JP5310200B2 - Dope switching method and optical film manufacturing apparatus - Google Patents

Description

  The present invention relates to a technique for producing an optical film by a solution casting method, and particularly to a technique for switching between two types of dopes supplied to a casting die.

  In recent years, in a liquid crystal television, a polarizing plate using a retardation film has been widely used in order to enlarge a viewing angle. The current polarizing plate is configured by sandwiching a polarizer between a retardation film disposed on the liquid crystal cell side and a polarizing plate protective film.

  Here, since the characteristics of the retardation film are ensured by changing the resin and additives, the composition of the dope (solution) is different from that of the polarizing plate protective film. Therefore, in order to produce the retardation film and the polarizing film using one optical film production apparatus, it is necessary to switch between the dope of the retardation film and the dope of the polarizing plate protective film.

  As a conventional optical film manufacturing apparatus using a solution casting method, an apparatus having a casting die for casting a dope onto an endless belt and a common line for supplying the first dope or the second dope to the casting die is known. ing.

  Further, in Cited Document 1, when the pump for supplying the dope to the casting die is switched from the first pump to the second pump, the flow rate of the second pump to be switched is reduced while the flow rate of the first pump being used is reduced. A technique is disclosed in which a flow rate adjusting valve is controlled based on a pressure value detected by a first pressure sensor during a flow rate switching step for increasing the flow rate to suppress pressure fluctuations in the outlet path.

JP 2008-68440 A

  In the above conventional apparatus, when switching the dope having a different composition, the dope is switched by injecting the second dope into the common line and pushing out the first dope remaining in the common line.

  However, there is a problem that switching takes time because the dope is short-cut in the pipe and the wall dope is not easily pushed out.

  Moreover, in the technique of patent document 1, the flow rate switching step is performed for switching the liquid feed pump in order to change the film thickness of the optical film, and not for switching the type of dope.

  Therefore, in the flow rate switching step of Patent Document 1, the flow rate of the first pump is gradually decreased, and at the same time, the flow rate of the second pump to be switched is gradually increased.

  Therefore, even if the technique of Patent Document 1 is applied to a technique for switching the type of dope, the dope with a constant flow rate cannot be supplied to the casting die, and an optical film with a constant film thickness can be produced without stopping production. It is difficult to manufacture.

  The objective of this invention is providing the dope switching method and optical film manufacturing apparatus which can manufacture the optical film with a fixed film thickness at the time of dope switching, and can perform dope switching in a short time.

  (1) A dope switching method according to one aspect of the present invention is a dope switching method for switching a dope supplied to a casting die from a first dope to a second dope in an optical film manufacturing apparatus that manufactures an optical film by a solution casting method. The optical film manufacturing apparatus includes a three-way valve, a first supply line that supplies the first dope to the three-way valve, a second supply line that supplies the second dope to the three-way valve, A first circulation line connected to the first supply line and circulating the first dope, a second circulation line connected to the second supply line and circulating the second dope, and a dope flowing out of the three-way valve Common line for supplying the casting die to the casting die, first and second circulation valves provided in the first and second circulation lines, and first and second circulation valves provided in the first and second supply lines. And a dope switching step of gradually increasing the second dope flowing out from the three-way valve to the common line and gradually decreasing the first dope flowing out from the three-way valve to the common line, In the dope switching step, the second circulation valve is controlled so that the pressure or flow rate of the second dope flowing into the three-way valve is constant while the flow rate of the second pump is constant. Features.

  An optical film manufacturing apparatus according to another aspect of the present invention is an optical film manufacturing apparatus that manufactures an optical film by a solution casting method, and includes a three-way valve and a first supply line that supplies a first dope to the three-way valve. A first circulation line for circulating the first dope, a second supply line for supplying the second dope to the three-way valve, a second circulation line for circulating the second dope, and the three-way valve. A common line for supplying the dope to the casting die, first and second circulation valves provided in the first and second circulation lines, and first and second provided in the first and second supply lines. A control unit for gradually increasing the second dope flowing out from the three-way valve to the common line and gradually decreasing the first dope flowing from the three-way valve to the common line; , The serial flow of the second pump while the constant flow rate, characterized in that the pressure or flow rate of the second doped flowing into the three-way valve to control the second circulation valve to be constant.

  According to these configurations, the dope switching step of gradually increasing the second dope flowing out from the three-way valve to the common line and gradually decreasing the first dope flowing out of the three-way valve to the common line is performed. In the implementation, the second circulation valve is controlled so that the pressure or flow rate of the second dope flowing into the three-way valve is constant while the flow rate of the second pump is kept constant.

  That is, since the pressure or flow rate of the second dope flowing into the three-way valve is made constant, the flow rate of the second dope flowing out of the three-way valve as the flow rate of the first dope flowing out of the three-way valve gradually decreases. As a result, the flow rate of the dope flowing out from the three-way valve to the common line can be made constant.

  Thereby, even when the dope is switched, an optical film having a constant film thickness can be manufactured, and the dope can be switched without stopping the manufacturing of the optical film.

  Further, since the first supply line and the second supply line are connected to the casting die via the three-way valve and the common line, the first supply line and the second supply line are directly connected to the casting die. Compared with the configuration, the extrusion amount of the first dope can be reduced.

  As a result, the dope switching can be completed in a short time (for example, about several hours).

  (2) The first and second dopes preferably have a viscosity of 10 Pa · s (Pascal second) to 1000 Pa · s.

  This configuration defines the viscosities of the first and second dopes applied to the present dope switching method, and defines a dope having a relatively high viscosity.

  (3) It is preferable that the piping capacity of the common line is 100L (liter) or more and 1000L or less.

  This configuration defines the pipe capacity of the common line.

  (4) The three-way valve includes first and second valves for adjusting the flow rates of the first and second dopes, and the dope switching step flows into the three-way valve at the same time as the second valve is gradually opened. It is preferable to adjust the opening degree of the second circulation valve so that the pressure or flow rate of the second dope is constant.

  According to this configuration, the pressure or flow rate of the second dope flowing into the three-way valve can be made constant by relatively simple control.

  (5) In the dope switching step, it is preferable that the first valve is gradually closed at the same time as the flow rate of the first pump is gradually decreased while the first circulation valve is closed.

  According to this configuration, with the first circulation valve closed, the flow rate of the first pump is gradually decreased and at the same time the first valve is gradually closed. The flow rate of the first dope flowing out from the three-way valve to the common line can be gradually reduced while securing the flow rate of the first dope flowing in to some extent.

  (6) In the dope switching step, it is preferable that the first valve is gradually closed at the same time as making the flow rate of the first pump constant while the first circulation valve is opened.

  According to this configuration, since the first valve is gradually closed while the first circulation valve is opened and the first valve is gradually closed, the backflow of the first dope is prevented and the three-way valve flows into the three-way valve. The flow rate of the first dope flowing out from the three-way valve to the common line can be gradually decreased while securing the flow rate of the first dope to some extent.

  (7) In the dope switching step, the constant flow rate of the second pump is preferably set to a flow rate at the time of manufacturing an optical film.

  According to this configuration, since the flow rate of the second pump is set to the flow rate at the time of manufacturing the optical film, the flow rate of the dope flowing out from the three-way valve can be made about the flow rate at the time of manufacturing the optical film. Sometimes an optical film with a preferred thickness can be produced.

  According to the present invention, an optical film having a constant film thickness can be produced even at the time of dope switching, and the dope can be switched without stopping the production of the optical film. Also, the dope switching can be completed in a short time.

It is the schematic which shows the whole structure of the optical film manufacturing apparatus with which the dope switching method by one embodiment of this invention is implemented. The timing chart of the dope switching process by one embodiment of this invention is shown. The timing chart when employ | adopting the dope switching process by one embodiment of this invention is shown. It is the table | surface which put together the Example.

  Hereinafter, a dope switching method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an overall configuration of an optical film manufacturing apparatus in which a dope switching method according to an embodiment of the present invention is implemented. This optical film manufacturing apparatus manufactures an optical film by a solution casting method, a supplying step of supplying a resin solution (dope) in which a transparent resin is dissolved to a casting die D, and a traveling endless belt support A casting process for casting a dope on the film 12 to form a casting film, a peeling process for peeling the casting film from the endless belt support 12, and a drying process for drying the peeled casting film. . In addition, as an optical film manufacturing apparatus, it is not limited to what is shown in FIG. 1, You may employ | adopt the thing of another structure.

  The optical film manufacturing apparatus includes a supply unit A1 that performs the above-described supply process, a film formation unit A2 that performs the casting process, the peeling process, and the drying process, and a controller C that performs overall control of the optical film manufacturing apparatus. And an operation unit M that receives instructions from the operator.

  The film forming unit A2 includes an endless belt support 12, a peeling roller 14, a stretching device 15, a drying device 16, a winding device 18, and the like. The endless belt support 12 is drivably supported by a pair of driving rollers and a driven roller, and forms a web made of the dope 19 cast from the casting die D, and is dried while being conveyed. To do.

  The peeling roller 14 peels the optical film from the endless belt support 12. The stretching device 15 stretches the peeled optical film in a direction (width direction) perpendicular to the transport direction of the optical film. The drying device 16 dries the stretched optical film while being transported by a transport roller.

  The endless belt support 12 is a metal endless belt having a mirror surface and traveling infinitely. As the endless belt, for example, a belt made of stainless steel or the like is preferably used from the viewpoint of peelability of the optical film. From the viewpoint of effectively utilizing the width of the endless belt support 12, the width of the cast film cast by the casting die D is preferably 80 to 99% with respect to the width of the endless belt support 12. Further, instead of the endless belt support 12, a rotating metal drum having a mirror surface (endless drum support) may be used.

  And the endless belt support body 12 dries the solvent in dope, conveying the cast film (web) formed on the surface. This drying is performed by, for example, heating the endless belt support 12 or blowing heated air on the web. At that time, although the temperature of the web varies depending on the dope solution, the range of −5 to 70 ° C. is preferable and the range of 0 to 60 ° C. is preferable in consideration of the conveyance speed and productivity accompanying the evaporation time of the solvent. More preferred. The higher the temperature of the web, the faster the solvent can be dried. However, when the temperature is too high, the web tends to foam or the flatness tends to deteriorate.

  When the endless belt support 12 is heated, for example, a method of heating the web on the endless belt support 12 with an infrared heater, a method of heating the front and back surfaces of the endless belt support 12 with an infrared heater, the endless belt support 12 There is a method of heating by heating air on the back surface, and it can be appropriately selected if necessary.

  In addition, when blowing heated air, the wind pressure of the heated air is preferably 50 to 5000 Pa in consideration of the uniformity of solvent evaporation and the like. The temperature of the heating air may be dried at a constant temperature, or may be supplied in several steps in the running direction of the endless belt support 12.

  The time between casting the dope 19 on the endless belt support 12 and peeling the web from the endless belt support 12 varies depending on the film thickness of the resin film to be produced and the solvent used. Considering the peelability from the endless belt support 12, it is preferably in the range of 0.5 to 5 minutes.

  The traveling speed of the endless belt support 12 is preferably about 50 to 300 m / min, for example. Further, the ratio (draft ratio) of the running speed of the endless belt support 12 to the flow rate of the dope discharged from the casting die D is preferably about 0.5 to 2. When the draft ratio is within this range, the cast film can be stably formed. For example, if the draft ratio is too large, there is a tendency to cause a phenomenon called neck-in in which the cast film is reduced in the width direction, and if so, a wide resin film cannot be formed.

  The peeling roller 14 is disposed near the surface of the endless belt support 12 on the side where the dope 19 is cast, and the distance between the endless belt support 12 and the peeling roller 14 is preferably 1 to 100 mm. . Using the peeling roller 14 as a fulcrum, the dried web (optical film) is pulled by applying tension to the dried web (optical film). When the optical film is peeled from the endless belt support 12, the optical film is stretched in the transport direction (Machine Direction: MD direction) of the optical film by the peeling tension and the subsequent transport tension. For this reason, it is preferable that the peeling tension and the conveyance tension when peeling the optical film from the endless belt support 12 are 50 to 400 N / m.

  Moreover, the residual solvent rate of the optical film when the optical film is peeled from the endless belt support 12 is the peelability from the endless belt support 12, the residual solvent rate at the time of peeling, the transportability after peeling, and after transporting and drying. Considering the physical characteristics of the resulting resin film, it is preferably 30 to 200% by mass. In addition, the residual solvent rate of an optical film is defined by following formula (1).

Residual solvent ratio (mass%) = {(M ₁ −M ₂ ) / M ₂ } × 100 (1)
Here, M ₁ is shows the mass at any point in the optical film, M ₂ shows the mass after drying for 1 hour at 115 ° C. The optical film was measured M _1.

  The stretching device 15 stretches the optical film in a direction (Transverse Direction: TD direction) (width direction) perpendicular to the transport direction. Specifically, the both ends in the direction perpendicular to the transport direction of the optical film are gripped with clips or the like as gripping means, and the distance between the opposing clips is increased, thereby stretching in the TD direction.

  The drying device 16 includes a plurality of conveyance rollers, and dries the optical film while conveying the optical film between the rollers. In that case, you may dry using heating air, infrared rays, etc. independently, and you may dry using heating air and infrared rays together. It is preferable to use heated air from the viewpoint of simplicity. The drying temperature varies depending on the residual solvent ratio of the optical film. The drying temperature is appropriately selected depending on the residual solvent ratio in the range of 30 to 180 ° C. in consideration of drying time, shrinkage unevenness, stability of expansion and contraction, and the like. Just decide. Moreover, it may be dried at a constant temperature, or may be divided into two to four stages of temperature, and may be divided into several stages of temperature. Further, the optical film can be stretched in the MD direction while being transported in the drying device 16.

  The winding device 18 is a drying device 16 that winds the dried optical film around a winding core to a required length. In addition, it is preferable that the temperature at the time of winding is cooled to room temperature in order to prevent abrasion, loosening, and the like due to shrinkage after winding. The winder to be used can be used without any particular limitation, and may be a commonly used one, such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up.

  The supply part A1 for supplying the dope to the casting die D includes the pots K1, K2, supply lines L1, L2 (first and second supply lines), circulation lines L11, L21 (first and second circulation lines), and a pump. CP1 and CP2 (first and second pumps), circulation valves V1 and V2 (first and second circulation valves), three-way valve B, common line L3, pressure gauges P1 to P3, and casting die D .

  The pot K1 stores the first dope. The pot K2 stores the second dope. The supply line L1 is configured by, for example, a tubular member disposed between the hook K1 and the three-way valve B, and supplies the first dope stored in the hook K1 to the three-way valve B. The supply line L2 is configured by, for example, a tubular member disposed between the hook K2 and the three-way valve B, and supplies the second dope stored in the hook K2 to the three-way valve B.

  The circulation line L11 is constituted by a tubular member disposed between a predetermined position on the supply line L1 between the three-way valve B and the pump CP1 and the shuttle K1, and the first dope flowing through the supply line L1 is transferred to the shuttle. By returning to K1, the first dope is circulated.

  The circulation line L21 is constituted by a tubular member disposed between a predetermined position on the supply line L2 between the three-way valve B and the pump CP2 and the shuttle K2, and the second dope flowing in the supply line L2 is supplied to the shuttle. By returning to K1, the second dope is circulated.

  The pump CP1 is constituted by, for example, a gear pump, and flows the first dope in the supply line L1 from the pot K1 toward the three-way valve B. Here, the pump CP1 may adjust the flow rate of the first dope according to the control of the controller C, or may adjust the flow rate of the first dope according to the operation of the operator. In the case of the operation by the operator, for example, a mode for adjusting the flow rate of the pump CP1 by providing an adjustment unit for adjusting the flow rate in the pump CP1 and causing the operator to operate the adjustment unit may be adopted. A mode may be adopted in which an adjustment unit for adjusting the flow rate of CP1 is provided, and an operator operates the adjustment unit to adjust the flow rate of pump CP1.

  The pump CP2 is constituted by a gear pump, for example, and allows the second dope in the supply line L2 to flow from the hook K2 toward the three-way valve B. Here, the pump CP2 may adjust the flow rate of the second dope according to the control of the controller C, or may adjust the flow rate of the second dope according to the operation of the operator. When the operation is performed by the operator, for example, an adjustment unit for adjusting the flow rate may be provided in the pump CP2, and the operation unit M may be operated to adjust the flow rate of the pump CP2 by operating the adjustment unit. It is also possible to provide an adjustment unit for adjusting the flow rate of the pump CP2, and the operator adjusts the flow rate of the pump CP2 by operating the adjustment unit.

  The circulation valve V1 is disposed on the circulation line L11. The opening degree is adjusted by the control of the controller C or by the operation from the operator, and is returned from the supply line L1 to the hook K1 via the circulation line L11. Adjust the dope flow rate. Here, when the opening degree of the circulation valve V1 is adjusted by the operation of the operator, a mode in which the operator directly operates the circulation valve V1 may be employed, or an operation button for operating the circulation valve V1 on the operation unit M. And the operator may adjust the opening degree of the circulation valve V1 by operating the operation button.

  The circulation valve V2 is arranged on the circulation line L21, and the opening degree is adjusted by the control of the controller C or by the operation of the operator, and is returned from the supply line L2 to the hook K2 via the circulation line L21. Adjust the dope flow rate. Here, when the opening degree of the circulation valve V2 is adjusted by the operation of the operator, a mode in which the operator directly operates the circulation valve V2 may be employed, or an operation button for operating the circulation valve V2 on the operation unit M. And the operator may adjust the opening degree of the circulation valve V2 by operating the operation button.

  The three-way valve B includes inlets H1 and H2, outlet H3, and valves B1 and B2. The supply line L1 is connected to the inflow port H1, and the first dope flows in. The supply line L2 is connected to the inlet H2, and the second dope flows in. The common line L3 is connected to the outflow port H3, and the first dope and the second dope flow out to the common line L3.

  The opening of the valve B1 is adjusted according to the control of the controller C or according to the operation of the operator, and the flow rate of the first dope flowing out to the common line L3 is adjusted. The opening of the valve B2 is adjusted according to the control of the controller C or according to the operation of the operator, and the flow rate of the second dope flowing out to the common line L3 is adjusted.

  Here, when adjusting the opening degree of the valves B1 and B2 by the operation of the operator, a mode in which the operator directly operates the valves B1 and B2 may be adopted, or the valves B1 and B2 are operated by the operation unit M. A mode in which the operation buttons are provided and the opening degree of the valves B1 and B2 is adjusted by operating the operation buttons may be adopted.

  The common line L3 is configured by a tubular member disposed between the three-way valve B and the casting die D, and supplies the dope flowing out from the three-way valve B to the casting die D. Here, the dope capacity in the common line L3 is preferably, for example, 100 L (liter) or more and 1000 L or less. The dope can be switched in a short time by reducing the capacitance of the common line L3.

  Thus, since the supply line L1 and the supply line L2 are connected to the casting die D via the three-way valve B and the common line L3, the feeding line L1 and the supply line L2 are directly connected to the casting die D. Compared with the structure connected to, the amount of extrusion of the first dope can be reduced. As a result, the dope switching can be completed in a short time (for example, about several hours).

  The pressure gauge P1 is provided at a predetermined position on the downstream side of the supply line L1 (for example, in the vicinity of the three-way valve B), detects the pressure of the first dope flowing through the supply line L1, and outputs detection data to the controller C.

  The pressure gauge P2 is provided at a predetermined position (for example, in the vicinity of the three-way valve B) on the downstream side of the supply line L2, detects the pressure of the second dope flowing through the supply line L2, and outputs detection data to the controller C.

  The pressure gauge P3 is provided at a predetermined position (for example, in the vicinity of the three-way valve B) of the common line L3, detects the dope pressure flowing through the common line L3, and outputs detection data to the controller C.

  The casting die D casts a resin solution (dope) 19 in which a transparent resin is dissolved on the surface of the endless belt support 12. Here, the casting die D is supplied with the dope 19 from the common line L3 connected to the upper end. Then, the supplied dope 19 is discharged from the casting die D onto the endless belt support 12, and a web is formed on the endless belt support 12.

  The detection data of the pressure gauges P1 to P3 may be displayed on the display unit E under the control of the controller C, or the display unit E is provided in the pressure gauges P1 to P3. It may be displayed.

  The controller C controls the entire optical film manufacturing apparatus.

  Hereinafter, the composition of the resin solution (dope) used in the present embodiment will be described.

  The resin solution used in this embodiment is obtained by dissolving a transparent resin in a solvent.

  The transparent resin is not particularly limited as long as it is a resin having transparency when formed into a substrate by a solution casting method or the like, but is easy to manufacture by the solution casting method, a hard coat layer, etc. It is preferable that it is excellent in adhesiveness with other functional layers and is optically isotropic. Here, the transparency means that the visible light transmittance is 60% or more, preferably 80% or more, and more preferably 90% or more.

  Specific examples of the transparent resin include cellulose ester resins such as cellulose diacetate resin, cellulose triacetate resin, cellulose acetate butyrate resin, and cellulose acetate propionate resin; polyethylene terephthalate resin and polyethylene naphthalate resin. Acrylic resins such as polymethyl methacrylate resins; Polysulfone (including polyether sulfone) resins, polyethylene resins, polypropylene resins, cellophane, polyvinylidene chloride resins, polyvinyl alcohol resins, ethylene vinyl alcohol resins, Shinji Vinyl resins such as tactic polystyrene resins, cycloolefin resins and polymethylpentene resins; polycarbonate resins; polyarylate resins Polyetherketone resins; polyether ketone imide resin; can be mentioned fluorine-based resin or the like; a polyamide resin. Among these, cellulose ester resins, cycloolefin resins, polycarbonate resins, and polysulfone (including polyethersulfone) resins are preferable. Furthermore, cellulose ester resins are preferred, and among cellulose ester resins, cellulose acetate resins, cellulose propionate resins, cellulose butyrate resins, cellulose acetate butyrate resins, cellulose acetate propionate resins, and cellulose triacetate resins are preferred, Cellulose triacetate resin is particularly preferred. Moreover, the said transparent resin may use the transparent resin illustrated above independently, and may use it in combination of 2 or more type.

  Next, a dope switching process according to the present embodiment for switching the dope supplied to the casting die D from the first dope to the second dope will be described.

  First, the three-way valve B is adjusted so that the second dope flowing out from the three-way valve B to the common line L3 is gradually increased and the first dope flowing out from the three-way valve B to the common line L3 is gradually decreased.

  At this time, the controller C monitors the pressure gauge P2 in a state where the flow rate of the pump CP2 is constant, and circulates so that the pressure of the second dope flowing into the three-way valve B becomes constant. The valve V2 may be controlled. Alternatively, the operator sets the flow rate of the pump CP2 to a constant flow rate, monitors the pressure gauge P2, and operates the operation unit M so that the pressure of the second dope flowing into the three-way valve B becomes constant. The valve V2 may be adjusted.

  Specifically, the controller C or the operator performs the dope switching step by adjusting the opening of the circulation valve V2 so that the pressure of the second dope flowing into the three-way valve B becomes constant at the same time that the valve B2 is gradually opened. carry out. Thereby, the pressure of the second dope flowing into the three-way valve B can be made constant by a relatively simple procedure. When the controller C monitors the pressure gauge P2 and controls the circulation valve V2, the controller C may employ, for example, PID (Proportional Integral Differential) control, PI (Proportional Integral) control, or the like.

  Since the pressure of the second dope flowing into the three-way valve B is made constant by performing the dope switching step in this way, the flow rate of the first dope flowing out from the three-way valve B gradually decreases. As a result of gradually increasing the flow rate of the second dope flowing out from the three-way valve B, the flow rate of dope flowing out from the three-way valve B to the common line L3 can be made constant. As a result, the dope switching can be completed in a short time (for example, about several hours).

  In the dope switching step, it is preferable that the flow rate of the pump CP1 is gradually decreased while the valve B1 is gradually closed while the circulation valve V1 is closed. Accordingly, the backflow of the first dope is prevented, and the flow rate of the first dope flowing out from the three-way valve B to the common line L3 is gradually decreased while securing the flow rate of the first dope flowing into the three-way valve B to some extent. Can do. This procedure may be performed automatically by the controller C or manually by the operator.

  Further, as the first and second dopes, dopes having a relatively high viscosity having a viscosity of 10 Pa · s (Pascal second) or more are employed.

  Moreover, in said dope switching process, it is preferable to make the fixed flow volume of pump CP2 into the flow volume at the time of manufacture of an optical film. Thereby, since the flow rate of the pump CP2 is set to the flow rate at the time of manufacturing the optical film, the flow rate of the dope flowing out from the three-way valve B can be made about the flow rate at the time of manufacturing the optical film. An optical film having a preferable film thickness can be produced. In this procedure, the controller C or the operator may set a predetermined flow rate.

  FIG. 2 shows a timing chart of the dope switching process according to the present embodiment. The waveforms in the first to sixth stages respectively indicate the opening degree of the circulation valve V1, the opening degree of the circulation valve V2, the flow rate of the pump CP1, the flow rate of the pump CP2, the opening degree of the valve B1, and the opening degree of the valve B2. Yes. The dope switching process is started when the operation unit M receives an instruction for starting the dope switching process from the operator.

  As shown in the sixth stage of FIG. 2, the opening degree of the valve B2 is gradually increased at a constant rate from fully closed to fully open. Further, as shown in the fourth stage in FIG. 2, the flow rate of the pump CP2 is constant. Further, as shown in the second stage of FIG. 2, the controller C or the operator adjusts the opening degree of the circulation valve V2 so that the pressure value of the second dope measured by the pressure gauge P2 is constant. Along with this, the opening degree of the circulation valve V2 gradually decreases.

  As shown in the first stage of FIG. 2, the circulation valve V1 is fully closed during the dope switching process. Further, as shown in the third stage of FIG. 2, the pump CP1 is gradually decreased so that the flow rate becomes, for example, a predetermined value R1 (for example, the maximum value) to a predetermined value R2 (R2 <R1; for example, 0).

  Further, as shown in the fifth stage of FIG. 2, the valve B1 is gradually decreased at a constant rate so that the opening degree is fully opened to fully closed.

  Accordingly, the first dope of the common line L3 is pushed out by the second dope, and at the end of the dope switching process, the first dope is pushed out completely by the second dope, and the common line L3 is filled with the second dope. Yes.

  The rate at which the flow rate of the pump CP1 shown in the third stage in FIG. 2 decreases, the rate at which the opening of the valve B1 shown in the fifth stage in FIG. 2 gradually decreases, and the valve B2 shown in the sixth stage in FIG. As the rate at which the opening gradually increases, a value determined in advance based on the time required from the start to the end of the dope switching step is adopted. Further, as the time required from the start to the end of the dope switching step, the time until the first dope is removed from the common line L3 is obtained by experiment, and the obtained time may be adopted. Specifically, the time required for the dope switching step can be a time for the second dope, for example, about three times the common line L3 to flow out from the common line L3, for example, a time of several minutes to several hours. Can be adopted.

  Here, when the operation unit M receives an instruction to start the dope switching process, the controller C gradually decreases the flow rate of the pump CP1 and the opening degree of the valve B1 at a predetermined rate, and the valve B2 The controller C or the operator feeds back the circulation valve V2 so that the pressure value measured by the pressure gauge P2 becomes constant at the same time that the pump CP1 and the valves B1 and B2 are sequence-controlled so that the opening degree of the valve gradually increases. Control is sufficient.

  Thus, according to the dope switching method according to the present embodiment, an optical film having a constant film thickness can be manufactured even at the time of switching the dope, and the dope is switched without stopping the manufacturing of the optical film. be able to. Also, the dope switching can be completed in a short time.

  In the dope switching step, the opening degree of the circulation valve V2 is adjusted so that the pressure of the second dope flowing into the three-way valve B becomes constant at the same time that the valve B2 is gradually opened. Not. That is, the dope switching step is performed by so-called flow rate control, in which the opening degree of the circulation valve V2 is adjusted so that the flow rate is constant rather than the pressure of the second dope flowing into the three-way valve B at the same time as the valve B2 is gradually opened. Also good. In this case, a flow meter may be provided instead of the pressure gauges P1 to P3. Also in this case, in the form in which the controller C adjusts the opening degree of the circulation valve V2, the controller C may adopt PID control, PI control, etc., and make the flow rate of the second dope constant.

  In the dope switching step, the first dope is switched to the second dope. However, the present invention is not limited to this, and the second dope may be switched to the first dope. In this case, the second dope may be switched to the first dope similarly to the case where the first dope is switched to the second dope.

  In the dope switching step, the flow rate of the pump CP1 is gradually decreased and the valve B1 is gradually closed while the circulation valve V1 is closed. However, the present invention is not limited to this. In other words, the flow rate of the pump CP1 may be kept constant while the circulation valve V1 is opened, and the valve B1 may be gradually closed.

  FIG. 3 shows a timing chart when this dope switching step is adopted. As shown in the first stage of FIG. 3, the circulation valve V1 is fully opened, and as shown in the third stage of FIG. 3, the flow rate of the pump CP1 is made constant, and the valve B1 is gradually opened at a constant rate. is decreasing.

  Accordingly, the backflow of the first dope is prevented, and the flow rate of the first dope flowing out from the three-way valve B to the common line L3 is gradually decreased while securing the flow rate of the first dope flowing into the three-way valve B to some extent. Can do.

  Specifically, the controller C or the operator performs the dope switching step by adjusting the opening of the circulation valve V2 so that the pressure of the second dope flowing into the three-way valve B becomes constant at the same time that the valve B2 is gradually opened. carry out. Thereby, the pressure of the second dope flowing into the three-way valve B can be made constant by relatively simple control.

  Next, examples of the present invention will be described. FIG. 4 is a table summarizing the examples. This table | surface has shown 10 types of Examples 1-10 when the arbitrary two dope compositions are employ | adopted as a 1st and 2nd dope among the following three dope compositions 1-dope composition 3. FIG.

<Dope composition 1>
Cellulose triacetate (Mn = 148000, Mw = 310000, Mw / Mn = 2.1) 100
Triphenyl phosphate 8
Ethyl phthalyl ethyl glycolate 2
Methylene chloride 440
Ethanol 40
Tinuvin 109 (Ciba Specialty Chemicals) 0.5
Tinuvin 171 (Ciba Specialty Chemicals) 0.5
Aerosil 972V (Nippon Aerosil Co., Ltd.) 0.2
<Dope composition 2>
Cellulose triacetate propionate 100
(Acetyl group substitution degree + propionyl group substitution degree = 2.4 Mn = 6000, Mw = 180000, Mw / Mn = 3.00)
Triphenyl phosphate 8
Ethyl phthalyl ethyl glycolate 2
Methylene chloride 360
Ethanol 60
Tinuvin 109 (Ciba Specialty Chemicals) 0.5
Tinuvin 171 (Ciba Specialty Chemicals) 0.5
Aerosil 972V (Nippon Aerosil Co., Ltd.) 0.2
<Dope composition 3>
Norbornene resin (Arton G, manufactured by JSR) 100 parts by mass ethylphthalyl ethyl glycolate 2
Triphenyl foscate 8
Methylene chloride 250
Ethanol 10

  In the table of FIG. 4, the supply line 1 indicates the supply line L1 of FIG. 1, and the supply line 2 indicates the supply line L2 of FIG. “Dope type” indicates which one of the dope compositions 1 to 3 was adopted, and “1” to “3” shown in the table indicate that the dope compositions 1 to 3 were used, respectively.

  “Viscosity” indicates the viscosity of the dope at 35 ° C. “Flow rate” indicates how the flow rate is changed, “down” indicates that the flow rate is reduced, and “constant” indicates that the flow rate is constant.

  “Circulation line valve” indicates how the circulation valves V1 and V2 shown in FIG. 1 are controlled. The “control method” indicates how the circulation valve V2 of the circulation line L21 is controlled. The “three-way valve outlet flow rate deviation” is an absolute value (= | R) of the difference between the average value AVE1 and each measured value R of the flow rate with respect to the average value AVE1 of the dope flowed out from the outlet H3 of the three-way valve B. -AVE1 |) indicates the ratio of the average value (= (average value of | R-AVE1 | / AVE1) × 100). “Piping after the three-way valve” indicates the capacity of the common line L3 shown in FIG. 1 in units of liters (L). “Thickness deviation after pushing three times the pipe capacity after switching the three-way valve” starts switching from the supply line L1 to the supply line L2, and then applies the second dope having a capacity three times that of the common line L3 to the common line. The deviation of the film thickness of the manufactured optical film is shown after flowing out from L3.

  In addition, the comparative example 1 and the comparative example 2 in the table | surface of FIG. 4 changed the dope using the method different from the dope manufacturing method by this Embodiment. In Comparative Example 1, the circulation line valve (circulation valve V1) of the supply line 1 is controlled so that the pressure of the supply line 1 becomes constant. In Comparative Example 2, the circulation line valve (circulation valve V1) of the supply line 1 and the circulation line valve (circulation valve V2) of the supply line 2 are both closed, and the supply line 1 (supply line) is used without using the circulation line. The flow rate of the pump CP1 is controlled so that the pressure of L1) is constant, and the flow rate of the pump CP2 is gradually increased so that the pressure of the supply line 2 (supply line L2) is constant.

  In Examples 1 to 8 and Comparative Examples 1 and 2, in the three-way valve B, the opening degree of the valve B1 is gradually decreased, and the opening degree of the valve B2 is gradually increased. Further, in Examples 1 to 4 and 6 to 8, pressure control, that is, the opening degree of the circulation valve V2 is controlled so that the dope pressure in the supply line 2 is constant. In Example 5, the flow rate control is performed. That is, the opening degree of the circulation valve V2 is controlled so that the dope flow rate in the supply line 2 becomes constant.

  In Examples 1 to 8, a “three-way valve outlet flow rate deviation” of 1% to 5% was obtained, whereas in Comparative Examples 1 and 2, “three-way valve outlet side” The "flow rate deviation" is 12%, and it can be seen that the dope switching method according to the present embodiment stabilizes the flow rate of the dope flowing through the common line L3.

  Further, due to this, in Examples 1 to 8, the film thickness deviation is around 1%, and in Example 4, the film thickness deviation is “0.5%”, which is extremely low. In Examples 1 and 2, the film thickness deviation is “8%”, which is much larger than that in Examples 1 to 8, and the film thickness is more stable in the dope switching method according to this embodiment. I understand.

A1 Supply part A2 Film formation part B Three-way valve B1, B2 Valve C Controller CP1, CP2 Pump D Casting die H1, H2 Inlet H3 Outlet K1, K2 Pot L1, L2 Supply line L11, L21 Circulation line L3 Common line M Operation part P1 Pressure gauge P2 Pressure gauge V1, V2 Circulation valve

Claims (8)

In an optical film manufacturing apparatus for manufacturing an optical film by a solution casting method, a dope switching method for switching a dope supplied to a casting die from a first dope to a second dope,
The optical film manufacturing apparatus includes:
A three-way valve,
A first supply line for supplying the first dope to the three-way valve;
A second supply line for supplying the second dope to the three-way valve;
A first circulation line connected to the first supply line and circulating the first dope;
A second circulation line connected to the second supply line and circulating the second dope;
A common line for supplying the dope flowing out of the three-way valve to the casting die;
First and second circulation valves provided in the first and second circulation lines;
First and second pumps provided in the first and second supply lines,
A dope switching step of gradually increasing the second dope flowing from the three-way valve to the common line and gradually decreasing the first dope flowing from the three-way valve to the common line;
The dope switching step controls the second circulation valve so that the pressure or flow rate of the second dope flowing into the three-way valve is constant while the flow rate of the second pump is constant. The dope switching method characterized by this.   The dope switching method according to claim 1, wherein the first and second dopes have a viscosity of 10 Pa · s or more and 1000 Pa · s or less.   The dope switching method according to claim 1 or 2, wherein a pipe capacity of the common line is 100L or more and 1000L or less. The three-way valve includes first and second valves for adjusting the flow rates of the first and second dopes,
The dope switching step adjusts the opening degree of the second circulation valve so that the pressure or flow rate of the second dope flowing into the three-way valve becomes constant at the same time as the second valve is gradually opened. The dope switching method according to claim 1.   5. The dope switching method according to claim 4, wherein in the dope switching step, the first valve is gradually closed at the same time as the flow rate of the first pump is gradually decreased while the first circulation valve is closed.   5. The dope switching method according to claim 4, wherein in the dope switching step, the first valve is gradually closed simultaneously with a constant flow rate of the first pump with the first circulation valve opened.   The dope switching method according to any one of claims 1 to 6, wherein in the dope switching step, the constant flow rate of the second pump is set to a flow rate at the time of manufacturing an optical film. An optical film manufacturing apparatus for manufacturing an optical film by a solution casting method,
A three-way valve,
A first supply line for supplying a first dope to the three-way valve;
A first circulation line for circulating the first dope;
A second supply line for supplying a second dope to the three-way valve;
A second circulation line for circulating the second dope;
A common line for supplying the dope flowing out of the three-way valve to the casting die;
First and second circulation valves provided in the first and second circulation lines;
First and second pumps provided in the first and second supply lines;
A controller that gradually increases the second dope flowing from the three-way valve to the common line and gradually decreases the first dope flowing from the three-way valve to the common line;
The control unit controls the second circulation valve so that the pressure or flow rate of the second dope flowing into the three-way valve is constant while the flow rate of the second pump is constant. An optical film manufacturing apparatus.

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