Shape measurement method of film roll, shape measurement device of film roll, and manufacturing method of film

Abstract

To provide a shape measurement method of a film roll, which enables highly accurate shape measurement without being affected by a slight tilt between a roll axis of the film roll and a moving axis of a measurement device.SOLUTION: A shape measurement method of a film roll includes: arranging displacement sensors at any two or more points surrounding an outer periphery of the film roll in a plane perpendicular to a roll axis direction of the film roll; finding coordinates of points where the displacement sensors intersect with the outer periphery of the film roll while moving the displacement sensors in the roll axis direction of the film roll to obtain a profile of the film roll in the roll axis direction; calculating an ellipse that approximates the profile in the roll axis direction of the film roll including the coordinates of the two or more points; and measuring a change of an outer diameter in the roll axis direction of the film roll on the basis of a difference between the profile in the roll axis direction of the film roll including the coordinates of the two or more points and the calculated ellipse.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the shape of a film roll, an apparatus for measuring the shape of a film roll, and a method for manufacturing a film. [Background technology]

[0002] Conventionally, computer magnetic tapes used in digital data recording systems are regulated by standards for each recording / playback system, and magnetic tapes compatible with the so-called D8, DLT, and DDS types are known. These magnetic tapes have at least a magnetic layer containing ferromagnetic powder and a binder on a non-magnetic support, and a backcoat layer on the other side to prevent winding irregularities and maintain good running durability.

[0003] Magnetic tapes are generally manufactured through the steps of preparing the coating liquid for each layer, applying the resulting coating liquid to a non-magnetic support, drying, calendering (smoothing), cutting to specified dimensions, and packaging by winding the resulting tape into a cartridge. In the steps of preparing the coating liquid for each layer and applying the resulting coating liquid to a non-magnetic support, the coating thickness is adjusted taking into account the thickness of the non-magnetic support to prevent uneven coating. In recent years, significant advances have been made in the means of transmitting terabytes of information at high speeds, enabling the transfer of images and data containing enormous amounts of information. However, this has also created a demand for advanced technologies for recording, reproducing, and storing such data. Recording and reproducing media include flexible disks, magnetic drums, hard disks, and magnetic tape. Magnetic tape, in particular, has a large recording capacity per reel and is less expensive to manage than hard disks, making it a popular choice for data backup and archiving. Furthermore, the handling of big data has led to a broadening range of uses for magnetic tape, resulting in increased demand for reliability in data storage under a wide range of environmental conditions (especially high temperature and humidity conditions), as well as reliable performance for stable data recording and retrieval over multiple runs at high speeds.

[0004] Furthermore, in order to improve the reduction in reproduction output due to thickness loss of the magnetic layer, a magnetic recording medium has been disclosed which has a lower non-magnetic layer formed on a non-magnetic support by dispersing inorganic powder in a binder, and a thin upper magnetic layer having a thickness of 1.0 μm or less formed by dispersing ferromagnetic powder in a binder while the non-magnetic layer is still wet.

[0005] In response to the demand for recording enormous amounts of information in recent years, the thickness of each layer of magnetic tape has been reduced, and high precision in the thickness of non-magnetic supports has been required.

[0006] The plastic film used for the non-magnetic support is manufactured by extruding a resin material into a film using an extruder, stretching the film, and then winding it up into a roll for shipment.

[0007] Conventionally, the method for controlling thickness unevenness of a film has been to measure the change in the diameter of the film roll by contacting a linear gauge with one side of the outer periphery of the film roll and moving it in the axial direction of the roll, thereby detecting thickness unevenness from the change in the roll diameter (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-230810 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-230811 Summary of the Invention [Problem to be solved by the invention]

[0009] However, all of the methods described in the above patent documents suffer from the problem that even a slight deviation in the parallelism between the roll axis of the film roll and the movement axis of the measuring device reduces measurement accuracy. In recent years, high accuracy has been required for measuring thickness variations, but these methods have not been able to meet this requirement. The inventors investigated the cause of this problem and found that even a slight deviation in the parallelism between the roll axis of the film roll and the movement axis of the measuring device causes the vertical cross section of the film roll to become out of round, and the change in the roll axis of the film roll and the movement axis of the measuring device causes errors in the measurement values ​​that are greater than the required accuracy. Furthermore, because the change in the outer diameter of a film roll is very small, on the order of several hundred to several tens of μm, moving the measuring device parallel to the roll axis of the film roll to measure changes in outer diameter within this range requires the use of an extremely high-precision movement mechanism, which inevitably results in a very expensive device.

[0010] An object of the present invention is to provide a film roll shape measurement method and device, and a film manufacturing method using the film roll shape measurement method, which enable highly accurate shape measurement without being affected by slight tilt between the roll axis of the film roll and the movement axis of the measuring device. [Means for solving the problem]

[0011] In order to solve this problem, the present invention comprises the following configuration. (1) A method for measuring the shape of a film roll, comprising: arranging displacement sensors at two or more arbitrary points surrounding the outer periphery of the film roll in a plane perpendicular to the roll axis direction of the film roll; determining the coordinates of the points where the displacement sensors intersect with the outer periphery of the film roll while moving the displacement sensors in the roll axis direction of the film roll; acquiring a profile in the roll axis direction; and calculating an ellipse that approximates the profile in the roll axis direction of the film roll, including the coordinates of the two or more points; and measuring the change in the outer diameter of the film roll in the roll axis direction based on the difference between the profile in the roll axis direction of the film roll, including the coordinates of the two or more points, and the calculated ellipse. (2) A method for measuring the shape of a film roll, in which displacement sensors are placed at any five points surrounding the outer periphery of the film roll in a plane perpendicular to the roll axis direction of the film roll, the minor axis of an ellipse containing the coordinates of the five points is calculated, and the change in the outer diameter of the film roll in the roll axis direction is measured based on the minor axis of the calculated ellipse. (3) A film roll shape measuring device for carrying out the method described in (1) or (2). (4) A method for producing a film, comprising a step of automatically adjusting the film thickness based on shape data of the film roll obtained by the method according to any one of (1) to (3). (5) The method for producing a film according to (4), wherein the step of automatically adjusting the film thickness includes a step of determining a target deviation value per film at each position in the width direction of a roll diameter distribution curve of a target film roll shape, and controlling the thickness of the die, which is set as a target value of a parameter that controls the gap between the die. [Effects of the Invention]

[0012] According to the present invention, the shape of a film roll can be measured with high accuracy without being affected by a slight tilt between the roll axis of the film roll and the movement axis of the measuring device. [Brief explanation of the drawings]

[0013] [Figure 1] 1 shows an example of an apparatus for carrying out the film roll shape measuring method of the present invention, where (A) is a front view, (B) is a side view, (C) is a front view when a displacement sensor 2" is installed, and (D) is a front view when displacement sensors 2"' and 2"" are installed. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below with reference to preferred embodiments, but the present invention is not limited thereto.

[0015] One aspect of the present invention is a method for measuring the shape of a film roll, which includes arranging displacement sensors at two or more arbitrary points surrounding the outer periphery of the film roll in a plane perpendicular to the roll axis direction of the film roll, determining the coordinates of the points where the displacement sensors intersect with the outer periphery of the film roll while moving the displacement sensors in the roll axis direction of the film roll, acquiring a profile in the roll axis direction, and calculating an ellipse that approximates the profile in the roll axis direction of the film roll, which includes the coordinates of the two or more points, and measuring the change in outer diameter in the roll axis direction of the film roll based on the difference between the profile in the roll axis direction of the film roll, which includes the coordinates of the two or more points, and the calculated ellipse.

[0016] An example of an apparatus for carrying out the film roll shape measuring method of the present invention is shown in Figure 1. In Figure 1, reference numeral 1 denotes a film roll whose outer diameter is to be measured in the present invention, and is formed by winding and laminating a film F formed from a resin around a bobbin B. Reference numerals 2 and 2' denote displacement sensors. The film roll 1 is fixed onto a cart 3. The cart 3 is designed to move horizontally.

[0017] The displacement sensors are arranged at two or more arbitrary points surrounding the outer periphery of the film roll in a plane perpendicular to the roll axis direction of the film roll, and in Figures 1(A) and 2(B), displacement sensors 2, 2' are arranged at two arbitrary points surrounding the outside of the film roll 1. While moving the displacement sensors 2, 2' in the roll axis direction of the film roll, the coordinates of the points where the displacement sensors 2, 2' intersect with the outer periphery of the film roll are determined to obtain a profile in the roll axis direction and calculate an ellipse that approximates the profile in the roll axis direction of the film roll including the coordinates of the two or more points. The displacement sensors 2, 2' are preferably fixed on displacement sensor fixing frames 5 on both the left and right sides of the film roll 1, sandwiching the film roll 1 therebetween, at the height of the roll axis of the film roll 1.

[0018] The two displacement sensors 2, 2' set as described above are brought into contact with the surface of the film roll 1, and measure the distance (displacement) from each of the sensors 2, 2' to the surface of the film roll.

[0019] The distances to the film roll surface detected by the two displacement sensors 2 and 2' are input to a processing unit (CPU) via amplifiers, and the CPU calculates the coordinates of the points where the sensors 2 and 2' intersect with the film roll surface from the distances measured by the two displacement sensors 2 and 2'.

[0020] When the carriage 3 is moved at a constant speed and the film roll 1 passes the positions of the displacement sensors 2 and 2', the coordinates of two points are measured over time based on the distance to the surface of the film roll 1 at each point in the carriage travel direction Td.

[0021] The coordinates of the two measured points are obtained as P(xp, yp, Tdn) and Q(xq, yq, Tdn). From the coordinates P and Q thus obtained (xp, Tdn) and Q(xq, Tdn), an ellipse R (minor axis, major axis, center coordinate x, center coordinate Td, inclination θ of the ellipse) that approximates these is calculated. The ellipse R may be calculated, for example, as follows. The variables of the ellipse R are the minor axis r, major axis r', center coordinate xR, center coordinate TdR, and inclination θ of the ellipse R. The difference between the coordinates P and Q and the ellipse R is calculated using the least squares method, and this is then calculated using the solver in the spreadsheet software (Microsoft Excel (registered trademark) for Microsoft 365 MSO). Here, the slope θ of the ellipse R may be found from the slope of an approximate linear line of the measured coordinates of the two points P(xp, yp, Tdn) and Q(xq, yq, Tdn). In Figures 3(C) and 4(D), 2" is a displacement sensor. The major axis r' of the ellipse R may be determined from the gradient θo of a linear line approximating (yo, Tdn) by the following equation, by providing a new displacement sensor 2'' at a position on the outer periphery of the film roll that is perpendicular to the center of the line connecting the displacement sensors 2, 2', and obtaining coordinates O(xo, yo, Tdn) in the same way as coordinates P(xp, yp, Tdn) and Q(xq, yq, Tdn). Long axis r'=short axis r×1 / cos(θo) In the present invention, the change in outer diameter in the roll axis direction of the film roll is measured based on the difference between the calculated ellipse and the profile of the film roll in the roll axis direction including the coordinates of the two or more points. That is, the difference S between the calculated ellipse R and the measured coordinates P and Q of the two points (the profile of the film roll in the roll axis direction including the coordinates of the two or more points) is recorded and saved as the change in outer diameter in the axial direction of the film roll 1. This record can be displayed on the display unit of the CPU or printed out on a printer. That is, the S calculated above can measure the change in the outer diameter of the film roll 1, that is, the change in shape.

[0022] One aspect of the present invention is a method for measuring the shape of a film roll, which includes arranging displacement sensors at any five or more points surrounding the outer periphery of the film roll in a plane perpendicular to the roll axis direction of the film roll, calculating the minor axis of an ellipse that includes the coordinates of the five points, and measuring the change in the outer diameter of the film roll in the roll axis direction based on the calculated minor axis of the ellipse.

[0023] In Figure 4(D), displacement sensors 2"' and 2"" are installed to obtain the respective coordinates P(xp, yp, Tdn), Q(xq, yq, Tdn), P"'(xp"', yp"', Tdn), Q""(xq"', yq"', Tdn), and O(xo, yo, Tdn). At each Tdn, the ellipse R' passing through the coordinates of the five points (xp, yp), (xp"', yp"'), (xq, yq), (xq"', yq""), and (xo, yo) is calculated, and the minor axis r of the calculated ellipse R' is found.

[0024] The ellipse R' may be calculated, for example, as follows. The variables of the ellipse R' are the minor axis r, major axis r', center coordinate xR', center coordinate yR', and slope θ of the ellipse R'. The difference between the ellipse R' and the coordinates of the five points (xp, yp), (xp"', yp"'), (xq, yq), (xq"", yq""), and (xo, yo) is calculated using the least squares method, and this is then calculated using the solver in the spreadsheet software (Microsoft Excel (registered trademark) for Microsoft 365 MSO).

[0025] The profile (r, Tdn) of the obtained minor diameter r can be used to measure the change in the outer diameter of the film roll 1, that is, the change in shape.

[0026] According to the above-described measurement method, highly accurate shape measurement can be performed without being affected by the tilt of the film roll.

[0027] One aspect of the present invention is a film roll shape measuring device that implements the film roll shape measuring method.

[0028] Another aspect of the present invention is a film manufacturing method that includes a step of automatically adjusting the film thickness based on the shape data of the film roll obtained by the above-mentioned method for measuring the shape of the film roll. In this case, if the step of automatically adjusting the film thickness includes a step of determining a target deviation value per film sheet at each position in the width direction of the roll diameter distribution curve of the target shape of the film roll, and controlling the thickness of the die, which is set as a target value for a parameter controlling the gap between the die, this is preferable because a film with minimal thickness unevenness can be efficiently obtained. [Example]

[0029] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0030] (film and film rolls) The methods for producing the films and film rolls used in the examples and comparative examples are described below. Low molecular weight polyethylene terephthalate was obtained by an ester exchange reaction between dimethyl terephthalate and ethylene glycol, and then a polycondensation reaction was carried out using antimony trioxide, magnesium acetate, and trimethyl phosphate as the main catalysts.The resulting material was then extruded into cold water in the form of strands and immediately cut to obtain pellets (polyester A) containing at least 99% by mass of polyethylene terephthalate.

[0031] 90 parts by mass of the above-mentioned pellets (polyester A) and a 10% by mass water slurry of alumina particles with an average primary particle size of 0.02 μm, to which zirconia beads with an average particle size of 0.5 mm were added, were fed into a co-rotating, vented twin-screw kneading extruder heated to 280°C, and the mixture was stirred at 3,000 rpm for 2 hours, and then filtered to remove the zirconia beads. 10 parts by mass of the water slurry (1 part by mass as alumina particles) was then fed, and the vent hole was kept at a reduced pressure of 1 kPa or less to remove the water, yielding particle-containing pellets (polyester B) containing 1% by mass of alumina particles and having an intrinsic viscosity of 0.62.

[0032] 90 parts by mass of the above-mentioned pellets (polyester A) and a 5% by mass aqueous slurry of colloidal silica particles with an average particle size of 0.20 μm, to which glass beads with an average particle size of 0.05 mm had been added, were fed into a co-rotating, vented twin-screw kneading extruder heated to 280°C. The slurry was stirred at 3,000 rpm for 2 hours, and then filtered to remove the glass beads. 10 parts by mass of this aqueous slurry (0.5 parts by mass as colloidal silica particles) was then fed, and the vent hole was maintained at a reduced pressure of 1 kPa or less to remove the water, yielding particle-containing pellets (polyester C) containing 0.5% by mass of colloidal silica particles and having an intrinsic viscosity of 0.62.

[0033] 94 parts by mass of the above-mentioned pellets (polyester A) and a 5% by mass aqueous slurry of colloidal silica particles with an average particle size of 0.06 μm, to which glass beads with an average particle size of 0.05 mm had been added, were fed into a co-rotating, vented twin-screw kneading extruder heated to 280°C. The slurry was stirred at 1,000 rpm for 2 hours, and then filtered to remove the glass beads. 6 parts by mass of this aqueous slurry (0.3 parts by mass as colloidal silica particles) was then fed, and the vent hole was maintained at a reduced pressure of 1 kPa or less to remove the water, yielding particle-containing pellets (polyester D) containing 0.3% by mass of colloidal silica particles and having an intrinsic viscosity of 0.62.

[0034] The pellets obtained by the above method (Polyester A) and pellets of PEI "Ultem" (registered trademark) 1010 manufactured by SABIC Innovative Plastics were fed into a co-rotating, vented twin-screw kneading extruder (manufactured by The Japan Steel Works, Ltd., screw diameter 30 mm, screw length / screw diameter = 45.5) equipped with three kneading paddle kneading sections heated to a temperature of 280°C, and melt-extruded at a shear rate of 100 sec-1 and a residence time of 1 minute to obtain two-component composition pellets (Polyester E) containing 50 mass% polyetherimide.

[0035] Two extruders, E1 and E2, were used. Extruder E1 was heated to 280°C. The A layer raw materials were 29 parts by weight of polyester A, 4 parts by weight of polyester E, and 67 parts by weight of pellets containing colloidal silica particles with an average particle size of 0.06 μm (polyester D). These were dried under reduced pressure at 180°C for 3 hours and then fed into extruder E2, also heated to 280°C. The B layer raw materials were 7 parts by weight of polyester A, 4 parts by weight of polyester E, 25 parts by weight of pellets containing 1% by weight of alumina particles (polyester B), and 64 parts by weight of pellets containing 0.5% by weight of colloidal silica particles (polyester C). These were then dried under reduced pressure at 180°C for 3 hours and then fed into extruder E2. These were then merged in a T-die so that the B layer was facing the casting drum surface to form a two-layer laminate. The two layers were then cooled and solidified while applying a static charge to the casting drum at a surface temperature of 25°C, yielding a laminated unstretched sheet. At this time, the residence time for maintaining the melted state from melting to cooling and solidifying was set to 20 minutes.

[0036] While holding both ends of this laminated unstretched sheet with multiple clips, it was preheated to 100°C in a simultaneous biaxial stretching machine and stretched to 3.5 times the original length in the MD direction and 3.6 times the original length in the TD direction at a stretching temperature of 100°C for 6 seconds. Subsequently, it was subjected to a second-stage stretching process at 190°C for 6 seconds, stretching to 1.2 times the original length in the MD direction and 1.5 times the original length in the TD direction. It was then heat-set at 220°C for 8 seconds, cut at the clip-held portions, and wound up to obtain a 4.6 μm-thick biaxially oriented polyester film. The resulting film was cut to a width of 1 m and wound up to 10,000 m onto a 167 mm outer diameter plastic core (FWP Core, Tenryu Composites Co., Ltd.) at a speed of 50 m / min, a tension of 80 N / m, and a surface pressure of 220 N / m, to obtain a 1,000 mm TD film roll.

[0037] (Actual shape of film roll) The prepared film roll was fixed to a dolly so that it was horizontal to the roll axis direction of the film roll, and displacement sensors were placed at three points on the outer periphery of the film roll on a plane perpendicular to the axial direction of the film roll. The displacement sensors were moved parallel to the roll axis direction of the film roll to determine the coordinates of the points where they intersect with the outer periphery of the film roll, and the change in outer diameter of the film roll in the roll axis direction was measured from the coordinates of the three points. The measurement results are shown in Table 1.

[0038] (tilted film roll) The prepared film roll was fixed to a dolly so that the angle was 4 degrees in the vertical direction and 2 degrees in the horizontal direction relative to the roll axis of the film roll.

[0039] Example 1 As shown in FIG. 1(A) and FIG. 2(B), the displacement sensors 2 and 2' are arranged symmetrically on the left and right sides of the roll axis of the film roll, and at the height of the roll axis of the film roll. The two displacement sensors 2, 2' set as described above measured the distance (displacement) from each of the sensors 2, 2' of the film roll to the surface of the film roll. The distances to the film roll surface detected by the two displacement sensors 2 and 2' were input to a processing unit (CPU) via an amplifier. The CPU calculated the coordinates of the points where the sensors 2 and 2' intersected with the film roll surface from the distances measured by the two displacement sensors 2 and 2'. The cart 3 was moved at a constant speed so that the film roll passed the positions of the displacement sensors 2 and 2', and the coordinates of two points were measured over time based on the distance to the surface of the film roll at each point in the cart traveling direction Td. The coordinates of the two measured points P(xp, yp, Tdn) and Q(xq, yq, Tdn) were obtained. From the obtained coordinates P and Q (xp, Tdn) and Q (xq, Tdn), the ellipse R (minor axis, major axis, center coordinate x, center coordinate Td, inclination θ of the ellipse) that approximates these was calculated. The ellipse R was calculated as follows. The variables of the ellipse R were defined as the minor axis r, major axis r', central coordinate xR, central coordinate TdR, and inclination θ of the ellipse R. The difference between the coordinates P and Q and the ellipse R was calculated using the least squares method, and this was then calculated using the solver in the spreadsheet software (Microsoft Excel (registered trademark) for Microsoft 365 MSO). The difference S between the calculated ellipse R and the coordinates of the two measured points P and Q was obtained as the shape of the original film roll. The results are shown in Table 1.

[0040] Example 2 The original shape of the film roll was obtained in the same manner as in Example 1, except that the slope θ of the ellipse R was calculated from the slope of the approximate linear line of the coordinates of the two measured points P (xp, yp, Tdn) and Q (xq, yq, Tdn). The results are shown in Table 2.

[0041] Example 3 The major axis r' of the ellipse R was obtained as the original shape of the film roll in the same manner as in Example 1, except that a new displacement sensor 2" was installed at a position on the outer periphery of the film roll perpendicular to the center of the line connecting the displacement sensors 2, 2', and coordinates O(xo, yo, Tdn) were obtained in the same manner as coordinates P(xp, yp, Tdn) and Q(xq, yq, Tdn), and the major axis r' was calculated from the slope θo of a linear line approximating (yo, Tdn) using the following formula. The results are shown in Table 2.

[0042] Long axis r'=short axis r×1 / cos(θo) Example 4 As shown in Figure 4(D), displacement sensors 2"' and 2"" were installed to obtain the respective coordinates P(xp, yp, Tdn), Q(xq, yq, Tdn), P"'(xp"', yp"', Tdn), Q""(xq"', yq"', Tdn), and O(xo, yo, Tdn). At each Tdn, the ellipse R' passing through the coordinates of the five points (xp, yp), (xp"', yp"'), (xq, yq), (xq"', yq"'), and (xo, yo) was calculated, and the minor radius r of the calculated ellipse R' was found. The ellipse R' was calculated as follows. The variables of the ellipse R' were defined as the minor axis r, major axis r', central coordinate xR', central coordinate yR', and inclination θ of the ellipse R'. The difference between the ellipse R' and the coordinates of the five points (xp, yp), (xp"', yp"'), (xq, yq), (xq"", yq""), and (xo, yo) was calculated using the least squares method, and this was then calculated using the solver in the spreadsheet software (Microsoft Excel (registered trademark) for Microsoft 365 MSO). The profile of the minor axis r (r, Tdn) was obtained by taking the change in the outer diameter of the film roll as the shape of the original film roll. The results are shown in Table 3.

[0043] (Comparative Example 1) A displacement sensor was placed as shown in Figure 3(C) to obtain the coordinates of three points: P (x1, y1), Q (x2, y2), and R (x3, y3). These were then used to calculate the radius of the circle containing these three points. The radius of the circle thus obtained was taken as the shape of the original film roll. The results are shown in Table 3. The radius of the circle was calculated as follows. The coordinates of the three points P(x1,y1), Q(x2,y2), and R(x3,y3) are expressed as the following general formula for a circle: x 2 +y 2 +ax+by+c=0 and obtain a simultaneous equation with the coefficients a, b, and c in this general formula as variables.

[0044] ax1+by1+c=-(x1 2 +y1 2 ) ax2+by2+c=-(x2 2 +y2 2 ) ax3+by3+c=-(x3 2 +y3 2 ) Next, by solving the simultaneous equations, a, b, and c can be found. Substituting these a, b, and c into the original general equation and transforming it gives: (x+a / 2) 2 +(y+b / 2) 2 =a 2 / 4+b 2 / 4-c and the radius of the circle is (a 2 / 4+b 2 / 4-c) 1 / 2 It will be shown as follows.

[0045] [Table 1]

[0046] [Table 2]

[0047] [Table 3] [Explanation of symbols]

[0048] 1 roll of film 2,2',2",2"',2"" displacement sensor 3 carts 4. Running track 5 Displacement sensor fixing frame F film B Bobbin

Claims

1. Displacement sensors are arranged at two or more arbitrary points surrounding the outer periphery of the film roll within a plane perpendicular to the roll axis direction of the film roll; While moving the displacement sensor in the roll axis direction of the film roll, coordinates of the point where the displacement sensor intersects with the outer periphery of the film roll are obtained, and a profile in the roll axis direction is acquired. calculating an ellipse that approximates a profile of the film roll in the roll axis direction, the ellipse including the coordinates of the two or more points; measuring a change in outer diameter of the film roll in the roll axis direction based on a difference between a profile of the film roll in the roll axis direction including the coordinates of the two or more points and the calculated ellipse; Method for measuring the shape of film rolls.

2. Displacement sensors are arranged at five arbitrary points surrounding the outer periphery of the film roll within a plane perpendicular to the roll axis direction of the film roll; A method for measuring the shape of a film roll, which calculates the minor axis of an ellipse including the coordinates of the five points, and measures the change in the outer diameter of the film roll in the roll axis direction based on the minor axis of the calculated ellipse.

3. An apparatus for measuring the shape of a film roll, which implements the method according to claim 1 or 2.

4. Based on the shape data of the film roll obtained by the method according to claim 1 or 2, A method for manufacturing a film, including a step of automatically adjusting film thickness.

5. 5. The film manufacturing method according to claim 4, wherein the step of automatically adjusting the film thickness includes a step of determining a target deviation value per film at each position in the width direction of a roll diameter distribution curve of a target film roll shape, and controlling the thickness of the die set as a target value of a parameter that controls the gap between the die.

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