WO2022138069A1

WO2022138069A1 - Corrected thickness measurement device, corrected thickness measurement method, film manufacturing method, and polyester film

Info

Publication number: WO2022138069A1
Application number: PCT/JP2021/044459
Authority: WO
Inventors: 佑記福岡; 洋介飯野; 充内山
Original assignee: 富士フイルム株式会社
Priority date: 2020-12-24
Filing date: 2021-12-03
Publication date: 2022-06-30

Abstract

Provided are: a corrected thickness measurement device and corrected thickness measurement method such that it is possible to accurately measure the thickness of a thin film; a film manufacturing method; and a polyester film in which the unevenness of a coated thin functional layer has been suppressed. The present invention comprises: a step for obtaining a first thickness profile using the thickness in one direction of a film as measured by a radiation thickness gauge; a step for averaging the first thickness profile to obtain an average first thickness profile; a step for obtaining a second thickness profile using the thickness in the one direction of the film as measured by a spectral interference-type thickness gauge; a step for averaging the second thickness profile to obtain an average second thickness profile; and a step for multiplying the values of the second thickness profile by a value M obtained by raising the ratio W (αⁿ/ βⁿ) of the value α of the average first thickness profile and the value β of the average second thickness profile at each position in the one direction of the film, to the 1/nth power to obtain a corrected thickness profile.

Description

Corrected thickness measuring device, corrected thickness measuring method, film manufacturing method, and polyester film

The present invention relates to a corrected thickness measuring device, a corrected thickness measuring method, a film manufacturing method, and a polyester film.

Various films such as polyester films are used in a wide range of applications from the viewpoints of processability, mechanical properties, electrical properties, dimensional stability, transparency, chemical resistance, etc., for example, decorative films or decorative films. It is used as a support and protective film for dry film photoresists. The dry film photoresist has a structure in which a photosensitive resin layer (resist layer) is laminated on a support, and then a protective film is further laminated. In recent years, dry film photoresists have been used in the touch panel field for etching applications in the wiring forming process, protective film forming applications for protecting wiring portions such as copper or ITO (indium tin oxide) and silver nanoparticles, and interlayer insulating film applications. It's being used.

As a method for producing various films such as polyester film, for example, Patent Document 1 describes a method for producing a polyester film roll. In Patent Document 1, the thickness of the continuously formed running film is measured with high accuracy, and the roll shape value (diameter) in the width direction of the wound film roll is measured to satisfy the roll shape. The film thickness is adjusted by feeding back to the adjustment of the temperature or the gap.

Further, Patent Document 2 describes a step of extruding a molten polymer into a cooling roll through a gap of an extrusion die, a step of stretching in the longitudinal direction and the transverse direction, and 0.1% in the longitudinal direction while holding the end portion of the film. Described is a method for producing a biaxially stretched film having a thickness of less than 10 μm, which comprises a step of relaxing at a relaxation rate larger than 3% in the lateral direction and a step of winding the film. It is described that the film thickness is measured before the film winding process, and the gap width of the extrusion die is controlled based on the measured value of the film thickness to prevent the film thickness unevenness from occurring. Has been done.

International Publication No. 2001/048661 Japanese Unexamined Patent Publication No. 2000-12909

In recent years, in each field such as the above-mentioned decorative film or dry film photoresist, the base film used is required to have high precision smoothness due to thinning, smoothing, or high precision of the coating layer. Has been done. Further, as the thickness of the base film becomes thinner, the influence of the thickness unevenness of the base film increases. In particular, in a thin film having a thickness of 100 μm or less, the influence of thickness unevenness is even greater. Therefore, in the thin film as described above, coating unevenness also occurs in the thin functional layer coated on the thin film.
The thickness unevenness is caused by the thickness of the film being different depending on the position of the film. The thickness unevenness indicates the distribution of the thickness of the film.

However, as in Patent Document 1, the thickness of the continuously formed running film is measured with high accuracy, or the roll shape value (diameter) in the width direction of the wound film roll is measured and simply fed back. However, when the thickness of the film is thin, the thickness cannot be measured accurately due to the large variation in measurement, and the unevenness of the thickness of the film cannot be controlled accurately.
Further, as in Patent Document 2, the thickness of the film is measured before the step of winding the film, and the gap width of the extrusion die is controlled based on the measured value of the thickness of the film to control the unevenness of the thickness of the film. Even if the film thickness is thin, it may not be possible to accurately measure the thickness due to the large measurement variation, and it may not be possible to accurately control the thickness unevenness of the film.
As described above, in the above-mentioned thin film having a thickness of 100 μm or less, the thickness cannot be accurately measured due to the large measurement variation. Therefore, even if the film thickness is simply measured, the thickness unevenness of the film is accurately controlled. I can't. Therefore, at present, in order to produce a film having a thin thickness, it is necessary to measure the thickness with higher accuracy.

An object of the present invention is to provide a corrected thickness measuring device capable of accurately measuring the thickness of a thin film, a corrected thickness measuring method, and a film manufacturing method.
Another object of the present invention is to provide a polyester film in which coating unevenness of a thin functional layer coated on the thin functional layer is suppressed.

In order to achieve the above object, one aspect of the present invention includes a first thickness profile calculation unit for obtaining a first thickness profile using the thickness in one direction of the film measured by a radiation thickness meter, and a first thickness profile calculation unit. The second thickness profile is obtained by using the first average thickness profile calculation unit for averaging the thickness profile of the first average thickness profile and the thickness in one direction of the film measured by the spectral interference type thickness meter. A second thickness profile calculation unit for obtaining an average thickness profile, a second average thickness profile calculation unit for averaging the second thickness profile to obtain an average second thickness profile, and an average first position at each position in one direction of the film. The ratio W expressed by (value α to the nth power) / (value β to the nth power) of the value α of the thickness profile and the value β of the average second thickness profile is calculated, and each position in one direction is calculated. The present invention provides a correction thickness measuring device having a correction thickness profile calculation unit for obtaining a correction thickness profile by multiplying the value of the second thickness profile in (1) by a value M obtained by multiplying the ratio W by 1 / n. ..
The radiation thickness gauge and the spectroscopic interferometry thickness gauge preferably measure the film after biaxial stretching.
One direction of the film is preferably the width direction of the film orthogonal to the transport direction of the film.

One aspect of the present invention is a step of obtaining a first thickness profile using the thickness of the film measured by a radiation thickness meter in one direction, and an average treatment of the first thickness profile to average the first thickness. The step of obtaining the profile, the step of obtaining the second thickness profile using the thickness in one direction of the film measured by the spectral interference type thickness gauge, and the step of averaging the second thickness profile are performed to average the second thickness. The step of obtaining the thickness profile and the value α of the average first thickness profile and the value β of the average second thickness profile at each position in one direction of the film are (value α to the nth power) / (value β). The ratio W represented by (nth power) is calculated, and the value of the second thickness profile at each position in one direction is multiplied by the value M obtained by multiplying the ratio W by 1 / n to obtain a corrected thickness profile. It provides a correction thickness measuring method including a step.
The thickness of the film measured by the radiation thickness meter in one direction and the thickness of the film measured by the spectroscopic interferometry thickness meter in one direction are preferably the thickness in one direction of the film after biaxial stretching.
One direction of the film is preferably the width direction of the film orthogonal to the transport direction of the film.

One aspect of the present invention is a step of manufacturing a film, a step of measuring the thickness of the film manufactured by a radiation thickness meter in one direction to obtain a first thickness profile, and a step of averaging the first thickness profile. A step of processing and obtaining an average first thickness profile, a step of measuring the thickness in one direction of a film manufactured by a spectral interference type thickness gauge, and a step of obtaining a second thickness profile, and a second thickness profile are performed. The step of averaging to obtain the average second thickness profile, and the value α of the average first thickness profile and the value β of the average second thickness profile at each position in one direction of the film (value α). The ratio W represented by (nth power of) / (value β to the nth power) is calculated, and the value M obtained by multiplying the value of the second thickness profile at each position in one direction by the ratio W to the power of 1 / n is obtained. The present invention provides a method for producing a film, which comprises a step of obtaining a corrected thickness profile and a step of adjusting the manufacturing conditions of the film based on the corrected thickness profile to manufacture the film. One direction of the film is preferably the width direction of the film orthogonal to the transport direction of the film.

In one aspect of the present invention, the difference between the maximum value and the minimum value in the corrected thickness profile obtained by measuring with the corrected thickness measuring device is 1.0% or less with respect to the average value of the corrected thickness profile. Is to provide.
One aspect of the present invention provides a polyester film in which the difference between the maximum value and the minimum value in the corrected thickness profile obtained by measuring with a corrected thickness measuring device is less than 0.1 μm.
In one aspect of the present invention, the difference between the maximum value and the minimum value in the corrected thickness profile obtained by measuring by the corrected thickness measuring method is 1.0% or less with respect to the average value of the corrected thickness profile. Is to provide.
One aspect of the present invention provides a polyester film in which the difference between the maximum value and the minimum value in the corrected thickness profile obtained by measuring by the corrected thickness measuring method is less than 0.1 μm.

According to the present invention, the thickness of a thin film can be measured with high accuracy. In addition, a thin film can be manufactured with small thickness unevenness.
Further, it is possible to provide a polyester film in which coating unevenness of the thin functional layer to be coated is suppressed.

It is a schematic perspective view which shows an example of the film manufacturing apparatus used in the film manufacturing method of the embodiment of this invention. It is a top view which shows an example of the stretching machine used in the manufacturing method of the film of the embodiment of this invention. It is a schematic diagram which shows an example of the correction thickness measuring apparatus used in the film manufacturing method of the embodiment of this invention. It is a graph which shows an example of the measurement result of a film. It is a schematic diagram which shows the procedure of making a correction thickness profile using the correction thickness measuring apparatus of embodiment of this invention. It is a schematic diagram which shows the procedure of making a correction thickness profile using the correction thickness measuring apparatus of embodiment of this invention. It is a schematic diagram which shows the procedure of making a correction thickness profile using the correction thickness measuring apparatus of embodiment of this invention. It is a schematic diagram which shows the procedure of making a correction thickness profile using the correction thickness measuring apparatus of embodiment of this invention. It is a flowchart which shows an example of the manufacturing method of the film of embodiment of this invention. It is an example of the correction thickness profile measured by the correction thickness measuring apparatus of embodiment of this invention is a graph. It is an example of the correction thickness profile by a radiation thickness gauge. It is a graph explaining the control of the film thickness in consideration of the oscillating cut of the film manufacturing method of the embodiment of this invention.

Hereinafter, the corrected thickness measuring device, the corrected thickness measuring method, the film manufacturing method, and the polyester film of the present invention will be described in detail based on the preferred embodiments shown in the attached drawings.
It should be noted that the figures described below are exemplary for explaining the present invention, and the present invention is not limited to the figures shown below.
In the following, "-" indicating the numerical range includes the numerical values described on both sides. For example, when ε is a numerical value ε _a to a numerical value ε _b , the range of ε is a range including the numerical value ε _a and the numerical value ε _b , and is expressed in mathematical symbols as ε _a ≤ ε ≤ ε _b .
Angles such as "angle represented by a specific numerical value", "parallel", and "orthogonal" include, unless otherwise specified, an error range generally acceptable in the art.
The amount of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified.
The term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes.

[Film manufacturing equipment]
FIG. 1 is a schematic perspective view showing an example of a film manufacturing apparatus used in the film manufacturing method of the embodiment of the present invention. FIG. 2 is a plan view showing an example of a stretching machine used in the method for producing a film according to an embodiment of the present invention.
The film manufacturing apparatus 10 shown in FIG. 1 uses a melt extrusion method, and is a melt extrusion method that uses a T die casting method. The film manufacturing apparatus 10 includes, for example, an extruder 12, an extrusion die 13, a casting roll 14, a longitudinal stretching section 15, a transverse stretching section 16, a cutting section 17, and a winding section 18. Further, the film manufacturing apparatus 10 includes a radiation thickness gauge 22, a spectroscopic interference type thickness gauge 24, a correction thickness measuring device 26, and an adjusting unit 28.
The film manufacturing apparatus 10 includes a control unit (not shown) that controls each part of the film manufacturing apparatus 10 in addition to the above-described configuration. The control unit controls the operation of each part during the production of the film.
In the following description, a polyester film will be described as an example of the film, but the film is not limited to the polyester film. Hereinafter, the film is a polyester film unless otherwise specified. The film manufacturing apparatus 10 manufactures a biaxially stretched polyester film.

As the extruder 12, a known extruder equipped with one or two or more screws is used.
The extruder 12 is performed, for example, by heating polyester, which is a raw material of a film, to a temperature equal to or higher than the melting point, and rotating the screw to melt and knead it. The raw material of the film, that is, polyester, is melted in the extruder 12 by heating and kneading with a screw to form a melt.
The melt is supplied from the extruder 12 to the extruder 13 through, for example, a gear pump (not shown), a filter (not shown), and the like.

The extrusion die 13 extrudes the melt supplied by the extruder 12 onto the casting roll 14. With the extrusion die 13, the melt may be extruded in a single layer or in multiple layers. The extrusion die 13 is also simply referred to as a "die" (see JIS (Japanese Industrial Standards) B8650: 2006, a) Extruder, No. 134). The extrusion die 13 is also called a T die.
In the melt extrusion method, it is preferable to replace the inside of the extruder 12 with nitrogen from the viewpoint of suppressing thermal decomposition in the extruder, for example, hydrolysis of polyester. Further, the extruder 12 is preferably a twin-screw extruder in that the kneading temperature can be kept low.

The casting roll 14 is a film-shaped molding of the melt extruded from the extrusion die 13. The melt extruded from the extrusion die 13 is brought into contact with the casting roll 14, and the melt is cooled and solidified on the casting roll 14 to form the melt into a film. When cooling the melt, it is more preferable to blow air on the melt, and it is more preferable to blow cold air on the melt.

The temperature of the casting roll 14 is preferably more than (Tg-10 ° C.) and (Tg + 30 ° C.) or less, more preferably (Tg-7 ° C.) to (Tg + 20 ° C.), and more preferably (Tg-5 ° C.) to (Tg + 10 ° C.). Especially preferable. Hereinafter, "Tg" is the glass transition temperature of the raw material of the film, and in the case of polyester, it is the glass transition temperature of polyester.
Further, the temperature of the polyester film and each member can be measured by using a non-contact thermometer, for example, a radiation thermometer.
When the casting roll 14 is used, it is preferable to improve the adhesion between the casting roll and the melt. Examples of the method for improving the adhesion include an electrostatic application method, an air knife method, an air chamber method, a vacuum nozzle method, and a touch roll method.
The molded product cooled and molded by using the casting roll 14, that is, the unstretched film F is stripped from the casting roll 14 by using a stripping member such as a stripping roll. The unstretched film F is an unstretched polyester film.

The longitudinally stretched portion 15 stretches the unstretched film F in the transport direction MD. The longitudinally stretched portion 15 turns the unstretched film F into _a uniaxially stretched film F1. The vertically stretched portion 15 includes, for example, a heating portion for heating the unstretched film F and a plurality of rolls 15a having different velocities. The unstretched film F is stretched in the transport direction MD by a plurality of rolls 15a having different velocities to obtain _a uniaxially stretched film F1. The uniaxially stretched film F ₁ is a film after uniaxial stretching, and is a uniaxially stretched polyester film.
_The width direction of the unstretched film F and the width direction of the uniaxially stretched film F1 and the width direction of the _biaxially stretched film F2, which are orthogonal to the transport direction MD, are referred to as TD. Further, stretching in the transport direction MD is called longitudinal stretching. The biaxially stretched film F ₂ is a film after biaxial stretching, and is a biaxially stretched polyester film.

_The transversely stretched portion 16 stretches the uniaxially stretched film F1 in the width direction TD. The transversely stretched portion 16 turns the uniaxially stretched film F1 into _a _biaxially stretched film F2. The laterally stretched portion 16 has, for example, _a width in _a state where both ends of the uniaxially stretched film F1 are gripped by clips 16a provided at both ends in the width direction and the uniaxially stretched film F1 is conveyed in the transport direction MD. It is stretched in the direction TD to obtain a _biaxially stretched film F2.

The cut portion 17 cuts both ends of the biaxially stretched film F ₂ . The trimming step described later is carried out by the cutting portion 17.
Both ends of the biaxially stretched film F ₂ are gripped by the clip 16a of the laterally stretched portion 16, and the cutting portion 17 cuts the portion gripped by the clip 16a.
The configuration of the cutting portion 17 is not particularly limited, and for example, a slitter is used. The slitter has, for example, a roll blade.

The winding portion 18 winds the _biaxially stretched film F2 whose both ends are cut by the cutting portion 17 in a roll shape. The take-up portion 18 provides a film roll 20 of the biaxially stretched film F ₂ . It is conveyed from the cutting portion 17 to the winding portion 18 by a plurality of guide rollers 19.
The configuration of the winding portion 18 is not particularly limited, and includes, for example, a winding core 18a and a driving unit (not shown) for rotating the winding core 18a. The drive unit has, for example, a motor. The biaxially stretched film F ₂ is attached to the winding core 18a, and the winding core 18a is rotated by the driving unit to wind the biaxially stretched film F ₂ in a roll shape. As a result, the film roll 20 of the biaxially stretched film F ₂ is obtained.

The adjusting unit 28 adjusts the film manufacturing conditions based on the corrected thickness profile obtained by the corrected thickness measuring device 26, and is connected to the corrected thickness measuring device 26, the extruder 12, and the extrusion die 13. .. Based on the corrected thickness profile, the adjusting unit 28 determines the film manufacturing conditions, for example, in the extrusion die 13, the die lip spacing, the die lip temperature, the temperature of the melt extruded from the extrusion die, or the amount of the melt in the width direction TD. , Or adjust the temperature of the melt supplied from the extruder 12.

As the laterally stretched portion 16, for example, the device having the configuration shown in FIG. 2 can be used.
The laterally stretched portion 16 shown in FIG. 2 includes a pair of

annular rails

30a and 30b, and gripping members 31a to 31l attached to each annular rail and movable along the rails. The

annular rails

30a and 30b are arranged symmetrically with _each other in the width direction TD with the uniaxially stretched film F1 interposed therebetween. The laterally stretched portion 16 grips the uniaxially stretched film F1 by the gripping members 31a to _31l , and stretches the uniaxially stretched film F1 in the width direction TD by moving the gripping members 31a to _31l along the rail. ..

The transversely stretched portion 16 has a preheating region 32, a stretching region 33, a heat fixing region 34, a heat relaxation region 35, and a cooling region 36 in this order from the upstream side of the transport direction MD, that is, the longitudinal stretching portion 15. Have.
Each of the above-mentioned regions of the laterally stretched portion 16 is divided by a windshield curtain, and the temperature in the region can be individually adjusted by hot air or the like.
The preheating region 32 is _a region for preheating the uniaxially stretched film F1.
The stretched region 33 is _a region in which the preheated uniaxially stretched film F1 is stretched by applying tension to the TD in the width direction. As shown in FIG. ₂ , in the stretched region 33, the uniaxially stretched film F1 is stretched from the width L0 to the width L1.
The heat-fixing region 34 is _a region where the uniaxially stretched film F1 to which tension is applied is heated and heat-fixed while being tensioned.
The heat relaxation region 35 is a region for heat relaxation of the tension of the heat _- fixed uniaxially stretched film F1 by heating the heat _- fixed uniaxially stretched film F1.
As shown in FIG. ₂ , in the heat relaxation region 35, the uniaxially stretched film F1 is reduced (relaxed) from the width L1 to the width L2.

The cooling region 36 is a region for cooling the heat _- relaxed uniaxially stretched film F1. By cooling the uniaxially stretched film F ₁ , the shape of the uniaxially stretched film F ₂ can be fixed.
FIG. ₂ shows that the width of the uniaxially stretched film F1 carried into the cooling region 36 is L2, and the width of the _biaxially stretched film F2 carried out from the cooling region 36 is L3. ..

Gripping

members

31a, 31b, 31e, 31f, 31i, and 31j that can move along the annular rail 30a are attached to the annular rail 30a. The annular rail 30b is attached with gripping

members

31c, 31d, 31g, 31h, 31k, and 31l that are movable along the annular rail 30b.
The gripping

members

31a, 31b, 31e, 31f, 31i, and 31j grip _one end of the uniaxially stretched film F1 in the width direction TD. The gripping

members

31c, 31d, 31g, 31h, 31k, and 31l grip the _other end of the uniaxially stretched film F1 in the width direction TD. The gripping members 31a to 31l are generally referred to as chucks, clips and the like.
The gripping

members

31a, 31b, 31e, 31f, 31i, and 31j move counterclockwise along the annular rail 30a. The gripping

members

31c, 31d, 31g, 31h, 31k, and 31l move clockwise along the annular rail 30b.

_The gripping members 31a to 31d move along the

annular rail

30a or 30b while gripping the end of the uniaxially stretched film F1 in the preheating region 32, and the stretching region 33, the heat fixing region 34, and the heat relaxation region 35. To the cooling region 36. Next, the gripping

members

31a and 31b and the gripping

members

31c and 31d are end portions on the downstream side of the cooling region 36 in the transport direction MD in the order of transport direction, for example, the grip release point P and the grip release point in FIG. After separating the end portion of the _biaxially stretched film F2 at Q, the film further moves along the

annular rail

30a or 30b and returns to the preheating region 32. In the above process, the uniaxially stretched film F ₁ moves in the direction of the transport direction MD to preheat in the preheating region 32, stretch in the stretching region 33, heat-fix in the heat fixing region 34, and heat relaxation region. Heat relaxation at 35 and cooling at the cooling region 36 are performed, and the film is stretched laterally.

By adjusting the moving speed of the gripping members 31a to _31l , the transport speed of the uniaxially stretched film F1 can be adjusted. Further, the gripping members 31a to 31l can independently change the moving speed.

As described above, the laterally stretched portion ₁₆ enables laterally stretching the uniaxially stretched film F1 in the width direction TD in the stretched region 33. On the other hand, the laterally stretched portion ₁₆ can also stretch the uniaxially stretched film F1 in the transport direction MD by changing the moving speed of the gripping members 31a to 31l. That is, it is also possible to simultaneously perform biaxial stretching in the transport direction MD and the width direction TD using the transverse stretching portion 16.
The laterally stretched portion 16 may further have another gripping member in addition to the gripping members 31a to _31l in order to support the uniaxially stretched film F1.

The radiation thickness gauge 22 measures the thickness of the _biaxially stretched film F2 by using radiation. As the radiation thickness gauge 22, for example, a β-ray transmission attenuation type thickness gauge or an infrared transmission attenuation type thickness gauge can be used.
The radiation thickness gauge 22 is arranged above the biaxially stretched film F ₂ . The radiation thickness gauge 22 measures, for example, the thickness of the biaxially stretched film F ₂ by scanning in the width direction TD. The measuring method of the radiation thickness gauge 22 is not limited to the method of scanning in the width direction TD.
The spectroscopic interferometry thickness gauge 24 is a measuring method using the refractive index of the film, and a known one can be appropriately used. The spectroscopic interferometry type thickness gauge 24 measures the thickness in the width direction TD using, for example, a line scan type.
It is preferable that the radiation thickness gauge 22 and the spectroscopic interference type thickness gauge 24 have the same measurement position on the _biaxially stretched film F2. For the spectral interferometry type thickness gauge 24, for example, MCPD-9800 (multi-channel spectroscope) manufactured by Otsuka Electronics Co., Ltd. and SI-T80 (model) manufactured by Keyence Co., Ltd. can be used.

The correction thickness measuring device 26 obtains a correction thickness profile using the film thickness measured by the radiation thickness gauge 22 and the film thickness measured by the spectral interference type thickness gauge 24. The corrected thickness profile shows the thickness of the film with high accuracy, and shows the thickness unevenness with high accuracy. The corrected thickness profile is used in the production of the film, and feedback control is performed based on the corrected thickness profile, and the production conditions of the film are adjusted. The film manufacturing conditions are, for example, in the extrusion die 13, the die lip spacing, the die lip temperature, the temperature of the melt extruded from the extrusion die, or the amount of melt in the width direction TD, or the melt supplied from the extruder 12. The temperature etc.
The correction thickness measuring device 26 has a radiation thickness gauge 22 and a spectroscopic interference type thickness gauge 24 having different configurations, but is not limited to this, and includes a radiation thickness gauge 22 and a spectral interference type thickness gauge 24. It may be configured.
As shown in FIG. 3, the correction thickness measuring device 26 includes a first thickness profile calculation unit 40, a first average thickness profile calculation unit 42, a second thickness profile calculation unit 44, and a second average thickness profile calculation unit 46. It has a correction thickness profile calculation unit 47, a memory 48, and a control unit 49.

The first thickness profile calculation unit 40, the first average thickness profile calculation unit 42, the second thickness profile calculation unit 44, the second average thickness profile calculation unit 46, and the correction thickness profile calculation unit 47 are all in memory. It is connected to 48. The memory 48 includes a first thickness profile calculation unit 40, a first average thickness profile calculation unit 42, a second thickness profile calculation unit 44, a second average thickness profile calculation unit 46, and a correction thickness profile calculation unit 47. Information such as the obtained corrected thickness profile is stored. The configuration of the memory 48 is not particularly limited, and is composed of, for example, a DRAM (Dynamic Random Access Memory) or a ferroelectric memory.
Further, the first thickness profile calculation unit 40, the first average thickness profile calculation unit 42, the second thickness profile calculation unit 44, the second average thickness profile calculation unit 46, the memory 48, and the correction thickness profile calculation unit 47. Is connected to the control unit 49, and the control unit 49 controls operations such as exchange of information. The correction thickness measuring device 26 also has a ROM (Read Only Memory) and the like (not shown).
The correction thickness measuring device 26 obtains a correction thickness profile by executing a program (computer software) stored in a ROM or the like on the control unit 49. The correction thickness measuring device 26 may be configured by a computer in which each part functions by executing a program as described above, or may be a dedicated device in which each part is configured by a dedicated circuit.

FIG. 4 is a graph showing an example of the measurement result of the film. In FIG. 4, the vertical axis indicates the thickness measurement value and the degree of orientation, and the horizontal axis indicates the position in the width direction.
Reference numeral 50 shown in FIG. 4 indicates an example of the measurement result of the polyester film having a thickness of 25 μm by the radiation thickness gauge 22. Reference numeral 52 indicates an example of the measurement result of the polyester film having a thickness of 25 μm by the spectroscopic interferometry thickness gauge 24. Reference numeral 54 indicates an example of the measurement result of the measured degree of orientation of the polyester film.

Reference numerals

50, 52, and 54 are the results of measurement along the width direction TD of the polyester film. The polyester film is biaxially stretched.
The degree of orientation of the film is measured using a microwave transmission type molecular orientation meter, for example, MOA-6004, manufactured by Oji Measuring Instruments Co., Ltd.

As shown in FIG. 4, the measurement result of the polyester film having a thickness of 25 μm by the radiation thickness gauge 22 shown by the reference numeral 50 is compared with the measurement result of the polyester film having a thickness of 25 μm by the spectral interferometry type thickness gauge 24 shown by the reference numeral 52. The amplitude of the measured value is large, and the variation of the measured value is large. The variation in the measured value means the measurement accuracy, and the large variation in the measured value means that the measurement error is large.
The radiation thickness gauge 22 has a variation in the measured value of about 1 μm, and the smaller the film thickness, the greater the influence of the variation in the measured value. Therefore, when the radiation thickness gauge 22 is used, the measured values vary widely, and when only the measured values of the radiation thickness gauge 22 are used for controlling the film thickness, the accuracy of controlling the film thickness is low.
As a method of controlling the thickness of the film, the thickness of the continuously formed running film is measured with high accuracy, and the extrusion die 13 (based on the measured thickness) so as to eliminate the unevenness of the film thickness ( The method of adjusting the thickness unevenness of the film by adjusting the die lip temperature or the gap between the die lips (see FIG. 1) is preferably used.

On the other hand, the measurement result of the polyester film having a thickness of 25 μm by the spectroscopic interferometric thickness gauge 24 indicated by reference numeral 52 is influenced by the degree of orientation of the film, and the thickness decreases as the degree of orientation increases.
Since the refractive index of a molecularly oriented film such as a stretched polyester film is different in the film, when the spectroscopic interference type thickness gauge 24 is used for measuring the thickness, the measured thickness reflects only the thickness of the film. It also includes the influence of the refractive index (orientation) of the film. Therefore, it is not suitable for measuring the thickness of the stretched polyester film.

Here, FIGS. 5 to 8 are schematic views showing a procedure for creating a corrected thickness profile using the corrected thickness measuring device according to the embodiment of the present invention. The vertical axis of FIGS. 5 to 8 shows the measured thickness of the film (μm), and the horizontal axis shows the position (mm) in the width direction.
The correction thickness measuring device 26 shown in FIG. 3 utilizes the thickness of the film measured by the radiation thickness gauge 22 and the thickness of the film measured by the spectroscopic interference type thickness gauge 24.
The first thickness profile calculation unit 40 (see FIG. 3) is connected to the radiation thickness gauge 22. Information on the film thickness measured by the radiation thickness gauge 22 is input.
The second thickness profile calculation unit 44 (see FIG. 3) is connected to the spectroscopic interferometry thickness meter 24. Information on the film thickness measured by the spectral interferometry thickness gauge 24 is input.

The first thickness profile calculation unit 40 obtains the first thickness profile 56 shown in FIG. 5 by using the thickness in one direction of the film measured by the radiation thickness gauge 22. In addition, one direction of the film is, for example, the width direction TD (see FIG. 1).
The first average thickness profile calculation unit 42 (see FIG. 3) averages the first thickness profile 56 shown in FIG. 5 to obtain the average first thickness profile 57 shown in FIG. Reference numeral 57a shown in FIG. 6 indicates an averaged point.
The method of averaging the first thickness profile 56 to obtain the average first thickness profile 57 is not particularly limited, and the averaging process is performed using, for example, a moving average or an interval average. For the moving average or the section average, the average number of times and the section distance are set as appropriate. Further, for example, in the averaging process, the averaged points are plotted. Here, the averaged point may be a value obtained by adding two or more points and dividing by the number of points. That is, in the averaging process, the averaged points may be average values. Further, the averaged point may be the value of the middle point among the points arranged by arranging two or more points in ascending or large order. That is, in the averaging process, the averaged points may be the median value.
The moving average width of the moving average is preferably 100 to 400 mm, more preferably 180 to 280 mm.
Further, the number of sections in the section average is preferably set so that the width of one section is 50 to 300 mm, and more preferably 50 to 150 mm, when the width of the film is divided by the number of sections. preferable. The number of sections is preferably divided into 5 to 100 equal parts, and more preferably 10 to 40 equal parts.

The second thickness profile calculation unit 44 obtains the second thickness profile 58 shown in FIG. 5 by using the thickness in one direction of the film measured by the spectral interferometry type thickness meter.
The second average thickness profile calculation unit 46 (see FIG. 3) averages the second thickness profile to obtain the average second thickness profile 59 shown in FIG. Reference numeral 59a shown in FIG. 6 indicates an averaged point.
The method of averaging the second thickness profile 58 to obtain the average second thickness profile 59 is not particularly limited, and the averaging process is performed using, for example, a moving average or an interval average. For the moving average or the section average, the average number of times and the section distance are set as appropriate. Further, for example, in the averaging process, the averaged points are plotted. Here, since the averaged points are the same as the averaged points described in the above-mentioned averaging process of the first thickness profile 56, detailed description thereof will be omitted.
Further, the moving average width of the moving average and the number of sections in the section average are the same as the moving average width of the moving average and the number of sections in the section average of the first thickness profile 56 described above. Omit.

The correction thickness profile calculation unit 47 (see FIG. 3) obtains the correction thickness profile 61 shown in FIG.
Specifically, the correction thickness profile calculation unit 47 sets the average first thickness profile value α and the average second thickness profile value β at each position in one direction of the film, that is, at each position in the width direction. The ratio W expressed by (value α to the nth power) / (value β to the nth power) is calculated. The above-mentioned ratio W is represented by W = (α ⁿ / β ⁿ ).
Then, in one direction, in FIG. 6, the value of the second thickness profile at each position in the width direction is multiplied by the value M obtained by raising the ratio W to the power of 1 / n to obtain the corrected thickness profile 61 shown in FIG. The obtained data of the correction thickness profile 61 is stored in the memory 48 (see FIG. 3).
The calculated value M is represented, for example, as in the profile 65 shown in FIG. The above-mentioned value M is represented by M = W ^{1 / n} = (α ⁿ / β ⁿ ) ^{1 / n} , and is a correction amount for the value of the second thickness profile. For example, the above-mentioned data of the ratio W and the data of the value M are temporarily stored in the memory 48 and used for calculating the correction thickness profile 61.
As described above, the correction thickness measuring device 26 obtains the correction thickness profile 61.
The corrected thickness profile 61 shown in FIG. 8 shows the state of the film before control, and does not show the state of the finally obtained film.

In addition to the above method, the following method can also be used as a method for obtaining the corrected thickness profile 61. The ratio _WA expressed by (value β to the nth power) / (value α to the nth power) of the average second thickness profile value β and the average first thickness profile value α at each position in the width direction. calculate. The above-mentioned ratio _WA is represented by _WA = (β ⁿ / α ⁿ ).
The value of the second thickness profile at each position in the width direction is divided by the value _MA obtained by multiplying the ratio WA by 1 / _n to obtain the corrected thickness profile 61 shown in FIG. It is represented by _MA = _WA ^{1 / n} = (β ⁿ / α ⁿ ) ^{1 / n} . The value of the corrected thickness profile is represented by (value of the second thickness profile) / ( _MA ).
Further, as described above, both the value α and the value β are raised to the nth power, and the ratio W is raised to the 1 / nth power, but n of the nth power and n of the 1 / nth power are the same value. The value of n may be a positive value or a negative value, and is not particularly limited, but it is preferable that n> 1. n is preferably an integer for ease of calculation, and for example, n is preferably 2 or 3. The upper limit of the value of n is preferably about n = 10 from the viewpoint of calculation time. Further, the value of n may be n <1.

When the correction thickness profile 61 obtained by the correction thickness measuring device 26 is used for controlling the thickness of the film, for example, a plurality of die lips arranged in the width direction TD (see FIG. 1) of the extrusion die 13 (see FIG. 1). The section corresponds to each of the above. The difference from the target thickness of the film in each section is calculated. Here, an allowable range is set in advance for the difference from the target thickness of the film. If the difference from the target thickness of the film in each section is within the allowable range, control is not performed in the corresponding section.
On the other hand, when the difference from the target thickness of the film exceeds the allowable range, the die lip interval or the die lip temperature is adjusted in the corresponding section. For example, when the thickness of the film of the correction thickness profile 61 is thinner than the target thickness of the film, the distance between the die lips is widened. Further, for example, when the thickness of the film of the correction thickness profile 61 is thicker than the target thickness of the film, the distance between the die lips is narrowed.

Further, the number of feedbacks may be set in advance and controlled so that the difference from the target thickness of the film in each section is within the allowable range. In this case, the film manufacturing conditions are adjusted so that the difference from the target thickness of the film in each section becomes smaller even if the difference from the target thickness in each section is within the allowable range by the set number of feedbacks. Further, even if the difference from the target thickness of the film in each section is out of the allowable range, the adjustment of the film manufacturing conditions is stopped by the set number of feedbacks.

<Correction thickness measurement method and film manufacturing method>
Next, a correction thickness measuring method and a film manufacturing method will be described.
As a method for producing a film, for example, a film is produced using a film manufacturing apparatus 10 (see FIG. 1). As the correction thickness measuring method, for example, a correction thickness measuring device 26 (see FIG. 1), a radiation thickness gauge 22 (see FIG. 1), and a spectroscopic interference type thickness gauge 24 (see FIG. 1) are used.
FIG. 9 is a flowchart showing an example of a film manufacturing method according to the embodiment of the present invention.
First, the film thickness is measured using a radiation thickness gauge 22 (see FIG. 1) (step S10). For example, the radiation thickness gauge 22 shown in FIG. 1 is scanned in the width direction TD to measure the thickness of the _biaxially stretched film F2 after lateral stretching and before winding. By this measurement, the first thickness profile 56 shown in FIG. 5 is created and obtained (step S11). Step S11 is a step of obtaining a first thickness profile.

Next, the first thickness profile 56 shown in FIG. 5 is averaged to obtain, for example, an averaged point 57a (see FIG. 6). The position of the averaged point 57a in the width direction TD and the number of the averaged points 57a are set in advance. The method of the averaging process is not particularly limited, and as described above, a moving average or an interval average is used.
Next, the averaged points 57a (see FIG. 6) are plotted to create and obtain an average first thickness profile 57 shown in FIG. 6 (step S12). Step S12 is a step of obtaining an average first thickness profile 57.

The film thickness is measured in parallel with step S10 or after step S12 using a spectroscopic interferometric thickness gauge 24 (see FIG. 1) (step S14). For example, the spectroscopic interferometric thickness gauge 24 shown in FIG. 1 is scanned in the width direction TD to measure the thickness of the _biaxially stretched film F2 after lateral stretching and before winding. By this measurement, the second thickness profile 58 shown in FIG. 5 is created and obtained (step S15). Step S15 is a step of obtaining a second thickness profile.

Next, the second thickness profile 58 shown in FIG. 5 is averaged to obtain, for example, an averaged point 59a (see FIG. 6). The position of the averaged point 59a in the width direction TD and the number of the averaged points 59a are set in advance. It is preferable that the position and number of the averaging points 59a in the width direction are the same as the position and number of the above-mentioned averaging points 57a in the width direction. The method of the averaging process is not particularly limited, and a moving average or an interval average is used as described above.
Next, the averaged points 59a (see FIG. 6) are plotted to create and obtain an average second thickness profile 59 shown in FIG. 6 (step S16). Step S16 is a step of obtaining an average second thickness profile 59.

Next, the value α of the average first thickness profile 57 and the value β of the average second thickness profile 59 at each position in the width direction TD of the film are (value α to the nth power) / (value β n). The ratio W represented by (squared) is calculated. W = (α ⁿ / β ⁿ ). Further, the value M obtained by multiplying the ratio W by the power of 1 / n is calculated. As a result, for example, the profile 65 shown in FIG. 7 is obtained. In addition, M = (α ⁿ / β ⁿ ) ^{1 / n} .
The corrected thickness profile 61 shown in FIG. 8 is created and obtained by multiplying the value γ of the second thickness profile 58 at each position in the width direction TD by the value M obtained by multiplying the ratio W by 1 / n (step S18). .. Step S18 is a step of obtaining the corrected thickness profile 61.
That is, when the value of an arbitrary position in the width direction TD of the correction thickness profile 61 is C, the value of the arbitrary position in the width direction TD of the correction thickness profile 61 is C = γ × M.
Regarding the corrected thickness profile, specifically, for example, at the position D1 in the width direction of FIG. 6, the value α ₁ of the average _first thickness profile 57 is 24.73, and the average second thickness profile 59. The value β ₁ of is 24.97.
The ratio W (value α ⁿ / value β ⁿ ) is W = (24.73) ² / (24.97) ² = 0.9809 when n = 2. The value M is M = W ^1/2 = 0.9904.
Further, the value of the position D1 of the _second thickness profile 58 is 25.01. Therefore, the value C ₁ of the correction thickness profile 61 at the position D ₁ is 25.01 × ((24.73) ² / (24.97) ² ) ^1/2 = 24.77. In this way, the value at each position of the correction thickness profile 61 is obtained. The method up to step S18 is the correction thickness measuring method.
When obtaining the value at each position of the correction thickness profile 61, the case of n = 2 has been described, but it is not limited to n = 2 as described above, and n> 1 is preferable as described above. For example, even when n = 3, the value at each position of the correction thickness profile 61 can be obtained in the same manner as n = 2.

In the film manufacturing method, as the next step of step S18, there is a step of adjusting the film manufacturing conditions based on the corrected thickness profile to manufacture the film. In this way, the thickness of the film is controlled to produce the film.
Specifically, when the corrected thickness profile 61 is used to control the thickness of the film, a determination condition is set in advance, and the film is manufactured based on the determination condition (step S20) (step S22). It is determined whether to adjust the manufacturing conditions (step S24).
For example, in step S20, as a determination condition, for example, a section is provided in a region corresponding to each of a plurality of die lips arranged in the width direction of the extrusion die 13 (see FIG. 1), and the difference from the target thickness of the film in each section. Set the tolerance for.
For example, in step S20, it is determined whether the difference from the target thickness of the film in each section is within the allowable range. If the difference from the target thickness of the film is within the permissible range, the film manufacturing conditions are not adjusted in the section corresponding to the permissible range. If the difference from the target thickness of the film is within the permissible range in all the sections, the film production is continued as it is without adjusting the film production conditions (step S22).

On the other hand, in step S20, when the difference from the target thickness of the film exceeds the allowable range, the film manufacturing conditions are adjusted (step S24). In step S24, for example, in the section where the difference from the target thickness of the film exceeds the allowable range, the die lip interval or the die lip temperature is adjusted.
For example, when the thickness of the film of the correction thickness profile 61 is thinner than the target thickness of the film, the distance between the die lips is widened. Further, for example, when the thickness of the film of the correction thickness profile 61 is thicker than the target thickness of the film, the distance between the die lips is narrowed.
As described above, the film production conditions are adjusted to carry out the film production (step S22). Up to step S22 is a film manufacturing method.

The film is manufactured after adjusting the film manufacturing conditions in step S24, but the present invention is not limited to this. For example, after adjusting the film manufacturing conditions in step S24, the process returns to step S10 and step S14, the correction thickness profile 61 is created again, and the difference from the target thickness of the film in each section is within the allowable range. May be determined (step S20). This may be repeated until the difference from the target thickness of the film in each section is within the allowable range. That is, the feedback control may be repeatedly executed, and the adjustment of the film manufacturing conditions and the creation of the corrected thickness profile may be repeatedly executed until the target thickness of the film is converged. The film manufacturing conditions are as described above.

In the manufactured film, the difference between the maximum value and the minimum value in the correction thickness profile obtained by measuring with the correction thickness measuring device or the correction thickness measurement method is 1.0 with respect to the average value of the correction thickness profile. % Or less,
In particular, in a film having a thickness of 25 μm or less, the thickness can be measured with high accuracy, and the thickness unevenness of the obtained film is small, that is, the difference between the maximum value (T _max ) and the minimum value (T _min ) in the corrected thickness profile is large. It can be as small as 1.0% or less with respect to the average value of the corrected thickness profile.
Further, in the manufactured film, the difference between the maximum value and the minimum value in the correction thickness profile obtained by measuring with the correction thickness measuring device or the correction thickness measuring method is less than 0.1 μm.
In particular, in a film having a thickness of 25 μm or less, the thickness can be measured with high accuracy, and the thickness unevenness of the obtained film is small, that is, the difference between the maximum value (T _max ) and the minimum value (T _min ) in the corrected thickness profile is shown. The R value to be obtained can be reduced to less than 0.1 μm.
For example, the R value can be less than 0.1 μm in the width direction.

In step S20, as a determination condition, an allowable range for the difference from the target thickness of the film in each section is set, but the determination condition is not limited to this. The number of feedbacks can also be used as a determination condition.
In step S20, the number of feedbacks may be set in advance and controlled so that the difference from the target thickness of the film in each section is within the allowable range. In this case, in step S20, the set number of feedbacks is determined, and in step S24, the film manufacturing conditions are adjusted. When the number of feedbacks is used, the film manufacturing conditions are adjusted so that the difference from the target thickness of the film in each section becomes smaller even if the difference is within the allowable range. Further, even if the difference from the target thickness of the film in each section is out of the allowable range, the adjustment of the film manufacturing conditions is stopped by the set number of feedbacks.

The number of feedbacks described above is not particularly limited, but the larger the number, the more precise the control. Considering the process load, it is preferably more than 10 times and 100 times or less.
If the number of feedbacks is the above-mentioned number, the R value represented by the difference between the maximum value (T _max ) and the minimum value (T _min ) in the correction thickness profile can be reduced, and the time required for feedback control becomes long. And the length of the film to be measured does not increase.

It should be noted that the above-mentioned steps S10, S11, S12 and steps S14, S15, S16 are executed in parallel, but the present invention is not limited thereto.
For example, steps S10, S11, and S12 may be executed first, or steps S14, S15, and S16 may be executed first, depending on the measurement order by the radiation thickness gauge 22 and the spectral interferometry thickness gauge 24. .. If there is measurement data from the radiation thickness gauge 22 and the spectral interferometry thickness gauge 24, steps S10 and S14 are omitted, and steps S11 and S12 and steps S15 and S16 are executed in parallel. can.
When the thickness in the width direction was measured by the correction thickness measuring device 26, the variation in the measured values was small and the film thickness unevenness could be measured with high accuracy as shown in the correction thickness profile 62 shown in FIG. On the other hand, with the radiation thickness gauge alone, as in the corrected thickness profile 64 shown in FIG. 11, the measured values vary widely, and the film thickness unevenness cannot be measured with high accuracy.

(Each manufacturing process of film)
Hereinafter, each manufacturing process of the film will be described.
A detailed description of the configuration, functions, and the like of each of the above-mentioned parts will be described together with a description of each manufacturing process included in the manufacturing method of the present embodiment described below.
Each step of the film manufacturing method will be specifically described with reference to the film manufacturing apparatus 10 shown in FIG.

[Extrusion molding process]
In the extrusion molding step, an unstretched polyester film is formed from, for example, a raw material polyester by an extrusion molding method using the above-mentioned extrusion die 13 (see FIG. 1).
The extrusion molding method is a method of molding a raw material resin into a desired shape by extruding the raw material resin using an extruder 12 (see FIG. 1).
In the extruder 12, for example, polyester is heated to a temperature equal to or higher than the melting point and melted to obtain a melt. The melt may be extruded in a single layer or in multiple layers.
The melt extruded from the extrusion die 13 is brought into contact with the casting roll 14 (see FIG. 1), and the melt is cooled and solidified on the casting roll 14 to form the melt into a film. The temperature of the casting roll is as described above.

In the extrusion molding step, it is preferable to improve the adhesion between the casting roll 14 and the melt. The method for increasing the adhesion between the casting roll 14 and the melt is as described above.
The unstretched polyester film cooled and formed by using the casting roll 14 is stripped from the casting roll 14 by using a stripping member such as a stripping roll.

[Vertical stretching process]
The longitudinal stretching step is a step of stretching the unstretched film F (see FIG. 1) in the transport direction MD, and is executed by the longitudinally stretched portion 15 (see FIG. 1). In the longitudinal stretching step, the unstretched film F is stretched in the transport direction MD by two or more rolls 15a having different transport speeds in the longitudinally stretched portion 15, to form _a uniaxially stretched film F1. It is a process to do.
In the longitudinal stretching step, the unstretched film F is longitudinally stretched by transporting the unstretched film F while applying tension to the unstretched film F by two or more rolls 15a (see FIG. 1) having different transport speeds in the longitudinally stretched portion 15. Will be.

In the longitudinal stretching step, the unstretched film F may be preheated before the longitudinal stretching. For example, by preheating the unstretched polyester film, the polyester film can be easily stretched vertically.
The preheating temperature of the unstretched film F is preferably (Tg-20) to (Tg + 50) ° C, more preferably (Tg-10) to (Tg + 40) ° C, and even more preferably (Tg-10) to (Tg + 30) ° C. Specifically, the preheating temperature in the longitudinal stretching step is preferably 70 to 120 ° C, more preferably 75 to 110 ° C, and even more preferably 75 to 100 ° C.

The transport speed (peripheral speed) of the unstretched film F by the roll 15a is not particularly limited as long as it is slower than the roll 15a on the downstream side in the transport direction, but is preferably 5 to 60 m / min, more preferably 10 to 50 m / min, and 15 -45 m / min is more preferable.
The transport speed (peripheral speed) of the unstretched film F by the roll 15a on the downstream side is not particularly limited as long as it is faster than the roll 15a on the upstream side, but is preferably 40 to 160 m / min, more preferably 50 to 150 m / min. It is preferable, and more preferably 60 to 140 m / min.

The draw ratio in the longitudinal stretching step may be appropriately set depending on the intended use, but is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and further preferably 2.8 to 4.0 times. preferable.

The stretching speed in the longitudinal stretching step is preferably 800 to 1500% / sec, more preferably 1000 to 1400% / sec, still more preferably 1200 to 1400% / sec. Here, the "stretching speed" is a value obtained by dividing the length Δd in the transport direction of the film stretched in 1 second in the longitudinal stretching step by the length d ₀ in the transport direction of the film before stretching, as a percentage. It is a represented value.

The roll 15a is not particularly limited, and a known roll used for stretching a plastic film can be used, but it is preferable that the material constituting the surface layer including the surface of each roll is a metal, ceramic or fluororesin. It is more preferably ceramic. Chromium is preferred as the metal. As the ceramic, chromium oxide or alumina oxide is preferable, and chromium oxide is more preferable. As the fluororesin, polytetrafluoroethylene is preferable.

The unstretched film F may be heated in the longitudinal stretching step. The heating temperature is preferably (Tg-20) to (Tg + 50) ° C, more preferably (Tg-10) to (Tg + 40) ° C, and even more preferably (Tg) to (Tg + 30) ° C. Specifically, the heating temperature in the longitudinal stretching step is preferably 70 to 120 ° C, more preferably 80 to 110 ° C, and even more preferably 85 to 100 ° C.

The unstretched film F may be heated on only one side of the unstretched film F or on both sides.
Further, the method for heating the unstretched film F in the longitudinal stretching step is not limited to the heater, and the method for heating the unstretched film F with a heated roll other than the roll 15a described above and the unstretched film F. A method such as a method of applying warm air to the heater can be mentioned.
Examples of the method for heating each roll include a method of providing a heater inside the roll and a method of providing a pipe inside the roll and allowing the heated fluid to flow in the pipe.

Further, as described above, the longitudinally stretched portion 15 used in the longitudinal stretching step may be provided with two or more preheats for preheating the unstretched film before the longitudinal stretching, and may be provided with two or more low-speed stretching rolls used for the longitudinal stretching. May be.
Further, the roll 15a or the like included in the vertically stretched portion 15 is not particularly limited, and may be two opposing rolls (a pair of rolls) or only one roll in contact with one surface of the unstretched film F. good.

<Cooling process>
It may have a cooling step of cooling the uniaxially stretched film obtained by the longitudinal stretching step. In this case, the uniaxially stretched film is cooled by contacting it with a cooling roll (not shown) provided in the cooling unit (not shown).

(Cooling conditions)
The condition of the cooling step is the cooling rate of the film by the cooling roll, that is, the value obtained by dividing the temperature of the film, which is lowered from the contact of the film with the cooling roll to the time when the film is separated from the cooling roll, by the time of contact between the film and the cooling roll. , 50 ° C./sec or higher, more preferably 120 ° C./sec or higher, further preferably 150 ° C./sec or higher, and particularly preferably 180 ° C./sec or higher. When the cooling rate is within the above range, the occurrence of turbulent defects in the film can be further suppressed.
The upper limit of the above-mentioned cooling rate is not particularly limited, but is preferably 300 ° C./sec or less.

The cooling rate of the film by the cooling roll can be adjusted by the surface temperature of the cooling roll and the transport speed of the film by the cooling roll and the opposing roll.
The cooling rate of the film by the cooling roll is measured by using a non-contact thermometer, the temperature of the film at the position in contact with the cooling roll (film temperature at the time of contact) and the temperature of the film at the position away from the cooling roll (at the time of separation). It is obtained from the measured value of film temperature), the length of the contact surface between the film and the cooling roll in the transport direction, and the transport speed of the film by the cooling roll and the facing roll.

When the above-mentioned film is a polyester film, the temperature of the polyester film in contact with the cooling roll in the cooling step is preferably 80 ° C. or higher, more preferably 90 ° C. or higher in that the occurrence of disorder defects in the polyester film can be further suppressed. , 95 ° C. or higher is more preferable. The upper limit is not particularly limited, but 120 ° C. or lower is preferable.
In the cooling step, the temperature of the film away from the cooling roll is preferably 80 ° C. or lower, more preferably 50 ° C. or lower, in that the occurrence of turbulent defects in the polyester film can be further suppressed. The lower limit is not particularly limited, but is preferably 15 ° C. or higher.
In the cooling step, the temperature of the polyester film lowered from the contact with the cooling roll to the separation from the cooling roll is preferably 10 ° C. or higher, preferably 30 ° C. or higher in that the occurrence of turbulent defects in the polyester film can be further suppressed. The above is more preferable, and the temperature is more preferably 40 ° C. or higher. The upper limit is not particularly limited, but is preferably 100 ° C. or lower.
The temperature of the film and the temperature change in the cooling step can be measured by the above-mentioned method using a non-contact thermometer.

(Secondary cooling process)
In the cooling step using the cooling unit, the unstretched film F cooled by the cooling roll may be further subjected to a secondary cooling treatment of further cooling by a second cooling roll (not shown).
The second cooling roll has a function of cooling while conveying the unstretched film F. The surface temperature of the second cooling roll is not particularly limited as long as it is equal to or lower than the surface temperature of the cooling roll, but is preferably 15 to 50 ° C.
The number of the second cooling rolls may be one or two, or may be three. Further, the secondary cooling process may be performed using a device other than the cooling roll.

<Transverse stretching process>
The transverse stretching step is _a step of stretching the uniaxially stretched film F1 in the width direction TD (hereinafter, also referred to as “transverse stretching”). More specifically, it is a step of stretching the uniaxially stretched film F ₁ in the width direction TD using the laterally stretched portion 16 to form the biaxially stretched film F ₂ .

As described above, the transversely stretched portion 16 (see FIG. ₁ ) applies tension in the width direction to the uniaxially stretched film F1 (see FIG. ₁ ) while heating to obtain the uniaxially stretched film F1. It is a device that stretches in the width direction. As the laterally stretched portion 16, the one shown in FIG. 2 described above is used, but in addition to this, a known laterally stretched portion such as a tenter is used.
The tenter is divided by a windbreak curtain and has a large number of zones whose temperature can be individually adjusted by hot air or the like. Specific examples of the tenter having such a zone include a tenter having a preheating zone, a transverse stretching zone, a heat fixing zone, a heat relaxation zone, and a cooling zone in order from the upstream side in the transport direction.

_In the transverse stretching step, it is preferable to preheat the uniaxially stretched film F1 before the transverse stretching. By preheating the uniaxially stretched film F ₁ , the uniaxially stretched film F ₁ can be easily laterally stretched.
The preheating temperature of the uniaxially stretched film F ₁ is preferably (Tg-10) to (Tg + 60) ° C, more preferably (Tg) to (Tg + 50) ° C. Specifically, the preheating temperature of the uniaxially stretched film F1 is preferably 80 to ₁₂₀ ° C, more preferably 90 to 110 ° C.

The draw ratio in the transverse stretching step is preferably larger than the draw ratio in the above-mentioned longitudinal stretching step. The stretching ratio in the transverse stretching step is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, still more preferably 3.5 to 4.5 times.

The area magnification represented by the product of the stretching ratio in the longitudinal stretching step and the stretching ratio in the transverse stretching step is preferably 12.8 to 15.5 times, more preferably 13.5 to 15.2 times, and 14. It is more preferably 0 to 15.0 times. When the area magnification is equal to or more than the above lower limit value, the molecular orientation in the width direction TD becomes good. Further, when the area magnification is not more than the above-mentioned upper limit value, it is easy to maintain a state in which the molecular orientation is difficult to be relaxed when subjected to the heat treatment.

The stretching speed in the transverse stretching step is preferably 8 to 80% / sec, more preferably 10 to 75% / sec, still more preferably 15 to 60% / sec.
When producing a polyester film having a coating layer, it is preferable to apply a coating liquid for forming a coating layer on the polyester film stretched in the transport direction MD, and then laterally stretch the film. By the above method, the adhesion of the coating layer can be improved.

<Heat treatment process>
It may have a step (hereinafter, also referred to as “heat treatment step”) of heat-treating the biaxially stretched film F ₂ (see FIG. 1) stretched in the width direction by the transverse stretching step. Examples of the heat treatment step include a heat fixing step and a heat relaxation step. The heat treatment step preferably has at least one of a heat fixing step and a heat relaxation step, and more preferably has both a heat fixing step and a heat relaxation step.
The heat treatment step including the heat fixing step and the heat relaxation step is carried out, for example, by using the transverse stretching portion 16 or the tenter including the heat fixing zone and the heat relaxation zone in the above-mentioned transverse stretching step.

<Heat fixing process>
As a heat treatment for the film stretched laterally by the transverse stretching step, a heat fixing step and a heat relaxation step are performed.
When the above-mentioned film is a polyester film, in the heat fixing step, the biaxially oriented polyester film obtained by the transverse stretching step is heated and heat-fixed. By crystallizing the polyester by heat fixing, shrinkage of the polyester film can be suppressed.
The heat fixing step is carried out, for example, in the heat fixing region 34 (see FIG. 2) of the above-mentioned transverse stretching portion 16.

The surface temperature (heat fixing temperature T1) of the polyester film in the heat fixing step is preferably 190 to 240 ° C., more preferably 200 to 240 ° C., and even more preferably 210 to 230 ° C.
In the heat fixing step, the heat treatment is performed while controlling the maximum temperature reached on the surface of the film to be the above-mentioned heat fixing temperature T1.

In the heat fixing step, the variation in the surface temperature in the film width direction is preferably 0.5 to 10.0 ° C, more preferably 0.5 to 7.0 ° C, still more preferably 0.5 to 5.0 ° C. 0.5 to 4.0 ° C. is particularly preferable. By controlling the variation in the surface temperature in the film width direction within the above range, the variation in the crystallinity in the width direction can be suppressed.

Examples of the heating method include a method of applying hot air to the film and a method of radiant heating of the film. Examples of the device used in the method of radiant heating include an infrared heater.

The heating time in the heat fixing step is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, and even more preferably 5 to 10 seconds.

<Heat relaxation process>
In the heat relaxation step, the film heat-fixed by the heat-fixing step is heated at a temperature lower than that of the heat-fixing step to heat-relax the film. Residual strain of the film can be alleviated by heat relaxation.
The heat relaxation step is carried out, for example, in the heat relaxation region 35 of the laterally stretched portion 16 described above.

The surface temperature (heat relaxation temperature T2) of the film in the heat relaxation step is preferably 5 ° C. or higher lower than the heat fixation temperature T1, more preferably 15 ° C. or higher, further preferably 25 ° C. or higher, further preferably 30 ° C. The lower temperature is particularly preferable. That is, the heat relaxation temperature T2 is preferably 235 ° C or lower, more preferably 225 ° C or lower, further preferably 210 ° C or lower, and particularly preferably 200 ° C or lower.
The lower limit of the heat relaxation temperature T2 is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, still more preferably 120 ° C. or higher.
In the heat relaxation step, the heat treatment is performed while controlling the maximum temperature reached on the surface of the film to be the above-mentioned heat relaxation temperature T2.

<Cooling process>
The film manufacturing method comprises a cooling step of cooling the heat-relaxed film. The cooling step and the expansion step described later are carried out, for example, in the cooling region 36 of the laterally stretched portion 16 described above.

Examples of the method for cooling the film in the cooling step include a method of blowing air (preferably cold air) on the film and a method of bringing the film into contact with a temperature-adjustable member (for example, a temperature control roll).

In the film manufacturing method, it is preferable to carry out the cooling step so that the cooling rate V of the film is 2200 to 3500 ° C./min. By adjusting the cooling rate V within the above range, it is possible to reduce the uneven thickness of the functional layer laminated on the biaxially oriented film.
Although the details of the mechanism by which the thickness unevenness of the functional layer is reduced by specifying the range of the cooling rate V are not clear, the cooling that can efficiently lower the temperature of the film surface and suppress the temperature unevenness of the film surface. It is presumed that by setting the speed, the strain inherent in the film after cooling can be reduced, and the generation of waviness due to the high temperature treatment at the time of laminating the functional layer can be suppressed.
From the above viewpoint, the cooling rate V in the cooling step is preferably 2200 to 3000 ° C./min, more preferably 2300 to 2600 ° C./min.

The cooling rate V of the film in the cooling step can be measured using a non-contact thermometer. For example, when the cooling step is carried out in the cooling region 36 of the laterally stretched portion ₁₆ described above, the surface temperature of the uniaxially stretched film F1 carried into the cooling region 36 from the heat relaxation region 35 and the surface temperature of the uniaxially stretched film F1 carried out from the cooling region 36. _The surface temperature of the uniaxially stretched film F1 is measured to obtain a temperature difference ΔT (° C.) between the two. _The cooling rate V is obtained by dividing the obtained temperature difference ΔT (° C.) by the residence time ts of the uniaxially stretched film F1 in the cooling region 36.
The cooling speed of the uniaxially stretched film F ₁ can be adjusted by the operating conditions of the cooling device and the transport speed of the film.

It is preferable that the above-mentioned heat fixing step, heat relaxation step, and cooling step in the film manufacturing method are continuously carried out in this order. As a result, it is possible to reduce the load (heat history) due to repeated heating and cooling of the film, reduce the distortion inherent in the film, and suppress the occurrence of streak defects.

<Expansion process>
The method for producing a film includes an expansion step of expanding the heat-relaxed film in the width direction in the above-mentioned cooling step.
“Expanding the film in the width direction” in the cooling step means the film width at the end of the cooling step (L3 in FIG. 2) rather than the film width of the film at the start of the cooling step (L2 in FIG. 2). It means applying tension in the width direction to the film during the cooling process so that

In the cooling step, the method of expanding the film in the width direction is not particularly limited. For example, when a biaxially oriented film is manufactured using the above-mentioned transversely stretched portion 16, the cooling region 36 is more than the distance between the annular rails 30a (see FIG. 2) and 30b (see FIG. 2) at the starting point of the cooling region 36. By increasing the distance between the

annular rails

30a and 30b at the end point (grip release point P (see FIG. 2) and grip release point Q (see FIG. 2)) of (see FIG. 2), each grip member in the cooling step The uniaxially stretched film F ₁ to be gripped can be expanded in the width direction.
The expansion step may be carried out continuously or intermittently from the start to the end of the cooling step as long as the film width is expanded before and after the cooling step, or may be carried out only at one time during the cooling step.

The expansion ratio in the width direction of the film by the expansion step, that is, the ratio of the film width at the end of the cooling step to the film width before the start of the cooling step is not particularly limited as long as it is larger than 0, but the effect of the present invention is more effective. In terms of excellence, the percentage b of the above-mentioned expansion rate is preferably 0.001% or more, and more preferably 0.01% or more.
The upper limit is not particularly limited, but the percentage b of the above-mentioned expansion rate is preferably 1.3% or less, more preferably 1.2% or less, and further preferably 1.0% or less. When a strong tension is applied in the transport direction in order to transport the film at high speed by setting the expansion rate of the film width to the above upper limit value or less (for example, when the tension in the transport direction is 100 N / m or more). ), It is possible to suppress the disorder of the cut surface in the trimming step described later, and further, the breakage of the film due to the cutting disorder.

<Trimming process>
The trimming step is a step of cutting both end portions gripped by the clip 16a (see FIG. 1) of the laterally stretched portion 16 of the biaxially stretched film F ₂ . After the trimming step, a winding step is carried out.

<Rolling process>
It has a winding step of obtaining a roll-shaped biaxially stretched film F ₂ by winding the biaxially stretched film F ₂ after the trimming step obtained by performing the above-mentioned transverse stretching step by a winding unit 18. .. The biaxially stretched film F ₂ is the film of the present invention.
By going through the above steps, the biaxially stretched film F ₂ can be manufactured. The control of the thickness unevenness of the biaxially stretched film F ₂ is carried out as described above.

(Off oscillate)
FIG. 12 is a graph illustrating control of film thickness in consideration of oscillating cutting in the method for producing a film according to the embodiment of the present invention.

The cutting portion 17 shown in FIG. 1 cuts both end portions of the biaxially stretched film F ₂ along the transport direction MD, but is not limited thereto. For example, in the width direction TD, both end portions of the biaxially stretched film F ₂ may be cut by changing the cutting position in a triangular wavy shape. This cutting method is called oscillating cutting. In this case, the lengths of both end portions of the biaxially stretched film F ₂ after cutting change in the width direction TD along the transport direction MD. It is preferable to straighten both end portions of the biaxially stretched film F ₂ after cutting the oscillate in a direction parallel to the transport direction MD. For example, an EPC (engineering position controller) is used for correction. By oscillating, the surface of the film roll 20 becomes flat after winding.

When the oscillate is cut, it is preferable to arrange a thickness gauge (not shown) after the correction. The thickness gauge arranged after the correction has the radiation thickness gauge 22 and the spectral interferometry thickness gauge 24 described above. The thickness of the biaxially stretched film F ₂ after the edge is straightened, which is measured by a thickness gauge, is measured, and this measured value is used for the above-mentioned corrected thickness measurement and the production of the film.

The end face of the oscillated, cut biaxially stretched film F ₂ is corrected by using the measurement data of the radiation thickness gauge 22 and the measurement data of the spectral interference type thickness gauge 24, respectively, on the measurement data. , The thickness data of the biaxially stretched film F ₂ after straightening can be calculated, and this calculated data can be used for the above-mentioned correction thickness measurement and the production of the film.

When the oscillate cut is performed, the above-mentioned feedback control is performed using the thickness of the film after the oscillate cut on the measurement data of the radiation thickness gauge 22 and the measurement data of the spectroscopic interference type thickness gauge 24. The profile of the film shown in 70 can be obtained. On the other hand, when the above-mentioned feedback control is performed without using the thickness of the film after oscillating, the profile of the film shown by reference numeral 72 in FIG. 12 is obtained.
In both the film profile 70 and the film profile 72 of FIG. 12, the thickness of the widthwise TD of the long film to be wound is measured over the entire length of the film, and the widthwise TD of the long film is measured. The average value of the thickness is shown.
When the oscillate cutting is performed, the feedback control can be performed by using the thickness of the film after the oscillating cutting, so that the film thickness can be made flat as compared with the case where the film thickness after the oscillating cutting is not used.

<Polyester film>
The polyester film is a film-like object containing polyester as a main polymer component. Here, the "main polymer component" means the polymer having the highest content (mass) among all the polymers contained in the film.
The polyester film may contain one kind of polyester alone or may contain two or more kinds of polyesters.

(polyester)
Polyester is a polymer having an ester bond in the main chain. Polyester is usually formed by polycondensing a dicarboxylic acid compound and a diol compound, which will be described later.
The polyester is not particularly limited, and known polyesters can be used. Examples of the polyester include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN), and PET is preferable.

The intrinsic viscosity of the polyester is preferably 0.50 dl / g or more and less than 0.80 dl / g, and more preferably 0.55 dl / g or more and less than 0.70 dl / g.
The melting point (Tm) of the polyester is preferably 220 to 270 ° C, more preferably 245 to 265 ° C.
The glass transition temperature (Tg) of polyester is preferably 65 to 90 ° C, more preferably 70 to 85 ° C.

The method for producing polyester is not particularly limited, and a known method can be used. For example, polyester can be produced by polycondensing at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst.

-catalyst-
The catalyst used for producing the polyester is not particularly limited, and a known catalyst that can be used for synthesizing the polyester can be used.
Examples of the catalyst include alkali metal compounds (for example, potassium compounds and sodium compounds), alkaline earth metal compounds (for example, calcium compounds and magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, and antimony. Examples thereof include compounds, titanium compounds, germanium compounds and phosphorus compounds. Of these, titanium compounds are preferable from the viewpoint of catalytic activity and cost.
Only one kind of catalyst may be used, or two or more kinds of catalysts may be used in combination. At least one metal catalyst selected from potassium compounds, sodium compounds, calcium compounds, magnesium compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, and phosphorus compounds. It is preferable to use in combination, and it is more preferable to use a titanium compound and a phosphorus compound in combination.

As the titanium compound, an organic chelated titanium complex is preferable. The organic chelated titanium complex is a titanium compound having an organic acid as a ligand.
Examples of the organic acid include citric acid, lactic acid, trimellitic acid, and malic acid.
As the titanium compound, the titanium compound described in paragraphs 0049 to 0053 of Japanese Patent No. 5575671 can also be used, and the contents of the above-mentioned publication are incorporated in the present specification.

-Dicarboxylic acid compound-
The dicarboxylic acid compound is preferably a dicarboxylic acid or a dicarboxylic acid ester, and examples thereof include an aliphatic dicarboxylic acid compound, an alicyclic dicarboxylic acid compound, an aromatic dicarboxylic acid compound, and a methyl ester compound or an ethyl ester compound thereof. .. Of these, aromatic dicarboxylic acid or methyl aromatic dicarboxylic acid is preferable.

Examples of the aliphatic dicarboxylic acid compound include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecandic acid, dimer acid, eicosandionic acid, pimelic acid, azelaic acid, and methylmalonic acid. And ethylmalonic acid.
Examples of the alicyclic dicarboxylic acid compound include adamantandicarboxylic acid, norbornnedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid.

Examples of the aromatic dicarboxylic acid compound include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 1,8-naphthalenedicarboxylic acid. , 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylindandicarboxylic acid, anthracendicarboxylic acid, phenanthrangecarboxylic acid, and 9,9'-bis (4-carboxy). Phenyl) fluorenic acid can be mentioned.
Of these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferable, and terephthalic acid is more preferable.

Only one type of dicarboxylic acid compound may be used, or two or more types may be used in combination. When terephthalic acid is used as the dicarboxylic acid compound, terephthalic acid may be used alone, or may be copolymerized with another aromatic dicarboxylic acid such as isophthalic acid or an aliphatic dicarboxylic acid.

-Glycol compound-
Examples of the diol compound include an aliphatic diol compound, an alicyclic diol compound, and an aromatic diol compound, and an aliphatic diol compound is preferable.

Examples of the aliphatic diol compound include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neo. Examples include pentyl glycol, preferably ethylene glycol.
Examples of the alicyclic diol compound include cyclohexanedimethanol, spiroglycol, and isosorbide.
Examples of the aromatic diol compound include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis (4-hydroxyphenyl) fluorene.
Only one kind of diol compound may be used, or two or more kinds may be used in combination.

-End sealant-
In the production of polyester, an end-capping agent may be used if necessary. By using the end sealant, a structure derived from the end sealant is introduced into the end of the polyester.
As the terminal encapsulant, a known end encapsulant can be used without limitation. Examples of the terminal encapsulant include oxazoline compounds, carbodiimide compounds, and epoxy compounds.
As the terminal encapsulant, the contents described in paragraphs 0055 to 0064 of JP-A-2014-189002 can also be referred to, and the contents of the above-mentioned publication are incorporated in the present specification.

-Polyester manufacturing conditions-
The reaction temperature is not limited and may be appropriately set according to the raw material. The reaction temperature is preferably 260 to 300 ° C, more preferably 275 to 285 ° C.
The pressure is not limited and may be appropriately set according to the raw material. The pressure is preferably 1.33 × 10 ^-3 to 1.33 × 10 ^-5 MPa, more preferably 6.67 × 10 ^-4 to 6.67 × 10 ^-5 MPa.

As a method for synthesizing polyester, the methods described in paragraphs 0033 to 0070 of Japanese Patent No. 5575671 can also be used, and the contents of the above-mentioned publication are incorporated in the present specification.

The polyester content in the polyester film is preferably 85% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, still more preferably 98% by mass or more, based on the total mass of the polymer in the polyester film. Especially preferable.
The upper limit of the polyester content is not limited and can be appropriately set within a range of 100% by mass or less with respect to the total mass of the polymer in the polyester film.

When the polyester film contains polyethylene terephthalate, the content of the polyethylene terephthalate is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and 98 to 100% by mass with respect to the total mass of the polyester in the polyester film. % Is more preferable, and 100% by mass is particularly preferable.

The polyester film may contain components other than polyester (for example, catalyst, unreacted raw material component, water, etc.).
The polyester film preferably contains substantially no particles. Here, "substantially free of particles" means that the content of particles is 50 with respect to the total mass of the polyester film when the elements derived from the particles are quantitatively analyzed by fluorescent X-ray analysis. It is defined as having a mass of ppm or less, preferably 10% by mass or less, and more preferably not more than the detection limit. This means that even if the particles are not actively added to the base film, the contamination component derived from foreign matter, the raw material resin, or the dirt adhering to the line or device in the film manufacturing process is peeled off and mixed in the film. This is because it may be done.

(Thickness)
The thickness of the polyester film is preferably 100 μm or less, more preferably less than 50 μm, further preferably 40 μm or less, and particularly preferably 25 μm or less, in terms of being able to suppress an increase in haze value and being excellent in laminating property. The lower limit of the thickness is not particularly limited, but 3 μm or more is preferable, 4 μm or more is more preferable, and 10 μm or more is further preferable, from the viewpoint of improving the strength and the workability.
The thickness of the polyester film is measured by the above-mentioned corrected thickness measuring device or the corrected thickness measuring method.
The polyester film is 1.0% or less with respect to the average value of the corrected thickness profile. The lower limit of the above ratio is preferably 0%.
Further, in the polyester film, the R value represented by the difference between the maximum value (T _max ) and the minimum value (T _min ) in the corrected thickness profile is less than 0.1 μm. The lower limit of the above R value is preferably 0 μm.

(density)
The density of the polyester film is preferably 1.39 to 1.41 g / cm ³ , more preferably 1.395 to 1.405 g / cm ³ , and even more preferably 1.398 to 1.400 g / cm ³ .
The density of the polyester film can be measured using an electronic hydrometer (product name "SD-200L", manufactured by Alpha Mirage Co., Ltd.).

(Haze)
When a polyester film is used as a support for a dry film resist, high transparency is required. In particular, higher transparency is required when forming a fine pattern such as a line and space of 50 μm or less. In that respect, the haze of the polyester film is preferably 1% or less, more preferably 0.5% or less, further preferably 0.4% or less, and particularly preferably 0.3% or less. The smaller the haze, the better, so the lower limit of the haze is not limited. If the lower limit of the haze is set for convenience, it is 0% or more. By setting the haze to the above-mentioned upper limit or less, it is possible to reduce the scattering of ultraviolet light by the polyester film, which is the support of the resist layer when the resist layer is laminated on the polyester film and then irradiated with ultraviolet rays for exposure. It is possible to improve the state of the resist pattern wall surface such as distortion and omission in the subsequent patterning of the resist.

Haze is measured by a method according to JIS K7105 using a haze meter (for example, NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

(B ^* value)
When a polyester film is used as a support for a dry film resist, high transparency is required. In that respect, the b ^* value in the L ^* a ^* b ^* color system is preferably 0 to 1, more preferably 0 to 0.8, further preferably 0 to 0.6, and particularly preferably 0 to 0.4. preferable. When the b ^* value in the L ^* a ^* b ^* color system is 0 to 1, the yellowness of the film can be reduced, so that the hue of the film can be made almost colorless. As a result, the polyester film can be preferably applied, for example, in applications where high visibility is required, for example, in display devices.

The b ^* value in the L ^* a ^* b ^* color system is measured by a transmission method using a spectral color difference meter (for example, SE-2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

The present invention is basically configured as described above. Although the corrected thickness measuring device, the corrected thickness measuring method, the film manufacturing method, and the polyester film of the present invention have been described in detail above, the present invention is not limited to the above-described embodiment and does not deviate from the gist of the present invention. Of course, various improvements or changes may be made in the above.

Hereinafter, the features of the present invention will be described in more detail with reference to examples. The materials, reagents, amounts of substances and their ratios, operations and the like shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following examples.
In each step of this embodiment, a non-contact thermometer (AD-5616 (product name), manufactured by A & D, emissivity 0.95) is used to measure the temperature of the central portion in the width direction of the film five times. The arithmetic mean value of the obtained measured values was used as the measured value of the surface temperature of the film.

[Example 1]
<Extrusion molding process>
Pellets of polyethylene terephthalate were produced using a titanium compound (citrate chelated titanium complex, VERTEC AC-420, manufactured by Johnson Matthey) described in Japanese Patent No. 5575671 as a polymerization catalyst. The obtained pellets were dried to a water content of 50 ppm or less, charged into a hopper of a uniaxial kneading extruder having a diameter of 30 mm, and then melted and extruded at 280 ° C. The melt was passed through a filter (pore diameter 3 μm) and then extruded from the die into a cooling drum at 25 ° C. to obtain an unstretched film made of polyethylene terephthalate. The extruded melt was brought into close contact with the cooling drum by the electrostatic application method.
The melting point (Tm) of polyethylene terephthalate constituting the unstretched film was 258 ° C., and the glass transition temperature (Tg) was 80 ° C.

<Vertical stretching process>
The above-mentioned unstretched film was subjected to a longitudinal stretching step by the following method.
A uniaxially oriented film was produced by passing a preheated unstretched film between two pairs of rolls having different peripheral speeds and stretching the film in the vertical direction (conveyance direction) under the following conditions.
(Vertical stretching conditions)
Preheating temperature: 75 ° C
Stretching temperature: 90 ° C
Stretching ratio: 3.4 times Stretching speed: 1300% / sec

<Transverse stretching process>
The film subjected to the longitudinal stretching step was stretched in the width direction using a tenter under the following conditions to prepare a biaxially stretched film.
(Transverse stretching conditions)
Preheating temperature: 100 ° C
Stretching temperature: 120 ° C
Stretching ratio: 4.3 times Stretching speed: 50% / sec

<Heat fixing process>
The biaxially stretched film subjected to the above-mentioned transverse stretching step was heated under the following conditions using a tenter to perform a heat fixing step of heat-fixing the film.
(Heat fixing conditions)
Heat fixation temperature T1: 227 ° C
Heat fixing time: 6 seconds

<Heat relaxation process>
Next, the heat-fixed film was heated under the following conditions to perform a heat relaxation step of relaxing the tension of the film. Further, in the heat relaxation step, the film width was reduced as compared with the end of the heat fixing step by narrowing the distance (tenter width) between the gripping members of the tenter that grips both ends of the film. The following heat relaxation rate ΔLr was obtained from the film width L2 at the end of the heat relaxation step with respect to the film width L1 at the start of the heat relaxation step by the formula Lr = (L1-L2) / L1 × 100.
(Heat relaxation conditions)
Heat relaxation temperature T2: 190 ° C
Heat relaxation rate Lr: 4%

<Cooling process and expansion process>
The heat-relaxed film was subjected to a cooling step of cooling under the following conditions. Further, in the cooling step, an expansion step was carried out in which the film width was expanded as compared with the time when the heat relaxation step was completed by widening the tenter width.
The cooling rate V below is the film surface measured at the time of loading into the cooling region 36, with the residence time from when the film is carried into the cooling region 36 of the laterally stretched portion 16 shown in FIG. 2 until it is carried out as the cooling time ta. It was obtained by dividing the temperature difference ΔT (° C.) between the temperature and the film surface temperature measured at the time of carrying out the cooling region 36 by the cooling time ta.
Further, the following expansion ratio ΔL was obtained from the film width L3 at the end of the cooling step with respect to the film width L2 of the polyester film at the start of the cooling step by the formula ΔL = (L3-L2) / L2 × 100.
(Cooling conditions)
Cooling speed V: 2500 ° C / min Cooling time ta: 3.1 seconds (expansion condition)
Expansion rate ΔL: 0.6%

<Rolling process>
With respect to the film cooled by the cooling step, the film was continuously cut along the transport direction at a position 20 cm from both ends in the width direction of the film using a trimming device, and both ends of the film were trimmed. Next, an extrusion process (knurling) was performed on a region from both ends of the film to 10 mm in the width direction, and then the film was wound up at a tension of 40 kg / m.
A biaxially stretched film was produced by the above method. The width of the obtained biaxially stretched film was 1.5 m, and the winding length was 1600 m.

When winding the biaxially stretched film, the film thickness in the width direction TD of the film and the film thickness of the film transfer direction MD are transferred by using a radiation thickness meter and a spectral interference type thickness meter. Directional MD, that is, 1600 m along the longitudinal direction of the film was measured.
The correction thickness profile was obtained by the above-mentioned correction thickness measurement method using the measurement results of the radiation thickness gauge and the spectral interferometry thickness gauge. From the corrected thickness profile, the corrected thickness unevenness in the width direction of the film and the corrected thickness unevenness in the transport direction of the film were obtained. Information on the corrected thickness unevenness in the width direction of the film and the corrected thickness unevenness in the film transport direction are fed back to the temperature of the extrusion die, which is the manufacturing condition of the film, the temperature condition of the melt extruded from the extrusion die, and the like. It was controlled so that the correction thickness unevenness in the width direction and the correction thickness unevenness in the transport direction of the film were reduced, that is, the unevenness of the film surface in the width direction and the transport direction was eliminated. During the control, the feedback control was repeated 30 times.

[Example 2]
In Example 2, the number of feedbacks was different from that in Example 1, and other than that, it was the same as in Example 1. In Example 2, the number of feedbacks was 40 times.
[Example 3]
In Example 3, the number of feedbacks was different from that in Example 1, and other than that, it was the same as in Example 1. In Example 3, the number of feedbacks was 45 times.
[Example 4]
In Example 4, the number of feedbacks and the target thickness of the film were different from those in Example 1, and other than that, it was the same as in Example 1. In Example 4, the number of feedbacks was 45, and the target thickness of the film was 31 μm.
[Example 5]
In Example 5, the number of feedbacks and the target thickness of the film were different from those in Example 1, and other than that, it was the same as in Example 1. In Example 5, the number of feedbacks was 45, and the target thickness of the film was 38 μm.

Immediately before winding, the corrected thickness in the width direction of the film was measured. The average value of the corrected thickness in the film width direction was defined as the thickness _{Ta, and the difference between the maximum thickness T max} _and the minimum thickness T _min was defined as the R value (μm). That is, R value (μm) = (T _max −T _min ) (μm)
Further, the R value / thickness was defined as the ratio of thickness unevenness (%).
That is, the ratio of thickness unevenness (%) ₌ ((T _max −T _min ) / Ta) × 100 (%). The thickness unevenness ratio (%) is the ratio of the difference between the maximum value and the minimum value in the above-mentioned corrected thickness profile to the average value of the corrected thickness profile.
Further, the corrected thickness in the transport direction of the film was also measured in the same manner as the corrected thickness in the width direction of the film, and the above-mentioned R value and the ratio (%) of the thickness unevenness in the transport direction were obtained.

The coating unevenness shown below was evaluated for each of the biaxially stretched films of Examples 1 to 5. Table 1 shows the evaluation results of coating unevenness.
[Uneven coating]
While transporting the biaxially stretched film of Examples 1 to 5, a coating liquid for a base layer composed of the following formulation A was applied to the surface of the biaxially stretched film using a slit-shaped nozzle, and then under a temperature condition of 90 ° C. An underlayer was formed by drying the coating film. Next, while transporting the biaxially stretched film on which the base layer is formed, a coating liquid for a black layer consisting of the following formulation B is applied onto the base layer, and then the coating film is dried under a temperature condition of 90 ° C. Formed a black layer. The transport speed of the biaxially stretched film when forming the base layer and the black layer was 70 m / min.
A biaxially stretched film provided with a base layer and a black layer was placed on a light table, and color unevenness of the black layer was visually observed at a position 1 m away from the biaxially stretched film.
A biaxially stretched film provided with the base layer and the black layer was formed according to the above method except that the drying temperature conditions at the time of forming the base layer and the formation of the black layer were both changed to 120 ° C. The observation was made in.
Based on the observation results of each biaxially stretched film manufactured with the drying temperature condition of the coating film set to 90 ° C. or 120 ° C., the coating unevenness of the biaxially stretched film was evaluated according to the following criteria.

(Prescription A: Coating liquid for base layer)
-PVA205 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd., saponification degree 88%, polymerization degree 550): 32.2 parts by mass-polyvinylpyrrolidone (manufactured by ISP Japan Co., Ltd., K-30): 14.9 parts-distilled water : 524 parts by mass, methanol: 429 parts by mass

(Prescription B: Coating solution for black layer)
Resin-coated carbon black produced in accordance with paragraphs 0036 to 0042 of Japanese Patent No. 5320652: 13.1 parts by mass ・ Dispersant: Dispersant 1 according to paragraph [0103] of International Publication No. 2017/208849. 0.65 parts by mass ・ Polymer (benzyl methacrylate / methacrylic acid = 72/28 molar ratio random copolymer, weight average molecular weight 37,000): 672 parts by mass ・ Propropylene glycol monomethyl ether acetate: 79.53 Mass part

(Evaluation criteria)
A: Regarding the color unevenness of the black layer, the unevenness failure of the black layer is not visible. B: Regarding the color unevenness of the black layer, the unevenness failure of the black layer is slightly visible, but it is within the allowable range.
C: Regarding the color unevenness of the black layer, many unevenness failures of the black layer can be seen.

As shown in Table 1, in Examples 1 to 5, it was possible to obtain a polyester film having a small ratio of R value and thickness unevenness and good coating unevenness.
In addition, in the configuration of only the radiation thickness gauge, the thickness unevenness could not be measured due to the variation of the measured values as in the corrected thickness profile 64 shown in FIG. Therefore, it is not possible to obtain information on the corrected thickness unevenness with the configuration of only the radiation thickness gauge, and further, the evaluation of the coating unevenness and the like is not performed.
With the configuration of only the spectral interferometry type thickness gauge, the thickness unevenness cannot be measured due to the influence of the degree of orientation of the film as in the measurement result of the polyester film having a thickness of 25 μm by the spectral interferometry type thickness gauge 24 shown in FIG. rice field. For this reason, it is not possible to obtain information on the corrected thickness unevenness with the configuration of only the spectral interferometry type thickness gauge, and further, the evaluation of the coating unevenness and the like is not performed.

[Example 10]
Using the biaxially stretched film prepared in Example 1 as a support, a dry film for forming a touch panel protective film was prepared by the following procedure.
A coating liquid for forming a second transparent transfer layer consisting of the following formulation D was applied to the surface of the biaxially stretched film produced in Example 1 and dried at 90 ° C. to form a second transparent transfer layer. Next, a coating liquid for forming a first transparent transfer layer consisting of the following formulation E was applied onto the second transparent transfer layer and then dried at 70 ° C. to form the first transparent transfer layer. The thickness of the second transparent transfer layer was 5.0 μm, and the thickness of the first transparent transfer layer was about 80 nm. Finally, a polyethylene terephthalate film having a thickness of 16 μm was pressure-bonded to the surface of the first transparent transfer layer as a protective film to prepare a transfer film for forming a touch panel protective film.
The obtained transfer film had no change in the refractive index due to uneven coating, no transfer failure, and had good characteristics. When contact holes were formed in the obtained transfer film with reference to [0122] to [0128] of International Publication No. 2018/186428, a good pattern could be formed.

<Prescription D: Coating liquid for forming the second transparent transfer layer>
・ Aronix TO-2349 (Toa Synthetic Co., Ltd., carboxylic acid-containing monomer) 0.93 parts ・ A-DCP (Shin-Nakamura Chemical Industry Co., Ltd., bifunctional, molecular weight 304) 5.6 parts ・ 8UX-015A (Taisei Fine Chemicals Co., Ltd.) Company, Urethane acrylate) 2.80 parts ・ Binder (polymer of glycidyl methacrylate adduct of cyclohexyl methacrylate / methyl methacrylate / methacrylic acid / methacrylic acid, 51.5 / 2 / 26.5 / 20%, weight average molecular weight (Mw) = 29000, acid value = 95 mgKOH) 15.59 parts ・ Polymerization initiator IRGACURE OXE-02 (BASF) 0.11 parts ・ Polymerization initiator Omnirad 907 (BASF, 2-methyl-1- (4-) Methylthiophenyl) -2-morpholinopropane-1-one) 0.21 part ・ N-phenylglycine 0.03 part ・ Block isocyanate (Asahi Kasei Chemicals Co., Ltd., Duranate WT32-B75P) 3.63 part ・ Benzoimidazole 0. 09 parts ・ Surface active agent (DIC Co., Ltd., Megafuck F-551) 0.02 parts ・ 1-methoxy-2-propyl acetate 31.08 parts ・ Methyl ethyl ketone 40.0 parts

<Prescription E: Coating liquid for forming the first transparent transfer layer>
・ Nanouse OZ-S30M (ZrO ₂ particle methanol dispersion, Nissan Chemical Industry Co., Ltd., non-volatile content 30.5%) 4.34 parts ・ Ammonia water (25%) 7.82 parts ・ Monoisopropanolamine 0.02 parts ・Binder (allyl methacrylate / methacrylic acid copolymer, 40/60 mol%, weight average molecular weight (Mw) = 38000) 0.24 part, Aronix TO-2349 (Toa Synthetic Co., Ltd.) 0.03 part, benzotriazole 0.03 Part ・ Surfactant (DIC Co., Ltd., Megafuck F-444) 0.01 part ・ Ion exchanged water 21.5 part ・ Methanol 66.0 part

[Example 11]
Using the biaxially stretched film prepared in Example 1 as a support, a dry film for forming an etching resist was prepared by the following procedure.
A coating liquid for forming a thermoplastic resin layer consisting of the following formulation F was applied to the surface of the biaxially stretched film produced in Example 1 and dried at 80 ° C. to form a thermoplastic resin layer. Next, a coating liquid for forming a water-soluble resin layer consisting of the following formulation G was applied onto the thermoplastic resin layer and then dried at 80 ° C. to form a water-soluble resin layer. Further, a coating liquid for forming a photosensitive resin layer consisting of the following formulation H was applied onto the water-soluble resin layer and then dried at 80 ° C. to form a photosensitive resin layer. The thickness of the thermoplastic resin layer was 2 μm, the thickness of the water-soluble resin layer was 1 μm, and the thickness of the photosensitive resin layer was 2 μm. Finally, a polyethylene terephthalate film having a thickness of 16 μm was pressure-bonded to the surface of the photosensitive resin layer as a protective film to prepare a transfer film for forming an etching resist.
When the obtained transfer film was exposed with reference to [0429] to [0430] of International Publication No. 2019/151534 and the visibility was confirmed, the line and space pattern was clearly visible.

<Prescription F: Coating liquid for forming a thermoplastic resin layer>
・ Polymer of benzyl methacrylate / methacrylic acid / acrylic acid (75/10/15 mass%, molecular weight 30,000, solid content concentration 30%) 22.7 parts ・ 3,6-bis (diphenylamino) fluorane 0.12 parts A-1, oxime sulfonate type photoacid generator 0.2 part, tricyclodecanedimethanol diacrylate 3.32 part, 8UX-015A (Taisei Fine Chemical Co., Ltd.) described in paragraph 0227 of JP2013-047765A. , 15 functional) 1.66 parts ・ Aronix TO-2349 (Toa Synthetic Co., Ltd.) 0.55 parts ・ Surfactant (DIC Co., Ltd., Megafuck F-552) 0.02 parts

<Prescription G: Coating liquid for forming a water-soluble resin layer>
-Polyvinyl alcohol (Kuraray Poval 4-88LA, manufactured by Kuraray Co., Ltd.) 3.22 parts-Polyvinyl pyrrolidone (manufactured by Nippon Catalyst Co., Ltd., K-30) 1.49 parts-Surfactant (Megafuck F-444, DIC stock) Company) 0.0035 parts, methanol (Mitsubishi Gas Chemical Company, Ltd.) 57.1 parts, ion-exchanged water 38.12 parts

<Prescription H: Coating liquid for forming a photosensitive resin layer>
・ Polymer of styrene / methacrylic acid / methyl methacrylate (52/29/19 mass%, molecular weight 60,000, solid content concentration 30%) 25.2 parts ・ Leuco crystal violet 0.06 parts ・ Photopolymerization initiator (2) -(2-Chlorophenyl) -4,5-diphenylimidazole dimer) 1.03 parts · 4,4'-bis (diethylamino) benzophenone 0.04 parts · (N-phenylcarbamoylmethyl-N-carboxymethylaniline 0) .02 parts ・ Ethylated bisphenol A dimethacrylate NK ester BPE-500 (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) 5.61 parts ・ Aronix M-270 (manufactured by Toa Synthetic Co., Ltd.) 0.58 parts ・ Phenotiazine 0.04 parts・ 4-Hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone 0.002 parts ・ Surfactant (DIC Co., Ltd., Megafuck F-552) 0.048 parts ・ Propropylene glycol monomethyl ether acetate 19.7 parts・ Methyl ethyl ketone 43.8 parts

[Example 12]
Using the biaxially stretched film produced in Example 4 as a support, a release film for producing a ceramic green sheet was produced by the following procedure.
A coating liquid for forming a release layer made of the following formulation J was applied to the surface of the biaxially stretched film produced in Example 4 and dried at 120 ° C. to form a release layer. The thickness of the release layer was 0.1 μm. Next, the ceramic slurry consisting of the following formulation K was applied onto the release layer so that the thickness after drying was 0.5 μm, and then dried at 90 ° C. The slurry surface and the back surface of the biaxially stretched film were overlapped with each other, and a load of 1 kg / cm ² was applied for 10 minutes, and then the release film was peeled off to obtain a ceramic green sheet.
The obtained ceramic green sheet had good characteristics without coating unevenness and transfer failure.

<Prescription J: Coating liquid for forming a release layer>
-Silicone resin (SRX-345 manufactured by Toradau Corning Co., Ltd., addition reaction type silicone) 10 parts-Platinum catalyst (SRX-212 manufactured by Toradau Corning Co., Ltd.) 0.1 parts-Toluene / methyl ethyl ketone mixed solvent 490 parts

<Prescription K: Ceramic Rally>
-Polyvinyl butyral (Sekisui Chemical Co., Ltd., Eslek BH-3) 5 parts-Barium titanate (Fuji Titanium Industry Co., Ltd., HPBT) 50 parts-Toluene / ethanol mixed solvent 45 parts

10 Manufacturing equipment 12 Extruder 13 Extruder die 14 Casting roll 15 Longitudinal stretching part 15a Roll 16 Horizontal stretching part 16a Clip 17 Cutting part 18 Winding part 18a Winding core 19 Guide roller 20 Film roll 22 Radiation thickness gauge 24 Spectral interference type thickness gauge 26 Compensation thickness measuring device 28 Adjusting

part

30a,

30b Circular rail

31a, 31b, 31c, 31d, 31e, 31f, 31g, 31h, 31i, 31j, 31k, 31l Gripping member 32 Preheating area 33 Stretching area 34 Thermal fixing area 35 Heat Relaxation area 36 Cooling area 40 1st thickness profile calculation unit 42 1st average thickness profile calculation unit 44 2nd thickness profile calculation unit 46 2nd average thickness profile calculation unit 47 Corrected thickness profile calculation unit 48 Memory 49 Control unit 56 First Thickness Profile 57 Average First Thickness Profile 58 Second Thickness Profile 59 Average

Second Thickness Profile

61, 62, 64 Corrected Thickness Profile 65

Profile

70, 72 Film Profile F Unstretched Film F ₁ Uniaxial Stretched Film F ₂ Biaxially stretched film MD transport direction P grip release point Q grip release point S10, S11, S12, S14, S15, S16, S18, S20, S22, S24 step TD width direction

Claims

A first thickness profile calculation unit that obtains a first thickness profile using the thickness of the film in one direction measured by a radiation thickness meter.
A first average thickness profile calculation unit for averaging the first thickness profile and obtaining an average first thickness profile.
A second thickness profile calculation unit that obtains a second thickness profile using the thickness of the film in one direction measured by a spectroscopic interferometry thickness meter.
A second average thickness profile calculation unit for averaging the second thickness profile and obtaining an average second thickness profile.
(Value α to the nth power) / (value β to the nth power) of the value α of the average first thickness profile and the value β of the average second thickness profile at each position of the film in the one direction. The ratio W represented by is calculated, and the value of the second thickness profile at each position in the one direction is multiplied by the value M obtained by multiplying the ratio W by 1 / n to obtain a corrected thickness profile. A correction thickness measuring device having a correction thickness profile calculation unit.
The corrected thickness measuring device according to claim 1, wherein the radiation thickness gauge and the spectroscopic interferometry thickness gauge measure the film after biaxial stretching.
The corrected thickness measuring device according to claim 1 or 2, wherein the one direction of the film is the width direction of the film orthogonal to the transport direction of the film.
A step of obtaining a first thickness profile using the thickness of the film in one direction measured by a radiation thickness gauge.
A step of averaging the first thickness profile to obtain an average first thickness profile, and
A step of obtaining a second thickness profile using the thickness of the film in one direction measured by a spectral interferometry thickness gauge.
A step of averaging the second thickness profile to obtain an average second thickness profile, and
(Value α to the nth power) / (value β to the nth power) of the value α of the average first thickness profile and the value β of the average second thickness profile at each position of the film in the one direction. The ratio W represented by is calculated, and the value of the second thickness profile at each position in the one direction is multiplied by the value M obtained by multiplying the ratio W by 1 / n to obtain a corrected thickness profile. A correction thickness measuring method having a process.
The thickness of the film measured by the radiation thickness meter in the one direction and the thickness of the film measured by the spectroscopic interferometry thickness meter in the one direction are the thickness of the film after biaxial stretching in the one direction. The corrected thickness measuring method according to claim 4.
The corrected thickness measuring method according to claim 4, wherein the one direction of the film is the width direction of the film orthogonal to the transport direction of the film.
The process of manufacturing the film and
A step of measuring the thickness of the produced film in one direction with a radiation thickness meter to obtain a first thickness profile, and
A step of averaging the first thickness profile to obtain an average first thickness profile, and
A step of measuring the thickness of the manufactured film in the one direction with a spectroferometric thickness meter to obtain a second thickness profile, and a step of obtaining a second thickness profile.
A step of averaging the second thickness profile to obtain an average second thickness profile, and
(Value α to the nth power) / (value β to the nth power) of the average first thickness profile value α and the average second thickness profile value β at each position of the film in the one direction. The ratio W represented by is calculated, and the value of the second thickness profile at each position in the one direction is multiplied by the value M obtained by multiplying the ratio W by 1 / n to obtain a corrected thickness profile. Process and
A film manufacturing method comprising a step of adjusting the film manufacturing conditions based on the corrected thickness profile to manufacture the film.
The film manufacturing method according to claim 7, wherein the one direction of the film is the width direction of the film orthogonal to the transport direction of the film.
The difference between the maximum value and the minimum value in the correction thickness profile obtained by measuring with the correction thickness measuring device according to any one of claims 1 to 3 is 1.0 with respect to the average value of the correction thickness profile. % Or less, polyester film.
A polyester film in which the difference between the maximum value and the minimum value in the correction thickness profile obtained by measuring with the correction thickness measuring device according to any one of claims 1 to 3 is less than 0.1 μm.
The difference between the maximum value and the minimum value in the corrected thickness profile obtained by measuring by the corrected thickness measuring method according to any one of claims 4 to 6 is 1.0 with respect to the average value of the corrected thickness profile. % Or less, polyester film.
A polyester film in which the difference between the maximum value and the minimum value in the corrected thickness profile obtained by measuring by the corrected thickness measuring method according to any one of claims 4 to 6 is less than 0.1 μm.