JP5623269B2 - Casting apparatus, casting film forming method and solution casting method - Google Patents

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

  In recent years, it has been desired to reduce the thickness of optical films. However, the cellulose ester film having a reduced thickness is likely to change in optical characteristics when the humidity of the use environment changes or when stress is generated in the cellulose ester film. This is due to the property that the cellulose ester used as a raw material tends to change its optical characteristics depending on humidity and has high photoelasticity.

  Therefore, it is conceivable to employ another polymer as a raw material for a thin polymer film having stable optical characteristics. 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.

  The inventor made a thin polymer having stable optical characteristics by forming a multi-layer cast film having a second layer made of another polymer overlapping a first layer made of cellulose acylate in a solution casting method. It has been found that the film can be manufactured.

  However, as shown in FIGS. 20 and 21, when a plurality of dopes containing different polymers are simultaneously flowed on a support 190 that runs in the direction A, a multilayer cast film formed on the support 190 is formed. In 195, the thickness unevenness 198 occurs frequently. This thickness unevenness 198 is caused by destabilization of the interface between the first layer 201 and the second layer 202. The destabilization of the interface refers to a phenomenon in which a part of the dope forming the second layer 202 enters the first layer 201. Then, if the multilayer cast film 195 in which the thickness unevenness occurs is peeled off as it is, the thickness unevenness remains in the finally obtained multilayer film.

  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 is a casting apparatus in which a dope flows down from a slot-shaped dope outlet opening to a block-shaped casting apparatus body toward a support, and a casting film made of the dope is formed on the support. A first flow path that is provided in the casting apparatus main body and in which a first dope containing the first polymer flows; and a second polymer having a lower viscosity and a lower elastic modulus than the first polymer, and is higher than the first dope. From the first dope and the second dope, the second dope having a viscosity flows, and is positioned between the second flow path provided in the casting apparatus main body, the first flow path, and the second flow path. A buffer flow path through which a low-viscosity buffer solution flows, a downstream junction in which the outlet of the first flow path and the outlet of the second flow path open in the casting apparatus body, and the first Provided in the middle of one of the flow path and the second flow path, and the buffer And a upstream converging portion outlet of the flow path is opened, and wherein the buffer solution and the confluent portion making a multi-layer dope consisting positioned between the first doping and the second doping and both doped, the merging unit And a multi-layer dope flow path through which the multi-layer dope flows, the first layer made of the first dope, the buffer layer made of the buffer solution, and the second dope A multilayer casting film in which the second layer sequentially overlaps is formed on the support. The buffer solution includes one of the first polymer and the second polymer, and the upstream merging portion includes the buffer solution-containing polymer of the first dope and the second dope, It is preferable to join the buffer solution containing the common polymer.

Further, the present invention provides a casting apparatus in which a dope flows down from a slot-shaped dope outlet opening in a block-shaped casting apparatus main body toward a support, and a casting film made of the dope is formed on the support. The first dope includes a first flow path in the casting apparatus body through which a first dope containing the first polymer flows, and a second polymer having a lower viscosity and a lower elastic modulus than the first polymer. The second dope having a higher viscosity flows, and is positioned between the second flow path provided in the casting apparatus main body, the first flow path, and the second flow path, and the first polymer or the first flow path . look including one of 2 polymers, the a buffer solution flow path buffer flows of low viscosity than the first doping and the second doping, is provided in the casting apparatus main body, said first flow path An outlet and an outlet of the second channel are opened, and the buffer channel A merging portion for forming a multi-layer dope comprising the first dope and the second dope and the buffer solution located between the two dopes, and a merging portion and the dope outlet. A multilayer dope flow path in which a layer dope flows, and a multilayer flow in which a first layer made of the first dope, a buffer layer made of the buffer solution, and a second layer made of the second dope are sequentially overlapped A cast film is formed on the support.

Further, the present invention provides a casting apparatus in which a dope flows down from a slot-shaped dope outlet opening in a block-shaped casting apparatus main body toward a support, and a casting film made of the dope is formed on the support. In the casting apparatus main body, a first flow path through which a first polymer and a first dope containing a first solvent that dissolves the first polymer flows, and a lower viscosity and a lower elastic modulus than the first polymer. The second polymer and the second solvent dissolving the second polymer , the second dope having a higher viscosity than the first dope flows, the second flow path provided in the casting apparatus body, and the second 1 passage and located between the second flow path, wherein Ri Do from the first solvent and the second solvent is compatible to the liquid, a buffer solution having a low viscosity than the first doping and the second doping A flowing buffer solution channel, and provided in the casting apparatus main body. The buffer solution is located between the first dope and the second dope and both dopes, wherein the outlet of the first channel and the outlet of the second channel are opened, communicate with the outlet of the buffer channel. A first layer composed of the first dope, a confluence part for forming a multilayer dope comprising: a multi-layer dope flow path through which the multi-layer dope flows; A multilayer cast film in which the buffer layer made of the buffer solution and the second layer made of the second dope are sequentially overlapped is formed on the support.

Before Kiryunobe device comprises the first flow path, the second flow path, the buffer solution flow path, and a feed block the merging portion is provided, and a casting die wherein the dope outlet is provided It is preferable. Moreover , it is preferable that the second flow path is arranged between the paired first flow paths.

  The present invention also provides a casting film in which a dope flows down from a slot-shaped dope outlet opening to a block-shaped casting apparatus main body toward a support, and a casting film made of the dope is formed on the support. In the forming method, the first dope containing a first polymer and the second dope containing a second polymer having a lower viscosity and a lower elastic modulus than the first polymer and having a higher viscosity than the first dope are cast. When merging in the main body of the apparatus, a buffer solution having a viscosity lower than that of both the dopes is caused to flow between the two dopes to form a multi-layer dope composed of the two dopes and a buffer solution positioned between the two dopes. And a step of allowing the multilayer dope to flow down from the dope outlet, and a buffer layer made of the buffer solution and a second layer made of the second dope overlap in order on the first layer made of the first dope. Multi-layer casting membrane is used as the support And having a film formation step of forming.

The merging step includes a first merging step in which one of the first dope and the second dope and the buffer solution are merged to flow the first dope and the buffer solution in parallel, and the parallel dosing step. It is preferable to perform a second merging step in which the other dope is joined from the buffer solution side to the first dope and the buffer solution that have been flown through . Further, it is preferable that the in buffer that is part of the one of the first polymer or the second polymer. Further, in the first merging step, it is preferable that the buffer solution is merged with one of the first dope and the second dope containing a polymer common to the polymer contained in the buffer solution.

  The first dope includes a first solvent that dissolves the first polymer, the second dope includes a second solvent that dissolves the second polymer, and the buffer solution includes the first solvent and the solvent. It is preferable to consist of a liquid compatible with the second solvent. Moreover, it is preferable that the said buffer solution consists of a common component of a said 1st solvent and a said 2nd solvent.

  In the casting apparatus main body, the two first dopes are caused to flow, the second dope is caused to flow between the two first dopes, the one between the first dope and the second dope, and the other. The flow step of flowing the buffer solution between the first dope and the second dope is performed before the merging step, and in the film forming step, one of the first layers made of the first dope A first buffer layer made of the buffer solution, a second layer made of the second dope, a second buffer layer made of the other buffer solution, and a third layer made of the other first dope layer in order. It is preferable to form a multilayer casting film on a support.

  The second polymer is preferably acrylic, and the first polymer is preferably cellulose acylate.

  The solution casting method of the present invention is a method of peeling off the multilayer casting film that has become capable of being conveyed independently after the casting film forming method described above from the support to form a wet film. And a film drying step of drying the wet film.

  It is preferable to perform a film cooling process for cooling the multilayer cast film on the support body before the stripping process until the film can be conveyed independently.

  According to the present invention, since the first dope and the second dope are merged via the buffer solution flowing between the first dope and the second dope, the distortion of the polymer molecules contained in the first dope can be suppressed. it can. And if the distortion | strain of the polymer molecule contained in the 1st dope is suppressed, the interface in the dope after joining can be stabilized. Therefore, according to the present invention, it is possible to produce a thin polymer film having stable optical characteristics while preventing thickness unevenness due to destabilization of the interface.

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 1st casting apparatus provided in the casting chamber. It is a YZ plane sectional view showing the outline of the 1st feed block. It is a YZ plane sectional view showing the outline of the 1st merge part. It is a perspective view which shows the outline | summary of a vane and a distribution pin. It is a YZ plane sectional view showing an outline of the 2nd merge part. It is a perspective view which shows the outline | summary of a casting die. It is a YZ plane sectional view showing an outline of a casting die. It is XZ plane sectional drawing which shows the outline | summary of a casting die. It is XY plane sectional drawing of a 1st multilayer dope flow path. It is XY plane sectional drawing of the 2nd multilayer dope channel. 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 cut surface of a multilayer casting film. It is a YZ plane sectional view showing an outline of the 2nd feed block. It is explanatory drawing which shows the outline | summary of the 2nd solution casting apparatus. It is a YZ plane sectional view showing an outline 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. It is a top view which shows a mode that the thickness nonuniformity produced in the multilayer cast film. It is a schematic diagram which shows the outline | summary of the bb line | wire cut surface of the multilayer cast film in which the thickness nonuniformity produced.

  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 properties of the entire multilayer film 10, the second polymer that is the raw material of the second layer 10b is an optical property required for the multilayer film 10 (light transmission). And the like that satisfy the characteristics). On the other hand, as a polymer that is a raw material for the first layer 10a and a polymer that is a raw material for the third layer 10c, in addition to satisfying the restrictions of the solution film forming method described above, the properties that do not hinder the optical properties exhibited by the second layer 10b It is preferable to use one having (translucency etc.). The polymer used as the raw material of the first layer 10a and the polymer used as the raw material of the third layer 10c may be the same polymer or different polymers. Hereinafter, the case where the first polymer is used as the polymer that is the raw material of the first layer 10a and the polymer that is the raw material of the third layer 10c will be described. 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.

(Solution casting equipment)
As shown in FIG. 2, the solution casting apparatus 11 is for making a multilayer film 10 and includes a casting chamber 12, a pin tenter 13, a drying chamber 15, a cooling chamber 16, and a winding chamber 17.

  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 FIGS. 2 and 3, the casting apparatus 20 provided above the casting drum 22 includes a feed block 51 for producing a multilayer dope and a multilayer dope produced by the feed block 51. And a casting die 52 that flows out to the bottom. The feed block 51 and the casting die 52 are each provided with a temperature control device (not shown). The temperature control device keeps the temperature of the feed block 51 and the casting die 52 constant within a predetermined range.

  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 can decompress the upstream side of the bead in the movement direction of the peripheral surface 22c so that the pressure on the upstream side of the peripheral surface 22c 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 storage tank 56a of the first dope 45a by a pipe 55a including a pump 54a. Similarly, the feed block 51 is connected to the storage tank 56b of the second dope 45b by a pipe 55b having a pump 54b, and to the storage tank 56c of the third dope 45c by a pipe 55c having a pump 54c. Further, the feed block 51 is connected to a storage tank 56x for the first buffer solution 45x by a pipe 55x having a pump 54x, and to a storage tank 56y for a second buffer solution 45y by a pipe 55y having a pump 54y.

(First to third dope)
The first dope 45a is obtained by dissolving the first polymer in the dope solvent, the second dope 45b is obtained by dissolving the second polymer in the dope solvent, and the third dope 45c is formed by the first dope 45c. A polymer is dissolved in a dope 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. 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. In addition, the viscosity of each dope 45a-45c can be calculated | required based on JISK7117.

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.

(First and second polymers)
The elastic modulus of the first polymer is higher than that of the second polymer, and the viscosity of the first polymer is higher than that of the second polymer.

(First and second buffer solutions)
The first buffer solution 45x and the second buffer solution 45y have lower viscosities than the dopes 45a to 45c. Moreover, it is preferable that the 1st buffer solution 45x and the 2nd buffer solution 45y consist of a solution compatible with the solvent for dope contained in each dope 45a-45c. The viscosity of the first buffer solution 45x may be equal to or different from that of the second buffer solution 45y. The viscosity of the first buffer solution 45x and the second buffer solution 45y is preferably 1 Pa · second to 15 Pa · second, and more preferably 1 Pa · second to 10 Pa · second. The viscosities of the first buffer solution 45x and the second buffer solution 45y can be obtained based on JIS K 7117.

  The first buffer solution 45x and the second buffer solution 45y are each preferably the same as the dope solvent. When the dope solvent is a mixture of a plurality of solvents, the common component of the mixture may be the first buffer solution 45x and the second buffer solution 45y. The first buffer solution 45x and the second buffer solution 45y may contain a polymer. The polymers contained in the first buffer solution 45x and the second buffer solution 45y may be the same or different. Examples of the polymer contained in the first buffer solution 45x and the second buffer solution 45y include a first polymer and a second polymer, and it is preferable that any one of them is contained.

  The polymer concentration in the first buffer solution 45x and the second buffer solution 45y may be the same or different. The polymer concentration in the first buffer solution 45x and the second buffer solution 45y is preferably less than 5% by mass.

  Details of the first polymer, the second polymer, and the dope solvent will be described later.

(Feed block)
As shown in FIG. 4, the feed block 51 includes a first dope channel 61a through which the first dope 45a flows, a second dope channel 61b through which the second dope 45b flows, and a third dope flow through which the third dope 45c flows. From a feed block body 51a having a path 61c, a first buffer channel 61x through which the first buffer solution 45x flows, and a second buffer channel 61y through which the second buffer solution 45y flows and formed in a block shape Become.

  The through hole provided in the feed block main body 51a is formed so as to penetrate in the Z direction from the top to the bottom. From the upper side to the lower side, the second dope channel 61b, the first junction 61j, the first multilayer dope channel 61p, the second junction 61k, and the second multilayer dope flow through the through hole. A path 61q is sequentially provided. By the second dope channel 61b, the inlet 51i that opens to the upper surface of the feed block main body 51a and the first junction 61j communicate with each other. Further, the first junction 61j and the second junction 61k communicate with each other through the first multilayer dope channel 61p. Then, the second multi-layer dope flow path 61q communicates the second junction 61k and the outlet 51o that opens to the lower surface of the feed block main body 51a.

  A first buffer channel 61x and a second buffer channel 61y are provided on both sides in the Y direction of the second dope channel 61b. Further, a first dope channel 61a and a third dope channel 61c are provided on both sides in the Y direction of the first multilayer dope channel 61p.

  As shown in FIGS. 4 and 5, the outlet 61bo of the second dope channel 61b is opened above the first junction 61j, and the outlet of the first buffer channel 61x is located on both sides in the Y direction of the outlet 61bo. 61xo and the outlet 61yo of the second buffer channel 61y are opened.

The feed block 51 is provided with a pair of vanes 63j. The vane 63j partitions the adjacent flow paths 61x and 61b from the adjacent flow paths 61b and 61y. The wedge-shaped vane 6 3 j is arranged so that the sharp tip portion is directed to the first joining portion 61 j. A swing shaft 66j is provided at the end of the vane 6 3 j on the opposite side of the sharp tip portion. The vane 6 3 j is attached so as to be swingable about the swing shaft 66j.

  Distribution pins 65j are provided at the outlet 61xo of the flow path 61x and the outlet 61yo of the flow path 61y, respectively. As shown in FIG. 6, the distribution pin 65j has a cylindrical shape, and a pin main body 65ja that is rotatable about an axis, and a notch groove formed in the circumferential direction on the peripheral surface of the pin main body 65ja. 65jb. The pin body 65ja is arranged so that the rotation axis is parallel to the X direction. It is preferable that the depth of the notch groove and the width in the X direction are gradually increased or gradually decreased toward the circumferential direction.

  As shown in FIG. 5, the area Sxo of the outlet 61xo, the area Sbo of the outlet 61bo, and the area Syo of the outlet 61yo are respectively determined by the rotation of the pair of distribution pins 65j and the swing of the pair of vanes 63j. Can be adjusted independently.

  As shown in FIG. 7, an outlet 61po of the first multilayer dope channel 61p opens above the second junction 61k, and an outlet of the first dope channel 61a is located on both sides of the outlet 61po in the Y direction. 61ao and the outlet 61co of the third dope channel 61c are opened. Between the adjacent flow paths 61a and 61p and between the adjacent flow paths 61p and 61c, a vane 63k that partitions each flow path is provided. Distribution pins 65k are provided at the outlet 61ao of the flow path 61a and the outlet 61co of the flow path 61c. The vane 63k has a structure similar to that of the vane 63j, is disposed such that an acute end portion is directed to the second joining portion 61k, and is attached to be swingable about the swing shaft 66k.

  The distribution pin 65k has the same structure as the distribution pin 65j, and is provided so as to be rotatable about an axis. By rotating the distribution pin 65k as a pair and swinging the vane 63k as a pair, the area Sao of the outlet 61ao, the area Spo of the outlet 61po, and the area Sco of the outlet 61co can be independently adjusted. it can.

  As shown in FIG. 4, the control unit 68 is connected to the pumps 54a to 54y, the swing shafts 66j and 66k, and the distribution pins 65j and 65k, respectively. Accordingly, the pumps 54 a to 54 y send out the dopes 45 a to 45 c and the buffer solutions 45 x to 45 y to the feed block 51 under a control unit 68 at a predetermined volume flow rate. Further, the vanes 63j and 63k and the distribution pins 65j and 65k are set under a control unit 68 so as to be in a predetermined direction.

(Casting die)
As shown in FIG. 8, 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 FIGS. 9 and 10, 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 on the upper surface of the casting die body 70, and an outlet 69 o of the slot 69 is opened on the lower surface of the casting die body 70. The inlet 69i is connected to the outlet 51o of the flow path 61q.

  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 is formed to be orthogonal to the X direction.

  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 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 post-widening slot portion 79 from the upstream side to the downstream side in the flow direction. The first widening slot portion 77 gradually increases. 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.

  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 and the buffer solutions 45 x to 45 y are sent to the casting apparatus 20 by the pumps 54 a to 54 y. The temperatures of the dopes 45a to 45c and the buffer solutions 45x to 45y are kept substantially constant in the range of 30 ° C. to 35 ° C., and the temperature of the peripheral surface 22c is kept substantially constant in the range of −10 ° C. to 10 ° C. Be drunk.

  The casting apparatus 20 creates a multilayer dope from the dopes 45 a to 45 c and the buffer solutions 45 x to 45 y, 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. The multilayer casting film 21 includes a first layer on the casting drum 22 side (back side), a third layer on the front side, and a second layer between the first layer and the third layer. As a result of cooling the multilayer casting film 21 on the casting drum 22, at least the dope forming the first layer 21a 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 effect | action of this invention in the casting apparatus 20 is demonstrated. As shown in FIG. 4, under the control of the control unit 68, the second dope 45b and the buffer solutions 45x to 45y sent to the feed block 51 flow toward the first junction 61j. In the 1st junction part 61j, each buffer solution 45x-45y merges from the Y direction both sides of the 2nd dope 45b. The first dope 91v composed of the second dope 45b and the buffer solutions 45x and 45y flowing on both sides of the second dope 45b is formed by the merging of the second dope 45b and the buffer solutions 45x and 45y (FIG. 11). reference). The first multilayer dope 91v includes a first buffer layer 91x composed of a first buffer solution 45x flowing in one of both sides in the short direction (Y direction) of the first multilayer dope channel 61q, and the first multilayer dope The second dope flowing between the first buffer solution 45x and the second buffer solution 45y, and the second buffer layer 91y made of the second buffer solution 45y flowing on the other side of the channel 61q in the short direction (Y direction). And a second layer 91b made of 45b.

  Returning to FIG. 4, the first multi-layer dope 91v created by the first junction 61j flows to the second junction 61k. In the second junction 61k, the dopes 45a and 45c merge from both sides in the Y direction of the first multilayer dope 91v, that is, from the buffer solution 45x side and the buffer solution 45y side. The second multi-layer dope 91w is formed by the merging of the first multi-layer dope 91v, the first dope 45a and the third dope 45c (see FIG. 12). The second multi-layer dope 91w includes a first layer 91a made of the first dope 45a, a third layer 91c made of the third dope 45c, and a first buffer layer located between the first layer 91a and the third layer 91c. 91x, the second layer 91b, and the second buffer layer 91y.

When the thickness of the first buffer layer 91x is TH _91x and the thickness of the second layer 91b is TH _91b , the value of (TH _91x / TH _91b ) is preferably 0.01 or more and 0.2 or less. When the thickness of the second buffer layer 91y is TH _91y , the value of (TH _91y / TH _91b ) is preferably 0.01 or more and 0.2 or less. When the thickness of the first layer 91a is TH _91a , the value of (TH _91a / TH _91x ) is preferably 0.05 or more and 0.5 or less, and when the thickness of the third layer 91c is TH _91c , The value of (TH _91c / TH _91x ) is preferably 0.05 or more and 0.5 or less. The thickness of the first buffer layer 91x may be equal to or different from the thickness of the second buffer layer 91y.

  The second multilayer dope 91w produced by the feed block 51 is sent to the casting die 52 through the second multilayer dope channel 61q (see FIG. 9). The second multilayer dope 91w 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 widening slot portion 77 and the second widening slot portion 78, the second multi-layer dope 91w flows while expanding in the X direction until reaching the first liquid contact surface 81a of the pair of inner deckle plates 80. In the post-widening slot portion 79, the second multilayer dope 91w flows toward the outlet 69o with a constant flow width. Then, the second multilayer dope 91w flows out from the outlet 69o toward the casting drum 22 (see FIG. 13). The second multilayer dope 91w flowing out from the outlet 69o forms a bead 92 until reaching the casting drum 22, and after reaching the casting drum 27, the multilayer casting film 21 on the peripheral surface 22c. Form. As shown in FIG. 14, the multilayer cast film 21 includes a first layer 21a made of the first dope 45a, a first buffer layer 21x made of the first buffer solution 45x, and a second layer 21b made of the second dope 45b. The second buffer layer 21y made of the second buffer solution 45y and the third layer 21c made of the third dope 45c are sequentially overlapped. The 1st buffer layer 21x and the 2nd buffer layer 21y lose | disappear at the stage of the drying process of the wet film 30 performed by the transfer part 29 or the pin tenter 13, and become the multilayer film 10 (refer FIG. 1).

  In the feed block 51, when dopes containing different polymers are directly joined together, the polymer molecules contained in the first dope having a lower viscosity than the second dope, that is, the first polymer molecules are distorted. This strain of the first polymer molecule induces disturbance of the interface of the multilayer dope. Then, when the multilayer dope having a disordered interface flows out of the casting die 52, the disorder of the interface in the multilayer dope becomes a thickness unevenness 198 (see FIG. 21) of the multilayer casting film 195 and remains. End up.

  The thickness ΔG of the thickness unevenness 198 tends to appear more prominently as the speed difference ΔV between the two dopes at the time of merging increases. However, it is difficult to adjust the speeds of the two dopes at the time of merging until the thickness unevenness 198 does not occur.

  In the present invention, since the dopes containing different polymers are merged through a buffer solution having a viscosity lower than that of both dopes, it is possible to suppress distortion of the polymer molecules caused by the difference in speed between the two dopes at the time of merging. it can. Therefore, according to the present invention, it is possible to form a multilayer cast film while suppressing thickness unevenness as compared with the conventional case. As a result, it becomes easy to manufacture a multilayer film having a uniform thickness.

The state of the interface in the first multilayer dope 91v is due to the difference in the average flow velocity of the dope and the buffer solution in the first junction 61j. In the first junction 61j (see FIG. 5), the relationship between the average flow velocity V45b of the second dope 45b, the average flow velocity V45x of the first buffer solution 45x, and the average flow velocity V45y of the second buffer solution 45y is expressed by the following equation (k−1). ) And (k-2) are not satisfied, the polymer molecules contained in the buffer solution are distorted, so that the interface in the multilayer dope 91v becomes unstable.
Formula (k-1) V45b <V45x
Formula (k-2) V45b <V45y

Here, each average flow velocity V45b, 45x, 45y is represented by the following formulas (k-3) to (k-5).
Formula (k-3) V45b = Q45b / Sbo
Formula (k-4) V45x = Q45x / Sxo
Formula (k-5) V45y = Q45y / Syo

  Q45b is a volume flow rate of the second dope 45b sent to the first junction 61j. Similarly, Q45x is a volume flow rate of the first buffer solution 45x sent to the first merge portion 61j, and Q45y is a volume flow rate of the second buffer solution 45y sent to the first merge portion 61j. The volume flow rates Q45b, Q45x, and Q45y can be independently adjusted to a predetermined range by controlling each pump by the control unit 68. Therefore, by controlling each pump, each distribution pin, and each vane, the second dope 45 and each buffer solution 45x, 45y are merged so as to satisfy the above formulas (k-1) to (k-2). Therefore, the interface in the multilayer dope 91v can be more reliably stabilized.

The value of ΔV _x−b (= V45x−V45b) and the value of ΔV _y−b (= V45y−V45b) are preferably 0.02 m / second or more, more preferably 0.05 m / second or more. preferable. When the values of ΔV _x-b and ΔV _y-b are less than 0.02 m / sec, the interface disturbance in the multilayer dope 91v becomes obvious, which is not preferable. The values of ΔV _x−b and ΔV _y−b are preferably 0.2 m / second or less, and more preferably 0.1 m / second or less. When the values of ΔV _x-b and ΔV _y-b exceed 0.1 m / sec, the pressure in the flow paths 61x and 61y increases, and as a result, casting becomes difficult. Note that ΔV _x−b and ΔV _y−b may be equal or different.

In the first merging portion 61j, the merging angle θ _b−x where the second dope 45b and the first buffer 45x merge is preferably 5 ° or more and 30 ° or less. In the first merging portion 61j, the merging angle θ _{b−y at which} the second dope 45b and the second buffer 45y merge is preferably 5 ° or more and 30 ° or less.

  In order to further stabilize the interface in the second laminated dope and more reliably prevent thickness unevenness, the flow rate ratio of the first buffer solution 45x (= Q45x / Qs) and the flow rate ratio of the second buffer solution 45y (= Q45y / Qs) is preferably 5% or more and 15% or less. Here, the volume flow rate of the dope and the liquid for forming the multilayer cast film is added. For example, when a multilayer cast film is formed using the first to third dopes 45a to 45c and the first to second buffer solutions 45x to 45y, Qs is expressed as (Q45a + Q45b + Q45c).

In the above embodiment, after the second dope 45b, the first buffer solution 45x, and the second buffer solution 45y are joined at the first junction 61j to form the first multilayer dope 91v, the second junction 61k The first dope 45a and the third dope 45c and the first multi-layer dope 91v are merged to form the second multi-layer dope 91w, but the present invention is not limited to this. For example, a feed block 101 as shown in FIG.

  As shown in FIG. 15, the feed block 101 is similar to the feed block 51 in that the first dope channel 61a, the second dope channel 61b, the third dope channel 61c, and the first buffer channel 61x. And a second buffer solution channel 61y, and is composed of a feed block main body 101a formed in a block shape.

The first through hole provided in the feed block main body 101a is formed so as to penetrate in the Z direction from the top to the bottom. In the first through hole, a second dope channel 61b, a second junction 61k, and a second multilayer dope channel 61q are sequentially provided from the top to the bottom. Through the second dope channel 61b, the inlet 101i that opens to the upper surface of the feed block body 101a and the second junction 61k communicate with each other. In addition, the second multi-layer dope channel 61q communicates the second junction 61k and the outlet 101o that opens to the lower surface of the feed block body 101a .

  The feed block body 101a on both sides in the Y direction of the second dope channel 61b is provided with a first side through hole and a second side through hole. A first multi-layer dope flow that communicates with the first side through-hole from the top to the bottom through the first dope channel 61a, the first junction 61ja, the first junction 61ja, and the second junction 61k. A path 61pa is sequentially provided. A first buffer channel 61x is provided between the first dope channel 61a and the second dope channel 61b. An outlet of the first dope channel 61a and an outlet of the first buffer channel 61x are opened in the first junction 61ja. Similarly, in the second side through-hole, from the upper side to the lower side, the first dope channel 61c, the first merging portion 61jc, the first merging portion 61jc, and the first merging portion 61k communicate with each other. A layer dope channel 61pc is provided sequentially. A second buffer channel 61y is provided between the third dope channel 61c and the second dope channel 61b. An outlet of the third dope channel 61c and an outlet of the second buffer channel 61y are opened in the first junction 61jc. The outlet of the second dope channel 61b opens above the second junction 61k, and the outlet of the first multi-layer dope channel 61pa and the second outlet on both sides in the Y direction of the outlet of the second dope channel 61b. The outlet of one multi-layer dope channel 61pc opens.

  The feed block main body 101a is provided with a vane 63ja, a vane 63jc, a vane 63ka, and a vane 63kc. The vane 63ja partitions the first dope channel 61a and the first buffer channel 61x, and the vane 63jc partitions the third dope channel 61c and the second buffer channel 61y. The vane 63ka partitions the second dope channel 61b and the first multilayer dope channel 61pa, and the vane 63kc partitions the second dope channel 61b and the first multilayer dope channel 61pc. In the first junction 65ja, a distribution pin 65jx is provided at the outlet of the first buffer channel 61x. Further, in the first junction 65jc, a distribution pin 65ji is provided at the outlet of the second buffer solution flow path 61y. Further, in the second junction 65k, distribution pins 65ka and 65kc are provided in the flow paths 61pa and 61pc, respectively. The structure of each vane and distribution pin is the same as that of the vane 63j and the distribution pin 65j.

  Next, an outline of a method for forming a multilayer cast film using the feed block 101 will be described. In the first merge portion 61ja, the first dope 45a and the first buffer solution 45x merge, and the first dope 45a and the first buffer solution 45x located on the second dope channel 61b side with respect to the first dope 45a. A first multi-layer dope 91va consisting of The first multilayer dope 91va flows through the first multilayer dope flow path 61pa to the second junction 61k.

  In the first merging portion 61jc, the third dope 45c and the second buffer solution 45y merge, and the third dope 45c and the second buffer solution 45y located on the second dope channel 61b side with respect to the third dope 45c A first multi-layer dope 91vc consisting of The first multilayer dope 91vc flows to the second junction 61k through the first multilayer dope channel 61pc.

  In the second dope channel 61b, the second dope 45b flows. In the 2nd junction part 61k, each dope 45a-45c joins and the 2nd multilayer dope 91w is made. In the present invention, the first multi-layer dope 91va merges with the second dope 45b from the first buffer solution 45x side, and the first multi-layer dope 91vc merges with the second dope 45b from the first buffer solution 45y side. Therefore, the first buffer solution 45x is interposed when the first dope 45a and the second dope 45b merge, and the second buffer solution is used when the second dope 45b and the third dope 45c merge. 45y will intervene. Thus, according to the present invention, since the distortion of the first polymer molecule can be suppressed as compared with the case where the first dope 45a to the third dope 45c are directly joined, the multilayer cast film is formed while preventing the thickness unevenness. be able to.

In the above embodiment, the flow paths are provided symmetrically in the feed block body, but the present invention is not limited to this. For example, in the feed block 101 shown in FIG. 15, instead of omitting the first merging portion 61ja, a merging portion is separately provided in the second dope channel 61b on the upstream side of the second merging portion 61k. Further, the first buffer channel 61x is provided so that the outlet of the first buffer channel 61x opens to the junction. According to such a feed block, a multi-layer dope can be produced by the merge shown in the following (a) to (d). Therefore, according to this feed block, a multilayer cast film can be formed while preventing thickness unevenness. The following (c) and (d) may be performed simultaneously, or one may be performed first and the other may be performed later.
(A) Merge the second dope 45b and the first buffer solution 45x (b) Merge the third dope 45c and the second buffer solution 45y (c) After (a), The first dope 45a is merged from the first buffer solution 45x side. (D) The multi-layer dope by the merge of (b) is merged from the second buffer solution 45y side to the second dope.

  In the above embodiment, a plurality of merging portions where dopes and buffer solutions merge are provided, but the present invention is not limited to this, and one merging portion is provided, and all the dopes and buffer solutions are merged at the merging portion at the same time. May be.

  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. 16, the solution casting apparatus 111 includes 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 second multilayer dope 91 w that has flowed 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 flows out the second multilayer dope 91w 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 five-layer structure, but the present invention is not limited to this, and a three-layer structure, a four-layer structure, or six or more layers. It is good also as a multilayer structure. When producing a multilayer casting film or a multilayer film having a three-layer structure, the first dope, the second dope, and the first buffer solution may be used. In the case of producing a multilayer cast film or a multilayer film having a multilayer structure of six layers or more, for example, at least one of the first dope 45a to the third dope 45c may be a multilayer dope. When at least one of the first dope 45a to the third dope 45c is a multi-layer dope, a layer made of a buffer solution may be provided between a layer made of one dope and a layer made of two dopes. 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. 17) may be used. The casting die 130 includes a block-shaped casting die main body 130a provided with first to third through holes.

The through-hole provided in the casting die body 130a is formed so as to penetrate in the Z direction from the top to the bottom. From the upper side to the lower side, the second dope channel 61b, the first junction 61j, the first multilayer dope channel 61p, the second junction 61k, and the second multilayer dope flow through the through hole. A path 61q and a widened slot portion 61r having the same shape as the slot 69 shown in FIGS. 9 and 10 are provided.

By the second dope channel 61b, the inlet opening on the upper surface of the casting die body 130a and the first junction 61j communicate with each other. Further, the first junction 61j and the second junction 61k communicate with each other through the first multilayer dope channel 61p. Then, the second multi-layer dope channel 61q and the widening slot portion 61r allow the second joining portion 61k and the outlet opening on the lower surface of the casting die body 130a to communicate with each other.

  A first buffer channel 61x and a second buffer channel 61y are provided on both sides in the Y direction of the second dope channel 61b. The outlet of the second dope channel 61b opens above the first junction 61j, and the first buffer channel 61x and the second buffer solution flow on both sides in the Y direction of the outlet of the second dope channel 61b. The exit of the path 61y opens. Further, a first dope channel 61a and a third dope channel 61c are provided on both sides in the Y direction of the first multilayer dope channel 61p. Above the second junction 61k, the outlet of the first multilayer dope channel 61p opens, and on both sides in the Y direction of the outlet of the first multilayer dope channel 61p, the first dope channel 61a and the third dope channel 61p are opened. The exit of the dope channel 61c opens. Further, the flow paths 61a to 61y are connected to the pipes 54a to 54y via the manifolds 131a to 131y, respectively.

  In the first merging portion 61j, the first buffer solution 45x and the second buffer solution 45y merge with the second dope 45b from both sides in the Y direction to form the first multilayer dope 91v. Moreover, in the 2nd junction part 61k, the 1st dope 45a and the 3rd dope 45c each merge from the Y direction both sides with respect to the 1st multilayer dope 91v, and the 2nd multilayer dope 91w is produced. Thus, the casting die 130 can form the multilayer casting film on the support while preventing the thickness unevenness by flowing out the second multilayer dope 91w.

  In the present invention, any of the casting apparatus 20 having the feed block 51 and the casting die 52 and the multi-manifold casting die 130 may be used.

  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. 18, a first casting die 141 that flows out of the first dope 45a, and a second casting die 142 that flows out of the second dope 45b, the second buffer solution 45y, and the third dope 45c simultaneously, May be sequentially arranged in the moving direction above the moving support 143. As the first casting die 141, a through hole extending in the Z direction may be provided in the block-shaped feed block main body, and the second dope may be circulated through the through hole. In addition, as the second casting die 142, a feed block 51 (see FIG. 4) or a feed block 101 (see FIG. 15) in which the flow paths 61a and 61x are omitted may be used.

  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. The second casting die 142 joins the second dope 45b and the third dope 45c via the second buffer solution 45y to create a multi-layer dope. The second casting die 142 flows out the multi-layer dope toward the first dope film 145a, so that the film made of the multi-layer dope overlaps the first dope film 145a. The film made of the multilayer dope has a layer structure in which the second layer made of the second dope 45b, the second buffer layer made of the second buffer solution 45y, and the third layer made of the third dope 45c are sequentially overlapped. . In this way, the first casting die 141 and the second casting die 142 allow the first layer, the second layer, the second buffer layer, and the third layer to sequentially overlap the multilayer casting film 145 having a four-layer structure. Can be formed.

  Further, as shown in FIG. 19, a first casting die 151 that simultaneously flows out the first dope 45a, the first buffer 45x, and the second dope 45b, and a second casting die 152 that flows out the third dope 45c, May be sequentially arranged in the moving direction above the moving support 143. As the first casting die 151, a feed block 51 (see FIG. 4) or a feed block 101 (see 15) in which the flow paths 61c and 61y are omitted may be used. Further, as the second casting die 152, a through hole extending in the Z direction may be provided in the block-shaped feed block main body, and the third dope may be circulated through the through hole.

  The first casting die 151 joins the first dope 45a and the second dope 45b via the first buffer solution 45x to create a multi-layer dope. The first casting die 151 flows out the multilayer dope toward the moving support 143, so that the film 154 made of the multilayer dope overlaps on the moving support 143. The film 154 has a three-layer structure in which a first layer made of the first dope 45a, a first buffer layer made of the first buffer solution 45x, and a second layer made of the second dope 45b are sequentially overlapped. When the second casting die 152 flows out of the third dope 45 c, a film made of the third dope 45 c is formed on the film 154. Thus, the first casting die 151 and the second casting die 152 form a multilayer casting film 156 in which the first layer, the first buffer layer, the second layer, and the third layer are sequentially overlapped. Can do. The film 154 may be used as a laminated casting film as it is.

  Next, details of the components of the first polymer, the second polymer, and the dope solvent will be described.

(First polymer)
As the first polymer, for example, cellulose acylate can be used. As the cellulose acylate, triacetyl cellulose (TAC) is particularly preferable. Of the cellulose acylates, those 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) are 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.

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

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

  Among 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.

(Buffer solution)
For example, dichloromethane is preferably used as the first buffer solution 45x and the second buffer solution 45y. Moreover, it is preferable to use a mixture of dichloromethane and methanol as the first buffer solution 45x and the second buffer solution 45y. When using the mixture comprised from a dichloromethane and methanol, it is preferable that the mass ratio of the dichloromethane which occupies for a mixture is 70% or more and less than 100%, for example, and the mass ratio of the methanol which occupies for a mixture is less than 30%.

(Multilayer film)
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.

  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.

  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 refraction 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 3 were performed. Detailed description will be given in Experiment 1, and in Experiments 2 to 3, description of the same conditions as in Experiment 1 is 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.

(First buffer)
The composition of the first buffer 45x is as follows.
Dichloromethane 80% by mass
Methanol 20% by mass

(Second buffer)
The composition of the second buffer 45y is as follows.
Dichloromethane 80% by mass
Methanol 20% by mass

  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. The viscosity μx of the first buffer solution 45x was 5 Pa · sec, and the viscosity μy of the second buffer solution 45y was 5 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 second multilayer dope 91w to be substantially constant at approximately 34 ° C., a jacket (not shown) is provided in the feed block 51 and the casting die 52, and the heat transfer medium supplied into the jacket The temperature was adjusted.

  As shown in FIG. 4, the controller 68 sent the dopes 45 a to 45 c and the buffer solutions 45 x and 45 y to the feed block 51 through the pumps 54 a to 54 c, 54 x and 54 y at a predetermined volume flow rate. The flow rate ratio (= Q45x / Qs) of the first buffer solution 45x and the flow rate ratio (= Q45y / Qs) of the second buffer solution 45y were values shown in Table 1. In the 1st junction part 61j, the 1st multilayer dope 91v formed by joining each buffer solution 45x and 45y from the Y direction both sides of the 2nd dope 45b was made. In the 2nd junction part 61k, each dope 45a, 45c was joined from the Y direction both sides of the 1st multilayer dope 91v, and the 2nd multilayer dope 91w was made. The feed block 51 sent the second multilayer dope 91 w to the casting die 52. The casting die 52 caused the second multilayer dope 91w 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 is 160 μm, the thickness of the first layer 21a and the third layer 21c is 10 μm, respectively, and the thickness of the first buffer layer and the second buffer layer is 15 μm, respectively. Met. 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.

  Table 1 shows the evaluation results for Q45x / Qs, Q45y / Qs, and each evaluation item.

(Experiments 2-3)
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. In Experiment 3, the multilayer film 10 was made only from the first to third dopes 45a to 45c without using the first buffer solution 45x and the second buffer solution 45y.

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 45x 1st buffer solution 45y 2nd buffer solution 51 Feed block 52 Casting die

Claims (17)

In the casting apparatus in which the dope flows down from the slot-shaped dope outlet opening to the block-shaped casting apparatus body toward the support, and the casting film made of the dope is formed on the support.
A first flow path provided in the casting apparatus main body and through which a first dope containing a first polymer flows;
Including a second polymer having a lower viscosity and lower elastic modulus than the first polymer, a second dope having a higher viscosity than the first dope flows, and a second flow path provided in the casting apparatus body;
A buffer solution channel that is located between the first channel and the second channel and through which a buffer solution having a viscosity lower than that of the first dope and the second dope flows;
In the casting apparatus main body, the downstream side merging portion where the outlet of the first channel and the outlet of the second channel open, and the flow of either the first channel or the second channel. A multi-layer comprising the buffer solution provided between the first dope and the second dope and the two dopes , provided in the middle of the path, and having an upstream junction where an outlet of the buffer channel opens. A junction where dope is made,
A multi-layer dope flow path through which the multi-layer dope flows, wherein the merging portion and the dope outlet communicate with each other;
A multilayer casting film in which a first layer made of the first dope, a buffer layer made of the buffer solution, and a second layer made of the second dope are sequentially overlapped is formed on the support. Casting equipment. The buffer solution contains either the first polymer or the second polymer,
And in the upstream converging portion, the casting of claim 1, wherein the joins the containing polymer of the buffer of the first doping and the second doping to include a common polymer and the buffer apparatus. In the casting apparatus in which the dope flows down from the slot-shaped dope outlet opening to the block-shaped casting apparatus body toward the support, and the casting film made of the dope is formed on the support.
A first flow path provided in the casting apparatus main body and through which a first dope containing a first polymer flows;
Including a second polymer having a lower viscosity and lower elastic modulus than the first polymer, a second dope having a higher viscosity than the first dope flows, and a second flow path provided in the casting apparatus body;
Located between the first passage and the second flow path, viewed contains one of the first polymer or the second polymer, a buffer solution having a low viscosity than the first doping and the second doping A buffer flow path through which
Provided in the casting apparatus main body, the outlet of the first channel and the outlet of the second channel are opened, communicated with the outlet of the buffer channel, and the first dope and the second dope A merging section for forming a multilayer dope comprising the buffer solution located between the two dopes;
A multi-layer dope flow path through which the multi-layer dope flows, wherein the merging portion and the dope outlet communicate with each other;
A multilayer casting film in which a first layer made of the first dope, a buffer layer made of the buffer solution, and a second layer made of the second dope are sequentially overlapped is formed on the support. Casting equipment. In the casting apparatus in which the dope flows down from the slot-shaped dope outlet opening to the block-shaped casting apparatus body toward the support, and the casting film made of the dope is formed on the support.
A first flow path through which a first dope that is provided in the casting apparatus main body and that contains a first polymer and a first solvent that dissolves the first polymer ;
A second polymer having a lower viscosity and a lower elastic modulus than the first polymer, and a second solvent that dissolves the second polymer , the second dope having a higher viscosity than the first dope flows, and the inside of the casting apparatus body A second flow path provided in
Buffering of the first flow passage and located between the second flow path, the first Ri Do from the solvent and the second solvent is compatible to the liquid, the first doped and lower viscosity than the second doped A buffer flow path through which the liquid flows;
Provided in the casting apparatus main body, the outlet of the first channel and the outlet of the second channel are opened, communicated with the outlet of the buffer channel, and the first dope and the second dope A merging section for forming a multilayer dope comprising the buffer solution located between the two dopes;
A multi-layer dope flow path through which the multi-layer dope flows, wherein the merging portion and the dope outlet communicate with each other;
A multilayer casting film in which a first layer made of the first dope, a buffer layer made of the buffer solution, and a second layer made of the second dope are sequentially overlapped is formed on the support. Casting equipment. The casting apparatus includes a feed block provided with the first flow path, the second flow path, the buffer flow path, and the merging portion, and a casting die provided with the dope outlet. The casting apparatus according to any one of claims 1 to 4 , characterized in that: The casting apparatus according to any one of claims 1 to 5 , wherein the second flow path is disposed between the pair of first flow paths. In the casting film forming method, the dope is flowed down from the slot-shaped dope outlet opening to the block-shaped casting apparatus main body toward the support, and the casting film made of the dope is formed on the support.
The first dope containing the first polymer and the second dope containing the second polymer having a lower viscosity and lower elastic modulus than the first polymer and having a higher viscosity than the first dope are merged in the casting apparatus main body. A buffer solution having a viscosity lower than that of the two dopes is caused to flow between the two dopes, and a merging step for forming a multilayer dope composed of the two dopes and a buffer solution positioned between the two dopes;
The multilayer dope is caused to flow down from the dope outlet, and a buffer layer made of the buffer solution and a second layer made of the second dope are sequentially overlapped with the first layer made of the first dope. And a film forming step of forming a film on the support. The merging step includes
A first merging step of merging any one of the first dope and the second dope and the buffer solution to flow the first dope and the buffer solution in parallel;
The casting film forming method according to claim 7 , wherein a second merging step of merging the first dope and the buffer solution flowing in parallel with each other from the buffer solution side is performed. The buffer solution contains either the first polymer or the second polymer,
9. The casting according to claim 8, wherein in the first merging step, the buffer solution is merged with one of the first dope and the second dope containing a polymer common to the polymer contained in the buffer solution. Method for forming a film. 9. The method for forming a cast film according to claim 7 , wherein the buffer solution includes any one of the first polymer and the second polymer. 10. The first dope includes a first solvent that dissolves the first polymer;
The second dope includes a second solvent that dissolves the second polymer,
The method for forming a cast film according to any one of claims 7 to 10 , wherein the buffer solution comprises a solution that is compatible with the first solvent and the second solvent. The method for forming a cast film according to claim 11, wherein the buffer solution comprises a common component of the first solvent and the second solvent. In the casting apparatus main body, the two first dopes are caused to flow, the second dope is caused to flow between the two first dopes, the one between the first dope and the second dope, and the other. Performing a flow step of flowing the buffer solution between the first dope and the second dope before the merging step,
In the film forming step, one of the first layers made of the first dope is formed on one of the first buffer layer made of the buffer solution, the second layer made of the second dope, and the second layer made of the other buffer solution. buffer layer and the other of said third layer comprising a first doping according to any one of the preceding claims 7 and forming a strip-shaped multilayer casting film overlapping sequentially on a support 12 A method for forming a cast film. The method for forming a cast film according to any one of claims 7 to 13 , wherein the second polymer is acrylic. The method of forming a cast film according to claim 14, wherein the first polymer is cellulose acylate. After performing the casting film forming method according to any one of claims 7 to 15, 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 process for drying the wet film. 17. The solution casting method according to claim 16 , wherein a film cooling step for cooling the multilayer cast film on the support is carried out before the stripping step until it is in a state where it can be independently carried. .

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