Optically anisotropic laminate, method for manufacturing same, circularly polarizing plate, and image display device

Abstract

Provided is an optically anisotropic laminate including a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer satisfies formula (1), the second optically anisotropic layer satisfies formula (2), the first optically anisotropic layer and the second optically anisotropic layer satisfy the relationship of formula (3), the optically anisotropic laminate satisfies formula (4), an NZ coefficient of each of the first optically anisotropic layer and the second optically anisotropic layer satisfies formula (5), and the angle formed by the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is 90°.　(1): nx1 > ny1 ≥ nz1 (2): nz2 > nx2 > ny2 (3): |Re2(450) / Re2(550) - Re1(450) / Re1(550)| ≥ 0.12 (4): Re(450) < Re(550) < Re(650) (5): - 1.5 ≤ NZ1 + NZ2 < 0.1

Description

Optically anisotropic laminate, method for producing the same, circularly polarizing plate and image display device

[0001] The present invention relates to an optically anisotropic laminate, a method for producing the same, a circularly polarizing plate, and an image display device.

[0002] BACKGROUND ART Image display devices such as organic electroluminescence image display devices (hereinafter, sometimes referred to as "organic EL image display devices") and liquid crystal image display devices are sometimes provided with a retardation film (Patent Documents 1 to 5).

[0003] International Publication No. 2020 / 137409 International Publication No. 2021 / 085031 JP 2004-145139 A U.S. Patent Publication No. 2016 / 0025913 JP 2014-026266 A (Corresponding Publication: U.S. Patent Application Publication No. 2015 / 168624 A)

[0004] In one embodiment of providing a retardation film in an image display device, the retardation film is combined with a linear polarizer to form a circular polarizing plate for the purpose of suppressing external light reflection on the display surface of the image display device. In this embodiment, the circular polarizing plate is required to be able to suppress coloring due to external light reflection both in the front direction and in the oblique direction of the display surface.

[0005] In order to suppress the external light reflection, the present inventors have developed in Patent Documents 1 and 2 a retardation film to be combined with a linear polarizer in a circular polarizing plate, which is an optically anisotropic laminate having a first optically anisotropic layer that satisfies predetermined optical properties and a second optically anisotropic layer that satisfies predetermined optical properties, wherein the sum of the NZ coefficient of the first optically anisotropic layer and the NZ coefficient of the second optically anisotropic layer is within a predetermined range, and the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer are orthogonal to each other. However, there is still room for development and improvement in retardation films that can suppress the external light reflection.

[0006] An object of the present invention is to provide an optically anisotropic laminate and a method for producing the same, which can realize an image display device in which coloring of the display surface when viewed from an oblique direction is suppressed; a circularly polarizing plate which can realize an image display device in which coloring of the display surface when viewed from an oblique direction is suppressed; and an image display device using the same.

[0007] The present inventors have found that the above-mentioned problems can be solved by satisfying new optical conditions, such as a large difference in wavelength dispersion between the first optically anisotropic layer and the second optically anisotropic layer, and a small sum of the NZ coefficients of the two layers, and have completed the present invention.

[0008] <1> An optically anisotropic laminate including a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer satisfies the following formula (1): The second optically anisotropic layer satisfies the following formula (2): An in-plane retardation Re1(550) of the first optically anisotropic layer at a wavelength of 550 nm, an in-plane retardation Re1(450) of the first optically anisotropic layer at a wavelength of 450 nm, an in-plane retardation Re2(550) of the second optically anisotropic layer at a wavelength of 550 nm, and an in-plane retardation Re2(450) of the second optically anisotropic layer at a wavelength of 450 nm satisfy the following formula (3): The optically anisotropic laminate satisfies the following formula (4): An NZ coefficient NZ1 of the first optically anisotropic layer and an NZ coefficient NZ2 of the second optically anisotropic layer satisfy the following formula (5): An optically anisotropic laminate, wherein the angle formed between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is 85° to 95°. nx1>ny1≧nz1 (1) nz2>nx2>ny2 (2) |Re2(450) / Re2(550)−Re1(450) / Re1(550)|≧0.12 (3) Re(450)<Re(550)<Re(650) (4) −1.5≦NZ1+NZ2<0.1 (5) where nx1 represents the refractive index in an in-plane direction of the first optically anisotropic layer that is the direction giving the maximum refractive index, ny1 represents the refractive index in an in-plane direction of the first optically anisotropic layer that is orthogonal to the direction giving nx1, and nz1 represents the refractive index in the thickness direction of the first optically anisotropic layer; nx2 represents the refractive index in the in-plane direction of the second optically anisotropic layer, in the direction giving the maximum refractive index, ny2 represents the refractive index in the in-plane direction of the second optically anisotropic layer, in the direction perpendicular to the direction giving nx2, and nz2 represents the refractive index in the thickness direction of the second optically anisotropic layer; Re(450), Re(550), and Re(650) represent the in-plane retardation of the optically anisotropic laminate at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. <2> The optically anisotropic laminate according to <1>, wherein Re1(550), Re1(450), Re2(550), and Re2(450) satisfy the following formulas (6) and (7):Re1(450) / Re1(550)<Re2(450) / Re2(550) (6) Re1(550)>Re2(550) (7) <3> The optically anisotropic laminate according to <1> or <2>, wherein Re1(550) and Re2(550) satisfy the following formula (8): 100 nm≦(Re1(550)−Re2(550))≦180 nm (8) <4> The optically anisotropic laminate according to any one of <1> to <3>, wherein Re1(550) and Re2(550) satisfy the following formula (9) and formula (10): 250 nm ≧ Re1(550) ≧ 170 nm (9) 110 nm ≧ Re2(550) ≧ 30 nm (10) <5> The optically anisotropic laminate according to any one of <1> to <4>, wherein NZ1 and NZ2 satisfy the following formula (11): −0.9<NZ1 + NZ2< 0.1 (11) <6> The optically anisotropic laminate according to any one of <1> to <5>, wherein the first optically anisotropic layer is a layer obtained by stretching a first resin layer, and the first resin layer contains a resin having a positive intrinsic birefringence value. <7> The optically anisotropic laminate according to any one of <1> to <6>, wherein the second optically anisotropic layer is a layer obtained by stretching a second resin layer, and the second resin layer contains a resin having a negative intrinsic birefringence value. <8> A circular polarizing plate comprising a linear polarizer and the optically anisotropic laminate according to any one of <1> to <7>. <9> The circular polarizing plate according to <8>, wherein the angle between the absorption axis of the linear polarizer or the transmission axis of the linear polarizer and the slow axis of the first optically anisotropic layer is 40° to 50°. <10> The circular polarizing plate according to <8> or <9>, comprising the linear polarizer, the first optically anisotropic layer, and the second optically anisotropic layer, in this order. <11> The circular polarizing plate according to <8> or <9>, comprising the linear polarizer, the second optically anisotropic layer, and the first optically anisotropic layer, in this order. <12> An image display device comprising the circular polarizing plate according to any one of <8> to <11> and an organic electroluminescence element, the image display device comprising the linear polarizer, the optically anisotropic laminate, and the organic electroluminescence element, in this order.<13> A method for producing an optically anisotropic laminate according to any one of <1> to <7>, comprising: Step 1 of stretching a first resin film containing a resin having a positive intrinsic birefringence value to obtain a first optically anisotropic layer; Step 2 of applying a coating liquid containing a resin having a negative intrinsic birefringence value onto a substrate to form a second resin layer, thereby obtaining an intermediate laminate including the substrate and the second resin layer; Step 3 of bidirectionally stretching the intermediate laminate to form a second optically anisotropic layer on the substrate; and Step 4 of overlaying the first optically anisotropic layer and the second optically anisotropic layer so that the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optical anisotropy is 85° to 95°. <14> The method for producing an optically anisotropic laminate according to <13>, wherein step 2 is a step of obtaining a long intermediate laminate comprising the long substrate and the long second resin layer as the intermediate laminate, and step 3 is a step of bidirectionally stretching the intermediate laminate comprising a step of stretching the long intermediate laminate in a stretching direction parallel to the longitudinal direction to obtain a stretched laminate comprising the second resin layer having a slow axis parallel to the width direction, and a step of stretching the stretched laminate in a direction oblique to the width direction to obtain a second optically anisotropic layer having a slow axis angle with respect to the width direction in the range of 30° to 80°. <15> The method for producing an optically anisotropic laminate according to <13> or <14>, wherein the thickness of the second resin layer obtained in step 2 is 11 μm or less.

[0009] According to the present invention, it is possible to provide an optically anisotropic laminate and a method for producing the same, which can realize an image display device in which coloring of the display surface when viewed from an oblique direction is suppressed; a circularly polarizing plate which can realize an image display device in which coloring of the display surface when viewed from an oblique direction is suppressed; and an image display device using the same.

[0010] FIG. 1 is a perspective view that schematically shows the state of an evaluation model that is set when calculating chromaticity in simulations of the examples and comparative examples.

[0011] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents. The components of the embodiments shown below can be combined as appropriate.

[0012] In the following description, unless otherwise specified, the in-plane retardation Re of a certain layer is a value expressed by Re = (nx - ny) x d. The thickness direction retardation Rth of a certain layer is a value expressed by Rth = {(nx + ny) / 2 - nz} x d, unless otherwise specified. Furthermore, the NZ coefficient (NZ) of a certain layer is a value expressed by NZ = (nx - nz) / (nx - ny), unless otherwise specified. The NZ coefficient can be calculated by NZ = Rth / Re + 0.5. Here, nx represents the refractive index in the direction perpendicular to the thickness direction of the layer (in-plane direction) and giving the maximum refractive index (slow axis direction), ny represents the refractive index in the in-plane direction of the layer and perpendicular to the nx direction, nz represents the refractive index in the thickness direction of the layer, and d represents the thickness of the layer. The measurement wavelength is 550 nm, unless otherwise specified.

[0013] In the following description, the slow axis of a certain layer refers to the slow axis in the plane of the layer, unless otherwise specified.

[0014] In the following description, unless otherwise specified, the front direction of a certain surface means the normal direction of the surface, and specifically refers to the direction of the polar angle of 0° and the azimuthal angle of 0° of the surface.

[0015] In the following description, unless otherwise specified, the tilt direction of a certain surface means a direction that is neither parallel nor perpendicular to the surface, and specifically refers to a direction in which the polar angle of the surface is in the range of greater than 0° and less than 90°.

[0016] In the following description, unless otherwise specified, the directions of elements as "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effects of the present invention, for example, within a range of ±5°.

[0017] In the following description, a "long" film refers to a film having a length that is 5 times or more its width, preferably 10 times or more its width, and specifically refers to a film having a length that can be wound into a roll for storage or transportation. There is no particular upper limit to the length of a long film, and it can be, for example, 100,000 times or less its width.

[0018] In the following description, unless otherwise specified, the width direction of a long film refers to the in-plane direction of the film that is perpendicular to the longitudinal direction of the film. Usually, the longitudinal direction of a long film coincides with the film transport direction.

[0019] In the following description, unless otherwise specified, the terms "polarizing plate," "circularly polarizing plate," "plate," "λ / 2 plate," and "λ / 4 plate" include not only rigid members but also flexible members such as resin films.

[0020] In the following description, the angle formed by the optical axes (absorption axis, transmission axis, slow axis, etc.) of each layer in a member having multiple layers represents the angle when the layer is viewed from the thickness direction, unless otherwise specified.

[0021] In the following description, "a polymer having a positive intrinsic birefringence" and "a resin having a positive intrinsic birefringence" mean "a polymer whose refractive index in the stretching direction is greater than the refractive index in the direction perpendicular to the stretching direction" and "a resin whose refractive index in the stretching direction is greater than the refractive index in the direction perpendicular to the stretching direction," respectively. Furthermore, "a polymer having a negative intrinsic birefringence" and "a resin having a negative intrinsic birefringence" mean "a polymer whose refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular to the stretching direction" and "a resin whose refractive index in the stretching direction is smaller than the refractive index in the direction perpendicular to the stretching direction," respectively. The intrinsic birefringence can be calculated from the dielectric constant distribution.

[0022] In the following description, unless otherwise specified, the term "adhesive" includes not only adhesives in the narrow sense but also pressure-sensitive adhesives having a shear storage modulus of less than 1 MPa at 23° C. The term "adhesive" in the narrow sense refers to an adhesive having a shear storage modulus of 1 MPa to 500 MPa at 23° C. after energy ray irradiation or heat treatment.

[0023] 1. Overview of Optically Anisotropic Laminate An optically anisotropic laminate according to one embodiment of the present invention includes a first optically anisotropic layer and a second optically anisotropic layer. The optically anisotropic laminate may include any optional layer as necessary.

[0024] The optically anisotropic laminate according to this embodiment satisfies the optical properties represented by the following formulas (1) to (5), and the angle formed between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is 85° to 95°.

[0025] nx1>ny1≧nz1 (1) nz2>nx2>ny2 (2) |Re2(450) / Re2(550)−Re1(450) / Re1(550)|≧0.12 (3) Re(450)<Re(550)<Re(650) (4) -1.5≦NZ1+NZ2<0.1 (5)

[0026] According to this embodiment, the optically anisotropic laminate satisfies the above formulas (1) to (5), and the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is a right angle or an angle close to a right angle, so that when combined with a linear polarizer to form a circular polarizing plate, it is possible to obtain an optically anisotropic laminate that can suppress external light reflection over a wide wavelength range and can suppress coloring in the tilt direction of the surface on which the circular polarizing plate is provided (for example, the display surface of an image display device). Furthermore, such an optically anisotropic laminate can usually suppress coloring not only in the tilt direction of the surface but also in the front direction.

[0027] Furthermore, according to this embodiment, by satisfying formula (3), a material with high wavelength dispersion can be used for the first optically anisotropic layer or the second optically anisotropic layer. When the wavelength dispersion is high, the retardation required to realize the desired reverse wavelength dispersion characteristic becomes small, so that the layer containing the material with high wavelength dispersion can be made thinner, and the thickness of the optically anisotropic laminate itself can be made thinner.

[0028] Furthermore, since the thickness of the optically anisotropic layer can be reduced as described above, for example, when an optically anisotropic layer using a resin with high wavelength dispersion is formed by a coating method, the thickness of the coating layer containing the resin and a solvent can also be reduced. Therefore, the coating layer can be dried under general drying conditions, such as heat treatment under atmospheric pressure. Furthermore, the amount of residual solvent in the resin layer obtained by drying the coating layer can be reduced, and the retardation expression by stretching can be improved, so that an optically anisotropic layer with desired optical properties can be easily formed.

[0029] 2. Optical Properties of Optically Anisotropic Laminate The optically anisotropic laminate according to this embodiment satisfies the above formulas (1) to (5).

[0030] In formula (1) (nx1>ny1≧nz1), nx1 represents the refractive index in the in-plane direction of the first optically anisotropic layer that gives the maximum refractive index, ny1 represents the refractive index in the in-plane direction of the first optically anisotropic layer that is perpendicular to the direction that gives nx1, and nz1 represents the refractive index in the thickness direction of the first optically anisotropic layer.

[0031] Formula (1) indicates that the first optically anisotropic layer can function as a so-called positive A plate or a negative B plate.

[0032] In formula (2) (nz2>nx2>ny2), nx2 represents the refractive index in the in-plane direction of the second optically anisotropic layer that gives the maximum refractive index, ny2 represents the refractive index in the in-plane direction of the second optically anisotropic layer that is perpendicular to the direction that gives nx2, and nz2 represents the refractive index in the thickness direction of the second optically anisotropic layer.

[0033] Formula (2) indicates that the second optically anisotropic layer can function as a so-called positive B plate. Formula (2) indicates that the second optically anisotropic layer is a layer having different refractive indices in three directions (nx2, ny2, and nz2), i.e., a layer having biaxiality.

[0034] In formula (3) (|Re2(450) / Re2(550)-Re1(450) / Re1(550)|≧0.12), Re1(450) and Re1(550) represent the in-plane retardation of the first optically anisotropic layer at wavelengths of 450 nm and 550 nm, respectively, and Re2(450) and Re2(550) represent the in-plane retardation of the second optically anisotropic layer at wavelengths of 450 nm and 550 nm, respectively.

[0035] Formula (3) indicates that there is a large difference between the wavelength dispersion of the in-plane retardation of the first optically anisotropic layer and the wavelength dispersion of the in-plane retardation of the second optically anisotropic layer. The value of "|Re2(450) / Re2(550)-Re1(450) / Re1(550)|" is usually 0.12 or more, preferably 0.15 or more, more preferably 0.2 or more, and particularly preferably 0.25 or more. The larger the value, the better, but it may be, for example, 0.7 or less. In this way, an optically anisotropic laminate comprising a first optically anisotropic layer and a second optically anisotropic layer in which the difference in wavelength dispersion of the in-plane retardation is a predetermined value or more can easily obtain reverse wavelength dispersion characteristics in the laminated state. Therefore, the optically anisotropic laminate can be combined with a linear polarizer to form a circular polarizer that functions over a wide wavelength range.

[0036] Furthermore, the optically anisotropic laminate according to this embodiment more preferably satisfies the following formula (6): Re1(450) / Re1(550)<Re2(450) / Re2(550) (6)

[0037] Formula (6) indicates that the wavelength dispersion of the second optically anisotropic layer is greater than the wavelength dispersion of the first optically anisotropic layer.

[0038] The value of "Re2(450) / Re2(550)" is preferably 1.05 or more, more preferably 1.10 or more, particularly preferably 1.20 or more, and even more particularly preferably 1.25 or more. The upper limit is not particularly limited, but may be, for example, 1.8 or less, 1.7 or less, or 1.6 or less. When the value of "Re2(450) / Re2(550)" is within the above range, a difference in wavelength dispersion between the first optically anisotropic layer and the second optically anisotropic layer is likely to occur, and the retardation required to achieve the desired reverse wavelength dispersion characteristics is reduced, making it possible to reduce the thickness of the circular polarizing plate and to obtain a circular polarizing plate that can effectively suppress coloring due to reflection of external light.

[0039] The value of "Re1(450) / Re1(550)" may be, for example, 0.8 or more, 0.9 or more, or 1.0 or more, and is preferably 1.05 or less, more preferably 1.03 or less, and particularly preferably 1.01 or less. When "Re1(450) / Re1(550)" is within the above range, a difference in wavelength dispersion between the first optically anisotropic layer and the second optically anisotropic layer is likely to occur, and the retardation required to achieve the desired reverse wavelength dispersion characteristics is reduced, making it possible to reduce the thickness and obtain a circular polarizing plate that can effectively suppress coloring due to reflection of external light.

[0040] Furthermore, the optically anisotropic laminate according to this embodiment preferably satisfies the following formula (7): Re1(550)>Re2(550) (7)

[0041] Equation (7) indicates that the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm is larger than the in-plane retardation of the second optically anisotropic layer at a wavelength of 550 nm.

[0042] The value of "(Re1(550)-Re2(550))" is usually greater than 0, and preferably is a value that allows the optically anisotropic laminate to function as a λ / 4 plate. Specifically, the optically anisotropic laminate preferably satisfies the following formula (8): 100 nm≦(Re1(550)-Re2(550))≦180 nm (8)

[0043] The value of "(Re1(550) - Re2(550))" is preferably 100 nm or more, more preferably 110 nm or more, even more preferably 120 nm, and is preferably 180 nm or less, more preferably 160 nm or less, even more preferably 150 nm or less. When "(Re1(550) - Re2(550))" is within the above range, a circularly polarizing plate that can effectively suppress coloring due to reflection of external light can be obtained.

[0044] In the optically anisotropic laminate according to this embodiment, it is preferable that both the formula (6) and the formula (7) are satisfied. A thin second optically anisotropic layer can be formed using a resin having a negative intrinsic refractive index with large wavelength dispersion and small retardation. Since resins having a negative intrinsic birefringence value are relatively expensive, the thickness of the second optically anisotropic layer can be reduced, thereby reducing the manufacturing cost.

[0045] The value of Re1(550) satisfies the above formulas (1) to (8), and preferably satisfies the following formula (9): 250 nm ≧ Re1(550) ≧ 170 nm (9)

[0046] More specifically, Re1(550) is preferably 170 nm or more, more preferably 180 nm or more, particularly preferably 190 nm or more, and is preferably 250 nm or less, more preferably 240 nm or less, particularly preferably 230 nm or less. When the in-plane retardation Re1(550) is in the above range, a circularly polarizing plate having high antireflection performance and high coloring suppression performance can be configured.

[0047] The value of Re2(550) satisfies the above-mentioned formulas (1) to (8), and preferably satisfies the following formula (10): 110 nm ≧ Re2(550) ≧ 30 nm (10)

[0048] More specifically, Re2(550) is preferably 30 nm or more, more preferably 40 nm or more, particularly preferably 50 nm or more, and is preferably 110 nm or less, more preferably 100 nm or less, particularly preferably 90 nm or less. When the in-plane retardation Re2(550) is in the above range, a circular polarizing plate having high antireflection performance and high coloring suppression performance can be configured.

[0049] In the optically anisotropic laminate, the ratio (Re1(450)-Re2(450)) / (Re1(550)-Re2(550)) may be, for example, 0.82 or more, 0.84 or more, or 0.85 or more. The upper limit of the ratio may be, for example, less than 1.0.

[0050] In formula (4) (Re(450)<Re(550)<Re(650)), Re(450), Re(550), and Re(650) represent the in-plane retardation of the optically anisotropic laminate at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.

[0051] Formula (4) indicates that the in-plane retardation of the optically anisotropic laminate has a reverse wavelength dispersion characteristic. When the optically anisotropic laminate satisfies formula (4), the polarization state of light passing through the optically anisotropic laminate can be uniformly converted over a wide wavelength range. Therefore, by combining such an optically anisotropic laminate with a linear polarizer, coloring due to external light reflection on the display surface of an image display device can be effectively suppressed over a wide wavelength range. Since optically anisotropic laminates have a reverse wavelength dispersion characteristic, they usually have a larger in-plane retardation as the measurement wavelength becomes longer.

[0052] In formula (5) (-1.5≦NZ1+NZ2<0.1), NZ1 represents the NZ coefficient of the first optically anisotropic layer, and NZ2 represents the NZ coefficient of the second optically anisotropic layer. The sum of NZ1 and NZ2 (NZ1+NZ2) is usually -1.5 or more, preferably -1.0 or more, more preferably -0.9 or more, and even more preferably greater than -0.9. The sum (NZ1+NZ2) is usually less than 0.1, preferably less than 0.0, and more preferably less than -0.1. By keeping the sum of NZ1 and NZ2 within the above range, when the optically anisotropic laminate is combined with a linear polarizer, coloring due to external light reflection on the display surface of an image display device can be effectively suppressed over a wide wavelength range.

[0053] In this embodiment, it is particularly preferable that the sum (NZ1+NZ2) satisfies the following formula (11): −0.9<NZ1+NZ2<0.1 (11)

[0054] NZ1 is a value calculated by (nx1-nz1) / (nx1-ny1), and is a positive value from formula (1). NZ1 is preferably 1.0 or more, more preferably 1.01 or more, and even more preferably 1.02 or more, and is preferably 1.3 or less, more preferably 1.2 or less, and even more preferably 1.1 or less.

[0055] NZ2 is a value calculated by (nx2-nz2) / (nx2-ny2), and from formula (2), NZ2 is a negative value. NZ2 is preferably -2.5 or more, more preferably -2.3 or more, even more preferably -2.1 or more, and preferably -1.0 or less, preferably -1.05 or less, more preferably -1.1 or less. By keeping NZ2 within the above range, it is possible to enhance biaxiality.

[0056] The in-plane retardation Re1(590) of the first optically anisotropic layer at a wavelength of 590 nm is preferably 185 nm or more, more preferably 190 nm or more, even more preferably 195 nm or more, and is preferably 270 nm or less, more preferably 250 nm or less, even more preferably 230 nm or less. When the in-plane retardation Re1(590) of the first optically anisotropic layer falls within the above range, coloring due to external light reflection on the display surface of an image display device can be effectively suppressed over a wide wavelength range when the optically anisotropic laminate is combined with a linear polarizer.

[0057] The in-plane retardation Re2(590) of the second optically anisotropic layer at a wavelength of 590 nm is preferably 45 nm or more, more preferably 50 nm or more, and even more preferably 55 nm or more, and is preferably 120 nm or less, more preferably 100 nm or less, and even more preferably 90 nm or less. When the in-plane retardation Re2(590) of the second optically anisotropic layer falls within the above range, coloring due to external light reflection on the display surface of an image display device can be effectively suppressed over a wide wavelength range when the optically anisotropic laminate is combined with a linear polarizer.

[0058] When the in-plane retardation Re1(590) of the first optically anisotropic layer at a wavelength of 590 nm falls within the above range, the first optically anisotropic layer can usually function as a λ / 2 plate. Also, when the in-plane retardation Re2(590) of the second optically anisotropic layer at a wavelength of 590 nm falls within the above range, the second optically anisotropic layer can usually function as a λ / 4 plate. Therefore, when the Re1(590) of the first optically anisotropic layer and the Re2(590) of the second optically anisotropic layer are within the above range, the optically anisotropic laminate can function as a broadband λ / 4 plate that combines a λ / 2 plate and a λ / 4 plate.

[0059] In this embodiment, the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is 85° to 95°. In other words, the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is a right angle or an angle close to a right angle. If the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is θ, then θ is usually 85° or more, preferably 87° or more, more preferably 88° or more, and even more preferably 89° or more, and is usually 95° or less, preferably 93° or less, more preferably 92° or less, even more preferably 91° or less, and most preferably 90°. When θ is in the above range, when the optically anisotropic laminate according to this embodiment is combined with a linear polarizer, external light reflection in the front direction and in the oblique direction of the display surface of an image display device can be suppressed, and coloring can be suppressed.

[0060] When the optically anisotropic laminate is long, it is preferable that one of the slow axes of the first optically anisotropic layer and the second optically anisotropic layer forms an angle within a specific range close to 45° with respect to the width direction of the optically anisotropic laminate. Specifically, the angle is preferably 40° or more, more preferably 42° or more, even more preferably 43° or more, particularly preferably 44° or more, and preferably 50° or less, more preferably 48° or less, even more preferably 47° or less, and particularly preferably 46° or less. Furthermore, in this case, it is preferable that the other of the slow axes of the first optically anisotropic layer and the second optically anisotropic layer forms an angle within a specific range close to 135° with respect to the width direction of the optically anisotropic laminate. Specifically, the angle is preferably 130° or more, more preferably 132° or more, even more preferably 133° or more, particularly preferably 134° or more, and preferably 140° or less, more preferably 138° or less, even more preferably 137° or less, and particularly preferably 136° or less. A typical long linear polarizer has an absorption axis parallel or perpendicular to the width direction of the linear polarizer. A long optically anisotropic laminate including a first optically anisotropic layer and a second optically anisotropic layer having a slow axis in a direction forming an angle within the above range with respect to the width direction can be simply attached to the typical linear polarizer so that the width direction of the optically anisotropic laminate is parallel to the width direction of the linear polarizer to obtain a circular polarizing plate. Therefore, the attachment of the optically anisotropic laminate and the linear polarizer can be performed by roll-to-roll processing, making it particularly easy to produce a circular polarizing plate.

[0061] The retardation and slow axis direction of the optically anisotropic laminate according to this embodiment and its constituent layers can be measured using a retardation meter (for example, "AxoScan" manufactured by Axometrics).

[0062] The total light transmittance of each of the first optically anisotropic layer and the second optically anisotropic layer is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. The total light transmittance of the second optically anisotropic layer is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more.

[0063] The haze of the first optically anisotropic layer is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%. The haze of the second optically anisotropic layer is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%.

[0064] The total light transmittance of the optically anisotropic laminate is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more.

[0065] The haze of the optically anisotropic laminate is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%.

[0066] The total light transmittance can be measured using an ultraviolet-visible spectrometer in the wavelength range of 400 nm to 700 nm, and the haze can be measured using a haze meter in accordance with JIS K7361-1997.

[0067] 3. Thickness of Optically Anisotropic Laminate and Constituent Layers The thickness of the first optically anisotropic layer and the thickness of the second optically anisotropic layer can be adjusted as desired within the range in which the above-mentioned optical properties are obtained. The thickness of the first optically anisotropic layer and the thickness of the second optically anisotropic layer can be typically 0.5 μm or more, more preferably 1 μm or more, and typically 150 μm or less, more preferably 100 μm or less.

[0068] In this embodiment, the thickness of the second optically anisotropic layer is preferably smaller than that of the first optically anisotropic layer. In this case, the thickness of the first optically anisotropic layer is preferably 20 μm or more, more preferably 25 μm or more, even more preferably 30 μm or more, and preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less. Furthermore, the thickness of the second optically anisotropic layer is preferably 1 μm or more, more preferably 1.5 μm or more, even more preferably 2.0 μm or more, and preferably 10 μm or less, more preferably 9 μm or less, more preferably 8 μm or less. This is because the thickness of the first optically anisotropic layer and the thickness of the second optically anisotropic layer being within the above ranges allows the thickness of the retardation film, which can suppress external light reflection, to be thin.

[0069] The ratio of the thickness (d1) (μm) of the first optically anisotropic layer to the thickness (d2) of the second optically anisotropic layer is preferably more than 70 / 30, more preferably 80 / 20 or more, even more preferably 90 / 10 or more, and preferably less than 99 / 1, preferably 97 / 3 or less, more preferably 95 / 5 or less. In the optically anisotropic laminate according to this embodiment, by satisfying formulas (1) to (5), it is possible to reduce the thickness of the second optically anisotropic layer while still allowing the retardation of the second optically anisotropic layer to be favorably exhibited. As a result, it is possible to configure a circularly polarizing plate having high antireflection performance and high coloring suppression performance, and it is possible to realize an optically anisotropic laminate that can be manufactured at low cost.

[0070] The thickness of the optically anisotropic laminate can be adjusted arbitrarily within the range in which the above-mentioned optical properties are obtained. Specifically, from the viewpoint of thinning, the thickness is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 15 μm or more, and is preferably 200 μm or less, more preferably 150 μm or less, particularly preferably 100 μm or less.

[0071] <4. Materials for Constituent Layers of Optically Anisotropic Laminate> The materials for forming the first optically anisotropic layer and the second optically anisotropic layer are arbitrary. Each of the first optically anisotropic layer and the second optically anisotropic layer typically contains a resin and is formed from a resin. The resin contained in each of the first optically anisotropic layer and the second optically anisotropic layer may be a resin with a positive or negative intrinsic birefringence value. However, it is usually preferred that the resin contained in the first optically anisotropic layer be a resin with a positive intrinsic birefringence value, and that the resin contained in the second optically anisotropic layer be a resin with a negative intrinsic birefringence value.

[0072] Resins having a positive intrinsic birefringence value usually contain polymers having a positive intrinsic birefringence value. Examples of such polymers include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfides such as polyphenylene sulfide; polyvinyl alcohol; polycarbonate; polyarylate; cellulose ester; polyethersulfone; polysulfone; polyallylsulfone; polyvinyl chloride; alicyclic structure-containing polymers; rod-shaped liquid crystal polymers; and the like. These polymers may be used alone or in combination of two or more in any ratio. Among them, alicyclic structure-containing polymers, cellulose esters, and polycarbonates are preferred, with alicyclic structure-containing polymers being particularly preferred. The alicyclic structure-containing polymer may be a cyclic olefin-based polymer. The cyclic olefin-based polymer refers to a polymer having a structural unit obtained by polymerizing a cyclic olefin or a hydrogenated product thereof. The cyclic olefin may or may not have a substituent.

[0073] The alicyclic structure-containing polymer is a polymer containing an alicyclic structure in the repeating unit, and is usually an amorphous polymer. As the alicyclic structure-containing polymer, either a polymer containing an alicyclic structure in the main chain or a polymer containing an alicyclic structure in the side chain can be used. Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, but from the viewpoint of thermal stability, a cycloalkane structure is preferred. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, particularly preferably 6 or more, and preferably 30 or less, more preferably 20 or less, particularly preferably 15 or less.

[0074] In the alicyclic structure-containing polymer, the proportion of repeating units containing an alicyclic structure is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the proportion of repeating units containing an alicyclic structure is within the above range, an optically anisotropic laminate having excellent heat resistance can be obtained.

[0075] Examples of polymers containing an alicyclic structure include (1) norbornene-based polymers, (2) monocyclic olefin polymers, (3) cyclic conjugated diene polymers, (4) vinyl alicyclic hydrocarbon polymers, and hydrogenated products thereof. Among these, cyclic olefin polymers and norbornene-based polymers are preferred, with norbornene-based polymers being particularly preferred. Examples of norbornene-based polymers include ring-opening polymers of monomers containing a norbornene structure, ring-opening copolymers of monomers containing a norbornene structure and other monomers copolymerizable therewith, and hydrogenated products thereof; addition polymers of monomers containing a norbornene structure, and addition copolymers of monomers containing a norbornene structure and other monomers copolymerizable therewith. Among these, from the viewpoint of transparency, hydrogenated ring-opening polymers of monomers containing a norbornene structure are particularly preferred. The alicyclic structure-containing polymer can be selected from the polymers disclosed in, for example, JP 2002-321302 A.

[0076] Examples of cellulose esters include lower fatty acid esters of cellulose (e.g., cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate). Lower fatty acids refer to fatty acids having 6 or fewer carbon atoms per molecule. Cellulose acetates may include triacetyl cellulose (TAC) and cellulose diacetate (DAC).

[0077] The total acyl substitution degree of the cellulose ester is preferably 2.20 to 2.70, more preferably 2.40 to 2.60. The total acyl substitution degree can be measured in accordance with ASTM D817-91. The weight average polymerization degree of the cellulose ester is preferably 350 to 800, more preferably 370 to 600.

[0078] Polycarbonates usually have repeating units containing a carbonate bond (-O-C(=O)-O-). Examples of polycarbonates include polymers having a structural unit derived from a dihydroxy compound and a carbonate structure (a structure represented by -O-(C=O)-O-). Examples of dihydroxy compounds include bisphenol A. The structural unit derived from a dihydroxy compound contained in a polycarbonate may be of one type or two or more types.

[0079] The weight-average molecular weight (Mw) of the polymer contained in the resin having a positive intrinsic birefringence value is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, and preferably 100,000 or less, more preferably 80,000 or less, particularly preferably 50,000 or less. When the weight-average molecular weight is within this range, the mechanical strength and moldability of the optically anisotropic layer are well balanced. The weight-average molecular weight is the weight-average molecular weight in terms of polyisoprene or polystyrene measured by gel permeation chromatography (GPC) using cyclohexane as a solvent. However, if the sample is insoluble in cyclohexane, toluene may be used as the GPC solvent.

[0080] The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the polymer contained in the resin having a positive intrinsic birefringence value is preferably 1.2 or more, more preferably 1.5 or more, particularly preferably 1.8 or more, and preferably 3.5 or less, more preferably 3.0 or less, particularly preferably 2.7 or less. When the molecular weight distribution is at least the lower limit of the above range, the productivity of the polymer can be increased and the production cost can be reduced. On the other hand, when the molecular weight distribution is at most the upper limit, the amount of low molecular weight components is reduced, thereby suppressing relaxation during exposure to high temperatures and improving the stability of the optically anisotropic layer.

[0081] The proportion of the polymer in the resin having a positive intrinsic birefringence value is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and particularly preferably 90 to 100% by weight. When the proportion of the polymer is within this range, the optically anisotropic layer can have sufficient heat resistance and transparency.

[0082] The resin having a positive intrinsic birefringence value may further contain an optional component in combination with the polymer. Examples of the optional component include stabilizers such as antioxidants, heat stabilizers, light stabilizers, weather stabilizers, ultraviolet absorbers, and near-infrared absorbers; plasticizers; etc. These components may be used alone or in combination of two or more in any ratio.

[0083] Resins having a negative intrinsic birefringence value typically include polymers having a negative intrinsic birefringence value, such as aromatic group-containing polymers, polyacrylonitrile polymers, polymethyl methacrylate polymers, or multiple copolymers thereof.

[0084] As a polymer having a negative intrinsic birefringence value, Patent Document 1 describes an example in which a styrene-maleic acid copolymer (a styrene-based polymer) is used, and Patent Document 2 describes an example in which poly(2-vinylnaphthalene) is used. However, in the present embodiment, for example, by using a polymer different from the polymers exemplified in Patent Documents 1 and 2, an optically anisotropic laminate satisfying formulas (1) to (5) can be easily produced.

[0085] The aromatic group-containing polymer is a polymer containing an aromatic group-containing unit and is obtained by polymerizing an aromatic group-containing monomer. Examples of the aromatic group contained in the aromatic group-containing monomer include a phenyl group, a naphthyl group (e.g., a 2-naphthyl group), a fluorenediyl group (e.g., a fluorene-9,9-diyl group), and groups having a structure in which a hydrogen atom on the ring of these groups is substituted with a substituent.

[0086] One group of examples of aromatic group-containing polymers includes polyesters, polycarbonates, and polyestercarbonates that contain polymerized units that contain fluorene-9,9-diyl groups.

[0087] Another group of examples of aromatic group-containing polymers includes aromatic vinyl polymers. Aromatic vinyl polymers are polymers containing aromatic vinyl units, and the aromatic vinyl units are units having a structure obtained by polymerizing an aromatic vinyl compound. However, in the present application, the polymerized units are not limited by their production method. Examples of aromatic vinyl units include the polymerized unit (A-1) contained in the hydrogenated block copolymer [C] described below and preferred examples thereof.

[0088] The proportion of the polymer in the resin having a negative intrinsic birefringence value is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. When the proportion of the polymer is in this range, appropriate optical properties can be exhibited.

[0089] A particularly preferred example of the aromatic vinyl polymer is the hydrogenated block copolymer [C] described below. The hydrogenated block copolymer [C] contains a combination of polymer block [A] and polymer block [B]. The term "hydrogenated" in the term "hydrogenated block copolymer [C]" indicates that the hydrogenated block copolymer [C] contains a polymer block [B] containing a hydrogenated linear conjugated diene unit. The hydrogenated block copolymer [C] also includes block copolymers obtained by a production method that does not involve a hydrogenation reaction, so long as it contains polymer block [A] and polymer block [B]. The resin containing this hydrogenated block copolymer [C] is usually a thermoplastic resin.

[0090] The polymer block [A] contains an aromatic vinyl unit. As described above, the aromatic vinyl unit refers to a polymerized unit having a structure obtained by polymerizing an aromatic vinyl compound. The aromatic vinyl compound includes aromatic vinyl compounds and derivatives thereof. The aromatic vinyl compound refers to a hydrocarbon compound having a structure in which a vinyl group is bonded to an aromatic ring. Furthermore, the derivatives of aromatic vinyl compounds include compounds having a structure in which one or more hydrogen atoms of an aromatic vinyl compound are substituted with a substituent. The aromatic vinyl unit includes polymerized units obtained by any production method, so long as they have the structure.

[0091] A preferred example of the aromatic vinyl unit is a polymer unit represented by the following formula (A-1):

[0092]

[0093] In formula (A-1), R Ｃ represents a group selected from the group consisting of a phenyl group, a biphenyl group, a naphthyl group, an anthracene group, a phenanthrene group, a naphthacene group, a pentacene group, and a terphenyl group. From the viewpoint of particularly facilitating the production of an optically anisotropic laminate having desired optical properties, R ｃ As the alkyl group, a naphthyl group is preferred.

[0094] In formula (A-1), R １ ~R ３ each independently represents a group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 12 carbon atoms. Examples of such an alkyl group include a methyl group, an ethyl group, a propyl group, and a hexyl group. From the viewpoint of particularly facilitating the production of an optically anisotropic laminate having desired optical properties, R ２ and R ３ are hydrogen atoms, and more preferably R １ , R ２ and R ３ are all hydrogen atoms.

[0095] A particularly preferred example of the aromatic vinyl unit is a polymer unit represented by the following formula (a-1): The polymer unit represented by formula (a-1) represents a vinylnaphthalene unit.

[0096]

[0097] The aromatic vinyl unit can be obtained, for example, by polymerizing an aromatic vinyl compound. Examples of aromatic vinyl compounds include vinylnaphthalene and its derivatives. Examples of vinylnaphthalene include 1-vinylnaphthalene and 2-vinylnaphthalene. Examples of vinylnaphthalene derivatives include α-methyl-1-vinylnaphthalene, α-ethyl-1-vinylnaphthalene, α-propyl-1-vinylnaphthalene, α-hexyl-1-vinylnaphthalene, α-methyl-2-vinylnaphthalene, α-ethyl-2-vinylnaphthalene, α-propyl-2-vinylnaphthalene, and α-hexyl-2-vinylnaphthalene. Among these, 2-vinylnaphthalene is preferred from the viewpoint of industrial availability.

[0098] The aromatic vinyl-based units contained in the hydrogenated block copolymer [C] may be of one type or of two or more types. Thus, the aromatic vinyl-based compounds for forming the aromatic vinyl-based units may be used singly or in combination of two or more types in any ratio.

[0099] The proportion of aromatic vinyl units in the polymer block [A] is preferably high. Specifically, the proportion of aromatic vinyl units in the polymer block [A] is preferably 50% by weight to 100% by weight, more preferably 75% by weight to 100% by weight, and particularly preferably 100% by weight. When the proportion of aromatic vinyl units in the polymer block [A] is as high as described above, it is particularly easy to produce an optically anisotropic laminate having desired optical properties.

[0100] The polymer block [A] may contain any polymerized unit other than the aromatic vinyl-based unit. Examples of such any polymerized unit include a polymerized unit having a structure obtained by polymerizing any monomer copolymerizable with an aromatic vinyl-based compound, and a polymerized unit having a structure formed by hydrogenating such a polymerized unit.

[0101] The polymer block [B] contains a hydrogenated linear conjugated diene unit. The hydrogenated linear conjugated diene unit refers to a polymerized unit having a structure obtained by polymerizing and hydrogenating a linear conjugated diene compound. The linear conjugated diene compound includes a linear conjugated diene compound and a derivative thereof. The linear conjugated diene compound refers to a linear hydrocarbon compound having a conjugated diene structure. Furthermore, the derivative of the linear conjugated diene compound includes a compound having a structure in which one or more hydrogen atoms of a linear conjugated diene compound are substituted with a substituent. The hydrogenated linear conjugated diene unit includes a polymerized unit obtained by any production method, so long as it has the structure.

[0102] Preferred examples of the hydrogenated linear conjugated diene unit include a polymer unit represented by the following formula (B-1) and a polymer unit represented by the following formula (B-2).

[0103]

[0104] In formula (B-1) and formula (B-2), R ４ ~R ９ each independently represents a group selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 6 carbon atoms. Examples of such an alkyl group include a methyl group, an ethyl group, a propyl group, and a hexyl group. From the viewpoint of particularly facilitating the production of an optically anisotropic laminate having desired optical properties, R ４ ~R ９ are preferably each independently a hydrogen atom or a methyl group.

[0105] Particularly preferred examples of the hydrogenated linear conjugated diene unit include polymerization units represented by any one of the following formulas (b-1) to (b-5). The polymerization units represented by any one of formulas (b-1) to (b-3) represent hydrogenated isoprene units. Furthermore, the polymerization units represented by formula (b-4) or (b-5) represent hydrogenated butadiene units.

[0106]

[0107] The hydrogenated linear conjugated diene unit can be obtained, for example, by a method including a step of polymerizing a linear conjugated diene compound to obtain a linear conjugated diene unit, and a step of hydrogenating a double bond, if any, present in the linear conjugated diene unit. The linear conjugated diene unit refers to a polymerized unit having a structure obtained by polymerizing a linear conjugated diene compound. The linear conjugated diene unit includes polymerized units obtained by any production method, so long as they have the structure.

[0108] Examples of the chain conjugated diene compound include compounds represented by the following formula (bm).

[0109]

[0110] A preferred example of the chain conjugated diene compound is butadiene (R in formula (bm)). ４ ~R ９ where all of R in formula (bm) are hydrogen atoms), isoprene (where R in formula (bm) are hydrogen atoms), ４ ~R ９ Among R ６ or R ７ where R is a methyl group and the others are hydrogen atoms), 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, and 2,4-dimethyl-1,3-pentadiene. Of these, butadiene and isoprene are more preferred from the viewpoint of obtaining an optically anisotropic laminate excellent in transparency, heat resistance, and processability.

[0111] After polymerizing a linear conjugated diene compound to obtain linear conjugated diene units, hydrogenated double bonds of the linear conjugated diene units are obtained to obtain hydrogenated linear conjugated diene units. This hydrogenation may be carried out in a system containing polymer block [A]. For example, after obtaining a block copolymer containing polymer block [A] obtained by polymerizing an aromatic vinyl compound and polymer block [D] obtained by polymerizing a linear conjugated diene compound, the double bonds contained in polymer block [D] of the block copolymer may be selectively hydrogenated to obtain polymer block [B] containing hydrogenated linear conjugated diene units. In this case, the method for hydrogenating the double bonds of the linear conjugated diene units is usually selected to hydrogenate the aliphatic double bonds of the linear conjugated diene units contained in polymer block [D] without hydrogenating the aromatic unsaturated bonds of the aromatic vinyl units contained in polymer block [A].

[0112] The hydrogenation rate of the double bonds of the chain conjugated diene units is preferably 90% or more, more preferably 95% or more, and particularly preferably 97% or more. When the hydrogenation rate is as high as above, it is particularly easy to produce an optically anisotropic laminate having desired optical properties. １ It can be measured by H-NMR.

[0113] The hydrogenated block copolymer [C] may contain one or more types of hydrogenated linear conjugated diene units. Thus, the linear conjugated diene compounds for forming the hydrogenated linear conjugated diene units may be used alone or in combination of two or more types in any ratio.

[0114] The proportion of hydrogenated linear conjugated diene units in the polymer block [B] is preferably high. Specifically, the proportion of hydrogenated linear conjugated diene units in the polymer block [B] is preferably 50% by weight to 100% by weight, more preferably 75% by weight to 100% by weight, and particularly preferably 100% by weight. When the proportion of hydrogenated linear conjugated diene units in the polymer block [B] is as high as described above, it is particularly easy to produce an optically anisotropic laminate having desired optical properties.

[0115] The polymer block [B] may contain any polymerized unit other than the hydrogenated linear conjugated diene unit. Examples of such any polymerized unit include a polymerized unit obtained by polymerizing a linear conjugated diene compound and having a remaining unhydrogenated double bond (such as a linear conjugated diene unit), a polymerized unit having a structure obtained by polymerizing any monomer copolymerizable with a linear conjugated diene compound, and a polymerized unit having a structure formed by hydrogenating such a polymerized unit.

[0116] In the hydrogenated block copolymer [C], the ratio wA / wB of the weight fraction wA of the polymer block [A] to the weight fraction wB of the polymer block [B] is preferably within a specific range. More specifically, the ratio wA / wB of the weight fraction wA to the weight fraction wB is usually 50 / 50 or more, preferably 55 / 45 or more, particularly preferably 60 / 40 or more, and usually 85 / 15 or less, preferably 82 / 18 or less, particularly preferably 80 / 20 or less. When the ratio wA / wB is within the above range, it is possible to easily produce an optically anisotropic laminate having reverse wavelength dispersion characteristics. Furthermore, when the ratio wA / wB is within the above range, it is usually possible to easily adjust the optical properties other than the wavelength dispersion characteristics of the optically anisotropic laminate to desired values.

[0117] The weight fraction wA of the polymer block [A] refers to the ratio of the weight of the polymer block [A] to the total weight of the polymer block [A] and the polymer block [B]. When the resin used as the material for the optically anisotropic laminate contains multiple types of hydrogenated block copolymers [C], the weight fraction wA of the polymer block [A] referred to here refers to the ratio of the weight of the polymer block [A] to the total weight of the polymer block [A] and the polymer block [B] in the entire multiple types of hydrogenated block copolymers [C] contained therein.

[0118] The weight fraction wB of the polymer block [B] refers to the ratio of the weight of the polymer block [B] to the total weight of the polymer block [A] and the polymer block [B]. When the resin used as the material for the optically anisotropic laminate contains multiple types of hydrogenated block copolymers [C], the weight fraction wB of the polymer block [B] referred to here refers to the ratio of the weight of the polymer block [B] to the total weight of the polymer block [A] and the polymer block [B] in the entire multiple types of hydrogenated block copolymers [C] contained therein.

[0119] The weight fraction wA of the polymer block [A] and the weight fraction wB of the polymer block [B] are １ It can be measured by H-NMR.

[0120] The molecular structure of the hydrogenated block copolymer [C] is not particularly limited as long as it contains the polymer block [A] and the polymer block [B], and may be a molecular structure having any block configuration. For example, the hydrogenated block copolymer [C] may be a linear block copolymer or a graft block copolymer.

[0121] Examples of linear block copolymers include diblock copolymers having a block structure of [A]-[B] in which a polymer block [A] and a polymer block [B] are linked together; triblock copolymers having a block structure of [A]-[B]-[A] in which a polymer block [A], a polymer block [B], and another polymer block [A] are linked together in this order; and linear block copolymers having a block structure in which a larger number of polymer blocks are linked together. Examples of block structures in which a larger number of polymer blocks are linked together include [A]-([B]-[A]) ｎ -[B]-[A], and [B]-([A]-[B]) ｎ -[A]-[B] (n is an integer of 1 or more).

[0122] An example of a graft-type block copolymer is a block copolymer having a block structure of [A]-g-[B] in which a polymer block [B] is linked to a polymer block [A] as a side chain.

[0123] From the viewpoint of particularly facilitating the production of an optically anisotropic laminate having desired optical properties, the hydrogenated block copolymer [C] preferably has a molecular structure having two or more polymer blocks [A] and one or more polymer blocks [B] per molecule, and more preferably is a triblock copolymer having a block structure of [A]-[B]-[A].

[0124] The hydrogenated block copolymer [C] contained in the resin as a material for the optically anisotropic laminate may be one type or two or more types.

[0125] The resin having a negative intrinsic birefringence value may further contain an optional component in combination with the polymer. Examples of the optional component include the same optional components as those that may be contained in the resin having a positive intrinsic birefringence value. One type of optional component may be used alone, or two or more types may be used in combination in any ratio.

[0126] The resin having a positive intrinsic birefringence value and the resin having a negative intrinsic birefringence value described above can both be formed into a resin layer, and the resin layer can be stretched to exhibit desired optical properties.

[0127] <5. Optional Layers of Optically Anisotropic Laminate> The optically anisotropic laminate may include any layer other than the first optically anisotropic layer and the second optically anisotropic layer, as needed. Examples of the optional layer include any layer having optical isotropy. This optional layer having optical isotropy typically has an in-plane retardation of 10 nm or less at a wavelength of 550 nm. Examples of the optional layer having optical isotropy include a protective film layer for protecting the first optically anisotropic layer and the second optically anisotropic layer; and an adhesive layer for adhering the first optically anisotropic layer and the second optically anisotropic layer. Examples of the protective film layer include a film used as a substrate for an intermediate laminate in the manufacturing method described below. In addition, the adhesive used in the adhesive layer may be, for example, the same adhesive as that used in the manufacturing of the polarizing plate described below.

[0128] <6. Manufacturing Method of Optically Anisotropic Laminate> The manufacturing method of the optically anisotropic laminate of the present invention is not particularly limited, and the laminate can be manufactured by any method. In the optically anisotropic laminate of the present invention, the first optically anisotropic layer is preferably a layer obtained by stretching a first resin layer, and the first resin layer contains a resin having a positive intrinsic birefringence value. Furthermore, in the optically anisotropic laminate of the present invention, the second optically anisotropic layer is preferably a layer obtained by stretching a second resin layer, and the second resin layer contains a resin having a negative intrinsic birefringence value. An optically anisotropic laminate having the above configuration can be manufactured, for example, by a manufacturing method including the following steps. Hereinafter, this manufacturing method will be described as the manufacturing method of the present invention.

[0129] Step 1: A step of stretching a first resin film containing a resin having a positive intrinsic birefringence value to obtain a first optically anisotropic layer. Step 2: A step of applying a coating liquid containing a resin having a negative intrinsic birefringence value onto a substrate to form a second resin layer, thereby obtaining an intermediate laminate including the substrate and the second resin layer. Step 3: A step of bidirectionally stretching the intermediate laminate to form a second optically anisotropic layer on the substrate. Step 4: A step of overlapping the first optically anisotropic layer and the second optically anisotropic layer so that the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optical anisotropy is 85° to 95°.

[0130] 6.1. Step 1 Step 1 is a step of stretching a first resin film containing a resin having a positive intrinsic birefringence value to obtain a first optically anisotropic layer.

[0131] The first resin film containing a resin having a positive intrinsic birefringence value used in step 1 is a film-like first resin layer. The first resin film can be produced by a melt molding method or a solution casting method, with the melt molding method being preferred. Among the melt molding methods, extrusion molding, inflation molding, and press molding are preferred, with the extrusion molding method being particularly preferred.

[0132] The first resin film is usually obtained as a long resin film. By preparing the first resin film as a long resin film, some or all of the steps in producing the first optically anisotropic layer can be performed in-line, making the production simple and efficient.

[0133] The stretching method for the first resin film can be any appropriate method depending on the optical properties desired to be achieved by stretching. In this embodiment, the stretching method for the first resin film is not particularly limited, but unidirectional stretching (uniaxial stretching) is preferred. This is because unidirectional stretching of the first resin film can enhance the uniaxiality of the layer containing a resin having a positive intrinsic birefringence value. Unidirectional stretching includes, for example, free-end uniaxial stretching and fixed-end uniaxial stretching. In step 1, the first resin film may be stretched once in one direction or two directions.

[0134] The stretching direction of the first resin film is not particularly limited. Stretching of the first resin film may include stretching in an oblique direction. A first optically anisotropic layer can be obtained as an obliquely stretched film by a production method including stretching in an oblique direction. An obliquely stretched film refers to a film produced by a production method including stretching in an oblique direction. An obliquely stretched film usually exhibits a slow axis that is neither parallel nor perpendicular to its width direction. Therefore, a slow axis that forms a predetermined angle with respect to the width direction can be easily exhibited in the first optically anisotropic layer as an obliquely stretched film. Therefore, a circularly polarizing plate can be easily produced by roll-to-roll laminating the first optically anisotropic layer as an obliquely stretched film with a polarizing film having a transmission axis in the width direction and the second optically anisotropic layer.

[0135] The stretching ratio of the first resin film is preferably 1.1 times or more, more preferably 1.3 times or more, particularly preferably 1.5 times or more, and is preferably 4 times or less, more preferably 3 times or less, particularly preferably 2.5 times or less. When stretching is performed in two or more directions, it is desirable that the product of the stretching ratios in each direction falls within the above range. By keeping the stretching ratio within the above range, it is easy to obtain a first optically anisotropic layer having desired optical properties.

[0136] The stretching temperature of the first resin film is preferably Tg1 or higher, more preferably "Tg1 + 2°C" or higher, particularly preferably "Tg1 + 5°C" or higher, and preferably "Tg1 + 40°C" or lower, more preferably "Tg1 + 35°C" or lower, particularly preferably "Tg1 + 30°C" or lower. Here, Tg1 represents the glass transition temperature of a resin having a positive intrinsic birefringence value. By setting the stretching temperature within the above range, the molecules contained in the first resin film can be reliably oriented, making it possible to easily obtain a first optically anisotropic layer having the desired optical properties.

[0137] The glass transition temperature of the resin can be measured using a differential scanning calorimeter (for example, "DSC6220SII" manufactured by Nano Technology Co., Ltd.) in accordance with JIS K 6911 at a temperature rise rate of 10°C / min.

[0138] In step 1 (method for producing the first optically anisotropic layer), any other steps may be performed in addition to the steps described above. For example, when a long first optically anisotropic layer is produced using a long first resin film, a trimming step may be performed in which the first optically anisotropic layer is cut into a desired shape. By performing the trimming step, a sheet of the first optically anisotropic layer having the desired shape is obtained. In addition, for example, a step of providing a protective layer on the first optically anisotropic layer may be performed.

[0139] <6.2. Step 2> Step 2 is a step of applying a coating liquid containing a resin having a negative intrinsic birefringence value onto a substrate to form a second resin layer, thereby obtaining an intermediate laminate including the substrate and the second resin layer. In step 3 described below, the intermediate laminate is bidirectionally stretched to form a second optically anisotropic layer on the stretched substrate. In the following description, the intermediate laminate before stretching obtained in step 2 may be referred to as a first intermediate laminate, and the intermediate laminate including the second optically anisotropic layer obtained in step 3 may be referred to as a second intermediate laminate.

[0140] A resin film is usually used as a substrate that can be used for the first intermediate laminate. The resin that can be used for the resin film is usually a thermoplastic resin. Furthermore, a long resin film is usually used as the resin film as the substrate. A long second optically anisotropic layer can be formed on the long substrate, and by superposing this on a long first optically anisotropic layer by roll-to-roll, a long optically anisotropic laminate can be obtained, and therefore, the optically anisotropic laminate can be produced efficiently.

[0141] The resin contained in the substrate usually contains a thermoplastic polymer. Examples of polymers that can be used for the substrate include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; acrylic polymers such as polymethyl methacrylate; cellulose polymers such as triacetyl cellulose; polycarbonates; and the like, with polyolefins being preferred. One type of polymer may be used alone, or two or more types may be used in combination. The resin contained in the substrate contains the polymer and may contain optional components as necessary. The optional components may be appropriately selected from the optional components that can be contained in the resin having the above-mentioned positive intrinsic birefringence value.

[0142] The resin contained in the substrate may be, for example, a resin having a positive intrinsic birefringence value as described above.

[0143] The substrate may have a single structure consisting of the above-mentioned resin layer, or may have a multi-layer structure having, for example, a resin layer and a release layer provided on at least one of the resin layers. Examples of materials used for the release layer include known release agents.

[0144] The thickness of the substrate is not particularly limited as long as it is sufficient to support the second resin layer, but is usually about 50 μm to 200 μm.

[0145] Specific examples of the resin having a negative intrinsic birefringence value used in step 2 include those mentioned above. By using a resin having a negative intrinsic birefringence value as the resin for forming the second optically anisotropic layer, it is possible to easily produce a second optically anisotropic layer having desired optical properties.

[0146] The coating liquid may contain a solvent in addition to the resin having a negative intrinsic birefringence value. The solvent is preferably one that can dissolve or disperse the resin having a negative intrinsic birefringence value, and particularly preferably one that can dissolve the resin having a negative intrinsic birefringence value. One type of solvent may be used alone, or two or more types may be used in combination at any ratio. The concentration of the resin having a negative intrinsic birefringence value in the coating liquid is preferably adjusted so that the viscosity of the coating liquid falls within a range suitable for coating, and may be, for example, 1% by weight to 50% by weight.

[0147] There are no limitations on the method for applying the coating liquid, and examples of the coating method include curtain coating, extrusion coating, roll coating, spin coating, dip coating, bar coating, spray coating, slide coating, print coating, gravure coating, die coating, and gap coating.

[0148] A coating liquid containing a resin having a negative intrinsic birefringence value is applied to a substrate to form a layer of the coating liquid. If necessary, the coating liquid layer is dried to remove the solvent, thereby forming a second resin layer on the substrate, thereby obtaining a first intermediate laminate. The drying method is not limited, and drying methods such as heat drying and reduced pressure drying can be used.

[0149] The drying temperature and drying time are not particularly limited, but can be set to realistic conditions when a long substrate is continuously transported along a transport path and continuously produced. Specifically, the drying temperature is preferably 100° C. or higher, more preferably 110° C. or higher, and is preferably 170° C. or lower, more preferably 160° C. or lower. The drying time is preferably 60 seconds or higher, more preferably 120 seconds or higher, and is preferably 10 minutes or shorter, more preferably 5 minutes or shorter.

[0150] By performing the drying as necessary, the amount of residual solvent in the second resin layer in the first intermediate laminate after step 2 and before being subjected to step 3, i.e., the ratio of the mass of the solvent to the mass of the second resin layer, can be controlled to a predetermined upper limit or less. The amount of residual solvent is preferably 10% or less, more preferably 7% or less. The amount of residual solvent can be determined by measuring the amount of solvent used in preparing the coating liquid contained in the second resin layer by an appropriate measurement method such as headspace gas chromatography mass spectrometry.

[0151] The thickness of the second resin layer obtained in step 2 is not particularly limited as long as it can exhibit desired optical properties and obtain a second optically anisotropic layer in step 3 described below, but is preferably 12 μm or less, more preferably 11 μm or less, even more preferably 10 μm or less, and is preferably 3 μm or more, more preferably 3.5 μm or more, even more preferably 4 μm or more. This is because the amount of residual solvent in the second resin layer can be reduced, resulting in a second resin layer that exhibits good retardation upon stretching.

[0152] The thickness of the second resin layer at which the desired optical properties are exhibited can be determined by preparing samples for physical property measurement of various thicknesses using a resin having a negative intrinsic birefringence value, stretching the samples under various stretching conditions, and then drying the second resin layer until it is sufficiently dry, such that the amount of residual solvent in the second resin layer is 1% by weight or less, allowing stable measurements, and measuring the retardation exhibited by each material. Based on such measured values, the relationship between the thickness and stretching conditions and the retardation exhibited thereby can be determined, and the target retardation and target thickness can be determined based on this relationship.

[0153] In step 2, it is preferable to form a long second resin layer by applying a coating liquid to the long substrate described above and drying it as necessary.

[0154] 6.3. Step 3 Step 3 is a step of bidirectionally stretching the first intermediate laminate to form a second optically anisotropic layer on the substrate.

[0155] The stretching method of the first intermediate laminate is usually bidirectional stretching (biaxial stretching). By bidirectionally stretching the first intermediate laminate, the biaxiality of the second optically anisotropic layer containing a resin having a negative intrinsic birefringence value can be enhanced. Bidirectional stretching includes, for example, sequential biaxial stretching and simultaneous biaxial stretching.

[0156] The stretching direction of the first intermediate laminate is not particularly limited. The stretching of the first intermediate laminate preferably includes stretching in an oblique direction. A manufacturing method including stretching in an oblique direction can produce a second optically anisotropic layer as an obliquely stretched film. An obliquely stretched film usually exhibits a slow axis that is neither parallel nor perpendicular to its width direction. Therefore, a slow axis that forms a predetermined angle with respect to the width direction can be easily exhibited in the second optically anisotropic layer as an obliquely stretched film. Therefore, a circularly polarizing plate can be easily manufactured by laminating the second optically anisotropic layer as an obliquely stretched film with a polarizing film having a transmission axis in the width direction and the first optically anisotropic layer using a roll-to-roll process.

[0157] A preferred example of the bidirectional stretching method including stretching in an oblique direction is a method using a long first intermediate laminate, which includes the following steps 3-1 and 3-2.

[0158] Step 3-1: A step of stretching a long intermediate laminate in a stretching direction parallel to the longitudinal direction to obtain a stretched laminate including a second resin layer having a slow axis parallel to the width direction. Step 3-2: A step of stretching the stretched laminate in a direction oblique to the width direction to obtain a second optically anisotropic layer in which the slow axis angle of the resin layer with respect to the width direction is in the range of 30° to 80°.

[0159] In step 3-1, the first intermediate laminate is stretched in a stretching direction parallel to the longitudinal direction to form a stretched laminate. The stretched laminate can typically be a stretched film. Stretching in the stretching direction parallel to the longitudinal direction is typically performed by conveying the long first intermediate laminate using a longitudinal stretching machine or the like. The stretching direction of the first intermediate laminate is preferably a direction that forms an angle of 90° with respect to the width direction of the first intermediate laminate, i.e., the longitudinal direction, but may typically include an error of ±5°, preferably ±3°. Therefore, the angle between the stretching direction and the width direction in step 3-1 is preferably in the range of 85° to 95°, more preferably 87° to 93°, and particularly preferably 90°. In step 3-1, a stretched laminate is obtained that includes a substrate and a second resin layer stretched in the stretching direction. The stretched laminate has a second resin layer with a slow axis parallel to the width direction. The slow axis of the second resin layer is preferably in the width direction, i.e., the angle of the slow axis with respect to the width direction is preferably 0°, but an error of usually ±5°, preferably ±3° may be included. Therefore, the angle of the second resin layer with respect to the width direction after stretching in step 3-1 is preferably −5° to +5°, more preferably −3° to +3°, and particularly preferably 0°.

[0160] In step 3-2, the stretched laminate is stretched in a direction oblique to the width direction to form a second optically anisotropic layer having a slow axis angle in the range of 30° to 80° with respect to the width direction. Stretching in the oblique direction is usually performed by conveying a long stretched laminate using a tenter stretching machine. The stretching direction of the stretched laminate is an oblique direction, and is appropriately adjusted taking into account the stretching ratio in the longitudinal direction in step 3-1 so that the slow axis angle of the second optically anisotropic layer is in the range of 30° to 80° with respect to the width direction.

[0161] The stretching ratio of the first intermediate laminate is preferably 1.1 times or more, more preferably 1.2 times or more, particularly preferably 1.3 times or more, and is preferably 4 times or less, more preferably 3 times or less, particularly preferably 2.5 times or less. It is desirable that the product of the stretching ratios in two directions of the first intermediate laminate falls within the above range. By keeping the stretching ratio within the above range, it is easy to obtain a second optically anisotropic layer having desired optical properties.

[0162] The stretching temperature of the first intermediate laminate is preferably "Tg2 - 15°C" or higher, more preferably Tg2 or higher, even more preferably "Tg2 + 2°C" or higher, particularly preferably "Tg2 + 5°C" or higher, and is preferably "Tg2 + 40°C" or lower, more preferably "Tg2 + 35°C" or lower, particularly preferably "Tg2 + 30°C" or lower. Here, Tg2 represents the glass transition temperature of a resin having a negative intrinsic birefringence value. By setting the stretching temperature within the above range, the molecules contained in the second resin layer can be reliably oriented, making it possible to easily obtain a second optically anisotropic layer having the desired optical properties.

[0163] Step 3 may be carried out simultaneously with step 1 or may be carried out prior to step 1. In step 2 (method for producing the second optically anisotropic layer), any step may be further carried out in addition to the steps described above. For example, any step exemplified in step 1 (method for producing the first optically anisotropic layer) may be carried out.

[0164] <6.4. Step 4> Step 4 is a step of overlaying the first optically anisotropic layer and the second optically anisotropic layer. In Step 4, the first optically anisotropic layer and the second optically anisotropic layer are overlaid so that the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is 85° to 95°. In other words, the layers are overlaid so that the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer are perpendicular to each other. The angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is preferably 90°, but may include an error within a range of, for example, ±5°, ±3°, ±2°, or ±1°. Therefore, the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer can be, for example, 85° to 95°, 87° to 93°, 88° to 92°, or 89° to 91°. By adopting such an embodiment, by using a circularly polarizing plate including the obtained optically anisotropic laminate in a display device, reflection of external light can be suppressed, and when the display surface is viewed from an oblique direction, reflection of external light can be suppressed and coloring can be effectively suppressed.

[0165] In step 4, an optically anisotropic laminate can usually be obtained in a state in which one surface of the first optically anisotropic layer and the surface of the second intermediate laminate facing the second optically anisotropic layer are laminated together. That is, in step 4, a laminate can be obtained in which the first optically anisotropic layer, the second optically anisotropic layer, and the substrate are provided in this order. The substrate can be used, for example, as a protective film layer for the optically anisotropic laminate.

[0166] In step 4, the first optically anisotropic layer and the second optically anisotropic layer may be laminated directly on each other, or may be laminated via an adhesive layer between them. Here, "directly" contacting one layer with another layer means that there is no other layer between the two layers.

[0167] In step 4, the first optically anisotropic layer is usually superimposed on the second optically anisotropic layer side of the second intermediate laminate, and the substrate of the second intermediate laminate can be used as a protective film layer for the second optically anisotropic layer in the obtained optically anisotropic laminate.

[0168] <6.5. Step 5> In the present invention, after step 4, step 5 may be performed in which the substrate is removed from the laminate including the first optically anisotropic layer, the second optically anisotropic layer, and the substrate. This step is optional. As a method for removing the substrate, a method of peeling the substrate from the second optically anisotropic layer is usually used.

[0169] When the manufacturing method of the optically anisotropic laminate of the present invention includes step 5, the series of steps 4 and 5, in which the second optically anisotropic layer provided on the substrate as the second intermediate laminate is superimposed on the first optically anisotropic layer and then the substrate is peeled off, can also be considered as a step of transferring the second optically anisotropic layer from the substrate of the second intermediate laminate to the first optically anisotropic layer.

[0170] 7. Circularly Polarizing Plate A circularly polarizing plate according to one embodiment of the present invention includes a linear polarizer and an optically anisotropic laminate. By providing this circularly polarizing plate on the display surface of an image display device, reflection of external light can be suppressed. A circularly polarizing plate including the above-described optically anisotropic laminate can suppress reflection of external light and effectively suppress coloring when the display surface is viewed. The suppression of coloring can be achieved in the tilt direction of the display surface, and can also usually be achieved in the front direction of the display surface.

[0171] The circular polarizing plate may comprise a linear polarizer, a first optically anisotropic layer, and a second optically anisotropic layer in this order, or a linear polarizer, a second optically anisotropic layer, and a first optically anisotropic layer in this order, with the former being more preferred.

[0172] Furthermore, the angle formed by the absorption axis or transmission axis of the linear polarizer and the slow axis of the first optically anisotropic layer is preferably in a specific range close to 45°. Specifically, the angle is preferably 40° or more, more preferably 42° or more, even more preferably 43° or more, particularly preferably 44° or more, and preferably 50° or less, more preferably 48° or less, even more preferably 47° or less, and particularly preferably 46° or less. Furthermore, in this case, the angle formed by the absorption axis or transmission axis of the linear polarizer and the slow axis of the second optically anisotropic layer is preferably in a specific range close to 135°. Specifically, the angle is preferably 130° or more, more preferably 132° or more, even more preferably 133° or more, particularly preferably 134° or more, and preferably 140° or less, more preferably 138° or less, even more preferably 137° or less, and particularly preferably 136° or less.

[0173] Any linear polarizer can be used as the linear polarizer.Examples of linear polarizers include a film obtained by adsorbing iodine or a dichroic dye onto a polyvinyl alcohol film, and then uniaxially stretching the film in a boric acid bath; a film obtained by adsorbing iodine or a dichroic dye onto a polyvinyl alcohol film, stretching the film, and further modifying a part of the polyvinyl alcohol units in the molecular chain into polyvinylene units; Among these, a polarizer containing polyvinyl alcohol is preferred as the linear polarizer.

[0174] When natural light is incident on a linear polarizer, only one polarized light is transmitted. The degree of polarization of this linear polarizer is not particularly limited, but is preferably 98% or more, more preferably 99% or more. The thickness of the linear polarizer is preferably 5 μm to 80 μm.

[0175] The above-described circularly polarizing plate may further include an optional layer. Examples of the optional layer include a polarizer protective film layer, an adhesive layer for bonding a linear polarizer and an optically anisotropic laminate together, a hard coat layer such as an impact-resistant polymethacrylate resin layer, a matte layer for improving the slipperiness of the film, a reflection suppressing layer, an antifouling layer, and an antistatic layer. Only one of these optional layers may be provided, or two or more layers may be provided.

[0176] 8. Image Display Device The above-described circular polarizer can be provided in an image display device such as a liquid crystal display device or an electroluminescent image display device. In particular, it is preferable to provide the circular polarizer in an organic electroluminescent image display device. This organic electroluminescent image display device includes a circular polarizer and an organic electroluminescent element (hereinafter, sometimes referred to as an "organic EL element" as appropriate). This organic electroluminescent image display device typically includes a linear polarizer, an optically anisotropic laminate, and an organic EL element, in this order.

[0177] The organic EL element includes a transparent electrode layer, a light-emitting layer, and an electrode layer in this order, and the light-emitting layer can emit light when a voltage is applied between the transparent electrode layer and the electrode layer. Examples of materials constituting the organic light-emitting layer include polyparaphenylene vinylene-based, polyfluorene-based, and polyvinyl carbazole-based materials. The light-emitting layer may also include a laminate of multiple layers emitting different colors of light, or a mixed layer in which a dye layer is doped with a different dye. The organic EL element may also include functional layers such as a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, an equipotential surface forming layer, and a charge generation layer.

[0178] The image display device can suppress reflection of external light on the display surface. Specifically, only a portion of the light incident from outside the device, namely linearly polarized light, passes through a linear polarizer, and then passes through an optically anisotropic laminate, becoming circularly polarized light. The circularly polarized light is reflected by a light-reflecting component within the image display device (such as a reflective electrode in an organic EL element) and passes through the optically anisotropic laminate again, becoming linearly polarized light having a vibration direction perpendicular to the vibration direction of the incident linearly polarized light, and no longer passing through the linear polarizer. Here, the vibration direction of linearly polarized light refers to the vibration direction of the electric field of linearly polarized light. This achieves the reflection suppression function.

[0179] Since the optically anisotropic laminate has the above-described optical properties, the organic EL image display device can exhibit a reflection suppressing function, thereby effectively suppressing reflection of external light on the display surface and suppressing coloring.

[0180] The degree of coloring is the color difference ΔE between the chromaticity measured by observing a reflective display surface and the chromaticity of a black display surface without reflection. ＊ The chromaticity can be evaluated by measuring the spectrum of light reflected from the display surface, multiplying this spectrum by the spectral sensitivity (color matching function) corresponding to the human eye to find tristimulus values ​​X, Y, and Z, and then calculating the chromaticity (a ＊ , b ＊ , L ＊ ) can be obtained by calculating the color difference ΔE ＊ ab is the chromaticity (a0 ＊ , b0 ＊ , L0 ＊ ), and chromaticity when illuminated by external light (a1 ＊ , b1 ＊ , L1 ＊ ) can be calculated from the following formula (X).

[0181]

[0182] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below, and can be practiced with any modifications within the scope of the claims of the present invention and their equivalents.

[0183] In the following description, the "%" and "parts" that represent amounts are by weight unless otherwise specified. Furthermore, the operations described below were carried out at room temperature (20°C ± 15°C) and atmospheric pressure (1 atm) unless otherwise specified.

[0184] [Evaluation Methods] (Thickness) The thickness of the laminate and each layer was measured using a film thickness measurement system ("F20" manufactured by Filmetrics).

[0185] (Method of Measuring Retardation) The retardation was measured using a retardation meter (Axometrics' "AxoScan") at a temperature of 23° C. The wavelength for measuring nx1, ny1, nz1, and Re1 (nm) of the first optically anisotropic layer, nx2, ny2, nz2, and Re2 (nm) of the second optically anisotropic layer, and Re (nm) of the optically anisotropic laminate was all 550 nm.

[0186] (Method of Measuring the Direction of the Slow Axis) The direction of the slow axis of each layer constituting the optically anisotropic laminate was measured using a retardation meter (AxoScan manufactured by Axometrics).

[0187] (Measurement of Residual Solvent Amount) A coating liquid containing a resin having negative intrinsic birefringence was applied to a substrate, and the film (intermediate laminate) was dried to form a resin layer. Approximately 5 mg of sample was taken from a portion near the center of the film and weighed. The sample was subjected to measurement by HS-GC-MS (headspace gas chromatography-mass spectrometry) to measure the amount of solvent (1,3-dioxolane) contained in the sample. Details of the measurement device and measurement conditions are as follows. Headspace device: Shimadzu Corporation, product name "HS20" Sample loop: 1 mL Heating conditions: 200°C, 30 minutes Gas chromatograph-mass spectrometer: Shimadzu Corporation, product name "GCMS-QP2010 Ultra" Column: J&W DB-624 (60 m x 0.32 mm x 1.8 μm) Heating conditions: 35°C x 5 minutes → heat to 230°C at 10°C / min → 230°C x 5 minutes Interface temperature: 230°C Ion source temperature: 230°C Split ratio: 5

[0188] Since the substrate is considered not to contain any solvent, the measured amount of solvent is considered to be the amount of solvent contained in the resin layer. The amount of residual solvent (mass %) in the second resin layer was calculated from the mass of the second resin layer contained in the sample and the measured amount of solvent.

[0189] (Color difference ΔE by simulation ＊ Calculation of ab) Using "LCD Master" manufactured by Shintech Co., Ltd. as simulation software, the circularly polarizing plates manufactured in each of the examples and comparative examples were modeled, and the following calculations were performed.

[0190] The following evaluation model was set for the simulation. A circular polarizing plate was placed on the reflective surface of a mirror having a flat reflective surface. The mirror was an ideal mirror capable of specularly reflecting incident light with a reflectance of 100%. The circular polarizing plate had the same layer structure as those obtained in each example and comparative example. The polarizer constituting the circular polarizing plate was a commonly used polarizing plate with a polarization degree of 99.99%, while the optically anisotropic laminate had the same optical properties as those produced in each example and comparative example. The circular polarizing plate was placed so that its surface facing the optically anisotropic laminate faced the reflective surface. Therefore, the reflective surface, optically anisotropic laminate, and linear polarizer were arranged in this order.

[0191] 1 is a perspective view showing a schematic diagram of an evaluation model set up when calculating color space coordinates in simulations of Examples and Comparative Examples. As shown in FIG. 1, the color space coordinates observed on the reflective surface 10 of a mirror provided with a circular polarizer when illuminated by a D65 light source (not shown) were calculated. Furthermore, the color space coordinates when not illuminated by a light source were calculated as a0. ＊ =0, b0 ＊ =0, L0 ＊ = 0. Then, from (i) the color space coordinates when illuminated by the light source and (ii) the color space coordinates when not illuminated by the light source, the color difference ΔE ＊ I searched for ab.

[0192] The color difference ΔE ＊ The calculation of ab is performed in the observation direction 20 where the polar angle ρ with respect to the reflecting surface 10 is 0°, and the color difference ΔE in the front direction is ＊ The polar angle ρ represents the angle formed with respect to the normal direction 11 of the reflecting surface 10.

[0193] Furthermore, the color difference ΔE ＊ The calculation of ab was performed in an observation direction 20 where the polar angle ρ relative to the reflecting surface 10 was 60°. This calculation at polar angle ρ = 60° was performed multiple times by moving the observation direction 20 in the azimuthal direction, with the azimuthal angle φ in 5° increments within a range of 0° or more and less than 360°. The azimuthal angle φ represents the angle between a direction parallel to the reflecting surface 10 and a certain reference direction 12 parallel to the reflecting surface 10. The color difference ΔE in the calculated multiple observation directions 20 was＊ The average of ab is calculated to obtain the color difference ΔE in the tilt direction at a polar angle ρ = 60°. ＊ ab was obtained.

[0194] (Method for visually evaluating circularly polarizing plates in the front direction and inclined directions) An image display device (Apple Watch (registered trademark) (first generation)) equipped with an organic EL image display device was prepared. This image display device was disassembled, and the polarizing plate attached to the surface of the organic EL image display device was peeled off to expose the reflective electrode. The surface of this reflective electrode was attached to the surface of the circularly polarizing plate obtained in each example and comparative example opposite the linear polarizer via an adhesive (CS9621 manufactured by Nitto Denko Corporation). This resulted in a sample equipped with the reflective electrode, adhesive, and circular polarizing plate in this order.

[0195] The circular polarizer sample on the reflective electrode was visually observed under sunlight on a sunny day. Front observation (observation in the front direction) was performed at a polar angle of 0° and an azimuth angle of 0°. As a result of the observation, a case where a chromatic color was clearly visible was judged as "poor." A case where a chromatic color was slightly visible but weaker than in the "poor" case was judged as "good." A case where a chromatic color was not visible was judged as "excellent." Observation in an oblique direction (observation in an oblique direction) was performed at a polar angle of 60° and in all directions of the circular polarizer. As a result of the observation, a case where a chromatic color clearly exhibited azimuth angle dependence was judged as "poor." A case where a chromatic color slightly exhibited azimuth angle dependence but weaker than in the "poor" case was judged as "good." A case where no azimuth angle dependence of the chromatic color was visible was judged as "excellent."

[0196] [Example 1] (1-1. Preparation of thermoplastic resin (COP)) Pellet-shaped norbornene-based resin ("ZEONOR 1215" manufactured by Nippon Zeon Co., Ltd.; glass transition temperature 126°C) was dried at 100°C for 5 hours to obtain a thermoplastic resin (COP).

[0197] (1-2. Formation of First Optically Anisotropic Layer) The resin (COP) obtained in (1-1) was fed to an extruder, passed through a polymer pipe and a polymer filter, and extruded into a sheet form from a T-die onto a casting drum. The extruded resin (COP) was cooled to obtain a long single-layer resin film with a thickness of 70 μm. The obtained resin film was wound into a roll and collected.

[0198] The resin film was drawn from the roll and fed to a tenter stretching machine. Using this tenter stretching machine, the resin film was stretched at a stretching temperature of 140°C and a stretching ratio of 1.75 times in a stretching direction at an angle of 45° relative to the width direction of the resin film to obtain a first optically anisotropic layer. The first optically anisotropic layer was cooled to room temperature and then wound up into a roll and recovered. The thickness of the obtained first optically anisotropic layer was 40 μm. Furthermore, the nx1, ny, and nz of the first optically anisotropic layer were measured to determine Re1 and the NZ coefficient NZ1. The retardation Re1 was 224 nm, and the NZ coefficient NZ1 was 1.03. The in-plane retardations Re1(450), Re1(550), and Re1(650) at wavelengths of 450 nm, 550 nm, and 650 nm were also measured, and the wavelength dispersion ratio (Re1(450) / Re1(550)) was calculated to be 1.01. The angle of the slow axis of the first optically anisotropic layer was measured to be 45° with respect to the width direction.

[0199] (1-3. Synthesis of Thermoplastic Resin A (Resin A)) Thermoplastic resin A (Resin A) having a negative intrinsic birefringence value was synthesized according to the following procedure. 1,000 ml of toluene as a solvent and 0.58 mmol of n-butyllithium as a polymerization catalyst were placed in a dried, nitrogen-purged pressure reactor, and then 31 g of 2-vinylnaphthalene as monomer A was added and reacted at 25°C for 1 hour to carry out a first-stage polymerization reaction. After completion of the first-stage polymerization reaction, 50 g of isoprene as monomer B was added and reacted for an additional 1 hour at 25°C to carry out a second-stage polymerization reaction. As a result, a diblock copolymer having a block structure of (2-vinylnaphthalene block)-(isoprene block) was obtained in the reaction mixture. Thereafter, 31 g of 2-vinylnaphthalene as monomer A was further added to the reaction mixture and reacted for 1 hour at 25°C to carry out a third-stage polymerization reaction. As a result, a triblock copolymer having a block structure of (2-vinylnaphthalene block)-(isoprene block)-(2-vinylnaphthalene block) was obtained in the reaction mixture. The reaction mixture was poured into a large amount of 2-propanol, and the triblock copolymer was precipitated and separated.

[0200] The obtained triblock copolymer was dissolved in 1,400 ml of p-xylene to prepare a solution. 15.2 g of p-toluenesulfonyl hydrazide was added to the solution, and the mixture was allowed to react at 130°C for 8 hours. This reaction added hydrogen to the double bonds of the isoprene units. After completion of the hydrogenation, the reaction solution was poured into a large amount of 2-propanol, and an (A)-(B)-(A) triblock copolymer (resin A) was obtained as a bulk product.

[0201] The obtained triblock copolymer was analyzed by NMR. As a result, the weight ratio of 2-vinylnaphthalene units to hydrogenated isoprene units in the triblock copolymer was 55:45, and therefore the weight fraction of block (A) was 50%. The hydrogenation rate of the triblock copolymer was 99%. The weight average molecular weight of the triblock copolymer measured by GPC was 250,000. The glass transition temperature of the triblock copolymer measured by TMA was 145°C.

[0202] (1-4. Formation of second optically anisotropic layer) Resin A obtained in (1-3) was mixed with 1,3-dioxolane to obtain a coating liquid containing resin A. The concentration of resin A in this coating liquid was 15 wt %.

[0203] The resin (COP) obtained in (1-1) was fed to an extruder, passed through a polymer pipe and a polymer filter, and extruded into a sheet form from a T-die onto a casting drum. The extruded resin (COP) was cooled to obtain a long single-layer resin film with a thickness of 70 μm. The obtained resin film was wound into a roll and collected as a substrate film.

[0204] The substrate film was pulled out from the roll and transported along a transport path. On the transport path, the coating liquid was continuously applied onto the substrate film to form a layer of the coating liquid. The coating liquid layer was then dried at 120°C for 3 minutes to obtain a second resin layer. This resulted in a long first intermediate laminate having a layer structure of (second resin layer) / (substrate film). A portion of the obtained first intermediate laminate was cut out to measure the amount of residual solvent in the second resin layer, and the 1,3-dioxolane content was found to be 11%.

[0205] The obtained first intermediate laminate was continuously stretched downstream of the coating process in the conveying path. Stretching was first performed using a longitudinal stretching machine, with the stretching direction at an angle of 90° relative to the width direction of the intermediate laminate. The stretching ratio was 1.5 times and the stretching temperature was 135°C. Next, a tenter stretching machine was used, with the stretching direction at an angle of 30° relative to the width direction of the intermediate laminate. The stretching ratio was 1.8 times and the stretching temperature was 133°C. This resulted in a long second intermediate laminate including a second optically anisotropic layer, which is a stretched product of the second resin layer, and a substrate film.

[0206] (1-5. Evaluation of the second optically anisotropic layer) A glass substrate was prepared by laminating an adhesive ("CS9621" manufactured by Nitto Denko Corporation) to the glass substrate. The second optically anisotropic layer of the second intermediate laminate was laminated on the adhesive layer, and then the substrate film was peeled off to obtain an evaluation sample. Using the obtained evaluation sample, the retardation, dispersion ratio, and direction of the slow axis of the second optically anisotropic layer were measured using the same procedures as in the evaluation of the first optically anisotropic layer. The retardation Re2 of the second optically anisotropic layer was 84 nm, the NZ coefficient was -1.70, and the wavelength dispersion ratio (Re1(450) / Re1(550)) was 1.32. The direction of the slow axis of the second optically anisotropic layer was 135° relative to the width direction. The direction of the slow axis of the second optically anisotropic layer was bidirectionally stretched at 90° and 30° to the width direction, resulting in an angle of 45°, and since it had a negative intrinsic birefringence value, the direction was reversed by 90° to that of the first optically anisotropic layer.

[0207] (1-6. Formation of Optically Anisotropic Laminate) An adhesive ("CS9621" manufactured by Nitto Denko Corporation) was provided between the obtained first optically anisotropic layer and the second optically anisotropic layer of the second intermediate laminate, and the two were laminated together. The lamination was performed so that the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer formed an angle of 90°. Thereafter, the substrate film was peeled off from the laminate including the first optically anisotropic layer, the adhesive layer, and the second optically anisotropic layer. By the above procedure, an optically anisotropic laminate including the first optically anisotropic layer, the adhesive layer, and the second optically anisotropic layer was obtained. The retardation of the obtained optically anisotropic laminate was measured.

[0208] (1-7. Circular Polarizing Plate) A long polyvinyl alcohol resin film dyed with iodine was prepared. This film was stretched in the longitudinal direction at an angle of 90° with respect to the width direction of the film to obtain a linear polarizer as a long polarizing film. This linear polarizer had an absorption axis in the longitudinal direction of the linear polarizer and a transmission axis in the width direction of the linear polarizer.

[0209] The linear polarizer and the optically anisotropic laminate obtained in (1-6) were bonded together with their longitudinal directions parallel to each other so that the linear polarizer and the first optically anisotropic layer faced each other via an optically isotropic pressure-sensitive adhesive ("CS9621" manufactured by Nitto Denko Corporation), thereby obtaining a circularly polarizing plate. The obtained circularly polarizing plate had a layer structure of (linear polarizer) / (first optically anisotropic layer) / (second optically anisotropic layer).

[0210] The color difference ΔE of the obtained circularly polarizing plate ＊ The ab was calculated and visually evaluated.

[0211] [Examples 2, 3 and 6] Optically anisotropic laminates were obtained in the same manner as in Example 1, except that the stretching temperature during formation of the first optically anisotropic layer was adjusted to 140.9°C in Example 2, 141.8°C in Example 3, and 140.2°C in Example 6 to adjust Re1, and the coating amount of the coating liquid was adjusted so that the thickness (µm) and residual solvent amount (%) of the second resin layer after drying would be as shown in Table 1. Furthermore, the first optically anisotropic layer, the second optically anisotropic layer, and the optically anisotropic laminate were evaluated in the same manner as in Example 1.

[0212] [Example 4] An optically anisotropic laminate was obtained in the same manner as in Example 1, except that Re1 was adjusted by adjusting the stretching temperature during formation of the first optically anisotropic layer, as in Example 2, and that during formation of the second optically anisotropic layer, the longitudinal stretching ratio of the first intermediate laminate (second resin layer) was 1.3 times, the stretching temperature was 135°C, and the oblique stretching ratio was 1.8 times, and the stretching temperature was 135°C. The first optically anisotropic layer, the second optically anisotropic layer, and the optically anisotropic laminate were evaluated in the same manner as in Example 1.

[0213] [Example 5] An optically anisotropic laminate was obtained in the same manner as in Example 1, except that Re1 was adjusted by adjusting the stretching temperature during formation of the first optically anisotropic layer, as in Example 2, and that during formation of the second optically anisotropic layer, the longitudinal stretching ratio of the first intermediate laminate (second resin layer) was 1.7 times, the stretching temperature was 135°C, and the oblique stretching ratio was 1.8 times, and the stretching temperature was 131°C. The first optically anisotropic layer, the second optically anisotropic layer, and the optically anisotropic laminate were evaluated in the same manner as in Example 1.

[0214] Example 6 (2-1. Synthesis of Thermoplastic Resin B (Resin B)) Thermoplastic resin B (Resin B) having a negative intrinsic birefringence value was synthesized by the following procedure. A triblock copolymer was obtained by the same procedure as in (1-3) of Example 1, except that the ratio of the added monomers was changed as follows. The weight ratio of 2-vinylnaphthalene units to hydrogenated isoprene units was 50:50, and the glass transition temperature was 146°C. The amount of 2-vinylnaphthalene added in the first polymerization reaction was 28 g. The amount of isoprene added in the second polymerization reaction was 56 g. The amount of 2-vinylnaphthalene added in the third polymerization reaction was 28 g.

[0215] (2-2. Optically anisotropic laminate and circularly polarizing plate) An optically anisotropic laminate and a circularly polarizing plate were obtained and evaluated by the same procedures as in Example 1, except that Re1 was adjusted by adjusting the stretching temperature during the formation of the first optically anisotropic layer as in Example 3, and that Resin B obtained in (2-1) above was used instead of Resin A obtained in (1-3) above.

[0216] Example 7 (3-1. Synthesis of Thermoplastic Resin C (Resin C)) Thermoplastic resin C (Resin C) having a negative intrinsic birefringence value was synthesized by the following procedure. A triblock copolymer was obtained by the same procedure as in (1-3) of Example 1, except that the ratio of the added monomers was changed as follows. The weight ratio of 2-vinylnaphthalene units to hydrogenated isoprene units was 60:40, and the glass transition temperature was 146°C. The amount of 2-vinylnaphthalene added in the first polymerization reaction was 34 g. The amount of isoprene added in the second polymerization reaction was 44 g. The amount of 2-vinylnaphthalene added in the third polymerization reaction was 34 g.

[0217] (3-2. Optically anisotropic laminate and circularly polarizing plate) An optically anisotropic laminate and a circularly polarizing plate were obtained and evaluated by the same procedures as in Example 1, except that the resin C obtained in (3-1) above was used instead of the resin A obtained in (1-3) above.

[0218] [Comparative Example 1] The same operations as in Example 1 were performed, except that Re1 was adjusted by adjusting the thickness of the first resin film as in Example 2, and the following procedure was performed when forming the second optically anisotropic layer, and an optically anisotropic laminate and a circularly polarizing plate were obtained and evaluated. The first intermediate laminate was not longitudinally stretched, but was only obliquely stretched. For the oblique stretching, a tenter stretching machine was used, and the stretching direction was at an angle of 45° with respect to the width direction. During stretching, the stretching ratio was 1.8 times, and the stretching temperature was 136°C.

[0219] [Comparative Example 2] According to the manufacturing method described in Example 1 of Patent Document 2 (WO 2021 / 085031), an optically anisotropic laminate containing a norbornene-based resin (COP) as the first optically anisotropic layer and poly(2-vinylnaphthalene) as the second optically anisotropic layer was manufactured and evaluated. The thickness of the first resin film before stretching was 100 μm. The drying conditions for the coating layer containing poly(2-vinylnaphthalene) formed on the first resin film were 120 ° C. and 3 minutes. When dried under the above drying conditions, the residual solvent amount of the second resin layer was 36.7%, and no retardation was observed even when stretched.

[0220] [Comparative Example 3] An optically anisotropic laminate containing a norbornene-based resin (COP) as the first optically anisotropic layer and poly(2-vinylnaphthalene) as the second optically anisotropic layer was produced and evaluated in the same manner as in Comparative Example 2, except that the drying conditions for the coating layer containing poly(2-vinylnaphthalene) were 120°C and 2 hours, and in accordance with the production method described in the examples of Patent Document 2. In addition, a circularly polarizing plate was produced and evaluated using the same procedures as in Example 1.

[0221] The evaluation results for the thickness and residual solvent amount of the second resin layer after drying are shown in Table 1, and the evaluation results for the optically anisotropic laminate and its constituent layers are shown in Tables 2 to 5. The abbreviations in Tables 4 and 5 have the following meanings. "Dispersion ratio 1": the ratio of the in-plane retardation Re1(450) at a wavelength of 450 nm to the in-plane retardation Re1(550) at a wavelength of 550 nm of the first optically anisotropic layer (Re1(450) / Re1(550)); "Dispersion ratio 2": the ratio of the in-plane retardation Re2(450) at a wavelength of 450 nm to the in-plane retardation Re2(550) at a wavelength of 550 nm of the second optically anisotropic layer (Re2(450) / Re2(550)); "Dispersion difference": the absolute value of the difference between the dispersion ratio 1 of the first optically anisotropic layer and the dispersion ratio 2 of the second optically anisotropic layer in the optically anisotropic laminate (|Re2(450) / Re2(550)-Re1(450) / Re1(550)|); "Dispersion ratio 3": In the optically anisotropic laminate, the ratio is calculated by "(Re1(450)-Re2(450)) / (Re1(550)-Re2(550))". "Re1": In-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm. "Re2": In-plane retardation of the second optically anisotropic layer at a wavelength of 550 nm. "Re": In-plane retardation of the optically anisotropic laminate at a wavelength of 550 nm. "NZ1": NZ coefficient of the first optically anisotropic layer. "NZ2": NZ coefficient of the second optically anisotropic layer. "NZ1+NZ2": Sum of the NZ coefficient of the first optically anisotropic layer and the NZ coefficient of the second optically anisotropic layer. "COP": Norbornene-based resin ("ZEONOR 1215" manufactured by ZEON Corporation). "Resin A": Thermoplastic resin A having a negative intrinsic birefringence. "Resin B": Thermoplastic resin B having a negative intrinsic birefringence value; "Resin C": Thermoplastic resin C having a negative intrinsic birefringence value; "VN": Poly(2-vinylnaphthalene)

[0222]

[0223]

[0224]

[0225]

[0226]

[0227] As shown in Examples 1 to 7, it was confirmed that the optically anisotropic laminates satisfying the formulas (1) to (5) could suppress coloring of the image display device in the front direction and in the oblique direction when used as a circular polarizer. On the other hand, it was confirmed that it was difficult to suppress coloring of the image display device in the oblique direction in Comparative Examples 1 and 3, which did not satisfy the formulas (1) to (5).

[0228] 10 Reflecting surface 11 Normal direction of reflecting surface 12 Reference direction 20 Observation direction φ Azimuth angle ρ Polar angle

Claims

1. An optically anisotropic laminate comprising a first optically anisotropic layer and a second optically anisotropic layer, wherein the first optically anisotropic layer satisfies the following formula (1); the second optically anisotropic layer satisfies the following formula (2); the in-plane retardation Re1(550) of the first optically anisotropic layer at a wavelength of 550 nm, the in-plane retardation Re1(450) of the first optically anisotropic layer at a wavelength of 450 nm, the in-plane retardation Re2(550) of the second optically anisotropic layer at a wavelength of 550 nm, and the in-plane retardation Re2(450) of the second optically anisotropic layer at a wavelength of 450 nm satisfy the following formula (3); the optically anisotropic laminate satisfies the following formula (4); the NZ coefficient NZ1 of the first optically anisotropic layer and the NZ coefficient NZ2 of the second optically anisotropic layer satisfy the following formula (5); An optically anisotropic laminate, wherein the angle formed between the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is 85° to 95°. nx1>ny1≧nz1 (1) nz2>nx2>ny2 (2) |Re2(450) / Re2(550)−Re1(450) / Re1(550)|≧0.12 (3) Re(450)<Re(550)<Re(650) (4) −1.5≦NZ1+NZ2<0.1 (5) where nx1 represents the refractive index in an in-plane direction of the first optically anisotropic layer that is the direction giving the maximum refractive index, ny1 represents the refractive index in an in-plane direction of the first optically anisotropic layer that is orthogonal to the direction giving nx1, and nz1 represents the refractive index in the thickness direction of the first optically anisotropic layer; nx2 represents the refractive index in the in-plane direction of the second optically anisotropic layer in the direction that gives the maximum refractive index, ny2 represents the refractive index in the in-plane direction of the second optically anisotropic layer in the direction perpendicular to the direction that gives nx2, and nz2 represents the refractive index in the thickness direction of the second optically anisotropic layer; Re(450), Re(550), and Re(650) represent the in-plane retardation of the optically anisotropic laminate at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.

2. The optically anisotropic laminate according to claim 1, wherein Re1(550), Re1(450), Re2(550), and Re2(450) satisfy the following formulas (6) and (7): Re1(450) / Re1(550)<Re2(450) / Re2(550) (6) Re1(550)>Re2(550) (7) 3. The optically anisotropic laminate according to claim 1, wherein Re1(550) and Re2(550) satisfy the following formula (8): 100 nm≦(Re1(550)−Re2(550))≦180 nm (8) 4. The optically anisotropic laminate according to claim 1, wherein Re1(550) and Re2(550) satisfy the following formulas (9) and (10): 250 nm ≧ Re1(550) ≧ 170 nm (9) 110 nm ≧ Re2(550) ≧ 30 nm (10) 5. The optically anisotropic laminate according to claim 1, wherein NZ1 and NZ2 satisfy the following formula (11): −0.9<NZ1+NZ2<0.1 (11) 6. The optically anisotropic laminate according to claim 1, wherein the first optically anisotropic layer is a layer obtained by stretching a first resin layer, and the first resin layer contains a resin having a positive intrinsic birefringence value.

7. The optically anisotropic laminate according to claim 1, wherein the second optically anisotropic layer is a layer obtained by stretching a second resin layer, and the second resin layer contains a resin having a negative intrinsic birefringence value.

8. A circularly polarizing plate comprising: a linear polarizer; and the optically anisotropic laminate according to claim 1.

9. The circularly polarizing plate according to claim 8, wherein the angle between the absorption axis of the linear polarizer or the transmission axis of the linear polarizer and the slow axis of the first optically anisotropic layer is 40° to 50°.

10. The circular polarizing plate according to claim 8, comprising the linear polarizer, the first optically anisotropic layer, and the second optically anisotropic layer in this order.

11. The circular polarizing plate according to claim 8, comprising the linear polarizer, the second optically anisotropic layer, and the first optically anisotropic layer in this order.

12. An image display device comprising the circular polarizer according to claim 8 and an organic electroluminescence element, the image display device comprising the linear polarizer, the optically anisotropic laminate, and the organic electroluminescence element in this order.

13. A method for producing an optically anisotropic laminate according to claim 1, comprising: Step 1: stretching a first resin film containing a resin having a positive intrinsic birefringence value to obtain a first optically anisotropic layer; Step 2: applying a coating liquid containing a resin having a negative intrinsic birefringence value onto a substrate to form a second resin layer, thereby obtaining an intermediate laminate comprising the substrate and the second resin layer; Step 3: bidirectionally stretching the intermediate laminate to form a second optically anisotropic layer on the substrate; and Step 4: overlaying the first optically anisotropic layer and the second optically anisotropic layer so that the angle between the slow axis of the first optically anisotropic layer and the slow axis of the second optical anisotropy is 85° to 95°.

14. The method for producing an optically anisotropic laminate according to claim 13, wherein step 2 is a step of obtaining a long intermediate laminate comprising a long substrate and a long second resin layer as the intermediate laminate; and step 3 is a step of bidirectionally stretching the intermediate laminate comprising a step of stretching the long intermediate laminate in a stretching direction parallel to the longitudinal direction to obtain a stretched laminate comprising the second resin layer having a slow axis parallel to the width direction, and a step of stretching the stretched laminate in a direction oblique to the width direction to obtain a second optically anisotropic layer having a slow axis angle with respect to the width direction in the range of 30° to 80°.

15. The method for producing an optically anisotropic laminate according to claim 13, wherein the second resin layer obtained in step 2 has a thickness of 11 μm or less.

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