JP2002187197A - Measuring method for film thickness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring method for a film thickness giving a good measured result by eliminating an error in on-line measuring of a film thickness by watching a wrinkle. SOLUTION: An on-line measuring method for a film thickness is equipped with a means for measuring an amount of a wrinkle of a plastic film wherein a film tension in a widthwise direction and/or a moving direction of the film is adjusted to decrease the amount of the wrinkle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring film thickness, and more particularly, to a method for measuring film thickness on-line by monitoring wrinkles for errors in film thickness measurement and obtaining good measurement results. It relates to a thickness measuring method.

[0002]

2. Description of the Related Art In the process of manufacturing a film made of a thermoplastic resin such as polyester, polyamide, or polypropylene, it is required to control the thickness of the film in a width direction to a predetermined profile, for example, a uniform thickness over the entire width. The adjustment of the thickness of the film is usually controlled based on thickness data measured by a non-contact transmission thickness gauge.

This thickness gauge is configured to measure thickness data for each position while moving a running film in the width direction. In order to prevent damage to the film, a transmission type thickness gauge is used, but there are spots necessary to receive the amount of the transmitted material. Originally, it is desirable that the shape of the film in this spot is flat, but it is difficult to make it substantially flat because the film is conveyed at high speed, and there are wrinkles and tilts. Would.

However, if wrinkles or tilts occur, the weight of the film in the spot increases, and the transmission-type thickness gauge indicates that the film is thicker than the actual film thickness, and the error is superimposed. Occurs.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to eliminate a measurement error caused by wrinkles and inclinations in a film thickness measurement using a transmission-type online thickness gauge. It is what it was.

[0006]

According to the present invention, there is provided, in accordance with the present invention, a method for online film thickness measurement comprising means for measuring the amount of wrinkles in a plastic film, wherein the amount of wrinkles is reduced. This can be achieved by a film thickness measuring method characterized by adjusting the film tension in the width direction and / or the flow direction so as to reduce the film thickness.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic process diagram schematically illustrating a film forming process for carrying out the present invention. In FIG. 1, 1 is a film, 2 is a transmission type thickness gauge, 3 is a guide roll, and 4 is a wrinkle amount measuring device.

In the measuring method of the present invention configured as described above, the transmission type thickness meter 2 scans the film in the width direction in a direction orthogonal to the running direction of the film to measure the film thickness online. it can.

In the present invention, the thickness of the film is preferably measured by a transmission-type online thickness gauge, and the weight per unit area of the film is measured by upper and lower heads arranged with the film interposed therebetween. Although a method for determining the thickness of the film is preferable, it is naturally applicable to a thickness gauge that affects the measured thickness value due to wrinkles.

Such transmission type online thickness gauges include, for example, a type that determines the thickness of a film by the amount of transmitted radiation, a type that determines the thickness of a film by the amount of transmitted light, and a film that determines the thickness of a film by the amount of transmitted ultrasonic waves. For obtaining the thickness of the sheet.

FIG. 2 is a schematic diagram for explaining that a thickness measurement value is thicker than an actual error due to wrinkles. The width of the film is monitored by the wrinkle amount measuring device 4 including an image sensor, and can be recognized by the change in the width of the film.

In the present invention, the amount of wrinkles in the film is measured, for example, by measuring the width of the film and comparing it with the width of the film when the film has no wrinkles, by measuring the sag of the film, Examples include a method of measuring wrinkles of a film as an image and measuring the flapping of a measurement portion of the film.

Here, an apparatus for measuring the amount of wrinkles using an image sensor will be described. There is no particular limitation as long as wrinkles can be detected, such as a method of monitoring the size.

Assuming that the actual width of the film is a mm and the width of the film measured by the wrinkle amount measuring device 4 is b mm, if a = b, no wrinkles are formed.
If a> b, it can be said that wrinkles are present. Then, the amount of the detected thickness is measured as a / b times as thick as the average of the entire width.

In the present invention, the amount of wrinkles in the plastic film is measured, and when this amount is out of the allowable range, the film tension in the width direction and / or the flow direction is adjusted so as to reduce the amount of wrinkles. The allowable range can be, for example, a range of a measurement error of a wrinkle amount.

The range of the measurement error of the wrinkle amount varies depending on the type of the wrinkle amount measurement device to be used, the thickness of the film to be measured, and the like. Is about 5 μm, the range of the measurement error is 0.100%. Incidentally, the allowable range of the amount of wrinkles may be a range determined from the required quality of the product film.

When the result of the measurement of the amount of wrinkles is within the allowable range, the measurement is performed as it is. When the result is out of the allowable range, the speed of the nip rolls installed before and after the guide roll 3 is adjusted to adjust the tension in the traveling direction. The wrinkling can be returned to the original state by performing the wrinkling again.

When it is desired to further reduce the amount of wrinkles, particularly when it is desired to eliminate wrinkles, a proper thickness measurement can be performed within an allowable range by adjusting a device provided on the guide roll for imparting tension to the film in the width direction. be able to.

[0020]

The present invention will be further described with reference to the following examples. Various characteristic values in the present invention were measured as follows. Note that the present invention is not limited to the following examples unless it exceeds the gist.

(1) Film Thickness A β-ray thickness gauge was used as a radiation transmission type thickness gauge.

(2) Wrinkle amount detecting device A wrinkle amount measuring device using an image sensor. In this embodiment,
An image sensor CV-500 manufactured by Keyence Corporation was used, and an edge detection function was used.

(3) Optical Thickness Meter As an optical thickness gauge, a method of obtaining a film value from a value obtained by Fourier transforming an interference spectrum between reflected light on the front surface and light reflected on the back surface of the film and a refractive index of the film. Was used. In the present embodiment, MCPD-20 manufactured by Otsuka Electronics Co., Ltd.
00 was used.

Example 1 Polyethylene-2 containing 0.02% by weight of calcium carbonate particles having an average particle diameter of 0.6 μm and 0.2% by weight of silica particles having an average particle diameter of 0.1 μm.
After 6-naphthalate is dried at 180 ° C. for 5 hours, it is supplied to an extruder hopper, melted at 300 ° C., extruded using a T-type extrusion die, surface finish 0.3S, surface temperature 60 ° C.
And rapidly solidified on a casting drum held in the above-mentioned manner to obtain an unstretched film.

The unstretched film is preheated at 75 ° C.
830 ° C above 14mm between low and high speed rolls
The film was stretched to 5.1 times by heating with an infrared heater having a surface temperature of, cooled rapidly, and then supplied to a stenter and stretched 4.8 times in the transverse direction at 125 ° C. Followed by 240
After heat setting at 10 ° C. for 10 seconds, 1.
After a relaxation treatment of 0%, a biaxially oriented film having a thickness of 4.5 μm was obtained.

This film was conveyed between the guide rolls 3a and 3b, and between them, the profile in the width direction was measured online using the transmission type thickness meter 2. A β-ray thickness gauge was used as the transmission type thickness gauge used here. Although the film was cut to 3000 mm before being sent to the guide roll 3a, the width was measured to be 2995 mm when measured with a wrinkle amount detection device 4 (a wrinkle amount measurement device using an image sensor) at a thickness measurement position. . At this time, the measurement error is 0.167%. Production continued as it was, and the thickness of the produced film was measured with an optical thickness gauge.
It should be 0.167% thicker on average, but there are many wrinkles in some places, and there was a difference of 4.5 ± 0.02 μm between thick and thin places.

Since the allowable range of the measurement error was 0.100%, the production could not be continued as it was, and the speed of the nip rolls before and after the guide roll was adjusted. Film width 29
98 mm. This results in a measurement error of 0.06
It was 7%, which was within the allowable range, so production was possible. The production was continued as it was, and the thickness of the produced film was measured with an optical thickness gauge. As a result, a roll having a very uniform profile of 4.5 ± 0.01 μm was obtained without any partial wrinkles.

[0028]

According to the present invention, what could not be accurately measured without measuring the film thickness off-line after film formation in the past can now be accurately measured on-line. It greatly contributes to the improvement of the quality, and has a great effect.

[Brief description of the drawings]

FIG. 1 is a schematic process diagram schematically illustrating a film forming process for implementing the present invention.

FIG. 2 is a schematic diagram illustrating that a thickness measurement value is thicker than an actual error due to wrinkles.

[Explanation of symbols]

 Reference Signs List 1 film 2 transmission thickness gauge 3 guide roll 4 wrinkle amount measuring device 5 measurement spot

Claims (9)

[Claims] An on-line film thickness measurement method comprising means for measuring the amount of wrinkles in a plastic film, wherein the film tension in the width direction and / or the flow direction is adjusted so as to reduce the amount of wrinkles. A method for measuring the thickness of a film. 2. The thickness of the film is measured by measuring the weight per unit area of the film with upper and lower heads disposed across the film using a transmission type online thickness gauge, and determining the thickness of the film from the obtained result. And measuring the thickness of the film while moving in the width direction of the film.
3. The method for measuring the thickness of a film described in 1. 3. The method for measuring the thickness of a film according to claim 2, wherein the transmission-type on-line thickness meter is a method for determining the thickness of the film based on the amount of transmitted radiation. 4. The method for measuring the thickness of a film according to claim 2, wherein the transmission type online thickness gauge is a system for determining the thickness of the film based on the amount of transmitted light. 5. The method for measuring the thickness of a film according to claim 2, wherein the transmission type thickness meter is a method for obtaining the thickness of the film based on an amount of transmitted ultrasonic waves. 6. The method for measuring the thickness of a film according to claim 1, wherein the wrinkle amount is measured by measuring the width of the film. 7. The method for measuring the thickness of a film according to claim 1, wherein the amount of wrinkles is measured by measuring a sag of the film. 8. The method for measuring the thickness of a film according to claim 1, wherein the amount of wrinkles is measured by measuring wrinkles of the film as an image. 9. The film thickness measuring method according to claim 1, wherein the wrinkle amount is measured by measuring the flapping of a measurement portion of the film.