JP6671495B2 - Method for producing thermoplastic resin film - Google Patents

Description

  The present invention relates to a method for producing a thermoplastic resin film.

Thermoplastic resin films are used in various applications such as optical films and films for protecting the back surface of solar cells.
Examples of the thermoplastic resin film include a cellulose resin film such as a cellulose acylate film, an acrylic resin film, a polycarbonate film, and a cyclic olefin resin film.
These thermoplastic resin films are prepared by melting a raw material resin with an extruder, extruding the resin into a die (for example, a T-die), discharging the extruded resin from the die as a film-like molten resin, and cooling and solidifying the resin (hereinafter, referred to as “the resin”). The film is also formed by a "melt extrusion method").

JP-A-2000-280315 or JP-A-2000-025089 discloses a die apparatus and a lip lower surface cleaning apparatus for a die apparatus used in a method for producing a resin extruded product or a thermoplastic resin film by a conventional melt extrusion method. Described in (1).
JP-A-2000-280315 describes an extruded product made of a cyclic olefin resin having a surface roughness of 0.3 μm or less in terms of a maximum roughness Rt.
Japanese Patent Application Laid-Open No. 2000-025089 discloses a lip lower surface cleaning device for a die device, wherein a frit remover is formed on a lower surface of a flyer rod bar.

  The problem to be solved by one embodiment of the present invention is to provide a method for producing a thermoplastic resin film in which the generation of die lines is suppressed when producing a resin film by a melt extrusion method.

The above object is achieved by the following means.
<1> A film-shaped molten resin is discharged from a die with a die swell ratio of 1.3 or less, and a discharge direction of the film-shaped molten resin from the die discharge port and a film surface direction of the film-shaped molten resin at a die discharge port. The step of contacting the film-like molten resin with a cooling roll while restricting the maximum angle θ to 45 ° or less, and a step of starting take-off, and after the start of take-off, further discharging the film-like molten resin from the die, A step of cooling and winding the discharged film-like molten resin while taking it up with the cooling roll, and a method of manufacturing a thermoplastic resin film.
<2> The above-described regulation is performed by making the auxiliary roll disposed between the die and the cooling roll and the film-shaped molten resin come into contact with each other over the entire width of the film-shaped molten resin. Method for producing a thermoplastic resin film.
<3> The method for producing a thermoplastic resin film according to <1>, wherein the regulation is performed by bringing the regulating plate disposed between the die and the cooling roll into contact with the film-shaped molten resin. .
<4> The above-mentioned regulation is performed by generating wind by a blowing means arranged between the die and the cooling roll, and performing the above-mentioned regulation by contacting the wind with the film-like molten resin. Method for producing a thermoplastic resin film.
<5> In the step of cooling and winding, a touch roll that presses the cooling roll is used, and the resin passes between the cooling roll and the touch roll to any one of <1> to <4>. A method for producing the thermoplastic resin film according to the above.

<6> In the step of starting the take-up, the oxygen concentration at the die discharge port is set to 1% or less from the time when the molten resin is extruded to the die until the time when the film-like molten resin starts to be discharged from the die. > The method for producing a thermoplastic resin film according to any one of <5>.
<7> The method for producing a thermoplastic resin film according to any one of <1> to <6>, wherein the lip portion of the die has a surface energy of 60 mN / m or less.
<8> The method for producing a thermoplastic resin film according to any one of <1> to <7>, wherein an emission line width of an edge portion on a discharge port side of the lip portion of the die is 10 μm or less.
<9> After the step of starting the take-up and before the step of cooling and winding, the angle between the direction of discharge of the film-like molten resin from the die discharge port and the direction of the film surface of the film-like molten resin is 45 °. ° after moving one or both of the die and the cooling roll to a position that is less than or equal to, including the step of removing the regulating means, the thermoplastic resin film according to any one of <1> to <8> Production method.
<10> After the step of removing the regulating means, and before the step of cooling and winding, one or both of the die and the cooling roll are further moved to reduce the distance between the discharge port of the die and the cooling roll. The method for producing a thermoplastic resin film according to <9>, comprising a step of reducing the size.

  According to one embodiment of the present invention, there is provided a method for producing a thermoplastic resin film in which the occurrence of die lines is suppressed when producing a resin film by a melt extrusion method.

FIG. 2 is a schematic cross-sectional view illustrating an example of a cross section in a thickness direction of a thermoplastic resin film 10. FIG. 2 is a schematic perspective view showing an example of a thermoplastic resin film 10 in which a streak-shaped dent D (die line) is generated in a direction of an arrow 20. It is the schematic for demonstrating the place which has started taking over. It is the schematic which shows an example of the whole structure of a film forming apparatus. FIG. 3 is a schematic cross-sectional view for explaining a state of a resin near a discharge port of a die when the resin is discharged. FIG. 3 is a schematic diagram showing a positional relationship when the die 12 and the film-like molten resin 30 at the time of ejection are observed from the film surface direction of the film-like molten resin 30 (the side surface of the die). It is the schematic which shows an example at the time of using two auxiliary rolls in a take-off process. It is the schematic which shows an example at the time of using two restriction | limiting plates in a pick-up process. It is the schematic which shows an example at the time of blowing the wind on both sides of resin from the film surface direction of the film-like molten resin 30. It is the schematic which shows an example when the wind which is blowing in parallel with the discharge direction of a film-like molten resin to one side and the other surface of a resin is observed from the film surface direction of the film-like molten resin 30. It is the schematic which shows the place where wind is blown to resin from both sides of resin in a taking-off process. FIG. 8 is a schematic diagram illustrating an example of a case where a regulating unit removing step and a moving step are performed after a pick-up starting step using two auxiliary rolls 50 illustrated in FIG. 7.

  In the following description, `` to '' representing a numerical range means a range including numerical values described as a lower limit and an upper limit before and after the value, and when a unit is attached only to the upper limit or the lower limit, the It means that the unit is the same in the entire numerical range.

(Method for producing thermoplastic resin film)
The method for producing a thermoplastic resin film according to the present disclosure discharges a film-like molten resin from a die with a die swell ratio of 1.3 or less, and discharges the film-like molten resin from a die discharge port at a die discharge port. A step of bringing the film-shaped molten resin into contact with a cooling roll and starting take-off while regulating the maximum angle θ between the film-form molten resin and the film surface direction to 45 ° or less (hereinafter also referred to as a “take-off start step”) ) And after starting the take-up, further discharging the film-like molten resin from the die, cooling and winding the discharged film-like molten resin with the cooling rolls (hereinafter, also referred to as “film manufacturing step”). ).

2. Description of the Related Art Conventionally, when a film is manufactured by a melt extrusion method using a die, a streak-shaped dent (hereinafter, also referred to as a “die line”) occurs in a discharge direction of the film (a discharge direction of a film-like molten resin from a die). There was a case.
Specifically, as shown in FIGS. 1 and 2, a dent in the thickness direction of the film was sometimes recognized as a streak-like defect that was continuous in the direction in which the film was discharged from the die.
FIG. 1 is a schematic cross-sectional view showing an example of a cross section in the thickness direction of the thermoplastic resin film 10, in which a generated dent D is shown.
FIG. 2 is a schematic perspective view showing an example of the thermoplastic resin film 10 in which a streak-shaped dent D (die line) occurs in the direction of the arrow 20.

The inventors of the present invention have conducted intensive studies and have found that the occurrence of the dents D on the film surface is caused by the deterioration of the resin (hereinafter, also referred to as “meani”) adhering to the lip of the die. This was considered to be due to the fact that the resin was discharged from the die in a state where the resin was depressed in a streak shape.
Also, usually, in the production of a thermoplastic resin film by a melt extrusion method using a die, the resin is discharged from the die as a film-like molten resin in a state where the die and the cooling roll are separated, and the discharged film-like molten resin is, for example, This can be started by starting the film-like molten resin while pulling by hand.
FIG. 3 is a schematic diagram for explaining a state where the take-up is started. The film-like molten resin 30 discharged through the lip portion 32 of the die 12 is taken by the hand 14 and the resin wrinkles are extended. In this state, a state is shown in which the resin is sandwiched between the cooling roll 16 and the touch roll 18 to start picking up. Reference numeral 32 indicates a lip portion of the die.
The present inventors, when starting the above-mentioned take-up, the resin is pulled diagonally by the cooling roll, or pulled by hand, and the resin shakes due to wind, the lip of the resin and the die It was considered that the contact of the parts was the cause of the occurrence of scum.

As a method of suppressing the adhesion of the mist, for example, Japanese Patent Application Laid-Open No. 2000-280315 discloses a method of improving the releasability of a resin by using tungsten carbide or the like as a material of a lip portion of a die to improve the generation of the mist. Are described.
As a method for removing generated dust, Japanese Unexamined Patent Application Publication No. 2000-025089 discloses a lip lower surface cleaning device for a die device, characterized in that an eye drop removing body is formed on the lower surface of the brushed rod bar. Have been.
However, according to the method described in Japanese Patent Application Laid-Open No. 2000-280315, the present inventors have found that although it is difficult to generate mist, it has not been possible to completely prevent the occurrence of mist and die lines still occur. I found that you might.
Further, even if the lip lower surface cleaning device described in Japanese Patent Application Laid-Open No. 2000-025089 is used, cleaning cannot be performed well when dirt is strongly adhered. Have been found to be the cause of the occurrence. In particular, it has been found that washing is likely to be insufficient when a high-viscosity resin or a resin that is easily oxidized is used because a high-viscosity resin or an adhered resin degraded by thermal oxidation adheres firmly.

Therefore, the present inventors have conducted intensive studies and, as a result, have found that the production method of a thermoplastic resin film according to the present disclosure suppresses the occurrence of die lines.
The detailed mechanism by which die line generation is suppressed is unknown, but is considered as follows.
By setting the die swell ratio to 1.3 or less, the thickness of the film-like molten resin discharged from the die is reduced, so that the film-like molten resin is prevented from adhering to the lip portion of the die, and It is assumed that as a result of the suppression of the occurrence, the occurrence of the die line is suppressed.
In addition, the film-shaped molten resin is cooled while restricting the maximum angle θ between the direction in which the film-shaped molten resin is discharged from the die discharge port and the film surface direction of the film-shaped molten resin at the die discharge port to 45 ° or less. It is presumed that the film-like molten resin is prevented from adhering to the lip portion of the die by being brought into contact with the roll and starting to be taken out, and as a result, the occurrence of die lines is suppressed as a result of the suppression of the generation of the mold. .
The resin manufactured by the method for manufacturing a thermoplastic resin film according to the present disclosure is particularly preferably used for an optical film or the like because generation of die lines is suppressed.

In the present specification, the “film-like molten resin” may be a resin component alone or a resin composition containing an additive.
Further, the film-like molten resin may be referred to as “resin”, and the thermoplastic resin film may be referred to as “film”.

<Film forming equipment>
First, an example of the entire configuration of a film forming apparatus (thermoplastic resin film manufacturing apparatus) used in the method for manufacturing a thermoplastic resin film according to the present disclosure will be schematically described with reference to the drawings.
FIG. 4 is a schematic diagram illustrating an example of the entire configuration of a film forming apparatus for performing the method for manufacturing a thermoplastic resin film according to the present disclosure. A film forming apparatus 110 shown in FIG. 4 is connected to a hopper 112 into which a thermoplastic resin as a raw material resin is charged, an extruder 114 that melts the thermoplastic resin supplied from the hopper 112, and an extruder 114 through a pipe 140. A gear pump 116 for stabilizing the amount of molten resin (molten resin) extruded, a filter 118 for filtering the molten resin, a die 120 for melting and extruding the molten resin into a film, and a high-temperature discharged from the die 120 A contact roll (touch roll) that sandwiches the thermoplastic resin 100 discharged from the die 120 between the plurality of cooling rolls (casting rolls) 122, 124, and 126 that cool the thermoplastic resin in multiple stages, and the first cooling roll 122. ) 128. Although not shown, a peeling roll that peels the thermoplastic resin film 100 from the last third cooling roll 126 and a winder that winds the cooled film are usually provided. The extruder 114, the gear pump 116, the filter 118, and the die 120 are connected by a pipe 140, respectively.
The film forming apparatus illustrated in FIG. 4 is merely an example of a film forming apparatus used in the method for manufacturing a thermoplastic resin film according to the present disclosure, and the method for manufacturing a thermoplastic resin film according to the present disclosure is not limited thereto. However, it is also possible to use another known film forming apparatus.

(Raw material resin)
The raw material resin used for producing the film-like molten resin is not particularly limited as long as it is a thermoplastic resin, and may be selected according to the use of the film to be produced.
For example, a cyclic olefin resin, an acrylic resin, a polycarbonate resin and the like can be mentioned.
It is considered that a resin such as a cyclic olefin resin, which generally has a high melt viscosity and is easily oxidized, is liable to generate mist.
In the method for producing a thermoplastic resin film according to the present disclosure, even in these resins, occurrence of die buildup is suppressed, and generation of a die line is suppressed, and thus it is considered to be particularly useful when these resins are used. Can be

-Cyclic olefin resin-
The cyclic olefin resin is a polymer resin having a cyclic olefin structure. Examples of the polymer resin having a cyclic olefin structure include (1) a norbornene-based polymer, (2) a monocyclic cyclic olefin polymer, and ( 3) Polymers of cyclic conjugated dienes, (4) vinyl alicyclic hydrocarbon polymers, and hydrides of (1) to (4).
For example, an addition (co) polymer cyclic polyolefin containing at least one structural unit represented by the following general formula (II) and, if necessary, at least one repeating unit represented by the general formula (I) are further included. And an addition (co) polymer cyclic polyolefin. Further, a ring-opened (co) polymer containing at least one kind of the structural unit represented by the general formula (III) can also be suitably used.

In the general formulas (I), (II), and (III), m represents an integer of 0 to 4, R ^{1 to} R ⁶ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, X ^{1 to} X ³ and Y ^{1 to} Y ³ each independently represent a hydrogen atom, a hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, a hydrocarbon group having 1 to 10 carbon atoms substituted with a halogen atom,-(CH _{^{2) n COOR 11, - (}} CH 2) n OCOR 12, - (CH 2) n NCO, - (CH 2) n NO 2, - (CH 2) n CN, - (CH 2) n CONR 13 R 14 _{^{, - (CH 2) n NR}} 13 R 14, - (CH 2) n OZ, - (CH 2) n W, or consists ^{X 1} and ^Y 1, ^{X 2} and ^{Y 2} or ^{X 3} and ^{Y 3,} and _(-CO) represents ₂ O or _(-CO) 2 ^{NR 15 R 11, R 12, R 13} , R 14, and ^{R 15} represents a hydrogen atom or a hydrocarbon group having a carbon number of 1 to 20, Z represents a hydrocarbon group substituted with a hydrocarbon group or halogen, W is It represents _{^{SiR 16 p D 3-p,}} (R 16 represents a hydrocarbon group having 1 to 10 carbon atoms, D is a halogen atom, -OCOR ¹⁶ or ^{-OR 16,} p represents an integer of 0 to 3 ), N represents an integer of 0 to 10.

By introducing a highly polarizable functional group into all or some of the substituents of X ^{1 to} X ³ and Y ^{1 to} Y ³ , the retardation (Rth) in the thickness direction of the optical film is increased, and the in-plane letter is increased. It is possible to increase the development of the dating (Re). A film having a high Re expression can have a high Re value by being stretched during the film forming process.

  Norbornene-based addition (co) polymers are disclosed in JP-A-10-7732, JP-T-2002-504184, U.S. Patent No. 2004/229157, or WO 2004/070463. The norbornene-based addition (co) polymer is obtained by addition-polymerizing norbornene-based polycyclic unsaturated compounds. In addition, if necessary, a norbornene-based polycyclic unsaturated compound, ethylene, propylene, butene; conjugated dienes such as butadiene and isoprene; non-conjugated dienes such as ethylidene norbornene; acrylonitrile, acrylic acid, methacrylic acid, and maleic anhydride It is also possible to carry out addition polymerization with a linear diene compound such as an acid, an acrylic ester, a methacrylic ester, a maleimide, vinyl acetate and vinyl chloride. This norbornene-based addition (co) polymer is commercially available from Mitsui Chemicals, Inc. under the trade name of Apel (registered trademark), and has a different glass transition temperature (Tg), for example, APL8008T (Tg: 70 ° C.), APL6013T ( (Tg: 125 ° C.) or APL6015T (Tg: 145 ° C.). Pellets such as TOPAS8007, 6013, and 6015 are commercially available from Polyplastics. In addition, Appear 3000 is commercially available from Ferrania.

Norbornene-based polymer hydrides are disclosed in JP-A-1-240517, JP-A-7-196736, JP-A-60-26024, JP-A-62-19801, JP-A-2003-159767 or JP-A-2004-309797. As disclosed in each of the publications, for example, polycyclic unsaturated compounds are subjected to addition polymerization or metathesis ring-opening polymerization followed by hydrogenation. In the norbornene-based polymer used in the method for producing a thermoplastic resin film according to the present disclosure, R ^{5 to} R ⁶ are preferably a hydrogen atom or a methyl group, and X ³ and Y ³ are each a hydrogen atom, a chlorine atom, and —COOCH _3. Preferably, other groups are appropriately selected. The norbornene-based resin is commercially available from JSR Corporation under the trade name Arton (registered trademark) G or Arton F, and from Zeon Corporation, Zeonor (registered trademark) ZF14, ZF16, and Zeonex. (Zeonex (registered trademark)) 250 or Zeonex 280 are commercially available, and these can be used.

  Further, in the method for producing a thermoplastic resin film according to the present disclosure, various additives (for example, a deterioration inhibitor, an ultraviolet ray inhibitor, a retardation (optical anisotropy) regulator, Fine particles, release accelerators, infrared absorbers, etc.), which may be solid or oily.

It is preferable that the thermoplastic resin as the raw material resin and the additives to be added as necessary are mixed and pelletized before the melt film formation.
In pelletizing, it is preferable to dry the thermoplastic resin and additives in advance. When the thermoplastic resin is dried, for example, a method of heating in a heating furnace at 90 ° C. for 8 hours or more can be used, but the drying method is not limited thereto. The heating temperature and the heating time during drying may be selected in consideration of the glass transition temperature Tg or the melting point of the resin.

  Drying can be substituted by using, for example, a vent-type extruder for pelletizing the thermoplastic resin. When pelletizing, the additives can be introduced from a raw material introduction port or a vent port in the middle of the extruder.

The size of the pellets, for example, the cross-sectional area of ^{1 mm} 2 to 300 mm ^2, the length 1mm~30mm by weight, more preferably cross-sectional area ^{2 mm} 2 100 mm ^2, length 1.5Mm～10mm.

It is preferable to reduce the water content in the pellets before the melt film formation. The method for drying the pellets is often dried using a dehumidifying air dryer, but is not particularly limited as long as the desired moisture content is obtained. It is preferable to use a means such as heating, blowing, decompression, stirring, etc., alone or in combination, to efficiently perform the drying. Further, it is preferable that the drying hopper has an insulating structure.
The drying temperature of the pellets is preferably 0 to 200C, more preferably 40 to 180C, and particularly preferably 60 to 150C.

  The water content of the thermoplastic resin used as the raw material resin is preferably 1.0% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0.01% by mass or less.

(Extruder)
The raw material resin (pellet) described above is charged into the hopper 112 and supplied to the extruder 114.
As the extruder, a known extruder can be used, and examples thereof include a single-screw extruder of a screw type such as full flight, mudock, and dalmage, and a twin-screw extruder of the same direction or a different direction. . For example, those described in JP-A-2009-154518 and JP-A-2008-194856 can be mentioned.

(Gear pump)
In order to improve the accuracy of the thickness of the film, it is important to keep the fluctuation of the discharge amount low. Preferably, a gear pump 116 is provided between the extruder 114 and the die 120, and a fixed amount of molten resin is supplied from the gear pump 116.
The gear pump is housed in a state in which a pair of gears including a drive gear and a driven gear are meshed with each other, and by driving the drive gear to mesh and rotate both gears, a molten state is formed from a suction port formed in the housing. The resin is sucked into the cavity, and a predetermined amount of the resin is discharged from a discharge port also formed in the housing. Even if the resin pressure at the tip of the extruder slightly fluctuates, the fluctuation is absorbed by using a gear pump, and the fluctuation of the resin pressure downstream of the film forming apparatus becomes very small, and the thickness fluctuation is improved. . By using the gear pump, it is possible to make the fluctuation width of the resin pressure in the die portion within ± 1%.

  In order to improve the quantitative supply performance by the gear pump, a method of changing the rotation speed of the screw to suppress the fluctuation of the pressure before the gear pump can also be used. A high-precision gear pump using three or more gears is also effective.

(filter)
In order to prevent foreign matter from being mixed with higher accuracy, it is preferable to provide a filter 118 after passing through the gear pump 116. As the filter 118, it is preferable to provide a filtering device incorporating a so-called leaf-type disc filter. Filtration can be performed by providing one filtration unit, or multi-stage filtration performed by providing a plurality of filtration units. The filtration accuracy of the filter medium is preferably higher, but the filtration accuracy is preferably 15 μm to 3 μm, more preferably 10 μm to 3 μm, due to the pressure resistance of the filter medium and the increase in filtration pressure due to clogging of the filter medium. In particular, when using a leaf-type disc filter device that finally filters foreign substances, it is preferable to use a filter medium with high filtration accuracy in terms of quality, and adjust with the number of sheets loaded to ensure appropriate pressure resistance and filter life. It is possible to
The type of the filter medium is preferably a steel material in terms of being used under high temperature and high pressure, and among the steel materials, it is particularly preferable to use stainless steel, steel and the like, and it is particularly preferable to use stainless steel in terms of corrosion. .
As a structure of the filter medium, for example, a sintered filter medium formed by sintering a long metal fiber or metal powder can be used in addition to a filter medium formed by knitting a wire, and a sintered filter medium is preferable in terms of filtration accuracy and filter life.

[Die]
The molten resin (melt) continuously sent to the die 120 via the extruder 114, the gear pump 116 and the filter 118 is melt-extruded from the die 120 into a film.
As the die 120, a fish tail die or a hanger coat die may be used in addition to a generally used T die.
The die according to the method for producing a thermoplastic resin according to the present disclosure is not particularly limited, and a die known in the field of a method for producing a thermoplastic resin film can be used.
For example, the dies described in JP-A-2009-154518 and JP-A-2008-194856 are exemplified.
Immediately before the die 120, a static mixer for improving the uniformity of the resin temperature may be inserted.
The die is one of the facilities that influence the thickness accuracy of the film, and a die capable of controlling the thickness with high accuracy is preferable. Usually, the thickness can be adjusted at intervals of 40 mm to 50 mm, but a die of a type capable of adjusting the film thickness at intervals of preferably 35 mm or less, more preferably 25 mm or less is preferable.
In addition, in order to improve the uniformity of the film, it is preferable to design the die so as to minimize the unevenness in the temperature of the die and the unevenness in the flow velocity in the width direction. An automatic thickness adjusting die that measures the thickness of the downstream film, calculates the thickness deviation, and feeds the result back to the die thickness adjustment is also effective in reducing the thickness variation in long-term continuous production.

  A single-layer film-forming device with low equipment cost is generally used for film production, but in some cases, a film having two or more types of structures can be produced using a multilayer film-forming device with a functional layer provided on the outer layer. It is. Generally, it is preferable to laminate the functional layer on the surface layer thinly, but the layer ratio is not particularly limited.

−Surface energy of die lip−
The surface energy of the lip of the die used in the method for producing a thermoplastic resin film according to the present disclosure is preferably 60 mN / m or less, and more preferably 50 mN / m or less, from the viewpoint of suppressing the occurrence of die lines. More preferably, it is 40 mN / m or less.
The lower limit is not particularly limited, and may be 0 mN / m or more.
When the surface energy of the lip portion of the die is within the above range, the resin is excellent in the releasability at the lip portion of the die, and the generation of the die is suppressed. Therefore, it is considered that the generation of the die line is further suppressed.
As the surface energy of the lip portion of the die, a value calculated from the contact angle with water and methylene iodide using the Fowkes-Owens equation was used. The contact angle is measured using a contact angle meter CA-X manufactured by Kyowa Interface Science Co., Ltd.
The surface energy of the lip can be achieved, for example, by forming the material forming the lip into a material such as hard chrome plating, tungsten carbide, diamond-like carbon, or ultra chrome.

-Bright line width at the edge of the die lip on the discharge port side-
The bright line width of the edge portion on the discharge port side of the lip portion of the die used in the method for producing a thermoplastic resin film according to the present disclosure is preferably 10 μm or less, and more preferably 7 μm or less, from the viewpoint of suppressing the occurrence of die lines. More preferably, it is more preferably 5 μm or less.
The lower limit of the bright line width is not particularly limited, but is preferably 1 μm or more.
It is considered that the reduction of the bright line width makes it difficult for the resin to adhere to the lip portion, thereby suppressing the occurrence of mesas, thereby further suppressing the occurrence of the die line.

[Cooling roll, touch roll]
Under the above conditions, the film-like molten resin discharged from the die is cooled and solidified on a cooling roll to obtain a film. By heating the film-shaped molten resin with a far-infrared heater before the film-shaped molten resin comes into contact with the cooling roll, a leveling effect is developed on the drum and the surface thereof becomes substantially uniform. The distribution and die line can be reduced.
It is preferable to use a method such as an electrostatic application method, an air knife method, an air chamber method, a vacuum nozzle method, or a touch roll method on the cooling roll to increase the close contact between the cooling roll and the melt-extruded sheet. It is preferable to use a roll method. When the touch roll method is used, it is considered that when the resin is sandwiched between the cooling roll and the touch roll, the resin is greatly pulled, so that the adhesion of the resin is likely to occur. Therefore, when the touch roll method is used, it is considered that the effect of suppressing the die line is particularly easily obtained by the method for manufacturing a thermoplastic resin film according to the present disclosure. The touch roll method is a method of arranging a touch roll on a cooling roll and shaping the film surface. The touch roll is not a normal roll having high rigidity, but a roll having elasticity is preferable.

  The temperature of each of the touch rolls is preferably higher than Tg-10 ° C of the resin and not higher than Tg + 30 ° C of the resin, more preferably not lower than Tg−7 ° C of the resin and not higher than Tg + 20 ° C of the resin, and further preferably not lower than Tg−5 ° C of the resin. Tg + 10 ° C. or lower. The temperature of the cooling roll is preferably in the same temperature range.

  As the touch roll, for example, the touch rolls described in JP-A-11-314263 and JP-A-11-235747 can be used.

  Further, it is more preferable to perform slow cooling using a plurality of cooling rolls. When a plurality of cooling rolls are used, the touch roll is arranged in contact with the first cooling roll on the most upstream side (closer to the die) in a pick-up start step described later. For example, a method using three cooling rolls is exemplified, but not limited thereto.

The diameter of each roll is preferably 50 mm to 5000 mm, more preferably 100 mm to 2000 mm, and still more preferably 150 mm to 1000 mm.
The distance between adjacent rolls is preferably 0.3 mm to 300 mm, more preferably 1 mm to 100 mm, and still more preferably 3 mm to 30 mm.
Further, it is preferable that the line speed on the most upstream side of the cooling roll is set to 20 m / min to 70 m / min.

  The thickness of the unstretched film manufactured by the method for manufacturing a thermoplastic resin film according to the present disclosure may be determined according to the application, for example, when used as an optical film, from the viewpoint of mechanical strength and light transmittance. , 20 μm to 250 μm, more preferably 25 μm to 200 μm, and still more preferably 30 μm to 180 μm.

<Recovery start process>
Hereinafter, a pick-up start step included in the method for manufacturing a thermoplastic resin film according to the present disclosure will be described.
The takeoff start step in the present disclosure is, for example, a step of starting discharge of the film-like molten resin from the die in a state where the die and the cooling roll are separated from each other, and bringing the discharged film-like molten resin into contact with the cooling roll.
After the takeover start step, the production of the thermoplastic film is started by the above-described method.

[Die swell ratio]
In the pickup start step according to the present disclosure, the film-shaped molten resin is discharged from the die with the die swell ratio being 1.3 or less.
The method of discharging the film-like molten resin from the die is as described above.
From the viewpoint of suppressing the occurrence of die lines, the die swell ratio is preferably 1.2 or less, and more preferably 1.1 or less.
The lower limit of the die swell ratio is not particularly limited, and may be 1 or more.
The die swell ratio is a value of the ratio of the thickness of the resin immediately after discharge to the thickness of the resin at the discharge port inside the die (the thickness of the resin immediately after discharge / the thickness of the resin at the discharge port inside the die). In other words, the smaller the die swell ratio, the less the resin immediately after the discharge has expanded in the thickness direction.
FIG. 5 is a schematic cross-sectional view for explaining the state of the resin near the discharge port of the die at the time of discharging the resin.
FIG. 5 is a cross-sectional view in the thickness direction of the resin. When the resin 30 is discharged from the discharge port 40 of the die 12 in the discharge direction indicated by the arrow 38, the discharge port of the discharged resin 30 inside the die is provided. Compared to the resin thickness 34 at 40, the resin thickness 36 immediately after ejection is thicker. The ratio of the resin thickness 36 immediately after discharge to the resin thickness 34 at the discharge port 40 inside the discharge port die (the resin thickness 36 immediately after discharge / the resin thickness 34 at the discharge port 40 inside the die) is: , Die swell ratio.
If the die swell ratio is 1.3 or less, the contact area between the lip portion 32 of the die 12 and the film-like molten resin 30 and the pressure at the time of contact are reduced, so that the occurrence of die buildup is suppressed, and the occurrence of die lines is reduced. It is thought to be suppressed.

The die swell ratio is calculated from the resin thickness at the discharge port inside the die, which is a value specific to the die, and the resin thickness immediately after the discharge, which is measured by taking an image of the discharge port and analyzing the image during resin discharge. Is done.
In addition, the die swell ratio can be reduced by increasing the opening of the lip portion of the die (lip opening) and the temperature at which the resin is melted, and decreasing the flow rate of the resin.
The degree of opening of the lip, the temperature at which the resin is melted, and the flow rate of the resin may be set so that the die swell ratio is 1.3 or less according to the type of resin, melt viscosity, and the like.
For example, the opening of the lip portion is preferably 1.0 to 25 times, more preferably 3.0 to 20 times, even more preferably 5.0 to 15 times the thickness of the resin film to be manufactured.
The temperature at which the resin is melted is preferably 100C to 400C, more preferably 150C to 350C, and even more preferably 200C to 300C.
The flow rate of the resin is preferably 1 mm / s to 30 mm / s, more preferably 2 mm / s to 20 mm / s, and still more preferably 3 mm / s to 10 mm / s.

(Regulation means and regulation method)
In the takeoff start step according to the present disclosure, the maximum angle θ between the discharge direction of the film-shaped molten resin from the die discharge port and the film surface direction of the film-shaped molten resin at the die discharge port is set to 45 ° or less. The film-shaped molten resin is brought into contact with a cooling roll while regulating.
The regulation may be performed at the time when the film-shaped molten resin is brought into contact with the cooling roll.
The maximum angle θ is preferably 30 ° or less, and more preferably 20 ° or less. The lower limit of the maximum angle θ is not particularly limited, and may be 0 ° or more.
When the film-like molten resin is pulled by hand and brought into contact with the cooling roll, from the viewpoint of suppressing the resin from shaking by pulling by hand, the above-described regulation is performed after discharging the film-like molten resin from a die. It is preferable to perform the process continuously from a point before the film-like molten resin is pulled by hand to a point of contacting the film-like molten resin with the cooling roll.
That is, it is preferable that after the start of the regulation, the film-shaped molten resin is pulled by hand and brought into contact with the cooling roll.

[Maximum angle θ between the discharge direction of the film-like molten resin from the die discharge port and the film surface direction of the film-like molten resin]
The discharge direction of the film-like molten resin from the die discharge port is determined by the shape of the discharge port of the die, the shape of the flow path in the die, or the method of applying pressure to the resin. Direction.
The direction is not particularly limited, but in the film forming apparatus, in order to suppress the resin from contacting the lip of the die, it is preferable to set the direction of gravity according to the arrangement of the die.
The direction of the film surface of the film-like molten resin refers to the direction of the film surface of the resin actually formed into a film.
The direction in which the film-like molten resin is discharged from the die discharge port, and the direction of the film surface of the film-like molten resin, the maximum angle θ formed between the discharge port and the auxiliary roll or control plate described later as the control means. From the position with the auxiliary roll or the regulating plate, it is calculated as the tangential direction of the end of the auxiliary roll or the regulating plate passing through the discharge port. When wind is used as the regulating means, the calculation is performed by photographing the ejection of the resin from the film surface direction of the resin and determining the position of the film surface from the image.
FIG. 6 is a schematic diagram showing a positional relationship when the die 12 and the film-like molten resin 30 at the time of discharge are observed from the film surface direction of the film-like molten resin 30 (the side surface of the die).
In the method for producing a film-like molten resin according to the present disclosure, the angle θ between the discharge direction 42 of the film-like molten resin from the die discharge port and the film surface direction 44 of the film-like molten resin 30 is restricted to 45 ° or less. .
In FIG. 6, the auxiliary roll 50 forms an angle between the discharge direction 42 of the film-like molten resin from the die outlet and the film surface direction 44 of the film-like molten resin 30 in both directions of the film-like molten resin 30. The angle θ (the maximum angle θ described above) is restricted to 45 ° or less.
In FIG. 6, the above-mentioned maximum angle θ is regulated to be 45 ° or less in both directions of the one surface and the other surface of the film. ° or less.
If the maximum angle θ is regulated so as to be 45 ° or less in only one of the directions, in the take-off step, the resin is pulled in that direction and attached to the cooling roll, so that the die discharge port In the above, while controlling the maximum angle θ between the direction of discharge of the film-like molten resin from the die discharge port and the film surface direction of the film-like molten resin to 45 ° or less, the film-like molten resin is brought into contact with a cooling roll. , It is possible to start taking over.

[Auxiliary roll]
In the take-off step, the regulation is preferably performed by bringing the auxiliary roll disposed between the die and the cooling roll into contact with the film-shaped molten resin over the entire width of the film-shaped molten resin. To be in contact over the entire width means that the auxiliary roll is in contact with all the straight lines connecting one point at one end in the width direction of the film-like molten resin and one point at the other end.
Not in contact with the entire width, for example, in the embodiment in which only the both ears of the film-shaped molten resin are in contact with the roll, and the center is not in contact with the roll, the portion and the roll in contact with the film-shaped molten resin roll discharged from the die discharge port A difference in the flow velocity of the resin occurs at a portion that is not in contact with the portion, and the die swell ratio at any portion increases, which may cause a die line.
The method of fixing the auxiliary roll is not particularly limited, but it is preferable that the auxiliary roll is fixed to the die by an auxiliary roll connecting member so that the auxiliary roll can follow the swing of the die and the movement of the die.
In addition, it is preferable that the auxiliary roll is in horizontal contact with the width direction of the film-shaped molten resin.
Further, the auxiliary roll may be removed by a regulating unit removing step described later after the taking-up step.

The diameter of the auxiliary roll is not particularly limited, but is preferably 10 mm to 200 mm, and more preferably 20 mm to 100 mm.
The length of the auxiliary roll in the width direction of the resin is longer than the length of the film-like molten resin in the width direction, specifically, preferably 0 mm to 200 mm longer than the die discharge port width, and more preferably 0 to 100 mm longer. More preferably, in this specification, the width direction of the film-shaped molten resin refers to a direction perpendicular to the direction of discharging the film-shaped molten resin on a plane on the film surface of the film-shaped molten resin.
The distance between the auxiliary roll and the discharge port of the die is preferably from 10 mm to 200 mm, more preferably from 20 mm to 100 mm.
The distance between the auxiliary roll and the discharge port of the die refers to the distance between the contact point where the film-shaped molten resin contacts the auxiliary roll and the discharge port of the die.
The auxiliary roll may have a heating means in order to suppress the film-like molten resin from being cooled by the auxiliary roll and to cause cooling unevenness in the film-like molten resin. The temperature of the auxiliary roll is preferably from 20C to 120C, more preferably from 25C to 100C.
Although the surface material of the auxiliary roll is not particularly limited, polytetrafluoroethylene (PTFE), electroless nickel plating, or the like is preferable from the viewpoint of preventing the resin from sticking to the auxiliary roll.
The number of auxiliary rolls may be only one, but may be two or more, and preferably two.
When two or more auxiliary rolls are arranged, it is preferable that the film-like molten resin pass between at least two auxiliary rolls from the viewpoint of stabilizing the position of the film-like molten resin.

FIG. 7 is a schematic diagram illustrating an example of a case where two auxiliary rolls are used in the take-off process.
In FIG. 7, the film-like molten resin 30 discharged from the die 12 passes between the two auxiliary rolls 50 to discharge the film-like molten resin from the die discharge port and the film-like molten resin film. The maximum angle θ with the plane direction is restricted to 45 ° or less.
In FIG. 7, the auxiliary roll 50 is fixed by an auxiliary roll connecting member 52 connected to a die.
According to the embodiment shown in FIG. 7, while the maximum angle θ between the discharge direction of the film-shaped molten resin from the die discharge port and the direction of the film surface of the film-shaped molten resin is restricted to 45 ° or less, the film is formed by hand 14. The molten resin 30 can be guided to the cooling roll 16.

(Regulation plate)
In the take-off step, it is preferable that the regulation is performed by bringing the regulation plate disposed between the die and the cooling roll into contact with the film-like molten resin.
It is preferable that the regulating plate and the film-shaped molten resin are in contact with each other over the entire width of the film-shaped molten resin. To be in contact over the entire width means that the regulating plate is in contact with all the straight lines connecting one point at one end in the width direction of the film-like molten resin and one point at the other end.
The method of fixing the regulating plate is not particularly limited, but it is preferable that the regulating plate is fixed to the die so that the regulating plate can follow the swing of the die and the movement of the die.
In addition, it is preferable that the restricting plate is in contact with the film-shaped molten resin horizontally with respect to the width direction.
The number of regulating plates may be only one, but may be two or more, and preferably two.
When two or more regulating plates are arranged, it is preferable that the film-like molten resin pass between at least two regulating plates from the viewpoint of stabilizing the position of the film-like molten resin.
Further, the regulating plate may be removed by a regulating unit removing step described later after the taking-off step.

The length of the regulating plate in the width direction of the resin is preferably longer than the length of the film-like molten resin in the width direction. Specifically, it is preferably 0 mm to 200 mm longer than the die discharge port width, more preferably 0 to 100 mm longer.
The distance between the regulating plates is not particularly limited, but is preferably 5 mm to 50 mm, more preferably 10 mm to 30 mm.
Although the surface material of the regulating plate is not particularly limited, polytetrafluoroethylene (PTFE), electroless nickel plating, or the like is preferable from the viewpoint of suppressing the resin from sticking to the regulating plate.
The distance between the regulating plate and the die is not particularly limited, but is preferably 0 mm to 200 mm, and more preferably 20 mm to 100 mm.
The distance between the regulating plate and the die is defined as the angle θ between the direction in which the film-like molten resin is discharged from the die discharge port and the direction of the film surface of the film-like molten resin is θ. Means the distance between the contact point in contact with the regulating plate and the discharge port of the die.
The thickness of the regulating plate is not particularly limited, and may be any thickness that does not prevent the resin from being attached to the cooling roll, but is preferably 1 mm to 10 mm.

FIG. 8 is a schematic diagram illustrating an example of a case where two regulating plates are used in the take-off process.
In FIG. 8, the film-like molten resin 30 discharged from the die 12 passes between the two regulating plates 60, so that the resin and the ends of the regulating plates come into contact with each other. The maximum angle θ between the resin discharge direction and the film surface direction of the film-like molten resin is restricted to 45 ° or less.
In FIG. 7, the two regulating plates 60 are directly fixed to the die 12.
According to the embodiment shown in FIG. 8, while controlling the maximum angle θ between the discharge direction of the film-like molten resin from the die discharge port and the direction of the film surface of the film-like melt resin to 45 ° or less, the film is formed by hand 14. The molten resin 30 can be brought into contact with the cooling roll 16.

(Blowing means)
In the take-off step, it is preferable that the regulation is performed by generating wind by a blowing means disposed between the die and the cooling roll, and bringing the wind into contact with the film-shaped molten resin.
It is preferable that the wind and the film-like molten resin are in contact with each other over the entire width of the film-like molten resin. To be in contact with the entire width means that the wind is in contact with all the straight lines connecting one point at one end in the width direction of the film-like molten resin and one point at the other end.
It is preferable that the wind be in contact with the film-shaped molten resin horizontally with respect to the width direction.
The above wind may be regulated, for example, by blowing the wind from both sides to the resin, or by sending the wind in parallel with the discharge direction of the film-like molten resin, to pull the resin in an oblique direction, A mode in which the wind hits the resin only when the shaking occurs and the angle between the direction of discharge of the film-like molten resin from the die discharge port and the direction of the film surface of the film-like molten resin at the die discharge port increases. It may be.
From the viewpoint of stabilizing the position of the resin, it is preferable to blow air to the resin from both sides of the resin, and from the viewpoint of avoiding a temperature drop of the resin, wind is blown to the left and right of the resin in parallel with the discharge direction of the film-like molten resin. It is preferable to send.
In the case where air is blown to the resin from both sides of the resin, it is preferable that the wind blown to the resin is blown at an angle such that the wind blows along the film surface of the resin in the discharge direction of the film-like molten resin.
When blowing the resin from both sides of the resin, the distance between the position where the wind is blown and the die discharge port is preferably 10 mm to 200 mm, and more preferably 20 mm to 100 mm. Further, from the viewpoint of setting the above θ to 45 ° or less, it is preferable that the position where the wind is blown is the same position on both sides of the resin from both sides.
When the wind is sent in parallel with the discharge direction of the film-like molten resin, the direction of the wind is preferably the same as the discharge direction of the film-like molten resin.
When the air is sent in parallel to the direction in which the film-shaped molten resin is discharged, the position where the wind is generated may be on the cooling roll side of the die discharge port or on the opposite side.
When the position is closer to the cooling roll than the position of the die discharge port, the distance between the position where the air is blown out and the die discharge port is preferably 10 mm to 200 mm, and more preferably 20 mm to 100 mm.
When sending wind in parallel with the discharge direction of the film-shaped molten resin, the distance between the blown-out wind and the discharge direction of the film-shaped molten resin is preferably 10 mm to 200 mm, and more preferably 20 mm to 100 mm. .
In the case where the wind is sent in parallel with the discharge direction of the film-like molten resin, it is preferable to send the wind to both sides of the resin from the viewpoint of stabilizing the position of the resin.
As the blowing means, known blowing means can be used without limitation, and examples thereof include a fan, a blower, and an air knife.
The method of fixing the blower is not particularly limited, but it is preferable that the blower is fixed to the die in order to allow the blower to follow the swing of the die and the movement of the die.
The blower may have a blower that generates wind, a blower unit such as a blower nozzle that actually blows the wind, and a blower path that connects the blower and the blower unit. In the above aspect, when the blower is fixed to the die, only the blower unit needs to be fixed to the die.
FIG. 9 is a schematic diagram showing an example of a case where the wind is blown to both sides of the resin when observed from the film surface direction of the film-like molten resin 30.
In FIG. 9, air is blown to the resin from blowing units 70 arranged on both sides of the film-like molten resin 30. Arrow 74 indicates the direction of the wind. A blowing path 72 is attached to the blowing unit 70, and the blowing path 72 is connected to a blowing device (not shown).
FIG. 10 is a schematic view showing an example in which air is blown on one side and the other side of the resin in parallel with the discharge direction of the film-like molten resin when observed from the film surface direction of the film-like molten resin 30. It is.
In FIG. 10, air is blown from a blower unit 70 disposed on both sides of the film-like molten resin 30 to one surface and the other surface of the resin in parallel with the discharge direction of the film-like molten resin. Arrow 74 indicates the direction of the wind. A blowing path 72 is attached to the blowing unit 70, and the blowing path 72 is connected to a blowing device (not shown).

The length of the region to be blown in the width direction is preferably 10 mm to 200 mm longer than the die discharge port width, and more preferably 30 mm to 100 mm longer.
The speed of the blown air is preferably 1 m / s to 30 m / s, and more preferably 2 m / s to 20 m / s.
The temperature of the blown air is preferably Tg−50 ° C. to Tg + 100 ° C., and more preferably Tg ° C. to Tg + 50 ° C.

FIG. 11 is a schematic view showing a state where air is blown to the resin from both sides of the resin in the take-off process.
In FIG. 11, the film-like molten resin 30 discharged from the die 12 passes between the winds blown from the two blowing units 70, so that the discharge direction of the film-like molten resin from the die discharge port and the film The maximum angle θ of the molten resin with the film surface direction is restricted to 45 ° or less.
Wind is blown from the two blowing units 70 to the film-like molten resin 30.
In FIG. 11, the blower unit 70 is fixed by fixing the blower path 72 to a die.
According to the embodiment shown in FIG. 11, the film 14 is formed by the hand 14 while the maximum angle θ between the discharge direction of the film-like molten resin from the die discharge port and the direction of the film surface of the film-like melt resin is restricted to 45 ° or less. The molten resin 30 can be brought into contact with the cooling roll 16.

−Oxygen concentration at die discharge port−
In the step of initiating the take-up, from the viewpoint of suppressing the generation of the die line, the oxygen concentration at the die discharge port is set to 5% from the time when the molten resin is extruded to the die until the time when the film-like molten resin starts to be discharged from the die. It is preferably at most 1%, more preferably at most 1%, still more preferably at most 5,000 ppm, particularly preferably at most 1,000 ppm.
It is considered that, by lowering the oxygen concentration, the oxidation of the resin is suppressed, and the generation of the die is suppressed, so that the generation of the die line is suppressed.
In a so-called steady state in which the film-like molten resin is continuously discharged from the die, it is considered that there is almost no contact between the extruder and the die discharge port with oxygen. However, when the resin is started to be discharged from the die, the resin at the head is exposed to oxygen, so that the resin may be deteriorated and have a high viscosity.
Therefore, it is possible to reduce the viscosity of the resin discharged from the die discharge port by reducing the oxygen concentration between the time when the molten resin is extruded into the die and the time when the film-shaped molten resin starts discharging from the die, Since the die swell ratio is reduced, it is considered that the occurrence of mess, which is the cause of the die line, is suppressed.
The lower limit of the oxygen concentration is not particularly limited, and may be 0% or more.
The oxygen concentration can be achieved, for example, by shielding the die discharge port with a shielding member and replacing the space in the shielding member with nitrogen.

<Film manufacturing process>
In the method for producing a thermoplastic resin film according to the present disclosure, after the start of take-up, the film-like molten resin is further discharged from the die, and the discharged film-like molten resin is cooled and wound up while being taken up by the cooling roll. Process (film manufacturing process).
In the film manufacturing process, it is preferable that a resin is passed between the cooling roll and the touch roll using a touch roll that presses the cooling roll.

  In the step of further discharging the film-like molten resin from the die, cooling and winding the discharged film-like molten resin while taking it up with the cooling roll, a method of discharging the film-like molten resin, cooling while taking up with the cooling roll For details of the method, the above-described method can be used.

(Winding)
After peeling off the cooled film (unstretched film) from the cooling roll, the film is wound up via a nip roll (not shown).

  It is also preferable to trim both ends before winding. Any type of trimming cutter, such as a rotary cutter, shear blade, knife, etc., may be used. Regarding the material, either carbon steel or stainless steel may be used. Generally, it is preferable to use a carbide blade or a ceramic blade because the life of the blade is long and generation of cutting chips is suppressed. The portion cut off by trimming may be crushed and used again as a raw material.

  It is also preferable to carry out a thickening process (knurling process) on one end or both ends. The height of the concavities and convexities formed by the thickness increasing process is preferably 1 μm to 200 μm, more preferably 10 μm to 150 μm, and further preferably 20 μm to 100 μm. The thickening process may be convex on both surfaces or convex on one surface. The width of the thickening process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm, and still more preferably 5 mm to 20 mm. Extrusion can be performed at room temperature to 300 ° C.

  The formed film may be stretched as it is (online stretching), or may be wound once and then sent out again for stretching (offline stretching).

  At the time of winding, it is also preferable to attach a laminating film on at least one side from the viewpoint of preventing scratches. The thickness of the lami film is preferably 5 μm to 200 μm, more preferably 10 μm to 150 μm, and still more preferably 15 μm to 100 μm. The material is, for example, polyethylene, polyester, or polypropylene, and is not particularly limited.

(Stretching)
The formed film may be subjected to one or both of transverse stretching and longitudinal stretching, and may be subjected to relaxation treatment in combination with stretching. For example, the following combinations can be implemented.

  In the stretching step, it is also preferable to carry out a combination of the transverse stretching and the longitudinal stretching. In this case, it is more preferable to perform transverse stretching after longitudinal stretching.

(Relaxation treatment)
By performing relaxation treatment after stretching, dimensional stability can be improved. Thermal relaxation is preferably performed after longitudinal stretching or lateral stretching, or both, and more preferably after lateral stretching. The relaxation treatment may be performed online continuously after stretching, or may be performed offline after winding after stretching.

<Regulator removal step and transfer step>
The method for producing a thermoplastic resin film according to the present disclosure includes a step of starting the above-mentioned take-up from the viewpoint of suppressing the occurrence of uneven thickness of the thermoplastic resin film due to uneven cooling of the film-like molten resin (a take-up start step). After that, before the step of cooling and winding (film manufacturing step), the angle between the discharge direction of the film-like molten resin from the die discharge port and the film surface direction of the film-like molten resin is 45 ° or less. It is preferable to include a step of removing the regulating means (regulating means removing step) after moving one or both of the die and the cooling roll to the position.
The angle is preferably 30 ° or less, and more preferably 20 ° or less. In the regulating unit removing step, for example, the above-described auxiliary roll, regulating plate, or blowing unit is removed.
The removal of the regulating means means that the air blown by the auxiliary roll, the regulating plate, and the blowing unit is removed so as not to touch the film-like molten resin.
When the method for producing a thermoplastic resin film according to the present disclosure includes a moving step described below, in the regulating means removing step, the regulating means is removed so as not to hinder the movement of one or both of the die and the cooling roll in the moving step. Is preferred.
In addition, the method of manufacturing a thermoplastic resin film according to the present disclosure is configured such that the cooling and winding step (film manufacturing step) is performed after the take-off start step from the viewpoint of suppressing the thickness unevenness of the thermoplastic resin film due to cooling unevenness. Before ()), it is preferable to include a step (moving step) of moving one or both of the die and the cooling roll to reduce the distance between the discharge port of the die and the cooling roll.
In the case of including the regulating means removing step and the moving step, the moving step may be performed after the removing step of the regulating means (regulating means removing step) and before the cooling and winding step (film manufacturing step). preferable.

FIG. 12 is a schematic view showing an example of a case where a regulating means removing step and a moving step are performed after the take-off start step using the two auxiliary rolls 50 shown in FIG.
In FIG. 12, the auxiliary roll connecting member 52 has been moved, and the auxiliary roll 50 has been moved to the opposite side of the die from the resin discharge port.
In FIG. 12, the auxiliary roll 50 is removed and the die 12 and the cooling roll 16 are moved so that the distance between the die 12 and the cooling roll 16 is reduced.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist of the present invention. Unless otherwise specified, “parts” are based on mass.

(Example 1)
As the resin, a cyclic olefin-based resin pellet (ARTON, manufactured by JSR Corporation) was used. After preliminarily drying the resin pellets at 90 ° C. for 5 hours, the resin pellets were put into a hopper provided in an extruder and melted at a temperature of 285 ° C. using a melt extruder. Thereafter, the molten resin sent out from the gear pump was filtered with a leaf disk filter having a filtration accuracy of 5 μm. Thereafter, the auxiliary roll is used to regulate the maximum angle θ ≦ 5 ° between the discharge direction of the film-like molten resin from the die discharge port and the film surface direction of the film-like molten resin at the die discharge port. did. At this time, the lip opening of the die discharge port was adjusted so that the die swell ratio was 1.1.
Two auxiliary rolls were used as shown in FIG. The surface material of the auxiliary roll was polytetrafluoroethylene (PTFE), and the distance between each auxiliary roll and the discharge port of the die was 50 mm. The width of the auxiliary roll was the same as the width of the die discharge port.
Thereafter, the film-shaped molten resin was discharged onto the cooling roll 1 (CR1) set at 122 ° C., and the pressure was reduced by the touch roll to start the take-off (take-off start step).
After the start of the take-up, the cooling roll was horizontally moved to a position where the cooling roll was not inclined even without regulation, the auxiliary roll was lifted as shown in FIG. 12, and the cooling roll was moved vertically to approach the die discharge port.
Thereafter, the film-shaped molten resin is passed through a cooling roll 2 (CR2) and a cooling roll 3 (CR3), and then wound up through a nip roll, and the end is slit to have a width of 1400 mm, a length of 1600 m and a thickness of 1600 m. A thermoplastic resin film having a thickness of 80 μm was obtained.

  The following evaluation was performed on the obtained thermoplastic resin film. The evaluation results are shown in Table 1.

<Evaluation of die line>
-The die line was visually checked and evaluated according to the following criteria.
A: The number of die lines per 1 m of film width is less than 10.
B: The number of die lines per 1 m of the film width is 10 or more and less than 20.
C: The number of die lines per 1 m of the film width is 20 or more and less than 30.
D: The number of die lines per 1 m of film width is 30 or more.

<Evaluation of film thickness unevenness>
The film thickness was measured at an interval of 1 mm using an off-line contact-type continuous thickness meter (manufactured by Anritsu Corporation, Film Thickness Tester KG601B). It measured about 3 m length of a film about a film conveyance direction. The film thickness unevenness was evaluated according to the following criteria.
A: The thickness unevenness in the film transport direction is less than ± 0.5 μm.
B: The thickness unevenness in the film transport direction is ± 0.5 μm or more and less than ± 1.0 μm.
C: The thickness unevenness in the film transport direction is ± 1.0 μm or more and less than ± 1.5 μm.
D: The thickness unevenness in the film transport direction is ± 1.5 or more.

<Comprehensive evaluation>
Among the evaluations of the die line and the film thickness unevenness, the worse one was taken as the comprehensive evaluation result.

<Surface energy of lip>
As the surface energy of the lip portion of the die, a value calculated from the contact angle with water and methylene iodide using the Fowkes-Owens equation was used. The contact angle was measured using CA-X manufactured by Kyowa Interface Science Co., Ltd.

(Example 2)
A thermoplastic resin film was manufactured and evaluated in the same manner as in Example 1, except that the maximum angle θ was set to θ = 10 ° and an auxiliary roll was disposed.

(Example 3)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 1 except that the auxiliary roll was arranged with the maximum angle θ being θ = 20 °.

(Example 4)
A thermoplastic resin film was manufactured and evaluated in the same manner as in Example 1 except that the auxiliary roll was disposed with the maximum angle θ being θ = 30 °.

(Example 5)
A thermoplastic resin film was manufactured and evaluated in the same manner as in Example 1 except that the maximum angle θ was set to the maximum angle θ = 45 ° and the auxiliary roll was disposed.

(Comparative Example 1)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 1 except that the regulating means was not provided and the maximum angle θ was set to θ = 50 °.

(Example 6)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 1 except that the casting film method was used instead of the touch roll method.

(Example 7)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 2, except that the casting film method was used instead of the touch roll method.

(Example 8)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3 except that the casting film method was used instead of the touch roll method.

(Example 9)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 4 except that the casting film method was used instead of the touch roll method.

(Example 10)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 5, except that the casting film method was used instead of the touch roll method.

(Example 11)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3, except that the lip opening of the die was adjusted so that the die swell ratio was 1.15.

(Example 12)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3, except that the lip opening of the die was adjusted so that the die swell ratio was 1.2.

(Example 13)
A thermoplastic resin film was manufactured and evaluated in the same manner as in Example 3, except that the lip opening of the die was adjusted so that the die swell ratio was 1.3.

(Comparative Example 2)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3, except that the lip opening of the die was adjusted so that the die swell ratio was 1.4.

(Example 14)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3, except that a regulating plate was attached below the die discharge port instead of the auxiliary roll as a regulating means.
The length of the regulating plate in the width direction is the same length as the die discharge port, the length of the regulating plate in the resin discharge direction is 50 mm, the interval between the regulating plates is 20 mm, and the surface material of the regulating plate is polytetrafluoroethylene (PTFE). , The thickness of the regulating plate was 3 mm

(Example 15)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3, except that a device for blowing a slit wind was used instead of the auxiliary roll as a regulating means.

(Example 16)
Until the film-like molten resin starts to be discharged from the die, the thermoplastic resin film was formed in the same manner as in Example 3 except that the die discharge port was surrounded by a heat-resistant resin structure and nitrogen was sealed so that the oxygen concentration was 10%. Manufactured and evaluated.

(Example 17)
A thermoplastic resin film was produced in the same manner as in Example 3 except that the die discharge port was surrounded by a heat-resistant resin and nitrogen was sealed so that the oxygen concentration became 5% until the film-like molten resin started to be discharged from the die. , Was evaluated.

(Example 18)
A thermoplastic resin film was manufactured in the same manner as in Example 3 except that the die discharge port was surrounded by a heat-resistant resin and nitrogen was sealed so that the oxygen concentration became 1% until the film-like molten resin started to be discharged from the die. , Was evaluated.

(Example 19)
Until the film-like molten resin starts to be discharged from the die, a thermoplastic resin film was manufactured in the same manner as in Example 3 except that the die discharge port was surrounded by a heat-resistant resin and nitrogen was sealed so that the oxygen concentration was 5000 ppm. An evaluation was performed.

(Example 20)
Until the film-like molten resin starts to be discharged from the die, a thermoplastic resin film was manufactured in the same manner as in Example 3, except that the die discharge port was surrounded by a heat-resistant resin and nitrogen was sealed so that the oxygen concentration was 1000 ppm. An evaluation was performed.

(Example 21)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 20, except that the surface material of the die lip was diamond-like carbon (DLC), the surface energy of the lip portion of the die was 28 mN / m, and the bright line width of the lip portion was 15 μm. Was done.

(Example 22)
A thermoplastic resin film was manufactured and evaluated in the same manner as in Example 20, except that the surface material of the die lip was ultrachrome plated, the surface energy of the lip portion of the die was 46 mN / m, and the bright line width of the lip portion was 20 μm. .

(Example 23)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 20, except that the surface material of the die lip was made of tungsten carbide, the surface energy with the film-like molten resin was 42 mN / m, and the lip emission line width was 5 μm. .

(Comparative Example 3)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 23 except that the film swing preventing device was not provided.

(Example 24)
A thermoplastic resin film was manufactured and evaluated in the same manner as in Example 3 except that an acrylic resin (Delpet 80N manufactured by Asahi Kasei Corporation) was used as the resin.

(Example 25)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3 except that polycarbonate (PC, Caliber 301 manufactured by Sumika Styron Polycarbonate Co., Ltd.) was used as the resin.

(Example 26)
A thermoplastic resin film was produced and evaluated in the same manner as in Example 3, except that a cyclic olefin copolymer (COC, TOPAS6013 manufactured by Polyplastics Co., Ltd.) was used as the resin.

  Table 1 shows melt extrusion conditions and evaluation results of the films produced in each example.

In Table 1, in the column of the maximum angle θ, the maximum angle θ between the discharge direction of the film-like molten resin from the die discharge port and the film surface direction of the film-like molten resin in the die discharge port,
In the column of the die swell ratio, the die swell ratio when the film-like molten resin is discharged from the die, in the column of the regulating means, the regulating means used,
In the column of film forming method, whether the touch roll method or the casting drum method was used,
In the column of the initial die lip oxygen concentration, the oxygen concentration at the die discharge port between the time when the molten resin is extruded to the die and the time when the film-like molten resin starts to be discharged from the die,
In the field of surface energy, the surface energy of the lip of the die is
In the column of lip material, the material of the lip part of the die,
In the column of bright line width (μm), the bright line width of the edge portion on the discharge port side of the lip portion of the die is
In the column of resin type, type of resin used,
In the column of die line evaluation, the result of the above die line evaluation,
In the column of number / m, the number of die lines in the above die line evaluation is shown.
In the column of thickness unevenness evaluation, the results of the above thickness unevenness evaluation,
In the column of μm, the measurement results of the thickness unevenness in the above-mentioned thickness unevenness evaluation are described, and in the column of the comprehensive evaluation, the above-described overall evaluation is described.
The description of HCr in the column of the lip material indicates hard chrome plating, the description of DLC indicates diamond-like carbon, and the description of WC indicates tungsten carbide.

  As shown in Table 1, when the die swell ratio is set to 1.3 or less, the film-like molten resin is discharged from the die, and the discharge direction of the film-like molten resin from the die discharge port at the die discharge port and the film-like molten resin In the embodiment in which the step of bringing the film-like molten resin into contact with the cooling roll and starting take-up was performed while restricting the maximum angle θ between the resin and the film surface direction to 45 ° or less, the number of die lines was 30 / all. m and the thickness unevenness was less than 1.5 μm.

DESCRIPTION OF SYMBOLS 10 Thermoplastic resin film 12 Die 14 Hand 16 Cooling roll 18 Touch roll 20 Direction of film discharge from die 30 Film-like molten resin (resin)
32 Die lip portion 34 Resin thickness at discharge port 40 inside die 36 Resin thickness just after discharge 38 Discharge direction 40 Discharge port 42 Discharge direction of film-like molten resin from die discharge port 44 Film-like molten resin 30 Film surface direction 50 Auxiliary roll 52 Auxiliary roll connecting member 60 Regulation plate 70 Blowing unit 72 Blowing path 74 Wind direction 100 Thermoplastic resin 110 extruded in a film shape Film forming device (thermoplastic resin film manufacturing device)
112 Hopper 114 Extruder 116 Gear Pump 118 Filter 120 Die 122 First Cooling Roll 124 Second Cooling Roll 126 Third Cooling Roll 128 Contact Roll 140 Piping D Recess θ The discharge direction 42 of the film-like molten resin from the die discharge port, and the film Of the angle between the film-shaped molten resin 30 and the film surface direction 44

Claims (9)

The film-shaped molten resin is discharged from the die with the die swell ratio being 1.3 or less, and the discharge direction of the film-shaped molten resin from the die discharge port and the film surface direction of the film-shaped molten resin at the die discharge port are formed. A step of contacting the film-like molten resin with a cooling roll while restricting the maximum angle θ to 45 ° or less, and starting take-off;
After the start of taking, the film-like molten resin is further discharged from the die, and the discharged film-like molten resin is cooled and wound while being taken up by the cooling roll,
After the step of initiating the take-up, before the step of cooling and winding, the angle between the discharge direction of the film-like molten resin from the die discharge port and the film surface direction of the film-like molten resin is 45 ° or less. after moving either or both of the die and the cooling roll becomes located, see containing and a step of removing the restriction means,
The surface energy of the lip portion of the die is 52 mN / m or less;
A method for producing a thermoplastic resin film.   The thermoplastic resin according to claim 1, wherein the auxiliary roll disposed between the die and the cooling roll and the film-shaped molten resin are in contact with each other over the entire width of the film-shaped molten resin to perform the regulation. A method for manufacturing a resin film.   The method for producing a thermoplastic resin film according to claim 1, wherein the regulation is performed by bringing a regulating plate disposed between the die and the cooling roll into contact with the film-like molten resin.   2. The thermoplastic resin according to claim 1, wherein air is generated by air blowing means disposed between the die and the cooling roll, and the restriction is performed by contact between the air and the film-like molten resin. 3. A method for manufacturing a resin film.   The heat according to any one of claims 1 to 4, wherein, in the step of cooling and winding, a touch roll that presses the cooling roll is used, and a resin passes between the cooling roll and the touch roll. A method for producing a plastic resin film.   In the step of starting the take-off, the oxygen concentration at the die discharge port is set to 1% or less from the time when the molten resin is extruded to the die until the time when the film-like molten resin starts to be discharged from the die. Item 6. The method for producing a thermoplastic resin film according to any one of items 5. The method for producing a thermoplastic resin film according to any one of claims 1 to 6 , wherein a bright line width of an edge portion on a discharge port side of the lip portion of the die is 10 µm or less. After the step of removing the regulating means, and before the step of cooling and winding, a step of further moving one or both of the die and the cooling roll to reduce the distance between the discharge port of the die and the cooling roll. The method for producing a thermoplastic resin film according to claim 1 , comprising: The method for producing a thermoplastic resin film according to any one of claims 1 to 8, wherein the thermoplastic resin is an acrylic resin, a polycarbonate, or a cyclic olefin resin.