Circularly polarizing plate and organic electroluminescence display device

Abstract

The present invention addresses the problem of providing a circularly polarizing plate and an organic EL display device capable of improving the visibility of black from an oblique direction. A circularly polarizing plate according to the present invention which has, in this order, a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer, wherein: both the first optically anisotropic layer and the fourth optically anisotropic layer satisfy formula (1); the second optically anisotropic layer satisfies formula (2); and the third optically anisotropic layer is obtained by immobilizing a twisted-alignment discotic liquid crystal compound in which the thickness direction is the axis of twisting.　Formula (1): nx=ny>nz, formula (2): nz=nx>ny

Description

Circular polarizer, organic electroluminescence display device

[0001] The present invention relates to a circular polarizer and an organic electroluminescence display device.

[0002] Optically anisotropic layers having refractive index anisotropy are used in various applications such as antireflection films for display devices and optical compensation films for liquid crystal display devices. Patent Document 1 discloses a retardation plate having two types of optically anisotropic layers that exhibit predetermined optical properties.

[0003] Patent No. 5960743

[0004] On the other hand, in recent years, there has been a demand for further improvement in the visibility of organic electroluminescence (EL) display devices, specifically, for further improvement in the visibility of black when the organic EL display device is viewed from an oblique direction. In other words, when the organic EL display device is viewed from an oblique direction, there is a demand for the black color to appear even blacker without containing other colors.

[0005] The present inventors attached the circularly polarizing plate specifically disclosed in Patent Document 1 to an organic EL display element and evaluated its visibility from an oblique direction, and found that there was room for improvement in the visibility of black.

[0006] An object of the present invention is to provide a circular polarizing plate and an organic EL display device that can achieve improved visibility of black from an oblique direction.

[0007] As a result of extensive research into the problems of the prior art, the present inventors have found that the above-mentioned problems can be solved by combining a plurality of optically anisotropic layers having predetermined refractive index anisotropy.

[0008] That is, it has been found that the above object can be achieved by the following configuration.

[0009] [1] A circular polarizing plate having a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer in this order, wherein the first optically anisotropic layer and the fourth optically anisotropic layer both satisfy the following formula (1), the second optically anisotropic layer satisfies the following formula (2), and the third optically anisotropic layer is a layer in which a discotic liquid crystal compound is fixed that is twist-oriented with the thickness direction as the helical axis. Formula (1): nx = ny > nz Formula (2): nz = nx > ny [2] A circular polarizer comprising a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer, in this order, wherein the first optically anisotropic layer and the fourth optically anisotropic layer both satisfy the following formula (1), and the second optically anisotropic layer and the third optically anisotropic layer both comprise layers formed by fixing a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis. Formula (1): nx = ny > nz [3] The circular polarizer according to [1], wherein the second optically anisotropic layer is a layer formed by fixing a vertically aligned discotic liquid crystal compound. [4] The circular polarizer according to any one of [1] to [3], wherein the second optically anisotropic layer and the third optically anisotropic layer are directly adjacent to each other. [5] The circularly polarizing plate according to any one of [1] to [4], wherein the in-plane slow axis of the second optically anisotropic layer at the surface facing the third optically anisotropic layer is parallel to the in-plane slow axis of the third optically anisotropic layer at the surface facing the second optically anisotropic layer. [6] The circularly polarizing plate according to [1], wherein the angle between the absorption axis of the linear polarizer and the in-plane slow axis of the second optically anisotropic layer is 94 to 114°, the in-plane retardation of the second optically anisotropic layer at a wavelength of 550 nm is 138 to 198 nm, the twist angle of the twisted liquid crystal compound in the third optically anisotropic layer is 71 to 91°, and the value of the product Δnd of the refractive index anisotropy Δn of the third optically anisotropic layer measured at a wavelength of 550 nm and the thickness d of the third optically anisotropic layer is 130 to 190 nm.[7] The circularly polarizing plate according to [2], wherein the angle formed between the absorption axis of the linear polarizer and the in-plane slow axis of the second optically anisotropic layer on the surface facing the first optically anisotropic layer is 85 to 95°, the twist angle of the twisted liquid crystal compound in the second optically anisotropic layer is 16 to 36°, the value of the product Δnd of the refractive index anisotropy Δn of the second optically anisotropic layer measured at a wavelength of 550 nm and the thickness d of the second optically anisotropic layer is 252 to 312 nm, the twist angle of the twisted liquid crystal compound in the third optically anisotropic layer is 68 to 88°, and the value of the product Δnd of the refractive index anisotropy Δn of the third optically anisotropic layer measured at a wavelength of 550 nm and the thickness d of the third optically anisotropic layer is 110 to 170 nm. [8] The circular polarizer according to any one of [1] to [7], wherein the first optically anisotropic layer has a thickness direction retardation of 0 to 60 nm at a wavelength of 550 nm, and the fourth optically anisotropic layer has a thickness direction retardation of 10 to 90 nm at a wavelength of 550 nm. [9] The circular polarizer according to any one of [1] to [8], wherein the first optically anisotropic layer is a cellulose acylate film, and the fourth optically anisotropic layer is a cellulose acylate film or a layer formed by fixing a horizontally aligned discotic liquid crystal compound.

[10] The circular polarizer according to any one of [1] to [9], wherein the second optically anisotropic layer and the third optically anisotropic layer each contain two or more chiral dopants.

[11] The circular polarizer according to

[10] , wherein at least one of the two or more chiral dopants contained in the second optically anisotropic layer and the third optically anisotropic layer has a photoisomerizable double bond and a binaphthyl moiety.

[12] An organic electroluminescent display device having the circular polarizer according to any one of [1] to

[11] .

[13] A circular polarizer having, in this order, a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, and a third optically anisotropic layer, wherein the first optically anisotropic layer and the second optically anisotropic layer are each independently a layer having fixed therein a vertically aligned discotic liquid crystal compound or a layer having fixed therein a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis, and the third optically anisotropic layer is a layer having fixed therein a horizontally aligned discotic liquid crystal compound.

[14] An organic electroluminescent display device having the circular polarizer according to

[13] .

[0010] According to the present invention, it is possible to provide a circular polarizing plate and an organic EL display device that can achieve improved visibility of black from an oblique direction.

[0011] Fig. 1 is an example of a schematic cross-sectional view of a first embodiment of a circular polarizer of the present invention. Fig. 2 is a diagram showing the relationship between the absorption axis direction of a linear polarizer and the in-plane slow axes of the second optically anisotropic layer and the third optically anisotropic layer in one aspect of the first embodiment of the circular polarizer of the present invention. Fig. 3 is a schematic diagram showing the relationship between the absorption axis direction of a linear polarizer and the in-plane slow axes of the second optically anisotropic layer and the third optically anisotropic layer when observed from the direction of the white arrow in Fig. 1. Fig. 4 is an example of a schematic cross-sectional view of a second embodiment of a circular polarizer of the present invention. Fig. 5 is a diagram showing the relationship between the absorption axis direction of a linear polarizer and the in-plane slow axes of the second optically anisotropic layer and the third optically anisotropic layer in one aspect of the second embodiment of the circular polarizer of the present invention. Fig. 6 is a schematic diagram showing the relationship between the absorption axis direction of a linear polarizer and the in-plane slow axes of the second optically anisotropic layer and the third optically anisotropic layer when observed from the direction of the white arrow in Fig. 4. Fig. 7 is an example of a schematic cross-sectional view of a third embodiment of the circular polarizer of the present invention. Fig. 8 is a diagram showing the relationship between the absorption axis direction of a linear polarizer and the in-plane slow axes of each of the first optically anisotropic layer and the second optically anisotropic layer in one aspect of the third embodiment of the circular polarizer of the present invention. Fig. 9 is a schematic diagram showing the relationship between the absorption axis direction of a linear polarizer and the angle between each of the in-plane slow axes of each of the first optically anisotropic layer and the second optically anisotropic layer when observed from the direction of the white arrow in Fig. 7. Fig. 10 is a cross-sectional view of a composition layer for explaining step 1. Fig. 11 is a cross-sectional view of a composition layer for explaining step 2. Fig. 12 is a diagram showing the helical twisting power (HTP) (μm －１ ) × concentration (mass%) and light irradiation dose (mJ / cm ２ 13 is a schematic diagram of a graph plotting the relationship between the weighted average helical twisting power (μm －１ ) and light irradiation dose (mJ / cm ２14 is a cross-sectional view of a composition layer for explaining the case where step 5 is carried out. FIG. 15 is an example of a schematic cross-sectional view of one embodiment of the organic electroluminescence display device of the present invention.

[0012] The present invention will be described in detail below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the upper and lower limits. In this specification, the upper or lower limit of a numerical range described in a stepwise manner may be replaced with the upper or lower limit of another stepwise manner. In this specification, the upper or lower limit of a numerical range described in a stepwise manner may be replaced with a value shown in the Examples. In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. When two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. Next, the terms used in this specification will be explained.

[0013] In this specification, "(meth)acrylate" is a notation representing "acrylate" or "methacrylate", "(meth)acrylic" is a notation representing "acrylic" or "methacrylic", and "(meth)acryloyl" is a notation representing "acryloyl" or "methacryloyl".

[0014] In this specification, the in-plane slow axis is defined at 550 nm unless otherwise specified.

[0015] In this specification, Re(λ) and Rth(λ) represent the in-plane retardation and the thickness direction retardation, respectively, at a wavelength λ. Unless otherwise specified, the wavelength λ is 550 nm. In the present invention, Re(λ) and Rth(λ) are values ​​measured at a wavelength λ using an AxoScan (manufactured by Axometrics). By inputting the average refractive index ((nx + ny + nz) / 3) and film thickness (d (μm)) into AxoScan, the following slow axis direction (°) is calculated: Re(λ) = R0(λ) Rth(λ) = ((nx + ny) / 2 - nz) × d. Note that R0(λ) is displayed as a numerical value calculated by AxoScan, but it means Re(λ).

[0016] In this specification, the refractive indices nx, ny, and nz are measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) with a sodium lamp (λ = 589 nm) as a light source. When measuring wavelength dependency, measurements can be made using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in combination with an interference filter. Values ​​from the Polymer Handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can also be used. Examples of average refractive index values ​​for major optical films are listed below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

[0017] In this specification, "light" means actinic rays or radiation, such as the bright line spectrum of a mercury lamp, far ultraviolet rays typified by excimer lasers, extreme ultraviolet rays (EUV light: Extreme Ultraviolet), X-rays, ultraviolet rays (UV: Ultraviolet), and electron beams (EB: Electron Beam). Of these, ultraviolet rays are preferred.

[0018] In this specification, "visible light" refers to light of 380 to 780 nm. In addition, in this specification, unless otherwise specified, the measurement wavelength is 550 nm. In addition, in this specification, the angular relationship (e.g., "perpendicular," "parallel," etc.) is intended to include the range of error acceptable in the technical field to which the present invention pertains. Specifically, this means that the angle is within a range of less than ±10° from the exact angle, and the error from the exact angle is preferably within a range of ±5° or less, and more preferably within a range of ±3° or less.

[0019] A feature of the circular polarizer of the present invention is that it has three or more optically anisotropic layers that satisfy predetermined optical properties. In Patent Document 1, by arranging two optically anisotropic layers that satisfy predetermined optical properties, when the circular polarizer is applied to an organic EL display device, black tinting in the front direction is suppressed, but the suppression of coloring in oblique directions is insufficient. In contrast, in the present invention, a new optically anisotropic layer is added to compensate for the retardation of the two optically anisotropic layers against oblique light, thereby achieving the suppression of black tinting in oblique directions.

[0020] <First embodiment> A circularly polarizing plate according to a first embodiment of the present invention comprises a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer in this order, wherein the first optically anisotropic layer and the fourth optically anisotropic layer both satisfy the following formula (1), the second optically anisotropic layer satisfies the following formula (2), and the third optically anisotropic layer is a layer in which a discotic liquid crystal compound is fixed that is twist-oriented with the thickness direction as the helical axis: Formula (1): nx = ny > nz Formula (2): nz = nx > ny In the above formulas (1) and (2), nx refers to the refractive index in the in-plane slow axis direction of the optically anisotropic layer (the direction in which the in-plane refractive index is maximum), ny refers to the refractive index in the in-plane direction perpendicular to the in-plane slow axis of the optically anisotropic layer, and nz refers to the refractive index in the thickness direction of the optically anisotropic layer. A first embodiment of the circular polarizer of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of the first embodiment of the circular polarizer of the present invention. FIG. 2 is a diagram showing the relationship between the absorption axis direction of the linear polarizer and the in-plane slow axes of the second optically anisotropic layer and the third optically anisotropic layer in the first embodiment of the circular polarizer of the present invention, where the linear polarizer, the first optically anisotropic layer, and the fourth optically anisotropic layer are omitted from FIG. 2. FIG. 3 is a diagram showing the relationship between the absorption axis direction of the linear polarizer and the angle between the in-plane slow axes of the second optically anisotropic layer and the third optically anisotropic layer when observed from the white arrow in FIG. 1 .

[0021] 1 includes a linear polarizer 12, a first optically anisotropic layer 14, a second optically anisotropic layer 16a, a third optically anisotropic layer 18a, and a fourth optically anisotropic layer 20. The third optically anisotropic layer 18a is a layer formed by fixing a discotic liquid crystal compound (DLC: Discotic Liquid Crystal) that is twisted and aligned with the thickness direction as the helical axis. Each component will be described in detail below.

[0022] (Linear polarizer 12) The linear polarizer 12 may be any component capable of converting natural light into specific linearly polarized light, such as an absorptive polarizer. The type of polarizer is not particularly limited, and commonly used polarizers can be used, such as iodine-based polarizers, dye-based polarizers using dichroic dyes, and polyene-based polarizers. Iodine-based polarizers and dye-based polarizers are generally produced by adsorbing iodine or a dichroic dye into polyvinyl alcohol and then stretching the resulting mixture. A protective film may be disposed on one or both sides of the polarizer.

[0023] (First Optically Anisotropic Layer 14) From the viewpoint of a simple manufacturing process, a transparent resin film is preferred for the first optically anisotropic layer 14. The transparent resin film refers to a film having a visible light transmittance of 60% or more, preferably 80% or more, and more preferably 90% or more.

[0024] The retardation value in the thickness direction of the first optically anisotropic layer 14 at a wavelength of 550 nm (Rth(550)) is preferably 0 to 60 nm, more preferably 10 to 60 nm, and even more preferably 10 to 50 nm, from the viewpoint of further suppressing black tinge when an organic EL display device to which the circular polarizer of the present invention is applied is viewed from an oblique direction (hereinafter simply referred to as "the viewpoint of further suppressing black tinge"). The in-plane retardation value (Re(550)) of the first optically anisotropic layer 14 at a wavelength of 550 nm is not particularly limited, but is preferably 0 to 20 nm, more preferably 0 to 10 nm.

[0025] The material for forming the first optically anisotropic layer 14 is preferably a polymer excellent in optical performance transparency, mechanical strength, thermal stability, moisture-blocking properties, isotropy, etc. Examples of polymer films that can be used for the first optically anisotropic layer 14 include cellulose acylate films (e.g., cellulose triacetate film, cellulose diacetate film, cellulose acetate butyrate film, and cellulose acetate propionate film), polyolefin films such as polyethylene and polypropylene, polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone films, polyacrylic films such as polymethyl methacrylate, polyurethane films, polycarbonate films, polysulfone films, polyether films, polymethylpentene films, polyether ketone films, (meth)acrylonitrile films, and films of polymers having an alicyclic structure (norbornene-based resins (Arton: product name, manufactured by JSR Corporation, amorphous polyolefins (Zeonex: product name, manufactured by Zeon Corporation))). Among these, triacetyl cellulose, polyethylene terephthalate, or a polymer having an alicyclic structure is preferable as the material for the polymer film. Also, the first optically anisotropic layer 14 is preferably a cellulose acylate film.

[0026] The first optically anisotropic layer 14 may contain various additives (e.g., optical anisotropy adjusters, wavelength dispersion adjusters, fine particles, plasticizers, UV inhibitors (UV absorbers or UV scattering agents), anti-degradation agents, and release agents).

[0027] The thickness of the first optically anisotropic layer 14 is preferably 0.5 to 60 μm, and more preferably 1 to 40 μm from the viewpoint of suitability for continuous production.

[0028] (Second Optically Anisotropic Layer 16a) The second optically anisotropic layer 16a is a layer disposed between the first optically anisotropic layer 14 and the third optically anisotropic layer 18a described below. The second optically anisotropic layer 16a may be any layer exhibiting predetermined optical properties, and is preferably, for example, a layer formed by fixing a vertically aligned discotic liquid crystal compound. The "fixed" state refers to a state in which the alignment of the liquid crystal compound is maintained. Specifically, it is preferable that the layer has no fluidity, and can stably maintain the fixed alignment state without causing any change in the alignment state due to an external field or external force, usually within a temperature range of 0 to 50°C, or, under more severe conditions, within a temperature range of -30 to 70°C.

[0029] In this specification, "vertical alignment" refers to a state in which the discotic plane of a discotic liquid crystal compound (in the case of a rod-shaped liquid crystal compound, this refers to the long axis direction; the same applies hereinafter) is aligned perpendicular to the main surface of the optically anisotropic layer and in the same direction (optically uniaxial). Here, "perpendicular" does not require strict perpendicularity, but refers to an orientation in which the tilt angle between the discotic plane of the discotic liquid crystal compound and the main surface of the optically anisotropic layer is greater than 70°. Furthermore, "unidirectional" does not require strict uniformity, but refers to a state in which, when the slow axis orientations are measured at any 20 positions within the plane, the maximum difference between the slow axis orientations at the 20 positions (the difference between the two slow axis orientations with the largest difference) is less than 10°. Meanwhile, in this specification, "horizontal alignment" refers to a state in which the discotic plane of a discotic liquid crystal compound is aligned parallel to the main surface of the optically anisotropic layer and in the same direction (optically uniaxial). Here, "parallel" does not necessarily mean that the alignment is strictly parallel, but means that the angle between the discotic plane of the discotic liquid crystal compound and the main surface of the optically anisotropic layer is less than 10°.

[0030] The in-plane retardation (Re(550)) of the second optically anisotropic layer 16a at a wavelength of 550 nm is preferably from 138 to 198 nm, more preferably from 148 to 188 nm, in order to further suppress black tinting.

[0031] As shown in Fig. 2, the angle θ1 between the absorption axis direction of the linear polarizer 12 and the in-plane slow axis of the second optically anisotropic layer 16a is preferably 94 to 114°, and more preferably 99 to 109°, in order to further suppress black tinting. Fig. 2 will be described in detail. The arrows in the second optically anisotropic layer 16a in Fig. 2 represent the in-plane slow axes on each surface, and the dashed lines represent the absorption axis direction of the linear polarizer. As shown in Fig. 2, the in-plane slow axis on the surface 161a of the second optically anisotropic layer 16a opposite to the third optically anisotropic layer 18a side is parallel to the in-plane slow axis on the surface 162a of the second optically anisotropic layer 16a facing the third optically anisotropic layer 18a, and the angle θ1 between both in-plane slow axes and the absorption axis direction of the linear polarizer is 94 to 114°. 3, when observed from the side indicated by the white arrow in Fig. 1 (when the linear polarizer 12 is observed from the side of the fourth optically anisotropic layer 20), the in-plane slow axis of the second optically anisotropic layer 16a is rotated clockwise by θ1° with respect to the absorption axis direction of the linear polarizer indicated by the dashed line. In other words, the in-plane slow axis of the second optically anisotropic layer 16a is located at a position rotated clockwise by θ1°.

[0032] The discotic liquid crystal compound used to form the second optically anisotropic layer 16a is not particularly limited, and known discotic liquid crystal compounds can be used. Examples of discotic liquid crystal compounds that can be preferably used include those described in paragraphs

[0020] to

[0067] of JP-A No. 2007-108732 and paragraphs

[0013] to

[0108] of JP-A No. 2010-244038. Discotic liquid crystal compounds may be used alone or in combination of two or more.

[0033] The discotic liquid crystal compound may have a polymerizable group. The type of the polymerizable group is not particularly limited, and is preferably a functional group capable of undergoing an addition polymerization reaction, more preferably a polymerizable ethylenically unsaturated group or a ring-polymerizable group, and further preferably a (meth)acryloyl group, a vinyl group, a styryl group, or an allyl group.

[0034] As will be described in detail later, the second optically anisotropic layer 16a is preferably a layer formed by fixing a discotic liquid crystal compound having a polymerizable group by polymerization, and more preferably a layer formed by fixing a discotic liquid crystal compound having a vertically aligned polymerizable group by polymerization.

[0035] The thickness of the second optically anisotropic layer 16a is preferably 0.5 to 5 μm.

[0036] (Third Optically Anisotropic Layer 18a) The third optically anisotropic layer 18a is a layer disposed between the second optically anisotropic layer 16a and the fourth optically anisotropic layer 20. As shown in FIG. 1, the third optically anisotropic layer 18a is a layer formed by fixing a discotic liquid crystal compound DLC that is twisted and aligned with the thickness direction (z-axis direction in FIG. 1) as the helical axis. The third optically anisotropic layer 18a is preferably a layer formed by fixing a chiral nematic phase having a so-called helical structure. When forming the phase, it is preferable to use a mixture of a liquid crystal compound exhibiting a nematic liquid crystal phase and a chiral agent described below. The meaning of the "fixed" state is as described above.

[0037] The value of the product Δnd of the refractive index anisotropy Δn of the third optically anisotropic layer 18a measured at a wavelength of 550 nm and the thickness d of the third optically anisotropic layer 18a is preferably 130 to 190 nm, more preferably 140 to 180 nm, in order to further suppress the occurrence of black tints. Note that the refractive index anisotropy Δn refers to the refractive index anisotropy of the liquid crystal molecules in the optically anisotropic layer. The value of the thickness d when calculating the product Δnd is expressed in units of "nm." The above Δnd is measured using an Axometrics AxoScan (polarimeter) device and the device analysis software of the same company.

[0038] The twist angle of the liquid crystal compound LC (the twist angle of the alignment direction of the liquid crystal compound LC) is preferably 81±10° (within a range of 71 to 91°), and more preferably 81±8° (within a range of 73 to 89°), in order to further suppress the occurrence of black tinting. The twist angle is measured using an Axometrics AxoScan (polarimeter) device and the device analysis software of the same company. The twisted alignment of the liquid crystal compound refers to the twisting of the liquid crystal compound from one main surface to the other main surface of the third optically anisotropic layer 18a around the thickness direction of the third optically anisotropic layer 18a. Accordingly, the alignment direction (in-plane slow axis direction) of the liquid crystal compound varies depending on the position in the thickness direction of the third optically anisotropic layer 18a.

[0039] The positional relationship of the in-plane slow axis of the third optically anisotropic layer 18a will be described using FIG. 2. The arrows in the third optically anisotropic layer 18a in FIG. 2 represent the in-plane slow axis on each surface. The in-plane slow axis of the second optically anisotropic layer 16a and the in-plane slow axis on the surface of the third optically anisotropic layer 18a facing the second optically anisotropic layer 16a are parallel. In other words, the angle between the in-plane slow axis on the surface 181a of the third optically anisotropic layer 18a facing the second optically anisotropic layer 16a and the absorption axis direction of the linear polarizer corresponds to the above-mentioned θ1. Furthermore, the in-plane slow axis on the surface 181a of the third optically anisotropic layer 18a facing the second optically anisotropic layer 16a and the in-plane slow axis on the surface 182a of the third optically anisotropic layer 18a opposite to the second optically anisotropic layer 16a form the above-mentioned twist angle. 1 (when the linear polarizer 12 is observed from the side indicated by the white arrow in Fig. 1), the in-plane slow axis of the surface 182a of the third optically anisotropic layer 18a opposite to the second optically anisotropic layer 16a side is rotated clockwise by a predetermined angle with respect to the in-plane slow axis of the surface 181a of the third optically anisotropic layer 18a facing the second optically anisotropic layer 16a. That is, as shown in Fig. 3, when observed from the side indicated by the white arrow in Fig. 1 (when the linear polarizer 12 is observed from the side indicated by the fourth optically anisotropic layer 20 in Fig. 1), the in-plane slow axis of the surface 182a of the third optically anisotropic layer 18a opposite to the second optically anisotropic layer 16a side is located at a position rotated clockwise by a predetermined angle of θ2° with respect to the in-plane slow axis of the second optically anisotropic layer 16a.

[0040] The discotic liquid crystal compound used to form the third optically anisotropic layer 18a is not particularly limited, and any known discotic liquid crystal compound can be used. Examples of the discotic liquid crystal compound include those described as the discotic liquid crystal compound used to form the second optically anisotropic layer 16a.

[0041] The liquid crystal compound may have a polymerizable group. The type of the polymerizable group is not particularly limited, and is preferably a functional group capable of undergoing an addition polymerization reaction, more preferably a polymerizable ethylenically unsaturated group or a ring-polymerizable group, and still more preferably a (meth)acryloyl group, a vinyl group, a styryl group, or an allyl group.

[0042] The third optically anisotropic layer 18a is preferably a layer formed by fixing a liquid crystal compound having a polymerizable group by polymerization, more specifically, a layer formed by fixing a liquid crystal compound having a twistedly aligned polymerizable group by polymerization.

[0043] The thickness of the third optically anisotropic layer 18a is preferably 0.5 to 5 μm.

[0044] In the present invention, it is preferable that the second optically anisotropic layer and the third optically anisotropic layer are directly adjacent to each other from the viewpoint of reducing the film thickness. In addition, the film thickness ratio between the second optically anisotropic layer 16a and the third optically anisotropic layer 18a (thickness of the second optically anisotropic layer 16a / thickness of the third optically anisotropic layer 18a) is preferably 0.5 to 2.

[0045] (Fourth Optically Anisotropic Layer 20) The fourth optically anisotropic layer 20 is a layer disposed on the surface of the third optically anisotropic layer 18a opposite to the second optically anisotropic layer 16a. The fourth optically anisotropic layer 20 may be any layer that exhibits predetermined optical properties, and is preferably a transparent resin film (particularly a cellulose acylate film) or a layer formed by fixing a horizontally aligned discotic liquid crystal compound. The meaning of the "fixed" state is as described above.

[0046] The retardation value in the thickness direction of the fourth optically anisotropic layer 20 at a wavelength of 550 nm (Rth(550)) is preferably 10 to 90 nm, more preferably 20 to 90 nm, still more preferably 30 to 90 nm, and particularly preferably 40 to 80 nm, in order to further suppress black tinting. The in-plane retardation value (Re(550)) of the fourth optically anisotropic layer 20 at a wavelength of 550 nm is not particularly limited, but is preferably 0 to 20 nm, more preferably 0 to 10 nm.

[0047] There are no particular limitations on the discotic liquid crystal compound that can be suitably used to form the fourth optically anisotropic layer 20, and any known discotic liquid crystal compound can be used. Examples of the discotic liquid crystal compound include those described as the discotic liquid crystal compound that can be used to form the second optically anisotropic layer 16a.

[0048] The liquid crystal compound may have a polymerizable group. The type of the polymerizable group is not particularly limited, and is preferably a functional group capable of undergoing an addition polymerization reaction, more preferably a polymerizable ethylenically unsaturated group or a ring-polymerizable group, and still more preferably a (meth)acryloyl group, a vinyl group, a styryl group, or an allyl group.

[0049] As will be described in detail later, the fourth optically anisotropic layer 20 is preferably a layer formed by fixing a liquid crystal compound having a polymerizable group by polymerization.

[0050] There are no particular restrictions on the transparent resin film that can be suitably used for the fourth optically anisotropic layer 20, and it is preferable that the transparent resin film has the same transmittance and is made of the same material as the transparent resin film described above for the first optically anisotropic layer 14. The fourth optically anisotropic layer 20 may also contain additives, such as an optical anisotropy adjuster, a wavelength dispersion adjuster, fine particles, a plasticizer, an ultraviolet protection agent (an ultraviolet absorber or an ultraviolet scattering agent), a deterioration inhibitor, and a release agent.

[0051] The thickness of the fourth optically anisotropic layer 20 is preferably 0.5 to 100 μm.

[0052] <Second Embodiment> A circular polarizer according to a second embodiment of the present invention comprises a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer in this order, wherein the first optically anisotropic layer and the fourth optically anisotropic layer both satisfy the following formula (1), and the second optically anisotropic layer and the third optically anisotropic layer both comprise layers formed by fixing a discotic liquid crystal compound that is twist-oriented with the thickness direction as the helical axis: Formula (1) nx = ny > nz Hereinafter, a second embodiment of the circular polarizer of the present invention will be described with reference to the drawings. Figure 4 shows a schematic cross-sectional view of the second embodiment of the circular polarizer of the present invention. Fig. 5 is a diagram showing the relationship between the absorption axis direction of the linear polarizer and the in-plane slow axes of the second and third optically anisotropic layers in a second embodiment of the circular polarizer of the present invention, and the first and fourth optically anisotropic layers are omitted in Fig. 5. Fig. 6 is a diagram showing the relationship between the absorption axis direction of the linear polarizer and the angles between the absorption axis direction of the linear polarizer and the in-plane slow axes of the second and third optically anisotropic layers when observed from the white arrows in Fig. 4.

[0053] The preferred embodiments of the first optically anisotropic layer 14 and the fourth optically anisotropic layer 20 in the second embodiment are the same as the preferred embodiments of the first optically anisotropic layer 14 and the fourth optically anisotropic layer 20 in the first embodiment.

[0054] (Second Optically Anisotropic Layer 16b) The second optically anisotropic layer 16b is a layer disposed between the first optically anisotropic layer 14 and a third optically anisotropic layer 18b described later. As shown in Fig. 4, the second optically anisotropic layer 16b is a layer formed by fixing a discotic liquid crystal compound DLC that is twisted and aligned with the thickness direction (z-axis direction in Fig. 4) as the helical axis.

[0055] The value of the product Δnd of the refractive index anisotropy Δn of the second optically anisotropic layer 16b measured at a wavelength of 550 nm and the thickness d of the second optically anisotropic layer 16b is preferably 252 to 312 nm, and more preferably 262 to 302 nm, in order to further suppress black tinting.

[0056] As shown in Figure 5, the angle θ1 between the absorption axis direction of the linear polarizer 12 and the in-plane slow axis of the second optically anisotropic layer 16b is preferably 85 to 95°, more preferably 87 to 93°, in order to further suppress the impartation of black color. The positional relationship of the in-plane slow axis of the second optically anisotropic layer 16b will be explained using Figure 5. The arrows in the second optically anisotropic layer 16b in Figure 5 represent the in-plane slow axes on each surface, and the dashed line represents the absorption axis direction of the linear polarizer. The angle (twist angle) θ2 between the in-plane slow axis of the surface 161b of the second optically anisotropic layer 16b opposite the third optically anisotropic layer 18b side and the in-plane slow axis of the surface 162b of the second optically anisotropic layer 16b facing the third optically anisotropic layer 18b is preferably 16 to 36°, more preferably 18 to 34°, in order to further suppress the impartation of black color. As shown in Figure 6, when observed from the side indicated by the white arrow in Figure 4 (when the linear polarizer 12 is observed from the side of the fourth optical anisotropic layer 20), the in-plane slow axis on the surface of the second optical anisotropic layer 16b facing the first optical anisotropic layer 14 is located at a position rotated by a predetermined angle θ2° clockwise based on the in-plane slow axis on the surface of the second optical anisotropic layer 16b facing the first optical anisotropic layer 14.

[0057] The thickness of the second optically anisotropic layer 16b is preferably 0.5 to 5 μm.

[0058] (Third Optically Anisotropic Layer 18b) The third optically anisotropic layer 18b is a layer disposed between the second optically anisotropic layer 16b and the fourth optically anisotropic layer 20. As shown in Fig. 4, the third optically anisotropic layer 18b is a layer formed by fixing a discotic liquid crystal compound DLC that is twist-oriented with the thickness direction (z-axis direction in Fig. 4) as the helical axis.

[0059] The value of the product Δnd of the refractive index anisotropy Δn of the third optically anisotropic layer 18b measured at a wavelength of 550 nm and the thickness d of the third optically anisotropic layer 18b is preferably 110 to 170 nm, and more preferably 120 to 160 nm, in order to further suppress black tinting.

[0060] The thickness of the third optically anisotropic layer 18b is preferably 0.5 to 5 μm.

[0061] In the present invention, it is preferable that the second optically anisotropic layer and the third optically anisotropic layer are directly adjacent to each other in terms of reducing the film thickness. Furthermore, the film thickness ratio between the second optically anisotropic layer 16b and the third optically anisotropic layer 18b (thickness of the second optically anisotropic layer 16b / thickness of the third optically anisotropic layer 18b) is preferably 0.5 to 2. In the second embodiment, the second optically anisotropic layer and the third optically anisotropic layer are both layers formed by fixing a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis. Therefore, when the second optically anisotropic layer and the third optically anisotropic layer are directly adjacent to each other, the second optically anisotropic layer and the third optically anisotropic layer can be distinguished from each other at the point where the continuity of the twisted alignment is lost, i.e., the point where the direction and amount of rotation of the twisted alignment differ.

[0062] The arrows in the third optically anisotropic layer 18b in Figure 5 represent the in-plane slow axes on each surface. The in-plane slow axis of the second optically anisotropic layer 16b is parallel to the in-plane slow axis of the surface of the third optically anisotropic layer 18b facing the second optically anisotropic layer 16b. In other words, the angle between the in-plane slow axis of the surface 181b of the third optically anisotropic layer 18b facing the second optically anisotropic layer 16b and the absorption axis direction of the linear polarizer corresponds to the above-mentioned θ1 + θ2. Furthermore, the angle (twist angle) θ3 between the in-plane slow axis of the surface 181b of the third optically anisotropic layer 18b opposite to the fourth optically anisotropic layer 20 side and the in-plane slow axis of the surface 182b of the third optically anisotropic layer 18b facing the fourth optically anisotropic layer 20 is preferably 68 to 88°, more preferably 70 to 86°, in order to further suppress black tinting. As shown in Figure 6, when observed from the side indicated by the white arrow in Figure 4 (when the linear polarizer 12 is observed from the side of the fourth optical anisotropic layer 20), the in-plane slow axis on the surface of the second optical anisotropic layer 16b facing the third optical anisotropic layer 18b is located at a position rotated by a predetermined angle θ3° clockwise based on the in-plane slow axis on the surface of the second optical anisotropic layer 16b facing the third optical anisotropic layer 18b.

[0063] <Third Embodiment> A circular polarizer according to a third embodiment of the present invention comprises a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, and a third optically anisotropic layer, in this order. The first optically anisotropic layer and the second optically anisotropic layer are each independently a layer containing a vertically aligned discotic liquid crystal compound or a layer containing a twisted discotic liquid crystal compound with the thickness direction as the helical axis, and the third optically anisotropic layer is a layer containing a horizontally aligned discotic liquid crystal compound. Hereinafter, the third embodiment of the circular polarizer of the present invention will be described with reference to the drawings. Figure 7 shows a schematic cross-sectional view of the third embodiment of the circular polarizer of the present invention. Figure 8 shows the relationship between the absorption axis direction of the linear polarizer and the in-plane slow axes of the first optically anisotropic layer and the second optically anisotropic layer in the third embodiment of the circular polarizer of the present invention. The third optically anisotropic layer is omitted from Figure 8. FIG. 9 is a diagram showing the relationship between the absorption axis direction of the linear polarizer and the angle between the in-plane slow axes of the first optically anisotropic layer and the second optically anisotropic layer when observed from the white arrow in FIG. 7 .

[0064] (First Optically Anisotropic Layer 16c) The first optically anisotropic layer 16c is a layer disposed between the linear polarizer 12 and the second optically anisotropic layer 18c described below. The first optically anisotropic layer 16c is a layer formed by fixing a vertically aligned discotic liquid crystal compound, or a layer formed by fixing a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis. The following describes the case where the first optically anisotropic layer 16c is a layer formed by fixing a vertically aligned discotic liquid crystal compound. Note that the discotic liquid crystal compound suitable for use in forming the first optically anisotropic layer 16c is not particularly limited, and any known discotic liquid crystal compound can be used. Examples of discotic liquid crystal compounds include those described as discotic liquid crystal compounds that can be used in forming the second optically anisotropic layer 16a.

[0065] The value of the product Δnd of the refractive index anisotropy Δn of the first optically anisotropic layer 16c measured at a wavelength of 550 nm and the thickness d of the first optically anisotropic layer 16c is preferably 138 to 198 nm, and more preferably 148 to 188 nm, in order to further suppress black tinting.

[0066] The thickness of the first optically anisotropic layer 16c is preferably 0.5 to 5 μm.

[0067] As shown in Figure 7, the angle θ1 between the absorption axis direction of the linear polarizer 12 and the in-plane slow axis of the first optically anisotropic layer 16c is preferably 94 to 114°, and more preferably 99 to 109°, in order to further suppress black tinting. Figure 7 will be explained in more detail. The arrows in the first optically anisotropic layer 16c in Figure 7 represent the in-plane slow axes on each surface, and the dashed lines represent the absorption axis direction of the linear polarizer. As shown in Figure 7, the in-plane slow axis of the surface 161c of the first optically anisotropic layer 16c opposite the second optically anisotropic layer 18c side is parallel to the in-plane slow axis of the surface 162c of the first optically anisotropic layer 16c facing the second optically anisotropic layer 18c, and the angle θ1 between both in-plane slow axes and the absorption axis direction of the linear polarizer is 94 to 114°. 8, when observed from the side indicated by the white arrow in Fig. 7 (when the linear polarizer 12 is observed from the side of the third optically anisotropic layer 22), the in-plane slow axis of the first optically anisotropic layer 16c is rotated clockwise by θ1° with respect to the absorption axis direction of the linear polarizer indicated by the dashed line. In other words, the in-plane slow axis of the first optically anisotropic layer 16c is located at a position rotated clockwise by θ1°.

[0068] (Second Optically Anisotropic Layer 18c) The second optically anisotropic layer 18c is a layer disposed between the first optically anisotropic layer 16c and the third optically anisotropic layer 22. The second optically anisotropic layer 18c is a layer formed by fixing a vertically aligned discotic liquid crystal compound, or a layer formed by fixing a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis. The following describes the case where the second optically anisotropic layer 18c is a layer formed by fixing a vertically aligned discotic liquid crystal compound. Note that there are no particular restrictions on the discotic liquid crystal compound that can be suitably used to form the second optically anisotropic layer 18c, and any known discotic liquid crystal compound can be used. Examples of discotic liquid crystal compounds include those described as discotic liquid crystal compounds that can be used to form the second optically anisotropic layer 16a. As shown in FIG. 7, the second optically anisotropic layer 18c is a layer formed by fixing a discotic liquid crystal compound DLC that is twisted and aligned with the thickness direction (z-axis direction in FIG. 7) as the helical axis.

[0069] The value of the product Δnd of the refractive index anisotropy Δn of the second optically anisotropic layer 18c measured at a wavelength of 550 nm and the thickness d of the second optically anisotropic layer 18c is preferably 130 to 190 nm, and more preferably 140 to 180 nm, in order to further suppress black tinting.

[0070] The twist angle of the liquid crystal compound LC (the twist angle of the alignment direction of the liquid crystal compound LC) is preferably 81±10° (within a range of 71 to 91°), and more preferably 81±8° (within a range of 73 to 89°), in that black tinting is further suppressed.

[0071] The thickness of the second optically anisotropic layer 18c is preferably 0.5 to 5 μm.

[0072] The positional relationship of the in-plane slow axis of the second optically anisotropic layer 18c will be described using Figure 8. The arrows in the second optically anisotropic layer 18c in Figure 8 represent the in-plane slow axis on each surface. The in-plane slow axis of the first optically anisotropic layer 16c and the in-plane slow axis on the surface of the second optically anisotropic layer 18c facing the first optically anisotropic layer 16c are parallel. In other words, the angle between the in-plane slow axis on the surface 181c of the second optically anisotropic layer 18c facing the first optically anisotropic layer 16c and the absorption axis direction of the linear polarizer corresponds to the above-mentioned θ1. Furthermore, the in-plane slow axis on the surface 181c of the second optically anisotropic layer 18c facing the first optically anisotropic layer 16c and the in-plane slow axis on the surface 182c of the second optically anisotropic layer 18c opposite the first optically anisotropic layer 16c form the above-mentioned twist angle. 7 (when the linear polarizer 12 is observed from the side indicated by the white arrow in Fig. 7), the in-plane slow axis of the surface 182c of the second optically anisotropic layer 18c opposite to the first optically anisotropic layer 16c side is rotated clockwise by a predetermined angle with respect to the in-plane slow axis of the surface 181c of the second optically anisotropic layer 18c facing the first optically anisotropic layer 16c. That is, as shown in Fig. 9, when observed from the side indicated by the white arrow in Fig. 7 (when the linear polarizer 12 is observed from the side indicated by the third optically anisotropic layer 22 in Fig. 7), the in-plane slow axis of the surface 182c of the second optically anisotropic layer 18c opposite to the first optically anisotropic layer 16c side is located at a position rotated clockwise by a predetermined angle of θ2° with respect to the in-plane slow axis of the first optically anisotropic layer 16c.

[0073] (Third Optically Anisotropic Layer 22) The third optically anisotropic layer 22 is a layer disposed on the surface of the second optically anisotropic layer 18c opposite to the first optically anisotropic layer 16c. The third optically anisotropic layer 22 may be any layer that exhibits predetermined optical properties, and is preferably a layer formed by fixing a horizontally aligned discotic liquid crystal compound. The discotic liquid crystal compound used to form the third optically anisotropic layer 22 is not particularly limited, and any known discotic liquid crystal compound may be used. Examples of discotic liquid crystal compounds include those described as discotic liquid crystal compounds used to form the second optically anisotropic layer 16a. The meaning of the "fixed" state is as described above.

[0074] The retardation value (Rth(550)) in the thickness direction of the third optically anisotropic layer 22 at a wavelength of 550 nm is preferably 30 to 90 nm, more preferably 40 to 80 nm, in order to further suppress black tinting. The in-plane retardation value (Re(550)) of the third optically anisotropic layer 22 at a wavelength of 550 nm is not particularly limited, but is preferably 0 to 20 nm, more preferably 0 to 10 nm.

[0075] The thickness of the third optically anisotropic layer 22 is preferably 0.5 to 5 μm.

[0076] If all layers of the optically anisotropic layer are made of liquid crystal, as in this embodiment, the total film thickness can be made thin, which is preferable from the viewpoints of thin layer weight reduction, curved surface design applications, flexible portion applications, etc. The total film thickness of the optically anisotropic layer is preferably 0.5 to 50 μm, more preferably 1 to 10 μm.

[0077] <Adhesive layer and pressure-sensitive adhesive layer> The circularly polarizing plate may have an adhesive layer or a pressure-sensitive adhesive layer between each layer. Examples of the adhesive layer include known adhesive layers. The adhesive layer is formed, for example, by applying an ultraviolet-curable adhesive to form a coating film and curing it by irradiating it with ultraviolet light. Examples of the pressure-sensitive adhesive layer include known pressure-sensitive adhesive layers.

[0078] As described in JP-A-11-149015, it is generally preferable to adjust the refractive index of each liquid crystal layer forming the laminate from the viewpoint of suppressing reflection. The difference in refractive index from the object to be adhered is preferably 0.1 or less, more preferably 0.08 or less, even more preferably 0.06 or less, and particularly preferably 0.03 or less. The thickness of the adhesive layer or pressure-sensitive adhesive layer is preferably 0.1 to 50 μm. From the viewpoint of thinning, it is more preferably 25 μm or less, even more preferably 15 μm or less, and particularly preferably 5 μm or less. From the viewpoint of suppressing interference unevenness, it is more preferably 5 μm or more, even more preferably 15 μm or more, and particularly preferably 25 μm or more.

[0079] When an adhesive layer or a pressure-sensitive adhesive layer is disposed between the liquid crystal layers, a highly refractive adhesive or pressure-sensitive adhesive may be used. To increase the refractive index, it is also preferable to use a highly refractive monomer or highly refractive metal fine particles. The highly refractive monomer preferably has a benzene ring skeleton in the molecule. Examples of monofunctional monomers having a benzene ring skeleton in the molecule include ethoxylated O-phenylphenol (meth)acrylate, O-phenylphenol glycidyl ether (meth)acrylate, para-cumylphenoxyethylene glycol (meth)acrylate, 2-methacryloyloxyethyl phthalate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, 2-acryloyloxypropyl phthalate, phenoxyethyl (meth)acrylate, EO-modified phenol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, EO-modified nonylphenol (meth)acrylate, PO-modified nonylphenol (meth)acrylate, phenyl glycidyl ether (meth)acrylate, neopentyl glycol benzoate (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, ECH-modified phenoxy (meth)acrylate, benzyl (meth)acrylate, and vinyl carbazole. Examples of highly refractive metal fine particles include inorganic particles. Components constituting inorganic particles include metal oxides, metal nitrides, metal oxynitrides, and simple metals. Metal atoms contained in the metal oxides, metal nitrides, metal oxynitrides, and simple metals include titanium atoms, silicon atoms, aluminum atoms, cobalt atoms, and zirconium atoms. Specific examples of inorganic particles include inorganic oxide particles such as alumina particles, alumina hydrate particles, silica particles, zirconia particles, and clay minerals (e.g., smectite). Zirconium oxide particles are preferred in terms of refractive index. The refractive index can be adjusted to a predetermined value by varying the amount of inorganic particles. The average particle size of the inorganic particles is not particularly limited, but when zirconium oxide is used as the main component, it is preferably 1 to 120 nm, more preferably 1 to 60 nm, and even more preferably 2 to 40 nm.

[0080] The average refractive index of the adhesive layer or pressure-sensitive adhesive layer is preferably 1.50 to 1.64, more preferably 1.52 to 1.64, and even more preferably 1.55 to 1.64.

[0081] <Other Layers> The circular polarizer may have layers other than the linear polarizer, the first optically anisotropic layer, the second optically anisotropic layer, the third optically anisotropic layer, and the fourth optically anisotropic layer. Examples of such layers include an alignment film. The alignment film can be formed by rubbing an organic compound (preferably a polymer), oblique deposition of an inorganic compound, forming a layer with microgrooves, or accumulating an organic compound (e.g., ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearate, etc.) using the Langmuir-Blodgett method (LB film). Furthermore, alignment films that exhibit alignment function upon application of an electric field, a magnetic field, or light irradiation (preferably polarized light) are also known. The alignment film is preferably formed by rubbing a polymer.

[0082] <Method for Manufacturing Circularly Polarizing Plate> The method for manufacturing the circularly polarizing plate described above is not particularly limited, and known methods can be used. In particular, the method for manufacturing the circularly polarizing plate described above can be continuously carried out using a roll-to-roll process. For example, a circularly polarizing plate can be manufactured by preparing first to fourth optically anisotropic layers exhibiting predetermined optical properties, and then bonding these optically anisotropic layers and a linear polarizer in a predetermined order via an adhesive layer (e.g., a pressure-sensitive adhesive layer or an adhesive layer). Alternatively, a circularly polarizing plate can be manufactured by sequentially preparing the second to fourth optically anisotropic layers on a long support, or on the first optically anisotropic layer as a support, using the polymerizable liquid crystal composition described below, and then bonding the layers to a linear polarizer. Alternatively, the method for bonding optically anisotropic layers described above and the method for forming an optically anisotropic layer using a polymerizable liquid crystal composition can be combined.

[0083] The method for producing the second to fourth optically anisotropic layers is not particularly limited, but a method using a composition containing a liquid crystal compound having a polymerizable group (for example, a rod-shaped liquid crystal compound having a polymerizable group and a discotic liquid crystal compound having a polymerizable group) (hereinafter simply referred to as a "polymerizable liquid crystal composition") is preferred. The method using a polymerizable liquid crystal composition will be described in detail below.

[0084] The polymerizable liquid crystal composition contains a liquid crystal compound having a polymerizable group. Examples of the liquid crystal compound include discotic liquid crystal compounds, as described above. The polymerizable liquid crystal composition may contain other components in addition to the liquid crystal compound having a polymerizable group. Examples of such other components include a polymerization initiator. The polymerization initiator used is selected depending on the type of polymerization reaction, and examples include a thermal polymerization initiator and a photopolymerization initiator. The content of the polymerization initiator in the polymerizable liquid crystal composition is preferably 0.01 to 20% by mass, and more preferably 0.5 to 10% by mass, based on the total solid content of the composition. The solid content refers to components capable of forming an optically anisotropic layer after removing the solvent, and is considered to be solid content even if the component is in a liquid state.

[0085] The polymerizable liquid crystal composition may contain a polymerizable monomer other than the liquid crystal compound having a polymerizable group. Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds, and polyfunctional radically polymerizable monomers are preferred. The content of the polymerizable monomer in the polymerizable liquid crystal composition is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total mass of the liquid crystal compound.

[0086] Other components that may be included in the polymerizable liquid crystal composition include, in addition to the above, alignment control agents (vertical alignment agents, horizontal alignment agents), surfactants, adhesion improvers, plasticizers, and solvents. To achieve helical alignment of the liquid crystal compound, the polymerizable liquid crystal composition preferably contains a chiral agent. The chiral agent is added to achieve helical alignment of the liquid crystal compound. However, of course, if the liquid crystal compound is an optically active compound, such as one having an asymmetric carbon atom in the molecule, the addition of a chiral agent is not necessary. Furthermore, depending on the manufacturing method and twist angle, the addition of a chiral agent may not be necessary. There are no particular limitations on the structure of the chiral agent, as long as it is compatible with the liquid crystal compound used in combination. Any known chiral agent (e.g., as described in "Liquid Crystal Device Handbook," edited by Committee 142 of the Japan Society for the Promotion of Science, Chapter 3, Section 4-3, "Chiral Agents for TN and STN," p. 199, 1989) can be used. In particular, in the first and second embodiments described above, it is preferable that both the second and third optically anisotropic layers contain two or more chiral agents, and it is more preferable that at least one of the chiral agents is a photosensitive chiral agent whose helical twisting power changes upon irradiation with light, and it is even more preferable that at least one of the chiral agents is a chiral agent having a photoisomerizable double bond and a binaphthyl moiety. The amount of the chiral agent used is not particularly limited, and is adjusted so as to achieve the above-mentioned twist angle.

[0087] Examples of methods for producing an optically anisotropic layer include a method of applying a polymerizable liquid crystal composition to form a coating film, subjecting the coating film to an alignment treatment to align the polymerizable liquid crystal compound, and then subjecting the coating film to a curing treatment. The object onto which the polymerizable liquid crystal composition is applied is not particularly limited, and examples include the above-mentioned long support and the first to third optically anisotropic layers. The object onto which the polymerizable liquid crystal composition is applied may be subjected to a rubbing treatment in order to orient the in-plane slow axis of the optically anisotropic layer to a predetermined direction. For example, a long support that has been subjected to a rubbing treatment may be used.

[0088] Examples of the method for applying the polymerizable liquid crystal composition include curtain coating, dip coating, spin coating, print coating, spray coating, slot coating, roll coating, slide coating, blade coating, gravure coating, and wire bar coating.

[0089] Next, the formed coating film is subjected to an alignment treatment to align the polymerizable liquid crystal compound in the coating film. The alignment treatment can be performed by drying the coating film at room temperature or by heating the coating film. In the case of a thermotropic liquid crystal compound, the liquid crystal phase formed by the alignment treatment can generally be transitioned by changes in temperature or pressure. In the case of a lyotropic liquid crystal compound, the transition can also be achieved by changing the composition ratio, such as the amount of solvent. The conditions for heating the coating film are not particularly limited, but the heating temperature is preferably 50 to 250°C, more preferably 50 to 150°C, and the heating time is preferably 10 seconds to 10 minutes. After heating the coating film, the coating film may be cooled, if necessary, before the curing treatment (light irradiation treatment) described below. The cooling temperature is preferably 20 to 200°C, more preferably 30 to 150°C.

[0090] Next, the coating film in which the polymerizable liquid crystal compound has been aligned is subjected to a curing treatment. The method of curing the coating film in which the polymerizable liquid crystal compound has been aligned is not particularly limited, and examples thereof include light irradiation treatment and heat treatment. Among these, from the viewpoint of manufacturability, light irradiation treatment is preferred, and ultraviolet irradiation treatment is more preferred. The irradiation conditions for the light irradiation treatment are not particularly limited, but are preferably 50 to 1000 mJ / cm. ２ The atmosphere during the light irradiation treatment is not particularly limited, but a nitrogen atmosphere is preferred.

[0091] In the method for producing a circularly polarizing plate, when producing the second optically anisotropic layer and the third optically anisotropic layer on the long support or the first optically anisotropic layer, it is preferable to carry out the following steps 1 to 5. By carrying out the following steps 1 to 5, a laminate of the second optically anisotropic layer and the third optically anisotropic layer can be produced in a single coating step. Step 1: A step of applying a polymerizable liquid crystal composition containing a chiral agent including at least a photosensitive chiral agent whose helical twisting power is changed by irradiation with light, and a discotic liquid crystal compound having a polymerizable group (hereinafter, in the explanation of Steps 1 to 5, this will also be simply referred to as a "liquid crystal compound") onto a long support or a first optically anisotropic layer to form a composition layer. Step 2: A step of subjecting the composition layer to a heat treatment to align the liquid crystal compound in the composition layer. Step 3: After Step 2, a step of irradiating the composition layer with light under conditions of an oxygen concentration of 1% by volume or more. Step 4: After Step 3, a step of subjecting the composition layer to a heat treatment. Step 5: After Step 4, a step of subjecting the composition layer to a curing treatment to fix the alignment state of the liquid crystal compound, thereby forming a second optically anisotropic layer and a third optically anisotropic layer. The procedures of each of the above steps are described in detail below.

[0092] (Step 1) Step 1 is a step of forming a composition layer by applying a polymerizable liquid crystal composition containing a chiral agent including at least a photosensitive chiral agent whose helical twisting power changes upon light irradiation, and a liquid crystal compound having a polymerizable group, onto a long support. By carrying out this step, a composition layer is formed that is subjected to the light irradiation treatment described below. The various components contained in the polymerizable liquid crystal composition are as described above, and the photosensitive chiral agent not described above will be described in detail below. The helical twisting power (HTP) of a chiral agent is a factor that indicates the helical alignment ability, expressed by the following formula (X): Formula (X) HTP=1 / (helical pitch length (unit: μm) × concentration of chiral agent relative to liquid crystal compound (mass %)) [μm －１ The helical pitch length refers to the length of the pitch P (=helical period) of the helical structure of a cholesteric liquid crystal phase, and can be measured by the method described on page 196 of Liquid Crystal Handbook (published by Maruzen Co., Ltd.).

[0093] A photosensitive chiral agent whose helical twisting power changes upon irradiation with light (hereinafter also simply referred to as "chiral agent A") may be liquid crystalline or non-liquid crystalline. Chiral agent A generally contains an asymmetric carbon atom. Note that chiral agent A may be an axially asymmetric compound or a planar asymmetric compound that does not contain an asymmetric carbon atom. Chiral agent A may have a polymerizable group.

[0094] Chiral agent A may be a chiral agent whose helical twisting power increases or decreases upon light irradiation. In this specification, "increase or decrease in helical twisting power" refers to an increase or decrease when the initial helical direction of chiral agent A (before light irradiation) is defined as "positive." Therefore, even when the helical twisting power continues to decrease upon light irradiation and exceeds 0, the helical direction becomes "negative" (i.e., when a helical twist is induced in the opposite helical direction to the initial helical direction (before light irradiation)), this also falls under the category of "a chiral agent whose helical twisting power decreases."

[0095] Examples of the chiral agent A include so-called photoreactive chiral agents. The photoreactive chiral agent has a chiral moiety and a photoreactive moiety that undergoes a structural change upon irradiation with light, and is, for example, a compound that significantly changes the twisting power of a liquid crystal compound depending on the amount of irradiation. Among them, the chiral agent A is preferably a compound having at least a photoisomerizable moiety, and it is more preferable that the photoisomerizable moiety has a photoisomerizable double bond. As the photoisomerizable moiety having the photoisomerizable double bond, a cinnamoyl moiety, a chalcone moiety, an azobenzene moiety, or a stilbene moiety is preferred in that photoisomerization is likely to occur and there is a large difference in helical twisting power before and after light irradiation, and a cinnamoyl moiety, a chalcone moiety, or a stilbene moiety is more preferred in that there is little visible light absorption. The photoisomerizable moiety corresponds to the photoreactive moiety that undergoes a structural change upon irradiation with light described above.

[0096] In step 1, at least the chiral agent A described above is used. Step 1 may be an embodiment in which two or more chiral agents A are used, or an embodiment in which at least one chiral agent A and at least one chiral agent whose helical twisting power does not change upon irradiation with light (hereinafter simply referred to as "chiral agent B") are used. Chiral agent B may be liquid crystalline or non-liquid crystalline. Chiral agent B generally contains an asymmetric carbon atom. Note that chiral agent B may be an axially asymmetric compound or a planar asymmetric compound that does not contain an asymmetric carbon atom. Chiral agent B may have a polymerizable group. Known chiral agents can be used as chiral agent B. Chiral agent B is preferably a chiral agent that induces a helix in the opposite direction to that of chiral agent A described above. That is, for example, if the helix induced by chiral agent A is right-handed, the helix induced by chiral agent B will be left-handed.

[0097] The content of the chiral agent A in the composition layer is not particularly limited, but is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less, relative to the total mass of the liquid crystal compound, in order to facilitate uniform alignment of the liquid crystal compound. The lower limit is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.05% by mass or more. The chiral agent A may be used alone or in combination of two or more. When two or more types of the chiral agent A are used in combination, it is preferable that the total content is within the above range.

[0098] The content of the chiral agent B in the composition layer is not particularly limited, but is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less, relative to the total mass of the liquid crystal compound, in order to facilitate uniform alignment of the liquid crystal compound. The lower limit is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.05% by mass or more. The chiral agent B may be used alone or in combination of two or more. When two or more types of the chiral agent B are used in combination, it is preferable that the total content is within the above range.

[0099] The total content of the chiral dopant in the composition layer (total content of all chiral dopants) is preferably 5.0% by mass or less, more preferably 4.0% by mass or less, and even more preferably 2.0% by mass or less, relative to the total mass of the liquid crystal compound. Although the lower limit is not particularly limited, it is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.05% by mass or more.

[0100] The method for forming a composition layer by applying the polymerizable liquid crystal composition is not particularly limited, and examples thereof include the above-mentioned methods for applying the polymerizable liquid crystal composition.

[0101] The thickness of the composition layer is not particularly limited, but is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and even more preferably 0.5 to 10 μm.

[0102] (Step 2) Step 2 is a step of subjecting the composition layer to a heat treatment to align the liquid crystal compound in the composition layer. By carrying out this step, the liquid crystal compound in the composition layer is brought into a predetermined alignment state. Optimal conditions for the heat treatment are selected depending on the liquid crystal compound used. In particular, the heating temperature is often 10 to 250°C, more often 40 to 150°C, and even more often 50 to 130°C. The heating time is often 0.1 to 60 minutes, and more often 0.2 to 5 minutes.

[0103] The absolute value of the weighted average helical twisting power of the chiral agent in the composition layer formed by step 1 is 0.0 to 1.9 μm -1 It is preferable that the thickness is 0.0 to 1.5 μm. -1 More preferably, it is 0.0 to 1.0 μm -1 More preferably, it is 0.0 to 0.5 μm -1 is particularly preferred, with zero being most preferred.

[0104] The weighted average helical twisting power of a chiral agent refers to the sum of the values ​​obtained by dividing the product of the helical twisting power of each chiral agent contained in the composition layer and the concentration (% by mass) of each chiral agent in the composition layer by the total concentration (% by mass) of the chiral agents in the composition layer when two or more types of chiral agents are contained in the composition layer. For example, when two types of chiral agents (chiral agent X and chiral agent Y) are used in combination, the weighted average helical twisting power is expressed by the following formula (Y): Formula (Y) Weighted average helical twisting power (μm －１ ) = (helix-inducing power of chiral agent X (μm －１ ) × concentration of chiral dopant X in the composition layer (% by mass) + helical twisting power of chiral dopant Y (μm －１ ) × concentration of chiral agent Y in composition layer (mass %)) / (concentration of chiral agent X in composition layer (mass %) + concentration of chiral agent Y in composition layer (mass %)) However, in the above formula (Y), when the helical direction of the chiral agent is right-handed, the helical induction power is a positive value. On the other hand, when the helical direction of the chiral agent is left-handed, the helical induction power is a negative value. That is, for example, when the helical induction power is 10 μm －１ In the case of the chiral agent, when the helical direction of the helix induced by the chiral agent is right-handed, the helix-inducing force is 10 μm －１ On the other hand, when the helical direction of the helix induced by the chiral agent is left-handed, the helical induction force is −10 μm －１ It is expressed as:

[0105] When the absolute value of the weighted average helical twisting power of the chiral dopant in the composition layer formed in step 1 is 0, a composition layer 24 in which the discotic liquid crystal compound DLC is vertically aligned is formed on the long support or the first optically anisotropic layer 14, as shown in Fig. 10. Fig. 10 is a schematic diagram of the cross section of the first optically anisotropic layer 14 and the composition layer 24. Note that the composition layer 24 shown in Fig. 10 contains chiral dopant A and chiral dopant B at the same concentration, and the helical direction induced by chiral dopant A is left-handed, and the helical direction induced by chiral dopant B is right-handed. Furthermore, the absolute value of the helical twisting power of chiral dopant A and the absolute value of the helical twisting power of chiral dopant B are assumed to be the same.

[0106] (Step 3) Step 3 is a step of irradiating the composition layer with light in the presence of oxygen after Step 2. The mechanism of this step will be explained below with reference to the drawings. As shown in FIG. 11 , in Step 2 described above, light is irradiated from the direction opposite the composition layer 20 side of the long support or the first optically anisotropic layer 14 (the direction indicated by the white arrow in FIG. 11 ) under conditions of an oxygen concentration of 1% by volume or more. Although light irradiation is performed from the first optically anisotropic layer 14 side in FIG. 11 , it may also be performed from the composition layer 24 side. Comparing the lower region 24A on the first optically anisotropic layer 14 side of the composition layer 24 with the upper region 24B on the opposite side from the first optically anisotropic layer 14 side, the surface of the upper region 24B is closer to the air, so the oxygen concentration in the upper region 24B is higher and the oxygen concentration in the lower region 24A is lower. Therefore, when the composition layer 24 is irradiated with light, polymerization of the liquid crystal compound in the lower region 24A proceeds easily, and the orientation of the liquid crystal compound is fixed. Furthermore, since the chiral agent A is also present in the lower region 24A, the chiral agent A is also photosensitive, and the helical twisting force changes. However, since the orientation of the liquid crystal compound is fixed in the lower region 24A, even when the irradiated composition layer is subjected to a heat treatment (step 4, described below), the orientation of the liquid crystal compound does not change. Furthermore, since the oxygen concentration is high in the upper region 24B, even when the composition layer is irradiated with light, polymerization of the liquid crystal compound is inhibited by oxygen, and polymerization does not proceed easily. Furthermore, since the chiral agent A is also present in the upper region 24B, the chiral agent A is photosensitive, and the helical twisting force changes. Therefore, when the heat treatment (step 4, described below) is performed, the orientation of the liquid crystal compound changes in accordance with the changed helical twisting force.

[0107] That is, by carrying out step 3, the alignment state of the liquid crystal compound is easily fixed in the region of the composition layer on the substrate side (lower region), whereas the alignment state of the liquid crystal compound is less likely to be solidified in the region of the composition layer opposite the substrate side (upper region), resulting in a state in which the helical twisting power changes depending on the photoexposed chiral dopant A.

[0108] Step 3 is carried out under conditions of an oxygen concentration of 1% by volume or more. In particular, the oxygen concentration is preferably 2% by volume or more, and more preferably 5% by volume or more, in order to easily form regions in which the liquid crystal compound has a different alignment state in the optically anisotropic layer. The upper limit is not particularly limited, but may be 100% by volume.

[0109] The irradiation intensity of the light irradiation in step 3 is not particularly limited and can be appropriately determined based on the helical twisting power of the chiral agent A. The irradiation amount of the light irradiation in step 3 is not particularly limited, but from the viewpoint of facilitating the formation of a predetermined optically anisotropic layer, it is preferable to use a light irradiation amount of 300 mJ / cm. ２ Preferably, 200 mJ / cm or less ２ The lower limit is 5 mJ / cm because a predetermined optically anisotropic layer is easily formed. ２ More than 10 mJ / cm is preferable. ２ The above is more preferable. The light irradiation in step 3 is preferably carried out at a temperature of 15 to 70°C (preferably 15 to 50°C).

[0110] The light used for photoirradiation may be any light to which the chiral agent A is photosensitive. In other words, the light used for photoirradiation is not particularly limited as long as it is actinic ray or radiation that changes the helical twisting power of the chiral agent A. Examples include the bright line spectrum of a mercury lamp, far ultraviolet light typified by an excimer laser, extreme ultraviolet light, X-rays, ultraviolet light, and electron beams. Of these, ultraviolet light is preferred.

[0111] (Step 4) Step 4 is a step of subjecting the composition layer to a heat treatment after step 3. By carrying out this step, the alignment state of the liquid crystal compound changes in the region in the composition layer where the helical twisting power of the chiral dopant A has changed due to the light irradiation. The mechanism of this step is explained below with reference to the drawings.

[0112] As described above, when step 3 is performed on the composition layer 22 shown in FIG. 10 , the orientation state of the liquid crystal compound is fixed in the lower region 24A, whereas polymerization of the liquid crystal compound is difficult to proceed in the upper region 24B, and the orientation state of the liquid crystal compound is not fixed. Furthermore, the helical twisting force of chiral agent A changes in the upper region 24B. When this change in the helical twisting force of chiral agent A occurs, the force twisting the liquid crystal compound in the upper region 24B changes compared to the state before light irradiation. This point will be explained in more detail. As described above, the composition layer 24 shown in FIG. 10 contains chiral agents A and B at the same concentrations, and the helical direction induced by chiral agent A is left-handed, while the helical direction induced by chiral agent B is right-handed. Furthermore, the absolute value of the helical twisting force of chiral agent A is the same as the absolute value of the helical twisting force of chiral agent B. Therefore, the weighted average helical twisting power of the chiral agent in the composition layer before light irradiation is 0. The above embodiment is shown in FIG. 12. In FIG. 12, the vertical axis represents the helical twisting power of the chiral agent (μm －１ The horizontal axis represents "light irradiation dose (mJ / cm) × concentration of chiral agent (mass%)", and the further this value is from zero, the stronger the helical twisting power. ２ First, the relationship between the chiral agent A and the chiral agent B in the composition layer before light irradiation corresponds to the point when the amount of light irradiation is 0, and the "helix twisting power of the chiral agent A (μm －１ ) × concentration (mass%) of chiral agent A and the absolute value of "helix-inducing power of chiral agent B (μm －１) × concentration (mass %) of chiral dopant B is equal to the absolute value of "helical twisting force of chiral dopant A, which induces left-handed helicity, and the helical twisting force of chiral dopant B, which induces right-handed helicity, cancel each other out. When light is irradiated to upper region 24B in this state and the helical twisting force of chiral dopant A increases with the amount of light irradiation as shown in FIG. 12, the weighted average helical twisting force of the chiral dopant in upper region 24B increases, and the left-handed helical twisting force becomes stronger, as shown in FIG. 13. In other words, the helical twisting force of the liquid crystal compound increases in the direction (-) of the helical twist induced by chiral dopant A as the irradiation dose increases. Therefore, when the composition layer 24 after step 3, in which such a change in weighted average helical twisting force has occurred, is subjected to a heat treatment to promote reorientation of the liquid crystal compound, as shown in FIG. 14 , in the upper region 24B, the liquid crystal compound DLC is twisted and aligned along the helical axis extending along the thickness direction of the composition layer 24. On the other hand, as described above, in the lower region 24A of the composition layer 24, the orientation state of the liquid crystal compound is fixed due to the progress of polymerization of the liquid crystal compound during step 3, so reorientation of the liquid crystal compound does not proceed. As described above, by performing step 4, multiple regions with different orientation states of the liquid crystal compound are formed along the thickness direction of the composition layer. The degree of twist of the liquid crystal compound DLC can be appropriately adjusted by the type of chiral dopant A used, the exposure dose in step 3, etc., and the twist angle of the third optically anisotropic layer described below can be achieved.

[0113] 12 and 13, an embodiment using a chiral agent whose helical twisting power increases upon light irradiation as chiral agent A has been described, but the present invention is not limited to this embodiment. For example, a chiral agent whose helical twisting power decreases upon light irradiation may be used as chiral agent A. In this case, the helical twisting power induced by chiral agent B increases upon light irradiation, resulting in a helical alignment of the liquid crystal compound in the direction of the rotation induced by chiral agent B. Furthermore, while an embodiment using both chiral agent A and chiral agent B has been described in FIGS. 12 and 13, the present invention is not limited to this embodiment. For example, an embodiment using two types of chiral agents A may be used. Specifically, an embodiment using both chiral agent A1 that induces left-handedness and chiral agent A2 that induces right-handedness may be used in combination. Chiral agents A1 and A2 may each independently be chiral agents whose helical twisting power increases or chiral agents whose helical twisting power decreases. For example, a chiral agent that induces left-handed helical twisting and whose helical twisting power increases upon irradiation with light may be used in combination with a chiral agent that induces right-handed helical twisting and whose helical twisting power decreases upon irradiation with light.

[0114] The optimum conditions for the heat treatment are selected depending on the liquid crystal compound used. In particular, the heating temperature is preferably the temperature at which the liquid crystal compound is heated from the state in step 3, and is often 35 to 250°C, more often 50 to 150°C, even more often more than 50°C and 150°C or less, and particularly often 60 to 130°C. The heating time is often 0.01 to 60 minutes, more often 0.03 to 5 minutes.

[0115] The absolute value of the weighted average helical twisting power of the chiral agent in the composition layer after light irradiation is not particularly limited, but the absolute value of the difference between the weighted average helical twisting power of the chiral agent in the composition layer after light irradiation and the weighted average helical twisting power before light irradiation is 0.05 μm. －１ More than this is preferred, and 0.05 to 10.0 μm －１ More preferably, 0.1 to 10.0 μm －１ is more preferable.

[0116] (Step 5) In step 5, the composition layer is subjected to a curing treatment after step 4 to fix the alignment state of the liquid crystal compound and form the second optically anisotropic layer and the third optically anisotropic layer. By carrying out this step, the alignment state of the liquid crystal compound in the composition layer is fixed, and as a result, a predetermined optically anisotropic layer is formed.

[0117] The curing method is not particularly limited, and examples thereof include photocuring and heat curing. Of these, photoirradiation is preferred, and ultraviolet irradiation is more preferred. For ultraviolet irradiation, a light source such as an ultraviolet lamp is used. The irradiation dose of light (e.g., ultraviolet) is not particularly limited, but is generally 100 to 800 mJ / cm. ２ The degree is preferable.

[0118] <Organic EL Display Device> The organic EL display device of the present invention has the above-described circular polarizer of the present invention. Typically, the circular polarizer is provided on an organic EL display panel of the organic EL display device. That is, the organic EL display device of the present invention has an organic EL display panel and the above-described circular polarizer of the present invention. As an example of an organic EL display device, as shown in FIG. 15 , an organic EL display device 100 has an organic EL display panel 26 and a circular polarizer 10a. As shown in FIG. 15 , a linear polarizer 12 is arranged on the outermost side.

[0119] The organic EL display panel 26 is a member in which a light-emitting layer or a plurality of organic compound thin films including a light-emitting layer are formed between a pair of electrodes, an anode and a cathode, and may have a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, a protective layer, etc. in addition to the light-emitting layer, and each of these layers may have other functions. Various materials can be used to form each layer.

[0120] Furthermore, it was revealed that the tint of black when viewed from an oblique direction differs depending on whether or not the organic EL display panel 26 has a hollow structure between the electrode and the circular polarizer. Examples of panels having a hollow structure include those using sealing glass, specifically SAMSUNG's GALAXY SII and GALAXY S4. Examples of panels without a hollow structure include those using thin film sealing, specifically SAMSUNG's GALAXY S8+, Apple's iPhone (registered trademark) X, and Huawei's P40 Pro. The circular polarizer of the present invention further suppresses the tint of black, particularly in panels without a hollow structure.

[0121] The present invention will be specifically described below based on examples. The materials, reagents, amounts and proportions of substances, procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the present invention is not limited to or by the following examples.

[0122] [Example 1] <Preparation of First Optically Anisotropic Layer> The following composition was placed in a mixing tank, stirred, and further heated at 90°C for 10 minutes. Thereafter, the obtained composition was filtered through filter paper with an average pore size of 34 µm and a sintered metal filter with an average pore size of 10 µm to prepare cellulose acylate solution 1. The solid concentration of solution 1 was 23.5 mass%, the amount of plasticizer added was the ratio relative to cellulose acylate, and the solvent of the dope was methylene chloride / methanol / butanol = 81 / 18 / 1 (mass ratio).

[0123] -------------------------------------------------- Cellulose acylate solution 1 -------------------------------------------------- Cellulose acylate (degree of acetyl substitution 2.86, viscosity average degree of polymerization 310) 100 parts by mass Sugar ester compound 1 (shown in chemical formula (S4)) 6.0 parts by mass Sugar ester compound 2 (shown in chemical formula (S5)) 2.0 parts by mass Silica particle dispersion (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 0.1 part by mass Solvent (methylene chloride / methanol / butanol) --------------------------------------------------

[0124]

[0125]

[0126] The solution 1 prepared above was cast using a drum film-forming machine. The solution was cast from a die onto a metal support cooled to 0°C, and the resulting web (film) was then peeled off. The drum was made of SUS (Steel Use Stainless Steel).

[0127] The web (film) obtained by casting was peeled from the drum and dried for 20 minutes in a tenter apparatus, which clipped both ends of the web with clips while transporting the film at 30 to 40°C. The web was then post-dried by zone heating while being transported by rolls. The resulting web was knurled and then wound up. The resulting cellulose acylate film (first optically anisotropic layer) had a thickness of 40 μm, an in-plane retardation Re(550) of 0 nm at a wavelength of 550 nm, and a thickness-direction retardation Rth(550) of 26 nm. The resulting cellulose acylate film (first optically anisotropic layer) also satisfied the above-mentioned formula (1), "nx = ny > nz."

[0128] <One-Side Saponification Treatment> The cellulose acylate film was passed through a dielectric heating roll at a temperature of 60°C to raise the film surface temperature to 40°C, and then an alkaline solution having the composition shown below was applied to the band surface of the film using a bar coater in an amount of 14 ml / m. ２ The coated film was then transported for 10 seconds under a steam-type far-infrared heater manufactured by Noritake Co., Ltd. that had been heated to 110° C. Subsequently, pure water was applied at a rate of 3 ml / m using the same bar coater. ２ Next, the film was washed with water using a fountain coater and then dried with an air knife three times, and then transported to a drying zone at 70° C. for 10 seconds to prepare a cellulose acylate film that had been saponified on one side.

[0129] ------------------------------------------------------------------- Alkaline solution --------------------------------------------------- Potassium hydroxide 4.7 parts by mass Water 15.8 parts by mass Isopropanol 63.7 parts by mass Surfactant SF-1:C １４ H ２９ O (CH ２ CH ２ O) ２０ H 1.0 mass part Propylene glycol 14.8 mass parts

[0130] <Formation of alignment film> A composition (A) for forming an alignment film having the following composition was continuously applied to the alkali saponified surface of the cellulose acylate film using a #9 wire bar, and the coating was dried with hot air at 60° C. for 60 seconds and then with hot air at 100° C. for 120 seconds. The thickness of the alignment film was 0.3 μm.

[0131] ------------------------------------------------------------------ Composition (A) for forming alignment film ------------------------------------------------------------------ Modified polyvinyl alcohol P1 (described below) 100 parts by mass Photopolymerization initiator (described below) 12.5 parts by mass Water 3286 parts by mass Methanol 1171 parts by mass

[0132] Modified polyvinyl alcohol P1 (in the formula below, the numerical value for each repeating unit represents the content (mol %) of each repeating unit relative to all repeating units.)

[0133] Photopolymerization initiator

[0134] <Formation of Second Optically Anisotropic Layer and Third Optically Anisotropic Layer> The alignment film prepared above was continuously subjected to a rubbing treatment. At this time, the longitudinal direction of the long film was parallel to the conveying direction, and the angle between the longitudinal direction of the film (conveying direction) and the rotation axis of the rubbing roller was 76°. The longitudinal direction of the film (conveying direction) was set to 90°, and when observed from the film side, the width direction of the film was set as the reference (0°) and clockwise directions were expressed as positive values. The rotation axis of the rubbing roller was at an angle of -14°. In other words, the position of the rotation axis of the rubbing roller was a position rotated 76° clockwise from the longitudinal direction of the film. Using the rubbed cellulose acylate film as a substrate, a composition (1) for forming an optically anisotropic layer containing a discotic liquid crystal compound having the following composition was applied using a Giesser coater to form a composition layer. The absolute value of the weighted average helical twisting power of the chiral agent in the composition layer was 0.0 μm. －１Next, the obtained composition layer was heated at 95°C for 80 seconds. This heating caused the discotic liquid crystal compound in the composition layer to be aligned in a predetermined direction. Thereafter, the composition layer was irradiated with ultraviolet light (irradiation dose: 14 mJ / cm) using a 365 nm LED (Light Emitting Diode) lamp (manufactured by Acroedge Co., Ltd.) at 40°C in oxygen-containing air (oxygen concentration: approximately 20% by volume). ２ Subsequently, the obtained composition layer was heated at 95°C for 40 seconds. After that, nitrogen purging was performed to adjust the oxygen concentration to 100 ppm by volume, and the composition layer was irradiated with ultraviolet light (irradiation dose: 200 mJ / cm) using a metal halide lamp (manufactured by Eye Graphics Co., Ltd.) at 75°C. ２ ), an optically anisotropic layer in which the alignment state of the liquid crystal compound was fixed was formed as the liquid crystal cured layer, and a laminate [layer structure: cellulose acylate film (resin film) / alignment film / liquid crystal cured layer] was produced. The laminate produced by the above procedure was cut parallel to the rubbing direction, and the liquid crystal cured layer was observed from the cross-sectional direction using a polarizing microscope. The liquid crystal cured layer had a thickness of 2.7 μm, and a 1.4 μm-thick region (second optically anisotropic layer) on the cellulose acylate film (resin film) side of the liquid crystal cured layer was homogeneously aligned with no twist angle, while a 1.3 μm-thick region (third optically anisotropic layer) on the opposite side of the optically anisotropic layer from the cellulose acylate film (resin film) showed a twisted alignment of the liquid crystal compound. Furthermore, the second optically anisotropic layer satisfied the above formula (2), "nz = nx > ny." The optical properties of the laminate were determined using Axometrics' AxoScan and its analysis software (Multi-Layer Analysis). The product (Δn2d2) of the in-plane refractive index anisotropy Δn2 and thickness d2 at a wavelength of 550 nm of the second optically anisotropic layer was 168 nm, the twist angle of the liquid crystal compound was 0 °, and the alignment axis angle of the liquid crystal compound relative to the long length direction was -104 ° on the substrate side and -104 ° on the side in contact with the third optically anisotropic layer. The product (Δn1d1) of the in-plane refractive index anisotropy Δn1 and thickness d1 at a wavelength of 550 nm of the third optically anisotropic layer was 160 nm, the twist angle of the liquid crystal compound was 81 °, and the alignment axis angle of the liquid crystal compound relative to the long length direction was -104 ° on the side in contact with the second optically anisotropic layer and -185 ° on the air side.

[0135] Optically anisotropic layer forming composition (1) ------------------------------------------------ 80 parts by mass of discotic liquid crystal compound 1 described below 20 parts by mass of discotic liquid crystal compound 2 described below 1 part by mass of alignment film interface aligning agent described below 0.1 part by mass of alignment film interface adhesion agent described below 1.06 parts by mass of left-handed twisted chiral agent described below 0.1 part by mass of right-handed twisted chiral agent described below 0.18 parts by mass of leveling agent B-1 described below 5 parts by mass of modified trimethylolpropane triacrylate described below 2 parts by mass of photopolymerization initiator (Irgacure 819, manufactured by BASF) 2 parts by mass of defoaming agent described below 105 parts by mass of methyl ethyl ketone

[0136] Discotic liquid crystal compound 1

[0137] Discotic liquid crystal compound 2

[0138] Alignment film interface alignment agent

[0139] Alignment film interface adhesive

[0140] Left-twisted chiral agent (in the formula below, Me represents a methyl group)

[0141] Right-twisted chiral agent

[0142] Leveling agent B-1 (weight average molecular weight: 16,000; in the formula below, the numerical value for each repeating unit represents the content (mass%) of each repeating unit relative to all repeating units.)

[0143] Modified trimethylolpropane triacrylate

[0144] Antifoaming agents

[0145] <Formation of Fourth Optically Anisotropic Layer> The following components were charged into a mixing tank and stirred under heating to prepare a cellulose acylate solution 2.

[0146] ──────────────────────────────────── Cellulose acylate solution 2 ────────────────────────────────── Cellulose acylate with an acetylation degree of 60.7 to 61.1% 100 parts by mass Triphenyl phosphate (plasticizer) 7.8 parts by mass Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass Methylene chloride (first solvent) 336 parts by mass Methanol (second solvent) 29 parts by mass 1-butanol (third solvent) 11 parts by mass ────────────────────────────────

[0147] In another mixing tank, the following retardation increasing agent (16 parts by mass), methylene chloride (92 parts by mass), and methanol (8 parts by mass) were charged and stirred under heating to prepare a retardation increasing agent solution. Cellulose acylate solution 2 (474 ​​parts by mass) was mixed with the retardation increasing agent solution (25 parts by mass), and the mixture was stirred thoroughly to prepare a dope. The amount of the retardation increasing agent added was 6.0 parts by mass relative to 100 parts by mass of cellulose acylate.

[0148] Retardation increasing agent

[0149] The obtained solution was cast using a band stretching machine. After the film surface temperature on the band reached 40°C, the film was peeled off from the band and dried with hot air at 70°C for 1 minute, and then dried with dry air at 140°C for 10 minutes. The obtained cellulose acylate film (fourth optically anisotropic layer) had a thickness of 60 μm, an in-plane retardation Re(550) of 0 nm at a wavelength of 550 nm, and a thickness direction retardation Rth(550) of 60 nm. The obtained cellulose acylate film (fourth optically anisotropic layer) also satisfied the above-mentioned formula (1), "nx = ny > nz."

[0150] <Preparation of Polarizer> A polyvinyl alcohol (PVA) film having a thickness of 80 μm was dyed by immersing it in an aqueous iodine solution having an iodine concentration of 0.05% by mass for 60 seconds at 30° C. Next, the obtained film was immersed in an aqueous boric acid solution having a boric acid concentration of 4% by mass for 60 seconds, while being longitudinally stretched to 5 times its original length, and then dried at 50° C. for 4 minutes to obtain a polarizer having a thickness of 20 μm.

[0151] <Preparation of Polarizer Protective Film> A commercially available cellulose acylate film, Fujitac TG40UL (manufactured by Fujifilm Corporation), was prepared and immersed in a 1.5 mol / L aqueous sodium hydroxide solution at 55°C, followed by thorough rinsing with water to remove the sodium hydroxide. The resulting film was then immersed in a 0.005 mol / L dilute sulfuric acid solution at 35°C for 1 minute, and then immersed in water to thoroughly rinse off the dilute sulfuric acid solution. Finally, the resulting film was thoroughly dried at 120°C to prepare a polarizer protective film having a saponified surface.

[0152] <Preparation of Circular Polarizing Plate> In the same manner as in the preparation of the polarizer protective film described above, the prepared optical film (first, second, and third optically anisotropic layers) was saponified, and the above-described polarizer and the above-described polarizer protective film were successively bonded to the surface of the first optically anisotropic layer using a polyvinyl alcohol-based adhesive. Furthermore, a fourth optically anisotropic layer was bonded to the surface side of the third optically anisotropic layer using a pressure-sensitive adhesive, thereby preparing a long circular polarizing plate (P-1). That is, the circular polarizing plate (P-1) had a polarizer protective film, a polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer, in this order. The absorption axis of the polarizer coincided with the longitudinal direction of the circular polarizer, the rotation angle of the in-plane slow axis of the second optically anisotropic layer with respect to the absorption axis of the polarizer was 104°, and the rotation angle of the in-plane slow axis of the surface of the third optically anisotropic layer opposite the second optically anisotropic layer with respect to the absorption axis of the polarizer was 185°. The rotation angle of the in-plane slow axis is expressed as an angle value that is positive in the counterclockwise direction and negative in the clockwise direction when observing the optically anisotropic layer from the polarizer side, with the longitudinal direction of the substrate being set as 0° as the reference.

[0153] [Example 2] <Formation of Alignment Film> A cellulose acylate film prepared in the same manner as in the first optically anisotropic layer of Example 1 was subjected to one-side saponification treatment in the same manner as in Example 1. Next, an alignment film-forming composition (B) having the following composition was continuously applied to the saponified surface using a #10 wire bar, and the film was dried with hot air at 60°C for 60 seconds and then with hot air at 100°C for 120 seconds. The thickness of the alignment film was 0.5 μm. In Example 2, the cellulose acylate film on which the alignment film had been formed was used as a substrate when forming the second optically anisotropic layer and the third optically anisotropic layer.

[0154] ------------------------------------------------------------------ Composition for forming alignment film (B) -------------------------------------------------- Modified polyvinyl alcohol (as shown below) 100 parts by mass Water 1,711 parts by mass Methanol 570 parts by mass ------------------------------------------------------------------

[0155] Modified polyvinyl alcohol (in the formula below, the numerical value for each repeating unit represents the content (mol %) of each repeating unit relative to all repeating units.)

[0156] <Formation of Second Optically Anisotropic Layer and Third Optically Anisotropic Layer> The alignment film prepared above was subjected to a rubbing treatment in the same manner as in Example 1, and then an optically anisotropic layer-forming composition (2) containing a discotic liquid crystal compound having the following composition was applied, heated, and irradiated with ultraviolet light to prepare a laminate [layer structure: cellulose acylate film (resin film) / alignment film / cured liquid crystal layer]. The laminate prepared by the above procedure was cut parallel to the rubbing direction, and the cured liquid crystal layer was observed from the cross-sectional direction using a polarizing microscope. The thickness of the cured liquid crystal layer was 2.7 μm, and a 1.4 μm-thick region on the cellulose acylate film (resin film) side of the cured liquid crystal layer (second optically anisotropic layer) exhibited homogeneous alignment without a twist angle, while a 1.3 μm-thick region on the opposite side of the optically anisotropic layer from the cellulose acylate film (resin film) exhibited twisted alignment of the liquid crystal compound. The second optically anisotropic layer satisfied the above formula (2) "nz = nx > ny". The optical properties of the laminate were determined using an Axometrics AxoScan and the company's analysis software (Multi-Layer Analysis). The product (Δn2d2) of the in-plane refractive index anisotropy Δn2 and the thickness d2 of the second optically anisotropic layer at a wavelength of 550 nm was 168 nm, the twist angle of the liquid crystal compound was 0°, and the alignment axis angle of the liquid crystal compound relative to the longitudinal direction was -104° on the substrate side and -104° on the side in contact with the third optically anisotropic layer. The product (Δn1d1) of the in-plane refractive index anisotropy Δn1 and the thickness d1 of the third optically anisotropic layer at a wavelength of 550 nm was 160 nm, the twist angle of the liquid crystal compound was 81°, and the alignment axis angle of the liquid crystal compound relative to the longitudinal direction was −104° on the side in contact with the second optically anisotropic layer and −185° on the air side.

[0157] Optically anisotropic layer-forming composition (2) ---------------------------------------------------------------- 80 parts by mass of the above discotic liquid crystal compound 1 20 parts by mass of the above discotic liquid crystal compound 2 1 part by mass of the above alignment film interface aligning agent 1.06 parts by mass of the above left-handed twisted chiral agent 0.1 part by mass of the above right-handed twisted chiral agent 0.18 parts by mass of the above leveling agent B-1 5 parts by mass of the above modified trimethylolpropane triacrylate 2 parts by mass of photopolymerization initiator (Irgacure 819, manufactured by BASF) 2 parts by mass of the above antifoaming agent 105 parts by mass of methyl ethyl ketone

[0158] <Formation of Fourth Optically Anisotropic Layer> A composition for forming an optically anisotropic layer (3) containing a discotic liquid crystal compound having the following composition was applied onto a cellulose acylate film using a Giesser coater to form a composition layer. The film on which the composition layer was formed was heated with hot air at 116°C for 1 minute, and then irradiated with a 365 nm UV-LED at an irradiation dose of 150 mJ / cm at a UV temperature of 78°C while purging with nitrogen so that the atmosphere had an oxygen concentration of 100 volume ppm or less. ２ The film was irradiated with ultraviolet light of 1000 kJ / cm. The film thickness of the formed liquid crystal alignment layer (fourth optically anisotropic layer) was 2 μm. The in-plane retardation Re(550) at a wavelength of 550 nm was 0 nm, and the thickness direction retardation Rth(550) at a wavelength of 550 nm was 60 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film surface was 0°, and it was confirmed that the discotic liquid crystal compound was aligned horizontally with respect to the film surface. The formed liquid crystal alignment layer (fourth optically anisotropic layer) also satisfied the above formula (1) "nx = ny > nz."

[0159] ------------------------------------------------ Optically anisotropic layer-forming composition (3)------------------------------------------------ 80 parts by mass of the above discotic liquid crystal compound 1 20 parts by mass of the above discotic liquid crystal compound 2 12 parts by mass of the above modified trimethylolpropane triacrylate 3 parts by mass of the following polymerization initiator S-1 (oxime type) 0.6 parts by mass of the following leveling agent B-2 0.6 parts by mass of the following polymer P-1 (specific polymer) unevenly distributed on the base material side 360 ​​parts by mass of methyl isobutyl ketone 90 parts by mass of ethyl propionate 25 parts by mass of methyl ethyl ketone

[0160] Polymerization initiator S-1

[0161] Leveling agent B-2 (weight average molecular weight: 12,500; in the formula below, the numerical value for each repeating unit represents the content (mass%) of each repeating unit relative to all repeating units.)

[0162] Base material side unevenly distributed polymer P-1 (weight average molecular weight: 7800)

[0163] <Preparation of Optical Laminate> The surfaces of the third optically anisotropic layers of the films containing the second and third optically anisotropic layers prepared above, and the surfaces of the fourth optically anisotropic layers of the films containing the fourth optically anisotropic layers, were each treated once using a corona treatment device under conditions of an output of 0.3 kW and a treatment speed of 7.6 m / min. Next, ultraviolet-curable adhesive composition 1 was applied to the surface side of the fourth optically anisotropic layer of the film containing the fourth optically anisotropic layer to form an adhesive composition layer, and the surfaces of the third optically anisotropic layers of the films containing the second and third optically anisotropic layers were laminated so that their longitudinal directions were parallel. Next, the obtained laminate was irradiated with a high-pressure mercury lamp at an irradiation dose of 600 mJ / cm. ２The adhesive composition layer was cured by irradiating it with ultraviolet light (wavelength 365 nm) to form an adhesive layer having a thickness of 1 μm. Furthermore, the substrates (cellulose acylate film and alignment film) of the second optically anisotropic layer and the third optically anisotropic layer were peeled off to prepare an optical laminate having the second optically anisotropic layer, the third optically anisotropic layer, the adhesive layer, the fourth optically anisotropic layer, and the cellulose acylate film in this order. ------------------------------------------------------------------ UV-curable adhesive composition 1 ------------------------------------------------------------------ Celloxide 2021P (manufactured by Daicel Corporation) 67.0 parts by mass 2-Ethylhexyl glycidyl ether 9.6 parts by mass Rikaresin DME-100 (manufactured by New Japan Chemical Co., Ltd.) 19.1 parts by mass CPI-100P (manufactured by San-Apro Ltd.) 4.3 parts by mass ------------------------------------------------------------------

[0164] <Preparation of Circularly Polarizing Plate> A polarizer was prepared using the same procedure as in Example 1, and then Fujitac TG40UL as a polarizer protective film and TJ25 (manufactured by Fujifilm Corporation) as a first optically anisotropic layer were successively laminated together using a polyvinyl alcohol-based adhesive. The thickness of TJ25 was 25 μm, the in-plane retardation Re(550) at a wavelength of 550 nm was 0 nm, and the retardation in the thickness direction Rth(550) at a wavelength of 550 nm was 20 nm. Furthermore, TJ25 satisfied the above formula (1) of "nx = ny > nz." Next, the TJ25 surface side of the linear polarizer and the second optically anisotropic layer surface side of the prepared optical laminate were treated once using a corona treatment device under conditions of an output of 0.3 kW and a treatment speed of 7.6 m / min, and then ultraviolet-curable adhesive composition 1 was applied to the TJ25 surface side to form an adhesive composition layer, and the second optically anisotropic layer surface side of the optical laminate was bonded to the ultraviolet-curable adhesive composition 1. Furthermore, the obtained laminate was irradiated with an ultraviolet-curable adhesive composition 1 using a high-pressure mercury lamp at an irradiation dose of 600 mJ / cm. ２The adhesive composition layer was cured by irradiating it with ultraviolet light (wavelength 365 nm) to form an adhesive layer having a thickness of 1 μm. The substrate (cellulose acylate film) of the fourth optically anisotropic layer was peeled off, and a circularly polarizing plate having, in this order, a polarizer protective film, a polarizer, a first optically anisotropic layer, an adhesive layer, a second optically anisotropic layer, a third optically anisotropic layer, an adhesive layer, and a fourth optically anisotropic layer was produced.

[0165] [Example 3] A circularly polarizing plate was prepared in the same manner as in Example 1, except that a horizontally aligned layer of the same discotic liquid crystal as the fourth optically anisotropic layer in Example 2 was used instead of a cellulose acylate film as the fourth optically anisotropic layer.

[0166] [Example 4] A circularly polarizing plate was produced in the same manner as in Example 1, except that the rubbing angle of the alignment film, the amount of chiral agent in the composition (1) for forming an optically anisotropic layer, the coating amount, and the irradiation amount of the 365 nm LED lamp were adjusted to achieve the desired optical properties.

[0167] [Example 5] A circularly polarizing plate was produced in the same manner as in Example 2, except that TJ25 was not used as the polarizer protective film and that UV-curable adhesive composition 1 was applied directly to the polarizer surface. Note that in Table 1 below, Example 5 is described as a circularly polarizing plate that does not have a first optically anisotropic layer but has second to fourth optically anisotropic layers, which is an example that corresponds to the third embodiment described above.

[0168] Example 6 A circularly polarizing plate was produced in the same manner as in Example 1, except that the fourth optically anisotropic layer in Example 1 was replaced with a cellulose acylate film containing the UV absorber shown below. <Formation of Fourth Optically Anisotropic Layer> The following composition was charged into a mixing tank, stirred, and further heated at 90°C for 10 minutes. The resulting composition was then filtered through filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm to prepare cellulose acylate solution 1. The solids concentration of solution 2 was 23.5% by mass, the amount of plasticizer added was the ratio relative to the cellulose acylate, and the solvent for the dope was methylene chloride / methanol / butanol = 81 / 18 / 1 (mass ratio).

[0169] -------------------------------------------------- Cellulose acylate solution 2 -------------------------------------------------- Cellulose acylate (degree of acetyl substitution 2.86, viscosity average degree of polymerization 310) 100 parts by mass Sugar ester compound 1 (shown in chemical formula (S4)) 6.0 parts by mass Sugar ester compound 2 (shown in chemical formula (S5)) 2.0 parts by mass Silica particle dispersion (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 0.1 part by mass UV absorber below 2.1 parts by mass Solvent (methylene chloride / methanol / butanol) --------------------------------------------------

[0170] UV absorbers

[0171] The solution 1 prepared above was cast using a drum film-forming machine. The solution was cast from a die onto a metal support cooled to 0°C, and then the resulting web (film) was peeled off. The drum was made of SUS.

[0172] The web (film) obtained by casting was peeled from the drum and dried for 20 minutes in a tenter apparatus, which clipped both ends of the web with clips while transporting the film at 30 to 40°C. The web was then post-dried by zone heating while being transported with a roll. The resulting web was knurled and then wound up. The resulting cellulose acylate film (fourth optically anisotropic layer) containing a UV absorber had a film thickness of 40 μm, an in-plane retardation Re(550) of 0 nm at a wavelength of 550 nm, and a thickness-direction retardation Rth(550) of 26 nm. The resulting cellulose acylate film (fourth optically anisotropic layer) satisfied the above-mentioned formula (1), "nx = ny > nz."

[0173] [Example 7] A circularly polarizing plate was produced in the same manner as in Example 2, except that the thickness of the fourth optically anisotropic layer was changed from 2 μm to 1 μm. The fourth optically anisotropic layer had an in-plane retardation Re(550) of 0 nm at a wavelength of 550 nm and a thickness direction retardation Rth(550) of 44 nm at a wavelength of 550 nm.

[0174] [Comparative Example 1] A circularly polarizing plate was produced in the same manner as in Example 1 except that an alignment film was formed on a cellulose acylate film having an in-plane retardation Re(550) and a thickness direction retardation Rth(550) of 0 nm, i.e., an optically anisotropic layer that does not satisfy the above formula (1) "nx = ny > nz," and that the film was subjected to a rubbing treatment and coated with an optically anisotropic layer-forming composition (1).

[0175] <Preparation of Organic EL Display Device and Evaluation of Display Performance> (Installation on Display Device) A SAMSUNG GALAXY S8+ equipped with an organic EL panel was disassembled, the circular polarizer was peeled off, and the circular polarizer prepared in the above example was attached to the display device so that the polarizer protective film was positioned on the outside.

[0176] (Evaluation of display performance) The produced organic EL display device was set to display black, and under bright light, a fluorescent lamp was shone on it at a polar angle of 45°, and reflected light was observed from all directions. The azimuth angle dependency of color change was evaluated according to the following criteria. The results are shown in Table 1. 4: No color change was visible (acceptable). 3: Color change was visible, but very slight (acceptable). 2: Color change was slightly visible, and there was also some reflected light, which was unacceptable. 1: Color change was visible, and there was a lot of reflected light, which was unacceptable.

[0177]

[0178] As shown in Table 1, when the circular polarizer of Comparative Example 1, which does not correspond to any of the first to third embodiments, was used, the azimuth angle dependency of the color change reached an unacceptable level, and it was found that the visibility of black from an oblique direction was poor. In contrast, when the circular polarizers of Examples 1 to 7, which correspond to the first to third embodiments, were used, the azimuth angle dependency of the color change reached an acceptable level, and it was found that the visibility of black from an oblique direction was improved.

[0179] 10a, 10b Circular polarizer 12 Linear polarizer 14, 16c First optically anisotropic layer 16a, 16b, 18c Second optically anisotropic layer 18a, 18b, 22 Third optically anisotropic layer 20 Fourth optically anisotropic layer 24 Composition layer 24A Lower region 24B Upper region 26 Organic EL display panel 100 Organic EL display device

Claims

1. A circular polarizing plate having a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer in this order, wherein the first optically anisotropic layer and the fourth optically anisotropic layer both satisfy the following formula (1), the second optically anisotropic layer satisfies the following formula (2), and the third optically anisotropic layer is a layer formed by fixing a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis: Formula (1) nx = ny > nz Formula (2) nz = nx > ny 2. A circular polarizing plate having a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, and a fourth optically anisotropic layer in this order, wherein the first optically anisotropic layer and the fourth optically anisotropic layer both satisfy the following formula (1), and the second optically anisotropic layer and the third optically anisotropic layer both are layers formed by fixing a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis: Formula (1) nx=ny>nz 3. The circularly polarizing plate according to claim 1, wherein the second optically anisotropic layer is a layer formed by fixing a vertically aligned discotic liquid crystal compound.

4. The circularly polarizing plate according to claim 1 or 2, wherein the second optically anisotropic layer and the third optically anisotropic layer are directly adjacent to each other.

5. A circularly polarizing plate according to claim 1 or 2, wherein the in-plane slow axis of the second optically anisotropic layer on the surface facing the third optically anisotropic layer is parallel to the in-plane slow axis of the third optically anisotropic layer on the surface facing the second optically anisotropic layer.

6. The circular polarizing plate according to claim 1, wherein the angle formed between the absorption axis of the linear polarizer and the in-plane slow axis of the second optically anisotropic layer is 94 to 114°, the in-plane retardation of the second optically anisotropic layer at a wavelength of 550 nm is 138 to 198 nm, the twist angle of the twistedly aligned liquid crystal compound in the third optically anisotropic layer is 71 to 91°, and the value of the product Δnd of the refractive index anisotropy Δn of the third optically anisotropic layer measured at a wavelength of 550 nm and the thickness d of the third optically anisotropic layer is 130 to 190 nm.

7. The circular polarizer according to claim 2, wherein the angle formed between the absorption axis of the linear polarizer and the in-plane slow axis of the second optically anisotropic layer on the surface facing the first optically anisotropic layer is 85 to 95°, the twist angle of the twisted liquid crystal compound in the second optically anisotropic layer is 16 to 36°, the value of the product Δnd of the refractive index anisotropy Δn of the second optically anisotropic layer measured at a wavelength of 550 nm and the thickness d of the second optically anisotropic layer is 252 to 312 nm, the twist angle of the twisted liquid crystal compound in the third optically anisotropic layer is 68 to 88°, and the value of the product Δnd of the refractive index anisotropy Δn of the third optically anisotropic layer measured at a wavelength of 550 nm and the thickness d of the third optically anisotropic layer is 110 to 170 nm.

8. A circularly polarizing plate according to claim 1 or 2, wherein the first optically anisotropic layer has a thickness direction retardation of 0 to 60 nm at a wavelength of 550 nm, and the fourth optically anisotropic layer has a thickness direction retardation of 10 to 90 nm at a wavelength of 550 nm.

9. A circularly polarizing plate according to claim 1 or 2, wherein the first optically anisotropic layer is a cellulose acylate film, and the fourth optically anisotropic layer is a cellulose acylate film or a layer formed by fixing a horizontally aligned discotic liquid crystal compound.

10. The circularly polarizing plate according to claim 1 or 2, wherein the second optically anisotropic layer and the third optically anisotropic layer each contain two or more types of chiral agents.

11. The circularly polarizing plate according to claim 10, wherein at least one of the two or more chiral agents contained in the second optically anisotropic layer and the third optically anisotropic layer has a photoisomerizable double bond and a binaphthyl moiety.

12. An organic electroluminescence display device comprising the circular polarizer according to claim 1 or 2.

13. A circular polarizing plate having, in this order, a linear polarizer, a first optically anisotropic layer, a second optically anisotropic layer, and a third optically anisotropic layer, wherein the first optically anisotropic layer and the second optically anisotropic layer are each independently a layer formed by fixing a vertically aligned discotic liquid crystal compound or a layer formed by fixing a discotic liquid crystal compound that is twisted and aligned with the thickness direction as the helical axis, and the third optically anisotropic layer is a layer formed by fixing a horizontally aligned discotic liquid crystal compound.

14. An organic electroluminescence display device comprising the circular polarizer according to claim 13.

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