JPWO2011148834A1 - Manufacturing method of optical film - Google Patents

Abstract

In order to provide an optical film manufacturing method capable of manufacturing an optical film having a stable performance when an optical film is manufactured by a solution casting film forming method, a dope obtained by dissolving a raw material resin in a solvent is used as an endless belt support from a die. A solution casting manufacturing apparatus comprising: a casting process for casting a dope film thereon to form a web; and after peeling the web from the endless belt support, at least a stretching process, a drying process, and a winding process. In the method for producing an optical film for producing a thin optical film, the die has a pressure reducing means on the upstream side in the moving direction of the endless belt support and a pressure means on the downstream side, and the pressure reducing means The absolute value of ΔPH / ΔPL is 0.02 to 1.0, where ΔPL is the difference between the pressure due to pressure and atmospheric pressure, and ΔPH is the difference between the pressure due to the pressurizing means and atmospheric pressure. Method for producing an optical film to be.

Description

  The present invention relates to a method for producing an optical film.

  In recent years, the demand for liquid crystal display devices has increased due to the widespread use of liquid crystal displays mounted on automobiles, large liquid crystal television displays, mobile phones, notebook computers, and the like. A liquid crystal display device is widely used as a monitor because it saves space and energy compared to a conventional CRT display device. Furthermore, it is also spreading for TV. In such a liquid crystal display device, an optical film is used, and its demand is rapidly increasing.

  By the way, as an optical film used for a liquid crystal display device, for example, a polarizing film of a polarizing plate has a cellulose ester film laminated as a protective film on one side or both sides of a polarizer made of a stretched polyvinyl alcohol film.

  Such an optical film is required to have a smooth surface without optical defects. In particular, as the size of monitors and TVs increases and the definition becomes higher, these required qualities are becoming stricter.

  One method for producing an optical film is a solution casting method. In this method, a resin is dissolved in a solvent, and the solution (dope) is cast from a dope outlet of a casting die onto an endless belt-like support that rotates and moves the dope film. In this method, after a predetermined amount of solvent is evaporated, the film is peeled off from the endless belt-like support and further stretched as necessary. In this method, if the moving speed of the endless belt-like support is increased in order to increase productivity, the dope film and the endless belt-like support that have landed on the endless belt-like support as the endless belt-like support moves. There is a problem involving entrained air during the period.

  By entraining the entrained air, 1) the adhesion between the dope film and the endless belt-like support is deteriorated, and the dope film flutters until reaching the endless belt-like support, and a film with poor flatness is formed. 2) There is a problem that a film with poor flatness can be formed when the entrained air goes out through a dope film cast on an endless belt-like support. In order to cope with this problem, a method is generally used in which a decompression chamber is provided on the upstream side of the endless belt-like support at the dope outlet and the dope film is in close contact with the support, but the required quality is still satisfied. Further studies are underway as there are no.

  For example, a pressure reducing device that applies gas pressure to the upstream side in the moving direction of the endless belt of a die (corresponding to a casting die) that discharges a resin film and a pressure device that applies gas pressure to the downstream side are provided. A method for producing a resin film (corresponding to an optical film) that stabilizes the behavior of the resin film immediately before landing on the endless belt or immediately after landing, and suppresses the fluctuation amount of the endless belt, thereby realizing extremely stable casting as a whole. Is known (for example, see Patent Document 1).

  However, it has been found that when an optical film is produced by the method described in Patent Document 1, the performance is not stable, and the required quality associated with the recent increase in size and definition of monitors and TVs cannot be obtained.

  From such a situation, when manufacturing an optical film by the solution casting film forming method, development of an optical film manufacturing method capable of manufacturing an optical film with stable performance is desired.

JP 2000-176952 A

  This invention is made | formed in view of the said situation, The objective is providing the manufacturing method of the optical film which can manufacture the optical film with the stable performance, when manufacturing an optical film by the solution casting film forming method. It is.

  The above object of the present invention can be achieved by the following constitution.

1. A casting step of casting a dope film in which a raw material resin is dissolved in a solvent is cast on an endless belt support from a die to form a web, and after peeling the web from the endless belt support, at least a stretching step In the method for producing an optical film for producing an optical film of a thin film by a solution casting production apparatus having a drying step and a winding step,
The die has pressure reducing means on the upstream side in the moving direction of the endless belt support, and pressure means on the downstream side,
The difference between the pressure by the pressure reducing means and the atmospheric pressure is ΔPL,
When the difference between the pressure by the pressurizing means and the atmospheric pressure is ΔPH,
An absolute value of ΔPH / ΔPL is 0.02 to 1.0.

  2. 2. The method for producing an optical film as described in 1 above, wherein the pressurizing means is a gas spraying device that applies dynamic pressure in the width direction of the dope film.

  3. 3. The method for producing an optical film as described in 2 above, wherein the wind speed of the gas emitted from the gas spraying device is 5 m / s to 20 m / s.

  4). 4. The method for producing an optical film according to any one of 1 to 3, wherein the pressurizing unit is a pressurizing chamber that applies a static pressure to the dope film with a gas.

  5. 5. The method for producing an optical film as described in 3 or 4 above, wherein the temperature of the gas is 20 ° C. to 50 ° C.

  6). 6. The method for producing an optical film as described in any one of 3 to 5, wherein the gas contains 1000 ppm to 10,000 ppm of a solvent contained in the dope.

  7). 7. The method of manufacturing an optical film according to any one of 1 to 6, wherein the decompression unit is a suction device that applies a dynamic pressure in a width direction of the dope film.

  8). 7. The method for producing an optical film according to any one of 1 to 6, wherein the decompression means is a decompression chamber that applies a static pressure in the width direction of the dope film.

  9. The pressure distribution in the width direction of the dope film or cast film by the pressurizing means is ± 0.1% to ± 5.0% with respect to the pressure of the pressurizing means. The manufacturing method of the optical film any one of 1-8.

  10. Any one of 1 to 9 above, wherein a pressure distribution in the width direction of the dope film by the decompression means is ± 0.2% to ± 5.0% with respect to the pressure of the decompression means. The manufacturing method of the optical film of description.

  11. The pressure variation of the pressurizing unit is 0.1% to 1.0%, and the ratio of the pressure variation of the pressure reducing unit is 0.1 to 1.0. The manufacturing method of the optical film of any one of 1-10.

  12 12. The method for producing an optical film as described in any one of 1 to 11, wherein a difference ΔPH between the pressure of the pressurizing unit and atmospheric pressure is 20 Pa to 1000 Pa.

  13. 13. The method for producing an optical film according to any one of 1 to 12, wherein a difference ΔPL between the pressure of the decompression means and the atmospheric pressure is 400 Pa to 1500 Pa.

  14 14. The method for producing an optical film according to any one of 1 to 13, wherein the moving speed of the endless belt support is from 50 m / min to 200 m / min.

  15. 15. The method for producing an optical film as described in any one of 1 to 14, wherein the fluctuation range of the distance between the surface of the endless belt support and the dope outlet of the die is 100 μm or less.

  The present inventor, when landing the dope film from the dope outlet of the casting die on the endless belt-like support by the solution casting film forming method, the upstream side in the moving direction of the endless belt-like support of the casting die The reason why the performance is not stable even if an optical film is manufactured by providing a pressure reducing device (pressure reducing chamber) for applying gas pressure to a pressure device and a pressure device (pressurizing chamber) for applying gas pressure downstream. As a result of the examination, the following was found. The reason why the performance is not stable is due to drying unevenness due to film thickness unevenness and optical value unevenness due to fluctuation of the film thickness itself.

  Since stabilization of the film thickness is dominant for performance stabilization, the film thickness is not stable even when the amplitude width of the endless belt-like support is suppressed when manufacturing an optical film by the solution casting film forming method. Have estimated that the film thickness can be stabilized by suppressing the amplitude width of the dope film when landing the dope film on the endless belt-like support to form the cast film.

  The reason why the film thickness of the cast film formed on the endless belt-like support becomes unstable is that when the dope film is landed on the endless belt-like support, along with the high-speed conveyance of the endless belt-like support The generated entrained air collides with the dope film and shakes the dope film. Also, the entrained air is taken in between the endless belt-like support and the casting film, so that the adhesion between the endless belt-like support and the casting film is improved. Worsens and the cast film flutters. The accompanying air refers to a wind generated along the endless belt-like support in the moving direction of the endless belt-like support as the endless belt-like support moves. In order to suppress the entrainment of the entrained air, a pressure reducing device (decompression chamber) that applies gas pressure to the upstream side in the moving direction of the endless belt-like support of the casting die, and adhesion between the endless belt-like support and the casting film In order to improve the property and suppress the fluttering, a pressurizing device (pressurizing chamber) for applying a gas pressure is provided on the downstream side. A gas flow generated by operating the decompression device (decompression chamber) and the pressurization device (pressurization chamber) collides with the dope film so that the dope film is shaken and stabilized on the endless belt-like support. It was estimated that the dope film did not land.

As a result of further investigation on why the gas flow generated by operating the decompression device (decompression chamber) and the pressurization device (pressurization chamber) collides with the dope film, the following was found.
1) In order to suppress entrainment of entrained air that occurs during high-speed conveyance of an endless belt-like support, increasing the degree of decompression of the decompression device (decompression chamber) increases the flow rate of the gas flowing into the decompression chamber and causes the dope film to sway. It becomes unstable.
2) By suppressing the entrainment of entrained air, increasing the adhesion between the endless belt-like support and the casting film, and increasing the degree of pressurization of the pressurizing device (pressurizing chamber) in order to suppress fluttering of the casting film. When the gas from the pressurizing chamber flows into the decompression chamber, the dope film is shaken by the gas and becomes unstable.

  For these reasons, when the dope film is landed on the endless belt-like support, the dope film shakes, entrainment of air entrains, the adhesion of the cast film on the endless belt-like support increases, and the flutter is suppressed at the same time. It was found that it is important to balance the pressure in the decompression chamber (decompression degree) and the pressure in the pressurization chamber (pressurization degree).

  As a result of further investigation, it has been found that there is an optimum range of the balance between the pressure in the decompression chamber (decompression degree) and the pressure in the pressurization chamber (pressurization degree), and the objective effect of the present invention is limited to only the optimum range. It is understood that the above can be achieved, and the present invention has been achieved.

  When manufacturing an optical film by the solution casting film forming method, an optical film manufacturing method capable of manufacturing an optical film with stable performance could be provided.

It is a schematic diagram of the manufacturing process which shows an example of the manufacturing method of the optical film by a solution casting method. FIG. 2 is a schematic enlarged view of a portion indicated by A in FIG. 1 when the decompression means is a decompression chamber and the pressurization means is a pressurization chamber. FIG. 2 is a schematic enlarged view of a portion indicated by A in FIG. 1 when the decompression means is a decompression chamber and the pressurization means is a gas blowing device. FIG. 2 is a schematic enlarged view of a portion indicated by A in FIG. 1 when the pressure reducing means is a suction device and the pressure means is a pressure chamber. FIG. 2 is a schematic enlarged view of a portion indicated by A in FIG. 1 when the decompression unit is a suction device and the pressurization unit is a gas spraying device.

  Although an embodiment of the present invention will be described with reference to FIGS. 1 to 5, the present invention is not limited to this.

  FIG. 1 is a schematic view of a production process showing an example of a method for producing an optical film by a solution casting method.

  In the figure, reference numeral 1 denotes a process for producing an optical film by a solution casting method. The manufacturing process 1 includes a casting process 1a, a dope supply process 1b, a first drying process 1c, a second drying process 1d, and a winding process 1e.

  The casting process 1a includes an endless belt-like support 1a1 that travels endlessly (in the direction of the arrow in the figure) and a dope 2 in which the resin supplied from the dope supply process 1b is dissolved in a solvent. The die 1a2 to be cast is used.

  The dope supply process 1b uses a dope supply tank 1b1 and a supply pipe 1b2 for supplying the dope 2 to the dice 1a2.

  3 is a flow in which a dope film 2a1 (see FIG. 2) flowing down from a dope outlet 1a25 (see FIG. 2) of the die 1a2 is landed on the endless belt-like support 1a1 on the endless belt-like support 1a1. The peeling point which peels the web of the state which the film 2a solidified is shown, 4 shows the peeled web. The die 1a2 has a decompression means 1a3 on the upstream side in the transport direction (arrow direction in the figure) of the endless belt-like support 1a1, and a pressurization means 1a4 on the downstream side.

  Examples of the decompression unit 1a3 include a decompression chamber that applies static pressure to the dope film 2a1 (see FIG. 2), or a suction device that applies dynamic pressure. Examples of the pressurizing unit 1a4 include a pressurizing chamber that applies a static pressure to the dope film 2a1 (see FIG. 2) and the casting film 2a, or a gas blowing device that applies a dynamic pressure. The combination of the decompression unit 1a3 and the pressurization unit 1a4 can be appropriately selected as necessary. The most preferable combination includes a combination of a decompression chamber and a pressurization chamber.

  The casting process 1a has a heating device (not shown), and removes the solvent so that the casting film 2a formed on the endless belt-like support 1a1 can be peeled from the endless belt-like support 1a1. It is arranged for this purpose. A higher concentration of the resin of the dope 2 is preferable because the drying load after casting on the endless belt-like support 1a1 can be reduced. However, if the concentration of the resin is too high, the load at the time of filtration increases. The accuracy becomes worse. The concentration for achieving both of these is preferably 10% by mass to 35% by mass, and more preferably 15% by mass to 25% by mass.

  The heating means used for the heating device (not shown) is not particularly limited. For example, a method of heating the contact surface of the casting film 2a of the endless belt-like support 1a1 with an infrared heater, the back surface of the endless belt-like support 1a1 The method of spraying warm air on the back surface side, the method of spraying warm air on the surface of the casting film 2a, the method of heating the back surface of the endless belt-like support 1a1 with warm water or heating oil, and the like. After casting, the time until peeling differs depending on the film thickness of the cellulose ester film to be produced and the solvent used, but in consideration of peelability from the belt, film-forming efficiency, process length, etc., 0.5 to 5 minutes A range is preferred.

  The endless belt-like support to be used is preferably a mirror-finished surface, preferably a stainless steel belt or a drum whose surface is plated with a casting. The casting width can be 1 m to 4 m. The surface temperature of the endless belt-like support 1a1 in the casting step 1a is preferably set to −50 ° C. to a temperature at which the solvent does not boil and foam. A higher temperature is preferred because the drying speed of the cast film can be increased. However, if the temperature is too high, the cast film may foam or the planarity may deteriorate. The temperature of the preferred endless belt-like support is appropriately determined in the range of 0 to 100 ° C, and more preferably 5 ° C to 30 ° C. Alternatively, it is also preferable to peel the film from the drum in a state in which the cast film is gelled by cooling and contains a large amount of residual solvent. The method for controlling the temperature of the endless belt-shaped support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of bringing hot water into contact with the back side of the endless belt-shaped support. It is preferable to use hot water because heat is efficiently transmitted, and the time until the temperature of the endless belt-like support becomes constant is shorter. When using hot air, considering the temperature drop of the casting film due to the latent heat of vaporization of the solvent, use hot air that is higher than the target temperature while using hot air above the boiling point of the solvent and preventing foaming. There is. In particular, it is preferable to efficiently dry by changing the temperature of the endless belt-like support and the temperature of the drying air during the period from casting to peeling.

  The endless belt-like support 1a1 is held by the holding roll 1a11 and the holding roll 1a12, and rotates and moves between the holding roll 1a11 and the holding roll 1a12 (in the direction of the arrow in the drawing) as the holding roll rotates. Yes. The distance between the holding roll 1a11 and the holding roll 1a12 is greater than 0 m and within a range of 5 m or less, preferably 1 m to 5 m, more preferably 2 m to 5 m. In addition, one or both of the holding roll 1a11 and the holding roll 1a12 is provided with a driving device (not shown) for applying tension to the endless belt-like support 1a1, and thereby the endless belt-like support 1a1 is tensioned. Used in a stretched state. The dope film 2a1 (see FIG. 2) flowing out from the dope outlet 1a25 (see FIG. 2) of the die 1a2 is landed on the endless belt-like support 1a1 at the position held by the holding roll 1a12.

  The moving speed of the endless belt-shaped support 1a1 is preferably 50 m / min to 200 m / min in consideration of improvement of productivity, securing of initial drying time until the metal support can be peeled. In addition, a moving speed shows the value measured with the rotational speed of the roll which drives a metal support body.

  Reference numeral 3 denotes a peeling point at which the solidified web is peeled off from the cast film 2a cast and formed on the endless belt-like support 1a1 until the solvent can be peeled off. The temperature of the web at the peeling point is preferably -50 ° C to 40 ° C, more preferably 10 ° C to 40 ° C, and most preferably 15 ° C to 30 ° C. 4 shows the peeled web.

  The residual solvent amount of the web at the peeling point is desirably 150% or less from the viewpoint of film strength, and more preferably 120% or less. The residual solvent amount is represented by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass at an arbitrary point of the film, and N is the mass when a film having a mass of M is dried at 110 ° C. for 3 hours.

  The web 4 peeled at the peeling point 3 is conveyed to the first drying step 1c. The 1st drying process 1c has the drying box 1c3 which has the dry wind inlet 1c1 and the discharge port 1c2, the upper conveyance roll 1c4 which conveys the web 4, and the lower conveyance roll 1c5. The upper transport roll 1c4 and the lower transport roll 1c5 are composed of a plurality of sets, one set up and down. The first drying step 1c may be arranged as preliminary drying.

  The number of transport rolls disposed in the first drying step 1c varies depending on the drying conditions, the method, the length of the optical film to be manufactured, and the like, and is appropriately set. The upper conveyance roll 1c4 and the lower conveyance roll 1c5 are free rotation rolls that are not rotationally driven by a drive source. In addition, a transport roll that freely rotates is not used between the drying process and the winding process, and usually one to several transport drive rolls (roll driven to rotate by a drive source) are installed. Need. Basically, the purpose of the transport drive roll is to transport the resin film by its drive, so the transport of the resin film and the rotation of the drive roll are synchronized by nip or suction (air suction). With the mechanism.

  The second drying step 1d includes a drying box 1d3 having a dry air intake 1d1 and a discharge port 1d2, an upper transport roll 1d4 and a lower transport roll 1d5 for transporting the web 4. The upper transport roll 1d4 and the lower transport roll 1d5 are a pair of upper and lower, and are composed of a plurality of sets. The configuration of the second drying step 1d is the same as that of the first drying step 1c.

  The second drying step 1d is longer than the first drying step 1c for final drying, and the residual solvent amount of the web 4 after the drying process is adjusted in the first drying step 1c and the second drying step 1d. Is possible.

  In addition, although this figure showed the case where it had the 1st drying process 1c and the 2nd drying process 1d, a drying process may be lengthened to one and the 1st drying process 1c and the 2nd drying process 1d A stretching process may be disposed between the two, and after peeling from the endless belt-like support, a stretching process and a drying process may be disposed. It is possible to arrange appropriately according to the use of the optical film to be finished.

  In the 1st drying process 1c and the 2nd drying process 1d, you may use heating air, infrared rays alone, or heating air and infrared drying together as a drying means. It is preferable to use heated air in terms of simplicity. This figure shows the case where heated air is used. The drying temperature varies depending on the amount of residual solvent in the web when entering the drying process, but is appropriately selected depending on the amount of residual solvent in the range of 30 ° C to 180 ° C in consideration of drying time, shrinkage unevenness, stability of the amount of expansion and contraction, etc. The temperature may be determined at a certain temperature, or may be dried at a constant temperature, or may be divided into three to four stages of temperature and may be divided into several stages of temperature.

  Each step from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. It is needless to say that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  6 shows a film thickness measuring apparatus. The film thickness measuring device 6 needs to be arranged in at least one place between the casting process 1a and the winding process 1e. For example, it is possible to arrange between the casting process 1a and the first drying process 1c, between the first drying process 1c and the second drying process 1d, and between the second drying process 1d and the winding process 1e. It is. Of course, it is also possible to arrange at two places between the first drying step 1c and the second drying step 1d and between the second drying step 1d and the winding step 1e. This figure has shown the case where it arrange | positions at one place between the 2nd drying process 1d and the winding-up process 1e. When it arrange | positions between the 2nd drying process 1d and the winding-up process 1e, the film thickness and average film thickness of the width direction of a web will be measured. When it is arranged between the casting process 1a and the first drying process 1c, the film thickness in the width direction and the average film thickness of the web 4 peeled from the endless belt-like support 1a1 are measured.

  In the winding step 1e, a winding device (not shown) is used to wind the optical film 5 produced by drying the web 4 to a required length to be wound around the winding core. 1e1 shows the roll-shaped optical film wound up by the winding core. The temperature at the time of winding is preferably cooled to room temperature in order to prevent scratches and loosening due to shrinkage after winding. The winder to be used may be a commonly used winder, and can be wound by a winding method 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.

  The thickness of the optical film 5 wound in the winding step 1e is preferably 20 μm to 100 μm in consideration of ensuring transparency as an optical film for a liquid crystal display device, handling suitability during processing of a polarizing plate, material cost, and the like. The thickness indicates a value measured with an ultra-sensitive film thickness measuring instrument manufactured by Seiko EM Co., Ltd.

  The present invention relates to a method for producing an optical film having a stable film thickness when an optical film is produced by a solution casting method in a production process as shown in the figure. More particularly, the present invention relates to a method for producing an optical film having a stable film thickness by stably landing a dope film flowing down from a die on an endless belt-like support in the casting step.

  FIG. 2 is a schematic enlarged view of a portion indicated by A in FIG. 1 when the decompression means is a decompression chamber and the pressurization means is a pressurization chamber. FIG. 2A is a schematic enlarged plan view of a portion indicated by A in FIG. 1 when the decompression means is a decompression chamber and the pressurization means is a pressurization chamber. FIG. 2B is a schematic cross-sectional view along AA ′ in FIG.

  In the figure, 1a2 indicates a die. The die 1a2 has a pocket 1a23 composed of a block 1a21 and a block 1a22, and a slit 1a24. Reference numeral 1a25 denotes a dope outlet of the slit 1a24 from which the dope 2 supplied through the supply pipe 1b2 flows out. 2a1 shows the dope film flowing out from the dope outlet 1a25.

  Reference numeral 1a31 denotes a decompression chamber as decompression means. Reference numeral 1a32 denotes a suction pipe connected to a decompression blower (not shown). By sucking the inside of the decompression chamber 1a31 through the suction pipe 1a32, the inside of the decompression chamber 1a31 is decompressed, and a static pressure is applied to the dope film 2a1.

  The inside of the decompression chamber 1a31 is divided into a plurality (not shown) and has a plurality of decompression suction ports (not shown). Further, the decompression chamber divided into a plurality has an on-off valve for decompression adjustment, and the pressure of the decompression chamber (decompression degree) and the width direction pressure (decompression degree) are adjusted according to the degree of opening and closing of the valve. Is possible.

  Reference numeral 1a41 denotes a pressurizing chamber as a pressurizing means. Reference numeral 1a42 denotes a blower pipe connected to a blower blower (not shown). By sending gas to the inside of the pressurizing chamber 1a41 through the blower pipe 1a42, the inside of the pressurizing chamber 1a41 becomes pressurized, and a static pressure is applied to the dope film 2a1 and the casting film 2a. The inside of the pressurizing chamber 1a41 is divided into a plurality (not shown) and has a plurality of air supply ports (not shown). Moreover, the pressurizing chamber divided into a plurality has an on-off valve for pressurization adjustment, and the pressure in the pressurizing chamber (pressurization degree) and the width direction pressure (pressurization degree) depending on the degree of opening and closing of the valve. It is possible to make adjustments. 1a41a shows the attachment position of the measuring machine which measures the pressure inside the pressurizing chamber 1a41. The attachment position of the measuring machine is not particularly limited, but is preferably attached to the center in the pressurizing chamber, the end portion of the casting film amount, and the middle of the five places in order to increase accuracy.

  The width distribution of the dope film 2a1 in the decompression chamber 1a31 takes into account the vibration of the dope film, the scattering of the solvent flowing down to stabilize the dope film, the suppression of the film generated at the end of the dope film, etc. The pressure in the decompression chamber is preferably ± 0.2% to ± 5.0%. The pressure distribution indicates a value obtained by the following method. Five measurement ports were equally provided in the upper part of the decompression chamber, and the measurement was performed using a Manostar gauge manufactured by Yamamoto Denki Seisakusho. The pressure in the decompression chamber indicates an average value of measurement data obtained by measuring the five locations.

  Reference numeral 1b31a indicates a mounting position of a measuring instrument for measuring the pressure inside the pressure detection chamber 1b31. The attachment position of the measuring machine is not particularly limited, but it is preferably attached to the center in the decompression chamber, the both ends of the dope film, and the middle of them in order to increase accuracy.

  The difference ΔPL between the pressure in the decompression chamber and the atmospheric pressure is the adhesion of the doped film to the metal support, the scattering of the solvent flowing down to stabilize the edge of the doped film, and the film formation at the edge of the doped film In consideration of the above, it is preferably 400 Pa to 1500 Pa. Note that the pressure in the decompression chamber indicates a value measured with a Manostar gauge manufactured by Yamamoto Electric Mfg. Co., Ltd. in the same manner as the pressure distribution.

  The temperature of the gas supplied from the blower tube 1a42 to the inside of the pressurizing chamber 1a41 is preferably 20 ° C. to 50 ° C. in consideration of condensation, a film generated at the end of the dope film, and the like.

  The gas supplied from the blower tube 1a42 to the inside of the pressurizing chamber 1a41 contains 1000 ppm to 10000 ppm of the solvent contained in the dope in consideration of the film generated at the end of the dope film, uneven drying in the thickness direction due to rapid drying, etc. It is preferable. In addition, the solvent contained in dope shows the value measured with the multi gas analyzer by Innova.

  The pressure distribution in the width direction of the dope film 2a1 or the cast film 2a of static pressure applied to the dope film 2a1 and the casting film 2a by the pressurizing chamber 1a41 flows down for vibration of the dope film and stabilization of the dope film. Taking into account the scattering of the solvent to be applied and the suppression of the film generated at the end of the dope film, the pressure is preferably ± 0.1% to ± 5.0% with respect to the pressure in the pressurizing chamber 1a41.

  The pressure distribution in the width direction of the dope film 2a1 and the casting film 2a shows a value obtained by the following method. Five measurement ports were equally provided in the upper part of the pressurizing chamber, and the measurement was performed using a Manostar gauge manufactured by Yamamoto Denki Seisakusho. The pressure in the pressurizing chamber 1a41 indicates an average value of measurement data obtained by measuring the five locations.

  The pressure fluctuation in the pressurizing chamber 1a41 is ± 0.1% to ± 5%, and the ratio to the pressure fluctuation in the decompression means 1a3 is attributed to the adhesion of the doped film to the metal support and the doped film vibration. In consideration of retardation unevenness due to stress unevenness, it is preferably 0.1 to 1.0.

  The fluctuation of the pressure in the pressurizing chamber 1a41 indicates a value obtained by the following method.

  The difference ΔPH between the pressure in the pressurization chamber and atmospheric pressure is the adhesion of the doped film to the metal support, the scattering of the solvent flowing down to stabilize the edge of the doped film, and the generation of a film at the edge of the doped film Considering suppression and the like, it is preferably 20 Pa to 1000 Pa. The pressure in the pressurizing chamber is a value measured with a Manostar gauge manufactured by Yamamoto Electric Co., Ltd.

  When the difference between the pressure in the decompression chamber 1a31 and the atmospheric pressure when casting the dope 2 on the endless belt-like support 1a1 is ΔPL, and the difference between the pressure in the pressurizing chamber 1a41 and the atmospheric pressure is ΔPH, ΔPH The absolute value of / ΔPL is 0.02 to 1.0.

  When the absolute value of ΔPH / ΔPL is less than 0.02, there is a limit to the pressure reduction effect for maintaining the adhesion of the doped film to the metal support during high-speed film formation, and the adhesion deteriorates. The amplitude width of the film increases and does not stably land on the endless belt-like support, and the stress applied to the dope film varies, resulting in uneven retardation, which is not preferable as an optical film.

  When the absolute value of ΔPH / ΔPL exceeds 1.0, the pressure in the pressurizing chamber 1a41 becomes larger than the pressure in the decompression chamber 1a31, so that drying unevenness occurs due to the blowing of pressurized air during the initial drying of the dope film. Since it becomes streaky optical unevenness, it is not preferable as an optical film.

  The difference ΔPH between the pressure in the pressurizing chamber 1a41 and the atmospheric pressure is the absolute value of the difference between the measured pressure value and the atmospheric pressure by measuring the pressure in the pressurizing chamber with a Manostar gauge manufactured by Yamamoto Electric Manufacturing Co., Ltd. Was calculated.

  The difference ΔPH between the pressure in the decompression chamber 1a31 and the atmospheric pressure is obtained by measuring the pressure in the decompression chamber with a Manostar gauge manufactured by Yamamoto Electric Mfg. Co., Ltd. and calculating the absolute value of the difference between the measured pressure value and the atmospheric pressure. I asked for it.

  The distribution of the applied pressure in the width direction of the casting film 2a in the pressurizing chamber 1a41 is the vibration of the dope film, the scattering of the solvent flowing down to stabilize the dope film, the suppression of the film generated at the end of the dope film, etc. In view of the above, it is preferable to be ± 0.1% to ± 5% with respect to the average pressure in the pressurizing chamber. The average pressurizing force of the pressurizing chamber 1a41 was measured with a manostar gauge manufactured by Yamamoto Electric Manufacturing Co., Ltd., with five measurement ports equally wide at the top of the pressurizing chamber. The pressure in the pressurizing chamber indicates an average value obtained by measuring the five locations.

  P represents the distance between the surface of the endless belt-like support 1a1 and the dope outlet 1a25 of the die 1a2. The fluctuation range of the distance P is preferably 100 μm or less in consideration of variations in film thickness due to expansion / contraction of the dope film, vibrations, and the like. The distance P was measured with a laser displacement meter manufactured by Keyence Corporation.

  FIG. 3 is a schematic enlarged view of a portion indicated by A in FIG. 1 when the decompression means is a decompression chamber and the pressurization means is a gas spraying device. FIG. 3A is a schematic enlarged plan view of the portion indicated by A in FIG. 1 when the decompression means is a decompression chamber and the pressurization means is a gas blowing device. FIG. 3B is a schematic cross-sectional view taken along the line BB ′ of FIG.

  In the figure, 1a'4 indicates a pressurizing means. 1a'41 shows the gas spraying device as a pressurizing means. The gas blowing device 1a'41 has a box structure having a gas supply pipe 1a'42 connected to a blower blower (not shown) and a slit-like gas outlet 1a'43. The gas blowing device 1a'41 applies dynamic pressure to the dope film 2a1 by blowing the gas supplied from the gas supply pipe 1a'42 to the dope film 2a1 from the gas blowing port 1a'43.

  The interior of the gas blowing device 1a'41 is divided into a plurality of parts to form a gas blowing chamber (not shown), (not shown), and has a plurality of gas blowing ports (not shown). In addition, the gas blowing chamber divided into a plurality has an on-off valve for pressurization adjustment, and it becomes possible to adjust the gas wind speed and the width of the gas in the width direction depending on the degree of opening and closing of the valve. Yes.

  The wind speed of the gas exiting from the gas outlet 1a'43 of the gas blowing device 1a'41 is the vibration of the dope film, the scattering of the solvent flowing down for the stabilization of the dope film, and the suppression of the film generated at the end of the dope film. In view of the above, it is preferably 5 m / s to 20 m / s. In addition, a wind speed shows the value measured with Nippon Kanomax Kurimo Master anemometer.

  The temperature of the gas supplied from the gas supply pipe 1a'42 to the gas blowing device 1a'41 is the same as that of the pressurizing chamber 1a41 shown in FIG.

  The gas supplied from the gas supply pipe 1a'42 to the gas blowing device 1a'41 is the same as the pressurizing chamber 1a41 shown in FIG.

  The pressure distribution in the width direction of the dope film 2a1 of the dynamic pressure applied to the dope film 2a1 by the gas blowing device 1a'41 is the vibration of the dope film, the scattering of the solvent flowing down for the dope film stabilization, the dope Considering suppression of the film generated at the end of the film, etc., it is preferably ± 0.1% to ± 5.0% with respect to the pressure of the gas outlet 1a′43.

  The pressure distribution in the width direction of the dope film 2a1 is a value obtained by the following method. The pressure of the wind blown out from the slit under a preset wind speed condition was measured by Nippon Kanomax Kurimo Master anemometer.

  The pressure of the gas outlet 1a'43 is the average value of the measurement data measured by the Kokumo Kanomax Corp. Kurimo Master anemometer at five locations in the width direction of the pressure of the wind blown out from the slit under the preset wind speed conditions. Show.

  The variation of the pressure (wind pressure) of the gas outlet 1a'43 is 0.1% to 1.0%, and the ratio to the variation of the pressure of the decompression means 1a3 is the adhesion of the dope film to the metal support, Considering retardation unevenness due to stress unevenness caused by the vibration of the doped film, it is preferably 0.1 to 1.0.

  The fluctuation of the pressure (wind pressure) at the gas outlet 1a'43 is a value obtained by the following method. The pressure of the wind blown out from the slit under a preset wind speed condition was measured by Nippon Kanomax Kurimo Master anemometer.

  The difference ΔPH between the pressure (wind pressure) of the gas outlet 1a'43 and the atmospheric pressure is the adhesion of the dope film to the metal support, the scattering of the solvent flowing down for stabilizing the end of the dope film, the dope In consideration of the suppression of the film formation at the end of the film, it is preferably 20 Pa to 1000 Pa. Note that the pressure (wind pressure) at the gas outlet 1a'43 was measured with a Nippon Canomax Kurimo Master anemometer.

  The difference between the reduced pressure in the decompression chamber 1a31 and the atmospheric pressure when casting the dope 2 on the endless belt-like support 1a1 is ΔPL, and the difference between the pressure (wind pressure) of the gas outlet 1a'43 and the atmospheric pressure is ΔPH. , The absolute value of ΔPH / ΔPL is the same as the absolute value of ΔPH / ΔPL shown in FIG.

  Other symbols are the same as those in FIG.

  FIG. 4 is a schematic enlarged view of a portion indicated by A in FIG. 1 when the decompression means is a suction device and the pressurization means is a pressurization chamber. FIG. 4A shows a schematic enlarged plan view of a portion indicated by A in FIG. 1 when the decompression means is a suction device and the pressurization means is a pressurization chamber. FIG. 4B is a schematic cross-sectional view along CC ′ of FIG.

  In the figure, reference numeral 1a'3 denotes a pressure reducing means. Reference numeral 1a'31 denotes a suction device as decompression means. The suction device 1a'31 has a box structure having a suction pipe 1a'32 connected to a decompression blower (not shown) and a slit-like gas suction port 1a'33. The suction device 1a'31 applies dynamic pressure by applying a negative wind speed to the dope film 2a1 by sucking the gas in the vicinity of the dope film 2a1 from the gas suction port 1a'33. The inside of the suction device 1a'31 is divided into a plurality of parts to form a gas suction chamber (not shown), and has a plurality of gas suction ports (not shown). Moreover, the gas suction chamber divided into a plurality has an opening / closing valve for suction adjustment, and it is possible to adjust the suction pressure degree of the gas suction chamber and the suction pressure in the width direction by the opening / closing degree of the valve. It has become.

  The wind speed (suction pressure) of the gas sucked from the gas suction port 1a'33 of the suction device 1a'31 is the vibration of the dope film, the scattering of the solvent flowing down to stabilize the dope film, and the end of the dope film. Considering suppression of the generated film, etc., it is preferably 5 m / s to 40 m / s (20 Pa to 1000 Pa). In addition, the wind speed (suction pressure) of gas shows the value which measured the differential pressure | voltage in the measurement port installed in the suction port with the Manostar gauge by Yamamoto Electric Mfg. Co., Ltd.

  The dynamic pressure applied to the dope film 2a1 by the suction device 1a'31 in the width direction of the dope film 2a1 is the vibration of the dope film, the scattering of the solvent flowing down to stabilize the dope film, the dope film Considering suppression of the film generated at the end, etc., it is preferably ± 0.2% to ± 5% with respect to the average suction pressure of the gas suction port 1a′33.

  The pressure distribution of the dope film 2a1 was measured by providing measurement ports at five positions of the width of the suction port of the suction device and connecting a manostar gauge manufactured by Yamamoto Electric Manufacturing Co., Ltd. there.

  The suction pressure of the gas suction port 1a'33 shows the average value of the measurement data measured at the above five locations.

  The variation of the suction pressure of the gas suction port 1a'33 is ± 0.2% to ± 5.0%, and the ratio with the variation of the pressure of the decompression means 1a4 is the adhesion of the dope film to the metal support, Considering retardation unevenness due to stress unevenness caused by the vibration of the doped film, it is preferably 0.1 to 1.0. The fluctuation of the suction pressure of the gas suction port 1a'33 is measured by measuring the measurement data measured by providing a measurement port at five positions of the suction port of the suction device and connecting a manostar gauge manufactured by Yamamoto Electric Manufacturing Co., Ltd. Average values are shown.

  The difference ΔPL between the suction pressure of the gas suction port 1a'33 and the atmospheric pressure is the adhesion of the dope film to the metal support, the scattering of the solvent flowing down to stabilize the end of the dope film, the end of the dope film It is preferable that the pressure is 400 Pa to 1500 Pa in consideration of the suppression of film formation at the part.

  When the dope 2 is cast on the endless belt-like support 1a1, the difference between the suction pressure of the suction device 1a'31 and the atmospheric pressure is ΔPL, and the difference between the pressure of the pressurizing chamber 1a41 and the atmospheric pressure is ΔPH. At this time, the absolute value of ΔPH / ΔPL is the same as the absolute value of ΔPH / ΔPL shown in FIG.

  Other symbols are the same as those in FIG.

  FIG. 5 shows a schematic enlarged view of the portion indicated by A in FIG. 1 when the decompression means is a suction device and the pressurization means is a gas spraying device. FIG. 5A is a schematic enlarged plan view of a portion indicated by A in FIG. 1 when the decompression means is a suction device and the pressurization means is a gas spraying device. FIG. 5B is a schematic cross-sectional view taken along the line DD ′ in FIG. Note that the reference numerals in the figure are synonymous with those in FIGS. 2, 3, and 4.

  The velocity of the gas coming out from the gas outlet 1a'43 of the gas blowing device 1a'41, the temperature of the gas supplied from the gas supply pipe 1a'42 to the gas blowing device 1a'41, and the gas blowing device from the gas supply pipe 1a'42 The gas supplied to 1a'41 is the same as that shown in FIG.

  The dynamic pressure applied to the dope film 2a1 by the gas blowing device 1a'41 in the width direction of the dope film 2a1 and the fluctuation of the pressure (wind pressure) of the gas outlet 1a'43 are the same as those shown in FIG. It is.

  The difference ΔPH between the pressure (wind pressure) at the gas outlet 1a′43 and the atmospheric pressure is the same as that shown in FIG.

  The wind speed (suction pressure) of the gas sucked from the gas suction port 1a'33 of the suction device 1a'31 is the same as that shown in FIG.

  The pressure distribution in the width direction of the dynamic dope film 2a1 applied to the dope film 2a1 by the suction device 1a'31 is the same as that shown in FIG.

  The variation of the suction pressure of the gas suction port 1a'33 is the same as that shown in FIG.

  The difference ΔPL between the suction pressure of the gas suction port 1a′33 and the atmospheric pressure is the same as that shown in FIG.

  The difference between the suction pressure of the suction device 1a'31 and the atmospheric pressure when casting the dope 2 on the endless belt-like support 1a1 is ΔPL, and the pressure (wind pressure) of the gas outlet 1a'43 and the atmospheric pressure When the difference is ΔPH, the absolute value of ΔPH / ΔPL is the same as the absolute value of ΔPH / ΔPL shown in FIG.

As shown in FIGS. 1 to 5, a dope obtained by dissolving a raw material resin in a solvent is formed by a die having a pressure reducing means on the upstream side in the moving direction of the endless belt support and a pressure means on the downstream side of the endless belt support. When a thin film optical film is produced by a solution casting production apparatus that casts a dope film on top and forms a web, the difference between the reduced pressure by the pressure reducing means and the atmospheric pressure is ΔPL, the pressure applied by the pressing means and the atmospheric pressure When the difference of ΔPH is ΔPH, the following effects can be obtained by manufacturing an optical film with an absolute value of ΔPH / ΔPL of 0.02 to 1.0.
1. Even with a film formed at high speed, an optical film with little retardation unevenness could be obtained.
2. Even with high-speed film formation, production without bubble entrainment has become possible.
3. An optical film with a stable film thickness can be produced.

  Next, the material relating to the method for producing the optical film of the present invention will be described.

(resin)
Resin used for the manufacturing method of the optical film of this invention does not have limitation in particular, Generally use of resin used by the solution casting method is possible. As a resin material for producing an optical film, for example, good adhesiveness with a polarizer and optical transparency are preferable requirements. The visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more.

  The resin is not particularly limited as long as it is a resin that forms an optical film having the above properties. For example, cellulose esters such as cellulose diacetate resin, cellulose triacetate resin, cellulose acetate butyrate resin, and cellulose acetate propionate resin. Resin, polyester resin, polycarbonate resin, polyarylate resin, polysulfone (including polyethersulfone) resin, polyethylene terephthalate resin, polyester resin such as polyethylene naphthalate resin, polyethylene resin, polypropylene resin, cellophane, polychlorinated resin Vinylidene resin, polyvinyl alcohol resin, ethylene vinyl alcohol resin, syndiotactic polystyrene resin, polycarbonate resin, cycloolefin resin, polymethyl Pentene resins, polyether ketone resins, polyether ketone imide resin, polyamide resin, fluorine resin, nylon resin, polymethylmethacrylate resin, and acrylic resin. Among these, cellulose ester resins, cycloolefin resins, polycarbonate resins, and polysulfone (including polyethersulfone) resins are preferable. In the present invention, cellulose ester resins, cycloolefin resins, and polycarbonate resins are particularly preferable in production. From the viewpoints of cost, transparency, adhesion and the like, it is preferably used.

  The cellulose ester resin will be described below. The cellulose ester-based resin is not particularly limited, and for example, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate propionate butyrate and the like are preferably used. In the case of cellulose triacetate, cellulose triacetate having a degree of polymerization of 250 to 400 and a bound acetic acid amount of 54% to 62.5% is preferable, and in particular, the bound acetic acid amount is 58% to 62.5%. It is preferable because excellent base strength can be obtained. More preferred is cellulose triacetate having a total acyl group substitution degree of less than 2.85.

  Cellulosic ester can be used either alone or as a mixture of cellulose ester synthesized from cotton linter and cellulose ester synthesized from wood pulp.

  For a specific method for producing a cellulose ester resin, for example, the method described in JP-A-10-45804 can be referred to.

  The number average molecular weight of the cellulose ester resin used in the present invention is preferably 70,000 to 300,000 because the strength is low if it is too low, and the viscosity of the solution may be too high if it is too high. A range of 80,000 to 200,000 is preferable.

  In the cellulose ester resin used in the present invention, it is preferable to use a large amount of a cellulose ester resin synthesized from a cotton linter having good peelability from the support because of high productivity efficiency. When the ratio of the cellulose ester resin synthesized from the cotton linter is 60% by mass or more, the effect of releasability becomes remarkable. Therefore, 60% by mass or more is preferable, more preferably 85% by mass or more, and further use alone. Most preferred.

  In the cellulose ester resin used in the present invention, a cellulose ester resin having a total acyl group substitution degree of less than 2.85 is preferable because the dimensional change can be reduced, and further a cellulose ester having a total acyl group substitution degree of less than 2.75. A cellulose resin is preferable, and a cellulose ester resin of less than 2.70 is particularly preferable.

  In the present invention, from the viewpoint of mechanical strength, dimensional stability, etc., it is preferable to add a plasticizer in the production of the optical film of the present invention. The amount of the plasticizer cannot be generally specified depending on the type of plasticizer used. However, the content is preferably 3% by mass to 30% by mass and preferably 10% by mass to 30% by mass with respect to the cellulose ester resin or the cellulose ester resin obtained by acylating cellulose with an acetyl group and an acyl group having 3 to 4 carbon atoms. % By mass is more preferable, and 15% by mass to 25% by mass is particularly preferable.

(Plasticizer)
The plasticizer that can be used in the present invention is not particularly limited. For example, phosphate plasticizer, phthalate plasticizer, trimellitic ester plasticizer, pyromellitic acid plasticizer, glycolate A plasticizer, a citrate ester plasticizer, a polyester plasticizer and the like can be preferably used.

  Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Examples of phthalate esters include diethyl phthalate , Dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, etc. Examples of pyromellitic acid ester plasticizers such as melitte include tetrabutyl pyromellitate and tetraphenyl pyromellite. As the glycolic acid ester type such as triethyl tetramethylpyromelitate, for example, triacetin, tributyrin, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. For example, triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2-ethylhexyl) citrate and the like can be preferably used.

  As the polyester plasticizer, for example, a copolymer of dibasic acid and glycol such as aliphatic dibasic acid, alicyclic dibasic acid, and aromatic dibasic acid can be used. The basic acid is not particularly limited, and for example, adipic acid, sebacic acid, phthalic acid, terephthalic acid, 1,4-cyclohexyl dicarboxylic acid and the like can be used.

  Examples of the glycol include ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol and the like. I can do it. These dibasic acids and glycols may be used alone or in combination of two or more. The molecular weight of the polyester is preferably in the range of 500 to 2000 as the weight average molecular weight from the viewpoint of compatibility with the cellulose resin.

  In the cellulose ester film of the present invention, it is preferable to use an ultraviolet absorber for protecting the liquid crystal material, and the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal. From the viewpoint of better liquid crystal display properties, those that absorb as little visible light as possible with a wavelength of 400 nm or more are preferably used.

  In the present invention, in a cellulose ester film having a film thickness of 20 μm to 200 μm, by providing a transmittance at a wavelength of 370 nm of 10% or less, a preferable polarizing plate can be provided without deteriorating the durability of the polarizing plate. it can. The transmittance at a wavelength of 370 nm is more preferably 5% or less, and particularly preferably 2% or less.

(UV absorber)
As the ultraviolet absorber that can be used in the present invention, an ultraviolet absorber having two or more aromatic rings in the molecule is particularly preferably used. Examples of commonly used compounds include, but are not limited to, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Alternatively, polymeric ultraviolet absorbers described in JP-A-6-148430 and JP-A-2000-273437 can also be preferably used. These ultraviolet absorbers may be used alone or in a mixture of two or more different types.

  Examples of the ultraviolet absorber preferably used in the present invention include a benzotriazole-based ultraviolet absorber and a benzophenone-based ultraviolet absorber, and in particular, an embodiment in which a benzotriazole-based ultraviolet absorber with less unnecessary coloring is added to the cellulose ester film. Is preferred.

  For example, the ultraviolet absorber may be added to the dope after the ultraviolet absorber is dissolved in an organic solvent such as alcohol, methylene chloride, dioxolane or the like, or may be added directly to the dope composition. Further, an ultraviolet absorber that does not dissolve in an organic solvent is solid-dispersed in a solution using a dissolver or a sand mill, and then added to a dope containing an organic solvent and a cellulose ester.

  The amount of the ultraviolet absorber preferably used in the present invention is preferably from 0.1% by mass to 5% by mass, more preferably from the viewpoint of ultraviolet absorption effect and transparency, based on the cellulose ester resin. 0.5 mass% to 2.5 mass%, more preferably 0.8 mass% to 2.0 mass%.

(Matting agent)
In the method for producing an optical film of the present invention, if necessary, fine particles such as silicon oxide may be added as a matting agent. Moreover, it is preferable that the fine particles typified by silicon oxide are surface-treated with an organic substance because the haze of the produced optical film can be reduced. Examples of the organic material preferable for the surface treatment include halosilanes, alkoxysilanes, silazane, and siloxane. The larger the average particle size, the greater the mat effect, and the smaller the average particle size, the better the transparency. Therefore, the average particle size of the preferred primary particles is 5 nm to 50 nm, more preferably 7 nm to 14 nm. .

  Examples of the fine particles of silicon oxide include AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Aerosil Co., Ltd., preferably AEROSIL 200, 200V, R972, R972V. , R974, R202, R812, and the like.

(Solvent for dope solution preparation)
The solvent used to prepare the dope solution used in the present invention may be used alone or in combination of two or more. However, it is possible to use a mixture of a good solvent and a poor solvent of the cellulose ester resin for production efficiency. In view of the above, it is preferable from the viewpoint of solubility of the cellulose ester resin that the amount of good solvent is larger. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70% by mass to 98% by mass of the good solvent, and 30% by mass to 2% by mass of the poor solvent.

  With a good solvent and a poor solvent, what dissolve | melts the cellulose-ester-type resin to be used independently is a good solvent, and what makes it swell independently or does not melt | dissolve is a poor solvent. Therefore, depending on the average degree of acetylation of the cellulose ester resin, the target of good solvent and poor solvent changes, for example, when acetone is used as a solvent, it becomes a good solvent when the bound acetic acid amount of the cellulose ester resin is 55%, When the amount of bound acetic acid is 60%, it becomes a poor solvent.

  The good solvent used in the present invention is not particularly limited. For example, in the case of cellulose triacetate, organic halogen compounds such as methylene chloride and dioxolanes, and in the case of cellulose acetate propionate, methylene chloride, acetone, Examples include methyl acetate.

  Further, the poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, i-propyl alcohol, n-butanol, cyclohexane, acetone, cyclohexanone and the like are preferably used.

(Dope)
As a method for dissolving the cellulose ester-based resin when preparing the dope solution, a general method can be used, but under pressure, at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil. A method of heating and stirring while stirring is more preferable because it can prevent the generation of massive undissolved material called gel or mamako. In addition, a method in which a cellulose ester resin is mixed with a poor solvent and wetted or swollen, and then mixed with a good solvent and dissolved is also preferably used.

  The type of the pressure vessel is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition to the pressure vessel, other instruments such as a pressure gauge and a thermometer are appropriately disposed. The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of the solvent is preferably a temperature in the range where the solvent used is at or above the normal pressure and the solvent does not boil from the viewpoint of the solubility of the cellulose ester, but is necessary if the heating temperature is too high. Increased pressure increases productivity. The range of preferable heating temperature is 45 ° C to 120 ° C, more preferably 60 ° C to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted at a set temperature so that the solvent does not boil.

  In addition to cellulose ester resin and solvent, additives such as necessary plasticizer and UV absorber can be mixed with solvent in advance, dissolved or dispersed, and then added to the solvent before dissolving cellulose ester resin. You may throw into the dope after melt | dissolving ester resin.

  After dissolution, take it out from the container while cooling, or take it out from the container with a pump and cool it with a heat exchanger etc., and use it for film formation, but the cooling temperature at this time may be cooled to room temperature It is more preferable to cool to a temperature 5 to 10 ° C. lower than the boiling point and perform casting at that temperature because the dope viscosity can be reduced.

  In the present invention, it is preferable that the optical film has less foreign matter. In particular, it is preferable that there are few foreign substances recognized in the polarization crossed Nicol state. The foreign matter recognized in the polarization crossed Nicol state is a state in which two polarizing plates are placed in a direct (crossed Nicol) state, a cellulose ester film is placed between them and the light from the light source is applied from the opposite side, Say. Such foreign matters are observed as bright spots due to leakage of light from the light source from the opposite side only at the locations of the foreign matters, so that the size and number of the foreign matters can be easily identified.

As for the number of foreign matters, it is preferable that there are 200 or less foreign matters having a size of 5 to 50 μm recognized in a polarization crossed Nicol state and substantially 0 foreign matters having a size of 50 μm or more per 250 mm ² area. More preferably, the number of foreign matters of 5 to 50 μm is 100 or less, more preferably 50 or less.

  In order to obtain the above-mentioned optical film with few foreign substances, no particular method is used, but for example, it can be achieved by filtering a dope composition obtained by dissolving a cellulose ester-based resin in a solvent using the following filter medium.

  As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. For this reason, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium in the range of 0.001 mm to 0.008 mm is more preferable, and a filter medium in the range of 0.003 mm to 0.006 mm is more preferable.

  The material of the filter medium is not particularly limited, and a normal filter medium can be used. However, a plastic filter medium such as polypropylene or Teflon (registered trademark) or a metal filter medium such as stainless steel is used to remove fibers. Etc. are preferred.

  The dope solution can be filtered by a normal method, but the method of filtering while heating in a temperature range above the boiling point of the solvent at normal pressure and at which the solvent does not boil is applied before and after the filter medium. The increase in differential pressure (hereinafter sometimes referred to as filtration pressure) is small and preferable. A preferred temperature range is 45 ° C to 120 ° C, more preferably 45 ° C to 70 ° C, and still more preferably 45 ° C to 55 ° C.

The filtration pressure is preferably smaller, preferably 1.6 × 10 ⁶ Pa or less, more preferably 1.2 × 10 ⁶ Pa or less, and 1.0 × 10 ⁶ Pa or less. Further preferred. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

  The optical film manufactured by the method for manufacturing an optical film of the present invention can be used as a member of an optical element or a display device, and this member is a member used in a liquid crystal display device, for example, a polarizing plate, Examples include a polarizing plate protective film, a retardation plate, a reflective plate, a viewing angle widening film, an optical compensation film, an antiglare film, an antireflective film, and an antistatic film. Among these, it is more preferable to apply to polarizing plates, polarizing plate protective films, retardation plates, and viewing angle widening films that have strict requirements on dimensional stability.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
(Preparation of dope)
Cellulose acetate propionate 100 parts by mass (acetyl group substitution degree + propionyl group substitution degree = 2.45, number average molecular weight (Mn) = 60000, weight average molecular weight (Mw) = 18000, Mw / Mn = 3.00)
Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Methylene chloride 360 parts by weight Ethanol 60 parts by weight Tinuvin 109 (manufactured by BASF Japan) 0.5 part by weight Tinuvin 171 (manufactured by BASF Japan) 0.5 parts by mass Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by mass The material of the above-mentioned dope composition 1 was put into a sealed container, heated, stirred and completely dissolved, and filtered. The filtration was performed through a sintered metal filter (capture particle size = 10 microns) after filtration by a filter press. Silicon dioxide fine particles (Aerosil R972V) were added after being dispersed in ethanol.

(Production of optical film)
As shown in FIG. 2 to FIG. 5, in the casting process of the manufacturing process shown in FIG. 1 in which the pressure reducing means and the pressure means are arranged on the upstream side in the moving direction of the endless belt-like support body of the die, When preparing the optical film by casting the prepared dope, the pressure of the decompression means and the pressure of the pressurization means are changed as shown in Table 1, and the wet film thickness is 300 μm from the die on the endless belt-like support. After casting, the film was peeled off from the endless belt-like support, dried in a drying step, wound up, an optical film having a length of 3000 m and a film thickness of 40 μm was prepared. 101 to 129.

  The film thickness after drying indicates a value measured with an ultra-sensitive film thickness measuring instrument manufactured by Seiko EM Co., Ltd.

  The maximum fluctuation width between the die dope outlet and the endless belt-like support was 100 μm. The fluctuation range of the height was performed by controlling the belt tension after providing the back roll. The fluctuation range is a value measured by a laser displacement meter manufactured by Keyence Corporation.

Casting condition Endless belt support Material: Stainless steel (SUS316) Width: 1800mm
Rotational speed (moving speed): 100m / min
Casting width: 1600mm
Surface temperature: 20 ° C
Pressurization chamber Size of pressurization chamber: width 1900mm x length 200mm x height 200mm
Pressurization method: performed by blowing air containing 3000 ppm of methylene chloride into the pressurizing chamber. The content of methylene chloride indicates a value measured with an Innova multi-gas analyzer.

  The pressure in the pressurization chamber was measured with a manostar gauge manufactured by Yamamoto Electric Mfg. Co., Ltd., as shown in FIG. It was set as the average value of data.

  The pressure distribution in the width direction of the dope film and the casting film in the pressurizing chamber was set to ± 1% with respect to the pressure in the pressurizing chamber. For the pressure distribution in the width direction of the dope film and casting film in the pressurizing chamber, values measured with a Manostar gauge manufactured by Yamamoto Electric Co., Ltd. were used.

  The variation in pressure in the pressurizing chamber was ± 0.2%, and the ratio to the variation in pressure in the decompression chamber was 0.4.

  The pressure in the pressurizing chamber was changed by adjusting the rotational speed control constant of the blower blower.

Gas spraying device Gas temperature: 20 ° C
Gas wind speed: 15m / s
Gas blowing port of gas blowing device: width 1900mm x slit gap 5mm
Pressurization method: It was performed by blowing air containing 3000 ppm of methylene chloride onto the dope film from the gas outlet.

  The content of methylene chloride indicates a value measured with an Innova multi-gas analyzer.

Pressure of blowing air: 500Pa
The pressure of the blown air was an average value of measurement data obtained by measuring the wind pressure blown at five locations between the slit of the die of the dope film and the endless belt-like support in advance with Nippon Kanomax Kurimo Master anemometer.

  The fluctuation of the pressure applied in the width direction of the dope film of the gas spraying device was set to ± 0.5% with respect to the pressure of the blowing air. For the fluctuation of the pressure applied in the width direction of the dope film of the gas spraying device, a value measured in advance by Nippon Kanomax Kurimo Master Anemometer was used.

Decompression chamber Size of decompression chamber: width 1900mm x length 200mm x height 200mm
The pressure in the decompression chamber is an average value of measurement data obtained by measuring the center of the decompression chamber, the both ends of the dope film, and the middle of them in a manostar gauge manufactured by Yamamoto Electric Manufacturing Co., Ltd. as shown in FIG. It was.

  The pressure fluctuation in the width direction of the dope film in the decompression chamber was set to ± 0.5% with respect to the pressure in the decompression chamber. For the fluctuation of the pressure applied in the width direction of the dope film in the decompression chamber, an average value of measurement data obtained by measuring five widths in the decompression chamber with a Yamamoto Electric Manufactory Manostar gauge was used.

  The fluctuation of the decompression chamber was ± 0.5%, and the ratio to the fluctuation of the pressure in the pressurization chamber was 0.2 at maximum.

  The pressure fluctuation in the decompression chamber was adjusted by adjusting the rotation speed control constant of the decompression blower, providing a buffer space between the decompression blower and the decompression chamber, or installing a plurality of intermediate plates in the decompression chamber.

Suction device Suction port of suction device: width 1900mm x slit gap 5mm
Pressure of suction device: 500Pa
The pressure of the suction device was previously measured by Nippon Kanomax Co., Ltd. Kurimo Master anemometer, and the suction pressure was measured at five points between the slit of the die of the dope film and the endless belt-like support to obtain the average value of the measurement data.

  The pressure fluctuation in the width direction of the dope film of the suction device was set to ± 1% with respect to the pressure of the suction device. For the fluctuation of the pressure applied in the width direction of the dope film of the suction device, five widths were measured in advance with Nippon Kanomax Kurimo Master anemometer, and the average value of the measurement data was used.

ΔPH *: Indicates the absolute value of the differential pressure between the pressure in the pressurizing chamber and the atmospheric pressure.
ΔPL *: Indicates the absolute value of the differential pressure between the pressure in the decompression chamber and the atmospheric pressure.
ΔPH / ΔPL *: absolute value of the ratio of the pressure difference ΔPH between the pressure in the pressurizing chamber and the atmospheric pressure and the pressure difference ΔPL between the pressure in the decompression chamber and the atmospheric pressure. Sample No. No. 129 used air containing no solvent as the blowing gas.

Evaluation Each sample No. From Table 101 to 129, the film thickness variation and unevenness were measured by the following method, and the results of evaluation according to the evaluation rank shown below are shown in Table 2.

Measurement method of film thickness variation Cut out 0.2m from the beginning and end of winding of the prepared sample, measure 200 points at 1mm interval in TD (Transverse Direction) direction and 5 points at 300mm interval in MD (Machine Direction) direction. It was determined by calculation using the following formula.

Film thickness variation = (maximum film thickness-minimum film thickness) / average film thickness Measurement method Unevenness of the prepared sample between the polarizing plate and the polarizing plate in a crossed Nicol state until light passes through under transmitted light The shade of transmitted light was visually observed by shifting the crossed Nicols.

  In addition, the polarizing plate produced as follows was used for the polarizing plate.

(Preparation of polarizing film)
In order to produce a liquid crystal display device using the cellulose ester film produced in the above example, first, a polarizing film was produced. That is, a polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched at a temperature of 110 ° C. and a stretch ratio of 5 times. This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizing film.

(Preparation of polarizing plate)
Then, according to the following Step 1 to Step 5, the above polarizing film was coated with Konica Minolta KC4UY 40 μm cellulose triacetate film (polarizing plate protective film: T-1), and 40 μm thick cellulose acetate prepared in each Example. A polarizing plate was prepared by laminating a propionate film (retardation film: T-2).

  Step 1: The film was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain a polarizing plate protective film having a saponified side to be bonded to a polarizing film, and a retardation film. .

  Step 2: The polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was gently wiped off, and the polarizing plate protective film and retardation film treated in Step 1 were laminated and disposed on both sides of the polarizing film.

Step 4: a phase difference film laminated in step 3, a polarizing film, a back face side-polarizing plate protective film, 30 N / cm ² from the pressure 20 N / cm ^2, the conveyance speed was pasted at approximately 2m / min.

  Process 5: The sample which bonded together the polarizing film produced in process 4, the phase difference film, and the polarizing plate protective film was dried for 5 minutes in the 80 degreeC dryer, and the polarizing plate was produced.

  Samples for which unevenness could not be confirmed by polarizing plate evaluation were confirmed by panel evaluation produced as follows.

  The polarizing plate on the viewing side of the 40-inch display KLV-40J3000 made by SONY, which is a VA mode type liquid crystal display device, is peeled off from the viewing side, and the polarizing plate prepared above is aligned so that the absorption axes of the polarizing plates coincide with each other. The VA mode type liquid crystal display device was produced by pasting to a glass surface of In that case, it bonded so that retardation film T-2 might become a liquid crystal cell side.

Evaluation rank of unevenness ◎: No unevenness is recognized even in evaluation by panel. ○: Density of transmitted light is not recognized. Δ: Light intensity of transmitted light is slightly observed. X: Light intensity of transmitted light is recognized.

  When the difference between the pressure by the pressure reduction means and the atmospheric pressure is ΔPL, and the difference between the pressure by the pressure means and the atmospheric pressure is ΔPH, the absolute value of ΔPH / ΔPL is cast from 0.02 to 1.0. Sample No. For 102 to 106, 109 to 113, 116 to 120, 123 to 127, and 129, excellent results were obtained in both film thickness fluctuation and unevenness. However, sample No. In 129, a film rarely occurred at the end of the cast film.

  Sample No. produced under the condition that the absolute value of ΔPH / ΔPL is less than 0.02. Nos. 101, 108, 115, and 122 resulted in poor unevenness on the polarizing plate.

  Sample No. manufactured under conditions where the absolute value of ΔPH / ΔPL exceeds 1.0. 107, 114, 121, and 128 resulted in inferior film thickness fluctuation and unevenness in the polarizing plate. The effectiveness of the present invention was confirmed.

Example 2
(Preparation of dope)
The same dope as that prepared in Example 1 was prepared.

(Production of optical film)
As shown in FIG. 3, the casting process of the manufacturing process shown in FIG. 1 is provided with a decompression chamber as decompression means on the upstream side in the moving direction of the endless belt-shaped support of the die and a gas blowing device as pressurization means on the downstream side. In the process, when the prepared dope was cast and an optical film was produced, as shown in Table 3, the sample No. of Example 1 was changed except that the wind speed and temperature of the gas emitted from the gas spraying apparatus were changed. The film was cast on an endless belt-like support with a wet film thickness of 300 μm on the endless belt-like support under the same conditions as 104, then peeled off from the endless belt-like support, dried in a drying step, wound up, 3000 m in length, and 40 μm in thickness. An optical film of Sample No. 201 to 207. As the gas, a gas containing 2000 ppm of the solvent contained in the dope was used. The amount of the solvent contained is a value measured by the same method as in Example 1.

  The wind speed and temperature of the gas indicate values measured with a Kurimo Master anemometer manufactured by Nippon Kanomax Co., Ltd.

  ΔPH *: Indicates the absolute value of the pressure difference between the pressure applied to the dope film and the atmospheric pressure. In addition, the pressure concerning a dope film | membrane shows an average pressure, and the value measured with the Nippon Kanomax Co., Ltd. Kurimo master anemometer was used.

  ΔPL *: Indicates the absolute value of the differential pressure between the pressure in the decompression chamber and the atmospheric pressure.

  ΔPH / ΔPL *: an absolute value of a ratio of a differential pressure ΔPH between the pressure applied to the dope film and the atmospheric pressure and a differential pressure ΔPL between the pressure in the decompression chamber and the atmospheric pressure.

Evaluation Each sample No. From Table 201 to 207, the film thickness variation and unevenness were measured by the same method as in Example 1, and the results of evaluation according to the same evaluation rank as in Example 1 are shown in Table 4.

  When the difference between the pressure by the decompression chamber, which is the decompression means, and the atmospheric pressure is ΔPL, and when the difference between the pressure applied to the dope film by the wind speed of the gas blown from the gas blowing device and the atmospheric pressure is ΔPH, the absolute value of ΔPH / ΔPL is Sample Nos. Made in the range of 0.02 to 1.0, the wind speed of the gas from the gas spraying device was 5 m / s to 20 m / s, and the gas temperature was 20 ° C. to 50 ° C. Nos. 201 to 206 showed excellent results in film thickness fluctuation and unevenness. Sample No. No. 207 had good film thickness variation but unevenness was slightly inferior. The effectiveness of the present invention was confirmed.

Example 3
(Production of optical film)
As shown in Table 5, the sample No. of Example 2 was changed except that the amount of the solvent contained in the gas was changed. An optical film was prepared under the same conditions as in sample No. 202, and sample no. 301 to 306. The solvent contained in the gas was methylene chloride used for preparing the dope.

Evaluation Each sample No. From Table 301 to 306, the film thickness variation and unevenness were measured by the same method as in Example 1, and the results of evaluation according to the same evaluation rank as in Example 1 are shown in Table 5.

  When the difference between the pressure by the decompression chamber, which is the decompression means, and the atmospheric pressure is ΔPL, and when the difference between the pressure applied to the dope film by the wind speed of the gas blown from the gas blowing device and the atmospheric pressure is ΔPH, the absolute value of ΔPH / ΔPL is Sample No. produced in the range of 0.02 to 1.0 and the amount of the solvent contained in the gas discharged from the gas spraying device was 1000 to 10,000 ppm. 302 to 305 showed excellent results in film thickness fluctuation and unevenness. The effectiveness of the present invention was confirmed.

Example 4
(Preparation of dope)
The same dope as that prepared in Example 1 was prepared.

(Production of optical film)
As shown in FIG. 2, the flow of the manufacturing process shown in FIG. 1 is provided with a pressure reducing chamber as a pressure reducing means on the upstream side in the moving direction of the endless belt-like support of the die and a pressure chamber as a pressure means on the downstream side. When casting the prepared dope and producing an optical film in the rolling step, as shown in Table 6, the ratio of the pressure distribution in the width direction of the dope film and the cast film in the width direction to the pressure in the pressure chamber ( %) Was changed except that the sample No. of Example 1 was changed. The film was cast on an endless belt-like support with a wet film thickness of 300 μm on the endless belt-like support under the same conditions as 104, then peeled off from the endless belt-like support, dried in a drying step, wound up, 3000 m in length, and 40 μm in thickness. An optical film of Sample No. 401 to 406. As the gas, a gas containing 2000 ppm of the solvent contained in the dope was used. The amount of the solvent contained is a value measured by the same method as in Example 1. Moreover, the fluctuation | variation of the pressure applied to the pressure direction of the pressurization chamber, the dope film | membrane of a pressurization chamber, and the casting film shows the value measured by the same method as Example 1. FIG.

  The ratio (%) of the pressure distribution in the width direction of the dope film and the casting film to the pressure in the decompression chamber was adjusted by adjusting the valve opening degree of a plurality of decompression suction ports.

  H *: The ratio (%) of the pressure distribution in the width direction of the dope film to the pressure in the decompression chamber.

  ΔPH *: Indicates the absolute value of the differential pressure between the pressure in the pressurizing chamber and the atmospheric pressure.

  ΔPL *: Indicates the absolute value of the differential pressure between the pressure in the decompression chamber and the atmospheric pressure.

  ΔPH / ΔPL *: absolute value of the ratio of the pressure difference ΔPH between the pressure in the pressurizing chamber and the atmospheric pressure and the pressure difference ΔPL between the pressure in the decompression chamber and the atmospheric pressure.

Evaluation Each sample No. Table 7 shows the results obtained by measuring film thickness fluctuation and unevenness from 401 to 406 by the same method as in Example 1 and evaluating according to the same evaluation rank as in Example 1.

  When the difference between the pressure (decompression) by the decompression chamber, which is the decompression means, and the atmospheric pressure is ΔPL, and the difference between the pressure (pressurization) applied to the dope film due to the wind speed of the gas discharged from the gas blowing device and the atmospheric pressure is ΔPH, The absolute value of ΔPH / ΔPL is in the range of 0.02 to 1.0, and the ratio (%) of the pressure distribution in the width direction of the doped film and the cast film to the pressure in the pressurizing chamber is 0.1% to 5 Sample No. produced as 0% 401 to 405 showed excellent results for film thickness fluctuation and unevenness. The effectiveness of the present invention was confirmed. However, sample No. No. 401 required a great amount of man-hours to adjust the gap of the width divider in the decompression chamber in order to suppress pressure fluctuations, and it took two full days to produce a film.

Example 5
(Preparation of dope)
The same dope as that prepared in Example 1 was prepared.

(Production of optical film)
As shown in FIG. 2, in the casting process of the manufacturing process shown in FIG. 1, a decompression chamber as a decompression means and a pressurization chamber as a pressurization means are arranged upstream in the moving direction of the endless belt-like support of the die. When preparing the optical film by casting the prepared dope, it was carried out except that the ratio of the pressure distribution in the width direction of the dope film in the decompression chamber to the pressure in the decompression chamber was changed as shown in Table 8 Sample No. 1 of Example 1 The film was cast on an endless belt-like support with a wet film thickness of 300 μm on the endless belt-like support under the same conditions as 104, then peeled off from the endless belt-like support, dried in a drying step, wound up, 3000 m in length, and 40 μm in thickness. An optical film of Sample No. 501 to 506. In addition, the fluctuation | variation of the pressure applied to the pressure direction of the decompression chamber and the width direction of the dope film | membrane of a decompression chamber shows the value measured by the same method as Example 1. FIG.

  The ratio (%) of the pressure distribution in the width direction of the dope film to the average pressure in the decompression chamber was adjusted by adjusting the valve opening degree of a plurality of air supply ports.

  G *: The ratio (%) of the pressure distribution in the width direction of the dope film and the casting film to the pressure in the pressurizing chamber.

  ΔPH *: Indicates the absolute value of the differential pressure between the pressure in the pressurizing chamber and the atmospheric pressure.

  ΔPL *: Indicates the absolute value of the differential pressure between the pressure in the decompression chamber and the atmospheric pressure.

  ΔPH / ΔPL *: absolute value of the ratio of the pressure difference ΔPH between the pressure in the pressurizing chamber and the atmospheric pressure and the pressure difference ΔPL between the pressure in the decompression chamber and the atmospheric pressure.

Evaluation Each sample No. Table 9 shows the results from 501 to 506, in which film thickness variation and unevenness were measured by the same method as in Example 1, and evaluated according to the same evaluation rank as in Example 1.

  When the difference between the pressure by the decompression chamber, which is the decompression means, and the atmospheric pressure is ΔPL, and when the difference between the pressure applied to the dope film by the wind speed of the gas blown from the gas blowing device and the atmospheric pressure is ΔPH, the absolute value of ΔPH / ΔPL is Sample prepared in the range of 0.02 to 1.0, and the ratio (%) of the pressure distribution in the width direction of the dope film and the casting film to the pressure in the pressurizing chamber is 0.2% to 5.0% No. From 502 to 505, film thickness fluctuation and unevenness both showed excellent results. Sample No. Although 501 is excellent in both film thickness fluctuation and unevenness, it took a great deal of man-hours to adjust the gap of the width divider in the pressurizing chamber in order to suppress pressure fluctuation, and it took two days until the film could be produced. The effectiveness of the present invention was confirmed.

Example 6
(Preparation of dope)
The same dope as that prepared in Example 1 was prepared.

(Production of optical film)
As shown in FIG. 2, the flow of the manufacturing process shown in FIG. 1 is provided with a pressure reducing chamber as a pressure reducing means on the upstream side in the moving direction of the endless belt-like support of the die and a pressure chamber as a pressure means on the downstream side. When producing the optical film by casting the prepared dope in the rolling step, the ratio between the change in pressure in the pressurizing chamber of the pressurizing means and the pressure change in the decompression chamber of the depressurizing means as shown in Table 10 The sample No. of Example 1 was changed except that The film was cast on an endless belt-like support with a wet film thickness of 300 μm on the endless belt-like support under the same conditions as 104, then peeled off from the endless belt-like support, dried in a drying step, wound up, 3000 m in length, and 40 μm in thickness. An optical film of Sample No. 601 to 606. In addition, the fluctuation | variation of the pressure of a pressurization chamber was performed by controlling the rotation speed control constant of a ventilation blower. The pressure fluctuation in the decompression chamber of the decompression means was controlled by controlling the rotational speed control constant of the decompression blower.

  ΔPH *: Indicates the absolute value of the differential pressure between the pressure in the pressurizing chamber and the atmospheric pressure.

  ΔPL *: Indicates the absolute value of the differential pressure between the pressure in the decompression chamber and the atmospheric pressure.

  ΔPH / ΔPL *: absolute value of the ratio of the pressure difference ΔPH between the pressure in the pressurizing chamber and the atmospheric pressure and the pressure difference ΔPL between the pressure in the decompression chamber and the atmospheric pressure.

Evaluation Each sample No. Table 11 shows the results obtained by measuring film thickness variation and unevenness from 601 to 606 by the same method as in Example 1 and evaluating according to the same evaluation rank as in Example 1.

  When the difference between the pressure in the decompression chamber, which is the decompression means, and the atmospheric pressure is ΔPL, and when the difference between the pressure applied to the dope film due to the wind speed of the gas blown from the gas blowing device and the atmospheric pressure is ΔPH, the absolute value of ΔPH / ΔPL is The range of 0.02 to 1.0, the average gas pressure fluctuation of the pressurizing means is 0.1 to 1.0, and the ratio with the pressure fluctuation of the decompression chamber of the decompression means is 0.1. Sample No. 1 produced as 1.0 to 1.0. From 602 to 605, the film thickness variation and unevenness both showed excellent results. Sample No. 601 is excellent in both film thickness fluctuation and unevenness, but it is necessary to reduce the rotation speed of the blower in order to suppress the pressure fluctuation, and it was dealt with by replacing it with a large capacity blower. However, since this blower cannot be controlled at low pressure, it requires capital investment because it is necessary in addition to a normal blower. The effectiveness of the present invention was confirmed.

Example 7
(Preparation of dope)
The same dope as that prepared in Example 1 was prepared.

(Production of optical film)
As shown in FIG. 2, the flow of the manufacturing process shown in FIG. 1 is provided with a pressure reducing chamber as a pressure reducing means on the upstream side in the moving direction of the endless belt-like support of the die and a pressure chamber as a pressure means on the downstream side. When producing the optical film by casting the prepared dope in the rolling step, as shown in Table 12, the difference ΔPH between the pressure of the pressurizing chamber and the atmospheric pressure of the pressurizing unit, and the pressure of the decompressing chamber of the depressurizing unit Except that the difference ΔPL from the atmospheric pressure was changed, the sample No. The film was cast on an endless belt-like support with a wet film thickness of 300 μm on the endless belt-like support under the same conditions as 104, then peeled off from the endless belt-like support, dried in a drying step, wound up, 3000 m in length, and 40 μm in thickness. An optical film of Sample No. 701 to 711. The pressure in the pressurization chamber was changed by controlling the rotation speed control constant of the pressurization blower. The pressure fluctuation in the decompression chamber of the decompression means was controlled by controlling the rotational speed control constant of the decompression blower.

ΔPH *: Indicates the absolute value of the differential pressure between the pressure in the pressurizing chamber and the atmospheric pressure.
ΔPL *: Indicates the absolute value of the differential pressure between the pressure in the decompression chamber and the atmospheric pressure.
ΔPH / ΔPL *: absolute value of the ratio of the pressure difference ΔPH between the pressure in the pressurizing chamber and the atmospheric pressure and the pressure difference ΔPL between the pressure in the decompression chamber and the atmospheric pressure.

Evaluation Each sample No. From Table 701 to 711, the film thickness variation and unevenness were measured by the same method as in Example 1, and the results of evaluation according to the same evaluation rank as in Example 1 are shown in Table 13.

  The absolute value of ΔPH / ΔPL is 0.02 to 1 when the difference between the pressure in the decompression chamber as the decompression means and the atmospheric pressure is ΔPL, and the difference between the pressure in the pressurization chamber of the pressurization means and the atmospheric pressure is ΔPH. Sample No. 2 produced in the range of 200 Pa to 1500 Pa and ΔPL and ΔPH. From 702 to 706, 709, and 710, the film thickness variation and unevenness all showed excellent results. The effectiveness of the present invention was confirmed.

Example 8
(Preparation of dope)
The same dope as that prepared in Example 1 was prepared.

(Production of optical film)
As shown in FIG. 2, the flow of the manufacturing process shown in FIG. 1 is provided with a pressure reducing chamber as a pressure reducing means on the upstream side in the moving direction of the endless belt-like support of the die and a pressure chamber as a pressure means on the downstream side. When casting the prepared dope and producing an optical film in the rolling step, the sample No. of Example 1 was changed except that the moving speed of the endless belt-like support was changed as shown in Table 14. The film was cast on an endless belt-like support with a wet film thickness of 300 μm on the endless belt-like support under the same conditions as 104, then peeled off from the endless belt-like support, dried in a drying step, wound up, 3000 m in length, and 40 μm in thickness. An optical film of Sample No. 801 to 806.

Evaluation Each sample No. Table 14 shows the results from 801 to 806, in which the film thickness variation and unevenness were measured by the same method as in Example 1 and evaluated according to the same evaluation rank as in Example 1.

  The absolute value of ΔPH / ΔPL is 0.02 to 1 when the difference between the pressure in the decompression chamber as the decompression means and the atmospheric pressure is ΔPL, and the difference between the pressure in the pressurization chamber of the pressurization means and the atmospheric pressure is ΔPH. Sample No. 2 produced in a range of 50 m / min to 200 m / min. From 802 to 805, the film thickness variation and unevenness both showed excellent results. However, sample no. Although 801 is excellent in both film thickness fluctuation and unevenness, there is a concern that the production efficiency is lowered due to the slow movement speed. The effectiveness of the present invention was confirmed.

Example 9
(Preparation of dope)
The same dope as that prepared in Example 1 was prepared.

(Production of optical film)
As shown in FIG. 2, the flow of the manufacturing process shown in FIG. 1 is provided with a pressure reducing chamber as a pressure reducing means on the upstream side in the moving direction of the endless belt-like support of the die and a pressure chamber as a pressure means on the downstream side. Sample No. of Example 1 except that the distance between the endless belt-like support and the dope outlet of the die was changed as shown in Table 15 when casting the prepared dope in the rolling process to produce an optical film. . The film was cast on an endless belt-like support with a wet film thickness of 300 μm on the endless belt-like support under the same conditions as 104, then peeled off from the endless belt-like support, dried in a drying step, wound up, 3000 m in length, and 40 μm in thickness. An optical film of Sample No. 901 to 905.

Evaluation Each sample No. Table 15 shows the results from 901 to 905, in which the film thickness variation and unevenness were measured by the same method as in Example 1 and evaluated according to the same evaluation rank as in Example 1.

  The absolute value of ΔPH / ΔPL is 0.02 to 1 when the difference between the pressure in the decompression chamber as the decompression means and the atmospheric pressure is ΔPL, and the difference between the pressure in the pressurization chamber of the pressurization means and the atmospheric pressure is ΔPH. Sample No. 2 produced with a range of variation in the distance between the endless belt-like support and the dope outlet of the die being 100 μm or less. From 902 to 905, the film thickness variation and unevenness both showed excellent results. The effectiveness of the present invention was confirmed.

DESCRIPTION OF SYMBOLS 1 Manufacturing process 1a Casting process 1a1 Endless belt-like support body 1a2 Dies 1a25 Dope outflow port 1a3, 1a'3 Decompression means 1a'31 Suction device 1a'33 Gas suction port 1a31 Decompression chamber 1a4, 1a'4 Pressurization means 1a ' DESCRIPTION OF SYMBOLS 41 Gas spraying apparatus 1a'43 Gas outlet 1a41 Pressurizing chamber 1b Dope supply process 1c 1st drying process 1d 2nd drying process 1e Winding process 2 Dope 2a1 Dope film 2a Casting film

Claims (15)

A casting step of casting a dope film in which a raw material resin is dissolved in a solvent is cast on an endless belt support from a die to form a web, and after peeling the web from the endless belt support, at least a stretching step In the method for producing an optical film for producing an optical film of a thin film by a solution casting production apparatus having a drying step and a winding step,
The die has pressure reducing means on the upstream side in the moving direction of the endless belt support, and pressure means on the downstream side,
The difference between the pressure by the pressure reducing means and the atmospheric pressure is ΔPL,
When the difference between the pressure by the pressurizing means and the atmospheric pressure is ΔPH,
An absolute value of ΔPH / ΔPL is 0.02 to 1.0. The method for producing an optical film according to claim 1, wherein the pressurizing unit is a gas spraying device that applies a dynamic pressure in a width direction of the dope film. The method for producing an optical film according to claim 2, wherein the wind speed of the gas emitted from the gas spraying device is 5 m / s to 20 m / s. The method for producing an optical film according to any one of claims 1 to 3, wherein the pressurizing unit is a pressurizing chamber that applies a static pressure to the dope film by a gas. The method for producing an optical film according to claim 3 or 4, wherein the temperature of the gas is 20 ° C to 50 ° C. 6. The method for producing an optical film according to claim 3, wherein the gas contains 1000 ppm to 10,000 ppm of a solvent contained in the dope. The method for producing an optical film according to claim 1, wherein the decompression unit is a suction device that applies a dynamic pressure in a width direction of the dope film. The method for producing an optical film according to any one of claims 1 to 6, wherein the decompression means is a decompression chamber that applies a static pressure in the width direction of the dope film. The pressure distribution in the width direction of the dope film or cast film by the pressurizing unit is ± 0.1% to ± 5.0% with respect to the pressure of the pressurizing unit. The method for producing an optical film according to any one of 1 to 8. The pressure distribution in the width direction of the dope film by the decompression means is ± 0.2% to ± 5.0% with respect to the pressure of the decompression means. 2. A method for producing an optical film according to item 1. The pressure fluctuation of the pressurizing means is 0.1% to 1.0%, and the ratio to the pressure fluctuation of the pressure reducing means is 0.1 to 1.0. 11. The method for producing an optical film according to any one of 1 to 10. 12. The method for producing an optical film according to claim 1, wherein a difference ΔPH between the pressure of the pressurizing unit and the atmospheric pressure is 20 Pa to 1000 Pa. The method for producing an optical film according to any one of claims 1 to 12, wherein a difference ΔPL between the pressure of the decompression means and the atmospheric pressure is 400 Pa to 1500 Pa. The method for producing an optical film according to any one of claims 1 to 13, wherein a moving speed of the endless belt support is 50 m / min to 200 m / min. The method for producing an optical film according to any one of claims 1 to 14, wherein a fluctuation range of a distance between a surface of the endless belt support and a dope outlet of the die is 100 µm or less.