JP2012068210A - Defect inspection method for antireflection transparent film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method enabling accurate detection of a defect by a foreign substance and a defect by a minute change in film thickness around the defect in manufacturing an antireflection film.SOLUTION: A defect inspection method for an antireflection transparent film comprises: imaging and image-processing a surface of an analyte; storing coordinates and the number of defective pixels at a location of a defect which is detected, and a defect image around a portion of the defect; then obtaining density with respect to n pixels in an outer circumferential direction around the portion of the defect of the stored defect image; and further, obtaining and processing density around the defect with respect to the defect image to determine a defect size.

Description

  The present invention relates to an antireflection film for protecting a display screen and preventing dust and preventing reflection of light from the outside in a display device such as a television or a personal computer.

  For display devices such as TVs and PCs, visibility is one of the most important quality characteristics. In general, to protect the display screen and prevent dust from being reflected on the surface of the display screen. The antireflection film manufactured by coating the transparent film with an antireflection material is attached. Accordingly, the antireflection film is required to have extremely strict quality in order to satisfy the above-described function.

  As a quality inspection method of the antireflection film, for example, as an alternative to the visual inspection of the antireflection film cut into a product size, light is irradiated from the upper part of the antireflection film, and the transmitted light is applied to the projection sheet. A method for inspecting whether there is a defect based on light and shadow projected and projected on the projection sheet has been proposed (Patent Document 1).

  Many defect inspection methods are performed on roll-shaped workpieces, and a defect inspection apparatus is provided in the process of manufacturing an antireflection film, particularly in the process of coating an antireflection material on a transparent film.

  For example, a line sensor camera that captures an image of an object to be inspected present on a transparent film, and an image processing device that detects defects by performing image processing on the captured image, and the line sensor camera has a light source around the lens. A defect inspection apparatus having a ring-type fluorescent lamp has been proposed (Patent Document 2).

  In addition, for example, a method has been proposed in which the antireflection film is irradiated with coherent inspection light, and the inspection light is reflected by an antireflection film that is a subject (Patent Document 3).

  However, any of the above-described defect inspection methods has a problem that it is difficult to accurately detect a defect due to a minute change in film thickness around the defect even though it can detect the center of a defect such as a foreign object. .

  In general, the production process of an antireflection film includes a coating / drying process in which an optical film is formed by performing coating / drying one or more times on a roll-shaped transparent film substrate. In the manufacturing process, a defect inspection apparatus is provided to detect defects.

  FIG. 1 shows a schematic configuration diagram of a defect inspection apparatus for an antireflection film that is generally used. Hereinafter, an outline of the defect inspection apparatus will be described with reference to FIG.

  The said defect inspection apparatus conveys a transparent film base material (5) in the direction shown by arrow (8) by the conveyance unit which consists of a some roller (1-4), and is based on illumination light sources (6) and (7). While illuminating the entire width of the material, the transparent film substrate is imaged by a plurality of line CCD cameras (9) so that the entire width direction of the substrate can be scanned. On the other hand, a signal corresponding to the transport distance of the transparent film base material (5) is simultaneously obtained from the rotary encoder (11), and the surface of the transparent film base material is imaged by the line CCD camera (9) at every constant transport distance. Next, the captured image is image-processed by the image processing device (10), the defective portion is extracted and determined, and the defect data (defect position is indicated to the control device (12) including the storage mechanism for the determined defect. This is a device having a mechanism for storing coordinates, the number of pixels of a line CCD camera, and density values as data in a file and a database.

  In general, in the defect extraction process, a binarization process is performed on a captured image with a preset threshold value to detect a defect. FIG. 3 illustrates the defect processing, and will be described below with reference to this figure.

  3A-1 shows a captured image (21), and FIG. 3A-2 shows an image signal of a line segment (22) of the captured image. The captured image (21) shown in FIG. 3 (a-1) is binarized with a preset threshold value to obtain a binary image (25) shown in FIG. 3 (b-1). FIG. 3 (b-2) shows a signal (26) obtained by binarizing the image signal (23) of FIG. 3 (a-2) with a preset threshold (24).

  However, in practice, as shown in FIG. 4, when the coating is performed in a state where the foreign matter adheres to the transparent film base material, or when the foreign matter is mixed in the coating liquid, the foreign matter is involved and applied. In this case, when the optical film (33) is formed on the transparent film substrate, a defect accompanied by the film thickness variation part (32) may occur in a crater shape centering on the foreign matter (31).

  Since the antireflection film according to the present invention has a characteristic that not only the foreign substance itself but also the crater-like film thickness fluctuation portion around the foreign substance has a great influence on the function of the antireflection film, Judgment is necessary based on the area of the entire crater, not just foreign matter. However, the conventional defect detection method has a problem that it is detected as a defect smaller than the actual film thickness variation portion, as described with reference to FIG.

JP 2003-172707 A JP 2005-62119 A JP 2006-112828 A

  The present invention provides an inspection method capable of accurately detecting a defect such as a foreign substance and a defect due to a minute change in film thickness around the defect.

  As a means for solving the above problems, the invention according to claim 1 is a defect inspection method for an antireflection transparent film, wherein the surface of the subject is imaged and image-processed, and the coordinates of the detected defect location are coordinated. In addition, the number of defective pixels and a defect image centered on the defective portion are stored, and then the density of the stored defect image is obtained for pixels corresponding to n pixels in the outer peripheral direction centering on the defective portion. It is a defect inspection method of the antireflection transparent film.

  The invention according to claim 2 is the defect inspection method for an antireflection transparent film according to claim 1, wherein the defect size is determined by acquiring and processing the density around the defect for the defect image. is there.

The inspection method of the present invention makes it possible to detect the area of the entire crater, thereby improving the defect detection accuracy of the inspection machine and improving the product quality assurance.

It is a schematic block diagram explaining an example of the conventional defect inspection apparatus. It is an inspection flowchart explaining an example of the conventional defect inspection apparatus. It is a figure explaining an example of the extraction process of the conventional defect. (A-1) An example of a captured image is shown. (A-2) An example of the image signal of the line segment of a captured image is shown. (B-1) An example of a binarized image is shown. (B-1) An example of a signal obtained by binarizing an image signal is shown. The cross-sectional schematic diagram of the coating film at the time of involving a foreign material during coating is shown. An example of the defect image preserve | saved centering on the defect part based on this invention is shown. An example of density acquisition in the case of n = 2 centering on a defect portion according to the present invention will be shown. It is a test | inspection flowchart based on this invention.

  The inspection method of the antireflection transparent film of the present invention will be described in detail below based on one embodiment.

  The inspection method of the antireflection transparent film of the present invention is an inspection having a function of storing an image of a detected defect and a function sufficient to perform the processing described below, in addition to the defect inspection apparatus described in the prior art. Is the method.

  That is, the inspection method of the present invention performs inspection as usual in the defect inspection apparatus, and stores a defect image centered on the defect portion in addition to the coordinates of the location detected as the defect and the number of defective pixels (see FIG. 5). Examples of stored defect images are shown).

  Next, the density is acquired for pixels corresponding to n pixels in the outer peripheral direction centering on the defect portion detected for the defect image (in FIG. 6, the density acquisition target pixel when n = 2 is shown).

  Next, the density of each pixel in the periphery of the defect is obtained, and the density is determined in a preset table to determine whether or not it is a defective part (examples are shown in Table 1).

  Next, the defect size is determined by combining the number of pixels determined as NG in the above determination and the number of defective pixels detected as defects at the time of inspection.

  That is, the inspection method according to the present invention will be described based on the inspection flow shown in FIG. 7. The surface of the transparent film substrate is imaged, and then the image processing is performed to extract the defective portion, and then the extracted defective portion Is stored together with the peripheral portion, the density around the defective portion is acquired, the defect peripheral pixel determination processing is performed on the stored image, and the defect size is determined.

1 to 4... Roller 5... Transparent film base material 6 and 7. Illumination light source 8... Transparent film base material transport direction 9. ... Rotary encoder 12 ... Control device 21 ... Captured image 22 ... Line segment 23 ... Image signal 24 ... Threshold 25 ... Binary image 26 ... Binary Signal 31 ... Foreign matter 32 ... Film thickness variation part 33 ... Optical film 34 ... Defect part 35 ... Pixel for density acquisition when n = 2

Claims (2)

  A method for inspecting defects in an antireflection transparent film, imaging and image processing of the surface of a subject, storing coordinates of defective portions and the number of defective pixels, and storing defect images centered on defective portions, A defect inspection method for an antireflection transparent film, wherein the density of the stored defect image is obtained for pixels corresponding to n pixels in the outer peripheral direction centering on the defect portion.   The defect inspection method for an antireflection transparent film according to claim 1, wherein the defect size is determined by acquiring and processing density around the defect for the defect image.