Film thickness deviation measuring method, film thickness deviation measuring device, film manufacturing method, and film manufacturing device

Abstract

The present invention provides a method for acquiring a film thickness deviation in a non-contact manner by a simple and safe device configuration. A method according to the present invention comprises: a one-point film thickness gradient measurement step in which an original position, which is a position of a light source without arranging a film 21 between a light source 22 and an optical sensor array 23, is acquired, an apparent position, which is a position of the light source 22 with the film 21 being arranged between the light source 22 and the optical sensor array 23, is acquired, and the thickness gradient of the film 21 is determined from the original position and the apparent position by using a predetermined formula; a multi-point film thickness gradient measurement step for performing the one-point film thickness gradient measurement step multiple times by changing the position of the light source 22; and a film thickness deviation profile calculation step for determining the film thickness deviation profile of the film 21 from the correspondence relationship between the position of the light source 22 and the thickness gradient of the film 21 by using a predetermined formula, the correspondence relationship being obtained by the multi-point film thickness gradient measurement step.

Description

Film thickness deviation measuring method, film thickness deviation measuring device, film manufacturing method, and film manufacturing device

[0001] The present invention relates to a method and apparatus for measuring film thickness deviation, a method and apparatus for producing a film, and a method and apparatus for producing a film.

[0002] A widely used method for in-line, non-contact measurement of the thickness of a resin film involves transmitting light such as X-rays or infrared rays through the film and calculating the thickness in accordance with the Beer-Lambert law based on the attenuation rate of the transmitted light (see, for example, Patent Documents 1 and 2). Patent Document 3 describes an optical interference film thickness measurement method in which a film is irradiated with white parallel light and the film thickness is calculated from the spectral intensity of the reflected light.

[0003] JP 2006-275750, JP 60-224002, JP 7-280523

[0004] The method of transmitting X-rays and measuring the attenuation rate of transmitted light described in Patent Document 1 generally requires a controlled area, which poses a safety problem. Also, the optical interference method described in Patent Document 3 has a problem in that the device configuration is complex, which tends to make the device expensive.

[0005] The present invention has been made in light of the above-mentioned problems, and aims to provide a film thickness deviation measurement method and device that can obtain film thickness deviation in a non-contact manner using a simple and safe device configuration, as well as a film manufacturing method and device that use the measurement method and device.

[0006] The inventors conducted various studies to solve the above-mentioned problems. As a result, they came up with the idea of ​​applying the background-directed schlieren method, which is used to calculate the density gradient of a fluid, to measuring the thickness deviation of a solid film. However, the background-directed schlieren method typically calculates the amount of movement of a background image between two photographs using a cross-correlation function, but calculating the cross-correlation function requires a large number of calculations. Therefore, the inventors came up with the idea of ​​using a point or line light source instead of a background image, and acquiring the position of the light source detected by a one-dimensional or two-dimensional photosensor array instead of calculating the amount of movement of the background image between two photographs. This enabled them to calculate a thickness deviation profile with a small amount of calculation, without the need for the calculation of a cross-correlation function, which requires a large number of calculations. Based on this knowledge, the inventors were able to calculate a film thickness deviation profile with a simple and safe device configuration and further studies, leading to the completion of the present invention.

[0007] That is, the gist of the present invention is as follows.

[0008] [1] A method for measuring film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, without placing a film to be measured between the light source and the one-dimensional or two-dimensional optical sensor array, and acquiring an original position, which is the position of the light source detected by the optical sensor array; an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring an apparent position, which is the position of the light source detected by the optical sensor array; a single-point film thickness gradient measurement step of determining a film thickness gradient of the film using the following equation (1) from the acquired original position and apparent position; a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source; and a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence between the position of the light source and the film thickness gradient obtained by the multi-point film thickness gradient measurement step. where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0009] [2] The method for measuring film thickness deviation described in [1], wherein in the multi-point film thickness gradient measurement step, the position of the optical sensor array is changed in accordance with the change in the position of the light source. [3] A method for measuring film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, without placing a film to be measured between the light source and the optical sensor array, and acquiring an original position, which is the position of the light source detected by the optical sensor array; an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring an apparent position, which is the position of the light source detected by the optical sensor array; a single-point film thickness gradient measurement step of determining a film thickness gradient of the film using the following equation (1): where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ: refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0010] [4] The method for measuring film thickness deviation described in [3], wherein in the multipoint film thickness gradient measurement step, the position of the light source is changed in accordance with the change in the position of the optical sensor array.

[0011] [5] A method for measuring film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, without placing a film to be measured between the light source and the one-dimensional or two-dimensional optical sensor array, and acquiring an original position, which is the position of the light source detected by the optical sensor array; an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring an apparent position, which is the position of the light source detected by the optical sensor array; a single-point film thickness gradient measurement step of determining a film thickness gradient of the film from the obtained original position and apparent position using the following formula (1): a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the irradiation direction of the light source; and a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following formula (2) from the correspondence between the light source irradiation point and the film thickness gradient obtained by the multi-point film thickness gradient measurement step. where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0012] [6] The method for measuring film thickness deviation described in [5], wherein in the multi-point film thickness gradient measurement step, the position of the optical sensor array is changed in accordance with a change in the irradiation direction of the light source.

[0013] [7] A method for measuring a film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, without placing a film to be measured between the light source and the optical sensor array, and acquiring an original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring an apparent position, which is the position of the light source detected by the optical sensor array, and comprising: a single-point film thickness gradient measurement step of determining a film thickness gradient of the film using the following equation (1): where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0014] [8] The method for measuring film thickness deviation described in [7], wherein in the multipoint film thickness gradient measurement step, the position of the light source is changed in accordance with a change in the detection direction of the optical sensor array.

[0015] [9] The method for measuring film thickness deviation of a film described in any one of [1] to [8], wherein the film is transported so as to pass between the light source and the optical sensor array, and the integral path C is a line segment that is approximately perpendicular to the transport direction of the object to be measured.

[0016]

[10] An apparatus for measuring a deviation in film thickness, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; a light source position changing means for changing the position of the light source; and a calculation unit for calculating the deviation in film thickness, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring the original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring the apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit for performing a single-point film thickness gradient measurement step of determining the film thickness gradient using the following formula (1) from the acquired original position and apparent position; and a multi-point film thickness gradient measurement unit for performing a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source using the light source position changing means. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the position of the light source and the film thickness gradient obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0017]

[11] The film thickness deviation measuring device according to

[10] , further comprising an optical sensor position changing means for changing the position of the optical sensor array.

[0018]

[12] An apparatus for measuring deviations in film thickness, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; an optical sensor position changing means for changing the position of the optical sensor array; and a calculation unit for calculating deviations in film thickness, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring an original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring an apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit that performs a single-point film thickness gradient measurement step of calculating a film thickness gradient from the acquired original position and apparent position using the following formula (1); and a multi-point film thickness gradient measurement unit that performs a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the optical sensor array using the optical sensor position changing means. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the light source irradiation points and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0019]

[13] An apparatus for measuring deviations in film thickness, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; a light source irradiation direction changing means for changing the irradiation direction of the light source; and a calculation unit for calculating deviations in film thickness, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring an original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring an apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit performing a single-point film thickness gradient measurement step of calculating a film thickness gradient from the acquired original position and apparent position using the following formula (1): a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the light source irradiation points and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0020]

[14] The film thickness deviation measuring device according to

[13] , further comprising an optical sensor position changing means for changing the position of the optical sensor array.

[0021]

[15] An apparatus for measuring a deviation in film thickness, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; a sensor detection direction changing means for changing the detection direction of the optical sensor array; and a calculation unit for calculating the deviation in film thickness, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring the original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring the apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit that performs a single-point film thickness gradient measurement step of calculating the film thickness gradient using the following formula (1) from the acquired original position and apparent position; and a multi-point film thickness gradient measurement unit that performs a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the detection direction of the optical sensor array using the sensor detection direction changing means. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the light source irradiation points and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0022]

[16] The film thickness deviation measuring device according to

[15] , further comprising a light source position changing means for changing the position of the light source.

[0023]

[17] A film manufacturing method in which a molten resin is discharged from a die having a plurality of lip gap adjustment means to form a film, wherein the film discharged from the die is transported along a preset path line, and the method comprises: an original position acquisition step of turning on a light source, which is a point light source or a line light source disposed opposite to the light source, and a one-dimensional or two-dimensional optical sensor array without disposing the film between the light source and the one-dimensional or two-dimensional optical sensor array, and acquiring an original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of disposing the film between the light source and the optical sensor array, turning on the light source, and acquiring an apparent position, which is the position of the light source detected by the optical sensor array, wherein the method comprises: a single-point film thickness gradient measurement step of determining a film thickness gradient of the film using the following equation (1) from the acquired original position and apparent position; a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source of the light from the light source; and a film thickness deviation profile calculation step of calculating a film thickness deviation profile of the film using the following equation (2) from the correspondence between the position of the light source and the film thickness gradient obtained by the multi-point film thickness gradient measurement step. a lip gap adjusting step of operating the lip gap adjusting means based on the film thickness deviation profile so that the film thickness deviation at each point on the film is equal to or less than a target value. where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0024]

[18] A film manufacturing apparatus that extrudes molten resin from a die having a plurality of lip gap adjustment means to form a film, comprising: a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, which are arranged opposite each other across a path line along which the film extruded from the die is transported; and a calculation unit that calculates a film thickness deviation of the film, comprising: a single-point film thickness gradient measurement unit that performs an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring an original position, which is the position of the light source detected by the optical sensor array, and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring an apparent position, which is the position of the light source detected by the optical sensor array, and calculates a film thickness gradient of the film from the acquired original position and apparent position using the following formula (1): and a multi-point film thickness gradient measurement unit that performs a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of calculating a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the position of the light source and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step; and a lip gap adjustment unit that operates the lip gap adjustment means based on the film thickness deviation profile so that the film thickness deviation at each point on the film is equal to or less than a target value. where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

[0025]

[19] The film manufacturing apparatus according to

[18] , further comprising a stretching machine for stretching the film downstream of the position on the pass line sandwiched between the light source and the optical sensor array.

[0026] According to the present invention, it is possible to obtain the film thickness deviation of a film in a non-contact manner using a simple and safe device configuration.

[0027] Fig. 1 is a conceptual diagram of an optical system for a background-directed Schlieren method in a fluid. Fig. 2 is a diagram showing the schematic configuration of an example of a film thickness deviation measuring device according to the present invention. Fig. 3 is a diagram showing the configuration of a calculation unit in a film thickness deviation measuring device. Fig. 4 is a diagram showing the schematic configuration of an example of a film manufacturing device according to the present invention. Fig. 5 is a diagram showing the schematic configuration of a film thickness deviation measuring device in an example. Fig. 6 is a diagram showing a film thickness deviation profile obtained in an example.

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example of the present invention, and the invention is not limited to the following content.

[0029] In the present invention, the background-oriented Schlieren method (hereinafter also referred to as the "BOS method"), which is used to calculate the density gradient of a fluid, is applied to measuring the film thickness deviation of a solid film. The BOS method for fluids measures the density gradient of a fluid by utilizing the phenomenon in which, when the background is viewed through the fluid, the background appears shifted due to a refractive index difference caused by the density gradient. Compared to the conventional Schlieren method, the BOS method for fluids has two advantages: the optical system for measurement is simple, and the density gradient can be quantified.

[0030] A conceptual diagram of the optical system of the BOS method for fluids is shown in Figure 1. As shown in Figure 1, the optical system for the BOS method for fluids comprises a measured object 11 made of fluid, a background image 12, and an imaging means 13. Figure 1 shows an apparent optical path 14 from the imaging means 13 and an actual optical path 15 due to the presence of the measured object 11. In this BOS method, the background image 12 is captured through the measured object 11. At this time, the position of the background image on the image captured by the imaging means 13 is shifted in proportion to the density gradient of the measured object 11.

[0031] In the phenomenon where the background image is captured with a deviation, the total deflection angle ε can be approximated by the ratio of the deviation amount Δh of the background image 12 in the captured image to the distance d between the object 11 and the background image 12. That is, it can be expressed as ε=Δh / d.

[0032] The total deflection angle ε is expressed by the following equation (3) by integrating the gradient ∂n / ∂x of the refractive index n of the object 11 in the direction perpendicular to the optical axis over the thickness (2×Δz) of the object 11. ０ is the refractive index experienced by light parallel to the optical axis.

[0033] Furthermore, the refractive index n and density ρ of the object 11 satisfy the relationship n=ρG+1, using the constant G of the Gladstone-Dale law. Therefore, the density gradient ∂ρ / ∂x of the object 11 is expressed by the following equation (4).

[0034] In the present invention, the optical system of the BOS method is used to obtain the gradient of the film thickness t of a solid film (film thickness deviation in the in-plane direction of the film), but the Gladstone-Dale law is not used. Instead, it is approximated that the only place where the in-plane gradient of the refractive index n of the object 11 to be measured occurs is at the portion of the film thickness that comes into contact with air. This makes it possible to obtain the following equation (5):

[0035] Here, x is a position vector within the film plane, t(x) is a film thickness deviation obtained by subtracting the film thickness of the object 11 at the origin x=0 from the film thickness of the object 11 at the position x within the film plane, dt(x) / dx is a film thickness gradient expressed by the in-plane total differential of the film thickness deviation t(x), and n ｔａｒｇｅｔ is the refractive index of the film, n ａｉｒ is the refractive index of the atmosphere,

[0036] Furthermore, by substituting ε=Δh / d into equation (5), the following equation (1) is obtained. Then, by integrating equation (1) along a certain path C, it is possible to measure the film thickness deviation t(x), which is the amount of change in film thickness from the set origin x = 0, and the following equation (2) is obtained.

[0037] where v is the unit tangent vector of the path C, is an operation of performing a line integration of the inner product of dt(x) / dx and v over an integral path C extending from the origin x=0 toward the measurement point.

[0038] Specific examples of the integral path C include a line segment parallel to or perpendicular to the long or short side of the film, and a reciprocating scanning path in which the film is scanned parallel to one side, then slightly moved in a direction perpendicular to that side, and then scanned in the opposite direction parallel to that side, repeating this process.

[0039] (Film Thickness Deviation Measuring Device) Next, an example of a film thickness deviation measuring device of the present invention will be described. FIG. 2 shows a schematic configuration of an example of a film thickness deviation measuring device of the present invention. The film thickness deviation measuring device 20 shown in FIG. 2 comprises a light source 22 which is a point light source or a line light source, a one-dimensional or two-dimensional optical sensor array 23, a calculation unit 24, and a light source position changing means (not shown). The film 21 to be measured is placed between the light source 22 and the optical sensor array 23. Note that the film thickness deviation measuring device 20 is preferably installed in a darkroom in order to accurately detect only the light emitted from the light source 22.

[0040] <Film> The film 21 to be measured is made of a material, such as resin or glass, that transmits light from the light source 21. This film includes thicker resin or glass that is sometimes called a sheet.

[0041] The film 21 is disposed between the light source 22 and the optical sensor array 23 with its thickness direction being approximately parallel to a line connecting the light source 22 and the optical sensor array 23 .

[0042] <Light Source> The light source 22 is either a point light source or a line light source. Furthermore, the light source 22 may be a display made of liquid crystal, LED, or organic EL that can be regarded as a point light source by illuminating only one or a few light-emitting elements, or a line light source that can be regarded as a line light source by illuminating only one or a few rows of light-emitting elements. The point light source or line light source may be, for example, an omnidirectional light source (i.e., one that does not irradiate light in only a specific direction), or a directional light source (i.e., one that irradiates light in only a specific direction).

[0043] The diameter of the point light source or the line width of the line light source is preferably 1 μm or more and 1000 μm or less, and more preferably 5 μm or more and 300 μm or less. By making the diameter or line width of the light source 22 1 μm or more, it is possible to reduce measurement errors in the position of the light source 22 while preventing the appearance of interference fringes. Furthermore, by making the diameter or line width of the light source 22 1000 μm or less, it is possible to reduce position measurement errors due to the size of the light source itself. It is more preferable that the diameter of the light source 22 or the line width of the line light source be 5 μm or more and 300 μm or less.

[0044] <Optical Sensor Array> The optical sensor array 23 is a collection of optical sensors 231, in which a plurality of optical sensors 231 are arranged one-dimensionally or two-dimensionally, and is disposed opposite the light source 22. For example, an image sensor can be used as the optical sensor array 23. Alternatively, an optical fiber cable for guiding detected light to the optical sensor 231 may be installed at the position of the optical sensor array 23 shown in FIG. 2 , with the actual optical sensor array 23 being installed in a separate location. By providing an optical fiber cable in this manner, for example, when the light source 22, film 21, and optical sensor array 23 are arranged vertically from below in this order, the main body of the optical sensor array 23 can be installed separately, thereby simplifying the support material for the optical sensor array 23.

[0045] The optical sensors 231 detect light emitted from the light source 22, and the position of the light source 22 is obtained based on which optical sensor 231 in the optical sensor array 23 detects the light emitted from the light source 22. The optical sensor array 23 may output the position of the optical sensor 231 that detects the light with the highest intensity, or, as is more commonly used, may output the intensity of light detected by all of the optical sensors 231 in the optical sensor array 23. The output of the optical sensor array 23 is input to the calculation unit 24 and used to calculate the film thickness deviation profile of the film 21. The optical sensors 231 must be able to detect the wavelength of light emitted from the light source 22.

[0046] In the optical sensor array 23, the smaller the interval between the optical sensors 231, the higher the resolution, which is preferable.

[0047] The width (area) of the optical sensor array 23 can be the width of the entire position where the optical sensor 231 can detect the light source 22. That is, it is calculated from an extension line connecting the light source 22, whose position or irradiation direction is changed, and the film 21, and the total deflection angle ε obtained from the maximum film thickness gradient expected for the film 21. Alternatively, when the position of the optical sensor array 23 is changed in accordance with a change in the position or irradiation direction of the light source 22, the width of the optical sensor array 23 can be made narrower than the width when the position of the optical sensor 231 is not changed. That is, it is sufficient that the width be centered on the irradiation direction of the light source 22 and be equal to the total deflection angle ε obtained from the maximum film thickness gradient expected for the film 21.

[0048] <Calculation Unit> The calculation unit 24 executes a process of calculating the film thickness deviation of the film 21 based on the position of the light source 22 detected by the optical sensor array 23. As shown in FIG. 3 , the calculation unit 24 has a single-point film thickness gradient measurement unit 241, a multi-point film thickness gradient measurement unit 242, and a film thickness deviation calculation unit 243.

[0049] <<Single-Point Film Thickness Gradient Measurement Unit>> The single-point film thickness gradient measurement unit 241 performs an original position acquisition process in which the light source 22 is turned on without placing the film 21 between the light source 22 and the optical sensor array 23, and acquires the original position, which is the position of the light source 22 detected by the optical sensor array 23. It also performs an apparent position acquisition process in which the film 21 is placed between the light source 22 and the optical sensor array 23, the light source 22 is turned on, and an apparent position, which is the position of the light source 22 detected by the optical sensor array 23. Then, it performs a single-point film thickness gradient measurement process in which the film thickness gradient of the film 21 is calculated using the following equation (1) from the acquired original position and apparent position, and outputs the calculated value.

[0050] If the optical sensor array 23 outputs the position of the optical sensor 231 that detected the light with the highest intensity, the output of the optical sensor array 23 may be input as the position of the light source 22. Alternatively, if the optical sensor array 23 outputs the intensities of light detected by all of the optical sensors 231, the position of the optical sensor 231 with the highest detected intensity may be calculated and input. Alternatively, the light intensity distribution may be approximated by, for example, a Gaussian distribution, and the position of the light source 22 may be calculated for continuous values ​​including intermediate positions between the optical sensors 231 and input. By comparing the input position of the light source 22 with and without the film 21, it is possible to obtain a vector Δh that represents the amount of displacement from the original position to the apparent position.

[0051] Refractive index n ｔａｒｇｅｔ and n ａｉｒ may be a fixed value, or may be calculated or manually input based on the temperature and the material of the film 21. The distance d between the light source 22 and the film 21 may be measured in advance and set to a fixed value. If the relative positions of the light source 22 and the film 21 change, the distance d may be a variable value calculated or measured each time. In particular, if the direction of light irradiation from the light source 22 is changed, the distance from the light source 22 to the irradiation position on the film 21 changes, so it is preferable to calculate or measure the distance each time.

[0052] <<Multi-point film thickness gradient measurement unit>> The multi-point film thickness gradient measurement unit 242 performs a multi-point film thickness gradient measurement process in which the single-point film thickness gradient measurement process for determining the film thickness gradient of the film 21 performed by the single-point film thickness gradient measurement unit 241 is repeated multiple times by changing the position of the light source 22, and outputs the results.

[0053] <<Film Thickness Deviation Profile Calculation Unit>> The film thickness deviation profile calculation unit 243 outputs the film thickness deviation t(x) of the film 21 calculated from the correspondence between the position of the light source 22 and the film thickness gradient of the film 21 output from the multipoint film thickness gradient measurement unit 242 using the following equation (2):

[0054] When determining the film thickness deviation profile t(x) of the film 21, the integral path C is not particularly limited, but can be, for example, a line segment parallel to or perpendicular to the long or short side of the film 21. Another example is a reciprocating scanning path in which scanning is performed parallel to one side of the film 21, followed by a slight movement in a direction perpendicular to the side, and then scanning in the opposite direction to the first scanning, parallel to the side, and repeating this process.

[0055] The film 21 can be configured to be transported so as to pass between the light source 22 and the optical sensor array 23, and the integration path C is a line segment that is approximately perpendicular to the transport direction of the film 21. In this case, the above equation (2) can be simplified to the following equation (6).

[0056] Since the position of the light source 22 is discrete, the equation (6) is also expressed as a discrete quantity x=kΔx corresponding to each position of the light source 22 .

[0057] <Light Source Position Changing Means> The light source position changing means changes the position of the light source 22. Any means capable of changing the position of the light source 22 can be used as the light source position changing means. Such means include a means for mounting the light source 22 on an O-frame, C-frame, or the like and moving the light source 22 in a one-dimensional direction. Another example of the light source position changing means is a means for suspending the light source 22 on a biaxial actuator, as in a 3D printer, and moving it two-dimensionally. Furthermore, a means for moving the light source 22 three-dimensionally can also be used as the light source position changing means.

[0058] A single film thickness deviation measuring device 20 may have a plurality of light sources 22. In this case, in order to avoid confusion between the plurality of light sources 22, it is preferable to stagger the light emission timing of the light sources 22, change the wavelength of the light sources 22, or install the light sources 22 at a distance sufficient to prevent confusion between the light sources 22. If the plurality of light sources 22 are sufficiently separated in terms of wavelength and physical distance, multiple points can be measured simultaneously, which is advantageous in terms of the scanning mechanism and time.

[0059] Furthermore, the film thickness deviation measuring device 20 may further include an optical sensor position changing means for changing the position of the optical sensor array 22. This allows the size (area) of the sensor array 23 to be reduced.

[0060] The above-described film thickness deviation measuring device includes a light source position changing means for changing the position of the light source 22. However, instead, an optical sensor position changing means for changing the position of the optical sensor array 23 may be provided. In this case, the position of the optical sensor array 23 is changed when performing the multi-point film thickness gradient measurement process. Examples of such a means include a means for mounting the optical sensor array 23 on an O-frame, C-frame, or the like and moving the optical sensor array 23 in a one-dimensional direction. Another example of the optical sensor position changing means is a means for suspending the optical sensor array 23 on a biaxial actuator, as in a 3D printer, and moving it two-dimensionally. Furthermore, a means for moving the optical sensor array 23 three-dimensionally may also be used as the optical sensor position changing means. In this case, the film thickness deviation measuring device 20 may further include a light source position changing means for changing the position of the light source 22. This allows the size (area) of the light source 22 to be reduced.

[0061] Furthermore, instead of providing a light source position changing means, a light source irradiation direction changing means for changing the irradiation direction of the light source 22 may be provided, and the irradiation direction of the light source 22 may be changed when performing the multi-point film thickness gradient measurement process. An example of the light source irradiation direction changing means is a means for changing the irradiation direction of light from the light source 22 by changing the orientation of the light source 22 itself or the support material on which the light source 22 is installed. In this case, the film thickness deviation measuring device 20 may further include an optical sensor position changing means for changing the position of the optical sensor array 23. This allows the size (area) of the optical sensor array 23 to be reduced.

[0062] Furthermore, instead of providing a light source position changing means, a sensor detection direction changing means for changing the detection direction of the optical sensor array 23 may be provided, and the detection direction of the optical sensor array 23 may be changed when performing the multi-point film thickness gradient measurement process. An example of the sensor detection direction changing means is a means for changing the detection direction of the optical sensor array 23 by changing the orientation of the optical sensor array 23 itself or the support material on which the optical sensor array 23 is installed. In this case, the film thickness deviation measuring device 20 may further include a light source position changing means for changing the position of the light source 22. This allows the size (area) of the light source 22 to be reduced.

[0063] (Film Thickness Deviation Measuring Method) The film thickness deviation measuring method according to the present invention comprises an original position acquiring step of turning on a light source, which is a point light source or a line light source, disposed opposite to each other, and a one-dimensional or two-dimensional optical sensor array without a film to be measured being disposed between the light source and the one-dimensional or two-dimensional optical sensor array, and acquiring an original position, which is the position of the light source detected by the optical sensor array; an apparent position acquiring step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring an apparent position, which is the position of the light source detected by the optical sensor array; and a single-point film thickness gradient measuring step of determining a film thickness gradient of the film from the determined original position and apparent position using the following equation (1): a multi-point film thickness gradient measuring step of performing the single-point film thickness gradient measuring step a plurality of times by changing the position at which light from the light source is irradiated onto the film; and a film thickness deviation profile calculating step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence between the position at which light from the light source is irradiated onto the film, obtained by the multi-point film thickness gradient measuring step, and the film thickness gradient of the film.

[0064] <One-Point Film Thickness Gradient Measurement Step> A one-point film thickness gradient measurement step is performed, which includes an original position acquisition step and an apparent position acquisition step.

[0065] <<Original Position Acquisition Process>> First, the light source 22, which is a point light source or line light source arranged opposite to the one-dimensional or two-dimensional optical sensor array 23, is turned on without placing the film 21 to be measured between the light source 22 and the one-dimensional or two-dimensional optical sensor array 23, and the original position, which is the position of the light source 22 detected by the optical sensor array 23, is acquired.

[0066] <<Apparent Position Acquisition Step>> Next, the film 21 is placed between the light source 22 and the optical sensor array 23, the light source 22 is turned on, and the apparent position, which is the position of the light source 22 detected by the optical sensor array 23, is acquired.

[0067] Then, from the acquired actual position and apparent position, the film thickness gradient of the film 21 is calculated using the above formula (1).

[0068] <Multi-Point Film Thickness Gradient Measurement Step> The single-point film thickness gradient measurement step described above is performed multiple times by changing the position where the light from the light source 22 is irradiated onto the film 21 .

[0069] <Film Thickness Deviation Profile Calculation Step> Next, the film thickness deviation profile of the film 21 is calculated using the above formula (2) from the correspondence relationship between the position of the light source 22 and the film thickness gradient of the film 21 obtained in the multipoint film thickness gradient measurement step.

[0070] In the multipoint film thickness gradient measurement process, the position of the optical sensor array 23 can be changed in accordance with the change in the position of the light source 22. This allows the size (area) of the sensor array 23 to be reduced.

[0071] In the above-described film thickness deviation measurement method, the position of the light source 22 is changed in the multi-point film thickness gradient measurement step. However, the position of the optical sensor array 23 may be changed instead. In this case, in the film thickness deviation profile calculation step, the film thickness deviation profile is calculated using the above formula (2) based on the correspondence between the position of the optical sensor array 23 and the film thickness gradient. Furthermore, in the multi-point film thickness gradient measurement step, the position of the light source 22 can be changed in accordance with the change in the position of the optical sensor array 23. This allows the size (area) of the light source 22 to be reduced.

[0072] Furthermore, in the multi-point film thickness gradient measurement process, instead of changing the position of the light source 22, the irradiation direction of the light source 22 may be changed. In this case, in the multi-point film thickness gradient measurement process, the position of the optical sensor array 23 can be changed in accordance with the change in the irradiation direction of the light source 22. This allows the size (area) of the optical sensor array 22 to be reduced.

[0073] Furthermore, in the multi-point film thickness gradient measurement step, the detection direction of the optical sensor array 23 may be changed instead of changing the position of the light source 22. In this case, in the film thickness deviation profile calculation step, the film thickness deviation profile is calculated using the above formula (2) based on the correspondence between the detection direction of the optical sensor array 23 and the film thickness gradient. Also, in the multi-point film thickness gradient measurement step, the position of the light source 22 can be changed in accordance with the change in the detection direction of the optical sensor array 23. This allows the size (area) of the light source 22 to be reduced.

[0074] The film 21 is transported so as to pass between the light source 22 and the optical sensor array 23, and the integral path C used to calculate the above equation (2) can be a line segment that is approximately perpendicular to the transport direction of the film 21.

[0075] The thickness deviation of the film 21 obtained by the above method can be displayed by a known visualization method. When the thickness deviation is calculated only in one specific direction, it is preferable to display it as a line graph. When the thickness deviation is calculated in an in-plane direction, it is preferable to display it as an overlaid line graph or a heat map. In this case, the thickness deviation is, for example, the thickness of the film 21 at the measurement point minus the thickness of the film 21 at the origin. For this reason, it may be more preferable to display the thickness as an absolute value by adding the thickness of the film 21 at the origin calculated by an appropriate method. Examples of methods for obtaining the thickness of the film 21 at the origin include a method of measuring only one point using a known thickness meter such as a contact type or transmission type, and a method of adopting a nominal thickness regardless of the actual thickness.

[0076] (Film manufacturing apparatus) Next, a film manufacturing apparatus according to the present invention will be described. The film manufacturing apparatus according to the present invention is a film manufacturing apparatus that extrudes molten resin from a die having a plurality of lip gap adjustment means to form a film, and includes a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, which are arranged opposite each other across a path line along which the film extruded from the die is transported, and a calculation unit that calculates a film thickness deviation of the film, and includes an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring an original position, which is the position of the light source detected by the optical sensor array, and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array, turning on the light source, and acquiring an apparent position, which is the position of the light source detected by the optical sensor array. a single-point film thickness gradient measurement unit that performs a single-point film thickness gradient measurement step of determining the film thickness gradient using the following equation (1) from the acquired actual position and apparent position; a multi-point film thickness gradient measurement unit that performs a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source; and a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining the film thickness deviation profile using the following equation (2) from the correspondence between the position of the light source and the film thickness gradient obtained by the multi-point film thickness gradient measurement step; and a lip gap adjustment unit that operates the lip gap adjustment means based on the film thickness deviation profile so that the film thickness deviation at each point on the film is equal to or less than a target value.

[0077] Figure 4 shows a schematic configuration of one example of a film production apparatus according to the present invention. The film production apparatus 30 shown in Figure 4 includes an extruder 35, a T-die 36, a cooling roll 37, a stretching machine 38, and a winder 39. The T-die 36 has a plurality of lip gap adjustment means 361. The film production apparatus 30 also includes a film thickness deviation measurement device having a light source 22, an optical sensor array 23, and a calculation unit 24.

[0078] <Extruder> The extruder 35 is equipped with one or more feeders or hoppers, and melts and kneads multiple types of resins and fillers as necessary. The extruder 35 can be either a single-screw extruder or a twin-screw extruder, and may be a multi-stage extruder. Furthermore, multiple extruders 35 may be provided and connected to the T-die 36. Note that it is preferable to provide a filter, a vent, or a gear pump to improve the quality of the extruded resin and stabilize the extrusion rate. The extruder 35 may have a known configuration.

[0079] <T-die> The T-die 36 discharges the molten resin extruded from the extruder 35 through a gap and continuously molds a resin film 31 having a target thickness. When the film 31 to be manufactured has a multi-layer structure, either the feed block method or the multi-manifold method can be applied. The feed block method is a method in which molten resins are joined together before entering the T-die. The multi-manifold method is a method in which single layers are spread inside the T-die and then joined together near the lip.

[0080] <<Lip Gap Adjusting Means>> A plurality of lip gap adjusting means 361 are provided along the lip longitudinal direction of the T-die 36. The lip gap adjusting means 361 adjusts the width of the lip gap in accordance with a command from the lip gap adjusting unit 40 or manual operation, thereby adjusting the film thickness of the molten resin and the film.

[0081] A known configuration may be employed as the lip gap adjustment mechanism of the lip gap adjustment means 361. Suitable examples of such mechanisms include a method in which the amount of depression is changed by rotating a threaded bolt, a heat bolt type in which a cartridge heater is built in and the lip gap is thermally expanded and contracted, and a method in which the lip gap is adjusted by applying hydraulic pressure to the bolt or T-die.

[0082] <Cooling Roll> The cooling roll 37 cools and solidifies the molten resin extruded from the lip gap of the T-die 36, and forms it into a film.

[0083] The cooling roll 37 is preferably equipped with a pinning device such as an electrostatic application type, a suction chamber type, or an air knife type, or a touch roll, for the purpose of suppressing thickness variations of the film 31 and improving surface properties. Furthermore, to increase the cooling rate of the molten resin, a portion of the cooling roll may be immersed in water or sprayed with water. <Stretching Machine> The stretching machine 38 is a device that is optionally installed in the film production apparatus 30 as needed and stretches the film formed by the cooling roll 37. The stretching machine 38 is located downstream of the position between the light source 22 and the optical sensor array 23 on the pass line. Stretching of the film may be performed as needed, and the film to be produced does not need to be stretched.

[0084] When stretching is performed using the stretching machine 38, various stretching methods can be applied. That is, a method of stretching only in the machine direction (MD direction: longitudinal direction), a method of stretching only in the width direction (TD direction), a method of sequentially stretching in the MD direction and the TD direction, and a method of simultaneously stretching in the MD direction and the TD direction can be applied. Furthermore, for example, a method of sequentially stretching in the MD direction and the TD direction and then re-stretching again in the MD direction or the TD direction can be applied. Regarding the stretching treatment, it is preferable to select and use a stretching method, including non-stretching, depending on the resin type and application of the film.

[0085] Furthermore, for longitudinal stretching in the MD direction, either single-stage stretching using a pair of rolls with a speed difference or multi-stage stretching using multiple pairs of rolls can be suitably applied. Furthermore, for the method of raising the temperature of the film for stretching, either a method using a preheating roll or a non-contact heating method using an infrared heater or the like can be suitably used. Furthermore, near the outlet of the stretching machine 38, the film may be subjected to a surface treatment such as a heat setting treatment for relaxing the film while heating or a corona treatment. The measured value of the film thickness deviation obtained by the film thickness deviation measuring device can also be used to control the stretching machine 38.

[0086] <Winding Machine 39> The winding machine 39 is a device that winds up the produced film into a roll. The film 31 wound into a roll becomes a product to be shipped.

[0087] It is preferable to install quality assurance equipment such as a surface inspection device, a pinhole inspection device, and a film thickness meter just before the winder 39. It is also preferable to trim the product to the desired width using a slitter or trimmer. Oscillation winding may be performed to prevent gauge bands during winding.

[0088] <Film Thickness Deviation Measuring Device> The film thickness deviation measuring device may have a configuration similar to that of the film thickness deviation measuring device 20 described above, and detailed description thereof will be omitted.

[0089] In the film manufacturing apparatus 30, the film 31 is transported along a preset path line, so the integral path C is preferably a line segment that is approximately perpendicular to the transport direction of the film 31.

[0090] The light source 22 and the optical sensor array 23 are preferably arranged opposite each other across the pass line of the film 31. In the example of FIG. 4 , the light source 22 and the optical sensor array 23 are arranged at the pass line position between the chill roll 37 and the stretching machine 38, but they may also be arranged before or downstream of the stretching machine 38. That is, the film thickness deviation measurement unit consisting of the light source 22 and the optical sensor array 23 can be installed anywhere from downstream of the T-die 36 to upstream of the winding machine 39. However, considering the speed of feedback control and the possibility that the refractive index of the film 31 may change due to processing by the stretching machine 38, it is preferable to install the light source 22 and the optical sensor array 23 upstream of the stretching machine 38. Furthermore, if the distance between the lip of the T-die 36 and the chill roll 37 increases due to the installation of the light source 22 and the optical sensor array 23, there is a risk of film thickness unevenness in the MD direction and necking in the TD direction becoming larger. For this reason, the film thickness deviation measurement unit is preferably installed downstream of the chill roll 37.

[0091] The light source 22 and the optical sensor array 23 are preferably installed on the same structure to prevent misalignment between the light source 22 and the optical sensor array 23 due to vibrations during operation, etc. Furthermore, it is more preferable that the installed structure can be pulled out offline during operation to calibrate the misalignment.

[0092] Other structures, such as glass windows, may be present in the gap between the film 31 and the light source 22, or between the film 31 and the optical sensor array 23. However, the structures must be able to transmit the light emitted from the light source 22 with sufficient intensity. If the other structures have a film thickness deviation, it is preferable to correct the calculated film thickness deviation of the film 31. However, if the distance between the light source 32 and the other structures is short and only has an acceptable effect on the calculated film thickness deviation of the film 31, correction may not be necessary. It is also more preferable that the other structures have no film thickness deviation.

[0093] The thickness deviation of the film 31 obtained by the above method can be displayed by a known visualization method. In the film manufacturing apparatus, it is preferable to display only the thickness deviation in the TD direction, from the viewpoint of feeding back information on the calculated thickness deviation to the control of the lip gap adjustment means. Furthermore, in order to know the fluctuation of the thickness deviation over time, it is more preferable to display, for example, a line graph with the TD coordinate on the horizontal axis and the thickness deviation on the vertical axis, with the color of the line changing over time.

[0094] <Lip Gap Adjustment Unit> The lip gap adjustment unit 40 generates and outputs a command for feedback control of the film thickness based on information about the film thickness deviation in the width direction input from the calculation unit 24 of the film thickness deviation measuring device. The lip gap adjustment unit 40 compares the actual film thickness deviation profile of the film 31 input from the calculation unit 24 of the film thickness deviation measuring device with a pre-input ideal film thickness deviation profile of the film 31. Then, it controls the lip gap adjustment means 361 to increase the lip gap corresponding to the TD direction coordinate in order to thicken portions where the actual film thickness deviation is thinner than the ideal film thickness deviation. It also controls the lip gap adjustment means 361 to decrease the lip gap corresponding to the TD direction coordinate in order to thin portions where the actual film thickness deviation is thicker than the ideal film thickness deviation.

[0095] In this way, the lip gap adjustment unit 40 controls the actual film thickness deviation so that it approximates the ideal film thickness deviation. That is, the measured film thickness deviation profile is compared with the ideal film thickness deviation profile of the film 31 to determine the film thickness difference in the film width direction at the position corresponding to each lip gap adjustment means 361. Then, each lip gap adjustment means 361 is feedback-controlled so that the difference falls within a predetermined range.

[0096] Here, necking occurs in the film 31 when it is discharged from the T-die 36, etc. For this reason, the distance from the TD center to a specific position on the film 31 calculated by the calculation unit 24 of the film thickness deviation measuring device generally differs from the distance from the TD center to the specific position on the molten resin when it is discharged from the T-die lip. Therefore, it is preferable that the lip gap adjustment unit 40 use various known methods to determine which lip gap adjustment means 361 to issue a command to when the difference between the actual film thickness deviation and the ideal film thickness deviation is detected at a specific TD coordinate.

[0097] It is also known that accuracy is improved by simultaneously operating multiple lip gap adjustment means 361 in consideration of influence coefficients, rather than operating only one. For this reason, it is preferable to weight the results of calculations performed using various known methods and operate multiple lip gap adjustment means 361 simultaneously.

[0098] (Film manufacturing method) Next, a film manufacturing method according to the present invention will be described. The film manufacturing method according to the present invention is a film manufacturing method in which molten resin is discharged from a die having a plurality of lip gap adjustment means to form a film, the film discharged from the die is transported along a preset path line, and includes an original position acquisition step in which, without placing the film between a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, the light source is turned on and the original position, which is the position of the light source detected by the optical sensor array, is acquired, and an apparent position acquisition step in which, with the film placed between the light source and the optical sensor array, the light source is turned on and the apparent position, which is the position of the light source detected by the optical sensor array, is acquired. a position acquisition step, and further comprising a single-point film thickness gradient measurement step of determining the film thickness gradient using the following equation (1) from the acquired actual position and apparent position; a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source; a film thickness deviation profile calculation step of calculating a film thickness deviation profile using the following equation (2) from the correspondence between the position of the light source and the film thickness gradient obtained by the multi-point film thickness gradient measurement step; and a lip gap adjustment step of operating the lip gap adjustment means based on the film thickness deviation profile so that the film thickness deviation at each point on the film is equal to or less than a target value.

[0099] In the film manufacturing method according to the present invention, the original position acquisition process, apparent position acquisition process, single-point film thickness gradient measurement process, and multi-point film thickness gradient measurement process are the same as those in the film thickness deviation measurement method according to the present invention described above, and therefore their explanations will be omitted.

[0100] <Lip Gap Adjustment Step> Based on the film thickness deviation profile calculated in the film thickness deviation profile calculation step, the lip gap adjustment unit 40 is operated so that the film thickness deviation at each point on the film 31 is equal to or less than a target value.

[0101] In the above film manufacturing method, similarly to the method for measuring film thickness deviation of the present invention, instead of changing the position of the light source 22 in the multi-point film thickness gradient measurement step, the direction of irradiation of the light from the light source 22 onto the film 21 can be changed. Furthermore, instead of changing the position of the light source 22 in the multi-point film thickness gradient measurement step, this can be done by changing the position of the film 21.

[0102] Furthermore, similarly to the method for measuring film thickness deviation of the present invention, in the multipoint film thickness gradient measurement process, the position of the optical sensor array 23 can be changed in accordance with the change in the irradiation position of the film 21 with light from the light source 22. This allows the size (area) of the sensor array 23 to be reduced.

[0103] While the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the invention. Furthermore, the films 21 and 31 in the above description include a resin composition and glass, which are generally called sheets because they are relatively thick.

[0104] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0105] (Measurement Conditions for this Example) In this example, the film 21 to be measured was a PET film extruded using a T-die method with an average film thickness of 86 μm and a standard deviation of film thickness in the TD direction of 4 μm. As the light source, only one row of light-emitting elements in the LCD was lit to form a line light source. The LCD had a 15.6-inch screen and a Full HD (1920 × 1080) resolution. A CMOS camera was used as the optical sensor array. The CMOS camera had a resolution of 4000 × 3000. As shown in FIG. 5 , the LCD display 52, PET film 51, and CMOS camera 53 were arranged vertically in this order. The vertical direction is perpendicular to the surface of the film 51. The vertical distance between the PET film 51 and the LCD display 52 was 120 mm, and the vertical distance between the PET film 51 and the optical sensor array 53 was 550 mm. The TD direction of the PET film 51 and the light emitting element row 521 that illuminated the light emitting elements of the liquid crystal display 52 were arranged so as to be perpendicular to each other.

[0106] (Process for Measuring Film Thickness Deviation) First, without placing the PET film, only one specific row of light-emitting element rows 521 in the liquid crystal display 52 was turned on, and the positions of the light-emitting element rows 521 were obtained by the CMOS camera 53 and defined as their original positions. Furthermore, the lit light-emitting element rows 521 were moved row by row, and the correspondence relationship between the positions of the lit light-emitting element rows 521 on the liquid crystal display 52 and their original positions was obtained. Next, the PET film 51 was placed between the liquid crystal display 52 and the CMOS camera 53 in the above-described positional relationship. Then, only one specific row of light-emitting element rows 521 in the liquid crystal display 51 was turned on, and the positions of the light-emitting elements were obtained by the CMOS camera 53 and defined as their apparent positions. Furthermore, the lit light-emitting element rows 521 were moved row by row, and the correspondence relationship between the positions of the lit light-emitting element rows 521 on the liquid crystal display 52 and their apparent positions was obtained. Through the above-described operations, the original positions and apparent positions corresponding to the positions of the lit light-emitting element rows 521 were obtained. Since the above-mentioned true position and apparent position are affected by the distortion of the CMOS camera, the correspondence between pixel coordinates and actual coordinates is not constant across the entire field of view. Therefore, the camera was calibrated in advance, and the actual coordinates were calculated using the obtained camera matrix and distortion coefficients.

[0107] Next, Δh was calculated as the TD direction displacement from the original position to the apparent position from the acquired original position and apparent position, and the film thickness gradient dt(x) / dx of the PET film corresponding to the lit light-emitting element row 521 was calculated using the following equation (1). Here, x is the TD coordinate of the PET film, and t(x) is the film thickness deviation obtained by subtracting the film thickness of the PET film at the origin x=0 of the TD coordinate from the film thickness of the PET film at the TD coordinate x. ｔａｒｇｅｔ is the refractive index of the PET film, 1.50, n ａｉｒ is set to 1.00, which is the refractive index of the atmosphere, and d is set to 100 mm, which is the vertical distance between the liquid crystal display and the PET film.

[0108] Furthermore, the thickness deviation profile t(x) in the TD direction of the PET film was calculated from the thickness gradient dt(x) / dx of the PET film obtained above using the following equation (6). Here, Δx is the TD length per pixel, and dt(k) / dx is the film thickness gradient dt(k) / dx calculated from equation (1) for the TD coordinate k.

[0109] The TD-direction film thickness deviation profile t(x) of the PET film obtained as described above is shown in Figure 6. For reference, Figure 6 also shows the film thickness profile obtained using a contact-type film thickness gauge with a dashed line. Note that the film thickness deviation measurement method of the present invention determines the amount of film thickness change from the origin, but not the absolute value of the film thickness. Therefore, for ease of viewing, a constant value is added to the film thickness deviation profile t(x) in Figure 6 so that the absolute value roughly matches that of the contact-type film thickness profile. Figure 6 confirms that the film thickness deviation profile obtained using the film thickness deviation measurement method of the present invention generally matches the film thickness profile obtained using a contact-type film thickness gauge. As described above, it was found that the present invention enables film thickness deviation to be obtained non-contact with a simple and safe device configuration.

[0110] According to the present invention, it is possible to obtain the film thickness deviation of a film in a non-contact manner using a simple and safe device configuration.

[0111] REFERENCE SIGNS LIST 11 Object to be measured 12 Background image 13 Imaging means 14 Apparent light path 15 Actual light path 20 Film film thickness deviation measuring device 21, 31 Film 22 Light source 23 Optical sensor array 231 Optical sensor 24 Calculation unit 241 Single-point film thickness gradient measuring unit 242 Multi-point film thickness gradient measuring unit 243 Film thickness deviation calculation unit 30 Film manufacturing device 35 Extruder 36 T-die 361 Lip gap adjusting means 37 Cooling roll 38 Stretching machine 39 Winder 40 Lip gap adjusting unit 51 PET film 52 Liquid crystal display 521 Row of light-emitting elements in the liquid crystal display 53 CMOS camera

Claims

1. A method for measuring film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point or line light source arranged opposite to a light source, and a one-dimensional or two-dimensional optical sensor array without placing a film to be measured between the light source and the optical sensor array, and acquiring the original position, which is the position of the light source detected by the optical sensor array; an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring the apparent position, which is the position of the light source detected by the optical sensor array; a single-point film thickness gradient measurement step of determining the film thickness gradient using the following equation (1) from the acquired original position and apparent position; a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source; and a film thickness deviation profile calculation step of determining the film thickness deviation profile using the following equation (2) from the correspondence between the position of the light source and the film thickness gradient obtained by the multi-point film thickness gradient measurement step. where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

2. The method for measuring film thickness deviation according to claim 1, wherein the position of the optical sensor array is changed in accordance with the change in the position of the light source in the multi-point film thickness gradient measuring step.

3. A method for measuring film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point or line light source arranged opposite to a one-dimensional or two-dimensional optical sensor array, without placing a film to be measured between the light source and the one-dimensional or two-dimensional optical sensor array, and acquiring the original position, which is the position of the light source detected by the optical sensor array; an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring the apparent position, which is the position of the light source detected by the optical sensor array; a single-point film thickness gradient measurement step of determining the film thickness gradient using the following equation (1) from the acquired original position and apparent position; a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the optical sensor array; and a film thickness deviation profile calculation step of determining the film thickness deviation profile using the following equation (2) from the correspondence between the position of the optical sensor array and the film thickness gradient obtained by the multi-point film thickness gradient measurement step. where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

4. The method for measuring film thickness deviation according to claim 3, wherein the position of the light source is changed in accordance with the change in the position of the optical sensor array in the multi-point film thickness gradient measuring step.

5. A method for measuring film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point or line light source arranged opposite to a light source, and a one-dimensional or two-dimensional optical sensor array without placing a film to be measured between the light source and the optical sensor array, and acquiring the original position, which is the position of the light source detected by the optical sensor array; an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring the apparent position, which is the position of the light source detected by the optical sensor array; a single-point film thickness gradient measurement step of determining the film thickness gradient using the following equation (1) from the acquired original position and apparent position; a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the irradiation direction of the light source; and a film thickness deviation profile calculation step of determining the film thickness deviation profile using the following equation (2) from the correspondence between the light source irradiation point and the film thickness gradient obtained by the multi-point film thickness gradient measurement step. where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

6. The method for measuring film thickness deviation according to claim 5, wherein the position of the optical sensor array is changed in accordance with a change in the irradiation direction of the light source in the multipoint film thickness gradient measuring step.

7. A method for measuring film thickness deviation, comprising: an original position acquisition step of turning on a light source, which is a point or line light source arranged opposite to a one-dimensional or two-dimensional optical sensor array, without placing a film to be measured between the light source and the one-dimensional or two-dimensional optical sensor array, and acquiring the original position, which is the position of the light source detected by the optical sensor array; an apparent position acquisition step of placing the film between the light source and the optical sensor array, turning on the light source, and acquiring the apparent position, which is the position of the light source detected by the optical sensor array; a single-point film thickness gradient measurement step of determining the film thickness gradient using the following equation (1) from the acquired original position and apparent position; a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the detection direction of the optical sensor array; and a film thickness deviation profile calculation step of determining the film thickness deviation profile using the following equation (2) from the correspondence between the detection direction of the optical sensor array and the film thickness gradient obtained by the multi-point film thickness gradient measurement step. where x is a position vector in the plane of the film, t(x) is a film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is a film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

8. The method for measuring film thickness deviation according to claim 7, wherein the position of the light source is changed in accordance with a change in the detection direction of the optical sensor array in the multipoint film thickness gradient measuring step.

9. A method for measuring film thickness deviation according to any one of claims 1 to 8, wherein the film is transported so as to pass between the light source and the optical sensor array, and the integral path C is a line segment that is approximately perpendicular to the transport direction of the object to be measured.

10. An apparatus for measuring film thickness deviation, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; a light source position changing means for changing the position of the light source; and a calculation unit for calculating the film thickness deviation, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring the original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring the apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit for performing a single-point film thickness gradient measurement step of determining the film thickness gradient using the following formula (1) from the acquired original position and apparent position; and a multi-point film thickness gradient measurement unit for performing a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the light source using the light source position changing means. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the position of the light source and the film thickness gradient obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

11. The film thickness deviation measuring device according to claim 10, further comprising an optical sensor position changing means for changing the position of said optical sensor array.

12. An apparatus for measuring deviations in film thickness, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; an optical sensor position changing means for changing the position of the optical sensor array; and a calculation unit for calculating deviations in film thickness, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring the original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring the apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit for performing a single-point film thickness gradient measurement step of determining the film thickness gradient using the following formula (1) from the acquired original position and apparent position; and a multi-point film thickness gradient measurement unit for performing a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the position of the optical sensor array using the optical sensor position changing means. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the light source irradiation points and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

13. An apparatus for measuring deviations in film thickness, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; a light source irradiation direction changing means for changing the irradiation direction of the light source; and a calculation unit for calculating deviations in film thickness, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring the original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring the apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit for performing a single-point film thickness gradient measurement step of calculating the film thickness gradient using the following formula (1) from the acquired original position and apparent position; and a multi-point film thickness gradient measurement unit for performing a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the irradiation direction of the light source using the light source irradiation direction changing means. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the light source irradiation points and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

14. The film thickness deviation measuring device according to claim 13, further comprising an optical sensor position changing means for changing the position of the optical sensor array.

15. An apparatus for measuring deviations in film thickness, comprising: a light source which is a point light source or a line light source; a one-dimensional or two-dimensional optical sensor array arranged opposite the light source; a sensor detection direction changing means for changing the detection direction of the optical sensor array; and a calculation unit for calculating deviations in film thickness, wherein the calculation unit has an original position acquisition step of turning on the light source without placing the film between the light source and the optical sensor array and acquiring the original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition step of placing the film to be measured between the light source and the optical sensor array and turning on the light source and acquiring the apparent position, which is the position of the light source detected by the optical sensor array, a single-point film thickness gradient measurement unit for performing a single-point film thickness gradient measurement step of calculating the film thickness gradient using the following formula (1) from the acquired original position and apparent position; and a multi-point film thickness gradient measurement unit for performing a multi-point film thickness gradient measurement step of performing the single-point film thickness gradient measurement step multiple times by changing the detection direction of the optical sensor array using the sensor detection direction changing means. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of determining a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the light source irradiation points and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step: where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

16. The film thickness deviation measuring device according to claim 15, further comprising a light source position changing means for changing the position of the light source.

17. A film manufacturing method in which molten resin is discharged from a die having multiple lip gap adjustment means to form a film, wherein the film discharged from the die is transported along a preset path line, and the method comprises: an original position acquisition process in which, without placing a film between a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, the light source is turned on and the original position, which is the position of the light source detected by the optical sensor array, is acquired; an apparent position acquisition process in which, with the film placed between the light source and the optical sensor array, the light source is turned on and the apparent position, which is the position of the light source detected by the optical sensor array, is acquired; a single-point film thickness gradient measurement process in which the film thickness gradient is calculated from the acquired original position and apparent position using the following formula (1); a multi-point film thickness gradient measurement process in which the single-point film thickness gradient measurement process is performed multiple times by changing the position of the light source from the light source; and a film thickness deviation profile calculation process in which the film thickness deviation profile is calculated using the following formula (2) from the correspondence between the position of the light source and the film thickness gradient obtained in the multi-point film thickness gradient measurement process. a lip gap adjusting step of operating the lip gap adjusting means based on the film thickness deviation profile so that the film thickness deviation at each point on the film is equal to or less than a target value. where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

18. A film manufacturing apparatus that extrudes molten resin from a die having multiple lip gap adjustment means to form a film, comprising: a light source, which is a point light source or a line light source, and a one-dimensional or two-dimensional optical sensor array, which are arranged opposite each other across a path line along which the film extruded from the die is transported; a calculation unit that calculates the film thickness deviation of the film, comprising: a single-point film thickness gradient measurement unit that performs an original position acquisition process in which the light source is turned on without the film being placed between the light source and the optical sensor array, and acquires the original position, which is the position of the light source detected by the optical sensor array; and an apparent position acquisition process in which the film to be measured is placed between the light source and the optical sensor array, and turns on the light source, and acquires the apparent position, which is the position of the light source detected by the optical sensor array, and performs a single-point film thickness gradient measurement process in which the film thickness gradient is calculated from the acquired original position and apparent position using the following formula (1); and a multi-point film thickness gradient measurement unit that performs a multi-point film thickness gradient measurement process in which the single-point film thickness gradient measurement process is performed multiple times by changing the position of the light source. a film thickness deviation profile calculation unit that performs a film thickness deviation profile calculation step of calculating a film thickness deviation profile of the film using the following equation (2) from the correspondence relationship between the position of the light source and the film thickness gradient of the film obtained by the multi-point film thickness gradient measurement step; and a lip gap adjustment unit that operates the lip gap adjustment means based on the film thickness deviation profile so that the film thickness deviation at each point on the film is equal to or less than a target value. where x is a position vector in the plane of the film, t(x) is the film thickness deviation obtained by subtracting the film thickness at the origin x=0 from the film thickness at the position x, and dt(x) / dx is the film thickness gradient expressed by the total in-plane differential of the film thickness deviation t. ｔａｒｇｅｔ : refractive index of the film n ａｉｒ : refractive index of the atmosphere Δh: vector representing the amount of displacement from the original position to the apparent position d: distance between the light source and the film v: unit tangent vector of path C is.

19. The film manufacturing apparatus according to claim 18, further comprising a stretching machine for stretching the film, downstream of a position on the pass line sandwiched between the light source and the optical sensor array.

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