JP2005231323A - Method for producing thermoplastic resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a film, which is capable of controlling a thickness at a width direction upon producing a film having a wide surface. <P>SOLUTION: A thermoplastic resin is melted by an extruder and extruded through a dice provided in the extruder to produce a sheet and the extruded thermoplastic resin sheet is recovered by adhering tightly to at least one cooling drum. A heat discharge amount from the whole surface except a lip part of the dice is adjusted to 500 W/m<SP>2</SP>or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a thermoplastic resin film, and more particularly to a method for producing a film capable of efficiently controlling thickness unevenness in the width direction when a film having a large area is produced.

  A film made of a thermoplastic resin used in a device that handles polarized light such as a liquid crystal display device is required to have optical homogeneity in addition to being optically transparent and low in birefringence. Therefore, in the case of a polarizer protective film for protecting a polarizer made of highly stretched polyvinyl alcohol or a film substrate for a plastic liquid crystal display device in which the glass substrate is replaced with a resin film, 1) birefringence and thickness 2) that the retardation of the film is small, 2) that the retardation of the film is difficult to change due to external stress, etc. 3) that the unevenness of these retardations is small in the plane in the plane direction and in the thickness direction. 4) It is required that the phenomenon of image distortion due to the so-called lens effect due to the unevenness of the film surface hardly occurs. That is, if the phase difference is large, the phase difference changes due to external stress, etc., the change of the phase difference in the surface is large, or there is a lens effect due to the unevenness of the film surface, the image quality of the liquid crystal display device is remarkably improved. Reduce. In other words, color jumping phenomenon such as partial color fading, and adverse effects such as image distortion occur.

  Therefore, as an optical film made of a thermoplastic resin used for a liquid crystal display device, an amorphous thermoplastic resin is a suitable material, such as engineering plastics such as polycarbonate, polyarylate, polysulfone, and polyethersulfone. Films made of cellulose plastics such as triacetylcellulose are known. When these plastic films are produced, various stresses are generated in the film being molded due to melt flow of the plastic, solvent drying shrinkage, heat shrinkage, conveyance stress, and the like. Therefore, a phase difference is likely to remain in the obtained film due to birefringence due to molecular orientation induced by these stresses. Therefore, there is a problem that a special process is applied to the film such as thermal annealing as necessary to reduce the remaining phase difference and the manufacturing process becomes complicated. Further, even when a film having a reduced remaining retardation is used, a new retardation is generated due to stress or deformation generated during the subsequent processing of the film. Furthermore, when a plastic film is used as a polarizing protective film, it is known that an unfavorable phase difference is generated in the film due to shrinkage stress of the polarizer, and the polarizing performance of the polarizing film is adversely affected.

  In order to solve these problems, an attempt has been made to obtain a plastic film having a smaller polarization, that is, a phase difference due to molecular orientation is less likely to occur. For example, a cyclic olefin film and an olefin film having a maleimide component have been proposed.

  Further, in the optical film application, the uniformity of the thickness of the film is particularly required due to optical homogeneity. For this reason, the film used for these uses has been conventionally produced by a solution casting method having excellent thickness uniformity. However, in recent years, it has been pointed out that the solvent casting method is contaminated with the environment by the solvent and the productivity is low, and the solution casting method is being changed to the melt extrusion method. However, until now, films formed by the melt extrusion method have a large thickness unevenness and are liable to cause die line, so that a polarizing plate protective film that requires strict thickness uniformity and optical characteristics is required. As a method for producing a film for optical use such as a retardation film, a melt extrusion method has hardly been put to practical use.

  Causes of uneven thickness in the melt extrusion method include fluctuations in the discharge rate when the resin is extruded into a sheet on the cooling drum by melt extrusion, film vibration of the melted sheet between the die and the cooling drum, cooling For example, uneven rotation of the drum. Therefore, various methods have been tried to improve the thickness unevenness.

  Patent Document 1 includes a thermoplastic polymer having a glass transition temperature of 150 ° C. or higher, a sheet thickness of 150 to 1000 μm, an in-plane thickness tolerance (Rmax) of 20 μm or less, and a sheet surface roughness of 0.1 μm or less. And a thermoplastic polymer sheet having a planar retardation of 20 nm or less is disclosed. As a preferred method for producing this sheet, a thermoplastic polymer is melt-extruded in a sheet form from a T die or a coat hanger die, and moved while maintaining the surface temperature difference between the front side and the back side of the molten sheet within 15 ° C. Then, it is disclosed that the molten sheet is subjected to a cooling step to be solidified.

Further, Patent Document 2 discloses that a thermoplastic polymer melt-extruded from a T die or a coat hanger die has a temperature (V1) of a heating portion of Tg ≦ V1 with respect to the glass transition temperature (Tg) of the thermoplastic polymer. ≦ Tg + 100 (° C.) in an atmosphere flowing on a roll whose surface is mirror-finished, moved in the heating part with the rotation of the roll, and the thermoplastic polymer sheet on the mirror surface of the roll, roll temperature (V2) Is transferred to a nip roll of Tg−30 ° C. ≦ Tg + 30 (° C.) to transfer the mirror surface, and then moved while being in close contact with the roll, and the roll temperature (V3) when peeling the thermoplastic polymer sheet from the roll is V3 < A method for producing a thermoplastic polymer sheet, which is Tg-100 (° C.) and is in the range of V3 <V2 <V1, is disclosed.
Recently, a display device such as a liquid crystal display device has been increased in size, and a large area of a member such as a film used for the display device has been required. When the film is used for a small screen such as a digital camera or a mobile phone, the uneven thickness in the width direction is not a problem. However, when the film is used for a large screen such as a large television, the uneven thickness in the width direction is also a problem. However, in order to obtain a film for use in a large screen, it has been found that in the method described in the above publication, film thickness unevenness occurs in a direction perpendicular to the longitudinal direction, that is, in the width direction. Therefore, a method for obtaining a large area film capable of efficiently controlling not only the longitudinal direction but also the thickness unevenness in the width direction is desired.

Japanese Patent Laid-Open No. 2000-219752 JP 2000-355040 A

  Therefore, an object of the present invention is to provide a film manufacturing method capable of efficiently controlling the thickness unevenness in the width direction when manufacturing a film having a large area.

  As a result of diligent studies to achieve the above object, the present inventor, in addition to having a complicated structure, is heated to a temperature as high as 200 ° C. or higher during melt extrusion, It was found that the amount of heat radiation was different at each part of the die. Then, it was found that the resin temperature unevenness inside the die was caused by the difference in the heat radiation amount of the die, and this resin temperature unevenness caused the resin flow unevenness, which in turn caused the thickness unevenness in the width direction. Then, it discovered that the said objective could be achieved by making the heat radiation amount of the die | dye to be used into a specific range, and also advanced research based on this knowledge, and came to complete this invention.

Thus, according to the present invention,
(1) A thermoplastic resin is melted by an extruder and extruded from a die attached to the extruder into a sheet shape, and the extruded sheet-shaped thermoplastic resin is formed in close contact with at least one cooling drum. A method for producing a thermoplastic resin film, wherein the amount of heat released from the entire surface of the die excluding the lip portion of the die is within 500 W / m ² ,
(2) The method for producing a thermoplastic resin film according to the above (1), wherein the variation in the amount of heat radiation from the entire surface of the die excluding the lip portion of the die is 200 W / m ^{2 or} less.
(3) The manufacturing method according to (1) or (2), wherein the width of the die is 1000 mm or more,
And (4) The production method according to any one of (1) to (3), wherein the thermoplastic resin is a polymer resin having an alicyclic structure.

  According to the present invention, it is possible to efficiently obtain a film having a large area with less uneven thickness, particularly less uneven thickness in the width direction.

Examples of the thermoplastic resin used in the present invention include polymethyl methacrylate resins, polycarbonate resins, polystyrene resins, polymer resins having an alicyclic structure, cellulose resins, vinyl chloride resins, polysulfone resins, poly resins. Examples include ether sulfone-based resins. Among these, a polymer resin having an alicyclic structure is preferable. When a polymer resin having an alicyclic structure is used, a film having high fluidity, good leveling property of film thickness during film formation, and good thickness accuracy can be obtained.
The alicyclic structure-containing polymer resin suitable for the present invention has an alicyclic structure in the main chain and / or side chain, and has an alicyclic structure in the main chain from the viewpoint of mechanical strength, heat resistance and the like. The thing containing is preferable.

  Examples of the alicyclic structure of the polymer include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene) structure. From the viewpoint of mechanical strength and heat resistance, cycloalkane. A structure or a cycloalkene structure is preferable, and a cycloalkane structure is most preferable. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, more preferably 5 to 15 in the mechanical strength, The properties of heat resistance and film formability are highly balanced and suitable. The proportion of the repeating unit containing the alicyclic structure in the alicyclic structure-containing polymer used in the present invention may be appropriately selected according to the purpose of use, but is preferably 30% by weight or more, Preferably it is 50% by weight or more, particularly preferably 70% by weight or more, and most preferably 90% by weight or more. It is preferable from the viewpoints of transparency and heat resistance of the film that the ratio of the repeating unit having an alicyclic structure in the polymer resin having an alicyclic structure is in this range.

Specifically, the polymer resin having an alicyclic structure includes (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, and (4) vinyl. Examples thereof include alicyclic hydrocarbon polymers and hydrogenated products thereof. Among these, norbornene-based polymers are more preferable from the viewpoints of transparency and moldability.
Specific examples of the norbornene-based polymer include ring-opening polymers of norbornene-based monomers, ring-opening copolymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization, and hydrogenated products thereof, norbornene-based polymers Examples include addition polymers of monomers and addition copolymers with other monomers copolymerizable with norbornene-based monomers. Among these, from the viewpoint of transparency, a ring-opening (co) polymer hydrogenated product of a norbornene-based monomer is most preferable.
The polymer resin having the alicyclic structure is selected from known polymers disclosed in, for example, JP-A-2002-332102.

Among norbornene polymers suitably used in the present invention, as a repeating unit, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1] are used. ^2,5 ] decane-7,9-diyl-ethylene structure, the content of these repeating units is 90% by weight or more based on the total repeating units of the thermoplastic norbornene resin, and X It is preferable that the ratio of the content ratio of Y and the content ratio of Y is 100: 0 to 40:60 in terms of a weight ratio of X: Y. By using such a resin, it is possible to obtain an optical film that has no dimensional change in the long term and is excellent in stability of optical characteristics.

Examples of the monomer having the X structure as a repeating unit as a polymer include norbornene monomers having a structure in which a 5-membered ring is bonded to a norbornene ring. More specifically, tricyclo [4.3.0.1 ^2,5] deca-3,7-diene (trivial name: dicyclopentadiene) and their derivatives (those having a substituent on the ring), 7,8-tricyclo [4.3.0.1 ^{0, 5} ] Dec-3-ene (common name: methanotetrahydrofluorene) and its derivatives.
Moreover, as a monomer which has a structure of Y as a repeating unit as a polymer, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene (common name: tetracyclododecene) and its derivatives (having a substituent in the ring).
Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different and a plurality may be bonded to the ring. Norbornene monomers can be used alone or in combination of two or more.

  Specifically, as a means for obtaining such a norbornene-based polymer, a) a copolymerization ratio of a monomer having a repeating unit with the structure of X as a polymer and a monomer having a repeating unit with the structure of Y as a polymer And a method of hydrogenating unsaturated bonds in the polymer as necessary, and b) a polymer having a repeating unit of the structure of X and a polymer having a repeating unit of the structure of Y The method of controlling by blend ratio is mentioned.

  The molecular weight of the thermoplastic resin used in the present invention was measured by gel permeation chromatography (hereinafter abbreviated as “GPC”) using cyclohexane (toluene when the polymer resin is not dissolved) as a solvent. The weight average molecular weight (Mw) in terms of isoprene is usually 10,000 to 100,000, preferably 15,000 to 80,000, more preferably 20,000 to 50,000. When the weight average molecular weight is in such a range, the mechanical strength and moldability of the film are highly balanced and suitable.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the thermoplastic resin used in the present invention is not particularly limited, but is usually 1.0 to 10.0, preferably 1.0 to 4.0, More preferably, it is the range of 1.2-3.5.

  In the present invention, other compounding agents may be added to the thermoplastic resin. The compounding agent is not particularly limited, but inorganic fine particles; antioxidants, heat stabilizers, light stabilizers, weathering stabilizers, UV absorbers, near infrared absorbers and other stabilizers; resins such as lubricants and plasticizers Modifiers; coloring agents such as dyes and pigments; antistatic agents and the like. These compounding agents can be used alone or in combination of two or more, and the compounding amount is appropriately selected within a range not impairing the object of the present invention.

  Examples of the antioxidant include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic antioxidants are preferable. By blending these antioxidants, film coloring and strength reduction due to oxidative degradation during film formation can be prevented without lowering transparency, low water absorption and the like. These antioxidants can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention. The amount is usually 0.001 to 5 parts by weight, preferably 0.01 to 1 part by weight.

  Examples of the die include known dies such as a T die and a coat hanger die. Examples of the material of the die include SCM steel and stainless steel such as SUS, but are not limited thereto.

In the present invention, the amount of heat released from the entire surface of the die excluding the lip portion of the die is set to 500 W / m ^{2 or} less, preferably 300 W / m ^{2 or} less. By making the amount of heat released from the entire surface of the die within the above range, the resin temperature unevenness inside the die (temperature difference between the vicinity of the heater and the part that is not) will be reduced, and the molten resin extruded from the die will not be uneven and melted. Since the flow unevenness until the resin in the state is cooled and fixed can be reduced, the thickness unevenness can be reduced.
The amount of heat released from the entire surface of the die excluding the lip portion of the die is determined as follows.
First, the die is divided into a die side surface portion, a die longitudinal portion, and a die upper surface portion, each portion is divided into predetermined sections, and the die surface temperature of each section is measured using a thermocouple.
Next, the heat dissipation amount Q of each section is calculated from the following formula (1).
Formula (1): Q (kcal / h) = U × A × ΔT
In the above formula (1), U is the overall heat transfer coefficient (kcal / m ² / h / ° C.), A is the heat transfer area, that is, the area (m ² ) of each section, and ΔT is the die surface temperature and the atmosphere around the die. It is the difference (° C) from the air temperature.
U is calculated in advance from the following equation (2).
Formula (2): U = Q ′ / A / ΔT
In the above formula (2), Q ′ is the heating amount of the heater in a constant temperature environment without flowing resin through the die.

In the present invention, the unevenness of the heat radiation from the entire surface of the die excluding the lip portion of the die is preferably 200 W / m ^{2 or} less, and more preferably 150 W / m ^{2 or} less.
Dispersion of heat dissipation from the entire surface of the die excluding the lip of the die is calculated by calculating the average heat dissipation from the heat dissipation of each category measured above, and the average heat dissipation and the maximum heat dissipation in each category or The maximum value among the differences from the minimum heat dissipation.

  The means for keeping the amount of heat released from the die surface within the above range is to keep the die warm by using a heat insulating material or the like; to reduce the temperature difference between the die temperature and the temperature around the die; It is possible to use an automatic bolt that can be remotely operated with a chalk bolt to keep the die warm without any gaps.

  The material of the die slip is not particularly limited, but hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, tungsten carbide, aluminum oxide, chromium oxide, super steel, etc. are sprayed or plated, Buffing as surface processing, lapping using a # 1000 or higher whetstone, flat cutting using a # 1000 or higher diamond whetstone (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. It is preferable to use a processed material. By using the above materials as the die slip material, the die line formed in the longitudinal direction of the film can be made inconspicuous when the film is mounted on a display device.

  Further, it is preferable to use volatile compounds such as amine nitrates, carboxylates and carbonates as antirust agents for die slip. Specific examples include dicyclohexylammonium nitrite, diisopropylammonium nitrite, dicyclohexylammonium caprylate, cyclohexylammonium carbamate, and cyclohexylamine carbonate. By using the above as the antirust agent for die slip, the die line formed in the longitudinal direction of the film can be made inconspicuous when the film is mounted on a display device.

  In the present invention, it is suitable when a die having a width of 1000 mm or more is used.

  Moreover, in this invention, it is preferable to predry the thermoplastic resin used before shape | molding a film. The preliminary drying is performed with a hot air dryer or the like, for example, in the form of pellets or the like. The drying temperature is preferably 100 ° C. or more, and the drying time is preferably 2 hours or more. By performing preliminary drying, the amount of volatile components in the film can be reduced, and foaming of the extruded thermoplastic resin can be prevented.

  In the present invention, the melting temperature of the thermoplastic resin in the extruder having a die is preferably 80 to 180 ° C. higher than the glass transition temperature of the resin, and 100 to 150 ° C. higher than the glass transition temperature. More preferably. If the melting temperature in the extruder is excessively low, the fluidity of the resin may be insufficient. Conversely, if the melting temperature is excessively high, the resin may be deteriorated.

A method for bringing the sheet-like thermoplastic resin extruded from the opening of the die into close contact with the cooling drum is not particularly limited, and examples thereof include an air knife method, a vacuum box method, and an electrostatic contact method.
The number of cooling drums is not particularly limited, but is usually two or more. Examples of the arrangement method of the cooling drum include, but are not limited to, a linear type, a Z type, and an L type. Further, the way of passing the sheet-like thermoplastic resin extruded from the opening of the die through the cooling drum is not particularly limited.

  In the present invention, the degree of adhesion of the extruded sheet-like thermoplastic resin to the cooling drum varies depending on the temperature of the cooling drum. If the temperature of the cooling drum is raised, adhesion will be improved, but if the temperature is raised too much, the sheet-like thermoplastic resin may not be peeled off from the cooling drum, and there is a possibility that a problem of winding around the drum may occur. Therefore, the cooling drum temperature is preferably (Tg + 30) ° C. or lower, more preferably (Tg−5) ° C. to (Tg−45) ° C., where Tg (° C.) is the glass transition temperature of the thermoplastic resin extruded from the die. Make it a range. By doing so, problems such as slipping and scratches can be prevented.

  In the present invention, the thermoplastic resin may be passed through a gear pump or a filter before the thermoplastic resin is melted in an extruder and extruded from a die attached to the extruder.

  The film obtained by the present invention is not particularly limited as long as it is a large-area film, but is particularly suitable for optical applications. Among them, for example, a polarizing plate protective film, a retardation film, a brightness enhancement film, a liquid crystal substrate, It is particularly suitable for a member used in a display device such as a liquid crystal display device such as a transparent conductive film, a touch panel substrate, a light diffusion sheet, and a prism sheet.

  When using the film obtained by this invention as a polarizing plate protective film, this is laminated | stacked through the suitable adhesive agent on the single side | surface or both surfaces of a polarizing plate. The polarizing plate can be obtained by doping a polyvinyl alcohol film with iodine or the like and then stretching it. As the adhesive layer, an adhesive having a base polymer of an appropriate polymer such as acrylic polymer, silicone polymer, polyester, polyurethane, polyether or synthetic rubber is used.

When the film obtained by the present invention is used as a retardation film, the film obtained by the present invention is stretched.
The stretching method includes a uniaxial stretching method such as a method of uniaxial stretching in the longitudinal direction using a difference in peripheral speed between rolls, a uniaxial stretching method in the transverse direction using a tenter stretching machine, and the interval between fixed clips. At the same time as stretching in the longitudinal direction using the guide rail, the biaxial stretching method that stretches in the transverse direction depending on the spread angle of the guide rail, and the longitudinal direction using the difference in the peripheral speed between the rolls, and both ends thereof A biaxial stretching method such as a sequential biaxial stretching method in which a clip is gripped and stretched in the transverse direction using a tenter stretching machine; a feed force, a pulling force, or a pulling force at different speeds can be applied in the lateral or longitudinal direction. And a method of continuously and obliquely stretching in the direction of an arbitrary angle θ with respect to the width direction of the film using a tenter stretching machine.

  By the method of extending | stretching diagonally, the elongate stretched film which has the slow axis of angle (theta) with respect to the width direction of a film can be obtained. That is, by setting the angle θ to an arbitrary value, the refractive index in the in-plane slow axis direction, the refractive index in the direction perpendicular to the in-plane slow axis, and the refractive index in the thickness direction are set to desired values. Can be. For example, a ½ wavelength plate that gives a ½ phase difference with respect to a predetermined wavelength and a ¼ wavelength plate that gives a ¼ phase difference can be used.

  The method of obliquely stretching is not particularly limited as long as it is continuously stretched in the direction of an angle of 1 to 50 degrees with respect to the width direction, and the polymer orientation axis is inclined to a desired angle. The method can be adopted. Examples of oblique stretching methods that can be used in the present invention include, for example, JP-A-50-83482, JP-A-2-113920, JP-A-3-182701, JP-A-2000-9912, Examples described in Japanese Unexamined Patent Publication No. 2002-86554, Japanese Unexamined Patent Application Publication No. 2002-22944, and the like.

  The temperature during the stretching treatment is preferably between (Tg-30 ° C) and (Tg + 60 ° C), more preferably (Tg-10 ° C), where Tg is the glass transition temperature of the amorphous thermoplastic resin. To (Tg + 50 ° C.). Moreover, a draw ratio is 1.01-30 times normally, Preferably it is 1.01-10 times, More preferably, it is 1.01-5 times.

The retardation film includes a half-wave plate that gives a half-wave phase difference with respect to a predetermined wavelength, a quarter-wave plate that gives a quarter-wave phase difference with respect to a predetermined wavelength, / Broadband quarter-wave plate with a half-wave plate and quarter-wave plate bonded at a specific angle, positive retarder (retardation device having a positive phase difference in the direction perpendicular to the element surface), negative letterer (A phase difference element having a negative phase difference in a direction perpendicular to the element surface).
The thickness of the retardation film is usually 30 to 200 μm.

  In the retardation film, a plurality of retardation films may be laminated so that each slow axis intersects at a predetermined angle. When laminating, a known laminating method may be used. Moreover, you may use an adhesive etc. in the case of lamination | stacking.

The present invention will be described in more detail with reference to reference examples, examples and comparative examples, but the present invention is not limited to the following examples.
Parts and% are based on weight unless otherwise specified.
Evaluation in this example was performed by the following method.
(1) Dies heat dissipation and variations The dice heat dissipation is measured as follows.
First, the die is divided into a die side surface portion, a die longitudinal portion, and a die upper surface portion, each portion is divided into predetermined sections, and the die surface temperature of each section is measured using a thermocouple.
Next, the heat dissipation amount Q of each section is calculated from the following formula (1).
Formula (1): Q (kcal / h) = U × A × ΔT
In the above formula (1), U is the overall heat transfer coefficient (kcal / m ² / h / ° C.), A is the heat transfer area, that is, the area (m ² ) of each section, and ΔT is the die surface temperature and the atmosphere around the die. It is the difference (° C) from the air temperature.
U is calculated in advance from the following equation (2).
Formula (2): U = Q ′ / A / ΔT
In the above formula (2), Q ′ is the heating amount of the heater in a constant temperature environment without flowing resin through the die.
Dispersion of heat dissipation from the entire surface of the die excluding the lip of the die is calculated by calculating the average heat dissipation from the heat dissipation of each category measured above, and the average heat dissipation and the maximum heat dissipation in each category or The maximum value among the differences from the minimum heat dissipation.
(2) The thickness of the film, the thickness unevenness in the width direction of the film, and the standard deviation of the thickness The thickness of the film is obtained by cutting the film into a strip shape (length of 5 m or more) having a width of 50 mm in the width direction. Is measured every 0.48 mm using a ROTARY CALIPER / contact-type thickness meter (manufactured by Meisei Co., Ltd., RC-1-200 / 1000). And let the arithmetic average value of the measured value be the thickness of a film. The standard deviation of the thickness of the film is calculated from the measured thickness value measured every 0.48 mm using the thickness meter.
When the thickness is measured in the width direction, the thickness unevenness in the width direction of the film is represented by the maximum value among the heights from adjacent peaks to valleys or from valleys to peaks.

(Example 1)
Using a hot air dryer in which pellets of norbornene polymer (hydrogenated ring-opening polymer of norbornene monomer, ZEONOR1420R, manufactured by Nippon Zeon Co., Ltd .; glass transition temperature (Tg) is 136 ° C.) were circulated. Dry at 100 ° C. for 4 hours. The pellets were extruded at 260 ° C. from a 50 mm single-screw extruder and a 1850 mm wide T-die equipped with a leaf disk-shaped polymer filter (filtration accuracy 30 μm), and three extruded sheet-form norbornene polymers were obtained. And cooled through a cooling drum (diameter 250 mm, drum temperature 120 ° C., take-off speed 0.35 m / s) to obtain a film 1 having a width of 1500 mm.
The entire die surface excluding the lip portion of the T-die uses a 200 mm thick calcium silicate heat insulating material, and the heat dissipation amount from the entire die surface excluding the die slip portion is 100 W / m ² . Covering to 50 W / m ² .
The thickness of the obtained film 1 was 100 μm, the thickness unevenness in the width direction was 0.5 μm, and the standard deviation was 0.3.

(Comparative Example 1)
A film 2 was obtained by molding in the same manner as in Example 1 except that the die was not covered with a heat insulating material. A film 2 was obtained by molding in the same manner as in Example 1 except that the heat insulating material was not provided. At this time, the heat radiation from the entire surface of the die excluding the die slip portion was 1000 W / m ² , and the uneven heat radiation was 500 W / m ² .
The thickness of the obtained film 2 was 100 μm, the thickness unevenness in the width direction was 1.5 μm, and the standard deviation was 0.3.

The following can be seen from the results of this example and the comparative example. According to the present invention, as shown in Example 1, when a thermoplastic resin film is produced by extruding into a sheet form from a die that is melted by an extruder and attached to the extruder, a die excluding a die slip portion is produced. When the heat radiation amount from the entire surface is 100 W / m ² and the heat radiation unevenness is 50 W / m ² , the thickness unevenness in the width direction of the obtained film is as small as 0.5 μm.
On the other hand, as shown in Comparative Example 1, when the heat radiation amount from the entire surface of the die excluding the die slip portion is 1000 W / m ² and the heat radiation unevenness is 500 W / m ² , the thickness in the width direction is Unevenness is as large as 1.5 μm.

Claims (4)

A process in which a thermoplastic resin is melted by an extruder and extruded from a die attached to the extruder into a sheet shape, and the extruded sheet-shaped thermoplastic resin is brought into close contact with at least one cooling drum and then molded and taken. In the manufacturing method of the thermoplastic resin film which has these, The heat dissipation from the whole die surface except the lip | rip part of the said die shall be 500 W / m < ² > or less, The manufacturing method of the thermoplastic resin film characterized by the above-mentioned. The method for producing a thermoplastic resin film according to claim 1, wherein the variation in heat radiation from the entire surface of the die excluding the lip portion of the die is set to 200 W / m ^{2 or} less. The method for producing a thermoplastic resin film according to claim 1 or 2, wherein the width of the die is 1000 mm or more. The method for producing a thermoplastic resin film according to any one of claims 1 to 3, wherein the thermoplastic resin is a polymer resin having an alicyclic structure.