Liquid crystal display device

Abstract

A liquid crystal display device comprising a first polarizer, a first optical anisotropic layer, a second optical anisotropic layer, a liquid crystal cell, and a second polarizer in the stated order, the liquid crystal cell including a pair of substrates and a liquid crystal molecular layer sealed between the substrates, and the alignment direction of the liquid crystal molecules in a black display state being parallel to the surface of the substrates, wherein the second optical anisotropic layer includes a specific A layer and a specific B layer, and the transmission axis of the first polarizer is parallel to the alignment direction of the liquid crystal molecules in the black display state.

Description

liquid crystal display device

[0001] The present invention relates to a liquid crystal display device.

[0002] Various display modes are known for liquid crystal display devices. In particular, IPS-mode liquid crystal display devices are known to have excellent characteristics such as a wide viewing angle, good color reproducibility, and high response speed.

[0003] Generally, a liquid crystal display device includes, in this order, a first polarizer that is a polarizer on the viewing side, a liquid crystal cell, and a second polarizer that is a polarizer on the rear side (opposite the viewing side). The liquid crystal display device may further include, as an optional component, a light source that is provided further rearward than the second polarizer. Light from the light source passes through the second polarizer, the liquid crystal cell, and the first polarizer and is emitted in a controlled state, thereby displaying an image that can be viewed by a viewer.

[0004] The liquid crystal display device may further include an optically anisotropic layer. Specifically, it has been proposed to provide films having various retardations between the first polarizer and the liquid crystal cell, thereby improving the optical characteristics. For example, it is known to provide various optical compensation layers to obtain a good viewing angle (e.g., Patent Documents 1 to 5).

[0005] Japanese Patent Application Laid-Open No. 11-133408 (Corresponding Publication: U.S. Patent No. 6,115,095) Japanese Patent Publication No. 2006-520008 (Corresponding Publication: U.S. Patent Application Publication No. 2005 / 200792) Japanese Patent Application Laid-Open No. 2014-13414 (Corresponding Publication: U.S. Patent Application Publication No. 2008 / 024703) Japanese Patent Application Laid-Open No. 2009-251443 (Corresponding Publication: U.S. Patent Application Publication No. 2009 / 257012) Japanese Patent Application Laid-Open No. 2021-173810

[0006] Although IPS-type liquid crystal display devices can achieve a wider viewing angle than other types, there is a demand for an even wider viewing angle, particularly in display devices for television receivers, in-vehicle display devices, and the like, where higher contrast than conventional devices is required when viewed from an oblique direction.

[0007] In addition, liquid crystal display devices are required to have high heat resistance because they may generate high temperatures during use and may be required to be used at high temperatures in certain applications such as in-vehicle display devices. In particular, liquid crystal display devices having an optically anisotropic layer can easily suffer from deterioration in display quality due to thermal deformation of the optically anisotropic layer, and therefore liquid crystal display devices in which such deterioration is suppressed are required.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid crystal display device that can achieve high contrast over a wide viewing angle and high heat resistance.

[0009] The present inventors have conducted studies to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved by providing an optically anisotropic layer between a first polarizer and a liquid crystal cell of a liquid crystal display device, which is a combination of multiple layers, each having specific optical properties, and have completed the present invention. That is, the present invention provides the following.

[0010] <1> A liquid crystal display device comprising, in this order, a first polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a liquid crystal cell, and a second polarizer, wherein the liquid crystal cell includes a pair of substrates and a liquid crystal molecular layer sealed between the substrates, and wherein the alignment directions of the liquid crystal molecules in a black display state are parallel to surfaces of the substrates, and the second optically anisotropic layer includes an A layer and a B layer, and satisfies the following formulas (e1), (e2), (e3), and (e4): nxA>nyA≧nzA (e1) nzB≧nxB>nyB (e2) ReA(450) / ReA(550)<ReB(450) / ReB(550) (e3) ReA(550)>ReB(550) (e4), nyA represents the refractive index in the in-plane direction of the A layer, which is perpendicular to the direction giving nxA; nzA represents the refractive index in the thickness direction of the A layer; ReA(450) represents the in-plane retardation of the A layer at a wavelength of 450 nm; ReA(550) represents the in-plane retardation of the A layer at a wavelength of 550 nm; nxB represents the refractive index in the in-plane direction of the B layer, which is the direction giving the maximum refractive index; nyB represents the refractive index in the in-plane direction of the B layer, which is perpendicular to the direction giving nxB; nzB represents the refractive index in the thickness direction of the B layer; ReB(450) represents the in-plane retardation of the B layer at a wavelength of 450 nm; ReB(550) represents the in-plane retardation of the B layer at a wavelength of 550 nm; a liquid crystal display device according to <1>, wherein the in-plane slow axis direction of the A layer and the in-plane slow axis direction of the B layer are perpendicular to each other, and the first optically anisotropic layer satisfies the following formula (e5): nz1>nx1≧ny1 (e5) where nx1 represents the refractive index in an in-plane direction of the first optically anisotropic layer that gives the maximum refractive index, ny1 represents the refractive index in an 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 a thickness direction of the first optically anisotropic layer, and the transmission axis of the first polarizer is parallel to the alignment direction of the liquid crystal molecules in the black display state.<3> The liquid crystal display device according to <1> or <2>, wherein the A layer and the B layer satisfy the following formula (e6): 30 nm≦(ReA(550)−ReB(550))≦230 nm (e6) <4> The liquid crystal display device according to any one of <1> to <3>, wherein the A layer and the B layer satisfy the following formula (e7) and formula (e8): 300 nm≧ReA(550)≧170 nm (e7) 140 nm≧ReB(550)≧50 nm (e8) <5> The liquid crystal display device according to any one of <1> to <4>, wherein the A layer and the B layer satisfy the following formula (e9): ReB(450) / ReB(550)-ReA(450) / ReA(550)≧0.2(e9) <6> The liquid crystal display device according to any one of <1> to <5>, wherein the A layer and the B layer satisfy the following formula (e10): 0.60≦(ReA(450)−ReB(450)) / (ReA(550)−ReB(550))≦0.98 (e10) <7> The liquid crystal display device according to any one of <1> to <6>, wherein the A layer and the B layer satisfy the following formulae (e11) and (e12): 1.05≧NzA≧0.95 (e11) 0.05≧NzB≧−0.05 (e12) where NzA represents the NZ coefficient of the A layer, and NzB represents the NZ coefficient of the B layer. <8> The liquid crystal display device according to any one of <1> to <7>, wherein the first optically anisotropic layer satisfies the following formula (e13): 70≧Re1(550)≧0.0 (e13), where Re1(550) represents the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm. <9> The liquid crystal display device according to any one of <1> to <8>, wherein the first optically anisotropic layer satisfies the following formula (e14): 0.60≦Rth1(450) / Rth1(550)≦1.20 (e14), where Rth1(450) represents the thickness direction retardation of the first optically anisotropic layer at a wavelength of 450 nm, and Rth1(550) represents the thickness direction retardation of the first optically anisotropic layer at a wavelength of 550 nm. <10> The liquid crystal display device according to any one of <1> to <9>, wherein the A layer is a stretched A layer obtained by stretching a pre-stretched A layer, and the pre-stretched A layer contains a resin (A) having a positive intrinsic birefringence value.<11> The liquid crystal display device according to any one of <1> to <10>, wherein the B layer is a stretched B layer obtained by stretching a pre-stretched B layer, and the pre-stretched B layer contains a resin (B) having a negative intrinsic birefringence value. <12> The liquid crystal display device according to any one of <1> to <11>, wherein the first optically anisotropic layer contains a mesogenic compound. <13> The liquid crystal display device according to any one of <1> to <12>, wherein the first optically anisotropic layer is a stretched F layer obtained by stretching a pre-stretched F layer, and the pre-stretched F layer contains a resin (F) having a negative intrinsic birefringence value.

[0011] According to the present invention, there is provided a liquid crystal display device that can achieve high contrast over a wide viewing angle and high heat resistance.

[0012] 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.

[0013] In the following description, in defining the relative orientation relationships of two or more members constituting a liquid crystal display device (the relationship between the alignment direction of liquid crystal molecules and the surface of the substrate, the relationship between the in-plane slow axis direction of Layer A and the in-plane slow axis direction of Layer B, the relationship between the transmission axis of the first polarizer and the transmission axis of the second polarizer, the relationship between the transmission axis of the polarizer and the alignment direction of liquid crystal molecules, etc.), unless otherwise specified, the terms "parallel" 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°, preferably ±3°, more preferably ±2°, and even more preferably ±1°.

[0014] In the following description, for layered structures such as films, the in-plane retardation Re is a value expressed by Re = (nx - ny) x d unless otherwise specified. The thickness direction retardation Rth is a value expressed by Rth = {(nx + ny) / 2 - nz} x d unless otherwise specified. The NZ coefficient Nz is a value expressed by "Nz = (nx - nz) / (nx - ny)". nx represents the refractive index in the direction perpendicular to the thickness direction (in-plane direction) that gives the maximum refractive index (slow axis direction), ny represents the refractive index in the in-plane direction that is perpendicular to the direction of nx, nz represents the refractive index in the thickness direction, and d represents the thickness. The measurement wavelength is 550 nm unless otherwise specified. The in-plane retardation and thickness direction retardation can be measured using a retardation meter ("AxoScan" manufactured by Axometrics).

[0015] In the following description, unless otherwise specified, the slow axis of a layer refers to the slow axis in the in-plane direction of the layer. In a member having multiple layers, the angle formed by the optical axes (absorption axis, transmission axis, slow axis, etc.) of the layers refers to the angle when the layers are viewed from the thickness direction, unless otherwise specified.

[0016] In the following description, the polar angle with respect to a certain plane refers to the angle with respect to the normal direction of the plane, where the normal direction of the plane is set to 0°.

[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, "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.

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

[0020] (Overview of Liquid Crystal Display Device) The liquid crystal display device of the present invention comprises, in this order, a first polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a liquid crystal cell, and a second polarizer. The liquid crystal cell includes a pair of substrates and a liquid crystal molecular layer sealed between them. The liquid crystal cell is a component that is driven as a display element in the display device, and can form an image by adjusting the light that passes through the liquid crystal cell. In the liquid crystal display device of the present invention, an observer usually views the screen from the first polarizer side.

[0021] In the liquid crystal display device of the present invention, in the black display state, the alignment direction of the liquid crystal molecules in the liquid crystal cell is parallel to the surface of the substrate, and the transmission axis of the first polarizer is parallel to the alignment direction of the liquid crystal molecules in the black display state. When the liquid crystal cell is driven, the alignment direction of the liquid crystal molecules is twisted at an angle from the transmission axis direction of the first polarizer, thereby increasing the amount of light transmitted through the liquid crystal cell and adjusting the transmitted light. This type of system is generally called the IPS system. The black display state of a liquid crystal display device refers to a state in which black is displayed across the entire display screen of the display device. Conversely, a state in which white is displayed across the entire display screen of the display device is called a white display state.

[0022] The orientation direction of liquid crystal molecules is the molecular direction in which a collection of such molecules exhibits an optically slow axis when the liquid crystal molecules are oriented. Liquid crystal molecules usually have a rod-like molecular structure, and the orientation direction of the molecules can usually be the direction of the long axis of the molecules when the liquid crystal molecules are nematically oriented and form a layer in a cell.

[0023] (First Polarizer and Second Polarizer) As the first polarizer and the second polarizer, a film that can transmit one of two linearly polarized light beams whose vibration directions intersect at right angles and absorb or reflect the other can be used. Here, the vibration direction of the linearly polarized light refers to the vibration direction of the electric field of the linearly polarized light. Such a film usually has a transmission axis of polarized light, and can transmit linearly polarized light beams whose vibration direction is parallel to the transmission axis, and can absorb or reflect linearly polarized light beams whose vibration direction is perpendicular to the transmission axis. The transmission axis of the first polarizer and the transmission axis of the second polarizer can usually be arranged to be orthogonal to each other.

[0024] Any linear polarizer can be used as the 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; and 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.

[0025] 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 upper limit of the degree of polarization can be 100% or less, or less than 100%. The thickness of the linear polarizer is preferably 5 μm to 80 μm.

[0026] Since a polarizer is usually a flexible film, from the viewpoint of improving handling ease and durability, it can be laminated with a protective film and incorporated into a device as a polarizing plate. A first optically anisotropic layer may be directly laminated to the back side of the first polarizer, thereby also exhibiting the function of a back-side protective film.

[0027] (Requirements for Second Optically Anisotropic Layer) The second optically anisotropic layer includes an A layer and a B layer, and satisfies the following formulae (e1), (e2), (e3), and (e4). nxA>nyA≧nzA (e1) nzB≧nxB>nyB (e2) ReA(450) / ReA(550)<ReB(450) / ReB(550) (e3) ReA(550)>ReB(550) (e4) where nxA represents the refractive index in the in-plane direction of layer A, the direction giving the maximum refractive index, nyA represents the refractive index in the in-plane direction of layer A, the direction perpendicular to the direction giving nxA, nzA represents the refractive index in the thickness direction of layer A, ReA(450) represents the in-plane retardation of layer A at a wavelength of 450 nm, ReA(550) represents the in-plane retardation of layer A at a wavelength of 550 nm, nxB represents the refractive index in the in-plane direction of layer B, the direction giving the maximum refractive index, nyB represents the refractive index in the in-plane direction of the B layer, which is perpendicular to the direction giving nxB; nzB represents the refractive index in the thickness direction of the B layer; ReB(450) represents the in-plane retardation of the B layer at a wavelength of 450 nm; and ReB(550) represents the in-plane retardation of the B layer at a wavelength of 550 nm.

[0028] The formula (e1) indicates that the A layer can function as a so-called positive A plate or negative B plate. The formula (e2) indicates that the B layer can function as a so-called negative A plate or positive B plate.

[0029] The formula (e3) indicates that the wavelength dispersion of the B layer is greater than the wavelength dispersion of the A layer.

[0030] The value of "ReB(450) / ReB(550)-ReA(450) / ReA(550)" is usually greater than 0 and preferably satisfies the following formula (e9): ReB(450) / ReB(550)-ReA(450) / ReA(550)≧0.2 (e9) The value of "ReB(450) / ReB(550)-ReA(450) / ReA(550)" is preferably 0.2 or greater, more preferably 0.24 or greater, and even more preferably 0.28 or greater. The larger the value, the better; however, it may be, for example, 0.7 or less. In this way, a second optically anisotropic layer having an A layer and a B layer with different wavelength dispersion characteristics of in-plane retardation can easily obtain reverse wavelength dispersion characteristics in a laminated state. Therefore, it can exhibit its function over a wide wavelength range.

[0031] The value of "ReB(450) / ReB(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, and is not particularly limited, and may be, for example, 1.8 or less. When the value of "ReB(450) / ReB(550)" is within the above range, a difference in the wavelength dispersion characteristics of the A layer and the B layer is likely to occur, and the retardation required to achieve the desired reverse wavelength dispersion characteristics becomes smaller, making it possible to reduce the film thickness, and particularly favorably achieving effects such as a wide viewing angle and good color reproducibility.

[0032] The value of "ReA(450) / ReA(550)" is not particularly limited, but may be, for example, 0.8 or more, preferably 1.05 or less, more preferably 1.03 or less, and particularly preferably 1.01 or less. When "ReA(450) / ReA(550)" is within the above range, a difference in the wavelength dispersion characteristics of the A layer and the B layer is likely to occur, and the retardation required to achieve the desired reverse wavelength dispersion characteristics becomes smaller, making it possible to reduce the thickness, and particularly advantageous effects such as a wide viewing angle and good color reproducibility can be obtained.

[0033] The value of (ReA(550)-ReB(550)) is usually greater than 0, and preferably a value that allows the second optically anisotropic layer to function as a λ / 4 plate. Specifically, the second optically anisotropic layer preferably satisfies the following formula (e6): 30 nm≦(ReA(550)-ReB(550))≦230 nm (e6)

[0034] The value of "ReA(550)-ReB(550)" is preferably 100 nm or more, more preferably 110 nm or more, and is preferably 180 nm or less, more preferably 160 nm or less. When "ReA(550)-ReB(550)" is in the above range, effects such as a wide viewing angle and good color reproducibility can be particularly well obtained.

[0035] The formula (e4) indicates that the magnitude of the in-plane retardation of the A layer at a wavelength of 550 nm is greater than that of the B layer.

[0036] The value of ReA(550) preferably satisfies the following formula (e7): 300 nm ≧ ReA(550) ≧ 170 nm (e7)

[0037] More specifically, ReA(550) is preferably 170 nm or more, more preferably 180 nm or more, particularly preferably 190 nm or more, and is preferably 300 nm or less, more preferably 280 nm or less, particularly preferably 270 nm or less. When the in-plane retardation ReA(550) is in the above range, effects such as a wide viewing angle and good color reproducibility can be particularly well obtained.

[0038] The value of ReB(550) preferably satisfies the following formula (e8): 140 nm ≧ ReB(550) ≧ 50 nm (e8)

[0039] More specifically, ReB(550) is preferably 50 nm or more, more preferably 55 nm or more, particularly preferably 60 nm or more, and is preferably 140 nm or less, more preferably 137 nm or less, particularly preferably 134 nm or less. When the in-plane retardation ReB(550) is in the above range, effects such as a wide viewing angle and good color reproducibility can be particularly well obtained.

[0040] In the second optically anisotropic layer, the angle formed by the in-plane slow axis direction of layer A and the in-plane slow axis direction of layer B is perpendicular. However, this angle does not have to be exactly 90°, and may include an error. The angle θ Ｄ is 85°≦θ Ｄ ≦95. More specifically, θ Ｄ is 85° or more, preferably 87° or more, more preferably 88° or more, 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 the angle between the slow axis of layer A and the slow axis of layer B is within the above range, effects such as a wide viewing angle and good color reproducibility can be obtained, and the heat resistance of the liquid crystal display device can be effectively improved. 85°≦θ Ｄ ≦95 means that if there is no distinction in the direction of rotation of the angle, 85°≦θ Ｄ Equivalent to ≦90.

[0041] The A layer and the B layer preferably satisfy the following formula (e10): 0.60≦(ReA(450)−ReB(450)) / (ReA(550)−ReB(550))≦0.98 (e10)

[0042] The value of (ReA(450)-ReB(450)) / (ReA(550)-ReB(550)) is preferably 0.60 or more, more preferably 0.65 or more, and particularly preferably 0.70 or more, and is preferably 0.98 or less, more preferably 0.95 or less, and particularly preferably 0.92 or less. When this value is within the above range, effects such as a wide viewing angle and good color reproducibility can be particularly well obtained.

[0043] The A layer and the B layer preferably satisfy the following formulas (e11) and (e12): 1.05≧NzA≧0.95 (e11) 0.05≧NzB≧−0.05 (e12) where NzA represents the NZ coefficient of the A layer, and NzB represents the NZ coefficient of the B layer. The value of NzA is preferably 0.95 or more, more preferably 0.97 or more, particularly preferably 0.99 or more, and preferably 1.05 or less, more preferably 1.03 or less, and particularly preferably 1.01 or less. The value of NzB is preferably −0.05 or more, more preferably −0.03 or more, particularly preferably −0.01 or more, and preferably 0.05 or less, more preferably 0.03 or less, and particularly preferably 0.01 or less. When the values ​​are within the above ranges, effects such as a wide viewing angle and good color reproducibility can be particularly well obtained.

[0044] There are no particular restrictions on the thickness of each of the layers A and B. The thickness of each of the layers A and B is independently preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 150 μm or less, more preferably 100 μm or less.

[0045] (Arrangement of second optically anisotropic layer) The second optically anisotropic layer is arranged between the first optically anisotropic layer and the liquid crystal cell, and the direction of its in-plane slow axis direction is not particularly limited, but from the viewpoint of well exhibiting effects such as a wide viewing angle and good color reproducibility, it is preferable that the in-plane slow axis direction of layer A is perpendicular to the transmission axis of the first polarizer.In addition, the in-plane slow axis direction of the second optically anisotropic layer as a whole usually coincides with the in-plane slow axis direction of layer A.It is preferable that the in-plane slow axis direction of the second optically anisotropic layer is perpendicular to the transmission axis of the first polarizer.

[0046] The positional relationship between the A layer and the B layer in the second optically anisotropic layer arranged in the liquid crystal display device of the present invention may be such that the A layer is on the viewing side, or the B layer is on the viewing side, from the viewpoint of optical properties.

[0047] (Requirements for First Optically Anisotropic Layer) The first optically anisotropic layer satisfies the following formula (e5): nz1>nx1≧ny1 (e5) where nx1 represents the refractive index in an in-plane direction of the first optically anisotropic layer that gives the maximum refractive index, ny1 represents the refractive index in an 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.

[0048] The formula (e5) indicates that the first optically anisotropic layer can function as a so-called positive B plate or positive C plate. By providing the first optically anisotropic layer in combination with the second optically anisotropic layer, the liquid crystal display device of the present invention can satisfactorily exhibit effects such as a wide viewing angle and good color reproducibility.

[0049] The first optically anisotropic layer preferably satisfies the following formula (e13): 70≧Re1(550)≧0.0 (e13) where Re1(550) represents the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm.

[0050] The formula (e13) indicates that the first optically anisotropic layer has no in-plane retardation or has only a small in-plane retardation. By providing such a first optically anisotropic layer in combination with the second optically anisotropic layer, effects such as a wide viewing angle and good color reproducibility can be more effectively exhibited.

[0051] The first optically anisotropic layer preferably satisfies the following formula (e14): 0.60≦Rth1(450) / Rth1(550)≦1.20 (e14) where Rth1(450) represents the thickness direction retardation of the first optically anisotropic layer at a wavelength of 450 nm, and Rth1(550) represents the thickness direction retardation of the first optically anisotropic layer at a wavelength of 550 nm.

[0052] The value of Rth1(450) / Rth1(550) is preferably 0.60 or more, more preferably 0.70 or more, and is preferably 1.20 or less, more preferably 1.15 or less.

[0053] The formula (e14) indicates that the wavelength dispersion of the thickness direction retardation of the first optically anisotropic layer is a small value within a predetermined range. By providing such a first optically anisotropic layer in combination with the second optically anisotropic layer, effects such as a wide viewing angle and good color reproducibility can be more effectively exhibited.

[0054] There is no particular limitation on the thickness of the first optically anisotropic layer, but the thickness of the first optically anisotropic layer is preferably 0.5 μm or more, more preferably 1.0 μm or more, and preferably 35 μm or less, more preferably 30 μm or less.

[0055] (Characteristics of the Combination of the First Optically Anisotropic Layer and the Second Optically Anisotropic Layer) In the liquid crystal display device of the present invention, the first optically anisotropic layer and the second optically anisotropic layer are combined to form an optically anisotropic laminate.

[0056] Such an optically anisotropic laminate preferably has a retardation capable of functioning as a λ / 4 plate. The optically anisotropic laminate has an in-plane retardation ReT(550) at a wavelength of 550 nm of preferably 75 nm or more, more preferably 100 nm or more, and preferably 180 nm or less, more preferably 160 nm or less. When the in-plane retardation ReT(550) of the optically anisotropic laminate is within the above range, effects such as a wide viewing angle and good color reproducibility can be particularly well obtained.

[0057] The optically anisotropic laminate preferably exhibits reverse wavelength dispersion. By virtue of the optically anisotropic laminate having reverse wavelength dispersion, effects such as a wide viewing angle and good color reproducibility can be particularly favorably obtained. Specifically, the optically anisotropic laminate preferably has a ReT(450) / ReT(550) value of 1 or less. Here, ReT(450) represents the in-plane retardation of the optically anisotropic laminate at a wavelength of 450 nm, and ReT(550) represents the in-plane retardation of the optically anisotropic laminate at a wavelength of 550 nm.

[0058] The value of ReT(450) / ReT(550) is preferably 0.75 or more, more preferably 0.80 or more, and is preferably 0.95 or less, more preferably 0.92 or less.

[0059] 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. The upper limit of the total light transmittance can be 100% or less, or less than 100%. The total light transmittance can be measured using an ultraviolet-visible spectrometer in the wavelength range of 400 nm to 700 nm.

[0060] (Materials for forming each layer) Any material may be used to form the A layer, B layer, and first optically anisotropic layer. Each of the A layer, B layer, and first optically anisotropic layer typically contains a resin and is formed from a resin. The resin contained in each of the A layer, B layer, and first optically anisotropic layer may be a resin with a positive or negative intrinsic birefringence value. However, it is generally preferred that the resin contained in the A layer be a resin with a positive intrinsic birefringence value, and that the resin contained in the B layer and the first optically anisotropic layer be a resin with a negative intrinsic birefringence value. Alternatively, the material constituting the first optically anisotropic layer may be appropriately selected from materials that can easily exhibit the optical properties required for a positive C plate.

[0061] 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.

[0062] 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.

[0063] In the alicyclic structure-containing polymer, the proportion of the repeating units containing the 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 the repeating units containing the alicyclic structure is within the above range, a second optically anisotropic layer having excellent heat resistance can be obtained.

[0064] 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.

[0065] 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).

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] A preferred example of the aromatic vinyl unit is a polymer unit represented by the following formula (A-1):

[0080]

[0081] 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 a second optically anisotropic layer having desired optical properties, R ｃ As the alkyl group, a naphthyl group is preferred.

[0082] 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 a second optically anisotropic layer 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.

[0083] 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.

[0084]

[0085] 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.

[0086] 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.

[0087] 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 a second optically anisotropic layer having desired optical properties.

[0088] 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.

[0089] 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.

[0090] 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).

[0091]

[0092] 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 a second optically anisotropic layer having desired optical properties, R ４ ~R ９ are preferably each independently a hydrogen atom or a methyl group.

[0093] 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.

[0094]

[0095] 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.

[0096] Examples of the chain conjugated diene compound include compounds represented by the following formula (bm).

[0097]

[0098] 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 a second optically anisotropic layer that is excellent in transparency, heat resistance, and processability.

[0099] 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].

[0100] The hydrogenation rate of the double bonds of the chain conjugated diene unit 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 a second optically anisotropic layer having desired optical properties. １ It can be measured by H-NMR.

[0101] 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.

[0102] The proportion of hydrogenated linear conjugated diene units in polymer block [B] is preferably high. Specifically, the proportion of hydrogenated linear conjugated diene units in 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 polymer block [B] is as high as described above, it is particularly easy to produce a second optically anisotropic layer having desired optical properties.

[0103] 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.

[0104] In the hydrogenated block copolymer [C], the weight fraction wA of the polymer block [A] and the weight fraction wB of the polymer block [B] satisfy the above-mentioned formula (1). 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-mentioned range, it is possible to easily produce a second optically anisotropic layer having reverse wavelength dispersion characteristics. Furthermore, when the ratio wA / wB is within the above-mentioned range, it is usually possible to easily adjust the optical characteristics other than the wavelength dispersion characteristics of the second optically anisotropic layer to desired values.

[0105] 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 second optically anisotropic layer 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.

[0106] 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 second optically anisotropic layer contains multiple types of hydrogenated block copolymers [C], 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] in the entire multiple types of hydrogenated block copolymers [C] contained.

[0107] 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.

[0108] 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.

[0109] 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).

[0110] 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.

[0111] From the viewpoint of particularly facilitating the production of a second optically anisotropic layer 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].

[0112] The hydrogenated block copolymer [C] contained in the resin as the material for the second optically anisotropic layer may be one type or two or more types.

[0113] 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.

[0114] The A layer, the B layer, and the first optically anisotropic layer may each include a liquid crystal alignment layer. The liquid crystal alignment layer can be preferably used as a material constituting the first optically anisotropic layer. The liquid crystal alignment layer is a cured layer obtained by curing a layer of a liquid crystal composition containing an aligned liquid crystal compound. Since the liquid crystal alignment layer is formed from a cured liquid crystal composition, it contains molecules of the liquid crystal compound.

[0115] In the liquid crystal alignment layer, the liquid crystal compound is preferably aligned so as to achieve the optical properties required for the liquid crystal alignment layer.

[0116] The liquid crystal compound is preferably polymerizable. Therefore, the liquid crystal compound preferably contains a polymerizable group such as an acryloyl group, a methacryloyl group, or an epoxy group in its molecule. The number of polymerizable groups per molecule of the liquid crystal compound may be one, but preferably two or more. A polymerizable liquid crystal compound can be polymerized in a liquid crystal phase and become a polymer so as not to change the direction showing the maximum refractive index in the refractive index ellipsoid of the molecules in the liquid crystal phase. Therefore, when a liquid crystal compound is polymerizable, it is possible to fix the alignment state of the liquid crystal compound in a liquid crystal alignment layer or increase the degree of polymerization of the liquid crystal compound to increase the mechanical strength of the liquid crystal alignment layer.

[0117] The liquid crystal compound may be used alone or in combination of two or more kinds in any ratio.

[0118] The liquid crystal composition may further contain optional components in combination with the liquid crystal compound, as necessary. The optional components may be used singly or in combination of two or more in any ratio. Examples of the optional components include polymerization initiators; surfactants; antioxidants; metals; metal complexes; metal oxides such as titanium oxide; colorants such as dyes and pigments; light-emitting materials such as fluorescent materials and phosphorescent materials; leveling agents; thixotropic agents; gelling agents; polysaccharides; ultraviolet absorbers; infrared absorbers; antioxidants; ion exchange resins; and the like. The amount of each of these components may be 0.1 to 20 parts by weight per 100 parts by weight of the total of the liquid crystal compounds.

[0119] Examples of liquid crystal compositions that can form a liquid crystal alignment layer include the liquid crystal composition described in JP 2002-333642 A, a composition containing a liquid crystal compound having a polymerizable group, a composition containing a side-chain liquid crystal polymer, and a composition containing a discotic liquid crystal compound. Examples of liquid crystal compounds having a polymerizable group include rod-shaped liquid crystal compounds having a polymerizable group described in JP-A-11-513360, JP 2002-030042, JP 2004-204190, JP 2005-263789, JP 2007-119415, JP 2007-186430, etc. Examples of side-chain liquid crystal polymer compounds include side-chain liquid crystal polymer compounds described in JP 2002-333642 A, JP 2003-177242, etc. Furthermore, examples of preferred liquid crystal compounds include "LC242" manufactured by BASF.

[0120] Curing of a liquid crystal composition is usually achieved by polymerization of a polymerizable compound contained in the liquid crystal composition. Therefore, a liquid crystal alignment layer usually contains polymers of some or all of the components contained in the liquid crystal composition. Therefore, if the liquid crystal compound is polymerizable, the liquid crystal alignment layer can be a layer containing a polymer of the liquid crystal compound. Normally, the liquid crystal property of a liquid crystal compound is lost by polymerization, but in the present application, such polymerized liquid crystal compounds are also included in the term "liquid crystal compound contained in a liquid crystal alignment layer."

[0121] In the liquid crystal alignment layer, the fluidity of the liquid crystal composition is lost. Therefore, the alignment state of the liquid crystal compound can usually be fixed in the liquid crystal alignment layer. The term "liquid crystal compound with a fixed alignment state" includes polymers of the above-mentioned liquid crystal compound. The liquid crystal alignment layer may contain liquid crystal compound molecules with a fixed alignment state in combination with liquid crystal compound molecules with a fixed alignment state, but it is preferable that all of the liquid crystal compound molecules contained in the liquid crystal alignment layer have a fixed alignment state.

[0122] The method for forming the liquid crystal alignment layer is not particularly limited, but for example, the liquid crystal alignment layer can be formed by carrying out the steps of forming a layer of a liquid crystal composition containing a liquid crystal compound on a base film, orienting the liquid crystal compound contained in the liquid crystal composition layer, and curing the liquid crystal composition layer.

[0123] Materials for forming the A layer, B layer, and first optically anisotropic layer, particularly materials for forming the first optically anisotropic layer, include materials that can easily exhibit the optical properties required for use as a positive C plate. Particularly preferred examples of such materials include materials containing a mesogenic compound. Specifically, an optically anisotropic layer formed from a material containing a specific positive C polymer and a mesogenic compound, as described in JP 2018-146636 A, can be preferably used as the first optically anisotropic layer.

[0124] The positive C polymer is a polymer in which, when a film of the positive C polymer is formed by a coating method using a solution of the positive C polymer, the refractive indices nx(P), ny(P), and nz(P) of the film satisfy nz(P)>nx(P)≧ny(P), where nx(P) represents the refractive index in the in-plane direction of the film that gives the maximum refractive index, ny(P) represents the refractive index in the in-plane direction of the film that is perpendicular to the nx direction, and nz(P) represents the refractive index in the thickness direction of the film.

[0125] The positive C polymer is preferably a polymer selected from the group consisting of polyvinylcarbazole, polyfumaric acid ester, cellulose derivatives, and combinations thereof. By using such a polymer as the positive C polymer, an optically anisotropic layer having a small Rth per unit thickness can be easily obtained. Specific examples of the positive C polymer include poly(9-vinylcarbazole); a copolymer of diisopropyl fumarate and 3-ethyl-3-oxetanylmethyl acrylate; and a copolymer of diisopropyl fumarate and cinnamic acid ester. One type of positive C polymer may be used alone, or two or more types may be used in combination in any ratio.

[0126] The mesogenic skeleton in a mesogenic compound, i.e., a compound having a mesogenic skeleton, refers to a molecular skeleton that essentially contributes to the generation of a liquid crystal phase in a low-molecular-weight or high-molecular-weight substance due to the anisotropy of its attractive and repulsive interactions. A mesogenic compound containing a mesogenic skeleton does not necessarily have liquid crystallinity capable of undergoing a phase transition to a liquid crystal phase by itself. Thus, a mesogenic compound may be a liquid crystal compound capable of undergoing a phase transition to a liquid crystal phase by itself, or a non-liquid crystal compound that does not undergo a phase transition to a liquid crystal phase by itself. Examples of mesogenic skeletons include units with rigid rod-like or disc-like shapes. Mesogenic skeletons are described in Pure Appl. Chem. 2001, Vol. 73 (No. 5), p. 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, Vol. 116, pp. 6340-6368.

[0127] In the optically anisotropic layer, the orientation of the mesogenic compound may or may not be fixed. For example, the mesogenic compound may be a polymer in which the orientation of the mesogenic skeleton is fixed by polymerization. Typically, a mesogenic compound can be polymerized while maintaining its orientation, and the orientation of the mesogenic compound is fixed by the polymerization. Therefore, the term "mesogenic compound with a fixed orientation" encompasses a polymer of the mesogenic compound. That is, in this application, the expression "containing a mesogenic compound" in an optically anisotropic layer encompasses not only the case where mesogenic compound molecules are present in the optically anisotropic layer, but also the case where a polymer containing polymerized units having a mesogenic skeleton, which is formed by polymerization of the mesogenic compound, is present in the optically anisotropic layer. Therefore, when the mesogenic compound is a liquid crystal compound having liquid crystallinity, the liquid crystal compound may exhibit a liquid crystal phase in the optically anisotropic layer, or may not exhibit a liquid crystal phase due to the orientation being fixed.

[0128] Specific examples of liquid crystal compounds such as reverse wavelength dispersion liquid crystal compounds, which are particularly preferred embodiments of the mesogenic compounds, include those described in JP-A-2014-123134 and JP-A-2018-146636.

[0129] (Preferred Form of Layer A) The layer A preferably contains a resin (A) having a positive intrinsic birefringence value and is formed from the resin (A). Examples of the resin (A) having a positive intrinsic birefringence value include the examples given above as the resin having a positive intrinsic birefringence value. The layer A is preferably a layer (stretched layer A) obtained by stretching a pre-stretched layer A containing a resin (A) having a positive intrinsic birefringence value. This makes it possible to easily form an layer A that satisfies the formula (e1).

[0130] In another embodiment, it is preferable that the layer A includes a liquid crystal alignment layer. Examples of the liquid crystal alignment layer that can be included in the layer A include the examples of the liquid crystal alignment layer described above.

[0131] In the liquid crystal alignment layer that can be included in the layer A, the liquid crystal compound is preferably homogeneously aligned, which makes it possible to easily realize the layer A that satisfies the formula (e1).

[0132] (Preferred Form of Layer B) Layer B preferably contains a resin having an intrinsic birefringence value with an opposite sign to that of the resin contained in Layer A, more preferably contains a resin (B) having a negative intrinsic birefringence value, and more preferably is formed from resin (B). Examples and preferred examples of resin (B) having a negative intrinsic birefringence value include the examples and preferred examples given above as the resin having a negative intrinsic birefringence value.

[0133] In particular, as the resin (B), a material having a negative intrinsic birefringence value and exhibiting a high degree of retardation upon stretching can be preferably used. As a material exhibiting a high degree of retardation, a material exhibiting a high degree of retardation can be appropriately selected from the examples of resins having a negative intrinsic birefringence value described above. As such a material exhibiting a high degree of retardation, an aromatic group-containing polymer is particularly preferred, and an aromatic vinyl polymer is particularly preferred. Among the aromatic vinyl polymers, the hydrogenated block copolymer [C] described above is particularly preferred.

[0134] The B layer is preferably a layer (stretched B layer) obtained by stretching a pre-stretched B layer containing a resin (B) having a negative intrinsic birefringence value, thereby making it possible to easily form the B layer satisfying the above formula (e2).

[0135] In another embodiment, it is preferable that layer B includes a liquid crystal alignment layer. Examples of the liquid crystal alignment layer that can be included in layer B include the examples of the liquid crystal alignment layer described above.

[0136] In the liquid crystal alignment layer that can be included in layer B, the liquid crystal compound is preferably homogeneously aligned, which makes it possible to easily realize layer B that satisfies formula (e2).

[0137] (Preferred form of first optically anisotropic layer) The first optically anisotropic layer is preferably a layer made of a material containing a mesogenic compound. Specific examples thereof include an optically anisotropic layer containing the above-mentioned positive C polymer and a mesogenic compound. This makes it possible to easily form a first optically anisotropic layer that satisfies the formula (e13).

[0138] In yet another embodiment, the first optically anisotropic layer preferably contains a resin (F) having a negative intrinsic birefringence value and is formed from the resin (F). Examples and preferred examples of the resin (F) having a negative intrinsic birefringence value include the examples and preferred examples given above as the resin having a negative intrinsic birefringence value (including those given as examples of materials containing a mesogenic compound). In yet another embodiment, the first optically anisotropic layer is preferably a layer (stretched F layer) obtained by stretching a pre-stretched F layer containing the resin (F) having a negative intrinsic birefringence value. This makes it possible to easily form a first optically anisotropic layer that satisfies the formula (e13).

[0139] (Method for Producing Second Optically Anisotropic Layer by Co-Stretching) The second optically anisotropic layer is preferably produced by a production method including the following steps.

[0140] Step (s1): Resin (A) is molded to form a film of a pre-stretch A layer. Step (s2): A coating liquid (B) containing a resin (B) is applied onto the pre-stretch A layer to form a pre-stretch B layer, thereby obtaining a pre-stretch laminate S including the pre-stretch A layer and the pre-stretch B layer. Step (s3): The pre-stretch laminate S is stretched to form a stretched laminate including an A layer that is a stretched product of the pre-stretch A layer, and a B layer that is a stretched product of the pre-stretch B layer.

[0141] The production method using steps (s1) to (s3) is a so-called co-stretching production method, and is particularly preferred because it makes it possible to easily produce a laminate of layer A and layer B whose in-plane slow axis directions are precisely perpendicular (90°) to each other.

[0142] The resin (A) used in step (s1) is a resin having a positive intrinsic birefringence value. Specific examples of resins having a positive intrinsic birefringence value include those described above. By using a resin having a positive intrinsic birefringence value as the resin (A) for forming the A layer, it is possible to easily produce an A layer having desired optical properties.

[0143] The molding method of the resin (A) in step (s1) is not particularly limited, and molding methods such as melt molding and solution casting can be used. Among these, melt molding is preferred. Among melt molding methods, extrusion molding, inflation molding, and press molding are preferred, and extrusion molding is particularly preferred. According to these methods, the pre-stretching A layer can be produced as a long film.

[0144] The resin (B) used in step (s2) is a resin having a negative intrinsic birefringence value. Specific examples of resins having a negative intrinsic birefringence value include those described above. By using a resin having a negative intrinsic birefringence value as the resin (B) for forming the B layer, it is possible to easily produce a B layer having desired optical properties.

[0145] The coating liquid (B) may contain a solvent in addition to the resin (B). The solvent is preferably one that can dissolve or disperse the resin (B), and particularly preferably one that can dissolve the resin (B). 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 (B) in the coating liquid (B) is preferably adjusted so that the viscosity of the coating liquid (B) falls within a range suitable for coating, and may be, for example, 1% by weight to 50% by weight.

[0146] There is no limitation on the method for applying the coating liquid (B), and examples of the application 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.

[0147] By applying a coating liquid (B) containing a resin (B), a layer of the coating liquid (B) is formed on the pre-stretching layer A. If necessary, the layer of the coating liquid (B) is dried to remove the solvent, thereby forming a pre-stretching layer B on the pre-stretching layer A, thereby obtaining a pre-stretching laminate S. There are no limitations on the drying method, and drying methods such as heat drying and reduced pressure drying can be used, for example.

[0148] The drying temperature and drying time are not particularly limited, but may be set to realistic conditions when a long film 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.

[0149] The thicknesses of the pre-stretching A layer and the pre-stretching B layer can be adjusted appropriately so that the A layer and the B layer have the desired thickness ratio and exhibit the desired optical properties.

[0150] In step (s3), the pre-stretch laminate S is stretched to obtain a stretched laminate. The slow axes of the A layer and the B layer contained in the stretched laminate form a predetermined angle. The pre-stretch A layer contains a resin (A) having a positive intrinsic birefringence value, and the pre-stretch B layer contains a resin (B) having a negative intrinsic birefringence value. Therefore, by stretching the pre-stretch laminate S including the pre-stretch A layer and the pre-stretch B layer, the pre-stretch A layer develops a slow axis in the same direction as the normal stretching direction, preferably the same direction, and the pre-stretch B layer develops a slow axis in the direction of approximately 90°, preferably 90°, relative to the normal stretching direction.

[0151] In addition to the above steps (s1) to (s3), the method for producing the second optically anisotropic layer may include any other step, for example, the step of providing a protective layer on the second optically anisotropic layer.

[0152] (Optional Components of Liquid Crystal Display Device) The liquid crystal display device of the present invention may include an optional layer in addition to the first polarizer, first optically anisotropic layer, second optically anisotropic layer, liquid crystal cell, and second polarizer described above. Examples of the optional layer include a polarizer protective film layer; an adhesive layer for bonding the various layers; 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; an antistatic layer; and the like. Only one of these optional layers may be provided, or two or more layers may be provided.

[0153] In addition to the above-described layers, the liquid crystal display device of the present invention may include any components necessary for constituting a liquid crystal display device, such as a light source located on the rear side of the second polarizer, wiring and a control device for driving the liquid crystal cell, and a housing for accommodating these components.

[0154] (Method for manufacturing liquid crystal display device) The method for manufacturing a liquid crystal display device is not particularly limited, and for example, a liquid crystal display device can be constructed by assembling a group of components including the first polarizer, first optically anisotropic layer, second optically anisotropic layer, liquid crystal cell, and second polarizer described above, as well as any other optional components as necessary. The method for assembling the group of components is not particularly limited, and can be performed by a known method. The first polarizer, first optically anisotropic layer, second optically anisotropic layer, liquid crystal cell, and second polarizer used in manufacturing a liquid crystal display device can be manufactured by the method described above, by a known manufacturing method, or by purchasing products. In particular, it is preferable to manufacture the second optically anisotropic layer by a manufacturing method including the steps (s1) to (s3) described above.

[0155] 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.

[0156] 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.

[0157] [Evaluation Methods] (Thickness) The thickness of the laminate and each layer was measured using a film thickness measurement system ("F20" manufactured by Filmetrics).

[0158] (Method for Measuring Retardation) The retardation was measured using a retardation meter (Axometrics' "AxoScan") at a temperature of 23° C. When determining the physical properties of each layer of an inseparable laminate, the sample was measured from multiple directions and calculated by fitting analysis using the attached multilayer analysis software.

[0159] (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).

[0160] (Method of Measuring Contrast) The contrast of the liquid crystal display devices obtained in the Examples and Comparative Examples was measured using a display goniophotometer ("DMS803" manufactured by Instrument Systems). Specifically, the luminance (unit: nit) in the black display state and the luminance (unit: nit) in the white display state were measured from a direction at a polar angle of 60° and an azimuthal angle (here, the angle with the absorption axis of the first polarizer at 0°) of 45° relative to the display surface, and the contrast was calculated from the ratio (white display state luminance / black display state luminance). A contrast of 350 or more was judged to be "good," and a contrast of less than 380 was judged to be "poor."

[0161] (Heat Resistance Test) The liquid crystal display devices obtained in Examples and Comparative Examples were left to stand in a thermostatic chamber at 85°C for 500 hours, then removed from the thermostatic chamber and placed in a dark room in a black display state. If light leakage was visually observed at the four corners of the liquid crystal display device, it was judged as "poor", and if no light leakage was visually observed, it was judged as "good".

[0162] (Example 1) (1-1. Layer A before stretching) A pellet-shaped norbornene-based resin ("ZEONOR 1215" manufactured by ZEON Corporation; glass transition temperature 126°C) was dried at 100°C for 5 hours to obtain a thermoplastic resin (A). This thermoplastic resin (A) was supplied 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 thermoplastic resin (A) was cooled to obtain a layer A before stretching, which was a long single-layer resin film with a thickness of 115 µm. The obtained film was wound into a roll and collected.

[0163] (1-2. Copolymer for Resin (B)) A dried, nitrogen-purged pressure reactor was charged with 1,000 ml of toluene as a solvent and 0.58 mmol of n-butyllithium as a polymerization catalyst, 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 to precipitate and separate the triblock copolymer.

[0164] 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 was obtained as a bulk product.

[0165] 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.

[0166] (1-3. Coating Liquid (B)) The copolymer obtained in (1-2) was mixed with 1,3-dioxolane to obtain a coating liquid (B). The concentration of the copolymer (corresponding to the resin (B)) in this coating liquid (B) was 15 wt %.

[0167] (1-4. Second Optically Anisotropic Layer) The pre-stretch A layer obtained in (1-1) was pulled out from the roll and transported along a transport path. On the transport path, the coating liquid (B) obtained in (1-3) was continuously coated on the pre-stretch A layer to provide a layer of the coating liquid (B). During coating, the amount of the coating liquid (B) was adjusted so that the thickness of the pre-stretch B layer was 4.5 μm. Furthermore, the layer of the coating liquid (B) was dried at 120° C. for 3 minutes. This cured the layer of the coating liquid (B) to form the pre-stretch B layer, and a long pre-stretch laminate S having a layer structure of (pre-stretch A layer) / (pre-stretch B layer) was obtained.

[0168] The obtained pre-stretched laminate S was continuously stretched downstream of the coating step in the conveying path. Stretching was performed by free-end uniaxial stretching using a longitudinal stretching machine, with the stretching direction being the longitudinal direction of the pre-stretched laminate S. The stretching ratio was 2.19 times, and the stretching temperature was 137°C. As a result, the pre-stretched A layer and the pre-stretched B layer in the pre-stretched laminate S were stretched to form the A layer and the B layer, respectively, to obtain a second optically anisotropic layer having a layer structure of (A layer) / (B layer).

[0169] The optical properties of the resulting second optically anisotropic layer (in-plane retardation, thickness direction retardation, and slow axis direction of each of the A layer, B layer, and the entire second optically anisotropic layer) were measured. The ReA(450) / ReA(550) ratio calculated from the in-plane retardation measurements was 1.01, and the ReB(450) / ReB(550) ratio was 1.31.

[0170] (1-5. First Optically Anisotropic Layer) A coating liquid was prepared by dissolving 35 parts by weight of a liquid crystal compound and 65 parts by weight of a positive C polymer in a mixed solvent to a solids concentration of 12%. The liquid crystal compound used was a photopolymerizable reverse wavelength dispersion liquid crystal compound IA (CN point: 96°C) having a structure represented by the following formula (IA). The positive C polymer used was a polyfumaric acid ester (a copolymer of diisopropyl fumarate and cinnamic acid ester, where R is an isopropyl group, the ratio of the number of polymerized units m and n is 85:15, and the molecular weight is 72,000) having polymerized units represented by the following formula (P1) and polymerized units represented by the following formula (P2). The mixed solvent used was a mixture of 80% by weight of 1,3-dioxolane and 20% by weight of MIBK.

[0171]

[0172]

[0173]

[0174] A long PET film ("Cosmoshine A4100" manufactured by Toyobo Co., Ltd., thickness 100 μm) was prepared as the substrate film. A coating liquid was continuously applied onto the surface of the substrate film to form a coating liquid layer. The thickness of the coating liquid layer was adjusted so that the thickness of the resulting first optically anisotropic layer would be 10.4 μm.

[0175] The coating liquid layer was then dried in an oven at 110°C for about 3 minutes to evaporate the solvent in the coating liquid layer. This resulted in a first optically anisotropic layer formed on the substrate film. The optical properties (in-plane retardation, thickness direction retardation, and slow axis direction) of the obtained first optically anisotropic layer were measured.

[0176] (1-6. 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° 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. The linear polarizer and the first optically anisotropic layer obtained in (1-5) were bonded together with their longitudinal directions aligned, 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). Next, the second optically anisotropic layer obtained in (1-4) was attached to the first optically anisotropic side of the laminate of the linear polarizer and the first optically anisotropic layer, with its longitudinal direction aligned, so that the first optically anisotropic layer and the second optically anisotropic layer faced each other via an optically isotropic pressure-sensitive adhesive ("CS9621" manufactured by Nitto Denko Corporation). The second optically anisotropic layer was oriented so that its Layer A side was the first optically anisotropic side. The in-plane slow axis direction of Layer A was perpendicular to the transmission axis of the first polarizer. Since the first optically anisotropic layer obtained in (1-5) was formed on a substrate film, the substrate film was peeled off and the first optically anisotropic layer was transferred during lamination. This resulted in a long polarizing plate having a layer structure of (first polarizer) / (first optically anisotropic layer) / (second optically anisotropic layer). The long polarizing plate was cut to appropriate dimensions to obtain a rectangular polarizing plate.

[0177] (1-7. Liquid Crystal Display Device) A liquid crystal display device (Apple iPad (10th Generation) (registered trademark)) equipped with an IPS mode liquid crystal cell was prepared. This liquid crystal display device included a viewer-side polarizer (corresponding to the first polarizer), a liquid crystal cell, and a rear-side polarizer (corresponding to the second polarizer). The transmission axis of the viewer-side polarizer and the transmission axis of the rear-side polarizer were orthogonal (forming an angle of 90°), the liquid crystal cell was in a black display state when no voltage was applied, and the transmission axis of the viewer-side polarizer was parallel to the alignment direction of the liquid crystal molecules of the liquid crystal cell in the black display state (forming an angle of 0°). Each of the viewer-side polarizer and the rear-side polarizer was combined with a protective film to form a polarizing plate. The protective film on the liquid crystal cell side of the rear-side polarizer was a film made of an isotropic material with no retardation.

[0178] This liquid crystal display device was disassembled, and the polarizing plate containing the viewer-side polarizer was peeled off to expose the surface of the liquid crystal cell. The surface of this liquid crystal cell was bonded to the rectangular polarizing plate obtained in (1-6) via an adhesive ("CS9621" manufactured by Nitto Denko Corporation). During bonding, the polarizing plate was oriented so that the first polarizer was on the viewer side. Furthermore, during bonding, the relationship between the first polarizer and the rear polarizer was adjusted so that the transmission axis of the first polarizer was perpendicular to the transmission axis of the rear polarizer (forming an angle of 90°). This resulted in a liquid crystal display device comprising, in this order, the first polarizer, the first optically anisotropic layer, the second optically anisotropic layer, the liquid crystal cell, and the second polarizer.

[0179] The optical in-plane axis directions of the layers, with the transmission axis direction of the first polarizer being taken as the reference 0°, are as follows: First polarizer transmission axis: 0° First optically anisotropic layer slow axis: - (isotropic) Layer B slow axis: 0° (longitudinal width direction: longitudinal stretching) Layer A slow axis: 90° (longitudinal direction: longitudinal stretching) Cell liquid crystal molecule black display state alignment direction: 0° Second polarizer transmission axis: 90°

[0180] The obtained liquid crystal display device was subjected to a contrast measurement and a heat resistance test.

[0181] Examples 2 to 5 Liquid crystal display devices were obtained and evaluated using the same procedures as in Example 1, except for the following changes. The coating amount during coating of coating liquid (B) in step (1-4) was changed, and the thickness of the B layer before stretching was changed as shown in Table 1 below. The stretching temperature and stretch ratio during stretching in step (1-4) were changed as shown in Table 1 below. The proportions of the liquid crystal compound and the positive C polymer during preparation of the coating liquid in step (1-5) were changed as shown in Table 2 below. The thickness of the coating liquid layer during coating of the coating liquid in step (1-5) was changed, and the thickness of the first optically anisotropic layer was changed as shown in Table 2 below.

[0182] Example 6 A liquid crystal display device was obtained and evaluated by the same procedures as in Example 1, except for the following changes. The coating amount during coating of coating liquid (B) in step (1-4) was changed, and the thickness of Layer B before stretching was changed as shown in Table 1 below. The stretching temperature and stretching ratio during stretching in step (1-4) were changed as shown in Table 1 below. The proportions of the liquid crystal compound and the positive C polymer during preparation of the coating liquid in step (1-5) were changed as shown in Table 2 below. The thickness of the coating liquid layer during coating of the coating liquid in step (1-5) was changed, and the thickness of the first optically anisotropic layer was changed as shown in Table 2 below. After drying the coating liquid in step (1-5), the dried coating liquid layer was further subjected to fixed-end uniaxial stretching together with the substrate film in a tenter stretching machine, and the stretched product was used as the first optically anisotropic layer. The stretching direction was the width direction of the long first optically anisotropic layer, and the stretching ratio was 1.2. The thickness shown in Table 2 is the thickness of the first optically anisotropic layer before stretching.

[0183] The optical in-plane axis directions of the layers, with the transmission axis direction of the first polarizer being taken as the reference 0°, are as follows: First polarizer transmission axis: 0° First optically anisotropic layer slow axis: 90° (longitudinal direction of long dimension: stretched in the width direction) Layer B slow axis: 0° (longitudinal width direction: stretched in the length direction) Layer A slow axis: 90° (longitudinal direction of long dimension: stretched in the length direction) Cell liquid crystal molecule black display state alignment direction: 0° Second polarizer transmission axis: 90°

[0184]

[0185]

[0186] (Comparative Example 1) (C1-1. Single-layer second optically anisotropic layer) Except for changing the extrusion conditions and changing the thickness of the resulting resin film, a pre-stretched film, which was a single-layer resin film with a thickness of 68 μm, was obtained and evaluated by the same procedure as in (1-1) of Example 1.

[0187] The obtained pre-stretched film was continuously stretched. Stretching was performed using a longitudinal stretching machine in the longitudinal direction of the pre-stretched film. The stretching ratio was 2.19 times and the stretching temperature was 137°C. This resulted in a single-layer second optically anisotropic layer.

[0188] (C1-2. First Optically Anisotropic Layer) A first optically anisotropic layer was obtained and evaluated by the same procedure as in step (1-5) of Example 1, except for the following changes: - The proportions of the liquid crystal compound and the positive C polymer in preparing the coating liquid were 35 parts by weight and 65 parts by weight, respectively. - The thickness of the coating liquid layer in applying the coating liquid was changed, and the thickness of the first optically anisotropic layer was set to 11.1 μm.

[0189] (C1-3. Polarizing plate and liquid crystal display device) A polarizing plate and a liquid crystal display device were obtained and evaluated by the same procedures as in steps (1-6) and (1-7) of Example 1, except for the following changes. As the second optically anisotropic layer, the one obtained in (C1-1) above was used instead of the one obtained in (1-4) of Example 1. As the first optically anisotropic layer, the one obtained in (C1-2) above was used instead of the one obtained in (1-5) of Example 1. During lamination in step (1-6), the slow axis of the second optically anisotropic layer was oriented perpendicular to the transmission axis of the first polarizer.

[0190] The optical in-plane axis directions of the layers, with the transmission axis direction of the first polarizer being taken as the reference 0°, are as follows: First polarizer transmission axis: 0° First optically anisotropic layer slow axis: - (isotropic) Second optically anisotropic layer slow axis: 90° (longitudinal direction of long dimension: longitudinal stretching) Cell liquid crystal molecule black display state alignment direction: 0° Second polarizer transmission axis: 90°

[0191] (Comparative Example 2) (C2-1. Single-Layer Second Optically Anisotropic Layer) 37.5 parts by weight of isosorbide (ISB), 91.5 parts by weight of 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF), 8.4 parts by weight of polyethylene glycol (PEG) having an average molecular weight of 400, 105.7 parts by weight of diphenyl carbonate (DPC), and 0.594 parts by weight of cesium carbonate (0.2 wt % aqueous solution) as a catalyst were each placed in a reaction vessel, and in a nitrogen atmosphere, the heat medium temperature of the reaction vessel was raised to 150°C, and the raw materials were dissolved (approximately 15 minutes) with stirring as necessary, as the first step of the reaction.

[0192] Next, the pressure in the reaction vessel was reduced from atmospheric pressure to 13.3 kPa, and the heat transfer medium temperature in the reaction vessel was increased to 190 ° C. over 1 hour, while the generated phenol was withdrawn from the reaction vessel. After maintaining the temperature in the reaction vessel at 190 ° C. for 15 minutes, in the second step, the pressure in the reaction vessel was reduced to 6.67 kPa, and the heat transfer medium temperature in the reaction vessel was increased to 230 ° C. over 15 minutes, and the generated phenol was withdrawn from the reaction vessel. As the stirring torque of the agitator increased, the temperature was increased to 250 ° C. in 8 minutes, and the pressure in the reaction vessel was reduced to 0.200 kPa or less to remove the generated phenol. After reaching a predetermined stirring torque, the reaction was terminated, and the resulting reaction product was extruded into water and pelletized to obtain a polycarbonate resin A containing structural units derived from a dihydroxy compound in a ratio of BHEPF / ISB / PEG = 42.9 mol% / 52.8 mol% / 4.3 mol%. The resulting polycarbonate resin A had a glass transition temperature of 126° C. and a reduced viscosity of 0.372 dL / g.

[0193] The obtained polycarbonate resin A was vacuum-dried at 80°C for 5 hours, and then a film-forming device equipped with a single-screw extruder (manufactured by Isuzu Chemical Engineering Co., Ltd., screw diameter 25 mm, cylinder set temperature: 220°C), a T-die (width 300 mm, set temperature: 220°C), a chill roll (set temperature: 120-130°C), and a winder was used to produce a pre-stretched film with a thickness of 100 μm. The obtained pre-stretched film was continuously stretched. Stretching was performed using a longitudinal stretching machine, and the stretching direction was the longitudinal direction of the pre-stretched film. The stretching ratio was 3.0 times, and the stretching temperature was 142°C. This resulted in a single-layer second optically anisotropic layer.

[0194] (C2-2. First Optically Anisotropic Layer) A first optically anisotropic layer was obtained and evaluated by the same procedure as in step (1-5) of Example 1, except for the following changes: - The proportions of the liquid crystal compound and the positive C polymer in preparing the coating liquid were 35 parts by weight and 65 parts by weight, respectively. - The thickness of the coating liquid layer in applying the coating liquid (B) was changed, and the thickness of the first optically anisotropic layer was set to 10.6 μm.

[0195] (C2-3. Polarizing plate and liquid crystal display device) A polarizing plate and a liquid crystal display device were obtained and evaluated by the same procedures as in steps (1-6) and (1-7) of Example 1, except for the following changes. As the second optically anisotropic layer, the one obtained in (C2-1) above was used instead of the one obtained in (1-4) of Example 1. As the first optically anisotropic layer, the one obtained in (C2-2) above was used instead of the one obtained in (1-5) of Example 1. During lamination in step (1-6), the slow axis of the second optically anisotropic layer was oriented perpendicular to the transmission axis of the first polarizer.

[0196] The optical in-plane axis directions of the layers, with the transmission axis direction of the first polarizer being taken as the reference 0°, are as follows: First polarizer transmission axis: 0° First optically anisotropic layer slow axis: - (isotropic) Second optically anisotropic layer slow axis: 90° (longitudinal direction of long dimension: longitudinal stretching) Cell liquid crystal molecule black display state alignment direction: 0° Second polarizer transmission axis: 90°

[0197] The evaluation results of the examples and comparative examples are shown in Tables 3 to 9 below. In the tables below, the units of Re and Rth are all nm. The orientation of the slow axis is always shown as an angle (unit: °) with the transmission axis of the first polarizing plate taken as 0°.

[0198]

[0199]

[0200]

[0201]

[0202]

[0203]

[0204]

[0205] As is clear from the above results, the liquid crystal display device of the present invention, which has a first optically anisotropic layer and a second optically anisotropic layer between the first polarizer and the liquid crystal cell, can exhibit good contrast and high heat resistance.

Claims

1. A liquid crystal display device comprising, in this order, a first polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a liquid crystal cell, and a second polarizer, wherein the liquid crystal cell includes a pair of substrates and a liquid crystal molecule layer encapsulated between the substrates, and the liquid crystal display device is such that the alignment direction of the liquid crystal molecules in the black display state is parallel to the surface of the substrates, and the second optically anisotropic layer includes an A layer and a B layer and satisfies the following formulas (e1), (e2), (e3), and (e4): nx A > ny A ≥ nz A (e1) nz B ≥ nx B > ny B (e2) Re A(450) / Re A(550) < Re B(450) / Re B(550) (e3) Re A(550) > Re B(550) (e4) where nx A represents the refractive index in the in-plane direction of the A layer in the direction giving the maximum refractive index, ny A represents the refractive index in the in-plane direction of the A layer in the direction orthogonal to the direction giving nx A, nz A represents the refractive index in the thickness direction of the A layer, Re A(450) represents the in-plane retardation of the A layer at a wavelength of 450 nm, Re A(550) represents the in-plane retardation of the A layer at a wavelength of 550 nm, nx B represents the refractive index in the in-plane direction of the B layer in the direction giving the maximum refractive index, ny B represents the refractive index in the in-plane direction of the B layer in the direction orthogonal to the direction giving nx B, nz B represents the refractive index in the thickness direction of the B layer, Re B(450) represents the in-plane retardation of the B layer at a wavelength of 450 nm, Re B(550) represents the in-plane retardation of the B layer at a wavelength of 550 nm, the angle formed by the in-plane slow axis direction of the A layer and the in-plane slow axis direction of the B layer is orthogonal, the first optically anisotropic layer satisfies the following formula (e5): nz 1 > nx 1 ≥ ny 1 (e5) where nx 1 represents the refractive index in the in-plane direction of the first optically anisotropic layer in the direction giving the maximum refractive index, ny 1 represents the refractive index in the in-plane direction of the first optically anisotropic layer in the direction orthogonal to the direction giving nx 1, nz 1 represents the refractive index in the thickness direction of the first optically anisotropic layer, and the transmission axis of the first polarizer is parallel to the alignment direction of the liquid crystal molecules in the black display state.

2. The liquid crystal display device according to claim 1, wherein the in-plane slow axis direction of the A layer is orthogonal to the transmission axis of the first polarizer.

3. The liquid crystal display device according to claim 1 or 2, wherein the A layer and the B layer satisfy the following formula (e6). 30 nm ≤ (ReA(550) - ReB(550)) ≤ 230 nm (e6) 4. The liquid crystal display device according to claim 1 or 2, wherein the A layer and the B layer satisfy the following formulas (e7) and (e8). 300 nm ≥ ReA(550) ≥ 170 nm (e7) 140 nm ≥ ReB(550) ≥ 50 nm (e8) 5. The liquid crystal display device according to claim 1 or 2, wherein the A layer and the B layer satisfy the following formula (e9). ReB(450) / ReB(550) - ReA(450) / ReA(550) ≥ 0.2 (e9) 6. The liquid crystal display device according to claim 1 or 2, wherein the A layer and the B layer satisfy the following formula (e10). 0.60 ≤ (ReA(450) - ReB(450)) / (ReA(550) - ReB(550)) ≤ 0.98 (e10) 7. The liquid crystal display device according to claim 1 or 2, wherein the A layer and the B layer satisfy the following formulas (e11) and (e12). 1.05 ≥ NzA ≥ 0.95 (e11) 0.05 ≥ NzB ≥ -0.05 (e12) However, NzA represents the NZ coefficient of the A layer, and NzB represents the NZ coefficient of the B layer.

8. The liquid crystal display device according to claim 1 or 2, wherein the first optically anisotropic layer satisfies the following formula (e13). 70 ≥ Re1(550) ≥ 0.0 (e13) However, Re1(550) represents the in-plane retardation of the first optically anisotropic layer at a wavelength of 550 nm.

9. The liquid crystal display device according to claim 1 or 2, wherein the first optically anisotropic layer satisfies the following formula (e14). 0.60 ≤ Rth1(450) / Rth1(550) ≤ 1.20 (e14) However, Rth1(450) represents the thickness-direction retardation of the first optically anisotropic layer at a wavelength of 450 nm, and Rth1(550) represents the thickness-direction retardation of the first optically anisotropic layer at a wavelength of 550 nm.

10. The liquid crystal display device according to claim 1 or 2, wherein the A layer is a stretched A layer obtained by stretching a pre-stretched A layer, and the pre-stretched A layer contains a resin (A) having a positive intrinsic birefringence value.

11. The liquid crystal display device according to claim 1 or 2, wherein the B layer is a stretched B layer obtained by stretching a pre-stretched B layer, and the pre-stretched B layer contains a resin (B) having a negative intrinsic birefringence value.

12. The liquid crystal display device according to claim 1 or 2, wherein the first optically anisotropic layer contains a mesogenic compound.

13. The liquid crystal display device according to claim 1 or 2, wherein the first optically anisotropic layer is a stretched F layer obtained by stretching a pre-stretched F layer, and the pre-stretched F layer contains a resin (F) having a negative intrinsic birefringence value.

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