Method for measuring curl of optical film and method for manufacturing optical film

Abstract

The present application provides a kind of optical film curling measuring method and the like capable of measuring curling value with high accuracy in short time.The curling measuring method of the present application is a method for measuring curling value indicating the degree of curling of sheet-shaped optical film (F) using optical sensor (1) provided with light projector (11) and light receiver (12), comprising: arrangement step (ST21), arranging light projector on one side of the side of optical film, and arranging light receiver on the other side of the side of optical film opposite to light projector across optical film;Light emitting and receiving step (ST22), projecting light beam (L) extending in up-down direction towards optical film using light projector, and receiving light transmitted through optical film without being blocked by optical film in light beam using light receiver;Curling value calculation step (ST23), calculating the curling value of optical film based on the length of up-down direction of transmitted light.

Description

Technical Field

[0001] This invention relates to a method for measuring the curl of an optical film, capable of determining a curl value that represents the degree of curl that may occur at the end of an optical film such as a sheet polarizer, and a method for manufacturing an optical film using this method. In particular, this invention relates to a method for measuring the curl of an optical film capable of measuring the curl value with high accuracy in a short time, and a method for manufacturing an optical film using this method. Background Technology

[0002] Polarizing plates have traditionally been used as constituent materials in liquid crystal display devices, organic EL display devices, and the like. Besides polarizing films, polarizing plates may also include retardation films, depending on the application. A polarizing film, for example, consists of a polarizer dyed with a dichroic substance such as iodine and a protective film protecting the polarizer. A strip-shaped polarizing film is manufactured by laminating a strip-shaped protective film onto at least one side of a strip-shaped polarizer. A strip-shaped optical laminate is manufactured by laminating a strip-shaped retardation film, etc., onto one side of the manufactured strip-shaped polarizing film. A strip-shaped release liner is laminating one side of the manufactured strip-shaped optical laminate, and a strip-shaped surface protective film is laminating the other side to manufacture a strip-shaped polarizing plate. The lamination of these strip-shaped films is typically performed in a roll-to-roll or roll-to-sheet manner. The manufactured strip-shaped polarizing plate is cut into sheets of a size and shape appropriate for the application and used in liquid crystal display devices, etc. It should be noted that when used in liquid crystal display devices, the release liner is peeled off, and the remaining components of the polarizing plate are glued to the liquid crystal display device, etc.

[0003] However, in sheet-like optical films such as polarizing plates manufactured as described above, curling (end warping) sometimes occurs, causing problems in use. If the degree of curling becomes severe, it will create obstacles when attaching the optical film to liquid crystal display devices, etc. Therefore, a curling value indicating the degree of curling is measured, and the size of the curling value is used to determine whether the optical film is a qualified or unqualified part, and unqualified parts are discarded.

[0004] Figure 1 This diagram is an example illustrating a conventional method for measuring curl value.

[0005] When measuring the curl value, the optical film F is placed on a flat mounting stage 5 with its lower side convex (the end of the optical film F is curved upwards). The vertical distance H from the upper surface of the mounting stage 5 to the outer edge of the optical film F (or, in the case of a rectangular optical film F, the vertical distance to its four corners) is measured. The distance H is measured by visually reading the scale of a vertically extending scale erected near the outer edge of the optical film F. The maximum value of distance H is taken as the curl value. In other words, when the optical film F is placed on a flat surface (the upper surface of the mounting stage 5) with its lower side convex, the vertical distance between the lowest point of the optical film F (the point at the same position as the upper surface of the mounting stage 5) and the highest point of the optical film F is taken as the curl value. If the curl value is below a specified threshold, the optical film F is considered a qualified product; if it exceeds the threshold, the optical film F is considered a defective product.

[0006] exist Figure 1 In the conventional measurement method shown, the operator performs the measurements manually, thus increasing the measurement time. Therefore, from the perspective of optical film manufacturing efficiency, it is difficult to measure all optical films, necessitating extraction and measurement, which may result in defective products being released. Furthermore, since the measurements are performed manually, there is a possibility of deviations in the measurement results from each operator.

[0007] Therefore, it is desirable to use optical sensors to automatically determine the curl value of optical films.

[0008] Figure 2 This is a side view (viewed from a horizontal direction orthogonal to the transport direction of the optical film) schematically illustrating a conventional measuring device for automatically measuring the curl value of an optical film using an optical sensor. Furthermore, in Figure 2 In the diagram, the X direction represents the horizontal direction, which is the transport direction of the optical film F; the Y direction represents the horizontal direction orthogonal to the X direction; and the Z direction represents the vertical direction (the thickness direction of the optical film F). (The following will discuss...) Figure 5 The same applies.

[0009] like Figure 2As shown, in conventional measuring apparatus 100', a reflective optical sensor equipped with a projector 11' and a receiver 12' is generally used. Specifically, for example, as the optical sensor, a sensor performing a light-cutting method as a type of triangulation is used; as the projector 11', a laser light source emitting a linear laser L' extending along the Y direction is used; and as the receiver 12', a region sensor camera with imaging elements such as CCD or CMOS arranged in a matrix is ​​used. Then, the laser L' is projected downwards in the Z direction from the projector 11' toward the upper surface of the optical film F. The receiver 12', having a viewing axis tilted relative to the Z direction, receives the reflected light of the laser L' reflected from the upper surface of the optical film F (the receiver 12' captures the laser L' illuminating the optical film F). Based on the captured image, the deformation state of the linear laser L' is analyzed, thereby determining the Z-direction position of the upper surface of the optical film F along the Y direction. The optical film F is placed on a belt conveyor 3 and transported along the X direction; therefore, from such... Figure 2 As shown in (a), the front end (downstream end in the transport direction) FT of the optical film F is positioned directly below the projector 11'. Figure 2 With the rear end (upstream end in the transport direction) FR of the optical film F positioned directly below the projector 11' as shown in (b), the Z-direction position of the upper surface of the optical film F is continuously measured, and the curl value of the optical film F can be calculated based on the measurement results. Specifically, for example, the curl value can be calculated based on the difference between the highest Z-direction position of the upper surface of the optical film F and the Z-direction position of the upper surface of the conveyor belt constituting the belt conveyor 3.

[0010] In the conventional measuring device 100' with the above-described structure, since a reflective optical sensor is used, therefore... Figure 2 As shown in (a), when the front end FT of the optical film F, which is tilted and curled (warped) in the upstream direction of the transport direction in its normal direction, is located directly below the projector 11', the reflected light of the laser L' with sufficient light intensity is easily reflected towards the receiver 12', so the position of the upper surface of the optical film F in the Z direction can be measured with relatively high accuracy.

[0011] However, as Figure 2 As shown in (b), when the rear end FR of the optical film F, which is curled up and tilted downstream in the transport direction along its normal direction, is located directly below the projector 11', depending on the surface condition of the optical film F, sometimes it does not reflect enough reflected light from the laser L' toward the receiver 12'. Therefore, in this case, the accuracy of measuring the position of the upper surface of the optical film F in the Z direction deteriorates. In addition, when the curling is extremely large, sometimes the reflected light cannot be received by the receiver 12', making it impossible to measure the position of the upper surface of the optical film F in the Z direction.

[0012] Thus, in conventional curl measurement methods that use reflective optical sensors, there is a problem that the curl value cannot be measured with high precision due to the influence of the curl direction and surface condition of the optical film.

[0013] For example, Patent Document 1 proposes a method for analyzing the curling of sheet-like (circular) optical films, but as a measuring device for determining the vertical distance to the optical film, a reflective optical sensor is used (paragraph 0044 of Patent Document 1). Figure 1 This may lead to the same problems as the previous methods for measuring curl.

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: Japanese Patent Application Publication No. 2020-85754 Summary of the Invention

[0017] The technical problem that the invention aims to solve

[0018] The present invention was made to solve the problems of the prior art mentioned above. Its objective is to provide a method for measuring the curl value of an optical film with high precision in a short time, and a method for manufacturing an optical film using the method.

[0019] Technical solutions for solving technical problems

[0020] To address the aforementioned issues, the present invention provides a method for measuring the curl of an optical film, using an optical sensor equipped with a projector and a receiver to measure a curl value representing the degree of curl of a sheet-like optical film. The method includes: a configuration step in which the projector is positioned on one side of the optical film, and the receiver is positioned on the other side of the optical film, opposite the projector, across the optical film; a projection and reception step in which a beam of light extending in a vertical direction is projected toward the optical film using the projector, and the receiver receives light transmitted through the beam that is not blocked by the optical film; and a curl value calculation step in which the curl value of the optical film is calculated based on the vertical length of the transmitted light.

[0021] In this invention, "side of the optical film" refers to the direction along the in-plane direction of the optical film (assuming a flat optical film that has not curled).

[0022] In addition, in this invention, "curl value" refers to the vertical distance between the lowest point and the highest point of the optical film when the optical film is placed on a flat surface with its lower side protruding.

[0023] According to the curl measurement method of the present invention, in the configuration step, a projector and a receiver are respectively configured opposite each other on one side and the other side of the optical film, separated by the optical film. Furthermore, in the projection and receiving steps, a beam of light extending in the vertical direction is projected towards the optical film using the projector, and the light receiver receives the light in the beam that is not blocked by the optical film and is transmitted through it. The vertical length of this transmitted light varies depending on the curl value of the optical film. Specifically, if the curl (warping at the end) of the optical film increases (the curl value increases), the vertical length of the light in the beam that is blocked by the optical film and is not transmitted through it increases, and therefore the vertical length of the transmitted light decreases. If the curl of the optical film decreases (the curl value decreases), the vertical length of the light in the beam that is blocked by the optical film and is not transmitted through it decreases, and therefore the vertical length of the transmitted light increases. Therefore, in the curl value calculation step, the curl value of the optical film can be calculated based on the vertical length of the transmitted light.

[0024] According to the curl measurement method of the present invention, since an optical sensor is used, automation is possible, and the curl value can be measured in a shorter time compared to manual measurement by an operator. Furthermore, as the optical sensor, a transmissive optical sensor is used, which includes a projector that projects a light beam extending in the vertical direction and a receiver that receives light transmitted through the unobstructed portion of the light beam projected from the projector. Therefore, it is less susceptible to the influence of the curl direction and surface condition of the optical film, and the curl value can be measured with high accuracy.

[0025] The curl measurement method of the present invention can also perform the light projection and light reception process when both the optical film and the optical sensor are stationary. Specifically, for example, the in-plane of the optical film is divided into multiple regions, and a configuration process is performed such that the optical film and the optical sensor are positioned corresponding to one region. For that one region, the light projection and light reception process and the curl value calculation process are performed while both the optical film and the optical sensor are stationary, and the curl value for that region is measured. Then, after performing a configuration process in which the optical film and the optical sensor are relatively moved to positions corresponding to other regions, the light projection and light reception process and the curl value calculation process are similarly performed while both the optical film and the optical sensor are stationary, and the curl value for those other regions is measured. It is considered that the maximum curl value of each region obtained by repeatedly performing this process on all regions is taken as the final curl value of the optical film. Alternatively, it is also considered that multiple optical sensors corresponding to multiple regions are used so that the processes can be performed on multiple regions simultaneously.

[0026] However, in the former case, although it can be completed in a shorter time compared to manual measurement, it requires repeated relative movement and stopping of the optical film and optical sensor, thus the measurement of the curl value takes time. Furthermore, in the latter case, the cost of the device increases due to the use of multiple optical sensors.

[0027] As described above, in order to avoid the problem of performing the light projection and light receiving process when both the optical film and the optical sensor are stationary, it is preferable that, in the light projection and light receiving process, the optical film and the optical sensor are moved relative to each other in the in-plane direction of the optical film (i.e., the optical film is moved while the optical sensor is stationary, or the optical sensor is moved while the optical film is stationary, or the optical film and the optical sensor are moved in opposite directions), while the light projector projects the light beam and the light receiver receives the transmitted light.

[0028] According to the preferred method described above, the light projection and light reception process is performed while the optical film and optical sensor are moved relative to each other. Therefore, it is not necessary to repeatedly move and stop the relative movement of the optical film and optical sensor, which can further shorten the measurement time of the curl value. It is not necessary to use multiple optical sensors, thus reducing the cost of the device.

[0029] In the preferred method described above, during the light projection and light receiving process, when the optical sensor is stationary while the optical film is moved, if the moving speed is too high, the front end of the optical film (the downstream end in the moving direction) will float up due to air resistance, and the curl value may be measured to be larger than the true value.

[0030] To avoid this situation, it is preferable that, in the light projection and light receiving process, the optical sensor is kept stationary, while the optical film is moved inward at a speed of 30 m / min or less, the light projector projects the light beam, and the light receiver receives the transmitted light.

[0031] According to the preferred method described above, by moving the optical film at a speed of 30 m / min or less in the in-plane direction, the lifting of the optical film tip can be suppressed, and the accuracy of the curl value measurement can be maintained. It should be noted that if the moving speed of the optical film is too low, the measurement time of the curl value will be longer; therefore, it is preferable to move it at a speed of 5 m / min or more.

[0032] In the preferred method described above, as a method of keeping the optical sensor stationary while moving the optical film during the light projection and light receiving process, it is considered to transport the optical film by placing it on the conveyor belt of a belt conveyor. In this case, if the in-plane flatness of the conveyor belt, especially the in-plane flatness of the area of ​​the conveyor belt on which the optical film is placed during the light projection and light receiving process, is poor, the posture of the optical film will change during transport, which may deteriorate the accuracy of the curl value measurement.

[0033] Therefore, it is preferable that, in the light projection and light receiving process, the optical sensor is kept stationary, while the optical film is placed on the conveyor belt of the belt conveyor for transport, and the light beam is projected using the light projector, and the transmitted light is received using the light receiver, so that the in-plane flatness of the area of ​​the conveyor belt on which the optical film is placed is less than 1.5 mm when the light projection and light receiving process is performed.

[0034] In the preferred method described above, "in-plane flatness" refers to the difference between the maximum and minimum values ​​of the vertical distance from the same vertical position that serves as a reference to multiple points within the area of ​​the conveyor belt carrying the optical film during the light projection and light reception process.

[0035] According to the preferred method described above, the in-plane flatness of the area of ​​the conveyor belt carrying the optical film is small, less than 1.5 mm (good in-plane flatness), when performing the light projection and light receiving process. Therefore, the posture of the optical film is difficult to change during transport, and the accuracy of the curl value measurement can be maintained.

[0036] As described above, when an optical film is transported on the conveyor belt of a belt conveyor, in order to reduce the in-plane flatness of the area of ​​the conveyor belt on which the optical film is placed during the light projection and light reception process, it is considered to configure a flat support plate that contacts the lower surface of the area of ​​the conveyor belt.

[0037] Therefore, preferably, in the light projection and light receiving process, while the optical film is being transported on the conveyor belt of the belt conveyor, the light beam is projected using the light projector and the transmitted light is received using the light receiver, a flat support plate is disposed below the area of ​​the conveyor belt on which the optical film is placed during the light projection and light receiving process, and the support plate is in contact with the lower surface of the area of ​​the conveyor belt.

[0038] In the preferred method described above, "flat support plate" refers to a support plate that is at least flat with the contact surface of the conveyor belt.

[0039] According to the preferred method described above, during the light projection and light reception process, a flat support plate disposed below the area of ​​the conveyor belt on which the optical film is placed contacts the lower surface of the area of ​​the conveyor belt. Therefore, the in-plane flatness of the area of ​​the conveyor belt can be easily reduced along the flat support plate.

[0040] In addition, to solve the above-mentioned problems, the present invention also provides a method for manufacturing an optical film, comprising: a manufacturing step for manufacturing a sheet-like optical film; an inspection step for inspecting the optical film; and a sorting step for sorting the optical film. In the inspection step, the curling measurement method is performed, and the optical film is determined to be a qualified or unqualified part based on the measured curling value of the optical film. In the sorting step, the optical film is sorted according to whether it is determined to be a qualified or unqualified part.

[0041] According to the manufacturing method of the present invention, the aforementioned curl measurement method is performed in the inspection process, thereby automating the inspection process. The subsequent sorting process can also be automated using a known sorting mechanism. Therefore, the inspection (curl value measurement) and sorting of qualified / unqualified parts of the optical film can be performed continuously and automatically, improving the manufacturing efficiency of the optical film. Furthermore, by performing the aforementioned curl measurement method in the inspection process, qualified and unqualified parts can be determined with high accuracy, reducing the possibility of incorrect sorting in the sorting process.

[0042] Invention Effects

[0043] According to the present invention, the curl value of the optical film can be measured with high precision in a short time, thereby improving the manufacturing efficiency of the optical film. Attached Figure Description

[0044] Figure 1 This diagram is an example illustrating a conventional method for measuring curl value.

[0045] Figure 2 This is a side view schematically illustrating a conventional measuring device for automatically measuring the curl value of an optical film using an optical sensor.

[0046] Figure 3 This is a flowchart illustrating the general steps of a method for manufacturing an optical film according to an embodiment of the present invention.

[0047] Figure 4 This is a schematic cross-sectional view illustrating a general configuration example of an optical film manufactured by a manufacturing method according to an embodiment of the present invention.

[0048] Figure 5 It is a schematic representation of execution. Figure 3 The diagram shows a schematic example of the structure of the inspection device for inspection procedure ST2. Detailed Implementation

[0049] Hereinafter, with appropriate reference to the accompanying drawings, a method for measuring the curl of an optical film according to an embodiment of the present invention and a method for manufacturing an optical film using the method will be described. In this embodiment, the case where the optical film is a polarizing plate will be used as an example for description. It should be noted that the figures are for reference only, and please note that the dimensions, scale, and shape of the constituent elements of the optical film and device shown in the figures may sometimes differ from the actual dimensions.

[0050] Figure 3 This is a flowchart illustrating the general steps of the method for manufacturing the optical film according to this embodiment.

[0051] like Figure 3 As shown, the manufacturing method of this embodiment includes a manufacturing step ST1, an inspection step ST2, and a sorting step ST3. The following describes each step ST1 to ST3.

[0052] <Manufacturing Process ST1>

[0053] In manufacturing process ST1, sheet-like optical thin films are manufactured.

[0054] Figure 4 This is a cross-sectional view schematically illustrating a general configuration example of an optical film manufactured by the manufacturing method of this embodiment.

[0055] like Figure 4 As shown, the optical film F of this embodiment includes a polarizing film F1, a phase difference film F2, an adhesive layer F3, a release liner F4, and a surface protective film F5.

[0056] [Polarizing film F1]

[0057] The polarizing film F1 is composed of a polarizer F11 and protective films F12 and F13 protecting the polarizer F11. In this embodiment, protective films F12 and F13 are attached to both sides of the polarizer F11, but it is not limited to this; as long as a protective film is attached to at least one side of the polarizer F11, it is acceptable.

[0058] (Polarizer F11)

[0059] Polarizer F11 is typically made of a resin film containing dichroic material.

[0060] As the 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 copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers are obtained by saponifying ethylene-vinyl acetate copolymers.

[0062] Examples of dichroic substances contained in resin films include iodine and organic dyes. These can be used alone or in combination of two or more. Iodine is preferred.

[0063] The resin film can be a single-layer resin film or a laminate of two or more layers.

[0064] As a specific example of a polarizer composed of a single-layer resin film, a polarizer in which the PVA-based resin film has undergone iodine staining and stretching treatment (typically uniaxial stretching treatment) can be cited. Iodine staining treatment is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after staining or during staining. Alternatively, staining 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.

[0065] As a specific example of a polarizer composed of a laminate, examples include a polarizer 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, drying it to form a PVA-based resin layer on the resin substrate, obtaining a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing the laminate to form a polarizer from the PVA-based resin layer. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Furthermore, stretching may, as needed, include air stretching of the laminate at a high temperature (e.g., above 95°C) before stretching in the aqueous boric acid solution. The resulting 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 for the purpose can be laminated on the peeled surface. Details of such a method for manufacturing a polarizer are described, for example, in Japanese Patent Application Publication No. 2012-73580. The entire contents of that publication are incorporated herein by reference.

[0066] The thickness of the polarizer F11 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.

[0067] Polarizer F11 preferably exhibits absorption dichroism at any wavelength within the range of 380 nm to 780 nm. The single-unit transmittance of polarizer F11 is preferably 40.0% to 45.0%, more preferably 41.5% to 43.5%. The degree of polarization of polarizer F11 is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0068] In manufacturing process ST1, a strip-shaped resin film is used as the raw material film. The raw material film is transported along the length direction (MD direction) while being immersed in various treatment baths to perform various treatments such as dyeing treatment and stretching treatment, thereby manufacturing a strip-shaped polarizer F11 with the above structure.

[0069] (Protective film F12, F13)

[0070] As protective films F12 and F13, any suitable resin film can be used. Examples of resin film forming materials include (meth)acrylic resins, cellulose resins such as diacetylcellulose and triacetylcellulose, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymers thereof. It should be noted that "(meth)acrylic resins" refers to acrylic resins and / or methacrylic resins. The forming materials of protective films F12 and F13 can be the same or different.

[0071] The thickness of the protective films F12 and F13 is typically 10 μm to 100 μm, preferably 20 μm to 40 μm. The thicknesses of the protective films F12 and F13 can be the same or different.

[0072] On the surfaces of the protective films F12 and F13 opposite to the polarizer F11, surface treatments such as hard coating, anti-reflective treatment, anti-adhesion treatment, and anti-glare treatment can be applied as needed. Furthermore / or, on the surfaces of the protective films F12 and F13 opposite to the polarizer F11, treatments can be applied to improve visual recognition when viewed through polarized sunglasses (typically, treatments to impart (elliptical) polarization or to impart ultra-high phase difference). It should be noted that when surface treatments are applied to form the surface treatment layer, the thickness of the protective films F12 and F13 includes the thickness of the surface treatment layer.

[0073] It should be noted that protective films F12 and F13 are laminated onto polarizer F11 via any suitable adhesive layer (not shown). Typical adhesives constituting the adhesive layer include PVA-based adhesives or ray-cured adhesives.

[0074] In manufacturing process ST1, a strip-shaped polarizing film F1 is manufactured by attaching strip-shaped protective films F12 and F13 having the above-described structure to a strip-shaped polarizing film F11.

[0075] [Phase difference film F2]

[0076] The retardation film F2 can be, for example, a compensation plate that provides a wide viewing angle, or a retardation plate (circular polarizer) used in conjunction with a polarizing film to generate circularly polarized light, such as a 1 / 2 wavelength plate or a 1 / 4 wavelength plate. The thickness of the retardation film F2 is, for example, 1 to 200 μm.

[0077] It should be noted that the phase retardation film F2 is laminated onto the polarization film F1 (protective film F13) via any suitable adhesive layer or bonding agent layer (not shown). Typical examples of adhesives constituting the adhesive layer include PVA-based adhesives or ray-cured adhesives.

[0078] In manufacturing process ST1, a strip-shaped phase retardation film F2 having the above-described structure is bonded to one side (protective film F13) of a strip-shaped polarizing film F1, thereby manufacturing a strip-shaped optical laminate.

[0079] [Adhesive layer F3]

[0080] The adhesive layer F3 is formed by applying adhesive to one side of the peeling liner F4, and then drying and curing the applied adhesive by heating it in an oven or similar means.

[0081] The heating temperature of the adhesive is preferably set in the range of 100°C to 160°C, more preferably in the range of 140°C to 160°C. It is preferably heated at this temperature for 20 seconds to 3 minutes, more preferably for 1 minute to 3 minutes.

[0082] Specific examples of adhesives forming adhesive layer F3 include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, quantity, combination, and proportion of monomers in the base resin forming the adhesive, as well as the amount of 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. Detailed information about the adhesive constituting adhesive layer F3 is described, for example, in Japanese Patent Application Publication No. 2014-115468, which is incorporated herein by reference. The thickness of adhesive layer F3 can be, for example, set to 10 μm to 100 μm.

[0083] [Peeling Gasket F4]

[0084] As the release liner F4, any suitable release liner can be used. Specific examples include plastic films, nonwoven fabrics, or paper with a surface coating applied using 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 release liner F4 can be, for example, set from 10 μm to 100 μm.

[0085] In manufacturing step ST1, while conveying the strip-shaped release liner F4 with the above-described configuration along its length direction (MD direction), an adhesive is applied. The applied adhesive is then dried by heating in an oven or similar source, thereby curing it to form the aforementioned adhesive layer F3. Then, the release liner F4 is bonded to a strip-shaped optical laminate (a laminate of polarizer F1 and retardation film F2) via the adhesive layer 3 formed on the strip-shaped release liner F4. Specifically, the adhesive layer F3 side of the strip-shaped release liner F4 (the release liner F4 with adhesive layer 3) is bonded to one side of the strip-shaped optical laminate (retardation film F2). Thus, a strip-shaped optical laminate containing polarizer F1, retardation film F2, adhesive layer F3, and release liner F4 is manufactured.

[0086] [Surface Protective Film F5]

[0087] The surface protective film F5 typically comprises a substrate and an adhesive layer. In this embodiment, the thickness of the surface protective film F5 is, for example, 30 μm or more. The upper limit of the thickness of the surface protective film F5 is, for example, 150 μm. It should be noted that, in this specification, "the thickness of the surface protective film" refers to the total thickness of the substrate and the adhesive layer.

[0088] 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.

[0089] Any suitable adhesive can be used as the adhesive that forms the adhesive layer. Examples of base resins for the adhesive include acrylic resins, styrene resins, silicone resins, urethane resins, and rubber resins.

[0090] In manufacturing step ST1, a strip-shaped surface protective film F5 is bonded to a strip-shaped optical laminate (a laminate of polarizer F1, retardation film F2, adhesive layer F3, and release liner F4). Specifically, the strip-shaped surface protective film F5 is bonded to the side of the optical laminate (the laminate of polarizer F1, retardation film F2, adhesive layer F3, and release liner F4) opposite to the side where the release liner F4 is bonded. Thus, a strip-shaped optical film (polarizer) F is manufactured.

[0091] Finally, in manufacturing process ST1, the long strip-shaped optical film F is cut into sizes and shapes (e.g., rectangles) appropriate for the application, thereby manufacturing sheet-shaped optical film F.

[0092] <Inspection Procedure ST2>

[0093] In inspection step ST2, the sheet-like optical thin film F manufactured in manufacturing step ST1 is inspected. For example... Figure 3 As shown, inspection step ST2 includes a configuration step ST21, a light projection and reception step ST22, a curl value calculation step ST23, and a judgment step ST24. The configuration step ST21, the light projection and reception step ST22, and the curl value calculation step ST23 in inspection step ST2 correspond to the curl measurement method of this embodiment.

[0094] Figure 5 This is a schematic diagram illustrating a general structural example of an inspection device that performs inspection procedure ST2. Figure 5 (a) is a side view of the inspection device (viewed from a horizontal direction orthogonal to the transport direction of the optical film F). Figure 5 (b) is a front view of the area around the optical sensor of the inspection device (viewed from the transport direction of the optical film F).

[0095] like Figure 5 As shown, the inspection apparatus 100 of this embodiment includes a transmissive optical sensor 1, which comprises: a projector 11 that projects a light beam extending along the Z direction (vertical direction); and a receiver 12 that is arranged opposite to the projector 11 with respect to the object being measured (optical film F in this embodiment), and receives light transmitted from the light beam L that is not blocked by the object being measured (optical film F in this embodiment). The projector 11 may be, for example, an LED light source that projects parallel light, and the receiver 12 may be, for example, a line sensor camera with imaging elements such as CCD or CMOS arranged in a straight line extending along the Z direction. For example, the Keyence Corporation's "High-Speed, High-Precision Dimensioning Instrument LS-9120" can be used as an optical sensor 1 with such a structure.

[0096] Furthermore, the inspection device 100 of this embodiment includes a computing device 2 that is connected to the optical sensor 1 (photodetector 12) and performs predetermined computational processing. For example, a computer equipped with a program for performing the predetermined computational processing can be used as the computing device 2.

[0097] Furthermore, the inspection device 100 of this embodiment includes a belt conveyor 3 for transporting the optical film F in the in-plane direction (X direction in this embodiment). The belt conveyor 3 has a pair of rollers 31 and a conveyor belt 32 mounted between the pair of rollers 31.

[0098] Furthermore, the inspection device 100 of this embodiment includes a flat support plate 4 arranged in contact with the lower surface of the conveyor belt 32. The support plate 4 is formed, for example, from a sheet of metal with at least a flat upper surface.

[0099] The following is for reference only. Figure 5 The following describes each step ST21 to ST24 of the inspection process ST2 performed by the inspection device 100 having the above structure.

[0100] [Configuration process ST21]

[0101] In the configuration step ST21, the light emitter 11 of the optical sensor 1 and the light emitter 11 of the light receiver 12 are configured on one side of the optical film F (in the Y direction in this embodiment). Figure 5 (b) In the example shown, the left side), the receiver 12 is positioned on the other side of the optical film F (in the Y direction in this embodiment) opposite to the projector 11, separated by the optical film F. Figure 5 (b) shows the example on the right).

[0102] Specifically, in this embodiment, during the light emission and reception process ST22 described later, the optical sensor 1 is kept stationary, while the optical film F is placed on the conveyor belt 32 of the belt conveyor 3 for transport. Therefore, the light emitter 11 and the light receiver 12 are arranged in a fixed position facing each other in the Y direction across the conveyor belt 32. Thus, from the time the optical film F, transported by the belt conveyor 3, reaches the position where the optical sensor 1 is arranged from the time the optical film F, transported by the belt conveyor 3, reaches the position where the optical sensor 1 is arranged from the time the optical film F, transported by the belt conveyor 3, reaches the position where the optical sensor 1 is arranged from the time the optical film F, transported by the belt conveyor 3, reaches the position where the optical sensor 1 is arranged from the time the optical film F, transported by the belt conveyor 3, reaches the position where the optical sensor 1 is arranged from the time the optical film F, transported by the belt conveyor 3, reaches the position where the optical sensor 1 is arranged from the time the optical film F, transported by the belt conveyor 3, reaches the position where the optical sensor 1 is arranged from the time the optical film F, reaches the position where the optical sensor 1 is arranged.

[0103] It should be noted that the optical film F is preferably placed on the conveyor belt 32 with its lower side protruding. When the optical films F are batch products with the same structure, the direction of curling tends to be roughly the same. Therefore, they can also be pre-collected in a storage container (not shown) with their lower sides protruding, and the optical films F can be discharged from the storage container in sequence and placed on the conveyor belt 32.

[0104] [Light emitting and receiving process ST22]

[0105] In the light projection and light receiving process ST22, a light projector 11 projects a light beam L extending in the Z direction toward the optical film F, and a light receiver 12 receives the light in the light beam L that is not blocked by the optical film F and passes through (transmitted light).

[0106] Specifically, in this embodiment, the optical sensor 1 is kept stationary (maintained in a fixed position), while the optical film F is placed on the conveyor belt 32 of the belt conveyor 3 for transport, and the light beam L is projected using the light projector 11 and the transmitted light is received using the light receiver 12.

[0107] Here, if the conveying speed of the belt conveyor 3 (equivalent to the movement speed of the optical film F in the X direction) is too high, the leading edge FT of the optical film F will float due to air resistance. As a result, the curling value calculated in the curling value calculation step ST23 described later may be measured as greater than the true value. To avoid this situation, it is preferable to set the conveying speed of the belt conveyor 3 to 30 m / min or less, preferably 20 m / min or less, more preferably 15 m / min or less, and even more preferably 10 m / min or less. In addition, if the conveying speed of the belt conveyor 3 is set too low, the time required to measure the curling value (the time required to perform the light emission and reception step ST22 and the curling value calculation step ST23 described later) will become longer. Therefore, it is preferable to set the conveying speed to 5 m / min or more.

[0108] Furthermore, if the in-plane flatness of the conveyor belt 32 of the belt conveyor 3, especially in the region S of the conveyor belt 32 on which the optical film F is placed during the light projection and light receiving process ST22 (i.e., the region of the conveyor belt 32 on which the optical film F is placed from the position where the optical sensor 1 is located at the front end FT of the optical film F to the position where the optical sensor 1 is located at the rear end FR of the optical film F is removed from the position where the optical sensor 1 is located), is poor, the posture of the optical film F will change during conveying, and the accuracy of the curl value calculated in the curl value calculation process ST23 described later may deteriorate.

[0109] To avoid this situation, the in-plane flatness of region S of conveyor belt 32 (the difference between the maximum and minimum values ​​of the distances in the Z direction from the same Z-direction position serving as a reference to multiple points (e.g., nine points equally spaced in a matrix) within region S of conveyor belt 32) is set to 1.5 mm or less, preferably 1.0 mm or less, more preferably 0.8 mm or less, and even more preferably 0.5 mm or less. This in-plane flatness can be evaluated, for example, by arranging multiple laser rangefinders (not shown) at the same Z-direction position above conveyor belt 32 and measuring the distance to the upper surface of conveyor belt 32 without the optical film F placed thereon using each laser rangefinder.

[0110] To reduce the in-plane flatness of region S of the conveyor belt 32, it is also considered to increase the tension of the conveyor belt 32 by adjusting the separation distance of a pair of rollers 31 (the distance in the conveying direction of the belt conveyor 3), or to arrange multiple other rollers between a pair of rollers 31, but this alone may not be sufficient. Therefore, in this embodiment, the tension is increased to contact the lower surface of the conveyor belt 32, specifically the lower surface of region S of the conveyor belt 32 (in... Figure 5 In the example shown, a flat support plate 4 is arranged in a manner that contacts a region slightly larger than region S. As a result, the in-plane flatness of region S of the conveyor belt 32 can be easily reduced (to 1.5 mm or less) along the flat support plate 4.

[0111] Furthermore, in order to calculate the curl value in the curl value calculation step ST23 described later, the emission of light by the emitter 11 and the reception of light by the receiver 12 are performed only during the period from when the front end FT of the optical film F reaches the position where the optical sensor 1 is located until the rear end FR of the optical film F leaves the position where the optical sensor 1 is located. Therefore, for example, it is preferable to provide a known proximity sensor (not shown) for detecting the moment when the front end FT of the optical film F reaches the position where the optical sensor 1 is located and the moment when the rear end FR of the optical film F leaves the position where the optical sensor 1 is located. The emission of light by the emitter 11 and the reception of light by the receiver 12 are performed only during the period from when the arrival of the front end FT is detected by the proximity sensor until the departure of the rear end FR is detected.

[0112] [Curling value calculation process ST23]

[0113] In the curl value calculation step ST23, the curl value of the optical film F is calculated based on the length of the transmitted light in the Z direction obtained by performing the light projection and light receiving step ST22.

[0114] Specifically, such as Figure 5As shown in (b), when the optical film F is not mounted on the conveyor belt 32, the light receiver 12 receives transmitted light with a length of L0 in the Z direction. When the optical film F is mounted on the conveyor belt 32, the light receiver 12 receives transmitted light with a length of L1 in the Z direction. The light receiver 12 calculates the value of L0-L1 and outputs it to the processing unit 2. More specifically, when the light receiver 12 is a line sensor camera as described above, the number of imaging elements receiving a predetermined amount of light increases when the optical film F is not mounted on the conveyor belt 32, and the number of imaging elements receiving a predetermined amount of light decreases when the optical film F is mounted on the conveyor belt 32. Therefore, the value obtained by converting the difference in the number of elements into length (i.e., the value of L0-L1) is output to the processing unit 2. The values ​​of L0-L1 are sequentially output to the processing unit 2 according to the scanning rate of the photodetector 12 (line sensor camera) from the time the optical film F reaches the position where the optical sensor 1 is located until the rear end FR of the optical film F disengages from the position where the optical sensor 1 is located. The value of LO is constant, but the value of L1 varies according to the degree of curling of the optical film F, therefore the value of L0-L1 also varies according to the degree of curling of the optical film F.

[0115] Then, the arithmetic unit 2 calculates the maximum value of the L0-L1 values ​​sequentially input from the light receiver 12 as the curl value.

[0116] [Judgment Process ST24]

[0117] In the judgment process ST24, the optical film F is determined to be a qualified or unqualified part based on the curl value measured (calculated) in the curl value calculation process ST23.

[0118] Specifically, the computing device 2 compares the calculated curl value of the optical film F with a preset stored threshold (e.g., 5 mm). If the curl value is below the threshold, the optical film F is determined to be a good product; if it exceeds the threshold, the optical film F is determined to be a defective product.

[0119] <Sorting Process ST3>

[0120] In the sorting process ST3, the optical film F is sorted according to whether it is a good product or a defective product as determined in the judgment process ST24 of the inspection process ST2.

[0121] Specifically, for example, a sorting mechanism (not shown) is arranged downstream of the belt conveyor 3, operating based on control signals from the computing device 2, and the optical film F is sorted by this sorting mechanism. For example, if the optical film F is determined to be a good product, the sorting mechanism receives a control signal indicating that it is a good product from the computing device 2, and transfers the optical film F, which has been transported to the sorting mechanism via the belt conveyor 3, to a recycling container (not shown) for good products for recycling. On the other hand, if the optical film F is determined to be a defective product, the sorting mechanism receives a control signal indicating that it is a defective product from the computing device 2, and transfers the optical film F, which has been transported to the sorting mechanism via the belt conveyor 3, to a recycling container (not shown) for defective products for recycling.

[0122] As a sorting mechanism, it can adopt various well-known structures, so detailed descriptions are omitted here.

[0123] According to the above-described method for measuring the curl of the optical film F (configuration step ST21, light projection and light reception step ST22, and curl value calculation step ST23), since the optical sensor 1 is used, it can be automated, and the curl value can be measured in a shorter time compared to manual measurement by an operator. In addition, as the optical sensor 1, a transmissive optical sensor 1 is used, which has a light projector 11 that projects a light beam L extending in the vertical direction (Z direction) and a light receiver 12 that receives the light transmitted through the unblocked light beam L projected from the light projector 11. Therefore, it is less affected by the curl direction and surface condition of the optical film F, and the curl value can be measured with high accuracy.

[0124] Furthermore, according to the manufacturing method of the optical film F in this embodiment, the curl measurement method of this embodiment is performed in the inspection step ST2, thus automating the inspection step ST2. The subsequent sorting step ST3 can also be automated using a sorting mechanism. Therefore, the inspection (curl value measurement) and sorting of good / defective products of the optical film F can be performed continuously and automatically, improving the manufacturing efficiency of the optical film F. Additionally, by performing the curl measurement method of this embodiment in the inspection step ST2, good and defective products can be accurately determined, reducing the possibility of incorrect sorting in the sorting step ST3.

[0125] Furthermore, in this embodiment, the example described is that the optical film F is placed on the conveyor belt 32 of the belt conveyor 3 for transport in the light projection and light receiving process ST22. However, the present invention is not limited to this, and other structures that allow the optical film F to move in its in-plane direction can also be used.

[0126] Alternatively, in the light projection and light receiving process ST22, the optical film F can be moved in the in-plane direction without keeping the optical sensor 1 stationary. Instead, a structure can be adopted in which the optical film F is stationary and the optical sensor 1 is moved in the in-plane direction of the optical film F using a single-axis worktable, or the optical film F and the optical sensor 1 can be moved in opposite directions in the in-plane direction of the optical film F.

[0127] Alternatively, the light-emitting and light-receiving process ST22 can be performed while both the optical film F and the optical sensor 1 are stationary. Specifically, for example, the in-plane of the optical film F is divided into multiple regions, and a configuration process ST21 is performed with the optical film F and the optical sensor 1 positioned corresponding to one region. For that region, while both the optical film F and the optical sensor 1 are stationary, the light-emitting and light-receiving process ST22 and the curling value calculation process ST23 are performed to measure the curling value for that region. Afterwards, after performing the configuration process ST21, which moves the optical film F and the optical sensor 1 relatively to positions corresponding to other regions, the light-emitting and light-receiving process ST22 and the curling value calculation process ST23 are similarly performed while both the optical film F and the optical sensor 1 are stationary to measure the curling values ​​for those other regions. Consider using the maximum curling value of each region obtained by repeatedly performing this process on all regions as the final curling value of the optical film F. Alternatively, multiple optical sensors 1 corresponding to multiple regions can be used so that processes ST21 to ST23 can be performed simultaneously on multiple regions.

[0128] Hereinafter, we will describe an example (Examples 1 to 4) of the results of measuring the curl value of the optical film F using the curl measurement method of this embodiment and an example (Comparative Examples 1 and 2) of the results of measuring the curl value of the optical film F using a conventional curl measurement method.

[0129] The optical film F used in Examples 1-4 and Comparative Examples 1 and 2 all have the following configuration (refer to...). Figure 4 ).

[0130] (1) Dimensions of optical film F: longitudinal (transport direction) length 160mm, transverse (horizontal direction orthogonal to the transport direction) length 230mm, thickness 216μm

[0131] (2) Surface protective film F5: It consists of a substrate formed of polyethylene terephthalate resin and an adhesive layer formed of acrylic adhesive, with a total thickness of 60 μm for the substrate and the adhesive layer.

[0132] (3) Protective film F12: formed of triacetylcellulose, with a thickness of 50 μm

[0133] (4) Polarizer F11: made of polyvinyl alcohol, with a thickness of 20 μm

[0134] (5) Protective film F13: formed of triacetylcellulose, 20 μm thick

[0135] (6) Phase retardation film F2: formed of cyclic olefin resin, with a thickness of 6 μm

[0136] (7) Adhesive layer F3: formed by acrylic adhesive, with a thickness of 20 μm

[0137] (8) Release liner F4: made of polyethylene terephthalate, 40 μm thick

[0138] <Example 1>

[0139] In Example 1, while transporting the optical film F using a belt conveyor 3 with a conveying speed set to 5 m / min, the light projection and light reception process ST22 is performed, and the curl value is calculated in the curl value calculation process ST23. The transport direction of the optical film F is changed to four directions (i.e., the placement direction of the optical film F on the conveyor belt 32 is changed to four directions at 90° intervals), and this is repeated 10 times for each direction, for a total of 40 curl values ​​are measured. In Example 1, by configuring the flat support plate 4 to contact the lower surface of region S of the conveyor belt 32, the in-plane flatness of the conveyor belt 32 is 0.5 mm.

[0140] <Example 2>

[0141] In Example 2, except that the conveying speed was set to 17 m / min, the curl value of the optical film F was measured in the same manner as in Example 1.

[0142] <Example 3>

[0143] In Example 3, except that the conveying speed was set to 27 m / min, the curl value of the optical film F was measured in the same manner as in Example 1.

[0144] <Example 4>

[0145] In Example 4, the curl value of the optical film F was measured in the same manner as in Example 2, except that the flat support plate 4 was not provided. In Example 4, the in-plane flatness of the conveyor belt 32 was 1.2 mm.

[0146] <Comparative Example 1>

[0147] In Comparative Example 1, such as Figure 1 As shown, the curl value of the optical film F was manually measured 10 times using a ruler.

[0148] <Comparative Example 2>

[0149] In Comparative Example 2, besides using Figure 2Apart from the reflective optical sensor (projector 11', receiver 12') shown, the curl value of the optical film F was measured in the same manner as in Example 1.

[0150] <Measurement Results>

[0151] Table 1 shows the measurement results of Examples 1-4 and Comparative Examples 1 and 2.

[0152] Table 1

[0153]

[0154] Table 1 shows "Production Cycle Time," which refers to the time required to measure the curl value of one optical film F. "Production Cycle Time Evaluation" indicates a cycle time greater than 5 seconds as "×," less than 5 seconds but greater than 2 seconds as "〇," and less than 2 seconds as "◎." "Error" refers to the difference between the average of the 10 curl values ​​measured in Comparative Example 1 (taken as the true value) and the largest difference between the true value and the 40 curl values ​​measured in Examples 1-4 and Comparative Example 2. "Error Evaluation" indicates an error greater than 1.5 mm as "×," less than 1.5 mm but greater than 1.0 mm as "△," and less than 1.0 mm as "〇."

[0155] As shown in Table 1, it can be seen that compared with Comparative Example 1, Examples 1-4 have smaller cycle times, enabling the curl value to be measured in a shorter time. Furthermore, it can be seen that in Examples 1-4, compared with Comparative Example 2, the error values ​​are smaller, allowing for high-precision measurement of the curl value.

[0156] In particular, in Examples 1 and 2, the conveying speed of the belt conveyor 3 is 20 m / min or less, thus sufficiently suppressing the lifting of the leading edge FT of the optical film F. Furthermore, in Examples 1 and 2, the in-plane flatness of the conveyor belt 32 is 1.0 mm or less, thus sufficiently suppressing changes in the posture of the optical film F during conveying. As a result, compared to Example 3, where the conveying speed of the belt conveyor 3 exceeds 20 m / min, and Example 4, where the in-plane flatness of the conveyor belt 32 exceeds 1.0 mm, the accuracy of the curl value measurement can be improved.

[0157] Explanation of reference numerals in the attached figures

[0158] 1: Optical Sensor

[0159] 2: Computing device

[0160] 3: Belt Conveyor

[0161] 4: Support plate

[0162] 11: Projector

[0163] 12: Light receiver

[0164] 100: Inspection device

[0165] F: Optical film

[0166] L: Beam

[0167] ST1: Manufacturing Process

[0168] ST2: Inspection Process

[0169] ST3: Sorting Process

[0170] ST21: Configuration Process

[0171] ST22: Light projection and light reception steps

[0172] ST23: Curl Value Calculation Procedure

[0173] ST24: Judgment Process

Claims

1. A method for measuring the curl of an optical film, comprising using an optical sensor equipped with a projector and a receiver to measure a curl value representing the degree of curl of a sheet-like optical film, characterized in that, have: In the configuration process, the light projector is positioned on one side of the optical film, and the light receiver is positioned on the other side of the optical film, across the optical film, in a manner opposite to the light projector. In the process of projecting and receiving light, the projector projects a beam of light extending in the vertical direction toward the optical film, and the receiver receives the light in the beam that is not blocked by the optical film and passes through. The curl value calculation process calculates the curl value of the optical film based on the vertical length of the transmitted light.

2. The method for measuring the curl of an optical film according to claim 1, characterized in that, In the light projection and light receiving process, the optical film and the optical sensor are moved relative to each other in the in-plane direction of the optical film while the light projector projects the light beam and the light receiver receives the transmitted light.

3. The method for measuring the curl of an optical film according to claim 2, characterized in that, In the light projection and light receiving process, while keeping the optical sensor stationary and moving the optical film at a speed of less than 30 m / min along the in-plane direction of the optical film, the light projector projects the light beam and the light receiver receives the transmitted light.

4. The method for measuring the curl of an optical film according to claim 2, characterized in that, In the light projection and light receiving process, while the optical sensor is stationary and the optical film is placed on the conveyor belt of a belt conveyor for transport, the light projector projects the light beam, and the light receiver receives the transmitted light. During the light projection and light reception process, the in-plane flatness of the area of ​​the conveyor belt on which the optical film is placed is less than 1.5 mm.

5. The method for measuring the curl of an optical film according to claim 2, characterized in that, In the light projection and light receiving process, the optical film is placed on the conveyor belt of a belt conveyor for transport, while the light projector projects the light beam and the light receiver receives the transmitted light. A flat support plate is disposed below the area of ​​the conveyor belt on which the optical film is placed during the light projection and light reception process, and contacts the lower surface of the area of ​​the conveyor belt.

6. A method for manufacturing an optical film, characterized in that, have: Manufacturing process, manufacturing sheet-like optical films; Inspection process, inspect the optical film; The sorting process involves sorting the optical films. In the inspection process, the curling measurement method according to any one of claims 1 to 5 is performed, and based on the measured curling value of the optical film, it is determined whether the optical film is a qualified or unqualified part. In the sorting process, the optical film is sorted according to whether it is a qualified or unqualified part.

Images