JP4912260B2 - Casting die, solution casting equipment and solution casting method - Google Patents

Description

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

  Polymer films (hereinafter referred to as films) are widely used as optical functional films because of their features such as excellent light transmittance, flexibility, and reduction in weight of thin films. Among them, cellulose ester films using cellulose acylate have toughness and low birefringence, so that liquid crystal display devices (LCDs) that have recently expanded in the market including photographic photosensitive films. ) Is used for an optical functional film such as a protective film of a polarizing plate or an optical compensation film.

  The main film production methods include a melt extrusion method and a solution casting method. The melt-extrusion method is a method in which a polymer is heated and dissolved as it is and then extruded with an extruder to produce a film, which has features such as high productivity and relatively low equipment cost. However, it is difficult to adjust the film thickness accuracy, and because fine lines (die lines) can be formed on the film, it is difficult to produce a high-quality film that can be used for optical functional films. is there. On the other hand, the solution casting method is a method in which a cast film formed by casting a polymer solution (dope) containing a polymer and a solvent on a support has self-supporting properties. In this method, the film is peeled off to form a wet film, and the wet film is further dried to form a film. Compared with the melt extrusion method, the optical functional film is excellent in optical isotropy and thickness uniformity, and a film with few contained foreign substances can be obtained. Therefore, the optical functional film is mainly produced by a solution casting method.

  This solution casting method prepares a polymer solution (hereinafter referred to as a dope) in which a polymer such as cellulose triacetate is dissolved in a solvent containing dichloromethane or methyl acetate as a main solvent. Furthermore, a predetermined additive is mixed with this dope to prepare a dope for casting. This dope is discharged from a casting die to form a casting bead, and a casting film is formed on a support such as a casting drum or an endless band. Then, the casting film is cooled to cause gelling of the casting film, thereby causing the casting film to exhibit self-supporting properties. Thereafter, the cast film is peeled off from the support as a wet film, and the dried wet film is wound up as a film.

Near the surface of the traveling support body, an accompanying wind that flows in the same direction as the traveling direction is generated. When this accompanying air flows into the vicinity of the casting bead formed between the outlet of the casting die and the support, the casting bead vibrates. When the casting bead vibrates, a failure (hereinafter referred to as a thickness unevenness failure) that causes unevenness in the film thickness of the finally obtained film occurs. Patent Document 1 discloses a solution casting method in which a decompression chamber is used to decompress the back side of a casting bead and prevent entrainment air from flowing into the vicinity of the casting bead.
JP 2006-123500 A

  In recent years, with the rapid increase in demand for liquid crystal display devices, a solution casting method with high production efficiency is strongly desired. Therefore, a solution casting method and solution casting equipment that can efficiently produce an optical functional film have been studied.

  However, when the solution film-forming method is performed at a high film-forming speed (for example, 40 m / min or more), a thickness unevenness failure occurs in the longitudinal direction of the obtained film, and the film-forming speed is increased. As a result, it has been found that this thickness unevenness failure occurs more remarkably.

  About the thickness unevenness failure under high-speed film formation, by using the decompression chamber described in Patent Document 1, the amount of decompression on the back side of the casting bead is increased to reduce the inflow of the accompanying air to the vicinity of the casting bead. Although it can be prevented, a turbulent air flow is generated in the vicinity of the casting bead as the amount of decompression increases. And this turbulent air flow can cause not only thickness unevenness failure but also secondary failure such as surface failure where wrinkles occur on the surface of the casting film. The invention described in Patent Document 1 alone is not sufficient.

  As a result of intensive studies, the inventors have found that this thickness unevenness failure is not caused only by the accompanying wind but by the behavior of the dope passing through the casting die.

  The present invention solves the occurrence of uneven thickness failure in a solution casting method, and provides a casting die, a solution casting equipment and a solution casting method capable of efficiently producing a film having a uniform thickness. The purpose is to do.

The present invention supplies a dope containing a polymer and a solvent from a supply port, discharges it from a flow outlet through a slot onto a traveling support, forms a cast film on the support, and the slot has The cross-sectional shape in the direction orthogonal to the outflow direction of the dope is a pair of first inner wall surfaces formed to extend in the first direction, and the second inner direction in the second direction orthogonal to the first direction. In a casting die formed in a slit shape by a pair of second inner wall surfaces formed so as to extend shorter than the wall surface, the first slot portion provided on the downstream side of the supply port; A second slot portion provided downstream of the first slot portion, wherein a flow path width between the first inner wall surfaces is narrower than a flow path width between the first inner wall surfaces of the first slot portion; Provided between one slot portion and the second slot portion; A connection slot portion in which a flow path width between the first inner wall surfaces gradually decreases from the first slot portion side toward the second slot portion side; the first inner wall surface and the second slot of the connection slot portion; And a downstream curved connecting surface having a substantially arcuate cross-section chamfered at a joint portion between the first inner wall surface and a curvature radius of the downstream curved connecting surface is 1 mm or more and 20 mm or less. To do.

It is preferable that an upstream curved connecting surface in which a joint portion between the first inner wall surface of the first slot portion and the first inner wall surface of the connection slot portion is chamfered in a substantially circular arc shape is provided. Moreover, it is preferable that the curvature radius of the said upstream side curved connection surface is 1 mm or more and 20 mm or less.

  It is preferable to provide a low friction layer formed on the first inner wall surface of the connection slot portion and having a smaller dynamic friction coefficient than the first inner wall surfaces of the first slot portion and the second slot portion.

  It is preferable that the main dope and the sub-dope having a viscosity lower than that of the main dope are supplied to the supply port as a laminated dope having a layer in the second direction. A main channel that communicates the main dope supply port to which the main dope is supplied and the supply port; a sub-channel that communicates the sub-dope supply port that supplies the sub-dope and the main channel; A merging portion that is provided in the main flow channel downstream of the communication portion with the flow channel and forms the laminated dope from the main dope that has passed through the main flow channel and the sub dope that has passed through the sub flow channel; It is preferable to provide.

  The traveling speed of the support is preferably 40 m / min or more. The support is preferably a drum that rotates about an axis. Furthermore, it is preferable that the polymer contains cellulose acylate.

  The solution casting apparatus of the present invention includes any one of the casting dies, and a drying device that dries the casting film peeled off from the support to form a film. .

  The solution casting method of the present invention uses any one of the casting dies to flow out the dope onto the support, and form the casting film from the dope on the support. The cast film peeled off from the support is dried.

  According to the present invention, the inner wall surface of the first slot and the inner wall surface of the connection slot, or the inner wall surface of the second slot and the inner wall surface of the connection slot are connected to each other in a curved manner, so that thickness unevenness failure is suppressed. The film in the desired width direction can be easily manufactured. In particular, the thickness unevenness failure appears remarkably at the time of high-speed film formation, but according to the present invention, the film in the desired width direction can be easily manufactured while suppressing the thickness unevenness failure even at the time of high-speed film formation. can do.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments listed here.

(Solution casting method)
FIG. 1 shows a schematic diagram of a film production line 10 used in the present embodiment. The film production line 10 includes a casting chamber 12, a pin tenter 13, a clip tenter 14, a drying chamber 15, a cooling chamber 16, and a winding chamber 17.

  The stock tank 20 is connected to the casting chamber 12 through a flow path described later. The stock tank 20 is provided with a stirring blade 20b rotated by a motor 20a and a jacket 20c, and a dope 24 containing a solvent and a polymer as a raw material for the film 22 is stored therein. The stock tank 20 is always adjusted so that the temperature of the dope 24 is substantially constant by the jacket 20c provided on the outer peripheral surface of the stock tank 20, and the rotation of the stirring blade 20b suppresses aggregation of polymers and the like. The dope 24 is kept in a uniform state.

  An intermediate layer dope channel 30a, a back layer dope channel 30b, and a surface layer dope channel 30c are connected between the stock tank 20 and a feed block described later. The dope 24 is fed by pumps 31a to 31c provided in the respective flow paths 30a to 30c. The pumps 31a to 31c are connected to a control unit (not shown). By this control unit, the pumps 31a to 31c send out each dope at a predetermined flow rate. A gear pump is preferably used as the pumps 31a to 31c. As the gear pump, any known gear pump may be used.

  A stock tank 33a is connected to the intermediate layer dope channel 30a via a pipe. The stock tank 33a stores the intermediate layer additive liquid 34a. A pump 35a is provided in a pipe connecting the flow path 30a and the stock tank 33a. The intermediate layer additive solution 34a in the stock tank 33a is sent to the intermediate layer dope channel 30a by the pump 35a and added to the dope 24 in the intermediate layer dope channel 30a. Thereafter, the dope 24 and the intermediate layer additive solution 34a are stirred and mixed by a static mixer (static mixer) 38a provided in the intermediate layer dope channel 30a to be uniform. Hereinafter, this dope is referred to as an intermediate layer dope 39a. In the intermediate layer additive liquid 34a, a solution (or dispersion liquid) containing additives such as an ultraviolet absorber, a retardation control agent, and a plasticizer in advance is placed.

  A stock tank 33b is connected to the dope channel 30b for the back surface layer through a pipe. The back surface additive liquid 34b is stored in the stock tank 33b. A pump 35b is provided in a pipe connecting the flow path 30b and the stock tank 33b. The back surface additive liquid 34b in the stock tank 33b is fed to the back layer dope channel 30b by the pump 35b and added to the dope 24 in the back layer dope channel 30b. Thereafter, the dope 24 and the back surface additive liquid 34b are stirred and mixed by the static mixer 38b provided in the back surface layer dope channel 30b to be uniform. Hereinafter, this dope is referred to as a back layer dope 39b.

  A stock tank 33c is connected to the surface layer dope channel 30c through a pipe. The stock tank 33c stores the surface layer additive liquid 34c. A pump 35c is provided in a pipe connecting the flow path 30c and the stock tank 33c. The surface layer additive liquid 34c in the stock tank 33c is fed to the surface layer dope flow path 30c by the pump 35c and added to the dope 24 in the surface layer dope flow path 30c. Thereafter, the dope 24 and the surface layer additive liquid 34c are stirred and mixed by the static mixer 38c provided in the surface layer dope flow path 30c to be uniform. Hereinafter, this dope is referred to as a surface layer dope 39c.

  When the back surface additive liquid 34b or the surface layer additive liquid 34c is wound, a peeling accelerator (such as citrate ester) that facilitates peeling from the casting band as a support, or a film is wound into a roll. In addition, an additive such as a matting agent (for example, silicon dioxide) or an anti-deterioration agent that suppresses adhesion between the film surfaces is previously contained. The back surface additive liquid 34b and the surface layer additive liquid 34c may contain additives such as a plasticizer, an optical property control agent such as an ultraviolet absorber, and a retardation control agent.

(Dope viscosity)
In this embodiment, the dope for the intermediate layer is used as the dope for forming the base layer (hereinafter referred to as the base layer forming dope), and the dope for the back layer is used as the dope for forming the surface layer (hereinafter referred to as the dope for forming the surface layer). 39b, a surface layer dope 39c is used. As the dope for forming the base layer, a dope suitable for the strength and optical function of the optical functional film to be produced is used, and as the dope for forming the surface layer, a dope for improving the planarity and slipperiness of the optical functional film is used. . In addition to the above, it is preferable to use a surface layer forming dope having a lower viscosity than the base layer forming dope. Thereby, the generation | occurrence | production of the streaks and the nonuniformity in the surface of the cast film mentioned later or the wet film, thickness nonuniformity, etc. can be prevented. Note that in a laminated film manufactured by the laminated co-casting method or the like and having a layer structure, a layer forming the main part of the film is referred to as a base layer, and a layer exposed on one or both sides of the base layer is referred to as a surface layer.

(Dope concentration)
The polymer concentration contained in the base layer forming dope is preferably 15% by weight or more and 30% by weight or less, and more preferably 20% by weight or more and 25% by weight or less. The polymer concentration contained in the surface layer forming dope is preferably 10% by weight to 25% by weight, more preferably 15% by weight to 25% by weight, and more preferably 19% by weight to 22% by weight. It is particularly preferred.

  The casting chamber 12 includes a feed block 51 for producing a laminated dope to be described later from three types of dopes 39a to 39c, a casting die 52 for flowing out the laminated dope, and a support, and a casting film 53 from the laminated dope. A casting drum (hereinafter referred to as a casting drum) 54, a peeling roller 55 for peeling the casting film 53 from the casting drum 54, temperature control devices 56 and 57, a condenser (condenser) 58, and a recovery A device 59 is provided. The control unit 60 is connected to the casting drum 54, the temperature control devices 56 and 57, and the recovery device 59.

  Further, the condenser 58 condenses and liquefies the solvent vaporized in the casting chamber 12. Under the control of the control unit 60, the recovery device 59 recovers the solvent condensed and liquefied by the condenser 58, and keeps the gas dew point TR of the atmosphere in the casting chamber 12 within a predetermined range. The gas dew point is a temperature at which the condensing and liquefaction of the solvent that vaporizes into the atmosphere in the casting chamber 12 starts. The recovered solvent is regenerated by a regenerator and then reused as a dope preparation solvent. Under the control of the control unit 60, the temperature adjustment device 57 keeps the temperature of the atmosphere in the casting chamber 12 within a predetermined range.

(Casting drum)
The casting drum 54 is rotated in the direction Z1 about the shaft 54a by a driving device (not shown) under the control of the control unit 60. Due to the rotation of the casting drum 54, the peripheral surface 54b travels in the direction Z1 at a predetermined speed ZV. The temperature control device 56 circulates the heat transfer medium adjusted to a desired temperature under the control of the control unit 60 in the flow path provided in the casting drum 54. By circulating the heat transfer medium, the temperature of the peripheral surface 54b of the casting drum 54 can be maintained at a desired temperature TS.

The width of the casting drum 54 is not particularly limited, but it is preferable to use a casting drum in the range of 1.1 to 2.0 times the casting width of the dope. It is preferable to use one that is polished so that the surface roughness of the peripheral surface 54b is 0.01 m or less. It is necessary to suppress surface defects on the peripheral surface 54b to a minimum. Specifically, there is no pinhole of 30 μm or more, and the number of pinholes of 10 μm or more and less than 30 μm is 1 / m ² or less, and the number of pinholes of less than 10 μm is preferably ² / m ² or less. The positional fluctuation in the vertical direction of the peripheral surface 54b accompanying the rotation of the casting drum 54 is preferably 200 μm or less. The speed fluctuation of the casting drum 54 is preferably 3% or less, and the meandering in the width direction that occurs when the casting drum 54 rotates once is preferably 3 mm or less.

  The material of the casting drum 54 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. The chromium plating treatment applied to the peripheral surface 54b of the casting drum 54 is preferably so-called hard chromium plating with a Vickers hardness Hv of 700 or more and a film thickness of 2 μm or more.

  The feed block 51 joins the dopes 39 a to 39 c sent from the flow paths 30 a to 30 c to create a laminated dope 61, and sends the laminated dope 61 having a predetermined flow rate to the casting die 52. The casting die 52 discharges the laminated dope 61 toward the peripheral surface 54b of the rotating casting drum 54. Thereafter, a casting film 53 is formed from the laminated dope 61 on the peripheral surface 54 b of the casting drum 54. While the casting drum 54 rotates about 3/4, self-supporting property due to gelation is developed in the casting film 53, and the casting film 53 is peeled off from the casting drum 54 by the peeling roller 55.

  Further, the decompression chamber 63 may be arranged on the upstream side in the direction Z <b> 1 with respect to the casting die 52. The decompression chamber 63 decompresses the back surface of the casting bead (the surface that comes into contact with the peripheral surface 54b of the casting drum 54 later) to a desired pressure. Under the control of a control unit (not shown), the decompression chamber 63 can decompress the back side of the casting bead in a range of −10 Pa to −2000 Pa. By reducing the pressure on the back side of the casting bead, the influence of the accompanying air generated by the rotation of the casting drum 54 is reduced, and a stable casting bead is formed between the casting die 52 and the casting drum 54, A cast film 53 with little thickness unevenness can be formed.

  On the downstream side of the casting chamber 12, a crossing portion 65, a pin tenter 13, and a clip tenter 14 are installed in this order. The transfer portion 65 introduces the wet film 68 peeled off by the peeling roller 55 into the pin tenter 13 by the roller 66. The pin tenter 13 has a large number of pin plates that pass through and hold both side edges of the wet film 68, and the pin plates travel on a track. Dry air is sent to the wet film 68 traveling by the pin plate, and the wet film 68 is dried to become the film 22.

  The clip tenter 14 has a number of clips that grip both side edges of the film 22, and these clips travel on the extending track. Dry air is sent to the film 22 traveling by the clip, and the film 22 is subjected to a drying process along with a stretching process in the film width direction.

  Ear clippers 70a and 70b are provided downstream of the pin tenter 13 and the clip tenter 14, respectively. The edge-cutting devices 70 a and 70 b cut both side edges of the film 22. The cut side edges are sent to the crushers 71a and 71b by air blowing, pulverized, and reused as a raw material such as a dope.

  A large number of rollers 75 are provided in the drying chamber 15, and the film 22 is wound around and conveyed. The temperature and humidity of the atmosphere in the drying chamber 15 are adjusted by an air conditioner (not shown), and the film 22 is dried by passing through the drying chamber 15. An adsorption recovery device 76 is connected to the drying chamber 15, and the solvent evaporated from the film 22 is absorbed and recovered.

  A cooling chamber 16 is provided on the outlet side of the drying chamber 15, and the film 22 is cooled in this cooling chamber 16 until it reaches room temperature. A forced neutralization device (static neutralization bar) 80 is provided downstream of the cooling chamber 16 to neutralize the film 22. Further, a knurling roller 81 is provided on the downstream side of the forced static elimination device 80, and knurling is applied to both side edges of the film 22. A winding machine 84 having a press roller 83 is installed in the winding chamber 17, and the film 22 is wound around the winding core in a roll shape.

(Feed block)
As shown in FIG. 2, the feed block 51 includes first to third inlets 91a to 91c connected to the flow paths 30a to 30c, an outlet 92 connected to the casting die 52, the first inlet 91a and the flow And a main channel 93 connecting the outlet 92. The sub flow path 94b communicates the second inflow port 91b and the main flow path 93, and the sub flow path 94c communicates the third inflow port 91c and the main flow path 93. A merging portion 95 is provided in the main flow passage 93 on the downstream side of the communication portion with the sub flow passages 94b and 94c. In the junction portion 95, a laminated dope 61 is formed in which the respective dopes 39a to 39c form layers in the direction SD. Distribution pins 96b and 96c formed in a columnar shape are provided so as to lie in the auxiliary flow channels 94b and 94c immediately before the communication portion with the main flow channel 93.

  As shown in FIG. 3, a cutout groove 97 that communicates the upstream side and the downstream side of the sub-channels 94b and 94c is provided on the peripheral surface of the distribution pin 96b. The width of the notch groove 97 in the axial direction A1 is formed so as to gradually narrow from the width WA1 to the width WA2 along the circumferential direction SA1. The width of the notch groove 97 is the length of the notch groove 97 in the direction of the axis A1 of the distribution pin 96b. The groove depth D1 of the notch groove 97 is preferably greater than 0 mm and not greater than 5 mm, more preferably greater than 0 mm and not greater than 4 mm. If the groove depth D1 exceeds 5 mm, it is difficult to ensure the film thickness distribution of the outermost layer, which is not preferable. The distribution pin 96c is also formed in the same shape as the distribution pin 96b.

  As shown in FIG. 2, the drive units 98b and 98c are connected to the distribution pins 96b and 96c, and rotate the distribution pins 96b and 96c in the direction SA1 or SA2 about the axis A1. The cross-sectional areas of the auxiliary flow paths 94b and 94c can be adjusted to a desired range by the drive units 98b and 98c.

(Casting die)
As shown in FIGS. 4 and 5, the casting die 52 is composed of the lip plates 100 and 101 and the side plates 102 and 103, and flows out from the inlet 104 that communicates with the outlet 92 of the feed block 51 and the laminated dope 61. And the slot 106 that communicates the inlet 104 and the outlet 105. The outlet 105 is provided at the tip of the casting die 52. Of the sides constituting the cross-sectional shape of the slot 106 when the laminated dope 61 is cut along a plane perpendicular to the direction B1 or B2 flowing in the slot 106, the direction of the long side is the direction LD, and the short side Is the direction SD. The cross-sectional shape of the slot 106 is preferably substantially rectangular, but the present invention is not limited to this. Of the inner wall surfaces of the slot 106, an inner wall surface formed so as to extend in the direction LD is defined as a first inner wall surface, and an inner wall surface formed so as to extend in the direction SD is defined as a second inner wall surface.

  Inner deckle plates 108 and 109 are provided at both ends of the slot 106 with respect to the direction LD. The inner deckle plates 108 and 109 are provided so as to be in close contact with the lip plates 100 and 101 and the side plates 102 and 103 through packing (not shown).

  The slot 106 is provided with a first slot portion 111, a second slot portion 112, and a third slot portion 113 from the inlet 104 toward the outlet 105. Further, a first connection slot portion 116 is provided between the first slot portion 111 and the second slot portion 112, and a second connection slot is provided between the second slot portion 112 and the third slot portion 113. A portion 117 is provided.

  The first slot portion 111 is formed so that the flow path width in the direction LD gradually becomes wider toward the downstream. The second slot part 112 is formed such that the flow path width in the direction SD is narrower than the flow path width in the direction SD of the first slot part 111, and the flow path width in the direction LD of the second slot part 112 is It is formed so as to be substantially the same as the direction LD flow path width of the first slot portion 111. The third slot portion 113 is formed such that the channel width in the direction SD is narrower than the channel width in the direction SD of the second slot portion 112, and the channel width in the direction LD of the third slot portion 113 is It is formed so as to become wider gradually toward the downstream.

  The first connection slot portion 116 is formed such that the flow path width in the direction SD gradually becomes narrower from the first slot portion 111 side toward the second slot portion 112 side. It is formed so as to be approximately the same as the flow path width in the direction LD of the slot 111. The second connection slot portion 117 is formed so that the flow path width in the direction SD gradually becomes narrower from the second slot section 112 side toward the third slot section 113 side, and the flow path width in the direction LD is It is formed to be substantially the same as the channel width of the slot portion 112.

  Here, the flow path width in the direction LD is the distance between the first inner wall surfaces, that is, the distance between the inner wall surface 108a of the pair of deckle plates 108 and the inner wall surface 109a of the deckle plate 109. The distance between the second inner wall surfaces, that is, the distance between the inner wall surface 100 a of the pair of lip plates 100 and the inner wall surface 101 a of the lip plate 101.

  An angle θ1 formed by the liquid feeding direction B1 of the laminated dope 61 flowing through the first slot portion 111 and the inner wall surface 116a constituting the first connection slot portion 116 of the first inner wall surface is 30 ° or more and 40 ° or less. It is preferable. Further, an angle θ2 formed by the liquid feeding direction B2 of the laminated dope 61 flowing through the second slot portion 112 and the inner wall surface 117a constituting the second connection slot portion 117 of the first inner wall surface is 30 ° or more and 40 ° or less. It is preferable that

The lip plates 100 and 101 and the inner deckle plates 108 and 109 constituting the feed block 51 and the casting die 52 are preferably made of precipitation hardening stainless steel. It is preferable to use a material having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. Moreover, what has corrosion resistance substantially equivalent to SUS316 in the forced corrosion test in electrolyte aqueous solution can also be used. Further, a material having corrosion resistance that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months is used. Further, it is preferable that the casting die 52 is manufactured by grinding a material that has passed one month or more after casting. Thereby, the planar shape of the laminated dope 61 flowing in the slot 106 of the casting die 52 is kept constant.

  The finish accuracy of the inner wall surface of the slot 106 and the main flow path 93 and the sub flow paths 94b and 94c (see FIG. 2) should be 3 μm or less in terms of surface roughness, and the straightness should be 1 μm / m or less in any direction. Is preferred. The average value of the channel width of the slot 106 in the direction SD is adjustable in the range of 0.5 mm to 3.5 mm by automatic adjustment. About the corner | angular part of the liquid-contact part of the lip | tip end of the casting die 52, R uses the thing of 50 micrometers or less over the full width of a slit. Further, it is preferable to use a material in which the shear rate of the dopes 39a to 39c in the slot 106 is adjusted to be 1 (1 / second) to 5000 (1 / second).

  As shown in FIG. 6, among the first inner wall surfaces, the inner wall surface 111 a constituting the first slot portion 111 is connected to the inner wall surface 116 a via the first upstream curved connection surface 120. Similarly, the inner wall surface 116a is connected to the inner wall surface 112a constituting the second slot portion 112 of the first inner wall surface via the second upstream curved connecting surface 121.

  The first upstream curved connecting surface 120 has a joint portion between the inner wall surface 111a and the inner wall surface 116a, and the joint portion is chamfered in a substantially arc shape in cross section. The second upstream-side curved connecting surface 121 has a joint portion between the inner wall surface 116a and the inner wall surface 112a, and this joint portion is chamfered in a substantially arc shape in cross section.

  As shown in FIG. 7, among the first inner wall surfaces, the inner wall surface 112 a constituting the second slot portion 112 is connected to the inner wall surface 117 a via the first downstream curved connection surface 122. Similarly, the inner wall surface 117a of the second connection slot portion 117 is connected to the inner wall surface 113a constituting the third slot portion 113 of the first inner wall surface via the second downstream curved connection surface 123.

  The first downstream-side curved connection surface 122 has a joint portion between the inner wall surface 112a and the inner wall surface 117a, and the joint portion is chamfered in a substantially arc shape in cross section. The second downstream curved connecting surface 123 has a joint portion between the inner wall surface 113a and the inner wall surface 117a, and this joint portion is chamfered in a substantially arcuate cross section.

  The joints of the first upstream curved connecting surface 120, the second upstream curved connecting surface 121, the first downstream curved connecting surface 122, and the second downstream curved connecting surface 123 have a curvature radius RK of 1 mm or more and 20 mm. Or less, preferably 5 mm or more and 20 mm or less.

  It is preferable that a low friction layer having a substantially uniform thickness is formed on the inner wall surfaces 116 a and 117 b of the first connection slot 116 and the second connection slot 117. The thickness of the low friction layer is preferably 5 μm or more and 500 μm or less.

  The dynamic friction coefficient of the low friction layer is lower than the dynamic friction coefficient of the inner wall surface formed so as to extend in the direction LD among the inner wall surfaces of the first slot portion 111 to the third slot portion 113. The dynamic friction coefficient of the low friction layer is preferably 0.4 or less, and more preferably 0.2 or less. The dynamic friction coefficient in this specification was measured according to the method prescribed in ASTM D-1894 using a thrust wear tester manufactured by Toyo Seiki Seisakusho.

  In order to sufficiently exhibit the effect of suppressing thickness unevenness, the surface roughness Ra of the low friction layer is preferably 0.01 μm or more and 3 μm or less, and more preferably 0.01 μm or more and 2 μm or less. The measuring method of surface roughness Ra is based on JIS B0001.

  The hardness Hv of the low friction layer is preferably 350 or more, and more preferably 600 or more. The measuring method of hardness Hv is based on JIS Z 2244.

A method for forming the low friction layer is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding method. When ceramics are used as the low friction layer, those that can be ground, have low porosity, are not brittle, have good corrosion resistance, have good adhesion to the casting die 71, and have no adhesion to the dope are preferable. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, and it is particularly preferable to use WC. The WC coating can be performed by a thermal spraying method or a vapor deposition method. It is also possible to use a fluorine coating as the low friction layer.

  During film formation, it is preferable to attach a temperature controller (for example, a heater, a jacket, etc.) so as to be maintained at a predetermined temperature. The casting die 52 is preferably a coat hanger type. Furthermore, it is more preferable to provide a thickness adjusting bolt (heat bolt) at a predetermined interval and attach an automatic thickness adjusting mechanism using a heat bolt. The heat bolt is preferably formed by setting a profile according to the amount of liquid fed by pumps (preferably high-precision gear pumps) 31a to 31c (see FIG. 1) according to a preset program. Further, feedback control may be performed by an adjustment program based on a profile of a thickness meter (for example, an infrared thickness meter) (not shown) in the film forming line 10. It is preferable that the thickness difference between any two points except the casting edge is adjusted within 1 μm, and the maximum difference in the width direction thickness is adjusted to 3 μm or less. Moreover, it is preferable to use the one whose thickness accuracy is adjusted to ± 1.5 μm or less.

  In addition, it is more preferable that the low friction layer is formed in the front-end | tip of the lip plates 100 and 101, ie, the periphery of the outflow port 105. FIG.

  Next, an example of a method for manufacturing the film 22 by the film manufacturing line 10 will be described with reference to FIG. In the stock tank 20, the temperature of the dope 24 is adjusted to be substantially constant in a range of 25 ° C. or more and 35 ° C. or less by flowing a heat transfer medium inside the jacket 20c, and is always made uniform by rotating the stirring blade 20b. ing.

  An intermediate layer dope 39a is prepared from the dope 24 stored in the stock tank 20 and a predetermined intermediate layer additive solution 34a. The prepared intermediate layer dope 39a is sent to the feed block 51 through the flow path 30a. Similarly, a back surface layer dope 39b is prepared from the dope 24 and the predetermined additive liquid 34b, and a front surface layer dope 39c is prepared from the dope 24 and the predetermined additive liquid 34c. The prepared back surface layer dope 39b is sent to the feed block 51 via the flow path 30b, and the prepared front surface layer dope 39c is sent to the feed block 51 via the flow path 30c. The feed block 51 creates a laminated dope 61 (see FIG. 2) in which each dope 39 a to 39 c forms a layer in the direction SD, and sends the laminated dope 61 to the casting die 52.

  The casting drum 54 rotates around the shaft 54a. Thereby, the peripheral surface 54a travels in the direction Z1 at the speed ZV. The speed ZV is preferably 40 m / min or more and 200 m / min or less, and more preferably 40 m / min or more and 150 m / min or less. The casting die 52 casts the laminated dope 61 to the casting drum 54 to form a casting film 53. Thereafter, the peeling roller 55 peels off the casting film 53 exhibiting self-supporting properties as a wet film 68 from the casting drum 54, and guides it to the pin tenter 13 through the transfer portion 65.

  In the pin tenter 13, a large number of pins are inserted and fixed at both end portions of the wet film 68, and then drying is promoted while the wet film 68 is conveyed to form the film 22. Then, the film 22 still containing the solvent is fed into the clip tenter 14. At this time, it is preferable that the residual solvent amount of the film 22 immediately before being sent to the clip tenter 14 is 50 to 150% by weight. In the present invention, the amount of solvent remaining in the film is shown on the basis of dry weight as the residual solvent amount. Further, the measurement method is to calculate {(xy) / y} × 100, where a sample is taken from the target film, x is the weight of the sample, and y is the weight after drying the sample. .

  In the clip tenter 14, drying is promoted while the film 22 is transported after the end portions on both sides of the film 22 are sandwiched by a number of clips that run endlessly by the movement of the chain. At this time, the film 22 is stretched by increasing the distance between the facing clips (film width) and applying tension in the width direction of the film 22. Thus, the film 22 is stretched in the width direction so that the molecules in the film 22 are oriented, and a desired retardation value can be imparted to the film 22.

  The film 22 that has exited the pin tenter 13 and the clip tenter 14 is cut at both end portions by the edge-cutting devices 70a and 70b. The film 22 having both ends cut off is taken up by the winder 84 in the take-up chamber 17 via the drying chamber 15 and the cooling chamber 16. Further, both end portions cut by the edge cutting devices 70a and 70b are crushed by the crushers 71a and 71b to be reused as dope preparation chips.

  The film 22 taken up by the winder 84 is preferably at least 100 m in the longitudinal direction (casting direction). The width of the film 22 is preferably 600 mm or more, and more preferably 1400 mm or more and 2500 mm or less. The present invention is also effective when the width is greater than 2500 mm. Furthermore, the present invention is also applied when manufacturing a thin film having a thickness of 20 μm or more or 80 μm or less.

  As shown in FIGS. 4 and 5, the laminated dope 61 (see FIG. 2) is supplied to the inlet 104 of the casting die 52 from the outlet 92 of the feed block 51. The laminated dope 61 supplied to the inflow port 104 flows out from the outflow port 105 through the slot 106.

  The laminated dope 61 sent to the slot 106 flows into the second slot portion 112 via the first slot portion 111 and the first connection slot portion 116. The laminated dope 61 that has passed through the second slot portion 112 flows out from the outlet 105 through the second connection slot portion 117 and the third slot portion 113.

  Since the flow path width of the first connection slot portion 116 in the direction SD becomes narrower from the first slot portion 111 side toward the second slot portion 112 side, the laminated dope 61 flowing into the first connection slot portion 116 has an inner wall surface. The laminated dope 61 passes through the first connection slot 116 while spreading in the direction LD due to contact with the inner wall surface 116a. When the laminated dope 61 passes through the first connection slot portion 116, the laminated dope 61 receives a shearing stress on the inner wall surface 116 a, and the shearing stress causes distortion in the polymer molecules included in the laminated dope 61. Similarly, the flow path width of the second connection slot portion 117 in the direction SD becomes narrower from the second slot portion 112 side toward the third slot portion 113 side. Therefore, the laminated dope that has flowed into the second connection slot portion 117 61 contacts the inner wall surface 117a, and the contact with the inner wall surface 117a causes the laminated dope 61 to pass through the second connection slot portion 117 while spreading in the direction LD. When the laminated dope 61 passes through the second connection slot portion 117, the laminated dope 61 receives a shear stress on the inner wall surface 117a, and the shear stress causes distortion in the polymer molecules contained in the laminated dope 61.

  When the laminated dope 61 in which a certain amount of polymer molecule distortion remains flows out of the outlet 105, the flow of the laminated dope 61 from the outlet 105 to the peripheral surface 54b becomes an unsteady flow. This unsteady flow induces a so-called melt fracture, and as a result, causes a thickness unevenness failure in the length direction in the casting film 53.

  In order to suppress the occurrence of distortion of the polymer molecule that induces the thickness unevenness failure, the inner surface 116a or 117a is not provided, and the channel width in the directions SD and LD is substantially uniform from the upstream side to the downstream side. When the laminated dope 61 is cast, the highly viscous laminated dope 61 flows out from the outlet 105 without sufficiently spreading in the LD direction when passing through the slot. As a result, in addition to the thickness unevenness failure, the film A non-uniform width or the like will occur.

  In the present invention, as shown in FIG. 7, the inner wall surface 112a, the inner wall surface 117a, and the joint portion between the inner wall surface 117a and the inner wall surface 113a, and the first downstream curved connecting surface 122 whose joint portions are chamfered in a substantially circular arc shape. Is provided with the second downstream curved connecting surface 123 chamfered in a substantially arc shape in cross section, so that the lamination dope 61 in the LD direction can be suppressed while suppressing the distortion of the polymer molecules generated when passing through the second connection slot portion 117. Can be expanded sufficiently. Similarly, as shown in FIG. 6, the first upstream curved connecting surface 120 in which the joint portion between the inner wall surface 111 a and the inner wall surface 116 a is chamfered in a substantially circular arc shape, and the joint between the inner wall surface 116 a and the inner wall surface 112 a. Since the second upstream curved connecting surface 121 whose portion is chamfered in a substantially arc-shaped cross section is provided, the laminated dope 61 in the LD direction is suppressed while suppressing the distortion of the polymer molecules generated when passing through the first connecting slot portion 116. Can be expanded sufficiently. Therefore, according to the present invention, it is possible to stabilize the flow of the laminated dope 61 from the outlet 105 to the peripheral surface 54b, and to manufacture a film having a desired width in which melt fracture is suppressed and thickness unevenness is suppressed. it can.

  The process in which the occurrence of uneven thickness failure is suppressed according to the present invention is presumed as follows. When the curved connection surfaces 120 to 123 are provided on the inner wall surface of the slot 106, an increase in the first normal stress difference generated in the dopes 39b and 39c in contact with the inner wall surface of the slot 106 in the laminated dope 61 is suppressed. When the dope 61 passes through the slot 106, the polymer molecules contained in the laminated dope 61 are less likely to be distorted. The first normal stress difference generated in the dopes 39b and 39c is preferably 0 Pa or more and 20000 Pa or less, more preferably 0 Pa or more and 16000 Pa or less, and preferably 0 Pa or more and 6000 Pa or less. If the first normal stress difference generated in the dopes 39b and 39c exceeds 20000 Pa, a thickness unevenness failure occurs, which is not preferable. In addition, under the same shear strain rate, the first normal stress difference generated in the dopes 39b and 39c is smaller than the first normal stress difference in the dope 39a, so that the occurrence of thickness unevenness failure is more sure. Can be suppressed.

  In the above embodiment, the curved connection surfaces 120 to 123 are provided as connection surfaces for connecting the first slot portions 111 to 113, the first connection slot portion 116, and the second connection slot portion 117, but the present invention is not limited to this. Instead, at least one of the connection surfaces connecting the first slot portions 111 to 113, the first connection slot portion 116, and the second connection slot portion 117 may be a curved connection surface. The position where the curved connection surface is formed is preferably closer to the outlet 105.

  In the above embodiment, the low friction layer is provided on both the inner wall surface 116a on the longitudinal side of the first connection slot portion 116 and the inner wall surface 117a on the longitudinal side of the second connection slot portion 117. However, the present invention is not limited to this. Instead, it may be provided on at least one of the inner wall surface 116a and the inner wall surface 117a.

  Further, in order to recover the distortion of the polymer molecules contained in the laminated dope 61 before the laminated dope 61 flows out from the outlet 105, the low friction layer is provided between the first connection slot 116 and the outlet 105, or It is preferable to provide the inner wall surface of the slot 106 between the second connection slot 117 and the outlet 105. Moreover, thickness unevenness failure can be suppressed as the formation position of the low friction layer is closer to the outflow port 105.

  In addition, a low friction layer may be provided in the entire slot 106 in order to efficiently recover the distortion of the polymer molecules contained in the laminated dope 61 in the slit 106 before the laminated dope 61 flows out from the outlet 105. The entire slot 106 extends in the direction SD or the inner wall surface extending in the direction SD or the direction LD included in the first slot portion 111 to the third slot portion 113, or in the direction SD included in the first connection slot portion 116 and the second connection slot portion 117. Refers to the inner wall. In addition, about the 1st slot part 111-the 3rd slot part 113 in which a low friction layer is provided, the 1st connection slot part 116, and the 2nd connection slot part 117, the flow path width of direction SD or direction LD is downstream from the upstream. It is not limited to the one that becomes narrower toward the side, but can also be used for each slot that becomes wider from the upstream side toward the downstream side or each slot that is substantially constant.

  In the above embodiment, the flow path width in the direction LD of the first slot portion 111, the second slot portion 112, the first connection slot portion 116, and the second connection slot portion 117 is substantially constant from the upstream side to the downstream side. However, the present invention is not limited to this, and the flow path width in the direction LD may become wider as it goes from the upstream side to the downstream side.

  As a method of casting a plurality of dopes for producing a multi-layer film, the above-mentioned simultaneous lamination co-casting, sequential casting, or a combination of both may be used. When performing simultaneous lamination and co-casting, the feed block 51 may be attached to the casting die 52 as in this embodiment, or a multi-manifold casting die (not shown) may be used. A film having a multilayer structure is formed by co-casting, so that the thickness of the air side layer (air surface layer) and / or the thickness of the support side layer is 0 in the total film thickness. It is preferably 5% to 30%. Furthermore, when performing simultaneous lamination co-casting, it is preferable to enclose the high-viscosity dope with the low-viscosity dope when casting the dope from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, when casting dope from a die slit to a support body, it is preferable that internal dope is enveloped by dope with a larger composition ratio of alcohol than the dope. In addition, this invention can be used for the casting process which casts one kind of dope, and a solution casting method.

  In the above embodiment, the feed block 51 is attached to the casting die 52 and simultaneous lamination and co-casting is performed. However, the present invention is not limited to this, and the feed block 51 is not used, and one type of casting dope is used. The present invention can also be applied to a form in which a cast film is formed.

  In this embodiment, the film 22 is used as the polymer film. However, the present invention can be applied to various polymer films.

  In the above embodiment, the casting drum 54 is used as the support. However, the present invention is not limited to this, and a casting band that is stretched around a roller and travels endlessly by the rotation of the roller may be used.

  In the above embodiment, the casting film 53 is made to exhibit self-supporting property by cooling. However, the present invention is not limited to this, and the casting film 53 has self-supporting property by drying the solvent contained in the casting film 53. You may let them.

(polymer)
Hereinafter, the raw material used when preparing dope 24 in this invention is demonstrated.

In the present embodiment, cellulose acylate is used as the polymer, and cellulose triacetate (TAC) is particularly preferable as the cellulose acylate. 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 (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose, A is the substitution degree of the acetyl group, and B is 3 carbon atoms. The substitution degree of the acyl group of ˜22. In addition, it is preferable that 90 weight% 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.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio at which the hydroxyl groups of cellulose are esterified at each of the 2-position, 3-position and 6-position (the substitution degree 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 the 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. Further, 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. These cellulose acylates By using, a solution (dope) having better solubility can be produced. In particular, when a non-chlorine organic solvent is used, a dope having excellent solubility, low viscosity and excellent filterability can be produced.

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

  The acyl group having 2 or more carbon atoms of the cellulose acylate in the present invention may be an aliphatic group or an aryl group, and is not particularly limited. For example, cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester and the like may be mentioned, 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.

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

  Among the above halogenated hydrocarbons, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. From the viewpoint of physical properties such as solubility of TAC, peelability from cast film support, mechanical strength and optical properties of film, one or several kinds of alcohols with 1 to 5 carbon atoms are mixed in addition to dichloromethane. It is preferable to do. The content of alcohol is preferably 2 to 25% by weight, more preferably 5 to 20% by weight, based on the entire solvent. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  Recently, a solvent composition that does not use dichloromethane has been studied for the purpose of minimizing the impact on the environment. In this case, an ether having 4 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferable. Sometimes used. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester and alcohol (that is, —O—, —CO—, —COO— and —OH) can also be used as a solvent.

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

  Next, examples of the present invention will be described. In each of the following Examples, Examples 1 to 3 are examples of embodiments of the present invention, and Comparative Examples 1 to 3 are comparative experiments with respect to Examples 1 to 3. Further, each example will be described in detail in Example 1, and for Examples 2, 3 and Comparative Examples 1 to 3, descriptions of the same conditions as Example 1 are omitted.

  Next, Example 1 of the present invention will be described. The formulation for preparing the polymer solution (dope) used for film production is shown below.

[Preparation of dope]
The prescription of the compound used for the preparation of the dope 24 is shown below.
Cellulose triacetate (substitution degree 2.8) 89.3% by weight
Plasticizer A (triphenyl phosphate) 7.1% by weight
Plasticizer B (biphenyldiphenyl phosphate) 3.6% by weight
80% by weight of solid content (solute) with a composition ratio of dichloromethane
Methanol 13.5 wt%
n-butanol 6.5% by weight
The dope 24 was prepared by appropriately adding to a mixed solvent consisting of The TAC concentration of the dope 24 was adjusted to be approximately 23% by weight. The dope 24 was filtered with a filter paper (Toyo Filter Paper Co., Ltd., # 63LB) and further filtered with a sintered metal filter (Nihon Seisen Co., Ltd. 06N, nominal pore size 10 μm), and further filtered with a mesh filter. It was put in the tank 20.

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

  A film 22 was produced using the film production line 10. The pumps 31a to 31c sent the dope 24 in the stock tank 20 to the feed block 51 as the dopes 39a to 39c via the flow paths 30a to 30b. The feed block 51 made a laminated dope 61 from each of the dopes 39 a to 39 c and sent the laminated dope 61 to the casting die 52. In order to adjust the temperature of the laminated dope 61 to approximately 34 ° C., a jacket (not shown) was provided on the casting die 52 and the temperature of the heat transfer medium supplied into the jacket was adjusted.

  The curved connection surfaces 120 to 123 are provided in the slit 106 of the casting die 52. The curvature radii KR of the curved connection surfaces 120 to 123 were approximately 20 mm.

  As the casting drum 54, a stainless steel cylinder having a peripheral surface 54b subjected to chrome plating and mirror finishing was used. Under the control of the control unit 60, the casting drum 54 was rotated by driving the shaft 54a. The speed ZV in the running direction Z1 of the peripheral surface 54b was set to about 100 m / min. Under the control of the control unit 60, the temperature adjustment device 36 adjusted the temperature TS of the peripheral surface 54 b of the casting drum 54 to approximately −10 ° C. The oxygen concentration in the dry atmosphere on the casting drum 54 was kept at 5 vol%. In order to maintain this oxygen concentration at 5 vol%, the air was replaced with nitrogen gas.

  In the casting die 52, the laminated dope 61 was cast on the peripheral surface 54b so that the thickness of the film 22 was 100 μm, and the casting film 53 was formed on the peripheral surface 54b. The decompression chamber 63 decompressed the back side of the casting bead and adjusted the pressure difference between the front side and the back side of the casting bead so that the length of the casting bead was 20 mm to 50 mm.

  After the casting film 53 became self-supporting by cooling, the casting film 53 was peeled off as a wet film 68 from the casting drum 54 using the peeling roller 55. In order to suppress the peeling failure, the peeling speed (peeling roller draw) was appropriately adjusted in the range of 100.1% to 110% with respect to the speed of the casting drum 54.

  The stripping roller 55 was guided to the moving portion 65 over the wet film 68. In the transfer section 65, dry air having a temperature of approximately 60 ° C. was applied to the wet film 68 to dry the wet film 68. A roller 66 provided in the crossing portion 65 guided the wet film 68 to the pin tenter 13.

  In the pin tenter 13, the wet film 68 was dried by applying dry air to the wet film 68. By this drying, the film 22 was obtained from the wet film 68. Thereafter, the pin tenter 13 sent the film 22 to the clip tenter 14. In the pin tenter 14, the film 22 was stretched in the width direction while drying air was applied to the film 22 to dry the film 22.

Both side edges of the film 22 sent from the pin tenter 13 and the clip tenter 14 were cut by the ear-cutting devices 70a and 70b. With NT cutter grinding, width and cut the side edges of substantially 50 mm, the side edges are cut crusher 71a by a cutter blower (not shown), aeolian to the average 80 mm ² approximately chips 71b did. This chip was used again as a raw material for dope production together with TAC flakes as a raw material for dope preparation.

  The film 22 that has passed through the edge-cutting device 71 b was sent to the drying chamber 15. The amount of residual solvent in the film 22 sent out from the ear clip device 71b was approximately 10% by weight on a dry basis. In the drying chamber 15, the film 22 was dried by applying dry air having a temperature of about 140 ° C. to the film 22.

  Then, the film 22 was conveyed to the winding chamber 17. The winding chamber 17 was kept at a room temperature of 28 ° C. and a humidity of 70%. Inside the winding chamber 17, an ion wind static elimination device (not shown) was also installed so that the charged voltage of the film 22 was −1.5 kV to +1.5 kV. Finally, the film 22 was taken up by the take-up roller 84 in the take-up chamber 17 while applying a desired tension with the press roller 83.

  A film 22 was manufactured in the same manner as in Example 1 except that the curved connection surfaces 120 to 123 having a curvature radius KR of about 10 mm were provided.

  A film 22 was manufactured in the same manner as in Example 1 except that the curved connection surfaces 120 to 123 having a curvature radius KR of about 1 mm were provided.

(Comparative Example 1)
A film was produced in the same manner as in Example 1 except that the curved connection surfaces 120 to 123 having a radius of curvature KR of about 0.8 mm were provided.

(Comparative Example 2)
A film was manufactured in the same manner as in Example 1 except that the curved connection surfaces 120 to 123 having a curvature radius KR of about 0.5 mm were provided.

(Comparative Example 3)
A film was manufactured in the same manner as in Example 1 except that the curved connection surfaces 120 to 123 were not provided on the inner wall surface of the slot 106.

[Evaluation]
The production conditions and evaluation results in each example and comparative example are summarized in Table 1. The evaluation results in Table 1 are the evaluation results of thickness unevenness evaluation, and the evaluation criteria are as follows.

  The film obtained in each example was measured for thickness unevenness. The procedure for measuring the thickness unevenness is as follows. First, an approximately 6 cm square sample film was cut out from the film produced in each example. Second, the refractive index difference of the sample film was measured using an apparatus that can convert the refractive index difference of the sample film into a thickness difference. As this device, FX-03 FRINGEANALYZER (manufactured by FUJINON Co., Ltd.) was used. Third, this refractive index difference was measured over the entire area of the sample film, and this average value was taken as thickness unevenness in each example. When the thickness unevenness obtained in this way is less than 1.5% with respect to the thickness of the film, this determination result is ◎, and 1.5% or more and 1.8% with respect to the thickness of the film. In the case of the following, this determination result was set as ◯, and when it was 1.8% or more, it was set as ×. In addition, the thickness of the film measured the thickness of six places of a film using the micrometer, and made the average value of this measured value the thickness of the film.

  From the above embodiment, it was found that the occurrence of uneven thickness failure can be suppressed by using the casting die 52 provided with the curved connection surfaces 120 to 123 in the slot 106.

It is explanatory drawing which shows the outline | summary of a film manufacturing line. It is sectional drawing of a feed block. It is a perspective view which shows the outline | summary of a distribution pin. It is IV-IV sectional view taken on the line of a casting die. It is a VV line sectional view of a casting die. It is a principal part enlarged view of VI part in FIG. It is a principal part enlarged view of the VII part in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film production line 12 Casting chamber 13 Pin tenter 14 Clip tenter 15 Drying chamber 16 Cooling chamber 17 Winding chamber 20 Stock tank 22 Film 24 Dope 51 Feed block 52 Casting die 53 Casting film 54 Casting drum 54a Shaft 54b Circumferential surface 55 Stripping roller 61 Multilayer dope 93 Main flow path 94b, 94c Sub flow path 106 Slit 111-113 1st-3rd slot 116-117 1st-2nd connection slot 111a-113a, 116a, 117a Inner wall surface 120-123 Curve Connection surface

Claims (11)

A dope containing a polymer and a solvent is supplied from a supply port, discharged from a flow outlet through a slot onto a traveling support, and a cast film is formed on the support,
The slot has a pair of first inner wall surfaces formed so that a cross-sectional shape in a direction orthogonal to the outflow direction of the dope extends in the first direction, and a second direction orthogonal to the first direction, In a casting die formed in a slit shape by a pair of second inner wall surfaces formed to extend shorter than the first inner wall surface,
The slot is
A first slot provided on the downstream side of the supply port;
A second slot portion provided on a downstream side of the first slot portion, wherein a flow path width between the first inner wall surfaces is narrower than a flow path width between the first inner wall surfaces of the first slot portion;
A connection slot provided between the first slot portion and the second slot portion, and the flow path width between the first inner wall surfaces becomes gradually narrower from the first slot portion side toward the second slot portion side. And
A downstream curved connecting surface chamfered in a substantially arc shape in cross section at a joint portion between the first inner wall surface of the connection slot portion and the first inner wall surface of the second slot portion ;
A casting die characterized in that a curvature radius of the downstream curved connecting surface is 1 mm or more and 20 mm or less .   2. An upstream curved connecting surface in which a joint portion between the first inner wall surface of the first slot portion and the first inner wall surface of the connection slot portion is chamfered in a substantially arc shape in cross section. The casting die described. The casting die according to claim 2, wherein a curvature radius of the upstream curved connecting surface is 1 mm or more and 20 mm or less.   2. A low friction layer formed on the first inner wall surface of the connection slot portion and having a dynamic friction coefficient smaller than that of the first inner wall surface of the first slot portion and the second slot portion. 4. The casting die according to any one of 3 to 3.   5. The laminated dope in which a main dope and a sub-dope having a lower viscosity than the main dope form a layer in the second direction is supplied to the supply port. 6. Casting die. A main channel that connects the main dope supply port to which the main dope is supplied and the supply port;
A sub-channel for communicating the sub-dope supply port for supplying the sub-dope and the main channel;
A merging portion that is provided in the main flow channel downstream of the communication portion with the sub flow channel and forms the laminated dope from the main dope that has passed through the main flow channel and the sub dope that has passed through the sub flow channel. When,
The casting die according to claim 5, comprising:   The casting die according to any one of claims 1 to 6, wherein a running speed of the support is 40 m / min or more.   The casting die according to any one of claims 1 to 7, wherein the support is a drum that rotates about an axis.   The casting die according to any one of claims 1 to 8, wherein the polymer contains cellulose acylate. A casting die according to any one of claims 1 to 9,
A drying device for drying the cast film peeled off from the support to form a film;
A solution casting apparatus comprising: Using the casting die according to any one of claims 1 to 9, the dope flows out onto the support.
Forming the cast film from the dope on the support;
A solution casting method comprising drying the cast film peeled off from the support.

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