JP5466056B2 - Solution casting method - Google Patents

Description

  The present invention relates to a solution casting method for producing a polymer film.

  Various polymer films such as a cellulose acylate film and a cyclic polyolefin film are used after being cut into dimensions according to the application. Cutting may be done with the polymer film alone before combining with the member to be combined, or it may be done with the member after combining with the member to be combined. For example, when manufacturing a polarizing plate, it cuts, after bonding together a polarizing film and the polymer film used as a protective film which protects this. The same applies when one of the pair of protective films disposed on both surfaces of the polarizing film is replaced with an optical compensation film (including a retardation film). That is, an optical compensation film may be used as a protective film.

  In order to make a polarizing plate from a film having a multilayer structure formed by laminating a polarizing film and a protective film, when cutting to a desired size, a cutting blade from one film surface to the multilayer structure film Press to cut. When the multilayer structure film is cut in this way, a crack may occur from the cut surface formed by the cutting to the inside of the protective film. The protective film in which cracks are caused by such cutting is evaluated as having poor processing suitability, and the commercial value of the resulting polarizing plate is significantly reduced.

  Moreover, when manufacturing a liquid crystal display, a polarizing plate is affixed on a glass substrate. At the time of this bonding, if the bonded state does not become an expected state, so-called rework is performed in which the polarizing plate is once peeled off from the glass substrate and then bonded again. In the protective film of the polarizing plate, a part of the protective film may remain on the glass substrate particularly during the reworking, when peeling off from the glass substrate. Thus, the protective film in which a part of the protective film remains on the glass substrate without being peeled off is evaluated as having poor reworkability and is not preferable.

  As a method for producing a polymer film used for optical applications such as the above display device, there is a solution casting method. In the solution casting method, a dope in which a polymer is dissolved in a solvent is cast on a support to form a cast film, and the cast film is solidified and peeled off. This is a method for producing a polymer film by drying a film. As known in the art, there are a dry casting method and a cooling gelation casting method depending on how the casting film is solidified.

  In the dry casting method, the casting film is dried to a desired drying level, and the casting film is hardened by this drying. That is, after peeling off, the cast film is dried and hardened to such an extent that the wet film can be conveyed.

  On the other hand, the cooling gelation casting method is a method in which the casting film is cooled to form a gel with a very high solvent residual rate, and gelation is promoted until it becomes hard enough to be transported even if it is peeled off. It is.

  Comparing the above-mentioned dry casting method with the cooling gelation casting method, the latter is remarkably advantageous in terms of production efficiency because it can be peeled off from the support while the solvent residual ratio is high. However, the polymer film obtained by the cooling gelation casting method is inferior to the polymer film obtained by the dry casting method in terms of the above processing suitability and reworkability.

  Various proposals have been made so far in order to efficiently produce, that is, to improve the amount of film produced per unit time as in the cooling gelation casting method while exhibiting the required performance. For example, in the method of Patent Document 1, a method is proposed in which a gas flow is sprayed at a peeling position where a cast film is peeled off from a support. According to this method, a film having a desired retardation can be efficiently produced.

  Moreover, in patent document 2, the wind with a wind speed of 20 m / sec or more is sprayed on the film surface peeled off from the support body of the wet film immediately after peeling so that it may become a perpendicular | vertical direction with respect to a film surface. According to this, even if the solvent residual rate at the time of peeling from the support is a high value of 100% or more, the patent document 2 stably peels the casting film from the support and has excellent flatness. It is said that a polymer film can be manufactured.

JP 2000-239403 A JP 2001-198933 A

  However, even if the methods of Patent Documents 1 and 2 are applied to a cooling gelation casting method that peels off at a high solvent residual rate and is dried, it is impossible to achieve both processing suitability and improvement in reworkability.

  Then, an object of this invention is to provide the solution casting method which improves the process appropriateness and rework property of the film produced by a cooling gelation casting system.

In order to solve the above problems, the present invention is a state in which a cast film formed by continuously casting a dope in which a polymer is dissolved in a solvent is cooled and solidified, and the solvent remains. In the solution casting method in which the wet film is dried to produce a film, the wet film is dried so that the longitudinal direction coincides with the width direction of the casting surface of the support. The wet film is wound around the peripheral surface of the roller provided on the opposite side of the support with respect to the transport path, and the cast film is peeled off by transporting the wet film. the space on the film surface and the first space, the space on the other film surface when the second space, as the conveying path of the wet film toward the roller is convex toward the second space side, the roller Ri second gas of the second space upstream from the support and the roller provides suction with a suction device upstream of the roller by vacuum the second space between the stripping position in which the casting film is peeled off The pressure of the two spaces is made smaller than the pressure of the first space.

  The suction device includes a chamber that partitions the second space to be decompressed from the external space, and controls the path of transport of the wet film toward the roller by adjusting the pressure in the chamber. Preferably, the path is controlled. Therefore, it is more preferable that an angle θ1 formed by the surface of the support and the wet film at the peeling position is in a range of 30 ° to 80 °.

  According to the solution casting method of the present invention, a film excellent in processing suitability and reworkability can be produced in spite of the cooling gelation casting method.

It is the schematic of the solution casting apparatus which implemented this invention. It is the schematic of a route control part. It is the schematic of a route control part.

  1 includes a wet film forming apparatus 17 that forms a wet film 16 from a dope 13 in which a polymer 11 is dissolved in a solvent 12, and holding means (not shown) for each side of the formed wet film. While holding and transporting, the first tenter 18 that proceeds to dry until a certain solvent residual ratio is reached, and the side of the wet film 16 is held by holding means (not shown) and further applied with appropriate tension in the width direction. The second tenter 19 that proceeds with drying, the roller drying device 22 that further promotes drying while transporting the wet film 16 that has passed through the second tenter 19 by the roller 21, and the dried film 23 are wound into a roll. And a winding device 24. In addition, the solution casting apparatus 10 includes each of the wet film 16 and the film 23 in each conveyance path between the second tenter 19 and the roller drying device 22 and between the roller drying device 22 and the winding device 24. A slit device (not shown) for cutting off the side end portion is provided, but the illustration is omitted.

  The wet film forming apparatus 17 includes a drum 29 as a support. The drum 29 has driving means (not shown), and is rotated in the circumferential direction by the driving means. By this rotation, the peripheral surface 29a becomes an endless casting surface on which the dope 11 is cast.

  Above the drum 29, a casting die 31 that flows out the dope 13 is provided. By continuously flowing out the dope 13 from the casting die 31 to the rotating drum 29, the dope 13 is cast on the drum 29 to form a casting film 32. In addition, regarding the dope 13 from the die 31 to the drum 29, a decompression chamber is provided upstream in the rotation direction of the drum 29, but the illustration is omitted. The decompression chamber sucks the atmosphere in the upstream area of the dope 13 that has flowed out to decompress the area.

  The cast film 32 is hardened to such an extent that it can be conveyed by the roller 48 to the first tenter 16 and then peeled off from the drum 29 in a state containing a solvent. The drum 29 has a temperature controller 34 that controls the peripheral surface 29a. By controlling the temperature of the peripheral surface 29a by the controller 34, the casting film 32 is cooled to a desired temperature and solidified by this cooling.

  When stripping, the wet film 17 is supported by a stripping roller (hereinafter referred to as stripping roller) 33, and the stripping position PP (see FIG. 2) where the casting film 32 is stripped from the drum 29 is fixed. Hold on.

  A path control unit 36 that controls the path of the wet film 16 toward the peeling roller 33 is provided upstream of the peeling roller 33.

  A method for peeling the casting film 32 from the drum 29 will be described later with reference to another drawing.

A plurality of rollers 48 are provided between the film forming apparatus 17 and the first tenter 18. The wet film 16 formed by peeling is conveyed by these rollers 48 and guided to the first tenter 18. In the first tenter 18, the side end of the wet film 16 is held by holding means (not shown), and the wet film 16 is dried while being conveyed by the holding means. The holding means is a plurality of pins (not shown). The wet film 16 is held by passing the pins through the side end portions of the wet film 16. The pins at the side ends move in the transport direction while applying appropriate tension to the width direction of the wet film 16.

  The second tenter 19 downstream of the first tenter 18 is also provided with a plurality of holding means for holding each side end of the wet film 16. This holding means is a clip that holds the side end of the wet film 16. The plurality of clips apply a predetermined tension to the width direction of the wet film 16 at a predetermined timing.

  Both the first and second tenters 18 and 19 are formed as chambers surrounding the conveyance path. Ducts (not shown) are respectively provided in the first and second tenters 18 and 19, and air supply nozzles (not shown) are provided in these ducts (not shown) so as to face the conveyance path of the wet film 16. None) and a plurality of suction nozzles (not shown) are formed. The inside of the first and second tenters 18 and 19 is maintained at a constant humidity and a solvent gas concentration by sending dry gas from the air supply nozzle and sucking gas from the suction nozzle. The wet film 16 is dried by passing through the insides of the first and second tenters 18 and 19. In the first tenter 18, the wet film 16 is dried to such an extent that the second tenter 19 can be gripped by the clip. On the other hand, the second tenter 19 determines the degree of drying to be achieved in consideration of the timing of tension application in the width direction.

  The wet film 16 that has passed through the second tenter 19 is removed by a slitting device (not shown) by continuously cutting each side end portion where the holding marks are held by the holding means with a cutting blade. The central portion between one side end and the other side end is sent to the roller dryer 22.

  When the wet film 16 is sent to the roller drying device 22, the wet film 16 is supported by the peripheral surfaces of the plurality of rollers 21 arranged side by side in the transport direction. Among these rollers 21, there is a driving roller that rotates in the circumferential direction, and the roller 21 is conveyed by the rotation of the driving roller.

  The roller drying device 22 includes a duct (not shown) through which the dried gas flows out, and is formed as a chamber that partitions the space into which the dried gas is sent from the outside. The roller drying device 22 has an exhaust port, and the inside of the roller drying device 22 is maintained at a constant humidity and a solvent gas concentration by sending dry gas from the duct and exhausting air from the exhaust port. By passing the inside of the roller drying device 22, the wet film 16 is dried to be a film 23.

  The film 23 dried by the roller dryer 22 is removed by continuously cutting each side end with a slitting blade (not shown) with a cutting blade. The central portion between one side end and the other side end is sent to the winding device 24 and wound into a roll.

  The stripping process will be specifically described with reference to FIGS. 2 and 3, the arrow Z1 indicates the conveyance direction of the wet film 16, and the arrow Z2 indicates the width direction of the wet film 16. The width direction of the peripheral surface 29a coincides with the width direction Z1 of the wet film 16. 2 and 3 are schematic views, and the peeling roller 33 is drawn smaller than the thickness of the wet film 16.

  In the following description, the space on one film surface side peeled from the drum 29 of the wet film 16 is referred to as a first space, and the space on the other film surface side is referred to as a second space. The stripping roller 33 is arranged so that the longitudinal direction thereof coincides with the width direction of the peripheral surface of the drum 29. The peeling roller 33 is provided on the opposite side of the drum 29 with respect to the conveyance path of the wet film 16. That is, since the drum 29 is provided in the first space, the peeling roller 33 is provided in the second space.

  The stripping roller 33 includes a driving unit 70 and a controller 71 that controls the driving unit 70. The driving means 70 causes the peeling roller 33 to rotate in the circumferential direction at a predetermined rotational speed. When a signal of the rotation speed of the set peeling roller 33 is input, the controller 71 controls the driving means 70 so that the peeling roller 33 rotates at the set speed.

  The stripping roller 33 supports the wet film 16 that has been guided on its peripheral surface, and conveys the wet film 16 by rotating. The drum 29 and the peeling roller 33 are arranged so that the wet film 16 is wound around the peeling roller 33 and a conveyance path downstream of the peeling roller 33 is determined. Thus, the casting film 32 is peeled off from the drum 29 by winding the wet film 16 around the peeling roller 33 and transporting the wet film 16 by the peeling roller 33.

  Note that the peeling roller 33 is not necessarily a driving roller, and may be a so-called driven roller that is driven when the peripheral surface is in contact with the wet film 16 being conveyed. In this case, another conveying means is provided downstream of the peeling roller 33. Then, the wet film 16 is supported by the peeling roller 33, and the wet film 16 is conveyed by the provided conveying means, whereby the casting film 32 is peeled off from the drum 29.

  The path control unit 36 is provided in the second space between the drum 29 and the peeling roller 33 and controls the wet film 16 to be conveyed along an intended path. The path control unit 36 includes a chamber 55 that partitions the space to be decompressed from the external space, a pump 56 that sucks the atmosphere inside the chamber 55, and a controller 57 that controls the suction force of the pump 56. When the signal of the set pressure in the chamber 55 is input, the controller 57 adjusts the suction force of the pump 56 so that the set pressure is reached.

  The chamber 55 includes a first member 61 that partitions the second space to be decompressed from an upstream external space in the transport direction Z1 of the wet film 16, a second member 62 that partitions the downstream external space, and a width direction Z2. A third member 63 and a fourth member 64 that partition from the external space on each side are provided, and a fifth member 65 that partitions from the lower external space. Further, the chamber 55 is formed with a first opening 68 facing the wet film 16 so as to be surrounded by the first member to the fourth members 61 to 64, and the gas outside the chamber 55 is passed through the first opening. 68 is aspirated. Of the plate-like first to fifth members 61 to 65, the first to fourth members 61 to 64 are arranged in an upright posture.

  The first member 61 is disposed to face the drum 29 and has a curved surface along the peripheral surface 29 a of the drum 29. In consideration of the thickness of the casting film 32, the first member 61 is disposed such that the distance from the drum 29 is in the range of 100 μm to 2500 μm. The upstream end 61U of the first member 61 in the transport direction Z1 is located upstream of the downstream end 29D of the drum 29.

  The second member 62 is disposed so as to face the peeling roller 33, and has a curved surface along the peripheral surface of the peeling roller 33. In consideration of the thickness of the wet film 16, the second member 62 is disposed such that the distance from the peeling roller 33 is in the range of 100 μm to 2500 μm. The downstream end 62 </ b> D of the second member 62 in the transport direction Z <b> 1 is located downstream of the upstream end 33 </ b> U of the peeling roller 33. The second member 62 is formed with a second opening 69 that is connected to the pump 56 and through which the gas inside the chamber 55 flows out.

  The third member 63 and the fourth member 64 are arranged so that the inner surfaces thereof are outside the side edges 16e of the wet film 16. Thereby, the wet film 16 until the path is stabilized does not collide with the third member 63 and the fourth member 64. The facing surface facing the wet film 16 is a curved surface so as not to overlap the intended path of the wet film 16 as shown in FIG. 2 when viewed from the side. It does not have to be a curved surface.

  The inside of the chamber 55 is in a depressurized state by sucking gas. When the inside of the chamber 55 is depressurized, the second space between the drum 29 and the peeling roller 33 is also depressurized so that the pressure is lower than that of the first space. As a result, the route is changed from a straight path (symbol A indicated by a broken line in FIG. 2) to a curved path so that the wet film 16 directed to the peeling roller 33 is pulled toward the chamber 55 side. When viewed from the side, the conveyance path has a convex shape toward the second space. Thus, the path control unit 36 is a suction unit that sucks the gas in the second space between the drum 29 and the peeling roller 33, and the second between the drum 29 and the peeling roller 33 by this suction. The space is depressurized so that the conveyance path of the wet film 16 is convex toward the second space.

  By making the conveyance path of the wet film 16 convex toward the second space, the force applied to the wet film 16 in the longitudinal direction out of the force applied to the wet film 16 for stripping is significantly reduced compared to the conventional case. Thus, more of the applied force can be used for peeling off. For this reason, the orientation of the polymer of the wet film 16 in the direction along the film surface (hereinafter referred to as plane orientation) can be suppressed, and as a result, both the processing suitability and the reworkability are improved.

  In the conventional method, if the peeling force is excessively large, the wet film 16 may be cut at the time of peeling. The higher the production speed, the higher the solvent residual rate at the time of stripping, so the adhesion between the cast film 32 and the drum 29 is greater. Therefore, as the film forming speed is increased, the stripping force is increased, so that the film can be easily cut. On the other hand, according to the above-described method of the present invention, the force applied for stripping can be reduced under a constant production speed, and as a result, the production speed can be further increased. There is also an effect. Moreover, according to the above method, since the gas is not sprayed onto the wet film 16 having a very high solvent residual ratio immediately after peeling, the smoothness of the film surface of the wet film 16 is maintained and contamination by foreign matter is maintained. Can also be avoided.

  By controlling the conveyance path of the wet film 16 toward the peeling roller 33 as described above, the angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the peeling position PP can be increased. For this reason, it becomes easy to suppress the force required for peeling off.

  The angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the stripping position PP is more preferably in the range of 30 ° to 80 °.

  When the angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the peeling position PP is increased, the winding center angle θ2 with respect to the peeling roller 33 becomes larger than the winding center angle in the case of the straight path A. . When the winding center angle θ2 is easily held large, the shape of the conveyance path between the drum 29 and the peeling roller 33 is also easy to hold while maintaining the convex shape.

  The winding center angle θ <b> 2 is a central angle in a sector shape including a winding region 72 where the wet film 16 is wound around the peeling roller 33 and the center of the cross section of the peeling roller 33.

  From the viewpoint of further increasing the angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the peeling position PP and the winding center angle θ2, the peeling roller 33 is driven as in the present embodiment. It is more preferable to use a driving roller instead of a roller. In order to maintain the shape of the conveyance path that is convex toward the second space side or to have a larger convexity, the rotational speed of the drive roller may be reduced. As described above, the angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the peeling position PP and the winding center angle θ2 define the conveyance path of the wet film 16 toward the peeling roller 33 as a chamber 55. In addition to the method of increasing the size only by the suction by the above, it is possible to increase the size by using the peeling roller 33 as a driving roller.

  In the present embodiment, the second space is decompressed so that the second space has a lower pressure than the first space, but the present invention is not limited to this. For example, the first space may be pressurized instead of or in addition to the decompression of the second space. However, this pressurization is not a dynamic pressure but a static pressure.

  The pressurization as the static pressure includes the first space and the straight path A of the wet film 16 in a chamber (not shown) so as to include a part on the downstream side of the drum 29 and a part on the upstream side of the peeling roller 33. ) And repeating the feeding operation for feeding gas into the chamber for a certain period of time and the stopping operation for stopping the feeding operation for a certain period of time. According to this method, it is possible to greatly suppress the generation of dynamic pressure such as gas blowing, and it is possible to apply pressure to the wet film 16 from the first space side. Even when the gap between the drum 29 and the stripping path roller 33 is a very small gap of about several millimeters, this method can surely create a pressure difference between the first space and the second space. Furthermore, the smoothness of the film surface can be more reliably maintained than when the gas is sucked from the slit-like opening extending in the width direction Z2.

  There is still another method for providing a pressure difference between the first space and the second space up to the drum 29 and the peeling roller 33. For example, a partition member for partitioning the internal space is provided in the chamber 17 (see FIG. 1) without using the chamber 55 and the chamber (not shown) surrounding the first space and the straight path A of the wet film 16. Thus, there is a method of providing the pressure difference. By controlling the pressure in each space formed by the partition member, a pressure difference can be created between the first space above the transport path of the wet film 16 and the second space below. When the distance between the drum 29 and the peeling roller 33 is 5000 μm or more, it is more preferable to apply the pressure difference using the chamber 55. When the distance is less than 5000 μm, the chamber 55 or the first space and the wet film 16 are used. Instead of using the chamber (not shown) surrounding the straight path A, the chamber 17 may be partitioned by a partition member to create the pressure difference.

  The pressure difference between the first space and the second space is preferably determined based on the solvent residual rate of the wet film 16 from the peeling position PP until it passes through the winding area of the peeling roller 33. It is preferable to increase the pressure difference and make the conveying path larger and convex as the solvent residual ratio increases. This is because the higher the solvent residual ratio, the stronger the adhesion between the drum 29 and the cast film 32 and the easier the wet film 16 breaks.

  The stripping position PP is formed on the downstream side in the rotation direction of the drum 29 toward the center in the width direction Z2. For this reason, the force applied in the longitudinal direction of the wet film 16 at the time of stripping increases toward the center in the width direction Z2, and the plane orientation increases. Therefore, at the stripping position PP, it is more preferable that the pressure in the second space becomes lower toward the center. Thereby, the film 23 whose plane orientation is constant in the width direction Z2 can be manufactured. In order to reduce the pressure in the second space toward the center at the stripping position PP, for example, an independent chamber (not shown) is further provided inside the chamber 55, and the chamber and the chamber 55 are separated from each other. There is a method of controlling each internal pressure independently.

  The present invention is particularly effective when the polymer 11 (see FIG. 1) is cellulose acylate.

  Below, the Example as this invention and the comparative example with respect to this invention are described.

  The film 23 was manufactured by the cooling gelation casting method. A partition member (not shown) is provided in the wet film forming apparatus 17 so as to create a pressure difference between the first space and the second space, and the first space is pressurized to a pressure 10 Pa higher than the atmospheric pressure, The conveyance path of the wet film 16 was convex on the second space side. Note that the pressure in the second space is equal to the atmospheric pressure. Accordingly, the film 23 was manufactured by changing the speed ratio between the drum 29 and the peeling roller 33 so that the peeling position PP becomes constant. In Table 1, the numerical values in the columns of “first space pressure (Pa)” and “second space pressure (Pa)” are values based on atmospheric pressure. That is, it is described as 0 (zero) when the pressure is equal to the atmospheric pressure, as a positive value when it is higher than the atmospheric pressure, and as a negative value when it is lower than the atmospheric pressure.

  With respect to the obtained film 23, processability and reworkability were evaluated by the following methods and standards. The results are shown in Table 1.

(A) Processing suitability The obtained film 23 was laminated on both sides of the polarizing film via an adhesive and adhered to produce a polarizing plate. The polarizing plate was punched into a 10 cm × 10 cm rectangle with a blade and used as an evaluation sample. Based on the following criteria, whether or not a crack has occurred from the edge of the long side of the evaluation sample, that is, the cut surface, to the inside of the film 23 and the degree of the confirmed crack were evaluated. The crack may be a crack from the cut surface of the film 23 toward the inside, or may be a separation between the polarizing film and the film 23. In the following criteria, A to C are levels at which workability is acceptable, and D is a level at which workability is unacceptable.

A: No cracks are observed, or cracks are generated, but the range of cracks is less than 25% of the length of the long side. B: The range of cracks is the long side. C: The range where the crack is generated is within the range of 50% or more and less than 75% of the length of the long side D: The crack is generated The range is 75% or more of the length of the long side

(I) Reworkability The obtained film 23 was laminated on both sides of the polarizing film with an adhesive and bonded to produce a polarizing plate. After the polarizing plate was bonded to the glass substrate, it was peeled off from the glass substrate. The degree of unremoved film 23 on the glass substrate was visually confirmed, and reworkability was evaluated based on the following criteria. In the following criteria, A to C are levels at which reworkability is acceptable, and D is a level at which reworkability is unacceptable.

A: No peeling residue is confirmed. B: Very little peeling residue is observed. C: There is slight peeling residue, but there is no practical problem. D: There is much peeling residue.

  A partition member (not shown) is provided inside the wet film forming apparatus 17 so as to create a pressure difference between the first space and the second space, and the second space is decompressed to a pressure 10 Pa lower than the atmospheric pressure, The conveyance path of the wet film 16 was convex on the second space side. The pressure in the first space is equal to the atmospheric pressure. Others are the same as in the first embodiment.

  In the embodiment using the solution casting apparatus shown in FIG. 1, that is, the path control unit 36 of FIG. 2, the second space was decompressed to a pressure 30 Pa lower than the atmospheric pressure. That is, the differential pressure P2-P1 obtained by subtracting the pressure P1 in the first space equal to the atmospheric pressure from the pressure P2 in the second space is −30 Pa. The convex shape was formed on the 2 space side. The stripping roller 33 is a driving roller. Accordingly, the film 23 was manufactured by adjusting the rotation speed ratio between the drum 29 and the peeling roller 33 so that the peeling position PP becomes constant.

  Using the path control unit 36, the second space is depressurized more than the first space (the differential pressure P2-P1 is −100 Pa), the conveyance path of the wet film 16 is convex toward the second space, and θ1 is 80 °. did. The pressure in the first space is equal to atmospheric pressure. Others were carried out in the same manner as in Example 3.

  The second space was depressurized more than the first space (the differential pressure P2-P1 was −30 Pa) using the path control unit 36, and the conveyance path of the wet film 16 was convex toward the second space. The pressure in the first space is equal to atmospheric pressure. The speed ratio between the drum 29 and the peeling roller 33 was adjusted by changing the speeds of the drum 29 and the peeling roller 33 so that the angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the peeling position PP was 30 °. Others were carried out in the same manner as in Example 3.

  The second space was depressurized more than the first space (the differential pressure P2-P1 was −30 Pa) using the path control unit 36, and the conveyance path of the wet film 16 was convex toward the second space. The pressure in the first space is equal to atmospheric pressure. The speed ratio between the drum 29 and the peeling roller 33 was adjusted by changing each speed of the drum 29 and the peeling roller 33 so that an angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the peeling position PP was 80 °. Others were carried out in the same manner as in Example 3.

  The second space was depressurized more than the first space (the differential pressure P2-P1 was −30 Pa) using the path control unit 36, and the conveyance path of the wet film 16 was convex toward the second space. The pressure in the first space is equal to atmospheric pressure. The speed ratio between the drum 29 and the peeling roller 33 was adjusted by changing the speeds of the drum 29 and the peeling roller 33 so that the angle θ1 formed between the peripheral surface 29a of the drum 29 and the wet film 16 at the peeling position PP was 90 °. Others were carried out in the same manner as in Example 3.

[Comparative example]
A film was produced by the cooling gelation casting method with the path control unit 36 removed from the solution casting apparatus 10 of FIG. The pressure difference between the first space and the second space was 0 (zero), and the wet film transport path from the drum 29 toward the peeling roller 33 was a straight path as indicated by symbol A in FIG. The speed ratio between the drum 29 and the peeling roller 33 was adjusted by changing the speeds of the drum 29 and the peeling roller 33 so that the angle θ2 formed between the peripheral surface 29a of the drum 29 and the wet film at the peeling position PP was 30 °.

  Regarding each film 23 obtained in Example 2 to Example 7 and the film obtained in Comparative Example, the processability and reworkability were evaluated by the same method and standard as in Example 1, respectively.

DESCRIPTION OF SYMBOLS 10 Solution casting apparatus 16 Wet film 17 Wet film formation apparatus 23 Film 29 Drum 32 Casting film 33 Stripping roller 36 Path control part 55 Chamber 72 Winding area

Claims (3)

A cast film formed by continuously casting a dope in which a polymer is dissolved in a solvent on a support is cooled and solidified, and peeled off in a state where the solvent remains, thereby forming a wet film, and the wet film In a solution casting method for producing a film by drying,
The wet film is wound around a peripheral surface of a roller provided on the opposite side of the support with respect to the transport path of the wet film, the longitudinal direction of the support being aligned with the width direction of the casting surface of the support. Hang and peel off the cast film by transporting the wet film,
When the space on one film surface of the wet film peeled off from the support is a first space and the space on the other film surface is a second space, a transport path for the wet film toward the roller is provided. A suction device sucks the gas in the second space upstream from the roller so as to protrude toward the second space, and the gap between the roller and the peeling position where the casting film is peeled off from the support. The solution casting method, wherein the pressure in the second space upstream from the roller is made smaller than the pressure in the first space by reducing the pressure in the second space . The suction device includes a chamber for partitioning the second space to be decompressed from an external space, and controls a transport path of the wet film toward the roller by adjusting a pressure in the chamber. The solution casting method according to claim 1 . 3. The solution-made product according to claim 2 , wherein an angle θ <b> 1 formed by the surface of the support and the wet film at the stripping position is set in a range of 30 ° to 80 ° by controlling the path. Membrane method.

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