WO2023021854A1

WO2023021854A1 - Method for inspecting optically transparent laminate

Info

Publication number: WO2023021854A1
Application number: PCT/JP2022/025868
Authority: WO
Inventors: 裕司山下; 浩次自然; ジョンビンユン
Original assignee: 日東電工株式会社
Priority date: 2021-08-17
Filing date: 2022-06-29
Publication date: 2023-02-23
Also published as: TW202309511A; CN117795288A; JPWO2023021854A1; KR20240045215A

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

Inspection method for light transmissive laminate

The present invention relates to a method for inspecting a light transmissive laminate.

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 removes foreign matter inside the laminate in order to prevent image display defects. There is a need to. Therefore, such a light-transmissive laminate is typically subjected to a foreign matter inspection. A foreign matter inspection is typically a transmission inspection carried out while conveying a long web of light-transmitting laminates, 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 increased remarkably, and as a result, remarkably high accuracy in foreign matter inspection of light-transmissive laminates has been required. Specifically, conventionally, if a defect of about 50 μm is detected, it is acceptable, but now it is necessary to detect a defect of about 10 μm. However, it is extremely difficult to detect such small defects in the foreign matter inspection carried out while conveying a long web as described above. Moreover, there is a problem that it is difficult to accurately detect defects when wrinkles or warps are present in the light-transmissive laminate.

JP 2005-062165 A

The present invention has been made to solve the above-mentioned problems, and its main purpose is to detect defects that are much smaller than those in the past, even if wrinkles or bends are present in the light-transmitting laminate. It is an object of the present invention to provide a method for inspecting a sheet-fed light-transmitting laminate that can be inspected.

According to one aspect of the present invention, there is provided a method for inspecting a sheet-fed light-transmissive laminate having a first principal surface and a second principal surface, wherein a displacement sensor detects the first principal surface of the light-transmissive laminate. detecting the height of the main surface to obtain displacement data; scanning the light-transmissive laminate with an optical system to create a coordinate map of defects from the resulting scanned image;
detecting a defect based on the coordinate map of the defect, and the height of the focal point of the optical system when scanning the light transmissive laminate to obtain the scanned image based on the displacement data; An inspection method is provided in which the distance between the position and the height position of the first main surface is maintained constant.
In one embodiment, creating the defect coordinate map includes scanning the light transmissive laminate multiple times with the optical system to create a plurality of preliminary coordinate maps; Integrating a preliminary coordinate map, wherein the distance between the height position of the focus and the height position of the first principal surface in each scan differs by a predetermined distance P.
In one embodiment, 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 determining the number of scans by dividing the difference between the maximum height and the reference height by the predetermined distance P and rounding the quotient to the first decimal place, Qa; Qb is the quotient obtained by dividing the difference by the predetermined distance P and rounded to the first decimal place; , the number of scans is Qa+Qb+Qc or more (1 or more when Qa+Qb+Qc=0).
In one embodiment, the number of times of scanning is Qa + Qb + Qc + 2, and from the height position of the first main surface of the light-transmitting laminate to the thickness direction upward (Qa + 1) × P distance from the height to the thickness direction downward A region up to a height of (Qb+Qc)×P is scanned while changing the distance between the height position of the focus and the height position of the first principal 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 the coordinate map of the defect are continuously performed for each field of view of the line camera in the width direction.
In one embodiment, the inspection method detects defects with a size of 50 μm or less.
In one embodiment, the light transmissive laminate is selected from optical films, adhesive sheets, and combinations thereof.
In one embodiment, the optical film is selected from polarizing plates, retardation plates, and laminates containing these.
In one embodiment, the thickness of the light transmissive laminate is 300 µm or less.

According to the method for inspecting a light-transmitting laminate according to an embodiment of the present invention, the displacement (undulation) of a sheet of light-transmitting laminate is detected, and the light-transmitting layer is detected so that the focus of imaging is along the undulation. By scanning the laminate, even if the light-transmitting laminate has wrinkles or warps, minute defects can be detected satisfactorily.

It is a flow figure explaining the inspection method of the light transmission layered product by the embodiment of the present invention. 1 is a schematic side view of an example of an inspection device that can be used in an inspection method according to an embodiment of the invention; FIG. It is a schematic diagram explaining a displacement data acquisition process. It is a schematic diagram explaining a displacement data acquisition process. FIG. 11 is a schematic diagram for explaining a scan number determination process; FIG. 4 is a schematic diagram for explaining the height position of the focal point when capturing a scanned image; FIG. 4 is a conceptual diagram illustrating an example of creation of a defect coordinate map;

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Also, all the drawings are schematic representations and do not represent the actual state accurately.

A. Outline of inspection method for light-transmissive laminate As shown in the flow diagram of FIG. detecting the height of the first main surface of the light-transmitting laminate with a displacement sensor to obtain displacement data (displacement data acquisition step); creating a defect coordinate map from the scanned image (defect coordinate map creating step); and detecting the defect based on the defect coordinate map (defect detecting step), preferably It further includes determining the number of scans (number of scans determination step). In the defect coordinate map creation step, the scanning of the light transmissive laminate is based on the obtained displacement data, and 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. This is done while maintaining a constant distance between By scanning the light-transmissive laminate in this way, it is possible to perform scanning that follows the displacement (undulation) of the first main surface, and as a result, even if wrinkles or warps exist in the light-transmissive laminate, Even if there is, a minute defect can be detected satisfactorily.

A-1. Inspection Apparatus FIG. 2 is a schematic side view of an example of an inspection apparatus that can be used in an inspection method according to an embodiment of the present invention. The inspection apparatus 100 shown in FIG. 2 includes a sample stage 10 that fixes a light-transmitting laminate to be inspected, an optical system 20 that includes an imaging unit that captures a scanned image, and a first main surface of the light-transmitting laminate ( A displacement sensor 30 for detecting the height of the upper surface), and a Z-axis movement control unit 40 for supporting the optical system 20 so as to be arbitrarily movable in the Z-axis direction. The displacement sensor 30 and the Z-axis movement control section 40 are supported by

support mechanisms

50a and 50b, and the sample stage 10 can be arbitrarily moved in the X-axis direction and the Y-axis direction by the XY-axis movement control section 60. FIG. 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 receives displacement information (for example, a displacement map) output from the displacement data processing unit. ), the height of the optical system 20 can be varied to correspond to the displacement pattern of the first principal surface. With such a configuration, the focal point of the optical system (imaging unit) can be set at a desired position (height) through a change in the position (height) of the optical system 20. As a result, The height position of the focal point of the optical system (imaging unit) can be controlled so that the distance from the height position of the first main surface during scanning is constant.

The sample stage 10 is configured to be arbitrarily movable in the X-axis direction and the Y-axis direction, as described above. With such a configuration, any region of the light-transmitting laminate can be inspected. The sample stage can include, for example, a stage base on which the light-transmissive laminate is placed, and fixing members for fixing the ends thereof. Alternatively, the sample stage may be configured to fix the light-transmitting laminate in the air. For example, the sample stage may be configured such that only the ends of the light-transmitting laminate can be gripped by a pair or two pairs of supporting members facing each other. can be From the viewpoint of reducing wrinkles and bending, the light-transmissive laminate may be fixed while being tensioned.

The optical system 20 includes an irradiation-side optical system for irradiating the light-transmissive laminate with inspection light and an imaging section. The imaging unit includes an imaging device and an imaging-side optical system that forms an image of inspection light reflected by the light-transmissive laminate on the imaging device. The irradiation-side optical system includes a coaxial epi-illumination system or an oblique illumination system, and the coaxial epi-illumination system is preferably used. Laser light is preferably used as the inspection light. The image-side optics may include an objective lens, an imaging lens, and the like. A CCD, a CMOS, or the like can preferably be exemplified as an imaging device. In addition, in this specification, the imaging unit may be referred to as a camera. In one embodiment, the imaging unit is a line camera.

The displacement sensor 30 is typically a non-contact displacement sensor. As the non-contact displacement sensor, a laser displacement sensor, an ultrasonic displacement sensor, and the like can be preferably exemplified.

The inspection device that can be used in the inspection method according to the embodiment of the present invention is not limited to the example illustrated above. Although the illustrated inspection apparatus 100 is a reflective inspection apparatus, a transmissive inspection apparatus can also be used. Defects such as air bubbles can be detected as white dots by the reflective inspection device, and defects such as foreign matter can be detected as black dots by the transmissive inspection device. In the case of a transmissive inspection apparatus, the illumination-side optical system (light source) is provided on the second main surface side, typically below the sample stage, and the sample stage is provided with a light-transmissive laminate so as to allow light to pass through. It can be configured in a shape (for example, frame-like) that can hold only the end of the body.

Further, for example, instead of arbitrarily moving the sample stage in the X-axis direction and the Y-axis direction, an XY-axis movement mechanism capable of arbitrarily moving the optical system and the displacement sensor in the X-axis direction and the Y-axis direction is provided. good too.

A-2. Light-Transmitting Laminate The light-transmitting laminate to be inspected includes any suitable light-transmitting laminate that requires inspection. Specific examples include optical films, pressure-sensitive adhesive sheets, and combinations thereof (for example, pressure-sensitive adhesive layer-attached optical films). Examples of optical films include polarizing plates, retardation plates, conductive films for touch panels, surface treatment films, and laminates obtained by appropriately laminating these according to the purpose (e.g., antireflection circular polarizing plate, touch panel polarizing plate with a conductive layer). A pressure-sensitive adhesive sheet typically includes a pressure-sensitive adhesive and a release film temporarily adhered to at least one side thereof. The light-transmitting laminate may typically be an optical film with a pressure-sensitive adhesive layer. The thickness of the light-transmissive laminate is preferably 300 μm or less, more preferably 280 μm or less, still more preferably 250 μm or less. According to the embodiment of the present invention, even in such a thin light-transmissive laminate, minute foreign matter can be detected satisfactorily. The lower limit of the thickness of the light transmissive laminate may be 30 μm, for example. In addition, in this specification, the thickness of the light-transmitting laminate is the thickness when the refractive index is taken into consideration, and is calculated based on the following formula (1). Also, the average refractive index in the formula (1) is calculated based on the following formula (2).
Thickness (μm) of the light-transmitting laminate when the refractive index is taken into consideration=Total thickness (μm) of each layer constituting the light-transmitting laminate/average refractive index (1)
Average refractive index = total refractive index of each layer constituting the light-transmitting laminate / number of layers constituting the light-transmitting laminate (2)

The light-transmitting laminate can be produced, for example, by laminating each layer constituting the light-transmitting laminate by so-called roll-to-roll. The light transmissive laminate has a first main surface and a second main surface. The first main surface is a surface (upper surface) on the imaging unit side. 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, more specifically adhesive It can be the surface of the agent layer. The produced long optically transparent laminate is cut into a predetermined size and subjected to inspection. The size may typically be a size that allows multiple final products to be obtained. After inspection, the light transmissive laminate can typically be cut to the final product size and shipped.

In one embodiment, the light-transmissive laminate may have a reflective protective film releasably attached to the first main surface when the laminate is subjected to inspection. 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)), it becomes difficult to detect surface displacement by the displacement sensor and to capture images by the imaging unit. In some cases, such problems can be avoided by temporarily applying a reflective protective film. A reflective protective film typically 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, detection of surface displacement by the displacement sensor and imaging by the imaging unit can be performed satisfactorily. Any appropriate configuration can be adopted as the reflective protective film as long as it has the above functions. Specifically, the reflective protective film can be composed of, for example, a cyclic olefin resin described in [0031] of JP-A-2019-099751. Examples of cyclic olefin resins include polynorbornene. A commercially available product may be used as the cyclic olefin resin. Specific examples of commercially available products include Zeonor and Zeonex manufactured by Nippon Zeon, Arton manufactured by JSR, Appel manufactured by Mitsui Chemicals, and Topas manufactured by 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 the occurrence of scratches on the reflective protective film and the adhesion of foreign matter to the reflective protective film, so that inspection can be performed with higher accuracy, and minute defects can be detected. can be accurately detected.

Depending on the number of scheduled inspections, multiple reflective protective films may be temporarily attached. For example, if two inspections are scheduled, by sticking two reflective protective films together, peeling off one outer reflective protective film before the second inspection allows the inner reflective protection to be removed. Since it is possible to prevent the occurrence of scratches on the film and the adhesion of foreign matter to the inner reflective protective film, it is possible to perform inspections more accurately and multiple times. Note that even when multiple inspections are scheduled, only one reflective protective film may be temporarily attached.

In one embodiment, a surface protective film may be detachably temporarily adhered to the surface of the reflective protective film (if there are multiple reflective protective films, the surface of the outermost reflective protective film). By temporarily attaching the surface protective film, it is possible to prevent the reflective protective film from being scratched, prevent foreign substances from adhering to the reflective protective film, and the like, so that inspection can be performed with higher accuracy. The surface protective film is typically peeled off during inspection. After completion of the inspection, the surface protective film that was peeled off during the inspection may be temporarily adhered to the surface of the light-transmitting laminate again, or another surface protective film may be temporarily adhered in a detachable manner.

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

Each step will be explained in detail below.

B. Displacement Data Acquisition Step In the displacement data acquisition step, the displacement sensor detects the height (displacement) of the first main surface of the light transmissive laminate to acquire displacement data. Typically, a displacement sensor is used to two-dimensionally scan the first main surface of the light transmissive laminate to detect its height. For example, as shown in FIG. 3, the first main surface 200a of the light transmissive laminate 200 is scanned linearly at a predetermined interval L to detect the height. The predetermined distance L is, for example, 1 mm to 100 mm, preferably 1 mm to 30 mm, more preferably 5 mm to 15 mm.

Detection of the height of the first main surface by the displacement sensor can be performed along a plurality of lines for each field of view in the width direction of the imaging section (typically, a line camera). For example, in the embodiment shown in FIG. 4, the height of the first main surface is detected as follows. First, the area to be inspected on the first main surface of the light-transmissive laminate is divided into N areas for each field of view (30 mm in the illustrated example) in the width direction of the imaging section. In the area 1 defined by the lines X1 and X4, the height of the first main surface from the starting point (coordinate Y ₀ ) to the end point (coordinate Y ₁₀₀ ) in the Y direction of the four lines X1 to X4 at intervals of 10 mm is sequentially measured. To detect. Next, in the region 2 defined by the lines X4 and X7, the height of the first main surface from the starting point (coordinate Y ₀ ) to the end point (coordinate Y ₁₀₀ ) in the Y direction of the four lines X4 to X7 at intervals of 10 mm is Detection is performed sequentially (height detection on line X4 may be omitted). By repeating the procedure up to area N, displacement data can be obtained for the entire first main surface of the light-transmissive laminate or the entire inspection target area. 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 area, and then the optical system may be scanned, or an image may be captured. The steps from obtaining the displacement data to creating the coordinate map of the defect are continuously performed for each field of view in the width direction of the part, and the same operation is repeated while sequentially shifting the field of view. You can do an inspection. Therefore, by detecting the height of the first main surface in one direction for each field of view, it is possible to obtain displacement data that matches the scanning pattern (scanning direction and position) of the optical system. It can contribute to efficiency of inspection.

A 2D or 3D shape profile (hereinafter also referred to as a displacement map) can be obtained by processing the obtained displacement data with any suitable algorithm. For example, a displacement map of the entire first main surface or a predetermined region, a displacement map in any cross section, a displacement map when viewed from any side, etc. can be obtained. Examples of such processing include processing using any suitable computer program such as a shape analysis program attached to the displacement sensor, a program created according to the purpose, etc. (for example, Auto Focus Whole Displacement Scan Mode Algorithm). .

C. Scan Count Determination Step As will be described later, in the defect coordinate map creation step, from the viewpoint of inspecting the light-transmitting laminate over the entire thickness direction, the height position of the first main surface of the light-transmitting laminate and the imaging A plurality of scans can be performed by changing the distance from the height position of the focus of the part by a predetermined distance P. Thus, in one embodiment, the number of scans is determined prior to the defect coordinate mapping process.

The number of scans is, for example, the reference height, maximum height and minimum height of the first main surface of the light-transmitting laminate determined based on the displacement data (hereinafter simply referred to as the reference height of the light-transmitting laminate , may be referred to as maximum height and minimum height) and the thickness of the light transmissive laminate.

As for the reference height of the light-transmitting laminate, the height of an arbitrary point on the first main surface can be used as the reference height. In one embodiment, the reference height of the light transmissive laminate is the median value of the maximum height and minimum height in the displacement data obtained with respect to the first principal surface, and is calculated as the arithmetic mean of both. Also, the maximum height and minimum height of the light transmissive laminate are the maximum height and minimum height in the displacement data, respectively. Alternatively, the assumed maximum height and the assumed minimum height calculated by extrapolation, interpolation, etc. based on the displacement data can be used as the maximum height and minimum height of the light-transmitting laminate, respectively.

The number of scans is, for example, Qa, the value obtained by dividing the difference between the maximum height and the reference height (|maximum height−reference height|) by a predetermined distance P and rounding off to the first decimal place, and the minimum height and the reference height. Qb is the value obtained by rounding the quotient obtained by dividing the difference (|minimum height−reference height|) by the predetermined distance P, and the quotient obtained by dividing the thickness of the light-transmitting laminate by the predetermined distance P. When Qc is a value obtained by rounding to the first decimal place, it can be determined to be Qa+Qb+Qc or more (however, when Qa+Qb+Qc is 0, 1 or more). By setting the number of scans to Qa+Qb+Qc or more, even if the light-transmissive laminate has wrinkles or warps, the effects of these are eliminated, and the entire thickness direction of the light-transmissive laminate can be inspected. can. The upper limit of the number of scans is not particularly limited, but from the viewpoint of production takt time, the number of scans may be, for example, 1 or more and 10 or less.

In one embodiment, the number of scans is Qa+Qb+Qc+1 or Qa+Qb+Qc+2, further adding a first pre-scan above the first main surface and/or a second pre-scan below the second main surface. can be done. By performing the first pre-scanning and/or the second pre-scanning, it is possible to reliably inspect the light transmissive laminate over the entire thickness direction.

A specific procedure for one embodiment of the scan number determination process will be described with reference to FIG. In this embodiment, the reference height, maximum height and minimum height of the light-transmitting laminate are determined from the displacement map shown in FIG. Determine the number of scans. The displacement map shown in FIG. 5(b) is a 2D shape profile showing the surface displacement of the first main surface when the light transmissive laminate 200 is viewed from the Y-direction − side in FIG. 5(a). As shown in FIG. 5(a), on the first main surface of the light-transmitting laminate 200, the displacement sensor 30 detects the surface displacement in four lines (line A to line D) at predetermined intervals, and auto focus is performed. (In FIG. 5(b), the maximum measured value is 160 μm at line B, and the minimum measured value is − 310 μm, and the assumed maximum and minimum heights obtained by interpolation are 190 μm and −340 μm, respectively). In this embodiment, the maximum height and minimum height in the obtained displacement data (actual measurement values) are used as the maximum height and minimum height of the light-transmitting laminate. 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 FIG. 5B is the height of the first main surface at the acquisition start point of the displacement data (the height of the first main surface that is initially focused).
Procedure A1: Based on the maximum height H _max (160 μm) and the minimum height H _min (−310 μm), determine a reference height of −75 μm.
Procedure A2: A value Qa is obtained by rounding off the quotient (2.35) obtained by dividing the difference (235 μm) between H _max and the reference height by the predetermined distance P (100 μm) (Qa=2).
Procedure A3: A value Qb is obtained by rounding off the quotient (2.35) obtained by dividing the difference (235 μm) between H _min and the reference height by the predetermined distance P (100 μm) (Qb=2).
Step A4: A value Qc is obtained by rounding off the quotient (2.5) obtained by dividing the thickness (250 μm) of the light-transmissive laminate by the predetermined distance P (Qc=3).
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 perform either or both of the first prescan and the second prescan The number of scans in each case can be 8 or 9).

D. Defect Coordinate Map Creation Step A defect coordinate map is created by scanning the light-transmissive laminate with inspection light and obtaining a scanned image. At this time, based on the displacement data, 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 main surface. In one embodiment, scanning is performed while adjusting the height position of the focal point so that the focal point of the imaging unit follows the displacement pattern of the first main surface.

Alignment between the displacement data and the scanning position can be performed, for example, by providing a reference mark in advance on the first main surface of the light-transmitting laminate and based on the position coordinates of the reference mark. Alternatively, alignment can be performed using the corners of the light-transmissive laminate as a reference.

By changing the relative positional relationship between the imaging unit and the light-transmitting laminate, scanning can be performed two-dimensionally over the entire inspection target area of the light-transmitting laminate. Preferably, the scanning direction of the imaging unit and the scanning direction of the displacement sensor are parallel, more preferably the same direction.

In the above scanning, a value calculated from displacement data using any appropriate algorithm can be used as the height position of the first main surface. For example, when a line camera is used as the imaging unit, the median value between the maximum height and the minimum height of the first main surface within the field of view in the width direction (eg, X direction) of the line camera is taken as the height position of the first main surface. Scanning is performed while changing the height position of the focal point of the line scan camera so as to follow the change in the height position of the first main surface in the scanning direction (for example, the Y direction) for each field of view. be able to. For example _, _specifically referring to FIG. Y coordinates from Y ₀ to Y ₁₀₀ , such _as the median of maximum and minimum heights at X4, . It is possible to scan while changing the height position of the focal point of the line camera so as to follow the height position of the first main surface that changes along with the movement of the line camera.

The scanning of the light-transmissive laminate is performed once or multiple times. Preferably, a plurality of scans determined in the scan count determination step are performed.

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

When scanning is performed multiple times, scanning can be performed while shifting the focus of the imaging unit by a predetermined distance P, as shown in FIG. The predetermined distance P is not limited within a range in which a clear scanned image can be obtained, and can be appropriately set according to the depth of focus (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, more preferably 40 μm to 60 μm. According to such a configuration, substantially all defects existing in the thickness direction can be detected with an appropriate number of scans. In the illustrated example, the focus is adjusted by moving the optical system (imaging unit) in the Z direction using the Auto Focus system, but the focus is adjusted by other means. good too. 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 these means may be combined.

As described above, when performing the first preliminary scan and the second preliminary scan, from the height position of the first main surface 200a of the light-transmitting laminate 200 to the thickness direction upward (Qa + 1) × P distance height From the height to the height of the distance (Qb + Qc) × P downward in the thickness direction, while changing the distance between the focal height position of the imaging unit and the first principal surface height position by a predetermined distance P for each scan. Scan. In this case, the scanning order is not particularly limited. Specifically, the first pre-scanning can be performed first, the scanning can be performed while shifting the focal point of the imaging unit downward in the thickness direction by a predetermined distance P, and finally the second pre-scanning can be performed. Further, for example, the first scanning is performed with the imaging unit focused on the first main surface (in other words, at the height position of the first main surface), and then the imaging unit is moved downward in the thickness direction. Sequential scanning is performed while shifting the focus, and after completion of the second preliminary scanning, sequential scanning is 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 scanning is performed. Scanning can be performed. Further, for example, the first scanning is performed with the imaging unit focused on the first main surface (in other words, at the height position of the first main surface), and then the imaging unit moves upward in the thickness direction. Sequential scanning is performed while shifting the focus, and after completion of the first preliminary scanning, sequential scanning is performed while shifting the focus of the imaging unit downward in the thickness direction from the height position of the first main surface, and finally the second preliminary scanning is performed. Scanning can be performed.

As a specific example, in the embodiment shown in FIG. 5, the maximum height, minimum height, standard height, and thickness of the light-transmitting laminate are 160 μm, −310 μm, −75 μm, and 250 μm, respectively, and the predetermined distance P is 100 μm. , when the number of scans is determined to be 9 (when the first prescan and the second prescan are added to the number of operations (7) calculated by Qa+Qb+Qc), the height position of the focal point of the imaging unit is A first scan is performed so as to maintain a distance of 300 μm upward from the height position of one principal surface, and then a total of 9 scans are performed while shifting the height position of the focal point downward by 100 μm. can.

When scanning is performed multiple times, a defect coordinate map (integrated XY coordinate map) is created by integrating a plurality of obtained preliminary coordinate maps using the scanned image obtained in each scanning as a preliminary coordinate map. be done.

For example, FIG. 7 shows an example of creating a defect coordinate map (integrated XY coordinate map) by integrating five preliminary coordinate maps. By integrating each image data as shown in FIG. 7, defects present in each coordinate map can be expressed on common XY coordinates. Thus, in the obtained defect coordinate map (integrated XY coordinate map), substantially all defects in the light-transmissive laminate are represented by XY coordinates (two-dimensional coordinates).

E. Defect Detection Step In the defect detection step, defects are detected based on the defect coordinate map. When detecting defects based on the integrated XY coordinate map, the same defect can be identified from the XY coordinates in all the preliminary coordinate maps, and the image with the highest contrast value can be detected as the defect. The depth (Z coordinate) of the defect can be specified from the focal position when the image was obtained.

According to the inspection method according to 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 can be for example 1 μm or more, also for example 3 μm or more, also for example 8 μm or more.

Defects can be detected as described above. After inspection, the light-transmitting laminate can typically be cut to the final product size and shipped as described above. Also as described above, after the inspection is completed, the peeled surface protective film may be re-attached temporarily to the light-transmissive laminate in a peelable manner, if necessary.

In the method for inspecting a light-transmissive laminate according to the embodiment of the present invention described in the above items B to E, from the displacement data acquisition step to the defect coordinate map creation step, the field of view in the width direction of the imaging unit (line camera) You can go every By continuously performing from the displacement data acquisition step to the defect coordinate map creation step for each field of view in the width direction of the imaging unit, it becomes unnecessary or extremely easy to align the displacement data and the scanning position. Since the number of scans can be optimized, highly accurate defect detection can be performed efficiently. Depending on the purpose, the steps from the displacement data acquisition step to the defect detection step may be performed for each field of view in the width direction of the imaging unit (line camera).

The method for inspecting a light-transmitting laminate according to an embodiment of the present invention can be suitably used for detecting defects in optical films, pressure-sensitive adhesive sheets, etc. in the manufacturing process of image display devices.

REFERENCE SIGNS LIST 10 sample stage 20 optical system 30 displacement sensor 40 Z-axis movement controller 50 support mechanism 60 XY-axis movement controller 100 inspection device 200 light transmissive laminate

Claims

A method for inspecting a sheet-fed light transmissive laminate having a first main surface and a second main surface, comprising:
obtaining displacement data by detecting the height of the first main surface of the light transmissive laminate with a displacement sensor;
scanning the light transmissive laminate with an optical system to create a coordinate map of the defects from the resulting scanned image; and
detecting a defect based on the coordinate map of the defect;
Scanning of the light transmissive laminate maintains 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 based on the displacement data. An inspection method that is carried out while
creating a coordinate map of the defects;
scanning the light transmissive laminate multiple times with the optical system to create a plurality of preliminary coordinate maps; and
integrating the plurality of preliminary coordinate maps;
2. The inspection method according to claim 1, wherein the distance between the height position of the focal point and the height position of the first main surface in each scan differs by a predetermined distance P.
The number of scans is 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. further comprising:
Qa is the value obtained by rounding the quotient obtained by dividing the difference between the maximum height and the reference height by the predetermined distance P, and the decimal point of the quotient obtained by dividing the difference between the minimum height and the reference height by the predetermined distance P. When Qb is the value rounded to the first place, and Qc is the value obtained by dividing the thickness of the light-transmissive laminate by the predetermined distance P and the first decimal place is rounded, the number of scans is Qa + Qb + Qc. 3. The inspection method according to claim 2, wherein the number is equal to or more (however, 1 or more when Qa+Qb+Qc=0).
the number of scans is Qa+Qb+Qc+2;
The area from the height of the distance of (Qa+1)×P in the thickness direction upward from the height position of the first main surface of the light-transmitting laminate to the height of the distance (Qb+Qc)×P in the thickness direction downward, 4. The inspection method according to claim 3, wherein scanning is performed while changing the distance between the height position of the focal point and the height position of the first main surface by the predetermined distance P.
The inspection method according to claim 3 or 4, wherein the predetermined distance P is 10 µm to 100 µm.
the optical system includes a line camera,
6. The inspection method according to claim 1, wherein obtaining the displacement data and creating the coordinate map of the defect are performed continuously for each field of view in the width direction of the line camera.
The inspection method according to any one of claims 1 to 6, which detects defects with a size of 50 μm or less.
The inspection method according to any one of claims 1 to 7, wherein the light-transmitting laminate is selected from an optical film, an adhesive sheet, and a combination thereof.
The inspection method according to claim 8, wherein the optical film is selected from a polarizing plate, a retardation plate, and a laminate containing these.
The inspection method according to any one of claims 1 to 9, wherein the thickness of the light transmissive laminate is 300 µm or less.