TWI573681B - Method and apparatus for forming casting film and solution casting method - Google Patents

Description

Method and device for forming cast film and solution film forming method

The present invention relates to a method and apparatus for forming a cast film and a method for forming a solution film.

A polymer film (hereinafter referred to as a film) is widely used as an optical film because of its excellent light transmittance, flexibility, and light weight thinning. Among them, a cellulose ester film such as cellulose halide is used in an optical film. The optical film is exemplified by a film for photo-sensing, and a protective film or a retardation film of a polarizing plate. The protective film or retardation film of the polarizing plate is a constituent member of a liquid crystal display device which has been expanding in the market in recent years.

As a method of producing a film, there is a solution film forming method. The solution film forming method has a casting film forming process, a film independent process, a peeling process, and a wet film drying process. In the cast film forming process, a flow of the polymer dissolved in a solvent is applied to form a cast film composed of a dope on the support. In the membrane independence process, the solvent is evaporated from the cast film until it can be transported independently, that is, hardened to a certain extent or more. In the peeling process, the cast film was peeled off from the support as a wet film. In the wet film drying process, the solvent is evaporated from the wet film to serve as a film.

Japanese Patent Publication No. 2006-306059 discloses a method of sequentially performing a film drying process for evaporating a solvent from a casting film and cooling a cast film in a film independence process until a film cooling process capable of independent transfer. According to the method of Japanese Laid-Open Patent Publication No. 2006-306059, the time required for curing the cast film before the stripping process is shorter than the film cooling process of the film drying process, and therefore, the peeling failure due to insufficient drying of the cast film can be avoided. (A tearing failure causing the peeled cast film to be shredded or a peeling residual failure of a portion of the cast film remaining on the support). As a result, since the support body speed can be increased, the production efficiency of the film can be improved as compared with the related art.

However, it is possible to improve the production efficiency of the film by the method of JP-A-2006-306059, but the optical characteristics (in-plane retardation Re or thickness direction retardation Rth, etc.) due to uneven thickness of the obtained film can be obtained. The unevenness has always been a problem. The reason why the unevenness of the optical characteristics is conspicuous is that the required specifications of the optical film are increased, and the thickness of the liquid crystal display device is reduced to promote the thinning of the optical film.

Accordingly, it is an object of the present invention to provide a method and a device for drying a cast film which can suppress the thickness unevenness as described above and which can efficiently produce a film, and a cast film for the solution film forming method.

The method for forming a cast film of the present invention is a method of forming a cast film in which a cast film is formed on a moving support. The moving support moves in a manner of repeatedly passing through the reaching position of the flowing concentrated liquid and peeling off the peeling position of the casting film. The method for forming a cast film includes a dope flow down step (A step), a film drying step (B step), a film cooling step (C step), a peeling step (D step), a support heating step (E step), and a film. Heating step (F step) and holding step (G step). In the step A, the dope is allowed to flow down the surface of the moving support. The dope contains a polymer and a solvent. In the step B, the solvent is evaporated from the aforementioned casting film formed on the surface of the moving support. The cast film is composed of the aforementioned dope. In the step C, the cast film is cooled to a state in which it can be independently transferred. The aforementioned cooling is performed after the aforementioned step B. In the step D, the cast film after the step C is peeled off from the moving support. In the E step, the aforementioned moving support after the aforementioned step D is heated before the next step B described above. In the step F, the casting film before the next step B is heated by the heat applied to the moving support in the above-described step E. In the G step, the moving support is held by the both end support members and the inner support member. The foregoing is carried out in the aforementioned A step. The both end support members of the surface support the surface of the moving support body on both outer sides in the width direction than the arrival position. The inner support member supports one end to the other end of the inner side of the moving support body.

It is preferable that the both end support members of the surface are nip rolls and the inner support members are support rolls.

The method for forming a cast film of the present invention is a method of forming a cast film in which a cast film is formed on a moving support. The moving support moves in a manner of repeatedly passing through the reaching position of the flowing concentrated liquid and peeling off the peeling position of the casting film. The method for forming a cast film includes a dope flow down step (H step), a film drying step (I step), a film cooling step (J step), a peeling step (K step), a support heating step (L step), and a film. Heating step (M step). In the H step, the dope is allowed to flow down to the moving support. The dope contains a polymer and a solvent. In the first step, the solvent is evaporated from the aforementioned casting film formed on the surface of the moving support. The cast film is composed of the aforementioned dope. In the J step, the cast film is cooled to a state in which it can be independently transferred. The aforementioned cooling is carried out after the aforementioned I step. In the K step, the cast film after the above J step is peeled off from the moving support. In the L step, the central portion in the width direction of the moving support body after the aforementioned K step is heated before the next step I. In the M step, the cast film before the next film drying step is heated by the heat applied to the moving support in the L step.

The solution film forming method of the present invention is a film forming method of producing a film by forming a cast film on a moving support and drying it. The moving support moves in a manner of repeatedly passing through the reaching position of the flowing concentrated liquid and peeling off the peeling position of the casting film. The solution film forming method includes a dope flow down step (A step), a film drying step (B step), a film cooling step (C step), a peeling step (D step), a support heating step (E step), and a film heating step. (F step), a holding step (G step), and a film drying step (N step). In the step A, the dope is allowed to flow down the surface of the moving support. The dope contains a polymer and a solvent. In the step B, the solvent is evaporated from the aforementioned casting film formed on the surface of the moving support. The cast film is composed of the aforementioned dope. In the step C, the cast film is cooled to a state in which it can be independently transferred. The aforementioned cooling is performed after the aforementioned step B. In the step D, the cast film after the step C is peeled off from the moving support. In the E step, the aforementioned moving support after the aforementioned step D is heated before the next step B described above. In the step F, the casting film before the next step B is heated by the heat applied to the moving support in the above-described step E. In the G step, the moving support is held by the both end support members and the inner support member. The foregoing is carried out in the aforementioned A step. The both end support members of the surface support the surface of the moving support body on both outer sides in the width direction than the arrival position. The inner support member supports one end to the other end of the inner side of the moving support body. In the N step, the solvent is evaporated from the casting film peeled off from the moving support to obtain a film.

The solution film forming method of the present invention is a film forming method of producing a film by forming a cast film on a moving support and drying it. The moving support moves in a manner of repeatedly passing through the reaching position of the flowing concentrated liquid and peeling off the peeling position of the casting film. The solution film forming method includes a dope flow down step (H step), a film drying step (I step), a film cooling step (J step), a peeling step (K step), a support heating step (L step), and a film heating step. (M step) and film drying device (P step). In the H step, the dope is allowed to flow down to the moving support. The dope contains a polymer and a solvent. In the first step, the solvent is evaporated from the aforementioned casting film formed on the surface of the moving support. The cast film described above is composed of a concentrated liquid that has flowed down. In the J step, the cast film is cooled to a state in which it can be independently transferred. The aforementioned cooling is carried out after the aforementioned I step. In the K step, the cast film after the above J step is peeled off from the moving support. In the L step, the central portion in the width direction of the moving support body after the aforementioned K step is heated before the next step I. In the M step, the cast film before the next film drying step is heated by the heat imparted to the moving support in the above-mentioned L step. In the step P, the solvent is evaporated from the casting film peeled off from the moving support to obtain a film.

The casting film forming apparatus of the present invention includes a moving support, a reaching portion supporting unit, a peeling portion supporting unit, a film cooling unit, a support heating unit, a film heating unit, a surface end support member, and an inner support member. The moving support is sequentially circulated through the reaching portion, the casting portion, the film drying portion, and the peeling portion. The concentrated liquid reaches the flow down in the aforementioned reaching portion. The dope contains a polymer and a solvent. The casting portion forms a casting film from the concentrated liquid that has flowed down. The film drying section evaporates the solvent from the casting film. The peeling portion peels off the cast film. The arrival portion supporting unit supports the aforementioned moving support located at the aforementioned reaching portion. The peeling portion supporting unit supports the aforementioned moving support body located at the peeling portion. The film cooling unit cools the cast film to a state in which it can be independently transferred while the moving support is separated from the film drying unit and reaches the peeling portion. The support heating unit heats the aforementioned moving support before leaving the peeling portion and reaching the film drying portion. The film heating unit heats the aforementioned cast film before reaching the film drying portion by heat obtained by the support heating unit. The both end support members of the surface include both end portions of the surface supporting the moving support in the width direction of the arrival position of the moving liquid supported by the reaching portion supporting means. The inner support member includes one end to the other end supporting the inner side of the moving support body on the reaching portion supporting means.

It is preferable that the both end support members of the surface are nip rolls and the inner support members are support rolls.

The casting film forming apparatus of the present invention includes a moving support, a reaching portion supporting unit, a peeling portion supporting unit, a film cooling unit, a support heating unit, and a film heating unit. The moving support is sequentially circulated through the reaching portion, the casting portion, the film drying portion, and the peeling portion. The concentrated liquid reaches the flow down in the aforementioned reaching portion. The dope contains a polymer and a solvent. The aforementioned casting portion is condensed by the aforementioned thick The liquid forms a cast film. The film drying section evaporates the solvent from the casting film. The peeling portion peels off the cast film. The arrival portion supporting unit supports the aforementioned moving support located at the aforementioned reaching portion. The peeling portion supporting unit supports the aforementioned moving support body located at the peeling portion. The film cooling unit cools the cast film to a state in which it can be independently transferred while the moving support is separated from the film drying unit and reaches the peeling portion. The support heating unit heats the center portion in the width direction of the moving support during the period from the peeling portion to the film drying portion. The film heating unit uses the heat obtained by the support heating unit to heat the aforementioned cast film before reaching the film drying portion.

According to the present invention, the dope flow down process, the film drying process, and the lift-off process are performed, and the time required from the film drying process to the peeling process can be shortened by the film cooling process performed between the film drying process and the peeling process. Further, since the support heating process for heating and moving the support is performed from the peeling process to the next film drying process, the film heating process of heating the cast film formed by the next dope flow down process from the back side can be performed. . The surface of the cast film can be smoothed by a film heating process. Thus, according to the present invention, it is possible to suppress thickness unevenness and efficiently produce a cast film or film.

Further, when the support heating process is performed immediately after the film cooling process, the moving support is warped by the heat history, but according to the present invention, the thickness unevenness of the cast film due to the warpage of the movable support can be suppressed.

(solution film making equipment)

As shown in FIG. 1, the solution film forming apparatus 10 has a casting unit 12, a drying unit 13, and a winding unit 14.

(casting unit)

The casting unit 12 produces a wet film 25 from the dope 24. The dope 24 contains a polymer 23 (referred to as a base polymer) 22 which is a raw material of the film 21 and a solvent 23 of the polymer 22. The details of the casting unit 12 will be described later.

(drying unit)

The drying unit 13 is a method in which the solvent 23 is evaporated from the wet film 25 and the film 21 is obtained from the wet film 25. The drying unit 13 includes a clip tenter 35, a slitter 36, a drying chamber 37, and a cooling chamber 38 that are sequentially disposed from the casting unit 12 toward the winding unit 14. In the transfer portion 40 between the casting unit 12 and the clip tenter 35, the belt-shaped wet film 25 sent from the casting unit 12 is conveyed to the clip tenter 35 by a plurality of rollers 41.

The clip tenter 35 has a sleeve 35a, a pair of rails, a clip 35b, and a dry air supply 35c. A moving path of the wetting film 25 is provided in the sleeve 35a. The guide rails accommodated in the sleeve 35a are provided on both sides of the moving path of the wet film 25. The plurality of clips 35b arranged along the guide rail are freely movable between the gripping state of the both side portions in the width direction of the holding wet film 25 and the releasing state of the gripping portions on both side portions in the releasing width direction, and are movably mounted along the guide rail. The plurality of clips 35b are connected in a ring shape by a chain (not shown). When the clip 35b passes the grip start position on the guide rail, the clip 35b is changed (changed) from the released state to the gripped state. Thus, the clip 35b holds the both side edges of the wet film 25 in the width direction. Further, when the clip 35b passes the grip release position on the guide rail, the clip 35b is changed (changed) from the grip state to the released state. In this way, the clip 35b releases the grip on both side edges in the width direction of the wet film 25.

The interval of the pair of guide rails increases as moving from the grip start position toward the grip release position. Here, 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 during the period from the grip start position to the grip release position. It is preferable that Wf2/Wf1 is 1.05 or more and 1.5 or less. The dry air supply device 35c that blows the dry air to the wet film 25 is provided above and below the movement path of the wet film 25.

The slitter 36 cuts the edge of the wet film 25. The cut side portion is sent to a crusher (not shown) by air supply, and is cut finely and reused as a raw material such as a dope.

A plurality of rollers 45 are disposed in the drying chamber 37. The wet film 25 is wound around the roller 45 while being conveyed. The adsorption recovery unit 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 recovering the solvent 23 in the drying chamber 37, the condensation point of the solvent 23 in the drying chamber 37 is adjusted within a constant range, and therefore, during the transfer in the drying chamber 37, the solvent 23 is evaporated from the wet film 25. As a result, the film 21 is obtained from the wet film 25. The film 21 is cooled in the cooling chamber 38 until the temperature becomes approximately room temperature.

(rolling unit)

The winding unit 14 includes a winding chamber 54 having a winding core 51, a winding drive unit (not shown), and a pressure roller 52. The core driving unit rotates the winding core 51 at a predetermined speed by a control unit (not shown). As a result, the film 21 is wound up on the winding core 51 at a predetermined take-up tension to form the film roll 55. The pressure roller 52 presses the film 21 wound around the winding core 51 toward the winding core 51 or the film roll 55 wound on the winding core 51. Thereby, it is possible to wind the film 21 while preventing air from entering between the films 21.

It is preferable that a knurling providing device 57 in which knurling is formed on both sides in the width direction of the film 21 is provided between the winding chamber 54 and the cooling chamber 38.

(Details of the casting unit)

As shown in FIG. 2, the casting unit 12 which forms the wet film 25 from the dope 24 is provided with the casting sleeve 75. The casting sleeve 75 is provided with a casting die 60, an endless belt 62, a surface layer forming device 63, a film drying device 64, a peeling roller 65, a belt moving mechanism 66, and first to fourth sealing members 71 to 74. The casting die 60 flows out of the dope 24. The endless belt 62 is a moving support that supports the concentrated liquid 24 that flows out and forms a casting film 61 composed of the dope 24. The surface layer forming device 63 forms a surface layer on the surface 61a of the casting film 61. The film drying device 64 evaporates the solvent 23 (refer to FIG. 1) from the casting film 61. The peeling roller 65 peels the casting film 61 from the endless belt 62. The belt moving mechanism 66 cyclically moves the endless belt 62 in a predetermined direction.

(annular belt moving mechanism)

The belt moving mechanism 66 is for guiding the endless belt 62 while guiding it in a predetermined direction. The belt moving mechanism 66 is provided with motors 66m for the respective rollers 66a to 66c and the driving roller 66c.

The rollers 66a to 66c are disposed in parallel with 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 disposed above the plane. An annular endless belt 62 which is formed by joining both ends of the sheet is wound around the rollers 66a to 66c. The belt inner 62b of the endless belt 62 is supported by rollers 66a to 66c. When the roller 66c is rotated by the driving of the motor 66m, the endless belt 62 circulates the moving rollers 66a to 66c by the rollers 66a, the rollers 66b, the rollers 66c, and the rollers 66a. Thus, the movement path 66r of the endless belt 62 is formed by the rollers 66a to 66c.

Each of the rollers 66x to 66z is a belt inner side 62b for supporting the endless belt 62, and they are disposed along the movement path 66r of the endless belt 62. The roller 66x is disposed between the roller 66c and the roller 66a. The roller 66y is disposed between the roller 66a and the roller 66b, and the roller 66z is disposed between the roller 66b and the roller 66c.

The endless belt 62 obtained by joining the both ends of the sheet is preferably made of stainless steel, and the SUS316 having sufficient corrosion resistance and strength is more preferable. The width of the endless belt 62 is preferably 1.1 times or more and 2.0 times or less of the casting width CW (refer to FIG. 6) of the dope 24, for example. The length of the endless belt 62 is preferably 20 m or more and 200 m or less, and the thickness of the endless belt 62 is preferably 0.5 mm or more and 2.5 mm or less. Further, it is preferable to use the endless belt 62 having a thickness unevenness of 0.5% or less with respect to the entire thickness. The belt surface 62a is preferably polished, and the surface roughness of the belt surface 62a is preferably 0.05 μm or less.

(sealing member)

The first to fourth sealing members 71 to 74 are provided in the movement path 66r of the endless belt 62. The first sealing member 71 is disposed so as to face the roller 66x so as to pass through the movement path 66r of the endless belt 62. The second sealing member 72 is disposed so as to face the roller 66y so as to pass through the movement path 66r of the endless belt 62. The third to fourth sealing members 73 to 74 are arranged in this order from the upstream side toward the downstream side in the moving direction (hereinafter referred to as the X direction) of the endless belt 62 so that the moving path 66r that passes through the endless belt 62 faces the roller 66c. .

The first sealing member 71 includes a windshield 71a attached to the casting chamber 75a and a labyrinth seal 71b attached to the windshield 71a. The windshield 71a has a wind shielding surface that blocks the flow of the gas in the casting sleeve 75. The windshield 71a protrudes from the inner wall surface of the casting sleeve 75 and extends toward the belt surface 62a of the endless belt 62. A labyrinth seal 71b is provided at the front end of the windshield 71a so as to be close to the belt surface 62a. The second to fourth sealing members 72 to 74 have the same configuration as the first sealing member 71.

The casting sleeve 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 by the respective rolls and the respective sealing members. The casting chamber 75a is formed by the first sealing member 71, the second sealing member 72, the roller 66x, and the roller 66y. Similarly, the film drying chamber 75b is formed of the second sealing member 72, the third sealing member 73, the roller 66y, and the roller 66c, and the separation chamber 75c is formed by the third sealing member 73, the fourth sealing member 74, and the roller 66c, and the support heating chamber 75d is formed by the first sealing member 71, the fourth sealing member 74, the roller 66c, and the roller 66x.

(casting room)

A casting die 60 is disposed in the casting chamber 75a. The casting die 60 is disposed so as to face the roller 66a so as to pass through the moving path 66r of the endless belt 62. An arrival portion is formed between the casting die 60 and the roller 66a. The casting die 60 has a slit outlet that flows out of the dope 24 toward the front end. The casting die 60 is disposed such that the slit outlet is adjacent to the portion of the endless belt 62 supported by the roller 66a. The dope 24 flowing out of the casting die 60 is cast on the belt surface 62a, and as a result, a strip-shaped cast film 61 is formed.

It is preferable to provide a decompression chamber 77 in the casting chamber 75a. The decompression chamber 77 is located on the upstream side in the X direction from the casting die 60, and is disposed adjacent to the casting die 60. Under the control of a control unit (not shown), the decompression chamber 77 depressurizes the upstream side of the liquid droplet in the X direction so that the pressure on the upstream side in the X direction of the liquid bead becomes lower than the downstream side in the X direction of the liquid bead. Here, the liquid bead is formed by the dope 24 which flows out from the casting die 60 and reaches the endless belt 62.

(film drying chamber)

In the film drying chamber 75b, a surface layer forming device 63 and a film drying device 64 are provided in this order from the upstream side toward the downstream side in the X direction along the moving path 66r, and the surface layer forming device supplies the surface layer forming wind 80 to the casting film 61, and the film drying device makes the solvent Evaporation from the casting film 61.

(surface layer forming device)

It is preferable that the surface layer forming device 63 is disposed on the most upstream side in the X direction of the film drying chamber 75b. As shown in FIGS. 3 and 4, the surface layer forming device 63 disposed close to the film surface 61a has an intake duct 81, a cover 82, a pre-intake nozzle 83, and a register 84. The intake duct 81 and the outer cover 82 are disposed in this order from the upstream side in the X direction toward the downstream side.

The intake duct 81 is formed to flow through the surface layer forming wind 80, and is disposed closer to the second sealing member 72 in the X direction and away from the film surface 61a. A pre-intake nozzle 83 is provided on the surface 81a of the intake duct 81 on the membrane surface 61a side. The pre-intake nozzle 83 follows the approaching membrane surface 61a from the upstream side in the X direction to the downstream side in the X direction. A pre-intake port 83a opening toward the belt surface 62a is provided at the front end of the pre-intake nozzle 83. As shown in FIG. 5, the pre-intake port 83a extends from one end of the endless belt 62 to the other end of the endless belt 62 in the width direction of the moving path 66r (hereinafter referred to as the Y direction). Further, it is preferable that the pre-intake port 83a and the surface 81a are on the same plane.

As shown in FIG. 3 and FIG. 4, the outer cover 82 guides the surface layer forming wind 80 sent from the pre-intake port 83a toward the downstream side in the X direction, and covers the casting film 61 in a state away from the casting film 61. The outer cover 82 is formed in a plate shape and extends from the intake duct 81 in the X direction to the vicinity of the film drying device 64 (for example, a film drying device described later), and extends from one end of the endless belt 62 to the endless belt in the Y direction. The other end of 62. The outer cover 82 has a guide surface 82a substantially parallel to the film surface 61a on the film surface 61a side. Further, it is preferable that the guide surface 82a and the surface 81a are on the same level.

An air passage 86 that forms the wind 80 formed from the surface of the pre-intake port 83a is formed between the guide surface 82a and the surface 81a and the belt surface 62a from the pre-intake port 83a to the downstream end portion of the outer cover 82 in the X direction. The interval from the surface 81a to the belt surface 62a is preferably 20 mm or more and 150 mm or less. The width of the air passage 86 in the Y direction may be, for example, 0.8 times or more and 1 or less times the width of the endless belt 62 in the Y direction. The length of the air passage 86 in the X direction may be determined according to the manufacturing conditions (the moving speed V of the surface 62a of the endless belt 62, etc.), and is preferably, for example, 1000 mm or more and 5000 mm or less.

The register 84 has a temperature controller (not shown) that adjusts the temperature of the surface layer forming wind 80 within a predetermined range, and a blower fan (not shown) that sends the surface layer forming wind 80 to the intake duct 81 at a predetermined air volume.

A side windshield 85 may be provided on the surface layer forming device 63. The side air louvers 85 are arranged in the Y direction and extend from the upstream end in the X direction of the intake duct 81 to the downstream end in the X direction of the outer cover 82. The side air dam 85 extends from the surface 81a and the guide surface 82a toward the belt surface 62a. As shown in Fig. 5, the surface 85a on the inner side in the Y direction of the side air deflector 85 and the inner surface 83b of the pre-intake nozzle 83 are preferably on the same plane.

(film drying device)

As shown in FIG. 2, the film drying device 64 is provided with a front film dryer 88 and a film drying machine 89 in this order from the upstream side toward the downstream side in the X direction.

(front film dryer)

The front film dryer 88 is disposed along the moving path 66r of the endless belt 62 from the portion of the roller 66y toward the roller 66b. The front film dryer 88 has a surface side air blower 91 disposed on the belt surface 62a side and delivering the front dry air 90, an inner side air blower 92 disposed on the belt inner side 62b side and delivering the front dry air 90, and a front dry air conditioner Device 93 (not shown).

(surface side air blower)

The front side air blower 91 is provided with an intake duct (not shown) and an exhaust duct (not shown). The intake port of the intake duct and the exhaust port of the exhaust duct face the front surface of the belt surface 62a. Further, the intake port of the intake duct and the exhaust port of the exhaust duct are extended from one end of the casting film 61 to the other end. Further, it is preferable that the intake port of the intake duct and the exhaust port of the exhaust duct are alternately arranged in the X direction.

(inside side air blower)

The inner side blower 92 is provided with an intake duct (not shown) and an exhaust duct (not shown) similarly to the front side blower 91. The intake port of the intake duct and the exhaust port of the exhaust duct are opposed to the front side of the belt inner 62b. Further, the intake port of the intake duct and the exhaust port of the exhaust duct are extended from one end of the casting film 61 to the other end. It is preferable that the intake port of the intake duct and the exhaust port of the exhaust duct are alternately arranged in the X direction.

The front dry air conditioner has a temperature controller (not shown) that adjusts the temperature of the front drying air 90 within a predetermined range, and a delivery fan (not shown) that sends the front drying air 90 to the intake duct at a predetermined air volume.

The front side air blower 91 sends the front dry air 90 from the air inlet toward the film surface 61a and sucks the front dry air 90 from the exhaust port. Similarly, the inner side blower 92 sends the front dry air 90 from the air inlet toward the belt inner 62b and sucks the front dry air 90 from the exhaust port.

Further, the front side air blower 91 can blow the front dry air 90 in the vertical direction to the film surface 61a. Similarly, the inner side blower 92 can blow the front dry wind 90 in the vertical direction to the belt inner side 62b.

(post film dryer)

The post film dryer 89 is disposed along the moving path 66r of the endless belt 62 from the portion of the roller 66b toward the roller 66c. The post-film dryer 89 has a parallel blower 95 disposed on the belt surface 62a side and delivering the post-drying air 94, a rear side air blower 96 disposed on the belt inner side 62b side, and a rear dry air conditioner (not shown). The parallel blowers 95 are disposed in order from the upstream side toward the downstream side in the X direction, and have parallel exhaust ducts 95a and parallel intake ducts 95b.

The parallel exhaust duct 95a and the parallel intake duct 95b are disposed on the belt surface 62a side, respectively. The exhaust port of the air 94 is dried after the exhaust gas is disposed in the parallel exhaust duct 95a. The exhaust port opening toward the downstream side in the X direction extends from one end of the endless belt 62 to the other end in the Y direction. The intake port of the dry air 94 after the delivery is set in the parallel intake duct 95b. An intake port that opens toward the upstream side in the X direction extends from one end of the casting film 61 to the other end.

The inner side blower 96 sends out the post-drying air 94, and has the same structure as the inner side blower 92. The post-drying air conditioner (not shown) has a temperature controller (not shown) that adjusts the temperature of the post-drying air 94 within a predetermined range, and sends the post-drying air 94 to the inside side air blower 96 at a predetermined air volume. A fan (not shown) for the air duct or parallel intake duct 95b.

(stripping 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, the outlet 75o of the casting sleeve 75 is opened in the peeling chamber 75c. The casting film 61 can be peeled off from the endless belt 62 by making the peripheral speed of the peeling roller 65 larger than the roller 66c. The casting film 61 peeled off from the endless belt 62 becomes the wet film 25, and is sent out from the outlet 75o to the drying unit 13 (refer to FIG. 1).

(support body heating chamber)

A support heating device 111 that sends the heated air 110 to the endless belt 62 is provided in the support heating chamber 75d. The support heating device 111 has a surface side heater 112 disposed on the belt surface 62a side, a back side heater 113 disposed on the belt inner side 62b side, and a heating air conditioner 114. Further, either one of the surface side heater 112 and the back side heater 113 may be omitted.

(surface side heater)

As shown in FIGS. 6 and 7, the front side heater 112 has an intake duct 112a and an exhaust duct (not shown). The intake port 112o of the intake duct 112a and the exhaust port of the exhaust duct face the front surface of the belt surface 62a. The intake port 112o and the exhaust port are respectively extended from one end of the endless belt 62 to the other end. That is, in the Y direction, the width of the intake port 112o and the exhaust port is wider than the casting width CW. Further, it is preferable that the intake port 112o and the exhaust port are alternately arranged in the X direction.

(inside heater)

The inside side heater 113 has an intake duct 113a and an exhaust duct (not shown). The intake port 113o of the intake duct 113a and the exhaust port 113i of the exhaust duct face the front side of the belt inner 62b. The intake port 113o and the exhaust port 113i are respectively extended from one end of the endless belt 62 to the other end. That is, in the Y direction, the widths of the intake port 113o and the exhaust port 113i are wider than the casting width CW. Further, it is preferable that the intake port 113o and the exhaust port 113i are alternately arranged in the X direction.

The heating air conditioner 114 has a temperature controller (not shown) that adjusts the temperature of the heating air 110 within a predetermined range, and an intake air that sends the heating air 110 to the surface side heater 112 and the inside side heater 113 with a predetermined air volume. A fan (not shown) for the ducts 112a and 113a.

The surface side heater 112 sends the heating air 110 from the air inlet 112o toward the belt surface 62a and sucks the heating air 110 from the exhaust port. The inside side heater 113 sends the heating air 110 from the intake port 113o toward the belt inner side 62b and sucks the heating air 110 from the exhaust port 113i.

Returning to Fig. 2, a roller thermostat 121 that adjusts the temperature of the roller 66a is attached to the roller 66a. A roller thermostat 122 that adjusts the temperature of the roller 66b is attached to the roller 66b. Thereby, the roller 66b evaporates the solvent from the casting film 61 by the heating of the casting film 61. At this time, the roller 66b can be included in the film drying device 64. A roller thermostat 123 of the cooling roller 66c is connected to the roller 66c. The roller 66c is cooled by the roller thermostat 123, and the roller 66c functions as a film cooling means for cooling the casting film 61 through the endless belt 62.

Further, although not shown, a solvent which is a gas can be formed in the casting sleeve 75 by providing a condensing device for condensing the solvent contained in the atmosphere in the casting sleeve 75 and a recovery device for recovering the condensed solvent. The liquefaction temperature (condensation point) is kept within a predetermined range.

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

(Summary of the casting film forming process)

The cast film forming process 126 for obtaining the wet film 25 from the dope 24 is performed by the casting unit 12 shown in FIG. The details of the cast film forming process 126 will be described later.

(wet film drying process)

The wet film drying process 127 for evaporating the solvent from the wet film 25 to form the film 21 is carried out by the drying unit 13 shown in Fig. 1.

The wetting film 25 introduced into the clip tenter 35 is conveyed by the clip 35b in a state in which both end portions in the width direction are gripped. The dry air supply device 35c blows a predetermined dry air to the surface and the inside of the wet film 25 between the grip start position and the grip release position. In this way, the solvent can be evaporated from the wet film 25. Further, since the interval of the guide rail is increased from the grip start position toward the grip release position, the wet film 25 can be stretched by the conveyance by the clip 35b. The in-plane retardation Re or the thickness direction retardation Rth can be adjusted by the stretching process.

The wetting film 25 introduced into the drying chamber 37 is wound around a plurality of rolls 45 while being conveyed. The solvent evaporates from the wetting film 25 conveyed within the sleeve 106a by adjusting the temperature or humidity of the atmosphere within the sleeve 106a. Thus, the wet film 25 becomes the film 21.

(Details of the cast film forming process)

As shown in FIG. 8, the cast film forming process 126 sequentially performs a dope flow down process 131, a casting process 132, a film heating process 133, a surface layer forming process 134, a film drying process 135, a film cooling process 136, a stripping process 137, and The support heating process 138.

As shown in Fig. 2, when the roller 66c is rotated by the driving of the motor 66m, the endless belt 62 is sequentially circulated in the respective chambers 75a to 75d in the casting sleeve 75. The temperatures of the rollers 66a to 66c are adjusted within a predetermined range by the roller thermostats 121 to 123. In the storage 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 storage 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 the thermostat provided in the casting die 60.

(casting room)

In the casting chamber 75a, the dope 24 flowing out from the casting die 60 is passed to the dope flowing down process 131 on the belt surface 62a (refer to Fig. 8), and the casting film 61 composed of the dope 24 is formed on the belt surface 62a. The casting process 132 (refer to FIG. 8) and the film heating process 133 of heating the casting film 61 (refer to FIG. 8).

(dope flow down process)

The casting die 60 continuously flows out of the dope 24 from the slit outlet toward the tape surface 62a. The concentrated liquid 24 flowing out of the slit outlet reaches the portion of the endless belt 62 supported by the roller 66a, that is, the reaching position DP on the belt surface 62a.

(casting process)

Since the endless belt 62 is in a moving state, the dope 24 reaching the reaching position DP is cast in the moving direction on the belt surface 62a. Thus, the casting film 61 composed of the dope 24 and having a casting width CW (refer to FIG. 6) is formed in a strip shape on the belt surface 62a.

The moving speed V of the endless belt 62 is preferably 200 m/min or less. If the moving speed V exceeds 200 m/min, it is difficult to form a liquid bead stably. The lower limit of the moving speed V may be considered in consideration of the productivity of the target film. The moving speed V can be, for example, 20 m/min or more, and can be 60 m/min or more.

The solvent content in the dope 24 flowing out of the casting die 60 is preferably 300% by mass or more and 450% by mass or less. This is because when the solvent content 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. When the solvent content in the dope 24 flowing out of the casting die 60 exceeds 450% by mass, the drying load in the film drying chamber 75b becomes large, and as a result, the production efficiency is lowered, which is not preferable.

Here, the solvent content is a dry amount reference indicating the amount of the solvent contained in the dope, the cast film, or each film, and the sample is taken from the target film, and the mass of the sample is set to x, and the mass after the dried sample is set to When y, it is expressed as {(xy)/y}×100.

The temperature of the dope 24 flowing out of the casting die 60 is preferably 20 ° C or more and the boiling point of the solvent or less. This is because when the temperature of the concentrated liquid 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 of the casting die 60 exceeds the boiling point of the solvent, foaming of the dope 24 occurs, which is not preferable. Further, it represents the lowest boiling point among the boiling points of a plurality of compounds.

(film heating process)

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

Here, the casting film after the formation, that is, the film surface 61a of the casting film 61 after the casting process 132 is not smooth (refer to FIG. 9). Therefore, thickness unevenness occurs on the casting film 61 after the casting process 132. It is considered that the thickness unevenness is caused by the vibration of the liquid bead. Further, the dope 24 of the casting film 61 which constitutes the casting process 132 contains a large amount of solvent and is easy to exhibit fluidity. Therefore, in the present invention, the film heating process 133 of the casting film 61 after the heating casting process 132 is performed by the heated endless belt 62. By the casting of the casting film 61 after the casting process 132, the fluidity of the dope 24 constituting the casting film 61 after the formation becomes large, and as a result, the film surface 61a of the casting film 61 after the formation becomes smooth (refer to the drawing) 10).

The length of the casting region 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 after formation to be smooth is ensured. The film heating process 133 is preferably performed on the casting film 61 having a solvent content of 300% by mass or more and 450% by mass or less.

The temperature of the roller 66a is within the range of the temperature of the belt surface 62a at the peeling position PP to be equal to or lower than the boiling point of the solvent by the roller thermostat 121.

(film drying chamber)

In the film drying chamber 75b, a surface forming process 134 (refer to FIG. 8) for blowing the surface layer forming wind 80 to the film surface 61a and a film drying process 135 (refer to FIG. 8) for evaporating the solvent from the casting film 61 are performed until casting A surface layer 61x is formed on the film surface 61a side of the film 61 (refer to FIG. 11).

(Surface formation process)

As shown in FIG. 4, the surface layer forming device 63 sends the surface layer forming wind 80 from the intake port 83a of the intake nozzle 83. The angle θ1 formed by the surface layer forming wind 80 from the air inlet 83a (the extending direction of the pre-injection nozzle 83) and the X direction is preferably 30° or more and 60° or less, and more preferably 45°. The surface layer forming wind 80 sent from the intake port 83a is guided from the upstream side in the X direction to the downstream side by the outer cover 82. The swirling flow of the surface layer forming wind 80 is easily generated in the vicinity of the film surface 61a of the casting film 61 by the cover 82 close to the casting film 61. In the portion where the spiral flow is generated, since the thermal energy of the surface layer forming wind 80 is easily transmitted to the casting film 61, the film surface 61a of the casting film 61 promotes evaporation of the solvent due to the spiral flow of the surface layer forming wind 80.

By the surface layer forming process 134, the casting film 61 becomes the surface layer 61x and the wetting layer 61y (refer FIG. 11). The surface layer 61x is formed on the film surface 61a side of the casting film 61, and is a portion which is further dried than the wet layer 61y located on the side of the endless belt 62 than the surface layer 61x. Therefore, the solvent content of the surface layer 61x is lower than that of the wet layer 61y.

Also, the surface of the surface layer 61x is smoothly formed. When the film drying process 135 is performed on the casting film 61 having the surface layer 61x, the surface of the surface layer 61x becomes the film surface 61a of the obtained casting film 61. Therefore, the cast film 61 having a smooth film surface 61a can be obtained by performing the surface layer forming process 134 on the casting film 61 which has passed through the film heating process 133.

The surface layer forming process 134 is preferably performed on the casting film 61 having a solvent content of 250% by mass or more and 400% by mass or less. The temperature of the surface layer forming wind 80 is preferably, for example, 30 ° C or more and 80 ° C or less. Further, it is preferable that the wind speed of the surface layer forming wind 80 is 5 m/sec or more and 25 m/sec or less.

(film drying process)

The film drying process 135a and the film drying process 135b are sequentially performed in the film drying process 135.

(front film drying process)

The front film dryer 88 performs a film drying process 135a before evaporating the solvent from the casting film 61. The front side air blower 91 blows the front dry air 90 to the film surface 61a to evaporate the solvent from the casting film 61. Further, the inner side air blower 92 blows the front dry air 90 to the belt inner side 62b, and heats the casting film 61 through the endless belt 62. The solvent is evaporated from the casting film 61 by the heating of the casting film 61.

(post film drying process)

The post film dryer 89 performs a film drying process 135b after evaporating the solvent from the casting film 61. The parallel blower 95 blows the dry air 94 to the film surface 61a of the casting film 61 to evaporate the solvent from the casting film 61. Further, the inner side blower 96 blows the dry air 94 to the belt inner side 62b, and heats the casting film 61 through the endless belt 62. The solvent is evaporated from the casting film 61 by the heating of the casting film 61. The post-film drying process 135b is preferably carried out until the solvent content of the casting film 61 is 110% by mass or more and 210% by mass or less.

The post film drying process 135b can be performed using the heat of the roller 66b. The roller thermostat 122 is preferably adjusted so that the temperature of the roller 66b is in the range of 20 ° C or more and 40 ° C or less.

The casting film 61 having a smooth film surface 61a can be obtained by performing each of the processes 131 to 135 (refer to FIG. 8) (refer to FIG. 12).

(stripping chamber)

A film cooling process 136 for cooling the endless belt 62 and a peeling process 137 for peeling the casting film 61 from the endless belt 62 are performed in the peeling chamber 75c.

(film cooling process)

The temperature of the roller 66c is in the range of 0 ° C or more and 17 ° C or less by the roller thermostat 123. Further, the temperature of the roller 66c is preferably in the range of 0 ° C to 15 ° C. The endless belt 62 which has been brought to a high temperature by the film drying process 135 is cooled by contact with the roller 66c. Then, the cast film 61 is cooled by the cooled endless belt 62. The film cooling process 136 proceeds to a state in which it can be independently transferred.

(peeling process)

In the peeling chamber 75c, a peeling process 137 (refer to FIG. 8) in which the casting film 61 which has been peeled off from the endless belt 62 is peeled off by the peeling roll 65 is used. The portion (the peeling position PP) supported by the roller 66c in the endless belt 62 is peeled off from the endless belt 62 into the peelable film 61. The casting film 61 peeled off from the endless belt 62 is sent as a wet film 25 from the outlet 75o. In order to suppress the variation in the orientation angle, it is preferable to carry out the peeling process 137 for the casting film 61 having a solvent content of 200% by mass or less. From the viewpoint of production efficiency, it is preferable to carry out the peeling process 137 for the casting film 61 having a solvent content of 100% by mass or more.

(support body heating process)

The endless belt 62 after peeling off the casting film 61 is returned to the casting chamber 75a via the support heating chamber 75d. When the concentrated liquid flow down process 131, the casting process 132, and the surface layer forming process 134 are continuously performed on the endless belt 62 which is cooled by the film cooling process 136, the film surface 61a is directly dried (refer to FIG. 9). . As a result, thickness unevenness occurs in the casting film 61. Since the thickness unevenness generated on the casting film 61 cannot be removed in the subsequent process, the thickness of the film 21 is eventually uneven.

Therefore, in the present invention, in order to perform the film heating process 133 between the (n+1)th casting process 132 and the (n+1)th surface formation process 134, the nth peeling process 137 and the (n) A support heating process 138 for heating the endless belt 62 is performed between the +1) times of the concentrated liquid flow down process 131.

In the support heating chamber 75d, the support heating process 138 for heating the endless belt 62 is performed by the support heating means 111. As shown in Fig. 6, the surface side heater 112 blows the heating air 110 to the belt surface 62a, and heats the endless belt 62 until the temperature of the belt surface 62a becomes a predetermined range. Similarly, the inner side heater 113 blows the heating air 110 to the belt inner side 62b, and heats the endless belt 62 until the temperature of the belt inner side 62b becomes a predetermined range.

The heating belt surface 62a in the support heating process 138 is preferably such that the temperature of the belt surface 62a in the casting region CZ becomes the range T1. Here, the range T1 is 8 ° C or more and the boiling point of the solvent is not more preferable, and the lower limit 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). Further, it is preferable that the temperature of the assembly (rollers 66a, 66x, etc.) functioning as the support heating means is in the range of T1.

In the present invention, by applying heat to the endless belt 62 in the support heating process 138, a film heating process 133 is applied to the casting film 61 formed on the endless belt 62 by the next casting process 132. . Therefore, according to the present invention, it is possible to suppress thickness unevenness and to efficiently produce a film.

Further, the film heating process 133 may be performed from the peeling position PP to the reaching position DP.

Next, other embodiments of the present invention will be described. The same components and members as those of the above-described embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted, and portions different from the above-described embodiments will be described in detail.

The support heating device 111 that blows the heating air 110 to at least one of the belt surface 62a and the belt inner surface 62b is used as the support heating means. However, the present invention is not limited thereto, and at least one of the belt surface 62a and the belt inner surface 62b may be used. The support heating device 141 of the heating roller that is in contact. As shown in Fig. 13, the support heating means 141 is provided with a surface heating roller 142 which is in contact with the belt surface 62a, an inner heating roller 143 which is in contact with the inner surface 62b, and a roller temperature adjustment of the temperature of the surface heating roller 142 and the inner heating roller 143. 144. The support heating device 141 heats the belt surface 62a so that the temperature at the time of passing through the casting region CZ (refer to FIG. 2) becomes the range T1 by the roller temperature adjuster 144.

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

In the above embodiment, the roller 66c cooled by the roller thermostat 123 is used as the film cooling means, but the present invention is not limited thereto. As shown in Fig. 14, the cooling unit 148 that cools the endless belt 62 before reaching the peeling position PP can also be used as a film cooling means. The cooling unit 148 disposed between the post-film dryer 89 and the cooling roll 66c in the film drying chamber 75b has a liquid supply means 149 for supplying liquid to the inner side 62b and a dry air 150 for ejecting the evaporating liquid by the inner side 62b. Device 151. The liquid supply method based on the liquid supply device 149 may be any one of a method of coating, spraying, and spraying a droplet. The liquid supply device 149 and the evaporation device 151 are disposed in this order along the movement path 66r of the endless belt 62 from the upstream side in the X direction toward the downstream side on the side of the belt inner side 62b. The liquid supply device 149 supplies the liquid to the belt inner 62b. If the evaporation device 151 blows the dry air 150 to the belt inner portion 62b, the liquid in the belt inner portion 62b evaporates. If the liquid in the inner portion 62b evaporates, the temperature of the inner portion 62b is lowered by the heat of vaporization of the liquid. Thus, the endless belt 62 can be cooled by the cooling unit 148.

The liquid may be evaporated before the endless belt 62 reaches the peeling position PP, and for example, dichloromethane or the like can be used.

At least one of the rollers 66c and 66z and the cooling unit 148 may be used as the film cooling means, and two of the rollers 66c and 66z and the cooling unit 148 may be combined, or three of them may be used.

In order to maintain the belt surface 62a horizontally in the casting zone CZ, it is preferred to arrange the roller 66a and the roller 66x in the same horizontal plane. Further, as shown in Fig. 15, a support roller 66d disposed on the same horizontal surface as the roller 66a and supporting the belt inner surface 62b may be provided between the roller 66a and the roller 66y.

Further, as shown in Fig. 16, a support roller 66e disposed on the same horizontal surface as the roller 66a and supporting the belt inner 62b may be provided between the roller 66a and the roller 66x. The temperature of the backup roller 66e can be adjusted by the roller thermostat 121 to be in the range T1. Thereby, the backup roll 66e functions as a support heating means.

Further, the temperature of the roller 66a can be adjusted to a range T1 by the roller thermostat 121. 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 thereto. For example, as shown in Fig. 17, the roller 66a and the roller 66b may be disposed on the same plane (e.g., a horizontal plane), and the roller 66c disposed between the roller 66a and the roller 66b may be disposed below the plane. Further, the roller 66Z may be disposed between the roller 66a and the roller 66b.

Further, the roller 66c shown in Fig. 2 has a function of supporting the endless belt 62 on the peeling position PP and a sealing function based on the third to fourth sealing members 73 to 74, but these functions can be separated. For example, the rollers 66c, 66f, and 66g of Fig. 17 correspond to the roller 66c shown in Fig. 2 . Further, the roller 66c of Fig. 17 has a function of supporting the endless belt 62 on the peeling position PP. The backup roller 66f of Fig. 17 and the third sealing member 73 cooperate to function as a seal. The backup roller 66g of Fig. 17 cooperates with the fourth sealing member 74 to function as a sealing. The roller thermostat 123 cools the roller 66c. The roller thermostat 123 can cool the roller 66f.

Further, the roller 66g can be heated by the roller thermostat 123. Thereby, the roller 66g functions as a support heating means.

Further, the roller 66a shown in Fig. 17 corresponds to the rollers 66a, 66x, and 66y shown in Fig. 2 being integrated.

Further, as shown in Fig. 18, the roller 66a and the roller 66c may be disposed on the same plane (e.g., a horizontal plane), and a roller 66b may be disposed between the roller 66a and the roller 66c. The roller 66b of the support belt inner portion 62b is disposed such that the endless belt 62 that moves from the roller 66a toward the roller 66c is substantially horizontal. Further, the roller 66b may be disposed above the roller 66a and the roller 66c. The roller 66a shown in Fig. 18 corresponds to the rollers 66a, 66x, and 66y shown in Fig. 2 being integrated.

In the above embodiment, in the support heating process 138, the endless belt 62 is heated in the entire Y direction, but only the casting zone CA of the casting width CW in the endless belt 62 may be heated (refer to FIG. 6). Part of (see Figure 19). Thereby, the non-casting zone other than the casting zone CA (refer to FIG. 6) in the endless belt 62 is not heated more than necessary, and therefore, in the film drying process 135, the casting film 61 can be reliably suppressed in the Y direction. Foaming on both sides. In addition, the central portion in the Y direction in the casting zone CA may be a heating portion, and both end portions in the Y direction in the casting zone CA may be non-heated portions. At this time, the width of the non-heated portion in the Y direction is, for example, 10 mm.

In addition, a support surface cleaning process of the cleaning tape surface 62a may be performed between the peeling process 137 and the support heating process 138. The peeling failure can be reliably suppressed by the support surface cleaning process. Further, the foreign matter remaining on the belt surface 62a can be removed by the surface cleaning process of the support (for example, a part of the cast film which is peeled off). This foreign matter becomes the cause of the vibration of the bead. Therefore, the vibration of the liquid droplet can be prevented by the surface cleaning process of the support. In order to clean the belt surface 62a, for example, a dry ice washing machine which sprays dry ice on the belt surface 62a is preferably used.

Further, a contact angle lowering process for reducing the contact angle of the belt surface 62a with respect to the dope 24 may be performed between the support heating process 138 and the next dope down process 131. By the contact angle lowering process, it is difficult for the carrying wind to flow between the liquid bead and the belt surface 62a. Therefore, the thickness unevenness of the cast film due to the inflow of the portable wind can be prevented by the contact angle lowering process. Here, the carrying wind refers to a wind that occurs in the vicinity of the belt surface 62a due to the movement of the endless belt 62 and flows in the X direction. In order to reduce the contact angle of the belt surface 62a with respect to the dope 24, it is preferred to apply a solvent to the belt surface 62a. The solvent used in the contact angle lowering process may be the same component as the solvent 23, or may be a component which is common to the solvent 23.

In the above embodiment, the timing at which the support heating process 138 is performed is set between the stripping process 137 and the dope down process 131, but may be between the casting process 132 and the film heating process 133. A cast film forming process 161 for performing the support heating process 138 between the casting process 132 and the film heating process 133 and a solution film forming process 162 having the cast film forming process 161 are shown in FIG.

The casting unit 165 which performs the casting film forming process 161 is shown in FIG. In the casting unit 165, a support heating device 168 as a support heating means is provided on the belt inner side 62b side of the casting zone CZ. The support heating device 168 has an inside side heater 113 and a heating air conditioner 114. The support heating device 168 heats the casting film 61 from the side of the endless belt 62 in order to heat the endless belt 62 from the side of the belt inner side 62b. Therefore, according to the support heating device 168, it is possible to suppress the formation of the surface layer on the casting film 61 and to perform heating of the casting film 61. When the support heating process is performed in the casting zone CZ, it is necessary to heat the endless belt 62 from the side of the belt inner side 62b. This is because if the endless belt 62 is heated from the belt surface 62a side, the surface layer forming process 134 is performed before the film heating process 133. Further, the temperature of the roller 66y can be set to the range T1 by the roller thermostat 121, and the roller 66y can function as a support heating means.

In addition, 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 near the casting film 61 in the film heating process 133 is higher than that in the vicinity of the casting film 61 in the surface layer forming process 134. The gas concentration of the solvent of the atmosphere is preferred. Here, the "gas concentration of the solvent in the atmosphere of the temperature Ta" is expressed as "(the mass of the gaseous solvent contained in the atmosphere of the temperature Ta) / (the mass of the gaseous solvent which is saturated in the atmosphere of the temperature Ta)" .

In the cast film forming process 161, the time at which the support surface cleaning process or the contact angle lowering process is performed may be between the stripping process 137 and the next dope down process 131. When the two processes are performed, it is preferable to carry out the process of the surface cleaning process of the support body and the process of lowering the contact angle.

Further, a contact angle lowering process for reducing the contact angle of the belt surface 62a with respect to the dope 24 may be performed between the support heating process 138 and the next dope down process 131. By the contact angle lowering process, it is difficult for the carrying wind to flow between the liquid bead and the belt surface 62a. Therefore, the thickness unevenness of the cast film due to the inflow of the portable wind can be prevented by the contact angle lowering process. Here, the carrying wind refers to a wind that occurs in the vicinity of the belt surface 62a due to the movement of the endless belt 62 and flows in the X direction. In order to reduce the contact angle of the belt surface 62a with respect to the dope 24, it is preferred to apply a solvent to the belt surface 62a. The solvent used in the contact angle lowering process may be the same component as the solvent 23, or may be a component which is contained in combination with the solvent 23.

In the casting film forming process of each process in turn, the heating of the endless belt 62 by the support heating process 138 is performed immediately after cooling by the film cooling process 136. The endless belt 62 which is heated immediately after cooling is easily warped. In particular, warpage in the Y direction of the endless belt 62 wound around each roller becomes a problem. That is, if the thick liquid flow down process 131 is directly performed on the warped endless belt 62, the interval from the slit outlet flowing down from the dope 24 to the belt surface 62a is deviated in the Y direction, thereby causing the liquid bead in the Y direction. The length L _B also varies. The deviation of the bead length L _B in the Y direction in the dope flow down process 131 appears as a thickness unevenness in the Y direction on the casting film 61 formed in the casting process 132.

Therefore, in order to prevent thickness unevenness caused by the warpage of the endless belt 62, it is preferable to carry out the support holding process in the dope flow down process 131.

As shown in FIGS. 22 and 23, the support holding device 201 that performs the support holding process includes a roller 66a and a nip roller 202. The nip roller 202 is disposed in the casting chamber 75a (see FIG. 2) so as to face the roller 66a through the transmission path 66r. The nip roll 202 is in contact with the wrap area LA of the endless belt 62. The winding area LA of the endless belt 62 means that the position TP1 at which the endless belt 62 which moves toward the roller 66a starts to contact the roller 66a on the belt surface 62a, and the position TP2 where the endless belt 62 which is in contact with the roller 66a leaves the roller 66a Part of it. It is preferable that the nip roller 202 is biased toward the endless belt 62 by the urging member. The arrival position DP at which the concentrated liquid 24 flowing down from the casting die 60 reaches is set in the winding area LA. Further, the nip roller 202 is disposed on both end sides of the moving path 66r (refer to FIG. 2) in the Y direction so as to be in contact with the suppressing position NP provided on both sides of the belt surface 62a in the Y direction of the reaching position DP.

Further, the suppression position NP is set at a position overlapping the arrival position DP or an upstream side of the arrival position DP in the X direction. The interval between the arrival position DP and the suppression position NP in the X direction is, for example, 0 mm or more and 300 mm or less.

Thus, the support holding device 201 performs the two directions of the holding loop 62 in the Y direction by the roller 66a supporting the belt inner surface 62b in the entire Y direction and the nip roller 202 supporting the outer side belt surface 62a of the Y position. The support at the end holds the process.

According to the support holding device 201, even if the endless belt 62 warped in the Y direction is guided between the casting die 60 and the roller 66a, the Y-direction ends of the endless belt 62 are held by the nip roller 202 and the roller 66a. unit. As a result, the warpage of the endless belt 62 is corrected at least at the reaching position DP. Therefore, thickness unevenness due to warpage of the endless belt 62 can be prevented according to the support holding device 201.

Further, in the cast film forming process 126 (refer to FIG. 8), when the arrival position DP is changed in the X direction, the nip roll 202 may be provided in accordance with the range in which the arrival position DP fluctuates.

In order to prevent thickness unevenness due to warping of the endless belt 62, only the central portion in the Y direction may be heated in the support heating process 138 (refer to FIG. 8). Thereby, in the both ends of the endless belt 62 in the Y direction, the scale due to the expansion by heating or the contraction by cooling becomes small, so that the occurrence of warpage can be suppressed.

As shown in FIGS. 24 and 25, the windshield block 210 disposed between the surface side heater 112 and the endless belt 62 is disposed in pairs so as to block both sides of the air inlet 112o in the Y direction. The opening width of the intake port 112o in the Y direction is smaller than the width of the endless belt 62 in the Y direction. Similarly, the windshield block 211 disposed between the inner side heater 113 and the endless belt 62 is disposed in pairs so as to block both sides of the air inlet 113o in the Y direction. The opening width of the intake port 113o in the Y direction is smaller than the width of the endless belt 62 in the Y direction.

The interval of the windshield 210 disposed in pairs in the Y direction may be greater than the casting width CW or may be equal to the casting width CW. Similarly, in the Y direction, the interval of the pair of windshield blocks 211 may be greater than the casting width CW or may be equal to the casting width CW.

Further, as shown in FIG. 24, the windshield blocks 210, 211 may be provided in the front side air blower 91 or the rear side air blower 92 of the front film dryer 88. Further, it may be arranged to block both sides of the intake port of the parallel blower 95 or the rear side blower 96 of the rear film dryer 89 in the Y direction.

The film 21 obtained by the present invention is particularly useful for a retardation film or a polarizing plate protective film.

The width of the film 21 is preferably 600 mm or more and 3,000 mm or less, more preferably 2,000 mm or more and 3,000 mm or less. Further, the present invention can also be applied when the width of the film 21 exceeds 3000 mm. The film thickness of the film 21 is preferably 30 μm or more and 120 μm or less.

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

The method of measuring the in-plane retardation Re is as follows. In-plane retardation Re The sample film was subjected to humidity conditioning at a temperature of 25 ° C and a humidity of 60% RH for 2 hours, and the retardation value measured from the vertical direction of 632.8 nm by an automatic birefringence meter (KOBRA 21DH Prince Metering Equipment Co., Ltd.) was used. In addition, Re is represented by the following formula.

Re=∣n1-n2∣×d

N1 represents the refractive index of the slow axis, n2 represents the refractive index of the phase axis 2, and d represents the thickness (film thickness) of the film.

The method of measuring the thickness direction retardation Rth is as follows. The sample film was conditioned for 2 hours at a temperature of 25 ° C and a humidity of 60% RH, and the value measured from the vertical direction was measured by an ellipsometer (M150 Japan Spectrophoto Co., Ltd.) according to 632.8 nm. The extrapolated value of the measured retardation value was calculated according to the following formula.

Rth={(n1+n2)/2-n3}×d

N3 represents the refractive index in the thickness direction.

(polymer)

The polymer 22 which is a raw material of the polymer film in the above embodiment is not particularly limited. When the solution film forming method is carried out, examples of the polymer include a cellulose halide or a cyclic polyolefin. On the other hand, in the case of performing the melt film forming method, examples of the raw material polymer include a cellulose halide, a lactone ring-containing polymer, a cyclic polyolefin, and a polycarbonate. Among them, cellulose halides and cyclic polyolefins are preferred, and cellulose acetates containing an acetate group and a propionate group, and a cyclic polyolefin obtained by addition polymerization are preferred, which are obtained by addition polymerization. The cyclic polyolefin is further preferred.

(cellulose cellulose)

As the cellulose halide, cellulose triacetate (TAC) is particularly preferred. Further, in the cellulose halide, it is more preferable that the ratio of the hydroxyl group of the cellulose esterified with a carboxyl group, that is, the degree of substitution of the mercapto group, satisfies all of the following formulae (I) to (III). Further, in the following formulae (I) to (III), A and B represent the degree of substitution of a mercapto group, A is a degree of substitution of an ethylidene group, and B is a degree of substitution of a mercapto group having 3 to 22 carbon atoms. Further, it is preferred that 90% by mass or more of the TAC is 0.1 mm to 4 mm.

(I) 2.0 A+B 3.0

(II)0 A 3.0

(III)0 B 2.9

The glucose unit constituting the cellulose which is β-1,4 bonded has a hydroxyl group which is free to the 2, 3 and 6 positions. The cellulose oxime is a polymer (polymer) obtained by esterifying a part or all of these hydroxy groups with a fluorenyl group having 2 or more carbon atoms. The degree of thiol substitution refers to the ratio of the hydroxyl groups of cellulose to the deuteration at the 2, 3, and 6 positions (the degree of substitution is 1 in 100% esterification).

The total degree of substitution is, 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. Wherein DS2 is the degree of substitution of the hydroxy group at the 2-position hydroxyl group of the glucose unit (hereinafter also referred to as "the thiol substitution degree of the 2-position"), and DS3 is the degree of substitution of the hydroxy group based on the thiol group at the 3 position (hereinafter also referred to as "3 position" The thiol substitution degree "), DS6 is the degree of substitution of the 6-hydroxyl group based on a thiol group (hereinafter also referred to as "6-position thiol substitution degree").

The mercapto group used in the cellulose halide of the present invention may be used alone or in combination of two or more kinds. When two or more kinds of sulfhydryl groups are used, one of them is preferably an ethylidene group. When the sum of the degrees of substitution based on the hydroxyl groups at the 2, 3, and 6 positions is DSA, and the sum of the hydroxyl groups at the 2, 3, and 6 positions is replaced by a thiol group other than the ethyl group, the DSB is used. The DSA+DSB value is preferably 2.22 to 2.90, and the 2.40 to 2.88 is particularly preferable. Further, the DSB is 0.30 or more, and 0.7 or more is particularly preferable. Further, in the DSB, 20% or more of the substituents of the 6-position hydroxyl group are preferable, but 25% or more of the substituents of the 6-position hydroxyl group are more preferable, 30% or more are further more preferable, and the substituent of 33% or more of the 6-position hydroxyl group is particularly good. Further, a cellulose halide having a degree of substitution at the 6-position hydroxyl group of the cellulose halide of 0.75 or more, further preferably 0.80 or more, and particularly 0.85 or more is also mentioned. A solution (dope) having a better solubility can be produced by these cellulose oximes. Particularly, a good solution can be produced in a non-chlorine organic solvent. It also produces a solution with low viscosity and excellent filterability.

The cellulose which is a raw material of the cellulose halide may be obtained from any one of cotton wool fibers and a slurry.

The fluorenyl group having a carbon number of 2 or more as the cellulose halide of the present invention may be an aliphatic group or an aryl group, and is not particularly limited. These may be, for example, an alkylcarbonyl ester, an olefinic carbonyl ester or an aromatic carbonyl ester of cellulose, an aromatic alkylcarbonyl ester or the like, and may each have a further substituted group. Preferred examples of such a group include a fluorenyl group, a butyl group, a pentyl group, a hexyl group, a octyl group, a decyl group, a dodecyl fluorenyl group, a tridecyl fluorenyl group, and a tetradecane fluorenyl group. Hexadecane group, octadecane decyl group, isobutyl fluorenyl group, tertiary butyl fluorenyl group, cyclohexane carbonyl group, oleoyl group, benzamyl group, naphthalenecarbonyl group, cinnamyl group and the like. Among these, propyl sulfonyl, butyl fluorenyl, dodecyl fluorenyl, octadecyl fluorenyl, tertiary butyl sulfonyl, oleoreyl, benzhydryl, naphthalenecarbonyl, cinnamyl, etc., more preferably, propyl sulfonyl, butyl fluorenyl Especially good.

(solvent)

Examples of the solvent 23 used for preparing the dope include aromatic hydrocarbons (for example, benzene, toluene, etc.), halogenated hydrocarbons (for example, dichloromethane, chlorobenzene, etc.), and alcohols (for example, 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 and methyl cellosolve) and many more. Further, in the present invention, the dope refers to a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

Among these, a halogenated hydrocarbon having 1 to 7 carbon atoms is preferably used, and dichloromethane is most preferred. From the viewpoint of the solubility of TAC, the peeling property of the cast film from the support, the mechanical strength of the film, and the optical properties of the film, one or several kinds of carbon atoms of 1 to 5 are mixed in addition to dichloromethane. The alcohol is preferred. The content of the alcohol is preferably 2% by mass to 25% by mass based on the entire solvent, more preferably 5% by mass to 20% by mass. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol or a mixture thereof is preferred.

However, in order to minimize the influence on the environment, the solvent composition in the case of not using methylene chloride has been studied recently. For this purpose, an ether having 4 to 12 carbon atoms and 3 carbon atoms are used. The ketone of ～12, the ester having 3 to 12 carbon atoms, and the alcohol having 1 to 12 carbon atoms are preferred. Sometimes these are mixed 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 be those having a cyclic structure. Further, a compound having two or more functional groups of an ether, a ketone, an ester, and an alcohol (that is, -O-, -CO-, -COO-, and -OH) can also be used as a solvent.

Further, the details of the cellulose halide are described in paragraphs [0140] to [0195] of Japanese Patent Laid-Open Publication No. 2005-104148. These descriptions can also be applied to the present invention. Further, in the paragraphs [0196] to [0516] of Japanese Patent Laid-Open Publication No. 2005-104148, solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers (UV agents), optical anisotropy control agents, and retardation inhibition are also known. Additives such as agents, dyes, deluters, strippers, and stripping accelerators are also described in detail.

In the case where the dope is cast in the present invention, it is possible to carry out the simultaneous lamination co-casting by laminating two or more kinds of dope simultaneously and laminating the co-casting or sequentially co-casting a plurality of dopes. In addition, two types of co-casting can be combined. In the simultaneous laminating co-flow delay, a casting die in which a feed head is mounted may be used, or a multi-groove type casting die may be used.

The cast film can be formed by simultaneous lamination co-casting or sequential lamination co-casting using the first dope containing the first polymer and the second dope containing the second polymer different from the first polymer. A laminated cast film composed of a layer on the support side (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. The base layer is composed of a first concentrated liquid, and the air surface layer and the support surface layer are composed of a second concentrated liquid.

When the first polymer and the second polymer are cellulose halides, the total thiol substitution degree Z1 of the fluorenyl group in the first polymer is lower than the total thiol substitution degree Z2 of the fluorenyl group in the second polymer. Preferably. In particular, the total thiol substitution degree Z1 of the fluorenyl group in the first polymer satisfies the formula (1), and the total thiol substitution degree Z2 of the fluorenyl group in the second polymer satisfies the formula (2).

Formula (1) 2.0 < Z1 < 2.7

Equation (2) 2.7 < Z2

From the viewpoint of the retardation of the wavelength dispersibility, the total substitution ratio Y1 of the degree of substitution X1 of the ethyl fluorenyl group of the cellulose halide used in the first polymer and the substitution ratio of the fluorenyl group having 3 or more carbon atoms satisfy the following formula ( 3) and (4) are preferred. Further, X1 and Y1 establish a relationship of X1 + Y1 = Z1 between the above Z1 of the above formula (1).

Equation (3) 1.0 < X1 < 2.7

Formula (4)0 Y1<1.5

From the viewpoint of the retardation of the wavelength dispersibility, the total substitution ratio Y2 of the degree of substitution X2 of the ethyl fluorenyl group of the cellulose halide used in the second polymer and the substitution ratio of the fluorenyl group having 3 or more carbon atoms satisfy the following formula ( 5) and (6) are preferred. Further, X2 and Y2 have a relationship of X2+Y2=Z2 between Z2 and the above formula (2).

Equation (5) 1.2 < X2 < 3.0

Equation (6)0 Y2<1.5

The viscosity of the second dope is lower than that of the first dope. The viscosity of each dope can be determined in accordance with JIS K 7117.

The second polymer is a cellulose halide, and the first polymer may be a polymer other than the cellulose halide. It is preferred to use a propylene resin as the first polymer.

(acrylic resin)

A methacrylic resin is also contained in the propylene resin, and a acrylate/methacrylate derivative, especially an acrylate/methyl acrylate (co)polymer, is known. The propylene resin is not particularly limited, but in order to obtain a film having a small photoelastic coefficient, it is composed of 50 to 99% by mass of methyl methacrylate unit and 1 to 50% by mass of other monomer units copolymerizable therewith. Preferably.

In the propylene resin, examples of the other monomer copolymerizable include an alkyl methacrylate having an alkyl group having 2 to 18 carbon atoms, an alkyl acrylate having an alkyl group number of 1 to 18, and Aromatic ethylene such as unsaturated, divalent carboxylic acid, styrene or α-methylstyrene such as α,β-unsaturated acid, maleic acid, fumaric acid or itaconic acid, such as acrylic acid or methacrylic acid. α,β-unsaturated nitrile such as acrylonitrile or methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, etc., which can be used alone or simultaneously Two or more kinds of monomers are used as the copolymerization component.

Among them, from the viewpoint of heat decomposition resistance or fluidity of the copolymer, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, etc. Preferably, methyl acrylate or n-butyl acrylate is preferred.

As a resin capable of forming a highly transparent optical film which exhibits little change in properties even in a high-temperature, high-humidity environment, the propylene resin is a propylene resin containing an alicyclic alkyl group as a copolymer component or is intramolecularly cyclized at a molecular host. A propylene resin in which a chain forms a cyclic structure is preferred. As an example of the propylene resin which forms a cyclic structure in the molecular main chain, a propylene-based thermoplastic resin including a polymer containing a lactone ring is exemplified as a preferred embodiment, and a preferred resin composition or synthesis method is described in Japan. Patent Publication No. 2006-171464. Further, a resin containing glutaric anhydride as a copolymerization component may be mentioned as another preferable aspect, and a copolymerization component or a specific synthesis method is described in Japanese Patent Laid-Open Publication No. 2004-070296.

The weight average molecular weight of the propylene resin is from 600,000 to 4,000,000, preferably from 800,000 to 3,000,000, and particularly preferably from 1,000,000 to 1.8 million. The weight average molecular weight of the propylene resin can be determined by gel permeation chromatography.

The method for producing the propylene resin is not particularly limited, and a known method such as suspension polymerization, emulsion polymerization, bulk polymerization or solution polymerization can be used. In the present invention, a plurality of propylene resins can also be used at the same time.

The propylene resin can also contain other thermoplastic resins. In the present invention, the thermoplastic resin has a glass transition temperature of 100 ° C or higher and a total light transmittance of 85% or more from the viewpoint of improving heat resistance or mechanical strength when the propylene resin is mixed into a film form. It is better.

The content ratio of the propylene resin to the other thermoplastic resin component in the propylene resin layer is a mass ratio of [propylene resin / (all thermoplastic resin)] × 100, preferably 30 to 99% by mass, more preferably 50 to 97% by mass. 60 to 95% by mass is further preferred. When the content ratio of the propylene resin in the propylene resin layer is 30% by mass or more, heat resistance can be sufficiently exhibited, which is preferable.

Examples of the other thermoplastic resin include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly(4-methyl-1-pentene); and halogens such as vinyl chloride and vinyl chloride resins; Polymer; styrene polymer such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyparaphenylene Polyester such as ethylene formate, polybutylene terephthalate or polyethylene naphthalate; polyamine; nylon 6, nylon 66, nylon 610; polyoxymethylene; polycarbonate; polyphenylene ether; Polyphenylene sulfide; polyetheretherketone; polybenzazole; polyether oxime; polyphenyl ester; polyamidoximine; rubbery polymerization of polybutadiene rubber, propylene rubber ABS resin or ASA resin Body and so on. The rubbery polymer is preferably a graft having a composition capable of being compatible with the cyclic polymer in the present invention, and is a rubbery polymer from the viewpoint of improving transparency when formed into a film. The average particle diameter is preferably 100 nm or less, more preferably 70 nm or less.

As the other thermoplastic resin, a resin which is thermodynamically compatible with the propylene resin is preferably used. As such another thermoplastic resin, an acrylonitrile-styrene copolymer or a polyvinyl chloride resin having an ethylene cyanide monomer unit and an aromatic vinyl monomer unit can be preferably used. Among these, the acrylonitrile-styrene copolymer can easily obtain an optical film having a total light transmittance of 85% or more under the conditions of a glass transition temperature of 120 ° C or more and a phase difference of 100 nm or less per 100 μm in the plane direction. Therefore, it is better. As the acrylonitrile-styrene copolymerization, specifically, the copolymerization ratio is in the range of 1:10 to 10:1 in terms of mole units.

When the first polymer is a propylene resin, if the first dope and the second dope are simultaneously laminated and co-cast, or stacked and co-cast, the thickness unevenness often occurs on the laminated cast film. This thickness unevenness is caused by the instability of the interface between the base layer composed of the first dope and the layer composed of the second dope (the support surface layer and the air surface layer). The destabilization of the interface refers to a phenomenon in which a part of the first concentrated liquid constituting the base layer enters the adjacent support surface layer or the air surface layer. In order to avoid destabilization of the interface, simultaneous co-casting or successive lamination is performed by using a confluent solution composed of a first dope, a second dope, and a buffer flowing between the first dope and the second dope. Stacked co-casting is preferred.

The viscosity of the buffer is lower than that of the first dope and the second dope. Further, it is preferred that the buffer be composed of a liquid which is compatible with the solvent contained in each dope. The viscosity of the buffer is preferably 1 Pa ‧ or more and 15 Pa ‧ or less, and more preferably 1 Pa ‧ sec. or more and 10 Pa ‧ sec or less. Further, the viscosity of the buffer can be determined in accordance with JIS K 7117.

It is preferred that the buffer is the same as the solvent contained in each dope. A polymer may be included in the buffer. The polymer contained in the buffer solution may, for example, be a first polymer or a second polymer, and it is preferred to include any of these polymers. The concentration of the polymer in the buffer is preferably less than 5% by mass.

By using a propylene resin as the first polymer, it is possible to suppress the thickness unevenness and efficiently produce an optical film whose optical characteristics are not easily changed by the generation of stress or the change in humidity.

[Examples]

(Experiments 1 to 8)

Experiments 1 to 8 were carried out according to the following methods. With regard to the details of each experiment, the experiment 1 will be described in detail, and the descriptions of the same portions as those of the experiment 1 will be omitted for the experiments 2 to 8 and the different portions will be described.

(Experiment 1)

The formulation of the compound used to prepare the dope 24 is shown below.

The solid content of the composition ratio as follows, ie

Cellulose triacetate (degree of substitution 2.86) 100 parts by mass,

Triphenyl phosphate (TPP) 10 parts by mass,

Light removal agent (AEROSIL R972) 0.03 parts by mass

The dope 24 is prepared by appropriately adding to a mixed solvent composed of the following, and stirring and dissolving, that is,

80 parts by mass of methylene chloride,

13.5 parts by mass of methanol,

n-Butanol 6.5 parts by mass.

The concentrated liquid 24 was filtered with a filter paper (manufactured by Toyo Filter Co., Ltd., #63LB), and then filtered with a sintered metal filter (06N, No. 10 μm, manufactured by Nippon Seisakusho Co., Ltd.), and further filtered with a mesh filter, and then placed. Into the storage tank.

[Triacetate cellulose]

Further, the cellulose triacetate (TAC) used herein has a residual amount of acetic acid of 0.1% by mass or less, a Ca content of 58 ppm, a Mg content of 42 ppm, an Fe content of 0.5 ppm, and contains 40 ppm of free acetic acid and 15 ppm of sulfate ion. By. Further, the degree of substitution of the ethyl hydrazine group with respect to the hydrogen at the 6-position hydroxyl group was 0.91. Further, 32.5% of the total ethyl fluorenyl group is an ethyl hydrazide group in which a hydrogen of a 6-hydroxy group is substituted. Further, the acetone extraction amount of the TAC extracted with acetone was 8% by mass, and the mass average molecular weight/number average molecular weight ratio was 2.5. Further, the obtained TAC had a yellowness index of 1.7, a haze of 0.08, and a transparency of 93.5%. The TAC is synthesized from cellulose taken from cotton.

A film 21 (having a width of 1950 mm) was produced in the solution film forming apparatus 10 shown in Fig. 1 by using the obtained dope 24. The casting unit 12 uses the one shown in Fig. 2. The casting unit 12 repeatedly performs the dosing flow down process 131, the casting process 132, the film heating process 133, the surface layer forming process 134, the film drying process 135, the film cooling process 136, the stripping process 137, and the support as shown in FIG. The cast film forming process 126 of the bulk heating process 138. The moving speed V of the endless belt was 100 m/min. In the peeling process 137 in the nth casting film forming process 126, the temperature of the tape surface 62a at the peeling position PP is T _PP (refer to Table 1). Further, at this time, the solvent content in the cast film was ZY _PP (refer to Table 1). The temperature of the belt surface 62a at the arrival position DP in the (n+1)th casting film forming process 126 was measured, and the temperature in the central portion in the Y direction was T _DPc (refer to Table 1), and the temperatures at both ends in the Y direction. Is T _DPe (refer to Table 1). Further, both end portions in the Y direction are portions which are 10 mm inward from both ends in the Y direction of the endless belt 62.

(Experiments 2 to 8)

The presence or absence of the film cooling process 136, the presence or absence of the film heating process 133, the presence or absence of the support heating process 138, the temperature T _PP of the tape surface 62a at the peeling position PP, and the solvent content in the cast film at the peeling position PP ZY _PP The film 21 was formed from the dope 24 in the same manner as in Experiment 1 except that the temperatures T _DPc and T _DPe of the tape surface 62a at the position DP were set as shown in Table 1.

(Evaluation)

In the solution film forming methods of Experiments 1 to 8, the evaluation was carried out in the following manner. The serial number of the evaluation result in Table 1 indicates the serial number attached to each evaluation item.

Peel evaluation

Investigate whether there is a peeling failure.

A: No peeling failure occurred during the stripping process.

B: A peeling failure occurred during the stripping process.

In this evaluation, A is qualified and B is unqualified.

2. Evaluation of thickness unevenness

The presence or absence of thickness unevenness of the film 21 was evaluated in the following order. The film 21 was measured for thickness unevenness. The thickness unevenness measurement order is as follows. First, a substantially 6 cm square sample film was cut out from the film 21. Second, the refractive index difference of the sample film was measured by a device capable of converting the refractive index difference of the sample film into a thickness difference. FX-03 FRINGEANALYZER (manufactured by Fuji Energy Co., Ltd.) was used as the device. Third, the refractive index difference was measured over the entire area of the sample film, and the average value was defined as the thickness unevenness of the laminated film. The thickness unevenness thus obtained was evaluated in accordance with the following criteria. Further, the thickness of the laminated film is an average value of the thicknesses of 6 samples of the sample film measured in micrometers.

A: The thickness unevenness is less than 1.5% with respect to the thickness of the film.

B: The thickness unevenness is 1.5% or more and less than 1.8% with respect to the thickness of the film.

C: thickness unevenness is 1.8% or more with respect to the thickness of the film.

In this evaluation, A and B are qualified, and C is unqualified.

Further, in Experiment 8, in the peeling evaluation, a peeling failure occurred, and it was obvious that the thickness unevenness of the film was large, and thus the evaluation was not carried out. Therefore, the column "2" of the evaluation result of Experiment 8 in Table 1 is described as "-".

3. Foaming evaluation

The cast film obtained was visually observed and investigated for blistering.

A: The foaming of the side portion was not confirmed.

B: Although foaming was confirmed at the side, it was limited to the portion cut by the slitter 36, and therefore there was no problem as a film for a product.

C: Foaming was confirmed until it became a part of the film for the product.

In this evaluation, A and B are qualified, and C is unqualified.

Experiments 21 to 22 and 51 to 52 were carried out in the following manner.

(Experiment 21)

In the above experiment 2, the film 21 was produced from the dope 24 in the same manner as in Experiment 2 except that the nip roll 202 (refer to Fig. 22) was provided. Further, the interval ΔX between the suppression position NP and the arrival position DP in the X direction is 0 mm.

(Experiment 22)

In the above experiment 2, the film 21 was produced from the dope 24 in the same manner as in Experiment 2 except that the nip roll 202 (refer to Fig. 22) was provided. The interval ΔX is 200 mm.

(Experiment 51)

In the above experiment 5, the film 21 was produced from the dope 24 in the same manner as in Experiment 2 except that the nip roll 202 (refer to Fig. 22) was provided. The interval ΔX is 0 mm.

(Experiment 52)

In the above experiment 5, the film 21 was produced from the dope 24 in the same manner as in Experiment 2 except that the nip roll 202 (refer to Fig. 22) was provided. The interval ΔX is 200 mm.

In Experiments 21 to 22 and 51 to 52, the amount of floating J of the belt was measured. Then, the floating amount J is determined under the following criteria.

A: The amount of float J is less than 50 μm.

B: The floating amount J is 50 μm or more and less than 100 μm.

C: The amount of float J is 100 μm or more and less than 200 μm.

D: The amount of float J is 200 μm or more.

In addition, the amount of floating J of the belt was measured as follows. First, a moving tension (60 N/mm ² ) is applied to the belt 62 wound around the rollers 66a to 66c to be cyclically moved in the moving path 66r. Next, in the winding area LA, the interval ΔCL between the roller 66a and the belt inner 62b is measured. Further, the maximum value of the interval ΔCL in the X direction and the Y direction is defined as the floating amount J of the belt.

In Table 2, the evaluation results of the floating amount J of Experiments 2 and 5 are shown together with Experiments 21 to 22 and 51 to 52.

10. . . Solution film making equipment

12, 165. . . Casting unit

13. . . Drying unit

14. . . Coiling unit

twenty one. . . membrane

twenty two. . . polymer

twenty three. . . Solvent

twenty four. . . Concentrate

25. . . Wet film

35. . . Clip tenter

35a. . . casing

35b. . . Clip

35c. . . Dry air supply machine

36. . . Slitting machine

37. . . Drying room

38. . . Cooling room

40. . . Transfer department

41, 45, 66a, 66b, 66c, 66f, 66g, 66x, 66y, 66z. . . Roll

46. . . Adsorption recovery unit

51. . . Core

52. . . Pressure roller

54. . . Take-up room

55. . . Film roll

57. . . Knurling device

60. . . Casting die

61. . . Cast film

61a. . . Membrane surface

61x. . . surface layer

61y. . . Wet layer

62. . . Annular band

62a. . . Belt surface

62b. . . Inside

63. . . Surface layer forming device

64. . . Membrane drying device

65. . . Stripping roller

66. . . With moving mechanism

66d, 66e. . . Support roller

66m, 99. . . motor

66r. . . Moving road

71. . . First sealing member

71a. . . Windshield

71b. . . Labyrinth seal

72. . . Second sealing member

73. . . Third sealing member

74. . . Fourth sealing member

75. . . Cast sleeve

75a. . . Casting chamber

75b. . . Membrane drying chamber

75c. . . Stripping room

75d. . . Support heating chamber

75o. . . Export

77. . . Decompression chamber

80. . . Surface formation

81. . . Intake duct

81a, 85a. . . surface

82. . . Cover

82a. . . Guide surface

83. . . Pre-intake nozzle / intake nozzle

83a. . . Pre-inlet/suction port

83b. . . inside

84. . . Cyclone

85. . . Side shelter

86. . . Wind road

88. . . Front film dryer

89. . . Film dryer

90. . . Front dry wind

91. . . Surface side blower

92, 96. . . Inside side air blower

94. . . Dry wind

95. . . Parallel blower

95a. . . Parallel exhaust duct

95b. . . Parallel intake duct

110. . . Heating wind

111, 141, 168. . . Support heating device

112. . . Surface side heater

112a, 113a. . . Intake duct

113. . . Inside side heater

113i. . . exhaust vent

112o, 113o. . . Air inlet

114. . . Heating wind regulator

121, 122, 123. . . Roller thermostat

125. . . Solution film forming method

126. . . Cast film formation process

127. . . Wet film drying process

131. . . Concentrated liquid flow down process

132. . . Casting process

133. . . Membrane heating process

134. . . Surface formation process

135. . . Membrane drying process

135a. . . Front film drying process

135b. . . Post film drying process

136. . . Membrane cooling process

137. . . Stripping process

138. . . Support heating process

142. . . Surface heating roller

143. . . Inside heating roller

144. . . Roller temperature regulator

148. . . Cooling unit

149. . . Liquid supply device

150. . . Dry wind

151. . . Evaporation device

161. . . Cast film formation process

162. . . Solution film forming method

201. . . Support holding device

202. . . Ram roll

210, 211. . . Wind shelter

CA. . . Casting zone

CW. . . Cast width

CZ. . . Casting area

DP. . . Arrival location

LA. . . Wound area

L _B . . . Bead length

NP. . . Suppression position

PP. . . Peeling position

TP1, TP2. . . position

X, Y. . . direction

Θ1. . . angle

Fig. 1 is an explanatory view showing an outline of a solution film forming apparatus.

Fig. 2 is a side view showing an outline of a first casting unit.

Fig. 3 is a perspective view showing an outline of a surface layer forming apparatus.

Fig. 4 is a cross-sectional view taken along line IV-IV of Fig. 5 showing an outline of a surface layer forming apparatus.

Fig. 5 is a cross-sectional view taken along line V-V of Fig. 4 showing an outline of a surface layer forming apparatus.

Fig. 6 is a perspective view showing an outline of a first support heating device.

Fig. 7 is a cross-sectional view taken along line VII-VII of Fig. 2 showing an outline of a first support heating device.

Fig. 8 is a process chart showing an outline of a first casting film forming process and a solution film forming method.

Fig. 9 is a cross-sectional view showing an outline of a cast film after formation.

Fig. 10 is a cross-sectional view showing an outline of a cast film after a film heating process.

Fig. 11 is a cross-sectional view showing an outline of a cast film after a surface layer forming process.

Fig. 12 is a cross-sectional view showing an outline of a cast film after a film drying process.

Fig. 13 is a side view showing an outline of a main part of a second casting unit.

Fig. 14 is a side view showing an outline of a third casting unit.

Fig. 15 is a side view showing an outline of a main part of a fourth casting unit.

Fig. 16 is a side view showing an outline of a main part of a fifth casting unit.

Fig. 17 is a side view showing an outline of a sixth casting unit.

Fig. 18 is a side view showing an outline of a seventh casting unit.

Fig. 19 is a cross-sectional view showing an outline of a second support heating device.

Fig. 20 is a process chart showing an outline of a second casting film forming process and a second solution film forming method.

Fig. 21 is a side view showing an outline of a main part of the eighth casting unit.

Fig. 22 is a side view showing an outline of a main part of the support holding device.

Fig. 23 is a plan view showing an outline of a winding area, an arrival position, and a suppression position set on the belt surface.

Fig. 24 is a side view showing an outline of a main part of a ninth casting unit.

Fig. 25 is a cross-sectional view taken along line XXV-XXV of Fig. 24 showing an outline of a support heating device.

twenty one. . . membrane

twenty four. . . Concentrate

25. . . Wet film

61. . . Cast film

125. . . Solution film forming method

126. . . Cast film formation process

127. . . Wet film drying process

131. . . Concentrated liquid flow down process

132. . . Casting process

133. . . Membrane heating process

134. . . Surface formation process

135. . . Membrane drying process

135a. . . Front film drying process

135b. . . Post film drying process

136. . . Membrane cooling process

137. . . Stripping process

138. . . Support heating process

Claims (8)

A method for forming a cast film, which is a method of forming a cast film on a moving support, wherein the moving support moves in a manner of repeatedly passing through a position at which the concentrated liquid flows down and a peeling position at which the cast film is peeled off, The method for forming a cast film includes the steps of: (A) flowing a dope to a surface of the moving support, the dope comprising a polymer and a solvent; and (B) forming a dope from the moving support. The casting film on the surface evaporates the solvent, the casting film is composed of the concentrated liquid flowing down; (C) cooling the casting film to be independently transportable, and the cooling is performed after the step B; (D) peeling the cast film after the step C from the moving support; (E) heating the moving support after the step D before the next step B; (F) using the above-mentioned E step The heat of the moving support body heats the casting film before the next step B; and (G) holding the moving support body by the both end support members and the inner support member, the 挟In the step A, both end portions of the support surface of the support member reaches a position closer to the ratio of the width direction of the surface movement of the two outer support member, the support member which supports an end of the inside supporting member moving to the other end. The method for forming a cast film according to claim 1, wherein The both ends of the surface support member are nip rolls, and the inner support members are support rolls. A method for forming a cast film, which is a method of forming a cast film on a moving support, wherein the moving support moves in a manner of repeatedly passing through a position at which the concentrated liquid flows down and a peeling position at which the cast film is peeled off, The method for forming a cast film includes the steps of: (H) flowing a dope to the moving support, the dope comprising a polymer and a solvent; and (I) forming a surface on the moving support. The casting film evaporates the solvent, the casting film is composed of the concentrated liquid flowing down; (J) cooling the casting film to be independently transportable, and the cooling is performed after the first step; (K) Removing the above-described cast film after the above-described J step from the moving support; (L) heating the central portion in the width direction of the moving support after the K step before the next step I; and (M) utilizing the aforementioned L The heat imparted to the moving support in the step is heated to the aforementioned cast film before the first step I. A method for forming a solution, which is a method for producing a film by forming a cast film on a moving support and drying, wherein the moving support reaches the reaching position by peeling down the concentrated liquid and the peeling of the cast film The method of moving the peeling position is characterized in that the solution forming method has the following steps: (A) flowing a dope to the surface of the moving support, the dope containing a polymer and a solvent; and (B) evaporating the solvent from the casting film formed on the surface of the moving support, the cast film (C) cooling the cast film to a state in which it can be independently transported, the cooling is performed after the step B, and (D) peeling the aforementioned step C from the moving support a casting film; (E) heating the aforementioned moving support after the step D before the next step B; (F) heating the heat applied to the moving support in the aforementioned E step, heating the next step B before (G) the above-mentioned moving support is held by the both end support members and the inner support member, and the holding is performed in the above-mentioned step A, and the support members at both ends of the surface are supported in the width direction from the arrival position. a surface of the outer movable support body on the outer side, the inner support member supports one end to the other end of the movable support body; and (N) the aforementioned peeling from the movable support body The solvent was evaporated in a cast film to obtain a film. A method for forming a solution, which is a method for producing a film by forming a cast film on a moving support and drying, wherein the moving support reaches the reaching position by peeling down the concentrated liquid and the peeling of the cast film The method of moving the peeling position is characterized in that the solution forming method has the following steps: (H) flowing the dope to the moving support, the dope comprising a polymer and a solvent; (I) evaporating the solvent from the casting film formed on the surface of the moving support, the cast film being (J) cooling the cast film to a state in which it can be independently transported, the cooling is performed after the first step; (K) peeling the casting after the J step from the moving support (L) heating the central portion in the width direction of the moving support body after the step K before the next step I; (M) heating the next one by using the heat given to the moving support in the aforementioned L step The casting film before the step; and (P) evaporating the solvent from the casting film peeled off from the moving support to obtain a film. A casting film forming apparatus comprising: a moving support body that sequentially circulates through an arrival portion, a casting portion, a film drying portion, and a peeling portion, and the concentrated liquid that reaches the flow in the reaching portion, the concentrated liquid a polymer and a solvent, wherein the casting film is formed by flowing down the dope, the film drying unit evaporates the solvent from the casting film, and the casting film is peeled off from the peeling portion; Supporting the moving support body located at the reaching portion; the peeling portion supporting unit supporting the moving support body located at the peeling portion; In the film cooling unit, the casting film is cooled to be independently transportable while the moving support is separated from the film drying unit and reaches the peeling portion, and the support heating unit is heated away from the peeling portion and reaches the film. The moving support body during the drying portion; the film heating unit, the casting film before reaching the film drying portion by heat obtained by the support heating unit; and the both end surface supporting members having the aforementioned arrival The support means for supporting both ends of the surface of the moving support body in the width direction than the arrival position of the concentrated liquid flowing therethrough; and the inner support member provided on the support portion supporting means for supporting the aforementioned Move one end of the inside of the support to the other end. The casting film forming apparatus according to claim 6, wherein the both end support members of the surface are nip rolls, and the inner support members are support rolls. A casting film forming apparatus comprising: a moving support body that sequentially circulates through an arrival portion, a casting portion, a film drying portion, and a peeling portion, and the concentrated liquid that reaches the flow in the reaching portion, the concentrated liquid a polymer and a solvent, wherein the casting portion forms a casting film from the concentrated liquid flowing down, wherein the film drying unit evaporates the solvent from the casting film, and the peeling portion peels off the casting film; and reaches the portion supporting unit; Supporting the aforementioned moving support located at the aforementioned reaching portion; The peeling portion supporting unit supports the moving support body located at the peeling portion, and the film cooling unit cools the cast film to be independently transferable while the moving support body leaves the film drying unit and reaches the peeling portion. a support heating unit that heats the center portion in the width direction of the moving support during the period from the peeling portion to the film drying portion, and the film heating unit reaches the foregoing by heat heating obtained by the support heating unit The aforementioned cast film before the film drying section.