JP2014108555A - Method for manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical film by which an optical film with reduced stripe defects can be manufactured in a melt film-forming process.SOLUTION: The method for manufacturing an optical film includes a process of melt-extruding a polycarbonate resin into a film, where a temperature condition is controlled to give a melt viscosity of 300 Pa s or more and 1,500 Pa s or less of the polycarbonate resin while discharged from a T-die, measured at a shear rate of 122 sec; and a lip edge of the T-die used has a radius R of less than 10 μm.

Description

  The present invention relates to a method for producing a polycarbonate resin film that can be used as an optical film.

  As a film forming method, a melt film forming method is known in which a thermoplastic resin is heated and melted by an extruder or the like, and then discharged into a film using a T-die and cooled and solidified. Although this method is superior in productivity to a solution casting method in which a solution in which a resin is dissolved in an organic solvent is cast into a sheet / film on a support and then dried to produce a film, There was a problem that streaky defects occurred in the direction of flow in the discharged film. Moreover, when using a film especially for an optical film use, since a stripe defect is detected as an optical distortion, it is requested | required to reduce a stripe defect with higher precision. Furthermore, there is a concern that the resin may be decomposed or gelled by heat melting, and there is a problem that the film quality is deteriorated in a resin having low thermal stability, and when a resin having low thermal stability is used, solution casting is performed. The law was selected.

  For this reason, when using polycarbonate-based resins, which often have problems with thermal stability, in optical film applications where the required quality of the film is high, a solution casting method (cast casting method) ) Is used.

  However, the solution casting method (cast casting method) has a limitation on the drying speed, and in order to increase productivity, it is necessary to extend the furnace length and a large-scale solvent recovery device. However, it is inferior to the melt film forming method. For this reason, a method for melting and forming a polycarbonate resin has been studied.

  In many cases, streak defects that cause problems in the melt film-forming method are caused by the film being rubbed against T-die scratches or lip deposits (eyes). As a countermeasure, the resin melt viscosity is lowered as much as possible (for example, a high temperature condition such as 280 to 300 ° C. is adopted as the molding temperature), and the film does not hit the scratches on the T-die lip or the adhered matter. A method has been taken (Patent Document 1). However, in the case of a polycarbonate resin, since a low molecular weight resin having a viscosity average molecular weight of 20000 or less is generally used, thermal stability such as generation of gel-like defects and contamination of rolls due to volatile components during a long period of operation. This caused the problem of lowering the film quality. In addition, since the film immediately after the T-die discharge is not stable, there is a problem that uneven orientation due to uneven thickness in the width direction and uneven cooling occurs.

  On the other hand, in Patent Document 2, an attempt is made to smoothen the film by thinning the film after discharging the T die with a forming roll against the generated streak defect, thereby thinning the streak defect. However, among the optical films, the polycarbonate-based resin film used as the retardation film needs to be heated when it is stretched later, so that a heat return occurs at that time, and stripe-like defects become obvious again. Therefore, it is not a fundamental solution.

JP 2007-141408 A JP 2009-166290 A

  As described above, several manufacturing methods have been proposed to eliminate streak-like defects in the melt film-forming method, but at the same time, defects that occur when extruded at a relatively high temperature, such as gel-like defects in the film. Production of a polycarbonate resin film that eliminates the above has not been realized. Accordingly, an object of the present invention is to provide a method for producing a film that can reduce streak-like defects and also reduce defects generated when extruded at a relatively high temperature.

  As a result of intensive studies, the present inventor can eliminate the gel-like defect when a relatively low temperature condition is selected, but at the same time, the streak-like defect cannot be eliminated. It was found that by setting R within a specific range, these problems can be solved simultaneously, and the present invention has been achieved.

  That is, the present invention is as follows.

(I) Temperature conditions under which the melt viscosity of the polycarbonate resin during T-die discharge is 300 Pa · s or more and 1500 Pa · s or less when the polycarbonate resin is melt-extruded and formed at a shear rate of 122 sec ^−1. And a lip edge R of a T die to be used is less than 10 μm.

  (Ii) The optical film according to (i), wherein the molten film discharged in a film form from a T die is nipped between the cast roll and the touch roll when the molten film contacts the cast roll. Manufacturing method.

  (Iii) The method for producing an optical film according to any one of (i) and (ii), wherein a polycarbonate-based resin having a viscosity average molecular weight of 12000 to 20000 is used.

  (Iv) The method for producing an optical film as described in any one of (i) to (iii), wherein a molten resin residence time from introduction of the extruder to T-die discharge is 15 minutes or less.

  (V) The temperature variation in the width direction of the molten film at the time of T-die discharge is 5 ° C. or less, and the temperature variation in the width direction of the film on the roll when nipping is formed is 5 ° C. or less (i )-(Iv) The manufacturing method of the optical film in any one.

(Vi) produced by the production method according to any one of (i) to (v), wherein the number of streak defects in the film is 1 or less per 200 mm width in the width direction film center 80%, the gel in the film the number of Jo disadvantage is five or / m ² or less, a polycarbonate resin film, wherein the number of stains like drawbacks adhering to the film is 5 / m ² or less.

  By using the present invention, it is possible to produce a film in which streak-like defects are reduced and defects caused when extruded at a relatively high temperature such as gel-like defects are also reduced. Therefore, it is possible to manufacture a film having a high required quality such as an optical film with a high yield rate.

Schematic perspective view showing the observation direction (arrow) when measuring the bright line width to determine R of the lip edge

The present invention provides a temperature at which the melt viscosity of a polycarbonate resin during T-die discharge is 300 Pa · s or more and 1500 Pa · s or less when measured at a shear rate of 122 sec ^-1 when a polycarbonate resin is melt-extruded. The present invention relates to a method for producing an optical film, characterized in that the R of the lip edge of the T die used is less than 10 μm.

  In general, melt extrusion film formation uses an extruder or the like to heat and knead a resin to melt and plasticize it, and discharge it from a slit-shaped die hole to obtain a molten film. By bringing the film into contact with a temperature-controlled roll or the like, the film is obtained by cooling and solidifying while maintaining the film shape.

  In the present invention, as an extruder, a single-screw extruder, a co-directional meshing twin-screw extruder, a co-directional non-meshing twin-screw extruder, a different-direction meshing twin-screw extruder, a different-direction non-meshing twin-screw extruder Various extruders such as a multi-screw extruder can be used. Among them, the single-screw extruder is preferable because the resin staying portion in the extruder is small, so that it is possible to prevent thermal deterioration of the resin during extrusion and the equipment cost is low. Moreover, it is preferable to use an extruder having a vent mechanism in order to remove residual volatile components in the resin and heating products in the extruder. The size (caliber) of the extruder can be selected according to the desired discharge amount.

  The form of the raw material of the resin charged into the extruder is preferably a solid state resin, particularly a 3 mm square pellet. The pellet-shaped resin is generally supplied into the extruder through a hopper attached to the raw material supply port of the extruder.

  In order not to cause hydrolysis or oxidative deterioration during processing, the resin charged into the extruder is preferably heated and dried in advance to remove moisture. The amount of water in the resin is preferably 200 ppm or less, and the drying condition for achieving this is 3 hours or more at an atmospheric temperature of 100 ° C. Further, in order to remove dissolved oxygen in the resin during drying, the inside of the dryer is preferably an inert gas atmosphere such as nitrogen.

  Drying can be performed by a method using a hopper type dryer, a method using a dryer before supplying the resin to the hopper and supplying the hopper so as not to absorb moisture, or a method using both. When the temperature of the resin is increased by the hopper, there is a possibility that blocking may occur or the extruder discharge may vary. Therefore, it is preferable to take a method of sufficiently drying at a high temperature using a dryer in advance before supplying the resin to the hopper and then using a hopper type dryer to form a low-temperature dehumidifying atmosphere so as to prevent moisture from entering. Specifically, before supplying the resin to the hopper, after drying it under necessary conditions (for example, 120 ° C. × 3 hours) using a dryer, the hopper type dryer is adjusted to 40 to 100 ° C. The amount can be suppressed and the extrusion stability can be compatible. In this case, it is necessary to secure time until the temperature of the resin stabilizes after the temperature of the resin before the resin is supplied to the hopper is changed from the temperature during drying to the temperature in the hopper dryer. Therefore, the capacity of the hopper dryer is preferably about 2 to 5 times the amount of extrusion per hour.

  As a screw used in a single screw extruder, a general full flight configuration having a compression ratio of about 2 to 3 can be used, but if necessary, a special kneading mechanism ( Mixing elements) may be provided. Examples of the kneading mechanism include barrier flight and unimelt.

  In this invention, it is necessary to adjust the extrusion conditions at the time of using an extruder as a melting means according to the thermoplastic resin to be used. For example, when using a polycarbonate-based resin having a viscosity average molecular weight of 12,000 to 20,000, it is preferable to set the temperature of the cylinder portion so that the resin temperature at the exit of the extruder is 220 to 280 ° C. More preferably it is. When the resin temperature is less than 220 ° C., the melt viscosity becomes very large, and therefore it may be difficult to torque over the extruder or form a film. On the other hand, when it exceeds 280 ° C., the resin is thermally deteriorated, and a gel-like defect may occur in the film. The resin temperature at the exit of the extruder is preferably a difference of 20 ° C. or less, particularly a difference of 10 ° C. or less, and further a difference of 5 ° C. or less with respect to the resin temperature at the time of die discharge. If the difference is greater than 20 ° C., it will be changed in the extrusion line from the resin temperature at the exit of the extruder to the temperature at the die discharge resin, and it will be difficult to change the temperature uniformly in this extrusion line. This is not preferable because temperature unevenness is likely to occur.

  The resin heated / melted by the extruder is then preferably fed to the die using a gear pump. By using a gear pump, the quantitativeness of the supply is remarkably improved, and it is effective in improving the film thickness unevenness.

  The molten resin quantitatively supplied from the gear pump or directly supplied from the extruder is supplied to the die through the flow path (extrusion line) and discharged from the die into a film. A foreign matter removal device may be provided in the extrusion line from the gear pump to the die, or in the extrusion line from the extruder to the die if no gear pump is used, or on the upstream side of the gear pump even when the gear pump is used. preferable. Thereby, the foreign material contained in the raw material resin or the foreign material generated by the extruder can be collected, and the foreign material in the film can be reduced.

  As the foreign matter removing device, a screen mesh, a pleated filter, a leaf disk filter, or the like can be used. Among these, a leaf disk type filter having a feature of being capable of filtration with a small volume and a large filtration area is preferable. From this feature, since the pressure loss with respect to the filtration capacity is smaller than that of other foreign matter removing devices, the filtration accuracy can be made fine. In addition, the time until the filter is clogged with a foreign substance becomes longer, which is preferable from the viewpoint of improving productivity.

  As the filter medium of the filter, for example, a sintered non-woven fabric of metal fibers can be used. It is preferable to select a filter having a nominal filtration accuracy (defined by the ability to cut a foreign substance of a specified size by 95%) of 1 to 20 μm, particularly 3 to 10 μm. After determining the filtration accuracy, the number and size (outer diameter) of the filter elements are determined in view of the production amount and the melt viscosity. In this case, in order to shorten the residence time, it is preferable to reduce the number / size of the elements as much as possible with respect to the pressure limit. On the other hand, when shear heat generation in the filter becomes a problem, on the contrary, it is preferable to increase the number of elements within a possible range and reduce the pressure. Moreover, it is preferable to design a flow path such as each gap in the filter so that there is no staying portion.

  In the present invention, various types of structures can be used as the die, but it is preferable to use a T die, for example, a general coat hanger die. Furthermore, what can adjust the clearance gap of the width direction arbitrary part of die lip by pushing in a volt | bolt etc. is preferable. In addition, the thickness distribution in the width direction of the film is measured in-line, and the lip gap corresponding to a position having a deviation from the desired thickness distribution can be automatically adjusted. For example, the thickness profile is adjusted using a thermally operated bolt. It is preferable.

  In the present invention, the R of the lip edge of the T die needs to be less than 10 μm and preferably less than 5 μm, at least in the range of the width of the film used as a product (desirably the full width of the die). In particular, by setting R of the lip edge of the T die within this range, it becomes possible to prevent the occurrence of streak-like defects even when the viscosity of the resin is set within the range described below. In addition, it is preferable to perform a ceramic spraying process on the die lip portion because the above-described lip edge R can be formed with high accuracy. On the other hand, since chipping is likely to occur when ceramic spraying is performed, it is preferable to manage the chip in a state without chipping, including chipping of a width and depth of 10 μm or less.

In the present invention, it is necessary to set the temperature condition so that the melt viscosity of the polycarbonate resin at the time of die discharge is 300 Pa · s or more and 1500 Pa · s or less when measured at a shear rate of 122 sec ⁻¹ . Under such high-viscosity conditions, streak-like defects are usually generated due to the die lip edge, but the occurrence of streak-like defects is suppressed by using a T-die having a lip edge R defined in the above range. It is possible. When the viscosity is less than 300 Pa · s, the elongation behavior immediately after the discharge of the die becomes unstable and thickness unevenness occurs, which is not preferable. On the other hand, when the viscosity is higher than 1500 Pa · s, a streak-like defect is generated even at the lip edge R, which is not preferable.

  At this time, it is preferable to use a polycarbonate-based resin having a viscosity average molecular weight in the range of 12000 to 20000 because it is easy to obtain an optimum temperature for thermal deterioration in the above viscosity range. If the viscosity average molecular weight exceeds 20000, it is not preferable because the resin temperature at the time of die discharge, which is in the above viscosity range, tends to be a temperature at which thermal deterioration exceeds 300 ° C. On the other hand, if the viscosity average molecular weight is less than 12,000, it is not preferable because it is likely that the strength of the film and the expression of retardation are not satisfied.

  Moreover, it is preferable that the molten resin residence time taken from an extruder introduction to T-die discharge be 15 minutes or less, and it is especially preferable that it is 10 minutes or less. This residence time is preferable because it is difficult for resin thermal degradation to occur.

  The molten film discharged from the die into a film can be cooled and solidified by various methods. However, the molten film is cast on a roll (hereinafter referred to as a cast roll, preferably temperature-controlled), and another is taken while being taken. It is preferable to make it cool and solidify by making it contact | connect to the roll (henceforth a cooling roll. It is preferable that it is temperature-controlled). In addition, when the molten film is in contact with the cast roll, it is preferable to perform pressure forming between the cast roll and a newly provided touch roll (hereinafter sometimes referred to as sandwich molding). In this case, the roll landing position of the film is stabilized and the thickness quality is improved, the cooling in the film width direction is also uniformed, and the orientation state at the time of cooling and solidification is uniform.

  Also, in order to make the orientation state of the film, which is often required for optical films, optimize the T-die channel design, or change the T-die temperature control setting value in the width direction. It is preferable to set the temperature variation in the width direction of the molten film to 5 ° C. or less, and it is preferable to set the film temperature variation on the roll to 5 ° C. or less by sandwiching and forming with a touch roll.

  The touch roll pressing mechanism detects the gap between the cast roll and the touch roll with a position sensor and controls the gap to be constant, and / or detects the load with which the touch roll presses the film with a pressure sensor. It is preferable to have a mechanism for controlling the pressure constant. Among these, it is preferable to control the load to be constant in order to make the orientation state of the film uniform and reduce temperature unevenness. At this time, in order to express the stress that the film receives, it is better to consider the linear pressure (kgf / cm) that is a value obtained by dividing the pressing load (kgf) by the film width (cm). This linear pressure is preferably set in the range of 3 to 20 kgf / cm. When the linear pressure is lower than 3 kg / cm, a portion that is not pressed in the film width direction tends to occur. As a result, the difference in surface properties between the pressed part and the unpressed part may be detected as a defect, which is not preferable. On the other hand, if the linear pressure is higher than 20 kg / cm, alignment unevenness tends to occur in the width direction, and the quality as a retardation film may be deteriorated.

  Moreover, in order to press the whole film width uniformly, it is preferable to use the roll designed by the use for a touch roll. Examples of the roll include a roll made of a relatively soft material such as rubber, a roll having a roll diameter that decreases from the center in the width direction to both ends, and an elastic roll having a double sleeve structure of a metal sleeve. Among these, an elastic roll having a double cylindrical structure of a metal sleeve is preferable because it has excellent roll surface properties and can uniformly press the width direction with a lower linear pressure.

  The cooling temperature of the cast roll may be usually set based on the glass transition temperature of the resin. The cast roll with which the film first comes into contact is the glass transition temperature of the thermoplastic resin ± 30 ° C., and the cooling roll is the glass transition temperature of ± 30 ° C. It is preferable that The touch roll is preferably set at ± 10 ° C. with respect to the cast roll.

  The film can be taken out by various methods, for example, by a method of taking up with a nip roll installed after the cooling roll and then winding it around the take-up core. At this time, since both ends of the film become thick due to the neck-in generated when the resin is discharged from the T-die, the film quality may be trimmed with a cutter or the like in order to make the product quality constant over the entire width.

According to the present invention, the number of streaky defects in the film is 1 or less per 200 mm width at the center of the film of 80%, the number of gel-like defects in the film is 5 / m ² or less, and the stains attached to the film It becomes possible to easily obtain a high-quality film having the number of defects of 5 pieces / m ² or less. Moreover, it can acquire as optical films, such as retardation film, by extending | stretching this with a extending machine.

  On the other hand, various polycarbonate-based resins can be used in the present invention, but they are particularly mass-produced and inexpensive, and the main component is composed of repeating units composed of 2,2-bis (4-hydroxyphenyl) propane (bisphenol A). Aromatic polycarbonates are preferred. The main component here refers to a repeating component composed of a compound occupying 50 mol% or more of the dihydroxy compound which is a raw material of polycarbonate. Therefore, even if 2,2-bis (4-hydroxyphenyl) propane (bisphenol A) is used alone, other dihydroxy compounds are added or copolymerized or mixed within a range not exceeding 50 mol%. It can be preferably used. Although it does not specifically limit as a dihydroxy compound used by copolymerizing or mixing, As an example, 1, 1-bis (4-hydroxy 2, 2-bis (4-hydroxy-3-methylphenyl) propane, 1, 1-, Bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, Bis (hydroxyaryl) alkanes such as 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 1,1-bis (4-hydroxyphenyl) ethylbenzene, 1,1-bis (4- Bis such as hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane Hydroxylaryl) cyclohexanes, fluorenes such as 9,9-bis (4-hydroxyphenyl) fluorene, dihydroxyaryls such as 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxy-3,3′-dimethylphenyl ether Ethers, 4,4'-dihydroxydiphenyl sulfide, dihydroxyaryl sulfides such as 4,4'-dihydroxy-3,3'-dimethylphenyl sulfide, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxy- And dihydroxyaryl sulfoxides such as 3,3′-dimethylphenyl sulfoxide, and compounds derived from the above compounds, which are suitable for the main component of the repeating unit consisting of bisphenol A. As long as bisphenol A is a cheap and easily available raw material, the more the bisphenol A component is used, the less expensive the optical film can be used. The repeating unit of bisphenol A is preferably 80 mol% or more, more preferably 90% or more, and particularly preferably 100 mol% (that is, alone).

  The present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the measuring method of each physical property measured in the following examples and comparative examples is as follows.

(1) Inspection of lip edge portion The lip edge portion is observed with a digital microscope from an angle of 45 ° at a magnification of 150 times (observed from the direction of the arrow in FIG. 1) to determine the bright line width. The value obtained by dividing by the value multiplied is taken as R of the edge portion.

(2) Number of streak defects The number of streak defects in the film was counted for the range of 80% in the width direction film center of the obtained stretched film, and the number of streak defects per 200 mm width was calculated. The stretched film was projected onto a screen with a point light source, and streaks appearing as shadows in the flow direction on the projected image were detected as streak defects. At this time, it was judged that the number of streak defects was 5 or less.

(3) Number of gel-like defects First, defects on the obtained stretched film were visually detected. The detected defects were magnified up to 500 times with a digital microscope, and no metal nuclei were seen at that time. Furthermore, when it was in a crossed Nicol state (a film was placed between two polarizing plates) No change was counted as a gel-like defect.

  In this experiment, gel-like defects were evaluated as representatives of defects generated when extruded at a relatively high temperature.

Example 1
A polycarbonate resin (Iupilon H-4000 manufactured by Mitsubishi Gas Chemical Co., Ltd., viscosity average molecular weight 15000, glass transition temperature 148 ° C.) is used as the thermoplastic resin. The hopper type dryer was transported to a φ65 mm single screw extruder. The extruder screw rotation speed was 50 rpm and the extruder set temperature was 240 ° C. so that the resin temperature was 240 ° C. at the outlet of the extruder and the discharge amount was 70 kg per hour. Next, the molten resin was extruded through a gear pump into a 10 μm cut leaf disk filter (5 inches) and a T die. The T die was polished so that the lip portion was ceramic sprayed, the R of the lip edge was 3 μm, and there was no chipping of 10 μm or more. The set temperature between the extruder and the T die (extrusion line) was 240 ° C. The resin temperature immediately after discharge at the T-die outlet was 240 ° C. Further, the residence time from the introduction of the extruder to the resin discharge was 9 minutes. The polycarbonate resin used had a melt viscosity of 1200 Pa · s at a shear rate of 122 sec ⁻¹ at 240 ° C.

  On the other hand, after the discharged molten film is sandwiched between a cast roll adjusted to 120 ° C. and an elastic touch roll adjusted to 120 ° C., it is cooled and solidified using a cooling roll adjusted to 115 ° C. The film was taken up at 10 m / min, and an original film having a film thickness of 70 μm was obtained on the winding core.

  The obtained polycarbonate resin raw film was stretched in the machine direction by a stretching machine to obtain a stretched polycarbonate resin film.

  The obtained stretched polycarbonate resin film was in a good state with no streak defects or gel defects observed.

(Example 2)
The test was performed under the same conditions as in Example 1 except that the touch roll was not used.

  The obtained stretched polycarbonate resin film was in a good state with no streak defects or gel defects observed. However, it was confirmed that the thickness unevenness in the width direction of the stretched polycarbonate resin film was larger than that in Example 1.

(Example 3)
The test was performed under the same conditions as in Example 1 except that the size of the leaf disk filter of 10 μm cut was 8 inches. At this time, the resin residence time was 20 minutes.

In the obtained stretched polycarbonate resin film, 2 streaky defects / 200 mm were observed, and 5 gel defects / m ^{2 were} observed. As a result, the stretched film was almost in good condition.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the melt viscosity at a shear rate of 122 sec ⁻¹ of the polycarbonate-based resin was 150 Pa · sec at the T-die outlet. The resin temperature at this time was 300 degreeC.

In the obtained stretched polycarbonate resin film, no streak-like defects were observed, but 50 gel defects / m ^{2 were} observed.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that the melt viscosity at a shear rate of 122 sec ⁻¹ of the polycarbonate-based resin was 2400 Pa · sec at the T-die outlet. The resin temperature at this time was 220 degreeC.

  In the obtained stretched polycarbonate resin film, 6 streaks / 200 mm were observed. On the other hand, no gel-like defects were observed.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that the lip edge R of the T die was 20 μm.

  In the obtained stretched polycarbonate resin film, 8 streaks / 200 mm were observed. On the other hand, no gel-like defects were observed.

Claims (6)

When the polycarbonate resin is melt-extruded, the temperature condition is such that the melt viscosity of the polycarbonate resin at the time of T-die discharge is 300 Pa · s or more and 1500 Pa · s or less when measured at a shear rate of 122 sec ^−1. A method for producing an optical film, wherein the R of the lip edge of the T die used is less than 10 μm.   The method for producing an optical film according to claim 1, wherein the molten film discharged in a film form from the T-die is nipped between the cast roll and the touch roll when the molten film contacts the cast roll. .   3. The method for producing an optical film according to claim 1, wherein a polycarbonate-based resin having a viscosity average molecular weight of 12,000 to 20,000 is used.   The method for producing an optical film according to any one of claims 1 to 3, wherein the molten resin residence time from the introduction of the extruder to the discharge of the T-die is 15 minutes or less.   The width direction temperature unevenness of the molten film at the time of T-die discharge is 5 ° C or less, and the width direction temperature unevenness of the film on the roll when nipping is formed is 5 ° C or less. 5. The method for producing an optical film according to any one of 4 above. It is manufactured by the manufacturing method according to any one of claims 1 to 5, wherein the number of streak-like defects in the film is 5 or less per 200 mm width at the center 80% in the width direction film, and the gel-like defects in the film. the number is five or / m ² or less, a polycarbonate resin film, wherein the number of stains like drawbacks adhering to the film is 5 / m ² or less.

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