JP2012083189A - Antireflection film defect inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film defect inspection device facilitating a defect extraction even if it is a low-contrast defect of the antireflection film.SOLUTION: This antireflection film defect inspection device manufactured by applying an antireflection material to a transparent film-like base material at least includes: conveying means for conveying the antireflection film; an inspection roller for pressing the conveyed antireflection film from the backside and having a black member at a circumferential surface; a roller for cleaning foreign objects stuck to the black member; means for illuminating the surface of the antireflection film pressed to the inspection roller; image pickup means for capturing an image of the illuminated antireflection film to acquire a captured image; image processing means processing the captured image to extract defects; and means adapted to output a defect detection signal to a manufacturing step when the defects are extracted.

Description

  The present invention relates to an apparatus for inspecting a defect of an antireflection film.

  The outermost surface of the display screen of a display device such as a liquid crystal display is manufactured by coating a transparent film with an anti-reflective material to protect the display screen from scratches, and to prevent contamination, antistatic, and reflection. An antireflection film is applied.

  In the production process of the antireflection film, coating and drying are performed one or more times on the roller-like long belt-like translucent film to form an optical film. FIG. 1 is a cross-sectional view showing an example of an antireflection film. The antireflection film shown in FIG. 1 includes a film substrate 1, a hard coat layer 2, and an antireflection layer 3.

  Defects in the antireflection film include optical defects due to variations in the thickness of the coated coating film and changes in hue, and defects such as foreign matter, scratches, and cosmetics. There are also defects such as scratches and dents on the film itself.

  A defect inspection machine is installed in the manufacturing process of the antireflection film to inspect defects. FIG. 2 is a schematic configuration diagram showing an example of a defect inspection apparatus for an antireflection film (hereinafter referred to as a film) that is generally used, and is a transport unit composed of a plurality of rollers 11 to 14 (transport by rotation of rollers). ), The film 15 is conveyed by the illumination light sources 16 and 17 using LEDs, fluorescent lamps, halogen lamps, xenon lamps, UV lamps, etc., and the film 15 is conveyed in the direction indicated by the arrow 18. The film is imaged by a plurality of line CCD cameras 19 (or two-dimensional cameras) so that the entire width direction of the film can be scanned. Both or one of the illumination light sources 16 and 17 is appropriately employed.

  On the other hand, a signal corresponding to the transport distance of the film 15 is acquired from the rotary encoder 21, and the film surface is imaged by the line CCD camera 19 at regular transport distances using the signal as an imaging timing signal. The processing device 20 performs image processing, extracts defective portions, and files defect data (coordinates indicating the position of the defect, the number of pixels of the line CCD camera, density values) to the control device 22 including the storage mechanism. And a defect inspection apparatus having a mechanism for storing the data as data in a database (hereinafter referred to as DB). In this case, instead of the rotary encoder 21, a timer that generates an imaging timing signal at every fixed conveyance distance may be used.

  In general, in the defect extraction process, a binarization process is performed on a captured image with a preset threshold value to extract a defect. 3A and 3B are diagrams for explaining the defect extraction process. FIG. 3A-1 shows a captured image 30 including the defective portion 31, and FIG. 3A-2 shows a line segment 32 of the captured image 30. FIG. The image signal 33 is shown. A signal 31-1 surrounded by a broken line 37 indicates a signal of the defective portion 31. The captured image 30 shown in FIG. 3 (a-1) is binarized with a preset threshold value 34 to obtain a binarized image 35 shown in FIG. 3 (b-1). FIG. 3B-2 shows a signal 36 obtained by binarizing the image signal 33 shown in FIG. 3A-2 with a preset threshold 34.

JP 2006-145493 A JP 2006-225451 A

  In the antireflection layer 3 of the antireflection film, as shown in FIG. 4, the interface reflected light 4 reflected at the interface between the hard coat layer 2 and the antireflection layer 3 is reflected on the surface of the antireflection layer 3. The surface reflection light 5 is changed to light having the same amplitude and opposite phase by the antireflection layer 3 and interference with the surface reflection light is realized. When a partial unevenness of the film thickness occurs in the antireflection layer 3, a difference occurs in the reduction of reflected light due to interference, and the optical defect is inspected.

On the other hand, the film back side is adjacent to a material having a refractive index different from that of the film, and the reflectance is higher than the following formula (1), and the intensity of the reflected light at the interface between the film back surface and the material having a different refractive index Get higher. Here, A is the refractive index of the film, and B is the refractive index of the substance in contact with the back side of the film.
Reflectivity = (refractive index A−refractive index B) / (refractive index A + refractive index B) (1)

  That is, since the intensity of the reflected light from the antireflection layer is weaker than the reflected light from the back surface of the film, the change in the reflected light due to the defect itself is so small that it is buried in the reflected light from the back surface of the film. It is not easy for a skilled person to visually check and inspect the reflected light change caused by the film thickness variation. Therefore, automatic inspection is desired, but defects due to film thickness variation are common. When a defect is extracted with a defect inspection machine, the defect is buried in the noise component. Generally, when a threshold is set to extract a defect, a non-defect portion is extracted as a pseudo defect. Therefore, it is difficult to inspect defects by image processing that is generally used.

  In other words, as shown in FIG. 3 above, the defect can be extracted by binarization processing in the case of the high-contrast defect 31, but in the case of the low contrast as shown in FIG. Therefore, it is impossible to extract only a low-contrast defect even if it is binarized with a certain threshold.

  That is, in the case of the captured image 41 including the low-contrast defect 40 shown in FIG. 5A, for example, when the binarization processing is performed on the image signal 43 of the line segment 42 at the threshold level 44 (FIG. The portions 46 and 47 are extracted as defect signals 53 and 54 as shown in FIG. 52 is a defect signal obtained at the defect portion 45. In the entire area of the captured image 41, noise portions are extracted as pseudo defects 48 to 51 as shown in FIG. 5C is a signal corresponding to the defect 40 in FIG. 5D. Similarly, 53 is a signal corresponding to the pseudo defect 50 obtained by binarizing the noise portion 46, and 54 is a signal corresponding to the noise portion 47. It is a signal corresponding to the pseudo defect 51 subjected to the value processing.

  In this way, when inspecting low-contrast defects in automatic defect inspection, the influence of reflected light from the back of the film is large, and there is also the influence of noise components, so even if illuminance adjustment or threshold setting is performed, the defect Inspection is difficult.

  As a result of illuminance adjustment and threshold setting, even if normal defect inspection can be done temporarily, it is possible to inspect low-contrast defects stably due to the influence of external light and changes in illumination light over time. difficult.

Therefore, in order to reduce the influence of the reflected light from the back surface, a UV lamp may be used as the illumination light source. This is because the TAC (Triacetyl Cellulose) film used for the base material of the anti-reflection film absorbs the wavelength of the UV lamp (ultraviolet light) and reduces the reflected light on the back side of the film. A method of inspecting defects with low contrast is employed.

  As described above, when inspecting a defect of an antireflection film with an automatic inspection apparatus, it is difficult to inspect a defect with low contrast, and when a UV lamp is used to facilitate the inspection, There is a problem that the equipment cost and the maintenance cost are increased due to the use of the UV lamp.

  Accordingly, the present invention has been made in view of such problems, and an object of the present invention is to provide an antireflection film defect inspection apparatus that facilitates defect extraction even with a low-contrast defect in an antireflection film.

The invention according to claim 1 of the present invention is a defect inspection apparatus for an antireflection film manufactured by coating an antireflection material on a transparent film-like substrate,
Conveying means for conveying the antireflection film;
An anti-reflection film to be conveyed is pressed from the back surface, an inspection roller having a black member on the circumferential surface, and
A roller for cleaning foreign matter adhering to the black member;
Means for illuminating the surface of the antireflection film pressed against the inspection roller;
An imaging means for capturing an image of the illuminated antireflection film to obtain a captured image;
Image processing means for processing the captured image and extracting defects;
An antireflection film defect inspection device comprising: means for outputting a defect detection signal when a defect is extracted.

  The invention according to claim 2 of the present invention is the antireflection film defect according to claim 1, wherein the black member is a member having a refractive index of 1.49 to 1.53 and having adhesiveness. Inspection equipment.

  The invention according to claim 3 of the present invention is the antireflection film defect inspection apparatus according to claim 1 or 2, wherein the black member is a soft urethane gel.

  The invention according to claim 4 of the present invention is the antireflection film defect inspection device according to claim 1, wherein the roller for cleaning the foreign matter includes an adhesive member having an adhesive force larger than that of the black member. It is.

  The invention according to claim 5 of the present invention is the antireflection film defect inspection apparatus according to any one of claims 1 to 4, which is provided in an antireflection film manufacturing process.

  According to the antireflection film defect inspection apparatus of the present invention, it is possible to easily inspect defects with low contrast generated in the antireflection film manufacturing process, and it is not necessary to use a conventionally used UV lamp. , Increase in equipment cost and maintenance cost can be suppressed.

The figure which shows an example of an antireflection film in a cross section. The schematic block diagram which shows an example of the defect inspection apparatus of the antireflection film generally used. The figure for demonstrating the extraction process of a defect. (A-1) is a figure which shows the captured image in which a defective part is included. (A-2) is a figure which shows the image signal of the line segment shown in a captured image. (B-1) is the figure which binarized the captured image shown by (a-1) with the threshold value set beforehand. (B-2) is the figure which binarized the image signal shown by (a-2). The figure explaining the effect | action which implement | achieves the antireflection by the antireflection layer of an antireflection film. The figure explaining the case where the binarization process is performed on the captured image including the low-contrast defect. FIG. 6A is a diagram illustrating a captured image including a low-contrast defect. (B) is a figure which shows the case where the binarization process is performed on the image signal of the line segment 42 of (a) figure by a threshold level. (C) is a figure which shows extracting a noise part as a defect signal. FIG. 6D is a diagram illustrating a pseudo defect of a noise portion extracted in the entire region of a captured image. The schematic block diagram which shows an example of the antireflection film defect inspection apparatus which concerns on this invention. The figure which shows the test | inspection roller with which the antireflection film defect inspection apparatus which concerns on this invention was equipped. (A) is a figure which shows the cross section of an inspection roller. (B) is the figure seen from the front of an inspection roller. The figure which shows the luminance distribution waveform graph of the image imaged with the imaging camera. (A) is a figure which shows the luminance distribution waveform graph when not using an inspection roller. (B) is a figure which shows a luminance distribution waveform graph at the time of pressing a black member from the film back surface. (C) is a figure which shows the luminance distribution waveform graph which becomes easy to extract a defect, even if it is a low contrast defect, when a black member is pressed from the film back surface. It is a figure for demonstrating the conveyance means of the film which concerns on this invention, and is a figure which shows the case where an antireflection film defect inspection apparatus is provided in the manufacturing line. The figure for demonstrating the conveyance means different from FIG. 9 of the film which concerns on this invention, and the case where it is provided in the inspection exclusive line. The figure (a) explaining making the film surface imaged with the imaging camera which concerns on this invention into a plane is a case where the film surface imaged with an imaging camera is a curved surface. (B) is the case of the Example of this invention which used the film surface imaged with an imaging camera as a plane. The figure explaining the means to remove the foreign material adhering to the surface of the test | inspection roller which concerns on this invention.

  Hereinafter, an embodiment for carrying out an antireflection film defect inspection apparatus according to the present invention will be described with reference to the drawings.

  FIG. 6 is a schematic configuration diagram showing an example of an antireflection film defect inspection apparatus according to the present invention. The anti-reflection film defect inspection apparatus presses the anti-reflection film (hereinafter referred to as a film) 61 from the back surface with a roller 63 and a roller 64 that are conveying means for conveying the anti-reflection film (hereinafter referred to as film) 61 in the conveying direction indicated by an arrow 62, An inspection roller 65 provided with a black member on the peripheral surface, a roller 66 for cleaning foreign matter adhering to the black member, an illumination light source 67 as a means for illuminating the film 61, and an imaging device as a means for imaging the illuminated film 68, an image processing unit 69 that is an image processing unit that processes a captured image and extracts a defect, and a defect signal output unit 70 that is a unit that outputs a defect detection signal when a defect is extracted. The defect signal output unit 70 feeds back a defect signal to the antireflection film manufacturing process or activates a buzzer or a display lamp to notify the operator of the occurrence of the defect.

  FIG. 7A shows a cross section of the inspection roller 65 provided in the antireflection film defect inspection apparatus according to the present invention. The inspection roller 65 includes a black member 65-2 on the surface of a rigid core material 65-1. As shown in FIG. 7B, the black member 65-2 is wound on the circumference of the full width of the core member 65-1 of the inspection roller. Reference numerals 65-3 and 65-4 denote shafts of the inspection roller 65.

Here, by using the black member, incident light at the interface between the film and the black member is transmitted and absorbed, whereby the intensity of the reflected light is weakened. Furthermore, the refractive index of the film is about 1
. By using a member having a refractive index of 1.49 to 1.53 while being 51, the reflected light at the boundary between the back surface of the film and the black member for the reason shown in the above formula (1) The strength can be weakened.

  FIG. 8 is a graph of the luminance distribution waveform of an image captured by the imaging camera, in which the horizontal axis is a position in the width direction of the film, and the vertical axis is a value obtained by digitizing the luminance of the captured image (analog) in 256 levels. Indicates. A graph 71 in FIG. 8A shows a luminance distribution waveform when the inspection roller 65 is not used. In this case, since the light from the antireflection layer and the light from the back surface are received, the overall brightness is high. In addition, the defect portion indicated by the broken line 72 where the low-contrast defect exists is almost entirely different from the noise portion and is buried in the noise component. Therefore, in order to make it easy to inspect the defective portion, there is a means for increasing the illuminance and increasing the brightness as a whole to increase the contrast ratio as indicated by an arrow 81. In this case, the brightness is high overall, When the illuminance is increased until the defective part appears prominently, a part of the defect exceeds the luminance limit (graph 73), and the defective part is saturated as indicated by a broken line 72-1, thereby obtaining an accurate luminance distribution. It becomes impossible.

  On the other hand, FIG. 8B shows a graph of the luminance distribution waveform when the black member is pressed from the back surface of the film, and the graph 71 of the luminance distribution waveform when the inspection roller 65 is not used (FIG. 8A). (Same as the graph 71 shown in FIG. 4), the black member is pressed against the back surface of the film, so that reflection from the back surface of the film can be suppressed, and the overall luminance level can be lowered as shown by the arrow 82 (graph 74). . In this state, even if the defect has a low contrast as shown in FIG. 8C, by further increasing the illuminance, the graph 74 of the luminance distribution waveform shows the luminance shown by the graph 75 as shown by the arrow 83. It becomes a graph of the distribution waveform. As a result, the luminance difference between the defect and the noise component can be increased without being saturated within the luminance limit, and the defect indicated by the broken line 72-2 can be easily extracted.

  The black member is a black member having a refractive index of 1.49 to 1.53 equivalent to that of the film as described above. Furthermore, it is desirable that the black member has adhesiveness, and the adhesiveness is a member whose adhesive force does not change even when continuously used. By setting it as the member which has adhesive force, the foreign material adhering to a film can be adhere | attached and it can be made to transfer to the black member side.

  The rotation speed of the inspection roller is controlled so that the circumferential speed of the inspection roller is the same as the film feed speed so that friction does not occur between the inspection roller and the film.

  FIG. 9 is a view for explaining a film conveying means. The film 61 is conveyed in the conveying direction indicated by the arrow 62 by the roller 63 and the roller 64 which are conveying means from the tail end of the antireflection film production line. In this case, the roller 63 and the roller 64 may be rotated at a rotational speed controlled at the same circumferential speed as the conveyance speed of the film 61, or may be rotated by contact friction with the film 61 by a roller called a free roller. The film 61 is taken up by a take-up roller 76 provided at the end of the roller 64. The take-up roller 76 is provided with a rotation motor (not shown), and the film 61 is tensioned.

  Further, by pressing the inspection roller 65 from the back side of the film, the film 61 can be brought into close contact with the inspection roller 65 and conveyed while suppressing fluttering, so that an image without unevenness in imaging can be obtained.

Although the case where the antireflection film defect inspection apparatus of the present invention is provided in-line in the antireflection film manufacturing process is exemplified above, it may be used on an inspection-dedicated line as shown in FIG. That is, the film 61 is unwound from the unwinding roller 77, passed through the roller 63, the roller 64, and the roller 64 and then wound on the winding roller 76. The film 61 is tensioned by a brake mechanism (not shown) provided on the unwind roller 77 and a rotation motor (not shown) provided on the take-up roller 76, and further, the film 61 is pressed against the back surface of the film 61 by pressing the inspection roller 65 from the back surface of the film. Can be conveyed while keeping fluttering in close contact with the inspection roller 65.

  FIG. 11 is a diagram illustrating that the film surface imaged by the imaging camera is a flat surface. FIG. 11A is a diagram showing a case where the film 61 and the inspection roller 65 are in contact with each other in a spherical state. In this case, the illumination light 78-1 illuminated on the spherical surface is reflected and diffused by the spherical surface. Thus, a captured image with uneven light intensity is obtained. In particular, this effect becomes significant when the imaging camera 19 is a two-dimensional camera.

  FIG. 11B is a view for explaining the inspection roller 65 for solving the above problem, and a soft urethane gel is used as the black member 65-2 wound around the surface of the inspection roller 65. By using a soft member, the contact area between the film and the black urethane gel is increased, and the film surface imaged by the imaging camera can be made flat, so the reflected light reflected by the illumination light 78-1 on the plane is The reflected light 79-2 has no diffusion, and a stable image can be obtained.

  FIG. 12 is a view for explaining a means for removing foreign matter adhering to the surface of the inspection roller 65. The foreign matter adhering to the surface of the inspection roller 65 is generated when the foreign matter adhering to the film 61 is transferred to the inspection roller 65 or the foreign matter floating in the air adheres to the inspection roller 65. When foreign matter adheres to the surface of the roller 65, the reflectance increases at the boundary between the film back surface and air due to the difference between the refractive index of the film and the refractive index of air around the foreign matter. The intensity of reflected light at the interface of the inspection roller 65 is increased, the luminance difference between the defective portion and the noise portion is reduced, and there is a problem that the defective portion cannot be inspected.

  The means for removing the foreign matter adhering to the surface of the inspection roller shown in FIG. 12 is an adhesive cleaning roller 66 provided so as to be in contact with the inspection roller 65. Further pressing and rotating in the same direction 86 as the rotation direction 85 of the inspection roller 65. At this time, the circumferential speed of the inspection roller 65 and the cleaning roller 66 may be controlled to the same speed, or the cleaning roller 66 may be made free to rotate while being in contact with the inspection roller 65.

  The cleaning roller 66 is obtained by, for example, winding a member 66-2 having adhesive force around a core material 66-1 having rigidity. By using a member 66-2 having an adhesive strength that is greater than that of the black member 65-2, the foreign matter adhering to the black member 65-2 is transferred to the member 66-2 having the adhesive strength of the cleaning roller 66. The foreign matter once transferred to the member 66-2 having the adhesive force of the cleaning roller 66 is not retransferred to the black member 65-2.

  As described above, according to the antireflection film defect inspection apparatus according to the present invention, it is possible to easily inspect defects having low contrast generated in the antireflection film manufacturing process, and a conventionally used UV lamp is used. There is no need, and as a result, an increase in equipment costs and maintenance costs can be suppressed.

DESCRIPTION OF SYMBOLS 1 ... Film base material 2 ... Hard-coat layer 3 ... Antireflection layer 4 ... Interface reflected light 5 ... Surface reflected light 11-14 ... Roller 15 ... Film 16, 17 ... light source 18 ... arrow 19 indicating the direction in which the film is conveyed ... line CCD camera 21 ... rotary encoder 20 ... image processing device 30 ... captured image 31 including defect 31 .... Defect portion 31-1 ... Signal 32 of defect portion 31 ... Line segment 33 of captured image 30 ... Image signal 34 of line segment of captured image 30 ... Threshold value 35 ... Captured image 30 ... Binarized image 36... Image signal 33 binarized signal 37... Broken line 40 indicating defect 31... Low contrast defect 41... Captured image 42 including defect 40 having low contrast ... Line segment 43 in the captured image 41 ... Image signal 44 of line segment 42 in image 41... Threshold level 45... Defect portion 46 and 47... Noise portion 48 to 51. 54 ... Defect signal 61 ... Antireflection film 62 ... Arrows 63, 64 ... Roller 65 ... Inspection roller 65-1, ... Core material of inspection roller indicating the conveyance direction of the antireflection film 65-2 ... Black members 65-3, 65-4 ... Inspection roller shaft 66 ... Cleaning roller 66-1 ... Cleaning roller core 66-2 ... Cleaning roller adhesive force , Illumination light source 68, imaging device 69, image processing unit 70, defect signal output unit 71, luminance distribution waveform graph 72 when no inspection roller is used, low A broken line 72-1 indicating a contrast defect portion. A broken line 72-2 indicating a signal indicating a luminance waveform with saturated contrast ... a defect portion 73 that facilitates extraction of a low-contrast defect ... a luminance distribution waveform graph 71 when the inspection roller is not used, Luminance distribution waveform graph 74 in the case of raising ... Brightness distribution waveform graph 76 in the case of using an inspection roller ... Winding roller 77 ... Unwinding rollers 78-1, 78-2 ... Illumination light 79 -1 ... Diffused reflected light 79-2 ... Non-diffused reflected light 81 ... Arrow 82 indicating the direction of increasing the contrast ratio ... Decreasing the overall luminance level when an inspection roller is used Arrow 83 indicating direction: Arrow 85 indicating the direction in which the luminance distribution waveform is increased by further increasing the illuminance when the inspection roller is used. Arrow 86 indicating the rotation direction of the inspection roller. Arrow indicating the direction of rotation

Claims (5)

A device for inspecting defects of an antireflection film produced by coating an antireflection material on a transparent film-like substrate, at least,
Conveying means for conveying the antireflection film;
An anti-reflection film to be conveyed is pressed from the back surface, an inspection roller having a black member on the circumferential surface, and
A roller for cleaning foreign matter adhering to the black member;
Means for illuminating the surface of the antireflection film pressed against the inspection roller;
An imaging means for capturing an image of the illuminated antireflection film to obtain a captured image;
Image processing means for processing the captured image and extracting defects;
An antireflection film defect inspection device comprising: means for outputting a defect detection signal to a manufacturing process when a defect is extracted.   2. The antireflection film defect inspection apparatus according to claim 1, wherein the black member is a member having a refractive index of 1.49 to 1.53 and having adhesiveness.   The antireflection film defect inspection apparatus according to claim 1, wherein the black member is a soft urethane gel.   The antireflection film defect inspection apparatus according to claim 1, wherein the roller for cleaning the foreign matter includes an adhesive member having an adhesive force larger than that of the black member.   The antireflection film defect inspection apparatus according to claim 1, which is provided in an antireflection film manufacturing process.

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