Polarizing plate and display device

Abstract

The present invention provides a polarizing plate capable of achieving low reflectance when applied to a display device, and a display device. This polarizing plate comprises: a polarizer; an optically anisotropic layer X having an in-plane retardation; and an adjacent layer X adjacent to the optically anisotropic layer X. The difference between the refractive index of the optically anisotropic layer X and the refractive index of the adjacent layer X in the transmission axis direction of the polarizer is 0.15 or less, the refractive index anisotropy Δn of the optically anisotropic layer X is 0.09 or less, and the angle formed by the transmission axis of the polarizer and the in-plane slow axis of the optically anisotropic layer X is 20° or less.

Description

Polarizing plate, display device

[0001] The present invention relates to a polarizing plate and a display device.

[0002] Polarizing plates including optically anisotropic layers having refractive index anisotropy are used in various applications such as anti-reflection applications in display devices, etc. For example, Patent Document 1 discloses a polarizing plate including a retardation film on which a predetermined optically anisotropic layer is laminated.

[0003] Japanese Patent Application Laid-Open No. 2022-184691

[0004] The present inventors combined the retardation film described in Patent Document 1 with a polarizer and applied it to a display device as a polarizing plate, and evaluated the reflection characteristics of the resulting display device from the polarizing plate side. As a result, it was found that further reduction in reflectance was necessary in some cases.

[0005] In view of the above circumstances, an object of the present invention is to provide a polarizing plate that can achieve low reflectance when applied to a display device. Another object of the present invention is to also provide a display device.

[0006] 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 the following configuration.

[0007] (1) A polarizing plate comprising a polarizer, an optically anisotropic layer X having an in-plane retardation, and an adjacent layer X adjacent to the optically anisotropic layer X, wherein the difference between the refractive index of the optically anisotropic layer X and the refractive index of the adjacent layer X in the transmission axis direction of the polarizer is 0.15 or less, the refractive index anisotropy Δn of the optically anisotropic layer X is 0.09 or less, and the angle between the transmission axis of the polarizer and the in-plane slow axis of the optically anisotropic layer X is 20° or less. (2) The polarizing plate according to (1), wherein the optically anisotropic layer X is a layer formed using a thermotropic liquid crystal compound. (3) The polarizing plate according to (1) or (2), further comprising an optically anisotropic layer Y having a retardation in the thickness direction, wherein the optically anisotropic layer Y is disposed on the side of the optically anisotropic layer X opposite to the adjacent layer X side, so that the optically anisotropic layer X and the optically anisotropic layer Y are adjacent to each other. (4) The polarizing plate according to (3), further comprising an adjacent layer Y disposed on the side opposite to the optically anisotropic layer X side of the optically anisotropic layer Y and adjacent to the optically anisotropic layer Y, wherein the difference in refractive index between the optically anisotropic layer X and the optically anisotropic layer Y in the transmission axis direction of the polarizer is 0.15 or less, and the difference in refractive index between the optically anisotropic layer Y and the adjacent layer Y in the transmission axis direction of the polarizer is 0.15 or less. (5) The polarizing plate according to (3) or (4), wherein the optically anisotropic layer Y is a layer formed using a thermotropic liquid crystal compound. (6) The polarizing plate according to any one of (3) to (5), wherein the thickness of the optically anisotropic layer Y is 520 nm±40 nm, 690 nm±40 nm, 860 nm±40 nm, or 980 nm or more. (7) A display device comprising a display element and the polarizing plate according to any one of (1) to (6). (8) The display device according to (7), wherein the display element is an organic electroluminescence display element.

[0008] According to the present invention, it is possible to provide a polarizing plate that can realize low reflectance when applied to a display device. Also, according to the present invention, it is possible to provide a display device.

[0009] 2 is a diagram conceptually illustrating an embodiment of the polarizing plate of the present invention. It is a diagram illustrating the relationship between the absorption axis of the polarizer and the in-plane slow axes of the second optically anisotropic layer and the third optically anisotropic layer in an embodiment of the polarizing plate of the present invention. It is a schematic diagram illustrating the relationship between the angle between the absorption axis of the 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.

[0010] 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 lower and upper limits. In this specification, the in-plane slow axis and in-plane fast axis are defined at a wavelength of 550 nm unless otherwise specified. In other words, unless otherwise specified, for example, when referring to the in-plane slow axis direction, it means the direction of the in-plane slow axis at a wavelength of 550 nm. In this specification, the refractive index is defined at a wavelength of 550 nm unless otherwise specified.

[0011] In the present invention, 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 OPMF-1 (manufactured by OptoScience). By inputting the refractive index ((nx + ny + nz) / 3) and film thickness (d) 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 using the AxoScan OPMF-1, but it means Re(λ).

[0012] In this specification, the refractive index ((nx + ny + nz) / 3) is measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) with a sodium lamp (λ = 589 nm) as a light source. Furthermore, 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. In the case of liquid crystal compounds, the average refractive index can be measured by measuring a film fixed in the optically isotropic phase using this method. Values ​​in the Polymer Handbook (John Wiley & Sons, Inc.) and catalogs for 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).

[0013] In this specification, A plates and C plates are defined as follows. There are two types of A plates: positive A plates (positive A plates) and negative A plates (negative A plates). When the refractive index in the in-plane slow axis direction (the direction in which the in-plane refractive index is maximum) of the film is nx, the refractive index in the in-plane direction perpendicular to the in-plane slow axis is ny, and the refractive index in the thickness direction is nz, the positive A plates satisfy the relationship of formula (A1), and the negative A plates satisfy the relationship of formula (A2). Note that the positive A plates have a positive Rth value, and the negative A plates have a negative Rth value. Formula (A1) nx>ny≒nz Formula (A2) ny<nx≒nz Note that the above "≒" includes not only the case where the two are completely identical, but also the case where the two are substantially identical. "Substantially the same" means, for example, that "ny ≒ nz" also includes cases where (ny - nz) x d (where d is the film thickness) is -10 to 10 nm, preferably -5 to 5 nm, and "nx ≒ nz" also includes cases where (nx - nz) x d is -10 to 10 nm, preferably -5 to 5 nm. There are two types of C plates: positive C plates (positive C plates) and negative C plates (negative C plates). Positive C plates satisfy the relationship of formula (C1), while negative C plates satisfy the relationship of formula (C2). Note that positive C plates have a negative Rth value, and negative C plates have a positive Rth value. Formula (C1) nz > nx ≒ ny Formula (C2) nz < nx ≒ ny Note that the above "≒" includes not only cases where the two are completely identical, but also cases where the two are substantially identical. The term "substantially the same" includes, for example, the case where (nx-ny) x d (where d is the thickness of the film) is 0 to 10 nm, preferably 0 to 5 nm, in "nx≈ny".

[0014] The term "ultraviolet light" refers to light having a wavelength of 10 nm or more and less than 400 nm. In this specification, the terms "perpendicular" and "parallel" include the range of tolerance allowed in the technical field to which the present invention pertains. For example, they mean a deviation from the exact angle of ±5°, and the deviation from the exact angle is preferably within ±3°.

[0015] <Polarizing Plate> The polarizing plate of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of one embodiment of the polarizing plate of the present invention. As shown in FIG. 1, the circular polarizing plate 100 includes a polarizer 20, a first optically anisotropic layer 12, a second optically anisotropic layer 14, a third optically anisotropic layer 16, and a fourth optically anisotropic layer 18, in this order. The first optically anisotropic layer 12 is a negative C plate, the second optically anisotropic layer 14 is a negative A plate, the third optically anisotropic layer 16 is a layer formed by fixing a rod-shaped liquid crystal compound that is twisted and aligned along a helical axis extending in the thickness direction, and the fourth optically anisotropic layer 18 is a positive C plate. The in-plane slow axis of the second optically anisotropic layer 14 is parallel to the in-plane slow axis of the surface of the third optically anisotropic layer 16 facing the second optically anisotropic layer 14.

[0016] In the circular polarizing plate 100, the second optically anisotropic layer 14 corresponds to the optically anisotropic layer X having an in-plane retardation included in the polarizing plate of the present invention, and the first optically anisotropic layer 12 corresponds to the optically anisotropic layer Y having a retardation in the thickness direction included in the polarizing plate of the present invention. As shown in FIG. 1 , a first adhesion layer 30 is disposed between the second optically anisotropic layer 14 and the third optically anisotropic layer 16, and the first adhesion layer 30 is disposed adjacent to the second optically anisotropic layer 14. The first adhesion layer 30 corresponds to the adjacent layer X adjacent to the optically anisotropic layer X included in the polarizing plate of the present invention. As shown in FIG. 1 , a second adhesion layer 32 is disposed between the polarizer 20 and the first optically anisotropic layer 12, and the second adhesion layer 32 is disposed adjacent to the first optically anisotropic layer 12. The second adhesion layer 32 corresponds to the adjacent layer Y adjacent to the optically anisotropic layer Y included in the polarizing plate of the present invention. In the present invention, the polarizer 20, the second optically anisotropic layer 14, and the first adhesive layer 30 in the circular polarizing plate 100 are essential components, and the other components are optional components.

[0017] First, the characteristic characteristics between the members of the circular polarizer 100 will be described in detail below.

[0018] In the circular polarizing plate 100, the difference in refractive index between the second optically anisotropic layer 14 (the optically anisotropic layer X) and the first adhesive layer 30 (the adjacent layer X) in the transmission axis direction of the polarizer 20 is 0.15 or less, preferably 0.13 or less, more preferably 0.12 or less, in order to lower the reflectance in a display device including the polarizing plate of the present invention (hereinafter simply referred to as "the advantage of the present invention being superior"). The lower limit of this difference is not particularly limited, and is often 0 or more, more often 0.05 or more, and even more often 0.10 or more. When the difference in refractive index between the second optically anisotropic layer 14 (the optically anisotropic layer X) and the first adhesive layer 30 (the adjacent layer X) is equal to or less than the predetermined value, reflection at the interface between the second optically anisotropic layer 14 (the optically anisotropic layer X) and the first adhesive layer 30 (the adjacent layer X) is suppressed. In particular, since light passing through the polarizer 20 is polarized light parallel to the transmission axis, adjusting the refractive index difference in the transmission axis direction of the polarizer 20 can reduce the reflectance more than in conventional techniques. The method for adjusting the refractive index of the second optically anisotropic layer 14, which is the optically anisotropic layer X, is not particularly limited, and examples thereof include a method of adjusting the manufacturing conditions of the optically anisotropic layer (particularly, the heating temperature) and a method of using a predetermined additive, as described below. The refractive index of the second optically anisotropic layer 14, which is the optically anisotropic layer X, and the refractive index of the first adhesive layer 30, which is the adjacent layer X, are both refractive indices at a wavelength of 550 nm. The refractive index difference is measured as follows. When calculating the refractive index of the second optically anisotropic layer 14, which is the optically anisotropic layer X, in the transmission axis direction of the polarizer 20, first, the ne and no of the second optically anisotropic layer 14, which is the optically anisotropic layer X, are calculated. Specifically, the complex reflectance of the second optically anisotropic layer 14, which is the optically anisotropic layer X, at an incident angle of 50 to 70°, as determined by ellipsometry, is analyzed using an optical model that takes into account the anisotropy of the refractive index, to determine the n e and n o of the second optically anisotropic layer 14, which is the optically anisotropic layer X. Next, the refractive index in the transmission axis direction of the polarizer 20 is calculated from the obtained n e and n o. For example, when the transmission axis direction of the polarizer 20 is located at a position shifted by x degrees from n e, the refractive index nT in the transmission axis direction is calculated from the following formula: n T = n e * ( cos x ) / ( cos x + sin x ) + n e * ( sin x ) / ( cos x + sin x ) Note that the above refractive index is the refractive index at a wavelength of 550 nm.Furthermore, a measuring device such as an RC2 manufactured by Woollam or an SE-2000 manufactured by Semilab is used. Next, the refractive index of the first adhesion layer 30, which is the adjacent layer X in the transmission axis direction of the polarizer 20, is measured according to the same procedure as the method for measuring the refractive index of the second optically anisotropic layer 14, which is the optically anisotropic layer X in the transmission axis direction of the polarizer 20, as described above. As described above, the difference between the refractive index of the first adhesion layer 30, which is the adjacent layer X in the transmission axis direction of the polarizer 20, and the refractive index of the second optically anisotropic layer 14, which is the optically anisotropic layer X in the transmission axis direction of the polarizer 20, is calculated.

[0019] In the circular polarizing plate 100, the angle between the transmission axis of the polarizer 20 and the in-plane slow axis of the second optically anisotropic layer 14, which is the optically anisotropic layer X, is 20° or less. In particular, in terms of better effects of the present invention, the angle is preferably 18° or less, and more preferably 16° or less. There is no particular lower limit to the angle, and it is often 0° or more, often 5° or more, and more often 10° or more.

[0020] In the circular polarizing plate 100, the difference in refractive index between the second optically anisotropic layer 14 (optically anisotropic layer X) and the first optically anisotropic layer 12 (optically anisotropic layer Y) in the transmission axis direction of the polarizer 20 is not particularly limited, but is preferably 0.15 or less, more preferably 0.10 or less, and even more preferably 0.05 or less, in terms of better effects of the present invention. The lower limit of the difference is not particularly limited, and is often 0 or more, more often 0.02 or more, and even more often 0.03 or more. The refractive index of the second optically anisotropic layer 14 (optically anisotropic layer X) and the refractive index of the first optically anisotropic layer 12 (optically anisotropic layer Y) are both refractive indices at a wavelength of 550 nm. When the difference in refractive index between the second optically anisotropic layer 14, which is the optically anisotropic layer X, and the first optically anisotropic layer 12, which is the optically anisotropic layer Y, is equal to or less than the predetermined value, reflection is suppressed at the interface between the second optically anisotropic layer 14, which is the optically anisotropic layer X, and the first optically anisotropic layer 12, which is the optically anisotropic layer Y. Examples of a method for measuring the difference in refractive index include the methods described above for measuring the difference in refractive index between the second optically anisotropic layer 14, which is the optically anisotropic layer X, and the first adhesive layer 30, which is the adjacent layer X.

[0021] In the circular polarizing plate 100, the difference in refractive index between the first optically anisotropic layer 12 (optically anisotropic layer Y) and the second adhesive layer 32 (adjacent layer Y) in the transmission axis direction of the polarizer 20 is not particularly limited, but is preferably 0.15 or less, more preferably 0.14 or less, in terms of better effects of the present invention. The lower limit of this difference is not particularly limited, and is often 0 or more, more often 0.05 or more, and even more often 0.10 or more. When the difference between the refractive index of the first optically anisotropic layer 12 (optically anisotropic layer Y) and the second adhesive layer 32 (adjacent layer Y) is equal to or less than the predetermined value, reflection at the interface between the first optically anisotropic layer 12 (optically anisotropic layer Y) and the second adhesive layer 32 (adjacent layer Y) is suppressed. Examples of a method for measuring the difference in refractive index include the method described above for measuring the difference in refractive index between the second optically anisotropic layer 14 (optically anisotropic layer X) and the first adhesive layer 30 (adjacent layer X).

[0022] Each layer will be described in detail below.

[0023] (First Optically Anisotropic Layer 12) As described above, the first optically anisotropic layer 12 corresponds to the optically anisotropic layer Y having a phase difference in the thickness direction, which is included in the polarizing plate of the present invention. As described above, the first optically anisotropic layer 12 is preferably a negative C plate. The retardation in the thickness direction of the first optically anisotropic layer 12 at a wavelength of 550 nm is not particularly limited, but is preferably 5 to 100 nm, more preferably 10 to 90 nm, even more preferably 15 to 50 nm, and particularly preferably 30 nm or more and less than 40 nm, in order to minimize change in color when the polarizing plate of the present invention is applied to a display device and the display device is observed from an oblique direction at all azimuth angles.

[0024] The refractive index of the first optically anisotropic layer 12 is not particularly limited, but is preferably from 1.55 to 1.65, and more preferably from 1.57 to 1.63.

[0025] The first optically anisotropic layer 12 is not particularly limited in its configuration. For example, in the case of a negative C plate, it may be a layer formed by fixing a horizontally aligned discotic liquid crystal compound, or a resin film. The state in which the discotic liquid crystal compound is horizontally aligned refers to a state in which the discotic plane of the discotic liquid crystal compound is parallel to the main surface of the layer. Strict parallelism is not required, and the angle between the discotic plane and the main surface of the layer is preferably in the range of 0±20°, and more preferably 0±10°. In this specification, 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 is non-fluid and can stably maintain the fixed alignment without any change in the alignment due to an external field or external force, usually at a temperature range of 0 to 50°C, or more severely, at a temperature range of −30 to 70°C.

[0026] Known discotic liquid crystal compounds can be used, including, for example, the compounds described in paragraphs 0020 to 0067 of JP-A No. 2007-108732 and paragraphs 0013 to 0108 of JP-A No. 2010-244038.

[0027] The discotic liquid crystal compound may have a polymerizable group. In this specification, 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.

[0028] The type of resin constituting the resin film is not particularly limited, and examples thereof include TAC (triacetyl cellulose).

[0029] The first optically anisotropic layer 12 is preferably a layer formed by fixing a horizontally aligned discotic liquid crystal compound having a polymerizable group by polymerization, or a layer formed using a thermotropic liquid crystal compound.

[0030] The thickness of the first optically anisotropic layer 12 is not particularly limited. When the first optically anisotropic layer 12 is a layer formed by fixing a horizontally aligned discotic liquid crystal compound, the thickness is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm. When the first optically anisotropic layer 12 is a resin film, the thickness of the first optically anisotropic layer 12 is preferably 10 to 100 μm, more preferably 15 to 90 μm. In particular, the thickness of the first optically anisotropic layer 12 is preferably 520 nm±40 nm, 690 nm±40 nm, 860 nm±40 nm, or 980 nm or more, in terms of achieving superior effects of the present invention. The thickness of the first optically anisotropic layer 12 refers to the average thickness of the first optically anisotropic layer 12. The average thickness is determined by measuring the thickness at any five or more points on the first optically anisotropic layer 12 and calculating the arithmetic average.

[0031] (Second Optically Anisotropic Layer 14) As described above, the second optically anisotropic layer 14 corresponds to the optically anisotropic layer X having an in-plane retardation included in the polarizing plate of the present invention. As described above, the second optically anisotropic layer 14 is preferably a negative A plate. The in-plane retardation of the second optically anisotropic layer 14 at a wavelength of 550 nm is not particularly limited, but is preferably 120 to 240 nm, and more preferably 130 to 230 nm, in terms of providing superior effects of the present invention. The thickness direction retardation of the second optically anisotropic layer 14 at a wavelength of 550 nm is not particularly limited, but is preferably −120 to −60 nm, and more preferably −115 to −65 nm, in terms of providing superior effects of the present invention.

[0032] The refractive index anisotropy Δn of the second optically anisotropic layer 14 is 0.09 or less, and more preferably 0.08 or less, from the viewpoint of more excellent effects of the present invention. The lower limit of the refractive index anisotropy Δn of the second optically anisotropic layer 14 is not particularly limited, but from the viewpoint of thinning, it is preferably 0.03 or more, more preferably 0.05 or more. The refractive index anisotropy Δn means the refractive index anisotropy of the optically anisotropic layer (the difference between the refractive index on the in-plane slow axis and the refractive index on the in-plane fast axis). The refractive index anisotropy Δn is a value at a wavelength of 550 nm.

[0033] The refractive index of the second optically anisotropic layer 14 is not particularly limited, but is preferably from 1.55 to 1.65, and more preferably from 1.57 to 1.60.

[0034] The second optically anisotropic layer 14 may exhibit either forward wavelength dispersion (a property in which the in-plane retardation decreases as the measured wavelength increases) or reverse wavelength dispersion (a property in which the in-plane retardation increases as the measured wavelength increases). Note that the forward wavelength dispersion and reverse wavelength dispersion are preferably exhibited in the visible light region.

[0035] The second optically anisotropic layer 14 is not particularly limited in its configuration. For example, in the case of a negative A plate, examples include a layer formed by fixing a vertically aligned discotic liquid crystal compound whose optical axis (axis perpendicular to the discotic surface) is aligned in the same direction, and a stretched film. In terms of achieving better effects of the present invention, a layer formed by fixing a vertically aligned discotic liquid crystal compound whose optical axis (axis perpendicular to the discotic surface) is aligned in the same direction is preferred. Note that the state in which the discotic liquid crystal compound is vertically aligned means that the discotic surface of the discotic liquid crystal compound is parallel to the thickness direction of the layer. Note that strict parallelism is not required, and the angle between the discotic surface and the thickness direction of the layer is preferably in the range of 0±20°, more preferably 0±10°. Furthermore, the state in which the optical axes (axes perpendicular to the discotic plane) of the discotic liquid crystal compounds are aligned in the same direction does not necessarily mean that they are aligned in the same direction in strict terms, but rather means that when the slow axis orientations are measured at any 20 positions in 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 among the 20 slow axis orientations) is less than 2°. Examples of the discotic liquid crystal compound include the discotic liquid crystal compounds exemplified in the first optically anisotropic layer 12. The discotic liquid crystal compound may have a polymerizable group. The type of polymerizable group that the discotic liquid crystal compound may have is as described above.

[0036] The second optically anisotropic layer 14 is preferably a layer formed by fixing a discotic liquid crystal compound having a polymerizable group by polymerization, or a layer formed using a thermotropic liquid crystal compound.

[0037] The thickness of the second optically anisotropic layer 14 is not particularly limited, and is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 3.0 μm. The thickness of the second optically anisotropic layer 14 refers to the average thickness of the second optically anisotropic layer 14. The average thickness is determined by measuring the thickness at any five or more points on the second optically anisotropic layer 14 and calculating the arithmetic average.

[0038] (Third Optically Anisotropic Layer 16) The third optically anisotropic layer 16 is preferably a layer formed by fixing a rod-shaped liquid crystal compound that is twisted and aligned along a helical axis extending in the thickness direction. The third optically anisotropic layer 16 is preferably a layer formed by fixing a chiral nematic phase having a so-called helical structure. When forming the third optically anisotropic layer 16, it is preferable to use at least a rod-shaped liquid crystal compound and a chiral agent described below.

[0039] When the third optically anisotropic layer 16 is a layer formed by fixing rod-shaped liquid crystal compounds that are twisted and aligned along a helical axis extending in the thickness direction, the twist angle of the rod-shaped liquid crystal compounds (the twist angle of the alignment direction of the liquid crystal compounds) is not particularly limited and is often greater than 0° and not greater than 360°. From the viewpoint of achieving superior effects of the present invention, a twist angle within the range of 80±30° (50 to 110°) is preferred, and a twist angle within the range of 80±20° (60 to 100°) is more preferred. The twist angle is measured using an Axometrics AxoScan (polarimeter) device and its device analysis software. The twisted alignment of the rod-shaped liquid crystal compounds refers to a twist of the rod-shaped liquid crystal compounds from one main surface to the other main surface of the third optically anisotropic layer 16 around the thickness direction of the third optically anisotropic layer 16 as an axis. Accordingly, the orientation direction (in-plane slow axis direction) of the rod-shaped liquid crystal compounds varies depending on the position in the thickness direction of the third optically anisotropic layer 16. In the twisted orientation, the long axes of the rod-shaped liquid crystal compounds are arranged parallel to the main surface of the third optically anisotropic layer 16. However, strict parallelism is not required, and the angle formed between the long axes of the rod-shaped liquid crystal compounds and the main surface of the third optically anisotropic layer 16 is preferably in the range of 0±20°, more preferably 0±10°.

[0040] The value of the product Δnd of the refractive index anisotropy Δn of the third optically anisotropic layer 16 at a wavelength of 550 nm and the thickness d of the third optically anisotropic layer 16 is not particularly limited, but is preferably 120 to 240 nm, and more preferably 130 to 230 nm, in terms of better effects of the present invention. Δnd is measured using an AxoScan (polarimeter) device from Axometrics and its device analysis software.

[0041] The angle between the in-plane slow axis of the second optically anisotropic layer 14 and the in-plane slow axis of the third optically anisotropic layer 16 on the surface facing the second optically anisotropic layer 14 is not particularly limited, but is preferably in the range of 0 to 30°, and more preferably in the range of 0 to 20°.

[0042] The type of rod-shaped liquid crystal compound used to form the third optically anisotropic layer 16 is not particularly limited, and known compounds can be used. Examples of rod-shaped liquid crystal compounds include those described in claim 1 of JP-A-11-513019 and paragraphs 0026 to 0098 of JP-A-2005-289980. The rod-shaped liquid crystal compound may have a polymerizable group. The type of polymerizable group that the rod-shaped liquid crystal compound may have is as described above.

[0043] The third optically anisotropic layer 16 is preferably a layer formed by fixing a rod-shaped liquid crystal compound having a polymerizable group by polymerization. More specifically, it is more preferably a layer formed by fixing a rod-shaped liquid crystal compound having a twistedly aligned polymerizable group by polymerization.

[0044] The thickness of the third optically anisotropic layer 16 is not particularly limited, and is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 3.0 μm. The thickness of the third optically anisotropic layer 16 refers to the average thickness of the third optically anisotropic layer 16. The average thickness is determined by measuring the thickness at any five or more points of the third optically anisotropic layer 16 and calculating the arithmetic average.

[0045] (Fourth Optically Anisotropic Layer 18) The fourth optically anisotropic layer 18 is preferably a positive C plate. The retardation in the thickness direction of the fourth optically anisotropic layer 18 at a wavelength of 550 nm is not particularly limited, but is preferably −100 to −10 nm, more preferably −100 to −30 nm, in terms of better achieving the effects of the present invention.

[0046] The fourth optically anisotropic layer 18 is not particularly limited in its configuration. For example, in the case of a positive C plate, it may be a layer in which vertically aligned rod-shaped liquid crystal compounds are fixed, or a resin film. In terms of achieving better effects of the present invention, a layer in which vertically aligned rod-shaped liquid crystal compounds are fixed is preferred. Note that the state in which the rod-shaped liquid crystal compounds are vertically aligned means that the long axes of the rod-shaped liquid crystal compounds are parallel to the thickness direction of the fourth optically anisotropic layer 18. However, strict parallelism is not required, and the angle between the long axes of the rod-shaped liquid crystal compounds and the thickness direction of the fourth optically anisotropic layer 18 is preferably in the range of 0±20°, more preferably 0±10°.

[0047] As the rod-shaped liquid crystal compound, known compounds can be used. Examples of the rod-shaped liquid crystal compound include the rod-shaped liquid crystal compounds exemplified in the third optically anisotropic layer 16. The rod-shaped liquid crystal compound may have a polymerizable group. The types of polymerizable groups that the rod-shaped liquid crystal compound may have are as described above.

[0048] The fourth optically anisotropic layer 18 is preferably a layer formed by fixing a vertically aligned rod-shaped liquid crystal compound having a polymerizable group by polymerization.

[0049] The thickness of the fourth optically anisotropic layer 18 is not particularly limited, and is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm. The thickness of the fourth optically anisotropic layer 18 refers to the average thickness of the fourth optically anisotropic layer 18. The average thickness is determined by measuring the thickness at any five or more points on the fourth optically anisotropic layer 18 and calculating the arithmetic average.

[0050] (Polarizer) The polarizer 20 may be any component capable of converting natural light into specific linearly polarized light, such as an absorptive polarizer. The type of polarizer 20 is not particularly limited, and commonly used polarizers may be used, such as iodine-based polarizers, dye-based polarizers using dichroic materials, 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 material. A protective film may be disposed on one or both sides of the polarizer 20.

[0051] (Adhesion Layer) The first adhesion layer 30 and the second adhesion layer 32 are disposed between the respective members and have the function of adhering the members to each other. The refractive index of the first adhesion layer 30 and the second adhesion layer 32 is not particularly limited, but is preferably 1.40 to 1.55, and more preferably 1.45 to 1.50.

[0052] The first adhesive layer 30 and the second adhesive layer 32 may be a known pressure-sensitive adhesive layer or adhesive layer.

[0053] The thickness of the first adhesion layer 30 and the second adhesion layer 32 is preferably 0.1 to 50 μm. From the viewpoint of thinning, the thickness 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, the thickness is more preferably 5 μm or more, even more preferably 15 μm or more, and particularly preferably 25 μm or more.

[0054] (Other Components) The circularly polarizing plate 100 may include other components in addition to the components described above.

[0055] (Alignment Film) The circularly polarizing plate 100 may further include an alignment film. The alignment film may be disposed between each optically anisotropic layer. It is preferable that the circularly polarizing plate 100 does not include an alignment film between each optically anisotropic layer.

[0056] The alignment film can be formed by means of rubbing an organic compound (preferably a polymer), oblique vapor deposition of an inorganic compound, formation of a layer with microgrooves, or accumulation of an organic compound (e.g., ω-tricosanoic acid, dioctadecylmethylammonium chloride, methyl stearate) by 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. Examples of alignment films include photoalignment films. The thickness of the alignment film is not particularly limited as long as it can exhibit alignment function, but is preferably 0.01 to 5.0 μm, more preferably 0.05 to 2.0 μm, and even more preferably 0.1 to 0.5 μm.

[0057] (Substrate) The circularly polarizing plate 100 may further have a substrate. The substrate is preferably a transparent substrate. Note that a transparent substrate refers to a substrate having a visible light transmittance of 60% or more, preferably 80% or more, and more preferably 90% or more. The thickness of the substrate is not particularly limited, but is preferably 10 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 90 μm.

[0058] The substrate may also be composed of a laminate of multiple sheets. The surface of the substrate may be subjected to a surface treatment (e.g., glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment) to improve adhesion with a layer to be formed thereon. An adhesive layer (undercoat layer) may also be formed on the substrate. The substrate may also be a so-called temporary support. For example, after forming an optically anisotropic layer on the substrate, the substrate may be peeled off from the optically anisotropic layer, if necessary.

[0059] (Axial Relationship of Each Layer) Fig. 2 is a diagram showing the relationship between the absorption axis of the polarizer 20 and the in-plane slow axes of the second optically anisotropic layer 14 and the third optically anisotropic layer 16 in the circular polarizer 100 shown in Fig. 1. The arrow in the polarizer 20 in Fig. 2 represents the absorption axis, and the arrows in the second optically anisotropic layer 14 and the third optically anisotropic layer 16 represent the in-plane slow axes in the respective layers. Fig. 3 is a diagram showing the angular relationship between the absorption axis of the polarizer 20 (dashed line) and the in-plane slow axes (solid lines) of the second optically anisotropic layer 14 and the third optically anisotropic layer 16 when observed from the white arrow in Fig. 1. The rotation angle of the in-plane slow axis is expressed as a positive angle in the counterclockwise direction and a negative angle in the clockwise direction, with the absorption axis of the polarizer 20 as the reference (0°) when observed from the white arrow in Fig. 1. Furthermore, when observed from the white arrow in Figure 1, the twist direction of the liquid crystal compound is determined as right-handed (clockwise) or left-handed (counterclockwise) based on the in-plane slow axis on the surface of the front side (opposite the polarizer 20 side) of the third optically anisotropic layer 16.

[0060] As shown in Figures 2 and 3, the angle φa1 between the absorption axis of the polarizer 20 and the in-plane slow axis of the second optically anisotropic layer 14 is 76°. More specifically, the in-plane slow axis of the second optically anisotropic layer 14 is rotated by 76° (76° counterclockwise) with respect to the absorption axis of the polarizer 20. Note that Figures 2 and 3 show an embodiment in which the in-plane slow axis of the second optically anisotropic layer 14 is at a position of 76°, but the present invention is not limited to this embodiment and may be in the range of 70 to 90°. In other words, the angle between the absorption axis of the polarizer 20 and the in-plane slow axis of the second optically anisotropic layer 14 is in the range of 70 to 90°. In other words, the angle between the transmission axis of the polarizer 20 and the in-plane slow axis of the second optically anisotropic layer 14 is 20° or less (0 to 20°). As shown in Figure 2, in the second optically anisotropic layer 14, the in-plane slow axis at the surface 141 of the second optically anisotropic layer 14 facing the polarizer 20 is parallel to the in-plane slow axis at the surface 142 of the second optically anisotropic layer 14 facing the third optically anisotropic layer 16.

[0061] 2 and 3, the in-plane slow axis of the second optically anisotropic layer 14 is parallel to the in-plane slow axis of the surface 161 of the third optically anisotropic layer 16 facing the second optically anisotropic layer 14. Although Figures 2 and 3 show an embodiment in which the in-plane slow axis of the second optically anisotropic layer 14 is parallel to the in-plane slow axis of the surface 161 of the third optically anisotropic layer 16 facing the second optically anisotropic layer 14, the present invention is not limited to this embodiment, and it is preferable that the angle formed by the in-plane slow axis of the second optically anisotropic layer 14 and the in-plane slow axis of the surface 161 of the third optically anisotropic layer 16 facing the second optically anisotropic layer 14 is within the range of 0 to 30°. Therefore, for example, when observed from the white arrow in Figure 1, the in-plane slow axis of the second optically anisotropic layer 14 on the surface 161 of the third optically anisotropic layer 16 facing the second optically anisotropic layer 14 may be positioned 30° clockwise or 30° counterclockwise with respect to the in-plane slow axis of the second optically anisotropic layer 14. As described above, the third optically anisotropic layer 16 is a layer formed by fixing rod-shaped liquid crystal compounds that are twisted and aligned along a helical axis extending in the thickness direction. Therefore, as shown in Figures 2 and 3, the in-plane slow axis of the third optically anisotropic layer 16 on the surface 161 facing the second optically anisotropic layer 14 and the in-plane slow axis of the third optically anisotropic layer 16 on the opposite side to the second optically anisotropic layer 14 form the twist angle described above (80° in Figure 2). That is, the angle φa2 formed by the in-plane slow axis at the surface 161 of the third optically anisotropic layer 16 facing the second optically anisotropic layer 14 and the in-plane slow axis at the surface 162 of the third optically anisotropic layer 16 opposite the second optically anisotropic layer 14 side is 80°. More specifically, the twist direction of the rod-shaped liquid crystal compound in the third optically anisotropic layer 16 is left-handed (counterclockwise), and the twist angle is 80°. Therefore, the angle formed by the absorption axis of the polarizer 20 and the in-plane slow axis at the surface 162 of the third optically anisotropic layer 16 opposite the second optically anisotropic layer 14 side is 4°. Note that, although FIGS. 2 and 3 show an embodiment in which the twist angle of the rod-shaped liquid crystal compound in the third optically anisotropic layer 16 is 80°, the present invention is not limited to this embodiment, and the twist angle of the rod-shaped liquid crystal compound is preferably within the range of 80±30°.In other words, it is preferable that the angle between the in-plane slow axis on surface 161 of the third optical anisotropic layer 16 facing the second optical anisotropic layer 14 and the in-plane slow axis on surface 162 of the third optical anisotropic layer 16 opposite the second optical anisotropic layer 14 is within the range of 80±30°.

[0062] As described above, in the embodiment shown in Figures 2 and 3, when the circular polarizer 100 is observed from the fourth optically anisotropic layer 18 side, the in-plane slow axis of the second optically anisotropic layer 14 is rotated 76° counterclockwise with respect to the absorption axis of the polarizer 20, and the twist direction of the rod-shaped liquid crystal compound in the third optically anisotropic layer 16 is counterclockwise (left-handed twist). Although the embodiment shown in Figures 2 and 3 has been described in detail with the rod-shaped liquid crystal compound twisted counterclockwise, the embodiment may also be clockwise. More specifically, when the circular polarizer 100 is observed from the fourth optically anisotropic layer 18 side, the in-plane slow axis of the second optically anisotropic layer 14 is rotated 76° clockwise with respect to the absorption axis of the polarizer 20, and the twist direction of the rod-shaped liquid crystal compound in the third optically anisotropic layer 16 may be clockwise (right-handed twist).

[0063] That is, in a circular polarizer, when the in-plane slow axis of the second optically anisotropic layer is rotated counterclockwise within a range of 70 to 90° with respect to the absorption axis of the polarizer as a reference when the circular polarizer is observed from the fourth optically anisotropic layer side, it is preferable that the twist direction of the rod-shaped liquid crystal compound in the third optically anisotropic layer is counterclockwise with respect to the in-plane slow axis of the surface of the third optically anisotropic layer facing the fourth optically anisotropic layer. Also, in a circular polarizer, when the in-plane slow axis of the second optically anisotropic layer is rotated clockwise within a range of 70 to 90° with respect to the absorption axis of the polarizer as a reference when the circular polarizer is observed from the fourth optically anisotropic layer side, it is preferable that the twist direction of the rod-shaped liquid crystal compound in the third optically anisotropic layer is clockwise with respect to the in-plane slow axis of the surface of the third optically anisotropic layer facing the fourth optically anisotropic layer.

[0064] <Production Method> The method for producing the circularly polarizing plate is not particularly limited, and may be any known method, such as a method in which a polarizer and a retardation film including the first to fourth optically anisotropic layers 12 to 18 are bonded together via an adhesive layer.

[0065] The method for producing the retardation film is not particularly limited, and known methods can be used. For example, the first to fourth optically anisotropic layers are each produced and then laminated together in a predetermined order via an adhesive layer (e.g., a pressure-sensitive adhesive layer or an adhesive layer), thereby producing a retardation film. The first to fourth optically anisotropic layers can be produced using an optically anisotropic layer-forming composition containing a liquid crystal compound having a polymerizable group, which can be used to form each of the first to fourth optically anisotropic layers.

[0066] Hereinafter, a method for producing optically anisotropic layers (first to fourth optically anisotropic layers) using a composition for forming an optically anisotropic layer containing a liquid crystal compound having a polymerizable group will be described in detail.

[0067] The liquid crystal compound having a polymerizable group (hereinafter also referred to as "polymerizable liquid crystal compound") contained in the composition for forming an optically anisotropic layer is as described above. As described above, a rod-shaped liquid crystal compound or a discotic liquid crystal compound is appropriately selected depending on the properties of the optically anisotropic layer to be formed. The content of the polymerizable liquid crystal compound in the composition for forming an optically anisotropic layer is preferably 60 to 99% by mass, more preferably 70 to 98% by mass, based on the total solid content of the composition for forming an optically anisotropic layer. The solid content refers to components capable of forming an optically anisotropic layer from which the solvent has been removed, and is considered to be solid content even if the component is in a liquid state.

[0068] The optically anisotropic layer-forming composition may contain compounds other than the liquid crystal compound having a polymerizable group. For example, the optically anisotropic layer-forming composition for forming the third optically anisotropic layer 16 preferably contains a chiral agent to helically align the liquid crystal compound. The chiral agent is added to helically align 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., described in "Liquid Crystal Device Handbook," edited by the Japan Society for the Promotion of Science, Committee 142, Chapter 3, Section 4-3, "Chiral Agents for TN and STN," p. 199, 1989) can be used. The amount of chiral agent used is not particularly limited, and is adjusted to achieve the above-mentioned twist angle.

[0069] The composition for forming an optically anisotropic layer may contain a polymerization initiator. The polymerization initiator to be used is selected depending on the type of polymerization reaction, and examples thereof include a thermal polymerization initiator and a photopolymerization initiator. The content of the polymerization initiator in the composition for forming an optically anisotropic layer is preferably 0.01 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total solid content of the composition for forming an optically anisotropic layer.

[0070] Other components that may be contained in the composition for forming an optically anisotropic layer include, in addition to those mentioned above, polyfunctional monomers, alignment control agents (vertical alignment agents, horizontal alignment agents), surfactants, adhesion improvers, plasticizers, and solvents.

[0071] Examples of methods for applying the composition for forming an optically anisotropic layer 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.

[0072] Next, the formed coating film is subjected to an alignment treatment to align the polymerizable liquid crystal compound in the coating film. For example, when forming the first optically anisotropic layer 12, the discotic liquid crystal compound is horizontally aligned. When forming the second optically anisotropic layer 14, the discotic liquid crystal compound is vertically aligned so that the optical axes (axes perpendicular to the disc surface) of the discotic liquid crystal compound are aligned in the same direction. When forming the third optically anisotropic layer 16, the rod-shaped liquid crystal compound is twistedly aligned. When forming the fourth optically anisotropic layer 18, the rod-shaped liquid crystal compound is vertically aligned.

[0073] The alignment treatment can be carried out 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 a change in temperature or pressure. In the case of a lyotropic liquid crystal compound, the transition can also be achieved by adjusting 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.

[0074] 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.

[0075] The refractive index of the optically anisotropic layer in the transmission axis direction of the polarizer can be adjusted by changing the type of compound used. For example, when forming the optically anisotropic layer, the refractive index of the resulting optically anisotropic layer can be adjusted by adjusting the type and content of an additive (e.g., a polyfunctional monomer) for adjusting the refractive index. Furthermore, the refractive index of the optically anisotropic layer in the transmission axis direction of the polarizer can be adjusted by changing the manufacturing conditions. For example, when the curing treatment performed when forming the optically anisotropic layer is a light irradiation treatment, the refractive index of the resulting optically anisotropic layer can be adjusted by performing a heat treatment together with the light irradiation treatment and adjusting the temperature of the heat treatment.

[0076] Although FIG. 1 illustrates an embodiment in which the first optically anisotropic layer 12 is a negative C plate, this is not limited to this embodiment and the layer may be a positive C plate. In other words, the configuration of the optically anisotropic layer Y is not limited to this embodiment. Furthermore, FIG. 1 illustrates an embodiment in which the second optically anisotropic layer 14 is a negative A plate, this is not limited to this embodiment and the layer may be a positive A plate. In other words, the configuration of the optically anisotropic layer X is not limited to this embodiment. Furthermore, FIG. 1 illustrates an embodiment in which the third optically anisotropic layer 16 is a layer formed by fixing rod-shaped liquid crystal compounds helically aligned along a helical axis extending in the thickness direction. However, this is not limited to this embodiment and the layer may be formed by fixing discotic liquid crystal compounds helically aligned along a helical axis extending in the thickness direction. Furthermore, FIG. 1 illustrates an embodiment in which the fourth optically anisotropic layer 18 is a positive C plate, this is not limited to this embodiment and the layer may be a negative C plate.

[0077] <Applications> The polarizing plate of the present invention can be used in various applications. For example, the polarizing plate of the present invention can be used as a circular polarizing plate. A circular polarizing plate is an optical element that converts unpolarized light into circularly polarized light. The circular polarizing plate of the present invention having the above-mentioned configuration is suitable for use in anti-reflection applications in display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescent displays (ELDs), and cathode ray tube displays (CRTs).

[0078] The polarizing plate of the present invention can be suitably applied to a display device. The display device of the present invention has a display element and the above-mentioned polarizing plate (preferably a circular polarizing plate). The display device of the present invention preferably has a surface protective film including a hard coat layer in addition to the display element and the above-mentioned polarizing plate. When the polarizing plate of the present invention is applied to a display device, it is preferably applied as the above-mentioned circular polarizing plate. In this case, the circular polarizing plate is arranged on the viewing side, and the polarizer in the circular polarizing plate is arranged on the viewing side. When the display device further has a surface protective film, the surface protective film is arranged further on the viewing side than the polarizer. The display element is not particularly limited, and examples thereof include an organic electroluminescence display element and a liquid crystal display element.

[0079] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment details, and treatment procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0080] Example 1 (Preparation of Cellulose Acylate Film) The following composition was charged into a mixing tank, stirred, and heated at 90°C for 10 minutes. The resulting composition was then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope. The solid content of the dope was 23.5% by mass, and the solvent for the dope was methylene chloride / methanol / butanol = 81 / 18 / 1 (mass ratio).

[0081] ------------------------------------------------ Cellulose acylate dope ------------------------------------------------ Cellulose acylate (acetyl substitution degree 2.86, viscosity average degree of polymerization 310) 100 parts by mass Sugar ester compound 1 (shown in the following formula (S4)) 6.0 parts by mass Sugar ester compound 2 (shown in the following 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) ------------------------------------------------

[0082]

[0083]

[0084] The dope prepared above was cast using a drum film-forming machine. The dope 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.

[0085] The web (film) obtained by casting was peeled from the drum and then 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. Subsequently, the web was post-dried by zone heating while being transported with a roll. The obtained web was knurled and then wound up. The obtained cellulose acylate film had a thickness of 40 μm, an in-plane retardation of 1 nm at a wavelength of 550 nm, and a thickness-direction retardation of 26 nm at a wavelength of 550 nm. The cellulose acylate film is also referred to as an optically anisotropic layer (1a).

[0086] 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. ２The 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 drained with an air knife three times, and then transported to a drying zone at 70° C. for 10 seconds to dry, thereby preparing an alkali-saponified cellulose acylate film.

[0087] --------------------------------------------------- Alkaline solution ----------------------------------- Potassium hydroxide 4.7 parts by mass Water 15.8 parts by mass Isopropanol 63.7 parts by mass Surfactant: C 14 H 29 O(CHCHO) 20 H 1.0 mass part Propylene glycol 14.8 mass parts

[0088] (Formation of Orientation Film) An orientation film coating solution 1 having the following composition was continuously applied to the alkali saponified surface of the cellulose acylate film using a #14 wire bar. The resulting coating film was then dried with hot air at 60°C for 60 seconds and then with hot air at 100°C for 120 seconds to obtain orientation film 1.

[0089] ------------------------------------------------------------------ Alignment film coating solution 1 -------------------------------------------------- Modified polyvinyl alcohol shown below: 28 parts by mass Citric acid ester (AS3, manufactured by Sankyo Chemical Co., Ltd.) 1.2 parts by mass Photopolymerization initiator (Irgacure 2959, manufactured by BASF) 0.84 parts by mass Glutaraldehyde 2.8 parts by mass Water 699 parts by mass Methanol 226 parts by mass ------------------------------------------------------------------

[0090] (Modified polyvinyl alcohol) Degree of polymerization: 300

[0091]

[0092] (Formation of Optically Anisotropic Layer (1b)) The alignment film 1 prepared above was continuously subjected to a rubbing treatment. At this time, the longitudinal direction of the long film (cellulose acylate film) was parallel to the transport direction, and the angle between the longitudinal direction of the film (transport direction) and the rotation axis of the rubbing roller was 76°. The longitudinal direction (transport direction) of the film was set to 90°, and when observed from the film side, the width direction of the film was set as the reference (0°) and the clockwise direction was expressed as a positive value, so the rotation axis of the rubbing roller was at -14°. In other words, when observed from the film side, the position of the rotation axis of the rubbing roller was rotated 76° clockwise with the longitudinal direction of the film as the reference.

[0093] Onto the rubbed alignment film, a composition for forming an optically anisotropic layer (1b) containing a discotic liquid crystal compound of the following composition was applied using a Giesser coater to form a composition layer. The resulting composition layer was then heated with hot air at 100°C for 2 minutes to dry the solvent and ripen the alignment of the discotic liquid crystal compound. Subsequently, the resulting composition layer was irradiated with UV light (500 mJ / cm) at 90°C. ２) was performed to fix the alignment of the discotic liquid crystal compound, thereby forming an optically anisotropic layer (1b) corresponding to the second optically anisotropic layer. The optically anisotropic layer (1b) corresponded to the optically anisotropic layer X and was a negative A plate. The thickness of the optically anisotropic layer (1b) was approximately 1.7 μm. Furthermore, the retardation at a wavelength of 550 nm was 158 nm. The average tilt angle of the discotic surface of the discotic liquid crystal compound with respect to the film surface was 90°, confirming that the compound was aligned perpendicular to the film surface. Furthermore, the angle of the in-plane slow axis of the optically anisotropic layer (1b) was parallel to the rotation axis of the rubbing roller, and when the width direction of the film was 0° (the longitudinal direction was 90° counterclockwise and −90° clockwise), the in-plane slow axis direction of the optically anisotropic layer (1b) was −14° when viewed from the optically anisotropic layer (1b) side.

[0094] ------------------------------------------------ Composition for forming optically anisotropic layer (1b) -------------------------------------------------- 80 parts by mass of discotic liquid crystal compound 1 described below 20 parts by mass of discotic liquid crystal compound 2 described below 0.55 parts by mass of alignment film interface aligning agent 1 described below 0.1 part by mass of fluorine-containing compound A described below 0.05 part by mass of fluorine-containing compound B described below 0.21 parts by mass of fluorine-containing compound C described below 10 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 3.0 parts by mass of photopolymerization initiator (Irgacure 907, manufactured by BASF) 200 parts by mass of methyl ethyl ketone --------------------------------------------------

[0095] Discotic liquid crystal compound 1

[0096]

[0097] Discotic liquid crystal compound 2

[0098]

[0099] Alignment film interface alignment agent 1

[0100]

[0101] Fluorine-containing compound A (in the following formula, a and b represent the content (% by mass) of each repeating unit relative to all repeating units, a represents 90% by mass and b represents 10% by mass. The weight-average molecular weight was 15,000.)

[0102]

[0103] Fluorine-containing compound B (The numerical value for each repeating unit represents the content (% by mass) of all repeating units. The weight-average molecular weight was 12,500.)

[0104]

[0105] Fluorine-containing compound C (the numerical value for each repeating unit represents the content (% by mass) relative to all repeating units. The weight-average molecular weight was 12,500.)

[0106]

[0107] By the above procedure, a laminate (1a-1b) was prepared in which the optically anisotropic layer (1a) and the optically anisotropic layer (1b) were laminated.

[0108] (Formation of Optically Anisotropic Layer (1d)) On the cellulose acylate film prepared above, an optically anisotropic layer-forming composition (1d) containing a rod-shaped liquid crystal compound having the following composition was applied using a Giesser coater to form a composition layer. Thereafter, both ends of the film were held, and a cooling plate (9°C) was placed on the side of the film on which the coating film was formed so as to be 5 mm away from the film, and a heater (75°C) was placed on the side opposite to the side on which the coating film was formed so as to be 5 mm away from the film, and the film was dried for 2 minutes. Next, the obtained film was heated with warm air at 60°C for 1 minute, and then irradiated with a 365 nm UV-LED at an irradiation dose of 100 mJ / cm while nitrogen purging was performed to adjust the atmosphere to an oxygen concentration of 100 ppm by volume or less. ２The resulting coating film was then annealed with hot air at 120°C for 1 minute to form an optically anisotropic layer (1d) corresponding to the fourth optically anisotropic layer. The resulting optically anisotropic layer (1d) was irradiated with UV light (ultra-high pressure mercury lamp; UL750; manufactured by HOYA) at room temperature through a wire grid polarizer at a dose of 7.9 mJ / cm. ２ (wavelength: 313 nm) on the film, thereby forming a composition layer having alignment controllability on the surface. The film thickness of the formed optically anisotropic layer (1d) was 0.7 μm. The in-plane retardation Re at a wavelength of 550 nm was 0 nm, and the retardation Rth in the thickness direction at a wavelength of 550 nm was −88 nm. The average tilt angle of the long axis direction of the rod-like liquid crystal compound with respect to the film plane was 90°, and it was confirmed that the compound was aligned perpendicular to the film plane.

[0109] ------------------------------------------------ Composition for forming optically anisotropic layer (1d) -------------------------------------------------- Rod-like liquid crystal compound (A) below: 100 parts by mass Polymerizable monomer (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.) 4.0 parts by mass Polymerization initiator S-1 (oxime type) below: 5.0 parts by mass Photoacid generator D-1 below: 3.0 parts by mass Polymer M-1 below: 2.0 parts by mass Vertical alignment agent S01 below: 2.0 parts by mass Photoaligning polymer A-1 below: 2.0 parts by mass Methyl ethyl ketone 42.3 parts by mass Methyl isobutyl ketone 627.5 parts by mass

[0110] Rod-like liquid crystal compound (A) (hereinafter referred to as a mixture of compounds)

[0111]

[0112] Polymerization initiator S-1

[0113]

[0114] Photoacid generator D-1

[0115]

[0116] Polymer M-1 (The numerical value for each repeating unit represents the content (% by mass) of all repeating units. The weight-average molecular weight was 58,000.)

[0117]

[0118] Vertical alignment agent S01

[0119]

[0120] Photoalignable polymer A-1 (The numerical value shown for each repeating unit indicates the content (mass%) of each repeating unit relative to all repeating units. The weight-average molecular weight was 69,800.)

[0121]

[0122] (Formation of Optically Anisotropic Layer (1c)) Next, on the optically anisotropic layer (1d) prepared above, a composition for forming an optically anisotropic layer (1c) containing a rod-shaped liquid crystal compound having the following composition was applied using a Giesser coater, and heated with hot air at 80°C for 60 seconds. Subsequently, the obtained composition layer was irradiated with UV (500 mJ / cm) at 80°C. ２ ) was performed to fix the alignment of the liquid crystal compound, thereby forming an optically anisotropic layer (1c) corresponding to the third optically anisotropic layer. The thickness of the optically anisotropic layer (1c) was 1.2 μm, Δnd at a wavelength of 550 nm was 173 nm, and the twist angle of the liquid crystal compound was 84°. When the width direction of the film was set to 0° (the longitudinal direction was 90°), when viewed from the optically anisotropic layer (1c) side, the in-plane slow axis direction (alignment axis angle of the liquid crystal compound) was 11° on the air side and 95° on the side in contact with the optically anisotropic layer (1d). The in-plane slow axis direction of the optically anisotropic layer was expressed as negative when clockwise (right-handed) and positive when counterclockwise (left-handed), with the width direction of the substrate set to 0° as the reference.

[0123] Composition for forming optically anisotropic layer (1c) ---------------------------------------------------------------- Rod-like liquid crystal compound (A) described above 100 parts by mass Ethylene oxide-modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 4 parts by mass Photopolymerization initiator (Irgacure 819, manufactured by BASF) 3 parts by mass Left-handed twisted chiral agent (L1) described below 0.60 parts by mass Fluorine-containing compound C described above 0.08 parts by mass Methyl ethyl ketone 156 parts by mass

[0124] Left-twisted chiral agent (L1) (Bu represents a butyl group)

[0125]

[0126] By the above procedure, a laminate (1c-1d) was prepared in which the optically anisotropic layer (1d) and the optically anisotropic layer (1c) were directly laminated on a continuous cellulose acylate film.

[0127] The surface side of the optically anisotropic layer (1b) formed on the optically anisotropic layer (1a) made of the long cellulose acylate film prepared above and the surface side of the optically anisotropic layer (1c) of the laminate (1c-1d) formed on the long cellulose acylate film prepared above were continuously bonded together via an adhesive A (trade name: SK2057, manufactured by Soken Chemical & Engineering Co., Ltd.) having a thickness of about 20 μm so that the angle between the in-plane slow axis of the optically anisotropic layer (1b) and the in-plane slow axis of the surface side of the optically anisotropic layer (1c) was 3°. Subsequently, the cellulose acylate film which was the optically anisotropic layer (1a) and the rubbed alignment film were peeled off to expose the surface of the optically anisotropic layer (1b) that had been in contact with the cellulose acylate film. In this way, an optical film (1d-1c-1b) was obtained in which the optically anisotropic layer (1d), the optically anisotropic layer (1c), and the optically anisotropic layer (1b) were laminated in this order on a long cellulose acylate film.

[0128] (Preparation of Linear Polarizing Plate) The support surface of a cellulose triacetate film TJ25 (manufactured by Fujifilm Corporation; thickness: 25 μm) was subjected to alkaline saponification treatment. Specifically, the support was immersed in a 1.5 N sodium hydroxide aqueous solution at 55°C for 2 minutes, then washed in a water bath at room temperature, and further neutralized with 0.1 N sulfuric acid at 30°C. After neutralization, the support was washed in a water bath at room temperature and further dried with hot air at 100°C to obtain a polarizer protective film. A rolled polyvinyl alcohol (PVA) film with a thickness of 60 μm was continuously stretched in the longitudinal direction in an iodine aqueous solution and dried to obtain a polarizer with a thickness of 13 μm. The luminous efficiency-corrected single transmittance of the polarizer was 43%. At this time, the absorption axis direction and the longitudinal direction of the polarizer were aligned. The polarizer protective film was attached to one surface of the polarizer using the PVA adhesive described below to prepare a linear polarizing plate.

[0129] (Preparation of PVA adhesive) 100 parts by mass of a polyvinyl alcohol resin having acetoacetyl groups (average degree of polymerization: 1200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%) and 20 parts by mass of methylol melamine were dissolved in pure water at a temperature of 30°C, and the resulting aqueous solution was adjusted to a solids concentration of 3.7% by mass, thereby preparing a PVA adhesive.

[0130] (Preparation of Circular Polarizing Plate) The surface of the optically anisotropic layer (1b) of the long optical film (1d-1c-1b) prepared above and the surface of the polarizer of the long linear polarizing plate prepared above (the surface opposite the polarizer protective film) were continuously bonded via an approximately 20 μm thick adhesive A (trade name: SK2057, manufactured by Soken Chemical & Engineering Co., Ltd.). Subsequently, the cellulose acylate film on the optically anisotropic layer (1d) side was peeled off to expose the surface of the optically anisotropic layer (1d) that had been in contact with the cellulose acylate film. In this way, a circular polarizing plate (P1) consisting of the optical film (1d-1c-1b) and a linear polarizing plate was prepared. At this time, the polarizer protective film, polarizer, optically anisotropic layer (1b), optically anisotropic layer (1c), and optically anisotropic layer (1d) were laminated in this order, and the angle formed between the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (1b) was 76°. The angle formed between the in-plane slow axis of the optically anisotropic layer (1b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (1b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (1d) was 5°.

[0131] Example 2 (Formation of Optically Anisotropic Layer (2a)) A long cellulose acylate film was prepared in the same manner as in Example 1, and an optically anisotropic layer-forming composition (2a) containing a discotic liquid crystal compound having the following composition was applied to the cellulose acylate film using a Giesser coater to form a composition layer. The film on which the composition layer had been 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 while purging with nitrogen so that the atmosphere had an oxygen concentration of 100 ppm by volume or less at a temperature of 95°C. ２ The resulting coating film was then annealed with hot air at 115°C for 25 seconds to form an optically anisotropic layer (2a) corresponding to the first optically anisotropic layer. The optically anisotropic layer (2a) was the optically anisotropic layer Y, and was a negative C plate. The resulting optically anisotropic layer (2a) was irradiated with UV light (ultra-high pressure mercury lamp; UL750; manufactured by HOYA) at room temperature through a wire grid polarizer at a dose of 7.9 mJ / cm. ２By irradiating the optically anisotropic layer (2a) with light (wavelength: 313 nm), a long film 1 was obtained in which the surface of the optically anisotropic layer (2a) was imparted with alignment controllability. The formed optically anisotropic layer (2a) had a film thickness of 0.7 μm. The in-plane retardation Re at a wavelength of 550 nm was 0 nm, and the thickness direction retardation Rth at a wavelength of 550 nm was 35 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film plane was 0°, and it was confirmed that the compound was aligned horizontally with respect to the film plane.

[0132] ------------------------------------------------ Composition for forming optically anisotropic layer (2a)------------------------------------------------ 4 parts by mass of discotic liquid crystal compound 1 shown below 1 part by mass of discotic liquid crystal compound 2 shown below 95.0 parts by mass of discotic liquid crystal compound 3 shown below 12.0 parts by mass of polymerizable monomer 1 shown below 3.0 parts by mass of polymerization initiator S-1 (oxime type) shown below 3.0 parts by mass of photoacid generator D-1 shown below 0.6 parts by mass of photoalignable polymer A-1 shown below 0.2 parts by mass of diisopropylethylamine 475 parts by mass of o-xylene --------------------------------------------------

[0133] Discotic liquid crystal compound 3

[0134]

[0135] Polymerizable Monomer 1

[0136]

[0137] Polymerization initiator S-1

[0138]

[0139] Photoacid generator D-1

[0140]

[0141] Photoalignable polymer A-1 (The alphabet in each repeating unit represents the content (% by mass) of each repeating unit relative to all repeating units, and a and b were 53% by mass and 47% by mass, respectively. The weight-average molecular weight was 183,000.)

[0142]

[0143] (Formation of Optically Anisotropic Layer (2b)) While the long film 1 was continuously transported without being wound up, an optically anisotropic layer-forming composition (2b) containing a discotic liquid crystal compound having the following composition was applied onto the optically anisotropic layer (2a) using a Giesser coater, and the layer was heated with hot air at 100°C for 120 seconds. Subsequently, the obtained composition layer was irradiated with UV light (100 mJ / cm) at 90°C. ２ ) was performed to fix the alignment of the liquid crystal compound, thereby forming an optically anisotropic layer (2b) (corresponding to a negative A plate) corresponding to the second optically anisotropic layer. The optically anisotropic layer (2b) corresponded to the optically anisotropic layer X and was a negative A plate. The thickness of the optically anisotropic layer (2b) was approximately 1.7 μm, and the in-plane retardation at a wavelength of 550 nm was 158 nm. The average tilt angle of the discotic surface of the discotic liquid crystal compound with respect to the film surface was 90°, and it was confirmed that the compound was aligned perpendicular to the film surface. When the width direction of the film was 0° (the longitudinal direction was 90° counterclockwise and −90° clockwise), the in-plane slow axis direction of the optically anisotropic layer (2b) was −14° when viewed from the optically anisotropic layer (2b) side.

[0144] ------------------------------------------------ Optically anisotropic layer-forming composition (2b)------------------------------------------------ 80 parts by mass of the above-mentioned discotic liquid crystal compound 1 20 parts by mass of the above-mentioned discotic liquid crystal compound 2 1.8 parts by mass of the alignment film interface aligning agent 1 described below 10.0 parts by mass of the above-mentioned polymerizable monomer 1 5.0 parts by mass of the above-mentioned polymerization initiator S-1 (oxime type) 0.1 parts by mass of the above-mentioned fluorine-containing compound A 0.21 parts by mass of the below-mentioned fluorine-containing compound D 0.06 parts by mass of the below-mentioned fluorine-containing compound E 2.1 parts by mass of the below-mentioned antifoaming agent 1 299 parts by mass of methyl ethyl ketone

[0145] Alignment film interface alignment agent 1

[0146]

[0147] Fluorine-containing compound D (The numerical value for each repeating unit represents the content relative to all repeating units. The weight-average molecular weight was 12,500.)

[0148]

[0149] Fluorine-containing compound E (The numerical value for each repeating unit represents the content relative to all repeating units. The weight-average molecular weight was 12,500.)

[0150]

[0151] Antifoaming agent 1

[0152]

[0153] According to the above procedure, the optically anisotropic layer (2a) and the optically anisotropic layer (2b) were directly laminated on the long cellulose acylate film, to obtain a laminated film (2a-2b) wound in a roll.

[0154] The surface side of the optically anisotropic layer (2b) of the laminate (2a-2b) formed on the long cellulose acylate film prepared above and the surface side of the optically anisotropic layer (1c) of the laminate (1c-1d) formed on the long cellulose acylate film prepared in Example 1 were continuously bonded together via an adhesive A (trade name: SK2057, manufactured by Soken Chemical & Engineering Co., Ltd.) having a thickness of about 20 μm so that the angle between the in-plane slow axis of the optically anisotropic layer (2b) and the in-plane slow axis of the surface side of the optically anisotropic layer (1c) was 3°. Subsequently, the cellulose acylate film on the optically anisotropic layer (2a) side was peeled off to expose the surface of the optically anisotropic layer (2a) that had been in contact with the cellulose acylate film. In this way, an optical film (2a-2b-1c-1d) was obtained in which an optically anisotropic layer (1d), an optically anisotropic layer (1c), an optically anisotropic layer (2b), and an optically anisotropic layer (2a) were laminated in this order on a long cellulose acylate film.

[0155] (Preparation of Circularly Polarizing Plate) The surface of the optically anisotropic layer (2a) of the long optical film (2a-2b-1c-1d) prepared above and the surface of the polarizer of the long linear polarizing plate prepared in Example 1 (the surface opposite the polarizer protective film) were continuously bonded via an approximately 20 μm thick adhesive A (trade name: SK2057, manufactured by Soken Chemical & Engineering Co., Ltd.). Subsequently, the cellulose acylate film on the optically anisotropic layer (1d) side was peeled off to expose the surface of the optically anisotropic layer (1d) that had been in contact with the cellulose acylate film. In this way, a circularly polarizing plate (P2) consisting of the optical film (2a-2b-1c-1d) and a linear polarizing plate was prepared. At this time, the polarizer protective film, polarizer, optically anisotropic layer (2a), optically anisotropic layer (2b), optically anisotropic layer (1c), and optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (2b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (2b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (2b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed by the polarizer absorption axis and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (1d) was 5°.

[0156] Example 3 (Formation of Optically Anisotropic Layer (3b)) An optically anisotropic layer (3b) was formed in the same manner as in Example 2, except that the temperature during UV irradiation in the preparation of the optically anisotropic layer (2b) was 100°C and the film thickness was changed. The thickness of the optically anisotropic layer (3b) was approximately 2.0 μm, and the in-plane retardation at a wavelength of 550 nm was 158 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film surface was 90°, and it was confirmed that the compound was oriented perpendicular to the film surface. When the width direction of the film was 0° (the longitudinal direction was 90° counterclockwise and −90° clockwise), the in-plane slow axis direction of the optically anisotropic layer (3b) was −14° when viewed from the optically anisotropic layer (3b) side.

[0157] (Preparation of Circularly Polarizing Plate) A circularly polarizing plate (P3) consisting of optical films (2a-3b-1c-1d) and a linear polarizing plate was prepared in the same manner as in Example 2. At this time, a polarizer protective film, a polarizer, an optically anisotropic layer (2a), an optically anisotropic layer (3b), an optically anisotropic layer (1c), and an optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (3b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (3b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (3b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the surface of the optically anisotropic layer (1c) on the side of the optically anisotropic layer (1d) was 5°.

[0158] Example 4 (Formation of Optically Anisotropic Layer (4b)) An optically anisotropic layer (4b) was formed in the same manner as in Example 2, except that in the preparation of the optically anisotropic layer (2b), an optically anisotropic layer-forming composition (4b) using Lumiplus LPK-2000 manufactured by Mitsubishi Gas Chemical Company, Inc. was used instead of polymerizable monomer 1, and the film thickness was changed. The thickness of the optically anisotropic layer (4b) was approximately 2.0 μm, and the in-plane retardation at a wavelength of 550 nm was 158 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film surface was 90°, confirming that the compound was oriented perpendicular to the film surface. When the width direction of the film was 0° (the longitudinal direction was 90° counterclockwise and −90° clockwise), the in-plane slow axis direction of the optically anisotropic layer (4b) was −14° when viewed from the optically anisotropic layer (4b) side.

[0159] ------------------------------------------------ Optically anisotropic layer-forming composition (4b)---------------------------------------------------------------- 80 parts by mass of the above discotic liquid crystal compound 1------------------------------------------------ 20 parts by mass of the above discotic liquid crystal compound 2------------------------------------------------ 1.8 parts by mass of the above alignment film interface aligning agent 1------------------------------------------------ 15.0 parts by mass of Lumiplus LPK-2000------------------------------------------------ 5.0 parts by mass of the above polymerization initiator S-1 (oxime type)------------------------------------------------ 0.1 part by mass of the above fluorine-containing compound A------------------------------------------------ 0.21 parts by mass of the above fluorine-containing compound D------------------------------------------------ 0.06 parts by mass of the above fluorine-containing compound E------------------------------------------------ 2.1 parts by mass of the above antifoaming agent 1------------------------------------------------ 299 parts by mass of methyl ethyl ketone----------------------------------------------------------------

[0160] (Preparation of Circularly Polarizing Plate) A circularly polarizing plate (P4) consisting of optical films (2a-4b-1c-1d) and a linear polarizing plate was prepared in the same manner as in Example 2. At this time, a polarizer protective film, a polarizer, an optically anisotropic layer (2a), an optically anisotropic layer (4b), an optically anisotropic layer (1c), and an optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (4b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (4b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (4b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the surface of the optically anisotropic layer (1c) on the side of the optically anisotropic layer (1d) was 5°.

[0161] Example 5 (Formation of Optically Anisotropic Layer (5a)) An optically anisotropic layer (5a) was formed in the same manner as in Example 2, except that the temperature during UV irradiation in the preparation of the optically anisotropic layer (2a) was 100°C and the film thickness was changed. The film thickness of the formed optically anisotropic layer (5a) was approximately 0.9 μm. The in-plane retardation Re at a wavelength of 550 nm was 0 nm, and the retardation in the thickness direction Rth at a wavelength of 550 nm was 35 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film plane was 0°, and it was confirmed that the compound was aligned horizontally with respect to the film plane.

[0162] (Preparation of Circularly Polarizing Plate) A circularly polarizing plate (P5) consisting of optical films (5a-2b-1c-1d) and a linear polarizing plate was prepared in the same manner as in Example 2. At this time, a polarizer protective film, a polarizer, an optically anisotropic layer (5a), an optically anisotropic layer (2b), an optically anisotropic layer (1c), and an optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (2b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (2b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (2b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the surface of the optically anisotropic layer (1c) on the side of the optically anisotropic layer (1d) was 5°.

[0163] Example 6 (Formation of Optically Anisotropic Layer (5a)) In the same manner as in Example 5, an optically anisotropic layer (5a) was formed.

[0164] (Formation of Optically Anisotropic Layer (3b)) An optically anisotropic layer (3b) was formed in the same manner as in Example 3.

[0165] (Preparation of Circularly Polarizing Plate) A circularly polarizing plate (P6) consisting of optical films (5a-3b-1c-1d) and a linear polarizing plate was prepared in the same manner as in Example 2. At this time, a polarizer protective film, a polarizer, an optically anisotropic layer (5a), an optically anisotropic layer (3b), an optically anisotropic layer (1c), and an optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (3b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (3b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (3b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the surface of the optically anisotropic layer (1c) on the side of the optically anisotropic layer (1d) was 5°.

[0166] Example 7 (Formation of Optically Anisotropic Layer (7a)) An optically anisotropic layer (7a) was formed in the same manner as in Example 2, except that the temperature during UV irradiation in the preparation of the optically anisotropic layer (2a) was 90°C. The film thickness of the formed optically anisotropic layer (7a) was approximately 0.7 μm. The in-plane retardation Re at a wavelength of 550 nm was 0 nm, and the retardation in the thickness direction Rth at a wavelength of 550 nm was 35 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film plane was 0°, and it was confirmed that the compound was aligned horizontally with respect to the film plane.

[0167] (Preparation of Circularly Polarizing Plate) A circularly polarizing plate (P7) consisting of optical films (7a-2b-1c-1d) and a linear polarizing plate was prepared in the same manner as in Example 2. At this time, a polarizer protective film, a polarizer, an optically anisotropic layer (7a), an optically anisotropic layer (2b), an optically anisotropic layer (1c), and an optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (2b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (2b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (2b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the surface of the optically anisotropic layer (1c) on the side of the optically anisotropic layer (1d) was 5°.

[0168] Example 8 (Formation of Optically Anisotropic Layer (8a)) An optically anisotropic layer (8a) was formed in the same manner as in Example 2, except that the film thickness was changed in the preparation of the optically anisotropic layer (2a). The film thickness of the formed optically anisotropic layer (8a) was 0.6 μm. The in-plane retardation Re at a wavelength of 550 nm was 0 nm, and the retardation in the thickness direction Rth at a wavelength of 550 nm was 35 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film plane was 0°, and it was confirmed that the compound was aligned horizontally with respect to the film plane.

[0169] (Preparation of Circularly Polarizing Plate) A circularly polarizing plate (P8) consisting of optical films (8a-2b-1c-1d) and a linear polarizing plate was prepared in the same manner as in Example 2. At this time, a polarizer protective film, a polarizer, an optically anisotropic layer (8a), an optically anisotropic layer (2b), an optically anisotropic layer (1c), and an optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (2b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (2b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (2b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the surface of the optically anisotropic layer (1c) on the side of the optically anisotropic layer (1d) was 5°.

[0170] Comparative Example 1 (Formation of Optically Anisotropic Layer (9a)) An optically anisotropic layer (9a) was formed in the same manner as in Example 2, except that the temperature during UV irradiation in the preparation of the optically anisotropic layer (2a) was 90°C. The film thickness of the formed optically anisotropic layer (9a) was 0.6 μm. The in-plane retardation Re at a wavelength of 550 nm was 0 nm, and the retardation in the thickness direction Rth at a wavelength of 550 nm was 35 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film plane was 0°, and it was confirmed that the compound was aligned horizontally with respect to the film plane.

[0171] (Formation of Optically Anisotropic Layer (9b)) An optically anisotropic layer (9b) was formed in the same manner as in Example 2, except that the temperature during UV irradiation in the preparation of the optically anisotropic layer (2b) was 80°C. The thickness of the optically anisotropic layer (9b) was approximately 1.4 μm, and the in-plane retardation at a wavelength of 550 nm was 158 nm. The average tilt angle of the discotic plane of the discotic liquid crystal compound with respect to the film surface was 90°, and it was confirmed that the compound was oriented perpendicular to the film surface. When the width direction of the film was 0° (the longitudinal direction was 90° counterclockwise and −90° clockwise), the in-plane slow axis direction of the optically anisotropic layer (9b) was −14° when viewed from the optically anisotropic layer (9b) side.

[0172] (Preparation of Circularly Polarizing Plate) A circularly polarizing plate (P9) consisting of optical films (9a-9b-1c-1d) and a linear polarizing plate was prepared in the same manner as in Example 2. At this time, a polarizer protective film, a polarizer, an optically anisotropic layer (9a), an optically anisotropic layer (9b), an optically anisotropic layer (1c), and an optically anisotropic layer (1d) were laminated in this order, and the angle formed by the absorption axis of the polarizer and the in-plane slow axis of the optically anisotropic layer (9b) was 76°. The angle formed by the in-plane slow axis of the optically anisotropic layer (9b) and the in-plane slow axis of the optically anisotropic layer (1c) on the surface facing the optically anisotropic layer (9b) was 3°. The twist angle of the liquid crystal compound in the optically anisotropic layer (1c) was 84°. The angle formed between the absorption axis of the polarizer and the in-plane slow axis of the surface of the optically anisotropic layer (1c) on the side of the optically anisotropic layer (1d) was 5°.

[0173] <Measurement of Optical Properties> Using an AxoScan OPMF-1 (manufactured by OptoScience Corporation), the dependence of Re on the light incident angle and the tilt angle of the optical axis (i.e., the tilt of the direction in which the refractive index of the optically anisotropic layer is maximized relative to the surface of the optically anisotropic layer) were measured at a wavelength of 550 nm, and the in-plane retardation Re at a wavelength of 550 nm and the retardation Rth in the thickness direction at a wavelength of 550 nm of the optically anisotropic layer were determined.

[0174] <Film Thickness Measurement> The thickness of the optically anisotropic layer was measured using a reflection spectroscopic film thickness meter FE3000 (manufactured by Otsuka Electronics Co., Ltd.).

[0175] <Measurement of Refractive Index> The complex reflectance at incident angles of 50 to 70° obtained by ellipsometry was analyzed using an optical model that took refractive index anisotropy into account to determine the n e and n o of the optically anisotropic layer. The refractive index anisotropy Δn was calculated from the n e and n o obtained. The refractive index in the direction of the polarizer's transmission axis was also calculated from the n e and n o obtained. For example, when the transmission axis direction of the polarizer is located at a position shifted x degrees from n e , the refractive index n T in the transmission axis direction is calculated using the following formula: n T = n e * (cos x) / (cos x + sin x) + n e * (sin x) / (cos x + sin x) Note that the above refractive index is at a wavelength of 550 nm. The measurement device used was a Woollam RC2 or a Semilab SE-2000. The refractive index in the direction of the polarizer's transmission axis was also calculated for adjacent layer X and adjacent layer Y using the same procedure as above.

[0176] <Measurement of reflectance> (Mounting on reflective substrate) The circular polarizer prepared above was attached to aluminum foil via adhesive A (product name: SK2057, manufactured by Soken Chemical & Engineering Co., Ltd.) to prepare a circular polarizer with a substrate simulating a display device. The reflectance from 400 to 700 nm was measured from the circular polarizer side of the circular polarizer with substrate using a spectrophotometer CM-700d, and the results of the luminous reflectance Y are shown in Table 1 below.

[0177] <Measurement of Oblique Color> A fluorescent lamp was shone from a polar angle of 45° onto the circular polarizer side of the prepared substrate-attached circular polarizer under bright light, and the reflected light was observed from all directions. The azimuth angle dependency of the color change was evaluated according to the following criteria. The results are shown in Table 1 below. A: No color difference was visible at all, or only a very slight color difference was visible. B: A slight color difference was visible, but within the acceptable range and no problems were encountered in use. C: A color difference was visible.

[0178] In Table 1, the "Refractive Index" column in the "Polarizer" column, the "Refractive Index" column in the "Adhesive (Adjacent Layer Y)" column, the "Refractive Index" column in the "Optically Anisotropic Layer Y" column, the "Refractive Index" column in the "Optically Anisotropic Layer X" column, and the "Refractive Index" column in the "Adhesive (Adjacent Layer X)" column all indicate the refractive index of each member in the transmission axis direction of the polarizer of each Example. In Table 1, the "Angle" column in the "Optically Anisotropic Layer X" column indicates the angle between the transmission axis of the polarizer and the in-plane slow axis of the optically anisotropic layer X.

[0179]

[0180] As shown in Table 1, the polarizing plate of the present invention exhibited the desired effects. Comparison of Example 1 with other Examples confirmed that the polarizing plate had a better effect when it had an optically anisotropic layer Y. Comparison of Example 7 with other Examples confirmed that the polarizing plate had a better effect when the difference between the refractive index of the optically anisotropic layer Y and the refractive index of the adjacent layer Y was within a predetermined range. Comparison of Example 8 with other Examples confirmed that the polarizing plate had a better effect when the optically anisotropic layer Y had a predetermined thickness.

[0181] 12 First optically anisotropic layer 14 Second optically anisotropic layer 16 Third optically anisotropic layer 18 Fourth optically anisotropic layer 20 Polarizer 30 First adhesive layer 32 Second adhesive layer 100 Circularly polarizing plate

Claims

1. A polarizing plate comprising: a polarizer; an optically anisotropic layer X having an in-plane retardation; and an adjacent layer X adjacent to the optically anisotropic layer X, wherein the difference between the refractive index of the optically anisotropic layer X and the refractive index of the adjacent layer X in the transmission axis direction of the polarizer is 0.15 or less; the refractive index anisotropy Δn of the optically anisotropic layer X is 0.09 or less; and the angle between the transmission axis of the polarizer and the in-plane slow axis of the optically anisotropic layer X is 20° or less.

2. The polarizing plate according to claim 1, wherein said optically anisotropic layer X is a layer formed using a thermotropic liquid crystal compound.

3. The polarizing plate according to claim 1, further comprising an optically anisotropic layer Y having a retardation in the thickness direction, the optically anisotropic layer Y being disposed on the side of the optically anisotropic layer X opposite to the adjacent layer X side, and the optically anisotropic layer X and the optically anisotropic layer Y being adjacent to each other.

4. The polarizing plate according to claim 3, further comprising an adjacent layer Y arranged on the opposite side of the optically anisotropic layer Y from the optically anisotropic layer X side and adjacent to the optically anisotropic layer Y, wherein the difference between the refractive index of the optically anisotropic layer X and the refractive index of the optically anisotropic layer Y in the transmission axis direction of the polarizer is 0.15 or less, and the difference between the refractive index of the optically anisotropic layer Y and the refractive index of the adjacent layer Y in the transmission axis direction of the polarizer is 0.15 or less.

5. The polarizing plate according to claim 3, wherein said optically anisotropic layer Y is a layer formed using a thermotropic liquid crystal compound.

6. The polarizing plate according to claim 3, wherein the thickness of the optically anisotropic layer Y is 520 nm±40 nm, 690 nm±40 nm, 860 nm±40 nm, or 980 nm or more.

7. A display device comprising a display element and the polarizing plate according to any one of claims 1 to 6.

8. The display device according to claim 7, wherein the display element is an organic electroluminescence display element.

Images