a cast film according to any one of claims 1 to 4 , wherein the film heating step is performed until the temperature of the moving support becomes 8 ° C or higher and lower than the boiling point of the solvent.   A skin layer forming step that is performed between the membrane heating step and the membrane drying step, and that applies a skin layer forming wind to the surface of the casting membrane to form a skin layer on the surface side of the casting membrane. The method for forming a cast film according to any one of claims 1 to 5, wherein: After performing the casting film forming method according to any one of claims 1 to 6,
A solution casting method comprising a film drying step of evaporating the solvent from the cast film peeled off from the movable support to obtain a film. A reaching portion where a flowing dope containing a polymer and a solvent reaches, a casting portion for forming a casting film from the flowing dope, a membrane drying portion for evaporating the solvent in the casting film made of the flowing dope, and A moving support that sequentially circulates and passes through the peeling portion where the casting film is peeled off,
Reaching portion support means for supporting the moving support located in the reaching portion;
Peeling part supporting means for supporting the movable support located in the peeling part;
A film cooling means for cooling the cast film until the movable support leaves the film drying section and reaches the peeling section until it is in a self-supporting state; and
A support heating means for heating the moving support until it leaves the peeling part and reaches the film drying part;
An apparatus for forming a cast film, comprising: a film heating means for heating the cast film before reaching the film drying section using heat applied by the support heating means.   9. The cast film forming apparatus according to claim 8, wherein the support heating means heats the moving support until it leaves the peeling portion and before reaching the reaching portion.   The apparatus for forming a cast film according to claim 8 or 9, wherein the support heating means heats the moving support from the reaching part to the film drying part.   In the support heating means, the casting area for forming the casting film set on the surface of the moving support is more than the non-casting area of the surface of the moving support except the casting area. The apparatus for forming a cast film according to any one of claims 8 to 10, wherein the movable support is heated so as to have a high temperature. Provided between the support heating means and the membrane drying section;
The skin layer forming wind is applied to the surface of the casting film to form a skin layer on the surface side of the casting film, and skin layer forming means is provided. Casting film forming apparatus. The casting part support means includes a casting part support roller,
The peeling part support means includes a peeling part support roller,
The casting film forming apparatus according to any one of claims 8 to 12, wherein the moving support is an endless band stretched over the casting part supporting roller and the peeling part supporting roller. .   14. The cast film forming apparatus according to claim 8, wherein the support heating means includes a heating air duct that applies heating air to the movable support.   15. The cast film forming apparatus according to claim 8, wherein the film cooling means cools the peeling portion supporting means. The film cooling means adjusts the temperature of the moving support in the peeling part to 5 ° C. or more and 15 ° C. or less,
The said support body heating means heats the said moving support body so that the temperature of the said moving support body in the said casting part may be 8 degreeC or more and below the boiling point of the said solvent, The casting of Claim 15 characterized by the above-mentioned. Film forming device.

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