JPH01202604A - Inline measurement of unstretched portion of film - Google Patents

Abstract

PURPOSE:To enable detection of the boundary between stretched and unstretched portions of a film, by interposing two sheets of polarizers between a projector and an image sensor. CONSTITUTION:A film 1 runs until it is released from a tenter clip and wound with a take off device after the completion of a stretching during the inline. An image sensor 3 is so arranged to cover the whole of an unstretched portion 4 at an end of the film 1 in a field of view. Then, polarizers 5 and 5' are inserted between a projector 2 and the image sensor 3 and a controller 7 processes a signal detected with a CCD of the image sensor 3 and a necessary data is stored to display. With such an arrangement, as there is a difference in the molecular orienting property between the stretched and unstretched portions 4 of the film 1, the use of the polarizers 5 and 5' enables continuous measurement of the boundary between the both portions and that between the unstretched portion and air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-line method for measuring the width of an unstretched portion existing at the end of a stretched film made of a thermoplastic synthetic resin.

More specifically, the present invention relates to an in-line measurement method of an unstretched portion of a stretched film in which an image sensor and a polarizer are combined.

[Prior Art] A film obtained by extruding a thermoplastic resin in a molten state through a flat die usually has a high elongation and an unstable shape, so it cannot be used for anything other than special purposes. Therefore, it is stretched in one direction or two directions to obtain an appropriate degree of elongation.

Generally, the film is stretched in the longitudinal direction with rollers and in the width direction with a grip tenter.
When stretching the film in the width direction, the ends of the film are held by clips, and the portion of the film held by the grips cannot be stretched, so the film cannot be completely stretched over its entire width. Therefore, the unstretched parts remaining at the ends of the film are cut off and disposed of as scraps after the completion of stretching, so the amount of unstretched parts remaining at the ends of the film depends on the yield of the product. Affect.

Furthermore, since fluctuations in the unstretched area can be determined by the behavior of the edge forming and stretching processes, measuring the width of the unstretched area at the end of stretching is one of the important elements for process control in the film forming process.

However, in the actual process, it is not possible to measure the boundary between the stretched and unstretched areas satisfactorily using a normal optical sensor, and workers must measure the boundary visually and at regular intervals using a ruler. This is the actual situation, and the accuracy was not satisfactory.

[Problems to be Solved by the Invention] The purpose of the present invention is to improve the above-mentioned deficiencies of the prior art, to detect the boundary between the stretched and unstretched parts of the film by a simple means during in-line production, and to constantly It is an object of the present invention to provide a novel in-line measurement method for the unstretched portion of a film, which allows accurate measurement.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

That is, at least the width of the film stretched in the transverse direction.
A film processing method characterized in that during the AM process, the width of an unstretched part existing at the end of the in-line film after stretching is measured by interposing two polarizers between a projector and an image sensor. This method is based on an in-line measurement method for the stretched section.

The present invention will be explained in more detail.

FIG. 1 is a block diagram illustrating an example of an apparatus for carrying out the method according to the invention.

In FIG. 1, a film 1 that has completed in-line stretching is released from a tenter flip (not shown) and is in a running state until it is wound into a winding device (not shown). A projector 2 and an image sensor 3 are fixed to one side through the film 1, respectively.

The image sensor 3 is arranged so that the entire unstretched portion 4 of the end (only the left side is shown in the figure) of the film 1 is within its field of view. And floodlight 2 and image sensor 3
Two polarizers 5.5' are inserted between them. One sheet is attached between the projector 2 and the film 1, and the other sheet is attached between the image sensor 3 and the film 1.

The floodlight 2 is an AC voltage power supply device (AClooV, 60H2
)6 via commercial power supply (AClooV.

60Hz>. A commercially available fluorescent lamp is used as the floodlight 2, and the floodlight 2 blinks at 120H2.

On the other hand, as an image sensor, the lens and COD (cha)
A device whose main part is a charge-coupled device (charge coupled device) is used. There is no need to use COD, and MOS (metal-oxide)
semiconductor>.

Signals detected by the CCD, which is the image sensor 3, are sent to the controller 7, where the signals are processed and necessary data is stored and displayed. 8 is an isolation amplifier, 9 is an external display device, and 10 is a signal transmission cable (R3232C>).

The reason for using a polarizer in the present invention is as follows.

As mentioned above, in the past, operators visually measured the unstretched portion of the film, but it was impossible to instantaneously measure the unstretched portion of the film that was traveling at high speed. The accuracy of measured values is also low.

Furthermore, depending on the type of film being manufactured, it may be difficult to distinguish between the stretched portion and the unstretched portion. For example, in the case of colored films and multilayer films, it is difficult to detect the boundary between the unstretched part and the stretched part.

Since there is a clear difference in molecular orientation between the unstretched part and the stretched part, the present inventors used a polarizer to clearly identify the boundary between the two and the unstretched part. We focused on the ability to distinguish the boundaries between the stretched portion and the air, which could not be determined visually, and when we carried out the experiment, we obtained results that were better than expected.

When using a polarizer, there are two cases: the unstretched area is a bright field and the background is a dark field, and the unstretched area is a dark field and the background is a bright field.The former case is used. This has the effect of reducing the effects of variations in light intensity due to dirt on the light source and insufficient light intensity due to misalignment between the image sensor and the light source. Therefore, it is preferable to adopt the former.

Figure 2 shows a photograph of the COD output measured in a bright field of an unstretched part of a certain film using a cathode ray tube oscilloscope, and Figure 3 shows a photograph of an unstretched part observed in a dark field.

As is clear from the photographs shown in FIGS. 2 and 3, better results were obtained when the unstretched portion was measured as a bright field.

The photographs shown in FIGS. 2 and 3 above were obtained by adjusting the angles formed by the polarization axes of the two polarizers to obtain the optimum conditions. Of course, even if the film is made of the same material, the optimal conditions will change if the stretching conditions change, so the optimal conditions should be adjusted according to the type and product number of the film. Of course, polarizer 5
．． 5- must be rotatable so that the polarization axes can be adjusted independently.

As is clear from FIGS. 2 and 3, the distance between the end of the unstretched part and the boundary between the unstretched part and the stretched part, that is, the width of the unstretched part, is measured as follows.

FIGS. 4 and 5 are schematic diagrams in which the observation photographs taken by the cathode ray tube oscillograph shown in FIGS. 2 and 3 are graphed as models.

The horizontal axis in FIGS. 4 and 5 represents a predetermined position within the field of view of the CCD sensor, and the vertical axis represents the intensity of light received by the CCD sensor.

The graphs in Figures 4 and 5 show that the CCD sensor is 15CA.
(obtained by one light emission from the projector 2)
It shows how the amount of light received at each position of the CCD sensor changes.

Therefore, in the case shown in FIG. 4, since the unstretched portion of the film is set as a bright field, the amount of light passing through the unstretched portion of the film is large.

In FIG. 4, the flat portion a on the left side is the amount of light that has passed through the blank portion located to the left of the unstretched end portion 4 shown in FIG. The portion that rises sharply from the flat portion a corresponds to the end of the unstretched portion, and the length of the slightly flat portion above corresponds to the width of the unstretched portion 4. The next sharp fall indicates the boundary between the unstretched part and the stretched part. The flat part C on the right shows the stretched part of the film 1. In this way, the sharp rises and falls indicate the respective boundaries, and the width of the unstretched portion 4 is the width between these rises and falls.

As shown in Fig. 4, the rising point is the point X where the light intensity starts to rise rapidly from the flat area on the left, and the falling point is the point Y where the light intensity has stopped falling sharply. The points are determined, and the distance between the points is set as the width W of the unstretched portion.

Figure 5 shows the unstretched part as a dark field. As in Figure 4, the X and Y points are determined and the width W of the unstretched part is determined.
This is what you get.

FIG. 6 is a schematic diagram showing the process in which a thermoplastic film is stretched, and the direction of arrow A indicates the direction in which the film flows.

In FIG. 6, an unstretched film B (not shown) in which a thermoplastic resin is extruded in a molten state from a die and cooled by a casting drum is continuously supplied to a longitudinal stretching region 11, where the film is The film is stretched in the longitudinal direction (longitudinal direction of the film) by two sets of rollers with different values. The film C stretched in the longitudinal direction is supplied to the transverse stretching region 12 and stretched in the transverse direction (width direction of the film) to become a biaxially stretched film D. This biaxially stretched film is rolled by a winding device (not shown). It is wound up.

Generally, a film produced by the method described above has a concave cross-sectional shape, with the unstretched film being thick at the edges and thinner at the center. This thick end portion is not eliminated in the longitudinal stretching region, nor is it eliminated in the horizontal stretching region. In particular, in polyolefin materials, especially polypropylene, which are subjected to neck stretching, unstretched portions remain at the ends. Therefore, in the film forming process for materials that exhibit such stretching behavior, the width of the unstretched portion 4 remaining at the end of the stretched portion affects the yield and physical properties of the product. measurement is important.

[Example] A 20W white fluorescent lamp was used as the light transmitter, and the following AC constant voltage power supply was used.

Manufacturer: Elco model: V-1005 Specifications: Input AC: 80-110V Output: AC: 100V Stability: AC: 100±1.5yrms The following detectors and controllers were used.

(1) Camera (manufactured by Nippon Nilexi Robvis Co., Ltd.) Model: H
4096CH Lens: f=100rnm (close-up ring, polarizing filter used) Image sensor: CCD 4096-bit camera field of view: Approx. 150mm Scan speed: 8, 3m5ec/SCAM (2
) Controller (manufactured by Nippon Electro Devices Co., Ltd.) Console: 20 Keyboard display: LCD 40 digits x 2, LEC 8 digits x 2 Output Analog O~5V One end of a biaxially stretched film (thickness: 8 μm) was measured.

FIG. 7(a) to FIG. 7(C) are cheats showing the results obtained in this embodiment.

The horizontal axis of the charts shown in FIGS. 7(a) to 7(C) represents time, and the vertical axis represents the width W of the unstretched portion shown in FIG.
mlTl is shown.

The width W of the unstretched part in these charts is 8゜3 m.
The value obtained by D/A converting the moving average of 100 values obtained by 5ec/SCAM is shown.

In the chart (I>) shown in Figure 7(a), periodic fluctuations appear, but this period corresponds to the period of one rotation of the grip chain in the stenter, and there is an abnormality in the drive system of the grip chain. I found out something.

The chart (IF) in FIG. 7(b) shows the measurements taken after the drive system of the grip chain was maintained.

No periodic fluctuations are observed in Chanid (n).

As a comparative example, the measurement without using a polarizer is shown in the chart (I[I) of FIG. 7(C).

[Effects of the Invention] By having the above-described configuration, the present invention exhibits the following excellent effects.

(1) It has become possible to continuously measure the width of the unstretched portion of a film during production, which previously could not be measured continuously in-line.

(2) By introducing a polarizer into the optical part of the detector, contrast at the boundary between the stretched and unstretched parts, which could not be obtained with normal light, can be obtained, improving measurement accuracy. This is based on the fact that there is anisotropy (difference in degree of orientation) between the stretched part and the unstretched part, and that it is combined with measurement using a polarizer.

(3) By using an image sensor as a sensor, the entire unstretched area is placed within the field of view of the image sensor, so it is possible to capture objects with two varying points of width at the same time with one sensor. Therefore, the equipment used for measurement can be simplified.

(4) Since all measuring parts can be fixed, there are fewer failures.
It can save labor in maintenance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the method according to the invention. Figure 2 shows a photograph of the COD output measured in a bright field of an unstretched part of a certain film using a cathode ray tube oscillograph, and Figure 3 shows a photograph of the unstretched part observed in a dark field. FIG. 4 is a schematic diagram in which the photograph of FIG. 2 is graphed as a model, and FIG. 5 is a schematic diagram in which the photograph in FIG. 3 is graphed as a model. FIG. 6 is a schematic diagram showing the process of stretching a thermoplastic film. 1: Film 2: Floodlight 3: Image sensor 4: Unstretched portion 5.5'-Polarizer 6: AC voltage power supply 7: Controller 8: Isolation amplifier

Claims (3)

[Claims] (1) During the manufacturing process of at least a horizontally stretched film, two polarizers are used between the projector and the image sensor to measure the width of the unstretched part that exists at the end of the inline film that has been stretched. An in-line measuring method for an unstretched part of a film, characterized in that measurement is performed by interposing the film. (2) The in-line measuring method for an unstretched portion of a film according to claim (1), wherein the stretched film is a polyolefin film. (3) The in-line measuring method for an unstretched portion of a film according to claim (2), wherein the stretched film is a polypropylene film.