JPWO2018159424A1 - Thermoplastic resin film and method for producing thermoplastic resin film - Google Patents

Abstract

The ratio Er30 at 30 ° C. of the elastic modulus ETD in the film width direction perpendicular to the film conveying direction to the elastic modulus EMD in the film conveying direction is 1.1 to 1.8, and the elastic modulus with respect to the elastic modulus EMD The difference between the maximum value Ermax and the minimum value Ermin selected from the ratio Er30 at 30 ° C., the ratio Er 90 at 90 ° C., the ratio Er 120 at 120 ° C., the ratio Er 150 at 150 ° C., and the ratio Er 180 at 180 ° C. Is a method for producing a thermoplastic resin film and a thermoplastic resin film.

Description

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

  The thermoplastic resin film is produced by melt extrusion of a thermoplastic resin to form a film, and then a process such as heat treatment such as stretching and thermal relaxation. In recent years, a thermoplastic resin film has been imparted with various functions by applying or sticking a functional material on the film, and is widely used as a functional film.

  On the other hand, in the case of a thin thermoplastic resin film, when heat treatment is performed in the process of imparting functionality to the film, streak wrinkles (wrinkles) extending in the film conveyance direction are formed in the film width direction during the heat treatment. May occur in multiple rows. Since the shape of the wrinkles is fixed by cooling after the heat treatment, the appearance of the wrinkles may be hindered as a failure such as film quality or coating unevenness.

As a technique related to the above, for example, in Japanese Patent Application Laid-Open No. 2014-238612, by using a base film having a tensile modulus of elasticity of 140 MPa or more with a film transport direction as a tensile direction, A technique for suppressing defects is disclosed.
Further, for example, Japanese Patent Application Laid-Open No. 2014-210433 discloses a polyester resin molded film having an elastic modulus at 30 ° C. and 100 ° C. in a specific range from the viewpoint of the shape stability and flexibility of the film. .

As described above, various studies have been made on the technology for improving the wrinkle or flatness of the film. For example, the transport tension in each process is lowered. However, wrinkles that tend to appear in a wavy shape in the film width direction are the ease of twisting of the film when thermally contracted with the heat treatment of the film, or the ease of movement of the film when the film is thermally expanded (for example, the surface of the transport roll) It appears due to film slipperiness, etc.).
Although the above Patent Documents 1 and 2 disclose a technique for improving the generation of wrinkles and the like by adjusting the elastic modulus in one direction of the film, simply adjusting the elastic modulus in the film transport direction, for example, A sufficient improvement effect cannot be expected in a film having such a property that a barrier is created when trying to relax the dimensional change in one direction due to thermal shrinkage or thermal expansion of the film in the other direction.
And the wrinkle which generate | occur | produces in a film becomes so remarkable that the thickness of a film is thin, and the magnitude | size of a wrinkle also becomes large.

The present disclosure has been made in view of the above.
A problem to be solved by an embodiment of the present disclosure is to provide a thermoplastic resin film in which the occurrence of wavy wrinkles is suppressed to a minimum.
Another problem to be solved by another embodiment of the present disclosure is that a thermoplastic resin film that is less likely to generate wavy wrinkles even when a thin thermoplastic resin film (preferably having a thickness of 200 μm or less) is heated and conveyed. It is in providing the manufacturing method of.

Specific means for achieving the above object includes the following aspects.
<1> The ratio Er ³⁰ at 30 ° C. in the elastic modulus E ^TD in the film width direction orthogonal to the film conveying direction of the elastic modulus E ^MD in the film conveying direction is 1.1 to 1.8, and Ratio Er ³⁰ of elastic modulus E ^TD relative to elastic modulus E ^MD , ratio Er ³⁰ at 30 ° C., ratio Er ⁹⁰ at 90 ° C., ratio Er ¹²⁰ at 120 ° C., ratio Er ¹⁵⁰ at 150 ° C., and ratio at 180 ° C. The thermoplastic resin film has a difference between a maximum value Er _max selected from Er ¹⁸⁰ and a minimum value Er _min of 0.7 or less.
<2> The thermoplastic resin film according to <1>, wherein the surface roughness Ra of at least one surface is 0.5 nm to 50 nm.
<3> The thermoplastic resin film according to <1> or <2>, wherein the thickness is 200 μm or less.
<4> The thermoplastic resin film according to any one of <1> to <3>, which is a polyester film or a cyclic polyolefin film.

<5> The method for producing a thermoplastic resin film according to any one of <1> to <4>,
Melting and extruding the raw material resin, cooling and molding a thermoplastic resin sheet;
Performing a first stretching in the longitudinal direction on the molded thermoplastic resin sheet to obtain a thermoplastic resin film;
Preheated part for preheating thermoplastic resin film, stretched part for stretching preheated thermoplastic resin film in the film width direction perpendicular to the longitudinal direction of the thermoplastic resin film, thermoplastic resin subjected to tension The thermoplastic resin film is sequentially conveyed to a heat fixing part for heating and fixing the film, a heat relaxing part for relaxing the tension, and a cooling part for cooling the thermally relaxed thermoplastic resin film. Stretching the step,
Including
The area magnification, which is the product of the draw ratio in the first draw and the draw ratio in the second draw, is 12.8 to 15.5 times,
The step of performing the second stretching is such that in the cooling part, the thermoplastic resin film that has been subjected to thermal relaxation is further tensioned in the film width direction, and −1 with respect to the film width at the end of thermal relaxation in the thermal relaxation part. It is a method for producing a thermoplastic resin film, wherein the thermoplastic resin film is expanded or reduced in the range of 5% to 3%.

<6> The step of performing the second stretching is the method for producing a thermoplastic resin film according to <5>, in which the thermoplastic resin film is stretched at a stretching speed of 8% / second to 45% / second in the stretching portion. is there.
<7> The thermoplastic resin film according to <5> or <6>, wherein the second stretching step is a step of stretching the thermoplastic resin film at a stretching speed of 15% / second to 40% / second in the stretching portion. It is a manufacturing method.
<8> The thermoplastic resin according to any one of <5> to <7>, wherein the second stretching step includes stretching the thermoplastic resin film at a stretching temperature of 100 ° C. to 150 ° C. in the stretching portion. It is a manufacturing method of a film.
<9> The thermoplastic resin according to any one of <5> to <8>, wherein the second stretching step includes stretching the thermoplastic resin film at a stretching temperature of 110 ° C. to 140 ° C. in the stretching portion. It is a manufacturing method of a film.

<10> Any one of <5> to <9>, wherein an area ratio, which is a product of a draw ratio in the first draw and a draw ratio in the second draw, is 13.5 times to 15.2 times. It is a manufacturing method of the thermoplastic resin film as described in one.
<11> In the cooling section, the second stretching step extends the thermoplastic resin film in a range of 0.0% to 2.0% with respect to the film width at the end of thermal relaxation in the thermal relaxation section. <5> to <10> The method for producing a thermoplastic resin film according to any one of <5> to <10>.
<12> The step of performing the first stretching is the heat described in any one of <5> to <11> in which the stretching is performed on the thermoplastic resin sheet at a stretching ratio of 2 to 5 times. It is a manufacturing method of a plastic resin film.

According to one embodiment of the present disclosure, a thermoplastic resin film in which generation of wavy wrinkles is suppressed is provided.
According to another embodiment of the present disclosure, there is provided a method for producing a thermoplastic resin film that is less likely to cause wavy wrinkles even when a thin thermoplastic resin film (preferably having a thickness of 200 μm or less) is heated and conveyed. Provided.

It is a top view which shows an example of a biaxial stretching machine. It is a conceptual diagram for demonstrating the mechanism in which twist arises by the anisotropy of the elastic modulus of a film. It is a front view for demonstrating the mechanism in which a twist arises in a film on a conveyance roll. It is a front view which shows the state which the film twisted and buckled on the conveyance roll.

Hereinafter, the thermoplastic resin film of the present disclosure and the manufacturing method thereof will be described in detail.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. In a numerical range described in stages in the present disclosure, an upper limit value or a lower limit value described in a numerical range may be replaced with an upper limit value or a lower limit value in another numerical range. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the values shown in the examples.

  In addition, in this specification, the term “process” is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term is used as long as the intended purpose of the process is achieved. include.

<Thermoplastic resin film>
The thermoplastic resin film of the present disclosure, for the elastic modulus of the film conveyance direction ^{E MD,} in the film width direction perpendicular to the film conveying direction of the elastic modulus ^{E TD,} the ratio ^{Er 30} at 30 ° C., 1.1 to 1. 8 and a ratio Er ³⁰ at 30 ° C., a ratio Er ⁹⁰ at 90 ° C., a ratio Er ¹²⁰ at 120 ° C., a ratio Er ¹⁵⁰ at 150 ° C., and a ratio Er ¹⁸⁰ at 180 ° C. The difference between the value Er _max and the minimum value Er _min is 0.7 or less.
Er ³⁰ , Er ⁹⁰ , Er ¹²⁰ , Er ¹⁵⁰ and Er ¹⁸⁰ are as follows.
Er ³⁰ represents the ratio of the elastic modulus E ^{TD in} the film width direction to the elastic modulus E ^{MD in the} film transport direction when the film temperature is 30 ° C.
Er ⁹⁰ represents the ratio of the elastic modulus E ^{TD in} the film width direction to the elastic modulus E ^{MD in the} film transport direction when the film temperature is 90 ° C.
Er ¹²⁰ represents the ratio of the elastic modulus E ^{TD in} the film width direction to the elastic modulus E ^{MD in the} film transport direction when the film temperature is 120 ° C.
Er ¹⁵⁰ represents the ratio of the elastic modulus E ^{TD in} the film width direction to the elastic modulus E ^{MD in the} film transport direction when the film temperature is 150 ° C.
Er ¹⁸⁰ represents the ratio of the elastic modulus E ^{TD in} the film width direction to the elastic modulus E ^{MD in the} film transport direction when the film temperature is 180 ° C.

The "difference between the maximum value _{Er max} and the minimum value _{Er ^min",} select ^{Er 30, Er 90, Er 120} , up from ^{Er 0.99} and ^{Er 180} value _{Er max} and the minimum value _{Er min,} the minimum from the maximum value _{Er max} It refers to the value obtained by subtracting the value Er _min .

  In the present disclosure, a thermoplastic resin film is also simply referred to as “film”, and a film having a thickness of 200 μm or less is also referred to as “thin film”. From the viewpoint of the effect of the embodiment of the present invention, the thickness of the thin film is preferably 100 μm or less, and more preferably 50 μm or less.

Although the manufacturing method of a thermoplastic resin film is explained in full detail later, a thin film is normally obtained by conveying and extending | stretching using a roll etc. Here, the film conveyance direction is also referred to as MD (Machine Direction) direction. The MD direction of the film is also referred to as the longitudinal direction of the film. Moreover, the width direction of a film is a direction orthogonal to the longitudinal direction of a film. The width direction of the film is also called a TD (Transverse Direction) direction in a film manufactured while conveying the film.
In this specification, the film conveyance direction is referred to as “MD” or “MD direction”, and the film width direction orthogonal to the film conveyance direction is referred to as “TD” or “TD direction”.

The thermoplastic resin film may be made highly functional or composite by laminating a plurality of thermoplastic resin films or laminating a functional layer on the thermoplastic resin film. In processing such a thermoplastic resin film, the film is usually stretched and heated while being conveyed by a roll or the like.
When a thin thermoplastic resin film is heated and conveyed, wrinkles (wrinkles) arranged in a concavo-convex shape tend to occur so as to wave in the TD direction of the thermoplastic resin film.
The following factors can be considered for this phenomenon.
(1) The elastic modulus in the TD direction is smaller than the elastic modulus in the MD direction.
As described above, the thermoplastic film is conveyed by a roll or the like. At this time, compressive stress acts in the TD direction by Poisson effect due to stress acting in the MD direction, such as transport tension. When the elastic modulus in the TD direction is smaller than the elastic modulus in the MD direction, the generated compressive stress in the TD direction disturbs the shape of the film in the TD direction, so that it is considered that twisting occurs in the TD direction of the film. That is, as shown in FIG. 2, when the polymer main chain (solid line in FIG. 2) exists along the MD direction and the molecular orientation in the MD direction is strong, the space between the main chains is a side chain (see FIG. The TD direction of the film connected only by the broken line in 2) has a weaker shape retention force than the MD direction, and the anisotropy of the film strength is increased. Therefore, it is estimated that the film tends to be wrinkled in the TD direction as shown in FIG. On the other hand, when the molecular orientation in the TD direction is strong (the polymer main chain is aligned in the TD direction), the molecular chain becomes resistance to deformation, and the film is wrinkled in the TD direction. It will be difficult.
That is, it is estimated that the ratio of the elastic modulus between the MD direction and the TD direction of the film can contribute to the generation of wrinkles.
(2) The holding force at the end in the TD direction of the film by the transport roll is strong.
During the heating process, the film tends to expand at the widths z ¹ and z ² at the end in the TD direction as shown in FIG. At this time, if the holding force at both ends of the film 3 on the surface of the transport roll 4 is strong, the expanded film 3 does not move in the TD direction, and the stress σ _x corresponding to the expansion escapes in the film thickness direction. Therefore, it is considered that the film 3 is twisted in the TD direction and buckled as shown in FIG. As a result, it is estimated that wrinkles appear in the TD direction of the film.
Since the roughness of the film surface also affects the holding force, it is estimated that it can contribute to the generation of wrinkles.

As described above, the film is cooled and solidified while wavy wrinkles are generated in the TD direction of the film, whereby unevenness derived from the wavy wrinkles remaining in the film is referred to as streaky in this specification. burr).
If the thermoplastic resin film has streak-like burrs, several harmful effects are likely to occur. Detrimental effects include, for example, difficulty in uniformly applying a coating solution on a film, winding failure (winding misalignment, wrinkles, etc.) during film winding, and functional layers such as a laminate layer on the film. In the case of pasting, bubbles may enter between the film and the functional layer.

Thin thermoplastic resin films have been conventionally used for magnetic tapes, for example. Conventionally, a coating solution using an organic solvent as a solvent is generally applied to the film, and the heating temperature to the film required to volatilize and remove the solvent has been low (for example, 100 ° C. or lower). However, in recent years, there is a tendency to use an aqueous solvent (a solvent containing water) for environmental protection, and the film may be heated at a high temperature of about 150 ° C. to volatilize and remove the aqueous solvent. In addition, a material that is cured by heating (so-called hardener) may be laminated on the film. Furthermore, when a film contains a hardening agent, a film may be heated at 170 to 180 degreeC.
When the film is heated as described above, wrinkles are more likely to occur in the film, and the occurrence of streak burrs is more likely to occur than in the past.

Under the above situation, the occurrence of streak burrs was examined.
It is considered that the streak burrs are caused by the film being deformed into a wrinkle shape due to thermal expansion due to heating of the film and the tension during film conveyance, and the film being fixed in the deformed state. The generation of streak burrs is a phenomenon that can occur anywhere in the heated process. Specifically, immediately after the molten resin is discharged onto the cooling roll in the film forming process, the film is stretched in the MD direction and then in the TD direction. This is a phenomenon that may occur after stretching, after annealing for removing the residual stress of the film, and after drying treatment after applying a coating solution on the film. Further, even when no streak burrs are observed in the film after film formation, streak burrs may appear through subsequent annealing or drying.
Conventionally, it is known that wrinkle-like deformation is suppressed by suppressing the transport tension during film transport in each step in the manufacturing process. However, suppressing the conveyance tension is in a trade-off relationship with maintaining good coating property or winding property, and a sufficient improvement effect cannot always be expected only by controlling the tension.
Moreover, for example, as described in Japanese Patent Application Laid-Open No. 2014-238612 and Japanese Patent Application Laid-Open No. 2014-210433, attempts have been made to improve wrinkles and other failures by paying attention to the elastic modulus in one direction of the film surface. In addition, the inhibitory effect on the occurrence of streak burrs is not sufficient.

The thermoplastic resin film and the manufacturing method thereof of the present disclosure are in view of the above circumstances.
The streak caused by heating is caused by the film being deformed and waved in the TD direction by the thermal expansion due to the heating of the film and the tension applied to the film during conveyance, and is generated. Therefore, in the thermoplastic resin film of the present disclosure, the elastic modulus E ^TD in the TD direction is made higher than the elastic modulus E ^MD in the MD direction, and the temperature dependence of the elastic modulus E ^TD is kept small.
Specifically, the ratio Er ³⁰ of the elastic modulus E ^TD to the elastic modulus E ^MD at 30 ° C. is 1.1 to 1.8, the ratio Er ³⁰ at 30 ° C., and the ratio Er ⁹⁰ at 90 ° C. ⁹⁰ The difference between the maximum value Er _max and the minimum value Er _min selected from the ratio Er ¹²⁰ at 120 ° C., the ratio Er ¹⁵⁰ at 150 ° C., and the ratio Er ¹⁸⁰ at 180 ° C. is 0.7 or less.
That is, when the polymer chain is aligned in the MD direction and the molecular orientation in the MD direction is strong, the anisotropy becomes stronger and the twist occurs in the TD direction, and the film is easily buckled and deformed. By arranging the chains in the TD direction and strengthening the molecular orientation in the TD direction, the molecular chains become resistant to deformation, and the film is less likely to buckle in the TD direction. In manufacturing a thermoplastic resin film, various heating temperatures can be considered during the heat treatment, and anisotropy of elastic modulus is observed in a wide temperature range of 30 ° C, 90 ° C, 120 ° C, 150 ° C, and 180 ° C. Since it is small, the buckling of the film in the TD direction is effectively suppressed.
Thereby, generation | occurrence | production of the wavy wrinkle (streaky burr | flash) of a thermoplastic resin film is suppressed.

In the thermoplastic resin film of the present disclosure, the ratio Er ³⁰ of the elastic modulus E ^TD to the elastic modulus E ^MD at 30 ° C. is 1.1 to 1.8.
When Er ³⁰ is 1.1 or more, the molecular chain becomes a resistance to deformation and the film is prevented from buckling, so that the generation of streak burrs is suppressed. The higher the value of Er ³⁰ , the higher the suppression effect on the streak burrs can be expected. Moreover, by making Er ³⁰ 1.8 or less, the molecular orientation in the TD direction does not increase excessively, and the tearing of the film can be suppressed.
Er ³⁰ is preferably 1.1 to 1.6 and more preferably 1.2 to 1.4 for the same reason as described above.

The elastic modulus E ^{MD in the} film transport direction and the elastic modulus E ^{TD in the} film width direction can be adjusted by the respective stretching ratios of MD stretching and TD stretching, the stretching speed, and the balance between MD and TD. Moreover, in the cooling part of a 2nd extending | stretching process, it can adjust also by adjustments, such as a ratio etc. which give a tension | tensile_strength further to the width direction with respect to the film extended | stretched by the extending part.

In the thermoplastic resin film of the present disclosure, the ratio Er ³⁰ at 30 ° C., the ratio Er ⁹⁰ at 90 ° C., the ratio Er ¹²⁰ at 120 ° C., the ratio Er ¹⁵⁰ at 150 ° C., and the ratio Er ¹⁸⁰ at 180 ° C. The difference between the selected maximum value Er _max and minimum value Er _min is 0.7 or less.
The difference between the maximum value Er _max and the minimum value Er _min indicates that variation in the ratio of elastic moduli at each temperature is suppressed. Since the difference between the maximum value Er _max and the minimum value Er _min is 0.7 or less, molecular orientation is preferentially made in the TD direction at any film temperature, and the heating temperature during the heat treatment is wide. Even in such a manufacturing process, the buckling of the film in the TD direction can be effectively suppressed.
The difference between the maximum value Er _max and the minimum value Er _min is preferably as small as possible. Specifically, the difference is preferably 0.6 or less, more preferably 0.5 or less, and more preferably 0.4 or less.
The lower limit of the difference between the maximum value Er _max and the minimum value Er _min is, for example, 0.1.

Er ³⁰ , Er ⁹⁰ , Er ¹²⁰ , Er ¹⁵⁰ , and Er ¹⁸⁰ are preferably in the following ranges from the viewpoint of minimizing the difference between the maximum value Er _max and the minimum value Er _min .
As Er ⁹⁰ , 1.1-1.8 are preferable, 1.2-1.6 are more preferable, 1.2-1.4 are still more preferable.
The Er ^120, preferably from 1.1 to 1.8, more preferably 1.2 to 1.6, more preferably 1.2 to 1.5.
As Er ¹⁵⁰ , 0.8-1.5 are preferable, 0.9-1.3 are more preferable, and 1.0-1.2 are still more preferable.
The Er ^180, preferably from 0.8 to 1.5, more preferably 0.9 to 1.3, more preferably 1.0 to 1.2.

  Adjustment of the elastic modulus ratio at each temperature is performed by adjusting the stretching ratio in the MD direction and the stretching ratio in the TD direction, or stretching in the process of stretching in the TD direction during film production (second stretching process described later). This can be done by adjusting the speed (stretching ratio / second).

Ratio of elastic modulus E ^{TD in} the film width direction perpendicular to the film conveying direction to elastic modulus E ^MD in the film conveying direction at each temperature of 30 ° C., 90 ° C., 120 ° C., 150 ° C. and 180 ° C. (Er; = elasticity The ratio E ^TD / elastic modulus E ^MD ) is a value obtained by the following method.
First, a sample piece is punched out from a film to be measured (width 6 × length 115 mm (JIS K 6251, dumbbell shape No. 5)). The obtained sample piece is pulled with Tensilon (manufactured by Toyo Seiki Co., Ltd., Strograph VE50) under the conditions of 50 mm between chucks and a pulling speed of 100 mm / min, and the elongation of the film with respect to the load is measured. A graph with the load on the horizontal axis and the elongation on the vertical axis is created from the measured values, and the elastic modulus is calculated from the tangent of the rising portion of the load-elongation curve. This operation is performed 5 times, and an average value of three points excluding the maximum value and the minimum value is defined as the elastic modulus. And about each temperature, it implements about each of the case where it pulls in a film conveyance direction, and the case where it pulls in a film width direction.
Here, the elastic modulus in the case of pulling the film conveying direction and E ^MD, denoted the elastic modulus when stretched in the film width direction E ^TD.
<Measurement conditions>
・ Measurement place: Hot air heating furnace ・ Measurement temperature: 30 ° C, 90 ° C, 120 ° C, 150 ° C, 180 ° C
(The set temperature of the furnace rises to the desired temperature in 1.5 minutes, and the temperature is set and the air volume is adjusted so that the temperature rise falls within 2 ° C. even after 1 minute has passed from the desired temperature.)
・ Temperature control: A test piece of the same type and size for temperature measurement is installed near the test piece, a thermocouple is attached to the test piece for temperature measurement, and the temperature at the time of measurement is monitored.
(The above “when the film temperature is 30 ° C.” refers to the case where the temperature of the test piece for temperature measurement is 30 ° C. The same applies to other temperatures.)
Test start timing: Pulling is started after reaching a desired temperature.

The surface roughness (Ra) of at least one surface of the thermoplastic resin film of the present disclosure is preferably 0.5 nm to 50 nm.
When Ra is 0.5 nm or more, for example, the slipperiness on the surface of the transport roll can be improved, and the effect of improving streak burrs is excellent. Further, when Ra is 50 nm or less, there is no failure in the appearance, and it is suitable for optical applications.
In general, the thermoplastic resin film expands in the TD direction during the heating step, but the holding force on the surface of the transport roll at the end in the TD direction of the film is strong, and the expanded film cannot move in the TD direction. Stress tries to escape in the thickness direction. As a result, wrinkles are generated so as to wave in the TD direction, resulting in streak burrs. In the thermoplastic resin film of the present disclosure, the occurrence of streak burrs in the film can be suppressed by adjusting the surface roughness (Ra) of the film to the above range.
Ra is expected to be more effective in reducing streak burrs as the value increases (that is, the surface becomes rougher). Above all, Ra is preferably 0.8 nm to 30 nm, and more preferably 1 nm to 20 nm, from the viewpoint of effectively reducing streak burrs while suppressing the influence on other properties.

  Ra is adjusted to a desired Ra value by adjusting the stretching speed (stretching ratio / second) in the step of stretching in the TD direction during film production (second stretching step described later) or by adjusting the stretching temperature. Can do. Specifically, Ra value can be increased (roughening the surface) by, for example, increasing the stretching speed when stretching in the TD direction or decreasing the stretching temperature when stretching in the TD direction. it can.

Ra is a value measured by the following method. That is,
Using a contact shape measuring machine (Mitutoyo FORMRACER EXTREME CS-5000 CNC), in accordance with JIS B 0601: 2001, measurement is performed 12 times in any position in the MD direction and the TD direction under the following conditions. The average of 10 points in the MD direction and 10 points in the TD direction from which the minimum value and the maximum value are removed is determined, and the average value of 20 points is defined as Ra.
<Conditions>
・ Measurement needle tip diameter: 0.5 μm
-Stylus load: 0.75mN
・ Measurement length: 0.8mm
・ Cutoff value: 0.08mm

The thickness of the thermoplastic resin film of the present disclosure is preferably in the range of 200 μm or less.
In the case of a thin film having a thickness of 200 μm or less, wavy wrinkles in the TD direction are particularly likely to occur due to heat treatment. Therefore, when the thickness is 200 μm or less, the effect of the thermoplastic resin film of the present disclosure is further exhibited.
As a thickness of a thermoplastic resin film, the range of 100 micrometers or less is more preferable, the range of 80 micrometers or less is still more preferable, and the range of 50 micrometers or less is still more preferable.
The lower limit value of the thickness of the thermoplastic resin film is, for example, 1 μm.

  The thickness of the thermoplastic resin film is measured at intervals of 50 mm over the entire width in the TD direction of the film using a tactile film thickness measuring machine (Mitutoyo ID-C112X). This operation is performed 5 sets at 1 m intervals in the MD direction, and the average value of the measured values is defined as the thickness.

Examples of the raw material resin for forming the thermoplastic resin film of the present disclosure include polyester and cyclic olefin resin.
As polyester, polyethylene terephthalate (Polyethylene terephthalate; PET) and polyethylene-2,6-naphthalate (Polyethylene naphthalate; PEN) are preferable, and PET is more preferable.
The cyclic olefin resin is a polymer resin having a cyclic olefin structure, and examples of the polymer resin having a cyclic olefin structure include (1) a norbornene-based polymer, (2) a monocyclic cyclic olefin polymer, ( 3) Polymers of cyclic conjugated dienes, (4) vinyl alicyclic hydrocarbon polymers, and hydrides of (1) to (4).

-Polyester-
Polyester is synthesized by copolymerizing a dicarboxylic acid component and a diol component. The polyester can be obtained, for example, by subjecting the (A) dicarboxylic acid component and the (B) diol component to an esterification reaction and / or transesterification reaction by a well-known method and polycondensing the reaction product. At this time, a trifunctional or higher polyfunctional monomer may be further copolymerized. Moreover, polyester may contain terminal blockers, such as an oxazoline type compound, a carbodiimide compound, and an epoxy compound.
In addition, about illustration, preferable aspects, such as a terminal blocker and a reaction catalyst, and details, such as polycondensation, description of Paragraphs 0051-0064, Paragraphs 0121-0124, and Paragraphs 0087-0111 of Unexamined-Japanese-Patent No. 2014-189002. Can be referred to.

(A) Examples of the dicarboxylic acid component include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid Aliphatic dicarboxylic acids such as ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexanedicarboxylic acid, decalin dicarboxylic acid, alicyclic dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4- Naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid, 4,4′-diphenyl dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, 5-sodium sulfo Isophthalic acid, phenyli Boy carboxylic acid, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) a dicarboxylic acid or its ester derivatives such as aromatic dicarboxylic acids such as fluorene acid.
(B) Examples of the diol component include fats such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol. Diols, cycloaliphatic dimethanol, spiroglycol, isosorbide and other alicyclic diols, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'-bis (4-hydroxyphenyl) ) Diol compounds such as aromatic diols such as fluorene.

(A) As a dicarboxylic acid component, the case where at least 1 sort of aromatic dicarboxylic acid is used is preferable. More preferably, the dicarboxylic acid component contains an aromatic dicarboxylic acid as a main component. A dicarboxylic acid component other than the aromatic dicarboxylic acid may be included. Examples of such a dicarboxylic acid component include ester derivatives such as aromatic dicarboxylic acids.
The “main component” means that the proportion of aromatic dicarboxylic acid in the dicarboxylic acid component is 80% by mass or more.
(B) As a diol component, the case where at least 1 sort of aliphatic diol is used is preferable. The aliphatic diol can contain ethylene glycol, and preferably contains ethylene glycol as a main component.
The main component means that the proportion of ethylene glycol in the diol component is 80% by mass or more.

  The amount of the diol component is preferably in the range of 1.015 mol to 1.50 mol, more preferably 1.02 mol to 1.30 mol, with respect to 1 mol of the dicarboxylic acid component and, if necessary, its ester derivative. And more preferably 1.025 mol to 1.10 mol. When the amount of the diol component is 1.015 or more, the esterification reaction proceeds well. Further, when the amount of the diol component is 1.50 mol or less, for example, by-production of diethylene glycol due to ethylene glycol dimerization is suppressed, and melting point, glass transition temperature, crystallinity, heat resistance, hydrolysis resistance, and weather resistance are suppressed. It is possible to maintain good characteristics such as properties.

  The raw material resin preferably contains a polyfunctional monomer having a total (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) of 3 or more as a copolymerization component. “The raw material resin contains a polyfunctional monomer as a copolymerization component” means that the raw material resin contains a structural unit derived from the polyfunctional monomer.

Examples of the structural unit derived from the polyfunctional monomer having the sum (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) of 3 or more include the structural units derived from carboxylic acids shown below. .
Examples of carboxylic acids having 3 or more carboxylic acid groups (a) (ie, polyfunctional monomers) include trifunctional aromatic carboxylic acids such as trimesic acid, trimellitic acid, pyromellitic acid, and naphthalenetricarboxylic acid. Anthracentricarboxylic acid, and the like. Examples of the trifunctional aliphatic carboxylic acid include methanetricarboxylic acid, ethanetricarboxylic acid, propanetricarboxylic acid, and butanetricarboxylic acid. Examples of the tetrafunctional aromatic carboxylic acid include Examples thereof include benzenetetracarboxylic acid, benzophenonetetracarboxylic acid, naphthalenetetracarboxylic acid, anthracenetetracarboxylic acid, and perylenetetracarboxylic acid. Examples of tetrafunctional aliphatic carboxylic acids include ethanetetracarboxylic acid, ethylenetetra Carboxylic acid, butane Examples thereof include tracarboxylic acid, cyclopentanetetracarboxylic acid, cyclohexanetetracarboxylic acid, adamantanetetracarboxylic acid, etc. Examples of pentafunctional or higher functional aromatic carboxylic acids include benzenepentacarboxylic acid, benzenehexacarboxylic acid, and naphthalenepentacarboxylic acid. , Naphthalene hexacarboxylic acid, naphthalene heptacarboxylic acid, naphthalene octacarboxylic acid, anthracene pentacarboxylic acid, anthracene hexacarboxylic acid, anthracene heptacarboxylic acid, anthracene octacarboxylic acid, and the like. For example, ethanepentacarboxylic acid, ethaneheptacarboxylic acid, butanepentacarboxylic acid, butaneheptacarboxylic acid, cyclopentanepentacarboxylic acid, cyclohexanepentacarboxylic acid Cyclohexanehexacarboxylic acid, adamantane penta carboxylic acid, and adamantane hexa acid.
These ester derivatives, acid anhydrides, and the like are listed as examples of carboxylic acids having 3 or more carboxylic acid groups (a) (that is, polyfunctional monomers), but are not limited thereto.

  Moreover, as the carboxylic acid having 3 or more carboxylic acid groups (a) (that is, a polyfunctional monomer), an oxyacid such as l-lactide, d-lactide, hydroxybenzoic acid, Those obtained by adding a derivative thereof or a combination of a plurality of such oxyacids are also preferably used.

Examples of polyfunctional monomers having a hydroxyl number (b) of 3 or more include trifunctional aromatic compounds such as trihydroxybenzene, trihydroxynaphthalene, trihydroxyanthracene, trihydroxychalcone, trihydroxyflavone, and trihydroxycoumarin. Examples of the trifunctional aliphatic alcohol include glycerin, trimethylolpropane, and propanetriol. Examples of the tetrafunctional aliphatic alcohol include pentaerythritol. As the polyfunctional monomer having a hydroxyl number (b) of 3 or more, a compound in which a diol is added to the hydroxyl terminal of the above compound is also preferably used.
These may be used individually by 1 type, or may use multiple types together as needed.

  Moreover, as other polyfunctional monomers other than the above, one molecule has both a hydroxyl group and a carboxylic acid group, and the total (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) is 3 The oxyacids which are the above are also mentioned. Examples of oxyacids include hydroxyisophthalic acid, hydroxyterephthalic acid, dihydroxyterephthalic acid, and trihydroxyterephthalic acid. In addition, as other polyfunctional monomers, oxyacids such as l-lactide, d-lactide, hydroxybenzoic acid, and derivatives thereof, and a combination of a plurality of such oxyacids are added to the carboxy terminus of the polyfunctional monomer. Are also preferably used.

  As for the content ratio in the raw material resin of the structural unit derived from a polyfunctional monomer, 0.005 mol%-2.5 mol% are preferable with respect to all the structural units in raw material resin. The content ratio of the structural unit derived from the polyfunctional monomer is more preferably 0.020 mol% to 1 mol%, and still more preferably 0.05 mol% to 0.5 mol%.

  A coating layer in which a functional group that is not used for polycondensation is formed on a polyester film when a polyester film is formed by the presence of a structural unit derived from a trifunctional or higher polyfunctional monomer in the raw material resin. By hydrogen bonding and covalent bonding with the components therein, the adhesion between the coating layer and the polyester film can be kept better, and the occurrence of peeling can be effectively prevented. Further, a structure in which a polyester molecular chain is branched from a structural unit derived from a trifunctional or higher polyfunctional monomer can be obtained, and entanglement between polyester molecules can be promoted.

  Conventionally known reaction catalysts can be used for the esterification reaction and / or the transesterification reaction. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and phosphorus compounds. Usually, it is preferable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst at an arbitrary stage before the polyester production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is.

When the thermoplastic resin film is a polyester film, the intrinsic viscosity (IV; Intrinsic Viscosity) of the polyester film is 0.55 dL / g or more and 0.90 dL from the viewpoint of improving the hydrolysis resistance of the polyester film and improving the weather resistance. / G or less, more preferably 0.60 dL / g or more and 0.80 dL / g or less, and still more preferably 0.62 dL / g or more and 0.78 dL / g or less.
The intrinsic viscosity (IV) is obtained by dividing the specific viscosity (η _sp = η _r −1) obtained by subtracting 1 from the ratio η _r (= η / η ₀ ; relative viscosity) of the solution viscosity η and the solvent viscosity η ₀ by the concentration. It is a value obtained by extrapolating the value to a state where the density is zero. IV is obtained from a solution viscosity at 25 ° C. by using a Ubbelohde viscometer, dissolving polyester in a 1,1,2,2-tetrachloroethane / phenol (= 2/3 [mass ratio]) mixed solvent.

When the thermoplastic resin film is a polyester film, the amount of terminal carboxy group [the amount of terminal COOH (also referred to as acid value), AV; Acid Value] of the polyester film is preferably 5 eq / ton or more and 35 eq / ton or less. The amount of terminal COOH is more preferably 6 eq / ton to 30 eq / ton, and still more preferably 7 eq / ton to 28 eq / ton.
In the present specification, “eq / ton” represents a molar equivalent per ton.
In AV, polyester is completely dissolved in a mixed solution of benzyl alcohol / chloroform (= 2/3; volume ratio), phenol red is used as an indicator, and titrated with a standard solution (0.025N KOH-methanol mixed solution). It is a value calculated from an appropriate amount.

-Cyclic olefin resin-
Examples of the cyclic olefin resin include addition (co) polymer cyclic polyolefin containing at least one repeating unit represented by the following general formula (II) and, if necessary, repeating represented by the following general formula (I) An addition (co) polymer cyclic polyolefin further containing at least one or more units may be mentioned. Moreover, as an example of cyclic olefin resin, the ring-opening (co) polymer which contains at least 1 sort (s) of cyclic repeating units represented with the following general formula (III) is also mentioned suitably.

Formula (I), (II), the 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 are each independently 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, or - represents a _{(CH 2) n} W. X ¹ and Y ¹ , X ² and Y ² , or X ³ and Y ³ may be combined with each other to form (—CO) ₂ O or (—CO) ₂ NR ¹⁵ . Here, R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and Z represents a hydrocarbon group or a hydrocarbon group substituted with a halogen. , W represents SiR ¹⁶ _p D _3-p , and n represents an integer of 0-10. D represents a halogen atom, —OCOR ¹⁶ or —OR ¹⁶ , R ¹⁶ represents a hydrocarbon group having 1 to 10 carbon atoms, and p represents an integer of 0 to 3.

By introducing a highly polarizable functional group into all or part of the substituents of X ^{1 to} X ³ and Y ^{1 to} Y ³ , the thickness direction retardation (Rth) of the optical film is increased, and an in-plane letter is formed. The expression of the foundation (Re) can be increased. A film having a high Re developability can increase the Re value by stretching in the film forming process.

Norbornene-based addition (co) polymers are disclosed in JP-A-10-7732, JP-T 2002-504184, US Patent Publication No. 2004 / 229157A1, International Publication No. 2004 / 070463A1, and the like. The norbornene-based addition (co) polymer is obtained by addition polymerization of norbornene-based polycyclic unsaturated compounds. In addition, the norbornene-based addition (co) polymer includes, as necessary, a norbornene-based polycyclic unsaturated compound, ethylene, propylene, butene; conjugated dienes such as butadiene and isoprene; non-conjugated dienes such as ethylidene norbornene; It may be obtained by addition polymerization of acrylonitrile, acrylic acid, methacrylic acid, maleic anhydride, acrylic acid ester, methacrylic acid ester, maleimide, vinyl acetate, vinyl chloride and other linear diene compounds.
Examples of norbornene-based addition (co) polymers on the market include, for example, Apel (trade name; glass transition temperature (Tg) different from Mitsui Chemicals, for example, APL8008T (Tg: 70 ° C.), APL6013T (Tg: 125 ° C), or APL6015T (Tg: 145 ° C), etc.), pellets such as TOPAS 8007, 6013, and 6015 from Polyplastics, and Appear 3000 from Ferrania.

Norbornene polymer hydrides are disclosed in JP-A-1-240517, JP-A-7-196636, JP-A-60-26024, JP-A-62-19807, JP-A-2003-159767, or JP-A-2004-2004. As disclosed in each publication such as No. 309979, it can be produced by addition polymerization or metathesis ring-opening polymerization of a polycyclic unsaturated compound and then hydrogenation.
In the norbornene-based polymer, in general formula (III), R ^{5 to} R ⁶ are preferably a hydrogen atom or —CH ₃ , X ³ and Y ³ are preferably a hydrogen atom, Cl, or —COOCH ₃ , and other groups are It is selected appropriately.
Examples of norbornene-based resins on the market include Arton G or Arton F (trade name) of JSR Corporation, Zeonor ZF14, ZF16, Zeonex 250, or Zeonex 250 of Nippon Zeon Corporation. 280 (trade name).

<Method for producing thermoplastic resin film>
The thermoplastic resin film of the present disclosure may be produced by any method as long as the above-described ratio Er ³⁰ and the difference between the maximum value Er _max and the minimum value Er _min satisfy a predetermined range. The thermoplastic resin film of the present disclosure is most suitably produced by the following method for producing a thermoplastic resin film of the present disclosure.
Hereinafter, the manufacturing method of the thermoplastic resin film of the present disclosure will be described in detail.

The method for producing a thermoplastic resin film of the present disclosure includes a step of melting and extruding a raw material resin, cooling to form a thermoplastic resin sheet (hereinafter, also referred to as “molding step”), and a longitudinal direction with respect to the thermoplastic resin sheet. A process of obtaining a thermoplastic resin film by performing a first stretching in the direction (MD) (hereinafter also referred to as a “first stretching process”), a preheating part for preheating the thermoplastic resin film, and a preheated thermoplastic Stretching part that stretches the resin film by applying tension in the film width direction orthogonal to the longitudinal direction of the thermoplastic resin film, heat fixing part that heats and heat-sets the thermoplastic resin film to which tension is applied, and the above The above-mentioned thermoplastic resin film is sequentially conveyed to a thermal relaxation part that relaxes the tension and a cooling part that cools the thermoplastic resin film that has been subjected to thermal relaxation, and a second stretching process (hereinafter referred to as “second stretching”). Also referred to as the Shin process ".) And includes,
The stretching ratio in the second stretching is larger than the stretching ratio in the first stretching, and the area ratio that is the product of the stretching ratio in the first stretching and the stretching ratio in the second stretching is 12 .8 times to 15.5 times,
The step of performing the second stretching further extends tension in the cooling part in the film width direction and expands in the range of −1.5% to 3% with respect to the film width at the end of thermal relaxation in the thermal relaxation part. Or reduce. For example, “−1.5%” means “1.5% reduction”.

In the method for producing a thermoplastic resin film of the present disclosure, the first stretching is performed on the thermoplastic resin sheet in the MD direction, and then the second stretching is performed in the TD direction. The stretch ratio in the second stretch is made larger than the stretch ratio in the second stretch, and the area ratio that is the product of the stretch ratio in the first stretch and the stretch ratio in the second stretch is 12. In addition to the ratio of 8 times to 15.5 times, in the step of performing the second stretching, the tension in the film width direction is already applied in the stretching part, and the tension is further applied in the film width direction in the cooling part after stretching. The film width is expanded or reduced within a range of -1.5% to 3% with respect to the film width at the end of thermal relaxation in the thermal relaxation portion. As above, for example, “−1.5%” means “1.5% reduction”.
Thereby, the thermoplastic resin film with which generation | occurrence | production of the wavy wrinkle (streaky burr | flash) was suppressed is obtained.

As described above, the method for producing a thermoplastic resin film of the present disclosure includes at least a forming step, a first stretching step, and a second stretching step, and may further include another step. Moreover, 1st extending | stretching means extending | stretching to the longitudinal direction (MD direction) of a film, and 2nd extending | stretching means extending | stretching to the width direction (TD direction) of a film.
In the method for producing a thermoplastic resin film of the present disclosure, the second stretching step conveys the thermoplastic resin film sequentially to the preheating part, the stretching part, the heat fixing part, the heat relaxation part, and the cooling part. It is done by doing.
Below, each process in the manufacturing method of the thermoplastic resin film of this indication is explained in full detail.

-Molding process-
In the forming step in the manufacturing method of the present disclosure, the raw material resin is melt-extruded and cooled to form a thermoplastic resin sheet.
The molding of the thermoplastic resin sheet is performed by charging the raw material resin and cooling the thermoplastic resin melt-extruded into a sheet shape on a casting roll.
The method for melting and extruding the raw material resin and the raw material resin are not particularly limited, but the intrinsic viscosity can be set to a desired intrinsic viscosity by a catalyst used for the synthesis of the raw material resin, a polymerization method, and the like.
Details of the raw material resin are as described above.

(Melting extrusion)
In the forming step, the raw material resin is melt-extruded and then subjected to cooling to form a thermoplastic resin sheet.
The raw material resin is melt-extruded, for example, by using an extruder equipped with one or two or more screws, heated to a temperature equal to or higher than the melting point of the raw material resin, rotating the screw, and melt-kneading. The raw material resin is melted in an extruder to become a molten resin (also referred to as melt) by heating and kneading with a screw. Further, from the viewpoint of suppressing thermal decomposition (for example, hydrolysis of polyester) in the extruder, it is preferable to perform melt extrusion of the raw material resin by replacing the inside of the extruder with nitrogen. The extruder is preferably a twin-screw extruder because the kneading temperature can be kept low.
The melted molten resin (melt) is extruded from an extrusion die through a gear pump, a filter, and the like. The extrusion die is also simply referred to as “die” (JIS B 8650: 2006, a) Extruder, see No. 134).
The melt may be extruded in a single layer or in multiple layers.

  When using polyester as the raw material resin and further including an end-capping agent in the raw material resin, the polyester raw material resin to which the end-capping agent has been added is melt-kneaded and reacted with the end-capping agent during melt-kneading in the molding step The raw material resin is melt extruded.

When the raw material resin is melt-extruded and cooled, the molten resin (melt) may be extruded from a die onto a casting roll to be formed into a sheet (that is, cast processing).
When extruding melt from the die, electrostatic casting method, air knife method, air chamber method, vacuum nozzle method, touch roll method, etc. are applied on the casting roll to bring the casting roll into close contact with the melt-extruded sheet. Is preferable. Among them, for example, when a polymer resin having a cyclic olefin structure is used as a raw material resin, it is preferable to improve the adhesion between the casting roll and the sheet by a touch roll method. The touch roll method is a method of shaping the surface of a sheet by placing a touch roll on a casting roll. The touch roll is preferably a roll having elasticity instead of a normal roll having high rigidity.

The temperature of the touch roll is preferably (Tg−10 ° C.) and (Tg + 30 ° C.) or less, and (Tg−7 ° C.) to (Tg + 20 ° C.), where Tg is the glass transition temperature of the melt-extruded sheet. Preferably, (Tg−5 ° C.) to (Tg + 10 ° C.) are more preferable. The temperature of the casting roll is preferably in the same temperature range.
Examples of touch rolls include touch rolls described in JP-A-11-314263 or JP-A-11-235747.

The thickness of the sheet-like molded body (thermoplastic resin sheet) obtained by the cast treatment is preferably 0.1 mm to 3 mm, more preferably 0.2 mm to 2 mm, and still more preferably 0.3 mm to 1.5 mm.
When the thickness of the thermoplastic resin sheet is 3 mm or less, a cooling delay due to heat storage of the melt can be avoided. Further, when the thickness of the thermoplastic resin sheet is 0.1 mm or more, the hydroxyl group and carboxy group in the thermoplastic resin sheet (preferably polyester sheet) are thermoplastic resin (preferably polyester) during the period from extrusion to cooling. It is suppressed that hydroxyl groups and carboxy groups that are diffused inside and cause hydrolysis are exposed to the resin surface.

The means for cooling the melt extruded from the extrusion die is not particularly limited, and may be any of applying cold air to the melt, bringing it into contact with a casting roll, spraying water, and the like. As the means for cooling the melt, only one of the means may be implemented, or two or more means may be combined.
The means for cooling the melt is preferably at least one of cooling by cold air and cooling using a casting roll, from the viewpoint of preventing oligomer adhesion to the film surface during continuous operation. Furthermore, it is particularly preferable that the melt extruded from the extruder is cooled with cold air, and the melt is brought into contact with a casting roll for cooling.

  Moreover, the thermoplastic resin sheet cooled using the casting roll etc. is peeled off from cooling members, such as a casting roll, using peeling members, such as a peeling roll.

-First stretching step-
In the first stretching step in the production method of the present disclosure, the first stretching in the longitudinal direction (MD direction) (hereinafter, also referred to as “longitudinal stretching” as appropriate) is performed on the thermoplastic resin sheet molded in the molding step. To obtain a thermoplastic resin film.

  In the first stretching, for example, the thermoplastic resin sheet is passed through a pair of nip rolls sandwiching the thermoplastic resin sheet, and the thermoplastic resin sheet is conveyed in the longitudinal direction of the thermoplastic resin sheet, while the thermoplastic resin sheet is conveyed in the conveyance direction. This can be done by applying tension between two or more pairs of nip rolls arranged side by side. Specifically, for example, when a pair of nip rolls A is installed on the upstream side in the conveyance direction of the thermoplastic resin sheet and a pair of nip rolls B is installed on the downstream side, the nip roll B on the downstream side is conveyed when the thermoplastic resin sheet is conveyed. Is made faster than the rotational speed of the upstream nip roll A, so that the thermoplastic resin sheet is stretched in the transport direction (MD direction). Note that two or more pairs of nip rolls may be installed independently on each of the upstream side and the downstream side. Moreover, you may perform 1st extending | stretching of a thermoplastic resin sheet using the extending | stretching apparatus provided with the nip roll.

It is preferable that the draw ratio at the time of the 1st extending | stretching of the thermoplastic resin sheet in a 1st extending process is adjusted smaller than the draw ratio in the 2nd extending | stretching in the 2nd extending process mentioned later. The larger the draw ratio by the first stretching, the higher the elastic modulus at normal temperature, but it is easy to relax by heating, and the elastic modulus tends to be low when reheated by heat treatment or the like. Therefore, the draw ratio by the first stretching is made smaller than the draw ratio by the second stretch in the TD direction, in other words, the stretch ratio by the second stretch is made larger than the stretch ratio by the first stretch. Thus, it is easy to obtain a thermoplastic resin film in which generation of streak burrs derived from wavy wrinkles is suppressed.
The stretching ratio of the thermoplastic resin sheet in the first stretching step is preferably 2 to 5 times, more preferably 2.5 to 4.0 times, and even more preferably 2.8 to 3.5 times.

In addition, the area ratio represented by the product of the draw ratio of the first stretch and the stretch ratio of the second stretch is the area of the thermoplastic resin sheet before the first stretch and the second stretch are performed. 12.8 times to 15.5 times.
The larger the area magnification, the higher the elastic modulus at normal temperature. In this case, the elastic modulus is easily relaxed by heating, and the elastic modulus is likely to be lowered when reheated by heat treatment or the like. In the present disclosure, when the area magnification is 12.8 times or more, the molecular orientation in the film width direction is improved, and thus the generation of streak burrs is effectively suppressed. Moreover, when the area magnification is 15.5 times or less, it is easy to maintain a state in which the molecular orientation is hardly relaxed when subjected to heat treatment.
The area magnification is preferably 13.5 times to 15.2 times, more preferably 14.0 times to 15.0 times, for the same reason as described above.

  The temperature during the first stretching of the thermoplastic resin film is preferably (Tg−20 ° C.) to (Tg + 50 ° C.), more preferably (Tg−10 ° C.), where Tg is the glass transition temperature of the thermoplastic resin film. It is-(Tg + 40 degreeC), More preferably, it is (Tg + 30 degreeC).

  In addition, as a means to heat a thermoplastic resin film, when extending | stretching using rolls, such as a nip roll, the thermoplastic resin film which touches a roll is provided by providing piping which can flow a heater and a warm solvent inside a roll. Can be heated. Even when a roll is not used, the thermoplastic resin film can be heated by spraying warm air on the thermoplastic resin film, contacting the thermoplastic resin film with a heat source such as a heater, or passing the vicinity of the heat source.

In the manufacturing method of the thermoplastic resin film of this indication, the 2nd extending process of extending a film in the TD direction is further included after the 1st extending process. Thereby, in the manufacturing method of the thermoplastic resin film of this indication, a thermoplastic resin film is made into the longitudinal direction (MD) of a thermoplastic resin film, and the film width direction (TD) orthogonal to the longitudinal direction of a thermoplastic resin film. Are stretched in at least two axes. The stretching in the MD direction and the TD direction may be performed at least once each.
The “film width direction (TD) orthogonal to the longitudinal direction (MD) of the thermoplastic resin film” is intended to mean a direction perpendicular (90 °) to the longitudinal direction (MD) of the thermoplastic resin film. However, a direction in which an angle with respect to the longitudinal direction (MD) can be regarded as 90 ° from a mechanical error or the like (for example, a direction of 90 ° ± 5 ° with respect to the MD direction) is included.

  In the present disclosure, as a method of biaxial stretching, in addition to a sequential biaxial stretching method in which first stretching (longitudinal stretching) and second stretching (lateral stretching) described later are performed separately, the first stretching ( Any of the simultaneous biaxial stretching methods in which the longitudinal stretching) and the second stretching (transverse stretching) are performed simultaneously may be used. The first stretching and the second stretching may be independently performed twice or more. Regardless of which of the longitudinal stretching and the lateral stretching is performed first, the generation of wavy wrinkles can be suppressed. Examples of the biaxial stretching include longitudinal stretching → lateral stretching, and longitudinal stretching → transverse stretching → longitudinal stretching. , Longitudinal stretching → longitudinal stretching → lateral stretching, transverse stretching → longitudinal stretching, and the like. Among these, as the biaxial stretching mode, from the viewpoint of ease of production, that is, production suitability, longitudinal stretching → lateral stretching is preferable as in the production method of the present disclosure.

-Second stretching step-
In the second stretching step in the production method of the present disclosure, the thermoplastic resin film subjected to the first stretching in the first stretching step is preheated with a preheating unit that preheats the stretched thermoplastic resin film. A stretched portion that stretches the thermoplastic resin film by applying tension in the film width direction orthogonal to the longitudinal direction of the thermoplastic resin film, a heat fixing portion that heats and heat-fixes the thermoplastic resin film subjected to tension, And the heat relaxation part that heats the tension is thermally transferred to the cooling part that cools the thermoplastic resin film that has been heat relaxed, and in the cooling part, further tension is applied in the film width direction to reduce the heat. It expands or contracts in the range of -1.5% to 3% with respect to the film width at the end of the thermal relaxation at the part. Thereby, second stretching (hereinafter, also referred to as “lateral stretching” as appropriate) is performed. Here, for example, “−1.5%” means “1.5% reduction”.

The second stretching step is a step of performing the second stretching (lateral stretching) in the film width direction orthogonal to the longitudinal direction of the thermoplastic resin film after the first stretching (longitudinal stretching), specifically, The second stretching (lateral stretching) can be performed by sequentially transporting the thermoplastic resin film in the following (a) to (e).
(A) a preheating portion for preheating the thermoplastic resin film after longitudinal stretching to a temperature at which it can be stretched;
(B) a stretched portion that stretches the preheated thermoplastic resin film by applying tension to the film width direction orthogonal to the longitudinal direction;
(C) a heat fixing part for crystallizing and heat-setting the thermoplastic resin film after performing longitudinal stretching and lateral stretching;
(D) a heat relaxation portion that heats the heat-fixed thermoplastic resin film, thermally relaxes the tension of the thermoplastic resin film, and removes residual strain of the film; and
(E) Cooling the thermoplastic resin film after heat relaxation, and simultaneously applying tension in the film width direction, −1.5% to 3% with respect to the film width at the end of heat relaxation in the heat relaxation portion Cooling section that expands or contracts within the range of

In the (e) cooling section in the second stretching step of the production method of the present disclosure, (b) tension is further applied in the film width direction after stretching in the film width direction (TD) in the stretching section, and in the heat relaxation section. The thermoplastic resin film is expanded or contracted in the range of -1.5% to 3% with respect to the film width at the end of thermal relaxation.
In the cooling part, when the expansion ratio or the reduction ratio in the TD direction of the thermoplastic resin film is −1.5% or more with respect to the film width at the end of the thermal relaxation in the thermal relaxation part, the elastic modulus at TD It is easy to obtain an increase effect. Further, when the expansion ratio or the reduction ratio in the TD direction of the thermoplastic resin film is 3% or less with respect to the film width at the end of the thermal relaxation in the thermal relaxation portion, it is effective for suppressing the breakage of the film.
The larger the area ratio and the second draw ratio, the higher the elastic modulus at room temperature, but it is more easily relaxed by heat, and the elastic modulus is likely to decrease with heat treatment. Therefore, the manufacturing method of the present disclosure suppresses relaxation by forcibly re-stretching the film that has been crystallized through heat setting while suppressing an increase in the area ratio due to the first stretching and the second stretching. However, the elastic modulus can be improved.
Among the above, the expansion ratio or the reduction ratio of the thermoplastic resin film in the TD direction in the cooling part is 0 for the film width at the end of the thermal relaxation in the thermal relaxation part for the same reason as described above. 0.0% to 2.0% is more preferable, and 1.5% to 1.8% is still more preferable.

  In the present disclosure, the “end point of thermal relaxation in the thermal relaxation part” refers to the time when the thermoplastic resin film enters the cooling part, that is, the rate at which the thermoplastic resin film shrinks in the width direction when the residual stress is relaxed. Refers to the point at which changes.

  In the second stretching step, the specific means is not limited as long as the thermoplastic resin film is laterally stretched in the above configuration, but a lateral stretching device or biaxial capable of processing each step constituting the above configuration. It is preferable to use a stretching machine.

-Axis stretching machine-
As shown in FIG. 1, the biaxial stretching machine 100 includes a pair of annular rails 60a and 60b, and gripping members 2a to 2l attached to the annular rails and movable along the rails. The annular rails 60a and 60b are arranged symmetrically with respect to the thermoplastic resin film 200. The annular rails 60a and 60b are stretched in the film width direction by holding the thermoplastic resin film 200 with the holding members 2a to 21 and moving along the rail. It is possible.

  The biaxial stretching machine 100 is an arrow which is a direction orthogonal to the direction (longitudinal direction) of the pre-heated portion 10 for pre-heating the thermoplastic resin film 200 and the pre-heated thermoplastic resin film 200 for the arrow MD of the thermoplastic resin film. Stretching section 20 that stretches by applying tension in the TD direction (film width direction), heat fixing section 30 that heats and heat-fixes the tensioned thermoplastic resin film, and heat setting A thermal relaxation part 40 that thermally relaxes the tension of the thermoplastic resin film that is heat-set by heating the thermoplastic resin film, and a cooling part 50 that cools the thermoplastic resin film that has been thermally relaxed via the thermal relaxation part. Consists of areas that contain.

Grip members 2a, 2b, 2e, 2f, 2i, and 2j that are movable along the annular rail 60a are attached to the annular rail 60a, and the annular rail 60b is movable along the annular rail 60b. Gripping members 2c, 2d, 2g, 2h, 2k, and 2l are attached. The gripping members 2a, 2b, 2e, 2f, 2i, and 2j grip one end in the TD direction of the thermoplastic resin film 200, and the gripping members 2c, 2d, 2g, 2h, 2k, and 2l The other end portion in the TD direction of the plastic resin film 200 is gripped. The gripping members 2a to 21 are generally referred to as chucks and clips.
The gripping members 2a, 2b, 2e, 2f, 2i, and 2j move counterclockwise along the annular rail 60a, and the gripping members 2c, 2d, 2g, 2h, 2k, and 2l move along the annular rail 60b. Move clockwise.

  The gripping members 2a to 2d grip the end portion of the thermoplastic resin film 200 in the preheating portion 10 and move along the annular rail 60a or 60b while being gripped, and the extending portion 20 and the gripping members 2e to 2h are located. It progresses through the thermal relaxation part 40 to the cooling part 50 in which the holding members 2i to 2l are located. Thereafter, the gripping members 2a and 2b and the gripping members 2c and 2d are separated from the end of the thermoplastic resin film 200 at the end on the downstream side in the MD direction of the cooling unit 50 in the transport direction, and then the annular rail 60a. Or it moves along 60b and returns to the preheating part 10. At this time, the thermoplastic resin film 200 moves in the direction of the arrow MD and sequentially preheats in the preheating unit 10, stretches in the stretching unit 20, heat fixing in the heat fixing unit 30, and heat relaxation in the heat relaxation unit 40. Then, cooling in the cooling unit 50 is performed, and transverse stretching is performed. The moving speed in each region such as the preheating portion of the gripping members 2 a to 2 l becomes the transport speed of the thermoplastic resin film 200.

The gripping members 2a to 2l can change the moving speeds independently.
The biaxial stretching machine 100 enables transverse stretching in which the thermoplastic resin film 200 is stretched in the TD direction in the stretching unit 20, but the thermoplasticity is changed by changing the moving speed of the gripping members 2a to 2l. The resin film 200 can be stretched also in the MD direction. That is, simultaneous biaxial stretching can be performed using the biaxial stretching machine 100.

  Although only 2a to 2l are shown as gripping members for gripping the end portion of the thermoplastic resin film 200 in the TD direction, in order to support the thermoplastic resin film 200, the biaxial stretching machine 100 has 2a to 2l. In addition, a gripping member (not shown) is attached. Hereinafter, the gripping members 2a to 2l may be collectively referred to as “grip member 2”.

(A. Preheating part)
In the preheating section, the thermoplastic resin film after longitudinal stretching in the first stretching (longitudinal stretching) step is preheated to a temperature at which stretching is possible.
As shown in FIG. 1, the thermoplastic resin film 200 is preheated in the preheating unit 10. In the preheating part 10, the thermoplastic resin film 200 is heated in advance before being stretched so that the thermoplastic resin film 200 can be easily stretched laterally.

The film surface temperature at the end point of the preheating part (hereinafter also referred to as “preheating temperature”) is (Tg−10 ° C.) to (Tg + 60 ° C.) when the glass transition temperature of the thermoplastic resin film 200 is Tg. Is preferable, and (Tg ° C.) to (Tg + 50 ° C.) is more preferable.
The end point of the preheating portion refers to the time when the preheating of the thermoplastic resin film 200 is finished, that is, the position where the thermoplastic resin film 200 is separated from the region of the preheating portion 10.

(B. Stretched part)
In the stretching portion, the thermoplastic resin film preheated in the preheating portion is stretched (laterally stretched) by applying tension to the width direction (TD direction) orthogonal to the longitudinal direction (MD direction).
Specifically, for example, in the stretched portion 20 shown in FIG. 1, the preheated thermoplastic resin film 200 is tensioned at least in the direction of the arrow TD orthogonal to the longitudinal direction of the thermoplastic resin film 200, and the thermoplastic resin film 200 is stretched transversely. For example, as shown in FIG. 1, the width of the thermoplastic resin film is extended from the width L0 to the width L1 to be wide.
Stretching (transverse stretching) in the direction (TD) perpendicular to the longitudinal direction (MD) of the thermoplastic resin film 200 is stretched in the direction of an angle perpendicular to the longitudinal direction (MD) of the thermoplastic resin film 200 (90 °). In consideration of mechanical error, it is not limited to only 90 °, but also includes stretching in a direction (90 ° ± 5 °) that can be regarded as perpendicular to the MD direction of the film.

  In the stretched portion 20, the area ratio of the thermoplastic resin film 200 (the product of the stretch ratio of the first stretch and the stretch ratio of the second stretch) is 12.8 times the area of the thermoplastic resin film 200 before stretching. ˜15.5 times. Details are as described above.

Moreover, as a film surface temperature at the time of lateral stretching of the thermoplastic resin film 200 (hereinafter also referred to as “second stretching temperature”), 100 ° C. to 150 ° C. is preferable, 110 ° C. to 140 ° C. is more preferable, and 120 More preferably, the temperature is from 130 ° C to 130 ° C.
If the second stretching temperature is 100 ° C. or higher, the risk of breakage due to excessive yield stress is reduced. Further, by adjusting the second stretching temperature (film surface temperature), it is possible to adjust the surface roughness Ra to the above-described range, and the film is not easily buckled by TD and heats a thin thermoplastic resin film. Even when transported, wavy wrinkles are less likely to occur.
Further, when the second stretching temperature is 150 ° C. or lower, the crystallization of the film itself is suppressed, so that it is difficult to break.

The stretching speed at the time of transverse stretching of the thermoplastic resin film 200 is, for example, 5% / second or more, preferably 8% / second or more, more preferably 10% / second or more, and further preferably 15% / second or more. .
The upper limit of the stretching speed at the time of transverse stretching of the thermoplastic resin film 200 is, for example, 50% / second or less, preferably 45% / second or less, more preferably 40% / second or less, and further preferably 30% or more. 20% / second or less is particularly preferable.
Here, the range of the stretching speed at the time of transverse stretching of the thermoplastic resin film 200 can be appropriately set by arbitrarily combining the above upper limit value and lower limit value. Examples of the stretching speed range during the transverse stretching of the thermoplastic resin film 200 include 8% / second to 45% / second, 15% / second to 40% / second, and 10% / second to 30%. There are 10% / second to 20% / second.
The stretching speed is the length Δd of the thermoplastic resin film stretched in 1 second from the length d ⁰ before stretching, and the length of the thermoplastic resin film before stretching (that is, when the preheated portion has passed). it is a representation of the length) divided by d ⁰ in percentage.
When the stretching speed is within the above range, stretching is performed at a relatively slow speed, so that stretching unevenness can be suppressed and the roughness of the film surface can be suppressed to a moderately low level.
Further, when the stretching speed is 8% / second or more, the stretching process does not become too long, and the crystallization of the film due to the long residence time is suppressed, so that it is difficult to break. Furthermore, when the stretching speed is 45% / second or less, it is effective for suppressing breakage of the film, and Ra can be suppressed from becoming too large.

As described above, the gripping members 2a to 2l can change the moving speed independently. Therefore, for example, the thermoplastic resin film 200 is increased by increasing the moving speed of the gripping member 2 on the downstream side in the extending portion 20MD direction of the extending portion 20 and the heat fixing portion 30 rather than the moving speed of the gripping member 2 in the preheating portion 10. It is also possible to perform longitudinal stretching for stretching the film in the transport direction (MD direction).
The longitudinal stretching of the thermoplastic resin film 200 in the second stretching step may be performed only by the stretching unit 20, or may be performed by the heat fixing unit 30, the heat relaxation unit 40, or the cooling unit 50 described later. In addition, the longitudinal stretching of the thermoplastic resin film 200 in the second stretching step may be performed at a plurality of locations among the stretching unit 20, the heat fixing unit 30, the heat relaxation unit 40, and the cooling unit 50.

(C. Heat fixing part)
In the heat setting part, the thermoplastic resin film that has already been subjected to longitudinal stretching and lateral stretching is heated and crystallized to be heat-set.
Heat setting refers to heating the thermoplastic resin film 200 while applying tension to the stretched portion 20 to crystallize a thermoplastic resin (for example, polyester).

In the heat fixing unit 30 shown in FIG. 1, the maximum reachable film surface temperature of the surface of the thermoplastic resin film 200 (in this specification, “heat setting temperature”, “ also referred to as T _{heat setting} ".) that it is preferably heated by controlling the film in the range of 160 ° C. to 240 ° C..
When the heat setting temperature is 160 ° C. or higher, the thermoplastic resin (for example, polyester) is easily crystallized, and the thermoplastic resin (for example, polyester) molecules can be fixed in a stretched state. Hydrolyzability is improved. In addition, when the heat setting temperature is 240 ° C. or lower, slippage hardly occurs at the portion where the molecules of the thermoplastic resin (for example, polyester) are entangled with each other, and the molecule is not easily contracted. Is suppressed. In other words, by heating so that the heat setting temperature is 160 ° C. to 240 ° C., the molecular crystals of the thermoplastic resin (for example, polyester) are oriented to improve the hydrolysis resistance of the thermoplastic resin film. Can do.
The heat setting temperature is preferably in the range of 170 ° C. to 230 ° C. and more preferably in the range of 175 ° C. to 225 ° C. for the same reason as described above.
The maximum film surface temperature (heat setting temperature) is a value measured by bringing a thermocouple into contact with the surface of the thermoplastic resin film.

Furthermore, when the heat setting temperature is controlled to 160 ° C. to 240 ° C., it is preferable that the variation in the maximum film surface temperature in the film width direction is 0.5 ° C. or higher and 10.0 ° C. or lower. In the film width direction, the variation in the maximum film surface temperature of the film is 0.5 ° C. or more, which is advantageous in terms of wrinkles during conveyance in the subsequent process, and the variation is 10.0 ° C. or less. By suppressing, variation in crystallinity in the width direction is suppressed. Thereby, the difference in slackness in the film width direction is reduced, the generation of scratches on the film surface during the production process is prevented, and the hydrolysis resistance is enhanced.
Among the above, the variation in the maximum reached film surface temperature is more preferably 0.5 ° C. or more and 7.0 ° C. or less, still more preferably 0.5 ° C. or more and 5.0 ° C. or less, for the same reason as described above. It is particularly preferably from 5 to 4.0 ° C.

Moreover, the heating to the film at the time of heat setting may be performed only from one side of the film or from both sides. For example, when the film is cooled on a casting roll after melt extrusion in the film forming process, the molded thermoplastic resin film is different in how it is cooled on one side and the opposite side, so the film curls. It has become easier. For this reason, it is preferable that the heating in the heat fixing unit is performed on the surface brought into contact with the casting roll in the film forming process. Curling can be eliminated by making the heating surface at the heat fixing part into a surface in contact with the casting roll, that is, a cooling surface.
In this case, the heating is performed in a range where the surface temperature immediately after heating on the heating surface in the heat fixing part is higher than the surface temperature of the non-heating surface opposite to the heating surface in the range of 0.5 ° C to 5.0 ° C. It is preferable to be carried out as follows. When the temperature of the heating surface during heat setting is higher than that of the opposite surface and the temperature difference between the front and back surfaces is 0.5 to 5.0 ° C., curling of the film is more effectively eliminated. From the viewpoint of the curl eliminating effect, the temperature difference between the heated surface and the non-heated surface on the opposite side is more preferably in the range of 0.7 to 3.0 ° C, 0.8 ° C to 2.0 ° C. The following is more preferable.

Moreover, in at least one of the heat fixing part 30 and the heat relaxation part 40, the method of heating the thermoplastic resin film may be a method of blowing hot air or a method of selectively radiantly heating with a heater. By selectively performing radiant heating on the thermoplastic resin film, the film surface temperature distribution in the TD direction can be controlled uniformly, and the quality (for example, thermal shrinkage) of the produced thermoplastic resin film is uniform. Can be made.
When the film is selectively radiantly heated in the heat relaxation unit 40, the radiant heating in the heat fixing unit 30 may be omitted, or the radiant heating in the heat fixing unit 30 may be performed in parallel.
Examples of the heater capable of radiant heating include an infrared heater, and a ceramic heater (ceramic heater) is particularly preferable.

When the film is heated in the heat setting part, the residence time in the heat setting part is preferably 5 seconds or more and 50 seconds or less. The residence time is the time during which the state in which the film is heated in the heat fixing part is continued. When the residence time is 5 seconds or longer, the change in crystallinity with respect to the heating time is small, and therefore, it is advantageous in that unevenness of crystallinity in the width direction is relatively less likely to occur. This is advantageous in terms of productivity because it is not necessary to extremely reduce the line speed.
Among these, the residence time is preferably 8 seconds or longer and 40 seconds or shorter, and more preferably 10 seconds or longer and 30 seconds or shorter, for the same reason as described above.

(D. Thermal relaxation part)
In the heat relaxation part, the heat-fixed thermoplastic resin film is heated, the tension of the thermoplastic resin film is thermally relaxed, and the residual strain of the film is removed. By this thermal relaxation, the film shrinks in at least one of the longitudinal direction and the transverse direction.

Heat relaxation is to heat the thermoplastic resin film that has been heat-fixed to relieve the tension of the thermoplastic resin film. Heating of the thermoplastic resin film at the heat relaxation portion should be performed as follows. Is preferred.
In the thermal relaxation part 40 shown in FIG. 1, the maximum ultimate film surface temperature of the surface of the thermoplastic resin film 200 is 5 ° C. than the maximum ultimate film surface temperature (T _{heat fixation} ) of the thermoplastic resin film 200 in the heat fixing part 30. The aspect which heats the thermoplastic resin film 200 so that it may become low temperature above is preferable.
Hereinafter, the highest reached film surface temperature of the surface of the thermoplastic resin film 200 during _{thermal relaxation} is also referred to as “thermal relaxation temperature (T _{thermal relaxation} )”.

In the thermal relaxation part 40, the thermal relaxation temperature (T _{thermal relaxation} ) is heated at a temperature 5 ° C. or more lower than the thermal fixing temperature (T _{thermal fixing} ) (T _{thermal relaxation} ≦ T _{thermal fixing−} 5 ° C.) to release the tension. By reducing the stretching tension, the dimensional stability of the thermoplastic resin film can be further improved.
When the T _{heat relaxation} is equal to or less than “T _{heat fixation} −5 ° C.”, the hydrolysis resistance of the thermoplastic resin film is more excellent. Moreover, it is preferable that T _{heat relaxation} is 100 degreeC or more at the point from which dimensional stability becomes favorable.
In addition, the T _{heat relaxation} is 100 ° C. or higher, and preferably than T _{heat setting} is 15 ℃ or higher temperature region lower (100 ° C. ≦ T _{heat relaxation} ≦ T _heat--15 ° C.), 110 ° C. or higher and more preferably than T _{heat setting} temperature is lower region 25 ° C. or higher (110 ° C. ≦ T _{heat relaxation} ≦ T _heat--25 ° C.), at 120 ° C. or higher, and lower 30 ° C. or higher than T _{heat set} It is particularly preferable that the temperature range (120 ° C. ≦ T _{thermal relaxation} ≦ T _heat setting−30 ° C.).
The T _{heat relaxation} is a value measured by bringing a thermocouple into contact with the surface of the thermoplastic resin film 200.

(E. Cooling part)
In a cooling part, the thermoplastic resin film after heat-relaxing in a heat relaxation part is cooled. Further, simultaneously with cooling of the thermoplastic resin film, tension is applied in the film width direction, and the film is expanded or contracted in a range of −1.5% to 3% with respect to the film width at the end of thermal relaxation in the thermal relaxation portion.
As shown in FIG. 1, in the cooling unit 50, the thermoplastic resin film 200 that has passed through the thermal relaxation unit 40 is cooled. By cooling the thermoplastic resin film 200 heated by the heat fixing part 30 or the heat relaxation part 40, the shape of the thermoplastic resin film 200 is fixed. FIG. 1 shows a biaxially stretched thermoplastic resin film having a width L2.
Here, the expansion of the film width in the cooling unit 50 may be performed using the same method as the stretching in the stretching unit 20 described above.
For reducing the film width in the cooling unit 50, the same method as the thermal relaxation of the film tension in the thermal relaxation unit 40 described above may be used.

  The thermoplastic resin film is separated from the region of the cooling unit by the gripping member that grips the thermoplastic resin film being separated from the thermoplastic resin film. For example, when the gripping member 2j shown in FIG. 1 is at the point P and the gripping member 21 is at the point Q, the end of the cooling unit 50 (the end in the MD direction) when the thermoplastic resin film 200 is separated is the point P. It is represented by a straight line connecting the point Q and the point Q.

The temperature of the surface (film surface) of the thermoplastic resin film (hereinafter also referred to as “cooling temperature”) at the outlet of the cooling part of the thermoplastic resin film 200 in the cooling part 50 is the glass transition temperature Tg of the thermoplastic resin film 200. When it is, it is preferable that it is lower than Tg + 50 degreeC. Specifically, the cooling temperature is preferably 25 ° C to 110 ° C, more preferably 25 ° C to 95 ° C, and further preferably 25 ° C to 80 ° C. When the cooling temperature is in the above range, it is possible to prevent the film from shrinking unevenly after releasing the clip.
Here, the cooling unit outlet refers to an end portion of the cooling unit 50 when the thermoplastic resin film 200 is separated from the cooling unit 50, and the holding member 2 that holds the thermoplastic resin film 200 (the holding member 2j in FIG. 1). And 2l) refers to a position where the thermoplastic resin film 200 is separated, that is, a straight line portion connecting the P point and the Q point.

Furthermore, in the cooling unit 50, the average cooling rate when the temperature of the surface (film surface) of the thermoplastic resin film is cooled from 150 ° C. to 70 ° C. may be in the range of 2 ° C./second to 100 ° C./second. preferable.
Here, an average cooling rate is calculated | required by measuring the film | membrane temperature of the film in a cooling zone with a radiation thermometer. That is, the cooling time (Z ÷ S) seconds from 150 to 70 ° C. is obtained from the distance Zm between the point where the film temperature becomes 150 ° C. and the point where the film temperature becomes 70 ° C. and the film transport speed Sm / second. From this, the average cooling rate is obtained by further calculating (150−70) ÷ (Z ÷ S).

By setting the average cooling rate to 2 ° C./second or more, insufficient cooling of the thermoplastic resin film in the stretching apparatus is suppressed, and the adhesiveness of the thermoplastic resin film is lowered. Therefore, in the process after the thermoplastic resin film is separated from the outlet of the cooling unit, it is difficult to cause a failure such as the thermoplastic resin film sticking to the roll for film conveyance. In addition, by setting the average cooling rate to 100 ° C./second or less, rapid cooling of the thermoplastic resin film is prevented, residual stress unevenness hardly occurs in the film surface, heat shrinkage rate unevenness is suppressed, and streak burrs are generated. It becomes difficult to occur.
The average cooling rate is more preferably 4 ° C / second to 80 ° C / second, and further preferably 5 ° C / second to 50 ° C / second.

  As temperature control means for heating or cooling the thermoplastic resin film 200 in preheating, stretching, heat setting, thermal relaxation, and cooling in the second stretching step, hot or cold air is blown over the thermoplastic resin film 200. Or bringing the thermoplastic resin film 200 into contact with the surface of a metal plate capable of temperature control or passing the vicinity of the metal plate.

(Recovery of film)
The thermoplastic resin film 200 cooled in the cooling process cuts the gripped portions gripped by the clips at both ends in the TD direction, and is wound up in a roll shape.

  In the second stretching step, it is preferable to relax the stretched thermoplastic resin film by the following method in order to further improve the hydrolysis resistance and dimensional stability of the produced thermoplastic resin film.

In the present disclosure, it is preferable to perform relaxation in the MD direction by the cooling unit 50 after performing the second stretching step after the first stretching (longitudinal stretching) step. That is,
In the preheating part 10, the both ends of the thermoplastic resin film 200 in the width direction (TD) are gripped by using at least two gripping members per one end. For example, one end portion in the width direction (TD) of the thermoplastic resin film 200 is held by the holding members 2a and 2b, and the other is held by the holding members 2c and 2d. Subsequently, the thermoplastic resin film 200 is conveyed from the preheating part 10 to the cooling part 50 by moving the holding members 2a to 2d.

  In such conveyance, a gripping member 2a (2c) that grips one end of the thermoplastic resin film 200 in the width direction (TD direction) in the preheating unit 10 and another gripping member 2b (2d) adjacent to the gripping member 2a (2c). ) And the other gripping member 2b (2d) adjacent to the gripping member 2a (2c), which grips one end of the thermoplastic resin film 200 in the width direction in the cooling unit 50. The conveyance speed of the thermoplastic resin film 200 is reduced by narrowing the distance between the two. With this method, the cooling unit 50 can perform relaxation in the MD direction.

The relaxation of the thermoplastic resin film 200 in the MD direction may be performed in at least a part of the heat fixing unit 30, the heat relaxation unit 40, and the cooling unit 50.
As described above, the thermoplastic resin film 200 is relaxed in the MD direction by narrowing the gap between the gripping members 2a-2b and the gap between the gripping members 2c-2d more downstream than the upstream side in the MD direction. be able to. Therefore, when heat relaxation in the MD direction is performed by the heat fixing unit 30 or the heat relaxation unit 40, when the gripping members 2a to 2d reach the heat fixing unit 30 or the heat relaxation unit 40, the gripping members 2a to 2d move. What is necessary is just to make speed | velocity low, to make the conveyance speed of the thermoplastic resin film 200 small, and to narrow the space | interval between the holding members 2a-2b and the space | interval between the holding members 2c-2d rather than the space | interval in the preheating part 10.

  Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. However, the embodiments of the present invention are not limited to the following examples as long as the gist of the present invention is not exceeded.

<Synthesis of polyester raw resin 1>
As shown below, terephthalic acid and ethylene glycol are directly reacted to distill off water, esterify, and then use a direct esterification method in which polycondensation is performed under reduced pressure, and polyester (Ti catalyst) by a continuous polymerization apparatus. System PET) was obtained.

(1) Esterification reaction In a first esterification reaction tank, 4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol are mixed for 90 minutes to form a slurry, and continuously at a flow rate of 3800 kg / h. It supplied to the 1st esterification reaction tank. Further, an ethylene glycol solution of a citrate chelate titanium complex (VERTEC AC-420, manufactured by Johnson Matthey) in which citric acid is coordinated to Ti metal is continuously supplied, and the average residence time is kept at 250 ° C. in the reaction vessel with stirring. The reaction was carried out for about 4.3 hours. At this time, the citric acid chelate titanium complex was continuously added so that the amount of Ti added was 9 ppm in terms of element. At this time, the acid value of the obtained oligomer was 600 equivalent / ton. In the present specification, “equivalent / t” represents a molar equivalent per ton.
This reaction product was transferred to a second esterification reaction vessel and reacted with stirring at a temperature in the reaction vessel of 250 ° C. and an average residence time of 1.2 hours to obtain an oligomer having an acid value of 200 equivalents / ton. The inside of the second esterification reaction tank is partitioned into three zones, and an ethylene glycol solution of magnesium acetate is continuously supplied from the second zone so that the amount of Mg added is 75 ppm in terms of element, From the third zone, an ethylene glycol solution of trimethyl phosphate was continuously supplied so that the amount of P added was 65 ppm in terms of element.

(2) the polycondensation reaction above-obtained esterification reaction product supplied to the first polycondensation reaction vessel continuously stirring, the reaction temperature 270 ° C., the reaction vessel pressure 20 torr (2.67 × 10 ^{- 3} MPa) and polycondensation with an average residence time of about 1.8 hours.
Further, it was transferred to the second double condensation reaction tank, and while stirring in this reaction tank, the reaction tank temperature was 276 ° C., the reaction tank pressure was 5 torr (6.67 × 10 ⁻⁴ MPa), and the residence time was about 1.2 hours. The reaction (polycondensation) was performed under the conditions.
Subsequently, it was further transferred to the third triple condensation reaction tank. In this reaction tank, the reaction tank temperature was 278 ° C., the reaction tank pressure was 1.5 torr (2.0 × 10 ⁻⁴ MPa), and the residence time was 1.5 hours. Reaction (polycondensation) was carried out under the conditions described above to obtain a reaction product (polyethylene terephthalate (PET)).

  Next, the obtained reaction product was discharged into cold water in a strand form and immediately cut to prepare polyester pellets (cross section: major axis: about 4 mm, minor axis: about 2 mm, length: about 3 mm).

About the obtained polyester, as a result of measuring as shown below using high resolution type high frequency inductively coupled plasma-mass spectrometry (HR-ICP-MS; AttoM manufactured by SII Nanotechnology), Ti = 9 ppm, Mg = 75 ppm, P = 60 ppm. P is slightly decreased with respect to the initial addition amount, but is estimated to have volatilized during the polymerization process.
The obtained polymer had IV = 0.67, the amount of terminal carboxy group (AV) = 23 eq / ton, melting point = 257 ° C., and solution haze = 0.3%. The measurement of IV and AV was performed by the following method.

~ Measurement of IV and AV ~
The intrinsic viscosity (IV) of the polyester raw resin is determined by dissolving the polyester raw resin in a 1,1,2,2-tetrachloroethane / phenol (= 2/3 [mass ratio]) mixed solvent. It calculated | required from the solution viscosity in 25 degreeC.
The amount of terminal COOH (AV) of the polyester raw material resin is determined by dissolving unstretched polyester films 1 to 4 in a mixed solution of benzyl alcohol / chloroform (= 2/3; volume ratio) and using phenol red as an indicator. Titrated with (0.025N KOH-methanol mixed solution) and calculated from the appropriate amount.
Polyester raw material resin 1 was synthesized as described above.

(Examples 1-15 and Comparative Examples 1-4)
<Preparation of unstretched polyester film>
The polyester raw material resin 1 was dried to a moisture content of 20 ppm or less and then charged into a hopper of a single-screw kneading extruder having a diameter of 50 mm. The polyester raw material resin 1 was melted at 300 ° C. and extruded from a die through a gear pump and a filter (pore diameter: 20 μm) under the following extrusion conditions. The dimensions of the die slit were adjusted so that the thickness of the polyester sheet was 0.4 mm. The thickness of the polyester sheet was measured by an automatic thickness meter installed at the exit of the casting roll.

  At this time, extrusion of the molten resin was performed under the condition that the pressure fluctuation was 1% and the temperature distribution of the molten resin was 2%. Specifically, the back pressure in the barrel of the extruder is 1% higher than the average pressure in the barrel of the extruder, and the piping temperature of the extruder is 2% higher than the average temperature in the barrel of the extruder. Heated as temperature. In extruding from the die, the molten resin was extruded onto a cooling casting roll and brought into close contact with the casting roll using an electrostatic application method. For the cooling of the molten resin, the temperature of the casting roll was set to 25 ° C., and cold air of 25 ° C. was blown out from the cold air generator installed facing the casting roll and applied to the molten resin. An unstretched polyester film (unstretched polyester film 1) having a thickness of 0.4 mm and a film width of 0.9 m was peeled from the casting roll by a peeling roll disposed opposite to the casting roll.

In addition, an unstretched polyester film 2 having a thickness of 2.8 mm (used in Example 12 below) and a thickness of 1. A 2 mm unstretched polyester film 3 (used in the following Example 13) and a 0.9 mm thick unstretched polyester film 4 (used in the following Example 14) were peeled off.
In addition, all the film widths are 0.9 m.

The obtained unstretched polyester films 1 to 4 each had an intrinsic viscosity IV = 0.64 dL / g, an amount of terminal carboxy groups (AV) = 25 equivalents / ton, and a glass transition temperature (Tg) = 72 ° C. .
Measurement of IV and AV was performed in the same manner as described above.

<Preparation of biaxially stretched polyester film>
The obtained unstretched polyester films 1 to 4 were sequentially biaxially stretched through the following steps to produce a biaxially stretched polyester film having a thickness of 31 μm and a film width (total length of TD) of 2.5 m. .

-First stretching step-
The unstretched polyester films 1 to 4 were passed between two pairs of nip rolls having different peripheral speeds, and the first stretching (longitudinal stretching) was performed in the MD direction (conveying direction) under the following conditions.
<Condition>
Preheating temperature: 80 ° C
Stretching temperature: 90 ° C
Stretch ratio: Magnification (times) shown in Table 1 below
Stretching stress: 12 MPa

-Second stretching step-
The polyester film (uniaxially stretched polyester film) subjected to longitudinal stretching was subjected to second stretching (lateral stretching) using the tenter (biaxial stretching machine) having the structure shown in FIG. 1 under the following method and conditions.

(Preheating part)
The preheating temperature was 110 ° C., and heating was performed so that stretching was possible.

(Extension part)
The preheated uniaxially stretched polyester film was stretched (laterally stretched) by applying tension to the film width direction (TD direction) perpendicular to the MD direction under the following conditions.
<Condition>
Stretching temperature: Temperature (° C) shown in Table 1 below
Stretch ratio: Magnification (times) shown in Table 1 below
Stretching stress: 18 MPa
Stretching speed: Stretching speed (% / second) shown in Table 1 below

In addition, the draw ratio at the time of performing said 1st extending | stretching and 2nd extending | stretching was adjusted, and the area ratio after 1st extending | stretching and 2nd extending | stretching was adjusted to the magnification shown in following Table 1.
The area ratio is the product of the draw ratio during the first drawing and the draw ratio during the second drawing.

(Heat fixing part)
Subsequently, the highest reach | attained film surface temperature (heat setting temperature) of the polyester film was controlled and crystallized within the following range.
Maximum film surface temperature (heat setting temperature T _{heat setting} ): 220 [° C]

(Heat relaxation part)
The polyester film after heat setting was heated to the following temperature to relax the tension of the film.
<Conditions>
-Thermal relaxation temperature (T _{thermal relaxation} ): 190 ° C
Thermal relaxation rate: TD direction (TD thermal relaxation rate; ΔL) = 5%

(Cooling section)
Next, the polyester film after heat relaxation was cooled at a cooling temperature of 65 ° C. At the same time, the polyester film was tensioned in the film width direction (TD direction) under the following conditions, and subjected to slight expansion or contraction treatment.
<Conditions>
Expansion or reduction magnification: Value (%) shown in Table 1 below
Expansion or contraction speed: 0.1% / second Note that the magnification indicates an expansion ratio or a reduction ratio with respect to the film width at the end of thermal relaxation in the thermal relaxation section. A negative value in Table 1 represents “reduction”.

-Film collection-
After cooling, both ends of the polyester film were trimmed by 20 cm. Then, after extruding (knurling) with a width of 10 mm at both ends, it was wound up with a tension of 25 kg / m.

  As described above, a biaxially stretched polyester (PET) film having a thickness of 31 μm was produced.

<Preparation of biaxially stretched cyclic polyolefin film>
In the production of the above PET film, except that the polyester raw material resin 1 is replaced with ARTON (registered trademark; specific gravity ρ: 1.08 g / cm ³ , glass transition temperature (Tg): 138 ° C., manufactured by JSR Corporation). A biaxially stretched cyclic polyolefin film (COP) was fabricated in the same manner as the above biaxially stretched polyester (PET) film.
In addition, 1st extending | stretching and 2nd extending | stretching were performed as follows.
That is, the first stretching (longitudinal stretching) is performed at a preheating temperature: 120 ° C., a stretching temperature: 140 ° C. and a stretching ratio of 3.5 times, and the second stretching (lateral stretching) is performed at a preheating temperature of the preheating portion: The above PET film was used except that it was performed at 120 ° C., the stretching temperature of the stretched part: 140 ° C., the stretch ratio of 4.2 times, the stretch rate: 18% / second, and the expansion ratio of the cooling part of 1.5%. The conditions were the same as those for the production.

<Measurement and evaluation>
The following measurements and evaluations were performed on the biaxially stretched polyester film and the biaxially stretched cyclic polyolefin film obtained as described above. The results of measurement and evaluation are shown in Table 1 below.

-1. Elastic modulus ratio E30 ^{, E90, E120, E150} and ^E180 −
From the biaxially stretched polyester film or the biaxially stretched cyclic polyolefin film, a sample piece having a width of 6 mm and a total length of 115 mm (JIS K 6251, dumbbell-shaped No. 5) was punched out. The obtained sample piece was pulled with Tensilon (manufactured by Toyo Seiki Co., Ltd., Strograph VE50) under the conditions of 50 mm between chucks and a tensile speed of 100 mm / min, and the elongation of the film relative to the load was measured. Next, a graph was created from the measured values with the load on the horizontal axis and the elongation on the vertical axis, and the elastic modulus was calculated from the tangent of the rising portion of the load-elongation curve. This operation was performed 5 times, and an average value of three points excluding the maximum value and the minimum value was defined as the elastic modulus.
For each temperature, it is carried out for each of the case of pulling in the film conveying direction and the case of pulling in the film width direction. The elastic modulus when pulled in the film conveying direction is E ^TD, and the elastic modulus when pulled in the film width direction is E ^TD .
<Measurement conditions>
・ Measurement place: Hot air heating furnace ・ Measurement temperature: 30 ° C, 90 ° C, 120 ° C, 150 ° C, 180 ° C
(The set temperature of the furnace was raised to the desired temperature in 1.5 minutes, and the temperature was set and the air volume was adjusted so that the temperature rise was kept within 2 ° C. even after 1 minute from the desired temperature.)
-Temperature control: A test piece of the same type and size for temperature measurement was installed in the vicinity of the test piece, a thermocouple was attached to the test piece for temperature measurement, and the temperature at the time of measurement was monitored.
Test start timing: Pulling was started after reaching the desired temperature.

-2. Surface roughness Ra-
Using a contact shape measuring machine (Mitutoyo FORMRACER EXTREME CS-5000 CNC), measurement was performed 12 times each at any position in the MD direction and TD direction of the biaxially stretched polyester film or biaxially stretched cyclic polyolefin film under the following conditions. The average of 10 points in the MD direction and 10 points in the TD direction from which the minimum and maximum values of Ra were removed was determined, and the average value of 20 points was defined as Ra.
<Conditions>
・ Measurement needle tip diameter: 0.5 μm
-Stylus load: 0.75mN
・ Measurement length: 0.8mm
・ Cutoff value: 0.08mm

-3. Film thickness
Using a tactile film thickness measuring machine (Mitutoyo ID-C112X), measurement was performed at 50 mm intervals over the entire width of the biaxially stretched polyester film or biaxially stretched cyclic polyolefin film in the TD direction. This operation was performed 5 sets at 1 m intervals in the MD direction, and the average value of the measured values was defined as the thickness.

-4. Streaky burrs
The biaxially stretched polyester film or the biaxially stretched cyclic polyolefin film was passed through a heating and conveying apparatus, and the maximum temperature of the film was 90 ° C., 120 ° C., 150 ° C. or 180 ° C., and the heating and conveying treatment was performed at a conveying tension of 1 MPa for 1 minute. . Then, the biaxially stretched polyester film or the biaxially stretched cyclic polyolefin film that has been subjected to the heating and conveying treatment is placed on a flat surface, and the biaxially stretched polyester film or the cyclic polyolefin is reflected so that the light of the fluorescent lamp installed on the indoor ceiling is reflected. The film was observed from an oblique direction, and the undulation of the reflected image of the fluorescent lamp reflected on the biaxially stretched polyester film or the biaxially stretched cyclic polyolefin film was evaluated according to the following evaluation criteria.
<Evaluation criteria>
AA: There is no undulation in the reflected image, and no streak burrs are observed.
A: Slightly burrs were observed partially, but the swell of the reflected image was weak and there was no practical problem.
B: Although the reflected image appears slightly undulating on the whole surface, it is not practically hindered.
C: Streak burrs are remarkably generated, and the swell of the reflected image is strong on the entire surface, causing practical problems.

As shown in Table 1, in the examples in which the elastic modulus ratio Er ³⁰ at 30 ° C. and the elastic modulus ratio Er in the temperature range from 30 ° C. to 180 ° C. were appropriately adjusted, even a film having a thickness of 200 μm or less The generation of streak burrs is suppressed, and the effect of suppressing streak burrs remarkably appears even in a thin film having a thickness of less than 100 μm.
On the other hand, in Comparative Examples 1 to 4 in which the elastic modulus ratio or the variation in elastic modulus ratio (difference between the maximum value Er _max and the minimum value Er _min ) deviates from the desired range, generation of wrinkles in the TD direction is suppressed. In addition, the occurrence of streak burrs was noticeable.

2a to 2l Gripping member 3 Film 4 Transport roll 10 Preheating unit 20 Stretching unit 30 Heat fixing unit 40 Thermal relaxation unit 50 Cooling unit 60a, 60b Annular rail 100 Biaxial stretching machine 200 Polyester film P, Q The gripping member is a thermoplastic resin film Release point MD Film transport direction (longitudinal direction)
TD film width direction L0, L1, L2 width length ^Z 1 of a thermoplastic resin film, ^{Z 2} expansion width sigma _x Stress

The disclosure of Japanese Patent Application No. 2017-037662 filed on Feb. 28, 2017 is incorporated herein by reference in its entirety.
All documents, patents, patent applications, and technical standards mentioned in this specification are specifically and individually described as individual documents, patents, patent applications, and technical standards are incorporated by reference. To the same extent, it is incorporated herein by reference.

Claims (12)

The ratio Er ³⁰ at 30 ° C. of the elastic modulus E ^{TD in} the film width direction perpendicular to the film conveying direction to the elastic modulus E ^MD in the film conveying direction is 1.1 to 1.8, and
The elastic modulus E ^TD relative to the elastic modulus E ^MD is the ratio Er ³⁰ at 30 ° C., the ratio Er ⁹⁰ at 90 ° C., the ratio Er ¹²⁰ at 120 ° C., the ratio Er ¹⁵⁰ at 150 ° C., and 180 ° C. A thermoplastic resin film in which the difference between the maximum value Er _max and the minimum value Er _min selected from the ratio Er ¹⁸⁰ is 0.7 or less.   The thermoplastic resin film according to claim 1, wherein the surface roughness Ra of at least one surface is 0.5 nm to 50 nm.   The thermoplastic resin film according to claim 1 or 2, wherein the thickness is 200 µm or less.   It is a polyester film or a cyclic polyolefin film, The thermoplastic resin film of any one of Claims 1-3. It is a manufacturing method of the thermoplastic resin film of any one of Claims 1-4, Comprising:
Melting and extruding the raw material resin, cooling and molding a thermoplastic resin sheet;
Performing a first stretching in the longitudinal direction on the thermoplastic resin sheet to obtain a thermoplastic resin film;
Preheated portion for preheating the thermoplastic resin film, stretched portion for stretching the preheated thermoplastic resin film in the film width direction perpendicular to the longitudinal direction of the thermoplastic resin film, thermoplastic with tension applied The thermoplastic resin film is sequentially transported to a heat fixing part for heating and fixing the resin film, a heat relaxation part for relaxing the tension, and a cooling part for cooling the thermoplastic resin film that has been heat relaxed. And performing the second stretching,
Including
The area ratio, which is the product of the draw ratio in the first draw and the draw ratio in the second draw, is 12.8 to 15.5 times,
In the step of performing the second stretching, in the cooling part, the thermoplastic resin film that has been subjected to thermal relaxation is further tensioned in the film width direction, and the film width at the end of the thermal relaxation in the thermal relaxation part is obtained. On the other hand, a method for producing a thermoplastic resin film, wherein the thermoplastic resin film is expanded or reduced in a range of -1.5% to 3%.   6. The method for producing a thermoplastic resin film according to claim 5, wherein the second stretching step comprises stretching the thermoplastic resin film at a stretching speed of 8% / second to 45% / second in the stretching portion.   The thermoplastic resin film according to claim 5 or 6, wherein, in the step of performing the second stretching, the thermoplastic resin film is stretched at a stretching speed of 15% / second to 40% / second in the stretching portion. Manufacturing method.   The thermoplastic resin according to any one of claims 5 to 7, wherein in the step of performing the second stretching, the thermoplastic resin film is stretched at a stretching temperature of 100 ° C to 150 ° C in the stretching portion. A method for producing a film.   The thermoplastic resin according to any one of claims 5 to 8, wherein in the step of performing the second stretching, the thermoplastic resin film is stretched at a stretching temperature of 110 ° C to 140 ° C in the stretching portion. A method for producing a film.   The area ratio, which is the product of the draw ratio in the first draw and the draw ratio in the second draw, is 13.5 to 15.2 times. The manufacturing method of the thermoplastic resin film of description.   The step of performing the second stretching includes the thermoplastic resin film in the cooling unit in a range of 0.0% to 2.0% with respect to the film width at the end of the thermal relaxation in the thermal relaxation unit. The manufacturing method of the thermoplastic resin film of any one of Claims 5-10 which expands.   The thermoplastic resin according to any one of claims 5 to 11, wherein in the step of performing the first stretching, a first stretching with a stretching ratio of 2 to 5 times is performed on the thermoplastic resin sheet. A method for producing a resin film.