JPS607203B2 - Film thickness measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a film thickness measuring device for a film, such as a polyethylene film, which has a dielectric constant different from that of air.

FIG. 1 is a side view showing an example of such a conventional film thickness measuring device.

In the device shown in the figure, a film 1 to be measured is passed between two electrodes 2 and 2a, and the film thickness of the film 1 is measured from the change in capacitance between the two electrodes at that time. Second
The figure is a side view showing another example of the conventional film thickness measuring device.

What is shown in the figure is that a light source 3 is placed on one side of the film 1 to be measured, a photodetector 4 is placed on the other side, and the attenuation of light that occurs when the light from the light source 3 passes through the film 1. The amount is detected by a photodetector 4, and the thickness of the film 1 is thereby measured. The two film thickness measuring instruments mentioned above both require electrodes or light sources and detectors to be placed on both sides of the film to be measured, which has the disadvantage of requiring a large amount of space to install the measuring instruments. Moreover, the fact that the film to be measured must be inserted between the two electrodes or between the light source and the photodetector results in a disadvantage that the operation becomes cumbersome.

This invention was made to eliminate the drawbacks of the prior art as described above, and therefore, an object of the invention is to provide a film thickness measuring device that requires less space for installation and is less cumbersome to operate. It's about doing. FIG. 3 is a diagram explaining the principle of this invention.

That is, as seen in the figure, according to the present invention, the film thickness measuring device 5 can measure the film thickness by simply contacting one side of the film. The gist of the configuration of this invention is to bring both electrodes of a capacitor, which is made up of a first electrode and a second electrode facing each other, into contact with one side of a film made of a transparent material, and to detect changes in capacitance of the capacitor at the time of contact. The main feature is that the thickness of the film is measured. Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a plan view showing one embodiment of the present invention (film thickness sensor), and FIG. 5 is a sectional view taken along line A-A in FIG. 4.

See these figures.

The insulator 7 holds the electrodes 6, 6a, thereby forming a capacitor. The exposed side of the electrodes 6, 6a is the contact surface of the film. That is, as shown in FIG. 5, the film to be measured is in contact with the contact surface, and therefore both electrodes 6, 6a forming the capacitor are in contact with one side of the film 1. The capacitance change is detected, and the thickness of the film is thereby measured.There are many existing conventional techniques for detecting the capacitance change, so any appropriate one may be used. As is clear from this, in the present invention, the electrodes 6 and 6a are each formed into a comb shape, and the comb teeth of one electrode are inserted between the comb teeth of the other electrode.

At this time, the exposed surface of the insulator 7 that holds the electrodes 6, 6a is positioned substantially on the same plane as the exposed surface of the electrodes 6, 6a. An embodiment of the present invention has been described above, and experimental data obtained by actually measuring the thickness of a film according to the present invention will be described next.

FIG. 6 is a plan view of the film thickness sensor used in the experiment.

This sensor is made by forming a copper foil on one side on an insulator and then forming a gap G in the center.
It is formed by a. 8 and 8a are lead wires.

The thickness of the copper foil is 18 mm. The gap G is formed by scraping off the steel foil, and the gap width is 0.
It is on the 1-0.2 side. The reason why the gap width was on the 0.1 to 0.2 side was because the copper foil was scraped off by hand. The dimensional relationships of other parts are as follows.
The results of experiments using the film thickness sensor shown in Figure 6 are shown in Figure 7.
As shown in the figure.

In FIG. 7, the contact shows the film thickness, and the vertical axis shows the capacitance change. The experimental conditions are as follows.

The room temperature was 25 qo, the humidity was 84%, and the material of the film was polyethylene. Films with a thickness of 22 m are stacked in one layer (22 rm), two layers (44 mm), three layers (66 mm), four layers (thin m), and five layers (1
10 m), 6 sheets stacked (i32 Am) and a total of 3 measurements
I returned the line.

From the graph of FIG. 7, it can be seen that capacitance changes due to film thickness are sufficiently observed, and it can be understood that the film thickness measuring device according to the present invention is practical.

As explained above, the film thickness measuring device of the present invention has the advantage that it requires less space for installation and is easy to use because it can measure from one side of the film.

[Brief explanation of the drawing]

1 and 2 are side views showing an example of a conventional film thickness measuring device, FIG. 3 is a diagram explaining the principle of the present invention, FIG. 4 is a plan view showing an embodiment of the present invention, and FIG. The figures are a sectional view taken along the line A-A in FIG. 4, FIG. 6 is a plan view of the film thickness sensor used in the experiment, and FIG. 7 is a graph showing the experimental results. Description of symbols, 1...Film, 2...Electrode, 3...Light source, 4...Photodetector, 5
... Film thickness measuring device, 6 ... Electrode, 7 ...
...Insulator, 8...Lead wire. Figure 1 2
Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A capacitor having a first electrode and a second electrode facing each other is brought into contact with one side of a film made of a dielectric material, and from the change in capacitance of the capacitor at the time of contact, the capacitance of the capacitor is determined. A film thickness measuring device characterized by measuring the film thickness of. 2. In the film thickness measuring device according to claim 1,
A film thickness measuring device characterized in that the first electrode and the second electrode are each formed in a comb shape, and the comb teeth of one electrode are inserted between the comb teeth of the other electrode.