JP2006337630A - Method for manufacturing multilayer optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer optical film made by sticking a polarizing film hardly having defect to a retardation film. <P>SOLUTION: In a method for manufacturing multilayer optical film, the retardation film having a constant width is conveyed in the length direction vertical to the width direction, wherein a pair of polarizers are arranged in cross Nicols in parallel to the film surface on both sides of the retardation film, an optical compensation film having a birefringent characteristic is arranged between the polarizer and the retardation film, light is projected from the external side of the one side polarizer, transmission light from the other side polarizer is received, a defect is detected from the brightness signal, subsequently, the retardation film is stuck to the polarizing film and, thereafter, the defect part is removed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a laminated optical film obtained by laminating a polarizing film and a retardation film.

Conventionally, in the manufacturing process of synthetic resin films and papers, various treatments are automatically performed in a long strip shape with a constant width, and finally cut into a predetermined shape according to product specifications. . Detection of a defective portion that does not satisfy the product specification is also automatically performed in a belt-like state, and a mark is provided so that the defective portion can be easily identified in a later process.
When manufacturing a polarizing film used for a liquid crystal display panel, in the process of manufacturing as a synthetic resin film or imparting polarization characteristics by stretching in a certain direction, the film is continuously in a long strip state. And cut out in a size and direction predetermined by the product specifications. When the defect inspection is automatically performed, the defect detection and the defect marking are performed along the film conveyance path. In the same manner for the retardation film, the detection of the defect and the marking of the defect are performed along the film conveyance path in a continuous state in a long and long film state.
The polarizing film and the retardation film thus obtained are bonded so as to have a predetermined axial angle, and are usually cut into chips of a predetermined size, except for chips having a defective portion based on the marks. It is a product of laminated optical film.

  As a method for inspecting defects such as foreign matter in a synthetic resin film, a synthetic resin film is projected from a light source onto the synthetic resin film, the transmitted light or reflected light is photographed with a camera, or a synthetic resin film is placed between two polarizing plates arranged in crossed Nicols. There is known a method of arranging and photographing a transmitted light from a light source with a camera and performing image processing on the captured image to inspect a defect (for example, refer to Patent Document 1).

  In addition, as a film defect marking method, a method of marking a linear mark on the side edge of a film including a defect, a method of directly marking a defect position, a predetermined range on both sides in the width direction with respect to the defect portion There is known a method of applying a mark to a position in the vicinity of (see Patent Document 2).

However, in the defect detection method described in Patent Document 1 and the like, when the synthetic resin film is a retardation film, the SN ratio of the luminance signal of the defect portion is low, the defect detection accuracy is low, and marking is performed reliably. Even if it uses a laminated optical film bonded with a polarizing film for a liquid crystal display panel, a defect will become apparent.
JP 2005-49158 A JP 2001-305070 A

  The objective of this invention is providing the laminated optical film formed by bonding the polarizing film with few defects, and retardation film.

  The present invention is a method for producing a laminated optical film by laminating a polarizing film and a retardation film, and transporting a retardation film having a certain width in a length direction perpendicular to the width direction, A pair of polarizers are arranged in crossed Nicols parallel to the film surface on both sides of the retardation film, an optical compensation film having birefringence characteristics is arranged between the polarizer and the retardation film, and one polarizer The laminated optical film is characterized in that light is projected from the outside of the optical element, the transmitted light from the other polarizer is received, the defect is detected from the luminance signal, and then bonded to the polarizing film, and then the defective part is removed. It is a manufacturing method.

  As described above, according to the present invention, a laminated optical film obtained by bonding a polarizing film with few defects and a retardation film can be obtained.

A polarizing film is a film having a function of transmitting only light in a specific vibration direction, and is manufactured by dyeing and stretching a polyvinyl alcohol film with iodine or the like. Sumikaran (registered trademark) (manufactured by Sumitomo Chemical Co., Ltd.) Etc. are commercially available.
The retardation film is a film having a function of compensating for the retardation, eliminating coloring, improving visibility, or widening the viewing angle, and extending a polycarbonate film or cycloolefin polymer. Manufactured by coating a film with liquid crystal, Sumikalite (registered trademark) (manufactured by Sumitomo Chemical Co., Ltd.), R-film (manufactured by Kaneka Corporation), Pure Ace (registered trademark) (manufactured by Teijin Limited), ZEONOR Film (registered trademark) (manufactured by Optes Co., Ltd.), Essina retardation film (manufactured by Sekisui Chemical Co., Ltd.), Konica Minolta Optical Film (manufactured by Konica Minolta Opto), Fuji Film WV FILM (Fuji Photo Film) Co., Ltd.), NH film for TFT viewing angle improvement (manufactured by Nippon Oil Corporation), LC film for STN color compensation (manufactured by Nippon Oil Corporation), etc.

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of a film defect detection and defect marking apparatus 10 according to the present invention. FIG. 2 is a simplified cross-sectional view showing the configuration of the phase difference film defect detection means 25 in the film defect detection and defect marking apparatus 10.
It is not preferable that the phase difference film 11 is present even if the surface defect is so small that it is difficult to identify with the naked eye, because it degrades the display image quality of the liquid crystal display device with high definition. Even with a relatively wide range of defects, it may be difficult to determine with the naked eye. Even a defect that is difficult to distinguish with the naked eye is detected as a defect 13 by the defect detection means 25.

  The retardation film 11 is conveyed at a constant speed in the conveyance direction 11a, the defect detection means 25 detects a defect, and the marking means 14 is installed downstream of the defect detection means in the conveyance direction 11a. The phase difference film 11 is pulled out from the state wound around the roll 16 and becomes an inspection object.

  The defect detection means 25 includes a lighting device 17, a pair of polarizers 22 and 23 arranged in crossed Nicols parallel to the sheet surface on both sides of the sheet surface of the retardation film 11 that is a film to be inspected, and the position of the polarizer. An optical compensation film 24 disposed between the phase difference films and having birefringence characteristics, an image pickup means 12 for picking up transmitted light from an illumination device that passes through these films, and an image for processing a luminance signal of the picked-up image The processing unit 19 is mainly configured.

  The illumination device 17 performs uniform illumination over the entire width direction of the retardation film 11. As the illumination device 17, a tubular light emitter such as a fluorescent lamp or a linear light source such as a transmission light is used. In the transmission light, a powerful light source such as a metal halogen lamp is disposed on the end face in the axial direction of a rod-shaped light guide, and the light incident on the end surface is guided to the side surface between both end surfaces to function as a rod-shaped light source. Laser light can be spread and irradiated. The light that the illuminating device 17 irradiates the retardation film 11 is set so as to have a wavelength and polarization characteristics that facilitate detection of the defect 13. The combination of the imaging means 12 and the illumination device 17 determines the types of defects 13 that can be efficiently detected. In order to make it possible to detect a plurality of types of defects 13, a plurality of combinations of the imaging unit 12 and the illumination device 17 are arranged along the transport direction 11a, and if any type of the defect 13 is detected, the marking unit Marking can also be made by 14.

The pair of polarizers 22 and 23 are arranged in parallel on both sides of the film surface of the retardation film that is the film to be inspected, and the polarizer 22 linearly deflects the light emitted from the illuminating device 17, and the retardation film To enter. The polarizer 23 is arranged in a crossed Nicols state with the polarizer 22 (a state in which the polarization axis of the polarizer 22 and the polarization axis of the polarizer 23 are orthogonal), and transmitted light that has passed through the retardation film and the optical compensation film 24. Among them, the transmitted light in the direction of the polarization axis of the polarizer 23 is transmitted. A known polarizer, usually a polarizing plate, is used for both the polarizer 22 and the polarizer 23.
The polarizer 23 may be disposed on the front surface of the illumination device 17, and the polarizer 22 may be attached to the camera. In order to facilitate the pair of polarizers in a crossed Nicols state, it is preferable that one polarizer can be rotated. In a state where there is no retardation film, the polarizer can be rotated so as to minimize the luminance signal value and can be easily placed in the crossed Nicols state.

As the optical compensation film 24, a film having substantially the same birefringence characteristics as the retardation film is preferably used. The optical compensation film is disposed between the retardation film and the polarizer 22 or between the retardation film and the polarizer 23. The optical compensation film is arranged to compensate for the birefringence anisotropy of the retardation film by the birefringence anisotropy. That is, light is elliptically polarized due to the birefringence characteristics of the retardation film, but is returned to linearly polarized light due to the birefringence characteristics of the optical compensation film. As a result, the SN ratio of the luminance signal of the defective portion is increased, and the defect can be detected more reliably.
It is preferable that the optical compensation film can be rotated so that the birefringence anisotropy of the retardation film can be easily compensated.

The imaging means 12 includes a plurality of cameras 21 in the width direction. The luminance signal of the image picked up by the image pickup means 12 is processed by the image processing device 19.
In an image processing apparatus, normally, a threshold value is provided for a luminance signal value, and if the signal value is equal to or greater than the threshold value, it is determined as a defect. The SN ratio of the luminance signal of the defective portion is large, and the defect can be detected with high accuracy by this method. It is preferable to determine by setting a threshold value after performing a shading process in order to clarify the normal region and the defect while keeping the luminance signal of the normal region constant. 128 gradations are added to the difference between the original image and, for example, the shading image obtained as an average of the normal areas to obtain a waveform image based on the 128 gradations, and a threshold is set for this image to determine a defect.

  As a method of marking a defect in a retardation film, a method of applying a linear mark to a side edge of a film including a defect, a method of directly marking a defect position, and a width direction with respect to a defect part described in Patent Document 2 Although it is possible to adopt a method of marking at a position that is in the vicinity of a predetermined range on both sides of the film, it is ensured that no defects are included when cutting out the film, and a decrease in yield is suppressed. In view of this, it is preferable to mark the defective portion at a position that is in the vicinity of a predetermined range on both sides in the width direction.

  Specifically, in FIG. 1, the marking means 14 is placed on the surface of the retardation film 11 on the surface of the retardation film 11 in the transport direction 11a. A linear mark 15 is applied in parallel.

  The conveyance speed of the retardation film 11 is detected by a conveyance speed detection device 18. The output from the conveyance speed detection device 18 is input to the control unit 20 together with the image processing result from the image processing device 19 that performs predetermined image processing on the image captured by the imaging unit 12. The control unit 20 is realized by, for example, an industrial personal computer, and performs determination of the presence / absence of a defect from the image processing result and detection of a position when the defect 13 exists. The control means 20 further adjusts the timing based on the output from the conveying speed detection device 18 so as to mark the defect existing position within a predetermined vicinity in the width direction, and sets the marking means 14 Operate. The marking means 14 includes a plurality of markers 31 in the width direction.

  FIG. 3 shows the concept of marking the defect 13 detected by the defect detection means 25 with the marking means 14. The imaging means 12 has a plurality of cameras 21 arranged in the width direction at regular intervals. Each camera 21,... Includes, for example, a one-dimensional CCD sensor in which 5000 pixels are arranged at high density as an image sensor. Since the workpiece width, which is the width of the retardation film 11 to be inspected, is in the range of, for example, 800 to 1300 mm, the inspection area as the imaging unit 12 has a width of 1300 mm. .. Are arranged in the inspection area, and the visual field 21a of each camera 21 is set to 250 mm. The field of view 21a of each camera 21,... Overlaps with the field of view 21a of the adjacent camera 21,.

  In the marking means 14, a plurality of markers 31,... Are arranged in the width direction at regular intervals, for example, 20 mm intervals. Each marker 31, ... is located on an extension of one of the cameras 21, ... in the visual field 21a, ... in the transport direction 11a. 1 detects the defect 13 in the images from the respective cameras 21,..., Selects the nearest marker 31... Sandwiching both sides of the defect 13 in the width direction. If there is a marker 31,... Between the markers 31,. Each marker 31,... Is in the form of a felt pen, and the linear mark 15 can be formed in the transport direction 11a by bringing the tip into contact with the surface of the retardation film 11. It is preferable that each marker 31,... Is covered with a cap when not in use to prevent the writing quality and the like from deteriorating due to evaporation of the solvent or diluent. Generally, when the defect 13 is detected between the positions of the markers 31,..., Marks 15 are provided on both sides of the detected position.

  FIG. 4 shows an example of the control concept when the control means 20 of FIG. 4 (b) and 4 (c) show marks 15b and 15c applied to large defects 13b and 13c in the width direction and the length direction in accordance with the concept of FIG. 4 (a).

  As shown in FIG. 4A, the surface of the retardation film 11 is partitioned by virtual blocks 40. Each block 40 is a square whose sides 41, 42, 43, and 44 are 20 mm in length in accordance with the arrangement pitch of the markers 31 in the width direction. The sides 41 and 42 are boundaries on the upstream side and the downstream side in the transport direction 11a, respectively, and the sides 43 and 44 are boundaries on one side and the other side in the width direction. When the defect 13 exists in each block 40, the markers at the positions of the sides 43 and 44 on both sides in the width direction are selected and marked. When the defect 13 is on one of the sides 43 and 44, a mark is also given to the side opposite to the side of the block adjacent to the side. Therefore, as shown in FIG. 4B, the defect 13b that is long in the width direction and spans a plurality of blocks is marked on the side that is sandwiched from both sides in the width direction and all the sides between them. Will be given.

  In FIG. 4A, when the defect 13 is on one of the sides 41 and 42, a mark is given to both sides in the width direction even in a block adjacent to that side as a boundary. Therefore, as shown in FIG. 4C, the defect 13c that is long in the length direction and spans a plurality of blocks is continuously extended by extending between the blocks to the side that is sandwiched from both sides in the width direction. Mark is given.

  Even if a single marker is used, a mark that sandwiches both sides of the defect 13 is applied if it can move in the transport direction 11a and the width direction at a higher speed than the transport speed of the retardation film 11. It is possible. However, control of the movement of the marker is complicated, and it is difficult to reliably mark when a plurality of defects 13 are detected at close positions. If a plurality of markers are moved, it becomes possible to mark many defects 13 at the same time, but the control becomes more complicated.

  Moreover, although the felt pen type thing is used as the marking means 14, other types of markers, such as an ink jet type, can also be used.

Similarly, defect inspection and defect marking can be performed on the polarizing film. In the defect inspection of the polarizing film, a polarizing film is used instead of the retardation film shown in FIG. 1, and the transmitted light is received, the image is processed to detect the defect from the luminance signal, the reflected light is received, and the image is processed. A method of detecting defects from the luminance signal, or a polarizer placed in crossed Nicols parallel to the film surface of the polarizing film, projecting light from the outside of the polarizing film or polarizer, and receiving transmitted light from the polarizer or polarizing film Then, the image processing is performed by a method of detecting a defect from the luminance signal.
The method for marking the defect of the polarizing film is the same as that for the retardation film, and the method of Patent Document 2 is preferably used.

The retardation film in which the defect is detected is bonded to the polarizing film so as to have a predetermined axial angle. A polarizing film is usually manufactured by transporting a film having a certain width in a length direction perpendicular to the width direction, and a defect inspection is performed. Usually, a polarizing film is cut out to an intermediate size and bonded to a retardation film.
The lamination of the retardation film and the polarizing film is performed by a known method using an acrylic adhesive or the like. Usually, one or two retardation films are bonded to the polarizing film depending on the purpose. That is, as a laminated optical film, a polarizing film with a retardation film bonded so as to have a predetermined axial angle, and a retardation film that is further bonded with a predetermined axial angle on the retardation film of this film. There is what I did.

  After laminating the retardation film and the polarizing film, a laminated optical film product is obtained except for the defective portion. Usually, a laminated optical film is cut into a chip having a size of a liquid crystal display panel to be used, and a laminated optical film product is obtained except for a chip having a defective portion.

  When laminating a retardation film and a polarizing film, new defects may occur due to adhesion of foreign matter or fine dust in the adhesive. Is preferred. At this time, the detected defect is manually marked. The newly detected defect portion is visually removed from the defect portion that has been automatically detected.

  It is preferable to mark the detected defective portion automatically and manually by the above-described method and remove the defective portion based on those marks because the defective portion can be surely removed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example.

Example 1
Using the apparatus shown in FIG. 1 and FIG. 2, defect detection and defect marking were performed on the retardation film (NH film for TFT viewing angle improvement application, retardation: 120 nm, manufactured by Nippon Oil Corporation) by the above-described method. .
As the optical compensation film, the above-mentioned retardation film that is the film to be inspected is used, arranged at right angles to the transport direction of the film to be inspected, and the birefringence of the retardation film that is the film to be inspected due to the anisotropy of the birefringence. Anisotropy of was compensated.
A polarizing film (Sumikaran (registered trademark), manufactured by Sumitomo Chemical Co., Ltd.) was used as a polarizer.
When the conveyance speed of the retardation film is set to 6 m / min, a defect is automatically detected with a threshold value of +178 in the waveform image based on 128 gradations obtained by image processing, and the detected defect is automatically marked. did.
As a result, the average number of defect markings was 17 / m.
Next, a polarizing film (Sumikaran (registered trademark) SBP grade, manufactured by Sumitomo Chemical Co., Ltd.) and a retardation film (Sumikalite (registered trademark) SES grade, manufactured by Sumitomo Chemical Co., Ltd.) are pasted on the retardation film. The laminated film was bonded to the retardation film side via an adhesive to obtain a laminated optical film.
This laminated optical film was cut into an easy-to-handle approximately 50 cm square, visually inspected, and manually marked for defects due to foreign matters mixed at the time of bonding.
Next, the laminated optical film provided with this mark was cut into a 2.2-inch chip. Among these chips, except the above-mentioned automatic marking and manually marked chips, the rest were used as products.
When the product of the laminated optical film thus obtained is bonded to a liquid crystal display panel and the quality of the laminated optical film is judged from the quality of the image, the defect rate is 1% or less.

Comparative Example 1
It was carried out in the same manner as in Example 1 except that automatic defect detection and automatic defect marking were not performed on the retardation film (NH film for TFT viewing angle improvement application, retardation: 120 nm, manufactured by Nippon Oil Corporation).
When the product of the laminated optical film thus obtained is bonded to a liquid crystal display panel and the quality of the laminated optical film is judged from the quality of the image, the defect rate is about 10%.

1 is a perspective view showing a schematic configuration of a film defect detection and defect marking apparatus 10 according to the present invention. It is the simplified sectional view which shows the structure of the defect detection means 25 about retardation film among the defect detection and defect marking apparatuses of FIG. It is a figure which shows the view of marking in the defect marking apparatus of FIG. It is a figure which shows an example of the view of control when the control means 20 of FIG. 1 operates the marking means 14 and gives marking.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Defect detection marking apparatus 11 Retardation film 11a Conveying direction 12 Imaging means 13, 13b, 13c Defect 14 Marking means 15 Mark 17 Illumination apparatus 18 Conveyance speed detection apparatus 19 Image processing apparatus 20 Control means 21, ... Camera 22, 23 Polarization Element 24 Optical compensation film 25 Defect detection means 31,..., Marker 40 Blocks 41, 42, 43, 44 sides

Claims (10)

In the method of manufacturing a laminated optical film by laminating a polarizing film and a retardation film,
A retardation film having a certain width is conveyed in a length direction perpendicular to the width direction. At that time, a pair of polarizers are arranged in parallel to the film surface on both sides of the retardation film in crossed Nicols, and An optical compensation film having birefringence characteristics is placed between the retardation films, light is projected from the outside of one polarizer, light transmitted from the other polarizer is received, and defects are detected from the luminance signal. Then, after pasting with a polarizing film, the manufacturing method of the laminated optical film characterized by removing a defective part.   The optical compensation film has birefringence characteristics substantially the same as the birefringence characteristics of the retardation film, and the optical compensation film compensates for the birefringence anisotropy of the retardation film by the birefringence anisotropy of the optical compensation film. The method for producing a laminated optical film according to claim 1, wherein a compensation film is disposed.   2. The method for producing a laminated optical film according to claim 1, wherein after the lamination with the polarizing film, the defect is further visually detected, and the defective portion is removed together with the defective portion of the retardation film.   The method for producing a laminated optical film according to claim 1, wherein the laminated optical film is bonded to a polarizing film in which a defect is detected.   5. The method for producing a laminated optical film according to claim 4, wherein the polarizing film is projected, the reflected light or transmitted light is received, and the defect of the polarizing film is detected from the luminance signal.   A polarizer is placed in crossed Nicols parallel to the film surface of the polarizing film, light is projected from the outside of the polarizing film or polarizer, light transmitted from the polarizer or polarizing film is received, and defects are detected from the luminance signal. The method for producing a laminated optical film according to claim 4.   The method for producing a laminated optical film according to claim 1 or 4, wherein the defective portion is marked, and the defective portion is removed based on the mark.   8. The method for producing a laminated optical film according to claim 7, wherein a mark is provided at a position near a predetermined range on both sides in the width direction with respect to the defective portion.   9. The method for producing a laminated optical film according to claim 8, wherein the mark is also applied in the middle when the positions where the mark is applied on both sides in the width direction are separated by a predetermined distance or more. The laminated optical film according to claim 1 or 4, wherein after the lamination with the polarizing film, the defect is further detected visually, the defect portion is marked, and the defect portion is removed based on the mark. Manufacturing method.

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