Method for inspecting and manufacturing optical films

Abstract

The present invention provides an optical film inspection method that enables high-precision and efficient inspection of optical films, and that can identify the positional information of defects in the optical film in the thickness direction. [Solution] The present invention comprises a macro inspection step ST1 for inspecting an optical film F using a first imaging means 1, and a micro inspection step ST2 for inspecting the optical film using a second imaging means 5. The micro inspection step controls the position of the imaging field of view VF2 of the second imaging means so that defects can be imaged based on the position information of defects D identified in the macro inspection step, moves the focal position of the second imaging means to multiple locations in the thickness direction of the optical film, and generates multiple imaged images by imaging each location. The evaluation target area EA corresponding to the defects and their vicinity is identified in the composite image obtained by combining the multiple imaged images, and the in-focus image is identified from the multiple imaged images based on the brightness value in the same pixel area as the evaluation target area, and detailed information of the defects is obtained based on the in-focus image.

Description

[Technical Field] 【0001】 The present invention relates to a method for inspecting an optical film, such as an optical laminate equipped with a polarizing plate, in a transport line that transports the optical film in one direction in the in-plane direction, and to a method for manufacturing an optical film using the same. In particular, the present invention relates to a method for inspecting and manufacturing an optical film that can inspect the optical film with high precision and efficiency, and can identify the positional information of defects in the optical film in the thickness direction. [Background technology] 【0002】 Optical films, such as optical laminates equipped with polarizing plates, used in image display devices like liquid crystal displays, require the elimination of defects such as foreign matter present within the optical film to prevent image display defects and maintain display performance. Therefore, optical films are inspected using an optical system equipped with a light source and imaging means to detect defects. 【0003】 In recent years, the display performance required of image display devices has increased dramatically. Consequently, the demands for inspection accuracy of optical films have also increased significantly, and there is a need to detect minute defects such as foreign objects and obtain detailed information about them. 【0004】 Therefore, the applicant proposes, for example, the method described in Patent Document 1. The method described in Patent Document 1 is a method for inspecting an optical film (particularly a long optical film), comprising: a pre-inspection step of inspecting the optical film using an optical system to detect defects; a macro-inspection step of inspecting the optical film using a first optical system equipped with a first imaging means to identify the precise location information of defects; and a micro-inspection step of inspecting the optical film after the macro-inspection step using a second optical system equipped with a second imaging means to obtain detailed information about defects. The second imaging means has a narrower imaging field and a higher imaging magnification than the first imaging means. In the micro-inspection step, the position of the imaging field of the second imaging means is controlled so that defects can be imaged based on the precise location information of defects identified in the macro-inspection step, and then detailed information about defects is obtained based on the image captured by the second imaging means of the optical film (claims 1, 4, etc. of Patent Document 1). 【0005】 Furthermore, in the method described in Patent Document 1, in a preferred embodiment, in the micro-inspection step, the focal position of the second imaging means is moved to multiple locations in the thickness direction of the optical film, and multiple images are generated by imaging the optical film with each of the multiple focal positions of the second imaging means (e.g., claim 3 of Patent Document 1). 【0006】 According to the method described in Patent Document 1, optical films can be inspected with high precision and efficiency. In particular, in the micro-inspection step, when the focal position of the second imaging means is moved to multiple locations in the thickness direction of the optical film to generate multiple imaging images, high-resolution imaging images can be generated for each, making it possible to inspect multiple locations in the thickness direction of the optical film with high precision. 【0007】 However, the method described in Patent Document 1 does not specifically propose how to identify the positional information of the defective optical film in the thickness direction. [Prior art documents] [Patent Documents] 【0008】 [Patent Document 1] Japanese Patent Publication No. 2023-111431 [Overview of the Initiative] [Problems that the invention aims to solve] 【0009】 The present invention was made to solve the problems of the prior art described above, and aims to provide an optical film inspection method that can inspect optical films with high precision and efficiency, and that can identify the positional information of defects in the optical film in the thickness direction, and a method for manufacturing optical films using the same. [Means for solving the problem] 【0010】 To solve the aforementioned problems, the present invention provides a method for inspecting an optical film in a transport line that transports the optical film in one direction in the in-plane direction, comprising: a macro inspection step of inspecting the optical film using a first optical system; and a micro inspection step of inspecting the optical film using a second optical system after the macro inspection step, wherein the macro inspection step identifies the in-plane position information of defects present in the optical film based on an image generated by imaging the optical film with a first imaging means provided in the first optical system, and the micro inspection step controls the position of the imaging field of a second imaging means provided in the second optical system, which has an imaging field of view narrower than the dimension in the in-plane direction perpendicular to the transport direction of the optical film, an imaging field of view narrower than that of the first imaging means, and an imaging magnification higher than that of the first imaging means, so that the defects can be imaged based on the position information of the defects identified in the macro inspection step. The present invention provides an inspection method for an optical film, comprising: an imaging field of view control step; an imaging image generation step of generating multiple imaging images by moving the focal position of the second imaging means to multiple locations in the thickness direction of the optical film and imaging the optical film with each of the multiple focal positions of the second imaging means; an evaluation target area identification step of generating a composite image by combining the multiple imaging images and identifying an evaluation target area in the composite image which is a pixel area corresponding to the defect and its vicinity, and which is a pixel area narrower than the imaging field of view of the second imaging means; a focus image identification step of each of the multiple imaging images, based on the brightness value in the same pixel area as the identified evaluation target area, to identify a focused image among the multiple imaging images that is considered to have been captured when the focal position of the second imaging means coincided with the defect; and an information details acquisition step of acquiring detailed information about the defect based on the identified focused image. 【0011】 According to the present invention, first, in the macro inspection step, the positional information of defects present in the optical film within the plane of the optical film is identified based on the image generated by imaging the optical film with the first imaging means provided in the first optical system. Next, according to the present invention, in the micro-inspection process, the following steps are performed: an imaging field control step, an imaging image generation step, an evaluation target area identification step, a focused image identification step, and a detailed information acquisition step. 【0012】 First, in the imaging field control step, the position of the imaging field of the second imaging means of the second optical system is controlled so that defects can be imaged, based on the location information of defects identified in the macro inspection step. The imaging field of the second imaging means is narrower than the dimension in the in-plane direction perpendicular to the transport direction of the optical film, narrower than the imaging field of the first imaging means, and has a higher imaging magnification than the first imaging means. Therefore, based on the image generated by this second imaging means with a narrow imaging field and high imaging magnification, detailed information about the defects can be obtained in the detailed information acquisition step described later. 【0013】 Next, in the image generation step, the focal position of the second imaging means is moved to multiple locations in the thickness direction of the optical film, and multiple images are generated by imaging the optical film with each of the multiple focal positions of the second imaging means. As a result, high-resolution images can be generated at multiple locations in the thickness direction of the optical film. To move the focal position of the second imaging means, the second imaging means may be moved in the thickness direction of the optical film, or the lens equipped in the second imaging means may be a variable focal length lens, and the focal position may be moved by changing the focal length of this lens. According to the imaging field control step and image generation step described above, the position of the imaging field of the second imaging means is controlled based on the location information of defects identified in the macro inspection step, and the optical film is only imaged at this controlled position. Therefore, inspection can be performed more efficiently compared to sequentially imaging the entire in-plane direction perpendicular to the transport direction of the optical film with the second imaging means without performing the macro inspection step. 【0014】 Next, in the evaluation target area identification step, multiple captured images are combined to generate a composite image, and the evaluation target area is identified in the composite image, which is a pixel area corresponding to a defect and its vicinity, and which is narrower than the imaging field of view of the second imaging means. Then, in the focused image identification step, for each of the multiple captured images, a focused image is identified from among the multiple captured images that is considered to have been captured when the focal position of the second imaging means coincided with the defect, based on the brightness value within the same pixel area as the identified evaluation target area. "The same pixel area as the evaluation target area" means a pixel area in each of the multiple captured images that has the same position and dimensions as the evaluation target area in the composite image. As described above, by identifying a focused image that is thought to have been captured when the focal position of the second imaging means coincided with the defect, the positional information of the defect in the thickness direction of the optical film can be determined. In other words, the positional information of the defect in the thickness direction of the optical film can be determined from the focal position of the second imaging means when the captured image identified as the focused image was generated. Furthermore, in the evaluation target area identification step, the evaluation target area is identified in a composite image created by combining multiple captured images, rather than identifying the evaluation target area for each individual captured image. This reduces processing time and allows for more efficient inspection compared to identifying the evaluation target area for each individual captured image. Additionally, since the evaluation target area is not the entire composite image but a portion of its pixel regions (and therefore, the same pixel region as the evaluation target area is also only a portion of the captured image, not the entire image), processing time is reduced and inspection is more efficient compared to identifying the focused image based on the brightness value of the entire captured image. 【0015】 Finally, in the detailed information acquisition step, detailed information about the defect is acquired based on the identified in-focus image. The in-focus image is an image captured when the focal position of the second imaging means matches the defect, i.e., it is a high-resolution image of the defect, and therefore, detailed information about the defect can be acquired with high accuracy based on this image. As described above, according to the present invention, an optical film can be inspected with high precision and efficiency, and further, the position information in the thickness direction of the defective optical film can be specified. 【0016】 Preferably, in the in-focus image specifying step, the standard deviation of the luminance values within the same pixel region as the specified evaluation target region is calculated, and among the plurality of captured images, the captured image in which the calculated standard deviation becomes the maximum value is specified as the in-focus image. 【0017】 According to the findings of the present inventors, the standard deviation of the luminance values within the same pixel region (that is, the pixel region corresponding to the defect and its vicinity) as the evaluation target region increases as the focal position of the second imaging means that captures the captured image approaches the defect in the thickness direction of the optical film. Therefore, according to the above preferred method, the in-focus image can be specified with high accuracy. Note that the method for specifying the in-focus image is not limited to the above preferred method. For example, the variance or coefficient of variation of the luminance values within the same pixel region as the specified evaluation target region may be calculated, and among the plurality of captured images, the captured image in which the calculated variance or coefficient of variation becomes the maximum value is specified as the in-focus image. 【0018】 In the present invention, for example, in the evaluation target region specifying step, a square region with a side length of 25 μm to 100 μm centered on the center or centroid of the pixel region corresponding to the defect in the composite image may be used as the evaluation target region. In the above preferred method, "center" simply means the geometric center without considering the luminance values of each pixel within the pixel region corresponding to the defect. "Centroid" means the center when the position of each pixel is weighted by the luminance value of each pixel within the pixel region corresponding to the defect. If the luminance value within the pixel region is constant, the "centroid" coincides with the "center". 【0019】 In the present invention, for example, in the captured image generation step, the focal position of the second imaging means may be moved in the thickness direction of the optical film at a pitch of 5 to 20 μm. In the above preferred method, the pitch to be moved may be constant or may be changed within the range of 5 to 20 μm. 【0020】 In the present invention, in the detailed information acquisition step, it is conceivable to acquire, as the detailed information of the defect, at least the position information in the thickness direction of the optical film of the defect, the size of the defect, and the contrast of the defect. In the above preferred method, the "contrast of the defect" means that in the focused image, when the sum of the luminance values of the pixel regions corresponding to the defect is Ia and the sum of the luminance values of the pixel regions corresponding to other than the defect is Ib, it is a value represented by the following formula (1). Contrast = |Ia - Ib| / (Ia + Ib) ···(1) 【0021】 Further, in order to solve the above problems, the present invention also provides a method for manufacturing an optical film, which includes a manufacturing process for manufacturing an optical film and an inspection process for inspecting the manufactured optical film by the inspection method according to claim 1 or 2. 【Effects of the Invention】 【0022】 According to the present invention, an optical film can be inspected with high precision and efficiency, and moreover, the position information in the thickness direction of the defective optical film can be specified. Therefore, by referring to the position information of the defect (including the position information in the thickness direction) and the detailed information of the defect in the optical film, various analyses such as investigating the cause of the defect can be efficiently performed. 【Brief Description of the Drawings】 【0023】 [Figure 1] It is a cross-sectional view schematically showing the schematic configuration of a long optical film inspected by the inspection method according to an embodiment of the present invention. [Figure 2] It is a flowchart showing the schematic process of the inspection method according to an embodiment of the present invention. [Figure 3]This is a schematic diagram illustrating an example of an inspection system for performing an inspection method according to one embodiment of the present invention. [Figure 4] Figure 2 is an explanatory diagram illustrating the image acquisition step ST22, the evaluation target area identification step ST23, and the focused image identification step ST24 shown in Figure 2. [Modes for carrying out the invention] 【0024】 The following describes an inspection method for an optical film according to one embodiment of the present invention, with reference to the attached drawings as appropriate, using the case where the optical film is an optical laminate equipped with a polarizing plate as an example. Please note that the figures are for reference only, and the dimensions, scale, and shape of the components shown in each figure may differ from those of the actual components. 【0025】 <Structure of optical film (optical laminate)> First, the structure of the optical film (optical laminate) to be inspected by the inspection method according to this embodiment will be described. This optical film is manufactured by a manufacturing process that performs various treatments described below. Figure 1 is a schematic cross-sectional view showing the general configuration of an optical film to be inspected by the inspection method according to this embodiment. As shown in Figure 1, the optical film F of this embodiment comprises a polarizing film PF, a phase difference film F4, an adhesive layer F5, a release liner F6, and a surface protection film F7. The laminate of the polarizing film PF and the phase difference film F4 constitutes the polarizing plate PP. The individual components of the optical film F will be described below. 【0026】 [Polarizing film PF] The polarizing film PF consists of a polarizer F1 and protective films F2 and F3 that protect the polarizer F1. In this embodiment, protective films F2 and F3 are laminated to both sides of the polarizer PF, but this is not the only option; it is sufficient if protective films are laminated to at least one side of the polarizer PF. 【0027】 (Polarizer F1) A polarizer F1 is typically composed of a resin film containing a dichroic substance. Any suitable resin film that can be used as a polarizer can be employed. Typically, the resin film is a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film. 【0028】 Any suitable resin can be used as the PVA resin for forming the above-mentioned PVA resin film. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer is obtained by saponifying ethylene-vinyl acetate copolymer. 【0029】 Examples of dichroic substances included in the resin film include iodine and organic dyes. These can be used individually or in combination of two or more. Iodine is preferably used. 【0030】 The resin film may be a single-layer resin film or a laminate of two or more layers. A specific example of a polarizer composed of a single layer of resin film is one in which a PVA-based resin film has been subjected to iodine dyeing and stretching (typically uniaxial stretching). Iodine dyeing is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio for uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing, or during dyeing. Dyeing may also be performed after stretching. If necessary, the PVA-based resin film may be subjected to swelling, crosslinking, washing, drying, etc. Specific examples of polarizers composed of laminates include polarizers composed of a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on this resin substrate, or polarizers composed of a laminate of a resin substrate and a PVA-based resin layer coated and formed on this resin substrate. 【0031】 The thickness of the polarizer F1 is preferably 15 μm or less, more preferably 1 μm to 12 μm, even more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm. The polarizer F1 preferably exhibits absorption dichroism at any wavelength within the range of 380 nm to 780 nm. The transmittance of polarizer F1 is preferably 40.0% to 45.0%, more preferably 41.5% to 43.5%. The degree of polarization of polarizer F1 is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher. 【0032】 (Protective film F2, F3) Any suitable resin film can be used as the protective films F2 and F3. Examples of resin film forming materials include (meth)acrylic resins, cellulose resins such as diacetylcellulose and triacetylcellulose, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. Note that "(meth)acrylic resin" means acrylic resin and / or methacrylic resin. The forming materials of protective films F2 and F3 may be the same or different. 【0033】 The thickness of protective films F2 and F3 is typically 10 μm to 100 μm, preferably 10 μm to 40 μm, and more preferably 20 μm to 40 μm. The thicknesses of protective films F2 and F3 may be the same or different. 【0034】 The surface of protective films F2 and F3 opposite to the polarizer F1 may be treated as needed with a hard coat, anti-reflective coating, anti-sticking coating, anti-glare coating, or other surface treatments. Furthermore / or, the surface of protective films F2 and F3 opposite to the polarizer F1 may be treated as needed with a treatment to improve visibility when viewed through polarized sunglasses (typically, a treatment to impart (elliptical) polarization function or a treatment to impart ultra-high phase difference). Note that if a surface treatment is applied and a surface treatment layer is formed, the thickness of protective films F2 and F3 includes the thickness of the surface treatment layer. 【0035】 The protective films F2 and F3 are laminated to the polarizer F1 via an arbitrary and suitable adhesive layer (not shown). Typical adhesives that make up the adhesive layer include PVA-based adhesives or activated energy ray-curing adhesives. 【0036】 [Phase contrast film F4] The phase difference film F4 may be, for example, a compensating plate that provides a wide viewing angle, or it may be a phase difference plate (circular polarizer) such as a half-wave plate or a quarter-wave plate used with a polarizing film to generate circularly polarized light. The thickness of the phase difference film F4 is, for example, 1 to 200 μm. 【0037】 The phase difference film F4 is formed, for example, from a layer or resin formed by polymerizing a polymerizable liquid crystal. A polymerizable liquid crystal is a compound that has polymerizable groups and liquid crystalline properties. A polymerizable group is a group that participates in the polymerization reaction, and is preferably a photopolymerizable group. Here, a photopolymerizable group is a group that can participate in the polymerization reaction by active radicals or acids generated from a photopolymerization initiator. Examples of polymerizable groups include vinyl groups, vinyloxy groups, 1-chlorovinyl groups, isopropenyl groups, 4-vinylphenyl groups, acryloyloxy groups, methacryloyloxy groups, oxyranyl groups, and oxetanyl groups. Among these, acryloyloxy groups, methacryloyloxy groups, vinyloxy groups, oxyranyl groups, and oxetanyl groups are preferred, and acryloyloxy groups are more preferred. The liquid crystalline properties of the polymerizable liquid crystal may be thermotropic or lyotropic, and if the thermotropic liquid crystal is classified by its degree of order, it may be either a nematic or smectic liquid crystal. Furthermore, examples of resins used to form the phase difference film F4 include polyarylate, polyamide, polyimide, polyester, polyaryletherketone, polyamideimide, polyesterimide, polyvinyl alcohol, polyfumarate, polyethersulfone, polysulfone, norbornene resin, polycarbonate resin, cellulose resin, and polyurethane. These resins may be used individually or in combination. 【0038】 The phase difference film F4 is laminated to the polarizing film PF (protective film F3) via any suitable adhesive layer or tack layer (not shown). Typical adhesives that make up the adhesive layer include PVA-based adhesives or activated energy ray-curing adhesives. 【0039】 [Adhesive layer F5] The adhesive layer F5 is formed by applying adhesive to one side of the release liner F6 and then curing the applied adhesive by heating and drying it in an oven or the like. The heating temperature of the adhesive is preferably set in the range of 100°C to 160°C, and more preferably in the range of 140°C to 160°C. At this heating temperature, it is preferably heated for 20 seconds to 3 minutes, and more preferably for 1 minute to 3 minutes. 【0040】 Specific examples of adhesives that form the adhesive layer F5 include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination and blending ratio of monomers that form the base resin of the adhesive, as well as the amount of crosslinking agent, reaction temperature, reaction time, etc., an adhesive with desired properties according to the purpose can be prepared. The thickness of the adhesive layer F5 can be, for example, 10 μm to 100 μm, preferably 10 μm to 40 μm, and more preferably 10 μm to 30 μm. 【0041】 [Peel-off Liner F6] Any suitable release liner can be used as the release liner F6. Specific examples include plastic films, nonwoven fabrics, or paper coated with a release agent. Specific examples of release agents include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents. Specific examples of plastic films include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. The thickness of the release liner F6 can be, for example, 10 μm to 100 μm. 【0042】 [Surface protection film F7] The surface protection film F7 typically comprises a substrate and an adhesive layer. The thickness of the surface protection film F7 (total thickness of the substrate and adhesive layer) is, for example, 30 μm or more. The upper limit of the thickness of the surface protection film F7 is, for example, 150 μm. 【0043】 The base material can be made of any suitable resin film. Examples of resin film forming materials include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Preferably, it is an ester resin (particularly polyethylene terephthalate resin). 【0044】 Any suitable adhesive can be used to form the adhesive layer. Examples of base resins for the adhesive include acrylic resins, styrene resins, silicone resins, urethane resins, and rubber resins. 【0045】 <Testing Method> The inspection method according to this embodiment for inspecting the optical film F having the configuration described above will be described below. The inspection method according to this embodiment is performed by an inspection step that follows the manufacturing process of the optical film F. In the inspection method according to this embodiment, the optical film F cut into sheet form is inspected. Figure 2 is a flowchart showing the schematic steps of the inspection method according to this embodiment. As shown in Figure 2, the inspection method according to this embodiment includes a macro inspection step ST1 and a micro inspection step ST2. Steps ST1 and ST2 will be described below. 【0046】 [Macro Inspection Process ST1] Figure 3 is a schematic diagram illustrating an example of an inspection system for carrying out the inspection method according to this embodiment. Figure 3(a) is a schematic perspective view showing the general configuration of the inspection system, and Figure 3(b) is a plan view showing an example of the imaging field in the macro inspection process ST1 and the micro inspection process ST2. In Figure 3, arrow X represents the transport direction (horizontal direction) of the optical film F transported by the belt conveyor BC in one direction in the in-plane direction (indicated by the thick arrow in Figure 3), arrow Y represents the in-plane direction (horizontal direction) perpendicular to the transport direction of the optical film F, and arrow Z represents the normal direction (thickness direction) of the surface of the optical film F. As shown in Figure 3(a), in the macro inspection process ST1, a single sheet of optical film F, which is transported in the X direction by a belt conveyor BC that constitutes the transport line, is inspected using the first optical system of the inspection system 100. 【0047】 The inspection system 100 includes a first optical system consisting of a first imaging means 1 positioned on one side of the optical film F in the Z direction (above the optical film F in the example shown in Figure 3(a)), a light source (not shown), and an inspection polarizing filter (not shown), etc., and an image processing means 2 electrically connected to the first imaging means 1, which identifies the location information of defects D by applying known image processing, such as binarization, to the captured image generated by imaging the optical film F with the first imaging means 1, to extract pixel regions with different brightness values ​​from other pixel regions. The inspection system 100 also includes a length measuring device 3 and a computing memory device 4 electrically connected to the image processing means 2 and the length measuring device 3. Furthermore, the inspection system 100 includes a second imaging means 5 used in the micro-inspection process ST2 described later. As the first imaging means 1, an area sensor in which image sensors are arranged in a matrix can be used, and for example, as shown in Figure 3(b), its imaging field of view VF1 is set to be wider than the dimensions of the optical film F. For example, if the dimensions of the optical film F are approximately 200 mm × 300 mm, the imaging field of view VF1 is preferably set to approximately 210 mm × 310 mm. 【0048】 In the macro inspection process ST1 of this embodiment, the optical film F can be inspected using multiple types of first optical systems. Specifically, the optical film F can be inspected using three types of first optical systems: a transmission optical system, a reflection optical system, and a crossed nicol optical system. In the transmission optical system, a light source (not shown) is positioned on the other side in the Z direction relative to the optical film F (below the optical film F in the example shown in Figure 3(a)), and the first imaging means 1 receives the light transmitted through the optical film F and forms an image (image) to generate an image (transmission image). In the reflection optical system, a light source (not shown) is positioned on one side in the Z direction relative to the optical film F (above the optical film F in the example shown in Figure 3(a)), similar to the first imaging means 1, and the first imaging means 1 receives the light reflected by the optical film F and forms an image (image) to generate an image (reflection image). In a crossed nicols optical system, a light source (not shown) is positioned on the other side in the Z direction relative to the optical film F (below the optical film F in the example shown in Figure 3(a)), an inspection polarizing filter (not shown) is positioned on one or the other side in the Z direction relative to the optical film F, and the first imaging means 1 receives the light transmitted through the optical film and forms an image (image) to generate an image (crossed nicols image). Although Figure 3(a) shows only a single first imaging means 1 for convenience, in reality, three first imaging means 1 corresponding to the three types of first optical systems are arranged side by side in the transport direction of the optical film F, and the optical film F is inspected using at least one of the first imaging means 1 of the three types of first optical systems. 【0049】 In the macro inspection process ST1 of this embodiment, when the first imaging means 1 images the optical film F, the transport of the optical film F is stopped (the belt conveyor BC is stopped). Specifically, the amount of movement of the optical film F in the transport direction (X direction) is measured by a measuring device 3 using a rotary encoder or the like, and input to the computing memory device 4. The computing memory device 4 then calculates the timing at which the optical film F reaches the imaging field VF1 of the first imaging means 1 based on the distance in the X direction between the measuring device 3 and the first imaging means 1 and the amount of movement of the optical film F in the X direction (the amount of movement measured by the measuring device 3). At the timing when the optical film F reaches the imaging field VF1, a control signal is sent to the drive unit (not shown) that drives the belt conveyor BC, and the belt conveyor BC starts to decelerate so that the transport of the optical film F is completely stopped (the belt conveyor BC is completely stopped). In this embodiment, the case in which the arithmetic memory device 4 also has the function of controlling the belt conveyor BC was described as an example, but it is not limited to this, and it is also possible to adopt a configuration in which a control device other than the arithmetic memory device 4 controls the belt conveyor BC. 【0050】 In the macro inspection step ST1 of this embodiment, the image processing means 2 identifies the position information (X1, Y1) of defects D present in the optical film F within the plane of the optical film F, based on the captured image generated by imaging the optical film F with the first imaging means 1. Specifically, the image processing means 2 extracts the pixel region corresponding to the defect D by applying known image processing, such as binarization, which extracts pixel regions with different brightness values ​​from other pixel regions, to the generated captured image, and identifies the center coordinates or centroid coordinates of the defect D as the position information (X1, Y1). The identified defect position information is input to and stored in the computing memory 4. 【0051】 [Micro-inspection process ST2] The micro-inspection process ST2 is performed after the macro-inspection process ST1. In the micro-inspection process ST2, the optical film F is inspected using the same inspection system 100 as in the macro-inspection process ST1. However, in the micro-inspection process ST2, the optical film F is inspected using a second optical system consisting of a second imaging means 5, which is located on one side of the optical film F in the Z direction (above the optical film F in the example shown in Figure 3(a)) and electrically connected to the image processing means 2, and a light source (not shown), etc. In this embodiment, the second imaging means 5 is located further downstream of the first imaging means 1 in the transport direction (X direction) of the optical film F. The second imaging means 5 is attached to a predetermined drive unit (not shown) consisting of a 3-axis stage or the like, and is movable in the X, Y, and Z directions by this drive unit. In this embodiment, the entire second optical system is attached to this drive unit, and the entire second optical system is movable in the X, Y, and Z directions by this drive unit. It is also possible to configure the system so that only the second imaging means 5 can move in the Z direction. As the second imaging means 5, an area sensor in which image sensors are arranged in a matrix can be used, and which has an imaging field of view narrower than the dimension in the in-plane direction (Y direction) perpendicular to the transport direction of the optical film F, an imaging field of view narrower than that of the first imaging means 1, and an imaging magnification higher than that of the first imaging means (for example, 10x to 50x). For example, if the dimensions of the optical film F are approximately 200 mm × 300 mm, the imaging field of view VF2 of the second imaging means 5 is preferably set to approximately 1 mm × 1 mm. The second imaging means 5 may be a color area sensor comprising an R (red) image sensor, a G (green) image sensor, and a B (blue) image sensor, or it may be a monochrome area sensor. When a color area sensor is used as the second imaging means 5, for example, it is conceivable to use only the image generated by the G image sensor in the micro-inspection process ST2. 【0052】 In the micro-inspection step ST2 of this embodiment, the optical film F can be inspected using multiple types of second optical systems. Specifically, the optical film F can be inspected using two types of second optical systems: a transmission optical system and a reflection optical system. In Figure 3(a), for convenience, only a single second imaging means 5 is shown, but in reality, two first imaging means 5 corresponding to the two types of second optical systems are arranged side by side, and the optical film F is inspected using at least one of the second imaging means 5 of the two types of second optical systems. The computing memory 4 then selects one of several types of second optical systems, sends a control signal to a drive unit (not shown) that drives the selected second optical system, and causes the selected second optical system to inspect the optical film F. In this embodiment, the case in which the arithmetic memory device 4 also has the function of controlling the drive unit of the second optical system was described as an example, but it is not limited to this, and it is also possible to adopt a configuration in which a control device other than the arithmetic memory device 4 controls the drive unit of the second optical system. 【0053】 Specifically, the micro-inspection process ST2 includes an imaging field control step ST21, an imaging image generation step ST22, an evaluation target area identification step ST23, a focused image identification step ST24, and a detailed information acquisition step ST25. Each step ST21 to ST25 will be described below. 【0054】 (Imaging field of view control step ST21) In the imaging field of view control step ST21, the computing memory 4 controls the position (position in the X and Y directions) of the second imaging means 5 of the selected second optical system, and consequently the position (position in the X and Y directions) of the imaging field of view VF2 of the second imaging means 5, based on the position information (X1, Y1) of the defect D identified in the macro inspection step ST1, so that the defect D can be imaged. Specifically, as shown in Figure 3(b), for example, the position of the imaging field of view VF2 of the second imaging means 5 is controlled so that the coordinate point corresponding to the position information (X1, Y1) of the defect D identified in the macro inspection step ST1 coincides with the center of the imaging field of view VF2. The position of the imaging field of view VF2 in which the defect D can be imaged can be calculated by the computing memory 4 based on the position information (X1, Y1) of the defect D. 【0055】 As described above, in the macro inspection step ST1 of this embodiment, when the optical film F is imaged by the first imaging means 1, the transport of the optical film F is stopped. In the micro inspection step ST2 of this embodiment, for example, if the distance between the first imaging means 1 and the second imaging means 5 in the X direction is short, it is possible to image the optical film F with the second imaging means 5 while it remains stopped in the macro inspection step ST1. However, if the distance between the first imaging means 1 and the second imaging means 5 in the X direction is long, it may be impossible for the second imaging means 5 to image the optical film F while it is stopped in the macro inspection process ST1 (even if the drive unit moves the second imaging means 5 in the X direction, the second imaging means 5 may not be able to image the defects D). In this case, the transport of the optical film F can be resumed after the macro inspection process ST1 is completed. The computing memory 4 then calculates the timing at which the defects D of the optical film F reach the imaging field VF2 of the second imaging means 5 based on the distance between the measuring instrument 3 and the second imaging means 5 in the X direction and the amount of movement of the optical film F in the X direction (the amount of movement measured by the measuring instrument 3). The memory 4 then sends a control signal to the drive unit (not shown) that drives the belt conveyor BC so that the transport of the optical film F completely stops (the belt conveyor BC completely stops) at the timing when the defects D of the optical film F reach the imaging field VF2, and starts decelerating the belt conveyor BC. 【0056】 (Image generation step ST22) Figure 4 is an explanatory diagram that schematically illustrates the captured image generation step ST22, the evaluation target area identification step ST23, and the focused image identification step ST24. In the image generation step ST22, after moving the position of the second optical system in the X and Y directions in the imaging field control step ST21, the focal position of the second imaging means 5 is set to multiple locations in the thickness direction of the optical film F (in the example shown in Figure 4(a), Z=Z1~Z n These are n locations up to (for example, n=20). Then, multiple captured images I are generated by imaging the optical film F with each of the second imaging means 5 which has multiple focal positions. Specifically, the entire second optical system or only the second imaging means 5 of the second optical system is moved in the Z direction by a drive unit (not shown), thereby moving the focal position of the second imaging means 5 in the Z direction at a pitch of 5 to 20 μm, for example. The pitch of movement may be constant or may be varied within the range of 5 to 20 μm. For example, the entire second optical system or only the second imaging means 5 of the second optical system may be sequentially moved in the Z direction so that the focal position of the second imaging means 5 matches the surface of each layer constituting the optical film F (polarizer F1 to surface protective film F7) (e.g., the upper surface of the surface protective film F7, the interface between the surface protective film F7 and the protective film F2). Then, an image I is generated at each position. 【0057】 (Step ST23: Identifying the evaluation target area) In the evaluation target area identification step ST23, as shown in Figure 4(b), the image processing means 2 generates a composite image SI by combining multiple captured images I. Specifically, the composite image SI is generated by accumulating the brightness values ​​of each pixel at the same coordinates that make up each of the multiple captured images I. When generating the composite image SI, it is conceivable to perform bit conversion (such as converting an 8-bit captured image I to 16 bits before combining, or converting a 16-bit composite image SI to 8 bits) or LUT (lookup table) processing (such as setting the minimum brightness value of the composite image SI to 0 and the maximum brightness value to 255) as needed, in order to facilitate the identification of the evaluation target area EA in the evaluation target area identification step ST23 described later. 【0058】 Then, in the evaluation target area identification step ST23, as shown in Figure 4(c), the image processing means 2 identifies the evaluation target area EA, which is a pixel area in the composite image SI corresponding to defect D and its vicinity, and which is narrower than the imaging field of view of the second imaging means 5. Specifically, by applying image processing such as binarization (preferably adaptive binarization) to the composite image SI, the pixel area corresponding to defect D is extracted, and the evaluation target area EA is identified based on the extracted pixel area corresponding to defect D. As the evaluation target area EA, although not limited to this, for example, it is conceivable to set an area of a square with a side length of 25 μm to 100 μm centered on the center or centroid of the pixel area corresponding to the defect D in the synthetic image SI. 【0059】 (Focused image identification step ST24) In the focused image identification step ST24, the image processing means 2 identifies, for each of a plurality (in the example shown in FIG. 4(a), n sheets) of captured images I, a focused image that is considered to have been captured in a state where the focus position of the second imaging means 5 coincides with the defect D, based on the luminance values within the same pixel area as the identified evaluation target area EA. In the present embodiment, the image processing means 2 calculates the standard deviation σ of the luminance values within the same pixel area as the identified evaluation target area EA, and identifies, as the focused image, the captured image among the plurality of captured images I in which the calculated standard deviation σ becomes the maximum value. As shown in FIG. 4(d), when the focus position of the second imaging means 5 is at a position of Z = Z1 to Z n among which Z = Z i and the standard deviation σ of the captured image I i captured at that time becomes the maximum value, the image processing means 2 identifies the captured image I i as the focused image. 【0060】 (Detailed information acquisition step ST25) In the detailed information acquisition step ST25, the image processing means 2 acquires detailed information on the defect D based on the identified focused image (captured image I i ). Specifically, the image processing means 2 of the present embodiment acquires, as detailed information on the defect D, at least position information in the thickness direction (Z direction) of the optical film F of the defect D, the size of the defect D, and the contrast of the defect D. The position information of the defect D in the Z direction can be specified and acquired from the focus position (Z = Z i ) of the second imaging means 5 when generating the focused image (captured image I i ). The size of the defect D is the focused image (captured image I iThis can be obtained by calculating the dimensions of the pixel region corresponding to the defect D extracted through image processing. The contrast of defect D is in the focused image (imaging image I). i In this case, if Ia is the sum of the brightness values ​​of the pixel regions corresponding to defect D, and Ib is the sum of the brightness values ​​of the pixel regions other than defect D, then the value can be calculated and obtained as shown in the following equation (1). Contrast = |Ia-Ib| / (Ia+Ib) ···(1) The detailed information about defect D obtained in step ST25 is input into and stored in the computing memory 4. 【0061】 According to the inspection method of this embodiment described above, in the imaging field control step ST21 and the image generation step ST22, the position of the imaging field VF2 of the second imaging means 5 is controlled based on the position information of the defects D identified in the macro inspection step ST1, and the optical film F is only imaged at this controlled position. Therefore, inspection can be performed more efficiently compared to sequentially imaging the entire in-plane direction (Y direction) perpendicular to the transport direction of the optical film F with the second imaging means 5 without performing the macro inspection step ST1. Furthermore, the positional information of the defect D in the thickness direction (Z direction) of the optical film F can be determined from the focal position of the second imaging means 5 when generating the captured image identified as the focused image in the focused image identification step ST24. Furthermore, in the evaluation target area identification step ST23, the evaluation target area EA is identified in a composite image created by combining multiple captured images, rather than identifying the evaluation target area EA for each of the multiple captured images. This reduces processing time and allows for more efficient inspection compared to identifying the evaluation target area EA for each of the multiple captured images. Additionally, since the evaluation target area EA is a pixel area of ​​a portion of the composite image, not the entire composite image (and therefore, the same pixel area as the evaluation target area EA is also a pixel area of ​​a portion of the captured image, not the entire image), this reduces processing time and allows for more efficient inspection compared to identifying the focused image based on the brightness value of the entire captured image. Furthermore, in the detailed information acquisition step ST25, detailed information about defect D is acquired based on the identified in-focus image. The in-focus image is an image captured when the focal position of the second imaging means 5 coincides with defect D, that is, a high-resolution image of defect D. Therefore, detailed information about defect D can be acquired with high accuracy based on this image. As described above, the inspection method according to this embodiment makes it possible to inspect the optical film F with high accuracy and efficiency, and also to identify the positional information of defects D in the thickness direction of the optical film F. 【0062】 In this embodiment, the case in which the optical film F to be inspected is an optical laminate equipped with a polarizing plate PP was described as an example, but the present invention is not limited to this and can be applied to various optical films, such as single-layer optical films or optical laminates having other configurations. 【0063】 Furthermore, although this embodiment has been described using the example of a case where the first optical system (first imaging means 1) and the second optical system (second imaging means 5) are arranged on the same transport line (belt conveyor BC), the present invention is not limited to this, and it is also possible to adopt an embodiment in which the second optical system is arranged on a separate transport line that follows the transport line in which the first optical system is arranged. 【0064】 Furthermore, although this embodiment has described the case of inspecting an optical film F cut into single sheets as an example, the present invention is not limited thereto. It can also be applied to long optical films, similar to the method described in Patent Document 1. In this case, for example, similar to the method described in Patent Document 1, in the pre-inspection step, the long optical film is inspected using an optical system to detect defects D. Then, in the macro inspection step ST1 of this embodiment, the long optical film is inspected using a first optical system equipped with a first imaging means 1 to identify the precise location information of defects D. Finally, in the micro inspection step ST2 of this embodiment, the long optical film F is inspected using a second optical system equipped with a second imaging means 5 to obtain detailed information about defects D. In this case, in the pre-inspection step, the imaging field of view of the imaging means constituting the optical system is set to be greater than or equal to the width of the long optical film, whereas in the macro inspection step ST1, instead of setting the imaging field of view VF1 of the first imaging means 1 to be wider than the width of the long optical film, as in this embodiment, it is preferable to set the imaging field of view VF1 of the first imaging means 1 to be narrower than the width of the long optical film. Furthermore, similar to the method described in Patent Document 1, it is preferable to associate the position information of the detected defect D with a first mark in the pre-inspection step, acquire the position information of the defect D by reading the first mark in the macro inspection step ST1, and control the position of the imaging field of view VF1 of the first imaging means 1 so that the defect D can be imaged based on the acquired position information of the defect D. Furthermore, for the contents other than the evaluation target area identification step ST23 and the focused image identification step ST24 of this embodiment, the same contents as those described in Patent Document 1 can be appropriately adopted. [Explanation of Symbols] 【0065】 1. First imaging means 2. Image processing means 3. Measuring instrument 4... Arithmetic storage means 5. Second imaging means 100... Inspection System BC... Belt conveyor D... Disadvantage EA... Evaluation Area F... Optical film ST1... Macro inspection process ST2... Microinspection Process ST21...Imaging field of view control step ST22...Image generation step ST23... Step to identify the evaluation target area ST24... Focused Image Identification Step ST25... Steps to obtain detailed information VF1... Imaging field of view VF2... Imaging field of view

Claims

[Claim 1] A method for inspecting an optical film in a transport line that transports an optical film in one direction in the in-plane direction, A macro inspection step in which the optical film is inspected using the first optical system, The process includes a micro-inspection step, which involves inspecting the optical film using a second optical system, after the macro-inspection step. The macro inspection step identifies the positional information of defects present in the optical film within the plane of the optical film based on the image generated by imaging the optical film with the first imaging means provided in the first optical system. The aforementioned micro-inspection process is: Based on the location information of the defects identified in the macro inspection step, the second imaging means of the second optical system controls the position of the imaging field of the second imaging means, which has an imaging field narrower than the dimension in the in-plane direction perpendicular to the transport direction of the optical film, an imaging field narrower than that of the first imaging means, and an imaging magnification higher than that of the first imaging means, so that the defects can be imaged. Image generation step: Generates multiple captured images by moving the focal position of the second imaging means to multiple locations in the thickness direction of the optical film, and imaging the optical film with each of the multiple focal positions of the second imaging means. A step to identify an evaluation target area: to generate a composite image by combining the plurality of captured images, and to identify an evaluation target area in the composite image that is a pixel area corresponding to the defect and its vicinity, and which is a pixel area narrower than the imaging field of view of the second imaging means; A focus image identification step for each of the plurality of captured images, based on the brightness value in the same pixel area as the identified evaluation target area, to identify a focused image from among the plurality of captured images that is considered to have been captured when the focal position of the second imaging means coincided with the defect. The process includes a detailed information acquisition step, which involves obtaining detailed information about the defects based on the identified focused image. Methods for inspecting optical films. [Claim 2] In the in-focus image identification step, the standard deviation of the luminance values ​​within the same pixel area as the identified evaluation target area is calculated, and among the multiple captured images, the image with the maximum calculated standard deviation is identified as the in-focus image. The method for inspecting an optical film according to claim 1. [Claim 3] In the step of identifying the evaluation target area, the evaluation target area is defined as a square region with sides of 25 μm to 100 μm, centered on the center or centroid of the pixel region corresponding to the defect in the composite image. A method for inspecting an optical film according to claim 1 or 2. [Claim 4] In the image generation step, the focal position of the second imaging means is moved in the thickness direction of the optical film at a pitch of 5 to 20 μm. A method for inspecting an optical film according to claim 1 or 2. [Claim 5] In the step of obtaining detailed information, the detailed information of the defect includes at least the positional information of the defect in the thickness direction of the optical film, the dimensions of the defect, and the contrast of the defect. A method for inspecting an optical film according to claim 1 or 2. [Claim 6] The manufacturing process for optical films, The invention comprises an inspection step of inspecting the manufactured optical film using the inspection method described in claim 1 or 2. A method for manufacturing optical films.

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