Manufacturing method of optical laminate

Abstract

To provide a manufacturing method of an optical laminate including a liquid crystal alignment solidification layer and capable of inhibiting a specific display unevenness when applied to an image display unit.SOLUTION: Provided is a manufacturing method of an optical laminate having a polarizer and a retardation layer including a first liquid crystal alignment solidification layer and a second liquid crystal alignment solidification layer. The manufacturing method includes: a first lamination step of performing lamination, interposing a first adhesion layer, so that the polarizer and the first liquid crystal alignment solidification layer face each other, while conveying the polarizer and the first liquid crystal alignment solidification layer to produce a first intermediate laminate; and a second lamination step of performing lamination, interposing a second adhesion layer, so that the first liquid crystal alignment solidification layer and the second liquid crystal alignment solidification layer face each other, while conveying the first intermediate laminate and the second crystal alignment solidification layer to produce a second intermediate laminate. A conveyance tension after the second lamination step exceeds 700 N and is less than 1,500 N.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention relates to a method for producing an optical laminate. [Background technology]

[0002] In recent years, image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices and inorganic EL display devices), have rapidly become popular. Image display devices often use optical laminates containing retardation films (e.g., antireflection films integrating polarizing plates and retardation films). In recent years, as demand for thinner image display devices has increased, so has the demand for thinner optical laminates. To achieve thinner optical laminates, progress has been made in thinning the retardation layer (retardation film), which contributes significantly to the thickness of the optical laminate. A typical example of a thin retardation film is a film (hereinafter referred to as a liquid crystal film) in which a liquid crystal compound is oriented and the orientation state is fixed. Because liquid crystal compounds have a significantly higher birefringence (Δn) than resins, the thickness of a liquid crystal film required to achieve a desired in-plane retardation can be significantly smaller than that of a stretched resin film. However, image display devices using optical laminates containing liquid crystal films may exhibit display unevenness (specifically, a phenomenon in which a thin line with a particularly noticeable pink color is visible in the absorption axis direction of the polarizer) depending on the viewing environment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-222282 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a method for manufacturing an optical laminate that includes a liquid crystal alignment solidified layer and that can suppress specific display unevenness when applied to an image display device. [Means for solving the problem]

[0005] [1] A method for manufacturing an optical laminate according to an embodiment of the present invention is a method for manufacturing an optical laminate having a polarizing plate and a retardation layer including a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer, and includes: a first lamination step in which the polarizing plate and the first liquid crystal alignment solidified layer are transported and laminated via a first adhesive layer so that the polarizing plate and the first liquid crystal alignment solidified layer face each other, thereby producing a first intermediate laminate; and a second lamination step in which the first intermediate laminate and the second liquid crystal alignment solidified layer are transported and laminated via a second adhesive layer so that the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer face each other, thereby producing a second intermediate laminate, wherein the transport tension after the second lamination step is more than 700 N and less than 1500 N. [2] In the above [1], the conveying tension after the second laminating step is 800N or more and 1350N or less. [3] In the above [1] or [2], the second adhesive layer is made of an active energy ray-curable adhesive. [4] In any one of the above items [1] to [3], the conveying tension up to the second laminating step is 100N or more and 400N or less. [5] In any of [1] to [4] above, the first lamination process includes transporting the long polarizing plate and the long first liquid crystal alignment solidified layer using rolls, and laminating the polarizing plate and the first liquid crystal alignment solidified layer using lamination rolls, and the second lamination process includes transporting the long first intermediate laminate and the long second liquid crystal alignment solidified layer using rolls, and laminating the first intermediate laminate and the second liquid crystal alignment solidified layer using lamination rolls. [Effects of the Invention]

[0006] According to an embodiment of the present invention, it is possible to realize an optical laminate that includes a liquid crystal alignment solidified layer and that can suppress specific display unevenness when applied to an image display device. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 2 is a schematic perspective view showing an example of a first lamination step in a method for producing an optical laminate according to one embodiment of the present invention. [Figure 1B] FIG. 2 is a schematic cross-sectional view showing an example of a polarizing plate used in a first lamination step of the method for producing an optical laminate according to one embodiment of the present invention. [Figure 1C] FIG. 2 is a schematic cross-sectional view showing an example of a laminate including a first liquid crystal alignment solidified layer used in a first lamination step of a method for producing an optical laminate according to one embodiment of the present invention. [Figure 1D] 1 is a schematic cross-sectional view showing an example of a first intermediate laminate produced in a first lamination step of a method for producing an optical laminate according to one embodiment of the present invention. [Figure 2A] FIG. 2 is a schematic perspective view showing an example of a second lamination step in the method for producing an optical laminate according to one embodiment of the present invention. [Figure 2B] FIG. 2 is a schematic cross-sectional view showing an example of a laminate including a second liquid crystal alignment solidified layer used in a second lamination step of a method for producing an optical laminate according to one embodiment of the present invention. [Figure 3A] 1 is a schematic cross-sectional view showing an example of an optical laminate produced by a method for producing an optical laminate according to one embodiment of the present invention. [Figure 3B] FIG. 2 is a schematic cross-sectional view showing an example of an optical laminate produced by a method for producing an optical laminate according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Representative embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiments, but these are merely examples and are not intended to limit the interpretation of the present invention. In this specification, "A and / or B" means either "A," "B," or "A and B."

[0009] (Definition of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is greatest (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation of a film measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation of a film measured with light of wavelength 550 nm at 23°C. Re(λ) is calculated by the formula: Re=(nx-ny)×d, where d(nm) is the thickness of the film. (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction of a film measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction of a film measured with light of wavelength 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth=(nx-nz)×d, where d (nm) is the thickness of the film. (4) Nz coefficient The Nz coefficient is calculated by Nz=Rth / Re. (5)Angle When angles are referred to herein, unless otherwise specified, the angles include angles in both clockwise and counterclockwise directions, so for example, "45°" includes ±45°.

[0010] A. Overview of the method for producing an optical laminate and the optical laminate A method for manufacturing an optical laminate according to an embodiment of the present invention is a method for manufacturing an optical laminate having a polarizing plate and a retardation layer including a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer. The method includes a first lamination step in which the polarizing plate and the first liquid crystal alignment solidified layer are laminated together through a first adhesive layer while transporting them to form a first intermediate laminate; and a second lamination step in which the first intermediate laminate and the second liquid crystal alignment solidified layer are laminated together through a second adhesive layer while transporting them to form a second intermediate laminate. In the manufacturing method, the transport tension after the second lamination step is greater than 700 N and less than 1500 N. FIG. 3A is a schematic cross-sectional view of an optical laminate that can be produced by a method for producing an optical laminate according to one embodiment of the present invention. The optical laminate 5 in the illustrated example includes a polarizing plate 11 and a retardation layer 40. The polarizing plate 11 and the retardation layer 40 are laminated via a first adhesive layer 12 (e.g., an adhesive layer or a pressure-sensitive adhesive layer). The polarizing plate 11 typically includes a polarizer 111 and protective layers (a first protective layer 112 and a second protective layer 113) disposed on the main surface of the polarizer 111 (on both sides of the main surface in the illustrated example). Depending on the purpose, the first protective layer 112 and / or the second protective layer 113 may be omitted. Therefore, the polarizing plate may be a so-called double-protected polarizing plate, a so-called single-protected polarizing plate, or may be composed of a polarizer alone.

[0011] The retardation layer 40 includes, in order from the polarizing plate 11 side, a first liquid crystal alignment solidified layer 21 and a second liquid crystal alignment solidified layer 31 laminated on the first liquid crystal alignment solidified layer 21 via a second adhesive layer 22. By using a liquid crystal alignment solidified layer as a retardation layer, a desired in-plane retardation can be achieved with a thickness significantly thinner than that of a stretched resin film. As a result, the optical laminate can be significantly thinner. In one embodiment, the retardation layer 40 as a whole (specifically, as a laminate having the first liquid crystal alignment solidified layer 21 and the second liquid crystal alignment solidified layer 31) has a circular polarization function or an elliptically polarization function. In this specification, when the retardation layer is described simply as a "retardation layer," it refers to the retardation layer as a whole. In this specification, the "liquid crystal alignment solidified layer" refers to a layer in which liquid crystal compounds are aligned in a predetermined direction within the layer and the alignment state is fixed. The "liquid crystal alignment solidified layer" is a concept that encompasses an alignment-hardened layer obtained by hardening a liquid crystal monomer.

[0012] In studying further thinning of an optical laminate including a liquid crystal alignment solidified layer as a retardation layer, the present inventors discovered a new problem: an image display device using an optical laminate including a liquid crystal alignment solidified layer as a retardation layer may exhibit specific display unevenness depending on the viewing environment. Specifically, the present inventors discovered that, in reflection under a three-wavelength light source, a phenomenon (sometimes referred to as linear unevenness) may occur in which a thin line with a particularly noticeable pink color in the absorption axis direction of the polarizer is visible throughout the display. As a result of extensive research into suppressing such linear unevenness, the present inventors discovered that linear unevenness can be suppressed by suppressing light interference in the optical laminate. In addition, the inventors investigated the cause of light interference in the optical laminate and found that unevenness in the thickness of the retardation layer including the adhesive layer can occur during the manufacturing process. Furthermore, they found that suppressing this unevenness in thickness can significantly suppress the above-mentioned linear unevenness, leading to the completion of the present invention. That is, such an effect of the embodiment of the present invention solves a newly discovered problem when considering further thinning of an optical laminate including a liquid crystal alignment solidified layer as a retardation layer, and is an unexpected and excellent effect. It goes without saying that the embodiment of the present invention can suppress the display unevenness that has been recognized in the past.

[0013] The reason why the optical laminate obtained by the manufacturing method according to the embodiment of the present invention exhibits the above-mentioned remarkable effects is not necessarily clear, but the following mechanism can be inferred. However, this mechanism is merely inferred and does not limit the present invention, nor does it restrict the present invention by this mechanism.

[0014] In a method for manufacturing an optical laminate according to an embodiment of the present invention, a first intermediate laminate is produced by laminating a polarizing plate and a first liquid crystal alignment solidified layer facing each other via a first adhesive layer in a first lamination step. A second intermediate laminate is produced by laminating a polarizing plate and a first liquid crystal alignment solidified layer of the first intermediate laminate facing each other via a second adhesive layer in a second lamination step. When transporting the thus-laminated second intermediate laminate, a higher transport tension of more than 700 N and less than 1500 N after the second lamination step is used. This is believed to suppress cure shrinkage during hardening of the second adhesive layer used in producing the second intermediate laminate. Therefore, even when the second adhesive layer is hardened, shrinkage of the polarizing plate (particularly the polarizer) and the retardation layer (the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer) accompanying hardening of the second adhesive layer is believed to be suppressed. This is believed to suppress cure shrinkage of the entire optical laminate (particularly the entire optical laminate including the polarizing plate and the retardation layer) during hardening of the adhesive layer, thereby suppressing thickness unevenness. Therefore, in the manufacturing method of the optical laminate according to the embodiment of the present invention, unevenness in thickness between the retardation layers of the optical laminate is suppressed, and it is thought that when the optical laminate is applied to an image display device, unevenness in display (linear unevenness) due to light interference is suppressed.

[0015] B. Details of the manufacturing method of the optical laminate Hereinafter, the method for producing an optical laminate according to an embodiment of the present invention will be described in more detail. FIG. 1A is a schematic perspective view illustrating a first lamination step in a method for producing an optical laminate according to one embodiment of the present invention. FIGS. 1B and 1C are each a schematic cross-sectional view illustrating an example of a laminate including a polarizing plate and a first liquid crystal alignment solidified layer that can be used in the first lamination step. FIG. 1D is a schematic cross-sectional view illustrating an example of a first intermediate laminate that can be produced in the first lamination step. FIG. 2A is a schematic perspective view illustrating a second lamination step in a method for producing an optical laminate according to one embodiment of the present invention. FIG. 2B is a schematic cross-sectional view illustrating an example of a laminate including a second liquid crystal alignment solidified layer that can be used in the second lamination step. FIG. 3A is a schematic cross-sectional view illustrating an example of an optical laminate produced by a method for producing an optical laminate according to one embodiment of the present invention. FIG. 3B is a schematic cross-sectional view illustrating an example of an optical laminate produced by a method for producing an optical laminate according to another embodiment of the present invention. Each step of the method for producing an optical laminate will be described in detail below with reference to FIGS. 1A to 3B.

[0016] B-1. First lamination process The first lamination step is a step of laminating a polarizing plate 11 (see FIG. 1B) and a first liquid crystal alignment solidified layer 21 (see FIG. 1C). Specifically, as shown in FIG. 1A, in the first lamination step, the polarizing plate 11 and the first liquid crystal alignment solidified layer 21 are transported and bonded together via a first adhesive layer 22 so that the polarizing plate 11 and the first liquid crystal alignment solidified layer 21 face each other. This produces a first intermediate laminate 100 (see FIG. 1D). The example shown in FIGS. 1C and 1D includes a first substrate 221 for forming the first liquid crystal alignment solidified layer 21. The first substrate 221 is typically peeled off and removed in the final step. Specifically, for example, the first substrate 221 can be peeled off before the second lamination step described below.

[0017] The first lamination step preferably includes conveying a long polarizing plate and a long first liquid crystal alignment solidified layer using rolls, and laminating the polarizing plate and the first liquid crystal alignment solidified layer using lamination rolls. In this manner, a long first intermediate laminate can be produced. The long first intermediate laminate can be wound into a roll. In this specification, "long" refers to an elongated shape in which the length is sufficiently longer than the width, and includes, for example, an elongated shape in which the length is 10 times or more, preferably 20 times or more, the width.

[0018] The transport tension before the first lamination step can be adjusted to any appropriate tension as long as the effects of the embodiment of the present invention are obtained. The transport tension before the first lamination step is preferably 100 N or more and 400 N or less. The transport tension before the first lamination step may be, for example, 150 N or more and 350 N or less, or may be, for example, 200 N or more and 300 N or less. When the transport tension is 100 N or more, the transportability of the polarizing plate and the first liquid crystal alignment solidified layer can be maintained well. When the transport tension is 400 N or less, curling of the first intermediate laminate to be produced can be effectively suppressed. In this specification, the term "transport tension" refers to the tension applied to members (polarizing plate, retardation layer, liquid crystal alignment solidified layer, substrate, each laminate, etc.) when transporting the members.

[0019] B-1-1. Polarizing plate B-1-1-1.Polarizer The polarizer 111 is typically made of a polyvinyl alcohol (PVA) resin film containing a dichroic material (e.g., iodine). Examples of PVA resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified ethylene-vinyl acetate copolymer.

[0020] The PVA resin preferably contains an acetoacetyl-modified PVA resin. With this configuration, a polarizer having desired mechanical strength can be obtained. The amount of the acetoacetyl-modified PVA resin is preferably 5% by weight to 20% by weight, and more preferably 8% by weight to 12% by weight, based on 100% by weight of the entire PVA resin. If the amount is within this range, a polarizer having better mechanical strength can be obtained.

[0021] The polarizer preferably contains iodide or sodium chloride (sometimes collectively referred to as a halide). Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, relative to 100 parts by weight of the PVA-based resin. In the manufacturing method described below, the halide is blended into a coating liquid that forms a PVA-based resin layer, which is a precursor of the polarizer, and can be finally introduced into the polarizer. Introducing a halide into the polarizer can improve the orientation of PVA molecules in the polarizer, thereby achieving a polarizer with excellent optical properties (typically, both a high degree of polarization and a high single-unit transmittance).

[0022] The polarizer preferably exhibits absorptive dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is preferably 41.0% to 46.0%, more preferably 42.0% to 45.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more. According to an embodiment of the present invention, even if the single transmittance is within the above range, the degree of polarization can be maintained within this range.

[0023] The thickness of the polarizer is, for example, 12 μm or less, preferably 10 μm or less, more preferably 8 μm, and even more preferably 7 μm. On the other hand, the thickness of the polarizer is, for example, 1 μm or more, preferably 3 μm or more. By combining such a thin polarizer with a liquid crystal alignment solidified layer, it becomes possible to significantly reduce the thickness of the optical laminate. Furthermore, if the thickness of the polarizer is within the above range, curling during heating can be effectively suppressed.

[0024] The polarizer can be produced by any appropriate method. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

[0025] Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as PVA films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with iodine or a dichroic substance such as a dichroic dye and stretched, and polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching it is preferred because of its excellent optical properties.

[0026] The dyeing with iodine is carried out, for example, by immersing the PVA film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment or while dyeing. Alternatively, the PVA film may be stretched and then dyed. If necessary, the PVA film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA film in water and washing it before dyeing, it is possible to wash away dirt and antiblocking agents on the surface of the PVA film, and also to swell the PVA film, thereby preventing uneven dyeing.

[0027] Specific examples of polarizers obtained using laminates include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and then stretching and dyeing the laminate to convert the PVA-based resin layer into a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. Stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching may optionally further include in-air stretching of the laminate at an elevated temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. Additionally, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment by heating while being transported in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an auxiliary in-air stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment, in this order. By introducing auxiliary stretching, it is possible to increase the crystallinity of PVA, even when PVA is coated on a thermoplastic resin, thereby achieving high optical properties. Furthermore, by simultaneously increasing the orientation of PVA in advance, problems such as a decrease in orientation or dissolution of PVA when immersed in water in the subsequent dyeing or stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disordering of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizer obtained through treatment steps in which the laminate is immersed in a liquid, such as a dyeing treatment and an underwater stretching treatment. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction through the drying shrinkage treatment.

[0028] B-1-1-2.Protective layer When the polarizing plate includes a protective layer, the protective layer may include a first protective layer and / or a second protective layer. The first protective layer and the second protective layer may have the same structure or different structures. The protective layer is composed of any appropriate resin film. Typical materials for the resin film include cellulose-based resins such as triacetyl cellulose (TAC), cycloolefin-based resins such as polynorbornene, (meth)acrylic resins, polyester-based resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin-based resins such as polyethylene, and polycarbonate-based resins. Typical examples of (meth)acrylic resins include (meth)acrylic resins having a lactone ring structure. Examples of (meth)acrylic resins having a lactone ring structure are described in, for example, JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP 2002-254544 A, and JP 2005-146084 A. These publications are incorporated herein by reference. The material for the resin film is preferably a cellulose-based resin, more preferably TAC. From the viewpoint of obtaining a polarizing plate having low moisture permeability and excellent durability, cycloolefin resins and (meth)acrylic resins are preferred.

[0029] The optical laminate is typically disposed on the viewing side of an image display device, and the first protective layer 112 is typically disposed on the viewing side. Therefore, the first protective layer 112 may be subjected to a surface treatment as needed. Examples of surface treatments include hard coating, anti-reflection, anti-sticking, and anti-glare treatments. Additionally / alternatively, the first protective layer 112 may be subjected to a treatment to improve visibility when viewed through polarized sunglasses (typically, by providing an (elliptical) polarization function or an ultra-high phase difference). By performing such a treatment, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the optical laminate may be suitably applied to image display devices that can be used outdoors.

[0030] The thickness of the protective layer is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and even more preferably 15 μm to 35 μm. If first protective layer 112 has been subjected to a surface treatment, the thickness of first protective layer 112 includes the thickness of the surface treatment layer.

[0031] B-1-1-3. Preparation of polarizing plates The polarizing plate can be produced, for example, as follows. In the case of a polarizer obtained using a single-layer resin film, a polarizing plate can be produced, for example, by bonding a protective layer to the polarizer via any appropriate adhesive layer (adhesive layer, pressure-sensitive adhesive layer). A polarizer obtained using a resin substrate / polarizer laminate can be produced, for example, by bonding a protective layer to the polarizer side of the resin substrate / polarizer of the laminate via any appropriate adhesive layer (adhesive layer, pressure-sensitive adhesive layer). If necessary, the resin substrate may be peeled from the laminate, and if necessary, another protective layer may be bonded to the surface from which the resin substrate has been peeled. Alternatively, the laminate may be produced as a polarizing plate by using the resin substrate as a protective layer. Details of the methods for producing such polarizers and polarizing plates are described, for example, in JP 2012-73580 A and Japanese Patent No. 6470455 A. The entire disclosures of these publications are incorporated herein by reference.

[0032] B-1-2. Formation of the first liquid crystal alignment solidified layer In the method for manufacturing an optical laminate according to an embodiment of the present invention, the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer described later may be the same. Therefore, when the liquid crystal alignment solidified layer is described in this specification, simply referring to it as the "liquid crystal alignment solidified layer" means that the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer are described collectively.

[0033] The liquid crystal alignment solidified layer may be formed on, for example, any appropriate substrate. As shown in FIG. 1C, the first liquid crystal alignment solidified layer 21 may be formed on a first substrate 221. Specifically, the first liquid crystal alignment solidified layer 21 may be formed by performing an alignment treatment on the surface of the first substrate 221, applying a coating liquid containing a liquid crystal compound to the surface, orienting the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. In one embodiment, the substrate is any appropriate resin film. Preferably, a triacetyl cellulose (TAC) film is used.

[0034] By using a liquid crystal compound, the difference between nx and ny of the resulting liquid crystal alignment solidified layer can be made significantly larger than that of a non-liquid crystal material, and the thickness of the liquid crystal alignment solidified layer required to obtain the desired in-plane retardation can be made significantly smaller. As a result, the optical laminate can be made thinner and lighter. In this embodiment, typically, rod-shaped liquid crystal compounds are aligned in the slow axis direction of the liquid crystal alignment solidified layer (homogeneous alignment).

[0035] Any appropriate alignment treatment can be adopted as the alignment treatment. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique deposition and photoalignment treatment. Any appropriate treatment conditions can be adopted for the various alignment treatments depending on the purpose.

[0036] The alignment of the liquid crystal compound is achieved by treating the liquid crystal compound at a temperature at which the liquid crystal compound exhibits liquid crystallinity depending on the type of liquid crystal compound. By performing such temperature treatment, the liquid crystal compound assumes a liquid crystal state and is aligned in accordance with the alignment treatment direction of the substrate surface.

[0037] In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.

[0038] Specific examples of liquid crystal compounds and details of the method for forming the alignment solidified layer are described in JP-A-2006-163343, the disclosure of which is incorporated herein by reference.

[0039] When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After the liquid crystal monomer is aligned, for example, the alignment state can be fixed by polymerizing or crosslinking the liquid crystal monomers with each other. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystals. Therefore, the formed liquid crystal alignment solidified layer does not undergo, for example, a transition to a liquid crystal phase, a glass phase, or a crystalline phase due to temperature changes, which is specific to liquid crystal compounds. As a result, the liquid crystal alignment solidified layer is not affected by temperature changes and has excellent stability.

[0040] Examples of liquid crystal compounds used in the liquid crystal alignment solidified layer include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable (i.e., a liquid crystal monomer). If the liquid crystal compound is polymerizable, the alignment state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it. Here, the polymer formed by polymerization is non-liquid crystal. Therefore, the formed liquid crystal alignment solidified layer does not undergo, for example, a transition to a liquid crystal phase, glass phase, or crystalline phase due to temperature changes, which is unique to liquid crystal compounds. As a result, the liquid crystal alignment solidified layer becomes a retardation layer that is not affected by temperature changes and has extremely excellent stability.

[0041] In one embodiment, the liquid crystal alignment solidified layer can be formed using a composition containing a polymerizable liquid crystal compound (polymerizable liquid crystal compound, i.e., liquid crystal monomer). In this specification, the polymerizable liquid crystal compound contained in the composition refers to a compound having a polymerizable group and liquid crystallinity. The polymerizable group refers to a group that participates in a polymerization reaction, preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can participate in a polymerization reaction by an active radical or acid generated from a photopolymerization initiator. Examples of liquid crystal monomers that can be used include polymerizable mesogen compounds described in JP-A-2002-533742 (WO 00 / 37585), EP 358208 (US Pat. No. 5,211,877), EP 66137 (US Pat. No. 4,388,453), WO 93 / 22397, EP 0261712, DE 19504224, DE 4408171, and GB 2280445. Specific examples of such polymerizable mesogenic compounds include LC242 (trade name) from BASF, E7 (trade name) from Merck, and LC-Sillicon-CC3767 (trade name) from Wacker-Chem.

[0042] The mechanism by which the liquid crystal compound exhibits liquid crystallinity may be thermotropic or lyotropic. The liquid crystal phase may be nematic or smectic. From the viewpoint of ease of production, the liquid crystallinity is preferably thermotropic nematic liquid crystal.

[0043] The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the type of the liquid crystal monomer, and specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

[0044] The birefringence Δn of the liquid crystal alignment solidified layer is preferably 0.06 or more, more preferably 0.08 or more, even more preferably 0.09 or more, and particularly preferably 0.10 or more. The upper limit of Δn may be, for example, 0.13, or may be, for example, 0.12. If Δn is within this range, the desired in-plane retardation can be achieved with a very thin thickness. As a result, the liquid crystal alignment solidified layer and the optical laminate can be made even thinner, which can ultimately contribute to significantly thinner image display devices.

[0045] The liquid crystal alignment solidified layer may exhibit a reverse wavelength dispersion characteristic in which the retardation value increases with the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value decreases with the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value hardly changes with the wavelength of the measurement light. In one embodiment, the liquid crystal alignment solidified layer exhibits a positive wavelength dispersion characteristic. In such cases, the effects of the present invention are remarkable.

[0046] In one embodiment, the Re(550) of the first liquid crystal alignment solidified layer is preferably 150 nm to 300 nm, more preferably 200 nm to 270 nm, and even more preferably 220 nm to 260 nm. In this case, the Re(550) of the second liquid crystal alignment solidified layer (described later) is preferably 100 nm to 200 nm, more preferably 110 nm to 160 nm, and even more preferably 110 nm to 130 nm. In this case, both the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer have in-plane retardation and therefore exhibit a refractive index characteristic of nx>ny. The first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer typically exhibit a refractive index characteristic of nx>ny=nz (positive A plate). Here, "ny=nz" encompasses not only the case where ny and nz are strictly equal, but also the case where ny and nz are substantially equal. That is, the Nz coefficients of the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer may each be 0.9 to 1.1.

[0047] The thickness of the first liquid crystal alignment solidified layer can be adjusted to obtain the desired in-plane retardation. In one embodiment, the thickness of the first liquid crystal alignment solidified layer can be, for example, 1.5 μm to 2.5 μm. As described above, according to an embodiment of the present invention, the thickness of the first liquid crystal alignment solidified layer can be made thinner than conventional layers, while further suppressing linear unevenness. The thickness of the second liquid crystal alignment solidified layer can also be adjusted to obtain the desired in-plane retardation. Specifically, the thickness can be, for example, 0.8 μm to 1.5 μm.

[0048] The angle between the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 14° to 16°. In this case, the angle between the slow axis of the second liquid crystal alignment solidified layer and the transmission axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably 74° to 76°. The direction of the slow axis of the first liquid crystal alignment solidified layer can be controlled by the above-mentioned alignment treatment. The angle between the slow axis of the first liquid crystal alignment solidified layer and the transmission axis of the polarizer and the angle between the slow axis of the second liquid crystal alignment solidified layer and the transmission axis of the polarizer may be reversed.

[0049] B-1-3. Formation of the first adhesive layer 1A, a polarizing plate 11 and a first liquid crystal alignment solidified layer 21 are laminated together via a first adhesive layer 12. This allows the production of a first intermediate laminate 100. The first adhesive layer can be formed by disposing or applying any appropriate pressure-sensitive adhesive or adhesive. Any appropriate configuration may be adopted for the first adhesive layer 12. As described above, the adhesive layer may be made of a pressure-sensitive adhesive or an adhesive.

[0050] The first adhesive layer is preferably made of an adhesive, more preferably an active energy ray curable adhesive, and in this case, the thickness of the adhesive layer is preferably 0.4 μm to 2.0 μm, more preferably 0.6 μm to 1.5 μm.

[0051] When the first adhesive layer is formed of an active energy ray-curable adhesive, it is preferable to laminate the polarizing plate and the first liquid crystal alignment solidified layer using lamination rolls by supplying the active energy ray-curable adhesive to at least one of the polarizing plate side and the first liquid crystal alignment solidified layer side while transporting the polarizing plate and the first liquid crystal alignment solidified layer with the rolls, and then laminating the polarizing plate and the first liquid crystal alignment solidified layer. Specifically, in forming the first adhesive layer, it is preferable to supply the active energy ray-curable adhesive to the side facing the polarizing plate and the first liquid crystal alignment solidified layer while transporting the polarizing plate and the first liquid crystal alignment solidified layer with the rolls, and then bond the polarizing plate and the first liquid crystal alignment solidified layer to be laminated. The active energy ray-curable adhesive can be supplied by any appropriate method. More specifically, as shown in FIG. 1A, the active energy ray-curable adhesive is supplied by supplying the active energy ray-curable adhesive (e.g., liquid adhesive 61) that can form the first adhesive layer 12 from a supply means 60 that can be provided between the lamination rolls 62. The supply means 60 can have any appropriate configuration. By supplying in this manner, the active energy ray-curable adhesive can be applied onto the polarizing plate 11 and / or the first liquid crystal alignment solidified layer 21, thereby forming the first adhesive layer 12. In this manner, the first intermediate laminate 100 can be produced.

[0052] The conveying tension of the first intermediate laminate after the first lamination step can be adjusted to any appropriate tension as long as the effects of the embodiment of the present invention are obtained. The conveying tension of the first intermediate laminate after the first lamination step may be, for example, 100 N or more and 400 N or less, or, for example, 150 N or more and 350 N or less, or, for example, 200 N or more and 300 N or less, similar to that before the first lamination step.

[0053] B-1-4. Hardening of the first adhesive layer When the first adhesive layer is made of an active energy ray-curable adhesive, the first lamination step may preferably be followed by a curing step of curing the first adhesive layer (hereinafter, sometimes referred to as a "first adhesive layer curing step"). Specifically, in the first adhesive layer curing step, the polarizing plate and the first liquid crystal alignment solidified layer are bonded together with the first adhesive layer interposed therebetween, and then the first adhesive layer is cured.

[0054] The first adhesive layer can be cured by any appropriate method depending on the type and composition of the adhesive constituting the first adhesive layer. When the first adhesive layer is composed of an active energy ray curable adhesive, the first adhesive layer can be cured preferably by irradiating it with active energy rays. Any appropriate conditions can be adopted as the curing conditions for the first adhesive layer. For example, ultraviolet rays can be used as the active energy rays. The cumulative light amount can be, for example, 500 to 1000 mJ / cm. 2 The irradiation direction may be, for example, a direction perpendicular to the transmission axis direction of the polarizing plate. The first adhesive layer curing step does not necessarily have to be performed after the first lamination step, and may be cured together with the second adhesive layer, for example, after the second lamination step described below. The first adhesive layer may also be cured, for example, in the first lamination step.

[0055] B-2.Second lamination process The second lamination step is a step of laminating the first intermediate laminate 100 (see FIG. 1D) and the second liquid crystal alignment solidified layer 31 (see FIG. 2B). Specifically, as shown in FIG. 2A, in the second lamination step, the first intermediate laminate 100 and the second liquid crystal alignment solidified layer 31 are transported and laminated together via the second adhesive layer 22 so that the first liquid crystal alignment solidified layer 21 and the second liquid crystal alignment solidified layer 31 face each other. In this way, the second intermediate laminate 200 can be produced.

[0056] The second lamination step preferably includes conveying the long first intermediate laminate and the long second liquid crystal alignment solidified layer using rolls, and laminating the first intermediate laminate and the second liquid crystal alignment solidified layer using lamination rolls. In this way, a long second intermediate laminate can be produced. The long second intermediate laminate can be wound into a roll.

[0057] The transport tension before laminating the first intermediate laminate and the second liquid crystal alignment solidified layer (up to the second lamination step) can be adjusted to any appropriate tension as long as the effects of the present invention are obtained. The transport tension up to the second lamination step is preferably 100 N or more and 400 N or less. The transport tension up to the second lamination step may also be, for example, 150 N or more and 350 N or less, or may be, for example, 200 N or more and 300 N or less. When the transport tension is 100 N or more, the transportability of the first intermediate laminate and the second liquid crystal alignment solidified layer can be maintained well. When the transport tension is 400 N or less, curling of the second intermediate laminate to be produced can be effectively suppressed.

[0058] B-2-1. Second liquid crystal alignment solidification layer Regarding the second liquid crystal alignment solidified layer, if the second liquid crystal alignment solidified layer has the same structure as the first liquid crystal alignment solidified layer (positive A plate), the explanation in the above section B-1-2 can be applied. Below, an example will be described in which the second liquid crystal alignment solidified layer is a positive C plate.

[0059] The refractive index characteristics of a positive C plate exhibit the relationship nz>nx=ny, for example. The thickness direction retardation Rth(550) of the positive C plate is preferably -20 nm to -300 nm, more preferably -30 nm to -250 nm, even more preferably -40 nm to -200 nm, and particularly preferably -50 nm to -150 nm. Here, "nx=ny" encompasses not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. In other words, the in-plane retardation Re(550) of the positive C plate can be less than 10 nm.

[0060] The positive C plate can be formed, for example, using a composition containing a side-chain thermotropic liquid crystal polymer. As the side-chain thermotropic liquid crystal polymer, a copolymer having a liquid crystalline monomer unit represented by general formula (I) and a non-liquid crystalline monomer unit represented by general formula (II) is preferably used. [ka] [ka]

[0061] In formula (I), R 1 is a hydrogen atom or a methyl group, and R 2 is a cyano group, a fluoro group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and X 1 is —CO 2 — or —OCO—. a is an integer of 1 to 6, and b and c are each independently 1 or 2.

[0062] In formula (II), R 3 is a hydrogen atom or a methyl group, and R 4 is an alkyl group having 7 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or a group represented by the following general formula (III). [ka]

[0063] In formula (III), R 5 is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

[0064] The positive C plate can be produced, for example, by preparing a coating solution containing the side-chain thermotropic liquid crystal polymer, applying the coating solution to a substrate (e.g., a PET substrate) that has been subjected to a vertical alignment treatment by any appropriate method, and then heating and drying the coating solution under any appropriate heating conditions to align the liquid crystals to form a liquid crystal layer. The liquid crystal layer can be cured by irradiating it with ultraviolet light, thereby producing a laminate having a substrate / second liquid crystal alignment solidified layer (positive C plate) configuration.

[0065] Specific examples of methods for forming a positive C plate include the methods described in paragraphs

[0020] to

[0028] of Japanese Patent Application Laid-Open No. 2002-333642. In this case, the thickness of the positive C plate is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

[0066] B-2-2.Second adhesive layer In the second lamination step, the second intermediate laminate 200 and the second liquid crystal alignment solidified layer 31 are laminated together via a second adhesive layer 22. The second adhesive layer 22 can be formed by disposing or applying any appropriate pressure-sensitive adhesive or adhesive. Any appropriate configuration may be adopted for the second adhesive layer 22. As described above, the adhesive layer may be made of a pressure-sensitive adhesive or an adhesive.

[0067] The second adhesive layer is preferably made of an active energy ray-curable adhesive. When the second adhesive layer is made of an active energy ray-curable adhesive, the effects of the present invention become more pronounced. The description of the first adhesive layer in Section B-1-3 can be used to explain the configuration of the second adhesive layer and the method for forming the second adhesive layer.

[0068] When the second adhesive layer is composed of an active energy ray-curable adhesive, when laminating the first intermediate laminate and the second liquid crystal alignment solidified layer using lamination rolls, it is preferable to supply the active energy ray-curable adhesive to at least one of the first liquid crystal alignment solidified layer side and the second liquid crystal alignment solidified layer side of the first intermediate laminate while transporting the first intermediate laminate and the second liquid crystal alignment solidified layer with the rolls, and then laminating them. Specifically, when forming the second adhesive layer, it is preferable to supply the active energy ray-curable adhesive to the side facing the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer while transporting the first intermediate laminate and the second liquid crystal alignment solidified layer with the rolls, and then laminating the first intermediate laminate and the second liquid crystal alignment solidified layer. The active energy ray-curable adhesive can be supplied by any appropriate method. Specifically, as shown in FIG. 2A , the active energy ray-curable adhesive is supplied by supplying the active energy ray-curable adhesive (e.g., liquid adhesive 61) that can form the second adhesive layer 22 from a supply means 60 that can be provided between lamination rolls 62. Any appropriate configuration can be adopted for the supply means 60. By supplying in this manner, the active energy ray-curable adhesive is applied onto the first intermediate laminate 100 (effectively the first liquid crystal alignment solidified layer 21) and / or the second liquid crystal alignment solidified layer 31, and the second adhesive layer 22 can be formed. In this manner, the second intermediate laminate 200 can be produced.

[0069] In the method for manufacturing an optical laminate according to an embodiment of the present invention, the conveying tension after laminating the first intermediate laminate and the second liquid crystal alignment solidified layer via the second adhesive layer, i.e., after the second lamination step, is greater than 700 N and less than 1500 N. The conveying tension after the second lamination step is preferably 750 N or more and 1400 N or less, more preferably 800 N or more and 1350 N or less, and even more preferably 1000 N or more and 1300 N or less. By keeping the tension within this range, the cure shrinkage of the second adhesive layer can be suppressed. Therefore, even when the second adhesive layer is cured, shrinkage of the polarizing plate (particularly the polarizer) and the retardation layer (the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer) accompanying the cure of the second adhesive layer can be suppressed. Therefore, cure shrinkage of the entire optical laminate (particularly the entire optical laminate including the polarizing plate and the retardation layer) can be suppressed, and thickness unevenness can be suppressed. As a result, when the optical laminate is applied to an image display device, linear unevenness due to light interference can be suppressed.

[0070] B-3. ​​Curing of the second adhesive layer (second adhesive layer curing process) When the second adhesive layer is made of an active energy ray-curable adhesive, the method preferably includes a curing step of curing the second adhesive layer (hereinafter also referred to as a second adhesive layer curing step). Specifically, in the second adhesive layer curing step, the first intermediate laminate 100 and the second liquid crystal alignment solidified layer 31 are bonded together with the second adhesive layer 22 interposed therebetween, and then the second adhesive layer 22 is cured. For the curing conditions in the second adhesive layer curing step, the explanation for the first adhesive layer curing step in Section B-1-4 may be cited.

[0071] In curing the second laminate layer, preferably, the long first intermediate laminate and the long second liquid crystal alignment solidified layer are roll-conveyed while being bonded together with the second adhesive layer interposed therebetween, and then the bonded laminate is cured by irradiating the second adhesive layer with active energy rays while being roll-conveyed. In the method for producing an optical laminate according to one embodiment of the present invention, the conveying tension in the second adhesive layer curing step may be preferably more than 700 N and less than 1500 N, more preferably 800 N or more and 1350 N or less, and even more preferably 1000 N or more and 1300 N or less.

[0072] In this manner, an optical stack according to an embodiment of the present invention can be manufactured (see FIG. 3A ). Even when the optical stack manufactured in this manner is applied to an image display device, the curing shrinkage of the second adhesive layer and / or the first adhesive layer, as well as the curing shrinkage of the entire optical stack, is suppressed, making it less likely to produce linear unevenness and display unevenness in the optical stack. Note that the first substrate 221 may be peeled from the first intermediate stack 100 after the first lamination step, and the resulting stack may be used in the second lamination step. The first substrate 221 may be peeled from the first intermediate stack 100 by any appropriate method. Furthermore, the second substrate 331 may be peeled from the second intermediate stack 200 and / or the optical stack 5 after the second lamination step. The second substrate 331 may also be peeled from the second intermediate stack 200 and / or the optical stack 5 by any appropriate method, similar to the first substrate 221. In this manner, an optical stack 50 as shown in FIG. 3B may be manufactured. The obtained optical laminate 50 can be placed on an image display panel or the like, with, for example, an adhesive layer interposed between the optical laminate 50 and the viewing side (specifically, the second liquid crystal alignment solidified layer side), to produce an image display device.

[0073] The obtained optical laminate may be in a continuous shape or in a sheet-like shape. A continuous optical laminate can be wound into a roll. A continuous optical laminate can be produced, for example, by the so-called roll-to-roll process as described above. A sheet-like optical laminate may be produced by cutting a continuous optical laminate into a predetermined size (typically, a size corresponding to an image display device), or by cutting each of the continuous laminates (polarizing plate, first intermediate laminate, and second intermediate laminate) and the liquid crystal alignment solidified layer into a predetermined size and then bonding them together using the procedure described above.

[0074] The obtained optical laminate can be placed on an image display panel or the like, with, for example, an adhesive layer interposed between the optical laminate and the viewing side (specifically, for example, the second liquid crystal alignment solidified layer side), to produce an image display device. [Example]

[0075] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Measurement and evaluation methods in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are by weight.

[0076] (1) Thickness The thickness was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., "MCPD9800"). (2) Linear unevenness The image display devices obtained in the examples and comparative examples were visually observed under a three-band fluorescent lamp in a non-illuminated state, and evaluated according to the following criteria. 1 (Excellent): No linear irregularities were observed even when observing with a polarizing plate attached to a three-wavelength fluorescent lamp 2 (Good): No linear irregularities were observed under normal observation using a three-wavelength fluorescent lamp 3 (Acceptable): Slight linear irregularities were observed under normal observation with a three-wavelength fluorescent lamp. 4 (Unacceptable): Linear unevenness that is practically unacceptable was observed during normal observation using a three-wavelength fluorescent lamp. 5 (poor): Linear irregularities were evident during normal observation under a three-wavelength fluorescent lamp.

[0077] [Production Example 1: Preparation of Adhesive A1 Constituting the First Adhesive Layer and the Second Adhesive Layer] Hydroxyethyl acrylamide (trade name "HEAA", manufactured by KJ Chemicals Co., Ltd.) 10 parts, 2-acetoacetoxyethyl methacrylate (trade name "AAEM", manufactured by Mitsubishi Chemicals Corporation) 4 parts, acryloylmorpholine (trade name "ACMO", manufactured by KJ Chemicals Co., Ltd.) 60 parts, tripropylene glycol diacrylate (trade name "Aronix M-220", manufactured by Toagosei Co., Ltd.) 11 parts, 4-vinylphenylboronic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 1 part, acrylic oligomer (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd.) 10 parts, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (trade name "Omnirad 819", manufactured by IGM Resins BV) 1 part, 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins BV) Two parts of ethylene glycol distearate (manufactured by BV Co., Ltd.) and one part of diethylthioxanthone (trade name "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd.) were stirred at 50°C for one hour to prepare adhesive A1.

[0078] [Example 1] 1. Preparation of optical laminate 1-1. Preparation of polarizer A long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of about 75° C. was used as the thermoplastic resin substrate, and one side of the resin substrate was subjected to a corona treatment. A PVA aqueous solution (coating solution) was prepared by dissolving 100 parts by weight of a PVA-based resin made by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFFIMER") in a 9:1 ratio, to which 13 parts by weight of potassium iodide was added, in water. The above PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60° C. to form a PVA resin layer with a thickness of 13 μm, thereby producing a laminate. The resulting laminate was uniaxially stretched 2.4 times in the machine direction (longitudinal direction) in an oven at 130°C (auxiliary in-air stretching treatment). Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilizing treatment). Next, the film was immersed in a dye bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be a desired value (dyeing treatment). Next, the sample was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). The laminate was then immersed in a boric acid aqueous solution (boric acid concentration 4 wt %, potassium iodide concentration 5 wt %) at a liquid temperature of 70°C and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment). Thereafter, the laminate was immersed in a cleaning bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment). Thereafter, the film was dried in an oven maintained at about 90°C, and brought into contact with a heated roll made of SUS whose surface temperature was maintained at about 75°C (drying shrinkage treatment). In this way, a polarizer with a thickness of approximately 5 μm was formed on the resin substrate, and a long polarizing plate having a resin substrate / polarizer configuration was obtained. The polarizer had a single transmittance Ts of 43.3%. The polarizer had an absorption axis in the longitudinal direction. Hereinafter, the absorption axis direction (longitudinal direction) will be referred to as the "0° direction," and the transmission axis direction (width direction) will be referred to as the "90° direction."

[0079] 1-2. Preparation of polarizing plate (PL1) An HC-COP film was attached to the surface of the obtained polarizer (the surface opposite to the resin substrate) via a UV-curable adhesive. The HC-COP film was a cycloolefin resin (COP) film (thickness: 25 μm) with an HC layer (thickness: 4 μm) formed on it, and the COP film was attached so that it faced the polarizer. The COP film had an Re(550) of 100 nm. The HC-COP film was attached so that the angle between the slow axis of the COP film and the absorption axis of the polarizer was 45°. Next, the resin substrate was peeled off, and a triacetyl cellulose (TAC) film (thickness: 20 μm) was attached to the peeled surface via a UV-curable adhesive, thus obtaining a long polarizing plate PL1 having a structure of HC layer / COP film (first protective layer) / polarizer / TAC film (second protective layer).

[0080] 1-3. Preparation of the first liquid crystal alignment layer (LC1) A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF "Paliocolor LC242"; chemical formula shown below) was dissolved in cyclopentanone to prepare a solution with a solids concentration of 30% by weight. A surfactant (BYK-Chemie "BYK-360") and a photopolymerization initiator (IGM Resins "Omnirad907") were added to the solution to prepare a liquid crystal composition solution. The surfactant and polymerization initiator were added in amounts of 0.01 and 3 parts by weight, respectively, per 100 parts by weight of the photopolymerizable liquid crystal compound. A commercially available triacetyl cellulose (TAC) film (Fujifilm, thickness: 80 μm) was prepared as a substrate. The liquid crystal composition was applied to the substrate using a bar coater to achieve an Re(550) of 120 nm and heated at 100°C for 3 minutes to align the liquid crystal. After cooling to room temperature, the film was exposed to an integrated light dose of 400 mJ / cm under a nitrogen atmosphere. 2 The resulting laminate was then photocured by irradiating it with ultraviolet light, yielding a long laminate having a substrate / first liquid crystal alignment solidified layer LC1 structure. The first liquid crystal alignment solidified layer was homogeneously aligned, and the slow axis direction of the first liquid crystal alignment solidified layer was in the 15° direction. The thickness of the first liquid crystal alignment solidified layer was 1.5 μm. [ka]

[0081] 1-4. Preparation of the second liquid crystal alignment layer (LC2) A long laminate having a substrate / second liquid crystal alignment solidified layer LC2 structure was obtained in the same manner as the first liquid crystal alignment solidified layer, except that the coating thickness was changed so that Re(550) was 240 nm. The slow axis direction of the second liquid crystal alignment solidified layer was 75°. The thickness of the second liquid crystal alignment solidified layer was 2.0 μm.

[0082] 1-5.First lamination process The long polarizing plate and long first liquid crystal alignment solidified layer prepared above were each roll-conveyed at the "Conveying tension up to the second lamination step" in Table 1. Adhesive A1 from Production Example 1 was applied to the second protective layer (TAC film) of the polarizing plate and the first liquid crystal alignment solidified layer, respectively, to form a first adhesive layer with a thickness of 1.0 μm after curing. The polarizing plate and the first liquid crystal alignment solidified layer were then laminated together with the first adhesive layer facing each other using a lamination roll. This produced a first intermediate laminate having a polarizing plate (first protective layer / polarizer / second protective layer) / first adhesive layer / first liquid crystal alignment solidified layer / substrate structure. Next, while the first intermediate laminate was being transported by rolls, ultraviolet light (integrated light amount 600 mJ / cm 2 ) to cure the first adhesive layer.

[0083] 1-6.Second lamination process Next, the long first intermediate laminate and the long laminate having the second liquid crystal alignment solidified layer LC2 and the substrate were roll-conveyed at the conveying tension shown in Table 1. Adhesive A1 from Production Example 1 was applied to the first liquid crystal alignment solidified layer of the first intermediate laminate and to the second liquid crystal alignment solidified layer of the laminate having the second liquid crystal alignment solidified layer LC2 and the substrate, respectively, to form a second adhesive layer with a thickness of 1.0 μm after curing. The first and second liquid crystal alignment solidified layers were then laminated together via the second adhesive layer using a lamination roll, with the first and second liquid crystal alignment solidified layers facing each other. This produced a second intermediate laminate comprising a polarizing plate (first protective layer / polarizer / second protective layer), first adhesive layer, first liquid crystal alignment solidified layer, second adhesive layer, second liquid crystal alignment solidified layer, and substrate.

[0084] 1-7. Hardening of the second adhesive layer Next, the second intermediate laminate was conveyed by rolls under the conveying tension shown in "Conveying tension after the second lamination step" in Table 1, while being irradiated with ultraviolet light (integrated light amount 600 mJ / cm 2 ) to cure the second adhesive layer, thereby obtaining an optical laminate.

[0085] 2. Fabrication of Image Display Device Next, the cover glass and the optical film on the viewing side of a commercially available liquid crystal display device (manufactured by Apple Inc., product name "iPad (registered trademark)", IPS mode) were removed, and the removed surface was cleaned.The second liquid crystal alignment solidified layer side of the optical laminate obtained above was then bonded to the cleaned surface via an acrylic adhesive (thickness 10 μm), thereby obtaining an image display device.The obtained image display device was subjected to the evaluation of the above-mentioned (2) "linear unevenness".The results are shown in Table 1.

[0086] [Examples 2 to 5, Comparative Example 1] An optical laminate and an image display device were produced in the same manner as in Example 1, except that the "transport tension after the second lamination step" was changed to that shown in Table 1. The obtained image display device was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0087] [Table 1] [Industrial Applicability]

[0088] The optical laminate according to the embodiment of the present invention can be suitably used in image display devices (typically, liquid crystal display devices and organic EL display devices). [Explanation of symbols]

[0089] 11 Polarizing plate 111 Polarizer 112 Protective layer (1st protective layer) 113 Protective layer (second protective layer) 21 First liquid crystal alignment solidification layer 221 Base material (1st base material) 100 First intermediate laminate 200 Second intermediate laminate 31 Second liquid crystal alignment solidification layer 331 Base material (second base material) 40 Retardation layer 5 Optical laminate 50 Optical laminate

Claims

1. A method for producing an optical laminate having a polarizing plate and a retardation layer including a first liquid crystal alignment solidified layer and a second liquid crystal alignment solidified layer, a first lamination step of laminating the polarizing plate and the first liquid crystal alignment solidified layer, while transporting the polarizing plate and the first liquid crystal alignment solidified layer, with the polarizing plate and the first liquid crystal alignment solidified layer facing each other via a first adhesive layer, to prepare a first intermediate laminate; a second lamination step of laminating the first intermediate laminate and the second liquid crystal alignment solidified layer via a second adhesive layer while transporting the first intermediate laminate and the second liquid crystal alignment solidified layer so that the first liquid crystal alignment solidified layer and the second liquid crystal alignment solidified layer face each other, thereby producing a second intermediate laminate; Including, The conveying tension after the second lamination step is more than 700 N and less than 1500 N. A method for producing an optical laminate.

2. The method for producing an optical laminate according to claim 1 , wherein a conveying tension after the second lamination step is 800 N or more and 1350 N or less.

3. The method for producing an optical laminate according to claim 1 , wherein the second adhesive layer is made of an active energy ray-curable adhesive.

4. The method for producing an optical laminate according to claim 1 , wherein a conveying tension up to the second lamination step is 100 N or more and 400 N or less.

5. the first lamination step includes transporting the long polarizing plate and the long first liquid crystal alignment solidified layer with rolls, and laminating the polarizing plate and the first liquid crystal alignment solidified layer with lamination rolls; 2. The method for producing an optical laminate according to claim 1, wherein the second lamination step includes conveying the long first intermediate laminate and the long second liquid crystal alignment solidified layer using rolls, and laminating the first intermediate laminate and the second liquid crystal alignment solidified layer using lamination rolls.

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