JP2015066743A - Flow casting device, and facility and method for forming solution film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow casting device preventing disarray of the interface between layers in a flow casting film in co-casting, and to provide a facility and method for forming a solution film.SOLUTION: A flow casting device is provided with a feed block and a flow casting die 52, and the feed block forms a laminar dope flow by making the first, second and third dopes confluent. In a confluent part, each of the ratios calculated by dividing the shear viscosity ηm of the second dope by those of the first and third dopes ηsa, ηsc is set in a prescribed range. The flow casting die 52 has the first and second laminar flow slots 77, 78 and an outflow slot 79 as an inner flow path 69 toward an outflow port 69o. The boundary between the second laminar flow slot 78 and the outflow slot 79 in the inner wall face of the lip plates 71 is formed so that the distance to the outflow port 69o gradually decreases from a center in an X direction toward a side edge. The center is made to be in a curved shape having the curvature radius R of 100 mm or more.

Description

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

  Polymer films having light permeability (hereinafter referred to as films) are widely used as optical films. Examples of the optical film include a photographic film, a protective film for a polarizing plate that is a constituent member of a liquid crystal display device, and a retardation film.

  A typical example of the light-transmitting polymer film is a cellulose acylate film containing cellulose acylate as a polymer component. The ester film is used for an optical film such as a protective film for a polarizing plate and a retardation film, which are constituent members of a liquid crystal display device whose market is expanding in recent years, including a photographic photosensitive film.

  The main production methods of the film include a melt extrusion method and a solution casting method. Most of the cellulose acylate films are produced by the solution casting method. The solution casting method uses a casting die to form a casting film by flowing a polymer solution containing a polymer and a solvent (hereinafter referred to as a dope) toward the support, and supports the casting film. It is a film-forming method that is peeled off from the body and dried.

  Examples of the cellulose acylate that is a polymer component of the cellulose acylate film include cellulose diacetate (DAC) and cellulose triacetate (TAC). Since DAC has strong adhesion to the support, it is difficult to peel off the cast film from the support. Therefore, when a DAC is used, a DAC dope containing DAC as a polymer component and a TAC dope containing TAC as a polymer component are cast by well-known co-casting, and casting with a TAC layer on both sides of the DAC layer. A film is formed. TAC is a higher-priced raw material than DAC, and it is desirable to form a TAC layer thinner in order to reduce the cost of the film.

  By the way, in co-casting, various casting dies have been proposed in order to stabilize the dope flow and produce a film having a more uniform thickness. For example, in the casting die of Patent Document 1, a manifold that widens the dope is formed in an internal flow path, and a slot from the manifold to the outlet is formed into a specific shape. This slot has a curved surface shape with a specific radius of curvature in the inlet direction of the casting die within a range of 5 to 20 mm with reference to the center in the widening direction. Further, the casting die of Patent Document 2 is provided with an inner deckle plate having a predetermined shape that regulates the flow width of the dope in the flow path following the outflow port. The inner flow path in which the inner deckle plate is provided has a slot portion that widens the flow of the dope, a slot portion that reduces the thickness of the widened dope flow, and guides the thinned dope flow toward the outlet. Slot portion.

JP 2009-066943 A JP 2012-131097 A

  However, in the above co-casting of the TAC dope and the DAC dope, the interface between the DAC layer and the TAC layer is disturbed in the cast film, and the thickness ratio of each layer becomes non-uniform. The film formed from this cast film shows cloudy unevenness when irradiated with light. This unevenness is usually observed in a region of about 300 mm to 1000 mm in the center in the width direction of the film, and is confirmed by a convex shape in the casting direction at the time of casting. Such unevenness is not solved even if the casting die described in Patent Documents 1 and 2 is used.

  Accordingly, an object of the present invention is to provide a casting apparatus, a solution casting apparatus, and a method for suppressing disturbance of the interface between layers in a casting film at the time of co-casting.

  The present invention provides a first dope for forming a first layer forming one film surface of a cast film, and a second layer having a higher viscosity than the first dope and thicker than the first layer. In a casting apparatus that forms a layered dope flow in which the first dope and the second dope are layered by joining the second dope in the internal flow path, widens the layered dope flow, and flows out from the outlet. The internal flow path includes a first dope slot portion through which the supplied first dope flows and a cross-sectional area perpendicular to the flow direction of the second dope through which the supplied second dope flows. The second dope slot part larger than the area, the first dope slot part and the second dope slot part are connected to join the first dope and the second dope, and the shear viscosity ηm of the second dope is changed to the first. Ratio divided by the shear viscosity ηs of the dope A merging portion having ηm / ηs in the range of 2 to 10 and a layered dope flow flow, the first length in the thickness direction is constant toward the outlet, and the second length in the width direction gradually increases. The first laminar flow slot portion and the first laminar flow slot portion are provided following the first laminar flow slot portion. The second length is constant toward the outlet and the first length is the first length of the first laminar flow slot portion. A second laminar flow slot portion that gradually decreases from the second laminar flow slot portion, and a first length and a second length that are provided following the second laminar flow slot portion; The boundary between the second laminar flow slot portion and the outflow slot portion of the wall surface portions that are equal and each have an outflow slot portion that follows the outflow port and faces in the thickness direction among the inner wall surfaces that constitute the internal flow path. And the distance is gradually reduced from the center in the width direction toward the side edge, It is configured to have a curved shape with a radius of curvature of 100 mm or more.

  It is preferable that the first length LTa of the first laminar flow slot portion and the first length LTb of the outflow slot portion satisfy the condition of 5 ≦ LTa / LTb ≦ 20.

  The solution casting apparatus of the present invention includes a first dope for forming a first layer forming one film surface of a casting film, a second layer having a higher viscosity than the first dope and being thicker than the first layer. The first dope and the second dope are layered to form a layered dope flow by joining the second dope for forming the substrate in the internal flow path, and the layered dope flow is widened and flows out from the outlet. The casting apparatus, the support that forms the casting film by continuously supporting the layered dope flow that has flowed out of the casting apparatus by the moving support surface, and the casting film that has been peeled off from the support are dried. The internal channel has a first dope slot portion through which the supplied first dope flows and a cross-sectional area perpendicular to the flow direction of the second dope through which the supplied second dope flows. Second doped slot portion larger than cross-sectional area in one doped slot portion The first dope slot portion and the second dope slot portion are connected to join the first dope and the second dope, and the shear viscosity ηm of the second dope is divided by the shear viscosity ηs of the first dope. The first portion in the thickness direction is constant, and the second length in the width direction is gradually increased toward the outflow port. The laminar flow slot portion is provided after the first slot portion. The second length is constant and the first length gradually decreases from the first length of the first laminar flow slot portion toward the outlet. A second laminar flow slot portion and a second laminar flow slot portion, the first length and the second length being equal to the first length and the second length of the second laminar flow slot portion, respectively. And an outflow slot portion that follows the outflow port. The boundary between the second laminar flow slot portion and the outflow slot portion of the wall portion facing each other in the thickness direction is formed such that the distance to the outflow port gradually decreases from the center in the width direction toward the side edge. It is configured to have a curved shape with a radius of curvature of 100 mm or more.

  It is preferable that the first length LTa of the first laminar flow slot portion and the first length LTb of the outflow slot portion satisfy the condition of 5 ≦ LTa / LTb ≦ 20.

  The solution casting method of the present invention is characterized in that, using the above casting apparatus, a casting film is formed on a traveling support, the casting film is peeled off as a film from the support, and the film is dried. Prepare.

  According to the present invention, the disturbance of the interface between layers in the casting film is suppressed during co-casting. For this reason, the cloudy nonuniformity which generate | occur | produces in the center part of the width direction when light is irradiated to a multilayer film is suppressed.

It is a section schematic diagram of a multilayer film. It is the schematic of the solution casting apparatus which implemented this invention. It is a perspective view which shows the outline | summary of a casting apparatus. It is the cross-sectional schematic in the YZ plane of a feed block. It is a graph which shows the relationship between a shear viscosity and a shear rate. It is the cross-sectional schematic in the YZ plane of a casting die. FIG. 7 is a schematic cross-sectional view of a casting die taken along the line VII-VII in FIG. 6. It is sectional drawing in XY plane of a layered dope flow. It is a schematic sectional drawing of a cast film. It is the schematic of the casting drum which implemented this invention. It is explanatory drawing of the nonuniformity in a multilayer film. It is a schematic sectional drawing explaining the nonuniformity part in a multilayer film.

  As shown in FIG. 1, the multilayer film 10 obtained by a solution casting apparatus to be described later that implements the present invention and wound in a roll shape has a first layer 10 a, a second layer 10 b, and a third layer 10 c. Overlapping in order. The first layer 10a and the third layer 10c are outer layers constituting the film surface of the multilayer film 10, and the second layer 10b is a central layer located between the first layer 10a and the third layer 10c. In FIG. 1, the boundary between layers is illustrated for convenience of explanation, but this boundary may not be recognized even by visual observation or observation with a microscope or the like.

  In the present embodiment, the polymer constituting the first layer 10a and the third layer 10c is made of the same material, and TAC (cellulose triacetate) is used. However, the polymers of the first layer 10a and the third layer 10c may be different from each other. The polymer constituting the second layer 10b is different from the polymer constituting the first layer 10a and the third layer 10c. In this embodiment, DAC (cellulose diacetate) is used as a polymer constituting the second layer 10b.

  The second layer 10b bears most of the optical characteristics as the multilayer film 10. For this reason, the polymer constituting the second layer 10b satisfies the optical characteristics required for the multilayer film 10, and the thickness of the second layer 10b is the same as that of the first layer 10a and the third layer 10c. Extremely thick compared.

  The thickness THb of the second layer 10b is 40 μm in this embodiment. However, the thickness THb of the second layer 10b is not limited to this. The present invention is effective when the thickness THb of the second layer 10b is in the range of 20 times to 50 times the thickness THa of the first layer 10a and the thickness THc of the third layer 10c. The effect of the present invention is remarkable when the range is 50 times or less.

  On the other hand, the polymer constituting the first layer 10a is easier to peel off from the casting band 22 (see FIG. 2) and the casting drum 120 (see FIG. 10) described later than the polymer constituting the second layer 10b. In addition to the above, a material that does not hinder the optical characteristics of the second layer 10b is used. Moreover, as a polymer which comprises the 3rd layer 10c, what does not inhibit the optical characteristic which the 2nd layer 10b exhibits is used. In addition, the detail about the polymer which comprises each layer 10a-10c is mentioned later.

  In the present embodiment, the thickness THa of the first layer 10a is equal to the thickness THc of the third layer 10c, and both are 1.5 μm. However, the thickness THa of the first layer 10a and the thickness THc of the third layer 10c are not limited to this, and may be equal to each other or different from each other. The present invention is effective when the thickness THa of the first layer 10a is in the range of 0.8 μm to 2.0 μm, and the effect is particularly remarkable when the thickness THa is 0.8 μm to 1.3 μm.

(Solution casting equipment)
The solution casting apparatus 11 is for producing the multilayer film 10, and as shown in FIG. 2, the casting chamber 12, the clip tenter 13, the drying chamber 15, the cooling chamber 16, and the winding are sequentially formed from the upstream side. Chamber 17.

  In the casting chamber 12, a casting apparatus 20 that forms and flows out a layered dope flow, which will be described later, a casting band 22 that forms a casting film 21 from the outflowing layered dope flow, rotating rollers 23 and 24, A stripping roller 25 for stripping the casting film 21 from the casting band 22, a temperature control device 26, blowers 27a to 27d, and the like are provided.

  A casting band 22 is stretched around the rotating rollers 23 and 24. The casting band 22 is annular. The rotating rollers 23 and 24 have rotating shafts 23a and 24a, and the rotating shafts 23a and 24a rotate in the circumferential direction by being rotated by a driving device (not shown). With this rotation, the casting band 22 moves continuously. The casting die 52 is provided on the rotating roller 23 in the present embodiment, but may be provided on the casting band 22 from the rotating roller 23 toward the rotating roller 24. Here, the axial direction of the rotation shafts 23a and 24a parallel to each other is defined as the X direction, the horizontal direction orthogonal to the X direction is defined as the Y direction, and the direction orthogonal to the horizontal plane is defined as the Z direction.

  The casting band 22 has a moving speed in the range of 10 m / min to 200 m / min, and the casting speed is set to 10 m / min to 200 m / min. In addition, the productivity of a film is inferior that a casting speed is less than 10 m / min. Moreover, when it exceeds 200 m / min, the layered dope (bead) flowing out from the casting apparatus 20 is not stably formed, and the smoothness of the film surface of the casting film 21 may deteriorate.

  The temperature control device 26 is for setting the temperature of the support surface 22a (see FIG. 3) of the casting band 22 that supports the casting membrane 21 to a predetermined value. The temperature control device 26 is attached to the rotating rollers 23 and 24, and includes a temperature adjusting unit (not shown) that adjusts the temperature of the heat transfer medium, and a flow path provided in the temperature adjusting unit and the rotating rollers 23 and 24. A heat transfer medium adjusted to a desired temperature. Due to the circulation of the heat transfer medium, the temperature of the casting band 22 is adjusted via the rotating rollers 23 and 24.

  The blowers 27 a to 27 d are for drying the casting film 21, and apply drying air to the casting film 21 that passes therethrough. The blowers 27 a to 27 d are provided on the downstream side in the moving direction of the casting band 22 with respect to the casting die 52. A labyrinth seal (not shown) that blocks dry air may be provided between the casting die 52 and the blower 27a. By installing this labyrinth seal, the surface variation of the casting film 21 due to the contact between the casting film 21 immediately after casting and the drying air is suppressed.

  A decompression chamber (not shown) may be arranged upstream of the casting die 52 in the moving direction of the casting band 22. This decompression chamber is for preventing bead cutting and shaking. The decompression chamber sucks the atmosphere upstream of the beads in the moving direction of the casting band 22, thereby lowering the pressure on the upstream side of the beads than the pressure on the downstream side. This pressure adjustment stabilizes the bead.

  A plurality of rollers 32 for guiding the wet film 30 formed by peeling the casting film 21 by the peeling roller 25 to the clip tenter 13 are arranged in the transition part 29 from the casting chamber 12 to the clip tenter 13. Is done. A blower (not shown) may be provided in the vicinity of the conveyance path of the wet film 30 set by the plurality of rollers 32. This blower device applies a predetermined wind to the wet film 30 in the crossover part 29 and proceeds to dry the wet film 30.

  The clip tenter 13 includes a plurality of clips as holding members that hold the side edges of the wet film 30, and conveys the wet film 30 by the movement of the clip. Further, by moving the clip in the width direction of the wet film 30, the width of the wet film 30 is increased, narrowed, or kept constant. The clip tenter is provided with a blower (not shown), and dry air is sent to the transported wet film 30 from the blower. Thereby, the wet film 30 dries and becomes the multilayer film 10.

  An ear clip device 34 may be provided downstream from the clip tenter 13, and the ear clip device 34 cuts off both side edges in the width direction of the multilayer film 10. The separated side edges are sent to the crusher 35 by air blowing, crushed, and reused as a raw material for dopes and the like.

  The drying chamber 15 is for further drying while transporting the multilayer film 10. A large number of rollers 37 are provided in the drying chamber 15, and the multilayer film 10 is wound around each of the rollers 37 and conveyed. The temperature and humidity of the atmosphere in the drying chamber 15 are adjusted by an air conditioner (not shown). Note that an adsorption recovery device is connected to the drying chamber 15, and the solvent evaporated from the multilayer film 10 is adsorbed by the adsorbent and recovered.

  A cooling chamber 16 is provided on the downstream side of the drying chamber 15, and the multilayer film 10 is cooled in the cooling chamber 16 to, for example, room temperature. A knurling roller 38 is provided downstream of the cooling chamber 16, and knurling is applied to both side edges of the multilayer film 10. The winding chamber 17 is provided with a winding machine 40 having a press roller 39, and the winding machine 40 winds the multilayer film 10 around the winding core 41.

  The first layer 10a of the multilayer film 10 is formed from the first dope 45a, the second layer 10b is formed from the second dope 45b, and the third layer 10c is formed from the third dope 45c. Details of the dopes 45a to 45c will be described later.

  As shown in FIG. 3, the casting apparatus 20 includes a feed block 51 and a casting die 52, and the dopes 45 a to 45 c are independently guided to the feed block 51, merged in the feed block 51, and layered. A layered dope flow 90 (see FIG. 4) is formed. The layered dope stream 90 is guided to the casting die 52 downstream of the feed block 51 and flows out toward the casting band 22. The feed block 51 and the casting die 52 are each provided with a temperature control unit (not shown), and the temperature of each of the dope 45a to 45c and the layered dope flow 90 flowing inside is adjusted.

  As shown in FIG. 4, a flow path (hereinafter referred to as an internal flow path) 53 of the dopes 45 a to 45 c and the layered dope flow 90 is formed inside the feed block 51. The internal flow path 53 and an internal flow path 69 to be described later serve as the internal flow path of the casting apparatus 20. The upper end portion of the internal flow path 53 is divided into three by two partition members 57. One central upstream end in the Y direction opens as an inlet 51i of the second dope 45b on the upper surface of the feed block 51, and the other two upstream ends are the first dope 45a on the opposite surface of the feed block 51 in the Y direction. And an entrance for the third dope 45c. As a result, the upper end portion of the internal flow channel 53 has the first dope slot portion 59a through which the supplied first dope 45a flows, the second dope slot portion 59b through which the second dope 45b flows, and the third dope 45c through which the first dope 45a flows. A 3-dope slot portion 59c is formed. The slot portions 59a to 59c are connected to each other at the downstream end, thereby forming a merge portion 62 where the first to third dopes 45a to 45c merge. A laminar dope flow 90 is formed by the junction 62. Downstream of the merging portion 62 is a first guide slot portion 63 that guides the layered dope flow 90 formed by the merging portion 62 to the outlet 51o.

  The partition member 57 includes a partition block 57a and a vane 57b. As shown in FIG. 4, the vane 57 b having a wedge-shaped cross section is disposed such that an acute tip portion is directed to the merge portion 62. A swing shaft 57c is provided at the end of the vane 57b on the opposite side of the tip portion, and the vane 57b is swingable about the swing shaft 57c.

  In addition, distribution pins 64 are provided at the outlet of the first doped slot portion 59a and the outlet of the third doped slot portion 59c. The distribution pin 64 has a cylindrical shape extending in the X direction, which is the depth direction of the paper surface of FIG. The distribution pin 64 is formed with a notch groove that is partially cut away in the circumferential direction. The depth of the cutout groove and the length in the X direction are gradually increased or gradually decreased toward the circumferential direction.

  Due to the rotation of the distribution pin 64 in the circumferential direction and the swing of each vane 57b, the distance in the Y direction of the outlet of the first doped slot 59a, the distance in the Y direction of the outlet of the second doped slot 59b, and The interval in the Y direction of the outlet of the third dope slot portion 59c is adjusted independently. Each cross-sectional area of the first doped slot portion 59a and the third doped slot portion 59c perpendicular to the flow direction of the first and third doped slots 45a, 45c is the flow of the second doped slot 45b in the second doped slot portion 59b. It is made smaller than the cross-sectional area perpendicular to the direction. Thereby, the multilayer film 10 in which the first layer 10a and the third layer 10c are thinner than the second layer 10b is manufactured.

  The control unit 66 is connected to each of the pumps 54a to 54c, each of the swing shafts 57c, and each of the distribution pins 64. Accordingly, the pumps 54 a to 54 c send out the dopes 45 a to 45 c to the feed block 51 under a control unit 66 at a predetermined volume flow rate. Further, the vane 57b and the distribution pin 64 are set so as to be in a predetermined direction under the control unit 66.

  The shear viscosity of the first dope 45a is ηsa, the shear viscosity of the third dope 45c is ηsc, and the shear viscosity of the second dope 45b is ηm. The junction 62 has a ratio ηm / ηsa obtained by dividing the shear viscosity ηm by the shear viscosity ηsa and a ratio ηm / ηsc obtained by dividing the shear viscosity ηm by the shear viscosity ηsc, both in the range of 2 to 10. In the present embodiment, since the ratio ηm / ηsa and the ratio ηm / ηsc are equal, they may be collectively described as “ηm / ηs”.

  In order to set the ratio ηm / ηs of the respective shear viscosities of the first to third dopes 45a to 45c in the merging portion 62 within the above range, the merging portion 62 is formed as follows. First, the shear rates of the first to third dopes 45a to 45c are obtained by a shear rate measuring machine. A commercially available shear rate measuring machine may be used, and in this embodiment, a capillary rheometer (Rheosol-CR100, manufactured by UBM) is used. In such a commercially available shear rate measuring machine, the shape of the extrusion nozzle through which the measurement object flows is cylindrical, while it is a plane orthogonal to the flow direction of the dopes 45a to 45c of the slot portions 59a to 59c of the feed block 51. The cross sectional shape of the merging portion 62 in the XY plane is a rectangle. Therefore, the shear viscosity in each of the slot portions 59a to 59c and the merging portion 62 is obtained from the shear rate in the capillary rheometer with the shear viscosity in the capillary rheometer.

  FIG. 5 shows the relationship between shear viscosity and shear rate measured by a capillary rheometer. The vertical axis represents the shear viscosity, which increases as it goes upward in FIG. The horizontal axis is the shear rate, and increases in the right direction in FIG. Thus, there is a certain relationship between the shear viscosity and the shear rate, and the curve is generally a downward-sloping curve. Based on the relationship between the shear viscosity and the shear rate, a shear rate γ (k) corresponding to the shear viscosity η measured by a capillary rheometer is obtained.

Here, the shear rate is γ (k), the shear stress is τ, the shear viscosity is η, the extrusion flow rate in the capillary rheometer is Q, the inner diameter in the hole of the extrusion nozzle is RI, the length of the extrusion nozzle is L, and the pressure loss is ΔP Then, there is the following relationship.
γ (k) = 4 × Q / τ × R ³ (1)
τ = RI × δP / 2 × L (2)
η = τ / γ (k) (3)

The shear rate γ when the extrusion nozzle is replaced with each of the rectangular slot portions 59a to 59c and the junction portion 62 is obtained as 6 × Q / (W × h ² ) as is well known. Using the shear rate γ (k) found in
γ (k) = 6 × Q / (W × h ² ) (4)
And Q is the sum of the flow rates of the first to third dopes 45a to 45c in the junction 62, W is the length of the junction 62 in the X direction, and h is the length of the junction 62 in the Y direction. is there. From this equation (4), h is obtained, and a joining portion 62 having this h is formed. Thereby, the ratio ηm / ηs of the shear viscosity falls within the above range.

  In the above example, the adjustment of each shear viscosity ηm, ηsa, ηsc is performed by adjusting the Y of the outlet of the second doped slot 59b, the outlet of the first doped slot 59a, and the outlet of the third doped slot 59c. This is done by adjusting each interval in the direction. However, instead of or in addition to this method, there is a method of adjusting the viscosity of each of the dopes 45a to 45c. For example, in order to increase the ratio ηm / ηsa and the ratio ηm / ηsc, the first dope 45a having a higher viscosity may be formed.

  As shown in FIGS. 6 and 7, the casting die 52 includes a pair of lip plates 71 and a pair of side plates 72. A pair of lip plates 71 extending in the X direction oppose each other in the Y direction. Each of the pair of side plates 72 is disposed at each end of the pair of lip plates 71 in the X direction, and these are opposed in the X direction. An inner deckle plate 80 for regulating the width of the layered dope flow 90 is disposed on the inner wall of each side plate 72. The internal flow path 69 of the casting die 52 is formed by being surrounded by a pair of lip plates 71 and an inner deckle plate 80 provided inside the pair of side plates 72.

  The internal channel 69 is formed so as to penetrate the casting die 52 in the Z direction. The upper end of the internal channel 69 opens as an inlet 69i of the layered dope flow 90 above the casting die 52, and the lower end opens as an outlet 69o of the layered dope flow 90 below the casting die 52. The cross-sectional shape of the internal flow path 69 in the XY plane orthogonal to the flow direction is a rectangular shape that is long in the X direction and short in the Y direction.

  The internal channel 69 has a second guide slot portion 76, a first laminar flow slot portion 77, a second laminar flow slot portion 78, and an outflow slot portion 79 from the inlet 69i toward the outlet 69o. . The second guide slot portion 76 is provided following the first guide slot portion 63 of the feed block 51, and guides the laminar dope flow 90 flowing in from the feed block 51 to the first laminar flow slot portion 77. As shown in FIG. 6, the first length in the Y direction of the internal flow path 69 in the XY plane is the second guide slot portion 76, the first laminar flow slot portion 77, and the outflow slot portion 79 toward the outlet 69 o. In the second laminar flow slot portion 78, it is gradually reduced. The first lengths in the Y direction of the second guide slot portion 76 and the first laminar flow slot portion 77 are equal to each other. On the other hand, the second length in the X direction of the internal flow path 69 in the XY plane is, as shown in FIG. 7, toward the outlet 69o, the second guide slot 76, the second laminar flow slot 78, and the outflow slot. Each of the portions 79 is constant, and the first laminar flow slot portion 77 continuously increases.

  On the inner wall surface of the lip plate 71, the boundary between the second laminar flow slot portion 78 and the outflow slot portion 79 has a distance from the outlet 69o from the center to the side edge in the X direction, as shown in FIG. It is formed by continuously decreasing. The center of this boundary is a curved shape that draws a convex arc on the inflow port 69i side, and its radius of curvature R is 100 mm or more. The central width W1 of the radius of curvature R is preferably in the range of 10 mm to 200 mm.

  The first length LTa of the first laminar flow slot 77 and the first length LTb of the outflow slot 79 satisfy the condition of 5 ≦ LTa / LTb ≦ 20.

  Next, the operation of the above configuration will be described. Under the control of the control unit 66, the dopes 45 a to 45 c sent to the feed block 51 by the pumps 54 a to 54 c are joined by the joining unit 62. By this merging, a layered dope flow 90 is formed in which the flows of the third dope 45c, the second dope 45b, and the first dope 45a overlap in the Y direction.

  As described above, the merging portion 62 is configured such that the shear viscosity ratio ηm / ηsa is in the range of 2 to 10. For this reason, the first dope 45a and the second dope 45b flow through the first guide slot portion 63 while forming a smooth interface without unevenness or an interface with unevenness close to smoothness. Similarly, the merging portion 62 is configured so that the shear viscosity ratio ηm / ηsc is in the range of 2 to 10. For this reason, the third dope 45c and the second dope 45b flow through the first guide slot portion 63 while forming a smooth interface without unevenness or an interface with unevenness close to smoothness.

  The layered dope flow 90 formed by the feed block 51 is guided to the casting die 52 by the first guide slot portion 63. The laminar dope flow 90 sent to the casting die 52 sequentially passes through the second guide slot portion 76, the first laminar flow slot portion 77, the second laminar flow slot portion 78, and the outflow slot portion 79.

  The first laminar flow slot portion 77 continuously increases in width while guiding the laminar dope flow 90 toward the second laminar flow slot portion 78. The second laminar flow slot portion 78 continuously decreases the thickness toward the outflow slot portion 79 while maintaining the width of the laminar dope flow 90 at the width of the first laminar flow slot portion 77. The outflow slot 79 guides and flows out toward the outflow port 69 o while maintaining the width and thickness of the laminar dope flow 90 at the width and thickness of the second laminar flow slot 78.

  The layered dope flow 90 that has passed through the outflow slot 79 flows out from the outflow port 69o toward the moving casting band 22. As a result, the layered dope flow 90 becomes a casting film 21 having a three-layer structure on the casting band 22. As shown in FIG. 9, the casting film 21 is in contact with the casting band 22, a first layer 21a formed from the first dope 45a, a second layer 21b formed from the second dope 45b, and a third layer 21b. And a third layer 21c formed from the dope 45c.

  Of the inner wall surface of the lip plate 71, the boundary between the second laminar flow slot portion 78 and the outflow slot portion 79 is gradually reduced in distance from the outlet 69o from the center to the side edge in the X direction as described above. The center is a curved shape with a radius of curvature R of 100 mm or more. For this reason, as shown in FIG. 9, the interface between the first layer 21a and the second layer 21b and the interface between the third layer 21c and the second layer 21b are both smooth surfaces or uneven surfaces that are close to smooth. A casting film 21 is formed. 9 shows the center of the casting film 21 in the width direction. Thereby, compared with the case where the radius of curvature R is less than 100 mm, the concentration of the pressure of the laminar dope flow 90 at the upper center of the second laminar flow slot portion 78 is suppressed, and the first layer 21a and the third layer 21c are reduced. The thickness of the dope stream to be formed is not reduced. Therefore, interface disturbance in the layered dope flow 90 is suppressed.

On the other hand, a layered dope flow is formed at the merged portion where the shear viscosity ratios ηm / ηsa and ηm / ηsc at the merged portion do not satisfy the above ranges, and this layered dope flow flows into the second laminar flow slot portion 78 and the outflow. In the cast film when it passes through a lip plate having an inner wall that does not satisfy the boundary shape with the slot 79, the interface of each layer has a larger unevenness. Specifically, as shown by a two-dot chain line K in FIG. 9, the first layer 21a enters the second layer 21b into an inverted M shape, and the third layer 21c enters the second layer 21b into an M shape. A cast film is formed. This is due to the following reasons (1) to (3). In addition, this FIG. 9 has shown the cross section of the center part of the casting film 12 in a X direction, and this cross-sectional position respond | corresponds to the cross-sectional position of the multilayer film 10 in alignment with the IX-IX line of FIG.
(1) The first and third dopes 45a and 45c are less likely to be pulled by the second dope 45b at the junction, and the second dope 45b enters the first and third dopes 45a and 45c downstream of the junction, and then the first , The third dope 45a, 45c pushes back the second dope 45b, thereby causing irregularities at the interface between the dopes in the layered dope flow.
(2) When the lamellar dope flow having such an uneven surface passes through the lip plate, the first and first laminar flow slit portions at the center in the X direction at the center of the first laminar flow slit portion and the second laminar flow slit portion, The thickness of the layer formed from the third dopes 45a and 45c becomes extremely thin due to the concentration of stress. (3) The layer formed from the first and third dopes 45a and 45c thus extremely thin is There is a difference in the residence time in the X direction before reaching the outlet.

  The first length LTa of the first laminar flow slot 77 and the first length LTb of the outflow slot 79 satisfy the condition of 5 ≦ LTa / LTb ≦ 20. For this reason, each dope 45a to 45c in the casting die 52 is held at a higher pressure than when LTa / LTb is less than 5, and the thickness 90a to 90c of each layer of the layered dope flow 90 is uniform in the width direction. become. Moreover, since each dope 45a-45c in the casting die | dye 52 is hold | maintained small pressure compared with the case where LTa / LTb is 20 or more, it is excellent in castability. “Excellent casting suitability” means that surface defects called shark skins on the casting film surface are suppressed. This sharkskin often occurs due to a rapid pressure drop when flowing out of the casting die outlet when the dope pressure is too high inside the casting die 52.

  The layered dope flow 90 flowing out of the casting die 52 forms the casting film 21 on the casting band 22. On the casting band 22, the casting film 21 is dried by the drying air from the blowers 27 a to 27 d and gelled before being peeled off. The stripping roller 25 strips the casting film 21 that has been gelled to the extent that it can be transported from the casting band 22 as a strip-shaped wet film 30, and the stripped wet film 30 passes through the crossing portion 29 to be clip tenter 13. To be guided to.

  The amount of residual solvent in the cast film 21 at the time of peeling is preferably in the range of 10% by mass to 100% by mass. In the present specification, the amount of solvent remaining in the casting film 21, the wet film 30, and the multilayer film 10 is shown on a dry basis, and this is the residual solvent amount. The amount of residual solvent is calculated as {(xy) / y} × 100, where x is the mass of the sample taken from the target film and y is the mass after the sample is dried. Ask.

  The wet film 30 is dried by being blown by the air blower of the crossing section 29. The temperature of the wind is preferably 20 ° C. or higher and 250 ° C. or lower. The multilayer film 10 sent out from the clip tenter 13 is sent to the drying chamber 15 after the side edge portion having a grip mark on the clip tenter 13 is cut out by the ear clip device 34.

  The drying chamber 15 is sent to the downstream side while supporting the multilayer film 10 with the roller 37. The multilayer film 10 is further dried by passing through the drying chamber 15 in which the temperature and humidity of the atmosphere are adjusted. The multilayer film is cooled to, for example, room temperature by passing through the cooling chamber 16.

  After the multilayer film 10 is cooled, knurling is imparted to both side edges by a knurling roller 38. The multilayer film 10 provided with the knurling is wound up in a roll shape around the winding core 41 in the winding chamber 17.

  As described above, since the casting film 21 in which the interfaces of the layers 21a to 21c are smoother than the conventional one is formed, the multilayer film 10 in which the interfaces of the layers 10a to 10c as shown in FIG. Is manufactured. Thereby, the multilayer film 10 permeate | transmits irradiation light more uniformly, and the cloudy nonuniformity is suppressed.

  In the said embodiment, although the self-supporting property was expressed in the casting film 21 by drying of the solvent contained in the casting film 21, it is not restricted to this. For example, the casting film 21 may exhibit self-supporting properties by cooling.

  In the above-described embodiment, the casting band 22 is used as the support for forming the casting film 21, which is stretched around the roller and moves by the rotation of the roller. However, the present invention is not limited to this. For example, instead of the casting band 22, a casting drum 120 may be used. In the casting chamber 12 in this case, as shown in FIG. 10, a casting device 20, a casting drum 120, a temperature control device 26, and the like are provided. In this case, it is preferable to use a pin tenter (not shown) described later instead of the clip tenter 13.

  The casting drum 120 has a shaft 120a arranged to be horizontal and a drum body 120b fixed to the shaft 120a. Here, the axial direction of the shaft 120a is the X direction. The shaft 120a is rotated by a driving device (not shown) under the control of a control unit (not shown), and the drum body 120b is rotated in the circumferential direction integrally with the shaft 120a. Due to the rotation of the drum main body 120b, the peripheral surface 120c of the drum main body 120b moves at a predetermined speed (for example, 50 m / min or more and 200 m / min or less). A temperature control device 26 is connected to the drum body 120b.

  The temperature of the peripheral surface 120c is kept substantially constant in the range of −10 ° C. or more and 10 ° C. or less by the temperature control device 26, whereby the cast film 21 is cooled and gelled before being peeled off. The stripping roller 25 strips the casting film 21 that has been gelled to the extent that it can be conveyed from the casting band 22 as a strip-shaped wet film 30, and the stripped wet film 30 is guided to the pin tenter via the crossover part 29. Is done. The amount of residual solvent in the cast film 21 at the time of peeling is preferably 200% by mass or more and 300% by mass or less.

  The pin tenter has a number of pins that hold through both side edges of the wet film 30. A plurality of pins are provided on each of a plurality of pin plates that can move on a predetermined track. The wet film 30 having both side edges held by the pins is conveyed by the movement of the pin plate. Dry air is sent to the wet film 30 being conveyed. Thereby, the wet film 30 dries and becomes the multilayer film 10. Note that the clip tenter 13 described above may be disposed between the pin tenter and the drying chamber 15. The clip tenter 13 is used when the multilayer film 10 is stretched in the width direction. The degree of widening by stretching is set according to the target optical characteristics.

  The casting film 21 formed in the above embodiment and the manufactured multilayer film 10 have a three-layer structure, but the present invention is not limited to this, and may have a multilayer structure of two layers or four layers or more. . In the case of two layers, a cast film composed of the first dope 45a and the second dope 45b is formed. In the case of four or more layers, the first dope 45a is used as the dope for forming the first layer 21a in contact with the casting band 22 and the casting drum 120, and the third dope 45c is used as the other outer layer to be exposed. In the case of four or more layers, the second dope 45b is used as the dope that overlaps in contact with the first dope 45a and the dope that overlaps in contact with the third dope 45c.

  Hereinafter, the raw material and each dope will be described. The first dope 45a and the third dope 45c are obtained by dissolving a polymer constituting the first layer 10a and the third layer 10c in a solvent. The second dope 45b is obtained by dissolving the polymer constituting the second layer 10b in a solvent.

  The second dope 45a has a higher viscosity than the first dope 45a and the third dope 45c. Further, the viscosity of the first dope 45a may be equal to or different from the viscosity of the third dope 45c. The viscosities of the dopes 45a to 45c can be determined based on JIS K 7117. The viscosity of each dope according to this measurement method is not particularly limited. For example, the viscosity of the second dope 45b is preferably 40 Pa · sec to 150 Pa · sec, and preferably 50 Pa · sec to 100 Pa · sec. Is more preferable. The viscosities of the first dope 45a and the third dope 45c are preferably 20 Pa · sec to 80 Pa · sec, and more preferably 30 Pa · sec to 50 Pa · sec.

As the polymer constituting the first layer 10a and the third layer 10c, for example, cellulose acylate can be used. As the cellulose acylate, triacetyl cellulose (TAC) is particularly preferable. Of the cellulose acylate resins, a ratio in which the hydroxyl group of cellulose is esterified with a carboxylic acid, that is, the substitution degree of the acyl group satisfies all of the following formulas (I) to (III) is more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group, A is the substitution degree of the acetyl group, and B is the substitution degree of the acyl group having 3 to 22 carbon atoms. It is. In addition, it is preferable that 90 mass% or more of TAC is a particle | grain of 0.1 mm-4 mm.
(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 of the hydroxyl group of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1).

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

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

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

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

  As the polymer constituting the second layer 10b, cellulose acylate is preferable, and cellulose diacetate is particularly preferable.

  The solvent used for each dope 45a-45c may be comprised from a single solvent component, and may be a mixture of a plurality of solvent components. Moreover, the prescription | regulation of the solvent of each dope 45a-45c may mutually be the same, and may differ. When the solvent prescriptions of the dopes 45a to 45c are different, the dopes 45a to 45c preferably include a common solvent component.

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

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

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

  Examples 1 to 4 were performed as examples of the present invention. Each example was carried out by the solution casting apparatus 11, and the shear viscosity ratios ηm / ηsa and ηm / ηsc at the junction 62 and the radius of curvature R described above were changed. The ratio of each shear viscosity and the radius of curvature R are shown in Table 1. In any of the embodiments, the shear viscosity ηsa of the first dope 45a and the shear viscosity ηsc of the third dope 45c in the junction 62 are equal, so in Table 1, the ratio of shear viscosity is simply “ηm / ηs”. It describes.

  The ratio of shear viscosity was adjusted by adjusting the distance in the Y direction between the first and third dope slot portions 59a and 59c connected to the merge portion 62 and the second dope slot portion 59b.

  The width of the manufactured multilayer film 10 is 1500 mm. The manufactured multilayer film 10 was evaluated for light transmittance. Evaluation was performed by the following method. 200 m was cut out in the longitudinal direction from the multilayer film 10 obtained in each Example, and it was set as the sample film of evaluation object. The sample film was irradiated with light from a light source onto an area having a width of 1000 mm at the center in the width direction. A halogen lamp was used as the light source.

  When the film surface opposite to the film surface irradiated with light is observed from the vertical direction, unevenness is confirmed as a line having a width as shown in FIG. Such unevenness is confirmed by, for example, a convex shape in the casting direction when forming the casting film, as shown in FIG. As shown by the solid lines in FIG. 12, the cross section of the non-uniform portion is that the thicknesses THa and THc of the first layer 10a and the third layer 10c are constant in the width direction, and the thickness of the second layer 10b is also the width direction It becomes constant at.

  On the other hand, the thickness of each layer 10a-10c has changed in the width direction of the multilayer film 10 in the cross section of the location with a nonuniformity. That is, as shown in FIG. 11, when the cross section along the width direction of the cloudy part (cross section along the XII-XII line) is confirmed, the thickness of the second layer 10b is shown by a two-dot broken line in FIG. The ratio of the thickness of the first layer 10a and the third layer 10c with respect to the width differs in the width direction. Specifically, the thicknesses THa and THc of the first layer 10a and the third layer 10c become thicker by ΔTHa and ΔTHc, respectively, in a cloudy place, and the thickness of the second layer 10b is ΔTHa and ΔTHc. It is thinner by the equivalent amount. When ΔTHa and ΔTHc were each 3 μm or more, they were visually recognized as cloudy unevenness. And the width W2 of this cloudy location respond | corresponds to the location where the ratio of thickness is changing in FIG.

  The number of this unevenness seen in the longitudinal direction was taken as the evaluation result. Although FIG. 11 shows a shape in which two protrusions are continuous in the width direction, the unevenness may be one in the width direction, or may be three or more. The number of unevenness was counted as “1” regardless of the number of convex shapes connected in the width direction. The evaluation results are shown in Table 1.

[Comparative example]
Comparative Examples 1 to 4 were carried out by changing the shear viscosity ratios ηm / ηsa and ηm / ηsc at the junction 62 and the radius of curvature R described above. The conditions for each comparative example are shown in Table 1. In Comparative Examples 1 to 4, as in Examples 1 to 4, since the shear viscosity ηsa of the first dope 45a and the shear viscosity ηsc of the third dope 45c in the junction 62 are equal, in Table 1, The shear viscosity ratio is simply described as “ηm / ηs”.

DESCRIPTION OF SYMBOLS 10 Multilayer film 11 Solution casting equipment 20 Casting apparatus 21 Casting film 21a, 21b 1st, 2nd layer 45a, 45b 1st, 2nd dope 51 Feed block 52 Casting die 59a, 59b 1st, 2nd Dope slot portion 62 Merge portions 77, 78 First and second laminar flow slot portions 79 Outflow slot portion

Claims (5)

A first dope for forming the first layer forming one film surface of the cast film and a second dope for forming a second layer having a higher viscosity than the first dope and thicker than the first layer. In a casting apparatus that forms a layered dope flow in which the first dope and the second dope overlap each other by joining the dope in an internal flow path, widens the layered dope flow, and flows out from the outlet ,
The internal flow path is
A first dope slot portion through which the supplied first dope flows;
The second dope that has been supplied flows, a second dope slot portion having a cross-sectional area perpendicular to the flow direction of the second dope larger than the cross-sectional area of the first dope slot portion;
The first dope slot portion and the second dope slot portion are connected to join the first dope and the second dope, and the shear viscosity ηm of the second dope is changed to the shear viscosity ηs of the first dope. A merging portion in which the ratio ηm / ηs divided by 2 is in the range of 2 to 10;
The laminar dope flow flows, toward the outlet, a first laminar flow slot portion in which the first length in the thickness direction is constant and the second length in the width direction gradually increases;
The second length is provided continuously to the first laminar flow slot portion, and the first length is constant from the first length of the first laminar flow slot portion toward the outlet. A gradually laminating second laminar flow slot;
The outlet is provided after the second laminar flow slot portion, and the first length and the second length are equal to the first length and the second length of the second laminar flow slot portion, respectively. And an outflow slot portion that follows
The boundary between the second laminar flow slot portion and the outflow slot portion of the wall surface portion facing in the thickness direction among the inner wall surfaces constituting the internal flow path is such that the distance from the outlet is from the center in the width direction. A casting apparatus, wherein the casting apparatus is formed to be gradually reduced toward a side edge, and the center has a curved shape with a radius of curvature of 100 mm or more.   The said 1st length LTa of the said 1st laminar flow slot part and the said 1st length LTb of the said outflow slot part satisfy | fill the conditions of 5 <= LTa / LTb <= 20. Casting equipment. A first dope for forming the first layer forming one film surface of the cast film and a second dope for forming a second layer having a higher viscosity than the first dope and thicker than the first layer. A casting device that forms a layered dope flow in which the first dope and the second dope are layered by joining the dope in an internal flow path, widens the layered dope flow, and flows out from the outlet; ,
A support that forms the casting film by continuously supporting the layered dope flow that has flowed out of the casting apparatus with a supporting surface that moves;
A drying device for drying the cast film peeled off from the support,
The internal flow path is
A first dope slot portion through which the supplied first dope flows;
The second dope that has been supplied flows, a second dope slot portion having a cross-sectional area perpendicular to the flow direction of the second dope larger than the cross-sectional area of the first dope slot portion;
The first dope slot portion and the second dope slot portion are connected to join the first dope and the second dope, and the shear viscosity ηm of the second dope is changed to the shear viscosity ηs of the first dope. A merging portion in which the ratio ηm / ηs divided by 2 is in the range of 2 to 10;
The laminar dope flow flows, toward the outlet, a first laminar flow slot portion in which the first length in the thickness direction is constant and the second length in the width direction gradually increases;
The second slot is provided continuously to the first slot portion, and the first length is gradually reduced from the first length of the first laminar flow slot portion toward the outlet. A second laminar slot portion;
The outlet is provided after the second laminar flow slot portion, and the first length and the second length are equal to the first length and the second length of the second laminar flow slot portion, respectively. And an outflow slot portion that follows
The boundary between the second laminar flow slot portion and the outflow slot portion of the wall surface portion facing in the thickness direction among the inner wall surfaces constituting the internal flow path is such that the distance from the outlet is from the center in the width direction. A solution casting apparatus characterized in that it is formed by gradually decreasing toward a side edge, and the center has a curved shape with a radius of curvature of 100 mm or more.   The said 1st length LTa of the said 1st laminar flow slot part and the said 1st length LTb of the said outflow slot part satisfy | fill the conditions of 5 <= LTa / LTb <= 20. Solution casting equipment. Using the casting apparatus according to claim 1 or 2, a casting film is formed on a traveling support,
The cast film is peeled off as a film from the support,
A solution casting method comprising drying the film.

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