TW202223451A - Method for detecting edge part of optical film - Google Patents

Abstract

Provided is a method for detecting the edge part of an optical film with which it is possible to reliably detect the edge part of an optical film affixed to a rectangular panel. The detection method includes: a transportation step for transporting a rectangular panel on which an optical film is laminated; an imaging step for imaging a target region including the edge part of the optical film on the rectangular panel; an optimum image selection step for selecting, from a plurality of images obtained by imaging the target region at a plurality of positions, an optimum image for detecting the edge part; and an edge part detection step for detecting the edge part in the optimum image. In the imaging step, light is sequentially beamed from a plurality of light sources disposed along the transportation direction in which the rectangular panels are transported, and the target region is imaged at a plurality of positions extending from the upstream side to the downstream side with respect to the transportation direction by a single imaging means.

Description

Edge detection method of optical film

The present invention relates to a method for detecting an edge of an optical film used in an optical display panel, and more particularly, to a method for detecting an edge of an optical film, which is used for inspecting a rectangular panel and an optical film attached to the rectangular panel. When there is a deviation in lamination between films, the optimal image that can most reliably detect the edge of the optical film is selected from a plurality of images captured, and the edge of the optical film is detected using the optimal image. department.

In the case of an optical display panel, various display functions can be realized by attaching various optical films having optical functions to a rectangular panel as necessary. In the manufacturing process of the optical display panel, after bonding the optical film to the surface of the rectangular panel, in order to confirm the accuracy of the bonding between the two, the inspection of the bonding state of the rectangular panel and the optical film (so-called bonding deviation inspection) is performed. As a conventional bonding deviation inspection method, the method described in Patent Document 1 and Patent Document 2 has been proposed, for example.

In Patent Document 1, it is disclosed that a corner portion of an optical display panel to which a polarizing plate and a liquid crystal panel are bonded is photographed by an area camera or a line camera which is arranged to be capable of photographing from vertically above the corner portion. The amount of deviation of the fit is calculated using the image captured by the camera. Moreover, in Patent Document 2, it is disclosed that it is possible to inspect the lamination deviation by using an area sensor camera to photograph the corners of the panel while conveying the optical display panel to which the optical film sheet is attached to the optical inspection chamber. Methods. In this method, the distance between the end of the optical detection chamber and the end of the optical film sheet is calculated from the captured image, and the lamination deviation is determined based on the distance. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2011-197281 [Patent Document 2] Japanese Patent Laid-Open No. 2016-118580 [Patent Document 3] Japanese Patent No. 4377964

[Problems to be Solved by Invention]

In the conventional bonding deviation inspection methods including Patent Document 1 and Patent Document 2, the optical display panel enters a certain area (hereinafter referred to as the target area) including the corners of both the rectangular panel and the optical film. Shoot when the camera is in the shooting area and reaches the shooting point. The photographing point is generally the position where the edge of the optical film on the optical display panel (generally the frontmost edge in the moving direction of the optical film) reaches the vertical downward direction of the camera. In the captured image, the edge of the optical film appears as a luminous line (bright line) because light from the light source is reflected at the edge of the optical film, and the image can be detected by recognizing the reflected light. The edge of the optical film inside the image. However, depending on the state of the edge of the optical film attached to the rectangular panel, it may be difficult to detect the edge only from an image captured when the edge reaches the imaging point.

For example, when the end face of the optical film in the captured image has a shape that does not easily reflect light from the light source, or when the reflected light from the end face is at an angle that does not easily reach the camera, it is difficult to detect the edge of the optical film. .

The object of the present invention is to provide a method for detecting the edge portion of an optical film, which is applied to an inspection method capable of accurately inspecting the lamination deviation between a rectangular panel and an optical film, and can reliably detect the lamination of the rectangular panel and the optical film. The edge of the optical film. [Technical means to solve problems]

The present invention is based on comparing the image obtained when the edge portion of the optical film is photographed by irradiating light from a light source arranged on the upstream side of the conveyance direction of the rectangular panel, and photographing the edge by irradiating light from a light source arranged on the downstream side in the conveying direction of the rectangular panel. It can be seen that the irradiation direction of the image in which the edge portion is easily detected is different depending on the position of the conveying direction of the optical film.

In the present invention, for an optical display panel in which an optical film is laminated on a rectangular panel, a plurality of images of the target area including the corners of the rectangular panel and the corners of the optical film are obtained by sequentially irradiating light from a plurality of light sources. , select the optimal image that can most reliably detect the edge of the optical film among the plurality of images, and use the optimal image to detect the edge of the optical film.

That is, the present invention provides an optical film edge detection method for detecting an edge of an optical film laminated on a rectangular panel, comprising: a conveying step of conveying the rectangular panel laminated with the optical film; a photographing step of photographing a rectangular panel the object area on the panel including the edge of the optical film; the best image selection step is to select the best image for detecting the edge from among a plurality of images obtained by photographing the object area at a plurality of positions image; and an edge detection step, which detects the edge in the best image. In the imaging step, light from a plurality of light sources arranged along the conveyance direction of the rectangular panel is sequentially irradiated, and a target area is imaged at a plurality of positions from the upstream side to the downstream side in the conveyance direction by one imaging means. The optimal image is selected according to the brightness of the middle edge of each image.

In one embodiment, it is preferable that the plurality of light sources include at least an upstream-side light source arranged on the upstream side of the conveying direction and a downstream-side light source arranged on the downstream side of the imaging means for the imaging target region. Preferably, in the photographing step, when the edge is positioned more upstream in the conveyance direction than the photographing point, which is a position where the edge reaches the vertical downward direction of the imaging means, light is irradiated from an upstream light source and photographed, and the edge is irradiated with light. When it is located on the downstream side in the conveyance direction from the imaging point, light is irradiated from the downstream side light source to photograph.

In one embodiment, preferably, in the optimal image selection step, the optimal image is selected according to the brightness of a plurality of locations set along the edge. Furthermore, in another embodiment, it is preferable that in the above-mentioned photographing step, a plurality of images are photographed while the rectangular panel is stopped for each photographing, and a light source arranged to face the width direction of the rectangular panel is further used. light to capture multiple images. [Effect of invention]

According to the present invention, the optimal image that can reliably detect the bright line of the edge of the optical film is selected from a plurality of images including a predetermined area of the edge of the optical film to be attached to the rectangular panel. This image can be used to inspect the misalignment of the optical film in an easier and more precise manner.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the case where a polarizing film is used as an optical film, a rectangular panel is used as a liquid crystal cell, and an optical display panel is a liquid crystal panel in which an optical film is bonded to the rectangular panel is explained as an example, but it is not limited to these. The present invention can also be used for inspection of various optical display panels produced by bonding a film having an optical function to a rectangular panel.

[Outline of liquid crystal panel manufacturing apparatus and polarizing film edge detection apparatus] The film edge detection method of the present invention can be used for, for example, an apparatus for producing a liquid crystal panel by continuously bonding a polarizing film fed from a roll to a liquid crystal cell (RTP system apparatus) In the liquid crystal panel produced, in order to check whether the polarizing film is attached to the surface of the liquid crystal cell in a state deviated from a predetermined bonding position (hereinafter, referred to as lamination deviation), the edge of the polarizing film is detected. department. In the RTP method, in the production process of the liquid crystal panel, a strip-shaped laminate in which a plurality of sheet-shaped polarizing films are supported on the strip-shaped release film through the adhesive layer, and only the normal sheet-shaped polarizing film without defects is used. A method of continuously manufacturing a liquid crystal panel by sequentially peeling off the release film together with the adhesive layer, and laminating with the liquid crystal cell through the adhesive layer. The continuous manufacturing system that realizes such a method is called "continuous lamination (RTP; Roll to Panel") in order to distinguish it from the conventional individual lamination system in which the pre-cut polarizing film sheet is attached to the liquid crystal cell. )" device. As the apparatus of the RTP method, for example, the apparatus described in Patent Document 3 can be used.

FIG. 1 is a schematic diagram showing an example of the configuration of a polarizing film edge detection device for detecting the edge of a polarizing film attached to a liquid crystal cell. This apparatus can be mounted, for example, as a part of an apparatus used as an inspection step for a step after bonding a polarizing film to a manufactured liquid crystal cell by the above-mentioned RTP method.

The apparatus shown in FIG. 1 is provided with: a conveyance path 1 for conveying a liquid crystal panel P manufactured by bonding a polarizing film F to a liquid crystal cell C; an illumination 2 arranged above the conveyance path 1; and a camera 3 arranged above Lighting 2. When the target area A of the liquid crystal panel P conveyed by the conveyance path 1 is within the imaging range of the camera 3, the illumination 2 is turned on a plurality of times from the upstream side to the downstream side in the conveyance direction D of the liquid crystal panel P, and by A plurality of images Is of the target area A are captured by the camera 3 . The target area A is an area for inspecting the lamination deviation between the liquid crystal cell C and the polarizing film F, and generally, the area including the edge CE and the corner CC of the liquid crystal cell C, and the area including the lamination on the liquid crystal cell C. The edge portion FE of the polarizing film F of the cell C (this is the edge portion to be detected) and the region of the corner portion FC are not limited to this, as long as the region includes at least the edge portions CE and FE. A plurality of images Is captured at a plurality of positions of the target area A are transmitted to a general-purpose computer, and the computer selects the best image for detecting the edge portion FE of the polarizing film F, and uses the selected best image Image detection edge FE.

It is preferable to use a plurality of illuminations 2 arranged along the conveyance direction D so as to irradiate the target area A with light from different directions. The plurality of illuminations 2 are sequentially turned on at a plurality of positions while the target area A is moving from the upstream side to the downstream side in the conveyance direction D. The plurality of illuminations 2 are preferably arranged at least on the upstream side and the downstream side of the conveyance direction D of the liquid crystal panel P (illuminations 21 and 22 in FIG. 1 ), and in addition, in the direction crossing the conveyance direction D (liquid crystal panel P). The width direction of the panel P) is also preferably arranged (lights 23 and 24 in FIG. 1 ). Since the illumination 2 is also arranged in the width direction of the liquid crystal panel P, the edge FS in the width direction of the polarizing film F can also be detected more reliably, so that a higher-precision lamination deviation inspection can be performed. In addition, as the illumination 2, for example, a plurality of light sources may be arranged in an annular shape, and a single annular illumination capable of individually and sequentially turning on the plurality of light sources may be used. When such a ring-shaped illumination is used, the target area A can be irradiated with light from a plurality of different directions by turning on the individual light sources from a plurality of places in the circumferential direction.

As the camera 3 used in the present invention, a line camera, an area camera, or the like can be used depending on the purpose. For example, when imaging the target area A while moving the liquid crystal panel P, it is preferable to use a line camera. In the case of using a line camera, the subject area A may be photographed while moving the line camera in a state in which the liquid crystal panel P is stopped. As a method of photographing the target area A while moving the liquid crystal panel P, an area camera can also be used to photograph with a shutter speed sufficiently faster than the moving speed of the liquid crystal panel P. The area camera can also be used when the liquid crystal panel P is stopped when the target area A is captured.

In the following embodiment, one illumination 21 and 22 are respectively arranged on the upstream side and the downstream side of the conveyance direction D of the liquid crystal panel P with respect to the target area A, and one illumination 23 is arranged in the width direction of the liquid crystal panel P, respectively. and 24, a plurality of images Is are captured by one camera 3, and an optimum image Ib for detecting the edge portion FE of the liquid crystal film F is selected from the images Is. Hereinafter, light from four illuminations 21 to 24 arranged along the conveyance direction D of the liquid crystal panel P in such a manner that the height from the conveyance surface of the liquid crystal panel P is constant and the irradiation directions are different will be used to convey the light from the edge portion FE. The present invention will be described as an embodiment of a method of sequentially turning on illumination while moving from the upstream side to the downstream side in the direction D to perform imaging.

[Detection of the edge of the polarizing film] (Transportation and photography of LCD panels) In the apparatus shown in FIG. 1 , a plurality of images Is are captured for the target area A including the edge CE and the corner CC of the liquid crystal cell C and the edge FE and the corner FC of the polarizing film F. The camera 3 arranged so as to be capable of photographing the target area A acquires a plurality of images Is during the period from entering the target area A to leaving the imaging range of the camera 3 in accordance with the timing at which the plurality of lights 21 and 22 are turned on. Specifically, during the period from entering and leaving the imaging range of the camera 3 from the target area A, the conveyance stop and imaging of the liquid crystal panel P are performed at a plurality of predetermined positions, thereby acquiring a plurality of images Is. The predetermined position can be when the edge FE of the polarizing film F is located on the upstream side in the conveying direction D with respect to the photographing point, when the photographing point is located at or close to the photographing point, or when the photographing point is on the downstream side in the conveying direction D, or the like. For example, the imaging system can turn on the upstream side lighting 21 when the edge portion FE is located on the upstream side in the conveyance direction D with respect to the shooting point, and turn on the upstream side lighting 21 and the downstream side lighting 22 in sequence when the edge portion FE is located at the shooting point, Alternatively, when the imaging point is located on the downstream side of the conveyance direction D, the downstream side lighting 22 is turned on, and this is performed. The number of images Is to be acquired is not particularly limited, and can be determined in consideration of the accuracy necessary for detecting the edge portion FE of the polarizing film F and the processing speed for selecting an optimum image for detecting the edge portion FE. Decide.

The imaging of the plurality of images Is is preferably performed by stopping the liquid crystal panel P moving from the upstream side to the downstream side every imaging as described above. However, it is not limited to this. The side may be performed sequentially while moving the liquid crystal panel P. In the case of shooting while moving the liquid crystal panel P, it is possible to open the shutter of the camera 3 according to the timing of the lighting of the lighting 21 and the lighting 22 during the period from entering the target area A to leaving the field of view of the camera 3 to shoot a picture. image, thereby obtaining a plurality of images Is. Alternatively, a plurality of images can be acquired by opening the shutter of the camera 3 during the period from entering the target area A to leaving the field of view of the camera 3 to continuously shoot, and during this period, the lighting 21 and the lighting 22 are sequentially turned on, respectively. Can be like Is. The acquired images Is are transmitted from the camera 3, for example, to a general-purpose computer (not shown) through wired or wireless transmission, and are stored in a memory portion such as a hard disk.

(Best image selection) The acquired plural images Is are taken out from the memory unit, and the optimal image Ib is selected from the images Is. The optimal image Ib is an image in which the edge portion FE of the polarizing film F attached to the liquid crystal cell C can be most reliably detected among the plurality of images Is. The selection of the best image is to measure the brightness of the edge portion FE of the polarizing film F for each of the plurality of images Is captured, obtain an evaluation score based on the brightness, and compare the obtained evaluations between the images. score, and the image with the highest evaluation score is selected as the best image Ib that can most reliably detect the edge FE.

FIG. 2 is a flowchart 200 showing the overall flow of the process of selecting the optimum image Ib from the plurality of images Is captured. 3 is a flowchart showing an example of the specific processing of the fractionation step for obtaining the evaluation scores of the plurality of images Is, and FIG. 4 is an image showing an example of the processing of the fractionation step. Hereinafter, a method of selecting the optimum image Ib will be specifically described with reference to FIGS. 2 to 4 . In addition, the content of the optimum image selection process shown in FIG. 2-FIG. 4 is only an example, and other processes can also be used depending on the type of optical display panel.

First, in s201 of the flowchart 200, while the liquid crystal panel P is conveyed from the upstream side to the downstream side in the conveyance direction D, a plurality of images Is are obtained. Next, in s202, for each of the plurality of images Is, the luminance of the film edge portion is measured, and the evaluation score of each image Is is obtained from the luminance. Next, in s203, the evaluation scores among the plurality of images Is are compared, and the image with the highest evaluation score is selected as the optimal image Ib that can most reliably detect the edge portion FE.

Next, each process in the flowchart 200 will be specifically described. The acquisition of the image described in s201 of the flowchart 200 is as described above in terms of the item of photographing the liquid crystal panel. Next, as shown in s202 of the flowchart 200, for each of the obtained plural images Is, an evaluation score for evaluating the possibility that the edge portion FE of the polarizing film F is definitely detected is obtained. Specifically, for each of the plurality of images Is, the luminance is measured at a plurality of parts including the edge portion FE, and the luminance of the plurality of parts is divided into fractions, for example, a total value, an average value, a maximum value, and the like are obtained, and the value as the evaluation score. The image with the highest evaluation score among the plurality of images Is is the best image Ib in which the edge portion FE can be detected most reliably.

FIG. 3 is a flowchart 300 , which shows that an evaluation score is obtained for each of a plurality of images Is to select an optimal image, and the edge of the polarizing film F is determined in each of the images Is Details of an example of the processing of the position of the part FE. First, in s301, a plurality of small regions (square SR1 shown in FIG. 4(a) ) including the position where the edge of the polarizing film is assumed to exist and the periphery thereof are set along the longitudinal direction of the edge of the polarizing film . A plurality of small areas are read from the alignment marks provided on the liquid crystal cell C, and according to the positions of the alignment marks, the positions where the polarizing film F can be adhered to the liquid crystal panel P according to specifications without deviation are calculated, and are set as follows the calculated location. Although the size of the small area is not limited, the length of the small area in the direction across the edge of the polarizing film is set so that even if the polarizing film F is adhered to the liquid crystal panel P unevenly, the edge will be located in the small area The inner length is better. In addition, the length of the small region along the longitudinal direction of the edge portion of the polarizing film is preferably set appropriately in consideration of the detection accuracy and processing speed of the edge portion. The number of small regions is not limited, but is preferably set in consideration of detection accuracy and processing speed of the edge portion. Luminance was measured in several small areas and graphed. The graph, as shown in FIG. 4( b ), can show the relationship between the distance in the direction from the end of the small region to the inside of the liquid crystal panel P and the luminance.

Next, at s302 , for each graph generated for each of the plurality of small regions, the intersection of the line representing the graph and the predetermined threshold TH for determining the presence or absence of the edge portion FE of the polarizing film F is searched for. When the luminance as the threshold TH is used, it can be assumed that the edge FE can be reliably detected in the image if the luminance is equal to or higher than the luminance, and the luminance is higher than the maximum luminance (OBmax) indicating the bright lines other than the edge FE. large value. Since the bright line of the edge portion FE shown in the image has a width, there are usually two intersections between the graph and the threshold value TH. Among the two intersections, the position CP1 corresponding to the intersection in the inner direction of the liquid crystal panel P is the position of the inner edge of the bright line representing the edge portion FE. When the positions of the inner edges of the small regions identified in this way are connected, the connected straight line represents the inner edge of the bright line of the edge FE (s303), and the position represents the bright line of the edge FE of the polarizing film F. Location.

On the other hand, in s304, for each of the plurality of small regions, the maximum luminance Bmax of the bright line representing the edge portion FE in the small region is fractionated. Fractionation can be expressed as a relative brightness when the brightness corresponding to the maximum incident energy that can be received by the light-receiving element of the camera 3 is 100, for example. Alternatively, the measured maximum brightness Bmax itself can be used as a fraction of the small area. By the fractionation of brightness, the fraction of the small area is expressed as, for example, 82 points, 85 points, 90 points, etc. After the score is calculated for each of the plurality of small regions, in s305, for example, the scores of all the small regions are totaled, and the total value is used as the evaluation score of the image. In addition, the evaluation score of the images is not limited to the total value of the scores of the small regions, as long as the detection reliability of the edge portion FE between the images can be judged. For example, the evaluation score of the image may be an average point of scores of a plurality of small regions, or the number of small regions whose scores are greater than or equal to a specific score. The evaluation score is thus obtained for each of the plurality of images Is, and the image with the highest evaluation score is used as the best image Ib.

As a specific example, for example, with respect to the two images A and B captured, 10 small areas are set along the edge FE, and the brightness of each small area is measured. If the total score of each small area in image A is 800 points and the total score of each small area in image B is 700 points, the image A with the higher evaluation score is judged to be more reliable The best image Ib of the edge of the polarizing film is detected accurately. In addition, the inner edge of the edge portion FE of the polarizing film F in the image A is a straight line connecting the inner edges of the 10 small regions.

The data generated in the process of obtaining the evaluation score and the position of the edge of the polarizing film (s202 of the process flow chart 200 and s301 to s305 of the process flow chart 300) are stored in a hard disk (not shown), for example, via a communication line. the memory department. The memorized data can be read from the memory unit as necessary, and can be used in subsequent steps, such as processing for obtaining the amount of deviation in fitting.

As described above, among the plurality of images Is captured, the optimal image Ib that can detect the edge portion FE of the polarizing film F attached to the liquid crystal cell C more accurately is selected. Using the selected optimal image Ib, the edge portion FE can be detected. For example, the relationship between the position of the detected edge portion FE and the position of the edge portion CE of the liquid crystal cell C can be obtained using the knowledge of those skilled in the art to which the invention belongs. The amount of lamination deviation of the polarizing film FE is determined by a known method.

As the edge portion FE of the selected optimum image Ib and its position, the edge portion detected during the process of selecting the optimum image Ib from the image selected as the optimum image Ib and its location. As another method, the detection process of the inner edge position (s301 to s301 of the flowchart 300) can be performed again for the selected optimum image Ib and for each of the plurality of images Is to select the optimum image Ib. s303) The same process is carried out, and the edge part FE and its position detected finally are used as the edge part and its position for calculating|requiring a fitting deviation amount. [Example]

Hereinafter, embodiments of the present invention will be described. In this example, a camera (CA-035C, manufactured by KEYENCE Co., Ltd.) and two lights (CA-DBR8, manufactured by KEYENCE Co., Ltd.) arranged above the conveyance path of the liquid crystal panel were used to obtain the liquid crystal panel. Two images of the edge of the front end of the polarizing film included in the panel. As a liquid crystal panel, a polarizing film with a thickness of 0.1 mm was attached to a 32-inch liquid crystal cell with a thickness of 1.6 mm. The two lightings are arranged one on the upstream side and one on the downstream side in the conveying direction of the liquid crystal panel with respect to the position of the camera, and are adjusted so that the light is irradiated to the shooting point vertically below the camera. The distance in the vertical direction between the position of the camera and the position of the liquid crystal panel was 91 mm, and the distance in the vertical direction between the position of the illumination and the position of the liquid crystal panel was 8 mm. The two captured images were evaluated using luminance measured by an image processing device (manufactured by KEYENCE Co., Ltd., XG-5000).

The evaluation results are shown in Table 1. In Table 1, "polarizing film edge position" means the position where the liquid crystal panel is stopped in order to capture two images (image 1 and image 2), "upstream side", "photographing point" and " "Downstream side" means when the edge of the polarizing film is located on the upstream side of the imaging point, when the edge is located on the imaging point, and when the edge is located on the downstream side of the imaging point, respectively. "Irradiation direction" refers to the position and direction of illumination that irradiates light toward the edge of the polarizing film when the liquid crystal panel is stopped for photographing. The illumination on the upstream side irradiates light to the edge portion, and the illumination disposed on the downstream side of the camera irradiates light toward the edge portion. Table 1 shows the "polarizing film edge position" and "irradiation direction" of each of Examples 1 to 5. In this embodiment, brightness is used as the evaluation score for selecting the best image. Three small regions including the position where the edge of the polarizing film exists and its periphery are selected (see FIG. 4 ), Bmax is measured for each of the three small regions, and the average brightness of the three Bmax obtained is used as an evaluation score.

In Example 1, the image 1 captured by the light irradiated from the upstream side when the edge of the polarizing film is on the upstream side is compared with the image 1 captured by the light irradiated from the downstream side when the edge of the polarizing film is on the upstream side. image 2, and choose the best image. Since the evaluation score ( 165 ) of Image 1 is higher than that of Image 2 ( 120 ), Image 1 is selected as the best image that can reliably detect bright lines at the edge of the polarizing film.

In Example 2, the image 1 captured in the same manner as in Example 1 was compared with the image 2 captured by the light irradiated from the downstream side when the edge of the polarizing film was at the imaging point, and the best image was selected. picture. Furthermore, in Example 3, the image 1 captured in the same manner as in Example 1 was compared with the image 2 captured by the light irradiated from the downstream side when the edge of the polarizing film was located on the downstream side, and the most best image. In Example 2 and Example 3, image 1 was selected.

In Example 4, the image 1 captured by the light irradiated from the upstream side when the edge of the polarizing film is located at the imaging point is compared with the image 1 captured by the light irradiated from the downstream side when the edge of the polarizing film is located on the downstream side. image 2, and choose the best image. In this example, since the evaluation score (150) of the image 2 is higher than the evaluation score (135) of the image 1, the image 2 is selected as the best one that can reliably detect the bright line at the edge of the polarizing film. image. In addition, in Example 5, the image 1 captured by the light irradiated from the upstream side when the edge of the polarizing film is located on the downstream side is compared with the image 1 captured by the light irradiated from the downstream side when the edge of the polarizing film is located on the downstream side. Take image 2 and choose the best image. In this example, Image 2 is also selected.

In Comparative Example 1, the edge of the polarizing film was located at the photographing point, and an image was obtained using a ring illumination (manufactured by KEYENCE Co., Ltd., CA-DRR8) arranged coaxially with a camera (manufactured by KEYENCE Co., Ltd., CA-035C). In any of the cases of Example 1 to Example 5, the evaluation score of the image as the best image is selected to be higher than the evaluation score of Comparative Example 1 (127). Therefore, by using the optimal image selected by the present invention, the bright line at the edge of the optical film can be detected more reliably than the image captured by the conventional technique.

1: Transportation road 2: Lighting 21, 22: Lighting 23, 24: Lighting 3: Camera A: Object area C: liquid crystal cell CC: Corner CE: edge D: conveying direction F: polarizing film FC: Corner FE: edge FS: edge P: LCD panel

1 : is a schematic diagram which shows the structure of the edge part detection apparatus for detecting the edge part of the polarizing film stuck to a liquid crystal cell used for manufacture of a liquid crystal panel. 2 is a flowchart showing a flow of a process of selecting an optimum image from a plurality of images captured in the method for detecting an edge portion of an optical film according to an embodiment of the present invention. Fig. 3 is a flowchart showing the details of the fractionation process in the method of one embodiment of the present invention. FIG. 4 is an image showing the steps of the fractionation process.

Claims (5)

A method for detecting the edge portion of an optical film, which is to detect the edge portion of an optical film laminated on a rectangular panel; it is characterized by: comprising: The conveying step is to convey the rectangular panel laminated with the optical film; The imaging step is to sequentially irradiate light from a plurality of light sources arranged along the conveyance direction of the rectangular panel to the target area including the edge of the optical film on the rectangular panel, and use one imaging means to irradiate the target area on the rectangular panel with light from a plurality of light sources. Shooting at multiple positions from the upstream side to the downstream side in the conveying direction; The optimal image selection step is to select an optimal image for detecting the edge from among a plurality of images obtained by photographing the object area at a plurality of positions, according to the brightness of the edge in each image images; and The edge detection step is to detect the edge in the best image. The optical film edge detection method according to claim 1, wherein, The plurality of light sources include at least an upstream light source arranged on the upstream side of the conveyance direction and a downstream light source arranged on the downstream side of the one imaging means, The photographing step includes irradiating light from the upstream light source and photographing when the edge is located more upstream in the conveying direction than a photographing point that is a position where the edge reaches the vertical lower side of the imaging means. When the edge portion is located on the downstream side in the conveyance direction from the imaging point, light is irradiated from the downstream light source to capture the image. The optical film edge detection method according to claim 1 or claim 2, wherein, The optimal image selection step includes selecting the optimal image based on the brightness of a plurality of locations set along the edge. The optical film edge detection method according to any one of claim 1 to claim 3, wherein, The photographing step includes photographing the plurality of images while stopping the rectangular panel for each photographing. The optical film edge detection method according to any one of claim 1 to claim 4, wherein, The photographing step includes further photographing the plurality of images using light from a light source arranged to face the width direction of the rectangular panel.

Images