JPH08338814A - Apparatus for detecting defect of film and manufacture for film - Google Patents

Abstract

PURPOSE: To accurately detect a pin hole of a small diameter of a light permeable film, by arranging an ultrasonic light source at the side of one face of the film and a photodetecting part having an image pickup device at the side of the other face of the film. CONSTITUTION: An ultrasonic light source 3 is arranged at the side of one face of a film 1, and a photodetecting part 4 having a built-in solid image pickup device 5 is set at the side of the other face of the film 1. Most of the ultraviolet rays from the light source 3 are reflected and absorbed by the film 1, not penetrating to the photodetecting part 4. Meanwhile, if a pin hole 2 is present on the film 1, the ultraviolet rays pass through the pin hole to reach the photodetecting part 4, are converted to an image signal by the device 5 and processed at a signal-processing device 6. As a result, the pin hole 2 is detected. Even women the film 1 shows a high permeability to visible lights, the ultraviolet rays are generally low in transmission and therefore the amount of ultraviolet rays passing through the pin hole 2 is greatly different from that of ultraviolet rays passing through other parts than the pin hole 2. The pin hole 2 is accordingly judged surely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting defects, especially pinholes, in a polymer film, and a method for producing a film using the apparatus.

[0002]

2. Description of the Related Art When manufacturing a polymer film, there are cases where the film has pinholes (holes) having a diameter of several tens of .mu.m to several tens of mm due to various causes, particularly in the steps such as melt molding and stretching. . When the film with this pinhole is shipped to users as a product, it causes various obstacles. For example, when the film is used as a base material for magnetic tape, etc., when the magnetic substance is applied to the film, the pinholes left on the manufactured magnetic tape may cause recording defects, resulting in defective products. Since the coating liquid bleeds out to the back side and stains the device in the coating process, it contaminates the back side of the normal part to make it a defective product, and it takes time and man-hours to stop and clean the dirty device. And caused a large decrease in yield.

Therefore, in order to guarantee the quality that a product having a pinhole defect is not shipped to the user, it is necessary to detect the pinhole with certainty. In addition, if pinhole defects frequently occur or occur periodically, pinholes can be quickly and reliably managed for process control so that defective parts are not immediately corrected by correcting the corresponding parts in the manufacturing process. It is necessary to detect. Since rapid response is required especially for process control, it is important to detect pinholes online while manufacturing the film, for example, after the stretching process or during the rewinding process.

Further, comparing a typical defect of a film, that is, a black dot and a pinhole, a pinhole becomes a more serious obstacle for defects of the same size, and both cause different occurrences, so that quality assurance is ensured. However, it is important to distinguish and detect both defects from both aspects of process control.

Conventionally, as an inspection device for pinholes and black spots, an image sensor type has been known in which a white fluorescent lamp is used as a light source and light transmitted through a film is received by a solid-state image pickup device. That is, a white fluorescent lamp is arranged on one side of the film, and a light receiving section using a solid-state image sensor is arranged on the other side.
By measuring the intensity of light transmitted through the film, pinholes or black spots on the film are detected. At this time, the pinhole and the black dot are associated with the bright defect and the dark defect, respectively, from the viewpoint of the video signal.

In an inspection using such an apparatus, as a means for improving the accuracy of detecting pinholes and black spots, for example, Japanese Patent Laid-Open No. 62-138740 discloses an AGC for a bright defect video signal (automatic). (Sensitivity adjustment circuit) and two series of AGC circuits for dark defect video signal AGC. In this method, the peak value of the bright defect signal differential wave height is different from that of the dark defect signal differential wave height.
While it was a factor of error in GC, AGC for bright defects
And an automatic sensitivity adjustment circuit of two circuits of AGC for dark defect are used together to detect with higher accuracy.

However, even if the bright defect video signal AGC and the dark defect video signal AGC are used together as described above, it is difficult to detect a pinhole having a small diameter in a film having high light transmittance. That is, in a film having high light transmittance, the amount of light passing through the pinhole and the amount of light passing through other parts are close to each other, and a sufficient output cannot be obtained as a bright defect signal, and it is difficult to set the determination level.
Furthermore, since the transmitted light is refracted and scattered around the periphery of the pinhole and the amount of light reaching the light receiving unit is reduced, the signal from the solid-state image sensor changes between dark / bright / dark. May be output and may be erroneously determined as a black dot. That is, it has been practically impossible to accurately detect a pinhole having a small diameter in a film having high light transmittance by the conventional technique.

[0008]

SUMMARY OF THE INVENTION It is, therefore, a first object of the present invention to provide an apparatus capable of accurately detecting a pinhole having a small diameter in a film having high light transmittance.

A second object of the present invention is to provide a film manufacturing method capable of accurately detecting small-diameter pinholes, minimizing the production of defective films, and increasing the yield. is there.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the film defect detecting apparatus of the present invention has a defect that a light source is arranged on one side of the film and a light receiving section having an image sensor is arranged on the other side. In the detection device, the light source is an ultraviolet light source.

In this defect detecting device, it is preferable that the light receiving portion or the light source is provided with an ultraviolet ray transmitting filter. Further, it is preferable that the ultraviolet light source includes a light emitting portion in which one ends of a plurality of optical fibers are linearly arranged. Further, it is preferable that the light emitting section is one in which a plurality of optical fibers are bundled into one bundle and are linearly arranged at regular intervals.

The film manufacturing method according to the present invention comprises a method of controlling the film manufacturing process based on the result of detecting the pinholes of the film by the defect detecting device as described above.

In the present invention, the type of film is not particularly limited, but examples of films to which the apparatus of the present invention is preferably applied include aramid film, polyimide film and polyphenylene sulfide film.

[0014]

In the present invention, the ultraviolet light emitted from the ultraviolet light source is applied to the film. At this time, the ultraviolet rays pass through the pinhole generation site as they are, but most of the ultraviolet rays are absorbed or reflected and cannot pass through the other parts. Therefore, the pinhole can be reliably detected by detecting the transmitted ultraviolet ray by the light receiving section using the (solid-state) image pickup element arranged on the other surface side of the film.
In particular, even if the film has a high transparency to visible light, the transparency to ultraviolet rays is usually low, so there is a large difference between the amount of ultraviolet rays that have passed through the pinhole and the amount of ultraviolet rays that have passed through other parts. A clear bright defect signal is obtained. Further, since the ultraviolet ray transmittance is low, there is almost no refraction and scattering at the peripheral edge of the pinhole, and even a pinhole having a small diameter can output only a bright defect signal and reliably detect the pinhole. That is, according to the defect detecting device of the present invention, it is possible to accurately detect a pinhole having a small diameter in a film having high light transmittance.

Further, according to the film manufacturing method of the present invention, the pinhole having a small diameter can be detected with high accuracy as described above, and it is not necessary to ship the product having the pinhole defect to the user. In case of frequent occurrence or periodic occurrence, it is possible to prevent the continuous production of products with pinholes by immediately correcting the corresponding parts in the manufacturing process, and as a result minimize the production of defective films and improve the yield. Can be increased.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a structure in which an ultraviolet light source 3 is arranged on one surface side of the film 1 and a light receiving section 4 having a solid-state image sensor 5 built therein is arranged on the other surface side. In FIG. 1, most of the ultraviolet light emitted from the ultraviolet light source 3 is reflected and absorbed by the film 1 and is not transmitted to the light receiving portion 4 side. On the other hand, when the pinhole 2 exists on the film 1, the ultraviolet rays pass through this and reach the light receiving unit 4, and are converted into a video signal by the solid-state imaging device 5, and the video signal is processed by the signal processing device 6. Then it is judged as a pinhole.

FIG. 2 shows a video signal of the pinhole portion detected by the light receiving section 4 in this way. The pulsed signal at the center is the pinhole, and the peripheral edge thereof is the output of the visible light component emitted from the external light and the ultraviolet light source and transmitted through the film. The diameter of the pinhole is about 400 μm. In this way, the output value of the bright defect at the pinhole in the video signal is significantly different from the values of other parts, and an appropriate threshold value is set for the video signal or an appropriate threshold value is set for the differential peak value of the video signal. By doing so, the pinhole can be easily determined.

If there is a pinhole defect in the product from the pinholes judged in this way, when the product is slit into a smaller width and rewound, the pinhole portion should not be included in the product. By changing the slit position or not making only the part including the pinhole the product when it is not possible, it is possible to avoid shipping defective products to the user and reduce the proportion of defective films. Furthermore, when pinhole defects frequently occur or occur periodically, the cause can be estimated from the frequency, or the facing portion of the manufacturing process can be estimated from the period, so that the corresponding portion of the manufacturing process can be corrected immediately. It becomes possible. As a result, it is possible to prevent continuous production of products having pinholes, and as a result, the production of defective films can be minimized and the yield can be increased.

There are two types of light receiving parts using a solid-state image pickup device, one in which pixels are arranged in a line (for example, in a straight line) and one in which pixels are arranged in a plane. When conducting a pinhole inspection of a normal film, it is often the case that the film to be measured is continuously inspected, and at this time it is required to perform the inspection continuously in the traveling direction of the film. . For this reason, it is preferable that the light receiving section is composed of a solid-state image sensor in which pixels are linearly arranged, and a light-receiving section and a light source using the solid-state image sensor are provided so that scanning can be performed in a direction perpendicular to the traveling direction of the film. It is preferable to arrange them. In this case, the solid-state image sensor in which the pixels are linearly arranged can change the resolution in the traveling direction of the film to be measured by changing the inspection speed. In addition, by arranging a plurality of light-receiving parts using the solid-state image sensor in the scanning direction, it is possible to simultaneously measure a wide field of view with high accuracy.

On the other hand, as the ultraviolet light source, for example, a black light fluorescent lamp, a germicidal fluorescent lamp, an ultraviolet lamp, an ultraviolet lamp having a line light guide at the emitting portion, and the like are suitable. The line light guide is a light guide in which one end of a plurality of optical fibers is linearly arranged and the other end is bundled in parallel, and by irradiating the other end bundled in parallel with ultraviolet rays from an ultraviolet lamp. The ultraviolet rays are uniformly emitted linearly from one end arranged in a straight line.

In particular, in the case of using a solid-state image pickup device in which pixels are linearly arranged, a black light fluorescent lamp, a germicidal fluorescent lamp, and a line light guide are provided in the emitting portion in order to obtain a uniform and uniform amount of ultraviolet rays. UV lamps are suitable.

Further, if the scanning frequency of the solid-state image pickup device is equal to or higher than the power supply frequency, it is preferable to turn on the high frequency in the case of a black light fluorescent lamp or a germicidal fluorescent lamp, and to turn on the direct current in the case of an ultraviolet lamp. Is preferred. High-frequency lighting is a method of lighting a fluorescent lamp by using a high-frequency voltage of about 30 kHz, and by applying a high-frequency voltage higher than the scanning frequency of the solid-state imaging device to the fluorescent tube, the change in the light amount due to blinking of the fluorescent tube is reduced. It is averaged within the scan period and does not affect the inspection.

It is necessary to select a wavelength suitable for the material of the film to be inspected as the wavelength of the ultraviolet ray used for the inspection.
In the case of polyester film, polypropylene film, etc., short wavelength ultraviolet rays (around 270 nm, for example, 24
0 to 300 nm), aramid film, polyimide film, polyphenylene sulfide film, etc., and long wavelength ultraviolet light (about 365 nm, for example, 300 to 300 nm).
400 nm) is preferably used.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a configuration in which the ultraviolet light source 3 is arranged on one surface side of the film 1 and the light receiving section 4 provided with the ultraviolet transmission filter 7 is arranged on the other surface side.
In FIG. 3, the ultraviolet light emitted from the ultraviolet light source 3 is
Most of the light is reflected and absorbed by the film 1 and is not transmitted to the light receiving portion side, only the ultraviolet rays passing through the pinhole 2 reach the light receiving portion 4, further transmitted through the ultraviolet light transmitting filter 7, and transmitted by the solid-state image sensor 5 to the video signal. Is converted to. On the other hand, the visible light component emitted from the ultraviolet light source 3 passes through the film 1 and reaches the light receiving portion 4, but is blocked by the ultraviolet transmission filter 7.
It does not enter the solid-state image sensor 5. After all, the solid-state image sensor 5
Therefore, only the ultraviolet rays that have passed through the pinhole 2 appear in the video signal, and the pinhole can be detected with a high S / N.

FIG. 4 shows such an ultraviolet transmission filter 7
It is a video signal of the pinhole portion detected by the light receiving section 4 provided with. The pinhole is the same as in FIG. The pulse-shaped signal at the center is the pinhole, and is almost 0 at other points. In such a video signal, the output other than the pinhole is 0, so that the S value is very high.
A pinhole can be determined by / N. The ultraviolet transmission filter 7 may be provided on the light source side.

Further, the ultraviolet light source used in the present invention will be described in detail below. When conducting a pinhole inspection of a film, it is often the case that the film to be measured is run continuously, especially when the pinhole inspection is performed online for process control. It is necessary to inspect the film traveling at high speed. As described above, in the configuration in which the light receiving unit is arranged so that scanning can be performed in the direction perpendicular to the traveling direction of the film, the resolution in the traveling direction of the film depends on the traveling speed of the film and the scanning speed of the solid-state image sensor. Decided. Therefore, in order to increase the resolution so that a pinhole with a small diameter can be detected, it is necessary to increase the scanning speed of the solid-state image sensor when the film traveling speed is determined by the film traveling speed.

In this case, since the output value of the solid-state image pickup device is determined by the product of the intensity of light applied to the pixel and the time, in order to increase the scanning speed and obtain an output with a sufficient S / N. Need to irradiate the solid-state imaging device with ultraviolet light of sufficient intensity.

By the way, in a fluorescent tube type ultraviolet light source such as a black light or a germicidal lamp, the wavelength range of the emitted ultraviolet spectrum is narrow, and the sensitivity of the solid-state image pickup element is lower than visible light with respect to ultraviolet light. However, if the scanning speed becomes faster, a sufficient S / N cannot be obtained.

On the other hand, since the ultraviolet lamp can irradiate strong ultraviolet rays, sufficient S / N can be obtained even if the scanning speed is fast. On the contrary, when the film is irradiated with strong ultraviolet rays for a long time, the irradiated film is It may degenerate.

That is, in order to detect a small-diameter pinhole of a film which is formed at a high speed online, it is sufficient for a solid-state image pickup device so that a sufficient S / N can be obtained even if the scanning speed is increased. It must be exposed to intense UV radiation, but it must be detectable with as little UV radiation as possible to ensure film quality.

By the way, in the pinhole detection according to the present invention, the ultraviolet rays which contribute to the pinhole output are only those which are emitted from the ultraviolet light source and pass through the pinhole of the film to reach the light receiving portion. A part of the ultraviolet light emitted from the ultraviolet light source is diffracted by the pinhole portion and passes through, and a part of the passed light reaches the light receiving portion. Therefore, if parallel light or light close to parallel light is applied only to the vicinity of the pinhole, the ultraviolet light emitted from the ultraviolet light source reaches the light receiving portion very efficiently.

Considering each ultraviolet light source from this point of view, in a fluorescent tube type ultraviolet light source, since the ultraviolet rays are diffused and emitted in all directions from each part of the fluorescent tube, the total ultraviolet rays irradiated to the film are The proportion of ultraviolet rays passing through the pinhole is small, but the proportion of the light passing through the pinhole to the light receiving portion is also small. Further, in an ultraviolet lamp, ultraviolet rays are radiated from a point-like light source in all directions, so the proportion of ultraviolet rays that pass through a pinhole in the total ultraviolet rays that are emitted to the film is small. The proportion of light reaching the light receiving portion is small.

On the other hand, FIG. 5 shows an embodiment of the present invention using an ultraviolet light source provided with a line light guide. Figure 5
Then, the line light guide 31 and the ultraviolet light source unit 34 in which one end 31a (emission part) of a plurality of optical fibers are linearly arranged and the other ends 31b (incidence part) are bundled in parallel are used.
The light of the ultraviolet lamp 32 in the ultraviolet light source unit 34 is incident on the other end 31b bundled in parallel while being collected by the mirror 33, and emitted from the one end 31a linearly arranged. The ultraviolet light emitted from the line light guide 31 is the film 1
Since the irradiation area above is a very thin straight line,
Since the ultraviolet rays that have efficiently passed through the pinhole 2 and have been emitted from the optical fiber are very close to parallel rays, the ultraviolet rays that have passed through the pinhole 2 reach the light receiving unit 4 extremely efficiently. As a form of the one end 31a (light emitting portion) of the optical fiber, one in which the optical fibers are linearly arranged in a line, one in which the optical fibers are linearly arranged in a plurality of lines, or a plurality (2 to 50) It is preferable to use one obtained by bundling the optical fibers of 1) in a bundle and linearly arranging the optical fibers at regular intervals.

In such a system, the image signal of the pinhole can be obtained with efficiency of several tens of times as high as that of the ultraviolet light source of the fluorescent tube system. Therefore, it is sufficient to increase the scanning speed of the solid-state image pickup device. It is possible to obtain various outputs, and it is possible to detect pinholes with a small diameter. Furthermore, since the amount of ultraviolet rays applied to the film is several tenths of the case of direct irradiation from an ultraviolet lamp, the film will not be denatured.

FIG. 6 shows a video signal of a pinhole portion detected by a structure using an ultraviolet light source provided with such a line light guide. The film traveling speed is 25m / min,
The scanning speed is 4 kHz and the pinhole diameter is 100 μm. The pulse-shaped signal at the center is a pinhole, and a sufficient S / N is obtained.

In order to further improve the efficiency of ultraviolet rays of the ultraviolet light source using this line light guide for the emitting portion,
It is more preferable to arrange a cylindrical lens (not shown) at the line light guide emission portion.

[0037]

【Example】

Example 1 A film defect detecting device having the structure shown in FIG. 1 was manufactured. A black light fluorescent tube was used as the ultraviolet light source 3, and a CCD using a CCD as the solid-state image sensor 5 was used as the light receiving section 4. The CCD has 2048 pixels, and the size of one pixel is 14 μm × 14 μm, and the arrangement of the light receiving portions is set so that this corresponds to 100 μm × 100 μm on the film. CCD scanning frequency is 30H
z.

FIG. 2 shows the output of a pinhole detected by using this defect detecting device. The film 1 uses an aramid film and the diameter of the pinhole is 400 μm. The center pulse represents the pinhole.

Example 2 A film defect detecting device having the structure shown in FIG. 3 was manufactured.
A black light fluorescent tube was used as the ultraviolet light source 3, and a CCD using a CCD as the solid-state image sensor 5 was used as the light receiving section 4. The ultraviolet transmission filter 7 used was an absorption type. The CCD has 2048 pixels, and the size of one pixel is 14 μm × 14 μm, and the arrangement of the light receiving portions is set so that this corresponds to 100 μm × 100 μm on the film. CCD scanning frequency is 30Hz
And

FIG. 4 shows the output of a pinhole detected by using this defect detecting device. The film 1 uses an aramid film and the diameter of the pinhole is 400 μm. The center pulse represents the pinhole.

Example 3 A film defect detecting device having the structure shown in FIG. 5 was manufactured. A mercury xenon discharge tube is used as the ultraviolet lamp 32, and a diameter of 220 μm is used as the line light guide 31.
2 m of 10 quartz fibers of 10
It was arranged at m intervals and used. As the light receiving part 4, a device using a CCD as the solid-state imaging device 5 was used. The ultraviolet transmission filter 7 used was an absorption type. CC
D is 2048 pixels, and the size of one pixel is 14μ
m × 14 μm, which is 100 μm × on the film
The arrangement of the light receiving portions was set so as to correspond to 100 μm.
The scanning frequency of the CCD is 4 kHz.

FIG. 6 shows the output of a pinhole detected by using the defect detecting device shown in FIG. 6. The film 1 uses an aramid film and the diameter of the pinhole is 100 μm. The film was continuously run at a speed of 25 m / min at the time of detection. The center pulse represents the pinhole, and S / N
Is over 20.

[0043]

According to the present invention, it is possible to accurately detect a pinhole having a small diameter in a film having high light transmittance.
Therefore, a film having a small-diameter pinhole defect is not shipped as a product, and as a result, the quality of the shipped product is improved.

Further, when a pinhole occurs, the situation can be quickly confirmed, and countermeasures can be taken. Therefore, the number of defective products to be manufactured is reduced, so that the film manufacturing cost is reduced. Can be reduced.

Further, according to the preferred embodiment of the defect detecting apparatus of the present invention, the pinholes of the film which is running at the film forming speed in the film manufacturing line can be detected online accurately.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a defect detecting device for a film of the present invention.

FIG. 2 is a diagram showing a video signal waveform of a pinhole having a diameter of 400 μm on an aramid film detected by using the apparatus of FIG.

FIG. 3 is a schematic configuration diagram showing another embodiment of the defect detecting device of the film of the present invention.

FIG. 4 is a diagram showing a video signal waveform of a 400 μm-diameter pinhole on an aramid film detected by using the apparatus of FIG.

FIG. 5 is a schematic configuration diagram showing still another embodiment of the film defect detection device of the present invention.

6 is a diagram showing a video signal waveform of a pinhole having a diameter of 100 μm on a running aramid film detected by using the apparatus of FIG.

[Explanation of symbols]

 1 film 2 pinhole 3 ultraviolet light source 4 light receiving part 5 solid-state image sensor 6 signal processing device 7 ultraviolet transmission filter 31 line light guide 31a line light guide emitting part 31b line light guide incident part 32 ultraviolet lamp 33 mirror 34 ultraviolet light source unit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Hanato 1-1-1, Sonoyama, Otsu City, Shiga Prefecture Toray Co., Ltd. Shiga Plant

Claims (8)

[Claims] 1. A defect detecting apparatus in which a light source is arranged on one side of a film and a light receiving section having an image sensor is arranged on the other side, wherein the light source is an ultraviolet light source. . 2. The defect detecting device for a film according to claim 1, wherein the light receiving unit or the light source includes an ultraviolet ray transmitting filter. 3. The film defect detecting device according to claim 1, wherein the ultraviolet light source includes a light emitting portion in which one ends of a plurality of optical fibers are linearly arranged. 4. The light emitting section in which one ends of the plurality of optical fibers are linearly arranged is a bundle of the plurality of optical fibers, which are linearly arranged at regular intervals. The defect detecting device for a film described in 1. 5. A film manufacturing process characterized in that the film manufacturing process is controlled based on a result of detecting a film defect by the film defect detecting device according to claim 1. Description: Method. 6. The method of manufacturing a film according to claim 5, wherein the film manufacturing process is controlled so that a product slit in a narrow width does not include defects. 7. The method of manufacturing a film according to claim 5, wherein the film manufacturing process is managed by correcting a process which is presumed to be a cause of the defect. 8. The method for producing a film according to claim 5, wherein the film is an aramid film.