Film thickness deviation measurement method, thin film manufacturing method, film thickness deviation measurement device, and thin film manufacturing device

Abstract

The invention provides a film thickness deviation measuring technology and a film manufacturing technology, which can acquire information of film thickness deviation of a film in a non-contact manner through a simple and safe device structure. Provided is a film thickness deviation measurement method for a film, in which a film to be measured is used as an object to be measured, a preset background image can be captured by an imaging means, and a reference image can be acquired. The reference image is an image obtained by capturing a background image by means of an imaging means in a state in which an object to be measured is not sandwiched, or an image obtained by calculating and deriving a visual representation based on the imaging means of the background image in a state in which the object to be measured is not sandwiched. The measurement image is an image in which the object to be measured is sandwiched between the background image and the imaging means and the background image is captured by the imaging means, and the amount of displacement of the background image in the two images is calculated on the basis of the acquired reference image and the measurement image, thereby obtaining the film thickness deviation of the object to be measured.

Description

Technical Field

[0001] This invention relates to techniques for non-contact measurement of film thickness deviation in thin films that transmit visible light, and to the manufacture of thin films using these thickness deviation measurement techniques. Particularly, this invention relates to techniques suitable for thin films whose visible light transmittance exceeds a specific value.

[0002] In addition, the thin film that allows visible light to pass through is made of, for example, resin or glass. Sheets are also included in this disclosure of thin films. Background Technology

[0003] The following method is widely used as a method for online, non-contact measurement of the thickness of resin films. This method involves transmitting X-rays, infrared rays, or other light through the film and measuring the film thickness based on the attenuation rate of the transmitted light, according to the Lambert-Beer law.

[0004] Furthermore, Patent Document 1 describes an optical interference method for measuring film thickness by irradiating white parallel light and calculating the film thickness based on the spectral intensity of the reflected light. Patent Document 2 describes an electrostatic capacitance method for measuring film thickness.

[0005] Most of these film thickness measurement methods involve mounting a sensor back and forth in a direction orthogonal to the transport direction of the material being measured while performing the measurement. However, in methods where the sensor is moved back and forth while measuring, the faster the film transport speed, the longer the interval between film thickness data points of the same width. Therefore, it is difficult to detect quality or operational abnormalities such as sudden changes in film thickness distribution. Moreover, there is a problem in separating film thickness variations in the transport direction from those in the width direction based on the film thickness data.

[0006] As prior art for such a problem, there exists the technology described in Patent Document 3.

[0007] Patent Document 3 uses multiple X-ray detection elements arranged in the width direction to detect the amount of transmitted X-rays. Moreover, Patent Document 3 discloses a method for determining the film thickness on a straight line orthogonal to the transport direction by tilting the multiple X-ray detection elements relative to the width direction according to the transport speed and measurement time.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 7-280523

[0011] Patent Document 2: Japanese Patent Application Publication No. 2019-2918

[0012] Patent Literature 3: Japanese Patent Application Laid-Open No. 2006-275750

[0013] Non-Patent Literature

[0014] Non-Patent Literature 1: "Improvement of a visualization method of a density gradient based on a Background Oriented Schlieren method", Sumio Kurenzaki et al., Transactions of the Japan Society of Mechanical Engineers (B Edition) Vol. 77, No. 784, 2391 pages, published on December 25, 2011 SUMMARY

[0015] PROBLEMS TO BE SOLVED BY THE INVENTION

[0016] According to the film thickness measuring apparatus described in Patent Literature 3, the plurality of X-ray detecting elements are inclined with respect to the width direction in accordance with the conveyance speed and the measurement time. Thereby, in Patent Literature 3, it is possible to measure the thickness on a straight line orthogonal to the advancing direction of the thin film. However, in the film thickness measuring apparatus described in Patent Literature 3, a plurality of X-ray detecting elements are required. Therefore, the film thickness measuring apparatus described in Patent Literature 3 has a problem that the equipment cost increases, and the maintenance cost increases due to the calibration between the X-ray detecting elements and the like.

[0017] The present application has been achieved in view of the above-described aspect. Furthermore, an object of the present application is to provide a film thickness deviation measuring technique capable of obtaining information of a film thickness deviation of a thin film in a non-contact manner by a simple and safe apparatus structure, and a thin film manufacturing technique using the measuring technique.

[0018] MEANS FOR SOLVING THE PROBLEMS

[0019] The inventors and the like have made intensive studies in order to solve the above-described problems. As a result of various studies, the inventors have conceived that the Background Oriented Schlieren method for calculating a density gradient of a fluid is applied to the film thickness deviation measurement of a thin film which is a solid. Then, the inventors have utilized the displacement amount (movement amount) of the background between a reference image photographed in a state where the object is not present and a measurement image photographed through the object. Furthermore, thereby, the inventors have obtained an insight that it is possible to obtain the film thickness deviation of the object by a simple and safe apparatus structure.

[0020] The present application has been achieved on the basis of the insight further studied.

[0021] Further, in order to solve the problem, one embodiment of the present application is a film thickness deviation measurement method, which is a film thickness deviation measurement method of a thin film, in which a thin film of a measurement target is taken as a measurement object, a pre-set background image can be photographed by a photographing unit to obtain a reference image, the reference image is an image obtained by photographing the background image by the photographing unit in a state where the measurement object is not sandwiched, or is an image obtained by calculating a visual representation based on the photographing unit in the state where the measurement object is not sandwiched, a measurement image is obtained by sandwiching the measurement object between the background image and the photographing unit and photographing the background image by the photographing unit, and a displacement amount of the background image in the obtained reference image and measurement image is calculated to obtain a film thickness deviation of the measurement object.

[0022] The film thickness deviation is obtained, for example, using the following (1) formula.

[0023] [mathematical formula 1]

[0024] wherein, t: film thickness deviation obtained by subtracting the film thickness of the measurement object at the origin from the film thickness of the measurement object at the measurement point n target : refractive index of the measurement object n air : refractive index of the atmosphere d: distance between the background image and the measurement object Δh: two-dimensional vector representing a displacement amount of the background image focused on in the measurement image with respect to the same background image in the reference image v: unit tangent vector of the path C cΔh vdl: operation of performing a line integral of an inner product of the Δh and the v over the integral path C from the origin toward the measurement point.

[0025] ​Also, another aspect of the present application is a film manufacturing method for forming a film capable of transmitting visible light by ejecting molten resin from a mold having a plurality of mold lip gap adjustment units, wherein the film ejected from the mold is conveyed along a predetermined route, a background image and a photographing unit that photographs the background image are arranged across the route, the film manufacturing method includes the following steps: acquiring a measurement image that is an image obtained by the photographing unit photographing the background image across the film; acquiring a reference image that is an image obtained by the photographing unit photographing the background image in a state where the film is not interposed between the background image and the photographing unit or is an image obtained by calculating a visual performance of the photographing unit in the state where the film is not interposed between the background image and the photographing unit; and comparing the acquired reference image and the acquired measurement image, calculating a film thickness deviation curve in the width direction of the film by calculating a displacement amount of the background image in the width direction of the film between the two images; and operating the mold lip gap adjustment units in a manner where a film thickness deviation of each point of the film becomes a target value based on the calculated film thickness deviation curve.

[0026] Effects of the Invention

[0027] According to the aspect of the present application, it is possible to acquire information on a film thickness deviation in a non-contact manner with a simple and safe device structure, with a film made of resin, glass, or the like as an object. Also, according to the aspect of the present application, it is possible to acquire information on a film thickness deviation in a non-contact manner, for example, over the entire length and the entire width of a film.

[0028] As a result, according to the aspect of the present application, it is possible to manufacture a film with higher precision, for example, by quickly reflecting information on a film thickness deviation acquired in the control of a mold lip gap adjustment unit when manufacturing a film. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a conceptual view of an optical system of the BOS method for quantitative visualization of density gradients of a fluid.

[0030] Figure 2 is a schematic configuration diagram of a film thickness deviation measuring device based on an embodiment of the present application.

[0031] Figure 3 is a diagram showing a configuration example of an arithmetic unit.

[0032] Figure 4 is a schematic configuration diagram of a film manufacturing device based on an embodiment of the present application.

[0033] Figure 5 is a diagram showing a displacement amount of a background in the MD direction and the TD direction in an example.

[0034] Figure 6 is a graph showing a film thickness deviation distribution in a film plane of an embodiment. DETAILED DESCRIPTION

[0035] Hereinafter, an embodiment based on the present application will be described with reference to the drawings.

[0036] In addition, the embodiment described below is one example of the present application, and the application is not limited to the following content.

[0037] (Principle of the present disclosure)

[0038] The present inventors considered applying a background-oriented schlieren method for calculating a density gradient of a fluid to measurement of a film thickness deviation of a film as a solid. In addition, the background-oriented schlieren method is also called a BOS method. Furthermore, as a result of various studies, it was thought to utilize a movement amount (displacement amount) of a background between a reference image photographed in a state where an object to be measured is not present and a measurement image photographed through the object to be measured. Furthermore, the inventors obtained the insight that by calculating the displacement amount of the background between the two images, the film thickness deviation of the object to be measured can be obtained with a simple and safe device structure.

[0039] Here, the BOS method is a quantitative visualization method of a density gradient of a fluid. This BOS method utilizes a phenomenon in which a background appears to be shifted due to a refractive index difference caused by a density gradient when the background is observed through a fluid to measure the density gradient (refer to Figure 1 ). In the present disclosure, this measurement principle is applied to a film as a solid, and a film thickness deviation of the film is measured. In addition, the BOS method has two advantages compared to a general schlieren method. These two advantages are that an optical system for measurement is simple, and quantification of a density gradient can be performed.

[0040] Figure 1 A conceptual diagram showing an optical system of the BOS method. As Figure 1 shown, the optical system of the BOS method includes an object to be measured 11 composed of a fluid, a background image 12, and a photographing unit 13. In Figure 1 , a visually apparent light path 14 from the photographing unit 13 and a true light path 15 caused by the interposition of the object to be measured 11 are shown. In the BOS method, the background image 12 is photographed through the object to be measured 11. At this time, the position of the background image on the image photographed by the photographing unit 13 is shifted in proportion to the density gradient of the object to be measured 11.

[0041] In this phenomenon, the total deviation angle ε can be approximated by the ratio of the shift amount Δh of the background image in the photographed image to the distance d between the object to be measured and the background image. That is, it can be expressed as "ε = Δh / d".

[0042] In addition, the total deviation angle ε is represented by the following (2). That is, the total deviation angle ε is calculated by integrating the density gradient of the refractive index n of the object in a direction orthogonal to the optical axis n / x is integrated over the thickness 2Δz of the object.

[0043] [Equation 2]

[0044] In addition, the refractive index n and the density p are in a relationship of n = pG + 1 using a constant G of the Gladstone-Dale law.

[0045] Therefore, the density gradient is represented by the following (3).

[0046] [Equation 3]

[0047] Moreover, in the present embodiment, in order to obtain the gradient of the film thickness t of the thin film composed of a solid (film thickness deviation), an optical system of the BOS method is used.

[0048] In the present embodiment, the Gladstone-Dale law is not used. Instead, in the present embodiment, the refractive index is approximated to have a gradient in the x direction only at a portion where the film thickness fluctuation portion contacts with air. Thereby, the following (4) is obtained. Note that the x direction is an arbitrary direction selected from the surface direction of the thin film as the object. The surface direction of the thin film is a two-dimensional direction orthogonal to the z direction.

[0049] [Equation 4]

[0050] Further, ε = Δh / d. Therefore, according to the equation of "ε = Δh / d" and the (4), the following (5) is obtained.

[0051] [Equation 5]

[0052] Then, by integrating the (5) in the x direction, the film thickness deviation can be measured. The film thickness deviation is an amount of change in the film thickness in the x direction from a set reference position x0.

[0053] By extending this idea, for example, the film thickness deviation in a two-dimensional direction along the x direction and the y direction of the surface of the thin film can be obtained.

[0054] As a specific means for obtaining the film thickness deviation, for example, a method using the following (1) can be given.

[0055] Further, in the present specification, a "reference image" refers to an image obtained by the imaging unit without imaging the background image via the measured object. In addition, a "measurement image" refers to an image obtained by the imaging unit with imaging the background image via the measured object.

[0056] [Equation 6]

[0057] Herein, t: film thickness deviation obtained by subtracting the film thickness of the measured object at the origin from the film thickness of the measured object at the measurement point n target : refractive index of the measured object n air : refractive index of the atmosphere d: distance between the background image and the measured object Δh: two-dimensional vector representing the displacement amount of the background image of interest on the measurement image with respect to the same background image in the reference image v: unit tangent vector of the path C cΔh vdl: operation of line-integrating the inner product of the Δh and the v over the integral path C from the origin toward the measurement point.

[0058] (Configuration of film thickness deviation measurement device)

[0059] Next, an example of the film thickness deviation measurement device of the present embodiment will be described.

[0060] Figure 2 A schematic configuration of the film thickness deviation measurement device 20 of the present embodiment is shown.

[0061] As shown in the schematic view of FIG. 1, Figure 2 The film thickness deviation measurement device 20 of the present embodiment is provided with a background image 22, an imaging unit 23 that images the background image 22, and an arithmetic unit 24.

[0062] The measured object 21 is a thin film that is the measurement target.

[0063] <Measured Object>

[0064] The measured object 21 is disposed in front of the background image in a state in which the film thickness direction is oriented toward the imaging direction at the time of taking the measurement image.

[0065] ​The measurement target of the present embodiment is a film that transmits visible light. Therefore, the imaging unit can image the background image 22 through the measurement target 21. In principle, the measurement target 21 transmits visible light at a transmittance of 10% or more, although this also depends on the film thickness of the measurement target.

[0066] In addition, the measurement target 21 preferably has a haze value of 20% or less, regardless of the value of the visible light transmittance. In addition, the haze value is more preferably 15% or less, and further preferably 5% or less.

[0067] Here, in the present embodiment, the visible light transmittance is the total light transmittance in the wavelength range of 400 to 700 nm, which is measured using a haze meter. In addition, the haze value is the ratio of the total light transmittance to the diffuse transmittance, which is also measured using a haze meter.

[0068] <BACKGROUND IMAGE>

[0069] The background image 22 can be any pattern, motif, or the like, as long as the position on the image obtained by the imaging unit imaging the background image changes depending on whether the measurement target 21 is interposed. For example, the top plate surface 25A of the stand 25 at a position corresponding to the background image 22 can have a zinc flower pattern, which is finely captured by the imaging unit 23. In this case, it is not necessary to separately provide the zinc flower pattern as the background image 22, and a special image can be provided as the background image.

[0070] In the case where there is no appropriate pattern as the background image 22, a random dot image or a stripe image having a periodic brightness distribution is preferably used as the background image. In addition, the random dot image and the stripe image can be binary or grayscale, or can be a color image, for example, painted in three colors of red, green, and blue. In addition, the background image 22 can be provided by directly drawing random dots on the top plate surface 25A of the stand 25, or by pasting a paper on which the background image is printed on the top plate surface 25A.

[0071] In addition, the display device that displays the background image can be provided at the position of the top plate surface of the stand 25, and the background image can be switched according to the passage of time or the condition of the measurement target. In such a structure in which the background image is displayed on the display, the actual resolution can also be improved by rapidly switching the image to vibrate the background image. The configuration of the background image is not limited to this, and can be provided by various known methods.

[0072] <IMAGING UNIT>

[0073] The imaging unit is a device that images the background image.

[0074] As the photographing unit 23, a digital camera such as a CCD camera or a CMOS camera can be used. In addition, the photographing unit 23 can be a face array camera or a line array camera. However, in a case where only a film thickness deviation in a specific direction is to be measured, a line array camera can be used as the photographing unit 23. In this case, an improvement in processing speed and a reduction in equipment cost are expected.

[0075] The photographing unit 23 can also be constituted by a collection of a plurality of cameras. In this case, the photographing area of one camera with respect to the object to be measured can be reduced. Thereby, the resolution can be improved, or a narrow angle camera can be applied. In this case, a reduction in the size of the device by reducing the area of the background image 22 can be expected.

[0076] In addition, in a case where the background image 22 is a black and white binary or a gray scale, the camera of the photographing unit 23 can also be a monochrome camera. In addition, in a case where the background image 22 is a color image, for example, a configuration can be made in which a color filter is provided between the photographing unit 23 and the object to be measured, and different colors are detected by a plurality of cameras. In this case, if a monochrome camera is applied as the camera of the photographing unit 23, it is preferable in terms of cost effectiveness and spatial resolution.

[0077] <Configuration relationship, etc.>

[0078] When a measurement image is photographed, the object to be measured is interposed between the photographing unit and the background image.

[0079] From the viewpoint of analysis operation, the object to be measured 21 and the background image 22 are preferably in a parallel configuration relationship. However, in a case where they cannot be configured in parallel due to constraints on the configuration of the device, appropriate correction can be made at the time of operation.

[0080] In addition, the farther apart the object to be measured 21 and the background image 22, the higher the film thickness deviation resolution. Therefore, the relative distance between the object to be measured 21 and the background image 22 is preferably 30 mm or more, more preferably 50 mm or more, and further preferably 200 mm or more. On the other hand, the closer the object to be measured 21 and the background image 22, the easier the focusing at the time of photographing. Therefore, the relative distance between the object to be measured 21 and the background image 22 is preferably 2000 mm or less, more preferably 1000 mm or less, and further preferably 600 mm or less. Moreover, the relative distance between the object to be measured 21 and the background image 22 is preferably between 30 and 2000 mm, more preferably between 50 and 1000 mm, and further preferably between 200 and 600 mm. The distance between the object to be measured 21 and the background image 22 is preferably determined in accordance with the required film thickness deviation resolution and the lens structure of the photographing unit 23.

[0081] From the viewpoint of the resolution of the arithmetic operation and the viewpoint of the prevention of defocus, the optical axis of the imaging unit 23 is preferably orthogonal to the measured object 21 and the background image 22. The distance between the imaging unit 23 and the measured object 21 is preferably determined based on the angle of view and the focal length of the imaging unit 23. Preferably, the distance is configured such that the measured object 21 and the background image 22 are not defocused and the range of the measured object 21 to be measured converges in the imaging range.

[0082] As shown in FIG. 1, the axis connecting the measured object 21, the background image 22, and the imaging unit 23 is vertically (orthogonal to the background image) configured. However, the axis can be set at a horizontal or any other arbitrary angle depending on the constraints of the setting environment and the like, and the orientation of the measured object 21, the background image 22, and the like. Figure 2

[0083] In the gap between the measured object 21 and the background image 22 or the measured object 21 and the imaging unit 23, there can be other structures (not shown) such as a glass window. However, the visible light transmittance of the structure is preferably 10% or more so that the measured object 21 and the background image 22 can be recognized by the imaging unit 23. Further, the visible light transmittance is more preferably 30% or more and further preferably 70% or more. Further, in the case where the structure has a film thickness deviation, it is preferable to correct the film thickness deviation of the measured object 21 by the displacement amount of the background image in the captured image or the calculated film thickness deviation. However, in the case where the distance between the background image 22 and the structure is short and the calculation result of the film thickness deviation of the measured object 21 only causes an allowable influence, the correction can not be performed. The structure is more preferably free from the film thickness deviation.

[0084] <Arithmetic unit>

[0085] The arithmetic unit 24 performs a process of calculating the film thickness deviation of the measured object based on the image captured by the imaging unit. Specifically, the arithmetic unit 24 performs a process of calculating the film thickness deviation of the measured object by calculating the displacement amount of the background image between the reference image and the measurement image. The displacement amount of the background image is determined, for example, by the movement amount of the region selected from the background image.

[0086] As shown in FIG. 1, the axis connecting the measured object 21, the background image 22, and the imaging unit 23 is vertically (orthogonal to the background image) configured. However, the axis can be set at a horizontal or any other arbitrary angle depending on the constraints of the setting environment and the like, and the orientation of the measured object 21, the background image 22, and the like. Figure 3

[0087] [Reference image acquisition unit]

[0088] The reference image acquisition unit 24A performs a process of acquiring a reference image. The reference image is an image that becomes a reference for comparison with the measurement image.

[0089] ​​As the process of acquiring the reference image, a first processing method and a second processing method can be exemplified.

[0090] [First processing method]

[0091] The first processing method acquires an image obtained by the imaging unit 23 imaging the background image 22 as the reference image. The acquisition of the reference image is performed when it is determined that the measured object 21 is not sandwiched between the imaging unit and the background image.

[0092] In addition, the reference image is an image that becomes a reference for correction. Therefore, in the case where the film thickness deviation is sought on line, it is sufficient to implement before acquiring information on the film thickness deviation with respect to the measured object as the object.

[0093] [Second processing method]

[0094] In the second processing method, the reference image is sought by calculating an image based on the visual representation of the imaging unit 23 of the background image 22 in a state where the measured object 21 is not sandwiched.

[0095] As the calculation method of the reference image, for example, there is a method of performing a projective transformation on the basis of the positional relationship between the imaging unit 23 and the background image 22 with respect to the data for printing of the background image 22, and thereby calculating the reference image. In addition, for example, as the calculation method of the reference image, an image of a mark on the background image outside the region of the measured object in the measurement image is detected. Further, there is a method of calculating a projective transformation matrix on the basis of the position of the mark, and calculating the reference image by performing a projective transformation on the data for printing constituting the background image 22. In such a calculation method of the reference image, instead of the image data obtained by imaging the background image 22, the data for printing of the background image 22 is held. Further, such a calculation method of the reference image is a method of calculating the reference image by transforming the data for printing into the visual representation from the imaging unit.

[0096] In this second processing method, the reference image is acquired by calculation, and therefore the reference image for correction can be acquired regardless of the presence or absence of the sandwiching of the measured object 21.

[0097] [Measurement image acquisition unit]

[0098] The measurement image acquisition unit 24B acquires, as a measurement image, image data of the background image imaged by the imaging unit in a state where the measured object as the object is sandwiched between the background image and the imaging unit.

[0099] The measurement image acquisition unit 24B can also acquire the measurement image each time the sandwiching position of the measured object changes relatively. Image processing of integrating a plurality of measurement images and transforming them into one measurement image can also be performed on the basis of a plurality of measurement images thus acquired.

[0100] <film thickness deviation calculation section>

[0101] The film thickness deviation calculation section 24C calculates the displacement amount between the respective background images based on the reference image acquired by the reference image acquisition section 24A and the measurement image acquired by the measurement image acquisition section 24B. Further, the film thickness deviation of the measured object is calculated from the displacement amount. The film thickness deviation calculation section 24C executes the process of calculating the film thickness deviation each time the measurement image acquisition section 24B acquires the measurement image. The measurement image acquisition section 24B acquires the measurement image.

[0102] [Calculation of displacement amount of background]

[0103] The method of calculating the displacement amount of the background image in the reference image and the background image of the measurement image can employ various known methods. As an example of the method, for example, template matching, wavelet analysis can be cited.

[0104] Template matching is a method used in a particle image velocimetry (PIV) method. In the case of using template matching, the reference image is divided into a small inspection window of, for example, 64 pixels on a side. Then, the operation of the cross-correlation coefficient of the image within the inspection window and the region of the same size of the measurement image is repeatedly executed in the entire region or a part of the region of the measurement image. Further, the point at which the cross-correlation coefficient is highest is calculated as the coordinates of the inspection window. In addition, the above-described explanation of template matching is an example. It is also possible to set the inspection window on the measurement image side, and to use the scanned image as the reference image. In addition, the inspection windows can also overlap each other, and further, the size of the inspection window can not be a square but a rectangular or the like. In addition, in order to reduce the amount of calculation, it is preferable to limit the scanning range by setting the safety rate to the maximum value at which the gradient of the film thickness deviation can be reasonably considered.

[0105] As the calculation method of the cross-correlation coefficient, various methods are known. Among them, from the viewpoint of robustness to luminance variation, it is preferable to apply a normalized cross-correlation coefficient, particularly a zero-mean normalized cross-correlation coefficient (ZNCC). However, the amount of calculation of the normalized cross-correlation coefficient increases. Therefore, particularly in the case of calculating the speed, it is preferable to apply a difference absolute value sum (SAD) or a difference square sum (SSD).

[0106] In addition, in template matching, it is known that a false vector is generated. In the countermeasure against the false vector, various known methods can be used. In the countermeasure against the false vector, for example, a method of setting a cutoff value to the cross-correlation coefficient, a method of allowing a small amount of false vectors of the calculation point in view of the fact that the film thickness deviation is an integrated value, or a combination thereof can be easily applied.

[0107] Further, the wavelet analysis is preferably applied to a case where the film thickness deviation is measured in only one specific direction. In a case where the displacement amount is calculated by the wavelet analysis, the background image 22 is preferably a fringe image having a periodic luminance distribution constituted by a wave having a prescribed spatial frequency. For example, a displacement amount calculated by setting a value obtained by reasonably considering a maximum value of a gradient of the film thickness deviation as a safety rate can be applied as a period, and a fringe image constituted by a luminance distribution represented by a sine wave adopted in the entire region can be applied as the background image. As a method using the wavelet analysis in the BOS method related to a fluid, for example, a method described in Non-Patent Literature 1 can be exemplified.

[0108] Here, the continuous wavelet transform is represented by the following equation (6).

[0109] [Equation 7]

[0110] where n denotes the number of elements of a column, xi denotes the i-th luminance, and Ψ(i) denotes a mother wavelet. Further, a conjugate complex of the wavelet function is represented by ψ with an overline (superscript bar). The reciprocal of the scale parameter a corresponds to a frequency. The shift parameter b corresponds to a spatial coordinate.

[0111] The mother wavelet Ψ(i) proposes various functions, and for example, a complex wavelet function of Morlet represented by the following equation (7) can be exemplified.

[0112] [Equation 8]

[0113] In the continuous wavelet transform, one-dimensional luminance distributions along the direction of the fringe are extracted from the reference image and the measurement image. Further, when the continuous wavelet transform is performed, intensities with respect to the frequency and the spatial coordinate can be obtained. As for the displacement amount of the background, the phase of the luminance distribution in each spatial coordinate can be calculated from the spatial distribution of the intensity obtained by the wavelet transform, and the displacement amount of the background can be calculated from the phase difference between the reference image and the measurement image. However, it is preferable to directly obtain the phase information in addition to the intensity when the continuous wavelet transform is performed by using the complex wavelet function, and the displacement amount of the background is calculated from the phase difference between the reference image and the measurement image. If the phase difference is multiplied by the period of the luminance distribution, the displacement amount Δh on the background image 22 is obtained. Further, as a function representing the luminance distribution of the background image 22, in a case where a specific function is used instead of the sine wave, a complex mother wavelet similar to the function is preferably used. Further, particularly in a case where the frequency of the fringe caused by the film thickness deviation does not greatly vary, even if the size of the window is constant with respect to the frequency, the influence does not become large. Therefore, by using the short-time Fourier transform instead of the continuous wavelet transform, the installation becomes simple.

[0114] [Calculation of film thickness deviation]

[0115] The film thickness deviation can be calculated using the displacement amount Ah of the background thus calculated. However, for example, the following (8) formula can be exemplified, which sets an integral path that first advances in the length direction of the measured object as a thin film from the origin, and then advances in a direction orthogonal to the outward direction.

[0116] [Equation 9]

[0117] Here, t(x, y): film thickness deviation obtained by subtracting the film thickness of the measured object at the origin (0, 0) from the film thickness of the measured object at the coordinates (x, y) n target : refractive index of the measured object n air : refractive index of the atmosphere d: distance between the background image and the measured object Ah: two-dimensional vector representing the displacement amount of the background image of interest on the measurement image with respect to the same background image in the reference image Ahx: x-direction component of the displacement amount of the background Ax: x-direction length of each pixel

[0118] The integral path is specifically drawn in the (8) formula. However, more generally, for example, it can be expressed in the form of the following (1) formula.

[0119] [Equation 10]

[0120] Here, t: film thickness deviation obtained by subtracting the film thickness of the measured object at the origin from the film thickness of the measured object at the measurement point n target : refractive index of the measured object n air : refractive index of the atmosphere d: distance between the background image and the measured object Ah: two-dimensional vector representing the displacement amount of the background image of interest on the measurement image with respect to the same background image in the reference image v: unit tangent vector of the path C cAh vdl: operation of line integrating the inner product of the Ah and the v over the integral path C from the origin toward the measurement point.

[0121] (Action, etc.)​

[0122] The film thickness deviation of the measured object obtained by the above method can be displayed by a known visualization method.

[0123] In a case where the film thickness deviation is calculated only for a specific one direction, it is preferable to be represented by a line graph. In addition, in a case where the film thickness deviation is calculated for the directions in the plane, it is preferable to be displayed in a heat map or by superimposing line graphs.

[0124] At this time, the film thickness deviation is, for example, a value obtained by subtracting the film thickness of the measured object at the origin from the film thickness of the measured object at the measurement point. Therefore, it is sometimes more preferable to represent the film thickness by an absolute value by adding the film thickness of the measured object at the origin calculated by a suitable method.

[0125] As a method of obtaining the film thickness of the measured object at the origin, a method of measuring only one point by a known film thickness meter of a contact type or a transmission type, a method of adopting a nominal film thickness regardless of the actual film thickness can be exemplified.

[0126] (Thin film manufacturing apparatus (thin film manufacturing method))

[0127] Next, the thin film manufacturing apparatus (thin film manufacturing method) of the present embodiment will be described.

[0128] Figure 4 A schematic structure of the thin film manufacturing apparatus 30 of the present embodiment is shown.

[0129] The thin film manufacturing apparatus 30 of the present embodiment has an extruder 35, a T-die 36, a cooling roll 37, a stretching machine 38, and a winding machine 39. The T-die 36 has a plurality of die lip gap adjustment units 361. In addition, the thin film manufacturing apparatus 30 of the present embodiment has a film thickness deviation measuring apparatus. The film thickness deviation measuring apparatus has the background image 32, the photographing unit 33, and the arithmetic unit 34 of the above-described structure. The reference numeral 40 is a die lip gap adjustment section.

[0130] <Extruder>

[0131] The extruder 35 has one or more hoppers or hoppers, and melts and kneads a plurality of resins and fillers as necessary. The extruder 35 can be any one of a single screw extruder or a twin screw extruder, and can be a multi-stage type. In addition, a plurality of extruders 35 can be provided and connected to the T-die 36. Note that, in order to improve the quality of the discharged resin and stabilize the extrusion amount, a filter, a degassing section, and a gear pump are preferably provided. The extruder 35 can adopt a known structure.

[0132] <T-die>

[0133] The T-die 36 discharges the molten resin extruded from the extruder 35 through a gap, continuously forming a resin film of the target film thickness. When the manufactured film has a multi-layer structure, either the feed block method or the manifold method can be applied. The feed block method involves converging the molten resin in front of the T-die. The manifold method involves expanding a single layer within the T-die and then converging it near the die lip.

[0134] [Die Lip Gap Adjustment Unit 361]

[0135] Multiple die lip gap adjustment units 361 are provided along the length of the die lip of the T-shaped mold 36. The die lip gap adjustment units 361 adjust the width of the die lip gap according to the instructions from the die lip gap adjustment section 40 or by manual operation, thereby adjusting the film thickness of the molten resin (film).

[0136] The die lip gap adjustment unit 40 generates and outputs instructions for feedback control of the film thickness based on the film thickness deviation in the width direction from the calculation unit 34.

[0137] As the die lip clearance adjustment mechanism of the die lip clearance adjustment unit 361, a known method can be used. Preferred examples of such mechanisms include methods that change the pressing amount by rotating the bolt after thread cutting, hot bolts that expand and contract due to thermal expansion and contraction caused by a built-in cylindrical heater, and methods that adjust by applying hydraulic pressure to the bolt or T-shaped die.

[0138] <Cooling Roller 37>

[0139] Cooling roller 37 cools and solidifies the molten resin discharged from the die lip gap of T-shaped mold 36, forming a film.

[0140] For the purpose of suppressing film thickness variations or improving surface properties, the cooling roller 37 preferably includes a pinning device or a contact roller with electrostatic application, suction chamber, or air knife methods. Additionally, to increase the cooling rate of the molten resin, a portion of the cooling roller can be immersed in water or sprayed with water.

[0141] <Stretching Machine 38>

[0142] The stretching machine is a device for stretching the film formed by the cooling roller 37. The stretching process can be performed as needed, or the produced film may not need to be stretched. The stretching machine 38 constitutes the stretching process.

[0143] When stretching is performed using the stretching machine 38, stretching in the conveyance direction (MD direction: length direction) and stretching in the width direction (TD direction) can be applied individually or in combination. That is, a method of stretching only in the MD direction, a method of stretching only in the TD direction, or a method of sequentially stretching in the MD direction and the TD direction, a method of simultaneously stretching in the MD direction and the TD direction, and the like. Further, various stretching methods such as a method of sequentially stretching in the MD direction and the TD direction and then re-stretching in the MD direction or the TD direction can be applied. As for the stretching process, a stretching method is preferably selected including no stretching, according to the resin type and the use of the film.

[0144] In addition, as for the longitudinal stretching of stretching in the MD direction, a one-stage stretching using a pair of rollers provided with a speed difference and a multi-stage stretching using a plurality of pairs of rollers can be exemplified. These can be appropriately used. Further, as for the film heating method for stretching, a method of using a preheating roller, a method of heating in a non-contact manner using an infrared heater or the like, and the like can be exemplified. These can be appropriately used. Further, a surface treatment such as a heat fixation process of relaxing while heating, a corona treatment, or the like can be performed near the outlet of the stretching machine 38. Note that the measured value of the film thickness deviation obtained by the film thickness deviation measuring device can be used for the control of the stretching machine 38.

[0145] <Winding machine 39>

[0146] The winding machine 39 is a device that winds the manufactured film into a roll shape. The film wound into a roll shape becomes a product for shipment.

[0147] It is preferable that a quality assurance device such as a surface inspection device, a pinhole inspection device, a film thickness gauge, or the like be provided immediately before the winding machine 39. In addition, it is preferable that a desired product width be formed by a slitting machine or a trimmer. In order to prevent a dark band at the time of winding, oscillation winding can be performed.

[0148] <Thickness deviation measuring device>

[0149] The thickness deviation measuring device can adopt the same structure as the thickness deviation measuring device of the above-described embodiment.

[0150] The background image and the photographing mechanism (photographing unit) are disposed opposite each other with respect to the route of the film. In Figure 4In the example of FIG. 1, the background image 32 and the photographing unit 33 are arranged at a position on the route between the chill roller 37 and the stretching machine 38. However, the background image 32 and the photographing unit 33 can also be arranged just before or downstream of the stretching machine 38. That is, the setting position of the film thickness deviation measuring section constituted by the background image 32 and the photographing unit 33 can be set at any position from the downstream of the T die 36 to the upstream of the winding machine 39. In consideration of the rapidity of feedback control and the case where the refractive index of the film 31 changes due to the processing by the stretching machine 38, it is preferable to set it upstream of the stretching machine 38. In addition, if the distance between the die lip of the T die 36 and the chill roller 37 is lengthened by providing the background image 32 and the photographing unit 33, the film thickness unevenness in the MD direction or the necking in the TD direction can possibly become large. Therefore, the film thickness deviation measuring section is preferably set downstream of the chill roller 37.

[0151] As with the above, the background image 32 is only an image that can detect the displacement amount when the position on the measurement image changes depending on the presence or absence of the film 31. In particular, as the background image 32, a random dot image or a stripe image having a periodic brightness distribution is preferable from the viewpoint of resolution.

[0152] As with the above, various digital cameras can be applied to the photographing unit 33. In the present example, in particular, by using a line camera, an improvement in processing speed and a reduction in equipment cost can be expected. The photographing unit 33 can also be a collection of a plurality of cameras.

[0153] In addition, by making the photographing unit 33 also function as a surface inspection device, foreign matter, defects, and the like can be detected early. In this case, a surface inspection operation section (not shown) that performs aspect inspection based on the image photographed by the photographing unit 33 is provided.

[0154] The background image 32 and the photographing unit 33 are preferably installed to the same structure. In this case, the positional displacement of the background image 32 and the photographing unit 33 caused by vibration and the like during operation can be suppressed. Furthermore, this structure installed for the purpose of correcting the positional displacement is more preferably a mechanism that can be pulled out offline during operation to photograph a reference image.

[0155] In addition, from the viewpoint of analysis operation and the viewpoint of preventing defocus, it is preferable to set the optical axis of the photographing unit 33 orthogonal to the film 31 and the background image 32. The axes connecting the film 31, the background image 32, and the photographing unit 33 can also be arranged vertically as in FIG. 1. However, the axes can also be set horizontally or at any arbitrary angle depending on the constraints of the setting environment and the like. Figure 4

[0156] ​In the gap between the film 31 and the background image 32 or between the film 31 and the photographing unit 33, there can be another structure which transmits visible light such as a glass window. However, the structure needs to be able to recognize the film 31 and the background image 32 by the photographing unit 33. In addition, in the case where the structure has a film thickness deviation, it is preferable to correct the displacement amount of the background image 32 or the film thickness deviation of the film 31 calculated. However, in the case where the distance between the background image 32 and the structure is short and the calculation result of the film thickness deviation of the measured object 31 has only an allowable influence, the correction can not be performed. In addition, it is more preferable that the structure has no film thickness deviation.

[0157] In the calculation unit 34, as described above, the film thickness deviation of the film is calculated by calculating the displacement amount of the background between the reference image and the measurement image. Then, the information of the film thickness deviation in the width direction of the film is supplied to the die lip gap adjustment unit 40.

[0158] As described above, the reference image is an image photographed or an image derived by calculation.

[0159] In addition, as described above, the measurement image is an image obtained by photographing the background image 32 by the photographing unit 33 with the film 31 interposed. In this example, the measured object is transported along the route at a predetermined transport speed. The transport speed at the film thickness deviation measurement position can be relatively slowed down by a ring beater device or the like.

[0160] As for the method of calculating the displacement amount of the background image between the reference image and the measurement image, various known methods can be employed as described above. However, in this example, the information of the film thickness deviation is fed back to the control of the die lip gap adjustment unit. From this viewpoint, it is preferable to calculate the film thickness deviation only in the TD direction. In addition, in the calculation of the displacement amount of the background image, it is particularly preferable to use wavelet analysis or short-time Fourier analysis.

[0161] The film thickness deviation is calculated using the displacement amount of the background image calculated by the above-described method. As for the calculation method, various integration paths can be employed as described above. However, in this example, from the viewpoint of feeding back the film thickness deviation to the control of the die lip gap adjustment unit, it is preferable to calculate only in the TD direction. For example, it is more preferable to use the following equation (9).

[0162] [Equation 11]

[0163] Herein, t(x): film thickness deviation obtained by subtracting the film thickness of the film 31 at the origin x = 0 from the film thickness of the film 31 at the TD direction coordinate x n target : refractive index of the film 31 n air : refractive index of atmosphere d: distance between background image 32 and film 31 Δhx: TD direction moving distance of background image focused on in measurement image with respect to same background image in reference image Δx: x direction length of each pixel

[0164] The film thickness deviation of film 31 obtained by the above method can be expressed by a known visualization method.

[0165] In the present embodiment, from the viewpoint of feeding back the information of the calculated film thickness deviation to the control of the die lip gap adjusting units, it is preferable to display only the TD direction. Further, in order to know the fluctuation of the film thickness deviation caused by the passage of time, it is more preferable to display a broken line graph in which the TD direction coordinate is set as the horizontal axis and the film thickness deviation is set as the vertical axis, while changing the color of the line with the passage of time.

[0166] In the die lip gap adjusting section 40, the actual film thickness deviation curve of film 31 obtained as described above is compared with the ideal film thickness deviation curve of film 31 inputted to the arithmetic section 34 in advance. Further, in order to make the portion where the actual film thickness is thinner than the ideal film thickness thicker, the die lip gap adjusting units 361 are controlled in such a manner that the die lip gap corresponding to the TD direction coordinate is increased. Further, in order to make the portion where the actual film thickness is thicker than the ideal film thickness thinner, the die lip gap adjusting units 361 are controlled in such a manner that the die lip gap corresponding to the TD direction coordinate is decreased. That is, the measured film thickness deviation curve is compared with the ideal film thickness deviation curve, and the difference of the film thickness at the position corresponding to each die lip gap adjusting unit 361 in the film width direction is calculated. Then, each die lip gap adjusting unit 361 is feedback controlled so that the difference converges to a prescribed range.

[0167] Here, the film is necked at the time of discharge from the T-shaped die, etc. Therefore, the distance from the TD direction central portion of film 31 to a specific position at the time of photographing by the photographing unit 33 is generally different from the distance from the TD direction central portion of the molten resin to the specific position at the time of discharge from the die lip of the T-shaped die. Therefore, in the die lip gap adjusting section 40, as to which die lip gap adjusting unit 361 should be instructed when the difference between the actual film thickness deviation and the ideal film thickness deviation is detected in a specific TD direction coordinate, it is preferable to perform the correspondence by a known various method.

[0168] Furthermore, it is known that instead of moving only one die lip gap adjustment unit 361, multiple die lip gap adjustment units 361 are moved simultaneously to improve accuracy, taking into account the influence coefficient. Therefore, it is preferable to perform weighted calculations based on various known methods, and simultaneously operate multiple die lip gap adjustment units 361.

[0169] The embodiments for carrying out the present invention have been described above. However, the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the invention. Furthermore, the films described above contain a resin composition commonly referred to as a sheet due to their thickness.

[0170] (other)

[0171] This disclosure may also take the following structure.

[0172] (1) A method for measuring film thickness deviation, which is a method for measuring the film thickness deviation of a thin film, wherein, The thin film of the object being measured is used as the analyte. It can capture a pre-set background image using the shooting unit. A reference image is obtained, which is either an image captured by the imaging unit without the object being measured being held in place, or an image obtained by calculating and deriving the background image without the object being measured being held in place, based on the visual representation of the imaging unit. A measurement image is obtained by capturing the background image using the imaging unit while the object being measured is sandwiched between the background image and the imaging unit. Based on the obtained reference image and measurement image, the displacement of the background image in the two images is calculated, thereby determining the film thickness deviation of the measured object.

[0173] (2) The film thickness deviation is calculated using equation (1) above.

[0174] (3) The integration path C is a path that moves from the origin to the first direction and then to the second direction. The first direction is either the length direction of the object being measured or a direction orthogonal to the length direction of the object being measured. The second direction is a direction orthogonal to the first direction.

[0175] (4) A method for measuring the film thickness deviation of the object to be measured, which is transported between the background image and the imaging unit. When the film thickness deviation of the test object to be measured is the film thickness deviation in the width direction of the test object. The integral path C is a line segment advancing from the origin in a direction orthogonal to the conveying direction.

[0176] (5) The background image is a random dot image, The displacement amount Δh of the background image is calculated by template matching using a normalized cross-correlation coefficient.

[0177] (6) The background image is a stripe image having a periodic brightness distribution constituted by waves having a prescribed spatial frequency, The displacement amount Δh of the background image is calculated by wavelet analysis.

[0178] (7) The visible light transmittance of the measured object is 10% or more.

[0179] (8) A film manufacturing method of extruding molten resin from a mold having a plurality of die lip gap adjustment units to form a film capable of transmitting visible light, wherein The film extruded from the mold is conveyed along a predetermined route, A background image and a photographing unit that photographs the background image are arranged across the route, The film manufacturing method includes the following steps: A measurement image is obtained, which is an image obtained by the photographing unit photographing the background image across the film; A reference image is obtained, which is an image obtained by the photographing unit photographing the background image in a state where the film is not interposed between the background image and the photographing unit, or is an image obtained by calculating a visual representation of the photographing unit in a state where the film is not interposed between the background image and the photographing unit; and The obtained reference image and the obtained measurement image are compared, and a film thickness deviation curve in the width direction of the film is calculated by calculating a displacement amount of the background image in the width direction of the film between the two images; and Based on the calculated film thickness deviation curve, the die lip gap adjustment units are operated in a manner in which the film thickness deviation of each point of the film becomes a target value.

[0180] (9) The visible light transmittance of the film formed by extrusion from the mold is 10% or more, The film manufacturing method includes a stretching step of stretching the film at a position in the route that is more downstream than the position at which the measurement image is obtained.

[0181] (10) A film thickness deviation measuring device is a film thickness deviation measuring device for a film that transmits visible light, wherein A film to be measured is used as a measured object, The film thickness deviation measuring device includes: a background image; a photographing unit that photographs the background image; a reference image acquisition unit that acquires a reference image, the reference image being an image obtained by photographing the background image by the photographing unit in a state in which the measured object is not sandwiched or an image obtained by calculating a visual representation of the photographing unit in a state in which the background image is not sandwiched by the measured object; a measurement image acquisition unit that acquires a measurement image, the measurement image being an image obtained by photographing the background image by the photographing unit in a state in which the measured object is sandwiched between the background image and the photographing unit; and a film thickness deviation calculation unit that calculates a displacement amount of the background image in the two images based on the acquired reference image and measurement image, and thereby calculates a film thickness deviation of the measured object.

[0182] (11) The background image is a random dot image.

[0183] (12) The background image is a fringe image having a periodic brightness distribution composed of waves having a prescribed spatial frequency.

[0184] (13) The measured object has a visible light transmittance of 10% or more.

[0185] (14) A thin film manufacturing device that extrudes molten resin from a mold having a plurality of die lip gap adjustment units to form a thin film capable of transmitting visible light, wherein the thin film extruded from the mold is conveyed along a predetermined route, a background image and a photographing unit that photographs the background image are arranged across the route, the thin film manufacturing device includes a measurement image acquisition unit that acquires a measurement image, the measurement image being an image obtained by photographing the background image by the photographing unit across the thin film; a reference image acquisition unit that acquires a reference image, the reference image being an image obtained by photographing the background image by the photographing unit in a state in which the thin film is not sandwiched between the background image and the photographing unit or an image obtained by calculating a visual representation of the photographing unit in a state in which the background image is not sandwiched by the thin film; and a film thickness deviation information acquisition unit that compares the acquired reference image and the acquired measurement image, calculates a film thickness deviation curve in a width direction of the thin film by calculating a displacement amount of the background image in the width direction of the thin film between the two images; and The die lip gap adjustment section adjusts the die lip gap based on the calculated film thickness deviation curve so that the film thickness deviation at each point becomes a target value.

[0186] (15) The film formed by ejecting from the mold has a visible light transmittance of 10% or more, A stretching machine is provided downstream of the position at which the image is taken by the imaging unit in the route, and the stretching machine stretches the film.

[0187] Embodiment

[0188] Hereinafter, an embodiment based on the present embodiment will be described. However, the following embodiment is merely an example of a more detailed description of the present application and does not limit the scope of the present application.

[0189] (Measurement conditions of the present embodiment)

[0190] In the present embodiment, as the film to be measured 21, a PET film is used as an object. In addition, as the background image 22, a photograph of a random dot image is used. As the imaging unit 23, a single-lens reflex camera is used. Furthermore, as shown in FIG. 1, the imaging unit 23 composed of the single-lens reflex camera, the film to be measured 21 composed of the PET film, and the background image 22 composed of the random dot image are arranged in the vertical direction. The vertical direction refers to a direction orthogonal to the surface of the background image 22. Figure 2

[0191] In this case, the PET film of the present embodiment is an unstretched film having an average film thickness of 95 μm formed by a T-die method. The PET film has a film thickness standard deviation of 1.8 μm in the MD direction and a film thickness standard deviation of 25 μm in the TD direction.

[0192] The PET film is arranged 50 mm apart from the random dot image, and the PET film is arranged 600 mm apart from the single-lens reflex camera.

[0193] (Measurement processing of film thickness deviation)

[0194] First, the reference image is obtained by taking the photograph of the background image in a state where the PET film is not present. That is, the photograph of the random dot image is taken by the single-lens reflex camera without passing through the PET film.

[0195] Next, the measurement image is obtained by taking the photograph of the background image in a state where the PET film is present. That is, the photograph of the random dot image is taken by the single-lens reflex camera with passing through the PET film.

[0196] Then, the two obtained images are taken into a personal computer, and the calculation processing performed by the calculation section 24 is performed to calculate the film thickness deviation.

[0197] ​In this example, first, the displacement amounts in the MD and TD directions of the background image between the two images are calculated respectively by pattern matching using ZNCC. Figure 5 The background displacement distribution showing the calculated displacement amounts is shown. ZNCC is a normalized cross-correlation of a template matching method.

[0198] Next, the film thickness deviation of each point is calculated using the above-described formula (8) from the background displacement distribution, and the film thickness deviation distribution shown in Figure 6 is obtained.

[0199] In addition, in Figure 5 and Figure 6 , the lateral direction is the MD direction, and the longitudinal direction is the TD direction. In addition, in Figure 5 and Figure 6 , the both end portions in the MD direction are regions where the film is not present and the background image is directly seen. The light and dark indicate the background displacement or the film thickness deviation.

[0200] As is clear from Figure 6 , the PET film used in this example has almost no film thickness variation in the MD direction. On the other hand, a periodic film thickness variation is observed in the TD direction.

[0201] Furthermore, it was confirmed that the period of the film thickness variation in the TD direction coincides with the interval of the heating bolts provided to the T-die, and reflects the width of the T-die lip gap caused by the heating bolts.

[0202] As described above, it is clear that by using the present application, the film thickness deviation data (information of the film thickness deviation) in one-dimensional or two-dimensional directions along the film surface can be non-contact measured with a simple and safe device structure.

[0203] Herein, the entire contents of Japanese Patent Application No. 2023-110735 (filed on July 5, 2023) from which priority is claimed are incorporated herein by reference as part of the disclosure. Herein, a limited number of embodiments are described by way of illustration, but the scope of the right is not limited thereto, and it will be obvious to those skilled in the art that modifications based on the above-described disclosed embodiments are possible.

[0204] Explanation of Reference Numerals

[0205] 20 film thickness deviation measuring device

[0206] 21 object to be measured

[0207] 22 background image

[0208] 23 imaging unit

[0209] 24 arithmetic unit

[0210] 24A reference image acquisition section

[0211] 24B measurement image acquisition section

[0212] 24C film thickness deviation calculation section

[0213] 25 stand

[0214] 25A top plate surface

[0215] 30 thin film manufacturing apparatus

[0216] 31 thin film (object to be measured)

[0217] 32 background image

[0218] 33 imaging unit

[0219] 34 arithmetic section

[0220] 35 extruder

[0221] 36 T-die

[0222] 37 cooling roll

[0223] 38 stretching machine

[0224] 39 winding machine

[0225] 40 die lip gap adjustment section

[0226] 361 die lip gap adjustment unit

Claims

1. A film thickness deviation measurement method, which is a film thickness deviation measurement method of a thin film, wherein a thin film to be measured is taken as a measured object, a pre-set background image is photographed by a photographing unit, a reference image is obtained, which is an image obtained by photographing the background image by the photographing unit in a state where the measured object is not sandwiched, or is an image obtained by calculating based on a visual appearance of the photographing unit in a state where the background image where the measured object is not sandwiched, a measurement image is obtained, which is an image obtained by photographing the background image by the photographing unit with the measured object sandwiched between the background image and the photographing unit, a displacement amount of the background image in the obtained reference image and measurement image is calculated, and a film thickness deviation of the measured object is obtained.

2. The film thickness deviation measurement method according to claim 1, wherein the film thickness deviation is obtained using the following (1) formula, [mathematical formula 1] t = ∫C (d + Δh) · v |v| dh wherein, t: film thickness deviation obtained by subtracting a film thickness of the measured object at an origin from a film thickness of the measured object at a measurement point d: distance between the background image and the measured object Δh: two-dimensional vector representing a displacement amount (movement amount) of a background image of interest on the measurement image with respect to the same background image in the reference image n target : refractive index of the measured object n air : refractive index of the atmosphere v: unit tangent vector of a path C 3. The film thickness deviation measurement method according to claim 2, wherein the integral path C is a path advancing from a pre-set origin in a first direction, and then advancing in a second direction, the first direction being either one of a length direction of the measured object and a direction orthogonal to the length direction of the measured object, and the second direction being a direction orthogonal to the first direction.

4. The film thickness deviation measurement method according to claim 2, wherein the film thickness deviation measurement method is a film thickness deviation measurement method of the measured object transported between the background image and the photographing unit, " c Δh vdl": an operation of line-integrating the inner product of the Δh and the v over the integral path C from the origin toward the measurement point. in a case where the film thickness deviation of the measured object to be measured is a film thickness deviation in a width direction of the measured object, the integral path C is a line segment advancing from the origin in a direction orthogonal to a transport direction.

5. The film thickness deviation measurement method according to any one of claims 1 to 4, wherein the background image is a random dot image, the displacement amount Δh of the background image is calculated by template matching using a normalized cross-correlation coefficient.

6. The film thickness deviation measurement method according to any one of claim 1, claim 2, or claim 4, wherein the background image is a fringe image having a periodic luminance distribution composed of waves having a prescribed spatial frequency, the displacement amount Δh of the background image is calculated by wavelet analysis.

7. The film thickness deviation measurement method according to any one of claims 1 to 6, wherein a visible light transmittance of the measured object is 10% or more.

8. A thin film manufacturing method of forming a thin film capable of transmitting visible light by ejecting molten resin from a mold having a plurality of die lip gap adjustment units, wherein ​ ​ ​ ​ ​ ​ ​ The film extruded from the die is transported along a predetermined route, A background image and a photographing unit that photographs the background image are arranged across the route, The film manufacturing method includes the following steps: A measurement image is obtained, which is an image obtained by the photographing unit photographing the background image across the film; A reference image is obtained, which is an image obtained by the photographing unit photographing the background image without the film being sandwiched therebetween or is an image obtained by calculating the background image in the state where the film is not sandwiched based on the visual performance of the photographing unit; The obtained reference image and the obtained measurement image are compared, and the displacement amount of the background image in the film width direction between the two images is calculated to obtain a film thickness deviation curve in the film width direction; and Based on the calculated film thickness deviation curve, the die lip gap adjustment unit is operated in a manner in which the film thickness deviation of each point of the film is a target value.

9. The film manufacturing method according to claim 8, wherein The film formed by extrusion from the die has a visible light transmittance of 10% or more, The film manufacturing method includes a stretching step of stretching the film at a position downstream of the position at which the measurement image is obtained in the route.

10. A film thickness deviation measuring device that measures the film thickness deviation of a film that transmits visible light, wherein A film to be measured is used as a measured object, The film thickness deviation measuring device includes: A background image; A photographing unit that photographs the background image; A reference image obtaining section that obtains a reference image, which is an image obtained by the photographing unit photographing the background image in a state where the measured object is not sandwiched therebetween or is an image obtained by calculating the background image in the state where the measured object is not sandwiched based on the visual performance of the photographing unit; A measurement image obtaining section that obtains a measurement image, which is an image obtained by the photographing unit photographing the background image in a state where the measured object is sandwiched between the background image and the photographing unit; and A film thickness deviation calculating section that calculates the displacement amount of the background image between the obtained reference image and measurement image to obtain the film thickness deviation of the measured object.

11. The film thickness deviation measuring device according to claim 10, wherein The background image is a random dot image.

12. The film thickness deviation measuring device according to claim 10, wherein The background image is a stripe image composed of waves having a predetermined spatial frequency and having a periodic luminance distribution.

13. The film thickness deviation measuring device according to any one of claims 10 to 12, wherein The measured object has a visible light transmittance of 10% or more.

14. A film manufacturing device that forms a film that transmits visible light by extruding molten resin from a die having a plurality of die lip gap adjustment units, wherein The film extruded from the die is transported along a predetermined route, The film formed by extrusion from the die has a visible light transmittance of 10% or more, A background image and a photographing unit that photographs the background image are arranged across the route, The film manufacturing apparatus includes: a measurement image acquisition section that acquires a measurement image, the measurement image being an image obtained by the photographing unit photographing the background image across the film; a reference image acquisition section that acquires a reference image, the reference image being an image obtained by the photographing unit photographing the background image in a state where the film is not interposed between the background image and the photographing unit or being an image obtained by calculating a visual appearance of the background image in a state where the film is not interposed based on the photographing unit; and a film thickness deviation information acquisition section that compares the acquired reference image and the acquired measurement image, calculates a film thickness deviation curve of the film in the width direction by calculating a displacement amount of the background image in the width direction of the film between the two images, and a die lip gap adjustment section that operates the die lip gap adjustment unit so that the film thickness deviation of each point becomes a target value based on the calculated film thickness deviation curve.

15. The film manufacturing apparatus according to claim 14, wherein a visible light transmittance of the film formed by being ejected from the die is 10% or more, a stretching machine that stretches the film is provided in the route downstream of the position at which the image is acquired by the photographing unit.

Images