JPH11101615A - Film thickness control device for sheet forming machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the thickness of a sheet immediately after being formed and the surface displacement of a slurry by measuring the thickness of the wet sheet formed on a first coating tool via the interference between two light fluxes in no contact, and comparing the thickness of the sheet measured by displacing a second coating tool with a target value. SOLUTION: A coating roll 3 is rotated in no-slurry state to measure the irregularities on the surface of the coating roll 3, and an interference optical system 15 is moved in the Z-direction to the position where 0-order interference fringes are visible on the surface of the coating roll 3. Light is fed from a light source 11 and is photographed by a CCD camera 19 to measure the relation between the roll angle and the height of the roll surface. A ceramic slurry 2 is filled in a slurry reservoir 1, and sheet forming is started. Light is fed from the light source 11 and is photographed by the CCD camera 19 to measure the relation between the roll angle and the height of the roll surface. The difference between the roll surface at the same roll angle and the height of the sheet surface, i.e., film thickness, is obtained, and it is compared with a target value to accurately control the sheet thickness at the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness control device for a sheet forming machine, for example, a device for controlling a film thickness of a sheet such as a ceramic green sheet.

[0002]

2. Description of the Related Art Conventionally, ceramic green sheets have been used in manufacturing multilayer ceramic capacitors and ceramic multilayer substrates. To produce a ceramic green sheet, a ceramic slurry is obtained by mixing a ceramic raw material powder adjusted to a required composition and a binder solution with each other, and then a transfer type sheet forming machine called a blade coater or a reverse roll coater. Is used to form a ceramic slurry into a sheet to obtain a ceramic green sheet.

[0003]

In controlling the film thickness of such a green sheet, it is common to measure the thickness of the dried sheet and control the molding conditions based on the thickness. However, in such a method, the thickness of the sheet cannot be measured until after drying, and thus the efficiency of the thickness control is poor.

On the other hand, there is a method in which a slurry-like green sheet immediately after molding is measured in a wet state by using a laser displacement meter. However, since the laser displacement meter (geometric measurement) is strongly affected by the scattered light of the particles inside the slurry, there has been a problem that accurate measurement of the sheet surface cannot be performed.

Accordingly, an object of the present invention is to provide a film thickness control apparatus for a sheet forming machine capable of measuring the thickness of a wet sheet immediately after molding and accurately measuring the surface displacement of slurry.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is a sheet forming machine for forming a slurry material into a sheet through a pair of coating tools arranged at a certain distance from each other. A sheet is formed on a first coating tool of the pair of coating tools, and the thickness of the sheet can be adjusted by displacing the second coating tool in a thickness direction of the sheet. A measuring means for measuring the film thickness of the wet sheet formed on the first coating tool in a non-contact manner by using interference of two light beams, and a second coating tool in a direction facing the first coating tool; A controller for displacing and adjusting the film thickness of the sheet, comparing the film thickness of the sheet measured by the measuring means with a target value, and supplying a command signal corresponding to the deviation to the actuator. Means and A film thickness control apparatus according to symptoms.

According to the apparatus of the present invention, the thickness of the sheet in the wet state immediately after molding is measured by the measuring means utilizing two-beam interference, so that the thickness of the sheet after drying is measured as compared with the case of measuring the thickness of the sheet after drying. Thickness control can be started immediately. Further, since the interference of white light is used for the film thickness measurement, the sheet surface displacement can be accurately measured without being strongly affected by the scattered light of the particles inside the slurry as in the case of the geometric measurement using a laser. Moreover, unlike the case of using laser (single-wavelength) interference, an absolute distance index (reference optical path length) can be used, which is suitable for measurement of an unstable surface such as a liquid surface. is there. The thickness of the sheet measured by the measuring means is compared with a target value, a command signal corresponding to the deviation is supplied to the actuator, and the second coating tool is displaced in a direction facing the first coating tool. By adjusting the thickness of the sheet, the thickness of the sheet can be accurately controlled to a target value. As a specific film thickness measuring method,
If the coating tool is a roll, measure the relationship between the roll rotation angle and the roll surface displacement before coating, and determine the difference between the slurry surface position during coating and the roll surface position at that rotation angle. The thickness may be determined by obtaining the thickness. In the present invention, the term “slurry” refers to a state in which solid particles are dispersed in a liquid.

In the sheet forming machine according to the present invention, the first coating tool comprises a coating roll, and the second coating tool comprises a doctor blade. The sheet formed on the coating roll is transferred to a continuous web. It may be a blade coater, the first coating tool is a coating roll, and the second coating tool is a metalling roll rotating in the opposite direction to the coating roll, and is formed on the coating roll. A reverse roll coater for transferring a sheet to a continuous web may be used. In any case, since the surface unevenness of the coating roll is small, highly accurate film thickness control is possible.

Generally, it is said that the measuring means of the two-beam interference optical system has a narrow measuring range (for example, about 2 μm). Therefore, by moving the interference optical system with respect to the first coating tool by the actuator so that the interference fringes fall within the measurement range, it is possible to expand the measurement range of the displacement.

As the measuring means, as described in claim 5, one light source, means for optically dividing light from the light source into monochromatic light and multicolor light through a filter, and monochromatic light and multicolor light are used. Are input in parallel, split into two beams,
A two-beam interference optical system that reflects one on the sheet surface and reflects the other on the reference surface, and an interference fringe image of the light reflected on the sheet surface and the light reflected on the reference surface were captured at the same time. Means for individually obtaining the monochromatic light image and the multicolor light image, means for detecting the position of the zero-order interference fringe from the maximum luminance position of the multicolor light image, and the position of the interference fringe at the sheet measurement point of the monochromatic light image. A means for measuring the displacement of the sheet measurement point from the position corresponding to the zero-order interference fringe is desirable. That is, the monochromatic light and the multicolor light are split into two light beams, respectively, and one is reflected by the sheet surface, and the other is reflected by the reference surface in the interference optical system. The monochromatic light and the multicolor light are superimposed, and an interference fringe image of the light reflected on the sheet surface and the light reflected on the reference surface is decomposed into a plurality of monochromatic light images by an imaging device such as a CCD to obtain, for example, a color image. . In this color image, the wavelengths of all the lights reinforce each other in a portion where the distance dr to the reference surface and the distance ds to the sheet surface are equal, and thus appear as a maximum luminance position, that is, a zero-order interference fringe. On the other hand, an interference fringe image by monochromatic light is obtained as one of the components of the color image. In a color image, since the input light is not a single wavelength, interference fringes are observed only in the vicinity of the 0th-order interference fringes. However, since an interference fringe image due to a single color light has a single wavelength, a clear fringe pattern over a wide range is obtained. Is obtained. In this fringe image, by counting the number of fringes from the position of the zero-order interference fringe obtained from the color image to the position of the interference fringe at the point where the displacement is to be measured, the displacement of the measurement point (reference plane) (Difference between the distance dr to the measurement point and the distance ds to the measurement point). As described above, since the displacement of the sheet surface is detected by simultaneously obtaining the interference fringes by the multi-color light image and the interference fringes by the single-color light image, the dynamic sheet thickness measurement which has been impossible in the related art is performed. Becomes possible.

[0011]

FIG. 1 shows a blade roll coater as an example of a sheet forming machine to which a film thickness control device according to the present invention is applied. As is well known, blade roll coaters
A part of the coating roll 3 is immersed in the ceramic slurry 2 stored in the slurry reservoir 1, and a part of the slurry 2 applied on the coating roll 3 is scraped off by a doctor blade 4 to form a thin film. The sheet 5 is transferred to a carrier film (continuous web) 6 running on the coating roll 3. The sheet 5 transferred to the carrier film 6 is conveyed to a drying step (not shown) and subjected to a drying process. The thickness of the sheet 5 in a wet state immediately before being formed into a sheet on the coating roll 3 and transferred to the carrier film 6 is measured by the measuring device 10.

FIG. 2 is a diagram showing a film thickness control system in the blade roll coater. The measuring device 10 includes, for example, a halogen light source 11 that emits white light. Light from the light source 11 is input to the interference optical system 14 through the filters 12 and 13. The filter 12 is, for example, an interference filter that passes only green light (wavelength: 548 nm, half-value width: 2 nm), and the filter 13 is green light (wavelength: 500 to 6).
This is a magenta filter that cuts (00 nm light).
The light that has passed through the filters 12 and 13 is sent to an interference optical system 15 by, for example, an optical fiber 14.

Inside the interference optical system 15, a beam splitter 16 and a reference surface 17 are provided.
Numeral 5 is movable in the direction of approaching and separating (Z direction) with respect to the coating roll 3 by the first actuator 18. The light that has passed through the filters 12 and 13 is split by the beam splitter 16 into two light beams having the same intensity. One light is reflected by the reference surface 17 and the other light is reflected by the surface of the sheet 5 that is the surface to be measured. . These reflected lights interfere with each other, and the interference fringe image becomes the color C arranged above the interference optical system 15.
The image is captured by the CD camera 19. CCD camera 19
Is for obtaining an image (intensity information) of light in each of the R, G, and B wavelength ranges, and its imaging data is sent to an image processing device 20 such as a personal computer.

In general, the light receiving characteristics of the RGB CCD camera 19 are low in monochromaticity (the light receiving ranges of R, G, and B are wide) as shown in FIG. Therefore, as described above, the filter 12,
13 allows the light on the input side to have the characteristics shown in FIG. 4, and the image of the green light received by the CCD camera 19 has a very high monochromaticity. Therefore, a clear green image can be easily extracted from the color image.

An image processing device 20 processes the image data of the CCD camera 19 and controls an actuator controller 21.
To output a command signal. A detection signal of a detector 22 that detects the rotation angle of the coating roll 3 is input to the image processing device 20, and the interference optical system 15 is controlled by the controller 21 via the controller 21.
The control signal is output to a first actuator 18 for moving the doctor blade 4 in the horizontal direction (X direction) and a second actuator 23 for moving the doctor blade 4 in the horizontal direction (X direction).

Here, a method of measuring the displacement of the surface S to be measured (sheet surface or roll surface) using the interference optical system 15 will be described with reference to FIGS. FIG. 5 shows an RGB color image and a green image at a certain time t = t ₀ , and FIG. 6 shows an RGB color image and a green image after t ₁ second from the time t ₀ . In the green image, a white line represents green and a black line represents black. Beam splitter 16
Ds is the distance from the beam to the surface S to be measured,
Assuming that the distance from 6 to the reference surface 17 is dr (= constant), in the color image captured by the CCD camera 19, the incident light is not a single wavelength, so that interference fringes are observed only near ds = dr. In addition, ds =
In the dr position, red, green, since constructive interference in blue three wavelengths (centerburst) occurs, detects the maximum luminance position as the position of the zero-order interference fringe C _0.
On the other hand, a green image, unlike a color image, has a single wavelength of light, so that a clear interference fringe image can be obtained not only near ds = dr but also around it. Then, the interference fringe interval is a half wavelength of green light, that is, 274 nm. Here, the zero-order interference fringe C of the green image at time t ₀
From position ₀ and the position of the interference fringes C _A measurement point A, to measure the displacement (step) [delta] ₀ and the reference surface 8 and the measurement surface S. FIG.
Since two interference fringes exist between the position of the zero-order interference fringe and the measurement point A, the displacement δ ₀ = 2 × 274 nm = 5
48 nm. Next, based on the RGB color image and the green image after t ₁ second, the measured surface S and the reference
And the displacement (step) δ ₁ with respect to. That is, in FIG.
Position of zero-order interference fringe C ₀ of green image and interference fringe C at measurement point A
_Since there are four interference fringes between _A and _A , the displacement δ ₁
= 4 × 274 nm = 1096 nm. Therefore,
The displacement of the measurement point A for t ₁ second is δ ₁ −δ ₀ = 548 nm
Becomes That is, the measurement point A is displaced by 548 nm toward the beam splitter 16 after t ₁ second. As described above, by continuously photographing the interference fringe image with the CCD camera 19 and performing the above-described analysis, it is possible to track a temporal displacement at an arbitrary measurement point A on the measured surface.

Next, a method for controlling the film thickness of the sheet according to the present invention using the above displacement measuring method will be described. First, the unevenness of the surface of the coating roll 3 is measured. Therefore, the coating roll 3 is rotated without slurry, and the first actuator 18 is driven to move the interference optical system 15 in the Z direction to a position where the zero-order interference fringes on the roll surface can be seen. Then, light enters from the light source 11 and the CCD camera 1
By taking an image at 9, the relationship between the roll angle and the height of the roll surface is measured. Next, the ceramic slurry 2 is put into the slurry reservoir 1, and sheet forming is started. At this time, the first actuator 18 is driven to move the interference optical system 15 in the Z direction to a position where the zero-order interference fringes on the slurry surface can be seen. Then, light is incident from the light source 11 and the CCD
By taking an image with the camera 19, the relationship between the roll angle and the height of the sheet surface is measured. Next, the difference between the height of the roll surface and the height of the sheet surface at the same roll angle, that is, the film thickness of the sheet, is calculated, the film thickness of the sheet is compared with a target value, and a command signal corresponding to the deviation is output to the first signal. 2 to the actuator 23 to displace the doctor blade 4 in the direction of approaching and separating from the coating roll 3. Specifically, the second actuator 23 is feedback-controlled so that the deviation approaches zero. In this way, by displacing the doctor blade 4 in the direction facing the coating roll 3, the thickness of the sheet can be accurately controlled to the target value. Further, since the thickness of the sheet is determined by the difference between the height of the roll surface and the height of the sheet surface, even if the coating roll 3 has wavy irregularities, the doctor blade 4 can be finely controlled in accordance with the unevenness. In addition, fluctuations in the thickness of the sheet can be suppressed.

FIG. 7 shows an example in which the present invention is applied to a reverse roll coater. In the figure, 30 is a slurry reservoir, 3
1 is a coating roll, 32 is a metalling roll, 33 is a backup roll, and a part of the ceramic slurry 34 applied on the coating roll 31 is used as a metalling roll 32.
Then, the sheet 35 is formed into a thin film, and the sheet 35 is transferred to a carrier film (continuous web) 36 running by a backup roll 33. The sheet 35 transferred to the carrier film 36 is conveyed to a drying step (not shown) and subjected to a drying process. Coating roll 31
The thickness of the sheet 35 in a wet state immediately before being formed on the sheet and transferred to the carrier film 36 is measured by the measuring device 40.

FIG. 8 shows a film thickness control system diagram in the reverse roll coater. 8, the same components as those in FIG. 2 are denoted by the same reference numerals, and a duplicate description will be omitted. Also in this case, first, the unevenness of the surface of the coating roll 31 is measured by the measuring device 40 using the two-beam interference system, and the relationship between the roll angle and the height of the roll surface is measured. Next, the slurry reservoir 30
Then, the sheet forming is started by charging the ceramic slurry 34 and the surface displacement of the sheet 35 is measured by the measuring device 40 to measure the relationship between the roll angle and the height of the sheet surface. Next, the difference between the height of the roll surface and the height of the sheet surface at the same roll angle, that is, the thickness of the sheet is obtained, and the second actuator 23 is feedback-controlled so that the thickness of the sheet approaches the target value. Thus, by displacing the metering roll 32 in the direction facing the coating roll 31, the film thickness of the sheet 35 can be accurately controlled to the target value.

The measuring means is not limited to one that separates white light into single-color light and double-color light by the filters 12 and 13 as in the embodiment and then enters the interference optical system 15. The reflected light (interference fringe image) incident on the optical system 15 and reflected from the interference optical system 15 may be optically divided into a monochromatic image and a multicolor image through a filter. In the above embodiment, a known device such as a Millau-type, Watson-type, or Linnik-type may be used as the interference optical system. In addition, green light was used as monochromatic light, but is not limited to this.
Of course, red or blue light may be used. Further, the sheet forming machine of the present invention is not limited to the blade roll coater and the reverse roll coater, and it is needless to say that other known sheet forming machines can be used.

[0021]

As is clear from the above description, according to the present invention, the thickness of the wet sheet immediately after molding is measured by the measuring means utilizing two-beam interference, and thus the thickness of the sheet after drying is measured. , The control of the film thickness of the sheet can be started immediately, and the efficiency of the film thickness control can be improved. Further, since the interference of white light is used for the film thickness measurement, the sheet surface displacement can be accurately measured without being strongly affected by the scattered light of the particles inside the slurry as in the case of the geometric measurement using a laser. Also, unlike the case of using laser (single-wavelength) interference, the absolute distance index (reference optical path length) can be used, so it is suitable for measurement of unstable surfaces such as liquid surfaces. Thickness measurements can also be made. Therefore, the thickness of the sheet can be accurately controlled to the target value.

[Brief description of the drawings]

FIG. 1 is a structural view of a blade roll coater to which a film thickness control device according to the present invention is applied.

FIG. 2 is a system diagram of a film thickness control device in FIG.

FIG. 3 is a light receiving characteristic diagram of an RGB CCD camera.

FIG. 4 is a spectrum diagram of light on the input side.

FIG. 5 shows a color interference fringe image and a green interference fringe image at a certain point in time.

FIG. 6 shows a color interference fringe image and a green interference fringe image after t ₁ second from a certain point in time.

FIG. 7 is a structural diagram of a reverse roll coater to which the present invention is applied.

8 is a system diagram of the film thickness control device in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slurry reservoir 2 Ceramic slurry 3 Coating roll 4 Doctor blade 5 Sheet 6 Carrier film (continuous web) 10 Measuring instrument 11 Light source 12, 13 Filter 15 Interference optical system 18 Interference optical system drive actuator 20 Image processing device 21 Controller 22 Angle detector 23 Thickness adjustment actuator

Claims (5)

[Claims] 1. A sheet forming machine for forming a slurry-like raw material into a sheet through a pair of coating tools arranged at a certain distance from each other, wherein the first raw material is formed on a first coating tool of the pair of coating tools. A second coating tool is displaced in a thickness direction of the sheet so that the thickness of the sheet can be adjusted. A film of a wet sheet formed on the first coating tool Measuring means for measuring the thickness in a non-contact manner using interference of two light beams; and displacing the second coating tool in a direction facing the first coating tool;
A thickness adjustment actuator for adjusting the thickness of the sheet, a control unit for comparing the thickness of the sheet measured by the measurement unit with a target value, and supplying a command signal corresponding to the deviation to the actuator, A film thickness control device comprising: 2. The coating tool according to claim 1, wherein the first coating tool is a coating roll, the second coating tool is a doctor blade, and the sheet formed on the coating roll is transferred to a continuous web. The film thickness control device in the sheet forming machine according to claim 1. 3. The first coating tool is a coating roll, the second coating tool is a metering roll rotating in the opposite direction to the coating roll, and the sheet formed on the coating roll is The apparatus according to claim 1, wherein the film is transferred to a continuous web. 4. A measurement in which said measuring means is moved with respect to the first coating tool such that an interference fringe image of light reflected on the sheet surface and light reflected on a reference surface of the measuring means falls within the photographing screen. 4. The apparatus according to claim 1, further comprising an actuator for driving means. 5. The measuring means comprises: one light source; means for optically dividing light from the light source into monochromatic light and bicolor light through a filter; monochromatic light and bicolor light are input in parallel; While splitting into two light beams and reflecting one on the sheet surface,
A two-beam interference optical system that reflects the other on the reference surface, and an interference fringe image of the light reflected on the sheet surface and the light reflected on the reference surface is formed by a single-color light image and a multi-color light image captured at the same time. Means for individually obtaining; means for detecting the position of the zero-order interference fringe from the maximum luminance position of the multicolor light image; position of the interference fringe at the sheet measurement point of the monochromatic light image and a position corresponding to the zero-order interference fringe 5. The apparatus according to claim 1, further comprising: means for measuring the displacement of the sheet measurement point.