Inspection method and inspection device for light permeable laminate

Abstract

To provide an inspection method for a light permeable laminate capable of detecting an especially finer foreign matter in comparison to conventional methods.SOLUTION: The inspection method for a light permeable laminate includes conducting a transmission inspection with a sheet-like light permeable laminate held at four corners thereof and fixed in mid-air, and detecting a defect in the light permeable laminate. In one embodiment, the inspection method further includes applying a tensile force to the light permeable laminate. In one embodiment, the inspection method detects a defect at a size of 8 to 50 μm in the light permeable laminate. In one embodiment, the light permeable laminate has a thickness of 300 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for inspecting a light-transmitting laminate. [Background technology]

[0002] A light-transmitting laminate (for example, an optical member, an optical laminate, an optical film, a light-transmitting adhesive sheet) applied to an image display device needs to remove foreign matter from inside the laminate in order to prevent image display defects and the like. Therefore, such a light-transmitting laminate is typically subjected to a foreign matter inspection. The foreign matter inspection is typically a transmission inspection performed while conveying a long web of the light-transmitting laminate, and in the transmission inspection, foreign matter and / or defects can be recognized as dark spots. In recent years, the display performance required for image display devices has become significantly higher, and as a result, the accuracy of foreign matter inspection of light-transmitting laminates has also been required to be significantly higher. Specifically, while it was previously acceptable to detect foreign matter and / or defects of about 50 μm, it has become necessary to detect foreign matter and / or defects of about 10 μm. However, in the foreign matter inspection performed while conveying the long web as described above, it is extremely difficult to detect such small foreign matter and / or defects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-062165 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to provide an inspection method for an optically transparent laminate that can detect much smaller foreign bodies and / or defects than conventional methods. [Means for solving the problem]

[0005] An inspection method for an optically transparent laminate according to an embodiment of the present invention includes performing a transmission inspection while grasping four sides of a sheet of optically transparent laminate and fixing it in a hollow space, and detecting defects in the optically transparent laminate. In one embodiment, the inspection method includes temporarily attaching a first surface protective film and a second surface protective film to both sides of the light-transmitting laminate; sucking the first surface protective film side of the light-transmitting laminate with a suction plate and fixing the light-transmitting laminate to the suction plate; peeling off the second surface protective film while the light-transmitting laminate is fixed to the suction plate; clamping the light-transmitting laminate between the suction plate and a lower grip of a holding member while the light-transmitting laminate is fixed to the suction plate; after clamping, stopping suction of the suction plate and starting suction of the lower grip to fix the light-transmitting laminate to the lower grip; separating the suction plate while the light-transmitting laminate is fixed to the lower grip; peeling off the second surface protective film while the light-transmitting laminate is fixed to the lower grip; The method includes: placing an upper grip at a position corresponding to the lower grip on the surface of the light-transmitting laminate opposite the lower grip, and gripping the light-transmitting laminate with the upper grip and the lower grip; and stopping suction of the lower grip. In one embodiment, the suction plate is provided at each of its long and short side ends with positioning portions that are protruding portions. In one embodiment, the positioning portion at the long side end of the suction plate and the positioning portion at the short side end of the suction plate are in contact with each other at one end to form a right-angled corner, and one corner of the light-transmitting laminate is abutted against the corner to achieve positioning. In one embodiment, the lower grip is supported by a lower grip support part, and a step for positioning the light-transmitting laminate is defined by the lower grip support part and the lower grip, and the outer edge of the light-transmitting laminate is abutted against the step for positioning. In one embodiment, the step is defined at a position corresponding to the positioning portion of the suction plate when the light-transmitting laminate is sandwiched between the suction plate and the lower grip. In one embodiment, the gripping member has a frame shape in a plan view, and an outer edge of the light-transmitting laminate is positioned to correspond to an outer edge of the gripping member. In one embodiment, the inspection method includes, after detecting the defect, temporarily and removably attaching the peeled first surface protection film or second surface protection film, or a surface protection film other than the first surface protection film or the first surface protection film, to at least one surface of the light-transmitting laminate. In one embodiment, the inspection method further includes applying tension to the light-transmitting laminate. In one embodiment, the inspection method detects defects having a size of 8 μm to 50 μm in the light-transmitting laminate. In one embodiment, detecting the defects includes: focusing an optical system of a predetermined magnification on the surface of the first main surface of the light-transmitting laminate, and scanning the light-transmitting laminate with the optical system to create an XY coordinate map of defects; shifting the focus of the optical system a predetermined distance inward in the thickness direction from the surface of the first main surface of the light-transmitting laminate, and scanning the light-transmitting laminate with the optical system to create another XY coordinate map of defects; and integrating the created XY coordinate maps of defects. In one embodiment, the detection of the defects includes repeating scanning of the optical system with the optical system a predetermined number of times while further shifting the focus of the optical system inward in the thickness direction of the optical sheet by the predetermined distance, thereby creating an XY coordinate map of a predetermined number of defects. In one embodiment, detecting the defect includes measuring the thickness direction position of the defect only at the defect occurrence coordinates in the XY coordinate map of the integrated defect using an optical system with a magnification higher than the specified magnification. In one embodiment, the light-transmitting laminate is selected from an optical film, a pressure-sensitive adhesive sheet, and a combination thereof. In one embodiment, the optical film is selected from a polarizing plate, a retardation plate, and a laminate including these. In one embodiment, the thickness of the light-transmitting laminate is 300 μm or less. According to another aspect of the present invention, there is provided an inspection device for a light-transmitting laminate, the inspection device comprising: a base frame; a gripping member provided on the base frame for gripping four sides of the light-transmitting laminate to fix the light-transmitting laminate in a hollow space; a suction plate pivotally attached via a rotation shaft to a plate support provided at one end of the base frame and configured to be positionable at a position opposite the gripping member by rotation about the rotation shaft; an imaging element for obtaining an image of the light-transmitting laminate; and a light source for emitting irradiation light for irradiating the light-transmitting laminate. The gripping members are composed of a first gripping member having a first upper grip and a first lower grip, a second gripping member having a second upper grip and a second lower grip, a third gripping member having a third upper grip and a third lower grip, and a fourth gripping member having a fourth upper grip and a fourth lower grip, and the first gripping member, the second gripping member, the third gripping member and the fourth gripping member grip each of the four sides of the light-transmitting laminate. Effect of the Invention

[0006] According to the inspection method for an optically transparent laminate according to an embodiment of the present invention, a transmission inspection is performed while a sheet of an optically transparent laminate is held at its four sides and fixed in midair, making it possible to detect foreign objects and / or defects that are much smaller (e.g., about 8 μm in size) than in the past. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1(a) is a schematic perspective view illustrating an example of a transmission inspection in one embodiment of the present invention; FIG. 1(b) is a schematic cross-sectional view taken along line BB in FIG. 1(a). [Diagram 2]FIG. 2 is a schematic perspective view showing an example of an apparatus for fixing a light-transmitting laminate in a hollow space in an embodiment of the present invention. [Diagram 3] 3(a) to 3(d) are schematic cross-sectional views illustrating a procedure for fixing a light-transmitting laminate in a hollow space using the device of FIG. [Figure 4] 3 is a schematic plan view illustrating a suction plate that can be used in the device of FIG. 2. [Diagram 5] 3(a) to 3(c) are schematic cross-sectional views of essential parts illustrating a gripping member that can be used in the apparatus of FIG. 2 and the details of a procedure for gripping a light-transmitting laminate by the gripping member. [Figure 6] FIG. 2 is a schematic plan view illustrating a means for applying tension to a light-transmitting laminate fixed in a hollow space in an embodiment of the present invention. [Figure 7] 1 is a schematic diagram illustrating focusing of an image pickup element in detecting defects in a transmission inspection. FIG. [Figure 8] 1 is a schematic perspective view illustrating scanning of an XY plane of a light-transmitting laminate by an imaging element in detecting defects in a transmission inspection. FIG. [Figure 9] FIG. 13 is a conceptual diagram illustrating an example of an XY coordinate map of defects in the detection of defects by transmission inspection. [Figure 10] 10 is a conceptual diagram illustrating an example of integrating XY coordinate maps of a predetermined number of defects in detecting defects in a transmission inspection. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, all the drawings are conceptually and diagrammatically represented for ease of understanding, and do not accurately depict actual conditions.

[0009] A. Overview of inspection method for light-transmitting laminates The inspection method for the light-transmitting laminate according to the embodiment of the present invention includes performing a transmission inspection while holding the four sides of a sheet of the light-transmitting laminate and fixing it in the air, and detecting defects in the light-transmitting laminate. FIG. 1(a) is a schematic perspective view illustrating an example of the transmission inspection; FIG. 1(b) is a schematic cross-sectional view taken along line BB in FIG. 1(a). The transmission inspection includes, for example, using an optical system to obtain an image of the light-transmitting laminate 10 held at four sides by a frame-shaped holding member 20. The holding member 20 has an upper grip 22 and a lower grip 24. The upper grip 22 is typically composed of a first upper grip 22a, a second upper grip 22b, a third upper grip 22c, and a fourth upper grip 22d corresponding to the four sides, respectively. The lower grip 24 is typically composed of a first lower grip 24a, a second lower grip 24b, a third lower grip 24c, and a fourth lower grip 24d corresponding to the first upper grip 22a to the fourth upper grip 22d, respectively. Therefore, for example, a gripping member having the first upper grip 22a and the first lower grip 24a may be referred to as a first gripping member 20a. The optical system includes, for example, an imaging element 30 arranged on one side (upper side in the illustrated example) of the light-transmitting laminate 10 to obtain an image of the light-transmitting laminate; and a light source 40 arranged on the other side (lower side in the illustrated example) of the light-transmitting laminate 10 to emit irradiation light for irradiating the light-transmitting laminate 10. Note that the imaging element 30 may be arranged below the light-transmitting laminate 10, and the light source 40 may be arranged above the light-transmitting laminate 10. The imaging element 30 captures a transmitted light (inspection light) image, and in the captured image, foreign objects and / or defects (hereinafter, may be simply referred to as foreign objects or defects depending on the context) can be recognized as dark spots. More specific embodiments of hollow fixation and transmission inspection will be described later. By performing a transmission inspection while holding the four sides of a sheet of light-transmitting laminate and fixing it in the air, it is possible to detect defects in the light-transmitting laminate, for example, 8 μm to 50 μm in size, preferably 8 μm to 30 μm in size, more preferably 8 μm to 20 μm in size, even more preferably 8 μm to 15 μm in size, and particularly preferably about 10 μm in size. Conventionally, foreign object inspection of a light-transmitting laminate such as an optical film has been performed while conveying a long web.According to such foreign body inspection, it is practically impossible to detect small foreign bodies (typically, those with a size of 50 μm or less). Conventionally, it was acceptable to detect foreign bodies of about 50 μm in size, so there was no particular problem with foreign body inspection by web transport. However, with the high accuracy of image display devices, the need to detect foreign bodies of about 10 μm in size has newly arisen. As a result of intensively studying such a problem, the present inventors have found that it may be due to flapping of the web during transport and / or vibration of the transport device, which prevents accurate images from being obtained by the imaging element. Then, as a result of trial and error, by cutting the light-transmitting laminate into sheets and performing a transmission inspection while the sheet-like light-transmitting laminate is fixed in the air (i.e., without being placed), not only can the adverse effects of flapping of the web during transport and / or vibration of the transport device be eliminated, but also the adverse effects of foreign bodies on the placement surface can be eliminated. As a result, it is possible to realize a highly accurate foreign body inspection and detect foreign bodies and / or defects of about 10 μm in size. In this way, the present invention solves a new problem that has not existed in the past. Furthermore, with the configuration of the embodiment of the present invention, the deflection can be significantly suppressed compared to the case where the light-transmitting laminate is supported or held at only two opposing sides and fixed in the air and a transmission inspection is performed, so that a more precise inspection is possible. In the illustrated example, the gripping member has four sub-members, the first gripping member 20a to the fourth gripping member 20d, but the gripping member may have two sub-members (for example, two L-shaped sub-members, one linear sub-member and one U-shaped sub-member), or may have three sub-members (for example, one L-shaped sub-member and two linear sub-members). The transmission inspection may be an edge transmission inspection in which an edge of the light-transmitting laminate is inspected, or a cross inspection in which inspection polarizing plates are arranged in crossed Nicols on both sides of the light-transmitting laminate, or in which an inspection polarizing plate is arranged in crossed Nicols on one side of the light-transmitting laminate when the light-transmitting laminate includes a polarizer.

[0010] B.Light transparent laminate The light-transmitting laminate may be any suitable light-transmitting laminate that requires foreign body inspection. Specific examples include optical films, adhesive sheets, and combinations thereof (for example, optical films with adhesive layers). Examples of optical films include polarizing plates, retardation plates, conductive films for touch panels, surface-treated films, and laminates in which these are appropriately laminated according to the purpose (for example, anti-reflection circular polarizing plates, polarizing plates with conductive layers for touch panels). The adhesive sheet typically includes an adhesive and a release film temporarily attached to at least one side of the adhesive. In one embodiment, the light-transmitting laminate may have a configuration of a low-reflection layer / substrate for low-reflection layer / retardation layer / polarizer / protective layer / hard coat layer. The thickness of the light-transmitting laminate is preferably 300 μm or less, more preferably 280 μm or less, and even more preferably 250 μm or less. According to an embodiment of the present invention, even in such a thin light-transmitting laminate, minute foreign bodies can be well detected. The lower limit of the thickness of the light-transmitting laminate may be, for example, 30 μm.

[0011] The light-transmitting laminate 10 can be produced, for example, by laminating the layers constituting the light-transmitting laminate by a so-called roll-to-roll process. The produced long light-transmitting laminate is cut into a predetermined size and subjected to foreign matter inspection. The size can be typically a size that can produce multiple final products. After the inspection, the light-transmitting laminate can be typically cut into the final product size and shipped.

[0012] The light-transmitting laminate 10 has a first main surface 10a and a second main surface 10b. In one embodiment, when the light-transmitting laminate is subjected to a foreign body inspection, a surface protective film may be temporarily attached in a peelable manner to at least one surface (typically, both surfaces). By temporarily attaching the surface protective film, it is possible to prevent the light-transmitting laminate from being scratched or from having foreign bodies attached to the light-transmitting laminate, and therefore it is possible to perform a foreign body inspection with higher accuracy. Furthermore, by temporarily attaching the surface protective film, it is possible to ensure the rigidity (stiffness) of the light-transmitting laminate when it is subjected to an inspection. The surface protective film is typically peeled off and removed during the inspection. After the inspection is completed, the surface protective film peeled off during the inspection may be temporarily attached again to the surface of the light-transmitting laminate, or another surface protective film may be temporarily attached in a peelable manner.

[0013] In one embodiment, a reflective protective film may be temporarily attached in a peelable manner to, for example, the first main surface 10a of the light-transmitting laminate 10. Depending on the type and configuration of the light-transmitting laminate (for example, when the light-transmitting laminate includes a low-reflection layer (AR layer)), the autofocus of the image sensor may not function on the first main surface of the light-transmitting laminate. However, by temporarily attaching the reflective protective film, the autofocus of the image sensor can be made to function well on the first main surface of the light-transmitting laminate even in such a case. The reflective protective film typically has a function of reflecting the irradiated light when the focus of an optical system with a predetermined magnification is adjusted to the surface of the first main surface of the light-transmitting laminate, and transmitting the inspection light. When the surface protective film is temporarily attached, the reflective protective film may typically be temporarily attached to the inside of the surface protective film.

[0014] In one embodiment, the reflective protective film satisfies the following relationship: y≧0.0181x-11.142 Here, x is the absolute value of the detection wavelength in the wavelength region of 650 nm to 800 nm, and y is the absolute value of the reflectance. With such a configuration, the autofocus of the imaging element can be made to function better. Any appropriate configuration can be adopted as the reflective protective film as long as it has the above-mentioned function. Specifically, the reflective protective film can be made of, for example, a cyclic olefin resin described in

[0031] of JP 2019-099751 A. An example of the cyclic olefin resin is polynorbornene. The cyclic olefin resin may be a commercially available product. Specific examples of commercially available products include Zeonoa and Zeonex manufactured by Zeon Corporation, Arton manufactured by JSR, Apel manufactured by Mitsui Chemicals, and Topas manufactured by TOPAS ADVANCED POLYMERS. The cyclic olefin resin film preferably contains 50% by weight or more of a cyclic olefin resin. In one embodiment, a hard coat layer may be formed on the surface of the reflective protective film. By forming a hard coat layer, it is possible to prevent scratches on the reflective protective film and adhesion of foreign matter to the reflective protective film, thereby enabling foreign matter inspection to be performed with higher accuracy and enabling accurate detection of minute foreign matter and / or defects.

[0015] A plurality of reflective protective films may be temporarily attached depending on the number of planned inspections. For example, if two foreign body inspections are planned, two reflective protective films may be attached together, and then one outer reflective protective film may be peeled off before the second foreign body inspection, thereby preventing scratches on the inner reflective protective film and adhesion of foreign bodies to the inner reflective protective film, and thus allowing multiple foreign body inspections to be performed with higher accuracy. Note that even if multiple inspections are planned, only one reflective protective film may be temporarily attached.

[0016] The surface protective film and the reflective protective film may be temporarily attached to the light-transmitting laminate by a roll-to-roll method (that is, before cutting), or may be temporarily attached after cutting.

[0017] Detection of defects in a transmission inspection will now be described in more detail.

[0018] C. Fixing the light-transmitting laminate in the hollow In the detection of defects, as described above, a sheet of the light-transmitting laminate 10 is fixed in the air with four sides held by the holding members 20. FIG. 2 is a schematic perspective view showing an example of an apparatus for fixing the light-transmitting laminate in the air; FIGS. 3(a) to 3(d) are schematic cross-sectional views for explaining the procedure for fixing the light-transmitting laminate in the air using such an apparatus. Note that FIGS. 3(a) to 3(d) are cross-sectional views seen from the holding member 20b side (the left side of FIG. 1(b)). The apparatus 100 in the illustrated example has a base frame 50 as a base, and a holding member 20 and a suction plate 60 provided on the base frame 50. The procedure for fixing the light-transmitting laminate in the air will be explained below.

[0019] First, as shown in FIG. 3(a), the light-transmitting laminate 10 is sucked and fixed by the suction plate 60. In the illustrated example, surface protective films 71 and 72 are temporarily attached to both sides of the light-transmitting laminate 10, and the surface protective film 71 is disposed on the suction plate 60 side. By sucking and fixing the light-transmitting laminate with the surface protective films temporarily attached to both sides of the light-transmitting laminate, the light-transmitting laminate can be fixed while maintaining its rigidity, making it easy to handle, and preventing wrinkles, deflections, and distortions. As a result, foreign matter inspection can be performed with high accuracy, and minute foreign matters and / or defects can be accurately detected.

[0020] The suction plate 60 is rectangular in plan view as shown in FIG. 4, has a fixing surface for fixing the light-transmitting laminate and a back surface, and has a plurality of suction holes 62 communicating between the fixing surface side and the back surface side. The suction plate 60 is pivotally attached to a plate support part 64 provided at one end of the base frame 50 via a rotation shaft 66. In one embodiment, the suction plate 60 may be provided with positioning parts 68, 68 at the long side end and the short side end as shown in FIG. 4. The positioning parts 68, 68 are, for example, convex parts, typically convex stripes. The positioning part of the long side and the positioning part of the short side are in contact with each other at one end so as to form a right-angled corner, and the light-transmitting laminate can be accurately positioned by abutting one corner of the light-transmitting laminate on the corner and fixing it by suction. As a result, more precise inspection is possible. In the illustrated example, the positioning parts 68 are provided on two sides, one of the long sides and one of the short sides, but they may be provided on four sides (i.e., in a frame shape). In this state, the surface protection film 72 is peeled off and removed from the light-transmitting laminate 10 .

[0021] Next, as shown in FIG. 3(b), the suction plate 60 is rotated toward the base frame 50 (clockwise in the illustrated example) with the light-transmitting laminate 10 fixed by suction, and disposed at a position facing the gripping member 20 (substantially, the lower grip 24), and the jig 90 supporting the gripping member 20 is raised by raising the lifting mechanism 80, so that the light-transmitting laminate 10 is sandwiched between the suction plate 60 and the lower grip 24 of the gripping member 20. Note that only the first lower grip 24a (first gripping member 20a) and the third lower grip 24c (third gripping member 20c) are depicted in the drawing. The same applies to the following explanations of FIG. 3(b) to FIG. 3(d). Here, the light-transmitting laminate 10 is positioned by, for example, the above-mentioned positioning parts 68, 68 so that its outer edge corresponds to the outer edge of the frame-shaped lower grip 24 (first lower grip 24a to first lower grip 24d). The lower grip 24 has a fixing surface for fixing the light-transmitting laminate and a back surface on the base frame side, and has a plurality of suction holes (not shown) that communicate between the fixing surface side and the back surface side. In the illustrated example, a positioning pin 82 is provided at a predetermined position on the lower grip 24 side of the lifting mechanism 80, and when the lifting mechanism 80 rises, the positioning pin 82 is inserted into a positioning hole 92 provided on the lifting mechanism side of the jig 90, and the clamping is performed in a state of accurate alignment. Furthermore, by adjusting the degree of lifting of the lifting mechanism 80, fine adjustment of the clamping is possible. After the light-transmitting laminate 10 is clamped between the suction plate 60 and the lower grip 24 of the gripping member 20, the suction of the suction plate 60 is stopped and the suction of the lower grip 24 is started, and the light-transmitting laminate 10 is fixed by suction to the lower grip 24.

[0022] Next, as shown in Fig. 3(c), with the light-transmitting laminate 10 held by suction with the lower grip 24, the suction plate 60 is rotated in a direction away from the base frame 50 (counterclockwise in the illustrated example) to expose the surface protective film 71 temporarily attached to the light-transmitting laminate 10. Thereafter, as shown in Fig. 3(c), the surface protective film 71 is peeled off and removed from the light-transmitting laminate 10.

[0023] Finally, as shown in FIG. 3(d), the upper grip 22 is disposed at a position corresponding to the lower grip 24 on the surface of the light-transmitting laminate 10 opposite to the lower grip 24, and the light-transmitting laminate 10 is gripped by the upper grip 22 and the lower grip 24. As a result, the four sides of the light-transmitting laminate 10 are gripped and fixed in the air. In this state, the light-transmitting laminate 10 is subjected to a transmission inspection (foreign body inspection). By performing a foreign body inspection in a state in which the four sides of the sheet-like light-transmitting laminate are gripped by the gripping members, the influence of fluttering due to transportation and / or vibration of the transport device can be eliminated, so that a foreign body inspection can be performed with high accuracy even after the surface protective film is peeled off, and minute foreign bodies and / or defects can be accurately detected. In addition, by peeling off the surface protective film, foreign bodies on the surface protective film are not detected, so that a synergistic effect with the above effect allows a foreign body inspection to be performed with higher accuracy. The gripped portion of the light-transmitting laminate is typically a non-product area in the final product (for example, in the case where the light-transmitting laminate is an optical film, a portion corresponding to an image non-display area).

[0024] With reference to Fig. 5(a) to Fig. 5(c), the gripping member 20 and the procedure for gripping the light-transmitting laminate 10 by the gripping member 20 will be described in detail. Fig. 5(a) to Fig. 5(c) are schematic cross-sectional views of the main parts for explaining such a procedure for the first gripping member 20a. The gripping mechanism is similar for the second gripping member 20b, the third gripping member 20c, and the fourth gripping member 20d. As shown in Fig. 5(a), in the gripping member 20a, the lower grip 24a is provided on the lower grip support part 25. The lower grip support part 25 is provided on the base part 28. The lower grip support part 25 has a convex part 25a, and the convex part 25a and the lower grip 24a define a step 25b for positioning the light-transmitting laminate 10. The step 25b is typically defined at a position corresponding to a positioning portion 68 (if present) of the suction plate when the light-transmitting laminate 10 is sandwiched between the suction plate 60 and the lower grip 24a. The upper grip support portion 26 is pivotally attached to the outer side of the lower grip support portion 25 of the base portion 28 via a rotation shaft 27. The upper grip 22a is provided at a distal portion of the upper grip support portion 26 with respect to the rotation shaft 27. In the illustrated example, the lower grip support portion 25 and the upper grip support portion 26 are provided on the base portion, but they may be provided on the jig 90.

[0025] Next, by rotating the suction plate 60 as described above, the light-transmitting laminate 10 is sandwiched between the suction plate 60 and the lower grip 24a of the gripping member 20a. Here, as shown in FIG. 5(b), the light-transmitting laminate 10 is positioned so that its outer edge abuts against the positioning step 25b. As a result, the outer edge of the light-transmitting laminate 10 corresponds to the outer edge of the frame-shaped lower grip 24a. Next, as described above, the suction of the suction plate 60 is stopped and the suction of the lower grip 24a is started, and the light-transmitting laminate 10 is fixed by suction to the lower grip 24a. Furthermore, as described above, after the suction plate 60 is separated, the surface protective film 71 is peeled off and removed from the light-transmitting laminate 10.

[0026] Next, in a state where the light-transmitting laminate 10 is suction-fixed to the lower grip 24a, as shown in FIG. 5(c), the upper grip support part 26 is rotated toward the light-transmitting laminate 10 (clockwise in the illustrated example), and the light-transmitting laminate 10 is gripped by the upper grip 22a and the lower grip 24a. After gripping, the suction of the lower grip 24a is stopped. Furthermore, as shown in FIG. 5(c), the rotating shaft 27 is fixed by the fixing means 29, so that the light-transmitting laminate 10 is fixed in the air. Any appropriate configuration may be adopted as the fixing means 29. In the illustrated example, the fixing means 29 is a screw, and the rotating shaft 27 can be fixed by tightening the screw and pressing it against the rotating shaft 27.

[0027] In one embodiment, tension may be applied to the light-transmitting laminate 10 fixed in the hollow. In this case, the first gripping member 20a and the third gripping member 20c, and the second gripping member 20b and the fourth gripping member 20d are configured to be relatively close to or spaced apart from each other. For example, as shown in FIG. 6, the first gripping member 20a is fixed, and tension may be applied to the second gripping member 20b, the third gripping member 20c, and the fourth gripping member 20d. The second gripping member 20b, the third gripping member 20c, and the fourth gripping member 20d may be configured to be slidable, and may be movable with a degree of play as long as tension is appropriately applied. The tension is typically applied in a direction in which the opposing gripping members are relatively spaced apart by an elastic member (e.g., a spring) 23. With this configuration, wrinkles, deflections, and distortions can be significantly suppressed in both the long side direction and the short side direction of the light-transmitting laminate 10. As a result, foreign body inspection can be performed with higher accuracy, and minute foreign bodies and / or defects can be accurately detected. The tension can be controlled by adjusting the strength of the spring itself and the tightness of the spring fixing screw.

[0028] D. Defect detection As described above, the detection of defects is typically performed using an optical system (including an image sensor 30 and a light source 40) as shown in FIG. 1. An example will be specifically described below. First, as shown on the left side of FIG. 7, the focus of an optical system (substantially, the image sensor 30) with a predetermined magnification (hereinafter, sometimes referred to as low magnification) is adjusted to the surface of the first main surface 10a of the light-transmitting laminate 10. In this state, the image sensor 30 scans the entire plane (XY plane) of the light-transmitting laminate 10 as shown in FIG. 8, and an XY coordinate map (first XY coordinate map) of defects is created. As described in the above item A, defects are recognized as dark spots, so that in the first XY coordinate map, defects in the vicinity of the first main surface 10a of the light-transmitting laminate 10 (up to a predetermined distance inward in the thickness direction from the first main surface) are recognized as dark spots on the image as shown in FIG. 9, for example. It should be noted that there are cases where minute defects at deep positions in the thickness direction (positions close to the second main surface) cannot be detected using only the first XY coordinate map. In contrast, according to an embodiment of the present invention, as described below, defects are detected by shifting a predetermined distance P inward in the thickness direction from the surface of the first main face, making it possible to accurately detect minute defects throughout the entire thickness direction of the light-transmitting laminate.

[0029] Next, as shown in the center of FIG. 7, the focus of the imaging element 30 is shifted a predetermined distance P inward in the thickness direction (Z direction) from the surface of the first main surface 10a of the light-transmitting laminate 10, and the focus is adjusted to a predetermined position inside the thickness direction of the light-transmitting laminate 10. In this state, the imaging element 30 scans the entire XY plane of the light-transmitting laminate 10 as shown in FIG. 8 in the same manner as above, to create an XY coordinate map of defects (a second XY coordinate map). In the second XY coordinate map, defects near a predetermined position inside the thickness direction of the light-transmitting laminate 10 (up to a predetermined distance from the predetermined position) are recognized as dark points on an image at a position substantially different from that in FIG. 9, for example. In this specification, the predetermined distance P may be referred to as an imaging pitch. The focusing of the imaging element may be achieved by any appropriate means. For example, the imaging element itself may be moved in the Z direction, the focal length of the imaging element may be changed by a lens or the like, or these may be combined. The illustrated example shows a form in which the focal length of the imaging element is changed by a lens or the like.

[0030] If necessary, as shown on the right side of FIG. 7, the focus of the imaging element 30 is further shifted by a predetermined distance P in the thickness direction (Z direction) to focus on the next predetermined position inside the thickness direction of the light-transmitting laminate 10. In this state, the imaging element 30 scans the entire XY plane of the light-transmitting laminate 10 as shown in FIG. 8 in the same manner as above to create an XY coordinate map of defects (third XY coordinate map). This operation is repeated a predetermined number of times as necessary to create a predetermined number of XY coordinate maps of defects. The imaging pitch and the number of XY coordinate maps of defects to be created can be appropriately set according to the total thickness of the light-transmitting laminate, the number of layers constituting the light-transmitting laminate, the thickness of each layer, and the like. The imaging pitch P is, for example, 10 μm to 100 μm, preferably 20 μm to 80 μm, and more preferably 40 μm to 60 μm. With this configuration, it is possible to detect substantially all defects present in the thickness direction (thus, substantially all defects in the light-transmitting laminate) and their rough positions without scanning the entire thickness direction with the imaging element. FIG. 7 shows a form in which three XY coordinate maps of defects are created, but the number of XY coordinate maps of defects created is not limited to this, and is preferably 2 to 10, more preferably 3 to 8, and even more preferably 4 to 6.

[0031] Next, the XY coordinate maps of a predetermined number of defects created as described above are integrated. For example, FIG. 10 shows an example of integrating the XY coordinate maps of five defects to create an XY coordinate map of defects (integrated XY coordinate map). By integrating each image data as shown in FIG. 10, defects present in each XY coordinate map can be represented on a common XY coordinate. In this way, an integrated XY coordinate map can be created. In the integrated XY coordinate map, substantially all defects in the light-transmitting laminate are represented in XY coordinates (two-dimensional coordinates).

[0032] The predetermined magnification (low magnification) of the imaging element in creating the integrated XY coordinate map as described above is preferably less than 10 times, and more preferably 5 times or less. The lower limit of the magnification may be, for example, 1.5 times. If the magnification is within this range, a wide range of the light-transmitting laminate can be efficiently imaged, and as a result, the integrated XY coordinate map can be efficiently created.

[0033] Next, the depth of the defect (the position in the thickness direction of the light-transmitting laminate) is measured. Here, it is difficult to detect defects over the entire plane and thickness direction of the light-transmitting laminate, and even if it could be realized, it is not practical in terms of cost, time, and efficiency. Therefore, in this embodiment, the position of the defect in the thickness direction is measured only at the defect occurrence coordinates in the integrated XY coordinate map. As described above, in the integrated XY coordinate map, substantially all defects in the light-transmitting laminate are represented in two-dimensional coordinates, so that the position of the defect in the thickness direction can be detected by measuring the position of the defect in the thickness direction only at the defect occurrence coordinates.

[0034] Measuring the depth of the defect includes focusing the imaging element on the surface of the first main surface of the light-transmitting laminate, and measuring the distance from the surface of the first main surface to the defect by moving the focus inward in the thickness direction of the light-transmitting laminate. Specifically, the focus of the imaging element is moved in the thickness direction, a position with high contrast is recognized as a focused position, and the distance from the surface of the first main surface to the focused position is determined as the position of the defect in the thickness direction. By detecting the exact position of the defect in the thickness direction, the inspection efficiency and shipping efficiency of the product can be significantly improved.

[0035] The magnification (high magnification) of the imaging element in measuring the depth of the defect as described above is preferably 10 times or more, and more preferably 20 times or more. The upper limit of the magnification may be, for example, 50 times. If the magnification is within this range, the position of the minute defect in the thickness direction can be reliably detected.

[0036] Defect depth measurement is described, for example, in JP-A-2001-124660, JP-A-2004-077261, and JP-A-2009-250893, the disclosures of which are incorporated herein by reference.

[0037] In one embodiment, the detection of the defect can be performed in a region where the variation in the thickness direction (Z direction) of the first main surface of the light-transmitting laminate per 1000 μm of the scanning distance by the imaging element in the XY coordinate map of the defect is preferably within ±10 μm, more preferably within ±8 μm. In another embodiment, the detection of the defect can be performed in a region where the bending angle of the light-transmitting laminate is preferably within ±0.57°, more preferably within ±0.50° with respect to the horizontal direction. That is, in any embodiment, the detection of the defect can be performed in a region where the bending of the light-transmitting laminate is very small. With this configuration, the focusing of the imaging element on the first main surface of the light-transmitting laminate (and, as a result, the subsequent focusing on a predetermined position inward in the thickness direction) can be performed very accurately. As a result, the position of the minute defect in the thickness direction can be accurately detected. Such a region where the bending of the light-transmitting laminate is very small can be realized by the fixing method of the light-transmitting laminate described in Section C above.

[0038] In this manner, the transmission inspection (detection of defects) can be performed. After the inspection, the light-transmitting laminate can be typically cut to the final product size and shipped, as described above. After the inspection, the peeled surface protective film may be temporarily attached to the light-transmitting laminate again in a peelable manner, as necessary, as described above. [Industrial Applicability]

[0039] The method for inspecting a light-transmitting laminate according to an embodiment of the present invention can be suitably used for detecting foreign matter in an optical film, an adhesive sheet, or the like in the manufacturing process of an image display device. [Explanation of symbols]

[0040] 10 Light-transparent laminate 20 Gripping member 30 Image sensor 40 light source 50 Base Frame 60 Suction Plate 71 Surface protection film 72 Surface protection film 80 Lifting mechanism 100 Inspection device for optically transparent laminate

Claims

1. A method for detecting defects in a light-transmitting laminate, comprising: performing a transmission inspection in a state in which four sides of a sheet of the light-transmitting laminate are gripped and fixed in a hollow space and in a state in which tension is applied to the light-transmitting laminate; The detection of the defect focusing an optical system having a predetermined magnification on the first main surface of the light-transmitting laminate, and scanning the light-transmitting laminate with the optical system to create an XY coordinate map of defects; shifting a focus of the optical system inward in a thickness direction from the surface of the first main surface of the light-transmitting laminate by a predetermined distance, and scanning the light-transmitting laminate with the optical system to create an XY coordinate map of another defect; and synthesizing the generated defect XY coordinate map; Including, A method for inspecting a light-transmitting laminate.

2. 2. The method for inspecting an optically transparent laminate according to claim 1, wherein the detection of the defects includes repeating a predetermined number of times of scanning the optical system with the optical system by further shifting the focus of the optical system inward in the thickness direction of the optically transparent laminate by the predetermined distance, thereby creating an XY coordinate map of a predetermined number of defects.

3. 3. The method for inspecting an optically transparent laminate according to claim 1, wherein the detection of the defect includes measuring the position of the defect in the thickness direction only at the defect occurrence coordinates in the XY coordinate map of the integrated defect using an optical system having a magnification higher than the predetermined magnification.

4. The method for inspecting a light-transmitting laminate according to any one of claims 1 to 3, further comprising detecting defects having a size of 8 µm to 50 µm in the light-transmitting laminate.

5. The method for inspecting a light-transmitting laminate according to claim 1 , wherein the light-transmitting laminate is selected from an optical film, a pressure-sensitive adhesive sheet, and a combination thereof.

6. The method for inspecting a light-transmitting laminate according to claim 5 , wherein the optical film is selected from the group consisting of a polarizing plate, a retardation plate, and a laminate including these.

7. The method for inspecting a light-transmitting laminate according to claim 1 , wherein the light-transmitting laminate has a thickness of 300 μm or less.

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