Method for manufacturing optical laminates

Abstract

This invention provides a method for manufacturing optical laminates that can suppress curling. [Solution] The method for manufacturing the optical laminate 100 according to the present invention includes a separator bonding step ST4 in which the separator 4 is bonded to the polarizing plate 10 via an adhesive layer 3 formed on the separator 4, and a separator peeling and bonding step ST5 in which, after the separator bonding step, the separator is peeled off from the adhesive layer and then bonded to the polarizing plate via the adhesive layer. In the separator peeling and bonding step, at least the peeling of the separator is performed at an absolute humidity of 10 g / m 3 This is performed in an environment with increased humidity.

Description

[Technical Field]

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

[0002] Conventionally, polarizers have been used as constituent materials for liquid crystal displays and organic EL displays. A polarizer comprises a polarizing film and, depending on the application, a phase difference film or the like. A polarizing film consists of, for example, a polarizer dyed with a dichroic substance such as iodine and a protective film that protects this polarizer. A long strip polarizing film is manufactured by laminating a long strip protective film to at least one side of a long strip polarizer. A long strip phase difference film or the like is then laminated to one side of the manufactured long strip polarizing film to produce a long strip polarizing plate. A long strip separator (release film) is laminated to one side of the manufactured long strip polarizing plate, and a long strip surface protective film is laminated to the other side to produce a long strip optical laminate. The lamination of these long strip films is usually carried out using a roll-to-roll or roll-to-sheet method. The manufactured long strip optical laminate is cut to the appropriate size and shape for use in liquid crystal displays and the like. When used in liquid crystal display devices, the separator is removed, and the remaining components of the optical laminate are attached to the liquid crystal display device.

[0003] Figure 6 is a flowchart showing a schematic example of a conventional optical laminate manufacturing method. As shown in Figure 6, the conventional optical laminate manufacturing method includes a polarizing film manufacturing step ST1', a phase difference film lamination step ST2', a tempering step ST3', a separator lamination step ST4', an inspection step ST5', and a surface protection film lamination step ST6'. In the polarizing film manufacturing process ST1', a long strip of resin film is used as the raw material, and while this raw material film is transported in the longitudinal direction, it is immersed in various treatment baths to perform various treatments such as dyeing and stretching, thereby manufacturing a long strip of polarizer. Then, a long strip of protective film is laminated to at least one side of the long strip of polarizer to manufacture a long strip of polarizing film. In the phase difference film lamination process ST2', a long strip of polarizing film (such as a half-wave plate or a quarter-wave plate) is laminated to one side of a long strip of polarizing film to produce a long strip of polarizing film.

[0004] In the humidity control process ST3', the moisture content of the polarizing plate is adjusted by humidifying it while transporting the long, strip-shaped polarizing plate in the longitudinal direction. In the separator bonding process ST4', an adhesive is applied to a long, strip-shaped separator while it is being transported in the longitudinal direction. This applied adhesive is then heated and dried in an oven or the like to harden it and form an adhesive layer. The adhesive layer side of this long, strip-shaped separator (separator with adhesive layer) is then bonded to one side of a long, strip-shaped polarizing plate to produce a long, strip-shaped intermediate in which the polarizing plate, adhesive layer, and separator are laminated. In inspection step ST5', the separator is peeled off while leaving the adhesive layer between the separator and the polarizing plate on the polarizing plate side, and the polarizing plate is inspected. Inspection methods for the polarizing plate include transmission inspection, crossed nicol inspection, and reflection inspection. After inspecting the polarizing plate in inspection step ST5', the peeled separator is reattached to the polarizing plate to return it to its original intermediate state. Note that conventional inspection step ST5' is performed in a non-humidified environment, i.e., in a normal atmosphere without humidity.

[0005] In the surface protection film lamination process ST6', a long strip of surface protection film is laminated to the side of the long strip of polarizing plate opposite to the side to which the separator is laminated. A long, strip-shaped optical laminate is manufactured through the polarizing film manufacturing process ST1' to the surface protective film lamination process ST6' described above.

[0006] However, optical laminates manufactured in the manner described above may develop curl (warping of the edges) after being cut to product size, which can be problematic in terms of use. For example, Patent Document 1 proposes using a specific material for the protective film protecting the polarizer as a method to suppress the curling of a polarizing film, but this method is not general-purpose because the material of the protective film is limited. There is a need for a method that can suppress curling without particularly changing the materials of the components of the optical laminate used conventionally. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2007-256568 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention was made to solve the problems of the prior art described above, and aims to provide a method for manufacturing an optical laminate that can suppress curling. [Means for solving the problem]

[0009] To solve the aforementioned problems, the inventors conducted diligent research and found that a decrease in the moisture content of the polarizing plate in conventional optical laminate manufacturing methods may be one of the causes of curling in optical laminates. Specifically, for example, in the polarizing film manufacturing process ST1', after a protective film is laminated to the polarizer, it is heated and dried in an oven or the like, which is thought to decrease the moisture content of the polarizing plate (polarizing film). Also, for example, if the phase difference film laminated to the polarizing film in the phase difference film lamination process ST2' is a layer formed by polymerizing polymerizable liquid crystal, it is thought that the curing heat generated during polymerization will decrease the moisture content of the polarizing plate. Thus, since conventional optical laminate manufacturing methods include processes that can decrease the moisture content of the polarizing plate, even if the moisture content of the polarizing plate is adjusted in the humidity control process ST3', it is thought that a sufficient moisture content cannot be maintained, resulting in curling of the optical laminate. The inventors, focusing on the above-mentioned causes, conducted further intensive studies and found that by humidifying the polarizing plate at the timing of peeling off the separator, which is generally made from a material with low moisture permeability, as in inspection step ST5', the moisture content of the polarizing plate can be efficiently increased through the adhesive layer remaining on the polarizing plate, and as a result, curling of the optical laminate can be suppressed. This invention was completed based on the above-mentioned findings of the inventors.

[0010] In other words, to solve the above problems, the present invention includes a separator bonding step of bonding the separator to a polarizing plate via an adhesive layer formed on the separator, and a separator peeling and bonding step of peeling the separator from the adhesive layer after the separator bonding step and then bonding the separator to the polarizing plate via the adhesive layer, wherein in the separator peeling and bonding step, at least the peeling of the separator is performed at an absolute humidity of 10 g / m 3 The present invention provides a method for manufacturing optical laminates, which is carried out in an environment with the above-mentioned level of humidity.

[0011] The separator peeling and bonding process of the present invention is not limited to the process of inspecting the polarizing plate. Without performing the inspection of the polarizing plate, it simply includes the process of bonding the separator after peeling the separator. Also, in the separator peeling and bonding process of the present invention, the peeled separator and the separator to be bonded may be the same separator or different new separators. That is, the separator peeling and bonding process of the present invention includes the case where, after peeling the separator from the adhesive layer (peeling only the separator while leaving the adhesive layer on the polarizing plate), the same separator is bonded again to the polarizing plate through the adhesive layer, and also includes the case where a new separator different from the peeled separator is bonded (replaced) to the polarizing plate through the adhesive layer. According to the present invention, in the separator peeling and bonding process, at least the peeling of the separator is performed in an environment humidified to an absolute humidity of 10 g / m 3 or more, so that the moisture content of the polarizing plate can be increased efficiently, and thus the curl of the optical laminate can be suppressed.

[0012] Preferably, in the separator peeling and bonding process, at least the peeling of the separator is performed inside a humidified housing. According to the above preferred method, it is only necessary to humidify only the inside of the housing where the separator is peeled (the outside of the housing does not need to be humidified), so that the moisture content of the polarizing plate can be increased more efficiently.

[0013] Preferably, the present invention includes a surface protection film bonding process of bonding a surface protection film to the polarizing plate after the separator peeling and bonding process.

[0014] Preferably, the separator peeling and bonding process also serves as an inspection process of inspecting the polarizing plate after peeling the separator. According to the above preferred method, since the separator peeling and bonding process also serves as an inspection process of the polarizing plate, it has the advantage that the manufacturing process becomes simpler compared to the case where this separator peeling and bonding process and the inspection process are provided separately.

[0015] Preferably, the separator peeling and lamination process is performed in an environment with a higher absolute humidity than the separator lamination process.

[0016] Preferably, the separator peeling and bonding process is performed inside a housing where a humidifier is located, and the humidifier maintains an absolute humidity of 10 g / m² inside the housing. 3 The humidification level will be increased to the above. [Effects of the Invention]

[0017] According to the present invention, curling can be effectively suppressed without particularly changing the material of the components of the optical laminate used in the conventional method. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic cross-sectional view showing the general structure of an optical laminate manufactured by a manufacturing method according to one embodiment of the present invention. [Figure 2] This is a flowchart showing the general steps of a method for manufacturing an optical laminate according to one embodiment of the present invention. [Figure 3] Figure 2 shows a schematic example of the general configuration of the apparatus that performs the separator peeling and bonding process ST5. [Figure 4] This figure schematically shows another example of the schematic configuration of the apparatus that performs the separator peeling and bonding process ST5 shown in Figure 2. [Figure 5] This is an explanatory diagram illustrating the evaluation method for curl. [Figure 6] This is a flowchart showing an example of a general process for manufacturing conventional optical laminates. [Modes for carrying out the invention]

[0019] The following describes a method for manufacturing an optical laminate according to one embodiment of the present invention, with appropriate reference to the attached drawings. Please note that the figures are for reference only, and the dimensions, scale, and shape of the optical laminate and device components shown in the figures may differ from those of the actual objects.

[0020] <Configuration of the optical laminate> First, the configuration of the optical laminate manufactured by the manufacturing method according to this embodiment will be described. Figure 1 is a schematic cross-sectional view showing the general structure of an optical laminate manufactured by the manufacturing method according to this embodiment. As shown in Figure 1, the optical laminate 100 of this embodiment comprises a polarizing film 1, a phase difference film 2, an adhesive layer 3, a separator 4, and a surface protection film 5. The laminate of the polarizing film 1 and the phase difference film 2 constitutes the polarizing plate 10. The laminate of the polarizing plate 10 and the adhesive layer 3 constitutes the first intermediate M1. The laminate of the first intermediate M1 and the separator 4 constitutes the second intermediate M2. The individual components of the optical laminate 100 will be described below.

[0021] [Polarizing film 1] The polarizing film 1 consists of a polarizer 11 and protective films 12 and 13 that protect the polarizer 11. In this embodiment, the protective films 12 and 13 are bonded to both sides of the polarizer 11, but this is not the only option; it is sufficient if the protective film is bonded to at least one side of the polarizer 11.

[0022] (Polarizer 11) The polarizer 11 is typically composed of a resin film containing a dichroic substance. Any suitable resin film that can be used as a polarizer can be employed. Typically, the resin film is a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film.

[0023] Any suitable resin can be used as the PVA resin for forming the above-mentioned PVA resin film. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer is obtained by saponifying ethylene-vinyl acetate copolymer.

[0024] The average degree of polymerization of PVA resins can be appropriately selected depending on the purpose. The average degree of polymerization is typically 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined in accordance with JIS K 6726-1994.

[0025] Examples of dichroic substances included in the resin film include iodine and organic dyes. These can be used individually or in combination of two or more. Iodine is preferably used.

[0026] The resin film may be a single-layer resin film or a laminate of two or more layers.

[0027] A specific example of a polarizer composed of a single layer of resin film is one in which a PVA-based resin film has been subjected to iodine dyeing and stretching (typically uniaxial stretching). Iodine dyeing is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio for uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing, or during dyeing. Dyeing may also be performed after stretching. If necessary, the PVA-based resin film may be subjected to swelling, crosslinking, washing, drying, etc.

[0028] Specific examples of polarizers composed of laminates include polarizers composed of a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or polarizers composed of a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer composed of a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be manufactured, for example, by applying a PVA-based resin solution to a resin substrate, drying it to form a PVA-based resin layer on the resin substrate, obtaining a laminate of the resin substrate and the PVA-based resin layer, and then stretching and dyeing this laminate to make the PVA-based resin layer a polarizer. In this embodiment, stretching typically includes immersing the laminate in a boric acid aqueous solution and stretching it. Furthermore, stretching may, if necessary, include air stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution. The resulting resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate, and any appropriate protective layer may be laminated onto this peeled surface according to the purpose. Details of such a polarizer manufacturing method are described, for example, in Japanese Patent Application Publication No. 2012-73580. The entire description of this publication is incorporated herein by reference.

[0029] The thickness of the polarizer 11 is preferably 15 μm or less, more preferably 1 μm to 12 μm, even more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0030] The polarizer 11 preferably exhibits absorption dichroism at any wavelength within the range of 380 nm to 780 nm. The 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 higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0031] (Protective film 12, 13) As the protective films 12 and 13, any appropriate resin film is used. Examples of the forming material of the resin film include (meth)acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. Note that the “(meth)acrylic resin” means an acrylic resin and / or a methacrylic resin. The forming materials of the protective films 12 and 13 may be the same as or different from each other. As will be described later, by performing the separator peeling and bonding step ST5 in a humidified environment, the moisture content of the polarizing plate 10 is increased. Therefore, it is preferable that the forming material of either one of the protective films 12 and 13 is a cellulose resin such as triacetyl cellulose with high moisture permeability. The moisture permeability of the forming material with high moisture permeability of either one of the protective films 12 and 13 is such that the moisture permeability in terms of 1 μm (the moisture permeability when the film thickness is 1 μm) is 25 g / (m 2 ·24 h) to 100 g / (m 2 ·24 h), preferably 40 g / (m 2 ·24 h) to 75 g / (m 2 ·24 h). On the other hand, the protective film 12 located on the side opposite to the adhesive layer 3 and the separator 4 of the polarizer 11 may be formed from a forming material with low moisture permeability such as a cycloolefin resin. The moisture permeability of the forming material with low moisture permeability is such that the moisture permeability in terms of 1 μm is 0.2 g / (m 2 ·24 h) to 3.4 g / (m 2 ·24 h), preferably 0.3 g / (m 2 ·24 h) to 1.7 g / (m 2 ·24 h). Even in such a case, in this embodiment, as will be described later, by peeling the separator 4 in the separator peeling and bonding step ST5 performed in a humidified environment, the moisture content of the polarizing plate 10 can be increased through the adhesive layer 3.

[0032] The thickness of the protective films 12 and 13 is typically 10 μm to 100 μm, preferably 10 μm to 40 μm, and more preferably 20 μm to 40 μm. The thicknesses of the protective films 12 and 13 may be the same or different.

[0033] The surfaces of the protective films 12 and 13 opposite to the polarizer 11 may be treated as needed with surface treatments such as hard coating, anti-reflective coating, anti-sticking coating, or anti-glare coating. Furthermore / or, the surfaces of the protective films 12 and 13 opposite to the polarizer 11 may be treated as needed with a treatment to improve visibility when viewed through polarized sunglasses (typically, a treatment to impart (elliptical) polarization function or a treatment to impart ultra-high phase difference). When a surface treatment is applied and a surface treatment layer is formed, the thickness of the protective films 12 and 13 includes the thickness of the surface treatment layer.

[0034] The protective films 12 and 13 are laminated to the polarizer 11 via an arbitrary and suitable adhesive layer (not shown). Typical adhesives that make up the adhesive layer include PVA-based adhesives and activated energy ray-curing adhesives.

[0035] [Phase difference film 2] The phase difference film 2 may be, for example, a compensating plate that provides a wide viewing angle, or it may be a phase difference plate (circular polarizer) such as a half-wave plate or a quarter-wave plate used with a polarizing film to generate circularly polarized light. The thickness of the phase difference film 2 is, for example, 1 to 200 μm.

[0036] The phase difference film 2 is formed, for example, from a layer or resin formed by polymerizing a polymerizable liquid crystal. A polymerizable liquid crystal is a compound that has polymerizable groups and liquid crystalline properties. A polymerizable group is a group that participates in the polymerization reaction, and is preferably a photopolymerizable group. Here, a photopolymerizable group is a group that can participate in the polymerization reaction by active radicals or acids generated from a photopolymerization initiator. Examples of polymerizable groups include vinyl groups, vinyloxy groups, 1-chlorovinyl groups, isopropenyl groups, 4-vinylphenyl groups, acryloyloxy groups, methacryloyloxy groups, oxyranyl groups, and oxetanyl groups. Among these, acryloyloxy groups, methacryloyloxy groups, vinyloxy groups, oxyranyl groups, and oxetanyl groups are preferred, and acryloyloxy groups are more preferred. The liquid crystalline properties of the polymerizable liquid crystal may be thermotropic or lyotropic, and if the thermotropic liquid crystal is classified by its degree of order, it may be nematic or smectic. Furthermore, examples of resins used to form the phase difference film 2 include polyarylate, polyamide, polyimide, polyester, polyaryletherketone, polyamideimide, polyesterimide, polyvinyl alcohol, polyfumarate ester, polyethersulfone, polysulfone, norbornene resin, polycarbonate resin, cellulose resin, and polyurethane. These resins may be used individually or in combination.

[0037] The phase difference film 2 is laminated to the polarizing film 1 (protective film 13) via any suitable adhesive layer or tack layer (not shown). Typical adhesives that make up the adhesive layer include PVA-based adhesives and activated energy ray-curing adhesives.

[0038] [Adhesive layer 3] The adhesive layer 3 is formed by applying adhesive to one side of the separator 4 and then curing the applied adhesive by heating and drying it in an oven or the like. The heating temperature of the adhesive is preferably set in the range of 100°C to 160°C, and more preferably in the range of 140°C to 160°C. At this heating temperature, it is preferably heated for 20 seconds to 3 minutes, and more preferably for 1 minute to 3 minutes.

[0039] Specific examples of adhesives that form the adhesive layer 3 include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination and blending ratio of monomers that form the base resin of the adhesive, as well as the amount of crosslinking agent, reaction temperature, reaction time, etc., an adhesive having the desired properties according to the purpose can be prepared. The base resin of the adhesive may be used alone or in combination of two or more types. From the viewpoint of transparency, processability and durability, acrylic adhesives are preferred. Details of the adhesives constituting the adhesive layer are described, for example, in Japanese Patent Application Publication No. 2014-115468, and the description in said publication is incorporated herein by reference. The thickness of the adhesive layer can be, for example, 10 μm to 100 μm, preferably 10 μm to 40 μm, and more preferably 10 μm to 30 μm.

[0040] [Separator 4] Any suitable separator can be used as separator 4. Specific examples include plastic films, nonwoven fabrics, or paper coated with a release agent. Specific examples of release agents include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents. Specific examples of plastic films include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. The thickness of separator 4 can be, for example, 10 μm to 100 μm.

[0041] [Surface protection film 5] The surface protection film 5 typically comprises a substrate and an adhesive layer. In this embodiment, the thickness of the surface protection film 5 is, for example, 30 μm or more. The upper limit of the thickness of the surface protection film 5 is, for example, 150 μm. In this specification, "thickness of the surface protection film" refers to the total thickness of the substrate and the adhesive layer.

[0042] The base material can be made of any suitable resin film. Examples of resin film forming materials include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Preferably, it is an ester resin (particularly polyethylene terephthalate resin).

[0043] Any suitable adhesive can be used to form the adhesive layer. Examples of base resins for the adhesive include acrylic resins, styrene resins, silicone resins, urethane resins, and rubber resins.

[0044] <Manufacturing method according to this embodiment> A method for manufacturing the optical laminate 100 having the configuration described above, according to this embodiment, will be described below. Figure 2 is a flowchart showing the schematic steps of the manufacturing method for the optical laminate 100 according to this embodiment. As shown in Figure 2, the manufacturing method according to this embodiment includes a polarizing film manufacturing step ST1, a phase difference film lamination step ST2, a humidity control step ST3, a separator lamination step ST4, a separator peeling and lamination step ST5, and a surface protection film lamination step ST6. Each step ST1 to ST6 will be described below.

[0045] [Polarizing film manufacturing process ST1] In the polarizing film manufacturing process ST1, a long strip of resin film is used as the raw material film. This raw material film is transported in the longitudinal direction (MD direction) and immersed in various treatment baths to perform various treatments such as dyeing and stretching, thereby manufacturing a long strip of polarizer 11. Then, long strips of protective films 12 and 13 are laminated onto the long strip of polarizer 11 to manufacture a long strip of polarizing film 1.

[0046] [Phase difference film lamination process ST2] In the phase difference film lamination process ST2, a long strip of phase difference film 2 is laminated onto one side (protective film 13) of a long strip of polarizing film 1 to manufacture a long strip of polarizing plate 10. Furthermore, if the optical laminate 100 does not include the phase difference film 2 (i.e., the polarizing plate 10 does not include the phase difference film 2), the phase difference film lamination process ST2 is unnecessary.

[0047] [Humidity Control Process ST3] In the humidity control process ST3, the moisture content of the polarizing plate 10 is adjusted by humidifying it while transporting the long, strip-shaped polarizing plate 10 in the longitudinal direction (MD direction). Humidification of the polarizing plate 10 can be performed, for example, using a general-purpose electric humidifier. In the humidity control process ST3, the ambient temperature is, for example, 20-50°C, the relative humidity of the atmosphere is, for example, 60-95%, and the humidification time is, for example, 1-60 minutes.

[0048] [Separator bonding process ST4] In the separator bonding process ST4, an adhesive is applied to a long, strip-shaped separator 4 while it is being transported in the longitudinal direction (MD direction). The applied adhesive is then heated and dried in an oven or the like to harden it, forming an adhesive layer 3. Then, the separator 4 is bonded to the long, strip-shaped polarizing plate 10 via the adhesive layer 3 formed on the separator 4. Specifically, the adhesive layer 3 side of the long, strip-shaped separator 4 (separator 4 with adhesive layer 3) is bonded to one side (phase difference film 2) of the long, strip-shaped polarizing plate 10. This produces a second intermediate M2 in which the polarizing plate 10, adhesive layer 3, and separator 4 are laminated.

[0049] [Separator peeling and bonding process ST5] In the separator peeling and lamination process ST5, the separator 4 is peeled from the adhesive layer 3 (leaving the adhesive layer 3 interposed between the separator 4 and the polarizing plate 10 on the polarizing plate 10 side, while only the separator 4 is peeled off), and then the separator 4 is laminated to the polarizing plate 10 via the adhesive layer 3. In this separator peeling and lamination process ST5, at least the peeling of the separator 4 is performed at an absolute humidity of 10 g / m 3 This process is carried out in an environment with the above level of humidification. The humidified environment is preferably one with an absolute humidity of 11 g / m³. 3 The above is more preferable, with an absolute humidity of 12 g / m². 3 The above is preferable, and more preferably, the absolute humidity is 13 g / m². 3 That concludes the explanation. Specifically, at least the separation of separator 4 is at an absolute humidity of 10 g / m². 3 This is performed inside the humidified enclosure 20. In this embodiment, the separator peeling and bonding process ST5 also serves as an inspection process for inspecting the polarizing plate 10 after the separator 4 has been peeled off. The peeling and bonding process ST5 of this embodiment will now be described in more detail.

[0050] Figure 3 is a schematic diagram illustrating an example of the general configuration of the apparatus that performs the separator peeling and lamination process ST5. Figure 3(a) is a side view (viewed from a horizontal direction perpendicular to the transport direction of each film), illustrating the inside of the housing 20 as seen through. Figure 3(b) is a view of the housing 20 shown in Figure 3(a) from the direction of arrow X1 shown in Figure 3(a). Figure 3(c) is a view of the housing 20 shown in Figure 3(a) from the direction of arrow X2 shown in Figure 3(a). The remaining small arrows shown in Figure 3(a) indicate the transport direction of each film. In the separator peeling and bonding process ST5, as described above, the second intermediate M2 produced in the separator bonding process ST4 is wound onto the feed roller R1 shown in Figure 3 and positioned at the upstream end of the apparatus (the upstream end in the transport direction of the second intermediate M2). The second intermediate M2, fed out from the feed roller R1, is then transported toward the peeling roller R2. At the peeling roller R2, the separator 4 is peeled away from the second intermediate M2 (only the separator 4 is peeled away, leaving the adhesive layer 3 on the polarizing plate 10 side), and the peeled separator 4 is transported toward the bonding roller R3.

[0051] Meanwhile, the first intermediate M1, which is a laminate of the polarizing plate 10 and the adhesive layer 3 obtained by peeling off the separator 4 from the second intermediate M2 with the peeling roller R2, is inspected by the inspection device 40. The inspection device 40 shown in Figure 3 is a device for performing transmission inspection and comprises a light source 40a, an imaging means 40b, and a calculation means (not shown). The imaging means 40b of the inspection device 40 receives light emitted from the light source 40a and transmitted through the first intermediate M1, forms an image, and outputs an electrical signal corresponding to the amount of light as an imaging signal to the calculation means. The calculation means generates a transmission image based on this input imaging signal. The calculation means then detects defects present in the first intermediate M1 (polarizing plate 10) by applying known image processing, such as binarization, to the generated transmission image to extract pixel regions whose brightness values ​​(pixel values) differ from other pixel regions. Furthermore, the inspection performed in the inspection process that also serves as the separator peeling and bonding process ST5 in this embodiment is not limited to the transmission inspection described above. It is also possible to employ a cross-nicol inspection that generates a cross-nicol image using light transmitted through an inspection polarizing filter and the first intermediate M1, which are positioned so as to be cross-nicols with respect to the polarization axis of the polarizer 11 of the polarizer plate 10, and detects defects present in the first intermediate M1 (polarizer plate 10) based on this cross-nicol image. It is also possible to employ a reflection inspection that generates a reflection image using light reflected by the first intermediate M1, and detects defects present in the first intermediate M1 (polarizer plate 10) based on this reflection image. Moreover, it is possible to perform any combination of the transmission inspection, cross-nicol inspection, and reflection inspection.

[0052] After being inspected by the inspection device 40, the first intermediate M1 is conveyed toward the bonding roller R3. The bonding roller R3 then bonds the separator 4 to the first intermediate M1 again. That is, the separator 4 is bonded to the polarizing plate 10 that constitutes the first intermediate M1 via the adhesive layer 3 that constitutes the first intermediate M1. This produces the second intermediate M2, which is then wound up by the winding roller R4. The separator 4 of the second intermediate M2 that is fed out from the feed roller R1 and the separator 4 of the second intermediate M2 that is wound up by the winding roller R4 are the same separator.

[0053] As described above, in the separator peeling and bonding process ST5 of this embodiment, at least the peeling of the separator 4 is performed at an absolute humidity of 10 g / m². 3 The above processes are carried out inside the humidified housing 20. In the example shown in Figure 3, the peeling of the separator 4 by the peeling roller R2, inspection by the inspection device 40, and bonding of the separator 4 by the bonding roller R3 are all carried out inside the housing 20. Specifically, the peeling roller R2, inspection device 40, and bonding roller R3 are all located inside the housing 20. As shown in Figure 3(b), an opening 21 is provided on the upstream side of the housing 20 (upstream in the direction of transport of the second intermediate body M2), with dimensions larger than the cross-sectional dimensions of the second intermediate body M2. The second intermediate body M2, fed out from the feed roller R1 located outside the housing 20, is transported through this opening 21 towards the peeling roller R2. Also, as shown in Figure 3(c), an opening 22 is provided on the downstream side of the housing 20 (downstream in the direction of transport of the second intermediate body M2), with dimensions larger than the cross-sectional dimensions of the second intermediate body M2. The second intermediate body M2 produced by the bonding roller R3 is transported through this opening 22 towards the winding roller R4 located outside the housing 20. If the dimensions of the openings 21 and 22 are too large, it may affect the humidification state inside the housing 20. Therefore, it is preferable to make the dimensions of the openings as small as possible, taking into consideration the largest cross-sectional dimensions of the second intermediate M2 and variations in the transport path (pass line) of the second intermediate M2, as long as they do not obstruct the transport of the second intermediate M2. A humidifier 30 is placed inside the casing 20, and this humidifier 30 maintains an absolute humidity of 10 g / m³ inside the casing 20. 3 The air is humidified to the above extent. The humidifier 30 is not limited to this, but for example, a general commercial electric heating type humidifier (for example, the "UC-MG series" electric heating type steam humidifier manufactured by U-CAN Co., Ltd.) can be used.

[0054] As described above, in the separator peeling and bonding process ST5, the separator 4 is peeled off by the humidifier 30, which maintains an absolute humidity of 10 g / m². 3 Since this is performed inside the humidified housing 20, the moisture content of the polarizing plate 10 can be efficiently increased via the adhesive layer 3 remaining on the first intermediate M1 after the separator 4 has been peeled off.

[0055] In the example shown in Figure 3, the peeled separator 4 and the separator 4 to be bonded are the same separator. However, the separator 4 to be bonded may be a new separator different from the peeled separator 4. The following describes the case where the peeled separator 4 and the separator 4 to be bonded are different in the separator peeling and bonding process ST5. In the following description, the separator 4 to be peeled (the separator 4 bonded in the separator bonding process ST4) will be referred to as "separator 4a," and the new separator 4 to be bonded in the separator peeling and bonding process ST5 will be referred to as "separator 4b" to distinguish between the two.

[0056] Figure 4 schematically shows another example of the schematic configuration of the apparatus that performs the separator peeling and lamination process ST5. Figure 4(a) is a side view (viewed from a horizontal direction perpendicular to the transport direction of each film) and shows the inside of the housing 20A as seen through. Figure 4(b) is a view of the housing 20A shown in Figure 4(a) from the direction of arrow X1 shown in Figure 4(a). Figure 4(c) is a view of the housing 20A shown in Figure 4(a) from the direction of arrow X2 shown in Figure 4(a). The remaining small arrows shown in Figure 4(a) indicate the transport direction of each film. In the separator peeling and bonding process ST5 using the apparatus shown in Figure 4, as described above, the second intermediate M2 produced in the separator bonding process ST4 is wound onto the feed roller R5 shown in Figure 4 and positioned at the upstream end of the apparatus (the upstream end in the transport direction of the second intermediate M2). The second intermediate M2, fed out from the feed roller R5, is then transported toward the peeling roller R6. At the peeling roller R6, the separator 4a is peeled off from the second intermediate M2 (only the separator 4a is peeled off while the adhesive layer 3 remains on the polarizing plate 10 side), and the peeled separator 4a is wound up by the winding roller R7.

[0057] Meanwhile, the first intermediate M1, which is a laminate of the polarizing plate 10 and the adhesive layer 3 obtained by peeling off the separator 4a from the second intermediate M2 by the peeling roller R6, is inspected by the inspection device 40 as described above and then conveyed toward the bonding roller R8. A new separator (a separator without the adhesive layer 3) 4b is prepared and wound onto the feed roller R9, and this separator 4b is fed out from the feed roller R9 and conveyed toward the bonding roller R8. The bonding roller R8 then bonds the separator 4b to the first intermediate M1. That is, the separator 4b is bonded to the polarizing plate 10 that constitutes the first intermediate M1 via the adhesive layer 3 that constitutes the first intermediate M1. This produces the second intermediate M2, which is then wound up by the winding roller R10. The separator 4 of the second intermediate M2 unwound from the dispensing roller R5 is separator 4a, but the separator 4 of the second intermediate M2 wound up by the winding roller R10 is separator 4b.

[0058] Even in the separator peeling and bonding process ST5 using the apparatus shown in Figure 4, at least the peeling of separator 4a was achieved with an absolute humidity of 10 g / m². 3 The above processes are carried out inside the humidified enclosure 20A. In the example shown in Figure 4, the peeling of the separator 4a by the peeling roller R6, inspection by the inspection device 40, and bonding of the separator 4b by the bonding roller R8 are all carried out inside the enclosure 20A. Specifically, the peeling roller R6, inspection device 40, and bonding roller R8 are all located inside the housing 20A. As shown in Figure 4(b), the upstream side of the housing 20A (the upstream side in the transport direction of the second intermediate body M2) is provided with an opening 21a larger than the cross-sectional dimensions of the second intermediate body M2 and an opening 21b larger than the cross-sectional dimensions of the separator 4a. The second intermediate body M2, which is fed out from the feed roller R5 located outside the housing 20A, is transported through the opening 21a toward the peeling roller R6. The separator 4a, which has been peeled by the peeling roller R6, is transported through the opening 21b toward the winding roller R7 located outside the housing 20A. Furthermore, as shown in Figure 4(c), the downstream side of the housing 20A (downstream in the direction of transport of the second intermediate body M2) is provided with an opening 22a larger than the cross-sectional dimensions of the second intermediate body M2 and an opening 22b larger than the cross-sectional dimensions of the separator 4b. The second intermediate body M2 produced by the bonding roller R8 is transported through the opening 22a toward the winding roller R10 located outside the housing 20A. The separator 4b, unwound from the unwinding roller R9 located outside the housing 20A, is transported through the opening 22b toward the bonding roller R8. If the dimensions of the openings 21a, 21b, 22a, and 22b are excessively large, it may affect the humidification state inside the housing 20A. Therefore, it is preferable that the openings 21a and 22a be as small as possible, taking into account the largest cross-sectional dimensions of the second intermediate M2 and variations in the transport path (pass line) of the second intermediate M2, as long as they do not obstruct the transport of the second intermediate M2. Similarly, it is preferable that the openings 21b and 22b be as small as possible, taking into account the largest cross-sectional dimensions of the separators 4a and 4b and variations in the transport path (pass line) of the separators 4a and 4b, as long as they do not obstruct the transport of the separators 4a and 4b. Furthermore, a humidifier 30 similar to the one shown in Figure 3 is also placed inside the housing 20A, and this humidifier 30 maintains an absolute humidity of 10 g / m³ inside the housing 20A. 3 The humidification level will be increased to the above.

[0059] In the separator peeling and bonding process ST5 using the apparatus shown in Figure 4, the peeling of the separator 4a was achieved by the humidifier 30, which maintained an absolute humidity of 10 g / m². 3 Since this is performed inside the humidified housing 20A, the moisture content of the polarizing plate 10 can be efficiently increased via the adhesive layer 3 remaining on the first intermediate M1 after the separator 4a has been peeled off.

[0060] [Surface protective film lamination process ST6] In this embodiment, the surface protection film lamination step ST6 is performed after the separator peeling and lamination step ST5. In the surface protection film lamination step ST6, a long strip-shaped surface protection film 5 is laminated to a long strip-shaped second intermediate M2. Specifically, the long strip-shaped surface protection film 5 is laminated to the side of the polarizing plate 10 constituting the second intermediate M2 that is opposite to the side to which the separator 4 is laminated. This produces a long strip-shaped optical laminate 100.

[0061] According to the manufacturing method of this embodiment described above, in the separator peeling and bonding step ST5, at least the peeling of the separator 4 is at an absolute humidity of 10 g / m². 3 Because the process is carried out in a highly humidified environment, the moisture content of the polarizing plate 10 can be increased efficiently. Therefore, curling can be effectively suppressed without changing the materials of the components of the conventionally used optical laminate 100. In this embodiment, the separator peeling and bonding process ST5 is described as also serving as an inspection process for the polarizing plate 10. However, the present invention is not limited to this, and it is also possible to perform the separator peeling and bonding process ST5 separately from the inspection process. Alternatively, it is also possible to adopt an embodiment in which no inspection is performed (i.e., the separator peeling and bonding process ST5 simply involves peeling and bonding the separator 4).

[0062] Furthermore, in this embodiment, the separator lamination process ST4 to the surface protection film lamination process ST6 have been described in which each film is performed in a long strip form, but the present invention is not limited thereto. For example, it is also possible to adopt an embodiment in which the long strip polarizing plate 10 produced by the phase difference film lamination process ST2 is humidified in the humidity control process ST3, cut to product size, and then the separator lamination process ST4 to the surface protection film lamination process ST6 are performed.

[0063] Furthermore, although this embodiment has described an example in which the polarizing plate 10 is a laminate of a polarizing film 1 and a phase difference film 2, the present invention is not limited thereto. It is also possible to adopt an embodiment in which the polarizing plate 10 is a laminate of a polarizing film 1, a phase difference film 2 and other components, an embodiment in which the polarizing plate 10 is a laminate of a polarizing film 1 and other components without a phase difference film 2, or an embodiment in which the polarizing plate 10 consists only of a polarizing film 1.

[0064] Below, we will describe an example of the results of evaluating the curl and moisture content of the second intermediate M2 of the optical laminate 100 manufactured by the manufacturing method (example) according to this embodiment shown in Figure 2, and an example of the results of evaluating the curl and moisture content of the second intermediate of the optical laminate manufactured by the conventional manufacturing method (comparative example) shown in Figure 6. The optical laminate 100 manufactured in the example and the optical laminate manufactured in the comparative example both have a structure in which the layers are stacked in the following order. (1) Surface protective film 5 (Base material: PET, thickness 38μm; Adhesive layer: Acrylic adhesive, thickness 10μm) (2) Cycloolefin protective film 12 with hard coat layer (thickness 3 μm) (total thickness 29 μm) (The cycloolefin protective film 12 has a moisture permeability of 0.9 g / m when calculated per μm) 2 (24 hours) (3) Adhesives (4) Polyvinyl alcohol-based polarizer 11 (thickness 12 μm) (5) Adhesives (6) Triacetylcellulose protective film 13 (thickness 20 μm) (The triacetylcellulose protective film 13 has a moisture permeability of 60 g / m when calculated per 1 μm) 2 (24 hours) (7) Adhesives (8) Polymerizable liquid crystal half-wave plate 2 (thickness 2.5 μm) (9) Polymerizable liquid crystal quarter-wave plate 2 (thickness 1.5 μm) (10) Acrylic adhesive layer 3 (thickness 28 μm) (11) Separator 4 (PET, 38μm thickness) In the example, the optical laminate 100 was manufactured by laminating the same separator 4 that was peeled off to the inspected polarizing plate 10 in the separator lamination step ST4 (no replacement with a new separator 4 was performed in the separator lamination step ST4). The same applies to the optical laminate manufactured in the comparative example. The second intermediate M2 is obtained by removing the surface protective film 5 from the above configuration of the optical laminate 100 in the example. The same applies to the second intermediate in the comparative example.

[0065] <Evaluation of moisture content> The moisture content of the second intermediate M2 in the example was determined by measuring the absolute humidity inside the housing 20 used in the separator peeling and lamination process ST5 with a humidifier 30 to 13 g / m². 3 The material was humidified, and samples of a predetermined size were cut from the long second intermediate M2 just before it entered the housing 20 and from the long second intermediate M2 just after it exited the housing 20. The absorbance of these samples was then measured for evaluation. Specifically, the absorbance of each sample was measured using a Kurabo RX-200 specular reflection infrared film thickness gauge under conditions of 23°C ± 5°C and 55% ± 10% relative humidity. In the separator peeling and lamination process ST5, the absolute humidity outside the housing 20 was 9.5 g / m². 3 Furthermore, the separator lamination process ST4, which precedes the separator peeling and lamination process ST5, also had an absolute humidity of 9.5 g / m². 3 It was executed under the following environment. In the comparative example, by stopping the humidifier 30 located inside the housing 20 (creating a non-humidified environment), the absolute humidity inside the housing 20 was set to the same as the outside, 9.5 g / m³. 3 Except for the aforementioned point, samples were cut from the second intermediate just before it entered the housing 20 and from the second intermediate just after it exited the housing 20, and the absorbance of these samples was measured, similar to the example.

[0066] Table 1 shows the absorbance measurement results for the examples and comparative examples. [Table 1] As shown in Table 1, in the comparative example, there was no change in the absorbance of the second intermediate immediately before entering the housing 20 and immediately after exiting it, whereas in the example, the absorbance of the second intermediate M2 was greater immediately after exiting the housing 20 than immediately before entering it. Since absorbance and moisture content have a positive correlation, it was possible to indirectly confirm that the moisture content of the second intermediate M2 (polarizing plate 10) increased in the example.

[0067] <Carl's evaluation> Figure 5 is an explanatory diagram illustrating the evaluation method for curl. As shown in Figure 5(a), in this embodiment, multiple rectangular optical laminates 100S with product size (148 mm in length x 70 mm in width) were cut along the TD direction of a long optical laminate 100. Although Figure 5(a) shows three optical laminates 100S for convenience, in reality, ten optical laminates 100S were cut along the TD direction of one optical laminate 100. This was done at both the leading and trailing ends of the optical laminate 100, resulting in a total of 20 optical laminates 100S. The curl of these 20 optical laminates 100S was then evaluated. As shown in Figure 5(b), when cutting the optical laminates 100S, they were cut diagonally so that the MD direction of the optical laminate 100 (corresponding to the direction of the absorption axis of the polarizer 11) was at a 45° angle to the long and short sides of the optical laminate 100S.

[0068] As shown in Figure 5(c), when evaluating the curl, the optical laminate 100S was placed on a flat mounting table 50 so that the lower side of the optical laminate 100S was convex (so that the curvature of the four corners of the optical laminate 100S was directed vertically upward), and the vertical distance H from the top surface of the mounting table 50 to each of the four corners of the optical laminate 100S was measured. The distance H was measured by placing a scale extending vertically near the corner of the optical laminate 100S and visually reading the scale's markings. When the optical laminate 100S was placed on the mounting table 50 with its lower side convex, the case where the side of the optical laminate 100S with the separator 4 was facing downwards (the side with the surface protective film 5 was facing upwards) was defined as a positive curl, and the measured distance H was used as the curl value. On the other hand, when the optical laminate 100S was placed on the mounting table 50 with its lower side convex, the case where the side of the optical laminate 100S with the separator 4 was facing upwards (the side with the surface protective film 5 was facing downwards) was defined as a negative curl, and the measured distance H was multiplied by -1 to calculate the curl value.

[0069] Next, as shown in Figure 5(d), the separator 4 was peeled off the optical laminate 100S. Then, the curl values ​​of the four corners of the laminate from which the separator 4 had been peeled off (the laminate of the first intermediate M1 and the surface protective film 5) were calculated using the same procedure as described above.

[0070] Furthermore, a product was deemed to pass if the curl values ​​of the four corners of the optical laminate 100S and the curl values ​​of the four corners of the laminate from which the separator 4 has been removed all satisfy the condition -5mm ≤ curl value ≤ 5mm, and failed if this condition was not met. For the comparative examples, the curl value was calculated using the same procedure as described in the examples above, and it was determined whether they passed or failed.

[0071] Table 2 shows the evaluation results for curl in the examples and comparative examples. [Table 2] As shown in Table 2, in the comparative example, 14 out of 20 optical laminates passed (pass rate 70%), whereas in the example, 19 out of 20 optical laminates 100S passed (pass rate 95%), indicating that curling was suppressed. [Explanation of Symbols]

[0072] 1. Polarizing film 10. Polarizing plate 11. Polarizer 12, 13... Protective film 2. Phase difference film 3. Adhesive layer 4... Separator 5. Surface protective film 100, 100S... Optical laminate ST1... Polarizing film manufacturing process ST2... Phase difference film lamination process ST3... Humidity control process ST4...Separator lamination process ST5...Separator peeling and lamination process ST6... Surface protective film lamination process

Claims

1. A separator bonding step involves bonding the separator to a polarizing plate via an adhesive layer formed on the separator, The separator peeling and lamination step includes, after the separator lamination step, peeling the separator from the adhesive layer and then laminating the separator to the polarizing plate via the adhesive layer, In the separator peeling and bonding process, at least the separator peeling must be at an absolute humidity of 10 g / m². ３ This is performed in an environment with increased humidity. A method for manufacturing optical laminates.

2. In the separator peeling and bonding process, at least the separator peeling is performed inside the humidified housing. A method for manufacturing an optical laminate according to claim 1.

3. The process includes a surface protection film lamination step, in which a surface protection film is laminated to the polarizing plate after the separator peeling and lamination step, A method for manufacturing an optical laminate according to claim 1 or 2.

4. The separator peeling and bonding process is performed in an environment with a higher absolute humidity than the separator bonding process. A method for manufacturing an optical laminate according to any one of claims 1 to 3.

5. The separator peeling and bonding process is performed inside the housing where the humidifier is located, and the humidifier brings the absolute humidity inside the housing to 10 g / m². ３ The humidification is increased to the above extent. A method for manufacturing an optical laminate according to any one of claims 1 to 4.

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