Method for manufacturing optical laminate

Abstract

Provided is a method for producing an optical laminate capable of suppressing curl. This method for producing an optical laminate (100) has a step for bonding a first optical film (F1) and a second optical film (F2), which include a polarizer (10), with an adhesive layer (3) interposed therebetween by means of a bonding roller (R1). The bonding roller is composed of a first roller (R1a) in contact with the first optical film and a second roller (R1b) in contact with the second optical film. The surface of the first roller is made of resin, and the surface of the second roller is made of metal or resin. The entry angle (alpha) of the first optical film to the bonding roller is adjusted so that the curl value in the TD direction of a laminate (F3) of the first optical film and the second optical film falls within a predetermined range, or the entry angle (alpha) of the first optical film to the bonding roller is adjusted so that the curl value in the TD direction falls within a predetermined range when the surface of the second roller is formed from a resin. The entry angle (beta) of the second optical film to the bonding roller is adjusted so that the curl value of the laminate (F3) in the TD direction falls within a predetermined range.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical laminate including at least a polarizing plate. In particular, the present invention relates to a method for manufacturing an optical laminate capable of suppressing curling. Background Art

[0002] Conventionally, a polarizing plate has been used as a constituent material for a liquid crystal display device, an organic EL display device, etc. The polarizing plate includes a polarizing film and, depending on the application, a retardation film or the like. The polarizing film is composed of, for example, a polarizer dyed with a dichroic substance such as iodine and a protective film for protecting the polarizer. A long strip-shaped polarizing film can be manufactured by attaching a long strip-shaped protective film to at least one surface of a long strip-shaped polarizer. A long strip-shaped retardation film or the like is attached to one surface of the manufactured long strip-shaped polarizing film, thereby manufacturing a long strip-shaped polarizing plate. A long strip-shaped release liner is attached to one surface of the manufactured long strip-shaped polarizing plate, and a long strip-shaped surface protective film is attached to the other surface, thereby manufacturing a long strip-shaped optical laminate. The attachment of these long strip-shaped films is usually performed in a roll-to-roll manner. The manufactured long strip-shaped optical laminate can be cut into dimensions and shapes corresponding to the application and used for a liquid crystal display device or the like. It should be noted that when used for a liquid crystal display device or the like, the release liner is peeled off, and the remaining constituent elements of the optical laminate are attached to the liquid crystal display device or the like.

[0003] Conventionally, the above-described optical laminate has generally been manufactured by a manufacturing method including a polarizing film manufacturing process, a retardation film attachment process, a release liner attachment process, an inspection process, and a surface protective film attachment process.

[0004] In the polarizing film manufacturing process, a long strip-shaped resin film is used as a base film, and various processes such as a dyeing process and a stretching process are performed by immersing the base film in various treatment baths while transporting the base film in the length direction, thereby manufacturing a long strip-shaped polarizer. Then, a long strip-shaped protective film is attached to at least one surface of the long strip-shaped polarizer, thereby manufacturing a long strip-shaped polarizing film.

[0005] In the retardation film attachment process, a long strip-shaped retardation film (a half-wave plate, a quarter-wave plate, etc.) is attached to one surface of the long strip-shaped polarizing film, thereby manufacturing a long strip-shaped polarizing plate.

[0006] In the stripping liner lamination process, while transporting a long strip-shaped stripping liner in the length direction, an adhesive is applied to it, and the applied adhesive is heated and dried using an oven or the like to cure it, thereby forming an adhesive layer. Then, the adhesive layer side of the long strip-shaped stripping liner (the stripping liner with the adhesive layer) is laminated on one side of a long strip-shaped polarizer, thereby manufacturing a long strip-shaped intermediate body formed by laminating the polarizer, the adhesive layer, and the stripping liner. Sometimes, an adhesive layer is also formed not only on the stripping liner but also on the polarizer, and the adhesive layer side of the stripping liner is laminated on the adhesive layer side of the polarizer, thereby manufacturing a long strip-shaped intermediate body.

[0007] In the inspection process, while leaving the adhesive layer sandwiched between the stripping liner and the polarizer on the polarizer side, only the stripping liner is peeled off, and the polarizer is inspected. Examples of the inspection method for the polarizer include transmission inspection, crossed Nicol inspection, reflection inspection, etc. After inspecting the polarizer in the inspection process, the peeled-off stripping liner is laminated on the polarizer again (including laminating a new stripping liner different from the peeled-off stripping liner on the polarizer), thereby restoring to the original state of the intermediate body.

[0008] In the surface protective film lamination process, a long strip-shaped surface protective film is laminated on the surface of the long strip-shaped polarizer on the side opposite to the side where the stripping liner is laminated.

[0009] However, for the optical laminate manufactured as described above, the cut optical laminate sometimes has curl (warpage at the end) that becomes a problem in use.

[0010] For example, in Patent Document 1, as a method for suppressing the curl of a polarizing film, a method of setting the material of the protective film for protecting the polarizer to a specific material is proposed. However, since the material of the protective film is limited, it cannot be used generally. A method for suppressing curl is desired without particularly changing the materials of the constituent elements of the conventional optical laminate.

[0011] Prior Art Documents

[0012] Patent Documents

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-256568 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] The present invention has been completed to solve the above problems of the prior art, and the object is to provide a method for manufacturing an optical laminate capable of suppressing curl.

[0016] Means for Solving the Problems

[0017] In order to solve the above problems, the inventors conducted in-depth research and found that in the conventional manufacturing method of an optical laminate, the material of the surface of the laminating roller and the entry angle of the film into the laminating roller in various film laminating processes (for example, the release liner laminating process, the re-laminating process of the release liner in the inspection process, the surface protective film laminating process) can affect the curl value (an index indicating the degree of curling) of the laminated body after lamination.

[0018] Specifically, it was found that when the surface of at least one roller constituting the laminating roller is formed of a resin such as rubber, the curl value of the laminated body after lamination in the direction orthogonal to the length direction (transport direction, MD direction) (TD direction) changes corresponding to the entry angle of the film in contact with this roller (hereinafter, appropriately referred to as the "resin roller") into the laminating roller.

[0019] Therefore, it can be understood that if the entry angle of the film in contact with the resin roller is adjusted so that the curl value of the laminated body after lamination in the TD direction falls within a given range, the curl value of the laminated body after lamination in the TD direction can be controlled within a given range, and further, the curl value of the finally manufactured optical laminate in the TD direction can be suppressed to a level that does not cause problems in use.

[0020] The present invention has been completed based on the above insights of the inventors.

[0021] That is, in order to solve the above problems, the present invention provides a method for manufacturing an optical laminate, the method having a step of laminating a long strip-shaped first optical film containing a polarizing plate transported along the length direction and a long strip-shaped second optical film transported along the length direction via an adhesive layer by a laminating roller, the laminating roller being composed of a first roller in contact with the first optical film and a second roller disposed opposite to the first roller and in contact with the second optical film, and the first optical film and the second optical film being laminated by making the first optical film and the second optical film enter between the first roller and the second roller. The surface of at least one of the first roller and the second roller is formed of a resin. When the surface of the first roller is formed of a resin, the entry angle of the first optical film into the laminating roller is adjusted so that the curl value of the laminate of the first optical film and the second optical film in the direction orthogonal to the length direction falls within a given range, or when the surface of the second roller is formed of a resin, the entry angle of the second optical film into the laminating roller is adjusted so that the curl value of the laminate of the first optical film and the second optical film in the direction orthogonal to the length direction falls within a given range.

[0022] In the present invention, the "entry angle of the first optical film into the laminating roll" means the angle formed by a vector that is orthogonal to the straight line passing through the rotation centers of the first roll and the second roll constituting the laminating roll in a cross-section orthogonal to the rotation centers of the first roll and the second roll, is directed toward the exit side of the laminating roll, and a vector representing the traveling direction of the first optical film until it contacts the laminating roll.

[0023] Similarly, the "entry angle of the second optical film into the laminating roll" means the angle formed by a vector that is orthogonal to the straight line passing through the rotation centers of the first roll and the second roll constituting the laminating roll in a cross-section orthogonal to the rotation centers of the first roll and the second roll, is directed toward the exit side of the laminating roll, and a vector representing the traveling direction of the second optical film until it contacts the laminating roll.

[0024] According to the present invention, when the first roll is a resin roll, by adjusting the entry angle of the first optical film contacting the first roll into the laminating roll, the curl value of the laminate of the first optical film and the second optical film in the TD direction can be controlled within a given range as found by the inventors, etc., and further, the curl value of the optical laminate in the TD direction can be suppressed to a level that does not cause problems in use.

[0025] In addition, when the second roll is a resin roll, by adjusting the entry angle of the second optical film contacting the second roll into the laminating roll, the curl value of the laminate of the first optical film and the second optical film in the TD direction can also be controlled within a given range, and further, the curl value of the optical laminate in the TD direction can be suppressed to a level that does not cause problems in use.

[0026] In the present invention, it is preferred that the surface of the above-mentioned first roll is formed of resin.

[0027] According to the above-mentioned preferred method, since the first roll contacting the first optical film including a polarizing plate is a resin roll whose surface is formed of resin, appearance defects such as scratches and dents on the polarizing plate can be suppressed.

[0028] In the present invention, preferably, when the surface of the above-mentioned first roll is formed of resin, a first conveying roll contacting the above-mentioned first optical film is arranged on the entry side of the above-mentioned laminating roll, and the position of the above-mentioned first conveying roll relative to the above-mentioned laminating roll is adjusted, thereby adjusting the entry angle of the above-mentioned first optical film into the above-mentioned laminating roll, or when the surface of the above-mentioned second roll is formed of resin, a second conveying roll contacting the above-mentioned second optical film is arranged on the entry side of the above-mentioned laminating roll, and the position of the above-mentioned second conveying roll relative to the above-mentioned laminating roll is adjusted, thereby adjusting the entry angle of the above-mentioned second optical film into the above-mentioned laminating roll.

[0029] In the above-described preferred method, the "inlet side of the laminating roller" means the upstream side in the conveying direction of the first optical film or the second optical film with respect to the laminating roller.

[0030] According to the above-described preferred configuration, by adjusting the position of the first conveying roller or the second conveying roller, it is possible to easily adjust the entry angle of the first optical film or the second optical film to the laminating roller.

[0031] In the present invention, a case where the second optical film is a release liner and the surface of the second roller is formed of metal can be exemplified.

[0032] In this case, since the second roller is a metal roller (hereinafter, a roller whose surface is formed of a metal such as iron is appropriately referred to as a "metal roller"), the entry angle of the first optical film to the laminating roller can be adjusted so that the curling value of the laminate of the first optical film and the second optical film in the TD direction falls within a given range.

[0033] In the present invention, a case where the second optical film is a surface protective film can be exemplified.

[0034] In the present invention, preferably, when the surface of the first roller is formed of resin, the entry angle of the first optical film to the laminating roller is adjusted to 75° or less (more preferably 60° or less), or when the surface of the second roller is formed of resin, the entry angle of the second optical film to the laminating roller is adjusted to 75° or less (more preferably 60° or less).

[0035] In the present invention, when the surface of the first roller is formed of resin, preferably, the surface of the first roller is formed of a rubber such as silicone rubber. Further, when the surface of the second roller is formed of resin, it is preferably formed of a rubber such as silicone rubber.

[0036] In summary, the present invention relates to the following matters.

[0037] [1] A method for manufacturing an optical laminate, the method comprising: a step of laminating a long strip-shaped first optical film containing a polarizer transported along the length direction and a long strip-shaped second optical film transported along the length direction via an adhesive layer by a laminating roll. The laminating roll is composed of a first roll in contact with the first optical film and a second roll disposed opposite to the first roll and in contact with the second optical film. The first optical film and the second optical film are laminated by making the first optical film and the second optical film enter between the first roll and the second roll. The surface of at least one of the first roll and the second roll is formed of resin. When the surface of the first roll is formed of resin, the entry angle of the first optical film into the laminating roll is adjusted so that the curl value of the laminate of the first optical film and the second optical film in the direction orthogonal to the length direction falls within a given range. Or, when the surface of the second roll is formed of resin, the entry angle of the second optical film into the laminating roll is adjusted so that the curl value of the laminate of the first optical film and the second optical film in the direction orthogonal to the length direction falls within a given range.

[0038] [2] The method for manufacturing an optical laminate according to [1], wherein the surface of the first roll is formed of resin.

[0039] [3] The method for manufacturing an optical laminate according to [1] or [2], wherein when the surface of the first roll is formed of resin, a first transport roll in contact with the first optical film is disposed on the inlet side of the laminating roll, and the position of the first transport roll relative to the laminating roll is adjusted, thereby adjusting the entry angle of the first optical film into the laminating roll. Or, when the surface of the second roll is formed of resin, a second transport roll in contact with the second optical film is disposed on the inlet side of the laminating roll, and the position of the second transport roll relative to the laminating roll is adjusted, thereby adjusting the entry angle of the second optical film into the laminating roll.

[0040] [4] The method for manufacturing an optical laminate according to any one of [1] to [3], wherein the second optical film is a release liner, and the surface of the second roll is formed of metal.

[0041] [5] The method for manufacturing an optical laminate according to any one of [1] to [3], wherein the second optical film is a surface protective film.

[0042] [6] The manufacturing method of the optical laminate according to any one of [1] to [5], wherein, when the surface of the first roller is formed of resin, the entry angle of the first optical film into the laminating roller is adjusted to 75° or less, or, when the surface of the second roller is formed of resin, the entry angle of the second optical film into the laminating roller is adjusted to 75° or less.

[0043] [7] The manufacturing method of the optical laminate according to any one of [1] to [6], wherein, when the surface of the first roller is formed of resin, the surface of the first roller is formed of rubber, and when the surface of the second roller is formed of resin, the surface of the second roller is formed of rubber.

[0044] Effects of the Invention

[0045] According to the present invention, curling can be effectively suppressed without particularly changing the material of the constituent elements of the optical laminate used in the past. Description of the Drawings

[0046] Figure 1 It is a cross-sectional view schematically showing the brief configuration of the optical laminate manufactured by the manufacturing method of one embodiment of the present invention.

[0047] Figure 2 It is a flowchart showing the brief process of the manufacturing method of the optical laminate of one embodiment of the present invention.

[0048] Figure 3 It schematically shows the execution of Figure 2 A diagram showing a brief configuration example of the apparatus for the release liner laminating step ST3 shown.

[0049] Figure 4 It is an explanatory diagram explaining the outline of the method for measuring the curling value.

[0050] Figure 5 It shows the Figure 2 A diagram showing an example of the results obtained by measuring the curling value in the TD direction and the curling value in the MD direction of the laminate F3 (second intermediate M2) manufactured by the release liner laminating step ST3 shown.

[0051] Figure 6 It is a diagram showing an example of the outline and results of the test conducted by the present inventors to examine the relationship between the amount of roll deflection and the curling value in the TD direction.

[0052] Figure 7 It is a diagram showing an example of the outline and results of the test conducted by the present inventors to measure the position of the surface of the first optical film F1.

[0053] Figure 8It is an explanatory diagram schematically explaining the reason why the curl value in the TD direction of the laminated body F3 after fitting, which is speculated by the present inventors, changes corresponding to the entry angle α of the first optical film F1 coming into contact with the first roll R1a as a resin roll with respect to the fitting roll R1.

[0054] Figure 9 It shows the result of measuring the curl value in the TD direction and the curl value in the MD direction of the laminated body F3 (second intermediate M2) manufactured by the peeling liner fitting process ST3 shown by Figure 2 Another example of the result obtained by measurement.

[0055] Figure 10 It schematically shows the Figure 2 Side view of a schematic configuration example of a device for reattaching the peeling liner 4 to the polarizing plate 10 again in the inspection process ST4 shown.

[0056] Figure 11 It shows the result of measuring the curl value in the TD direction and the curl value in the MD direction of the laminated body F3 (second intermediate M2) manufactured by the inspection process ST4 shown by Figure 2 An example of the result obtained by measurement.

[0057] Figure 12 It schematically shows the Figure 2 Side view of a schematic configuration example of a device for performing the surface protective film fitting process ST5 shown.

[0058] Figure 13 It shows the result of measuring the curl value in the TD direction of the laminated body F3 (optical laminated body 100) manufactured by the surface protective film fitting process ST5 shown by Figure 2 An example of the result obtained by measurement.

[0059] Figure 14 It schematically shows the Figure 2 Side view of a schematic configuration of another schematic configuration example and a reference example of a device for performing the surface protective film fitting process ST5 shown.

[0060] Figure 15 It shows the result of measuring the curl value in the TD direction of the laminated body F3 (optical laminated body 100) manufactured by the surface protective film fitting process ST5 shown by Figure 2 An example of the result obtained by measurement.

[0061] Symbol Explanation

[0062] 1 ··· Polarizing film

[0063] 3 ··· Adhesive layer

[0064] 4 ··· Peeling liner

[0065] 5... Surface protective film

[0066] 10... Polarizer

[0067] 100... Optical laminate

[0068] F1... First optical film

[0069] F2... Second optical film

[0070] M1... First intermediate

[0071] M2... Second intermediate

[0072] R1, R5, R9... Laminating rollers

[0073] R1a, R5a, R9a... First roller

[0074] R1b, R5b, R9b... Second roller

[0075] R2, R6, R10... First conveying roller

[0076] R3, R7, R11... Second conveying roller

[0077] α, β... Entrance angle Detailed implementation mode

[0078] Hereinafter, a method for manufacturing an optical laminate according to an embodiment of the present invention will be described with appropriate reference to the drawings. It should be noted that each drawing is shown for reference, and the dimensions, scales, and shapes of the components of the optical laminate and the device shown in each drawing may sometimes be different from the actual ones.

[0079] <Constitution of the optical laminate>

[0080] First, the constitution of the optical laminate manufactured by the manufacturing method of the present embodiment will be described.

[0081] Figure 1 It is a cross-sectional view schematically showing the brief constitution of the optical laminate manufactured by the manufacturing method of the present embodiment.

[0082] As Figure 1 shown, the optical laminate 100 of the present embodiment includes a polarizing film 1, a retardation film 2, an adhesive layer 3, a release liner 4, and a surface protective film 5. The laminate of the polarizing film 1 and the retardation film 2 constitutes a polarizer 10. The laminate of the polarizer 10 and the adhesive layer 3 constitutes a first intermediate M1. The laminate of the first intermediate M1 and the release liner 4 constitutes a second intermediate M2. Hereinafter, each component of the optical laminate 100 will be described.

[0083] [Polarizing film 1]

[0084] The polarizing film 1 is composed of a polarizer 11 and protective films 12 and 13 that protect the polarizer 11. In the present embodiment, the protective films 12 and 13 are attached to both sides of the polarizer 11, but it is not limited thereto, and as long as a protective film is attached to at least one side of the polarizer 11.

[0085] (Polarizer 11)

[0086] Typically, the polarizer 11 is composed of a resin film containing a dichroic substance.

[0087] As the resin film, any suitable resin film that can be used as a polarizer can be adopted. Typically, the resin film is a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film.

[0088] As the PVA-based resin for forming the above PVA-based resin film, any suitable resin can be used. For example, polyvinyl alcohol, ethylene-vinyl alcohol copolymer can be cited. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer.

[0089] The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. It should be noted that the average degree of polymerization can be obtained based on JIS K 6726-1994.

[0090] As the dichroic substance contained in the resin film, for example, iodine, organic dyes, etc. can be cited. They can be used alone or in combination of two or more. Iodine is preferably used.

[0091] The resin film can be a single-layer resin film or a laminate of two or more layers.

[0092] As a specific example of a polarizer composed of a single-layer resin film, a polarizer obtained by subjecting a PVA-based resin film to a dyeing treatment and a stretching treatment (typically a unidirectional stretching treatment) using iodine can be cited. The dyeing treatment using iodine can be carried out, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the unidirectional stretching is preferably 3 to 7 times. The stretching can be carried out after dyeing, or can be carried out while dyeing. In addition, dyeing can also be carried out after stretching. The PVA-based resin film can be subjected to a swelling treatment, a crosslinking treatment, a cleaning treatment, a drying treatment, etc. as needed.

[0093] As a specific example of a polarizer composed of a laminate, there can be mentioned: a polarizer composed of a resin substrate and a laminate of a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer composed of a resin substrate and a laminate of a PVA-based resin layer formed by coating on the resin substrate. A polarizer composed of a resin substrate and a laminate of a PVA-based resin layer formed by coating on the resin substrate can be produced by the following method: for example, a PVA-based resin solution is coated on the resin substrate and dried 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, the laminate is stretched and dyed to form a polarizer from the PVA-based resin layer. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. In addition, stretching may optionally include stretching the laminate in a gas atmosphere at a high temperature (for example, 95 °C or higher) before stretching in the aqueous boric acid solution. The obtained laminate of the resin substrate / polarizer can be used directly (that is, the resin substrate can be used as a protective layer of the polarizer), or the resin substrate can be peeled off from the laminate of the resin substrate / polarizer, and any appropriate protective layer corresponding to the purpose can be laminated on the peeled surface for use. The details of such a method for manufacturing a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire disclosure of this publication is incorporated herein by reference.

[0094] The thickness of the polarizer 11 is preferably 15 μm or less, more preferably 1 μm to 12 μm, further preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0095] The polarizer 11 preferably exhibits absorption dichroism at any wavelength in the wavelength range of 380 nm to 780 nm. The monomer transmittance of the polarizer 11 is preferably 40.0% to 45.0%, 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 further preferably 99.9% or more.

[0096] (Protective films 12, 13)

[0097] As the protective films 12, 13, any appropriate resin film can be used. As the forming material of the resin film, for example, there can be mentioned: (meth)acrylic resins, cellulose resins such as diacetate cellulose and triacetate cellulose, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, copolymer resins thereof, etc. It should be noted that the “(meth)acrylic resin” means an acrylic resin and / or a methacrylic resin. The forming materials of the protective films 12, 13 can be the same or different from each other.

[0098] The thickness of the protective films 12 and 13 is typically 10 μm to 100 μm, preferably 20 μm to 40 μm. The thicknesses of the protective films 12 and 13 may be the same or different from each other.

[0099] Surface treatments such as hard coating, antireflection treatment, anti-adhesion treatment, antiglare treatment, etc. can be performed on the surfaces of the protective films 12 and 13 on the side opposite to the polarizer 11 as needed. And / or, surface treatments for improving the visual recognition when visually recognizing through the polarized sunglasses (typically, treatments for imparting (elliptical) polarization function, treatments for imparting a very high retardation) can be performed on the surfaces of the protective films 12 and 13 on the side opposite to the polarizer 11 as needed. It should be noted that when a surface treatment layer is formed by performing a surface treatment, the thickness of the protective films 12 and 13 is the thickness including the surface treatment layer.

[0100] It should be noted that the protective films 12 and 13 are respectively laminated on the polarizer 11 through an arbitrary appropriate adhesive layer (not shown). As the adhesive constituting the adhesive layer, PVA-based adhesives or active energy ray-curable adhesives are typically cited.

[0101] [Retardation film 2]

[0102] The retardation film 2 can be, for example, a compensator for providing a wide viewing angle, or a retardation plate (circular polarizer) such as a 1 / 2 wave plate or a 1 / 4 wave plate for generating circularly polarized light for use in combination with a polarizing film. The thickness of the retardation film 2 is, for example, 1 to 200 μm.

[0103] The retardation film 2 is formed, for example, of a layer or a resin formed by polymerizing a polymerizable liquid crystal. The polymerizable liquid crystal is a compound having a polymerizable group and having liquid crystallinity. The polymerizable group is a group participating in a polymerization reaction, preferably a photopolymerizable group. Here, the photopolymerizable group is a group that can participate in a polymerization reaction by active radicals, acids, etc. generated by a photopolymerization initiator. As the polymerizable group, vinyl, vinyloxy, 1-chloroethylene, isopropenyl, 4-vinylphenyl, acryloyloxy, methacryloyloxy, epoxyethyl, oxetanyl, etc. can be cited. Among them, acryloyloxy, methacryloyloxy, vinyloxy, epoxyethyl, and oxetanyl are preferred, and acryloyloxy is more preferred. The liquid crystallinity of the polymerizable liquid crystal can be thermotropic liquid crystal or lyotropic liquid crystal. If the thermotropic liquid crystal is classified according to the degree of order, it can be nematic liquid crystal or smectic liquid crystal.

[0104] In addition, examples of the resin for forming the retardation film 2 include: polyarylate, polyamide, polyimide, polyester, polyaryletherketone, polyamideimide, polyesterimide, polyvinyl alcohol, polyfumarate, polyethersulfone, polysulfone, norbornene resin, polycarbonate resin, cellulose resin, and polyurethane. These resins can be used alone or in combination.

[0105] It should be noted that the retardation film 2 is adhered to the polarizing film 1 (protective film 13) via an arbitrary appropriate adhesive layer or adhesive layer (not shown) and laminated together. Representative examples of the adhesive constituting the adhesive layer include PVA-based adhesives or active energy ray-curable adhesives.

[0106] [Adhesive layer 3]

[0107] The adhesive layer 3 can be formed by applying an adhesive on one side of the release liner 4 and heating the applied adhesive using an oven or the like to dry it, thereby curing it. In addition, sometimes the adhesive layer 3 is formed not only on the release liner 4 but also on the retardation film 2 constituting the polarizing plate 10.

[0108] 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. At this heating temperature, it is preferably heated for 20 seconds to 3 minutes, more preferably heated for 1 minute to 3 minutes.

[0109] Specific examples of the adhesive for forming the adhesive layer 3 include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the types, amounts, combinations, and mixing ratios of the monomers of the base resin of the adhesive, as well as the mixing amount of the crosslinking agent, reaction temperature, reaction time, etc., an adhesive having desired characteristics 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, etc., an acrylic adhesive is preferred. Details of the adhesive constituting the adhesive layer are described, for example, in Japanese Patent Application Laid-Open No. 2014-115468, and the description of this publication is incorporated herein by reference. The thickness of the adhesive layer can be set to, for example, 10 μm to 100 μm.

[0110] [Release liner 4]

[0111] As the release liner 4, any suitable release liner can be used. As a specific example, a plastic film, a non-woven fabric, or paper surface-coated with a release agent can be cited. As specific examples of the release agent, silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents can be cited. As specific examples of the plastic film, polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film can be cited. The thickness of the release liner 4 can be set, for example, to 10 μm to 100 μm.

[0112] [Surface protective film 5]

[0113] The surface protective film 5 typically has a base material and an adhesive layer. In the present embodiment, the thickness of the surface protective film 5 is, for example, 30 μm or more. The upper limit of the thickness of the surface protective film 5 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 base material and the adhesive layer.

[0114] The base material can be composed of any suitable resin film. As the forming material of the resin film, the following can be cited: ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, copolymer resins thereof, etc. Ester resins (particularly polyethylene terephthalate resins) are preferred.

[0115] As the adhesive for forming the adhesive layer, any suitable adhesive can be used. As the base resin of the adhesive, for example, the following can be cited: acrylic resins, styrene resins, silicone resins, urethane resins, rubber resins.

[0116] <Manufacturing method of the present embodiment>

[0117] Hereinafter, a manufacturing method of the optical laminate 100 of the present embodiment will be described, which is used to manufacture the optical laminate 100 having the configuration described above.

[0118] Figure 2 It is a flowchart showing a brief process of the manufacturing method of the optical laminate 100 of the present embodiment.

[0119] As Figure 2 shown, the manufacturing method of the present embodiment includes: a polarizing film manufacturing step ST1, a retardation film laminating step ST2, a release liner laminating step ST3, an inspection step ST4, and a surface protective film laminating step ST5. Hereinafter, each step ST1 to ST5 will be described.

[0120] [Polarizing film manufacturing step ST1]

[0121] In the polarizing film manufacturing process ST1, a long strip-shaped resin film is used as the base film. While transporting the base film along the length direction (MD direction), it is immersed in various treatment baths to perform various treatments such as dyeing treatment and stretching treatment, thereby manufacturing the long strip-shaped polarizer 11. Then, by laminating the long strip-shaped protective films 12 and 13 on the long strip-shaped polarizer 11, the long strip-shaped polarizing film 1 is manufactured.

[0122] [Phase difference film laminating process ST2]

[0123] In the phase difference film laminating process ST2, the long strip-shaped phase difference film 2 is laminated on one side (protective film 13) of the long strip-shaped polarizing film 1, thereby manufacturing the long strip-shaped polarizing plate 10.

[0124] It should be noted that in the case where the optical laminate 100 does not include the phase difference film 2 (the polarizing plate 10 does not include the phase difference film 2), the phase difference film laminating process ST2 is not required.

[0125] [Release liner laminating process ST3]

[0126] In the release liner laminating process ST3, the following adhesive layer forming process is performed: while transporting the long strip-shaped release liner 4 along the length direction (MD direction), an adhesive is coated on it, and the coated adhesive is heated and dried using an oven or the like to cure it, thereby forming the adhesive layer 3. Then, the release liner 4 is laminated on the long strip-shaped polarizing plate 10 via the adhesive layer 3 formed on the long strip-shaped release liner 4. Specifically, the adhesive layer 3 side of the long strip-shaped release liner 4 (the release liner 4 with the adhesive layer 3) is laminated on one side (phase difference film 2) of the long strip-shaped polarizing plate 10. Thus, the second intermediate M2 formed by laminating the polarizing plate 10, the adhesive layer 3, and the release liner 4 is manufactured.

[0127] It should be noted that an adhesive layer 3 can be formed not only on the release liner 4 but also on the phase difference film 2 constituting the polarizing plate 10 to form a polarizing plate 10 with an adhesive layer 3. Then, the adhesive layer 3 side of the release liner 4 can be laminated with the adhesive layer side of the polarizing plate 10 to manufacture the second intermediate M2.

[0128] Figure 3 It is a diagram schematically showing a brief configuration example of the apparatus for performing the release liner laminating process ST3. Figure 3 (a) is a side view of the apparatus (a view observed from the horizontal direction (TD direction) orthogonal to the transporting direction (MD direction) of each film). Figure 3 The arrow shown in (a) represents the transporting direction of each film. Figure 3 (b) is for Figure 3 a side sectional view explaining the entry angle of the film in the laminating roller R1 shown in (a).

[0129] In the present invention, the film on one side adhered by the adhering roller is set as the first optical film F1, and the film on the other side is set as the second optical film F2. In the release liner adhering step ST3, the first optical film F1 is the polarizing plate 10 or the polarizing plate 10 with the adhesive layer 3, and the second optical film F2 is the release liner 4 with the adhesive layer 3. The first optical film F1 and the second optical film F2 are adhered via the adhesive layer 3 by the adhering roller R1, so that the laminate F3 of the first optical film F1 and the second optical film F2 can be manufactured. In the release liner adhering step ST3, the laminate F3 is the second intermediate M2.

[0130] Specifically, as Figure 3 (a) shows, on the inlet side of the adhering roller R1 (the upstream side of the transport direction of the first optical film F1 with respect to the adhering roller R1, which is the left side of the adhering roller R1 in the example shown in Figure 3 (a)), the first transport roller R2 in contact with the first optical film F1 is arranged, and the first optical film F1 is transported to the adhering roller R1 by the first transport roller R2. Similarly, on the inlet side of the adhering roller R1 (the upstream side of the transport direction of the second optical film F2 with respect to the adhering roller R1, which is the left side of the adhering roller R1 in the example shown in Figure 3 (a)), the second transport roller R3 in contact with the second optical film F2 is arranged, and the second optical film F2 is transported to the adhering roller R1 by the second transport roller R3.

[0131] For the first transport roller R2, its position relative to the adhering roller R1 (the position in the up-and-down direction in the present embodiment) can be adjusted. In the example shown in Figure 3 (a), the first transport roller R2 can move from the uppermost position shown by the solid line through the position shown by the dotted line to the lowermost position shown by the dash-dotted line. For example, a configuration can be adopted in which the rotating shaft of the first transport roller R2 is installed on a one-way brake via a bearing, and the position of the first transport roller R2 can be adjusted by driving the one-way brake.

[0132] On the other hand, the second transport roller R3 is fixed at a given position.

[0133] The adhering roller R1 is composed of a first roller R1a and a second roller R1b arranged opposite to the first roller R1a (opposite in the up-and-down direction in the example shown in Figure 3 ).

[0134] The first roller R1a is a roller that contacts the first optical film F1 and transports the first optical film F1 between the first roller R1a and the second roller R1b. The surface of the first roller R1a is a resin roller formed of resin (silicone rubber in the present embodiment).

[0135] The second roller R1b is a roller that contacts the second optical film F2 and transports the second optical film F2 between the first roller R1a and the second roller R1b. The second roller R1b is a metal roller whose surface is formed of metal (iron in this embodiment).

[0136] By introducing the first optical film F1 and the second optical film F2 between the first roller R1a and the second roller R1b, the first optical film F1 and the second optical film F2 are bonded to each other, and a laminate F3 of the first optical film F1 and the second optical film F2 is manufactured. The laminate F3 is transported by a transport roller R4 and wound up by a winding roller (not shown).

[0137] As Figure 3 (b) shows, in a cross section orthogonal to the rotation center C1 of the first roller R1a and the rotation center C2 of the second roller R1b, a straight line (imaginary line) passing through the rotation center C1 of the first roller R1a and the rotation center C2 of the second roller R1b is defined as a straight line CL. A vector (imaginary vector) orthogonal to the straight line CL and directed toward the out side of the bonding roller R1 (the downstream side in the transport direction of the first optical film F1 and the second optical film F2, the right side of the bonding roller R1 in the example shown in Figure 3 (b)) is defined as a vector VC. At this time, the entry angle α of the first optical film F1 into the bonding roller R1 is the angle formed by the vector VC and the vector representing the traveling direction of the first optical film F1 until it contacts the bonding roller R1. In addition, the entry angle β of the second optical film F2 into the bonding roller R1 is the angle formed by the vector VC and the vector representing the traveling direction of the second optical film F2 until it contacts the bonding roller R1.

[0138] Then, in the release liner bonding step ST3, the entry angle α of the first optical film F1 into the bonding roller R1 is adjusted so that the curl value of the laminate F3 in the direction orthogonal to the length direction (MD direction) (TD direction) falls within a given range. Specifically, the entry angle α is adjusted by adjusting the position of the first transport roller R2 relative to the bonding roller R1 in the vertical direction. When the first transport roller R2 is located at the uppermost position shown by a solid line in Figure 3 (a), the entry angle α becomes the minimum 0°, and when the first transport roller R2 is located at the lowermost position shown by a one-dot chain line, the entry angle α becomes the maximum value.

[0139] Hereinafter, a method for measuring the curl value will be described.

[0140] Figure 4 It is an explanatory diagram for explaining the outline of the method for measuring the curl value implemented in this embodiment.

[0141] As Figure 4As shown in (a), a rectangular second intermediate sample M21 having a product size (e.g., long side 160 mm × short side 80 mm for smartphone use) is cut out in the TD direction of the second intermediate M2 along the strip. In Figure 4 (a), three intermediate samples M21 are shown for convenience, but the actual number is not limited to this. The curl values are measured for a total of 100 second intermediate samples M21 obtained by performing this cutting on a plurality of second intermediates M2. It should be noted that, as Figure 4 (b) shows, when cutting out the second intermediate sample M21, the MD direction of the second intermediate M2 (corresponding to Figure 1 the absorption axis direction of the polarizer 11 shown) is cut out at an angle of 45° with respect to the long side and the short side of the second intermediate sample M21.

[0142] As Figure 4 (c) shows, when measuring the curl value, the second intermediate sample M21 is placed on a flat stage 20 in such a way that the lower side of the second intermediate sample M21 becomes convex (in such a way that the warping of the four corners of the second intermediate sample M21 faces upward in the vertical direction), and the vertical distance H from the upper surface of the stage 20 to each of the four corners of the second intermediate sample M21 is measured. The four corners of the second intermediate sample M21 are the corner TD1 and TD2 at both ends in the TD direction of the second intermediate M2 and the corner MD1 and MD2 at both ends in the MD direction of the second intermediate M2 before being cut out from the second intermediate M2. The distance H is measured by erecting a scale extending in the vertical direction near the corners of the second intermediate sample M21 and reading the scale of the scale by visual observation.

[0143] When the second intermediate sample M21 is placed on the stage 20 in such a way that the lower side becomes convex, the case where the side where the release liner 4 of the second intermediate sample M21 is located is the lower side (the side where the polarizer 10 is located is the upper side) is defined as positive curl, and the larger value obtained by measuring the distances H for the corners TD1 and TD2 respectively is directly used as the curl value in the TD direction. In addition, the larger value obtained by measuring the distances H for the corners MD1 and MD2 respectively is directly used as the curl value in the MD direction.

[0144] On the other hand, when the second intermediate sample M21 is placed on the placement table 20 such that the lower side thereof is convex, the case where the side where the release liner 4 of the second intermediate sample M21 is located is upward (the side where the polarizer 10 is located is downward) is defined as negative curling, and the distance H obtained by measuring with the diagonal portions TD1 and TD2 respectively is multiplied by -1, and the larger value of the absolute values thereof is calculated as the curling value in the TD direction. In addition, the distance H obtained by measuring with the diagonal portions MD1 and MD2 respectively is multiplied by -1, and the larger value of the absolute values thereof is calculated as the curling value in the MD direction.

[0145] Then, the average value of the curling values in the TD direction obtained by measuring 100 second intermediate samples M21 respectively is taken as the curling value in the TD direction of the second intermediate M2. Similarly, the average value of the curling values in the MD direction obtained by measuring 100 second intermediate samples M21 respectively is taken as the curling value in the MD direction of the second intermediate M2.

[0146] It should be noted that for the curling values in the TD direction and the MD direction of the optical laminate 100 described later, they can also be measured by the same measurement method as described above with reference to Figure 4 which has been described.

[0147] Figure 5 FIG. is an example showing the results obtained by measuring the curling values in the TD direction and the MD direction of the laminate F3 (second intermediate M2) manufactured by the release liner laminating step ST3. Specifically, Figure 5 are the results obtained by measuring the curling value of the laminate F3 (second intermediate M2) having a total thickness of 117 μm and having a structure laminated in the following order. In this laminate F3, the first optical film F1 is the polarizer 10, and the second optical film F2 is the release liner 4 with the adhesive layer 3. It should be noted that Figure 5 the results shown are the results obtained when the entry angle β of the second optical film F2 into the laminating roller R1 is 43°.

[0148] (1) Polarizer 10 (total thickness 65 μm)

[0149] (1-1) Protective film 12: Cycloolefin-based protective film with a hard coat (thickness 3 μm) (total thickness 29 μm)

[0150] (1-2) Polarizer 11: Polyvinyl alcohol-based polarizer (thickness 13 μm)

[0151] (1-3) Protective film 13: Triacetyl cellulose-based protective film (thickness 20 μm)

[0152] (1 - 4) Phase difference film 2: A laminate of a polymeric liquid crystal type 1 / 2 wave plate (thickness 1 μm) and a polymeric liquid crystal type 1 / 4 wave plate (thickness 2 μm) (total thickness 3 μm)

[0153] (2) Adhesive layer 3: An acrylic adhesive layer (thickness 14 μm)

[0154] (3) Release liner 4: A release liner made of polyethylene terephthalate (thickness 38 μm)

[0155] As Figure 5 shown, the first roller R1a is a resin roller. Corresponding to the entry angle α of the first film F1 that contacts the first roller R1a into the laminating roller R, the curl value in the MD direction of the laminated body F3 after lamination is substantially constant. In contrast, the curl value in the TD direction has changed.

[0156] Therefore, if the entry angle α of the first optical film F1 that contacts the first roller R1a into the laminating roller R1 is adjusted so that the curl value in the TD direction of the laminated body F3 after lamination falls within a given range, the curl value in the TD direction of the laminated body F3 after lamination can be controlled within the given range. Furthermore, the curl value in the TD direction of the finally manufactured optical laminate 100 can be suppressed to a level that does not cause problems in use. Specifically, if the data as Figure 5 shown is taken in advance and the entry angle α of the first optical film F1 that contacts the first roller R1a into the laminating roller R1 is adjusted based on this data so that the curl value in the TD direction of the laminated body F3 after lamination falls within a given range, then after adjustment, the curl value in the TD direction of the laminated body F3 after lamination can be controlled within the given range.

[0157] Hereinafter, the reason why the curl value in the TD direction of the laminated body F3 after lamination as described above changes corresponding to the entry angle α of the first optical film F1 that contacts the first roller R1a (which is a resin roller) among the first roller R1a and the second roller R1b that constitute the laminating roller R1 will be described based on the findings obtained by the present inventors through research.

[0158] Figure 6 is a diagram showing an example of the outline and results of an experiment conducted by the present inventors to examine the relationship between the amount of roller deflection and the curl value in the TD direction. Figure 6 (a) is a front view schematically showing the state in which no load is applied to the first roller R1a in this experiment (a view observed from the conveying direction (MD direction) of each film). Figure 6 (b) is a front view schematically showing the state in which a load is applied to the first roller R1a in this experiment. Figure 6(c) is a diagram showing an example of the result obtained by measuring the position of the surface (lower surface) of the first roll R1a in this test. Figure 6 (d) is a side sectional view for explaining the roll deflection amount. Figure 6 (e) is a diagram showing an example of the result of this test. It should be noted that in Figure 6 (a), Figure 6 (b), and Figure 6 (d), the illustration of the film is omitted.

[0159] As Figure 6 (a) shows, in a state where no load is applied to the first roll R1a (a state where the first roll R1a and the second roll R1b are in contact without load with a film (not shown) interposed therebetween), a plurality of one-dimensional laser rangefinders 20a are arranged along the rotation center C1 of the first roll R1a so as to face the surface (lower surface) of the first roll R1a, and the distance La from each one-dimensional laser rangefinder 20a to the surface (lower surface) of the first roll R1a is measured. The one-dimensional laser rangefinder 20a is a device that irradiates a dot-like laser and measures the distance to the irradiation position using the principle of triangulation.

[0160] Similarly, in a state where no load is applied to the first roll R1a, a plurality of one-dimensional laser rangefinders 20b are arranged along the rotation center C2 of the second roll R1b so as to face the surface (upper surface) of the second roll R1b, and the distance Lb from each one-dimensional laser rangefinder 20b to the surface (upper surface) of the second roll R1b is measured. The one-dimensional laser rangefinder 20b is the same device as the one-dimensional laser rangefinder 20a.

[0161] It should be noted that the separation distance L between the surface (lower surface) of the first roll R1a and the surface (upper surface) of the second roll R1b can be expressed as L = L0 - La - Lb using the separation distance L0 between the one-dimensional laser rangefinders 20a and 20b, which is a known value, and the measured distances La and Lb. It can be considered that the separation distance L is almost constant in a state where no load is applied to the first roll R1a.

[0162] Next, as Figure 6 (b) shows, the inventors applied a load F to the first roll R1a from the state shown in Figure 6 (a), and measured the distance La' from each one-dimensional laser rangefinder 20a to the surface (lower surface) of the first roll R1a and the distance Lb' from each one-dimensional laser rangefinder 20b to the surface (upper surface) of the second roll R1b in the same manner as above. Specifically, the load F applied to the rotation axis R11 of the first roll R1a was changed to various values, and the distances La' and Lb' were measured respectively in a state where each load F was applied.

[0163] It should be noted that the separation distance L' between the surface (lower surface) of the first roll R1a and the surface (upper surface) of the second roll R1b can be expressed by L' = L0 - La' - Lb', where L0 is the separation distance between the one-dimensional laser rangefinder 20a and the one-dimensional laser rangefinder 20b, which are known values, and La' and Lb' are the measured distances.

[0164] Then, based on the measured distances La, Lb, La', and Lb', the ΔL calculated by ΔL = L - L' = (L0 - La - Lb) - (L0 - La' - Lb') = La' - La + Lb' - Lb was calculated as the roll deformation amount at three positions.

[0165] As Figure 6 As shown in (b), in the state where a load is applied to the first roll R1a, flexure occurs in a manner that the rotation center C1 of the first roll R1a bulges downward. Therefore, the distance La' at the end of the first roll R1a (the end in the direction of the rotation center C1) is greater than the distance La' at the central portion of the first roll R1a (the central portion in the direction of the rotation center C1).

[0166] For Figure 6 the horizontal axis of (c), the position in the direction of the rotation center C1 of the first roll R1a corresponding to the TD direction of the first optical film F1 is plotted with a given position as the reference value (0 mm). Additionally, for Figure 6 the vertical axis of (c), the displacement amount of the measured distance La' relative to the reference value when a load is applied to the first roll R1a with the measured distance La in the state where no load is applied to the first roll R1a as the reference value (0 mm) is plotted as the position of the surface (lower surface) of the first roll R1a. When Figure 6 the vertical axis of (c) is positive, it means that the position of the surface of the first roll R1a is closer to the one-dimensional laser rangefinder 20a than the reference value. When Figure 6 the vertical axis of (c) is negative, it means that the position of the surface of the first roll R1a is farther from the one-dimensional laser rangefinder 20a than the reference value. From the example shown in Figure 6 (c), it can also be known that in the state where a load is applied to the first roll R1a, the greater the load, the greater the distance La' at the end of the first roll R1a is than the distance La' at the central portion of the first roll R1a, and the rotation center C1 of the first roll R1a flexes more in a downwardly convex manner.

[0167] Therefore, it can be considered that the separation distance L' is smaller at the end of the first roll R1a than at the central portion. Therefore, it can be considered that the roll deformation amount ΔL is greater at the end of the first roll R1a than at the central portion.

[0168] Note that, in order to properly bond the first optical film F1 and the second optical film F2 by the bonding roller R1, a load must be applied to the first roller R1a. Therefore, it can be considered that in the release liner bonding step ST3, the state shown in Figure 6 (b) is achieved, and the roller deformation amount ΔL is larger at the end of the first roller R1a than at the central portion.

[0169] As shown in Figure 6 (d), in the state where a load is applied to the first roller R1a, the surface (upper surface) of the first roller R1a, which is a resin roller, facing the second roller R1b is deformed and flattened. Therefore, not only the downward convex deflection of the first roller R1a but also the flattening amount of the first roller R1a (in this specification, referred to as "roller flattening amount") affects the above-described separation distance L' and further affects the roller deformation amount ΔL.

[0170] As shown in Figure 6 (d), if in a cross section orthogonal to the rotation center C1 of the first roller and the rotation center C2 of the second roller, the central angle of the second roller R1b corresponding to the flattened region of the first roller R1a is set as θ and the diameter of the first roller R1a is set as 2r, the roller flattening amount h can be geometrically expressed as h = r{1 - cos(θ / 2)}. Note that the central angle θ can be calculated by measuring the nip width expressed as rθ using a known pressure measurement sheet (Prescale) and a rubber roll nip detector (DigiNip).

[0171] The present inventors calculated the value obtained by removing the influence of the roller flattening amount h from the roller deformation amount ΔL as the roller deflection amount ε. That is, the roller deflection amount ε was calculated at three positions by ε = ΔL - h. Then, the relationship between the roller deflection amount ε and the curl value of the laminate F3 (the second intermediate M2) manufactured in the release liner bonding step ST3 in the TD direction was examined.

[0172] The relationship between the roller deflection amount ε and the curl value of the laminate F3 in the TD direction was examined for two cases where the diameter 2r of the first roller R1a was 180 mm and 250 mm (the diameter of the second roller R1b was the same). In the case where the diameter 2r of the first roller R1a was 180 mm, the applied load F was changed to three values of 0.13 MPa, 0.20 MPa, and 0.25 MPa by pressure conversion. In the case where the diameter 2r of the first roller R1a was 250 mm, the applied load F was changed to four values of 0.06 MPa, 0.10 MPa, 0.20 MPa, and 0.30 MPa by pressure conversion.

[0173] In the example showing the result of this experiment, Figure 6 the average value of the roller deflection amount ε calculated at three positions was plotted on the horizontal axis ofFigure 6 (e), for the vertical axis, when the diameter 2r of the first roller R1a is 180 mm, the change amount relative to the reference value is plotted with the curl value in the TD direction of the laminate F3 as the reference value when the applied load is the minimum of 0.13 MPa. When the diameter 2r of the first roller R1a is 250 mm, the change amount relative to the reference value is plotted with the curl value in the TD direction of the laminate F3 as the reference value when the applied load is the minimum of 0.06 MPa.

[0174] As Figure 6 As shown in (e), it can be seen that there is a relatively good correlation between the roll deflection amount ε and the curl value in the TD direction of the laminate F3. Therefore, it can be considered that the deflection of the first roller R1a as a resin roller affects the curl value in the TD direction of the laminate F3.

[0175] Based on the above test results, the inventors conducted a test to measure the position of the surface of the first optical film F1.

[0176] Figure 7 FIG. is an example showing the outline and results of the test conducted by the inventors to measure the position of the surface of the first optical film F1. Figure 7 (a) is a perspective view schematically showing the outline of this test. Figure 7 (b) is a side view schematically showing the outline of this test. In Figure 7 (b), the illustration of the two-dimensional rangefinder is omitted. Figure 7 (c) is a figure showing an example of the position of the surface of the first optical film F1 measured at the position P1 shown in Figure 7 (b). Figure 7 (d) is a figure showing an example of the position of the surface of the first optical film F1 measured at the position P2 shown in Figure 7 (b).

[0177] As Figure 7As shown in (a), the inventors arranged two two-dimensional laser rangefinders 30a and 30b so as to face the surface (upper surface) of the first optical film F1, and moved each of the two-dimensional laser rangefinders 30a and 30b along the TD direction of the first optical film F1, thereby measuring the distances from the two-dimensional laser rangefinders 30a and 30b to the surface (upper surface) of the first optical film F1. The two-dimensional laser rangefinders 30a and 30b are devices that irradiate linear lasers and measure the distance to the irradiation position using the principle of triangulation. In this experiment, the two-dimensional laser rangefinders 30a and 30b were arranged by adjusting their orientations so that the direction in which the linear laser extends is along the TD direction of the first optical film F1. The measurement ranges (measurement ranges in the TD direction of the first optical film F1) of the two-dimensional laser rangefinders 30a and 30b used in this experiment were each about 210 mm, which is smaller than the size of the first optical film in the TD direction. Therefore, by moving each of the two-dimensional laser rangefinders 30a and 30b along the TD direction of the first optical film F1 in the TD direction of the first optical film F1, the distances to the surface of the first optical film F1 were measured over the entire TD direction of the first optical film F1.

[0178] The two-dimensional laser rangefinders 30a and 30b were respectively arranged at both of the following two positions: the position facing the surface of the first optical film F1 at the position ( Figure 7 (position P1 shown in (b)) immediately before the first optical film F1 comes into contact with the first roller R1a, and the position facing the surface of the first optical film F1 at the position ( Figure 7 (position P2 shown in (b)) after the first optical film F1 comes into contact with the first roller R1a, and the distances to the surface of the first optical film F1 were measured at each of the positions P1 and P2. The load F applied to the first roller R1a was converted into four loads of 0.00 MPa, 0.13 MPa, 0.20 MPa, and 0.30 MPa by pressure conversion, and the distances to the surface of the first optical film F1 were measured at each of the positions P1 and P2 for each load F.

[0179] In the horizontal axes of Figure 7 (c) and Figure 7 (d) showing an example of the results of this experiment, the positions in the TD direction of the first optical film F1 were plotted with a given position as the reference value (0 mm). In addition, in the vertical axes of Figure 7 (c) and Figure 7 (d), the displacements of the measured distances relative to the reference value with a given distance as the reference value (0 mm) were plotted as the positions of the surface of the first optical film F1. In Figure 7 (c) and Figure 7When the vertical axis of (d) is positive, it means that the position of the surface of the first optical film F1 is closer to the two-dimensional laser rangefinders 30a and 30b compared to a given reference value. In Figure 7 (c) and Figure 7 when the vertical axis of (d) is negative, it means that the position of the surface of the first optical film F1 is farther from the two-dimensional laser rangefinders 30a and 30b compared to a given reference value.

[0180] As Figure 7 (c) shows, it can be seen that when a load F is applied to the first roller R1a at the position P1 before the first optical film F1 is about to contact the first roller R1a, the first optical film F1 deflects in a downward convex manner, and the greater the load F, the greater the degree of deflection.

[0181] On the other hand, it can be seen that when a load F is applied to the first roller R1a at the position P2 after the first optical film F1 contacts the first roller R1a, the first optical film F1 deflects in an upward convex manner, and the greater the load F, the greater the degree of deflection.

[0182] Figure 8 is an explanatory diagram schematically showing the reason why the curl value of the laminated body F3 in the TD direction after lamination changes corresponding to the entry angle α of the first optical film F1 in contact with the first roller R1a as a resin roller, which is speculated by the inventors based on the above results.

[0183] As described above with reference to Figure 6 If a load F is applied to the first roller R1a as a resin roller, the center of rotation C1 of the first roller R1a deflects in a downward convex manner. Therefore, it becomes the same state as when the diameter of the first roller R1a in contact with the first optical film F1 is larger at the central part of the first roller 1a than at the end part. The distance from the point where the first optical film F1 starts to contact the first roller 1a to the point where the first optical film F1 is laminated with the second optical film F2 is longer at the central part of the first roller 1a than at the end part. As a result, as Figure 8 shown, a force FC that causes the first optical film F1 before contacting the first roller R1a to move toward the central part comes into play. Thus, as described above with reference to Figure 7 (c), the first optical film F1 deflects in a downward convex manner.

[0184] On the other hand, as Figure 8 shown, after the first optical film F1 contacts the first roller R1a (at Figure 8(In the figure, the portion with dot-dash shading is shown). Since the first roller R1a is located below the first optical film F1, the first optical film F1 cannot be deflected in a downwardly convex manner. Instead, corresponding to the amount of deflection before coming into contact with the first roller R1a, the first optical film F1 will be inverted in an upwardly convex manner.

[0185] Furthermore, since the first optical film F1 is laminated with the second optical film F2 in a state where it has been inverted in an upwardly convex manner, it can be considered that the shape of the first optical film F1 that has been inverted in an upwardly convex manner will affect the curl value in the TD direction of the laminated body F3 after lamination, as described above with reference to Figure 6 (d). Furthermore, since the larger the entry angle α, the longer the length of the first optical film F1 in contact with the first roller R1a, it can be considered that the force FC that causes the first optical film F1 to move toward the central portion before coming into contact with the first roller R1a will also become larger. As a result, the amount of deflection of the first optical film F1 before coming into contact with the first roller R1a, and thus the amount of inversion of the first optical film F1 after coming into contact with the first roller R1a, will become larger. Consequently, the curl value in the TD direction of the laminated body F3 after lamination will change. It should be noted that if the amount of deflection of the first optical film F1 before coming into contact with the first roller R1a becomes too large, there is a risk of a gap being generated between the first optical film F1 and the second optical film F2, resulting in unsuccessful lamination, or the laminated body F3 developing wrinkles or creases.

[0186] Figure 9 FIG. shows another example of the results obtained by measuring the curl value in the TD direction and the curl value in the MD direction of the laminated body F3 (second intermediate M2) manufactured through the release liner lamination process ST3. Specifically, in Figure 9 this case, the first optical film F1 is a polarizing plate 10 with an adhesive layer 3 (thickness 14 μm), and the total thickness is 131 μm. Except for this, the results are those obtained by measuring the curl value of the laminated body F3 (second intermediate M2) having the same configuration as the example shown in Figure 5 . It should be noted that Figure 9 the results shown are those obtained when the entry angle β of the second optical film F2 into the laminating roller R1 is 43°.

[0187] As shown in Figure 9 , similar to the results shown in Figure 5 , corresponding to the entry angle α of the first film F1 into the laminating roller R, the curl value of the laminated body F3 in the MD direction is approximately constant, while in contrast, the curl value in the TD direction changes.

[0188] Therefore, if the entry angle α of the first optical film F1 in contact with the first roller R1a into the laminating roller R1 is adjusted such that the curl value in the TD direction of the laminated body F3 after lamination falls within a given range, the curl value in the TD direction of the laminated body F3 after lamination can be controlled within the given range, and furthermore, the curl value in the TD direction of the finally manufactured optical laminate 100 can be suppressed to a level that does not pose a problem in use. Specifically, if the data as shown in Figure 9 is taken in advance, and based on this data, the entry angle α of the first optical film F1 in contact with the first roller R1a into the laminating roller R1 is adjusted such that the curl value in the TD direction of the laminated body F3 after lamination falls within a given range, then after the adjustment, the curl value in the TD direction of the laminated body F3 after lamination can be controlled within the given range.

[0189] [Inspection process ST4]

[0190] In the inspection process ST4, after the long strip-shaped release liner 4 is peeled off from the adhesive layer 3 (the release liner 4 is peeled off only while the adhesive layer 3 sandwiched between the release liner 4 and the polarizing plate 10 remains on the side of the polarizing plate 10), the polarizing plate 10 (the first intermediate M1) is inspected. As the inspection method of the polarizing plate 10, detailed description is omitted, but well-known inspection methods such as transmission inspection, orthogonal Nicol inspection, and reflection inspection can be cited. In the inspection process ST4, after the polarizing plate 10 is inspected, the peeled release liner 4 is adhered to the polarizing plate 10 again (including the case where a new release liner 4 different from the peeled release liner 4 is adhered to the polarizing plate 10), thereby restoring to the original state of the second intermediate M2.

[0191] Figure 10 is a side view schematically showing a brief configuration example of the apparatus for adhering the release liner 4 to the polarizing plate 10 again in the inspection process ST4 (a view observed from the horizontal direction (TD direction) orthogonal to the conveying direction (MD direction) of each film). Figure 10 The arrows shown represent the conveying directions of the respective films.

[0192] As described above, in the present invention, the film on the side adhered by the laminating roller is set as the first optical film F1, and the film on the other side is set as the second optical film F2. In the inspection process ST4, the first optical film F1 is the first intermediate M1 (polarizing plate 10 and adhesive layer 3) after inspection, and the second optical film F2 is the release liner 4 (the peeled release liner 4, or a new release liner 4). The first optical film F1 and the second optical film F2 are adhered via the adhesive layer 3 by the laminating roller R5, thereby manufacturing the laminated body F3 of the first optical film F1 and the second optical film F2. In the inspection process ST4, the laminated body F3 is the second intermediate M2.

[0193] Specifically, as Figure 10 shown, on the inlet side of the laminating roller R5 (the upstream side in the transport direction of the first optical film F1 with respect to the laminating roller R5, which is the upper side of the laminating roller R5 in the example shown in Figure 10 ), a first transport roller R6 that contacts the first optical film F1 is arranged. The first optical film F1 is transported to the laminating roller R5 by the first transport roller R6. Similarly, on the inlet side of the laminating roller R5 (the upstream side in the transport direction of the second optical film F2 with respect to the laminating roller R5, which is the upper side of the laminating roller R5 in the example shown in Figure 10 ), a second transport roller R7 that contacts the second optical film F2 is arranged. The second optical film F2 is transported to the laminating roller R5 by the second transport roller R7.

[0194] For the first transport roller R6, its position relative to the laminating roller R5 (the position in the horizontal direction in this embodiment) can be adjusted. In the example shown in Figure 10 , the first transport roller R6 can move from the rightmost position shown by the solid line through the position shown by the dashed line to the leftmost position shown by the one-dot chain line. For example, a configuration can be adopted in which the rotation axis of the first transport roller R6 is mounted on a one-way brake via a bearing, and the position of the first transport roller R6 can be adjusted by driving the one-way brake.

[0195] On the other hand, the second transport roller R7 is fixed at a given position.

[0196] The laminating roller R5 is composed of a first roller R5a and a second roller R5b that are opposed to the first roller R5a (opposed in the horizontal direction in the example shown in Figure 10 ).

[0197] The first roller R5a is a roller that contacts the first optical film F1 and transports the first optical film F1 between the first roller R5a and the second roller R5b. The surface of the first roller R5a is a resin roller formed of resin (silicone rubber in this embodiment).

[0198] The second roller R5b is a roller that contacts the second optical film F2 and transports the second optical film F2 between the first roller R5a and the second roller R5b. The surface of the second roller R5b is a metal roller formed of metal (iron in this embodiment).

[0199] By making the first optical film F1 and the second optical film F2 enter between the first roller R5a and the second roller R5b, the first optical film F1 and the second optical film F2 are laminated to manufacture a laminate F3 of the first optical film F1 and the second optical film F2. The laminate F3 is transported by a transport roller R8 and wound up by a winding roller (not shown).

[0200] In the inspection process ST4, the entry angle α of the first optical film F1 into the laminating roller R5 is adjusted so that the curl value in the TD direction of the laminate F3 falls within a given range. The meaning of the entry angle α is the same as that described with reference to Figure 3 (b). Specifically, the entry angle α is adjusted by horizontally adjusting the position of the first conveying roller R6 relative to the laminating roller R5. When the first conveying roller R6 is located at the rightmost position shown by the solid line in Figure 10 , the entry angle α becomes the minimum 0°, and when the first conveying roller R6 is located at the leftmost position shown by the one-dot chain line, the entry angle α becomes the maximum value.

[0201] Figure 11 FIG. is an example showing the results obtained by measuring the curl value in the TD direction and the curl value in the MD direction of the laminate F3 (second intermediate M2) manufactured through the inspection process ST4. Specifically, Figure 11 is the result obtained by measuring the curl value of the laminate F3 (second intermediate M2) having the same configuration as the example shown in Figure 9 . It should be noted that Figure 11 the results shown are the results obtained when the entry angle β of the second optical film F2 into the laminating roller R1 is 43°.

[0202] As shown in Figure 11 , similar to the results shown in Figure 5 and Figure 9 , corresponding to the entry angle α of the first film F1 into the laminating roller R, the curl value of the laminated laminate F3 in the MD direction is substantially constant, while in contrast, the curl value in the TD direction changes.

[0203] Therefore, if the entry angle α of the first optical film F1 in contact with the first roller R5a into the laminating roller R5 is adjusted so that the curl value in the TD direction of the laminated laminate F3 falls within a given range, the curl value in the TD direction of the laminated laminate F3 can be controlled within the given range, and furthermore, the curl value in the TD direction of the finally manufactured optical laminate 100 can be suppressed to a level that does not cause problems in use. Specifically, if the data shown in Figure 11 is taken in advance and the entry angle α of the first optical film F1 in contact with the first roller R5a into the laminating roller R5 is adjusted based on this data so that the curl value in the TD direction of the laminated laminate F3 falls within a given range, then after the adjustment, the curl value in the TD direction of the laminated laminate F3 can be controlled within the given range.

[0204] [Surface protective film laminating process ST5]

[0205] In the surface protective film laminating step ST5, a long strip-shaped surface protective film 5 is laminated on a long strip-shaped second intermediate M2. Specifically, the long strip-shaped surface protective film 5 is laminated on one side of the polarizing plate 10 that constitutes the second intermediate M2 and is opposite to the side where the release liner 4 is laminated. Thus, a long strip-shaped optical laminate 100 can be manufactured.

[0206] Figure 12 It is a side view schematically showing a brief configuration example of an apparatus for performing the surface protective film laminating step ST5 (a view observed from the horizontal direction (TD direction) orthogonal to the conveyance direction (MD direction) of each film). Figure 12 (a) shows the first example, Figure 12 (b) shows the second example. Figure 12 The arrows shown represent the conveyance directions of the respective films.

[0207] As described above, in the present invention, the film on the side laminated by the laminating roller is defined as the first optical film F1, and the film on the other side is defined as the second optical film F2. In the surface protective film laminating step ST5, the first optical film F1 is the second intermediate M2, and the second optical film F2 is the surface protective film 5. The first optical film F1 and the second optical film F2 are laminated via the adhesive layer of the surface protective film 5 by the laminating roller R9, thereby manufacturing a laminate F3 of the first optical film F1 and the second optical film F2. In the surface protective film laminating step ST5, the laminate F3 is the optical laminate 100.

[0208] Specifically, as Figure 12 shown, for either the first example or the second example, a first conveyance roller R10 that contacts the first optical film F1 is disposed on the inlet side of the laminating roller R9 (the upstream side of the conveyance direction of the first optical film F1 with respect to the laminating roller R9, and the left side of the laminating roller R9 in the example shown in Figure 12 ), and the first optical film F1 is conveyed to the laminating roller R9 by the first conveyance roller R10. Similarly, a second conveyance roller R11 that contacts the second optical film F2 is disposed on the inlet side of the laminating roller R9 (the upstream side of the conveyance direction of the second optical film F2 with respect to the laminating roller R9, and the left side of the laminating roller R9 in the example shown in Figure 12 ), and the second optical film F2 is conveyed to the laminating roller R9 by the second conveyance roller R11.

[0209] Among them, in Figure 12 (a) the first example shown, for the first conveyance roller R10, its position relative to the laminating roller R9 (the position in the up-down direction in this embodiment) can be adjusted. In Figure 12In the first example shown in (a), the first conveying roller R10 can move from the uppermost position shown by the solid line through the position shown by the dashed line to the lowermost position shown by the one-dot chain line. For example, a configuration can be adopted in which the rotation axis of the first conveying roller R10 is mounted on a one-way brake via a bearing, and the position of the first conveying roller R10 can be adjusted by driving the one-way brake. On the other hand, the second conveying roller R11 is fixed at a given position.

[0210] On the other hand, in Figure 12 In the second example shown in (b), for the second conveying roller R11, its position relative to the laminating roller R9 (in the up-down direction in this embodiment) can be adjusted. In Figure 12 In the second example shown in (b), the second conveying roller R11 can move from the lowermost position shown by the solid line through the position shown by the dashed line to the uppermost position shown by the one-dot chain line. For example, a configuration can be adopted in which the rotation axis of the second conveying roller R11 is mounted on a one-way brake via a bearing, and the position of the second conveying roller R11 can be adjusted by driving the one-way brake. On the other hand, the first conveying roller R10 is fixed at a given position.

[0211] For either the first example or the second example, the laminating roller R9 is composed of a first roller R9a and a second roller R9b that are opposed to the first roller R9a (opposed in the up-down direction in the example shown). Figure 12 shown).

[0212] The first roller R9a in the first example and the second example is a roller that contacts the first optical film F1 and conveys the first optical film F1 between the first roller R9a and the second roller R9b. The first roller R9a is a resin roller whose surface is formed of resin (silicone rubber in this embodiment).

[0213] The second roller R9b in the first example and the second example is a roller that contacts the second optical film F2 and conveys the second optical film F2 between the first roller R9a and the second roller R9b. Similar to the first roller R9a, the second roller R9b is also a resin roller whose surface is formed of resin (silicone rubber in this embodiment).

[0214] By introducing the first optical film F1 and the second optical film F2 between the first roller R9a and the second roller R9b, the first optical film F1 and the second optical film F2 are laminated to manufacture a laminate F3 of the first optical film F1 and the second optical film F2. The laminate F3 is conveyed by the conveying roller R12 and wound up by a winding roller (not shown).

[0215] In the surface protective film laminating step ST5, in Figure 12In the case of the first example shown in (a), the entry angle α of the first optical film F1 into the laminating roller R9 is adjusted so that the curl value in the TD direction of the laminate F3 falls within a given range. The meaning of the entry angle α is the same as that described with reference to Figure 3 (b). Specifically, the entry angle α is adjusted by adjusting the position of the first conveying roller R10 relative to the laminating roller R9 in the vertical direction. When the first conveying roller R10 is located at the uppermost position shown by the solid line in Figure 12 (a), the entry angle α becomes the minimum value of 0°, and when the first conveying roller R10 is located at the lowermost position shown by the one-dot chain line, the entry angle α becomes the maximum value.

[0216] In addition, in Figure 12 the case of the second example shown in (b), the entry angle β of the second optical film F2 into the laminating roller R9 is adjusted so that the curl value in the TD direction of the laminate F3 falls within a given range. The meaning of the entry angle β is the same as that described with reference to Figure 3 (b). Specifically, the entry angle β is adjusted by adjusting the position of the second conveying roller R11 relative to the laminating roller R9 in the vertical direction. When the second conveying roller R11 is located at the lowermost position shown by the solid line in Figure 12 (b), the entry angle β becomes the minimum value of 0°, and when the second conveying roller R11 is located at the uppermost position shown by the one-dot chain line, the entry angle β becomes the maximum value.

[0217] Figure 13 is a diagram showing an example of the results obtained by measuring the curl value in the TD direction of the laminate F3 (optical laminate 100) manufactured through the surface protective film laminating step ST5. In Figure 13 , the data represented by the symbol α is the curl value in the TD direction obtained in the first example shown in Figure 12 (a), and the data represented by the symbol β is the curl value in the TD direction obtained in the second example shown in Figure 12 (b). Specifically, Figure 13 is the result of measuring the curl value in the TD direction of the laminate F3 (optical laminate) in which a surface protective film 5 with a total thickness of 48 μm (base material: polyethylene terephthalate with a thickness of 38 μm, adhesive layer: acrylic adhesive with a thickness of 10 μm) is pasted on the second intermediate M2 having the same configuration as the example shown in Figure 9 . It should be noted that Figure 13 the data represented by the symbol α is the data obtained when the entry angle β of the second optical film F2 into the laminating roller R9 is 30°. In addition, Figure 13The data represented by the symbol β is the data obtained when the entry angle α of the first optical film F1 into the laminating roller R9 is 30°.

[0218] As Figure 13 shown, for the first example, similar to the results shown by Figure 5 etc., the curl value of the laminated body F3 in the TD direction after lamination changed corresponding to the entry angle α of the first film F1 into the laminating roller R9. Similarly, for the second example, the curl value of the laminated body F3 in the TD direction after lamination changed corresponding to the entry angle β of the second film F2 into the laminating roller R9.

[0219] Therefore, in the case of the first example, if the entry angle α of the first optical film F1 in contact with the first roller R9a into the laminating roller R9 is adjusted in such a way that the curl value of the laminated body F3 in the TD direction after lamination reaches a given range, then the curl value of the laminated body F3 after lamination, that is, the TD direction curl value of the finally manufactured optical laminate 100, can be controlled within the given range, and the TD direction curl value of the optical laminate 100 can be suppressed to a level that does not cause problems in use. In addition, in the case of the second example, if the entry angle β of the second optical film F2 in contact with the second roller R9b into the laminating roller R9 is adjusted in such a way that the curl value of the laminated body F3 in the TD direction after lamination reaches a given range, then the curl value of the laminated body F3 after lamination, that is, the TD direction curl value of the finally manufactured optical laminate 100, can be controlled within the given range.

[0220] Specifically, in the case of the first example, if the data as Figure 13 shown is taken in advance and the entry angle α of the first optical film F1 in contact with the first roller R9a into the laminating roller R9 is adjusted based on this data in such a way that the curl value of the laminated body F3 in the TD direction after lamination reaches a given range, then after adjustment, the curl value of the laminated body F3 after lamination, that is, the TD direction curl value of the finally manufactured optical laminate 100, can be controlled within the given range. In addition, in the case of the second example, if the data as Figure 13 shown is taken in advance and the entry angle β of the second optical film F2 in contact with the second roller R9b into the laminating roller R9 is adjusted based on this data in such a way that the curl value of the laminated body F3 in the TD direction after lamination reaches a given range, then after adjustment, the curl value of the laminated body F3 after lamination, that is, the TD direction curl value of the finally manufactured optical laminate 100, can be controlled within the given range.

[0221] Figure 14It is a side view (a view observed from the horizontal direction (TD direction) orthogonal to the conveyance direction (MD direction) of each film) schematically showing another brief configuration example of the apparatus for performing the surface protective film laminating step ST5 and the brief configuration of the apparatus of a reference example. Figure 14 (a) shows the third example, Figure 14 (b) shows the reference example. Figure 14 The arrows shown represent the conveyance directions of the respective films.

[0222] In Figure 14 the third example shown in (a), the second roller R9b is a metal roller whose surface is formed of metal (iron in the present embodiment), and except for this point, it has the same configuration as Figure 12 the first example shown in (a).

[0223] In Figure 14 the reference example shown in (b), the second roller R9b is a metal roller whose surface is formed of metal (iron in the present embodiment), and except for this point, it has the same configuration as Figure 12 the second example shown in (b).

[0224] Figure 15 It is a view showing an example of the result obtained by measuring the curl value in the TD direction of the laminate F3 (optical laminate 100) manufactured by the surface protective film laminating step ST5. In Figure 15 it, the data represented by the symbol α is the curl value in the TD direction obtained in Figure 14 the third example shown in (a), and the data represented by the symbol β is the curl value in the TD direction obtained in Figure 14 the reference example shown in (b). It should be noted that Figure 15 the data represented by the symbol α is the data obtained when the entry angle β of the second optical film F2 into the laminating roller R9 is 30°. In addition, Figure 15 the data represented by the symbol β is the data obtained when the entry angle α of the first optical film F1 into the laminating roller R9 is 30°.

[0225] As Figure 15 shown, regarding the third example, similar to the results shown in Figure 5 etc., the curl value of the laminate F3 in the TD direction after lamination changed corresponding to the entry angle α of the first film F1 into the laminating roller R9. In contrast, regarding the reference example, the curl value of the laminate F3 in the TD direction after lamination was substantially constant corresponding to the entry angle β of the second film F2 into the laminating roller R9.

[0226] Therefore, in the case of Example 3, if the entry angle α of the first optical film F1 in contact with the first roller R9a into the laminating roller R9 is adjusted such that the curl value in the TD direction of the laminated body F3 after lamination falls within a given range, then the curl value in the TD direction of the laminated body F3 after lamination, that is, the final manufactured optical laminate 100, can be controlled within the given range, and the curl value in the TD direction of the optical laminate 100 can be suppressed to a level that does not pose a problem in use. Specifically, if the data as shown in Figure 15 is taken in advance, and based on this data, the entry angle α of the first optical film F1 in contact with the first roller R9a into the laminating roller R9 is adjusted such that the curl value in the TD direction of the laminated body F3 after lamination falls within a given range, then after the adjustment, the curl value in the TD direction of the laminated body F3 after lamination, that is, the final manufactured optical laminate 100, can be controlled within the given range.

[0227] In contrast, in the case of the reference example, even if the entry angle β of the second optical film F2 in contact with the second roller R9b into the laminating roller R9 is adjusted, the curl value of the laminated body F3 in the TD direction is substantially constant. Therefore, the curl value in the TD direction of the laminated body F3 after lamination, that is, the final manufactured optical laminate 100, cannot be controlled within the given range, and there is a risk that the curl value in the TD direction of the optical laminate 100 cannot be suppressed to a level that does not pose a problem in use.

[0228] According to the manufacturing method of the present embodiment described above, curling can be effectively suppressed without particularly changing the material of the constituent elements of the optical laminate 100 used in the past.

[0229] It should be noted that in the present embodiment, an example in which the present invention is applied, that is, the entry angle of the optical film in contact with the resin roller constituting the laminating roller into the laminating roller is adjusted, is described for the three processes of the release liner laminating process ST3, the inspection process ST4, and the surface protective film laminating process ST5. However, the present invention is not limited thereto. It can also be applied to only any one or two of the processes ST3 to ST5, or can also be applied to other processes of laminating films.

[0230] In addition, in the present embodiment, an example in which the polarizer 10 is a laminate of a polarizing film 1 and a retardation film 2 is described. However, the present invention is not limited thereto. It can also adopt a mode in which the polarizer 10 is a laminate of a polarizing film 1, a retardation film 2, and other constituent elements, a mode in which there is no retardation film 2 and the polarizer 10 is a laminate of a polarizing film 1 and other constituent elements, a mode in which only the polarizing film 1 exists in the polarizer 10, and the like.

Claims

1. A method for manufacturing an optical laminate, the method comprising: a step of bonding a long strip-shaped first optical film including a polarizing plate, which is conveyed along the length direction, and a long strip-shaped second optical film, which is conveyed along the length direction, via an adhesive layer by a bonding roll; the bonding roll is composed of a first roll that contacts the first optical film and a second roll that is disposed opposite to the first roll and contacts the second optical film. By making the first optical film and the second optical film enter between the first roll and the second roll, the first optical film and the second optical film are bonded together; the surface of at least one of the first roll and the second roll is formed of resin; when the surface of the first roll is formed of resin, the entry angle of the first optical film into the bonding roll is adjusted so that the curl value of the laminate of the first optical film and the second optical film in a direction orthogonal to the length direction falls within a given range. Or, when the surface of the second roll is formed of resin, the entry angle of the second optical film into the bonding roll is adjusted so that the curl value of the laminate of the first optical film and the second optical film in a direction orthogonal to the length direction falls within a given range.

2. The method for manufacturing an optical laminate according to claim 1, wherein, the surface of the first roll is formed of resin.

3. The method for manufacturing an optical laminate according to claim 1 or 2, wherein, when the surface of the first roll is formed of resin, a first conveying roll that contacts the first optical film is disposed on the inlet side of the bonding roll, and the position of the first conveying roll relative to the bonding roll is adjusted, thereby adjusting the entry angle of the first optical film into the bonding roll. Or, when the surface of the second roll is formed of resin, a second conveying roll that contacts the second optical film is disposed on the inlet side of the bonding roll, and the position of the second conveying roll relative to the bonding roll is adjusted, thereby adjusting the entry angle of the second optical film into the bonding roll.

4. The method for manufacturing an optical laminate according to claim 1 or 2, wherein, the second optical film is a release liner, the surface of the second roll is formed of metal.

5. The method for manufacturing an optical laminate according to claim 1 or 2, wherein, the second optical film is a surface protective film.

6. The method for manufacturing an optical laminate according to claim 1 or 2, wherein, when the surface of the first roll is formed of resin, the entry angle of the first optical film into the bonding roll is adjusted to 75° or less. Or, when the surface of the second roll is formed of resin, the entry angle of the second optical film into the bonding roll is adjusted to 75° or less.

7. The method for manufacturing an optical laminate according to claim 1 or 2, wherein, when the surface of the first roll is formed of resin, the surface of the first roll is formed of rubber, when the surface of the second roll is formed of resin, the surface of the second roll is formed of rubber.

Images