JP2012247343A - Defect inspection method of antireflection film and defect inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection method of an antireflection film substrate with which a standing-wave phenomenon of a simple film substrate that is not accompanied with a foreign substance is prevented from being recognized erroneously as a defect.SOLUTION: A defect inspection method of an antireflection film substrate 5 is provided. The method is characterized in that first reflection imaging optical systems 7 and 10 and second transmission imaging optical systems 6 and 9 are provided. The first reflection imaging optical systems 7 and 10 receive light reflected in an oblique direction in irradiation light that irradiates the film substrate 5. The second transmission imaging optical systems 6 and 9 receive light transmitted in a vertical direction in the irradiation light that irradiates the film substrate 5. If any defect is detected by the first reflection imaging optical systems, only in the case where a defect is also detected at the same position on the film substrate by the second transmission imaging optical systems, it is determined that there is a defect in that portion.

Description

  The present invention relates to an antireflection film that is attached to the surface of a display screen for image display to reduce external light reflection and make the display screen easier to see, and in particular, is caused by foreign matter involved in manufacturing the antireflection film. The present invention relates to an inspection method for optically identifying a defect to be detected and a mere wave of a base film, and an apparatus therefor.

  In display devices such as liquid crystal displays and plasma displays, “ease of viewing” is one of the most important quality characteristics. To achieve the quality, the display screen is protected from the outside with display screen protection and dust prevention. In order to prevent reflection of light, an antireflection film manufactured by forming a hard coat layer or an antireflection layer by coating on a transparent film (hereinafter also referred to as a film substrate or simply a film) is attached.

  The production of the antireflection film is carried out by applying the sol-gel solution mainly composed of a metal oxide to a long belt-like light-transmitting film substrate one or more times and drying the optical film having a predetermined thickness. Is forming. Defects that are manifested in the manufacturing process of the antireflection film include defects that can be optically detected due to variations in film thickness or changes in hue due to adhesion of foreign matter or contamination.

  Therefore, a defect inspection apparatus is introduced and installed in the antireflection film manufacturing process in order to detect defects. FIG. 1 is a schematic view showing an example of the configuration of an in-line defect detection device for an antireflection film according to the present invention, but generally the same configuration is generally used.

  Here, the substrate 5 is conveyed by a conveyance unit (conveyance by rotation of rollers) composed of a plurality of rollers 1 to 4, and an illumination light source 6 and an illumination light source 7 using an LED, a fluorescent lamp, a halogen lamp, a xenon lamp, or the like. Illuminates the entire width of the film substrate.

  A plurality of line CCD cameras 9 and CCD cameras 10 are arranged so that the width direction of the substrate can be fully scanned while the film substrate 5 is conveyed in the direction indicated by the arrow 8, and a signal corresponding to the conveyance distance of the substrate 5 is rotated. While acquiring from the encoder 13, the surface of the base material is imaged from a plurality of predetermined directions by the line CCD cameras 9 and 10 for every predetermined transport distance.

  The captured image is subjected to digital image processing by the image processing apparatuses 11 and 12, extraction and determination of a defective portion are performed, and for a portion determined as a defect, data indicating the attribute of the defect (coordinates indicating the position of the defect, The number of pixels and the density value of the line CCD camera are stored in a database of a storage mechanism and can be accessed through the control device 14 system.

  The imaging system for acquiring the image data includes a transmission optical system in which the illumination light source 6, the line CCD camera 9 and the image processing device 11 are combined, and a combination of the illumination light source 7, the line CCD camera 10 and the image processing device 12 in the reflection optical system. Either or both can be provided. FIG. 3 shows the above inspection flow. The same algorithm is used for image processing and the like in both the transmission optical system and the reflection optical system.

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. 2A and 2B are diagrams for explaining the defect extraction processing. FIG. 2A shows an analog captured image 21 and FIG. 2B shows an intensity distribution 23 of an image signal along a line segment 22 of the captured image. Indicates. When binarization processing is performed on the analog captured image 21 illustrated in FIG. 2A with a preset threshold, a digitized binarized image 25 illustrated in FIG. 2C is obtained. FIG. 2D shows a signal intensity 26 obtained by binarizing the digital image signal 23 of FIG.

In the production process of the antireflection film, coating and drying are performed once or a plurality of times on a long belt-like translucent film base material to form an optical film having desired optical characteristics. When coating is performed with foreign matter adhering to the base material, or when foreign matter is involved when foreign matter is mixed into the coating liquid, as shown schematically in FIG. Then, a defect accompanied by the film thickness variation portion 42 is generated in a crater shape. (Hereafter referred to as crater 42)
Due to the characteristics of the product, the film thickness variation part affects the antireflection function of the antireflection film, although it depends on its size. Therefore, as a product shipping standard, not only the position detection of the central foreign matter 41 but also the crater 42 It is necessary to perform defect determination with the entire area.

  It is known that the film thickness variation of the crater 42 can be detected by performing a reflection inspection using an ultraviolet light source having a wavelength range of 300 to 400 nm, and by using a transmission inspection in the visible wavelength region. It is known that foreign matter generated at the center of the crater 42 can be detected (see Patent Document 3).

JP 2009-16654 A JP 2010-34382 A JP 2006-038728 A

An example of a schematic configuration of the defect inspection apparatus is shown in FIG. This is done by image processing. However, when the film substrate 1 is transported, the film substrate vibrates between the roller 2 and the roller 3, and if the surface of the film is violated and the undulation is generated, the undulation is recognized and detected as a defect. There is.
Accordingly, an object of the present invention is to provide a defect inspection method that does not misrecognize the undulation phenomenon of a film base material without foreign matter as a defect.

In order to achieve the above-mentioned object, the invention according to claim 1 irradiates the film substrate with the first imaging optical system that receives light reflected in an oblique direction among the irradiation light irradiated on the film substrate. A second imaging optical system that receives light that passes through in the vertical direction of the irradiation light, and when the first imaging optical system detects a defect, the second imaging optical system also has the same position on the film substrate. Only when a defect has been detected, the defect inspection method for an antireflection film is characterized in that it is determined that the part has a defect.
The invention according to claim 2 is a first imaging optical system that receives light reflected in an oblique direction among irradiation light irradiated on the film substrate, and a vertical direction among irradiation light irradiated on the film substrate. A second imaging optical system that receives the light transmitted through the first imaging optical system, and an image processing device for digitally comparing and collating defect patterns obtained from the first imaging optical system and the second imaging optical system. It is set as the defect inspection apparatus of the antireflection film characterized by these.

According to the defect determination method using the defect inspection apparatus according to the present invention, the defect inspection apparatus misrecognizes a wave phenomenon of a pure film base material that does not involve a foreign material source generated when the film base material is transported as a “defect”. There is nothing. Therefore, efficient defect inspection is possible.

It is a conceptual diagram explaining schematic structure of the defect inspection apparatus which becomes this invention. (A)-(d) It is drawing explaining a mode that the analog pattern of a defect is digitized with a certain threshold value. It is a flowchart explaining the algorithm of a defect determination. It is a figure of the cross-sectional view which illustrates typically the presence of the defect on a film base material. It is a figure which illustrates typically the behavior of the reflected light and the transmitted light from the wave part of a film base material. (A) reflected light, (b) transmitted light. It is a flowchart explaining the algorithm of the image comparison of a reflective imaging system and a transmissive imaging system.

  Hereinafter, the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of the configuration of an inline defect detection device for an antireflection film according to the present invention.

  The film base 5 is transported in a direction indicated by an arrow 8 by a transport unit composed of a plurality of rollers 1 to 4 (transport by rotation of rollers), and an illumination light source 6 using an LED, a fluorescent lamp, a halogen lamp, a xenon lamp, or the like. And the entire width of the substrate is illuminated by the illumination light source 7.

  As an optical system for imaging the surface state of the film substrate 5, at least two systems are provided, one of which is a first imaging optical system (hereinafter referred to as a reflection imaging optical system) that captures a reflected image, and the other that is used to capture a transmission image. This is a second imaging optical system (hereinafter referred to as a transmission imaging optical system). The first imaging optical system includes a first light source 7, a line CCD camera 10, and an image processing device 12. The second optical system includes a second light source 6, a CCD camera 9, and an image processing device 11. ing. While the signal corresponding to the transport distance of the base material 5 is acquired from the rotary encoder 13, the surface of the base material is imaged from a plurality of predetermined directions by the line CCD cameras 9 and 10 at every constant transport distance.

  It is desirable that the focal points of the first line CCD camera 10 and the second line CCD camera 9 on the film base 5 are the same position, but this is not an absolute requirement because it may be difficult due to the arrangement of the CCD camera device. . This is because the same position acquired at different timings from the calculation of the transport distance by the rotary encoder can be electronically performed.

  The captured image is subjected to digital image processing by the first image processing device 11 and the second image processing device 12, extraction and determination of a defective part is performed in the first image processing, and a portion determined to be a defect is The comparison with the image data of the part in the second image processing apparatus is performed by the control apparatus 14 or any one of the image processing apparatuses 11 and 12. If it is also determined as a defect in the second image processing apparatus, it is determined as a genuine defect. If it is not judged, it is judged that the wave of the film base material was mistakenly recognized.

  An example of an algorithm for defect determination is shown in FIG. 3, but those satisfying several conditions such as the resolution of the CCD camera, the size of the foreign matter, the appearance shape, and the reproducibility are determined to be defects. None are not determined to be defective.

  As shown in FIG. 5A, the difference in imaging effect between the reflective imaging optical system and the transmissive imaging optical system is that, as shown in FIG. The detected reflected light intensity may be reduced and erroneously detected as a defect. Regarding the threshold value to be digitized from analog data, it is necessary to set in advance the simulation of the behavior of the reflected light of the pure wave portion in consideration of the refractive index and thickness of the film substrate and the antireflection layer.

  On the other hand, in the transmissive imaging optical system, as shown in FIG. 5B, it is difficult to be affected by undulations, and the amount of light reaching a part of the CCD camera is slightly reduced, but not as high as that of the reflective optical system. It is presumed that the light incident obliquely and reflected obliquely is more susceptible to the wave of the film substrate than the straight light. Therefore, a portion that is not determined to be a defect in both the reflection imaging system and the transmission imaging system is determined as an erroneous determination due to undulations, and is not determined as a defect.

  An outline of the above algorithm is shown in FIG. It is necessary to provide an inspection apparatus having a function of comparing and collating defect information detected by the transmission imaging optical system and defect information detected by the reflection imaging optical system at high speed. The collation / comparison processing of the digitized image data may be performed by the control device 14, may be any image processing device, or may be provided with a special processing device.

  In the inspection apparatus, inspection is performed as usual using a transmission optical system and a reflection optical system, and defect information such as coordinates of a portion detected as a defect is stored.

  For defects detected by the transmission optical system, use the defect coordinates to check whether they are detected as defects by the reflection optical system, and output only defects detected by both the transmission and reflection optical systems as defects. It is.

1, 2, 3, 4, transport roller 5, film base 6, second light source 7, first light source 8, cleaning unit (wiping)
9. CCD camera (second)
10. CCD camera (first)
11. Image processing device (second)
12. Image processing device (first)
13, rotary encoder 21, analog image 22 of defect area, reference plane 23 of sectional view, intensity distribution of analog signal (peak value thereof)
24, digitization threshold 25, digital image 26 of defect area, digital signal intensity distribution 41, foreign matter 42, film thickness variation portion 43, film substrate 44, crater

Claims (2)

  A first imaging optical system that receives light reflected in an oblique direction among irradiation light irradiated on the film base and a second that receives light transmitted in the vertical direction among irradiation light irradiated on the film base An imaging optical system, and when the first imaging optical system detects a defect, the second imaging optical system detects a defect at the same position on the film substrate only when the defect is detected at the site. A method for inspecting a defect of an antireflection film, characterized by determining that there is.   A first imaging optical system that receives light reflected in an oblique direction out of irradiation light irradiated on the film base, and a second that receives light transmitted in the vertical direction among irradiation light irradiated on the film base And an image processing apparatus for digitally comparing and comparing defect patterns obtained from the first imaging optical system and the second imaging optical system. Inspection device.

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