Inspection device for optical film, inspection method and manufacturing method

Abstract

To provide an inspection device for an optical film, capable of accurately detecting a defect such as a crack that may occur in the optical film.SOLUTION: An inspection device 100 includes a first light source 1 and a second light source 2 that are provided on one side in a normal direction of an optical film 10 and irradiate the optical film with light, an imaging unit 3 that is provided on the other side, and generates a captured image by capturing an image of the optical film, and an image processing unit 4 that detects a defect present in the optical film on the basis of the captured image. The first optical light source is provided so that an optical axis of the first light source is along a conveyance direction of the optical film when viewed from the normal direction of the optical film, and the second light source is provided so that an optical axis of the second light source is along a direction perpendicular to the conveyance direction. The imaging unit is placed so as to prevent light emitted from the first light source and the second light source from being directly received, and so as to prevent regular transmission light of light emitted from the first light source and the second light source to the optical film from being received.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an optical film inspection device and inspection method for detecting defects that occur in optical films, and a manufacturing method of an optical film using the inspection method. In particular, the present invention relates to an optical film inspection device, inspection method, and manufacturing method that can accurately detect defects such as cracks that may occur in optical films including stretched films such as polarizing films and retardation films. [Background technology]

[0002] In recent years, optical films including stretched films such as polarizing films and retardation films have been used not only in televisions and personal computers but also in a wide variety of display applications such as smartphones, smartwatches, and in-vehicle displays. These optical films are produced as long optical films by stretching, laminating, etc. using a roll-to-roll system, and then cut into sheets having shapes appropriate for their intended use.

[0003] If there is a defect in the optical film cut into sheets, the display performance of the display it is used in cannot be maintained. For this reason, the optical film cut into sheets is inspected by transmission inspection, crossed Nicol inspection, reflection inspection, etc., and if a defect is detected, the optical film is discarded.

[0004] Here, optical films including stretched films such as polarizing films and retardation films may develop minute fissure-like defects called cracks after being cut into sheets. If these cracks develop in a dense pattern, the display performance of the display in which the optical film is used cannot be maintained, and therefore it is desirable to detect dense cracks by inspection.

[0005] However, according to the investigations conducted by the present inventors, there is a problem in that the above-mentioned cracks cannot be detected with high accuracy by conventional inspection methods such as transmission inspection, crossed Nicol inspection, and reflection inspection.

[0006] For example, Patent Document 1 proposes a type of transmission inspection device for inspecting long optical films before they are cut into sheets. The inspection device has two light-emitting units, which are shifted upstream and downstream in the film running direction relative to the light-receiving units, and is arranged so that when there are no defects in the two light-emitting units, the light-receiving units are in a dark field state, and when there are defects, the light-receiving units are in a light-receiving state (Claim 1 of Patent Document 1, etc.). Specifically, in the inspection device described in Patent Document 1, when viewed from the normal direction of the film, the two light-emitting units have their optical axes facing in opposite directions, but are both arranged along the film transport direction (see, for example, Figure 1 of Patent Document 1).

[0007] According to the investigations conducted by the present inventors, it has been found that even if an inspection device such as that described in Patent Document 1 is applied to an optical film cut into sheets, cracks cannot be detected with high accuracy. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-122130 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the problems of the conventional technology as described above, and an object of the present invention is to provide an optical film inspection device, inspection method, and manufacturing method that can accurately detect defects such as cracks that may occur in optical films including stretched films such as polarizing films and retardation films. [Means for solving the problem]

[0010] To solve the above problems, the inventors of the present invention have thoroughly studied the arrangement of the light source and the imaging unit in transmission inspection. As a result, they have devised a method of preparing a first light source and a second light source as light sources, and arranging the first light source so that the optical axis of the first light source is aligned with the transport direction of the optical film when viewed from the normal direction of the optical film, and arranging the second light source so that the optical axis of the second light source is aligned with the direction perpendicular to the transport direction of the optical film. They then found that by arranging the imaging unit so as not to directly receive light emitted from the first light source and the second light source and so as not to receive specularly transmitted light irradiated onto the optical film from the first light source and the second light source, the contrast of pixel areas corresponding to defects such as cracks is increased in the captured image generated by the imaging unit, allowing for accurate detection of defects. In other words, they found that by arranging the first light source, the second light source, and the imaging unit in a specific manner, defects such as cracks that are difficult to detect using conventional transmission inspection can be accurately detected.

[0011] The present invention was completed based on the findings of the inventors described above. That is, in order to solve the above-mentioned problems, the present invention provides an inspection device for an optical film transported in a predetermined transport direction, comprising: a first light source and a second light source that are arranged on one side of the optical film in a normal direction and irradiate light onto the optical film; an imaging unit that is arranged on the other side of the optical film in the normal direction and generates an image by imaging the optical film; and an image processing unit that detects defects present in the optical film based on the image, wherein the first light source is arranged such that an optical axis of the first light source is along the transport direction when viewed from the normal direction of the optical film, and the second light source is arranged such that an optical axis of the second light source is along a direction perpendicular to the transport direction when viewed from the normal direction of the optical film, and the imaging unit is arranged so as not to directly receive light emitted from the first light source and the second light source, and so as not to receive specularly transmitted light of light irradiated onto the optical film from the first light source and the second light source.

[0012] In the present invention, the "optical axis of the first light source" means the central axis of the light (light flux) emitted from the first light source, and the "optical axis of the second light source" means the central axis of the light (light flux) emitted from the second light source. According to the present invention, the first light source, the second light source, and the imaging unit are arranged in a specific state, and as the inventors have found, the contrast of pixel regions corresponding to defects such as cracks is increased in the captured image generated by the imaging unit. Therefore, defects such as cracks can be detected with high accuracy by performing image processing such as binarization on the captured image using the image processing unit.

[0013] Preferably, the imaging unit generates a first captured image by imaging the optical film in a state where light is irradiated onto the optical film only from the first light source out of the first light source and the second light source, and generates a second captured image by imaging the optical film in a state where light is irradiated onto the optical film only from the second light source, and the image processing unit detects defects present in the optical film based on the first captured image and the second captured image.

[0014] According to the findings of the present inventors, imaging an optical film while irradiating the optical film with light from only one of the light sources is more likely to increase the contrast of pixel regions corresponding to defects such as cracks in one of the captured images (the first captured image or the second captured image) generated when light is irradiated from only one of the light sources than imaging an optical film while irradiating the optical film with light from both the first light source and the second light source simultaneously. In other words, the ease with which contrast is increased depends on the direction in which the defect such as a crack extends, and imaging an optical film while irradiating the optical film with light only from a light source having an optical axis in a direction approximately perpendicular to the direction in which the defect extends is more likely to increase the contrast of pixel regions corresponding to defects such as cracks. According to the above preferred configuration, the contrast of pixel regions corresponding to defects such as cracks in the first captured image or the second captured image is increased, thereby enabling more accurate detection of defects such as cracks.

[0015] Preferably, the imaging unit is positioned so that its visual axis forms an acute angle with respect to the normal to the optical film at the point where it intersects with the optical film, and the first light source and the imaging unit are positioned on the same side of the conveying direction with respect to the normal.

[0016] In the above-described preferred configuration, the "visual axis" of the imaging unit means the central axis of the imaging field of view of the imaging unit. According to the inventors' findings, the above-described preferred configuration increases the contrast of pixel areas corresponding to defects such as cracks in the captured image generated by the imaging unit, thereby enabling defects such as cracks to be detected with even greater accuracy.

[0017] Preferably, the imaging unit is arranged so that its visual axis forms an angle of 10° to 80° with respect to the normal line, and the first light source is arranged so that its optical axis forms an angle of 10° to 80° with respect to the normal line.

[0018] According to the inventors' findings, the above-described preferred configuration increases the contrast of pixel areas corresponding to defects such as cracks in the captured image generated by the imaging unit, thereby enabling defects such as cracks to be detected with even greater accuracy.

[0019] Preferably, the first light source is composed of a plurality of light sources arranged along a direction perpendicular to the conveying direction when viewed from the normal direction of the optical film, and / or the second light source is composed of a plurality of light sources arranged along a direction perpendicular to the conveying direction when viewed from the normal direction of the optical film.

[0020] According to the above preferred configuration, since the first light source and / or the second light source is composed of multiple light sources, the direction of light emitted from the first light source and / or the second light source can be multidirectional when viewed three-dimensionally, which may increase the contrast of pixel regions corresponding to defects such as cracks compared to when a single light source is used as the first light source and the second light source. Furthermore, depending on the type of optical film or the type of defect to be detected, it is also possible to emit light from only pre-selected light sources from the multiple light sources so as to increase the contrast of pixel regions corresponding to defects, which has the advantage of increasing the degree of freedom in inspection.

[0021] The present invention is preferably used when the image processing unit detects cracks as the defects.

[0022] The present invention is also preferably used when the optical film includes a stretched film.

[0023] In order to solve the above-mentioned problems, the present invention provides an inspection method for an optical film transported in a predetermined transport direction, comprising: a preparation step of arranging a first light source and a second light source that irradiate light onto the optical film on one side of the optical film in a normal direction, and an imaging unit that generates an image by imaging the optical film on the other side of the normal direction of the optical film; an image generation step of generating an image by imaging the optical film with the imaging unit in a state in which the optical film is irradiated with light from at least one of the first light source and the second light source; and a step of detecting defects present in the optical film based on the image. and a defect detection process for detecting defects by an image processing unit, wherein in the preparation process, the first light source is arranged so that the optical axis of the first light source is along the transport direction when viewed from the normal direction of the optical film, and the second light source is arranged so that the optical axis of the second light source is along a direction perpendicular to the transport direction when viewed from the normal direction of the optical film, and the imaging unit is arranged so that it does not directly receive light emitted from the first light source and the second light source and does not receive specularly transmitted light of light irradiated onto the optical film from the first light source and the second light source.

[0024] Furthermore, in order to solve the above-mentioned problems, the present invention is also provided as a method for manufacturing an optical film, which includes a cutting step of cutting a long optical film into sheets, and an inspection step of inspecting the cut sheets of optical film, in which the inspection method is performed on the cut sheets of optical film in the inspection step, and if a defect in the optical film is detected in the inspection step, the optical film is discarded. [Effects of the Invention]

[0025] The optical film inspection device and inspection method according to the present invention are capable of accurately detecting defects such as cracks that may occur in optical films including stretched films such as polarizing films, retardation films, etc. Furthermore, the optical film manufacturing method according to the present invention is capable of accurately detecting defects such as cracks that occur in sheet-like optical films in the inspection process using the inspection method according to the present invention, and if a defect is detected, the optical film is discarded, thereby reducing the risk of defective optical films being mixed into products. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a cross-sectional view showing an example of a schematic configuration of an optical film 10 that is an object to be inspected by an inspection device according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing a schematic configuration of an inspection device 100 according to an embodiment of the present invention. [Figure 3] 3 is a diagram showing an example of a second captured image generated by the imaging section 3 shown in FIG. 2. FIG. [Figure 4] 3 is a diagram schematically illustrating a schematic configuration of a modified example of the first light source 1 shown in FIG. 2. FIG. [Figure 5] 3 is a diagram schematically illustrating a schematic configuration of a modified example of the second light source 2 shown in FIG. 2. FIG. [Figure 6] 10A and 10B are diagrams illustrating an example of a method for eliminating the dead zone of the optical film 10. FIG. [Figure 7] FIG. 10 is a side view schematically showing the general configuration of a modified example of the inspection device 100. [Figure 8] 1 is a flow diagram showing an example of the outline of steps in a method for manufacturing an optical film 10 using an inspection method using an inspection device 100. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] An optical film inspection device according to one embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the drawings are for reference purposes only, and the dimensions, scale, and shapes of the components shown in the drawings may differ from the actual ones.

[0028] <Optical Film 10> First, the configuration of optical film 10, which is the object of inspection by the inspection device according to this embodiment, will be described. Fig. 1 is a cross-sectional view showing an example of the schematic configuration of an optical film 10 that is an object of inspection by the inspection device according to this embodiment. Fig. 1(a) shows the schematic configuration of an optical laminate 10A, which is an example of the optical film 10, and Fig. 1(b) shows the schematic configuration of an optical laminate 10B, which is another example of the optical film 10. In Fig. 1, X indicates the horizontal direction, which is the transport direction of the optical film 10, Y indicates the horizontal direction perpendicular to the X direction, and Z indicates the vertical direction (thickness direction of the optical film 10). The same applies to other figures described below.

[0029] The optical film 10 shown in FIG. 1 is cut into sheets each having a shape (rectangular in the example shown in FIG. 1) according to the intended use. 1(a) is configured by laminating a polarizer 11, protective films 12 and 13, a retardation film 14, a pressure-sensitive adhesive layer 15, and a release liner 16. The optical film 10 (optical laminate 10B) shown in FIG. 1(b) is configured by laminating a polarizer 11, protective films 12 and 13, a pressure-sensitive adhesive layer 15, a release liner 16, and an antireflection layer (AR coat) 17. Below, each component of the optical film 10 shown in FIG. 1 will be outlined.

[0030] [Polarizer 11] The polarizer 11 is typically made of a resin film containing a dichroic material. The resin film may be any appropriate resin film that can be used as a polarizer, and is typically a polyvinyl alcohol (PVA)-based resin film. Any appropriate resin can be used as the PVA-based resin for forming the PVA-based resin film. 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. Examples of dichroic materials contained in the resin film include iodine and organic dyes. These may be used alone or in combination of two or more. Iodine is preferably used.

[0031] 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 resin film is a PVA-based resin film that has been subjected to a dyeing treatment with iodine and a stretching treatment (typically, a uniaxial stretching treatment). The dyeing treatment with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio in the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after dyeing or while dyeing. Alternatively, the dyeing may be performed after stretching. If necessary, the PVA-based resin film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, etc. Specific examples of polarizers made of a laminate include a laminate of a resin substrate and a PVA-based resin layer laminated on the resin substrate, or a polarizer made of a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer made of a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer.

[0032] The thickness of the polarizer 11 is preferably 15 μm or less, more preferably 1 μm to 12 μm, still more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm. The polarizer 11 preferably exhibits absorptive dichroism at any wavelength within a wavelength range of 380 nm to 780 nm. The single transmittance of the polarizer 11 is preferably 40.0% to 45.0%, and more preferably 41.5% to 43.5%. The degree of polarization of the polarizer 11 is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0033] [Protection films 12 and 13] Any appropriate resin film can be used as the protective films 12 and 13. Examples of materials for forming the resin film include (meth)acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose (TAC), 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" refers to acrylic resins and / or methacrylic resins. The thickness of the protective films 12 and 13 is typically 10 μm to 100 μm, and preferably 20 μm to 40 μm. The laminate of the polarizer 11 and the protective films 12 and 13 constitutes the polarizing film PF.

[0034] [Retardation film 14] The retardation film 14 may be, for example, a compensation plate that provides a wide viewing angle, or a retardation plate (circular polarizer) that is used together with the polarizing film PF to generate circularly polarized light. The thickness of the retardation film 14 is, for example, 1 to 200 μm. The retardation film 14 is typically formed by subjecting any appropriate resin capable of realizing the above-described properties to a stretching treatment (typically, uniaxial stretching treatment). Examples of resins that form the retardation film 14 include polyarylates, polyamides, polyimides, polyesters, polyaryletherketones, polyamideimides, polyesterimides, polyvinyl alcohols, polyfumarates, polyethersulfones, polysulfones, norbornene resins, polycarbonate resins, cellulose resins, and polyurethanes. These resins may be used alone or in combination. Cycloolefin-based norbornene resins are preferred.

[0035] The polarizer 11, the protective films 12 and 13, and the retardation film 14 described above are laminated together via any suitable adhesive layer (not shown). Typical examples of the adhesive constituting the adhesive layer include a PVA-based adhesive and an activation energy ray-curable adhesive.

[0036] [Adhesive layer 15] In the case of the optical laminate 10A shown in FIG. 1(a), the pressure-sensitive adhesive layer 15 is interposed between the retardation film 14 and the release liner 16, and in the case of the optical laminate 10B shown in FIG. 1(b), the pressure-sensitive adhesive layer 15 is interposed between the protective film 13 and the release liner 16, and in either case, the pressure-sensitive adhesive layer 15 is a layer for laminating the release liner 16 with other components. Examples of adhesives that constitute the adhesive layer 15 include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. The thickness of the adhesive layer 15 can be set to, for example, 10 μm to 100 μm.

[0037] [Release Liner 16] Any appropriate configuration can be adopted for the release liner 16. Specific examples include plastic films, nonwoven fabrics, or paper whose surfaces are 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) films, polyethylene films, and polypropylene films. The thickness of the release liner 16 can be, for example, 10 μm to 100 μm.

[0038] [Anti-reflection layer 17] 1(b), the antireflection layer 17 is formed on the surface of the protective film 12 opposite to the polarizer 11. The antireflection layer 17 is formed by subjecting the protective film 12 to antireflection treatment (AR treatment).

[0039] The optical film 10 to be inspected by the inspection device according to this embodiment has the general configuration described above, is manufactured as a long optical film 10 by a roll-to-roll method, and is then cut into sheets having a shape appropriate for the intended use. Note that the detailed configuration of the optical film 10 is publicly known, and therefore will not be described here.

[0040] Here, after being cut into sheets, minute fissure-like defects called cracks may occur in the optical film 10 due to various factors such as mechanical contact with a conveying device during the conveying process. According to the findings of the present inventors, in the case of the optical laminate 10A shown in Fig. 1(a), cracks C are likely to occur in the retardation film 14, and in the case of the optical laminate 10B shown in Fig. 1(b), cracks C are likely to occur in the antireflection layer 17. The inspection device according to the present embodiment, which will be described below, is suitably used to detect the cracks C described above.

[0041] <Inspection device 100> Next, the configuration of the inspection device 100 according to this embodiment will be described. 2A and 2B are diagrams showing a schematic configuration of an inspection device 100 according to this embodiment, in which Fig. 2A is a plan view and Fig. 2B is a side view. 2, the inspection device 100 according to this embodiment is an inspection device for an optical film 10 that is conveyed in a predetermined conveyance direction (X direction in this embodiment) by a conveyance device such as a belt conveyor (not shown in FIG. 2), and includes a first light source 1, a second light source 2, an imaging unit 3, and an image processing unit 4. Although not shown in FIG. 2, the first light source 1, the second light source 2, and the imaging unit 3 are each supported by predetermined support means at predetermined positions on the conveyance line of the optical film 10. Each component of the inspection device 100 shown in FIG. 2 will be described below.

[0042] [1st light source 1] The first light source 1 is disposed on one side of the optical film 10 in the direction of the normal N (in this embodiment, on the upper side of the optical film 10 as shown in FIG. 2(b)), and irradiates the optical film 10 with light. The first light source 1 is not particularly limited as long as it emits light of a wavelength that can be transmitted through the optical film 10 and can irradiate the entire optical film 10 with light, but for example, an LED or a halogen lamp can be used. When viewed from the direction of the normal line N of the optical film 10, the first light source 1 is disposed so that the optical axis A1 of the first light source 1 is aligned with the transport direction (X direction) of the optical film 10. The first light source 1 is disposed so that the optical axis A1 forms an angle θ2 of 10° to 80° with respect to the normal line N, for example.

[0043] [Second light source 2] Similar to the first light source 1, the second light source 2 is arranged on one side of the optical film 10 in the direction of the normal N (in this embodiment, on the upper side of the optical film 10 as shown in FIG. 2(b)) and irradiates light onto the optical film 10. The second light source 2, like the first light source 1, is not particularly limited as long as it emits light of a wavelength that can be transmitted through the optical film 10 and can irradiate the entire optical film 10 with light, but for example, an LED or a halogen lamp can be used. The second light source 2 is arranged such that, when viewed from the normal N direction of the optical film 10, the optical axis A2 of the second light source 2 is aligned along a direction (Y direction) perpendicular to the transport direction (X direction) of the optical film 10.

[0044] [Image capture unit 3] The imaging unit 3 is disposed on the other side of the optical film 10 in the direction of the normal N (in this embodiment, below the optical film 10 as shown in FIG. 2(b)), and generates a captured image by capturing an image of the optical film 10. Specifically, the imaging unit 3 receives light that is irradiated onto the optical film 10 from the first light source 1 and the second light source 2 and that has passed through the optical film 10, and forms an image to generate a captured image. The imaging unit 3 is not particularly limited as long as it is sensitive to the wavelengths of light emitted from the first light source 1 and the second light source. For example, an area sensor camera using a CCD or CMOS as an imaging element can be used. When an area sensor camera is used as the imaging unit 3, for example, the imaging field of the imaging unit 3 is set so that the entire optical film 10 is included. Then, the transport of the optical film 10 transported in the X direction is stopped when the entire optical film 10 enters the imaging field of the imaging unit 3. After the imaging unit 3 has finished generating an image of the optical film 10 that has been stopped, it is preferable to transport the optical film 10 again in the X direction and continue transporting it until the next entire optical film 10 enters the imaging field of the imaging unit 3 (i.e., perform intermittent transport). However, the present invention is not limited thereto. When a line sensor in which multiple imaging elements are arranged in a straight line along the direction (Y direction) perpendicular to the transport direction of the optical film 10 is used as the imaging unit 3, it is also possible to continuously transport the optical film 10 without stopping the transport of the optical film 10 to generate an image.

[0045] The imaging unit 3 is disposed so as not to directly receive the light emitted from the first light source 1 and the second light source 2. In other words, the imaging unit 3 is disposed so as not to receive light that is not irradiated onto the optical film 10, out of the light emitted from the first light source 1 and the second light source 2. The imaging unit 3 is also disposed so as not to receive specularly transmitted light (light that passes through the optical film 10 and travels straight without being scattered) of the light that is irradiated onto the optical film 10 from the first light source 1 and the second light source 2. Specifically, the imaging unit 3 is disposed so that its visual axis V forms an acute angle (angle θ1) with respect to the normal N of the optical film 10 at the point where it intersects with the optical film 10. The angle θ1 is set, for example, to 10° to 80°. The imaging unit 3 is disposed on the same side of the normal N as the first light source 1 with respect to the transport direction of the optical film 10 (to the right of the normal N in the example shown in FIG. 2(b)). Note that in the example shown in FIG. 2, the imaging unit 3 is disposed so that the visual axis V of the imaging unit 3 is close to the optical axis A1 of the first light source 1 (i.e., close to the transport direction of the optical film 10). However, the present invention is not limited thereto, and the imaging unit 3 may be disposed so that the visual axis V of the imaging unit 3 is close to the optical axis A2 of the second light source 2 (i.e., close to the direction perpendicular to the transport direction of the optical film 10).

[0046] The imaging unit 3 can also generate a captured image by capturing an image of the optical film 10 in a state where the optical film 10 is simultaneously irradiated with light from both the first light source 1 and the second light source 2. However, in order to increase the contrast of pixel regions corresponding to cracks C in the captured image, it is preferable that the imaging unit 3 generate a first captured image by capturing an image of the optical film 10 in a state where the optical film 10 is irradiated with light only from the first light source 1 of the first light source 1 and the second light source 2, and generate a second captured image by capturing an image of the optical film 10 in a state where the optical film 10 is irradiated with light only from the second light source 2. Fig. 3 is a diagram showing an example of the second captured image generated by the imaging unit 3. As shown in Fig. 3, it can be seen that the pixel region corresponding to the crack C is brighter than the other regions and has a high contrast.

[0047] [Image processing unit 4] The image processing unit 4 is electrically connected to the imaging unit 3, and receives the captured image generated by the imaging unit 3. The image processing unit 4 detects defects (cracks C in this embodiment) present in the optical film 10 based on the captured image (for example, by performing image processing such as binarization on the captured image). When the imaging unit 3 generates the first captured image and the second captured image, the image processing unit 4 detects defects present in the optical film 10 by performing image processing on each of the first captured image and the second captured image. As the image processing unit 4, for example, a computer storing an image processing program for processing the captured image and detecting defects present in the optical film 10 can be used.

[0048] The inspection device 100 according to this embodiment has the configuration described above (the first light source 1, the second light source 2, and the image capturing unit 3 are arranged in a specific state), and therefore the contrast of the pixel region corresponding to the crack C is increased in the captured image generated by the image capturing unit 3. Therefore, by performing image processing such as binarization processing on the captured image by the image processing unit 4, the crack C can be detected with high accuracy.

[0049] 2 illustrates an example in which the first light source 1 and the second light source 2 are each a single light source, but the present invention is not limited to this. At least one of the first light source 1 and the second light source 2 can be configured with a plurality of light sources. Furthermore, even if a single light source is used, it is also possible to use a line light source that is longer than the dimension of the optical film 10, unlike the one shown in FIG. 2. That is, it is also possible to use a line light source that is longer than the dimension of the optical film 10 in the Y direction as the first light source 1, and a line light source that is longer than the dimension of the optical film 10 in the X direction as the second light source 2.

[0050] FIG. 4 is a diagram illustrating a schematic configuration of a modified first light source 1. FIG. 4(a) is a plan view, and FIG. 4(b) is a side view. The left diagrams of FIGS. 4(a) and 4(b) show the optical axes of the light sources in the modified first light source, and the right diagrams of FIGS. 4(a) and 4(b) explain the angles θ3 and θ4, respectively. As shown in FIG. 4, the first light source 1 included in the inspection device 100 may be configured with multiple light sources 1a, 1b, and 1c arranged along a direction (Y direction) perpendicular to the transport direction of the optical film 10 when viewed from the normal direction of the optical film 10. For convenience, FIG. 4 illustrates a case where the first light source 1 is configured with three light sources 1a, 1b, and 1c, but there is no limit to the number of light sources as long as there is multiple light sources. 4, the light sources 1a, 1b, and 1c are arranged in an arc shape (arranged along a predetermined arc) when viewed from the transport direction (X direction) of the optical film 10, but this is not limiting and they may be arranged in a straight line. As shown in the left diagrams of FIGS. 4(a) and 4(b), the optical axes A1a, A1b, and A1c of the light sources 1a, 1b, and 1c may be oriented in different directions, but the optical axis of the light sources 1a to 1c as a whole (the optical axis of the light source 1) is aligned with the transport direction (X direction) of the optical film 10, as in the case shown in FIG. As shown in the right diagram of FIG. 4( a), when viewed from the normal direction of the optical film 10, the angle formed by the line L connecting each of the light sources 1a, 1b, and 1c to the center C of the optical film 10 (only the line connecting the light source 1a to the center C of the optical film 10 is shown as a representative) and the direction perpendicular to the transport direction of the optical film 10 (the Y direction) is defined as θ3. As shown in the right diagram of FIG. 4( b), when viewed from the transport direction of the optical film 10, the angle formed by the line L connecting each of the light sources 1a, 1b, and 1c to the center C of the optical film 10 (only the line connecting the light source 1a to the center C of the optical film 10 is shown as a representative) and the direction perpendicular to the transport direction of the optical film 10 (the Y direction) is defined as θ4. The angle θ3 is preferably 45° to 135°, and the angle θ4 is preferably 10° to 170°.

[0051] FIG. 5 is a diagram illustrating a schematic configuration of a modified example of the second light source 2. FIG. 5(a) is a plan view, and FIG. 5(b) is a side view. As shown in FIG. 5, the second light source 2 provided in the inspection device 100 may be composed of multiple light sources 2a, 2b, and 2c arranged along a direction (Y direction) perpendicular to the transport direction of the optical film 10 when viewed from the normal direction of the optical film 10. For convenience, FIG. 5 illustrates a case where the second light source 2 is composed of three light sources 2a, 2b, and 2c. However, there is no limit to the number of light sources as long as there are multiple light sources. In addition, in FIG. 5, the light sources 2a, 2b, and 2c are arranged in an arc shape (arranged along a predetermined arc) when viewed from the transport direction (X direction) of the optical film 10. However, the arrangement is not limited thereto and may be linear. As shown in FIG. 5, the directions of the optical axes A2a, A2b, and A2c of the light sources 2a, 2b, and 2c may differ from one another, but the optical axis of the light sources 2a to 2c as a whole (the optical axis of the light source 2) is aligned along the direction (Y direction) perpendicular to the transport direction of the optical film 10, as in the case shown in FIG. 2.

[0052] Furthermore, when a belt conveyor is used as a transport device for transporting the optical film 10, the transport belt may enter the imaging field of view of the imaging unit 3, causing some of the light emitted from the first light source 1 and the second light source 2 and transmitted through the optical film 10 to be blocked by the transport belt, which may result in a situation where the light cannot be received by the imaging unit 3 (and therefore creating a dead zone in part of the optical film 10 that cannot be inspected). In this case, two inspection devices 100 and two belt conveyors are installed side by side in the transport direction (X direction) of the optical film 10, and the positions of the transport belts of each belt conveyor are shifted so that the dead zones of the optical film 10 that cannot be inspected by one inspection device 100 can be inspected by the other inspection device 100.

[0053] 6A and 6B are diagrams illustrating an example of a method for eliminating the dead zone of the optical film 10. Fig. 6A is a side view, and Fig. 6B is a plan view. In Fig. 6B, the first light source 1, the second light source 2, and the imaging unit 3 are not shown. As shown in FIG. 6, to eliminate the dead zone of the optical film 10, two inspection devices 100 and two belt conveyors 20 are installed side by side in the transport direction (X direction) of the optical film 10. Each belt conveyor 20 has a pair of rollers 21 and multiple conveyor belts 22 stretched between the pair of rollers 21. For the optical film 10 transported by one belt conveyor 20a located upstream in the transport direction, a portion of the light emitted from the first light source 1 and the second light source 2 of one inspection device 100 located upstream in the transport direction and transmitted through the optical film 10 is blocked by the conveyor belts 22 and cannot be received by the imaging unit 3, resulting in a dead zone. However, for the other belt conveyor 20b located downstream in the transport direction, the positions around which the conveyor belts 22 are stretched are shifted in the direction perpendicular to the transport direction of the optical film 10 (Y direction) relative to the conveyor belts 22 of the belt conveyor 20a (in the example shown in FIG. 6, the entire belt conveyor 20b is shifted). Therefore, light emitted from the first light source 1 and the second light source 2 of the other inspection device 100 located downstream in the conveyance direction and transmitted through the portion of the optical film 10 that was a dead zone on the upstream side in the conveyance direction can be received by the imaging unit 3 of the other inspection device 100, thereby enabling inspection. Therefore, by using the inspection devices 100 both upstream and downstream in the conveyance direction, the dead zone of the optical film 10 can be eliminated. Although not shown in Figure 6, there is no need to provide two image processing units 4 if they are electrically connected to and shared by both the imaging unit 3 on the upstream side in the conveying direction and the imaging unit 3 on the downstream side in the conveying direction.

[0054] Furthermore, the inspection device 100 may be configured to include a shielding plate so that the imaging unit 3 does not directly receive the light emitted from the first light source 1 and the second light source 2. 7 is a side view that schematically illustrates the general configuration of a modified example (inspection device including a shielding plate) of the inspection device 100. The inspection device 100 illustrated in FIG. 7 includes a shielding plate 5 that blocks light (light that is not irradiated onto the optical film 10) emitted from the first light source 1 and the second light source 2 so that the light that is not irradiated onto the optical film 10 is not directly received by the imaging unit 3. This ensures that the imaging unit 3 does not directly receive the light emitted from the first light source 1 and the second light source 2.

[0055] A method for manufacturing the optical film 10 using the inspection method using the inspection device 100 described above will now be described. FIG. 8 is a flow diagram showing an example of the outline of steps in a method for manufacturing the optical film 10 using the inspection method using the inspection device 100. 8, the method for manufacturing an optical film 10 according to this embodiment includes a cutting step ST1 and an inspection step ST2. In the cutting step ST1, a long optical film 10 is cut into sheets. In the inspection step ST2, the cut sheets of optical film 10 are inspected using an inspection device 100.

[0056] Specifically, in the inspection process ST2, a preparation process, an image generation process, and a defect detection process are executed. In the preparation step, a first light source 1 and a second light source 2 that irradiate light onto the optical film 10 are arranged on one side of the optical film 10 in the direction of the normal N (on the upper side of the optical film 10 in the example shown in FIG. 2(b) above), and an imaging unit 3 that generates a captured image by imaging the optical film 10 is arranged on the other side of the optical film 10 in the direction of the normal N (on the lower side of the optical film 10 in the example shown in FIG. 2(b) above). More specific arrangement conditions for the first light source 1, the second light source 2, and the imaging unit 3 are as described above. Then, in the captured image generation process, the optical film 10 is imaged by the imaging unit 3 while light is irradiated onto the optical film 10 from at least one of the first light source 1 and the second light source 2, thereby generating a captured image. Finally, in the defect detection step, the image processing unit 4 detects defects present in the optical film 10 based on the captured images.

[0057] In the manufacturing method of the optical film 10 according to this embodiment, if no defects are detected in the optical film 10 in the inspection process ST2 (if "No" in ST3 shown in Figure 8), the optical film is shipped as a product (ST4 shown in Figure 8). On the other hand, in the manufacturing method of the optical film 10 according to the present embodiment, if a defect is detected in the optical film 10 in the inspection step ST2 (if "Yes" is selected in ST3 in FIG. 8 ), the optical film 10 can be uniformly discarded (ST7 in FIG. 8 ) to reliably prevent the risk of the defective optical film 10 being mixed into the final product. However, in the example shown in FIG. 8 , as a preferred mode, in order to improve the product yield even if a defect is detected in the optical film 10 in the inspection step ST2, a portion of the optical film 10 is shipped as a final product if it meets predetermined conditions. Specifically, if a defect is detected in the optical film 10 in the inspection step ST2 (if "Yes" is selected in ST3 in FIG. 8 ), a visual inspection is performed in which an operator visually inspects the optical film 10 (ST5 in FIG. 8 ). If a defect is also detected in the visual inspection (if "Yes" is selected in ST6 in FIG. 8 ), the optical film 10 is discarded (ST7 in FIG. 8 ). On the other hand, if no defects are detected by visual inspection ("No" in ST6 shown in Figure 8), it is determined that the defect detection in inspection process ST2 was an overdetection, and the optical film 10 is shipped as a product (ST4 shown in Figure 8). As described above, according to the manufacturing method of the optical film 10 of this embodiment, in the inspection process ST2, defects such as cracks that occur in the sheet-like optical film 10 can be accurately detected using the inspection method by the inspection device 100, and if a defect is detected, the optical film 10 is basically discarded, thereby reducing the risk of defective optical film 10 being mixed into the product. [Explanation of symbols]

[0058] 1...1st light source 2...Second light source 3. Imaging unit 4. Image processing section 10. Optical film 100 Inspection equipment C···Crack

Claims

1. An inspection device for an optical film transported in a predetermined transport direction, a first light source and a second light source that are arranged on one side of the optical film in a normal direction and that irradiate the optical film with light; an imaging unit that is disposed on the other side of the optical film in the normal direction and that captures an image of the optical film to generate a captured image; an image processing unit that detects defects present in the optical film based on the captured image, the first light source is disposed such that an optical axis of the first light source is aligned along the transport direction when viewed from a normal direction of the optical film, the second light source is disposed such that an optical axis of the second light source is aligned along a direction perpendicular to the transport direction when viewed from a normal direction of the optical film, the imaging unit is arranged so as not to directly receive light emitted from the first light source and the second light source, and is also arranged so as not to receive specularly transmitted light of light irradiated onto the optical film from the first light source and the second light source. Optical film inspection equipment.

2. the imaging unit generates a first captured image by imaging the optical film in a state in which light is irradiated onto the optical film only from the first light source out of the first light source and the second light source, and generates a second captured image by imaging the optical film in a state in which light is irradiated onto the optical film only from the second light source, the image processing unit detects defects present in the optical film based on the first captured image and the second captured image. The optical film inspection device according to claim 1 .

3. the imaging unit is disposed so that a visual axis of the imaging unit forms an acute angle with a normal to the optical film at a point where the visual axis intersects with the optical film; the first light source and the imaging unit are disposed on the same side in the conveying direction with respect to the normal line. The optical film inspection device according to claim 1 or 2.

4. the imaging unit is arranged so that its visual axis forms an angle of 10° to 80° with respect to the normal line; The first light source is arranged so that its optical axis forms an angle of 10° to 80° with respect to the normal line. The optical film inspection device according to claim 3 .

5. the first light source is composed of a plurality of light sources arranged along a direction perpendicular to the transport direction when viewed from the normal direction of the optical film, and / or the second light source is composed of a plurality of light sources arranged along a direction perpendicular to the transport direction when viewed from the normal direction of the optical film. The optical film inspection device according to claim 1 or 2.

6. the image processing unit detects a crack as the defect. The optical film inspection device according to claim 1 or 2.

7. The optical film comprises a stretched film. The optical film inspection device according to claim 1 or 2.

8. 1. A method for inspecting an optical film transported in a predetermined transport direction, comprising: a preparation step of arranging a first light source and a second light source that irradiate the optical film with light on one side of the optical film in a normal direction, and arranging an imaging unit that generates a captured image by imaging the optical film on the other side of the optical film in the normal direction; a captured image generating step of generating a captured image by capturing an image of the optical film with the imaging unit in a state in which light is irradiated onto the optical film from at least one of the first light source and the second light source; a defect detection step of detecting defects present in the optical film based on the captured image by an image processing unit, In the preparation step, the first light source is disposed such that an optical axis of the first light source is aligned along the transport direction when viewed from a normal direction of the optical film; the second light source is disposed so that an optical axis of the second light source is aligned along a direction perpendicular to the transport direction when viewed from a normal direction of the optical film; the imaging unit is disposed so as not to directly receive the light emitted from the first light source and the second light source and so as not to receive specularly transmitted light of the light irradiated onto the optical film from the first light source and the second light source. Optical film inspection method.

9. a cutting step of cutting the long optical film into sheets; an inspection step of inspecting the cut sheet of the optical film, In the inspection step, the inspection method according to claim 8 is performed on the cut sheet of the optical film, If a defect in the optical film is detected in the inspection step, the optical film is discarded. A method for manufacturing an optical film.

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