JP4841924B2 - Optical film molding die and optical thermoplastic resin film manufacturing method - Google Patents

Description

  The present invention relates to a mold used for manufacturing a film such as a retardation compensation film in, for example, a liquid crystal display, and more specifically, a mold used for extrusion molding of a thermoplastic resin, and a heat using the mold. The present invention relates to a method for producing a plastic resin film.

  In recent years, in a retardation compensation film used for a liquid crystal display or the like, streaky color unevenness due to retardation unevenness has been a problem because quality deteriorates. The retardation compensation film is generally produced by stretching an unstretched raw fabric resin film and imparting distortion. However, if the thickness unevenness occurs in the raw resin film stage, the retardation unevenness due to the thickness unevenness occurs in the retardation compensation film obtained by stretching. Therefore, in order to reduce the variation in retardation, it is necessary to reduce the thickness variation of the raw resin film, and it is important to mold a resin film with excellent thickness accuracy in the manufacturing process of the raw resin film. It has become.

  From the above viewpoints, conventionally, in the production of an original film resin film for an optical film such as a retardation compensation film, since the thickness accuracy can be increased, a production method by a solution casting method has been frequently used.

  However, film formation by the solution casting method has problems that productivity is not sufficient and solvent cost is high. Therefore, the adoption of a film forming method by melt extrusion has been studied.

For example, Patent Document 1 below discloses a method for producing a polyvinyl alcohol film used for a polarizing plate of a liquid crystal display device, and a production method using a melt extrusion molding method. Here, it is described that a polyvinyl alcohol film with little thickness variation can be obtained by extrusion molding by using a die composed of a flexible lip and setting the radius of curvature R of the lip edge of the flexible lip to 200 μm or less.
JP 2002-28941 A

  However, as described in Patent Document 1, even when the lip interval is adjusted and the curvature radius R of the lip edge of the flexible lip is reduced, a resin film having a high thickness accuracy required for an optical film is extruded. It was still very difficult to obtain by molding.

An object of the present invention is to solve the problems described above, the excellent extrusion productivity, an optical film molding thickness accuracy required for the optical optical film is it possible to obtain a very high film use molds, and to provide a method of manufacturing such a thickness is very high-precision optical thermoplastic resin film.

  The present invention is a mold used for extrusion molding of a thermoplastic resin and provided with a lip edge composed of a flat portion formed by chamfering, the lip edge having a length direction and a width direction, The mold has rounded edges extending in the length direction of the lip edge on both side edges of the lip edge, and a bright line which is a width direction dimension of the lip edge when observed from a direction substantially perpendicular to the lip edge. The average value in the length direction of the lip edge of the width is 5 to 50 μm, the maximum value of the bright line width difference is 2 μm / 5 mm or less, and the edge width which is the dimension of the edge along the width direction of the lip edge The average value in the length direction of the lip edge is 2 μm or less.

  The method for producing a thermoplastic resin film according to the present invention is characterized by extruding a thermoplastic resin using a mold constituted according to the present invention.

  The metal mold | die which concerns on this invention is used for extrusion molding of a thermoplastic resin. The mold is provided with a lip edge composed of a flat portion formed by chamfering. The lip edge has a length direction and a width direction, and the mold has rounded edges that extend in the length direction of the lip edge on both side edges of the lip edge. A film is obtained by extruding a thermoplastic resin using this mold.

  In the present invention, when observed from a direction substantially orthogonal to the lip edge, the average value of the bright line width, which is the width direction dimension of the lip edge, in the lip edge length direction is 5 to 50 μm, and the bright line width difference is Since the maximum value is 2 μm / 5 mm or less and the average value of the edge width in the length direction of the lip edge which is the dimension of the edge along the width direction of the lip edge is 2 μm or less, the thermoplastic resin film The film can be stably extruded and a film with little thickness unevenness can be provided.

  In the method for producing a thermoplastic resin film according to the present invention, since the thermoplastic resin is extruded using the mold configured as described above, a film having a uniform thickness can be obtained in the width direction of the film. . Therefore, the obtained film can be suitably used as an optical film such as a retardation plate.

  Hereinafter, the present invention will be clarified by describing an embodiment of the present invention with reference to the drawings.

  The metal mold | die which concerns on one Embodiment of this invention is demonstrated referring FIG.1 and FIG.2. FIG. 1 is a schematic cross-sectional view showing a mold according to the present embodiment. The mold 1 has a flow path 2 and is configured such that resin is extruded from the flow path 2 through the discharge port 2a.

  As shown in a perspective view in FIG. 2A, the mold 1 has a land surface 1a and a top surface 1b orthogonal to the land surface 1a. A lip edge 1c is provided at the corner between the land surface 1a and the top surface 1b of the mold 1. The lip edge 1c consists of a flat portion formed by chamfering. In the mold 1, the internal angle θ formed by the top surface 1b and the lip edge 1c is 135 degrees. The lip edge 1c is an inclined surface that is inclined with respect to the land surface 1a.

  The lip edge 1 c has a length direction X and a width direction Y. The width direction of the extruded film corresponds to the length direction X of the lip edge. The mold 1 has edge portions 4 and 5 that extend in the length direction X of the lip edge 1c and are rounded on both side edges of the lip edge 1c. The edges 4 and 5 are connected to the land surface 1a and the top surface 1b, respectively.

  The feature of this embodiment is that the average value in the length direction X of the lip edge 1c having the bright line width is 5 to 50 μm, the maximum value of the bright line width difference is 2 μm / 5 mm or less, and the lip edge length direction X of the edge width. The average value at is set to 2 μm or less.

  A microscope is used to measure the bright line width which is the width direction dimension of the lip edge 1c and the edge width which is the dimension of the edge portions 4 and 5 along the width direction Y of the lip edge 1c.

  FIG. 2B is a perspective view for explaining a method of measuring the bright line width. Here, the microscope 6 is fixed so that light can be emitted from a direction inclined at an angle of 45 degrees from the direction perpendicular to the top surface 1b toward the lip edge 1c, that is, from a direction substantially perpendicular to the lip edge 1c. ing.

  The width of light along the width direction Y of the lip edge 1c, which is reflected at the lip edge 1c when the lip edge 1c is irradiated with constant light from the direction substantially orthogonal to the lip edge 1c. Is measured as the line width. That is, when observed from a direction substantially orthogonal to the lip edge 1c, the width direction dimension of the lip edge 1c is measured as the bright line width.

  Further, the bright line width is measured as described above at each measurement position at intervals of 5 mm while sliding the microscope 6 at intervals of 5 mm in the length direction X of the lip edge 1c. The average value of the bright line widths is obtained by averaging the bright line widths measured at this interval. Further, for each measured bright line width, the absolute value of the difference between the measured values of adjacent bright line widths is calculated as the bright line width difference, and the bright line width difference, which is the largest value, is set as the maximum bright line width difference.

  FIG. 3 is a diagram for explaining a method of measuring the edge width which is the dimension of the edges 4 and 5 along the width direction Y of the lip edge 1c. After fixing the microscope 6 at the same position as in the measurement of the bright line width, the microscope 6 irradiates the edges 4 and 5 with constant light from a direction substantially orthogonal to the lip edge 1c. As a result, the width of the light along the width direction Y of the lip edge 1 c of the portion where the light is reflected at the edges 4 and 5 is measured as the width of the edges 4 and 5.

  That is, as schematically shown in FIG. 3, when the edges 4 and 5 are observed from the microscope 6, the bright lines at the lip edge 1c are brighter on both side edges of the bright line width region of the width A of the lip edge 1c. No part is observed. The dimension B along the width direction Y of the lip edge 1c of this portion is measured as the width of the edge portions 4 and 5. The edges 4 and 5 appear to shine in this way because the light from the microscope 6 is partially reflected by the edges 4 and 5 and collected by the microscope 6. The edge width is measured at each measurement position at intervals of 5 mm while sliding the microscope 5 at intervals of 5 mm in the length direction X of the lip edge 1c. By averaging the measured edge widths, an average value of the edge widths is obtained.

  By the way, if the cross-sectional shape of the lip edge of the mold is curved, and the shape of the lip edge is partially different due to incomplete processing of the flow path surface or top surface, the width of the lip edge is actually However, when the bright line width of the lip edge is observed from a direction substantially orthogonal to the lip edge, the bright line width may be uniform. For example, if the outer edge of the cross-sectional shape of the lip edge is not a perfect circular arc and there is a part where the lip edge becomes wider toward the land surface side, there is actually a part where the width of the lip edge is different. However, when the bright line width is viewed from a direction substantially orthogonal to the lip edge, the bright line width may be uniform.

  In addition, when the cross-sectional shape of the lip edge of the mold is a curved surface, the direction substantially orthogonal to the lip edge, that is, the direction inclined at an angle of 45 degrees from the direction orthogonal to the top surface to the lip edge side. In some cases, the bright line width is different between the case where the lip edge is observed and the case where the lip edge is observed from a direction inclined at an angle of 30 degrees from the direction orthogonal to the top surface to the lip edge side. Therefore, when the cross-sectional shape of the lip edge is a curved surface, it is necessary to measure the bright line width from a plurality of angles in order to obtain a film with less thickness unevenness by grasping the shape of the lip edge. It was.

  In the present invention, since the lip edge 1c of the mold 1 is formed of a flat portion formed by chamfering, the bright line width may be measured from a direction substantially perpendicular to the lip edge 1c.

  As a method for processing the lip edge, there is a method in which the lip edge is manually polished with a grindstone or wrapping paper before and after the land surface 1a and the top surface 1b are mechanically ground. By performing manual polishing, it is possible to suppress the occurrence of lip edge burrs and the like due to mechanical grinding in the subsequent process.

  Next, chamfering is performed. The chamfering method is not particularly limited, but chamfering by machining is generally performed, and chamfering by hand polishing is preferably performed with high polishing accuracy.

  The chamfering method by machining is not particularly limited, but there are a method of grinding a grinding wheel for mechanical grinding to a chamfering angle in advance and performing mechanical grinding with this grinding stone, a method of performing mechanical grinding by inclining a mold by a chamfering angle, and the like. Can be mentioned.

  In the present invention, rather than reducing the average value of the bright line width, it is very important to make the bright line width uniform in the length direction X of the lip edge and to reduce the maximum value of the bright line width difference.

  In this invention, the average value in the length direction X of the lip edge 1c of the bright line width which is the width direction dimension of the lip edge 1c measured as described above is 5 to 50 μm. The smaller the bright line width, the more difficult it is for the staying resin, which is generally called die grease, that causes die lines to adhere to the lip edge. However, if the bright line width is too small, a lip edge defect is likely to occur in the lip edge grinding process, and a die line due to the defect may occur when a film is formed using a mold. . Therefore, in the present invention, the average value of the bright line width is in the above range.

  In the present invention, the maximum value of the bright line width difference measured as described above is 2 μm / 5 mm or less. If the maximum value of the bright line width difference is larger than 2 μm / 5 mm, the thickness unevenness of the film increases when the film is formed using a mold.

  In this invention, the average value in the length direction X of the lip edge 1c of the edge width which is the dimension of the edge parts 4 and 5 along the width direction Y of the lip edge 1c measured as described above is 2 μm or less. If the average value of the edge width is larger than 2 μm, the thickness unevenness of the film increases when the film is formed using a mold.

  In the mold 1, the internal angle θ formed by the top surface 1b and the lip edge 1c is 135 degrees. The internal angle θ between the top surface and the lip edge affects the processing accuracy of the lip edge and the generation of eye grease during film production, and is preferably in the range of 110 to 160 degrees, more preferably 120 to 150. Degrees, most preferably 135 degrees. However, even when the internal angle θ between the top surface and the lip edge is different from 135 degrees, for example, in the range of 110 to 160 degrees, the average value of the edge width of the lip edge is within the above range. There must be.

  The thermoplastic resin used in the production of the film is not particularly limited, but preferably an amorphous thermoplastic resin is used. An amorphous thermoplastic resin is a polymer that maintains an amorphous state that can hardly take a crystal structure, and examples thereof include polysulfone, polymethyl methacrylate, polystyrene, polycarbonate, polyvinyl chloride, and norbornene resins. . As for the said amorphous thermoplastic resin, only 1 type may be used and 2 or more types may be used together.

  In the production of the film, various additives may be added to the thermoplastic resin as necessary as long as the achievement of the object of the present invention is not hindered. Examples of such additives include various additives that prevent deterioration of the thermoplastic resin and improve the heat resistance, ultraviolet resistance, smoothness, etc. of the molded optical film. Antioxidants, lactone-based thermal deterioration inhibitors, benzophenone-based, benzotriazole-based, acrylonitrile-based ultraviolet absorbers; aliphatic alcohol ester-based, polyhydric alcohol partial ester-based and partial ether-based lubricants; Examples thereof include an antistatic agent such as an amine. These additives may be added alone or in combination of two or more.

  On the lip land surface of the mold, the straightness is preferably less than 10 μm, more preferably 5 μm or less, and the surface roughness is 0.1 μm or less as the Ry value defined in JIS B 0601. desirable. Further, it is desirable that there are no pits or pinholes, and the size of the lip edge chip is preferably less than 15 μm from the edge tip toward the inflow direction.

  As the material of the mold, a material having high hardness is preferable. In particular, the higher the hardness of the lip land as the die exit, the higher the machining accuracy such as the straightness, which is preferable. Usually, a surface treatment is applied to the mold, particularly the lip land surface. Although it does not specifically limit as a kind of surface treatment, Hard chrome plating (HCr), tungsten carbide (WC) electroless nickel, etc. are mentioned.

  In the present invention, the thermoplastic resin is extruded into a sheet form from a mold attached to an extruder, and then is in close contact with a cooling roll. FIG. 4 is a schematic configuration diagram of an apparatus in which the mold 12 according to the present invention is used and used for manufacturing a thermoplastic resin film. As shown in FIG. 4, the thermoplastic resin is extruded from the extruder 11 and supplied to the mold 12. A thermoplastic resin is formed into a film by the mold 12, and the film 15 is discharged, brought into contact with the cooling roll 13, and cooled. Reference numeral 14 denotes a touch roll, which is provided to bring the film 15 into contact with the cooling roll 13. The film 15 thus obtained is wound up through rolls 16 and 17.

  If a film is manufactured using the metal mold | die which concerns on this invention, the thickness nonuniformity of the film 15 can be reduced effectively. Here, the thickness unevenness means an absolute value of a difference between a thickness at a certain measurement point and a thickness at a position separated by 5 mm in the width direction of the film 15. In addition, the width direction of a film is comprised along the length direction X of the lip edge 1c.

  The semi-molten film 15 is discharged from the outlet of the mold 12, and the film 15 is brought into contact with the cooling roll 13. Here, the distance from the outlet of the mold 12 to the contact point where the film 15 contacts the cooling roll 13, that is, the air gap is preferably short. The shorter the air gap, the more the thickness variation due to disturbance can be reduced. Therefore, the air gap is desirably 70 mm or less.

  Further, when the film 15 comes into contact with the cooling roll 13, it is desirable that air does not enter between the cooling roll 13 and the film 15 and that the cooling rate is uniform over the entire surface. Therefore, it is desirable to press the film 15 toward the cooling roll 13 by pressing means such as the touch roll 14 in the vicinity of the downstream side of the contact.

  The pressing means is not limited to the touch roll 14, and an air knife or electrostatic pinning may be used. However, it is desirable to use a touch roll having a surface made of an elastic material because it is excellent in stability and the film 15 can be uniformly pressed against the cooling roll 13.

  Although the temperature of a cooling roll changes also with the kind of resin which comprises the film 15, when the glass transition point of resin currently used is set to Tg, it is desirable that it is the range of Tg-10 degreeC-Tg-100 degreeC. .

  In order to ensure the smoothness and transparency of the film, the surface roughness of the cooling roll 13 is 0.5 μm or less, preferably 0.3 μm or less, as the Ry value defined in JIS B0601. Although the said cooling roll 13 can be comprised with various materials, Preferably it consists of a metal, for example, what is comprised, for example by carbon steel, stainless steel, etc. is used suitably. When the cooling roll 13 made of metal is used, the temperature of the cooling roll 13 can be quickly maintained at a constant temperature, and the film 15 can be efficiently cooled.

  If the temperature of the mold 12 varies, the fluidity of the resin changes, so it is desirable that the temperature of the mold 12 is stable. Preferably, it is desirable that the temperature of the mold 12 at the portion contacting the molten resin constituting the film 15 is kept within the set temperature ± 0.5 ° C., more preferably within the set temperature ± 0.2 ° C. .

  In general, the roll temperature greatly affects the solidification point of the resin. Therefore, it is desirable to have a structure in which a temperature adjustment mechanism is connected to or built in the shaft core portion of the cooling roll 13 so that the cooling roll 13 can be adjusted to various temperatures. As a preferable temperature adjusting means, a temperature adjusting means of an electric heating system in which a sheathed heater is incorporated in the shaft core portion and heated so as to set the cooling roll 13 to an appropriate temperature, or a temperature adjusting means by electromagnetic induction action by an induction heating coil. Further, temperature adjusting means such as a heat medium circulation heating method in which a heat medium for temperature control is circulated through a flow path provided in the shaft core portion to heat the cooling roll to a set temperature can be used. Particularly preferred is a heat medium circulation heating method, and a gas or a liquid such as water or oil may be used as the heat medium. It is preferable to use a liquid such as water or oil having a large heat capacity. Preferable examples of such a heat medium flow path include those having a two-row spiral structure or a four-row spiral structure inside.

  Hereinafter, the present invention will be clarified by describing specific examples of the present invention.

(Film production)
A thermoplastic norbornene resin (manufactured by Nippon Zeon Co., Ltd., trade name “ZEONOR1420”, Tg = 135 ° C.) was prepared and pre-dried at a temperature of 110 ° C. for 3 hours.

  A film was obtained by extrusion molding using the apparatus schematically shown in FIG. In addition, the specification of the manufacturing apparatus shown in FIG. 4 is as follows.

Extruder 11... Single-screw extruder Mold 12... Effective width 1800 mm, single-sided bending type automatic die, flow channel surface treatment = HCr plating and WC spraying were prepared.

    Cooling roll 13: A three-roll system, an effective width of 1900 mm, and a heat medium temperature adjusting mechanism. Oil was used as the heat medium.

    Touch roll 14: A metal core roll with rubber lining.

  Using the above production apparatus, the extrusion speed from the extruder 11 is 120 kg / hour, the temperature of the mold 12 is 280 ° C., the temperature of the cooling roll 13 is 120 ° C., the temperature of the touch roll 14 is 110 ° C., and the film is effective. A film was manufactured by extrusion molding with a width of 1400 mm and an air gap of 65 mm.

(Measurement of bright line width)
The emission line width was measured using a microscope (manufactured by Keyence Corporation, Digital HF microscope VH8000). FIG. 2B is a diagram for explaining a method of measuring the bright line width. The microscope 6 is arranged so that light can be irradiated from a direction inclined by 45 degrees toward the lip edge 1c from the direction orthogonal to the top surface 1b, that is, from a direction substantially orthogonal to the lip edge 1c. With the microscope 6, the bright line width, which is the width of the light along the width direction of the lip edge 1c, reflected at the lip edge 1c was measured while irradiating the lip edge 1c with constant light. Moreover, the measurement of the bright line width difference was performed as follows.

  While the microscope 6 was slid in the length direction X of the lip edge 1c at intervals of 5 mm, the bright line width of the lip edge 1c was measured at each measurement position at intervals of 5 mm as described above. Also, the absolute value of the difference between the measured values of the adjacent bright line widths measured at intervals of 5 mm was calculated as the bright line width difference.

  Further, a microscope is arranged so that light can be emitted from a direction inclined at an angle of 75 degrees toward the lip edge 1c from the direction perpendicular to the top surface 1b, and the bright line width and the bright line width difference are reduced as described above. It was measured.

(Measurement of edge width)
The edge width was measured using a microscope (manufactured by Keyence Corporation, Digital HF microscope VH8000). The microscope 6 is arranged so that light can be irradiated from a direction inclined by 45 degrees toward the lip edge 1c from the direction orthogonal to the top surface 1b, that is, from a direction substantially orthogonal to the lip edge 1c. As shown in FIG. 3, when viewed from the microscope 6, shining portions shown shaded are seen on both side edges of the bright line width of the width A of the lip edge 1 c. The width B of the edges 4 and 5 along the width direction was measured as the edge width. In addition, the width of the edge parts 4 and 5 was measured as described above at each measurement position at intervals of 5 mm while sliding the microscope 6 at intervals of 5 mm in the length direction X of the lip edge 1c.

  Furthermore, the microscope was arranged so that light could be irradiated from a direction inclined at an angle of 75 degrees toward the lip edge 1c from the direction orthogonal to the top surface 1b, and the edge width was measured as described above.

(Evaluation of film)
About the film obtained as mentioned above, the thickness of the film was measured using the film thickness measuring device (the Seiko EM company make, contact-type thickness measuring device Millitron1240). Further, the thickness was measured at intervals of 5 mm in the width direction of the film, the film thickness was measured at each measurement position at intervals of 5 mm, and the average value was obtained. Moreover, the absolute value of the difference of the thickness of the adjacent measurement point of 5 mm space | interval was each calculated, and it was set as the film thickness difference, and the film thickness difference which is the largest value was made into the film thickness difference maximum value. In addition, since the width direction of the film is formed along the length direction X of the lip edge, when the thickness unevenness is large in the width direction of the film, the shape of the mold is not good in the length direction X of the lip edge. Means uniform.

  Moreover, the thickness unevenness was determined according to the following evaluation criteria.

Thickness nonuniformity judgment standard ○: 0.1 μm / 5 mm or less ×: Results exceeding 0.1 μm / 5 mm are shown in Table 1 below.

  As is apparent from Table 1, in the molds of Examples 1 and 2, the direction tilted at an angle of 45 degrees toward the lip edge 1c from the direction orthogonal to the top surface 1b, that is, the lip edge 1c. When observed from a substantially perpendicular direction, the average values of the bright line width were 20.5 and 25.0 μm, the maximum value of the bright line width difference was 2 μm / 5 mm or less, and the average value of the edge width was 2 μm or less. On the other hand, when observed from a direction inclined 75 degrees toward the lip edge 1c from the direction orthogonal to the top surface 1b, the bright line width and the edge width on one side were not observed. In the film manufactured using the mold of this example, the maximum thickness unevenness was as small as 0.10 μm / 5 mm or less.

  On the other hand, in the mold of Comparative Example 1, when observed from a direction inclined at an angle of 45 degrees from the direction orthogonal to the top surface 1b to the lip edge 1c side, the bright line width is 26.5 μm, and the bright line width difference is maximum. The value was 1.0 μm / 5 mm. On the other hand, when observed from a direction inclined at an angle of 75 degrees toward the lip edge 1c from the direction perpendicular to the top surface 1b, the edge width on one side is not observed, and the bright line width is 11.0 μm. The maximum difference was 0.9 μm / 5 mm. In the film manufactured using the mold of this comparative example, the maximum thickness unevenness was as large as 0.18 μm / 5 mm.

  Therefore, as is apparent from the evaluation of the examples and comparative examples, a lip edge composed of a flat portion formed by chamfering is provided, and the bright line is observed when observed from a direction substantially orthogonal to the lip edge 1c. By using a mold having an average width of 5 to 50 μm, a maximum bright line width difference of 2 μm / 5 mm or less, and an average edge width of 2 μm or less, the thickness accuracy of the film is increased. I know you get.

The typical sectional view showing the channel side of the metallic mold used by the present invention. (A) And (b) is a schematic perspective view for demonstrating the bright line width of the metal mold | die used in this invention, and a schematic perspective view for demonstrating the method to measure a bright line width. The schematic diagram for demonstrating the method to measure an edge part width | variety. The schematic block diagram of the manufacturing apparatus which is equipped with the metal mold | die which concerns on this invention and is used for manufacture of a film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mold 1a ... Land surface 1b ... Top surface 1c ... Lip edge 2 ... Flow path 2a ... Discharge port 4,5 ... Edge 6 ... Microscope 11 ... Extruder 12 ... Mold 13 ... Cooling roll 14 ... Touch roll DESCRIPTION OF SYMBOLS 15 ... Film 16, 17 ... Roll A ... Bright line width B ... Edge width X ... Length direction Y ... Width direction

Claims (2)

A mold that is used for extrusion molding of a thermoplastic resin and is provided with a lip edge composed of a flat portion formed by chamfering,
The lip edge has a length direction and a width direction, and the mold has rounded edges extending in the length direction of the lip edge on both side edges of the lip edge,
When observed from a direction substantially perpendicular to the lip edge, the average value of the bright line width, which is the width direction dimension of the lip edge, in the length direction of the lip edge is 5 to 50 μm, and the maximum bright line width difference is The value is 2 μm / 5 mm or less, and the average value in the length direction of the lip edge of the edge width, which is the dimension of the edge along the width direction of the lip edge, is 2 μm or less, optical film-forming die. A method for producing an optical thermoplastic resin film, comprising: extruding a thermoplastic resin using the mold according to claim 1.

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