JP2012131097A - Casting apparatus, forming method of cast film, and solution deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a thin polymer film in which thickness unevenness is suppressed and optical characteristics are stable.SOLUTION: A casting die 51 includes a block-shaped casting die body having a slot 69 penetrating through in Z-direction. In the slot 69, a before width-widening slot part 76, a first width-widening slot part 77, a second width-widening slot part 78 and an after width-widening slot part 79 are formed in this order from an inlet 69i to an outlet 69o. Inner deckle plates 80 are installed at both ends in the slot 69 in X-direction over the ranges from the first width-widening slot 77 in the slot 69 to the outlet 69o, respectively. A liquid-contacting surface 81 of each of the inner deckle plates 80 is formed of a first liquid-contacting surface 81a and a second liquid-contacting surface 81b. The first liquid-contacting surface 81a is formed orthogonal to X-direction, and extends from the first width-widening slot 77 to a midway position of the after width-widening slot 79. The second liquid-contacting surface 81b extends from a lower end of the first liquid-contacting surface 81a to the outlet 69o while toward the center in X-direction, of the after width-widening slot 79.

Description

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

  Polymer films having light permeability (hereinafter referred to as films) are lightweight and easy to mold, and thus are widely used as optical films. Among them, cellulose ester films using cellulose acylate are optical films such as a protective film for a polarizing plate and a retardation film, which are constituent members of liquid crystal display devices whose market is expanding in recent years, including photographic photosensitive films. It is used for.

  As a main method for producing a film, there are a melt extrusion method and a solution casting method (for example, Patent Document 1). The melt extrusion method is a method of producing a film by melting a polymer and then extruding it with an extruder, and has features such as high productivity and relatively low equipment cost. However, it is difficult to adjust the thickness of the film, and a failure that causes fine lines on the film is likely to occur. On the other hand, the solution casting method uses a casting die to flow a polymer solution containing a polymer and a solvent (hereinafter referred to as a dope) toward the support. The dope flowing out from the casting die forms a bead until reaching the support, and the dope reaching the support becomes a casting film. Next, after the casting film becomes self-supporting and can be conveyed, it is peeled off from the support to form a wet film. Then, the solvent is evaporated from the wet film to form a film. Compared with the melt extrusion method, the solution casting method is easy to adjust the thickness of the film, and it is easy to make the state of the film surface good. Furthermore, the solution casting method can obtain a film with few contained foreign substances. For these reasons, optical films are mainly manufactured by a solution casting method.

JP 2009-066943 A

  However, since cellulose ester has high water absorption, the cellulose ester film easily absorbs water. And the water absorption part which absorbed water will exist in the surface layer of the cellulose-ester film in which water absorption occurred, for example, a cellulose-ester film. The optical properties of the cellulose ester film (such as in-plane retardation Re and thickness-direction retardation Rth) vary due to the formation of the water absorbing portion. Further, since the water absorption part tends to expand due to water absorption, a stress is generated between the water absorption part and the dry part where no water absorption occurs. Due to the generation of this stress, the optical characteristics of the entire cellulose ester film (in-plane retardation Re, retardation Rth in the film thickness direction, etc.) will fluctuate.

  Therefore, in order to obtain a polymer film having stable optical properties, it is conceivable to employ a polymer different from cellulose acylate as a raw material for the polymer film. However, as a polymer used in the solution casting method, the solubility of the solvent is good, the time required for the casting film on the support to be able to be carried independently is short, and the peelability is good. For example, there are restrictions imposed on the solution casting method. At present, no polymer satisfying the constraint has been found.

  In the solution casting method, the inventor creates a cast film having a second layer made of another polymer and overlapping with the first layer made of cellulose acylate, thereby providing a thin polymer film having stable optical characteristics. It has been found that production is possible.

  However, it has been found that when this acrylic polymer is used as another polymer, for example, the bead between the casting die and the support, particularly both end portions in the width direction, become unstable. If casting is continued while both end portions of the bead are unstable, the thickness of the cast film becomes uneven, and eventually the thickness of the film becomes uneven.

  The present invention solves such problems, a casting apparatus, a casting film forming method and a solution casting method capable of producing a thin polymer film having stable optical characteristics while preventing thickness unevenness. The purpose is to provide.

  The present invention relates to a first dope containing a first polymer in a slot-like channel provided so as to penetrate a block-shaped casting apparatus main body, and a second polymer having a lower viscosity and a lower elastic modulus than the first polymer. A second dope having a viscosity higher than that of the first dope and flowing adjacent to the first dope. A belt-like multilayer casting film in which the second layer made of the second dope overlaps the first layer made of the first dope is allowed to flow down from the outlet of the flow path. In the casting apparatus to be formed, the multi-layer dope has a flow width regulating member extending from the inside of the flow path to the outlet of the flow path at both longitudinal ends of the flow path in the cross section in the flow direction. The wetted surface of the flow width regulating member in contact with A first wetted surface provided vertically and a second wetted contact extending from the downstream end of the first wetted surface to the outlet and extending from the end in the longitudinal direction toward the center from the downstream end toward the outlet. And a liquid level.

  When the length of the second liquid contact surface in the direction in which the multilayer dope flows along the first liquid contact surface is L1, and the length of the liquid contact surface in the longitudinal direction is L2, the first The gradient L2 / L1 of the two wetted surfaces is preferably 0.45 or more and 0.85 or less.

  The present invention also provides a first dope containing a first polymer in a slot-like flow path provided so as to penetrate the block-shaped casting apparatus main body and a first dope having a lower viscosity and a lower elastic modulus than the first polymer. An introduction step of introducing a second dope containing two polymers, the first dope on the short-side end side of the flow path, and a second dope adjacent to the first dope and having a higher viscosity than the first dope From the second dope to the first layer composed of the first dope, the flow step of flowing the multi-layer dope toward the outlet of the flow channel, the flow-down step of flowing down the multi-layer dope from the outlet of the flow channel And a film forming step of forming on the support a band-shaped multilayer cast film on which the second layer overlaps, and in the distribution step immediately before the flow-down step, the multi-layer dope is maintained with a constant flow width. A first distribution step to flow down and the first distribution work And performing a second circulation step of flowing down towards the multilayer dope flowing the flow widthwise ends to the outlet while the guide to the flow widthwise center at.

  When the angle formed by the flow direction of the multilayer dope in the first distribution step and the flow direction of the multilayer dope in the second distribution step is θ, the value of tan θ is 0.45 or more. It is preferably 0.85 or less.

  The second polymer is preferably acrylic. The first polymer is preferably cellulose acylate.

  After performing the above-described casting film forming method, the multi-layer casting film that can be conveyed independently is peeled off from the support to form a wet film, and both ends in the width direction are gripped. And a film drying step for drying the wet film. Moreover, it is preferable to perform the film | membrane cooling process which cools the said multilayer cast film on the said support body before the said peeling process until it will be in the state which can be conveyed independently.

  According to the present invention, the multi-layer dope is made to flow so as to fill the flow path provided in the casting die, and the portion of the multi-layer dope just before flowing out from the flow path outlet flows through both ends in the longitudinal direction of the flow path. Is guided to both ends in the longitudinal direction, among the beads formed between the outlet of the flow path and the support, both ends in the width direction are thicker than the center, so that the beads are stabilized. Therefore, according to the present invention, it is possible to produce a thin polymer film having stable optical characteristics while preventing thickness unevenness.

It is a schematic diagram which shows the outline | summary of the cross section of a multilayer film. It is explanatory drawing which shows the outline | summary of a 1st solution casting apparatus. It is a perspective view which shows the outline | summary of the casting apparatus provided in the casting chamber. It is YZ plane sectional drawing which shows the outline | summary of a casting apparatus. It is a perspective view which shows the outline | summary of a vane and a distribution pin. It is YZ plane sectional drawing which shows the outline | summary of a confluence | merging part vicinity. It is a perspective view which shows the outline | summary of a casting die. It is a VIII-VIII line sectional view showing an outline of a casting die. It is an IX part enlarged view which shows the outline | summary of an inner deckle board. It is XX sectional drawing which shows the outline | summary of a multilayer dope flow path. It is a side view which shows the outline | summary of the bead formed between a casting die and a casting drum. It is a schematic diagram which shows the outline | summary of the cross section of a multilayer casting film. It is a schematic diagram about the cross section of the bead in the XIII-XIII line. Illustration of the bead layer structure is omitted. It is explanatory drawing which shows the outline | summary of the 2nd solution casting apparatus. It is sectional drawing which shows the outline | summary of a multi-manifold type casting die. It is explanatory drawing which shows a mode that a multilayer casting film is formed by the 1st sequential casting method. It is explanatory drawing which shows a mode that a multilayer casting film is formed by the 2nd sequential casting method.

  As shown in FIG. 1, in the multilayer film 10, the first layer 10a, the second layer 10b, and the third layer 10c overlap in order. The first layer 10a and the third layer 10c are provided so as to be exposed on both surfaces of the multilayer film 10, and the second layer 10b is located between the first layer 10a and the third layer 10c.

  Since the second layer 10b is responsible for most of the optical characteristics of the entire multilayer film 10, the second polymer as the raw material of the second layer 10b satisfies the optical characteristics required for the multilayer film 10. Is used. On the other hand, as the first polymer that is a raw material for the first layer 10a and the third layer 10c, in addition to satisfying the restrictions of the solution film forming method described above, a polymer that does not impair the optical characteristics exhibited by the second layer 10b is used. Is preferred. Details of the first polymer and the second polymer will be described later.

  The thickness THs of the multilayer film 10 is preferably 20 μm or more and 80 μm or less, and more preferably 30 μm or more and 70 μm or less.

  The second layer 10b is preferably thicker than the first layer 10a and the third layer 10c. The thickness of the first layer 10a may be equal to or different from the thickness of the third layer 10c. When the thickness of the first layer 10a is THa and the thickness of the third layer 10c is THc, the value of {(THa + THc) / THs} is preferably 0.05 or more and 0.4 or less. It is preferable that it is 1 or more and 0.25 or less. The thickness THa of the first layer 10a is preferably 2 μm or more and 10 μm or less, and more preferably 3 μm or more and 6 μm or less. The thickness THb of the second layer 10b is preferably 15 μm or more and 75 μm or less, and more preferably 25 μm or more and 60 μm or less. The thickness THc of the third layer 10c is preferably 2 μm or more and 10 μm or less, and more preferably 3 μm or more and 6 μm or less.

  The multilayer film 10 is more brittle than a film made of the first polymer or a film made of the second polymer. The multilayer film 10 having high brittleness is highly suitable for machining such as cutting.

(Solution casting equipment)
The solution casting apparatus 11 is for making the multilayer film 10, and has a casting chamber 12, a pin tenter 13, a drying chamber 15, a cooling chamber 16, and a winding chamber 17, as shown in FIG.

  In the casting chamber 12, a casting apparatus 20 that flows out a multilayer dope described later, a casting drum 22 that forms a multilayer casting film 21 from the flowed-out multilayer dope, and a multilayer flow from the casting drum 22. A stripping roller 23 for stripping the spread film 21 is provided.

  As shown in FIGS. 2 and 3, the casting drum 22 includes a shaft 22a arranged to be horizontal and a drum body 22b attached to the shaft 22a. Hereinafter, the axial direction of the shaft 22a 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 drum body 22b is rotated around the shaft 22a by a driving device (not shown) under the control of the control unit. Due to the rotation of the drum body 22b, the peripheral surface 22c of the drum body 22b moves at a predetermined speed (for example, 50 m / min to 200 m / min). A temperature control device 24 is connected to the drum body 22b. The temperature control device 24 includes a temperature adjusting unit that adjusts the temperature of the heat transfer medium. The temperature control device 24 circulates a heat transfer medium adjusted to a desired temperature between the temperature adjusting unit and the flow path provided in the drum main body 22b. By circulating the heat transfer medium, the temperature of the peripheral surface 22c can be kept within a range in which the multilayer cast film can be cooled.

  The drum body 22b 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 22c is preferably so-called hard chromium plating with a Vickers hardness of Hv 700 or more and a film thickness of 2 μm or more.

  A pin tenter 13, a drying chamber 15, a cooling chamber 16, and a winding chamber 17 are sequentially installed downstream of the casting chamber 12. A roller 32 that introduces the wet film 30 peeled off by the peeling roller 23 into the pin tenter 13 is disposed in the transition portion 29 provided between the casting chamber 12 and the pin tenter 13. A blower (not shown) applies a predetermined wind to the wet film 30 conveyed by the roller 32.

  The pin tenter 13 has a number of pins that pass through and hold both side edges of the wet film 30. The pins are provided on a pin plate 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.

  An ear clip device 34 is provided downstream of the pin tenter 13. The edge-cutting 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.

  A large number of rollers 37 are provided in the drying chamber 15, and the multilayer film 10 is conveyed while being wound around these rollers 37. The temperature and humidity of the atmosphere in the drying chamber 15 are adjusted by an air conditioner (not shown), and the multilayer film 10 is dried by passing through the drying chamber 15. An adsorption recovery device is connected to the drying chamber 15, and the solvent evaporated from the multilayer film 10 is absorbed and recovered.

  A cooling chamber 16 is provided on the outlet side of the drying chamber 15, and the multilayer film 10 is cooled in this cooling chamber 16 until it reaches 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. In the winding chamber 17, a winding machine 40 having a press roller 39 is installed, and the multilayer film 10 is wound around the winding core 41 in a roll shape.

(Casting device)
As shown in FIG. 2, the casting apparatus 20 is provided above the casting drum 22, and feeds a multi-layer dope and a multi-layer dope produced by the feed block 51 to the casting drum 22. And a casting die 52. The feed block 51 and the casting die 52 are each provided with a temperature control unit (not shown).

  The decompression chamber 53 may be arranged upstream of the casting die 52 in the moving direction of the peripheral surface 22c. The decompression chamber 53 decompresses the upstream side in the moving direction of the bead to a desired pressure. The decompression chamber 53 can decompress the upstream side in the moving direction of the bead so that the pressure on the upstream side of the bead is lower than the pressure on the downstream side. The pressure difference between the upstream side and the downstream side of the bead is preferably 10 Pa or more and 2000 Pa or less.

  The feed block 51 is connected to the first storage tank 56a of the first dope 45a by a first pipe 55a including a first pump 54a. Similarly, the feed block 51 has a second storage tank 56b for the second dope 45b by a second pipe 55b having a second pump 54b, and a third storage for a third dope 45c by a third pipe 55c having a third pump 54c. Each is connected to the tank 56c. Details of the first dope 45a to the third dope 45c will be described later.

(Feed block)
As shown in FIGS. 3 and 4, the feed block 51 is formed in a block shape and includes a feed block main body 51 a having a through hole penetrating in the Z direction. A through hole inlet 51i is opened on the upper surface of the feed block main body 51a, and an outlet 51o of the through hole is opened on the lower surface of the feed block main body 51a. Two partition members 57 are arranged from the entrance to the upstream portion of the through hole. The partition member 57 partitions the upstream portion of the through hole into three flow paths (a first flow path 59a, a second flow path 59b, and a third flow path 59c). The second channel 59b is located between the first channel 59a and the third channel 59c. The second flow path 59b communicates with the pipe 55b. The first flow path 59a communicates with the pipe 55a, and the third flow path 59c communicates with the pipe 55c. Thus, in the through hole between the partition member 57 and the outlet 51o, a merging portion 62 for creating a multilayer dope by the merging of the first to third dopes 45a to 45c, and a multilayer dope flow for sending the multilayer dope to the outlet 51o A path 63 is sequentially provided from the upstream side toward the downstream side.

  The partition member 57 includes a partition block 57a and a vane 57b. As shown in FIGS. 4 and 5, the wedge-shaped vane 57 b is arranged 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 sharp tip portion. The vane 57b is swingably attached about the swing shaft 57c.

  Also, as shown in FIG. 6, distribution pins 64 are provided at the outlet 59ao of the first flow path 59a and the outlet 59co of the third flow path 59c.

  As shown in FIG. 5, the distribution pin 64 has a cylindrical shape, a pin main body 64 a that is rotatable about an axis, and a notch groove formed in the circumferential direction on the peripheral surface of the pin main body 64 a. 64b. The pin body 64a is arranged so that the axis direction is parallel to the X direction. It is preferable that the depth of the notch groove provided in each distribution pin 64 and the width in the X direction gradually increase or decrease gradually toward the circumferential direction.

  As shown in FIG. 6, by rotating each distribution pin 64 and swinging each vane 57b, the area of the outlet 59bo of the second flow path 59b, the area of the outlet 59ao of the first flow path 59a, and the third flow The area of the outlet 59co of the path 59c can be adjusted independently.

  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.

(Casting die)
As shown in FIG. 7, the casting die 52 includes a casting die body 70 having a slot 69. The casting die body 70 includes a pair of lip plates 71 and a pair of side plates 72. The pair of lip plates 71 provided in the X direction are arranged in the Y direction so as to be separated from each other. The pair of side plates are arranged in the X direction so as to close a gap between the pair of lip plates. Thus, a slot 69 surrounded by the pair of lip plates 71 and the pair of side plates 72 is formed in the casting die body 70.

  As shown in FIG. 8, the slot 69 is provided in the Z direction so as to penetrate the casting die body 70. An inlet 69 i of the slot 69 is opened at the upper part of the casting die body 70, and an outlet 69 o of the slot 69 is opened at the lower part of the casting die body 70. The cross-sectional shape of the slot 69 on the plane orthogonal to the flow direction (XY plane) is a rectangular shape that is long in the X direction and short in the Y direction.

  The slot 69 is provided with a pre-widening slot portion 76, a first widening slot portion 77, a second widening slot portion 78, and a post-widening slot portion 79 in order from the inlet 69i to the outlet 69o.

  Flow width regulating plates (hereinafter referred to as inner deckle plates) 80 are extended from the first widened slot portion 77 to the outlet 69o at both ends in the X direction of the slot 69. The length in the X direction of the slot 69 from the first widened slot portion 77 to the outlet 69 o is adjusted by the liquid contact surface 81 of the pair of inner deckle plates 80.

  The liquid contact surface 81 of the inner deckle plate 80 includes a first liquid contact surface 81a and a second liquid contact surface 81b that are continuous from the upstream side to the downstream side in the flow direction. The first liquid contact surface 81 a is formed to be orthogonal to the X direction, and extends from the first widened slot portion 77 to the middle of the widened slot portion 79. The second liquid contact plane 81b extends from the X-direction end side of the widened slot portion 79 toward the X-direction center side from the lower end portion of the first liquid contact plane 81a toward the outlet 69o.

  A portion surrounded by the wetted surface of the pair of lip plates 71 and the first wetted surface 81a of the pair of inner deckle plates 80 in the post-widened slot portion 79 is referred to as a first widened slot portion 79a. A portion surrounded by the liquid contact surface of the pair of lip plates 71 and the second liquid contact surface 81b of the pair of inner deckle plates 80 is referred to as a second widened slot portion 79b.

  The length in the X direction of the slot 69 on the XY plane is constant in the pre-widening slot portion 76, the second widening slot portion 78, and the first widening slot portion 79a from the upstream side to the downstream side in the flow direction. The first widened slot portion 77 gradually increases, and the second widened slot portion 79b gradually decreases. On the other hand, the length of the slot 69 in the XY plane in the Y direction is constant from the upstream slot portion 76 to the first widened slot portion 77 and the widened slot portion 79 from the upstream side to the downstream side in the flow direction. Yes, it gradually decreases at the second widened slot portion 78.

As shown in FIG. 9, the length from the upstream end to the downstream end of the second liquid contact plane 81b in the Z direction is L1, and the length from the upstream end to the downstream end of the second liquid contact plane 81b in the X direction is When L2 is set, the gradient (= L2 / L1) of the second liquid contact surface 81b is preferably 0.45 or more and 0.85 or less. Thus, when the angle of the multilayer dope flow direction V _79b and the angle between the multilayer dope in flow direction V _79a and a second widened rear slot 79b of the θ in the first widening back slot portion 79a, of tanθ The value corresponds to the gradient (= L2 / L1) of the second liquid contact plane 81b. In addition, it is preferable that (L2 / L1) is 0.5 or more and 0.65 or less. When the value of (L2 / L1) is less than 0.45, both side edges in the width direction of the multilayer casting film 21 are curled so as to stand up from the peripheral surface 22c of the casting drum 22 by evaporation of the solvent. . As a result, the ear break occurs. In addition, when the value of (L2 / L1) exceeds 0.85, both side edges in the width direction of the multilayer cast film 21 become too thick, which is not preferable because an ear fold occurs.

  Next, the solution casting method performed in the solution casting equipment 11 will be described. As shown in FIG. 2, the dopes 45 a to 45 c are sent to the casting apparatus 20 by the pumps 54 a to 54 c. Moreover, the temperature of dope 45a-45b is kept substantially constant in the range of 30 degreeC or more and 35 degrees C or less, and the temperature of the surrounding surface 22c is kept substantially constant in the range of -10 degreeC or more and 10 degrees C or less.

  The casting apparatus 20 creates a multilayer dope from the dopes 45 a to 45 c, and flows the multilayer dope out toward the rotating casting drum 22. On the casting drum 22, a strip-shaped multilayer casting film 21 made of multilayer dope is formed. As a result of cooling the multilayer casting film 21 on the casting drum 22, the dope forming the first layer 21a, the dope forming the second layer 21b, and the dope forming the third layer 21c are gelled. Due to this gelation, the multilayer cast film 21 is in a state where it can be conveyed independently.

  Here, the gelation includes a state in which the fluidity of the dope is lost in addition to a state in which the colloidal solution is solidified in a jelly shape. Note that “the fluidity of the dope is lost” means that when the solute is a polymer, the fluidity is lost while the solvent is retained in the molecular chain of the solute, and as a result, the fluidity of the solution is reduced. This includes a lost state and a state in which the fluidity of the solution is lost due to the interaction between the solvent molecules and the solute molecules when the solute is a low molecule.

  Thereafter, the peeling roller 23 peels off the multilayer casting film 21 that is in a state where it can be independently conveyed, from the casting drum 22 as a belt-like wet film 30, and to the pin tenter 13 through the crossing part 29. invite.

  The residual solvent amount of the multilayer cast film at the time of peeling is preferably 200% by mass or more and 300% by mass or less. In the present invention, the amount of the solvent remaining in the multilayer cast film or each film is shown on the basis of dry weight as the residual solvent amount. Moreover, the measurement method takes the sample from the target film, and when the mass of this sample is x and the mass after drying the sample is y, it is calculated as {(xy) / y} × 100. .

  The wet film 30 sent out from the casting chamber 12 is conveyed to the pin tenter 13 by the roller 32 of the crossover part 29. The blower device applies a predetermined wind to the wet film 30 to advance the drying of the wet film 30. By this drying, the wet film 30 becomes the multilayer film 10. The temperature of the wind is preferably 20 ° C. or higher and 250 ° C. or lower. The multilayer film 10 sent out from the pin tenter 13 is sequentially conveyed to the ear clip device 34, the drying chamber 15, the cooling chamber 16, and the winding chamber 17.

  Next, the operation in the casting apparatus 20 will be described. As shown in FIG. 4, the dopes 45 a to 45 c sent out to the feed block 51 are joined at the joining unit 66 under the control of the control unit 66. Then, a multi-layer dope 90 is formed by the merging of the respective dopes 45a to 45c (see FIG. 10). The multi-layer dope 90 includes a first layer 90 a composed of the first dope 45 a flowing in one of both sides in the short direction (Y direction) of the multi-layer dope channel 63, and the short direction of the multi-layer dope channel 63. (Y direction) It has the 3rd layer 90c which consists of the 3rd dope 45c which flows the other among both sides, and the 2nd layer 90b which consists of the 2nd dope 45b which flows between the 1st dope 45a and the 3rd dope 45c.

When the thickness of the first layer 90a is TH _90a , the thickness of the second layer 90b is TH _90b, and the thickness of the third layer 90c is TH _90c , the value of (TH _90a / TH _90b ) is 0.03 or more and 0 .6 or less is preferable. The value of (TH _90c / TH _90b ) is preferably 0.03 or more and 0.6 or less. The thickness _{TH 90a} of the first layer 90a is preferably 1mm or more 10mm or less, and more preferably 2mm or more than 6mm. The thickness _{TH 90b} of the second layer 90b is preferably 10mm or more 35mm or less, and more preferably 15mm or more 25mm or less. The thickness _{TH 90c} of the third layer 90c is preferably 1mm or more 10mm or less, and more preferably 2mm or more than 6mm.

  The multilayer dope 90 produced by the feed block 51 is sent to the casting die 52 through the multilayer dope channel 63 (see FIG. 8). The multi-layer dope 90 sent to the casting die 52 sequentially passes through the pre-widening slot portion 76, the first widening slot portion 77, the second widening slot portion 78, and the post-widening slot portion 79.

  In the first widened slot portion 77 and the second widened slot portion 78, the multilayer dope 90 that has passed through the pre-widened slot portion 76 flows toward the second widened slot portion 78 while spreading in the X direction. Thus, the first widened slot portion 77 and the second widened slot portion 78 allow the multilayer dope 90 to flow while expanding in the X direction until reaching the first liquid contact surface 81a of the pair of inner deckle plates 80.

  In the first widened slot portion 79a, the multilayer dope 90 flows toward the second widened slot portion 79b with a constant flow width. And in the slot part 79b after the 2nd widening, the multilayer dope 90 flows toward the exit 69o, the flow width becomes narrow gradually.

  Thus, the multi-layer dope 90 flows uniformly between the pair of inner deckle plates 80 from the slot portion 79 after widening to the outlet 69o without any gap.

  At the center in the X direction of the widened slot portion 79, the multilayer dope 90 flows in the Z direction toward the outlet 69o. At both ends in the X direction of the widened slot portion 79, the multilayer dope 90 flows along the first liquid contact plane 81a and the second liquid contact plane 81b. Then, the multilayer dope 90 that has passed through the widened slot 79 flows out from the outlet 69o toward the casting drum 27 (see FIG. 11). The multilayer dope 90 flowing out from the outlet 69o forms a bead 92 until it reaches the casting drum 27, and after reaching the casting drum 27, forms a multilayer casting film 21 on the peripheral surface 22c. To do. As shown in FIG. 12, the multilayer cast film 21 includes a first layer 21a made of the first dope 45a, a second layer 21b made of the second dope 45b, and a third layer 21c made of the third dope 45c. Overlapping in order.

  Here, when the inner deckle plate 80 having a liquid contact surface having only the first liquid contact surface 81a is used, both ends of the bead 92 in the X direction in the X direction are unstable. As a result, the thickness unevenness of the multilayer cast film 21 occurs. This destabilization of both ends of the bead 92 in the X direction includes the viscosity and elastic modulus of the second polymer included in the second layer 90b in the multilayer dope 90 included in the first layer 90a and the third layer 90c. This is considered to be due to being lower than that of the first polymer.

  In the present invention, since the inner deckle plate 80 is provided with the liquid contact surface 81 having the first liquid contact surface 81a and the second liquid contact surface 81b, the multilayer dope 90 is immediately before flowing out from the outlet 69o. The part which flows through X direction both ends can be brought near to the X direction center part. Accordingly, the outflow pressure of the multilayer dope 90 at both ends in the X direction is increased so that the outflow pressure of the multilayer dope 90 at both ends in the X direction becomes higher than the outflow pressure of the multilayer dope 90 at the center in the X direction. be able to. When the outflow pressure of the multilayer dope 90 has such a distribution, the bead 92 in the X direction is thicker at the X-direction end portions 92e than at the X-direction center portion 92c (see FIG. 13). As a result, it is possible to stabilize both ends 92e of the bead 92 in the X direction. Thus, according to the present invention, it is possible to cast the multilayer dope 90 while stabilizing both ends 92e of the bead 92 in the X direction, so that it is possible to prevent uneven thickness of the multilayer cast film 21. it can.

  The X direction both ends 92e are preferably formed on both ends in the X direction from the position Px through which the pin of the pin tenter 13 passes. When the thickness of the bead 92 at the central portion 92c in the X direction is Dc and the thickness of the end portions 92e in the X direction is De, the value of De / Dc is preferably greater than 1 and 1.2 or less. The De / Dc value may be obtained by dividing the thickness of both end portions in the width direction of the strip-shaped multilayer film 10 by the thickness of the central portion in the width direction of the multilayer film 10. Here, when the width of the multilayer film 10 is W, the width of both end portions in the width direction of the multilayer film 10 is 0.01 W or more and 0.05 W or less. The thickness of the multilayer film 10 can be measured with a contact-type film thickness meter.

  In the above embodiment, the Z direction is orthogonal to the horizontal plane, but the present invention is not limited to this, and the Z direction may intersect the horizontal plane.

  In the above embodiment, the casting drum 22 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 moves by the rotation of the roller may be used. In the above embodiment, the multilayer casting film 21 is self-supporting by cooling. However, the present invention is not limited to this, and the multilayer casting film 21 is dried by drying the solvent. The film 21 may exhibit self-supporting properties.

  Next, the solution casting apparatus 111 having a casting band as a support will be described. In the description of the solution casting equipment 111, parts and members different from the solution casting equipment 11 will be described, and the same parts and members as those of the solution casting equipment 11 will be denoted by the same reference numerals, and the description thereof will be omitted. .

  As shown in FIG. 14, the solution casting apparatus 111 has a casting chamber 12, a clip tenter 114, a drying chamber 15, a cooling chamber 16, and a winding chamber 17.

  In the casting chamber 12, a feed block 51 and a casting die 52 are provided. Below the casting die 52, rotating rollers 117 and 118 are provided. A casting band 120 is stretched around the rotating rollers 117 and 118. One end and the other end of the casting band 120 are connected, and the casting band 120 has an annular shape. The rotating rollers 117 and 118 are rotated by a driving device (not shown), and the casting band 120 moves with the rotation. The multilayer dope 90 flowing out of the casting die 52 forms the multilayer casting film 21 on the casting band 120.

  It is preferable that the moving speed of the casting band 120, that is, the moving speed is 10 m / min or more and 200 m / min or less. is there. When the casting speed is less than 10 m / min, the productivity of the film is inferior. Moreover, when it exceeds 200 m / min, a casting bead will not be formed stably and there exists a possibility that the planar shape of the multilayer casting film 21 may deteriorate.

  Further, in order to set the surface temperature of the casting band 120 to a predetermined value, it is preferable that the temperature control device 24 is attached to the rotary rollers 117 and 118. It is preferable that the temperature control device 24 adjusts the temperature of the casting band 120 within a range in which the multilayer casting film can be heated.

  Further, the casting chamber 12 includes blowers 123 to 125 that apply dry air to the multilayer casting film 21. The blowers 123 to 125 are provided downstream of the casting die 52 in the moving direction of the casting band 120. When dry air is applied to the multilayer casting film 21, the solvent evaporates from the multilayer casting film 21. A labyrinth seal that blocks dry air may be provided between the casting die 52 and the blower 123. By installing this labyrinth seal, it is possible to suppress the surface variation of the multilayer casting film 21 due to the contact between the multilayer casting film 21 immediately after casting and the drying air. Further, an air blower (hereinafter, referred to as a quick dry air blower) 127 that applies quick drying air to the multilayer cast film 21 may be provided between the casting die 52 and the air blower 123. In addition, when providing a labyrinth seal between the casting die 52 and the blower 127, the quick drying blower 127 may be provided between the labyrinth seal and the blower 127. When rapid drying air is applied to the multilayer casting film 21, the solvent contained in the multilayer casting film 21 evaporates at a higher evaporation rate than when the drying air is applied. Thereby, a skin layer can be formed on the surface of the multilayer casting film 21. In the initial stage of the process of evaporating the solvent from the multilayer casting film 21, by providing the skin layer on the multilayer casting film 21, the multilayer film 10 having an excellent surface shape can be produced.

  The clip tenter 114 has a number of clips that grip both side edges of the wet film 30 in the width direction, and these clips move on the stretching track. Dry air is sent to the wet film 30 that is moved by the clip, and the wet film 30 is subjected to a drying process along with a stretching process in the width direction.

  Next, an example of the manufacturing method of the multilayer film 10 in the solution casting apparatus 111 is demonstrated below.

  The casting band 120 is moved by the driving of the rotating rollers 117 and 118. The casting die 52 continuously causes the multilayer dope 90 to flow out onto the casting band 120. A casting bead is formed from the casting die 52 to the casting band 120, and the multilayer casting film 21 is formed on the casting band 120. The multilayer casting film 21 formed on the casting band 120 moves to the vicinity of the peeling roller 23 by the movement of the casting band 120. The quick drying blower 127 applies the quick drying air to the multilayer casting film 21. A skin layer is formed on the surface of the multilayer casting film 21 by rapid evaporation of the solvent in the multilayer casting film 21. The air blowers 123 to 125 apply dry air to the multilayer cast film 21. Due to the evaporation of the solvent in the multilayer casting film 21, the multilayer casting film 21 is in a state where it can be conveyed independently. The multilayer casting film 21 that can be independently conveyed can be peeled off from the casting band 120 by the peeling roller 23. It is preferable that the residual solvent amount at the time of peeling off the multilayer casting film 21 is 10% by mass or more and 100% by mass or less.

  The wet film 30 sent out from the casting chamber 12 is conveyed to the clip tenter 114 by the roller 32 of the crossover part 29. In the clip tenter 114, the wet film 30 is subjected to predetermined drying processing and stretching processing. The wet film 30 becomes the multilayer film 10 by the processing in the clip tenter 114. The multilayer film 10 sent out from the clip tenter 114 is sequentially conveyed to the ear clip device 34, the drying chamber 15, the cooling chamber 16, and the winding chamber 17.

  The multilayer cast film 21 formed in the above embodiment and the produced multilayer film 10 have a three-layer structure, but the present invention is not limited to this, and a two-layer structure or a multilayer structure of four or more layers. It is good.

  In the above embodiment, the casting apparatus 20 having the feed block 51 and the casting die 52 is used. However, the present invention is not limited to this, and instead of the casting apparatus 20, a multi-manifold casting die 130 (see FIG. 15) may be used. The casting die 130 includes a block-shaped casting die body provided with first to third flow paths 131a to 131c.

  The second flow path 131b extends in the Z direction so as to penetrate the casting die body, and an outlet 131bo of the second through hole 131b is opened on the lower surface of the casting die body. Further, in the middle of the second flow path 131b, the second manifold 133b and the merging portion 62 are sequentially formed from the upstream side toward the downstream side. The first through hole 131a and the third through hole 131c are provided so as to penetrate the casting die body, and are connected to the second through hole 131b at the junction 62. A first manifold 133a is provided in the first through hole 131a, and a second manifold 133b is provided in the second through hole 131b.

  The first manifold 133a communicates with the pipe 55a (see FIG. 2), the second manifold 133b communicates with the pipe 55b (see FIG. 2), and the third manifold 133c communicates with the pipe 55c (see FIG. 2). The shape of the second through hole 131b between the junction portion 62 and the outlet 131o is the same shape as the slot 69 (see FIG. 4).

  The first dope 45a is sent to the first through hole 131a, the second dope 45b is sent to the second through hole 131b, and the third dope 45c is sent to the third through hole 131c. In the merging portion 62, a multi-layer dope is created by the merging of the respective dopes 45a to 45c. By causing the multilayer dope to flow out from the outlet 130o toward the casting drum, a multilayer casting film can be formed on the casting drum.

  In the above embodiment, the multilayer cast film is formed by co-casting in which a plurality of dopes are simultaneously flowed out, but the present invention is not limited to this.

  For example, as shown in FIG. 16, a first casting die 141 that flows out the first dope 45a and a second casting die 142 that flows out the second dope 45b and the third dope 45c at the same time are connected to the moving support 143. You may arrange sequentially in a moving direction upwards. The first casting die 141 uses a casting apparatus 20 (see FIG. 2) in which the flow paths 59a and 59c are omitted, and a casting die 130 (see FIG. 15) in which the through holes 131a and 131c are omitted. It is preferable to distribute the first dope 45a through the passage 59b and the through hole 131b. The second casting die 142 uses the casting apparatus 20 (see FIG. 2) in which the flow path 59a is omitted, or the casting die 130 (see FIG. 15) in which the through hole 131a is omitted. The second dope 45b is preferably passed through the hole 131b, and the third dope 45c is preferably passed through the channel 59c and the through hole 131c.

  When the first casting die 141 flows out of the first dope 45a, a first dope film 145a made of the first dope 45a is formed on the moving support 143. When the second casting die 142 flows out the second dope 45b and the third dope 45c simultaneously, the second dope film made of the second dope 45b and the third dope made of the third dope 45c are formed on the first dope film 145a. Doped films overlap one after another. Thus, a multilayer cast film 145 is formed in which the first layer made of the first dope, the second layer made of the second dope, and the third layer made of the third dope are sequentially overlapped.

  Also, as shown in FIG. 17, a first casting die 151 that flows out the first dope 45a and the second dope 45b simultaneously, and a second casting die 152 that flows out the second dope 45b and the third dope 45c simultaneously, May be sequentially arranged in the moving direction above the moving support 143. The first casting die 151 uses the casting apparatus 20 (see FIG. 2) in which the flow path 59c is omitted, or the casting die 130 (see FIG. 15) in which the through hole 131c is omitted, and the flow path 59a and the penetration die 151. The first dope 45a is preferably passed through the hole 131a, and the second dope 45b is preferably passed through the channel 59b and the through hole 131b. The second casting die 152 uses a casting apparatus 20 (see FIG. 2) in which the flow paths 59a and 59c are omitted, and a casting die 130 (see FIG. 15) in which the through holes 131a and 131c are omitted. It is preferable to distribute the second dope 45b through the passage 59b and the through hole 131b.

  When the first casting die 151 flows out of the first dope 45a and the second dope 45b, on the moving support 143, a first layer made of the first dope 45a and a second layer made of the second dope 45b are formed on the first layer. A multi-layer doped film 154 composed of the second layer overlapping with the first layer is formed. Then, when the second casting die 152 flows out of the third dope 45c, the third dope film made of the third dope 45c sequentially overlaps the multilayer dope film 154. Thus, a multilayer cast film 156 is formed in which the first layer made of the first dope, the second layer made of the second dope, and the third layer made of the third dope are sequentially overlapped.

(First dope to third dope)
The first dope 45a is obtained by dissolving the first polymer in the first solvent, the second dope 45b is obtained by dissolving the second polymer in the second solvent, and the third dope 45c is provided by the third solvent. A polymer is dissolved in a third solvent.

  The first dope 45a has a lower viscosity than the second dope 45b, and the third dope 45c has a lower viscosity than the second dope 45b. 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. Although the viscosity of each dope is not particularly limited, for example, the viscosity of the second dope 45b is preferably 40 Pa · second to 150 Pa · second, and more preferably 50 Pa · second to 100 Pa · second. The viscosity of the first dope 45a and the third dope 45c is preferably 20 Pa · second to 80 Pa · second, and more preferably 30 Pa · second to 50 Pa · second.

The solvent concentration CS1 of the first solvent contained in the first dope 45a, the solvent concentration CS2 of the second solvent contained in the second dope 45b, and the solvent concentration CS3 of the third solvent contained in the third dope 45c are equal. preferable. The difference ΔCS _1-2 (= | CS1-CS2 |) between the solvent concentration CS1 and the solvent concentration CS2 is preferably 10% by mass or less, for example. Further, the difference ΔCS _3-2 (= | CS3-CS2 |) between the solvent concentration CS3 and the solvent concentration CS2 is preferably 10% by mass or less, for example. When the difference ΔCS _1-2 or the difference ΔCS _3-2 exceeds 10 mass%, the solvent concentration is high at the interface between the first layer and the second layer or the interface between the third layer and the second layer. This is because foreign substances (polymer aggregates) are generated in one layer as a result of the movement of the solvent from one layer to another layer having a low solvent concentration. The solvent concentration CS2 is preferably 10% by mass or more and 30% by mass or less, and more preferably 15% by mass or more and 25% by mass or less.

(polymer)
The first polymer and the second polymer are different, and the third polymer and the second polymer are different. The water absorption rate of the second polymer is preferably lower than the water absorption rate of the first polymer. The first polymer and the third polymer are preferably the same. The elastic modulus of the first polymer is higher than that of the second polymer, and the viscosity of the first polymer is preferably higher than the viscosity of the second polymer.

(First polymer)
As the first polymer, for example, a cellulose acylate resin can be used. As the cellulose acylate resin, 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 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. 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.

  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 of the present invention 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].

(Second polymer)
As the second polymer, an acrylic resin is preferably used.

(acrylic resin)
Acrylic resins include methacrylic resins, and acrylate / methacrylate derivatives, in particular, acrylate ester / methacrylate ester (co) polymers are well known. Although it does not restrict | limit especially as an acrylic resin, What consists of 50-99 mass% of methylmethacrylate units and 1-50 mass% of other monomer units copolymerizable with this has a small photoelastic coefficient. Preferred for obtaining a film.

  In the acrylic resin, the other copolymerizable monomer includes alkyl methacrylate having 2 to 18 carbon atoms in the alkyl group, alkyl acrylate having 1 to 18 carbon atoms in the alkyl number, acrylic acid, methacrylic acid, and the like. α, β-unsaturated acids, maleic acids, fumaric acids, dicarboxylic acids containing unsaturated groups such as itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β such as acrylonitrile and methacrylonitrile -Unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned, and these can be used alone or in combination of two or more monomers as a copolymerization component. .

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

  As a resin that can form a highly transparent optical film with little performance change even in high temperature and high humidity environments, acrylic resins contain alicyclic alkyl groups as copolymerization components, or have molecular mains by intramolecular cyclization. An acrylic resin in which a cyclic structure is formed in the chain is preferable. As an example of the acrylic resin in which a cyclic structure is formed in the molecular main chain, an acrylic thermoplastic resin containing a lactone ring-containing polymer can be cited as one preferred embodiment. No. 171464. Another preferred embodiment is a resin containing glutaric anhydride as a copolymerization component, and the copolymerization component and a specific synthesis method are described in JP-A-2004-070296.

  The weight average molecular weight of the acrylic resin is 600,000 to 4,000,000, preferably 800,000 to 3,000,000, and particularly preferably 1,000,000 to 1,800,000. The weight average molecular weight of the acrylic resin can be measured by gel permeation chromatography.

There is no restriction | limiting in particular as a manufacturing method of an acrylic resin, Well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization, can be used. In the present invention, a plurality of acrylic resins can be used in combination.
* Are you sure that underlined “Acrylic resin can be used in combination of two or more”?

  The acrylic resin can further contain another thermoplastic resin. In the present invention, the thermoplastic resin having a glass transition temperature of 100 ° C. or higher and a total light transmittance of 85% or higher is mixed with the acrylic resin to form a film. It is preferable in terms of improving the strength.

  The content ratio of the acrylic resin and other thermoplastic resin components in the acrylic resin layer is a mass ratio of [acrylic resin / (total thermoplastic resin)] × 100, preferably 30 to 99 mass%, more preferably 50. It is -97 mass%, More preferably, it is 60-95 mass%. A content ratio of the acrylic resin in the acrylic resin layer of 30% by mass or more is preferable because heat resistance can be sufficiently exhibited.

  Examples of the other thermoplastic resins include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins. Polymer; Styrenic polymer such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; Polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; Nylon 6, polyamides such as nylon 66, nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; polyether ether ketone; Terusaruhon; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as acrylic rubber ABS resin or ASA resin blended with; and the like. The rubbery polymer preferably has a graft portion having a composition compatible with the ring polymer in the present invention on the surface, and the average particle size of the rubbery polymer is improved in transparency when formed into a film. In view of the above, it is preferably 100 nm or less, and more preferably 70 nm or less.

  As the other thermoplastic resin, a resin that is thermodynamically compatible with an acrylic resin is preferably used. Preferred examples of such other thermoplastic resins include acrylonitrile-styrene copolymers having a vinyl cyanide monomer unit and an aromatic vinyl monomer unit, and a polyvinyl chloride resin. Among them, an acrylonitrile-styrene copolymer can easily provide an optical film having a glass transition temperature of 120 ° C. or more, a phase difference per 100 μm in the plane direction of 20 nm or less, and a total light transmittance of 85% or more. Therefore, it is preferable. Specifically, as the acrylonitrile-styrene copolymer, those having a copolymerization ratio in a molar unit of 1:10 to 10: 1 are usefully used.

(solvent)
The first to third solvents may be a single solvent or a mixture of a plurality of solvents. Any of the first to third solvents may be different or all may be the same. Further, two of the first to third solvents may be the same and the remaining may be different. When at least one of the first solvent to the third solvent is a mixture of a plurality of solvents, it is preferable that a common solvent is contained in all of the first solvent to the third solvent.

  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.

  By the way, recently, for the purpose of minimizing the influence on the environment, studies have been conducted on the solvent composition when dichloromethane is not used. For this purpose, ethers having 4 to 12 carbon atoms, 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 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.

  The multilayer film of the present invention preferably has a film width of 700 mm to 3000 mm, more preferably 1000 mm to 2800 mm, and particularly preferably 1500 mm to 2500 mm. The multilayer film of the present invention may have a film width of 2500 mm or more.

(Haze)
The haze of the multilayer film of the present invention is preferably less than 0.20%, more preferably less than 0.15%, and particularly preferably less than 0.10%. By setting the haze to less than 0.2%, the contrast ratio when incorporated in a liquid crystal display device can be improved. In addition, there is an advantage that the transparency of the film becomes higher and it is easier to use as an optical film.

(Re, Rth)
In the multilayer film of the present invention, the in-plane retardation Re (550) at a wavelength of 550 nm is larger than the in-plane retardation Re (440) at a wavelength of 440 nm. With such a wavelength dispersion characteristic, when the film of the present invention is incorporated in a liquid crystal display device, it is possible to solve the problem of color shift when observed obliquely when the liquid crystal display screen is displayed in black.

  In the multilayer film of the present invention, the retardation Rth (550) in the film thickness direction at a wavelength of 550 nm is larger than the retardation Rth (440) in the film thickness direction at a wavelength of 440 nm, which solves the problem of color shift. It is preferable from the viewpoint of facilitating.

  The multilayer film of the present invention is preferably a biaxial optical compensation film. Here, the optical compensation film is biaxial means nx, ny and nz of the optical compensation film (nx represents the refractive index in the slow axis direction in the plane, and ny is the refractive in the direction perpendicular to nx in the plane. Nz represents the refractive index in the direction orthogonal to nx and ny), and in the present invention, it is more preferable that nx> ny> nz. The fact that the film of the present invention exhibits biaxial optical characteristics is a preferable characteristic for reducing the problem of color shift when observed from an oblique direction in a liquid crystal display device, particularly a VA mode liquid crystal display device.

  In the multilayer film of the present invention, it is preferable that the wavelength dispersion of the retardation Re in the in-plane direction and the retardation Rth in the thickness direction becomes larger as the wavelength becomes longer than the light in the visible light region. Here, the light in the visible light region specifically has a wavelength of 380 to 780 nm, and it is preferable that the longer the wavelength, the larger the values of Re and Rth. By using such a film for the liquid crystal display device of the present invention, it is possible to further reduce coloring when the liquid crystal display device is viewed from an oblique direction.

  In the multilayer film of the present invention, when used for a retardation film, Re and Rth are appropriately selected depending on the design of the liquid crystal cell and the optical film, but the in-plane retardation Re is 0 nm at a measurement wavelength of 590 nm. It is preferable that <| Re | <10 nm and the retardation Rth in the film thickness direction is 0 nm <| Rth | ≦ 25 nm from the viewpoint of using as a retardation film for optical compensation for a liquid crystal display device. The Re is more preferably 0 nm <| Re | <5 nm. The Rth is more preferably 0 nm <| Rth | ≦ 10 nm.

  In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. In the present specification, the wavelength λ is 590 nm unless otherwise specified. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotary axis) (in the absence of the slow axis, any direction in the film plane) Is measured in 6 points from the inclined direction in 10 degree steps from the normal direction to 50 degrees on one side with respect to the normal direction of the film. KOBRA 21ADH calculates based on the retardation value, the assumed average refractive index, and the input film thickness value. The retardation value is measured from any two directions with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), and the value Re and Rth can also be calculated from the following formula (A-1), formula (A-2), and formula (B) based on the assumed average refractive index and the input film thickness value. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

Here, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction, nx, ny, and nz represent refractive indexes in respective principal axis directions of the refractive index ellipsoid, and d represents a film. Represents thickness.
Rth = ((nx + ny) / 2−nz) × d Formula (B)

(Photoelasticity)
The photoelastic coefficient of the multilayer film of the present invention is preferably −5.0 × 10 ⁻¹² (Pa ⁻¹ ) or more and 5.0 × 10 ⁻¹² (Pa ⁻¹ ) or less.

(Humidity stability)
The difference (ΔRth (10% -80%)) between Rth measured in an environment of temperature 25 ° C. and humidity 10% RH and Rth measured in an environment of temperature 25 ° C. and humidity 80% RH should be 10 nm or less. preferable.

  Next, in order to confirm the presence or absence of the effect of the present invention, Experiments 1 to 4 were performed. Detailed description will be given in Experiment 1, and in Experiments 2 to 4, description of the same conditions as in Experiment 1 will be omitted, and only different parts will be described.

(Preparation of the first dope)
Cellulose triacetate (substitution degree 2.8) 90% by mass
Additive A (acetic ester of adipic acid / ethylene glycol / propylene glycol condensate (number average molecular weight = 1000, ethylene glycol / propylene glycol ratio = 50/50)) 10% by mass
The solid content (solute) having the composition ratio of dichloromethane was 79% by mass.
Methanol 20% by mass
n-Butanol 1% by mass
The first dope 45a was prepared by appropriately adding to a mixed solvent consisting of The first dope 45a 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. Later, it was put in the first storage tank 56a.

(Preparation of second dope)
Acrylic 90% by mass
Additive A (acetic ester of adipic acid / ethylene glycol / propylene glycol condensate (number average molecular weight = 1000, ethylene glycol / propylene glycol ratio = 50/50) 10% by mass
The solid content (solute) having the composition ratio of dichloromethane was 79% by mass.
Methanol 20% by mass
n-Butanol 1% by mass
The second dope 45b was prepared by appropriately adding to a mixed solvent consisting of and stirring and dissolving. The second dope 45b 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. Later, it was put in the second storage tank 56b.

(Preparation of third dope)
Cellulose triacetate (substitution degree 2.8) 90% by mass
Additive A (acetic ester of adipic acid / ethylene glycol / propylene glycol condensate (number average molecular weight = 1000, ethylene glycol / propylene glycol ratio = 50/50)) 10% by mass
The solid content (solute) having the composition ratio of dichloromethane was 79% by mass.
Methanol 20% by mass
n-Butanol 1% by mass
The third dope 45c was prepared by appropriately adding to a mixed solvent consisting of The third dope 45c 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. Later, it was put in the third storage tank 56c.

  The viscosity μa of the first dope 45a was 20 Pa · sec, the viscosity μb of the second dope 45b was 50 Pa · sec, and the viscosity μc of the third dope 45c was 20 Pa · sec.

(Experiment 1)
The multilayer film 10 was manufactured with the solution casting apparatus 11 shown in FIG. In order to adjust the temperature of the multilayer dope 90 to be substantially constant at about 34 ° C., a jacket (not shown) is provided in the feed block 51 and the casting die 52, and the temperature of the heat transfer medium supplied into the jacket is adjusted. Adjusted. An inner deckle plate 80 having a liquid contact surface 81 is provided in the slot 69 of the casting die 52. The gradient (= L2 / L1) of the second liquid contact surface 81b provided on the inner deckle plate 80 is shown in Table 1.

  As shown in FIG. 4, the controller 66 sent the dopes 45 a to 45 c to the feed block 51 at a predetermined volume flow rate via the pumps 54 a to 54 c. In this way, the multi-layer dope 90 was formed in the merge portion 62 by the merge of the dopes 45a to 45c. The feed block 51 sent the multilayer dope 90 to the casting die 52. The casting die 52 caused the multilayer dope 90 to flow out onto the circumferential surface 22c, and the multilayer casting film 21 was formed on the circumferential surface 22c. In the multilayer cast film 21, the thickness of the second layer 21b was 160 μm, and the thicknesses of the first layer 21a and the third layer 21c were 10 μm, respectively. The multilayer casting film 21 that became self-supporting by cooling was peeled off from the casting drum 22 using a peeling roller 23. The amount of residual solvent at the time of peeling off the multilayer casting film 21 was 200% by mass or more and 270% by mass or less. The wet film 30 obtained by peeling off the multilayer casting film 21 was introduced into the pin tenter 13, and a drying process was performed. The multilayer film 10 was obtained from the wet film 30 by the drying process. After the multilayer film 10 was dried in the drying chamber 15, it was sent to the winding chamber 17 through the cooling chamber 16.

(Evaluation)
The manufactured multilayer film 10 was evaluated as follows.

1. Evaluation of thickness unevenness The multilayer film 10 was measured for thickness unevenness. The procedure for measuring the thickness unevenness is as follows. First, a sample film approximately 6 cm square was cut out from the multilayer film 10. 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 the thickness unevenness of the multilayer film. The thickness unevenness thus obtained was evaluated according to the following criteria. In addition, the thickness of a multilayer film is an average value of the thickness of six places of the sample film measured with the micrometer.
A: The thickness unevenness was less than 1.5% with respect to the thickness of the multilayer film 10.
A: The thickness unevenness was 1.5% or more and less than 1.8% with respect to the thickness of the multilayer film 10.
Δ: The thickness unevenness was 1.8% or more and less than 2.2% with respect to the thickness of the multilayer film 10.
X: The thickness unevenness was 2.2% or more with respect to the thickness of the multilayer film 10.

2. Ear Folding The visual observation was made as to whether or not the ear part breakage occurred in the multilayer cast film 21 and evaluated based on the following criteria.
○: No ear breakage occurred.
×: Ear part breakage occurred.

(Experiments 2-4)
A multilayer film 10 was produced in the same manner as in Experiment 1 except that the conditions were changed to the values shown in Table 1.

  Table 1 shows the gradient (= L2 / L1) of the second liquid contact surface 81b and the evaluation results for each evaluation item in Experiments 1 to 4. The number of the evaluation result in Table 1 represents the number assigned to each evaluation item.

DESCRIPTION OF SYMBOLS 10 Multilayer film 11 Solution casting equipment 20 Casting apparatus 22 Casting drum 45a 1st dope 45b 2nd dope 45c 3rd dope 51 Feed block 51 Casting die 69 Slot 79 Widened slot part 80 Inner deckle board 81a 1st 1 wetted plane 81b 2nd wetted plane

Claims (8)

A second dope containing a first dope containing a first polymer and a second polymer having a lower viscosity and a lower elastic modulus than the first polymer into a slot-like flow path provided so as to penetrate the block-shaped casting apparatus main body. A dope is flown and the first dope flowing on the short side end side of the flow path in the cross section in the flow direction and a second dope flowing adjacent to the first dope and having a higher viscosity than the first dope. Casting in which a layered dope is caused to flow down from an outlet of the flow path to form a belt-like multilayer cast film in which a second layer made of the second dope overlaps a first layer made of the first dope on a support. In the device
A flow width regulating member extending from the inside of the flow path to the outlet of the flow path at both longitudinal ends of the flow path in the cross section in the flow direction;
The liquid contact surface of the flow width regulating member that contacts the multilayer dope includes a first liquid contact surface provided vertically, a downstream end of the first liquid contact surface to the outlet, and from the downstream end. A casting apparatus comprising: a second liquid contact surface extending from the end in the longitudinal direction toward the center toward the outlet.   When the length of the second liquid contact surface in the direction in which the multilayer dope flows along the first liquid contact surface is L1, and the length of the liquid contact surface in the longitudinal direction is L2, the first The casting apparatus according to claim 1, wherein the gradient L2 / L1 of the two wetted surfaces is 0.45 or more and 0.85 or less. A second dope containing a first dope containing a first polymer and a second polymer having a lower viscosity and a lower elastic modulus than the first polymer into a slot-like flow path provided so as to penetrate the block-shaped casting apparatus main body. An introduction step of introducing a dope;
A multi-layer dope consisting of the first dope on the short-side end side of the flow channel and the second dope adjacent to the first dope and having a higher viscosity than the first dope is circulated toward the outlet of the flow channel. Distribution process,
A flow-down step of flowing down the multilayer dope from an outlet of the flow path;
A film forming step of forming on the support a band-shaped multilayer cast film in which the second layer made of the second dope overlaps the first layer made of the first dope,
In the distribution process immediately before the flow-down process,
A first distribution step for allowing the multilayer dope to flow down with a constant flow width;
Performing a second distribution step in which the multi-layer dope flowing at both ends in the flow width direction in the first flow step is flowed down toward the outlet while being guided toward the center in the flow width direction. Method for forming a film.   When the angle formed by the flow direction of the multilayer dope in the first distribution step and the flow direction of the multilayer dope in the second distribution step is θ, the value of tan θ is 0.45 or more. The cast film forming method according to claim 3, wherein the cast film is 0.85 or less.   The method for forming a cast film according to claim 3 or 4, wherein the second polymer is acrylic.   6. The method for forming a cast film according to claim 5, wherein the first polymer is cellulose acylate. After performing the casting film forming method according to any one of claims 3 to 6, the multilayer casting film which can be conveyed independently is peeled off from the support to form a wet film. Stripping process,
And a film drying step of drying the wet film held at both ends in the width direction.   8. The solution casting method according to claim 7, wherein a film cooling step for cooling the multilayer cast film on the support is performed before the stripping step until it is in a state where it can be independently conveyed. .

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