JP4595564B2 - Preparation method for foreign matter inspection of transparent film and foreign matter inspection method - Google Patents

Description

  The present invention relates to a method for preparing an inspection sample and a foreign matter inspection method for inspecting a foreign matter on a transparent film. More specifically, the present invention relates to a method for preparing a foreign matter inspection sample and a foreign matter inspection method with less foreign matter adhering during handling.

Foreign matter becomes a problem in transparent films such as polycarbonate films, polymethacrylate films, polyethylene terephthalate films, polyvinyl alcohol films, triacetyl cellulose films, and polyolefin films, particularly transparent films for optical applications.
These transparent films are used alone or laminated. These films or laminated films are often handled in a state in which a protective film is bonded to at least one side after production.

Inspection is indispensable because foreign matter on the transparent film becomes a product defect. For inspection, for example, two polarizing plates are placed in a crossed Nicols state, that is, their polarization axes are orthogonal to each other, a transparent film to be inspected is placed between the two polarizing plates, and light is emitted from the light source. The transmitted light screen is observed with a camera.
When the transparent film to be inspected is a protective film adhesive polarizing plate, the protective film adhesive polarizing plate to be inspected with respect to the inspection polarizing plate is arranged in a crossed Nicol state. The light transmitted through the protective film adhesive polarizing plate to be inspected is completely blocked by the inspection polarizing plate, but if there is a foreign object on the inspection polarizing plate side of the polarizing plate to be inspected, it is observed as a bright part Thus, foreign matter can be inspected. The foreign matter on the opposite side can be obtained by turning over the polarizing plate to be inspected and inspecting in the same manner (for example, see Patent Document 1 and Patent Document 2).
JP 2000-206327 A JP 2001-349839 A

The method of placing the transparent film to be inspected between the two polarizing plates arranged in the crossed Nicols is an excellent method, but it is a foreign substance inside the transparent film to be inspected, or adheres to the surface. It is difficult to determine whether it is a foreign object.
The transparent film generates static electricity when it comes into contact, friction or when the protective film is peeled off, and dust is likely to adhere to the surface. Dust adhering to the surface when inspecting foreign matter on the transparent film Is removed by air blow or the like, but it cannot be completely removed, and it takes time to grasp the adhered foreign matter.

  An object of the present invention is to provide a sample for inspection of a transparent film with little adhered foreign matter, and to facilitate foreign matter inspection because at least the operation of detecting and removing the adhered foreign matter is not necessary.

  As a result of diligent examination of a foreign matter inspection method for a transparent film in order to solve such a problem, the present inventor washed the transparent film in water and sandwiched both surfaces of the transparent film in water with two transparent glass plates. After that, the sample for foreign matter inspection produced by sandwiching the periphery of two transparent glass plates sandwiched with a transparent film in air with a glass plate prepared by sealing with a water-resistant tape has less adhered foreign matters, It has been found that an operation for detecting and removing the adhering foreign matter is not required, and the foreign matter inspection becomes easy, and the present invention has been completed.

That is, the present invention is to wash a transparent film for foreign matter inspection in water, hold both sides of the transparent film with water in the transparent glass plate as it is, and then waterproof the periphery of the glass plate in which the transparent film is held in the air. A method for producing a sample for foreign matter inspection of a transparent film, characterized by sealing with a tape.
Moreover, in the method of optically inspecting the foreign matter of the transparent film, the transparent film is washed in water as a sample for inspecting the foreign matter of the transparent film, and the two transparent glass plates on both sides of the transparent film in the water as it is Transparency characterized by using a transparent film sandwiched between two transparent glass plates sandwiched with a water-resistant tape after being sandwiched between two transparent glass plates sandwiched with a transparent film in air This is a film foreign matter inspection method.

  According to the method of the present invention, foreign matter adhering to the inspection sample of the transparent film can be reduced, and at least an operation for detecting and removing the foreign matter is not required, and foreign matter inspection is facilitated.

  The transparent film of the present invention is not particularly limited, and examples thereof include a polycarbonate film, a polymethacrylate film, a polyethylene terephthalate film, a polyvinyl alcohol film, a triacetyl cellulose film, and a polyolefin film.

FIG. 1 is a view showing an outline of a method for producing a foreign matter inspection sample of a transparent film of the present invention. The transparent film (1) to be inspected for foreign matter is washed in water (distilled water) to remove surface deposits. The washed transparent film is washed in distilled water and inserted between two transparent glass plates (2) having no adhered foreign matter, and the transparent film is sandwiched while removing bubbles. The sandwiched transparent glass plate is taken out from the water, and the periphery is sealed with a water-resistant tape (3). The transparent glass surface is wiped with a wiping cloth (4), moisture is removed, and a test sample is prepared.
Although a thin film of water is formed inside the two glass plates, it does not hinder foreign matter inspection.
Since it is carried out in water, there is no generation of static electricity, and the surface of the glass plate is less charged than the resin film. Accordingly, the foreign matter can be cleaned and removed, and the subsequent adhesion of the foreign matter can be suppressed.

FIG. 2 is a schematic view showing an example of an apparatus for inspecting foreign matters by transmitting light through a transparent film.
Two polarizing plates (5) and (6) are arranged between the light source (10) and the camera (20), and the transparent film to be inspected is sandwiched between two transparent glass plates in water. (7) is arranged. Here, the two polarizing plates are arranged in crossed Nicols, that is, in a state where their polarization axes are orthogonal to each other. The image signal from the camera is processed by the image processing device (30) to detect foreign matter and output to the monitor. When the transparent film to be inspected is a polarizing plate, only one of the two polarizing plates is disposed.

  The light from the light source (10) selectively transmits the polarization component in the polarization axis direction of the polarizing plate (5). If there is no foreign matter in the transparent film (7), the light transmitted through the transparent film is polarized. The image captured by the camera is darkened by being blocked by the plate (6). If there is a foreign substance in the transparent film, the polarization direction of the portion changes, passes through the polarizing plate (5), and a bright portion (bright spot) appears in a dark photographed image.

As a camera, a CCD camera is usually used, and an image signal obtained by photographing is subjected to image processing using a computer system by an image processing apparatus, and foreign matter is detected. Usually, the size of the foreign matter is grasped from the signal intensity.
Although it depends on the resolution of the CCD camera used, when a foreign object is visually inspected using a microscope instead of a CCD camera, it is possible to detect a smaller object due to the focus, but the detection range is narrow and the entire inspection is performed. It takes time and is not a preferable method for quickly inspecting many samples.

There are various shapes and sizes of foreign substances adhering to the transparent film, and a typical example is a lint-like one shown in FIG.
Such foreign matter has a ratio of the short component to the long component of the length component in the direction parallel to the moving direction of the film and the length component in the vertical direction equal to or less than the set value, The ratio of the area of the foreign object to the area obtained by multiplying the vertical length component is less than the set value, the ratio of the area of the foreign object to the square area whose diagonal is the maximum length of the foreign object is less than the set value, or the maximum of the foreign object It is possible to detect a foreign object having an area ratio of the foreign object to the area of a circle whose length is a diameter being equal to or less than a set value.

  FIG. 4 is a diagram for explaining this. The foreign matter is schematically shown as an elongated ellipse, and in (A), the white arrow indicates the moving direction of the film, the length component of the foreign matter in the parallel direction is indicated by X, and the length component in the vertical direction is indicated by Y. The size of the length component in the parallel direction and the length component in the vertical direction varies depending on the degree of inclination of the foreign material with respect to the moving direction of the film. In the present invention, it is determined that a foreign material having a ratio of a short component to a long component equal to or less than a set value is adhered to the surface. The set value depends on the type of film and the foreign matter in the adhesion environment, but in the case of a triacetyl cellulose film, it is usually determined by setting it to about 0.2 to 0.4, preferably about 0.3.

FIG. 4A is a diagram for explaining the area ratio of the foreign matter to the area XY obtained by multiplying the length component X of the foreign matter in the parallel direction and the length component Y in the vertical direction. FIG. 4B is a diagram illustrating the area ratio of a foreign object to a square area whose diagonal is the maximum length of the foreign object. FIG. 4C is a diagram for explaining the area ratio of a foreign object to the area of a circle whose diameter is the maximum length of the foreign object.
The set value depends on the type of film and the foreign material in the adhesion environment. However, in the case of a triacetyl cellulose film, the foreign material is usually multiplied by the length component in the vertical direction and the length component in the vertical direction. The set value of the ratio of the area is about 0.2 to 0.4, preferably about 0.3, and the set value of the area ratio of the foreign matter to the square area whose diagonal is the maximum length of the foreign matter is about 0.2. To 0.4, preferably about 0.3, and the set value of the area ratio of the foreign matter to the area of the circle whose diameter is the maximum length of the foreign matter is about 0.1 to 0.3, preferably about 0.2. It is determined by.

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

  In this manner, the lint-like adhered foreign matter shown in FIG. 3 is grasped, but the foreign matter in the transparent film can be detected by the magnitude of the signal intensity.

  In the sample for inspecting foreign matter of the transparent film produced by the method of the present invention, the attached foreign matter detected by the above method is hardly seen, and the operation for detecting this attached foreign matter can be omitted.

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

Example 1
The foreign matter inspection of the triacetyl cellulose film (TAC film) (A-1) was performed.
As shown in FIG. 1, the TAC film cut out at 25 × 17 cm was washed in distilled water to remove surface deposits. The washed TAC film was washed in distilled water and inserted between two glass plates (30 × 20 cm) having no adhered foreign matter, and the TAC film was sandwiched while removing bubbles. The sandwiched glass plate was taken out from the water, and the periphery was sealed with water-resistant tape. The glass surface was wiped with a wiping cloth to remove moisture, and a sample TAC film for inspection was prepared.

As shown in FIG. 2, between the light source (10) and the camera (20), two polarizing plates (5) and (6) are arranged in crossed Nicols, and the inspection TAC film produced between them ( 7) was placed. A 5000-pixel line camera equipped with a 180 W Metahara transmission light as a light source and a 55 mm macro lens as a camera was used.
Foreign matter inspection was performed while moving the sample at 3 m / min. The image signal from the camera was processed by the image processing device (30).

The ratio of the short component to the long component of the length component in the direction parallel to the moving direction of the film and the length component in the vertical direction is 0.3 or less, the length component in the parallel direction and the length in the vertical direction The ratio of the area of the foreign object to the area obtained by multiplying the components is 0.3 or less, the area ratio of the foreign object to the square area whose diagonal is the maximum length of the foreign object is 0.3 or less, or the maximum length of the foreign object No foreign matter having a foreign matter area ratio of 0.2 or less with respect to the area of the circle as the diameter was detected.
Foreign matter inspection was similarly performed on other samples of the TAC film. The results are shown in Table 1.

Comparative Example 1
A TAC film (A-1) cut out to 25 × 17 cm was directly bonded to a glass plate (30 × 20 cm) with an adhesive P3132 (manufactured by Lintec Corporation) to prepare a sample. Using this sample, foreign matter inspection was performed in the same manner as in Example 1. 1 m ² per 480 of the foreign matter is detected.
Foreign matter inspection was similarly performed on other samples of the TAC film. The results are shown in Table 1.

本発明の方法で作製した異物検査試料には図３で示す付着異物が検出されず、異物検査する際に付着異物を検出する操作を省略できる。

3 is not detected in the foreign matter inspection sample produced by the method of the present invention, and the operation of detecting the attached foreign matter can be omitted when the foreign matter inspection is performed.

It is a figure which shows the outline | summary of the method of producing the sample for foreign material inspection of the transparent film of this invention. It is a schematic diagram which shows an example of the apparatus which permeate | transmits light to a transparent film and test | inspects a foreign material. It is a figure which shows the example of the foreign material adhering to the transparency film. It is a figure for demonstrating the method to prescribe | regulate the shape of a foreign material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent film 2 Glass plate 3 Water-resistant tape 4 Wiping cloth 5 Polarizing plate 6 Polarizing plate 7 Transparent film 10 Light source 20 Camera 30 Image processing apparatus

Claims (4)

  The transparent film for foreign substance inspection is washed in water, and both sides of the transparent film are sandwiched between transparent glass plates in water, and then the periphery of the glass plate sandwiched in the air is sealed with water-resistant tape. A method for producing a sample for inspecting a foreign substance of a transparent film.   In the method of optically inspecting the foreign matter of the transparent film, the transparent film is washed in water as a sample for inspecting the foreign matter of the transparent film, and both sides of the transparent film are sandwiched between two transparent glass plates in the water. Then, a transparent film sandwiched between glass plates produced by sealing the periphery of two transparent glass plates sandwiched with a transparent film in air with a water-resistant tape is used. Foreign substance inspection method. Method of inspecting a foreign material optically method of claim 2 wherein the method by transmitting light transparency film for inspecting foreign matter.   A method for optically inspecting a foreign object is to move a transparent film between two polarizing plates arranged in crossed Nicols between a light source and a camera, and photograph the light from the transmitted light source with the camera. 3. The method according to claim 2, which is a method for inspecting foreign matter in the transparent film by treatment.

Images