Inspection method for light-transmitting laminates

Abstract

The present invention provides a method for inspecting an optically transparent laminate that makes it possible to detect defects which are markedly more minute, as compared to the prior art. This method for inspecting an optically transparent laminate is a method for inspecting a sheet of optically transparent laminate that has a first principal surface and a second principal surface, the method comprising: detecting the height of the first principal surface of the optically transparent laminate with a displacement sensor to obtain displacement data; scanning the optically transparent laminate with an optical system and creating a coordinate map of defects from scanning images obtained thereby; and detecting defects on the basis of the coordinate map of defects. The scanning of the optically transparent laminate is performed while a constant distance is maintained between the height position of the focus of the optical system when obtaining the scanning images and the height position of the first principal surface on the basis of the displacement data.

Description

Technical Field

[0001] The present invention relates to a method for inspecting a light-transmissive laminate.

Background Art

[0002] A light-transmissive laminate (for example, an optical member, an optical laminate, an optical film, a light-transmissive adhesive sheet) applied to an image display device needs to remove foreign matter inside the laminate in order to prevent image display defects and the like. Therefore, such a light-transmissive laminate is typically subjected to foreign matter inspection. The foreign matter inspection is typically a transmission inspection performed while conveying a long web of the light-transmissive laminate, and defects such as foreign matter can be recognized as dark spots in the transmission inspection. In recent years, the display performance required for image display devices has become extremely high, and as a result, extremely high accuracy in foreign matter inspection of light-transmissive laminates has also been required. Specifically, conventionally, defects of about 50 μm were allowed to be detected, but now it is necessary to detect defects of about 10 μm. However, in the foreign matter inspection performed while conveying a long web as described above, it is extremely difficult to detect such small defects. In addition, there is a problem that it is difficult to accurately detect defects when there are wrinkles or bends in the light-transmissive laminate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made to solve the above problems, and its main object is to provide a method for inspecting a sheet-like light-transmissive laminate that can detect extremely minute defects as compared with the prior art even when there are wrinkles or bends in the light-transmissive laminate.

Means for Solving the Problems

[0005] According to one aspect of the present invention, a method for inspecting a single-sheet light-transmitting laminate having a first main surface and a second main surface, comprising: detecting the height of the first main surface of the light-transmitting laminate with a displacement sensor to obtain displacement data; scanning the light-transmitting laminate with an optical system to create a coordinate map of defects from the scan image obtained thereby; and An inspection method is provided, which includes detecting defects based on a coordinate map of the defects, wherein the scanning of the light-transmitting laminate is performed while maintaining a constant distance between the height position of the focal point of the optical system and the height position of the first principal surface when obtaining the scanned image, based on the displacement data. In one embodiment, creating a coordinate map of the defects includes scanning the light-transmitting laminate multiple times with the optical system to create multiple preliminary coordinate maps, and integrating the multiple preliminary coordinate maps, wherein the distance between the height position of the focal point and the height position of the first principal surface differs by a predetermined distance P in each scan. In one embodiment, the number of scans is further determined based on the reference height, maximum height, and minimum height of the first main surface of the light-transmitting laminate determined based on the displacement data, and the thickness of the light-transmitting laminate, where Qa is the value obtained by rounding the first decimal place of the quotient obtained by dividing the difference between the maximum height and the reference height by the predetermined distance P, Qb is the value obtained by rounding the first decimal place of the quotient obtained by dividing the difference between the minimum height and the reference height by the predetermined distance P, and Qc is the value obtained by rounding the first decimal place of the quotient obtained by dividing the thickness of the light-transmitting laminate by the predetermined distance P, and the number of scans is Qa + Qb + Qc or greater (however, if Qa + Qb + Qc = 0, then 1 or greater). In one embodiment, the number of scans is Qa + Qb + Qc + 2, and the region from a height of (Qa + 1) × P upwards in the thickness direction to a height of (Qb + Qc) × P downwards in the thickness direction is scanned while changing the distance between the height of the focal point and the height of the first main surface by the predetermined distance P. In one embodiment, the predetermined distance P is 10 μm to 100 μm. In one embodiment, the optical system includes a line camera, and obtaining the displacement data and creating a coordinate map of the defects is performed sequentially for each field of view in the width direction of the line camera. In one embodiment, the inspection method detects defects with a size of 50 μm or less. In one embodiment, the light-transmitting laminate is selected from an optical film, an adhesive sheet, and a combination thereof. In one embodiment, the optical film is selected from polarizing plates, phase difference plates, and laminates containing these. In one embodiment, the thickness of the light-transmitting laminate is 300 μm or less. [Effects of the Invention]

[0006] According to the inspection method for light-transmitting laminates in an embodiment of the present invention, by detecting the displacement (undulation) of a single-sheet light-transmitting laminate and scanning the light-transmitting laminate so that the imaging focus follows the undulation, even minute defects can be detected well in the light-transmitting laminate, even if wrinkles or flexures are present. [Brief explanation of the drawing]

[0007] [Figure 1] This is a flowchart illustrating a method for inspecting a light-transmitting laminate according to an embodiment of the present invention. [Figure 2] This is a schematic side view of an example of an inspection device that can be used in the inspection method according to an embodiment of the present invention. [Figure 3] This is a schematic diagram illustrating the displacement data acquisition process. [Figure 4] This is a schematic diagram illustrating the displacement data acquisition process. [Figure 5] This is a schematic diagram illustrating the process for determining the number of scans. [Figure 6] This is a schematic diagram illustrating the height position of the focal point when capturing a scanned image. [Figure 7] This is a conceptual diagram illustrating an example of creating a coordinate map of defects. [Modes for carrying out the invention]

[0008] The embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Furthermore, all drawings are schematic and do not accurately depict the actual state.

[0009] A. Outline of the inspection method for light-transmitting laminates As shown in the flowchart of Figure 1, the method for inspecting a light-transmitting laminate according to an embodiment of the present invention includes: detecting the height of the first main surface of a single-sheet light-transmitting laminate having a first main surface and a second main surface using a displacement sensor to obtain displacement data (displacement data acquisition step); scanning the light-transmitting laminate with an optical system to create a coordinate map of defects from the scan image obtained thereby (defect coordinate map creation step); and detecting defects based on the coordinate map of defects (defect detection step), and preferably further including determining the number of scans (number of scans determination step). In the defect coordinate map creation step, scanning of the light-transmitting laminate is performed while maintaining a constant distance between the height position of the focal point of the optical system when obtaining the scan image and the height position of the first main surface, based on the obtained displacement data. By scanning the light-transmitting laminate in this manner, scanning that follows the displacement (undulation) of the first main surface can be performed, and as a result, even if wrinkles or bending exist in the light-transmitting laminate, minute defects can be detected well.

[0010] A-1. Inspection equipment FIG. 2 is a schematic side view of an example of an inspection apparatus that can be used in the inspection method according to an embodiment of the present invention. The inspection apparatus 100 shown in FIG. 2 includes a sample stage 10 for fixing a light-transmissive laminate to be inspected, an optical system 20 including an imaging unit for capturing a scanned image, a displacement sensor 30 for detecting the height of the first main surface (upper surface) of the light-transmissive laminate, and a Z-axis movement control unit 40 for supporting the optical system 20 so as to be movable arbitrarily in the Z-axis direction. The displacement sensor 30 and the Z-axis movement control unit 40 are supported by support mechanisms 50a and 50b, and the sample stage 10 can be moved arbitrarily in the X-axis direction and the Y-axis direction by an XY-axis movement control unit 60. Although not shown, the displacement sensor 30 is connected to a displacement data processing unit that analyzes or processes the measured displacement data, and the Z-axis movement control unit 40 changes the height of the optical system 20 based on displacement information (for example, a displacement map) output from the displacement data processing unit so as to correspond to the displacement pattern of the first main surface. With such a configuration, the focus of the optical system (imaging unit) can be set at a desired position (height) through the change in the position (height) of the optical system 20. As a result, the height position of the focus of the optical system (imaging unit) can be controlled so that the distance from the height position of the first main surface during scanning becomes constant.

[0011] As described above, the sample stage 10 is configured to be movable arbitrarily in the X-axis direction and the Y-axis direction. With such a configuration, any region of the light-transmissive laminate can be inspected. The sample stage may include, for example, a stage base on which the light-transmissive laminate is placed and a fixing member for fixing its end. Alternatively, the sample stage may be configured to be able to fix the light-transmissive laminate in a hollow manner. For example, it may be configured to be able to grip only the ends of the light-transmissive laminate with a pair or two pairs of opposing support members. From the viewpoint of reducing wrinkles and warping, the light-transmissive laminate may be fixed in a state where tension is applied.

[0012] The optical system 20 includes an irradiation-side optical system that irradiates the light-transmissive laminate with inspection light and an imaging unit. The imaging unit includes an image pickup device and an imaging-side optical system that forms an image of the inspection light reflected by the light-transmissive laminate on the image pickup device. Examples of the irradiation-side optical system include a coaxial epi-illumination system or an oblique illumination system, and the coaxial epi-illumination system can be preferably used. Preferably, laser light is used as the inspection light. The imaging-side optical system may include an objective lens, an imaging lens, etc. Examples of the image pickup device preferably include a CCD, a CMOS, etc. In this specification, the imaging unit may be referred to as a camera. In one embodiment, the imaging unit is a line camera.

[0013] The displacement sensor 30 is typically a non-contact displacement sensor. Examples of the non-contact displacement sensor preferably include a laser displacement sensor, an ultrasonic displacement sensor, etc.

[0014] The inspection apparatus that can be used in the inspection method according to the embodiment of the present invention is not limited to the above illustrated example. The illustrated inspection apparatus 100 is a reflection-type inspection apparatus, but differently, a transmission-type inspection apparatus can also be used. According to the reflection-type inspection apparatus, defects such as bubbles can be detected as white dots, and according to the transmission-type inspection apparatus, defects such as foreign matters can be detected as black dots. In the case of the transmission-type inspection apparatus, the irradiation-side optical system (light source) is provided on the second main surface side, typically below the sample stage, and the sample stage can be configured in a shape (for example, a frame shape) that can grip only the end of the light-transmissive laminate so that light can pass through.

[0015] Also, for example, instead of configuring the sample stage to be arbitrarily movable in the X-axis direction and the Y-axis direction, an XY-axis moving mechanism that can arbitrarily move the optical system and the displacement sensor in the X-axis direction and the Y-axis direction may be provided.

[0016] A-2. Light-transmissive laminate Examples of light-transmitting laminates to be inspected include any suitable light-transmitting laminate that requires inspection. Specific examples include optical films, adhesive sheets, and combinations thereof (e.g., optical films with an adhesive layer). Examples of optical films include polarizing plates, phase difference plates, conductive films for touch panels, surface treatment films, and laminates obtained by appropriately laminating these according to their purpose (e.g., anti-reflective circular polarizing plates, polarizing plates with a conductive layer for touch panels). An adhesive sheet typically includes an adhesive and a release film temporarily attached to at least one side thereof. A light-transmitting laminate is typically an optical film with an adhesive 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 embodiments of the present invention, even minute foreign matter can be detected well in such thin light-transmitting laminates. The lower limit of the thickness of the light-transmitting laminate may be, for example, 30 μm. In this specification, the thickness of the light-transmitting laminate is the thickness considering the refractive index, and is calculated based on the following formula (1). The average refractive index in formula (1) is calculated based on the following formula (2). The thickness of a light-transmitting laminate when considering the refractive index (μm) = sum of the thicknesses of each layer constituting the light-transmitting laminate (μm) ÷ average refractive index (1) Average refractive index = sum of refractive indices of each layer constituting the light-transmitting laminate ÷ number of layers constituting the light-transmitting laminate (2)

[0017] A light-transmitting laminate can be manufactured, for example, by laminating each layer constituting the light-transmitting laminate using a so-called roll-to-roll method. The light-transmitting laminate has a first main surface and a second main surface. The first main surface is the surface on the imaging unit side (top surface). The first main surface is, for example, the surface opposite to the image display cell to which the light-transmitting laminate is bonded; the second main surface is, for example, the surface on the image display cell side, and more specifically, may be the surface of the adhesive layer. The manufactured elongated light-transmitting laminate is cut to a predetermined size and subjected to inspection. This size is typically a size from which multiple final products can be obtained. After inspection is complete, the light-transmitting laminate can typically be cut to the final product size and shipped.

[0018] In one embodiment, a reflective protective film may be temporarily attached to the first main surface of the light-transmitting laminate in a peelable manner when subjected to inspection. Depending on the type and configuration of the light-transmitting laminate (for example, if the light-transmitting laminate includes a low-reflection layer (AR layer)), detection of surface displacement by a displacement sensor or imaging by an imaging unit may be difficult. By temporarily attaching a reflective protective film, such problems can be avoided. Typically, the reflective protective film reflects measurement light from the displacement sensor and inspection light from the optical system. 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 range of 650 nm to 800 nm, and y is the absolute value of the reflectance. With such a configuration, surface displacement can be detected by the displacement sensor and imaging can be performed well by the imaging unit. Any suitable configuration can be adopted as the reflective protective film, as long as it has the above functions. Specifically, the reflective protective film may be made of a cyclic olefin resin as described in

[0031] of Japanese Patent Application Publication No. 2019-099751. An example of a cyclic olefin resin is polynorbornene. Commercially available cyclic olefin resins may also be used. Specific examples of commercially available products include Zeonor and Zeonex from Nippon Zeon, Arton from JSR, Appel from Mitsui Chemicals, and Topas from TOPAS ADVANCED POLYMERS. The cyclic olefin resin film preferably contains 50% by weight or more of the 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 the adhesion of foreign matter to the reflective protective film, thereby enabling more accurate inspection and precise detection of minute defects.

[0019] Multiple reflective protective films may be temporarily attached depending on the number of inspections scheduled. For example, if two inspections are scheduled, two reflective protective films can be bonded together. By peeling off one of the outer reflective protective films before the second inspection, it is possible to prevent scratches on the inner reflective protective film and the adhesion of foreign matter to the inner reflective protective film, thus enabling more accurate multiple inspections. Alternatively, even if multiple inspections are scheduled, only one reflective protective film may be temporarily attached.

[0020] In one embodiment, a surface protection film may be temporarily attached to the surface of the reflective protective film (or to the outermost surface of the reflective protective film if multiple reflective protective films exist). By temporarily attaching the surface protection film, scratches on the reflective protective film and the adhesion of foreign matter to the reflective protective film can be prevented, thereby enabling inspection with higher precision. Typically, the surface protection film is peeled off during inspection. After the inspection is completed, the surface protection film that was peeled off during inspection may be temporarily attached again to the surface of the light-transmitting laminate, or another surface protection film may be temporarily attached in a peelable manner.

[0021] The reflective protective film and the surface protective film may be temporarily attached to the light-transmitting laminate by roll-to-roll (i.e., before cutting) or after cutting.

[0022] The following provides a detailed explanation of each step.

[0023] B. Displacement data acquisition process In the displacement data acquisition process, the height (displacement) of the first main surface of the light-transmitting laminate is detected by a displacement sensor, and displacement data is acquired. Typically, the height is detected by scanning the first main surface of the light-transmitting laminate in two dimensions using a displacement sensor. For example, as shown in Figure 3, the height is detected by scanning the first main surface 200a of the light-transmitting laminate 200 in a line at a predetermined interval L. The predetermined interval L is, for example, 1 mm to 100 mm, preferably 1 mm to 30 mm, and more preferably 5 mm to 15 mm.

[0024] The height of the first main surface can be detected by the displacement sensor along multiple lines for each field of view in the width direction of the imaging unit (typically a line camera). For example, in the embodiment shown in Figure 4, the height of the first main surface is detected as follows. First, the inspection area of ​​the first main surface of the light-transmitting laminate is divided into N regions for each field of view in the width direction of the imaging unit (30 mm in the illustrated example). In region 1 defined by lines X1 and X4, the starting point (coordinate Y0) to the ending point (coordinate Y) in the Y direction of four lines X1 to X4 spaced 10 mm apart100 The height of the first main surface up to ) is detected sequentially. Next, in the region 2 defined by lines X4 and X7, the starting point (coordinate Y0) to the ending point (coordinate Y) in the Y direction of the four lines X4 to X7 spaced 10 mm apart is detected. 100 The height of the first main surface is sequentially detected up to (height detection on line X4 may be omitted). By repeating this procedure up to region N, displacement data can be obtained for the entire first main surface of the light-transmitting laminate or the entire inspection target region. As will be described later, in the inspection method according to the embodiment of the present invention, displacement data may be acquired for the entire first main surface or the entire inspection target region, and then the optical system may be scanned. Alternatively, the steps from acquiring displacement data to creating a coordinate map of defects may be performed continuously for each field of view in the width direction of the imaging unit, and the same operation may be repeated by sequentially shifting the field of view to inspect the entire first main surface or the entire inspection target region. Therefore, by detecting the height of the first main surface in one direction for each of the above fields of view, displacement data that matches the scanning pattern of the optical system (scanning direction and position) can be obtained, which can contribute to improving the efficiency of inspection in the latter embodiment.

[0025] By processing the obtained displacement data using any appropriate algorithm, a 2D or 3D shape profile (hereinafter also referred to as a displacement map) can be obtained. For example, a displacement map of the entire first main surface or a predetermined area, a displacement map of an arbitrary cross-section, or a displacement map viewed from any side can be obtained. Such processing can be performed using any appropriate computer program, such as a shape analysis program attached to the displacement sensor or a program created according to the purpose (for example, the Auto Focus full-surface displacement scan mode algorithm).

[0026] C. Scan count determination process As will be described later, in the defect coordinate map creation process, from the viewpoint of inspecting the light-transmitting laminate over its entire thickness, multiple scans may be performed by changing the distance between the height position of the first main surface of the light-transmitting laminate and the height position of the focal point of the imaging unit by a predetermined distance P. Therefore, in one embodiment, the number of scans is determined before the defect coordinate map creation process.

[0027] The number of scans can be determined, for example, based on the reference height, maximum height, and minimum height of the first main surface of the light-transmitting laminate (hereinafter sometimes simply referred to as the reference height, maximum height, and minimum height of the light-transmitting laminate), which are determined based on displacement data, and the thickness of the light-transmitting laminate.

[0028] The reference height of the light-transmitting laminate can be any height at any point on the first main surface. In one embodiment, the reference height of the light-transmitting laminate is the median of the maximum and minimum heights in the displacement data obtained for the first main surface, and is calculated as the arithmetic mean of the two. Alternatively, the maximum and minimum heights of the light-transmitting laminate are the maximum and minimum heights in the said displacement data, respectively. Or, the assumed maximum and minimum heights calculated by extrapolation, interpolation, etc., based on the said displacement data can be used as the maximum and minimum heights of the light-transmitting laminate, respectively.

[0029] The number of scans can be determined to be at least Qa + Qb + Qc (however, if Qa + Qb + Qc is 0, then at least 1) when Qa is the value obtained by rounding the first decimal place of the quotient obtained by dividing the difference between the maximum height and the reference height (|maximum height - reference height|) by a predetermined distance P, Qb is the value obtained by rounding the first decimal place of the quotient obtained by dividing the difference between the minimum height and the reference height (|minimum height - reference height|) by a predetermined distance P, and Qc is the value obtained by rounding the first decimal place of the quotient obtained by dividing the thickness of the light-transmitting laminate by a predetermined distance P. By setting the number of scans to be at least Qa + Qb + Qc, even if the light-transmitting laminate has wrinkles or flexures, their effects can be eliminated and the light-transmitting laminate can be inspected over its entire thickness. There is no particular upper limit to the number of scans, but from the viewpoint of production cycle time, the number of scans may be, for example, between 1 and 10.

[0030] In one embodiment, the number of scans can be Qa+Qb+Qc+1 or Qa+Qb+Qc+2, further including a first preliminary scan above the first main surface and / or a second preliminary scan below the second main surface. Performing the first and / or second preliminary scans ensures that the light-transmitting laminate can be reliably inspected throughout its entire thickness.

[0031] Referring to Figure 5, a specific procedure for one embodiment of the scan count determination process will be described. In this embodiment, the reference height, maximum height, and minimum height of the light-transmitting laminate are determined from the displacement map shown in Figure 5(b), and the scan count is determined based on these values ​​and the thickness of the light-transmitting laminate. The displacement map shown in Figure 5(b) is a 2D shape profile showing the surface displacement of the first main surface when the light-transmitting laminate 200 is viewed from the Y-side in Figure 5(a). As shown in Figure 5(a), the displacement sensor 30 detects the surface displacement at four lines (lines A to D) at predetermined intervals on the first main surface of the light-transmitting laminate 200, and the map can be obtained by processing using the Auto Focus full-surface displacement scan mode algorithm (in Figure 5(b), the maximum height in actual measurements is 160 μm at line B, and the minimum height in actual measurements is -310 μm at line C. The assumed maximum and minimum heights obtained by interpolation are 190 μm and -340 μm, respectively). In this embodiment, the maximum and minimum heights in the acquired displacement data (actual values) are used as the maximum and minimum heights of the light-transmitting laminate. Furthermore, the thickness of the light-transmitting laminate (calculated by dividing the actual thickness (350 μm) by the average refractive index (1.4)) is 250 μm, and the predetermined distance P in each scan is 100 μm. Note that the height of 0 μm in Figure 5(b) is the height of the first principal surface at the starting point of displacement data acquisition (the height of the first principal surface that was initially in focus). Procedure A1: Maximum height H max (160 μm) and minimum height H min Based on (-310 μm), the reference height is determined to be -75 μm. Step A2:H max The difference between the reference height (235 μm) and the reference height is divided by a predetermined distance P (100 μm). The quotient (2.35) is rounded to the first decimal place to obtain the value Qa (Qa = 2). Procedure A3:H min The difference between the reference height (235 μm) and the reference height is divided by a predetermined distance P (100 μm). The quotient (2.35) is rounded to the first decimal place to obtain the value Qb (Qb=2). Procedure A4: Obtain Qc (Qc=3) by rounding the quotient (2.5) obtained by dividing the thickness of the light-transmitting laminate (250 μm) by a predetermined distance P to the first decimal place. Procedure A5: Determine the number of scans based on Qa, Qb, and Qc (the number of scans applied as Qa + Qb + Qc or more is 7 or more, and the number of scans when either or both of the first and second preliminary scans are performed may be 8 or 9).

[0032] D. Process for creating a coordinate map of defects A coordinate map of defects is created by scanning a light-transmitting laminate with inspection light and obtaining a scanned image. During this process, scanning is performed while maintaining a constant distance between the height position of the focal point of the optical system (imaging unit) and the height position of the first principal surface, based on the displacement data. In one embodiment, scanning is performed while adjusting the height position of the focal point of the imaging unit so that the focal point follows the displacement pattern of the first principal surface.

[0033] Alignment of displacement data with scanning position can be performed, for example, by pre-setting a reference mark on the first main surface of the light-transmitting laminate and using the position coordinates of that reference mark. Alternatively, alignment can be performed using the corners of the light-transmitting laminate as a reference.

[0034] Scanning can be performed two-dimensionally over the entire inspection area of ​​the light-transmitting laminate by changing the relative positional relationship between the imaging unit and the light-transmitting laminate. Preferably, the scanning direction of the imaging unit and the scanning direction of the displacement sensor are parallel, and more preferably, in the same direction.

[0035] In the above scanning, the height position of the first principal plane can be a value calculated from displacement data using any appropriate algorithm. For example, when a line camera is used as the imaging unit, the midpoint between the maximum and minimum heights of the first principal plane within the field of view in the width direction (e.g., X direction) of the line camera can be used as the height position of the first principal plane. For each field of view, the height position of the focal point of the line scan camera can be changed to follow the change in the height position of the first principal plane in the scanning direction (e.g., Y direction). For example, referring to Figure 4, with respect to region 1, the midpoint between the maximum and minimum heights of lines X1 to X4 detected at coordinate Y0, the midpoint between the maximum and minimum heights of lines X1 to X4 detected at coordinate Y1, ..., coordinate Y 100 The median of the maximum and minimum heights in lines X1 to X4 detected by Y0 to Y 100 The line camera can scan while changing the height of its focal point to track the height position of the first principal plane, which changes along with the movement of the Y coordinate up to that point.

[0036] The light-transmitting laminate is scanned once or multiple times. Preferably, the multiple scans determined in the scan count determination step are performed.

[0037] If scanning is performed only once, the entire inspection area is scanned with the imaging unit focused on the first main surface (in other words, at the height of the first main surface), or with the imaging unit focused at an arbitrary depth inside the light-transmitting laminate, and the scanned image obtained in this scan becomes the defect coordinate map (XY coordinate map).

[0038] When scanning is performed multiple times, as shown in Figure 6, the focus of the imaging unit can be shifted by a predetermined distance P. The predetermined distance P is not limited to the range in which a clear scanned image can be obtained, and can be appropriately set according to the depth of field of the optical system. The predetermined distance P is, for example, 10 μm to 100 μm, preferably 20 μm to 80 μm, and more preferably 40 μm to 60 μm. With such a configuration, substantially all defects present in the thickness direction can be detected with an appropriate number of scans. In the illustrated example, the focus is aligned by moving the optical system (imaging unit) in the Z direction using an Auto Focus system, but the focus may be aligned by other means. For example, the focal length of the imaging unit may be changed by a lens or the like, the height of the sample stage may be changed, or a combination of these means may be used.

[0039] As described above, when performing the first preliminary scan and the second preliminary scan, the region of the light-transmitting laminate 200 from a height of (Qa+1)×P upward in the thickness direction from the height position of the first main surface 200a to a height of (Qb+Qc)×P downward in the thickness direction is scanned, while changing the distance between the focal height position of the imaging unit and the height position of the first main surface by a predetermined distance P with each scan. In this case, the order of scanning is not particularly limited. Specifically, the first preliminary scan can be performed first, then the imaging unit's focus can be shifted by a predetermined distance P downward in the thickness direction, and finally the second preliminary scan can be performed. Alternatively, for example, the first scan can be performed with the imaging unit focused on the first main surface (in other words, at the height position of the first main surface), then sequential scans can be performed while shifting the focus of the imaging unit downward in the thickness direction, after the completion of the second preliminary scan, sequential scans can be performed while shifting the focus of the imaging unit upward in the thickness direction from the height position of the first main surface, and finally the first preliminary scan can be performed. For example, the first scan can be performed with the imaging unit focused on the first main surface (in other words, at the height of the first main surface), then sequentially scanning while shifting the focus of the imaging unit upward in the thickness direction, and after the completion of the first preliminary scan, sequential scanning can be performed while shifting the focus of the imaging unit downward in the thickness direction from the height of the first main surface, and finally a second preliminary scan can be performed.

[0040] As a specific example, in the embodiment shown in Figure 5, if the maximum height, minimum height, standard height, and light-transmitting laminate thickness are set to 160 μm, -310 μm, -75 μm, and 250 μm, respectively, and the predetermined distance P is set to 100 μm, and the number of scans is determined to be 9 (when the number of operations calculated by Qa + Qb + Qc (7 times) is increased by adding the first and second preliminary scans), the first scan is performed so that the height position of the focal point of the imaging unit is maintained at a distance of 300 μm above the height position of the first main surface, and then a total of 9 scans can be performed while shifting the height position of the focal point downward by 100 μm each time.

[0041] If multiple scans are performed, the scan images obtained from each scan are used as preliminary coordinate maps, and a faulty coordinate map (integrated XY coordinate map) is created by integrating these multiple preliminary coordinate maps.

[0042] For example, Figure 7 shows an example of creating a defect coordinate map (integrated XY coordinate map) by integrating five preliminary coordinate maps. As shown in Figure 7, by integrating each image data, defects present in each coordinate map can be represented on a common XY coordinate system. In this way, the resulting defect coordinate map (integrated XY coordinate map) represents virtually all defects in the light-transmitting laminate on an XY coordinate system (2D coordinate system).

[0043] E. Defect detection process In the defect detection process, defects are detected based on a defect coordinate map. When defects are detected based on an integrated XY coordinate map, the same defect can be identified from the XY coordinates in all preliminary coordinate maps, and the image with the highest contrast value can be detected as the defect. Furthermore, the depth of the defect (Z coordinate) can be determined from the focal point position when the image was obtained.

[0044] According to the inspection method of the embodiment of the present invention, defects with a size (maximum length) of 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less can be detected. The size of the detected defects may be, for example, 1 μm or more, 3 μm or more, or 8 μm or more.

[0045] As described above, defects can be detected. After the inspection is complete, the light-transmitting laminate can be cut to the final product size, as described above, and shipped. Also as described above, after the inspection is complete, if necessary, the peeled surface protective film may be temporarily attached to the light-transmitting laminate in a way that allows it to be peeled off again.

[0046] In the light-transmitting laminate inspection method according to the embodiments of the present invention described in sections B to E above, the steps from displacement data acquisition to defect coordinate map creation may be performed for each field of view in the width direction of the imaging unit (line camera). By continuously performing the steps from displacement data acquisition to defect coordinate map creation for each field of view in the width direction of the imaging unit, alignment between displacement data and scanning position becomes unnecessary or extremely easy, and the number of scans can be optimized for each scanning area, thereby enabling efficient detection of defects with high accuracy. Depending on the purpose, the steps from displacement data acquisition to defect detection may be performed for each field of view in the width direction of the imaging unit (line camera). [Industrial applicability]

[0047] The method for inspecting light-transmitting laminates according to embodiments of the present invention can be suitably used to detect defects in optical films, adhesive sheets, etc., during the manufacturing process of image display devices. [Explanation of symbols]

[0048] 10 Sample Stages 20 Optical system 30 Displacement Sensor 40 Z-axis movement control unit 50 Support mechanism 60 XY axis movement control section 100 Inspection device 200 Light transmitting laminate

Claims

1. A method for inspecting a single-sheet light-transmitting laminate having a first main surface and a second main surface, Displacement data is obtained by detecting the height of the first main surface of the light-transmitting laminate using a displacement sensor. Scanning the light-transmitting laminate with an optical system and creating a coordinate map of defects from the resulting scan image, and This includes detecting defects based on a coordinate map of the defects, The scanning of the light-transmitting laminate is performed based on the displacement data, while maintaining a constant distance between the height position of the focal point of the optical system and the height position of the first main surface when obtaining the scanned image. Creating a coordinate map of the defects is The optical system scans the light-transmitting laminate multiple times to create multiple preliminary coordinate maps, and This includes integrating the multiple preliminary coordinate maps, An inspection method in which the distance between the height position of the focal point and the height position of the first main surface differs by a predetermined distance P in each scan.

2. The method further includes determining the number of scans based on the reference height, maximum height, and minimum height of the first main surface of the light-transmitting laminate determined based on the displacement data, and the thickness of the light-transmitting laminate. The inspection method according to claim 1, wherein the number of scans is Qa + Qb + Qc or greater (however, 1 or greater when Qa + Qb + Qc = 0), where Qa is the value obtained by rounding the first decimal place of the quotient obtained by dividing the difference between the maximum height and the reference height by the predetermined distance P, Qb is the value obtained by rounding the first decimal place of the quotient obtained by dividing the difference between the minimum height and the reference height by the predetermined distance P, and Qc is the value obtained by rounding the first decimal place of the quotient obtained by dividing the thickness of the light-transmitting laminate by the predetermined distance P.

3. The number of scans is Qa + Qb + Qc + 2, The inspection method according to claim 2, wherein the region of the light-transmitting laminate from a height of (Qa + 1) × P upward in the thickness direction to a height of (Qb + Qc) × P downward in the thickness direction is scanned while changing the distance between the height position of the focal point and the height position of the first main surface by a predetermined distance P.

4. The inspection method according to claim 1, wherein the predetermined distance P is 10 μm to 100 μm.

5. The optical system includes a line camera, The inspection method according to claim 1, wherein obtaining the displacement data and creating the coordinate map of the defects are performed continuously for each field of view in the width direction of the line camera.

6. The inspection method according to claim 1, for detecting defects with a size of 50 μm or less.

7. The inspection method according to claim 1, wherein the light-transmitting laminate is selected from an optical film, an adhesive sheet, and a combination thereof.

8. The inspection method according to claim 7, wherein the optical film is selected from polarizing plates, phase difference plates, and laminates containing the same.

9. The inspection method according to claim 1, wherein the thickness of the light-transmitting laminate is 300 μm or less.

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