KR101125997B1 - A method for examinning a foreign substance on a transparent film - Google Patents

Abstract

An object of the present invention is to provide a foreign material inspection method of a transparent film which can remove foreign matters adhered to the transparent film surface, detect the number of foreign matters, and quickly determine whether the transparency film is good and accurate.

As a method of moving a transparent film between two polarizing plates arrange | positioned with orthogonal Nicole between a light source and a camera, imaging the light from the light source which passes through with a camera, and inspecting the foreign material in a transparent film by the image processing, The shape of a foreign material And after performing the removal process of the foreign material adhering to the transparent film surface from the signal intensity of the foreign material, the number of foreign objects is detected and it is characterized by the determination of the transparency film.

Foreign body inspection method

Description

Foreign material inspection method of transparency film {A METHOD FOR EXAMINNING A FOREIGN SUBSTANCE ON A TRANSPARENT FILM}

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the method of the foreign material test | inspection of a transparency film.

2 is a diagram illustrating an example of an image in which foreign matter is detected.

3 is a view for explaining a method for defining the shape of a foreign material.

4 is a diagram showing an example of a foreign material showing signal strength exceeding a high intensity threshold (threshold 2).

FIG. 5 is a diagram showing an example of a foreign material that exhibits a signal strength below the high intensity threshold (threshold 2) and higher than the low intensity threshold (threshold 1).

<Explanation of symbols for the main parts of the drawings>

1: polarizer

2: polarizer

3: transparency film

10: light source

20: camera

30: image processing apparatus

The present invention relates to a method for inspecting foreign matter of a transparent film. In detail, after performing the removal process of the foreign material adhering to the transparent film surface, it is related with the foreign material inspection method which detects the quantity of a foreign material and determines the quality of a transparent film.

Foreign materials are problematic for transparent films such as polycarbonate films, polymethacrylate films, polyethylene terephthalate films, polyvinyl alcohol films, acetylcellulose films, polyolefin films, norbornene-based films, and especially for optical applications.

These transparency films are used individually or in lamination. These films or laminated | multilayer film are often handled in the state which bonded the protective film to at least one surface after manufacture.

Foreign matter in the transparent film becomes a defect in the product, so inspection is indispensable. For example, the inspection may be performed by arranging two polarizing plates in a state of orthogonal cross nicol, that is, their polarization axis direction is orthogonal, and arranging a transparent film to be inspected between two polarizing plates and irradiating light from the light source to It is carried out by the method of observing the screen by the camera.

In the case where the transparent film to be inspected is a protective film adhesive polarizing plate, the protective film adhesive polarizing plate to be inspected is disposed in an orthogonal nicotine state with respect to the polarizing plate for inspection. Light passing through the protective film-adhesive polarizing plate to be inspected is completely blocked by the inspecting polarizing plate, but if water or the like exists on the side of the inspecting polarizing plate of the polarizing plate to be inspected, it is observed as a bright part, thereby inspecting foreign matters. have. The foreign material on the opposite side can be performed by inverting the polarizing plate to be inspected in the same manner (see Patent Document 1 and Patent Document 2, for example).

[Patent Document 1]

Patent Publication No. 2000-206327 (paragraph [0002])

[Patent Document 2]

Patent Publication 2001-349839 (paragraph [0012], paragraph [0013])

Although the method of arrange | positioning and implementing the transparent film to test between two polarizing plates arrange | positioned by this orthogonal nicol is an excellent method, it cannot determine whether it is a foreign material in the inside of the transparent film to test, or the foreign material adhering to the surface.

The transparent film tends to generate static electricity when contacting, rubbing, or peeling off the bonded protective film, and easily adheres to dust on the surface.

In the case of inspecting the foreign material of the transparent film, the dust attached to the surface is removed but not completely removed, which hinders precision.

An object of the present invention is to provide a foreign material inspection method of a transparent film that can remove foreign matters adhered to the transparent film surface and detect the number of foreign matters to quickly determine whether the transparency film is good and accurate.

MEANS TO SOLVE THE PROBLEM In order to solve such a subject, this inventor earnestly examined about the foreign material inspection method of a transparent film, As a result, the shape detected in the clean environment or the non-clean environment in which an optical material is handled generally is a foreign substance whose shape is flat or a yarn, or a relatively large thing. The foreign material is often not a foreign material derived from the transparent film existing inside the transparent film, and is determined by setting the aspect ratio or area ratio of the foreign material shape as a criterion, or by setting a threshold to the signal intensity of the image to determine the surface of the transparent film. After removing the adhering foreign matter, the number of the foreign matter was detected, and it was found that the quality of the transparent film could be quickly determined with good accuracy, and thus the present invention was completed.

That is, the present invention is a method of moving a transparent film between two polarizing plates arranged in orthogonal Nicole between a light source and a camera, photographing the light from the light source passing through with a camera, and inspecting the foreign material in the transparent film by the image processing. As a foreign material, the foreign material adhering to the surface of the transparent film from the shape of the foreign material and the signal strength of the foreign material is subjected to the removal process, and then the number of the foreign materials is detected to determine the quality of the transparent film. will be.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the method of the foreign material inspection of a transparency film. Two polarizing plates 1 and 2 are arrange | positioned between the light source 10 and the camera 20, and the transparent film 3 to test | inspect is arrange | positioned between them. Here, two polarizing plates are arrange | positioned in orthogonal nico mutually, ie, the state in which these polarization axis directions orthogonally cross each other. The image signal from the camera is processed by the image processing apparatus 30 to detect foreign substances and output them to the monitor. Moreover, when the transparency film to be examined is a polarizing plate, the said two polarizing plates are arrange | positioned only one side and are implemented.                     

Light from the light source 10 selectively transmits the polarization component in the direction of the polarization axis of the polarizing plate 1, and if there is no foreign material in the transparent film 3, the light passing through the transparent film is blocked by the polarizing plate 2 to prevent the camera. The photographed image shows a dark color. If there is a foreign material whose phase difference differs from the surrounding top part in a transparency film, the polarization state of that part will change, and a bright part (bright spot) will appear in a dark image | photographed image passing through the polarizing plate 2.

The inspection object of the present invention is not particularly limited as long as it is a transparent film. For example, a polycarbonate film, a polymethacrylate film, a polyethylene terephthalate film, a polyvinyl alcohol film, a triacetylcellulose film, a polyolefin film, a norbornene-based film, or the like Can be mentioned.

As a camera, a CCD camera is normally used, and the image signal obtained by imaging is image-processed using a computer system in an image processing apparatus, and a foreign material is detected.

2 shows an example of an image in which foreign matter is detected. In the figure, (A) is a foreign material in a transparent film, (B) is a seam type foreign material adhering to a transparent film, (C) is an example of a comparatively large foreign material adhering to a transparent film.

The foreign matter in the transparent film is due to a raw material, an insoluble material generated from the components constituting the film during the production of the transparent film, or an external substance.

Although foreign matters are inspected using a microscope instead of the CCD camera, foreign matters contained in the transparent film can be detected with good accuracy, but the detection range is narrow and time is required to inspect the whole. This is not a desirable method for quickly inspecting a large number of samples.

The foreign materials such as (B) and (C) of FIG. 2 are hardly observed when the inside of the transparent film is observed using a microscope, and also reduced from cleaning or the like of the detected transparent film. It is considered that it is a foreign material attached to the surface.

In the present invention, foreign matter adhering to the surface of the transparent film is first determined from the foreign matter shape and the signal strength.

The seams or elongate foreign matters are foreign matters attached to the surface of the transparent film. These are usually obtained by integrating the length component in the parallel direction of the foreign material and the length component in the vertical direction below the set value of the ratio of the short component to the long component among the length components of the foreign material parallel to the moving direction of the film and the vertical component. The ratio of the area of the foreign material to the area is less than or equal to the set value, the area ratio of the foreign material to the square area of the diagonal of the maximum length of the foreign material is less than the set value, or the area ratio of the foreign material to the area of the circle whose maximum length is the diameter. Below, what satisfies either of these is detected as a foreign material.

3 is a diagram for explaining this. The foreign material is typically shown as an elongated ellipse, and in (A), the white arrow indicates the moving direction of the film, and the length component in the parallel direction of the foreign material is represented by X and the length component in the vertical direction is Y. The magnitude of the length component in the parallel direction and the length component in the vertical direction changes depending on the degree of inclination of the foreign material with respect to the moving direction of the film. In this invention, it is determined that the foreign matter below the set value is the foreign matter adhering to the surface. Moreover, FIG.2 (B) shows the case where a foreign material is parallel with the moving direction of a film.

Although this setting value is based on the kind of film and the foreign material in an adhesion environment, in the case of a triacetyl cellulose film, it can be judged with good precision by setting it normally to about 0.2-0.4, Preferably it is about 0.3.

The area ratio of the foreign material to the area obtained by integrating the length component in the parallel direction of the foreign material and the length component in the vertical direction is less than or equal to the set value, and the area ratio of the foreign material to the square area that makes the maximum length of the foreign material diagonal is less than or equal to the predetermined value, or The foreign material whose area ratio of the foreign material to the area of the circle which makes the maximum length of a foreign material the diameter is below a set value is determined as a foreign material affixed on the transparent film surface.

3: (A) is a figure explaining the area ratio of the foreign material with respect to the area XY calculated | required by integrating the length component X of the parallel direction of the foreign material, and the length component Y of the vertical direction. FIG. 3B is a diagram for explaining the area ratio of the foreign matter to the area of a square with the maximum length of the foreign material diagonally. FIG. 3C is a diagram illustrating the area ratio of the foreign material to the area of the circle whose maximum length is the diameter of the foreign material.

Although the set value depends on the kind of film and foreign matter in the adhesion environment, in the case of a triacetyl cellulose film, the set value of the area ratio of the foreign matter to the area obtained by integrating the length component in the parallel direction and the length component in the vertical direction is usually about 0.2. ˜0.4, preferably about 0.3, and the set value of the area ratio of the foreign matter to the square area with the diagonal of the maximum length of the foreign material is about 0.2 to 0.4, preferably about 0.3, and the circle having the maximum length of the foreign material as the diameter. The set value of the area ratio of the foreign matter to the area of is about 0.1 to 0.3, preferably about 0.2.

Normally, an image signal is obtained for each pixel or pixel group, and the area is easily obtained from the number of pixels occupied by foreign matter from the length occupied by the pixel.

Furthermore, in the present invention, a high intensity threshold and a low intensity threshold are provided in the signal intensity, and an intensity signal below the low intensity threshold is a vibration of the base signal, and a foreign material that exhibits a signal exceeding the high intensity threshold is a foreign material attached to the transparent film surface. The removal process is performed.

The false signal due to the vibration of the base signal is deleted by the low intensity threshold (threshold value 1), and it is determined that the foreign matter that exhibits a signal exceeding the high intensity threshold (threshold value 2) is a foreign material attached to the transparent film surface (FIG. 4).

Next, the number of foreign substances (FIG. 5) which are less than a high intensity threshold (threshold value 2) and which show signal strength more than a low intensity threshold (threshold value 1) is detected, and the quality of a transparency film is determined.

The setting value of the number of foreign objects which determine the quality of a transparency film changes with kinds, uses, etc. of a transparency film. Moreover, also depending on the size of a foreign material, at least 1 setting value may be provided in the size of a foreign material, and the number of setting values may be provided regarding the magnitude | size of the upper and lower sides.

When triacetyl cellulose is used in a polarizing plate (bonding both sides of the polarizer to produce a polarizing plate), the influence of a large foreign material is large, so that the size of the foreign material is about 90 μm, and the size per 1 m ^{2 of} film area is usually set. If there are less than 150,000 foreign objects with a size of more than 90 μm and less than 2000 foreign materials with less than 90 μm, it can be judged as a good product.

In the transparent film, static electricity is generated when contacting, rubbing, or peeling off the bonded protective film, and dust easily adheres to the surface. Therefore, when producing the sample of the transparent film which performs a foreign material test | inspection, a foreign material may adhere or the attached foreign material may be inspected as it is. As much as possible, the sample film is cleaned to remove adhered foreign matter and inspect it with good precision, so that dust does not adhere.

Specifically, the transparent film extracted to a predetermined size is washed in distilled water to remove deposits on the surface, the washed TAC film is washed in distilled water and inserted between two glass plates free of adhering foreign substances. Fit the transparent film while removing it. The fitted glass plate is taken out of the water, the surroundings are sealed with a water-resistant tape, the glass surface is wiped with a wiping cross to remove moisture, and a sample for inspection is used. Since it is carried out in water, no static electricity is generated, and the surface of the glass plate has a low chargeability compared with the resin film. Therefore, the foreign matter can be washed and removed, and subsequent adhesion of the foreign matter is suppressed.

[Example]

Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

Example 1                     

The foreign material inspection of the triacetyl cellulose film (TAC film) was performed.

The TAC film (sample number: A-1) cut to 25x17 cm was washed in distilled water to remove deposits on the surface. The washed TAC film was washed in distilled water, and inserted between two glass plates (30 x 20 cm) without adherent foreign substances, and the TAC film was fitted while removing bubbles. The fitted glass plate was taken out of water and the circumference was sealed with water resistant tape. The glass surface was wiped with a wiping cross to remove moisture, and a sample of the TAC film for inspection was produced.

As shown in FIG. 1, the two polarizing plates 1 and 2 were arrange | positioned in orthogonal nico between the light source 10 and the camera 20, and the above-mentioned TAC film 3 for inspection produced between them was arrange | positioned. . A 5000-pixel line camera equipped with a 180 W metal halide lamp transmission light as a light source and a 55 mm macro lens as a camera was used.

The foreign material inspection was performed about the inspection range (12x7 cm), moving the sample at 3 m / min. The image signal from the camera was processed by the image processing apparatus 30.

In the area obtained by integrating the length component of the length component in the parallel direction with the length component in the vertical direction and the length component in the parallel direction and the length component in the vertical direction of the foreign material in the length component parallel to the moving direction of the film. Foreign material whose area ratio of the foreign material to the area of a foreign object is 0.3 or less, the area ratio of the foreign material to the square of the diagonal of the maximum length of the foreign material is 0.3 or less, or the area ratio of the foreign material to the area of the circle whose diameter is the maximum length of the foreign material. Silver was removed as foreign matter adhering to the film surface. In addition, there was no foreign matter included in this condition.                     

Next, high intensity | strength threshold and low intensity | strength threshold were provided in signal intensity, and the foreign material which shows the signal over a high intensity threshold was removed as a foreign material adhering to the transparent film surface. The number of foreign substances removed by this was 13 (1550 per 1 m <^2> ).

Furthermore, for foreign bodies below the high intensity threshold and showing signal strength above the low concentration threshold, the number of sizes greater than or equal to 90 μm and less than 90 μm was detected, and more than 90 μm and 13 (1550 per m ² ) and less than 90 μm. There were 31 (3690 per 1 m ² ).

The foreign material test was similarly performed about the other sample of a TAC film. The results are shown in Table 1.

Sample Attachment substance
(Number per 1 m ² ) bow
(Number per 1 m ² ) Remove to geometry Eliminate with signal strength 90 μm or more Less than 90 μm A-1 0 1550 1550 3690 B-1 0 2260 2140 2260 C-1 0 360 1310 2020 C-2 0 120 710 1790 D-1 0 950 1070 600

According to the method of the present invention, foreign matter adhering to the surface of the transparent film is removed and the number of foreign matters can be detected to quickly determine whether the transparent film is good and accurate, and shorten the time for finding out the cause of the foreign material generation, and also needlessly. The occurrence of defective products can be prevented.

Claims (6)

As a method of moving a transparent film between two polarizing plates arrange | positioned with orthogonal Nicole between a light source and a camera, imaging the light from the light source which passes through with a camera, and inspecting the foreign material in a transparent film by the image processing, The ratio of the short component to the long component of the length component of the foreign material parallel to the moving direction of the film and the length component of the vertical direction is below the set value, The area ratio of the foreign material to the area obtained by integrating the length component in the parallel direction of the foreign material and the length component in the vertical direction is less than or equal to the set value, The ratio of the area of the foreign material to the square area of the diagonal of the maximum length of the foreign material is less than or equal to the set value, or The foreign material whose area ratio of the foreign material to the area of the circle which makes the maximum length of the foreign material the diameter is below a set value is removed as a foreign material adhered to the transparent film surface, A high intensity threshold and a low intensity threshold are provided in the signal strength, and the intensity signal below the low intensity threshold is a vibration of the base signal, and the foreign matter that exhibits a signal exceeding the high intensity threshold is a foreign matter adhering to the transparent film surface after the removal treatment. ,  Detect the number of foreign objects, As a good product, the transparency film whose number of foreign objects whose size is more than a setting value is within a setting value, and the number of foreign materials whose size is less than a setting value is within a setting value, The foreign material inspection method of a transparency film characterized by determining the quality of a transparency film. delete delete delete The transparent film is a triacetyl cellulose film, and the ratio of the short component to the long component in the length component in the parallel direction with respect to the moving direction of the film and the length component in the vertical direction is 0.2 to 0.4 or less, the foreign material The ratio of the area of the foreign material to the area obtained by integrating the length component in the parallel direction and the length component in the vertical direction is 0.2 to 0.4 or less, and the area ratio of the foreign material to the square area having the maximum length of the foreign material diagonally is 0.2 to 0.4 or less, Or the foreign material inspection method that the area ratio of the foreign material with respect to the area of the circle which makes the maximum length of the foreign material a diameter is 0.1-0.3 or less. The transparent film of claim 1, wherein the transparent film is a triacetyl cellulose film, and the number of foreign matters having a size of 90 μm or more per 1500 m ² or less is less than 1500, and the number of foreign matters of less than 90 μm is less than 2000. The foreign material inspection method to determine that it is a favorable article.

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