JP2012171177A - Method and device for producing optical film, optical film, polarizing plate and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measure to suppress influence of accompanied wind on a cast ribbon in place of a measure to suck and eliminate the accompanied wind by a decompression chamber in a solution casting method.SOLUTION: In the method for producing the optical film having a process of forming a cast film by casting a resin solution on a moving supporting body from a die, a moving body moved to a direction opposite from a moving direction of the supporting body is disposed on the upstream side of the moving direction of the supporting body more than the die, and the following relationship is satisfied when the narrowest gap between a surface of the moving body and a surface of the supporting body is T; 0 mm<T≤2 mm. The moving body is moved during the process.

Description

  The present invention relates to an optical film manufacturing method and manufacturing apparatus, an optical film manufactured by the manufacturing method or manufacturing apparatus, a polarizing plate having the optical film as a protective film, and a liquid crystal using the optical film or the polarizing plate. The present invention relates to a display device.

  Conventionally, a solution casting method (solution casting film forming method) is known as one of methods for producing an optical film. In the solution casting method, a raw material resin is dissolved in a solvent, and a resin solution (dope) is prepared by adding various additives such as a plasticizer, a matting agent, an ultraviolet absorber, and an antioxidant as necessary. . The prepared resin solution is discharged from a die and cast onto a support that moves (runs or rotates) such as an endless belt or a drum. After the formed cast film (web) is dried to a certain degree on the support, it is peeled off from the support, and the peeled resin film is transported by various transport means while passing through a stretching device or a drying device. This is a method for producing an optical film.

  A liquid crystal display (LCD), which is one of the applications of optical films, has low voltage and low power consumption, can be directly connected to an IC circuit, and can be thinned. Widely used as display devices for portable terminals, digital still cameras, movie cameras, and the like. A liquid crystal display device has a basic configuration in which polarizing plates are provided on both sides of a liquid crystal cell. Since the polarizing plate allows only light with a polarization plane in a certain direction to pass, it plays an important role in visualizing changes in the orientation of the liquid crystal due to the electric field in the liquid crystal display device. The performance of the liquid crystal display device depends on the performance of the polarizing plate. Is greatly affected. A polarizing plate is the structure which laminated | stacked the protective film on both surfaces of the polarizer. Optical films are widely used as protective films for the polarizing plates.

  With the improvement of the quality of liquid crystal display devices, the improvement of the quality of polarizing plates and the improvement of the quality of protective films is required. In particular, in recent years, as liquid crystal display devices have become larger and thinner, optical films have been required to be larger (wider) and thinner (thinner) while maintaining high quality. ing. Therefore, there is a demand for optical films that are widened, thinned, and have good flatness.

  In addition, an increase in the production amount of optical films per unit time is also required for high-speed production of optical films. For this reason, the moving speed of the support increases, and the wind speed of the accompanying air generated along with the movement of the support tends to increase. As a result, the accompanying ribbon collides with the casting ribbon until the dope discharged from the die contacts the support, and the casting ribbon vibrates, resulting in uneven film thickness (horizontal stage) in the longitudinal direction of the optical film. And the malfunction that the planarity of an optical film is impaired becomes easy to produce more.

  As one of the measures for suppressing the influence of the entrained wind on the casting ribbon, for example, as described in Patent Document 1, a decompression chamber is arranged on the upstream side in the moving direction of the support rather than the die, In this decompression chamber, it is known that the upstream space of the casting ribbon is decompressed to suck and remove the accompanying air.

  However, the countermeasures for sucking and removing the accompanying air in the decompression chamber have the following problems. That is, as the moving speed of the support increases as the production speed increases, the negative pressure in the decompression chamber must be increased. As the negative pressure in the decompression chamber increases, the support is An airflow is generated from the end side in the width direction toward the center side, and this airflow causes a problem of suction disparity in which the suction of the accompanying air is stronger on the center side than on the end side. In addition, there is a limit to increasing the negative pressure in the decompression chamber.

JP 2009-11816 (paragraphs 0045 and 0066)

  Accordingly, an object of the present invention is to provide a measure for suppressing the influence of the accompanying air on the casting ribbon instead of the measure for sucking and removing the accompanying air in the decompression chamber in the solution casting method.

  The method for producing an optical film of the present invention is a method for producing an optical film having a step of forming a cast film by casting a resin solution from a die on a moving support, and the support moves more than the die. A moving body that moves in the direction opposite to the moving direction of the support is provided on the upstream side of the direction, and when T is the narrowest distance between the surface of the moving body and the surface of the support, 0 mm <T ≦ The moving body is moved during the process.

  According to this configuration, accompanying wind is generated as the moving body moves. This accompanying wind (moving body accompanying wind) has an opposite flow direction between the accompanying wind (supporting body accompanying wind) generated along with the movement of the support and the opposed portion of the support and the moving body. According to the knowledge of the present inventor, the thickness of the accompanying air slightly varies depending on the material of the support or the moving body, the moving speed, etc., regardless of whether the air is accompanied by the support or the moving body. However, in general, the thickness is about 2 mm on the surface of the support or moving body. Therefore, by setting the narrowest interval T between the surface of the moving body and the surface of the support to 2 mm or less (excluding 0 mm), the air accompanying the support and the moving body at the narrowest interval portion or its peripheral portion. The accompanying wind collides head-on, and the support accompanying wind is weakened or extinguished by the moving object accompanying wind. As a result, the influence of the air accompanied by the support on the casting ribbon can be suppressed, the occurrence of the horizontal stage of the optical film can be suppressed, and the flatness of the optical film can be ensured.

  If the narrowest distance T between the surface of the moving body and the surface of the support is 0 mm, the surface of the moving body and the surface of the support come into contact with each other, and the surface of the support is damaged. Cannot be obtained satisfactorily (for example, the shape of the scratch is transferred to the film surface).

  In the manufacturing method, the moving body is preferably a roll rotatable around an axis extending in the width direction of the support. This is because a moving body that moves in the direction opposite to the moving direction of the support body can be easily realized by a simple configuration and simple operation.

  In the manufacturing method, when the moving speed of the support is V1 and the moving speed of the moving body is V2, it is preferable that 1 ≦ V2 / V1 ≦ 2.5. This is because it is possible to reliably weaken or extinguish the air accompanying the support body with the air accompanying the moving body while avoiding excessive driving of the moving body.

  In the manufacturing method, 1 mm ≦ L ≦ 50 mm, where L is the shortest distance between the resin solution discharge port of the die and the narrowest distance between the surface of the moving body and the surface of the support. It is preferable that While avoiding the excessive movement of the moving object to the casting ribbon and avoiding the influence of the moving object's wind on the casting ribbon, the supporting object's accompanying wind that has been once weakened or disappeared by the moving object's wind is restored. This is because growth can be suppressed.

  In the manufacturing method, a vacuum chamber is provided between the die and the moving body, and the shortest distance between the suction port of the vacuum chamber and the narrowest interval portion between the surface of the moving body and the surface of the support body. When M is M, it is preferable that 1 mm ≦ M ≦ 50 mm. By providing a decompression chamber between the die and the moving body, when the remaining portion of the support accompanying air that has been weakened by the moving body accompanying air but has not disappeared is generated, the remaining portion is sucked and removed by the decompressing chamber. Because it can. Then, by setting the shortest distance M within the above range, it is possible to avoid excessive approach of the moving body to the decompression chamber, and to prevent the moving body accompanying air from being sucked and eliminated in the decompression chamber. This is because it is possible to suppress the regrowth of the support accompanying wind once weakened or disappeared by the accompanying wind.

  In the said manufacturing method, it is preferable that it is t1-20 degreeC <= t2 <= t1-1 degreeC when the temperature of a support body is t1 and the temperature of a moving body is t2. By making the temperature t2 of the moving body 1 ° C. or more lower than the temperature t1 of the supporting body, the air accompanying the supporting body was cooled by the moving body or the moving body accompanying air, but was weakened by the moving body accompanying air, but did not disappear. When the balance of the support accompanying air is generated, the viscosity of the balance is lowered and the energy of the balance is reduced. For this reason, even if the remaining portion of the support accompanying wind collides with the casting ribbon, the influence of the vibration that the casting ribbon receives is reduced. In addition, when a decompression chamber is provided, when the viscosity of the remaining portion of the support accompanying air is reduced and the energy of the remaining portion of the support accompanying air is reduced, the remaining portion of the support accompanying air is sucked and eliminated in the decompression chamber. This is because the elimination efficiency of the is improved. Further, by not lowering the temperature t2 of the moving body by more than 20 ° C. than the temperature t1 of the supporting body, the supporting body is accompanied by the moving body accompanying air while the supporting body accompanying air is cooled by the moving body or the moving body accompanying air. This is because the efficiency of weakening the wind can be sufficiently maintained.

  In the said manufacturing method, it is preferable that the surface of a moving body is a rough surface (for example, there exists an unevenness | corrugation). This is because the surface area of the moving body is increased, the contact area between the surface of the moving body and the air accompanying the support is increased, and the cooling efficiency of the air accompanying the support by the moving body is improved.

  In the said manufacturing method, it is preferable that the moving speed of a support body is 30 m / min-200 m / min. This is because it can contribute to high-speed production of optical films.

  In the said manufacturing method, it is preferable that the width | variety of a cast film is 1000 mm-2500 mm. This is because it contributes to enlargement (widening) of the optical film, and can contribute to enlargement of the protective film, the polarizing plate, and thus the liquid crystal display device.

  An optical film manufacturing apparatus of the present invention is an optical film manufacturing apparatus in which a step of casting a resin solution from a die on a moving support to form a cast film is performed, and the support of the support is more than the die. A moving body that moves in the direction opposite to the moving direction of the support is provided on the upstream side of the moving direction. When T is the narrowest distance between the surface of the moving body and the surface of the support, 0 mm < T ≦ 2 mm, and the moving body is moved during the process.

  According to this configuration, as in the method for producing the optical film, the moving body accompanying wind is generated, and the supporting body accompanying wind is weakened by the moving body accompanying wind or disappears. As a result, the influence of the air accompanied by the support on the casting ribbon can be suppressed, the occurrence of the horizontal stage of the optical film can be suppressed, and the flatness of the optical film can be ensured.

  The optical film of the present invention is manufactured by the manufacturing method or the manufacturing apparatus. This optical film is produced by suppressing the influence of the support-entrained wind on the casting ribbon, suppresses the occurrence of horizontal steps, has good flatness, and has excellent optical properties. Therefore, this optical film is of high quality.

  The polarizing plate of the present invention is characterized by having the optical film on at least one surface. This polarizing plate is manufactured by suppressing the influence of the optical film used as the protective film on the casting ribbon with the support-entrained wind, suppressing the occurrence of horizontal steps and having good flatness. And excellent optical properties. Therefore, this polarizing plate is of high quality.

  The liquid crystal display device of the present invention is characterized by using the optical film or the polarizing plate. In this liquid crystal display device, the optical film used as a protective film for the polarizing plate is manufactured by suppressing the influence of the support-entrained wind on the casting ribbon. It has flatness and excellent optical properties. Therefore, this liquid crystal display device is of high quality.

  ADVANTAGE OF THE INVENTION According to this invention, in the solution casting method, the countermeasure which suppresses the influence on the casting ribbon of an accompanying wind instead of the countermeasure which sucks and excludes an accompanying wind in a pressure reduction chamber is provided. As a result, it is possible to obtain a high-quality optical film that suppresses the occurrence of horizontal steps, has good flatness, and has excellent optical characteristics, and a polarizing plate and a liquid crystal display device using the optical film.

It is a schematic block diagram of the manufacturing apparatus of the optical film which concerns on the 1st Embodiment of this invention. It is a principal part enlarged view of the manufacturing apparatus of the optical film of FIG. It is a schematic block diagram of the manufacturing apparatus of the optical film which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram of the manufacturing apparatus of the optical film which concerns on the 3rd Embodiment of this invention. It is a principal part enlarged view of the manufacturing apparatus of the optical film of FIG. It is a principal part enlarged view of the manufacturing apparatus of the optical film which concerns on the 4th Embodiment of this invention.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to these embodiment.

<Optical film manufacturing equipment>
FIG. 1 is a schematic configuration diagram of an optical film manufacturing apparatus 1 according to the first embodiment of the present invention. The optical film manufacturing apparatus 1 manufactures an optical film by a solution casting method, and includes a casting apparatus 10, a stretching apparatus 20, a drying apparatus 30, and a winding apparatus 40.

  The casting apparatus 10 includes a die 11, an endless belt 12 that is a support, and a peeling roll 13. The die 11 is a resin solution (dope) 51 prepared by dissolving a raw material resin in a solvent and adding various additives such as a plasticizer, a matting agent, an ultraviolet absorber, and an antioxidant as necessary. A cast film (web) 52 is formed by casting on the endless belt 12 to be discharged and moved (running) (casting process). The endless belt 12 is wound around a pair of rolls 12a and 12a, and travels in the direction of the arrow in the drawing to convey the formed cast film 52. The cast film 52 is dried to some extent on the endless belt 12 by, for example, blowing warm air during the conveyance. The peeling roll 13 peels the conveyed casting film 52 from the endless belt 12, and sends the peeled casting film 52 (resin film 53) to the stretching device 20.

  The stretching device 20 uses a clip tenter, a pin tenter, or the like in the longitudinal direction while transporting the peeled resin film 53 as the cast film 52 by various transport means such as a transport roll (not shown). It extends | stretches in a conveyance direction (Machine Direction: MD direction) and / or a width direction (direction (Transverse Direction: TD direction) orthogonal to a conveyance direction).

  The drying device 30 evaporates the solvent by heating the stretched resin film 53 to a predetermined temperature while transporting it.

  The winding device 40 winds the dried resin film 53 as an optical film in a roll shape.

  In this embodiment, an optical film (that is, a cellulose triacetate film or a cellulose ester film) containing a cellulose ester resin such as cellulose triacetate (hereinafter sometimes simply referred to as cellulose ester) is produced as the optical film. But not only this but the optical film containing an acrylic resin and a cellulose-ester resin may be manufactured, for example.

[dice]
The resin solution discharged from the die 11 is prepared, for example, by dissolving a cellulose ester resin such as cellulose triacetate in a solvent containing a good solvent for the cellulose ester resin using a dissolution vessel. The content of the cellulose ester resin in the resin solution is preferably 15 to 30% by mass, for example.

  For dissolution of the cellulose ester resin, a method carried out at normal pressure, a method carried out below the boiling point of the solvent, a method carried out under pressure above the boiling point of the solvent, JP-A-9-95544, JP-A-9-95557, or Various dissolution methods such as a method using a cooling dissolution method as described in Kaihei 9-95538 and a method using a high pressure as described in Japanese Patent Application Laid-Open No. 11-21379 can be used. Among these, the method of pressurizing at a temperature equal to or higher than the boiling point of the solvent is preferable.

  After the resin is dissolved in the solvent, the resin solution is filtered through a filter medium and defoamed. For the filtration, it is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  The resin solution is sent to the die 11 by a liquid feed pump such as a pressurized metering gear pump. The die 11 is preferably one whose discharge port shape is adjustable. Further, a pressure die that can easily make the film thickness of the casting film 52 uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be arranged side by side, and the resin solution may be divided and discharged.

  The discharge speed for discharging the resin solution from the die 11 is preferably, for example, about 30 m / min to 200 m / min in consideration of the balance with the transport speed of the cast film 52 by the endless belt 12 and productivity. .

[Endless belt]
The endless belt 12 is a metal belt having a mirror-finished surface. The endless belt 12 is preferably made of stainless steel, for example, from the viewpoint of peelability of the cast film 52. The width of the casting film 52 cast by the die 11 is preferably 80 to 99% of the width of the endless belt 12 from the viewpoint of effectively utilizing the width of the endless belt 12, for example, 1000 mm to 2500 mm. is there. This contributes to the widening of the optical film, and can contribute to the enlargement of the protective film, the polarizing plate, and thus the liquid crystal display device.

  In the endless belt 12, the upper traveling portion and the lower traveling portion are horizontally moved in opposite directions by the rotation of the rolls 12a and 12a, and the casting film 52 cast from the die 11 is lowered to the start end portion of the upper traveling portion. It conveys to the middle of the curved transition part from the side running part to the upper running part. The cast film 52 is dried to some extent on the endless belt 12 during the conveyance. This drying is generally performed by, for example, a method in which warm air is blown from above the endless belt 12, a method in which warm air is blown on the back surface of the endless belt 12, and a heater is disposed above the endless belt 12. Then, a method of heating, a method of heating by arranging a heater on the back surface of the endless belt 12, and the like can be selected as appropriate and combined.

  The temperature of the cast film 52 at the time of drying is preferably −5 to 70 ° C., more preferably 0 to 60 ° C. in consideration of the time required for evaporation of the solvent, the conveyance speed, productivity, and the like. If the temperature of the casting film 52 is too high, the casting film 52 tends to foam or the flatness of the casting film 52 tends to deteriorate.

  When blowing warm air, the wind pressure is preferably 50 to 5000 Pa in consideration of the uniformity of solvent evaporation and the like. The temperature of the warm air may be dried at a constant temperature, or may be blown in several steps in the running direction of the endless belt 12. The temperature of the warm air is preferably about 20 to 60 ° C., for example.

  After the casting film 52 is formed on the endless belt 12, the time until the casting film 52 is peeled from the endless belt 12 varies depending on the film thickness of the optical film to be produced and the solvent used, but the endless belt 12. Considering the peelability from the film, it is preferably in the range of 0.5 to 5 minutes.

  The transport speed of the cast film 52 by the endless belt 12 (that is, the moving speed of the endless belt 12) is preferably about 30 m / min to 200 m / min from the viewpoint of contributing to high-speed production of the optical film. Moreover, it is preferable that ratio (draft ratio) of the conveyance speed of the cast film 52 by the endless belt 12 to the discharge speed of the resin solution from the die 11 is about 0.8 to 2.0. When the draft ratio is within this range, the casting film 52 can be stably formed. On the other hand, if the draft ratio is too large, a phenomenon called neck-in in which the casting film 52 contracts in the width direction tends to occur, which makes it difficult to manufacture a wide optical film.

[Peeling roll]
The peeling roll 13 is in contact with the surface of the endless belt 12 in a pressurized state, and peels the dried casting film 52 from the endless belt 12. The peeling tension at the time of peeling is preferably in the range of 50 to 400 N / m. Moreover, the residual solvent amount of the casting film 52 at the time of peeling is 30 to 200% by mass in consideration of peelability from the endless belt 12, transportability after peeling, physical properties of the optical film to be manufactured, and the like. It is preferable.

Here, the amount of residual solvent is defined by the following equation.
Residual solvent amount (%) = {(mass before heat treatment of cast film−mass after heat treatment of cast film) / mass after heat treatment of cast film} × 100
Note that the heat treatment for measuring the residual solvent amount is a heat treatment at 115 ° C. for 1 hour.

[Stretching device]
The stretching device 20 grips both ends in the width direction of the resin film 53 which is the cast film 52 peeled from the endless belt 12 with a clip tenter, a pin tenter, etc., and holds the resin film 53 in the longitudinal direction (MD direction) and / or Or it extends in the width direction (TD direction).

  Here, the stretching ratio in the TD direction of the resin film 53 is preferably about 0 to 50%. In general, when the stretching ratio is increased, the optical value of the optical film tends to be nonuniform. However, if the stretching ratio in the TD direction of the resin film 53 is 0 to 50%, it is possible to suppress the optical value of the optical film from becoming uneven. Therefore, an optical film having a uniform optical value and a wide width can be obtained. Moreover, when the width | variety of an optical film is wide, it is preferable also from the point of use to a large sized liquid crystal display device, the use efficiency of the film at the time of polarizing plate processing, and production efficiency.

Here, the stretching ratio in the TD direction is defined by the following equation.
Stretch ratio (%) in the TD direction = {(length in the width direction after stretching at a predetermined position of the film−length in the width direction before stretching at a predetermined position of the film) / before stretching at a predetermined position of the film Length in the width direction} × 100
The length in the width direction of the film is a value measured with a C-type JIS grade 1 steel scale.

Moreover, the draw ratio in the MD direction is defined by the following equation.
Stretching rate in MD direction (%) = {(Conveying speed of film after stretching−Conveying speed of film before stretching) / Conveying speed of film before stretching} × 100

[Drying equipment]
The drying device 30 includes a plurality of transport rolls, and dries the resin film 53 while passing the resin film 53 in a meandering manner between the rolls. In that case, you may dry using heating air, infrared rays, etc. independently, and you may dry using heating air and infrared rays together. It is preferable to use heated air from the viewpoint of simplicity. The drying temperature varies depending on the amount of residual solvent in the resin film 53, but is appropriately selected depending on the amount of residual solvent in the range of 30 to 180 ° C in consideration of drying time, shrinkage unevenness, stability of expansion and contraction, and the like. You can decide. Moreover, you may dry at a fixed temperature, for example, may divide into the temperature of 2-4 steps, and may divide into the temperature of several steps, and may dry.

[Winding device]
The winding device 40 winds the resin film 53 that has been stretched by the stretching device 20 and dried by the drying device 30 to a required length to be wound around the winding core. The temperature at the time of winding is preferably cooled to room temperature (for example, 20 ° C.) in order to prevent scratches or loosening due to shrinkage after winding. The equipment used for winding can be used without any particular limitation and may be generally used. Winding methods such as constant tension method, constant torque method, taper tension method, program tension control method with constant internal stress, etc. Can be rolled up.

  The width of the optical film to be wound here is preferably 1000 mm to 2500 mm, for example. Such a wide optical film is preferable from the viewpoints of use in a large liquid crystal display device, use efficiency of the film during polarizing plate processing, and production efficiency. In addition, the film thickness of the optical film is preferably 15 μm to 60 μm, for example, from the viewpoint of contributing to thinning (thinning) of the polarizing plate and the liquid crystal display device and stabilizing production of the film. Here, the film thickness is an average film thickness. For example, an optical film using a film thickness measuring instrument DH-150 manufactured by Tokyo Seimitsu Co., Ltd., a contact film thickness meter manufactured by Mitutoyo Co., Ltd., or the like. The film thickness is measured at 20 to 200 locations in the longitudinal direction and the width direction, and the average value of the measured values is shown as the film thickness.

  Moreover, the film thickness deviation in the width direction and the longitudinal direction of the optical film is 0.2 μm to 1.m from the viewpoint that the good flatness of the optical film is reliably maintained and the optical properties of the optical film are further improved. It is preferably 5 μm.

<Features of this embodiment>
FIG. 2 is an enlarged view of a main part of the optical film manufacturing apparatus 1 shown in FIG. FIG. 2 is an enlarged view of the vicinity of the start end portion of the upper traveling portion from the upper portion of the curved transition portion from the lower traveling portion to the upper traveling portion of the endless belt 12.

  In the figure, reference numeral 11a denotes a resin solution discharge port of the die 11, reference numeral 14 denotes a decompression chamber, reference numeral 14a denotes a suction port of the decompression chamber 14, reference numeral 15 denotes a rotating roll as a moving body, reference numeral X denotes a support accompanying wind, reference numeral Y Indicates a wind accompanied by a moving object. Also, in the figure, symbol A is the axis of the roll 12a of the endless belt 12, symbol B is the axis of the rotating roller 15, and symbol C is the position of the surface of the rotating roller 15 on the line connecting the axis A and the axis B. , D is the position of the surface of the endless belt 12 on the line connecting the shaft core A and the shaft core B, and E is the upstream side of the suction port 14a of the shaft core A and the decompression chamber 14 ("upstream" in this embodiment). Refers to the direction of movement of the endless belt 12 (see arrow V1 in FIG. 2; the same applies hereinafter). The position when the position C is shifted around the axis A on the line connecting the ends, F being the axis A position R when the position C is shifted around the axis A on the line connecting A and the upstream end of the discharge port 11a of the die 11 is a casting ribbon (discharged from the discharge port 11a of the die 11). Until the resin solution 51 is grounded on the endless belt 12. It shows the parts).

  As shown in FIG. 2, a decompression chamber 14 is provided upstream of the die 11 in the moving direction of the endless belt 12. A rotary roll 15 is provided further upstream than the decompression chamber 14. The rotating roll 15 is a roll that is rotatable around an axis B extending in the width direction of the endless belt 12. The rotary roll 15 is made of metal, for example, and is preferably made of stainless steel.

  The suction port 14 a of the decompression chamber 14 has the same length as or longer than the discharge port 11 a of the die 11 in the width direction of the endless belt 12. The rotary roll 15 has the same length as or longer than the suction port 14a of the decompression chamber 14 in the width direction of the endless belt 12.

  In the present embodiment, the die 11 is disposed above the starting end portion of the upper traveling portion of the endless belt 12. Therefore, the decompression chamber 14 and the rotating roll 15 are disposed around the upper portion of the curved transition portion from the lower traveling portion to the upper traveling portion of the endless belt 12. The suction port 14a of the decompression chamber 14 has an arcuate side shape along the curved transition portion of the endless belt 12.

  The rotating roll 15 moves (rotates) in the direction (see arrow V2) opposite to the moving direction of the endless belt 12 (see arrow V1). More specifically, the moving direction of the endless belt 12 at the position D and the moving direction of the rotary roll 15 at the position C are opposite to each other. Here, the interval between the position D and the position C is the narrowest interval T between the surface of the endless belt 12 and the surface of the rotary roll 15. Further, the portion between the position D and the position C is the narrowest interval portion between the surface of the endless belt 12 and the surface of the rotary roll 15.

  The support accompanying wind X generated along with the movement (running) of the endless belt 12 is generated on the surface of the endless belt 12. The direction of the support accompanying wind X is the same as the moving direction of the endless belt 12 (see arrow V1). The thickness of the support accompanying air X is about 2 mm. A moving body-accompanied wind Y generated with the movement (rotation) of the rotating roll 15 is generated on the surface of the rotating roll 15. The direction of the moving body accompanying wind Y is the same as the moving direction of the rotary roll 15 (see arrow V2). The thickness of the moving body accompanying wind Y is about 2 mm. The rotating roll 15 is arranged so that the narrowest interval T is 0 mm <T ≦ 2 mm. The rotating roll 15 is rotated during a period in which a step (i.e., a casting step) of forming the casting film 52 by casting the resin solution 51 from the die 11 on the moving endless belt 12 is performed. As a result, the support accompanying wind X and the moving body accompanying wind Y collide head-on at the narrowest interval part or its peripheral part, and the supporting body accompanying wind X is weakened by the moving object accompanying wind Y or disappears. As a result, the influence of the support-entrained wind X on the casting ribbon R can be suppressed, the occurrence of horizontal steps in the optical film can be suppressed, and the flatness of the optical film can be ensured.

  By making the narrowest interval T not 0 mm, it is possible to avoid contact between the surface of the endless belt 12 and the surface of the rotary roll 15, avoid damage to the surface of the endless belt 12, and obtain an optical film satisfactorily. (For example, the problem that the shape of the scratch is transferred to the film surface can be avoided).

  By using a roll 15 that is rotatable around an axis B extending in the width direction of the endless belt 12 as the moving body, the direction opposite to the moving direction of the endless belt 12 can be achieved with a simple configuration and a simple operation (rotation operation). A moving body that moves to the position is easily realized.

  The diameter of the rotary roll 15 is not specifically limited, For example, it is several mm-several cm. The smaller the diameter of the rotary roll 15, the better the layout and the greater the freedom of arrangement. However, the smaller the diameter of the rotating roll 15, the higher the number of rotations for achieving the target moving speed, and the deterioration of the rotating roll 15 is accelerated.

  In the present embodiment, the ratio (speed ratio) of the moving speed V2 of the rotary roll 15 to the moving speed V1 of the endless belt 12 is 1 ≦ V2 / V1 ≦ 2.5. Thereby, it is possible to reliably weaken or extinguish the support accompanying wind X with the moving body accompanying wind Y while avoiding excessive driving (for example, high rotation) of the rotating roll 15. Here, the moving speed V2 of the rotating roll 15 is more specifically the moving speed in the circumferential direction of the surface (circumferential surface) of the rotating roll 15.

  In the present embodiment, when the decompression chamber 14 is provided between the die 11 and the rotary roll 15, when the remaining portion of the support-entrained wind X that has been weakened by the moving-body accompanying wind Y but has not disappeared occurs. The remainder can be sucked out by the vacuum chamber 14 and removed.

  In the present embodiment, the suction port 14a of the decompression chamber 14 and the narrowest interval portion (the narrowest interval portion between the surface of the endless belt 12 and the surface of the rotary roll 15: the portion between the position D and the position C. 1 mm ≦ M ≦ 50 mm, where M is the shortest distance between them. In FIG. 2, the distance between the position E and the position C (the distance on the arc connecting the position E and the position C) is the shortest distance (chamber / roll distance) M. Thereby, excessive approach of the rotary roll 15 to the decompression chamber 14 is avoided, and the moving body-entrained wind Y is temporarily weakened by the moving body-entrained wind Y while avoiding being sucked and eliminated by the decompression chamber 14. Alternatively, it is possible to suppress the regrowth of the extinguished support wind X.

  The decompression chamber 14 may not be provided between the die 11 and the rotating roll 15. In that case, the resin solution discharge port 11a of the die 11 and the narrowest interval portion (the narrowest interval portion between the surface of the endless belt 12 and the surface of the rotary roll 15: the portion between the position D and the position C). 1 mm ≦ L ≦ 50 mm, where L is the shortest distance between the two. In FIG. 2, the distance between the position F and the position C (the distance on the arc connecting the position F and the position C) is the shortest distance (die / roll distance) L. This avoids excessive approach of the rotary roll 15 to the casting ribbon R and avoids the influence of the moving body-entrained wind Y on the casting ribbon R, while being weakened by the moving body-entrained wind Y, or It is possible to suppress the regrowth of the wind X accompanying the extinguished support.

  In the present embodiment, when the temperature of the endless belt 12 is t1 and the temperature of the rotary roll 15 is t2, t1-20 ° C. ≦ t2 ≦ t1-1 ° C. By making the temperature t2 of the rotating roll 15 lower by 1 ° C. or more than the temperature t1 of the endless belt 12, the support accompanying wind X is cooled by the rotating roll 15 or the moving object accompanying wind Y and is weakened by the moving object accompanying wind Y. However, when the remainder of the support-entrained wind X that has not disappeared occurs, the viscosity of the remainder is lowered, and the energy of the remainder is reduced. For this reason, even if the remaining portion of the support-entrained wind X collides with the casting ribbon R, the influence of vibration on the casting ribbon R is reduced. When the decompression chamber 14 is provided, the viscosity of the remaining portion of the support accompanying air X is lowered, and the energy of the remaining portion of the support accompanying air X is reduced. The removal efficiency when sucking and removing is improved. Further, the temperature t2 of the rotating roll 15 is not lowered below the temperature t1 of the endless belt 12 by more than 20 ° C., so that the support accompanying wind X is cooled by the rotating roll 15 or the moving body accompanying wind Y, and the moving body is accompanied. The efficiency of weakening the support-bearing wind X by the wind Y can be sufficiently maintained.

  In the present embodiment, the surface of the rotary roll 15 is a rough surface (for example, a surface with unevenness). Thereby, the surface area of the rotating roll 15 increases, the contact area of the surface of the rotating roll 15 and the support body accompanying wind X increases, and the cooling efficiency of the support body accompanying wind X by the rotating roll 15 improves.

  In addition, the uneven | corrugated shape of the surface of the rotating roll 15 is not specifically limited. For example, a large number of fine hemispherical protrusions may be regularly or scattered on the surface of the rotary roll 15, or a large number of fine hemispherical depressions may be regularly formed on the surface of the rotary roll 15. Or may be recessed in a scattered manner. Alternatively, a large number of fine ridges may be projected at random on the surface of the rotating roll 15 with an at random trajectory, or a large number of fine grooves may be formed on the surface of the rotating roll 15 with an at random trajectory. It may be recessed at random.

<Method for producing optical film>
By using the optical film manufacturing apparatus 1 configured as described above, an optical film 53 having a step of casting the resin solution 51 on the moving endless belt 12 to form a casting film 52 (casting step). The rotating roll 15 that moves in the direction opposite to the moving direction of the endless belt 12 is provided upstream of the die 11 in the moving direction of the endless belt 12, and the surface of the rotating roll 15 and the endless belt 12 are provided. When T is the narrowest distance between the surface of the material (the distance between the positions C and D), 0 mm <T ≦ 2 mm, and the rotating roll 15 is rotated as described above during the casting process. The manufacturing method of the optical film 53 may be implemented.

  And the optical film 53 manufactured by such a manufacturing method or the said manufacturing apparatus 1 is manufactured by suppressing the influence to the casting ribbon R of the support body accompanying wind X, and generation | occurrence | production of a horizontal stage occurs. Suppressed, has good flatness and excellent optical properties. Therefore, this optical film 53 is of high quality.

<Other embodiments>
Another embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is used for the component which is the same as that of 1st Embodiment, or is equivalent, and only a characteristic part is demonstrated.

  The optical film manufacturing apparatus 1 shown in FIGS. 1 and 2 uses an endless belt 12 as a support. Instead, as shown in FIG. 3, a drum 16 is used as a support. The optical film manufacturing apparatus 1 may be used (second embodiment). The drum 16 is moved (turned) to dry the casting film 52 formed on the peripheral surface thereof while being conveyed. The drum 16 is preferably a metal drum having a mirror-finished surface. The drum is preferably made of, for example, stainless steel from the viewpoint of peelability of the cast film 52. In the illustrated example, the decompression chamber 14 is not provided between the die 11 and the rotary roll 15, but it may be provided.

  As shown in FIGS. 4 and 5, a traveling belt 17 may be used as a moving body instead of the rotating roll 15 (third embodiment). The traveling belt 17 is composed of an endless belt wound between a pair of rolls 17a and 17a, and the lower traveling portion travels in the direction of the arrow V2 in the drawing, whereby the moving direction of the endless belt 12 (see arrow V1). ) To the opposite direction (see arrow V2) is realized. In this case, the traveling belt 17 is disposed in the vicinity of the starting end portion of the upper traveling portion of the endless belt 12. This is preferable because the upper traveling portion of the endless belt 12 and the lower traveling portion of the traveling belt 17 face each other in parallel. In the third embodiment, the symbol C is the position of the starting end of the lower traveling portion of the traveling belt 17, the symbol D is the position of the surface of the endless belt 12 immediately below the position C, and the symbol F is the discharge port 11 a of the die 11. The position when the position C is shifted horizontally is shown directly below the upstream end portion of. The interval between the position D and the position C is the narrowest interval T between the surface of the endless belt 12 and the surface of the traveling belt 17. Further, the portion between the position D and the position C is the narrowest interval portion between the surface of the endless belt 12 and the surface of the traveling belt 17. Further, the distance between the position F and the position C (the horizontal distance connecting the position F and the position C) is such that the resin solution discharge port 11a of the die 11 and the narrowest interval portion (the surface of the endless belt 12 and the running belt 17). Is the shortest distance (die / traveling belt distance) L between the narrowest distance between the surface and the surface: the portion between the position D and the position C).

  In the third embodiment, since the traveling belt 17 is used as the moving body, the distance between the surface of the endless belt 12 and the surface of the moving body is the maximum compared to the case where the rotating roll 15 is used as the moving body. The range of the narrow interval T is relatively long. As a result, the action of the support accompanying wind and the moving object accompanying wind colliding frontally and the support accompanying wind being weakened or extinguished by the moving object accompanying wind increases.

  As shown in FIG. 6, in the third embodiment, a decompression chamber 14 may be provided between the die 11 and the traveling belt 17 (fourth embodiment). In the fourth embodiment, the symbol E indicates the position when the position C is horizontally shifted directly below the upstream end of the suction port 14a of the decompression chamber 14. The distance between the position E and the position C (the horizontal distance connecting the position E and the position C) is such that the suction port 14a of the decompression chamber 14 and the narrowest interval portion (the surface of the endless belt 12 and the running belt 17). It is the shortest distance (chamber / running belt distance) M between the narrowest distance part between the surface and the part: the part between the position D and the position C).

  In addition, you may use the traveling belt 17 which is a moving body for the manufacturing apparatus of the optical film whose support body is the drum 16. FIG. In addition, in the optical film manufacturing apparatus in which the support body is the endless belt 12, the rotating roll 15 that is a moving body may be disposed in a horizontal portion near the start end portion of the upper running portion of the endless belt 12. In the above embodiment, the decompression chamber 14 is provided between the die 11 and the rotary roll 15 or the traveling belt 17. However, the present invention is not limited thereto, and the rotary roll 15 is provided between the die 11 and the decompression chamber 14. Alternatively, a traveling belt 17 may be provided.

  In the above embodiment, for example, “the narrowest interval T”, “the narrowest interval portion”, “the shortest distance L”, “the shortest distance M” and the like are merely examples, and are limited to those described in each embodiment. It is not done. For example, in FIG. 2, “shortest distance M” is “distance between position E and position C”, but it may be defined using “position D” or “axial core B”. Similarly, the “shortest distance L” is defined as “the distance between the position F and the position C”, but may be defined using the “position D” or the “axis B”. 5 and 6, the “narrowest interval T” is “the interval between the position D and the position C”. However, the upper traveling portion of the endless belt 12 and the lower traveling of the traveling belt 17 are parallel to each other. Any distance between the positions may be used as long as the distance is between the positions providing the shortest distance between the parts. Similarly, the “narrowest interval portion” is defined as “the portion between the position D and the position C”, but the shortest distance between the upper running portion of the endless belt 12 and the lower running portion of the running belt 17 that are parallel to each other. As long as it is a site | part between the positions which provide a space | interval, the site | part between any positions may be sufficient.

<Optical film>
As described above, in the present embodiment, as a representative example, an optical film including a cellulose ester resin such as cellulose triacetate is manufactured.

  As described above, for example, using a dissolution vessel, a thermoplastic resin composed of a cellulose ester resin or the like is dissolved in a mixed solvent of a good solvent and a poor solvent, and additives such as a plasticizer and an ultraviolet absorber are added thereto. To prepare a resin solution (dope).

  Next, the dope adjusted in the melting pot is fed to the casting die 11 by a conduit through, for example, a pressurized metering gear pump, and is transported infinitely, for example, on a support made of a rotationally driven stainless steel endless belt 12. The dope is cast from the casting die 11 at a position.

  When cellulose ester is used as the thermoplastic resin solution (dope), for example, the solid content concentration of the cellulose ester solution is preferably 15 to 30% by mass. If the solid content concentration of the cellulose ester solution (dope) is less than 15% by mass, sufficient drying cannot be performed on the support, and part of the dope film remains on the support during peeling, leading to belt contamination. It is not preferable. On the other hand, if the solid content concentration exceeds 30% by mass, the dope viscosity increases, and filter clogging is accelerated in the dope adjusting step, which is not preferable. Moreover, since a pressure becomes high at the time of casting on a support body and it becomes impossible to extrude, it is not preferable.

  In the method for producing an optical film by the solution casting film forming method of the present embodiment, various resins can be used as the film material, and among them, cellulose ester is preferable.

  A cellulose ester is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, cellulose acetate, cellulose acetate propionate, and cellulose acetate having an aliphatic polyester graft side chain are preferable. Other substituents may be included as long as the effects of the present invention are not impaired.

  As an example of cellulose triacetate, the substitution degree of acetyl group is preferably 2.0 or more and 3.0 or less. By setting the degree of substitution within this range, good moldability can be obtained, and desired in-plane direction retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as an optical film may be inferior, particularly the dimensional stability under wet heat, and if the substitution degree is too large, the necessary retardation characteristics may not be exhibited. There is.

  The cellulose used as a raw material for the cellulose ester used in the present embodiment is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  In the present embodiment, the number average molecular weight of the cellulose ester is preferably in the range of 20,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, 40000-200000 are preferable.

  In the present embodiment, various additives can be added to the cellulose ester.

  In the method for producing an optical film according to the present embodiment, a dope composition containing a cellulose ester and an additive for reducing the thickness direction retardation (Rt) can be used.

  In the method for producing an optical film according to the present embodiment, an organic solvent having good solubility for the cellulose derivative is referred to as a good solvent.

  Examples of good solvents include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, formic acid Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

  The dope preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent. These are gels that, after casting the dope onto the support, the solvent begins to evaporate and the proportion of alcohol increases, making the web gel, making the web strong and easy to peel off from the support It also serves as a solvating solvent or promotes dissolution of cellulose derivatives.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose derivatives and are called poor solvents.

  The most preferable solvent for dissolving a cellulose derivative, which is a preferable polymer compound satisfying such conditions, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethyl alcohol of 95: 5 to 80:20. Alternatively, a mixed solvent of methyl acetate: ethyl alcohol 60:40 to 95: 5 is also preferably used.

  The film in the present embodiment includes a plasticizer that imparts processability, flexibility, and moisture resistance to the film, fine particles (matting agent) that impart slipperiness to the film, an ultraviolet absorber that imparts an ultraviolet absorbing function, and deterioration of the film. You may contain the antioxidant etc. which prevent this.

  The plasticizer used in the present embodiment is not particularly limited, but is a cellulose derivative or a reactive metal compound capable of hydrolysis polycondensation so as not to generate haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting with the polycondensate by hydrogen bonding or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

  Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol ester plasticizers, glycolate plasticizers. Agents, citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, etc. can be preferably used, but polyhydric alcohol ester plasticizers, glycolate plasticizers are particularly preferred. And non-phosphate ester plasticizers such as polycarboxylic acid ester plasticizers.

  The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in this embodiment is represented by the following general formula (3).

Formula (3): R1- (OH) n
In the formula, R1 represents an n-valent organic group, and n represents a positive integer of 2 or more.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Examples of preferred polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, gallium Examples include lactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this embodiment, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose derivative is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Examples of preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, Tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, laccellic acid, etc., undecylen Examples thereof include unsaturated fatty acids such as acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Examples thereof include aromatic monocarboxylic acids and derivatives thereof, and benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose derivatives.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The glycolate plasticizer is not particularly limited, but a glycolate plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. As preferred glycolate plasticizers, for example, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be used.

  For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate and the like can be used, but in this embodiment, it is preferable that the phosphate ester plasticizer is not substantially contained.

  Here, “substantially does not contain” means that the content of the phosphoric ester plasticizer is less than 1% by mass, preferably 0.1% by mass, and particularly preferably not added.

  These plasticizers can be used alone or in combination of two or more.

  As for the usage-amount of a plasticizer, 1-20 mass% is preferable. 6-16 mass% is further more preferable, Most preferably, it is 8-13 mass%. If the amount of the plasticizer used is less than 1% by mass relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, so this is not preferred. If it exceeds 20% by mass, the plasticizer bleeds out from the film, and the film Since the physical properties of the material deteriorate, it is not preferable.

  In order to impart slipperiness to the cellulose derivative in the present embodiment, it is preferable to add fine particles such as a matting agent. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound.

  Examples of the fine particles of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide and the like. Of these, fine particles of a compound containing a silicon atom are preferred, and fine silicon dioxide particles are particularly preferred. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, 972, 972V, 974, 202, 812, 805, OX50, and TT600 manufactured by Nippon Aerosil Co., Ltd.

  Examples of the organic compound fine particles include fine particles such as acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  The primary particle size of the fine particles is not particularly limited, but the average particle size in the film is preferably about 0.05 to 5.0 μm. More preferably, it is 0.1-1.0 micrometer.

  When the cellulose ester film is observed with an electron microscope or an optical microscope, the average particle diameter of the fine particles indicates an average value of the lengths in the major axis direction of the particles at the observation position of the film. As long as the particles are observed in the film, they may be primary particles or secondary particles in which the primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

As an example of the measurement method, 10 vertical cross-sectional photographs are taken at random for each film, and the number of particles in 100 μm ² whose major axis length is in the range of 0.05 to 5 μm for each cross-sectional photograph. Count. The average value of the major axis lengths of the particles counted at this time is obtained, and a value obtained by averaging the average values of 10 locations is defined as the average particle size.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size added to the film often change, and what is important is that the fine particles are finally combined with the cellulose ester in the film to aggregate. And controlling the particle size formed.

  Here, if the average particle size of the fine particles exceeds 5 μm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. Moreover, when the average particle diameter of fine particles is less than 0.05 μm, it becomes difficult to impart slipperiness to the film.

  The fine particles are used by adding 0.04 to 0.8 mass% with respect to the cellulose ester. Preferably, 0.05 to 0.5 mass%, more preferably 0.05 to 0.35 mass% is added and used. When the amount of fine particles added is less than 0.04% by mass, the film surface roughness becomes too smooth, and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.8% by mass, the coefficient of friction on the film surface will be too low and winding deviation will occur during winding, or the transparency of the film will be low and haze will be high. The above range is essential because it has no value as a film.

  For the dispersion of the fine particles, it is preferable to treat the composition in which the fine particles and the solvent are mixed with a high-pressure dispersion apparatus. A high-pressure dispersion device is a device that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, the maximum pressure condition inside the apparatus is 1960 N / cm ² or more. Further, at that time, those having a maximum reaching speed of 100 m / sec or more and those having a heat transfer speed of 100 kcal / hr or more are preferable.

  Examples of the high-pressure dispersion device as described above include an ultra-high pressure homogenizer (trade name, Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and other examples include a Manton Gorin type high-pressure dispersion device such as Izumi Food Machinery. Examples thereof include a homogenizer.

  In the present embodiment, the fine particles are dispersed in a solvent containing 25 to 100% by mass of a lower alcohol, and then mixed with a dope in which a cellulose ester (cellulose derivative) is dissolved in a solvent, and the mixed solution is placed on a support. A cellulose ester film is obtained which is cast and dried to form a film.

  Here, as a content rate of a lower alcohol, Preferably it is 25-100 mass%, More preferably, it is 50-100 mass%.

  Examples of lower alcohols preferably include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by mass. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by mass, and more preferably 10 to 20% by mass.

  The ultraviolet absorbing function of the film is preferably imparted to various optical films such as a polarizing plate protective film, a retardation film, and an optical compensation film from the viewpoint of preventing deterioration of the liquid crystal. For such an ultraviolet absorbing function, a material that absorbs ultraviolet rays may be included in the cellulose derivative, and a layer having an ultraviolet absorbing function may be provided on a film made of the cellulose derivative.

  In this embodiment, examples of the ultraviolet absorber that can be used include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. However, a benzotriazole-based compound with little coloring is preferable. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used.

  As the ultraviolet absorber, those having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal and those having little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. preferable.

  In this embodiment, specific examples of useful UV absorbers include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert). -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butyl Phenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2 -Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, 2- (2'-hydro Cis-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate.

  Moreover, as a commercial item of an ultraviolet absorber, Tinuvin 109, Tinuvin 171 and Tinuvin 326 (all of which can be obtained commercially from BASF Japan) can be preferably used.

  Further, specific examples of the benzophenone-based compound that is an ultraviolet absorber that can be used in the present embodiment include 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, and 2-hydroxy-4-methoxy-5. -Sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane) and the like can be mentioned, but are not limited thereto.

  In the present embodiment, the blending amount of these ultraviolet absorbers is preferably in the range of 0.01 to 10% by mass, more preferably 0.1 to 5% by mass with respect to the cellulose ester (cellulose derivative). If the amount of the UV absorber used is too small, the UV absorbing effect may be insufficient, and if the amount of the UV absorber used is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

  Further, as the ultraviolet absorber that can be used in the optical film of the present embodiment, the polymer ultraviolet absorber (or ultraviolet absorbing polymer) described in JP-A-6-148430 and JP-A-2002-47357 is preferably used. Can be used. In particular, it is represented by the general formula (1) described in JP-A-6-148430, the general formula (2), or the general formulas (3), (6), and (7) described in JP-A-2002-47357. A polymer ultraviolet absorber is preferably used.

  In general, the antioxidant is also referred to as a deterioration inhibitor, but is preferably contained in a cellulose ester film as an optical film. That is, when a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film as an optical film may be deteriorated. The antioxidant has a role of delaying or preventing the film from being decomposed by, for example, halogen in the residual solvent in the film or phosphoric acid of the phosphoric acid plasticizer, so that it is preferably contained in the film. .

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0% by mass, more preferably 10 to 1000 ppm by mass relative to the cellulose derivative.

  In the present embodiment, the cellulose ester film as the finally produced optical film preferably has a moisture content of 0.1 to 5%, more preferably 0.3 to 4%, and 0.5 to 2%. More preferably it is.

  In the present embodiment, the cellulose ester film as the finally produced optical film desirably has a transmittance of 88% or more, more preferably 90% or more, and further preferably 92% or more.

  The optical film targeted by the present invention is a functional film used for various displays such as a liquid crystal display, a plasma display, and an organic EL display, particularly a liquid crystal display. It includes an optical compensation film such as a brightness enhancement film and a viewing angle expansion.

  The optical film according to the present embodiment can be particularly preferably used as a protective film for a polarizing plate for a large-sized liquid crystal display device or a liquid crystal display device for outdoor use as long as the above physical properties are satisfied.

<Polarizing plate>
When using the optical film which concerns on this embodiment as a transparent protective film for polarizing plates, a polarizing plate can be produced by a general method. It is preferable that an adhesive layer is provided on the back surface side of the optical film according to the present embodiment, and is bonded to at least one surface of a polarizer produced by immersion and stretching in an iodine solution.

  The polarizing plate which concerns on this embodiment is equipped with a polarizer and the transparent protective film arrange | positioned on the surface of the said polarizer, and the said transparent protective film is the said optical film. The polarizer is an optical element that emits incident light by converting it into polarized light.

  As the polarizing plate, for example, a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizer produced by immersing and stretching a polyvinyl alcohol film in an iodine solution. The thing which bonded together is preferable. Moreover, the said optical film may be laminated | stacked also on the other surface of the said polarizer, and another transparent protective film for polarizing plates may be laminated | stacked. As this transparent protective film for another polarizing plate, for example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC8UX-RHA (above, manufactured by Konica Minolta Opto Co., Ltd.) Etc. are preferably used. Or you may use resin films, such as cyclic olefin resin other than a cellulose-ester film, an acrylic resin, polyester, a polycarbonate. In this case, since the saponification suitability is low, it is preferable to perform an adhesive process on the polarizing plate through an appropriate adhesive layer.

  As described above, the polarizing plate uses the optical film as a protective film laminated on at least one surface side of a polarizer. In that case, when the said optical film functions as a phase difference film, it is preferable to arrange | position so that the slow axis of an optical film may be substantially parallel or orthogonal to the absorption axis of a polarizer.

  Moreover, as a specific example of the said polarizer, a polyvinyl alcohol-type polarizing film is mentioned, for example. Polyvinyl alcohol polarizing films include those obtained by dyeing iodine on polyvinyl alcohol films and those obtained by dyeing dichroic dyes. As the polyvinyl alcohol film, a modified polyvinyl alcohol film modified with ethylene is preferably used.

  The polarizer is obtained as follows, for example. First, a film is formed using a polyvinyl alcohol aqueous solution. The obtained polyvinyl alcohol film is uniaxially stretched and then dyed or dyed and then uniaxially stretched. And preferably, a durability treatment is performed with a boron compound.

  The thickness of the polarizer is preferably 5 to 40 μm, more preferably 5 to 30 μm, and more preferably 5 to 20 μm.

  When laminating a cellulose ester resin film on the surface of the polarizer, it is preferable to bond the cellulose ester resin film with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol. Moreover, in the case of resin films other than a cellulose ester-type resin film, it is preferable to carry out the adhesive process to a polarizing plate through a suitable adhesion layer.

  The polarizing plate as described above uses the optical film according to the present embodiment as a transparent protective film, so that the deformation of the optical film is sufficiently suppressed. For example, when applied to a liquid crystal display device It is possible to realize high image quality of the liquid crystal display device, such as improvement of contrast. Moreover, since the optical film applied as a transparent protective film of a polarizing plate also suppresses dimensional changes due to changes in humidity, for example, when applied to a liquid crystal display device, so-called corner unevenness can also be suppressed.

  Thus, the polarizing plate according to the present embodiment is a polarizing plate including a polarizer and two transparent protective films disposed on both sides of the polarizer so as to sandwich the polarizer, and the two sheets At least one of the transparent protective films is a polarizing plate characterized in that it is the optical film described above. This polarizing plate is manufactured by suppressing the influence of the optical film used as a protective film on the casting ribbon R of the wind X accompanied by the support, suppressing the occurrence of horizontal steps, and good flatness. And has excellent optical properties. Therefore, this polarizing plate is of high quality.

<Liquid crystal display device>
By incorporating a polarizing plate in which the optical film according to this embodiment is bonded as a protective film for a liquid crystal polarizing plate into a liquid crystal display device, it is possible to produce various liquid crystal display devices with excellent visibility. It is preferably used for a liquid crystal display device for outdoor use such as a liquid crystal display device and digital signage. The polarizing plate according to the present embodiment is bonded to the liquid crystal cell via the adhesive layer or the like.

  The polarizing plate according to this embodiment is a reflective, transmissive, transflective LCD or TN, STN, OCB, HAN, VA (PVA, MVA), IPS (including FFS), etc. It is preferably used in LCDs of various drive systems. In particular, in a large-screen display device having a screen size of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen, and the effect is maintained for a long time.

  In addition, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even during long-time viewing.

  The liquid crystal display device according to this embodiment includes a liquid crystal cell and two polarizing plates arranged so as to sandwich the liquid crystal cell, and at least one of the two polarizing plates is the polarizing plate. . Note that the liquid crystal cell is a cell in which a liquid crystal substance is filled between a pair of electrodes, and by applying a voltage to the electrodes, the alignment state of the liquid crystal is changed and the amount of transmitted light is controlled. In such a liquid crystal display device, the use of the polarizing plate according to the present embodiment uses an optical film whose deformation is sufficiently suppressed as a transparent protective film for the polarizing plate, so that the contrast and the like are improved. Thus, a high-quality liquid crystal display device is obtained. Moreover, since what used the optical film in which the dimensional change by the humidity change was suppressed was used for the polarizing plate as a transparent protective film, what is called a corner irregularity can also be suppressed.

  Thus, the liquid crystal display device according to the present embodiment is a liquid crystal display device including a liquid crystal cell and two polarizing plates arranged on both sides of the liquid crystal cell so as to sandwich the liquid crystal cell. At least one of the polarizing plates is a liquid crystal display device characterized in that it is the polarizing plate described above. In this liquid crystal display device, the optical film used as a protective film for the polarizing plate is manufactured by suppressing the influence of the support-entrained wind X on the casting ribbon R, and the occurrence of horizontal stages is suppressed. It has good flatness and excellent optical properties. Therefore, this liquid crystal display device is of high quality.

  Hereinafter, the present invention will be described in more detail through examples, but the present invention is not limited to these examples.

<Test 1>
[Preparation of cellulose ester solution (dope)]
The following raw materials were put into a sealed container, heated, stirred and completely dissolved and filtered to prepare a dope.

(Dope composition)
-100 parts by mass of cellulose triacetate (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)-8 parts by mass of triphenyl phosphate (plasticizer)-2 parts by mass of ethylphthalylethyl glycolate (plasticizer) Parts · Methylene chloride (good solvent) 440 parts by mass · Ethanol (poor solvent) 40 parts by mass · Tinuvin 109 (UV absorber, BASF Japan) 0.5 parts by mass · Tinuvin 171 (UV absorber, BASF Japan) 0.5 parts by mass) Aerosil 972V (matting agent, Nippon Aerosil Co., Ltd.) 0.2 parts by mass

[Production of cellulose ester film]
A cellulose ester film as an optical film was manufactured using an apparatus similar to the optical film manufacturing apparatus 1 shown in FIG. First, the dope was discharged from a die under the following conditions and cast on a support.

(Casting conditions)
-Support: Stainless steel endless belt-Support moving speed (V1): 100 m / min-Moving object: Stainless steel rotating roll (located upstream of the die, roll diameter: 0.9 cm)
・ Moving body moving speed (V2): 50 m / min (moving in the direction opposite to the moving direction of the support)
・ Narrowest interval (T): 0.5 mm (interval between roll surface and belt surface)
・ Shortest distance (L): 60 mm (distance between the die discharge port and the narrowest interval part)
-Dope temperature: 30 ° C
Support temperature (t1): 25 ° C
-Moving body temperature (t2): 25 ° C
-Casting film width: 2000mm

  The cast film (web) formed on the support is blown from above the support at a temperature of 45 ° C. with a wind speed of 10 m / sec. After being dried on the support, it was peeled from the support with a peeling roll. The residual solvent amount of the web at the time of peeling was 80% by mass.

  While transporting the peeled resin film, the first drying device was passed in a meandering manner and dried at 80 ° C. for 1 minute. Next, the film was passed through a stretching apparatus (biaxial stretching tenter) and stretched in the width direction (TD direction) at a stretching ratio of 25% in an atmosphere at 100 ° C. The residual solvent amount of the web at the time of stretching was 3 to 10% by mass. Next, the second drying device was passed in a meandering manner and dried at 125 ° C. Next, it cooled to 20 degreeC and wound up with the winding device, and manufactured the optical film (cellulose ester film) with a film thickness of 50 micrometers and a width | variety of 2200 mm.

<Test 2>
As shown in Table 1, an optical film was produced in the same manner as in Test 1 except that the narrowest distance T between the roll surface and the belt surface was 2.0 mm.

<Test 3>
As shown in Table 1, an optical film was produced in the same manner as in Test 1 except that the narrowest distance T between the roll surface and the belt surface was set to 3.0 mm.

<Test 4>
As shown in Table 1, the same procedure as in Test 1 was conducted except that a vacuum chamber was provided between the die and the rotating roll, and the shortest distance M between the suction port of the vacuum chamber and the narrowest interval portion was 60 mm. An optical film was produced.

<Test 5>
As shown in Table 1, an optical film was produced in the same manner as in Test 1 except that the rotating roll was not provided.

<Test 6>
As shown in Table 2, except that the moving speed V2 of the rotating roll was increased and the ratio (V2 / V1) of the moving speed V2 of the rotating roll to the moving speed V1 of the endless belt was 1.0, An optical film was produced in the same manner.

<Test 7>
As shown in Table 2, except that the moving speed V2 of the rotating roll was increased and the ratio (V2 / V1) of the moving speed V2 of the rotating roll to the moving speed V1 of the endless belt was 2.5, An optical film was produced in the same manner.

<Test 8>
As shown in Table 2, except that the moving speed V2 of the rotating roll was increased and the ratio (V2 / V1) of the moving speed V2 of the rotating roll to the moving speed V1 of the endless belt was 3.0, An optical film was produced in the same manner.

<Test 9>
As shown in Table 3, an optical film was produced in the same manner as in Test 1 except that the shortest distance L between the die discharge port and the narrowest interval portion was 50 mm.

<Test 10>
As shown in Table 3, an optical film was produced in the same manner as in Test 1 except that the shortest distance L between the die discharge port and the narrowest interval portion was 10 mm.

<Test 11>
As shown in Table 3, an optical film was produced in the same manner as in Test 1 except that the shortest distance L between the die discharge port and the narrowest interval portion was 1 mm.

<Test 12>
As shown in Table 3, an optical film was produced in the same manner as in Test 1 except that the shortest distance L between the die discharge port and the narrowest interval portion was 0.5 mm.

<Test 13>
As shown in Table 4, an optical film was produced in the same manner as in Test 1 except that the temperature t2 of the rotating roll was 24 ° C.

<Test 14>
As shown in Table 4, an optical film was produced in the same manner as in Test 1 except that the temperature t2 of the rotating roll was set to 7 ° C.

<Test 15>
As shown in Table 4, an optical film was produced in the same manner as in Test 1 except that the temperature t2 of the rotating roll was 4 ° C.

<Evaluation method>
[Horizontal evaluation]
It was visually observed whether or not horizontal steps (thickness unevenness in the longitudinal direction of the optical film) extending in the width direction occurred in the manufactured optical film, and evaluated according to the following criteria. The results are shown in Tables 1-4.

(Evaluation criteria)
A: The horizontal row cannot be confirmed.
B: The horizontal stage can be confirmed, and the pitch is less than 3 mm.
C: The horizontal stage can be confirmed, and the pitch is 3 mm or more.

<Consideration of results>
[Table 1]
Test 1 in which the narrowest distance T between the surface of the rotating roll and the surface of the endless belt was 0.5 mm and Test 2 in which the width was 2.0 mm were the same in the horizontal evaluation, and both were good. On the other hand, Test 3 in which the narrowest interval T was 3.0 mm was inferior in the horizontal evaluation to the same level as Test 5 in which the rotating roll was not provided. This is presumably because the surface of the rotary roll and the surface of the endless belt are too far apart, and the support accompanying air was not effectively weakened by the moving object accompanying air. Further, Test 4 having a decompression chamber between the die and the rotating roll was more excellent in lateral evaluation than Test 1. This is presumably because the remaining part of the supporter-accompanied wind that was weakened by the airflow accompanied by the moving body but did not disappear was sucked and eliminated by the decompression chamber.

[Table 2]
Tests 6 to 8, in which the ratio (V2 / V1) of the moving speed V2 of the rotating roll to the moving speed V1 of the endless belt is 1.0 or more, have a better lateral evaluation than Test 1 in which the ratio is 0.5. It was. This is thought to be due to the fact that a moving body-accompanied wind having a strength sufficient to surely weaken or extinguish the supporting body-accompanying wind was generated from the relationship between the relative strength of the supporting-air accompanying wind and the moving body-accompanying wind. It is done. In the case of Test 8 in which the speed ratio (V2 / V1) is 3.0, the rotational speed of the rotating roll exceeds 10,000 rpm (endless belt moving speed V1: 100 m / min, rotating roll moving speed V2: 300 m / min. Roll diameter: 0.9 cm, roll peripheral length: 2.826 cm, roll rotation speed: 300 m / min ÷ 2.826 cm = 10616 rpm). When the rotational speed is so high, the deterioration of the rotating roll is accelerated.

[Table 3]
Tests 9 to 11 in which the shortest distance L between the die discharge port and the narrowest distance between the roll / belt and the belt / belt is 50 mm to 1 mm were more excellent in lateral evaluation than Test 1 in which the distance was 60 mm. This is presumably because, if the shortest distance L is within the above range, the regrowth of the wind accompanied by the support that has been weakened once or disappeared is suppressed. In Test 12, where the shortest distance L was 0.5 mm, the lateral evaluation was the same level as Test 1. This is presumably because the rotating roll approached the casting ribbon excessively, and the influence of the moving body accompanying wind on the casting ribbon came out.

[Table 4]
Tests 13 and 14 in which the temperature t2 of the rotating roll is lower by 1 ° C. or more than the temperature t1 of the endless belt are more excellent in the horizontal evaluation than the test 1 in which the temperature t2 of the rotating roll and the temperature t1 of the endless belt are the same. It was. This is presumably because the wind accompanied by the support was cooled, the viscosity was lowered, the energy was reduced, and the influence of vibration on the casting ribbon was reduced. In Test 15, in which the temperature t2 of the rotating roll was lowered by over 20 ° C. from the temperature t1 of the endless belt, the lateral evaluation was the same level as Test 1. This is because the efficiency of weakening the supporter-accompanied wind due to the moving body-accompanied wind decreased (one of the causes is considered to be that the temperature of the moving-body-accompanying wind was too lower than the temperature of the supporter-accompanying wind). it is conceivable that.

DESCRIPTION OF SYMBOLS 1 Optical film manufacturing apparatus 10 Casting apparatus 11 Dice 11a Resin solution discharge port 12 Support body (endless belt)
12a Endless belt roll 13 Peeling roll 14 Decompression chamber 14a Suction port 15 Moving body (rotating roll)
16 Support (drum)
17 Mobile body (travel belt)
20 Stretching device 30 Drying device 40 Winding device 51 Resin solution (dope)
52 Casting membrane (web)
53 Resin film (optical film)
A Axial core of endless belt roll B Axial core of rotating roll R Casting ribbon X Supporting wind Y Moving body driving wind

Claims (13)

A method for producing an optical film comprising a step of casting a resin solution from a die on a moving support to form a cast film,
Provided with a moving body that moves in the direction opposite to the moving direction of the support body upstream of the die in the moving direction of the support body,
When the narrowest distance between the surface of the moving body and the surface of the support is T, 0 mm <T ≦ 2 mm,
The method for producing an optical film, wherein the moving body is moved during the step.   The method of manufacturing an optical film according to claim 1, wherein the movable body is a roll that is rotatable around an axis extending in the width direction of the support.   3. The method for producing an optical film according to claim 1, wherein 1 ≦ V2 / V1 ≦ 2.5, where V1 is a moving speed of the support and V2 is a moving speed of the moving body.   1 mm ≦ L ≦ 50 mm, where L is the shortest distance between the resin solution discharge port of the die and the narrowest distance between the surface of the moving body and the surface of the support. The manufacturing method of the optical film of any one of Claim 1 to 3 to do.   A vacuum chamber is provided between the die and the moving body, and when the shortest distance between the suction port of the vacuum chamber and the narrowest distance between the surface of the moving body and the surface of the support is M, 1 mm <= M <= 50mm It is the manufacturing method of the optical film of any one of Claim 1 to 3 characterized by the above-mentioned.   6. The optical system according to claim 1, wherein t1-20 ° C. ≦ t2 ≦ t1-1 ° C., where t1 is the temperature of the support and t2 is the temperature of the moving body. A method for producing a film.   The method for producing an optical film according to claim 6, wherein the surface of the moving body is a rough surface.   The method for producing an optical film according to any one of claims 1 to 7, wherein a moving speed of the support is from 30 m / min to 200 m / min.   The method for producing an optical film according to any one of claims 1 to 8, wherein the cast film has a width of 1000 mm to 2500 mm. An apparatus for producing an optical film in which a step of casting a resin solution from a die on a moving support to form a cast film is performed,
A moving body that moves in the direction opposite to the moving direction of the support is provided upstream of the die in the moving direction of the support,
When the narrowest distance between the surface of the moving body and the surface of the support is T, 0 mm <T ≦ 2 mm,
The apparatus for manufacturing an optical film is characterized in that the moving body is moved during the process.   The optical film manufactured by the manufacturing method of the optical film of any one of Claim 1 to 9, or the manufacturing apparatus of the optical film of Claim 10.   A polarizing plate comprising the optical film according to claim 11 on at least one surface.   A liquid crystal display device comprising the optical film according to claim 11 or the polarizing plate according to claim 12.

Images