Method for inspecting optical laminate

Abstract

Provided is an inspection method for an optical laminate capable of suppressing excessive detection of defects present on the surface of a release film and accurately detecting defects present between a polarizing plate and an optical film. The present invention includes the following steps: a transmission inspection step (S1) of detecting defect candidates based on a transmission image generated using light that has transmitted through an optical laminate (S); an orthogonal Nicol prism inspection step (S2) of detecting defect candidates based on an orthogonal Nicol prism image generated using light that has transmitted through a transmission inspection polarizing filter (6a, 6b) and the optical laminate, the transmission inspection polarizing filter (6a, 6b) being disposed in a manner so as to become an orthogonal Nicol prism with respect to the polarizing axis of a polarizing plate (10); a reflection inspection step (S3) of detecting defect candidates based on a reflection image generated using light that has been reflected by the optical laminate; and a calculation step (S4) of determining defect candidates that have been detected in both the transmission inspection step and the orthogonal Nicol prism inspection step but not in the reflection inspection step to be defects present between the polarizing plate and an optical film (20).

Description

Technical Field

[0001] This invention relates to an inspection method for an optical laminate formed by stacking a polarizer and an optical film, and further stacking a release film on the outermost side of at least one of them in the thickness direction. In particular, this invention relates to an inspection method for an optical laminate capable of suppressing over-detection of defects present on the surface of the release film and accurately detecting defects present between the polarizer and the optical film. Background Technology

[0002] Previously, there was a known inspection method that used optical methods to examine defects in optical laminates containing polarizers to determine the quality of the optical laminates.

[0003] As defects in optical laminates, examples include foreign matter (appropriately referred to as "adhesive foreign matter" in this specification) existing between the layers of the optical laminate (specifically, between the polarizer and the optical film constituting the optical laminate) and defects (foreign matter, dirt, damage, etc.) existing on the surface of the optical laminate.

[0004] The optical conditions that facilitate defect detection vary depending on the type of defect. Therefore, various inspection methods combining multiple optical conditions have been proposed.

[0005] For example, Patent Documents 1 and 2 propose an inspection method that detects defects in an optical film based on a transmitted image of the optical film generated using light transmitted through it and a reflected image of the optical film generated using light reflected from it (paragraphs 0023-0026 of Patent Document 1, claim 2 of Patent Document 2, etc.).

[0006] Furthermore, Patent Document 3 proposes an inspection method for detecting defects in an optical laminate based on a reflection image of the optical laminate and an orthogonal Nicol prism image of the optical laminate. The reflection image of the optical laminate is generated using light reflected by the optical laminate containing a polarizer, and the orthogonal Nicol prism image of the optical laminate is generated using light transmitted through the optical laminate and an inspection polarizing filter configured as an orthogonal Nicol prism relative to the polarization axis of the polarizer (claim 1 of Patent Document 3, etc.).

[0007] In the case of an optical laminate formed by stacking a polarizer and an optical film (e.g., a retardation film) and further stacking a release film (e.g., a separator, a surface protective film) on the outermost side of at least one of the layers in the thickness direction, defects (foreign matter, dirt, damage, etc.) present on the surface of the release film are harmless and do not pose a problem. This is because when using the optical laminate (e.g., bonding an optical laminate to a liquid crystal cell), the release film is peeled off without leaving any residue.

[0008] The inventors investigated an inspection method for detecting defects based on orthogonal Nicol prism images of optical laminates containing polarizers. They realized that while adhesive foreign matter present between the layers of the optical laminate could be detected, even harmless defects present on the surface of the release film were sometimes detected (over-detection). This resulted in optical laminates with defects only present on the surface of the release film (those without interlayer defects and therefore not a problem) being treated as defective products, leading to a lower yield rate for optical laminates.

[0009] Patent Document 3 describes the following: In order to suppress over-detection as described above, if the position of a defect candidate detected based on the reflection image of the optical laminate is the same as the position of a defect candidate detected based on the orthogonal Nicol prism image of the optical laminate, the defect candidate will not be treated as a defect (claim 1, paragraph 0083, etc. of Patent Document 3).

[0010] However, according to the results of the inventors' research, it has become clear that even inspection methods that combine reflective images and orthogonal Nicol prism images as described above sometimes fail to adequately suppress over-detection of harmless defects.

[0011] Furthermore, the inspection method described in Patent Document 1 is aimed at accurately counting the number of defects (paragraph 0007 of Patent Document 1), and is not a method to prevent over-detection of harmless defects.

[0012] Furthermore, the inspection method described in Patent Document 2 aims to accurately identify the type of defect (paragraph 0018 of Patent Document 2), rather than being a method to prevent over-detection of harmless defects.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: Japanese Patent Application Publication No. 2003-329601

[0016] Patent Document 2: Japanese Patent Application Publication No. 2012-167975

[0017] Patent Document 3: Japanese Patent No. 4960161 Summary of the Invention

[0018] The problem the invention aims to solve

[0019] The present invention was made to solve the problems of the prior art as described above, and its objective is to provide an inspection method for an optical laminate that can suppress over-detection of defects present on the surface of the release film and detect defects present between the polarizer and the optical film with high precision.

[0020] Solution for solving the problem

[0021] To address the aforementioned issues, the inventors conducted in-depth research and discovered that the defects detected in the transmission image and the orthogonal Nicol prism image, but not in the reflection image, are highly likely to be defects (adhesive foreign matter) existing between the polarizer and the optical film, and thus completed the present invention.

[0022] In order to solve the above-mentioned problems, the present invention provides an inspection method for an optical laminate, which is formed by stacking a polarizer and an optical film and further stacking a peel-off film on at least one of the outermost surfaces in the thickness direction. The inspection method for the optical laminate includes the following steps: a transmission inspection step, in which a transmission image of the optical laminate is generated using light transmitted through the optical laminate, and candidate defects present in the optical laminate are detected based on the transmission image; and an orthogonal nicotinic prism inspection step, in which an orthogonal nicotinic prism image of the optical laminate is generated using light transmitted through an inspection polarizing filter and the optical laminate, and candidate defects present in the optical laminate are detected based on the orthogonal nicotinic prism image, wherein the inspection polarizing filter is polarized relative to the polarizer. The optical axis is configured as an orthogonal Nicol prism; a reflection inspection process generates a reflection image of the optical stack using light reflected by the optical stack, and detects candidate defects existing in the optical stack based on the reflection image; and a calculation process determines a defect existing between the polarizer and the optical film based on the candidate defects detected in the transmission inspection process, the candidate defects detected in the orthogonal Nicol prism inspection process, and the candidate defects detected in the reflection inspection process, wherein, in the calculation process, candidate defects detected in both the transmission inspection process and the orthogonal Nicol prism inspection process but not detected in the reflection inspection process are determined to be defects existing between the polarizer and the optical film.

[0023] According to the present invention, in the transmission inspection process, candidate defects existing in the optical laminate are detected based on the transmission image of the optical laminate. The transmission image is generated, for example, by arranging a light source on one side of the optical laminate and an imaging unit on the other side, wherein the imaging unit receives light emitted from the light source and transmitted through the optical laminate to perform imaging (photography), thereby generating the transmission image. Candidate defects in the transmission image are detected, for example, by applying known image processing techniques such as binarization to extract pixel regions whose brightness values ​​(pixel values) differ from those of other pixel regions.

[0024] Furthermore, according to the present invention, in the orthogonal nicotinic prism inspection process, candidate defects existing in the optical stack are detected based on the orthogonal nicotinic prism image of the optical stack. The orthogonal nicotinic prism image is generated, for example, by arranging a light source and an inspection polarizing filter on one side of the optical stack, and arranging an imaging unit on the other side. The imaging unit captures and images (photographs) light emitted from the light source and passing through the inspection polarizing filter and the optical stack, thereby generating the orthogonal nicotinic prism image. In this case, a defect existing between the inspection polarizing filter and the polarizer of the optical stack causes the orthogonal nicotinic prism to collapse, therefore, in the orthogonal nicotinic prism image, the pixel area corresponding to the defect existing between the inspection polarizing filter and the polarizer becomes brighter (brightness value increases). Alternatively, an orthogonal nicotinic prism image can be generated by: placing a light source on one side of an optical stack, and placing an inspection polarizing filter and an imaging unit on the other side. The imaging unit receives light emitted from the light source and passing through the optical stack and the inspection polarizing filter to form an image, thereby generating an orthogonal nicotinic prism image. In this case, a defect existing between the polarizer and the inspection polarizing filter in the optical stack can cause the orthogonal nicotinic prism to break down. Therefore, in the orthogonal nicotinic prism image, the pixel region corresponding to the defect between the polarizer and the inspection polarizing filter becomes brighter (its brightness value increases). Defect candidates in the orthogonal nicotinic prism image can be detected, for example, by applying known image processing techniques such as binarization to extract pixel regions whose brightness values ​​(pixel values) differ from those of other pixel regions (specifically, pixel regions with brightness values ​​greater than other pixel regions).

[0025] Furthermore, according to the present invention, in the reflection inspection process, candidate defects existing in the optical laminate are detected based on the reflection image of the optical laminate. The reflection image is generated, for example, by arranging a light source and an imaging unit on one side of the optical laminate, and by having the imaging unit receive light emitted from the light source and reflected by the optical laminate to perform imaging (photography), thereby generating the reflection image. Candidate defects in the reflection image are detected, for example, by applying known image processing techniques such as binarization to extract pixel regions whose brightness values ​​(pixel values) differ from those of other pixel regions.

[0026] Furthermore, in this invention, "optical film" refers to an optical film that cannot be peeled off from the polarizer.

[0027] Furthermore, in this invention, "an inspection polarizing filter configured such that it is an orthogonal Nicol prism relative to the polarizing axis of the polarizer" is not limited to the case where the angle between the polarizing axis of the polarizer and the polarizing axis of the inspection polarizing filter is exactly 90°, but includes the case where the angle is within the range of 90°±10°.

[0028] Furthermore, in this invention, the transmission inspection process, the orthogonal Nicol prism inspection process, and the reflection inspection process do not necessarily have to be performed in this order, and can be performed in any order (including the case where multiple inspection processes are performed in a partially repeated manner).

[0029] Furthermore, according to the present invention, in the calculation process, defect candidates that are detected in both the transmission inspection process and the orthogonal Nicol prism inspection process but not detected in the reflection inspection process are determined to be defects (adhesive foreign matter) existing between the polarizer and the optical film.

[0030] Whether a defect candidate is detected in both the transmission inspection process and the orthogonal Nikkor prism inspection process is determined, for example, by whether a defect candidate detected in the orthogonal Nikkor prism inspection process exists at a location equal to (same as) or near the location of a defect candidate detected in the transmission inspection process. If a defect candidate detected in the orthogonal Nikkor prism inspection process exists at the same location, it is determined that the defect candidate was detected in both the transmission inspection process and the orthogonal Nikkor prism inspection process. On the other hand, if a defect candidate detected in the orthogonal Nikkor prism inspection process does not exist at the same location, it is determined that the defect candidate was not detected in both the transmission inspection process and the orthogonal Nikkor prism inspection process.

[0031] Whether a candidate defect detected in both the transmission inspection process and the orthogonal nicotron prism inspection process is detected in the reflection inspection process is determined, for example, by whether a candidate defect detected in the reflection inspection process exists at a position equal to (same as or near) the position of a candidate defect detected in both the transmission inspection process and the orthogonal nicotron prism inspection process. If a candidate defect detected in the reflection inspection process exists at the same position, it is determined that the candidate defect was detected in the reflection inspection process. On the other hand, if a candidate defect detected in the reflection inspection process does not exist at the same position, it is determined that the candidate defect was not detected in the reflection inspection process.

[0032] As previously stated, according to the inventors' insights, defect candidates detected in both the transmission image and the orthogonal Nikkor prism image but not in the reflection image are highly likely to be defects (adhesive foreign matter) existing between the polarizer and the optical film. According to the present invention, in the calculation process, defect candidates detected in both the transmission inspection process and the orthogonal Nikkor prism inspection process (i.e., detected in both the transmission image and the orthogonal Nikkor prism image) but not detected in the reflection inspection process (i.e., not detected in the reflection image) are determined to be defects existing between the polarizer and the optical film. Therefore, over-detection of defects existing on the surface of the release film can be suppressed, and defects existing between the polarizer and the optical film can be detected with high precision.

[0033] In this invention, preferably, the release film is a diaphragm, and when the optical film is located between the diaphragm and the polarizer, the inspection polarizing filter is disposed on the diaphragm side during the orthogonal Nicol prism inspection process.

[0034] When bonding the aforementioned optical laminate to the liquid crystal cell of an image display device, the diaphragm side is bonded to the liquid crystal cell (the diaphragm side is bonded after the diaphragm has been peeled off). When the diaphragm side of the optical laminate is bonded to the liquid crystal cell, defects existing between the polarizer and the liquid crystal cell in the optical laminate (specifically, defects existing between the polarizer and the optical film located closer to the liquid crystal cell than the polarizer) appear as bright spots in the image display device when the liquid crystal cell is driven, becoming a quality issue.

[0035] According to the preferred method described above, in the orthogonal Nicol prism inspection process, the inspection polarizing filter is arranged on the diaphragm side in the same manner as the liquid crystal cell. Therefore, defects that would be problematic when driving the liquid crystal cell (defects existing between the liquid crystal cell and the optical film) can be detected as defect candidates.

[0036] In this invention, if there are portions of the optical laminate where the orientation direction of the release film deviates significantly from the direction of the polarization axis of the polarizer, or where the orientation direction of the release film deviates significantly from the direction of the polarization axis of the inspection polarizing filter, then even if there are no defects between the inspection polarizing filter and the polarizer of the optical laminate, the state of the orthogonal prism will collapse at the aforementioned portions, and the detection accuracy of defect candidates in the orthogonal prism inspection process will also decrease.

[0037] Therefore, the present invention is applicable to cases where the orientation direction of the release film is within ±6° (more preferably within ±3.5°) of a predetermined orientation direction. In this way, if the release film has an aligned orientation direction (within ±6° of a predetermined orientation direction), then for optical laminates in which the release film and polarizer are stacked in a manner that aligns the predetermined orientation direction of the release film with the direction of the polarization axis of the polarizer, or in a manner that aligns the predetermined orientation direction of the release film with the direction of the polarization axis of the inspection polarizing filter (in other words, in a manner that orthogonalizes the predetermined orientation direction of the release film with the direction of the polarization axis of the polarizer), a decrease in the detection accuracy of defect candidates in the orthogonal Nicol prism inspection process can be prevented.

[0038] Preferably, the camera unit used to generate the transmission image in the transmission inspection process is the same as the camera unit used to generate the orthogonal nicotron prism image in the orthogonal nicotron prism inspection process, and the timing of the camera unit performing the imaging in the transmission inspection process is switched with the timing of the camera unit performing the imaging in the orthogonal nicotron prism inspection process.

[0039] According to the preferred method described above, the camera unit used to generate the transmission image is the same as the camera unit used to generate the orthogonal Nicol prism image. Therefore, the coordinates of the transmission image and the coordinates of the orthogonal Nicol prism image can be made highly consistent. Consequently, in the calculation process, it is possible to determine with high precision whether a defect candidate is detected in both the transmission inspection process and the orthogonal Nicol prism inspection process (for example, to determine with high precision whether a defect candidate detected in the orthogonal Nicol prism inspection process exists at a position equivalent to the position of a defect candidate detected in the transmission inspection process).

[0040] Preferably, the transmission inspection process and / or the orthogonal Nicol prism inspection process includes a noise removal process in which defect candidates with a size greater than a predetermined threshold are excluded from the defect candidates.

[0041] Defects (adhesive foreign matter) existing between the polarizer and the optical film in the optical laminate are more often smaller in size than defects existing on the surface of the release film.

[0042] According to the preferred method described above, in the transmission inspection step and / or the orthogonal nicotron prism inspection step, defect candidates whose size exceeds a predetermined threshold are excluded from the defect candidate list. Therefore, in the calculation step, the number of defect candidates detected in both the transmission inspection step and the orthogonal nicotron prism inspection step can be reduced. Consequently, it has the advantage of shortening the time required for the calculation step.

[0043] The effects of the invention

[0044] According to the present invention, it is possible to suppress over-detection of defects present on the surface of the release film and to detect defects present between the polarizer and the optical film with high precision. Attached Figure Description

[0045] Figure 1 This is a schematic diagram illustrating the outline structure of an inspection apparatus used to perform an inspection method for an optical laminate according to one embodiment of the present invention.

[0046] Figure 2 This is a flowchart illustrating the outline steps of the inspection method for the optical laminate according to this embodiment.

[0047] Figure 3 It is an illustrative description of... Figure 2 A diagram showing an example of a defect candidate detected in the transmission inspection process S1.

[0048] Figure 4 It is an illustrative description of... Figure 2 The figure shows an example of a defect candidate detected in the orthogonal Nicol prism inspection process S2.

[0049] Figure 5 It is an illustrative explanation Figure 1 The diagram shows the switching control performed by the control unit 9.

[0050] Figure 6 It is an illustrative description of... Figure 2 The figure shows an example of a defect candidate detected in the reflection inspection process S3.

[0051] Figure 7 It is an illustrative explanation Figure 2 The diagram shows the contents of the operation step S4. Detailed Implementation

[0052] Hereinafter, with appropriate reference to the accompanying drawings, a method for inspecting an optical laminate according to an embodiment of the present invention will be described.

[0053] Figure 1 This is a schematic diagram illustrating the outline structure of an inspection apparatus used to perform the inspection method for optical laminates according to this embodiment. Figure 1 (a) is a side view showing the outline structure of the inspection device. Figure 1 (b) is a cross-sectional view showing the schematic structure of the optical laminate. Figure 1 In the diagram, X represents the horizontal direction parallel to the transport direction of the optical laminate S, Y represents the horizontal direction orthogonal to the X direction, and Z represents the vertical direction.

[0054] <Optical laminate S>

[0055] First, the structure of the optical laminate S, the object of inspection of the inspection device 100 in this embodiment, will be explained.

[0056] like Figure 1 As shown in (b), the optical laminate S of this embodiment is cut into a chip shape corresponding to its application, and the polarizer 10 and optical films 20 and 30 are stacked, and release films 40 and 50 are further stacked on the outermost side in the thickness direction (Z direction). In this embodiment, the optical film 20 located on the side lower than the polarizer 10 is a phase retardation film, and the optical film 30 located on the side higher than the polarizer 10 is a protective film. In addition, in this embodiment, the release film 40 located on the side lower than the polarizer 10 is a diaphragm, and the release film 50 located on the side higher than the polarizer 10 is a surface protective film.

[0057] The following describes the constituent elements of the optical laminate S.

[0058] [Polarizing film 10]

[0059] The polarizer 10 is typically composed of a resin film containing dichroic substances.

[0060] As a resin film, any suitable resin film that can be used as a polarizer can be used. A representative resin film is a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film.

[0061] As the PVA-based resin for forming the above-mentioned PVA-based resin film, any suitable resin can be used. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer.

[0062] The average degree of polymerization of PVA-based resins can be appropriately selected according to the purpose. The average degree of polymerization is typically 1000–10000, preferably 1200–4500, and more preferably 1500–4300. Furthermore, the average degree of polymerization can be determined based on JIS K 6726-1994.

[0063] Examples of dichroic substances included in resin films include iodine and organic dyes. These can be used alone or in combination of two or more. Iodine is preferred.

[0064] The resin film can be a single-layer resin film or a laminate of two or more layers.

[0065] As a specific example of a polarizer composed of a single-layer resin film, examples include resin films obtained by stretching a PVA-based resin film (typically uniaxial stretching) and dyeing it with iodine. Iodine dyeing is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio for uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after dyeing or during dyeing. Alternatively, dyeing can be performed after stretching. Depending on the requirements, the PVA-based resin film may undergo swelling treatment, crosslinking treatment, cleaning treatment, drying treatment, etc.

[0066] As specific examples of polarizers composed of laminates, examples include polarizers composed of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer composed of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer composed of a resin substrate and a PVA-based resin layer coated on the resin substrate can be manufactured, for example, by coating a PVA-based resin solution onto a resin substrate and drying it to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution. Furthermore, stretching may also include, as needed, air stretching of the laminate at a high temperature (e.g., 95°C or higher) prior to stretching in the aqueous boric acid solution. The obtained resin substrate / polarizer laminate can be used directly (i.e., the resin substrate can be used as a protective layer for the polarizer), or the resin substrate can be peeled off from the resin substrate / polarizer laminate and any suitable protective layer corresponding to the purpose can be laminated on the peeled surface for use. Details of such a method for manufacturing a polarizer are described, for example, in Japanese Patent Application Publication No. 2012-73580. The entire description of that publication is incorporated herein by reference.

[0067] The thickness of the polarizer 10 is preferably less than 15 μm, more preferably 1 μm to 12 μm, even more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0068] The polarizer 10 preferably exhibits absorption dichroism at any wavelength within the range of 380 nm to 780 nm. The transmittance of the polarizer 10 is preferably 40.0% to 45.0%, more preferably 41.5% to 43.5%. The polarization degree of the polarizer 10 is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0069] [Phase retardation film 20]

[0070] The retardation film 20 can be, for example, a compensation plate that provides a wide viewing angle, or a retardation plate (circularly polarized light plate) used in conjunction with a polarizing film to generate circularly polarized light. The thickness of the retardation film 20 is, for example, 1 μm to 200 μm. Alternatively, other films such as protective films or reflective polarizers, as described later, can be used instead of the retardation film 20.

[0071] The retardation film 20 is typically formed from any suitable resin capable of achieving the aforementioned properties. Examples of resins forming the retardation film 20 include, for instance, polyarylates, polyamides, polyimides, polyesters, polyaryletherketones, polyamide-imides, polyesterimides, polyvinyl alcohol, polyfuric acid esters, polyethersulfones, polysulfones, norbornene resins, polycarbonate resins, cellulose resins, and polyurethanes. These resins can be used alone or in combination. Cycloolefin-based norbornene resins are preferred.

[0072] [Protective film 30]

[0073] As the protective film 30, any suitable resin film can be used. Examples of resin film forming materials include, for instance, cellulose resins such as (meth)acrylic resins, diacetylcellulose and triacetylcellulose, cyclic olefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymers thereof. Furthermore, "(meth)acrylic resin" refers to acrylic resins and / or methacrylic resins.

[0074] The thickness of the protective film 30 is typically 10 μm to 100 μm, and preferably 20 μm to 40 μm.

[0075] The protective film 30 may also be subjected to surface treatments such as hard coating, anti-reflective treatment, anti-adhesion treatment, and anti-glare treatment on the side opposite to the polarizer 10, as needed. And / or, the protective film 30 may be subjected to treatments to improve visibility when visually confirmed via polarized sunglasses (e.g., treatments to impart (ellipsoidal) polarization, treatments to impart ultra-high phase difference). Furthermore, when a surface treatment is performed to form a surface treatment layer, the thickness of the protective film 30 includes the thickness of the surface treatment layer.

[0076] Furthermore, the retardation film 20 and the protective film 30 are laminated to the polarizer 10 by bonding them respectively with any suitable adhesive layer (not shown). Representative examples of adhesives constituting the adhesive layer include PVA-based adhesives or activated energy-cured adhesives.

[0077] [Septum 40]

[0078] As the separator 40, any suitable separator can be used. Specific examples include plastic films, non-woven fabrics, or paper obtained by surface coating with a release agent. Specific examples of release agents include silicone-based release agents, fluorinated release agents, and long-chain alkyl acrylate-based release agents. Specific examples of plastic films include polyethylene terephthalate (PET) films, polyethylene films, and polypropylene films. The thickness of the separator can be set, for example, from 10 μm to 100 μm.

[0079] The diaphragm 40 is laminated to the phase retardation membrane 20 by bonding it with any suitable adhesive layer (not shown). Specific examples of adhesives constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, polyurethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, quantity, combination, and mixing ratio of the monomers of the base resin forming the adhesive, as well as the mixing amount of the crosslinking agent, reaction temperature, and reaction time, an adhesive with desired properties corresponding to the purpose can be prepared. The base resin of the adhesive can be used alone or in combination of two or more. From the viewpoints of transparency, processability, and durability, acrylic adhesives are preferred. Details of the adhesive constituting the adhesive layer are described, for example, in Japanese Patent Application Publication No. 2014-115468, the description of which is incorporated herein by reference. The thickness of the adhesive layer can be set, for example, from 10 μm to 100 μm. The storage modulus G' of the adhesive layer at 25°C can be set, for example, to 1.0 × 10⁻⁶. 4 [Pa]~1.0×10 6 [Pa]. Furthermore, the storage modulus can be determined, for example, by dynamic viscoelasticity measurement.

[0080] In this embodiment, the diaphragm 40 is a diaphragm whose orientation direction is within ±6° of a predetermined orientation direction. For example, if the polarization axis of the polarizer 10 in this embodiment is set to the X direction, the predetermined orientation direction of the diaphragm 40 is set to the Y direction, and the diaphragm 40 is stacked in such a way that the orientation direction of any part of the diaphragm 40 is within ±6° of the Y direction.

[0081] [Surface protective film 50]

[0082] The surface protective film 50 typically comprises a substrate and an adhesive layer. In this embodiment, the thickness of the surface protective film 50 is, for example, 30 μm or more. An upper limit for the thickness of the surface protective film 50 is, for example, 150 μm. Furthermore, in this specification, "the thickness of the surface protective film" refers to the combined thickness of the substrate and the adhesive layer.

[0083] The substrate can be composed of any suitable resin film. Examples of resin film forming materials include ester resins such as polyethylene terephthalate resins, cyclic olefin resins such as norbornene resins, olefin resins such as polypropylene resins, polyamide resins, polycarbonate resins, and copolymers thereof. Ester resins (especially polyethylene terephthalate resins) are preferred.

[0084] As the adhesive forming the adhesive layer, any suitable adhesive can be used. Examples of base resins for adhesives include acrylic resins, styrene resins, silicone resins, polyurethane resins, and rubber resins.

[0085] <Inspection Device 100>

[0086] Next, the structure of the inspection device 100 of this embodiment will be described.

[0087] The inspection apparatus 100 of this embodiment is an apparatus for inspecting an optical laminate S having the structure described above.

[0088] like Figure 1 As shown in (a), the inspection apparatus 100 of this embodiment includes: a plurality of belt conveyors 1 that transport the optical laminate S along the X direction; and cleaning rollers 2 for adsorbing and removing foreign matter attached to the outermost surface (uppermost and lowermost) of the optical laminate S. Furthermore, the inspection apparatus 100 of this embodiment includes a light source 3 and an imaging unit 4 for performing the transmission inspection process S1 described later. Additionally, the inspection apparatus 100 of this embodiment includes a pair of light sources 5a and 5b and a pair of inspection polarizing filters 6a and 6b for performing the orthogonal nicotinic prism inspection process S2 described later. The imaging unit 4 also serves as an imaging unit for performing the orthogonal nicotinic prism inspection process S2. Furthermore, the inspection apparatus 100 of this embodiment includes a light source 7 and an imaging unit 8 for performing the reflection inspection process S3 described later. Furthermore, the inspection device 100 of this embodiment includes a control calculation unit 9, which is electrically connected to the light source 3, the camera unit 4, the light sources 5a and 5b, the light source 7, and the camera unit 8. It controls their operation and processes the camera signals output from the camera unit 4 and the camera unit 8 to determine defects.

[0089] The following describes the components of the inspection device 100.

[0090] [Belt Conveyor 1]

[0091] The belt conveyor 1 has the following structure: an annular belt with rollers at both ends moves as the rollers rotate, thereby conveying the optical laminate S mounted on the belt. The optical laminate S, after being cut into chip shapes, is then mounted on... Figure 1On the belt conveyor 1 shown at the left end of (a), along the X direction towards Figure 1 The right side of (a) is sequentially transported by each belt conveyor 1. In this embodiment, as... Figure 1 As shown in (b), the optical laminate S is placed on a belt conveyor with the diaphragm 40 side facing down and is transported. The transport speed V of the belt conveyor 1 for transporting the optical laminate S is set to, for example, 50 mm / sec to 750 mm / sec.

[0092] [Cleaning Roller 2]

[0093] The cleaning roller 2 comprises: a pair of upper and lower rollers through which the optical laminate S passes; and a rolled adhesive tape that rotates in contact with each roller (illustration omitted). By bringing the upper and lower rollers into contact with the optical laminate S, foreign matter adhering to the outermost surface (top and bottom, i.e., the lower surface of the diaphragm 40 and the upper surface of the surface protective film 50) of the optical laminate S is adsorbed onto the rollers, and the foreign matter adsorbed on the rollers is transferred to the adhesive tape for removal.

[0094] Before performing the transmission inspection step S1 described later, by removing foreign matter present on the outermost surface of the optical laminate S to some extent by the cleaning roller 2, it is possible to further suppress over-detection of defects present on the surface of the release film (septum 40, surface protective film 50).

[0095] [Light Source 3]

[0096] Light source 3 is used to perform the transmission inspection process S1 described later. In this embodiment, it is disposed on the lower surface side (diaphragm 40 side) of the optical laminate S. The optical axis of light source 3 (in...) Figure 1 In (a) shown by the dashed line, the light source 3 emits light upward in the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S according to the control signal output from the control and arithmetic unit 9.

[0097] As for the light source 3, it is not limited as long as it can emit light of a wavelength that can pass through the optical laminate S, such as LEDs or halogen lamps.

[0098] [Camera Unit 4]

[0099] The camera unit 4 is used to perform the transmission inspection process S1 and the orthogonal Nicol prism inspection process S2, which will be described later. In this embodiment, it is disposed on the upper surface side (surface protective film 50 side) of the optical laminate S. The optical axis of the camera unit 4 (in...) Figure 1In diagram (a), the image unit 4, directed in the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S (shown by dashed lines), receives light emitted from the light source 3 and passing through the optical laminate S according to the control signal output from the control and calculation unit 9, and outputs an electrical signal corresponding to the light intensity as an image signal to the control and calculation unit 9. Additionally, the image unit 4, according to the control signal output from the control and calculation unit 9, receives light emitted from the light sources 5a and 5b and passing through the inspection polarizing filters 6a and 6b and the optical laminate S, and outputs an electrical signal corresponding to the light intensity as an image signal to the control and calculation unit 9. The focal point of the image unit 4 is set on the upper surface of the optical laminate S (the upper surface of the surface protective film 50).

[0100] In this embodiment, the imaging unit 4 is a line sensor that uses multiple imaging elements (CCD, CMOS) arranged in a straight line along a direction orthogonal to the transport direction (X direction) of the optical stack S and outputs imaging signals with a fixed scanning period (e.g., 7μsec to 14μsec). By using a line sensor as the imaging unit 4, the field of view in the X direction of the imaging unit 4 is reduced. Therefore, the following advantages can be obtained: the required illumination range in the X direction of the light emitted from the light sources 3, 5a, and 5b can also be narrowed, thereby alleviating the constraints related to the configuration of the light sources 3, 5a, and 5b. By transporting the optical stack S along the X direction and scanning the imaging elements of the line sensor along the Y direction, a two-dimensional transmission image is generated in the transmission inspection step S1 described later, and a two-dimensional orthogonal nicotinic prism image is generated in the orthogonal nicotinic prism inspection step S2 described later.

[0101] However, the camera unit 4 is not necessarily limited to a line sensor; for example, a two-dimensional camera with a high-speed shutter can also be used as the camera unit 4.

[0102] [Light sources 5a, 5b]

[0103] Light sources 5a and 5b are used to perform the orthogonal Nicol prism inspection step S2 described later. In this embodiment, they are disposed on the lower surface side (diaphragm 40 side) of the optical laminate S. The optical axes of light sources 5a and 5b (in...) Figure 1 (a) is illustrated by the dashed line, and the light source 5a is inclined in a direction relative to the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S. Specifically, the optical axis of the light source 5a is inclined in a direction downstream of the transport direction of the optical laminate S relative to the vertical direction, and the optical axis of the light source 5b is inclined in a direction upstream of the transport direction of the optical laminate S relative to the vertical direction. The light sources 5a and 5b emit light upward toward the optical laminate S according to the control signal output from the control arithmetic unit 9.

[0104] As light sources 5a and 5b, they are not limited as long as they can emit light of a wavelength that can pass through the optical laminate S; for example, LEDs and halogen lamps can be used.

[0105] Furthermore, in this embodiment, the camera unit 4 is used as a shared camera unit for both the transmission inspection process S1 and the orthogonal Nicol prism inspection process S2. That is, a structure is adopted in which the same camera unit 4 receives light emitted from the light source 3 and the light sources 5a and 5b, so that the direction of the optical axis of the light sources 5a and 5b is different from the direction of the optical axis of the light source 3. In addition, a pair of light sources 5a and 5b are arranged to ensure sufficient light quantity emitted from the inclined direction. However, for example, by using a coaxial incident optical system composed of a semi-transparent and semi-reflective mirror, it is also possible to make the direction of the optical axis of the light sources 5a and 5b face the same vertical direction as the direction of the optical axis of the light source 3, and it is also possible to set up a structure that does not use a pair of light sources 5a and 5b but uses a single light source.

[0106] [Inspection using polarizing filters 6a and 6b]

[0107] The polarizing filters 6a and 6b for inspection are configured such that they are orthogonal to the polarizing axis of the polarizer 10 of the optical stack S. For example, if the direction of the polarizing axis of the polarizer 10 is set to the X direction, then the polarizing axes of the polarizing filters 6a and 6b for inspection are configured such that the direction of the polarizing axis is the Y direction, which is orthogonal to the X direction. However, it is not limited to the case where the angle between the polarizing axis of the polarizer 10 and the polarizing axis of the polarizing filters 6a and 6b for inspection is exactly 90°, as long as it is within the range of 90° ± 10°.

[0108] The structure and manufacturing method of the polarizing filters 6a and 6b used for inspection are the same as those of the polarizer 10, therefore, detailed descriptions are omitted here.

[0109] In this embodiment, the inspection polarizing filters 6a and 6b are disposed on the lower surface side (septum 40 side) of the optical laminate S. Specifically, the inspection polarizing filter 6a is disposed between the optical laminate S and the light source 5a, and the inspection polarizing filter 6b is disposed between the optical laminate S and the light source 5b. Light emitted from the light source 5a passes through the inspection polarizing filter 6a and illuminates the optical laminate S, and light emitted from the light source 5b passes through the inspection polarizing filter 6b and illuminates the optical laminate S. In this embodiment, a defect existing between the inspection polarizing filters 6a and 6b and the polarizer 10 will cause the orthogonal nicotinic prism to collapse. Therefore, in the orthogonal nicotinic prism image of the optical laminate S generated in the orthogonal nicotinic prism inspection process S2 described later, the pixel area corresponding to the defect existing between the inspection polarizing filters 6a and 6b and the polarizer 10 becomes brighter (brightness value increases), and this defect can be detected as a defect candidate.

[0110] However, the present invention is not limited to this, and the inspection polarizing filters 6a and 6b can also be disposed on the upper surface side (surface protective film 50 side) of the optical stack S. Specifically, the following structure can also be adopted: an inspection polarizing filter is disposed between the optical stack S and the imaging unit, and light emitted from the light source 5a and 5b and passing through the optical stack S is received by the imaging unit 4 after passing through the inspection polarizing filter. In this case, the defect existing between the inspection polarizing filter and the polarizer 10 will cause the state of the orthogonal nicotinic prism to collapse. Therefore, in the orthogonal nicotinic prism image of the optical stack S generated in the orthogonal nicotinic prism inspection process S2 described later, the pixel area corresponding to the defect existing between the inspection polarizing filter and the polarizer 10 becomes brighter (the brightness value increases), and the defect can be detected as a defect candidate.

[0111] [Light Source 7]

[0112] Light source 7 is used to perform the reflection inspection step S3 described later. In this embodiment, it is disposed on the lower surface side (diaphragm 40 side) of the optical laminate S. The optical axis of light source 7 (in...) Figure 1 (a) is illustrated by the dashed line and is inclined relative to the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S. Figure 1 In the example shown in (a), the optical axis of the light source 7 is tilted upstream of the transport direction of the optical stack S relative to the vertical direction. However, it is not limited to this; the optical axis of the light source 7 can also be tilted downstream of the transport direction of the optical stack S relative to the vertical direction. Furthermore, for example, by employing a coaxial incident optical system composed of a semi-transparent mirror or the like, the optical axis of the light source 7 can also be oriented vertically. The light source 7 emits light upward toward the optical stack S according to the control signal output from the control processing unit 9.

[0113] As for the light source 7, it is not limited as long as it can emit light of a wavelength that can be reflected by the optical laminate S, such as LEDs or halogen lamps.

[0114] [Camera Unit 8]

[0115] The imaging unit 8 is an imaging unit used to perform the reflection inspection process S3 described later. In this embodiment, it is disposed on the lower surface side (diaphragm 40 side) of the optical laminate S. The optical axis of the imaging unit 8 (in...) Figure 1In (a) illustrated by the dashed line, the imaging unit 8, directed in the vertical direction (Z direction) parallel to the thickness direction of the optical laminate S, receives light emitted from the light source 7 and reflected by the optical laminate S according to the control signal output from the control and calculation unit 9, and outputs an electrical signal corresponding to the amount of light as an imaging signal to the control and calculation unit 9. The focal point of the imaging unit 8 is set on the lower surface of the optical laminate S (the lower surface of the diaphragm 40).

[0116] In this embodiment, the imaging unit 8, similar to the imaging unit 4, can be a line sensor that arranges multiple imaging elements (CCD, CMOS) in a straight line along a direction orthogonal to the transport direction (X direction) of the optical stack S and outputs imaging signals at a fixed scan period (e.g., 7 μsec to 14 μsec). By using a line sensor as the imaging unit 8, the field of view in the X direction of the imaging unit 8 is reduced. Therefore, the following advantages can be obtained: the required illumination range in the X direction of the light emitted from the light source 7 can also be narrowed, thereby alleviating the constraints related to the configuration of the light source 7. By transporting the optical stack S along the X direction and scanning the imaging elements of the line sensor along the Y direction, a two-dimensional reflection image is generated in the reflection inspection step S3 described later.

[0117] However, the camera unit 8 is not necessarily limited to a line sensor; for example, a two-dimensional camera with a high-speed shutter can also be used as the camera unit 8.

[0118] [Control and arithmetic unit 9]

[0119] The control and arithmetic unit 9 may be composed of, for example, a personal computer or a programmable logic controller (PLC) that has installed programs for performing the control and arithmetic processes described later.

[0120] <Inspection methods involved in this embodiment>

[0121] The following describes the inspection method for the optical laminate S according to this embodiment using the inspection device 100 described above.

[0122] Figure 2 This is a flowchart illustrating the outline steps of the inspection method for the optical laminate S according to this embodiment.

[0123] like Figure 2 As shown, the inspection method involved in this embodiment includes a transmission inspection process S1, an orthogonal Nicol prism inspection process S2, a reflection inspection process S3, and a calculation process S4.

[0124] The following describes each process S1 to S4.

[0125] [Transmission Inspection Procedure S1]

[0126] In the transmission inspection process S1, a transmission image of the optical laminate S is generated using light transmitted through it, and candidate defects present in the optical laminate S are detected based on this transmission image. Figure 2 (S11).

[0127] Specifically, before the optical stack S reaches directly below the camera unit 4, the light source 3 and the camera unit 4 are driven according to a control signal output from the control processing unit 9. Then, the camera unit 4 receives light emitted from the light source 3 and transmitted through the optical stack S to form an image, and outputs an electrical signal corresponding to the light intensity as an imaging signal to the control processing unit 9. The control processing unit 9 generates a two-dimensional transmission image based on the input imaging signal. Then, the control processing unit 9 detects defect candidates by applying known image processing techniques such as extracting brightness values ​​(pixel values), brightness values ​​(pixel values) of other pixel regions, and binarization of different pixel regions to the generated transmission image.

[0128] Figure 3 This is a diagram illustrating an example of a defect candidate detected in the transmission inspection process S1. Figure 3 (a) is a cross-sectional view schematically illustrating an example of a defect present in an optical laminate S. Figure 3 (b) is a schematic diagram illustrating an example of a defect candidate detected before the noise removal process S12 of the transmission inspection process S1. Figure 3 (c) is a diagram that schematically illustrates an example of a defect candidate remaining after the noise removal process S12 of the transmission inspection process S1.

[0129] exist Figure 3 In (a), reference numeral F1 indicates harmless foreign matter adhering to the surface of the diaphragm 40, which serves as a release membrane. Reference numeral F2 indicates harmless damage present on the surface of the diaphragm 40. Reference numeral F3 indicates harmful adhesive foreign matter present between the polarizer 10 and the retardation film 20. Reference numeral F4 indicates harmless foreign matter adhering to the surface of the surface protective film 50, which serves as a release membrane. Figure 3 (b) and (c) show the binarized transmission images. Figure 3 In (b), three foreign objects F1 (F1a~F1c), two damages F2 (F2a, F2b), one adhesive foreign object F3, and two foreign objects F4 (F4a, F4b) were identified as defect candidates. Figure 3 In (c), one foreign object F1 (F1c), one damage F2 (F2a), one adhesive foreign object F3, and two foreign objects F4 (F4a, F4b) are detected as defect candidates.

[0130] The transmission inspection process S1 in this embodiment includes a noise removal process ( Figure 2 In step S12), during the noise removal process, defect candidates whose size (e.g., area) is greater than a predetermined threshold are excluded from the defect candidate list. Therefore, the detected... Figure 3 In the defect candidates shown in (b), foreign objects F1a, F1b, and damage F2b, which are candidates for defects with larger dimensions, are excluded, becoming Figure 3 The state shown in (c).

[0131] [Orthogonal Nicol Prism Inspection Procedure S2]

[0132] In the orthogonal nicotinic prism inspection process S2, an orthogonal nicotinic prism image of the optical stack S is generated using light transmitted through inspection polarizing filters 6a and 6b and the optical stack S, and candidate defects existing in the optical stack S are detected based on this orthogonal nicotinic prism image. Figure 2 (S2).

[0133] Specifically, before the optical stack S reaches directly below the imaging unit 4, the light sources 5a and 5b and the imaging unit 4 are driven according to the control signal output from the control processing unit 9. Then, the imaging unit 4 receives light emitted from the light sources 5a and 5b, which passes through the inspection polarizing filters 6a and 6b and the optical stack S respectively, and performs imaging, outputting an electrical signal corresponding to the light intensity as an imaging signal to the control processing unit 9. The control processing unit 9 generates a two-dimensional orthogonal Nicol prism image based on the input imaging signal. Then, the control processing unit 9 detects defect candidates by applying known image processing techniques, such as binarization, to the generated orthogonal Nicol prism image to extract pixel regions whose brightness values ​​(pixel values) differ from those of other pixel regions (i.e., whose brightness values ​​increase).

[0134] Figure 4 This is a diagram illustrating an example of a defect candidate detected in the orthogonal Nicol prism inspection process S2. Figure 4 The binarized orthogonal Nicol prism image shows three foreign objects F1 (F1a-F1c), three damages F2 (F2b-F2d), and one adhesive foreign object F3, which were identified as defect candidates. Foreign object F4, attached to the surface of the protective film 50, is not located between the polarizer 10 and the inspection polarizing filters 6a and 6b; therefore, unlike the transmission image, it was not detected in the orthogonal Nicol prism image.

[0135] Furthermore, in this embodiment, the camera unit 4 used to generate the transmission image is the same as the camera unit 4 used to generate the orthogonal Nicol prism image. Therefore, the control operation unit 9 performs the following control: switching the timing of the camera unit 4 performing the imaging in the transmission inspection process S1 with the timing of the camera unit 4 performing the imaging in the orthogonal Nicol prism inspection process S2.

[0136] Specifically, the control unit 9 performs the following control: It switches the timing of light emission from the light source 3 used to generate the transmitted image and the timing of light emission from the light sources 5a and 5b used to generate the cross image, according to each scan cycle of the imaging unit 4. That is, the control unit 9 outputs a control signal to the light source 3 to emit light in one scan cycle, and then outputs control signals to the light sources 5a and 5b to emit light in the next scan cycle. The control unit 9 outputs a control signal to the light source 3 to emit light in the next scan cycle. The control unit 9 repeats the above actions until an optical stack S has completely passed directly below the imaging unit 4.

[0137] Figure 5 This diagram schematically illustrates the switching control performed by the control unit 9. As previously described, the control unit 9 switches the timing of light emitted from light source 3 with the timing of light emitted from light sources 5a and 5b according to each scanning cycle of the imaging unit 4. Thus, as... Figure 5 As shown in (a), the imaging unit 4 alternately captures light emitted from the light source 3 and transmitted through the optical stack S along the X direction at intervals corresponding to the scanning period. Figure 5 (a) shows the area indicated by the blank space) and the light emitted from light sources 5a and 5b and transmitted through the polarizing filters 6a and 6b and the optical stack S for inspection. Figure 5 The area in (a) with dotted shadows was imaged.

[0138] The control and processing unit 9, based on the scanning cycle of the camera unit 4, only... Figure 5 In (a), the region shown by the blank is extracted and synthesized along the X direction, thereby generating Figure 5 The transmitted image is as shown in (b). Furthermore, the control processing unit 9, based on the scanning cycle of the imaging unit 4, only... Figure 5 The region in (a) with dotted shading is extracted and composited along the X direction, thereby generating Figure 5 The orthogonal Nicol prism image shown in (c).

[0139] As described above, even if the camera unit 4 used to generate the transmission image is the same as the camera unit 4 used to generate the orthogonal Nicol prism image, the control operation unit 9 can generate the transmission image and the orthogonal Nicol prism image separately.

[0140] [Reflection Inspection Process S3]

[0141] In the reflection inspection process S3, a reflection image of the optical laminate S is generated using light reflected by the optical laminate S, and candidate defects present in the optical laminate S are detected based on this reflection image. Figure 2 (S3).

[0142] Specifically, during the timing immediately preceding the arrival of the optical stack S directly below the imaging unit 8, a control signal output from the control processing unit 9 is used to drive the light source 7 and the imaging unit 8. The imaging unit 8 then receives light emitted from the light source 7 and reflected by the optical stack S to form an image, and outputs an electrical signal corresponding to the light intensity as an imaging signal to the control processing unit 9. The control processing unit 9 generates a two-dimensional reflection image based on this input imaging signal. Then, the control processing unit 9 detects defect candidates by applying known image processing techniques, such as binarization, to the generated reflection image to extract pixel regions whose brightness values ​​(pixel values) differ from those of other pixel regions.

[0143] Figure 6 This is a diagram illustrating an example of a defect candidate detected in the reflective inspection process S3. Figure 6 The binarized reflection image is shown, with three foreign objects F1 (F1a to F1c) detected as defect candidates. The reflection image is generated using light reflected from the optical laminate S, thus only foreign objects F1 attached to the surface of the diaphragm 40 on the side where the light source 7 is located are detected. Figure 6 In the example shown, only foreign object F1 was detected, but sometimes damage F2, which is also present on the surface of diaphragm 40, is also detected.

[0144] [Calculation step S4]

[0145] In the calculation step S4, based on the defect candidates detected in the transmission inspection step S1, the defect candidates detected in the orthogonal Nicol prism inspection step S2, and the defect candidates detected in the reflection inspection step S3, a defect existing between the polarizer 10 and the optical film (in this embodiment, the retardation film 20) is determined. Figure 2 S4).

[0146] Specifically, in the calculation process S4, the calculation control unit 9 first determines whether a candidate defect has been detected in both the transmission inspection process S1 and the orthogonal Nicole prism inspection process S2. Figure 2(S41). Whether a defect candidate is detected in both the transmission inspection step S1 and the orthogonal nicotron prism inspection step S2 is determined by whether a defect candidate detected in the orthogonal nicotron prism inspection step S2 exists at a position equal to (same as) or near the position of a defect candidate detected in the transmission inspection step S1. Specifically, for example, the determination is made by whether the centroid of the defect candidate detected in the orthogonal nicotron prism inspection step S2 exists at a position equal to the centroid of the defect candidate detected in the transmission inspection step S1 (e.g., a position ±2 mm from the centroid). For determining whether a defect candidate detected in the orthogonal nicotron prism inspection step S2 exists at a position equal to the position of the defect candidate detected in the transmission inspection step S1, the coordinates of the transmission image must be consistent with the coordinates of the orthogonal nicotron prism image. In this embodiment, as described above, the camera unit 4 used to generate the transmission image is the same as the camera unit 4 used to generate the orthogonal Nicol prism image. Therefore, the coordinates of the transmission image and the orthogonal Nicol prism image are approximately the same, and there is no need to force the coordinates of the two images to be strictly identical. However, strictly speaking, according to the reference... Figure 5 As can be seen from the description, the coordinates of the transmission image and the orthogonal Nicol prism image deviate in the X direction from the interval corresponding to the scanning cycle of the camera unit 4. Therefore, the operation control unit 9 preferably corrects the amount of this deviation to make the coordinates of the two images consistent.

[0147] Figure 7 This is a diagram that schematically illustrates the contents of operation step S4.

[0148] Figure 7 Figure (a) is a schematic illustration of an example of a defect candidate identified in the calculation step S4 (specifically, S41) that is detected in both the transmission inspection step S1 and the orthogonal Nicol prism inspection step S2. As mentioned above. Figure 3 As shown in (c), in the transmission inspection process S1, foreign matter F1c, damage F2a, adhesive foreign matter F3, foreign matter F4a, and F4b are detected as defect candidates, as described above. Figure 4 As shown, in the orthogonal nicotron prism inspection process S2, foreign objects F1a-F1c, damage F2b-F2d, and adhesive foreign objects F3 are detected as defect candidates. For example, foreign object F1c detected in the transmission inspection process S1 is also detected in the orthogonal nicotron prism inspection process S2. Therefore, the calculation control unit 9 determines that foreign object F1c has been detected in both of these processes. Figure 2 S41: "Yes". On the other hand, for example, if damage F2a is detected in the transmission inspection process S1 but not in the orthogonal Nicol prism inspection process S2, the operation control unit 9 determines that damage F2a was not detected in either process. Figure 2 S41: "No"), and it is determined that the defect candidate (damage F2a) is not the adhesive foreign matter F3 present between the polarizer 10 and the retardation film 20. Figure 2 (S44). In this embodiment, by performing the same operation on all defect candidates detected in the transmission inspection process S1, it is determined that... Figure 7 The defect candidates shown in (a) (foreign object F1c, adhesive foreign object F3) are defect candidates detected in both the transmission inspection process S1 and the orthogonal Nicole prism inspection process S2.

[0149] Next, in the calculation process S4, the calculation control unit 9 determines whether the candidate defects detected in both the transmission inspection process S1 and the orthogonal Nicole prism inspection process S2 are detected in the reflection inspection process S3. Figure 2 (S42). Whether a defect candidate detected in both the transmission inspection step S1 and the orthogonal Nikkor prism inspection step S2 is detected in the reflection inspection step S3 is determined by whether a defect candidate detected in the reflection inspection step S3 exists at a position equal to (same as) or near the position of a defect candidate detected in both the transmission inspection step S1 and the orthogonal Nikkor prism inspection step S2. Specifically, for example, it is determined by whether the centroid of a defect candidate detected in the reflection inspection step S3 exists at a position equal to the centroid of a defect candidate detected in both the transmission inspection step S1 and the orthogonal Nikkor prism inspection step S2 (e.g., a position ±2 mm of the centroid). For determining whether a defect candidate detected in the reflection inspection step S3 exists at a position equal to the position of a defect candidate detected in both the transmission inspection step S1 and the orthogonal Nikkor prism inspection step S2, the coordinates of the transmission image and the orthogonal Nikkor prism image must be consistent with the coordinates of the reflection image. The coordinates of the transmitted image and the orthogonal Nicol prism image deviate from the coordinates of the reflected image in the X direction by the distance L between the image unit 4 and the image unit 8 in the X direction (refer to...). Figure 1 The time corresponding to (a) is obtained by dividing the transport speed V of the optical stack S. Therefore, the operation control unit 9 needs to correct this deviation to make the coordinates of the transmitted image and the orthogonal Nicole prism image consistent with the coordinates of the reflected image. In addition, the coordinates of the transmitted image and the orthogonal Nicole prism image may also deviate from the coordinates of the reflected image in the Y direction. Therefore, it is preferable that the operation control unit 9 uses known image processing to detect the edges (edges of the optical stack S) in the Y direction of the transmitted image and the orthogonal Nicole prism image and the edges (edges of the optical stack S) in the Y direction of the reflected image, so as to make the coordinates of the transmitted image and the orthogonal Nicole prism image consistent with the coordinates of the reflected image in a way that makes the positions of these edges consistent.

[0150] Figure 7 Figure (b) is a schematic illustration of an example of a defect candidate identified in the calculation step S4 (specifically, S42) that was not detected in the reflection inspection step S3. As mentioned above. Figure 7 As shown in (a), among the foreign matter F1c and adhesive foreign matter F3 detected in both the transmission inspection process S1 and the orthogonal Nicol prism inspection process S2, as described above... Figure 6 As shown, foreign object F1c was also detected in the reflection inspection process S3. Therefore, the operation control unit 9 determined that foreign object F1c was detected in the reflection inspection process S3. Figure 2 S42: "Yes"), and it is determined that the defect candidate (foreign object F1c) is not the adhesive foreign object F3 present between the polarizer 10 and the retardation film 20. Figure 2 (S44). On the other hand, among the foreign matter F1c and adhesive foreign matter F3 detected in both the transmission inspection process S1 and the orthogonal Nicole prism inspection process S2, as mentioned above... Figure 6 As shown, the adhesive foreign object F3 was not detected in the reflection inspection process S3. Therefore, the operation control unit 9 determined that the adhesive foreign object F3 was not detected in the reflection inspection process S3. Figure 2 S42: "No"), and determined that the defect candidate (adhesive foreign matter F3) is adhesive foreign matter F3 existing between the polarizer 10 and the phase difference film 20. Figure 2 (S43).

[0151] According to the inventors' understanding, defect candidates detected in both the transmission image and the orthogonal nicotinic prism image but not in the reflection image are highly likely to be defects (adhesive foreign matter) existing between the polarizer 10 and the retardation film 20. According to the inspection method of this embodiment, as described above, in the calculation step S4, defect candidates detected in both the transmission inspection step S1 and the orthogonal nicotinic prism inspection step S2 (i.e., detected in both the transmission image and the orthogonal nicotinic prism image) but not detected in the reflection inspection step S3 (i.e., not detected in the reflection image) are determined to be defects existing between the polarizer 10 and the retardation film 20. Therefore, over-detection of defects existing on the surface of the release film (septum 40, surface protective film 50) can be suppressed, and defects existing between the polarizer 10 and the retardation film 20 can be detected with high precision.

[0152] Furthermore, in this embodiment, an example is given as follows: the object of inspection is an optical laminate S formed by stacking optical films 20 and 30 (phase retardation film 20 and protective film 30) on both sides of the polarizer 10 in the thickness direction and stacking release films 40 and 50 (septum 40 and surface protective film 50) on the outermost sides of both sides in the thickness direction, but the present invention is not limited to this. As long as the optical laminate is formed by stacking at least one optical film (e.g., only phase retardation film 20) on the polarizer 10 and stacking a release film (e.g., only septum 40) on the outermost side of at least one side, it can be applied to various optical laminates.

[0153] Furthermore, in this embodiment, an example was given of an optical laminate S divided into chip-like sections, but the present invention is not limited thereto. Similar to the inspection methods described in Patent Documents 1 to 3, a structure can also be used to perform the inspection while transporting the long strip-shaped optical laminate in a roll-to-roll manner.

[0154] Furthermore, in this embodiment, the example given is that the light sources 3, 5a, 5b, and 7 are disposed on the lower surface side (septum 40 side) of the optical laminate S. However, the present invention is not limited to this, and a structure in which the light sources 3, 5a, 5b, and 7 are disposed on the upper surface side (surface protective film 50 side) of the optical laminate S (and the inspection polarizing filters 6a and 6b are also disposed on the upper surface side of the optical laminate S) can also be adopted. In this case, the imaging unit 4 is disposed on the lower surface side of the optical laminate S, and the imaging unit 8 is disposed on the upper surface side of the optical laminate S. Moreover, in this case, in the orthogonal Nicol prism inspection process S2, adhesive foreign matter present between the polarizer 10 and the protective film 30 is detected.

[0155] In addition, in this embodiment, the following example is given: the camera unit 4 for generating a transmission image in the transmission inspection step S1 is the same as the camera unit 4 for generating an orthogonal Nicol prism image in the orthogonal Nicol prism inspection step S2. However, the present invention is not limited to this, and the camera unit for generating the transmission image and the camera unit for generating the orthogonal Nicol prism image can also be provided separately.

[0156] Furthermore, in this embodiment, the example is given by describing the case where these steps are performed in the order of transmission inspection step S1, orthogonal nicotinic prism inspection step S2, and reflection inspection step S3 (wherein, timed repetition of imaging is performed in transmission inspection step S1 and orthogonal nicotinic prism inspection step S2). However, the present invention is not limited to this, and the steps can be performed in any order. Alternatively, the following process can be adopted: after performing transmission inspection step S1 and orthogonal nicotinic prism inspection step S2, only step S41 of calculation step S4 is performed first, and then step S42 of calculation step S4 is performed after performing reflection inspection step S3.

[0157] Explanation of reference numerals in the attached figures

[0158] 1: Belt conveyor; 2: Cleaning roller; 3, 5a, 5b, 7: Light source; 4, 8: Camera unit; 6a, 6b: Polarizing filter for inspection; 10: Polarizing film; 20: Phase difference film (optical film); 30: Protective film (optical film); 40: Separator (release film); 50: Surface protective film (release film); 100: Inspection device; S: Optical laminate; S1: Transmission inspection process; S2: Orthogonal Nicol prism inspection process; S3: Reflection inspection process; S4: Calculation process.

Claims

1. A method for inspecting an optical laminate, wherein the optical laminate is formed by stacking a polarizer and an optical film, and further stacking a peeling film on at least one of the outermost surfaces in the thickness direction, the method comprising the following steps: The transmission inspection process uses light transmitted through the optical laminate to generate a transmission image of the optical laminate, and uses the transmission image to detect candidate defects present in the optical laminate. The orthogonal nicotron prism inspection process uses light transmitted through an inspection polarizing filter and the optical stack to generate an orthogonal nicotron prism image of the optical stack, and detects candidate defects present in the optical stack based on the orthogonal nicotron prism image. The inspection polarizing filter is configured to be an orthogonal nicotron relative to the polarization axis of the polarizer. The reflection inspection process uses light reflected by the optical laminate to generate a reflection image of the optical laminate, and uses the reflection image to detect candidate defects present in the optical laminate. as well as The calculation process, based on the defect candidates detected in the transmission inspection process, the defect candidates detected in the orthogonal Nicol prism inspection process, and the defect candidates detected in the reflection inspection process, determines the defects existing between the polarizer and the optical film. In the calculation process, defects that are detected in the transmission inspection process and the orthogonal Nicol prism inspection process but not detected in the reflection inspection process are identified as defects existing between the polarizer and the optical film.

2. The method for inspecting optical laminates according to claim 1, characterized in that, The peeling membrane is a diaphragm. The optical film is located between the diaphragm and the polarizer. In the orthogonal Nicol prism inspection process, the inspection polarizing filter is positioned on the diaphragm side.

3. The method for inspecting optical laminates according to claim 1 or 2, characterized in that, The orientation of the release film is within ±6° relative to a predetermined orientation.

4. The method for inspecting optical laminates according to claim 1 or 2, characterized in that, The camera unit used to generate the transmission image in the transmission inspection process is the same as the camera unit used to generate the orthogonal Nicol prism image in the orthogonal Nicol prism inspection process. The timing for the camera unit to perform imaging in the transmission inspection process is switched to the timing for the camera unit to perform imaging in the orthogonal Nicol prism inspection process.

5. The method for inspecting optical laminates according to claim 1 or 2, characterized in that, The transmission inspection process and / or the orthogonal Nicol prism inspection process includes a noise removal process in which defect candidates with a size greater than a specified threshold are excluded from the defect candidates.

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