JP2008012839A - Manufacturing process of polymer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a polymer film having reduced unevenness in thickness and excellent optical characteristics with a good productivity. <P>SOLUTION: A dope is cast on a continuously rotating cast drum 32 through a casting die 21. The cast drum 32 with the cooled surface cools and gelatinizes the dope to form a gelatinous cast film 12. The cast film 12 moves on the rotating cast drum 32 and is fed into the gap formed between the surface of the cast drum 32 and the surface of the thickness correction roller 38. One side of the cast film 12 the other side of which is supported on the cast drum 32, is pressed with the thickness correction roller 38 so that the uneven thickness of the cast film 12 is corrected. A wet film 15 formed by stripping off a cast film 12 from the cast drum 32 is fed to a transit 17 and a tenter 21 and is dried, to form a film 20. Thus, the film 20 with reduced unevenness in thickness is manufactured with a good productivity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  In recent years, the demand for optical films used in image display devices such as liquid crystal display devices has increased. An optical film is a film having an optical function that is used for the purpose of ensuring high display quality of an image display device. For example, a protective film for a polarizing plate or a process in which light passes through a liquid crystal. Examples thereof include a retardation film that corrects the distortion (birefringence) of light by the retardation of the film (shift of light) and realizes an increase in viewing angle and an improvement in luminance. As such an optical film, a polymer film is mainly used because of its advantages such as high transparency and good workability, while it can be easily reduced in weight and thickness.

  The polymer film used for optical films has excellent transparency, durability, including heat resistance and weather resistance, and high display quality such as resolving power and contrast. It is required that the film is difficult to be scratched (abrasion resistance), has a high retardation value, and the like, and it is important that these characteristics are ensured uniformly in the plane.

  Generally, as a method for producing a polymer film, a melt film-forming method in which a polymer that is a main raw material of the film is heated and melted, and a solution that uses a dope that is a mixed solution obtained by mixing a polymer with a solvent, an additive, or the like And a film forming method. However, in the melt film forming method, there is a possibility that the polymer is deteriorated by heating and the transparency of the film is lowered. Therefore, the solution film forming method is mainly used as a method for manufacturing an optical film. In the solution casting method, a dope is cast on a traveling support to form a cast film, and then the peeled cast film is dried by a drying means to obtain a polymer film. In the following description, a cast film from peeling off from a support to drying to form a film is referred to as a wet film.

  In the solution casting method, the thickness of the casting film or the wet film is likely to be uneven due to the vibration of the film forming apparatus or the flow of wind. However, when such thickness non-uniformity, that is, unevenness in thickness occurs, the value of appearance decreases, and further, unevenness in optical characteristics corresponding to the unevenness in thickness occurs, resulting in a significant decrease in display quality. It is a problem.

Therefore, as a solution casting method for producing a polymer film with reduced thickness unevenness, for example, in Patent Document 1, a decompression chamber is provided in the vicinity of the discharge port for casting the dope, A method for adjusting the dope casting speed has been proposed. Patent Document 2 proposes a method in which a decompression chamber is provided in the vicinity of the discharge port, and the ribbon-like dope flow formed between the discharge port and the support, that is, the length of the casting bead is adjusted. Patent Document 3 proposes a method for producing a polymer film with reduced thickness unevenness by using a discharge port with an adjusted inner diameter and casting a solvent simultaneously with the dope. ing.
JP 2000-301588 A JP 2001-018241 A JP-A-2005-212193

  In Patent Documents 1 and 2, the casting bead having a uniform thickness is obtained by reducing the pressure in the vicinity of the casting bead using a decompression chamber and reducing the influence of wind flow and apparatus vibration to form a stable casting bead. ing. In Patent Document 3, the dope and the solvent are cast at the same time, so that the dope solidified product (skinning) that inhibits the stability of the casting bead is suppressed, and a casting film having a uniform film thickness is obtained. It is a method of forming. However, in any of the above methods, it is difficult to produce a polymer film that satisfies the reduction level of thickness unevenness required with the recent increase in size and definition of liquid crystal display devices. Furthermore, when producing a polymer film for optical use, it is naturally necessary to ensure excellent optical properties, but in addition, it is also important to ensure excellent productivity. In this respect as well, none of the above methods can solve the above problem. Therefore, it is desired to propose a method capable of producing a polymer film with excellent productivity while reducing thickness unevenness.

  Accordingly, an object of the present invention is to provide a method for producing a polymer film that can be used for optical applications with excellent productivity while reducing thickness unevenness as much as possible.

  The method for producing a polymer film of the present invention comprises a cast film forming step of casting a dope containing a polymer and a solvent on a support having a cooled traveling surface, and forming a cast film. A drying step of drying the cast film after peeling off to form a polymer film, and the temperature of the peripheral surface is from one side of the cast film containing the solvent in a proportion of 200% by weight or more and 300% by weight or less. It is characterized by pressing a thickness correction roller of −20 ° C. or more and 10 ° C. or less.

  It is preferable to press the thickness correction roller against one side of the casting film on the support. It is preferable to press the thickness correcting roller against one side of the cast film after being peeled off while being supported by a plurality of pass rollers.

  The surface tension of the thickness correction roller is preferably 30 mN / m or more and 33 mN / m or less. The thickness correction roller is a drive roller, and preferably rotates at the same speed as the support or the pass roller. Moreover, it is preferable that the surface temperature of said support body or pass roller is -20 degreeC or more and 10 degrees C or less.

  The present invention makes it possible to produce a polymer film that can be used for optical applications with excellent productivity while reducing thickness unevenness. Moreover, when the polymer film obtained by this invention is used for image display apparatuses, such as a liquid crystal display device, the optical nonuniformity is improved and the outstanding image quality can be ensured.

  Next, the manufacturing method of the polymer film which concerns on this invention is demonstrated, showing embodiment. In addition, the form given here is an example of the present invention, and does not limit the present invention.

  FIG. 1 is a schematic view of a film manufacturing facility 10 used in the present embodiment. In the film production facility 10, a dope is cast on a traveling support to form a casting film 12, and the casting film 12 is peeled off from the support to form a wet film 15. After that, the transfer part 17 for drying the wet film 15 while it is transported, the tenter 21 for drying the wet film 15 to form the film 20, and the drying for sufficiently promoting the drying of the film 20 A chamber 22, a cooling chamber 23 for cooling the film 20, and a winding chamber 24 for winding the film 20 in a roll shape are provided. The film production facility 10 is connected to a dope production facility 26 through a pipe 25, and the dope is appropriately sent from the dope production facility 26.

  The casting chamber 13 includes a feed block 30 for merging the dope, a dope discharge port, a casting die 31 for casting the dope on the support, and a casting film. In order to support the casting drum 32 as a support, the refrigerant supply device 33 for supplying the refrigerant used to adjust the surface temperature of the casting drum 32, and the casting film 12 peeled off from the support. Stripping roller 34, a condenser (condenser) 35 for condensing and liquefying the solvent gas floating in the casting chamber 13, a recovery device 36 for recovering the liquefied solvent, and the interior of the casting chamber 13 A temperature control device 37 for adjusting the temperature is provided. Further, in the vicinity of the casting drum 32, a thickness correcting roller 38 for correcting thickness unevenness of the casting film 12 is disposed.

The shape, material, size and the like of the casting die 31 are not particularly limited, but it is preferable to use a coat hanger type in order to keep the dope width to be cast substantially uniform. The width is preferably about 1.1 to 2.0 times the width of the film 20 as the final product for the purpose of safely forming a cast film having a desired width. . Further, it is preferable to use precipitation hardening type stainless steel as the material from the viewpoint of durability, heat resistance, corrosion resistance and the like. Furthermore, those having corrosion resistance that do not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months are preferable. However, from the viewpoint of corrosion resistance, those having corrosion resistance substantially equivalent to that of SUS316 in a forced corrosion test with an aqueous electrolyte solution can also be suitably used. In order to suppress thermal damage, it is preferable to use a material having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. Further, in order to form a casting film having excellent flatness, it is preferable to use a casting die 31 whose surface is polished to reduce unevenness.

A cured film is preferably formed at the tip of the dope discharge port of the casting die 31 for the purpose of improving wear resistance. The method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and nitriding treatment. Here, when ceramics are used as the cured film, grinding is possible, and the porosity is low, and the brittleness and the corrosion resistance are excellent, and the adhesiveness to the casting die 31 is excellent. What is inferior to adhesiveness with respect to dope to cast is preferable. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _3, etc. Among them, WC is preferably used. The WC coating can be performed by a thermal spraying method.

  It is preferable to attach a solvent supply device (not shown) to the end of the discharge port and supply a solvent for solubilizing the dope to be cast to both ends of the casting bead and the gas-liquid interface between the discharge port and the outside air. Thereby, since the dope discharged from the discharge port can be prevented from being locally dried and solidified, a stable casting bead can be formed, so that irregularities generated in the casting film 12 can be formed. Can be reduced. Moreover, since the possibility that the solidified dope is contained as a foreign substance in the casting bead or the casting film 12 can be eliminated, the film 20 having excellent transparency can be obtained. The solvent is not particularly limited as long as it is a compound having a composition capable of dissolving the dope. For example, 86.5 parts by weight of dichloromethane, 13 parts by weight of acetone, The mixture which mixed n-butanol and 0.5 weight part is mentioned. And when supplying the above mixture, using a pump with a pulsation rate of 5% or less, the supply amount is in the range of 0.1 to 1.0 mL / min for each side of the end of the discharge port. It is preferable to supply so that it becomes.

  The casting die 31 is attached with a decompression chamber 39 for decompressing the vicinity of the casting die 31. The decompression chamber 39 is provided with a jacket (not shown) that can maintain the internal temperature within a predetermined range, and the internal temperature is adjusted to be substantially constant when the dope is cast. To do.

  A driving device (not shown) is attached to the casting drum 32, and is continuously rotated while its rotational speed is controlled by this driving device. In addition, a flow path (not shown) for a cooling solvent (refrigerant) is formed inside the casting drum 32, and the refrigerant is supplied from the refrigerant supply device 33 into the flow path to be circulated or passed. Thus, the surface temperature is cooled within a desired range. The thickness correction roller 38 is provided with a temperature adjustment function for adjusting the surface temperature.

  The crossover part 17 is provided with a plurality of pass rollers 17a for supporting the wet film 15 and a drying device 40 for supplying drying air whose temperature is adjusted toward the wet film 15 to be conveyed.

  Inside the tenter 21, a pair of rails (not shown) previously arranged at desired intervals along the conveyance path of the wet film 15, and a plurality of pieces for holding the wet film 15. And a chain (not shown) to which the pins are attached. This chain is wound around the above-mentioned rail, and has a mechanism for traveling according to the rail. Thereby, the wet film 15 fixed with the pin is conveyed with the movement of the chain. In addition, since the rail interval is increased or reduced, the tenter 21 is composed of a plurality of sections having different rail intervals.

  At the downstream side of the tenter 21, an ear-cleaving device 42 for cutting off both side ends of the film 20 is provided. Further, a crusher 43 for pulverizing both side ends of the film 20 cut earlier as chips is connected to the ear-cut device 42.

  In the drying chamber 22, a plurality of rollers 45 for winding and transporting the film 20, an adsorption / recovery device 47 for adsorbing and collecting solvent gas floating inside the drying chamber 22, and the temperature inside the drying chamber 22 And a temperature adjusting device 48 for adjusting the temperature. Further, downstream of the cooling chamber 23, a forced static eliminating device 50 for setting the charged voltage of the film 43 within a predetermined range and a knurling application roller 51 for applying knurling to the film 20 are provided. Further, the winding chamber 24 is provided with a winding roller 54 and a press roller 55 for winding the film 20.

  A method for producing a polymer film using the film production equipment 10 will be described.

  The dope prepared in advance in the dope manufacturing facility 10 is sent to the feed block 30 through the pipe 25. After the dope is sent from the feed block 30 to the casting die 22, the dope is discharged from the discharge port of the casting die 22 toward the continuously rotating casting drum 32.

  The casting drum 32 is circulated or passed after the refrigerant adjusted to a predetermined temperature is sent from the refrigerant supply device 24 into the flow path formed therein, so that the surface of the casting drum 32 has a desired temperature range. It is cooled inside. At the time of casting the dope, the surface temperature of the casting drum 23 is preferably -20 ° C or higher and 10 ° C or lower. When the dope is cast on such a casting drum 32, the dope is cooled efficiently and effectively, and the gel-like casting film 12 is formed in a short time. Moreover, the casting drum 32 of this embodiment is adjusted so that the surface temperature may be −5 ° C. The speed fluctuation of the casting drum 32 is preferably 3% or less, and the casting drum 32 immediately below the casting die 31 forms a stable casting bead or a casting film 12 having excellent flatness. Therefore, it is preferable to adjust the vertical position fluctuation to 500 μm or less.

  The temperature of the dope to be cast is preferably 20 to 50 ° C. Thereby, the efficiency of cooling and gelating the dope on the casting drum 23 can be improved. In addition, it is preferable that the film thickness of the cast film 12 to form is 20-150 micrometers in film thickness of the film 20, Especially preferably, it is 25-100 micrometers.

  The casting film 12 on the casting drum 32 is further cooled over time, and gelation is promoted. In the present embodiment, the solvent that evaporates from the casting film 12 and floats inside the casting chamber 13 is condensed and liquefied by the condenser 35 during the formation of the casting film 12, and then the recovery device 36. To collect. Here, a regeneration device (not shown) is connected to the recovery device 36 to regenerate the recovered solvent. In addition, since this reproduction | regeneration solvent can be used as the solvent for dope preparation, it becomes possible to aim at reduction of raw material cost.

  While casting the dope, it is preferable to reduce the pressure behind the casting bead at (atmospheric pressure −2000 Pa) or more (atmospheric pressure −10 Pa) by the decompression chamber 39. Thereby, the flow of the wind causing the unevenness of the casting bead is reduced, and the casting bead is appropriately pulled backward, so that a stable casting bead can be formed. As a result, the casting film 12 can be formed while suppressing the occurrence of unevenness, and as a result, the film 20 with reduced thickness unevenness can be obtained. Moreover, it is preferable that the internal temperature of the decompression chamber 39 is adjusted to be substantially constant at all times by a built-in temperature adjustment function. In addition, although said temperature is not specifically limited, It is preferable that it is more than the condensation point of the solvent used for dope. The internal temperature of the casting chamber 13 is adjusted to be substantially constant in the range of −10 to 57 ° C. by the temperature control device 37 at all times.

  The casting film 12 moves according to the rotation of the casting drum 32. Then, as shown in FIG. 2, the sheet is fed into a gap A-A 'provided at a desired distance D1 between the surface of the casting drum 32 and the surface of the thickness correction roller 38. At this time, the surface temperature of the thickness correction roller 38 is adjusted so as to be −20 ° C. or more and 10 ° C. or less, and the gap A-A ′ contains a solvent containing 200% by weight or more and 300% by weight or less. The casting film 12 is fed.

  The casting film 12 passes through the gap A-A ′ so as to be sandwiched between the casting drum 32 and the thickness correction roller 38. Since the casting film 12 contains a large amount of solvent as described above, it is easily deformed and the film thickness is changed by being sandwiched between the gaps A-A ′ to which D1 is fixed. At this time, since the film thickness portion larger than D1 moves to a position where the film thickness is smaller than D1, the film thickness is adjusted to be substantially equal to D1. As a result, it is possible to obtain a casting film 12 whose film thickness is substantially equal to the interval D1, and in which uneven thickness is corrected efficiently and effectively including planar irregularities.

  However, since the casting film 12 having a residual solvent amount exceeding 300% by weight is unstable because gelation does not proceed until it has self-supporting property, when the thickness correcting roller 38 is pressed, the casting film 12 is pressed against the roller. 12 adheres and thickness unevenness worsens. On the other hand, even if the thickness unevenness correcting roller 38 is pressed against the casting film 12 having a residual solvent amount of less than 200% by weight, the shape hardly changes, so that it is difficult to obtain the effect of correcting the thickness unevenness. Further, when the thickness correcting roller 38 having a surface temperature exceeding 10 ° C. is pressed against the casting film 12, the temperature difference from the casting film 12 formed by cooling gelation is large. There is a risk of damage. On the other hand, when the surface temperature of the thickness correction roller 38 is lower than −20 ° C., solvent gas or the like floating around may be condensed on the surface. If the roller on which the condensation has occurred in this way is pressed against the casting film 12, the surface of the casting film 12 is damaged, which is not suitable. The surface temperature of the thickness correction roller 38 pressed against the casting film 12 may be adjusted as appropriate within the above range, but in order not to inhibit the cooling gelation of the casting film 12 or to cause thermal damage, It is preferable to adjust so that the difference with the surface temperature of the casting drum 32 becomes small.

  Regardless of the casting film 12, the thickness correcting roller 38 can also obtain an excellent correction effect of thickness unevenness by pressing against one side of the wet film 15 having a predetermined residual solvent amount on which one side is supported. FIG. 3 shows an example of a form in which the thickness correction roller 38 according to the present invention is pressed against the wet film 15. When pressing against the wet film 15, as shown in FIG. 3, an arbitrary one is selected from a plurality of pass rollers 17 a arranged at the crossover portion 17, and a thickness correcting roller 38 may be provided above the pass roller 17 a. . In this case, the thickness correcting roller 38 is disposed with a gap BB ′ so that the surface of the pass roller 17a and the surface of the thickness correcting roller 38 have a predetermined distance D2.

  In this case, the wet film 15 is conveyed downstream while being supported by the pass roller 17a, and is fed into the gap BB '. As a result, the wet film 15 is sandwiched between the pass roller 17a and the thickness correction roller 38, so that the pressing force by the thickness correction roller 38 is applied to one surface thereof, and the thickness unevenness of the wet film 15 can be corrected efficiently and effectively. As a result, it is possible to obtain a wet film 15 having a film thickness substantially equal to D2 and reduced thickness unevenness. The residual solvent amount of the wet film 15 fed into the gap BB ′ and the surface temperature of the thickness correcting roller 38 are the same as the conditions described above, and the description thereof is omitted here.

As described above, when the distances D1 and D2 between the gaps AA ′ and BB ′ through which the casting film 12 and the wet film pass are regulated, the thickness correcting roller 38 with respect to one surface of the casting film 12 or the wet film 15 is controlled. Since the pressing pressure can be controlled, it is possible to easily adjust the degree of correction of thickness unevenness. Here, in order to obtain a high effect of correcting the thickness unevenness, the pressure applied by the thickness correction roller 38 is set to 4.9 × 10 ⁴ N / m ² or more and 4.9 × 10 ⁶ N / m ² or less. preferable. Moreover, it is preferable that the surface tension of the thickness correction roller 38 at the time of pressing is 30 mN / m or more and 33 mN / m or less. This makes it possible to correct the thickness unevenness without scratching the surface of the casting film 12 or the wet film 15.

  The thickness correcting roller 38 is a drive roller and is preferably rotated at the same speed as the casting drum 32 or the pass roller 17a. Accordingly, the casting film 12 and the wet film 15 can be efficiently sandwiched between the casting drum 32, the pass roller 17a, and the thickness correcting roller 38 while suppressing the biting failure.

  Further, as the thickness correction roller 38, it is preferable to use a crown roller 60 whose diameter is gradually reduced from the center toward the both side ends as shown in FIG. 4, and the maximum outer diameter a1 and the minimum outer diameter a2 of the diameters are used. The difference is preferably 1 mm or more and 5 mm or less. When the crown roller 60 having such a configuration is used, the casting film 12 and the wet film 15 can be firmly sandwiched between the casting drum 32, the pass roller 17a, and the thickness correcting roller 38. The correction effect is obtained. The width W (mm) of the crown roller 60 is not particularly limited, and may be appropriately selected according to the widths of the casting film 12 and the wet film 15.

  The cast film 12 whose thickness unevenness has been corrected and whose film thickness has been adjusted is peeled off from the casting drum 32 while being supported by the stripping roller 34, thereby forming a wet film 15. In addition, it is preferable that the wet film 15 immediately after formation contains a solvent of 10 wt% or more and 200 wt% or less based on the solid content.

  While the wet film 15 is fed to the crossover part 17 and conveyed while being supported by the plurality of pass rollers 17a, the drying is accelerated by the drying air adjusted to a desired temperature supplied from the drying device 40. The temperature of the drying air is preferably substantially constant in the range of 20 ° C. to 250 ° C. However, the temperature of the drying air is not particularly limited, and may be arbitrarily determined within the above range in consideration of the raw material species such as the polymer and additive used for the dope and the production rate. In the transition section 17, if the rotational speed of the pass roller 17 a disposed near the exit of the transition section 17 is faster than that of the pass roller 17 disposed near the entrance of the transition section 17, an appropriate tension is applied to the wet film 15. In addition to being able to be transported without generating wrinkles or wrinkles, it is possible to control the retardation value by applying tension to the wet film 15 in a state with a large amount of residual solvent. Since an effect can also be acquired, it is preferable.

  The wet film 15 whose drying has been promoted is fed into the tenter 21. Inside the tenter 21, a plurality of pins are inserted into both end portions of the wet film 15 that has reached a predetermined position to fix the wet film 15, and then adjusted to different temperatures as the chain travels according to the rail. The inside of the section is conveyed. As a result, drying of the wet film 15 is promoted, so that the film 20 is obtained. Further, when drying is performed stepwise at different temperatures in this manner, the solvent does not rapidly evaporate from the wet film 15, so that drying can be promoted while reducing shape changes such as shrinkage due to volume reduction. Furthermore, in this embodiment, the wet film 15 is conveyed while changing the width of the rails, whereby the tension in the width direction is controlled and stretched and relaxed. Thereby, since the molecular orientation in the wet film 15 can be controlled, the film 20 having a desired retardation value can be obtained.

  The process of stretching or relaxing the wet film 15 in the width direction can also be performed at the transition part 17. At this time, it is preferable to stretch at least one direction of the transport direction and the width direction of the wet film 15 at a ratio of 0.5 to 300% with respect to the width before stretching. It should be noted that the drying temperature is preferably kept substantially constant while the tension is applied to the wet film 15 by the crossover part 17 or the tenter 21. Thereby, it can prevent that a difference arises in the grade of extending | stretching by the difference in drying temperature.

  The film 20 is fed into the ear-cutting device 42, and both end portions thereof are cut. Thereby, since the stab wound of the pin which arose in the film 20 previously can be removed, the film 20 excellent in planarity can be obtained. In addition, although the process which cuts off the both ends of the film 20 can also be abbreviate | omitted, it is preferable to carry out in any one from the casting chamber 13 to the winding chamber 24. FIG.

  The film 20 is fed into a preliminary drying chamber (not shown) provided between the ear-clipping device 42 and the drying chamber 22 and preliminarily dried. Thus, when preliminary drying is performed on the film 20 before being dried in the drying chamber 22, it is possible to prevent the film surface temperature of the film 20 from rapidly increasing in the drying chamber 22 and causing a shape change.

  The film 20 is fed into the drying chamber 22 whose internal temperature is adjusted by the temperature adjusting device 48. In the drying chamber 22, drying of the film 20 is sufficiently promoted while being wound around a plurality of rollers 45 and conveyed. Although the internal temperature of the drying chamber 22 is not particularly limited, the film surface temperature of the film 20 is used for the purpose of effectively evaporating the solvent without causing thermal damage to the polymer constituting the film 20. Is preferably adjusted to be 60 ° C. or higher and 145 ° C. or lower. In the present embodiment, the adsorption recovery device 47 is connected to the drying chamber 22 to recover the solvent gas evaporated from the film 20 at the time of drying. Then, after removing the solvent component, the drying chamber 22 is again supplied with the drying air. Supply as. Thereby, the manufacturing cost can be reduced by reducing the energy cost.

  The dried film 20 is fed into the cooling chamber 23. In the cooling chamber 23, the film 20 is gradually cooled so that it finally becomes substantially room temperature. Thereby, since it can suppress that wrinkles, a wrinkle, etc. generate | occur | produce on the surface of the film 20 by rapid temperature change, it becomes possible to obtain the film product excellent in planarity. In addition, the method of cooling the film 20 may be natural cooling, or a cooling device may be attached to the cooling chamber 23 to adjust the internal temperature thereof, and is not particularly limited. Further, if a humidity control chamber (not shown) is provided between the drying chamber 22 and the cooling chamber 23 and the film 20 is conditioned, and then sent to the cooling chamber 23, wrinkles and the like are generated on the surface of the film 20. If it is, it is preferable because an excellent wrinkle stretching effect can be obtained.

  The film 20 having a substantially room temperature is fed into the forced static eliminator 50, and the charged voltage is adjusted to be within a predetermined range (for example, −3 to +3 kV). Although FIG. 1 shows a mode in which the installation location of the forced static elimination device 50 is on the downstream side of the cooling chamber 23, the present invention is not limited to this position. Further, the film 20 is imparted with knurling by embossing the both end portions thereof by a knurling roller 51.

  Finally, the film 20 is fed into the take-up chamber 24 and taken up by the take-up roller 54 while adjusting the tension at the time of take-up with the press roller 55. Thereby, a roll-shaped film product is completed. The tension during winding is preferably gradually changed from the start to the end of winding. Moreover, it is preferable that the length of the film 20 wound up shall be at least 100 m or more in a conveyance direction, and it is preferable that the width direction is 1400-1800 mm. However, the present invention can obtain an effect even when it is larger than 1800 mm. Furthermore, the thickness of the completed film 20 is preferably 20 to 500 μm. More preferably, the thickness is 30 to 300 μm, and particularly preferably 35 to 200 μm. However, the present invention is also effective when producing a thin film having a film thickness of 15 to 100 μm.

  In the above description, the casting drum is used as the support. However, the support is not particularly limited as long as the surface can be cooled in a predetermined temperature range. For example, a casting band that is wound around a pair of drive rollers and travels endlessly can be used. Further, although the width and material of the support are not particularly limited, in order to form a stable casting film without excess or deficiency, the width of the support is 1.1 to 1.1 with respect to the casting width of the dope. About 2.0 times is preferable. Further, the material is preferably made of stainless steel from the viewpoint of corrosion resistance and the like, and more preferably made of SUS316 having sufficient corrosion resistance and strength. Furthermore, in order to form a cast film having excellent flatness, it is preferable that the surface is polished as much as possible.

  In the present embodiment, a pin type tenter having a plurality of pins is shown as the tenter 21, but the form of the tenter in the present invention is not particularly limited. For example, a clip or the like instead of the pin is used as a holding unit. An attached clip-type tenter can also be used. However, the wet film, which is a gel film formed by cooling and gelling the dope, is very unstable, so it is difficult to grip with a clip. It is preferable to use a mold tenter.

  The residual solvent amount in the present invention is the residual amount of solvent contained in a cast film, a wet film, or a film. However, when various kinds of solvents are present in the above-mentioned object, the sum of these solvents is defined as the residual solvent amount. The amount of the residual solvent is based on the dry amount, and a sample is taken from an object whose residual solvent amount is to be measured. The weight of the sample is x, and the weight after the sample is completely dried is y. Is a value calculated by {(xy) / y} × 100.

  Hereinafter, the dope according to the present invention will be described. The dope is a mixture obtained by mixing and preparing a desired polymer, organic solvent, or additive. In preparing the dope, it is preferable to use a cellulose ester as the polymer. Examples of the cellulose ester include lower fatty acid esters of cellulose such as cellulose triacetate, cellulose acetate propionate, and cellulose acylate butyrate. Among them, it is preferable to use cellulose acylate, and it is particularly preferable to use triacetyl cellulose (TAC). Thus, the film using a cellulose acylate is very excellent in transparency. In the present embodiment, triacetyl cellulose (TAC) is used as the polymer.

Further, among cellulose acylates, those in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies all of the following formulas (a) to (c) are more preferable. In the following formulas (a) to (c), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose, A represents the substitution degree of the acetyl group, and B represents 3 to 3 carbon atoms. 22 is the substitution degree of the acyl group. Moreover, it is preferable that 90 mass% or more of TAC is a particle | grain of 0.1-4 mm. However, the polymer that can be used in the present invention is not limited to cellulose acylate.
(A) 2.5 ≦ A + B ≦ 3.0
(B) 0 ≦ A ≦ 3.0
(C) 0 ≦ B ≦ 2.9

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

  The total degree of acylation substitution, that is, the value of 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, the value of DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the ratio of the hydrogen of the hydroxyl group at the 2-position in the glucose unit (hereinafter referred to as the acyl substitution degree at the 2-position), and DS3 is the hydroxyl group at the 3-position in the glucose unit. This is the rate at which hydrogen is substituted by an acyl group (hereinafter referred to as the 3-position acyl substitution degree), and DS6 is the rate at which the hydrogen at the 6-position hydroxyl group is substituted by an acyl group in a glucose unit (hereinafter, (Referred to as the degree of acyl substitution at the 6-position).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The sum of the degree of substitution of hydroxyl groups at the 2nd, 3rd and 6th positions by acetyl groups is DSA, and the sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acyl groups other than acetyl groups When DSB is DSB, the value of DSA + DSB is preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88.

  The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Furthermore, the value of DSA + DSB at the 6-position of cellulose acylate is 0.75 or more, more preferably 0.80 or more, and particularly preferably cellulose acylate of 0.85 or more. When such cellulose acylate is used, a dope having excellent solubility can be prepared. When the above cellulose acylate is used and a non-chlorine organic solvent is used, a dope having very excellent solubility, low viscosity and excellent filterability can be prepared.

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

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

  The details of the cellulose acylate that can be used in the present invention are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions also apply to the present invention. be able to.

  As the organic solvent for preparing the dope, it is preferable to use a compound that can dissolve the polymer to be used. In addition, in this invention, since dope means the mixture obtained by melt | dissolving or disperse | distributing a polymer in a solvent, the organic solvent inferior to the solubility with a polymer can also be used. Examples of organic solvents that can be suitably used include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chloroform, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n -Propanol, n-butanol, diethylene glycol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.), ethers (eg, tetrahydrofuran, methyl cellosolve, etc.) and the like. . Further, two or more kinds of solvents may be selected from these solvents and mixed solvents may be used. At this time, it is preferable to use a non-chlorine organic solvent because it is excellent in solubility and a dope having a low viscosity can be prepared.

  Hydrophobic solvents are preferred as the dope preparation solvent, and dichloromethane is most preferred as the hydrophobic solvent. Moreover, as said halogenated hydrocarbon, a C1-C7 thing is used preferably. Furthermore, from the viewpoint of the solubility of the polymer, the peelability of the cast film from the support, the mechanical strength of the film, the optical properties, etc., one or more alcohols having 1 to 5 carbon atoms are mixed with dichloromethane. It is preferable. The content of alcohol is preferably 2 to 25% by weight, more preferably 5 to 20% by weight, based on the entire solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc. Among them, it is preferable to use methanol, ethanol, n-butanol, or a mixture thereof.

  Recently, in order to minimize the influence on the environment, a solvent composition not using dichloromethane has also been proposed. For this purpose, ethers having 4 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are preferably used by being mixed as appropriate. These compounds may have a cyclic structure, and compounds having two or more functional groups of ether, ketone and ester, that is, any of —O—, —CO—, and —COO— are also organic solvents. Can be used as In addition, the organic solvent may have another functional group such as an alcoholic hydroxyl group. In addition, when it has two or more types of functional groups, the carbon atom number should just be in the prescription | regulation range of the compound which has any functional group, and it does not specifically limit.

  Depending on the purpose, the dope may be added with various known additives such as a plasticizer, an ultraviolet absorber (UV agent), a deterioration preventing agent, a slipping agent, and a peeling accelerator. For example, among the above, the plasticizer includes various known plastics such as phosphate ester plasticizers such as triphenyl phosphate and biphenyl diphenyl phosphate, phthalate ester plasticizers such as diethyl phthalate, and polyester polyurethane elastomers. An agent can be used.

  Moreover, it is preferable to add fine particles to the dope for the purpose of preventing adhesion between films or adjusting the refractive index. As the fine particles, a silicon dioxide derivative is preferably used. The silicon dioxide derivative in the present invention includes silicon dioxide and a silicone resin having a three-dimensional network structure. It is preferable to use a silicon dioxide derivative whose surface is alkylated. Fine particles that have been subjected to a hydrophobic treatment such as an alkylation treatment have excellent dispersibility in a solvent, so that a dope can be prepared without agglomeration of the fine particles, and a film can be produced. It is possible to produce a film with few state defects and excellent transparency. As described above, as the fine particles whose surface is alkylated, for example, Aerosil R805 (manufactured by Nippon Aerosil Co., Ltd.) that is commercially available as a silicon dioxide derivative having an octyl group introduced on its surface can be used. it can. In order to obtain a film with excellent transparency while obtaining the effect of adding fine particles, the content of fine particles with respect to the solid content of the dope is preferably 0.2% or less. Further, the average particle diameter is preferably 1.0 μm or less, more preferably 0.3 to 1.0 μm, and particularly preferably 0.4 to 0 so that the fine particles do not hinder the passage of light. .8 μm.

  Since it is preferable to use TAC as a polymer because of its advantages such as excellent transparency, when preparing a dope by mixing the polymer with TAC and further mixing an organic solvent or various additives, the total amount of the dope It is preferable that the content ratio of TAC is 5 to 40% by weight. More preferably, it is 15-30 weight%, Most preferably, it is 17-25 weight%. Moreover, it is preferable that the content rate of an additive (mainly a plasticizer) shall be 1-20 weight% with respect to the whole solid content in dope.

  Various additives and fine particles such as organic solvents, plasticizers, ultraviolet absorbers, deterioration inhibitors, slipping agents, release accelerators, optical anisotropy control agents, retardation control agents, dyes, release agents, etc. The details are described in paragraphs [0196] to [0516] of JP-A-2005-104148, and these descriptions can also be applied to the present invention. Further, it is a method for producing a dope using TAC. For example, materials, raw materials, additive dissolution methods and addition methods, filtration methods, defoaming, and the like are also disclosed in JP-A-2005-104148 [0517]. It is described in detail from paragraph to [0616] paragraph, and these descriptions can also be applied to the present invention.

  In this embodiment, although the form which manufactures a single layer film using 1 type of dope was shown, this invention is a multilayer structure which has a base layer and the surface layer distribute | arranged so that both surfaces of a base layer may be contact | connected It is also effective when manufacturing films. Thus, when producing a film having a multilayer structure, a plurality of types of dopes for preparing the base layer and the surface layer may be prepared, and these dopes may be cast together from a casting die. Also, the co-casting type is not particularly limited, and a plurality of types of dopes can be cast simultaneously using a feed block or a casting die in which a flow path is formed so as to have a desired layer structure. Alternatively, each dope may be cast on the support sequentially to form a multilayer structure step by step, or these methods may be combined.

  From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for each step, handling method, curling, winding method after flatness correction, solvent recovery method, film recovery method Up to this point, the details are described in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  The performance of the completed film, the degree of curling, the thickness, and the measuring methods thereof are described in paragraphs [1073] to [1087] of JP-A-2005-104148, and these descriptions are also included in the present invention. Can be applied.

  When the completed film is used as an optical film, it is preferable to treat at least one surface. This surface treatment is preferably at least one of vacuum glow discharge treatment, atmospheric pressure plasma discharge treatment, ultraviolet irradiation treatment, corona discharge treatment, flame treatment, acid treatment or alkali treatment.

Moreover, when a desired functional layer is provided on both surfaces or one surface of the film obtained in the present invention as a base, it can be used as a functional film. Examples of the functional layer include an antistatic layer, a cured resin layer, an antireflection layer, an easy-adhesion layer, an antiglare layer, and an optical compensation layer. Among these, at least one layer is preferably provided. For example, when an antireflection layer is provided, a functional film antireflection film capable of obtaining an image antireflection effect of a liquid crystal display device or the like can be obtained. The functional layer preferably contains at least one of additives such as a surfactant, a slip agent, a matting agent, and an antistatic agent. In this case, the content is 0.1 to 1000 mg / m ² is preferable. In addition, the functional layer for forming various functions to the film, the forming method, and the like are described in detail in paragraphs [0890] to [1072] of JP-A-2005-104148, and these descriptions are also described in this book. It can be applied to the invention.

  The film obtained by the present invention has characteristics such as a high retardation value and excellent transparency, although the thickness unevenness is very small. Therefore, it is particularly useful as a protective film for a polarizing plate which is a main constituent member of a liquid crystal display device. Regarding the use of the film obtained by the present invention, such as use as a protective film, in Japanese Patent Application Laid-Open No. 2005-104148, for example, from [1088] paragraph to [1265] paragraph, a TN type, STN liquid crystal display device is used. The type, VA type, OCB type, reflective type, and other examples are described in detail, and this description can also be applied to the present invention.

  Examples of the present invention and comparative examples will be shown below to specifically describe the present invention. However, the present invention is not limited to these examples and comparative examples.

  In Example 1, using the dope prepared by the following method with the dope manufacturing facility 26, a film was manufactured with the film manufacturing facility 10 shown in FIG.

  Add a retardation control agent (N-N-di-m-toluyl-N-P-methoxyphenyl-1,3,5-triazine-2,4,6-triamine) to the mixture of the following raw materials. The dope was prepared by stirring. In addition, the retardation control agent was added so that it might become 4.0 weight% with respect to the total weight, when it was set as the film.

[Dope raw material]
Cellulose triacetate (powder having a substitution degree of 2.84, a viscosity average polymerization degree of 306, a water content of 0.2% by weight, a viscosity of 6% by weight in a dichloromethane solution of 315 mPa · s, an average particle diameter of 1.5 mm, and a standard deviation of 0.5 mm ) 100 parts by weight dichloromethane 320 parts by weight methanol 83 parts by weight 1-butanol 3 parts by weight plasticizer A (triphenyl phosphate) 7.6 parts by weight plasticizer B (diphenyl phosphate) 3.8 parts by weight UV agent a: 2 (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole 0.7 parts by weight UV agent b: 2 (2'-hydroxy-3', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole 0.3 parts by weight of citric acid ester mixture (citric acid, monoethyl ester, diethyl ester, trie Glycol ester mixture) 0.006 parts by weight of fine particles (silicon dioxide (average particle size 15 nm), Mohs hardness: about 7) 0.05 parts by weight

[Production of film]
First, an appropriate amount of dope was sent from the dope production facility 26 to the feed block 30 through the pipe 25. Next, the dope was discharged from the discharge port of the casting die 31 onto the casting drum 32 whose surface was adjusted to −5 ° C. At this time, the discharge amount of the dope was adjusted so as to obtain a film 20 having a thickness of 80 μm.

  In this embodiment, the casting die 31 is provided with a jacket (not shown) having a slit having a width of 1.8 m as an ejection port and capable of adjusting the internal temperature. Further, as the casting drum 32, a drum made of SUS316 whose rotation speed can be controlled by a driving device (not shown) was installed immediately below the discharge port of the casting die 31. At the time of film formation, the rotational peripheral speed of the casting drum 32 is set to 100 m / min. The temperature inside the casting chamber 13 was constantly adjusted to 35 ° C. by the temperature control device 37. Further, a heat transfer medium whose temperature is adjusted is fed into the jacket of the casting die 31 to adjust the internal temperature of the casting die 31 so that the temperature of the dope to be cast is 36 ° C., and the feed block 30 and the piping. Etc. also kept the internal temperature at 36 ° C. by using a device having a temperature adjusting function.

As shown in FIG. 2, the casting film 12 is passed through a gap A-A 'in which the distance D1 is adjusted so that the pressing force of the thickness correcting roller 38 against the casting film 12 is 5 × 10 ⁴ N / m ^2. Thus, the casting film 12 was sandwiched between the casting drum 32 and the thickness correction roller 38. At this time, the casting film 12 having a residual solvent amount of 295% by weight was fed into the gap AA ′. The surface tension of the thickness correction roller 38 was 31 mN / m, and the surface temperature was 5 ° C.

The casting film 12 after passing through the gap A-A ′ was peeled off from the casting drum 32 while being supported by the peeling roller 34 to obtain a wet film 15. At this time, the tension applied at the time of stripping is 1 × 10 ² N / m ^2, and the stripping speed is in the range of 10 to 110% with respect to the speed of the casting drum 32 in order to suppress stripping failure. Adjusted. The surface temperature of the peeled wet film 15 was 15 ° C. Then, while the wet film 15 was fed into the crossover part 17 and conveyed while being supported by the plurality of pass rollers 17a, the wet film 15 was dried by sending dry air adjusted to 40 ° C. from the drying device 40. Moreover, in the transfer part 17, the uniaxial stretching was performed to the wet film 15 by providing about 30N tension | tensile_strength in the conveyance direction.

  The wet film 15 that promoted drying was fed into the tenter 21. As the tenter 41, a pin-type tenter provided with a plurality of pins that travel endlessly by traveling of the chain according to the distance between the rails and a plurality of sections equipped with a heating device was used. And after piercing the both ends of the wet film 15 with a plurality of pins, while transporting the inside of each section adjusted to a different temperature as the chain travels, drying of the wet film 15 is promoted to form a film 20. . In the tenter 21, the wet film 15 was stretched in the width direction by adjusting the interval between the rails.

Within 30 seconds from the tenter exit, an ear-cutting device 42 provided with an NT-type cutter was provided, and the film 20 was cut at a position of 50 mm from the both side ends toward the inside. Moreover, the both ends of the cut | disconnected film 20 were sent to the crusher 43 with the cutter blower (not shown), and it grind | pulverized to the chip | tip of about 80 mm < ² > on average. In this example, this chip was reused as a dope preparation raw material together with the TAC powder.

  In this embodiment, a preliminary drying chamber (not shown) is provided between the ear clip device 42 and the drying chamber 22, and the film 20 before being dried at high temperature in the drying chamber 22 is supplied by supplying 100 ° C. drying air. Preheated. Next, the film 20 having a residual solvent amount of 5% by weight was fed into the drying chamber 22. The drying chamber 22 was supplied with drying air whose temperature was adjusted from the temperature adjusting device 48 so that the film surface temperature of the film 20 was 140 ± 40 ° C. Further, while the film 20 was transported at a transport tension of 100 N / m while being wound around a plurality of rollers 45, the film 20 was dried for about 10 minutes until the residual solvent amount finally reached 1% by weight. Further, in the drying chamber 22, after the solvent gas floating inside is recovered by the adsorption recovery device 47 in which the adsorbent is activated carbon and the desorbent is dry nitrogen, the amount of water contained in the solvent gas is 0.3 weight. Moisture was removed until less than or equal to%. This gas was reused as a solvent for dope preparation.

  A humidity control chamber (not shown) is provided between the drying chamber 22 and the cooling chamber 23, and after supplying air with a temperature of 50 ° C. and a dew point of 20 ° C. to the film 20, The film 20 was conditioned by applying air at 90 ° C. and a humidity of 70%, and the curl generated on the film 20 was corrected. Then, after the humidity-controlled film 20 is sent to the cooling chamber 23 and gradually cooled to 30 ° C. or lower, the charged voltage of the film 20 is constantly adjusted to −3 to +3 kV with the forced static elimination device 50, Further, knurling was imparted to both end portions of the film 20 by a knurling imparting roller 51. When applying knurling, the width of knurling is set to 10 mm, and the pressing force by the knurling application roller is adjusted so that the height of the unevenness is 12 μm higher than the average thickness of the film 20, Embossed from.

  Finally, a winding roller 54 (φ169 mm) installed inside the winding chamber 24 is adjusted so that the winding start tension is 300 N / m and the winding end is 200 N / m. The pressing force of the press roller 55 against 54 was set to 50 N / m, and the film 20 was wound up. Thus, a roll-shaped film 20 having a residual solvent amount of 1% by weight and a film thickness of 80 μm was obtained. In the film manufacturing facility 10, the average drying rate of the casting film 12, the wet film 15, and the film 20 was set to 20% by weight / min throughout the entire process.

  The thickness unevenness and optical unevenness of the completed film were measured by the following methods, and evaluation was performed based on the measurement results. In each of Examples and Comparative Examples described later, the completed film is evaluated using this method, but the description in each section is omitted.

[Thickness unevenness]
A cut piece of the produced film was used as a sample, and the thickness unevenness of this sample was measured with a laser interferometer (manufactured by Fujinon Corporation). In addition, the film whose measured value is 1.5 μm or less is a level that can be used as a product, and the smaller the value, the better the level.

[Optical unevenness]
Using the prepared film as a sample, place the sample between a pair of crossed Nicols polarizing plates so that the transmission axis of one polarizing plate and the slow axis of the film coincide with each other. The light unevenness that can be visually recognized due to light leakage was observed. At this time, the case where the unevenness of light could not be confirmed was evaluated as “◯”, and the case where a large amount of unevenness in light was observed was evaluated as “x”. When the optical unevenness is ○, it can be said that the level is satisfactory as a product.

  When the thickness unevenness and the optical unevenness were evaluated by the above method, the thickness unevenness was 0.5 μm and the optical unevenness was ◯, and both values were very satisfactory as the product level.

In the second embodiment, the thickness correction roller 38 is arranged on the pass roller 17a of the crossover portion 17 as shown in FIG. 3, and the wet film 15 is formed in the gap BB 'formed by the pass roller 17a and the thickness correction roller 38. A film was produced in the same manner as in Example 1 except that the film was passed. At this time, the interval D2 was adjusted so that the pressing force of the thickness correction roller 38 against the wet film 15 was 4 × 10 ⁵ N / m ² . Further, the wet film 15 having a residual solvent amount of 280% by weight was fed into the gap BB ′. The surface tension and temperature of the thickness correction roller 38 are the same as those in the first embodiment. As a result of evaluating the thickness unevenness and the optical unevenness in the same manner as in Example 1, the thickness unevenness was 0.5 μm and the optical unevenness was ◯, and both values were very satisfactory as the product level.

In Example 3, as in Example 2, everything was carried out except that the thickness correcting roller 38 was disposed on the pass roller 17 of the crossover part 17 and the wet film 15 was passed through the gap BB ′ having the interval D2. A film was prepared in the same manner as in Example 1. At this time, a cast film having a residual solvent amount of 230% by weight was sent to the distance D2 adjusted so that the pressing force of the thickness correcting roller 38 against the wet film 15 was 3 × 10 ⁶ N / m ² . The rotational peripheral speed of the casting drum 32 is 80 m / min. It was. The surface tension and temperature of the thickness correction roller 38 are the same as those in the first embodiment. As a result of evaluating the thickness unevenness and the optical unevenness in the same manner as in Example 1, the thickness unevenness was 0.7 μm and the optical unevenness was ◯. Both values were very satisfactory as the product level.

  In Example 4, a film having a thickness of 80 μm was prepared in the same manner as Example 2 except that the surface tension of the thickness correction roller 38 was set to 34 mN / m. And as a result of evaluating thickness unevenness and optical unevenness as in Example 1, the thickness unevenness was 1.4 μm and the optical unevenness was Δ, both of which are inferior to Examples 1 to 3, but satisfactory as the product level. A good value was obtained.

[Comparative Example 1]
In Comparative Example 1, a film was produced in the same manner as in Example 1 except that the thickness correction roller 38 was not used. As a result of evaluating the thickness unevenness and the optical unevenness in the same manner as in Example 1, the thickness unevenness was 1.5 μm and the optical unevenness was x, and a satisfactory value as a product level could not be obtained.

[Comparative Example 2]
In Comparative Example 2, a film was produced in the same manner as in Example 3 except that the surface temperature of the thickness correction roller 38 was 15 ° C. As a result of evaluating the thickness unevenness and the optical unevenness in the same manner as in Example 1, the thickness unevenness was 1.7 μm and the optical unevenness was x, and it was not possible to obtain satisfactory values as the product level.

  From the above results, although there are some cases due to the difference in surface tension, when the thickness correction roller with the surface temperature adjusted while pressing the pressure against the film containing a lot of solvent, the thickness unevenness is uniform. It was confirmed that a film excellent in optical unevenness can be produced.

It is the schematic of an example of the film manufacturing equipment concerning this invention. It is the schematic of an example of the casting drum vicinity in which the thickness correction roller used in this embodiment was distribute | arranged. It is the schematic of an example which has arrange | positioned the thickness correction roller concerning this invention in the vicinity of the crossover part. It is the schematic of the crown roller which is an example of the thickness correction roller which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film manufacturing equipment 12 Casting film 15 Wet film 17 Transition part 17a Pass roller 20 Film 32 Casting drum 38 Thickness correction roller 60 Crown roller

Claims (6)

A casting film forming step of casting a dope containing a polymer and a solvent on a support having a cooled traveling surface to form a casting film;
A drying step of drying the cast film after peeling off from the support to form a polymer film,
Production of a polymer film, wherein a thickness correcting roller having a peripheral surface temperature of -20 ° C. or more and 10 ° C. or less is pressed from one side of a cast film containing the solvent in a proportion of 200% by weight or more and 300% by weight or less. Method.   The method for producing a polymer film according to claim 1, wherein the thickness correcting roller is pressed against one side of the casting film on the support.   The method for producing a polymer film according to claim 1 or 2, wherein the thickness correcting roller is pressed against one side of the cast film that has been peeled off while being supported by a plurality of pass rollers.   4. The method for producing a polymer film according to claim 1, wherein the thickness correction roller has a surface tension of 30 mN / m or more and 33 mN / m or less.   The method for producing a polymer film according to any one of claims 1 to 4, wherein the thickness correction roller is a driving roller and rotates at the same speed as the support or the pass roller.   The method for producing a polymer film according to any one of claims 1 to 5, wherein a surface temperature of the support or the pass roller is -20 ° C or higher and 10 ° C or lower.

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