Phase difference film, circularly polarizing plate, display device

Abstract

The present application provides a kind of phase difference film, circular polarizer and display device which are suitable for display device as circular polarizer in combination with polarizer, and the color tone change is small when observing display device from all azimuths of oblique direction.A kind of phase difference film, wherein, sequentially have the 1st optical anisotropic layer, the 2nd optical anisotropic layer, the 3rd optical anisotropic layer and the 4th optical anisotropic layer, the 1st optical anisotropic layer is C plate, the 2nd optical anisotropic layer is A plate, the 3rd optical anisotropic layer is the layer that liquid crystal compound is fixed by being twisted and oriented along the helical axis extending in the thickness direction, the 1st optical anisotropic layer, the 2nd optical anisotropic layer, the 3rd optical anisotropic layer and the 4th optical anisotropic layer have specified structure.

Description

Technical Field

[0001] This invention relates to a phase difference film, a circular polarizer, and a display device. Background Technology

[0002] Phase retardation films with anisotropic refractive index are used in various applications such as anti-reflective films for display devices and optical compensation films for liquid crystal display devices.

[0003] For example, Patent Document 1 discloses a phase difference plate in which two optical anisotropy layers displaying specified optical properties are stacked.

[0004] Patent Document 1: Japanese Patent No. 5960743

[0005] The inventors have confirmed that combining the optical film with an optical anisotropic layer described in Patent Document 1 with a polarizer to form a circular polarizer is suitable for use in display devices. Furthermore, when the display device is viewed from all angles in the tilt direction, the color tone changes significantly, indicating room for improvement. Summary of the Invention

[0006] In view of the above-mentioned actual situation, the object of the present invention is to provide a phase difference film that is combined with a polarizer to serve as a circular polarizer for display devices, and that exhibits small color tone changes when the display device is viewed from all angles in the tilt direction.

[0007] Furthermore, the present invention also aims to provide a circular polarizer and a display device.

[0008] Based on in-depth research into the problems of the prior art, the inventors discovered that the above-mentioned issues can be solved through the following structure.

[0009] (1) A phase retardation film, wherein it sequentially comprises a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer and a fourth optical anisotropic layer.

[0010] The first optical anisotropy layer is a C-plate.

[0011] The second optical anisotropy layer is plate A.

[0012] The third optical anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction.

[0013] The fourth optical anisotropy layer is a C-plate.

[0014] When the first optical anisotropy layer is a negative C-plate, the second optical anisotropy layer is a negative A-plate, the liquid crystal compound of the third optical anisotropy layer is a rod-shaped liquid crystal compound, and the fourth optical anisotropy layer is a positive C-plate.

[0015] When the first optical anisotropy layer is a positive C-plate, the second optical anisotropy layer is a positive A-plate, the liquid crystal compound of the third optical anisotropy layer is a disk-shaped liquid crystal compound, and the fourth optical anisotropy layer is a negative C-plate.

[0016] The angle between the in-plane slow axis of the second optical anisotropy layer and the in-plane slow axis of the third optical anisotropy layer on the surface of the second optical anisotropy layer is in the range of 0 to 30°.

[0017] (2) According to the phase difference film described in (1), wherein,

[0018] The twist angle of the liquid crystal compound is in the range of 80±30°.

[0019] (3) The phase difference film according to (1) or (2), wherein,

[0020] The absolute value of the retardation in the thickness direction of the first optical anisotropic layer at a wavelength of 550 nm is 5–100 nm.

[0021] (4) The phase difference film according to any one of (1) to (3), wherein,

[0022] The second optical anisotropic layer has an in-plane retardation of 120–240 nm at a wavelength of 550 nm.

[0023] (5) The phase difference film according to any one of (1) to (4), wherein,

[0024] The product of the refractive index anisotropy Δn of the third optical anisotropy layer and the thickness d of the third optical anisotropy layer at a wavelength of 550 nm, Δnd, is 120–240 nm.

[0025] (6) The phase difference film according to any one of (1) to (5), wherein,

[0026] The absolute value of the retardation in the thickness direction of the fourth optical anisotropic layer at a wavelength of 550 nm is 5–100 nm.

[0027] (7) A phase retardation film, wherein it sequentially comprises a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer and a fourth optical anisotropic layer.

[0028] The first optical anisotropic layer is in direct contact with the second optical anisotropic layer or is laminated with an adhesive layer in between.

[0029] The second optical anisotropic layer is in direct contact with the third optical anisotropic layer or is laminated with an adhesive layer in between.

[0030] The third optical anisotropic layer is in direct contact with the fourth optical anisotropic layer or is laminated with an adhesive layer in between.

[0031] At least one of the following requirements 1 to 4 must be met:

[0032] (8) A phase retardation film, wherein it comprises, in sequence, a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer and a fourth optical anisotropic layer.

[0033] The first optical anisotropy layer is a C-plate.

[0034] The second optical anisotropy layer is plate A.

[0035] The third optical anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction.

[0036] The fourth optical anisotropy layer is a C-plate.

[0037] At least one of the first optical anisotropic layer and the second optical anisotropic layer, the second optical anisotropic layer and the third optical anisotropic layer, and the third optical anisotropic layer and the fourth optical anisotropic layer is stacked with an adhesive layer between them.

[0038] The difference between the average refractive index of the adhesive layer and the average refractive index of the optical anisotropic layer adjacent to the adhesive layer is less than 0.10.

[0039] (9) The phase difference film according to (7) or (8), wherein,

[0040] The second optical anisotropic layer and the third optical anisotropic layer are stacked together with an adhesive layer in between.

[0041] The difference between the average refractive index of the adhesive layer and the average refractive index of the second optical anisotropic layer is less than 0.08.

[0042] The difference between the average refractive index of the adhesive layer and the average refractive index of the third optical anisotropic layer is less than 0.08.

[0043] (10) The phase difference film according to (8), wherein all of the following requirements 1 to 4 are satisfied:

[0044] (11) A circular polarizer comprising a polarizer and a phase difference film as described in any one of (1) to (10).

[0045] (12) A display device comprising any one of (1) to (10) a phase difference film or (11) a circular polarizer.

[0046] Invention Effects

[0047] According to the present invention, a phase retardation film that can be combined with a polarizer to serve as a circular polarizer for display devices and exhibits minimal hue variation when the display device is viewed from any angle in the tilt direction is provided.

[0048] Furthermore, according to the present invention, a circular polarizer and a display device can also be provided. Attached Figure Description

[0049] Figure 1 This is an example of a schematic cross-sectional view of the first embodiment of the phase difference film of the present invention.

[0050] Figure 2 This is an example of a schematic cross-sectional view of the first embodiment of the circular polarizer of the present invention.

[0051] Figure 3 This is a diagram showing the relationship between the absorption axis of the polarizer in the first embodiment of the circular polarizer of the present invention and the in-plane slow axis of each of the second and third optical anisotropic layers.

[0052] Figure 4 From Figure 2 A schematic diagram showing the angular relationship between the absorption axis of the polarizer and the in-plane slow axes of the second and third optical anisotropic layers when viewed in the direction of the white arrow.

[0053] Figure 5 This is an example of a schematic cross-sectional view of a second embodiment of the phase difference film of the present invention.

[0054] Figure 6 This is an example of a schematic cross-sectional view of a second embodiment of the circular polarizer of the present invention.

[0055] Figure 7 This is a diagram showing the relationship between the absorption axis of the polarizer and the in-plane slow axis of each of the second and third optical anisotropic layers in the second embodiment of the circular polarizer of the present invention.

[0056] Figure 8 From Figure 6 A schematic diagram showing the angular relationship between the absorption axis of the polarizer and the in-plane slow axes of the second and third optical anisotropic layers when viewed in the direction of the white arrow.

[0057] Figure 9 This is an example of a schematic cross-sectional view of a third embodiment of the phase difference film of the present invention.

[0058] Figure 10 This is an example of a schematic cross-sectional view of the fourth embodiment of the phase difference film of the present invention. Detailed Implementation

[0059] The present invention will now be described in detail.

[0060] In addition, in this specification, the numerical range indicated by “~” refers to the range included by taking the values ​​recorded before and after “~” as the lower limit and upper limit values.

[0061] Furthermore, unless otherwise specified, the in-plane slow axis and in-plane fast axis are defined at a wavelength of 550 nm. That is, unless otherwise specified, for example, the direction of the in-plane slow axis refers to the direction of the in-plane slow axis at a wavelength of 550 nm.

[0062] In this invention, Re(λ) and Rth(λ) represent the in-plane delay and the thickness direction delay at wavelength λ, respectively. Unless otherwise specified, wavelength λ is 550 nm.

[0063] In this invention, Re(λ) and Rth(λ) are values ​​measured at wavelength λ using an AxoScan OPMF-1 (manufactured by Opto Science, Inc.). They are calculated by inputting the refractive index ((nx+ny+nz) / 3) and film thickness (d(μm)) into the AxoScan.

[0064] Slow axis direction (°)

[0065] Re(λ)=R0(λ)

[0066] Rth(λ)=((nx+ny) / 2-nz)×d.

[0067] Additionally, R0(λ) is shown as a value calculated using AxoScan OPMF-1, representing Re(λ).

[0068] In this specification, the refractive index ((nx+ny+nz) / 3) is measured using an Abbe refractometer (NAR-4T, manufactured by ATAGO CO., LTD.) and a sodium lamp (λ=589nm) as the light source. Furthermore, in the case of measuring wavelength dependence, the measurement can be performed using a multi-wavelength Abbe refractometer DR-M2 (manufactured by ATAGO CO., LTD.) combined with an interference filter. In the case of liquid crystal compounds, the average refractive index can be measured by measuring films immobilized by optically isotropic phases using this method.

[0069] Furthermore, values ​​from the Polymer Handbook (JOHN WILEY & SONS, INC) and various optical film catalogs can be used. The average refractive index values ​​of the main optical films are exemplified below: cellulose acylate (1.48), cyclic olefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

[0070] In this specification, the A-board and C-board are defined as follows.

[0071] There are two types of A-plates: positive A-plates and negative A-plates. When the refractive index along the slow axis (the direction with the highest refractive index in the plane) is set as nx, the refractive index in the direction orthogonal to the slow axis in the plane is set as ny, and the refractive index along the thickness direction is set as nz, the positive A-plate satisfies equation (A1), and the negative A-plate satisfies equation (A2). Furthermore, Rth represents a positive value for the positive A-plate and a negative value for the negative A-plate.

[0072] Equation (A1) nx>ny≈nz

[0073] Equation (A2) ny<nx≈nz

[0074] Furthermore, the “≈” above includes not only cases where the two are exactly the same, but also cases where they are substantially the same. “Substantially the same” means, for example, that cases where (ny-nz)×d (where d is the film thickness) is -10 to 10 nm, preferably -5 to 5 nm, are also included in “ny≈nz”, and cases where (nx-nz)×d is -10 to 10 nm, preferably -5 to 5 nm, are also included in “nx≈nz”.

[0075] There are two types of C-plates: positive C-plates and negative C-plates. Positive C-plates satisfy the relationship in equation (C1), while negative C-plates satisfy the relationship in equation (C2). Furthermore, Rth represents a negative value for positive C-plates and a positive value for negative C-plates.

[0076] Equation (C1) nz>nx≈ny

[0077] Equation (C2) nz<nx≈ny

[0078] Furthermore, the “≈” above includes not only cases where the two are exactly the same, but also cases where they are substantially the same. “Substantially the same” means that, for example, the case where (nx-ny)×d (where d is the thickness of the film) is 0 to 10 nm, preferably 0 to 5 nm, is also included in “nx≈ny”.

[0079] In this specification, the average refractive index of optically anisotropic layers such as plate A, plate C, and a layer formed by fixing a liquid crystal compound twisted and oriented along a helical axis extending in the thickness direction is defined as Equation (N1). Furthermore, nx in Equation (N1) is the same as described above, referring to the refractive index in the slow axis direction (the direction with the highest refractive index within the plane), and ny is also the same as described above, referring to the refractive index in the direction orthogonal to the slow axis within the plane.

[0080] Equation (N1) (average refractive index) = (nx + ny) / 2

[0081] Furthermore, the average refractive index of the adhesive layer is also calculated using the above formula (N1). In addition, when the adhesive layer is optically isotropic, the refractive index in any in-plane direction of the adhesive layer is set as the above average refractive index.

[0082] The above average refractive index refers to the average refractive index at a wavelength of 550 nm.

[0083] Furthermore, as shown in the embodiments described later, the aforementioned average refractive index can be measured using a reflective spectrophotometer FE3000 (manufactured by Otsuka Electronics Co., Ltd.). Specifically, using the reflective spectrophotometer FE3000, the reflectance spectrum of the layer whose refractive index is to be measured is measured, and the aforementioned average refractive index can be calculated by applying an n-Cauchy dispersion formula to the obtained reflectance spectrum.

[0084] Furthermore, in this specification, when "layer A and layer B are stacked with an adhesive layer in between", the adhesive layer is stacked with layers A and B in a state of contact with layers A and B. That is, one surface of the adhesive layer is in contact with layer A, and the other surface is in contact with layer B, with the adhesive layer disposed between layers A and B.

[0085] In addition, in this specification, "visible light" refers to light with a wavelength of 400 to 700 nm. Furthermore, "ultraviolet light" refers to light with a wavelength of 10 nm or more but less than 400 nm.

[0086] Furthermore, in this specification, the terms "orthogonal" or "parallel" include the range of errors permissible in the technical field to which this invention pertains. For example, it may mean within ±5° of a tight angle, and the error from the tight angle is preferably within ±3°.

[0087] One characteristic of the phase retardation film of the present invention is the use of a combination of specified optical anisotropic layers.

[0088] <First Embodiment of the Phase Difference Film>

[0089] Hereinafter, a first embodiment of the phase difference film of the present invention will be described with reference to the accompanying drawings. Figure 1 A schematic cross-sectional view showing a first embodiment of the phase difference film of the present invention is shown.

[0090] The phase retardation film 10A has a first optical anisotropic layer 12A, a second optical anisotropic layer 14A, a third optical anisotropic layer 16A and a fourth optical anisotropic layer 18A in sequence.

[0091] The first optical anisotropic layer 12A is a negative C-plate, the second optical anisotropic layer 14A is a negative A-plate, the third optical anisotropic layer 16A is a layer formed by fixing rod-shaped liquid crystal compound LC that is twisted and oriented along a spiral axis extending in the thickness direction, and the fourth optical anisotropic layer 18A is a positive C-plate.

[0092] The in-plane slow axis of the second optical anisotropy layer 14A is parallel to the in-plane slow axis of the third optical anisotropy layer 16A on the surface of the second optical anisotropy layer 14A.

[0093] The following is a detailed description of each layer.

[0094] (First optical anisotropy layer 12A)

[0095] The first optical anisotropic layer 12A is a negative C plate.

[0096] The retardation in the thickness direction of the first optical anisotropic layer 12A at a wavelength of 550 nm is not particularly limited. However, from the viewpoint that the combination of the phase difference film and polarizer of the present invention can be used as a circular polarizer for display devices, and that the color tone change is smaller when the display device is viewed from all angles in the tilt direction (hereinafter, also referred to as "the effect of the present invention is superior"), 5 to 100 nm is preferred, and 10 to 90 nm is more preferred.

[0097] The structure of the first optical anisotropic layer 12A is not particularly limited as long as it is a negative C plate. Examples include layers and resin films formed by fixing a horizontally oriented disk-shaped liquid crystal compound.

[0098] Furthermore, the horizontal orientation of the disk-shaped liquid crystal compound refers to the parallelism between the disk surface of the liquid crystal compound and the main surface of the layer. However, strict parallelism is not required; the angle between the disk surface and the main surface of the layer is preferably in the range of 0 ± 20°, and more preferably in the range of 0 ± 10°.

[0099] Furthermore, in this specification, the "fixed" state refers to the state in which the orientation of the liquid crystal compound is maintained. Specifically, the preferred state is one in which the layer does not flow under normal conditions of 0 to 50°C, or more stringent conditions of -30 to 70°C, and its orientation morphology does not change due to external fields or forces, thus stably and continuously maintaining a fixed orientation morphology.

[0100] As a disc-shaped liquid crystal compound, known compounds can be used.

[0101] Examples of disk-shaped liquid crystal compounds include those described in paragraphs 0020 to 0067 of Japanese Patent Application Publication No. 2007-108732 and paragraphs 0013 to 0108 of Japanese Patent Application Publication No. 2010-244038.

[0102] Disc-shaped liquid crystal compounds can have polymerizable groups.

[0103] In this specification, there are no particular limitations on the type of polymerizable groups. Functional groups capable of undergoing addition polymerization are preferred, polymerizable olefinic unsaturated groups or cyclic polymerizable groups are more preferred, and (meth)acryloyl, vinyl, styrene or allyl are even more preferred.

[0104] There are no particular restrictions on the type of resin that makes up the resin film; for example, TAC (triacetyl cellulose) can be used.

[0105] The first optical anisotropic layer 12A is preferably a layer formed by polymerization of a horizontally oriented disk-shaped liquid crystal compound with polymerizable groups.

[0106] The thickness of the first optical anisotropic layer 12A is not particularly limited. When the first optical anisotropic layer 12A is a layer formed by fixing a horizontally oriented disk-shaped liquid crystal compound, it is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0107] When the first optical anisotropic layer 12A is a resin film, the thickness of the first optical anisotropic layer 12A is preferably 10 to 100 μm, more preferably 15 to 90 μm.

[0108] Furthermore, the thickness of the first optical anisotropic layer 12A refers to the average thickness of the first optical anisotropic layer 12A. The aforementioned average thickness is obtained by measuring the thickness of any five or more points of the first optical anisotropic layer 12A and then taking the arithmetic mean of them.

[0109] (Second optical anisotropy layer 14A)

[0110] The second optical anisotropy layer 14A is the negative A plate.

[0111] The in-plane retardation of the second optical anisotropic layer 14A at a wavelength of 550 nm is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably 120 to 240 nm, and more preferably 130 to 230 nm.

[0112] The retardation in the thickness direction of the second optical anisotropic layer 14A at a wavelength of 550 nm is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably -120 to -60 nm, and more preferably -115 to -65 nm.

[0113] The second optical anisotropy layer 14A can exhibit both forward wavelength dispersion (the characteristic that the in-plane delay decreases as the measurement wavelength increases) and reverse wavelength dispersion (the characteristic that the in-plane delay increases as the measurement wavelength increases). Furthermore, it is preferable to exhibit both forward and reverse wavelength dispersion in a wind-sensitive region.

[0114] The structure of the second optical anisotropy layer 14A is not particularly limited as long as it is a negative A plate. Examples include a layer formed by fixing a disk-shaped liquid crystal compound that is vertically oriented and whose optical axis (orthogonal to the disk surface) is in the same orientation, and a stretched film. From the viewpoint of better performance of the present invention, it is preferable to fix a layer formed by fixing a disk-shaped liquid crystal compound that is vertically oriented and whose optical axis (orthogonal to the disk surface) is in the same orientation.

[0115] Furthermore, the vertical orientation of the disk-shaped liquid crystal compound refers to the fact that the disk surface of the disk-shaped liquid crystal compound is parallel to the thickness direction of the layer. However, strict parallelism is not required; the angle between the disk surface and the thickness direction of the layer is preferably in the range of 0 ± 20°, and more preferably in the range of 0 ± 10°.

[0116] Furthermore, the arrangement of the optical axes (axis orthogonal to the disk surface) of the disk-shaped liquid crystal compound along the same orientation does not require them to be strictly in the same orientation. Rather, it means that when the slow axis orientation is measured at any 20 locations in the plane, the maximum difference between the slow axis orientations at the 20 slow axis orientations (the difference between the two slow axis orientations with the largest difference among the 20 slow axis orientations) is less than 10°.

[0117] As a disk-shaped liquid crystal compound, for example, the disk-shaped liquid crystal compound exemplified in the first optical anisotropy layer 12A can be cited.

[0118] Disc-shaped liquid crystal compounds can have polymerizable groups.

[0119] The types of polymerizable groups that a disc-shaped liquid crystal compound can have are as described above.

[0120] The second optical anisotropic layer 14A is preferably a layer formed by polymerization of a disk-shaped liquid crystal compound having polymerizable groups.

[0121] The thickness of the second optical anisotropic layer 14A is not particularly limited, but is preferably less than 10 μm, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0122] Furthermore, the thickness of the second optical anisotropic layer 14A refers to the average thickness of the second optical anisotropic layer 14A. The aforementioned average thickness is obtained by measuring the thickness of any five or more points of the second optical anisotropic layer 14A and then taking the arithmetic mean of them.

[0123] (Third optical anisotropy layer 16A)

[0124] The third optical anisotropy layer 16A is a layer formed by fixing a rod-shaped liquid crystal compound LC that is twisted and oriented along a helical axis extending in the thickness direction.

[0125] The third optical anisotropy layer 16A is preferably a layer formed by fixing a chiral nematic phase having a so-called helical structure. In addition, when forming the third optical anisotropy layer 16A, it is preferable to use at least a rod-shaped liquid crystal compound and a chiral reagent described later.

[0126] The twist angle (twist angle of the orientation direction of the liquid crystal compound) of the rod-shaped liquid crystal compound is not particularly limited, and is mostly greater than 0° and less than 360°. From the viewpoint of better effect of the present invention, it is preferred to be in the range of 80±30° (in the range of 50 to 110°), and more preferably in the range of 80±20° (in the range of 60 to 100°).

[0127] In addition, regarding the measurement method of the torsion angle, the AxoScan (polarimeter) device from Axometrics was used, and the device analysis software from Axometrics was used for measurement.

[0128] Furthermore, the twisted orientation of the rod-shaped liquid crystal compound refers to the twisting of the rod-shaped liquid crystal compound from one main surface of the third optical anisotropy layer 16A to another main surface, with the thickness direction of the third optical anisotropy layer 16A as the axis. At the same time, the orientation direction (in-plane slow axis direction) of the rod-shaped liquid crystal compound varies depending on its position in the thickness direction of the third optical anisotropy layer 16A.

[0129] In the twisted orientation, the long axis of the rod-shaped liquid crystal compound is arranged parallel to the main surface of the third optical anisotropic layer 16A. However, strict parallelism is not required; the angle between the long axis of the rod-shaped liquid crystal compound and the main surface of the third optical anisotropic layer 16A is preferably in the range of 0 ± 20°, and more preferably in the range of 0 ± 10°.

[0130] The value of the product Δnd of the refractive index anisotropy Δn of the third optical anisotropy layer 16A at a wavelength of 550 nm and the thickness d of the third optical anisotropy layer 16A is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably 120 to 240 nm, and more preferably 130 to 230 nm.

[0131] Regarding the measurement method of Δnd mentioned above, the AxoScan (polarimeter) device from Axometrics Corporation was used, and the device analysis software from Axometrics Corporation was used for measurement.

[0132] The angle between the in-plane slow axis of the second optical anisotropy layer 14A and the in-plane slow axis of the third optical anisotropy layer 16A on the surface of the second optical anisotropy layer 14A is in the range of 0 to 30°, preferably in the range of 0 to 20°.

[0133] There are no particular limitations on the type of rod-shaped liquid crystal compound used to form the third optical anisotropic layer 16A, and well-known compounds can be cited.

[0134] As rod-shaped liquid crystal compounds, examples include the compounds described in claim 1 of Japanese Patent Application Publication No. 11-513019 and paragraphs 0026 to 0098 of Japanese Patent Application Publication No. 2005-289980.

[0135] Rod-shaped liquid crystal compounds can have polymerizable groups.

[0136] The types of polymerizable groups that rod-shaped liquid crystal compounds can possess are as described above.

[0137] The third optical anisotropy layer 16A is preferably a layer formed by polymerization of a rod-shaped liquid crystal compound having polymerizable groups. More specifically, it is more preferably a layer formed by polymerization of a twistedly oriented rod-shaped liquid crystal compound having polymerizable groups.

[0138] The thickness of the third optical anisotropic layer 16A is not particularly limited, but is preferably less than 10 μm, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0139] Furthermore, the thickness of the third optical anisotropic layer 16A refers to the average thickness of the third optical anisotropic layer 16A. This average thickness is obtained by measuring the thickness of the third optical anisotropic layer 16A at any five or more points and then taking the arithmetic mean of these measurements.

[0140] (4th optical anisotropy layer 18A)

[0141] The fourth optical anisotropic layer 18A is a positive C-plate.

[0142] The retardation in the thickness direction of the fourth optical anisotropic layer 18A at a wavelength of 550 nm is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably -100 to -5 nm, and more preferably -100 to -30 nm.

[0143] The fourth optical anisotropy layer 18A has no particular restrictions on its structure as long as it is a positive C-plate. Examples include a layer formed by fixing vertically oriented rod-shaped liquid crystal compounds and a resin film. From the viewpoint of having better effects than the present invention, a layer formed by fixing vertically oriented rod-shaped liquid crystal compounds is preferred.

[0144] Furthermore, the vertical orientation of the rod-shaped liquid crystal compound means that the long axis of the rod-shaped liquid crystal compound is parallel to the thickness direction of the fourth optical anisotropic layer 18A. However, strict parallelism is not required; the angle between the long axis of the rod-shaped liquid crystal compound and the thickness direction of the fourth optical anisotropic layer 18A is preferably in the range of 0 ± 20°, and more preferably in the range of 0 ± 10°.

[0145] As a rod-shaped liquid crystal compound, known compounds can be used.

[0146] As a rod-shaped liquid crystal compound, for example, the rod-shaped liquid crystal compound exemplified in the third optical anisotropy layer 16A can be cited.

[0147] Rod-shaped liquid crystal compounds can have polymerizable groups.

[0148] The types of polymerizable groups that rod-shaped liquid crystal compounds can possess are as described above.

[0149] The fourth optical anisotropy layer 18A is preferably a layer formed by polymerization of a vertically oriented rod-shaped liquid crystal compound with polymerizable groups.

[0150] The thickness of the fourth optical anisotropic layer 18A is not particularly limited, but is preferably less than 10 μm, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0151] Furthermore, the thickness of the fourth optical anisotropic layer 18A refers to the average thickness of the fourth optical anisotropic layer 18A. This average thickness is obtained by measuring the thickness of the fourth optical anisotropic layer 18A at any five or more points and then taking the arithmetic mean of these measurements.

[0152] (Other components)

[0153] The phase retardation film 10A may also contain other components besides the first optical anisotropy layer 12A to the fourth optical anisotropy layer 18A mentioned above.

[0154] (Adhesive layer)

[0155] The phase retardation film 10A can have an adhesive layer between the optical anisotropic layers.

[0156] As an adhesive layer, well-known examples include adhesive layers and bonding agent layers.

[0157] As described in Japanese Patent Application Publication No. 11-149015, generally, from the viewpoint of suppressing reflection, the refractive index of each layer forming the retardation film (e.g., an optical anisotropic layer) is preferably adjusted. The refractive index difference with the bonded object is preferably 0.1 or less, more preferably 0.08 or less, even more preferably 0.06 or less, and particularly preferably 0.03 or less.

[0158] Furthermore, the thickness of the adhesive layer is preferably 0.1 to 50 μm. From the viewpoint of thinning, it is more preferably 25 μm or less, even more preferably 15 μm or less, and particularly preferably 5 μm or less. From the viewpoint of suppressing interference unevenness, it is more preferably 5 μm or more, even more preferably 15 μm or more, and particularly preferably 25 μm or more.

[0159] When an adhesive layer is placed between the layers of an optically anisotropic layer formed by fixing a liquid crystal compound, a high-refractive-index adhesive or bonding agent can also be used.

[0160] To improve the refractive index, it is preferable to use high-refractive-index monomers or high-refractive-index metal particles.

[0161] As a high-refractive-index monomer, it is preferred to have a benzene ring skeleton in the molecule. Examples of monofunctional monomers having a benzene ring skeleton in the molecule include ethoxylated o-phenylphenol ester (meth)acrylate, o-phenylphenol glycidyl ether (meth)acrylate, p-cumylphenoxyethylene glycol ester (meth)acrylate, 2-methacryloyloxyethyl phthalate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, 2-acryloyloxypropyl phthalate, phenoxyethyl ester (meth)acrylate, EO-modified phenol ester (meth)acrylate, phenoxydiethylene glycol ester (meth)acrylate, EO-modified nonylphenol ester (meth)acrylate, PO-modified nonylphenol ester (meth)acrylate, phenyl glycidyl ether (meth)acrylate, neopentyl glycol benzoate (meth)acrylate, nonylphenoxy polyethylene glycol ester (meth)acrylate, ECH-modified phenoxy ester (meth)acrylate, benzyl acrylate (meth)acrylate, and vinylcarbazole, etc.

[0162] Inorganic particles can be cited as examples of high-refractive-index metallic microparticles. Components constituting inorganic particles include metal oxides, metal nitrides, metal oxynitrides, and elemental metals. Metal atoms contained in the aforementioned metal oxides, metal nitrides, metal oxynitrides, and elemental metals can be categorized as titanium atoms, silicon atoms, aluminum atoms, cobalt atoms, and zirconium atoms. Specific examples of inorganic particles include alumina particles, alumina hydrate particles, silica particles, zirconium oxide particles, and inorganic oxide particles such as clay minerals (e.g., montmorillonite). From the viewpoint of refractive index, zirconium oxide particles are preferred.

[0163] The refractive index can be adjusted by changing the amount of inorganic particles.

[0164] There is no particular limitation on the average particle size of the inorganic particles, but when zirconium oxide is used as the main component, it is preferably 1 to 120 nm, more preferably 1 to 60 nm, and even more preferably 2 to 40 nm.

[0165] (Orientation film)

[0166] The retardation film 10A can also have an alignment film. The alignment film can also be disposed between the optical anisotropic layers.

[0167] In addition, such as Figure 1 As shown, the phase retardation film 10A preferably does not have an alignment film between each optical anisotropic layer.

[0168] Orientation films can be formed by methods such as triboelectric treatment with organic compounds (preferably polymers), oblique evaporation of inorganic compounds, forming layers with microgrooves, or accumulating organic compounds (e.g., ω-trisanoic acid, dioctadecylmethylammonium chloride, methyl stearate) based on the Langmuir-Blodgett process (LB film).

[0169] Furthermore, it is also known that alignment films can generate alignment functions by applying an electric field, a magnetic field, or irradiating with light (preferably polarized light).

[0170] The orientation film is preferably formed by friction treatment of the polymer.

[0171] As an example of an alignment film, photoalignment film can also be cited.

[0172] As long as the orientation function can be performed, there is no particular limitation on the thickness of the orientation film. It 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.

[0173] (Substrate)

[0174] The phase retardation film 10A may also have a substrate.

[0175] As a substrate, a transparent substrate is preferred. Furthermore, a transparent substrate refers to a substrate with a visible light transmittance of 60% or more, preferably 80% or more, and more preferably 90% or more.

[0176] The thickness of the substrate is not particularly limited, but it is preferably 10 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 90 μm.

[0177] Furthermore, the substrate can be made of multiple layers. To improve the adhesion between the substrate and the layers disposed on the substrate, surface treatments (e.g., glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment) can be applied to the surface of the substrate.

[0178] Furthermore, an adhesive layer (base coat) can be applied to the substrate.

[0179] The substrate can also be a so-called pseudo-support. For example, after an optical anisotropic layer is fabricated on the substrate, the substrate can be peeled off from the optical anisotropic layer as needed.

[0180] (Manufacturing method of phase retardation film)

[0181] There are no particular restrictions on the manufacturing method of the phase retardation film; well-known methods can be used.

[0182] For example, the first to fourth optical anisotropic layers can be manufactured separately and bonded together in a prescribed order with an adhesive layer (e.g., an adhesive layer or a bonding agent layer) in between, thereby manufacturing a phase retardation film.

[0183] Furthermore, the first to fourth optical anisotropic layers can be manufactured using an optical anisotropic layer forming composition, which can be formed separately and contains liquid crystal compounds having polymerizable groups.

[0184] The following describes in detail a method for manufacturing optical anisotropic layers (first optical anisotropic layer to fourth optical anisotropic layer) using a composition for forming optical anisotropic layers containing a liquid crystal compound having polymerizable groups.

[0185] The liquid crystal compound containing polymerizable groups (hereinafter also referred to as "polymerizable liquid crystal compound") contained in the composition for forming an optical anisotropic layer is as described above. Furthermore, as described above, rod-shaped liquid crystal compounds and disk-shaped liquid crystal compounds are appropriately selected according to the characteristics of the formed optical anisotropic layer.

[0186] The content of polymeric liquid crystal compound in the optical anisotropic layer forming composition is preferably 60 to 99% by mass, more preferably 70 to 98% by mass, relative to the total solid content of the composition.

[0187] In addition, solid components refer to components that can form optical anisotropic layers without solvent, and are also defined as solid components even if they are in liquid form.

[0188] The composition for forming an optical anisotropic layer may also contain compounds other than liquid crystal compounds having polymerizable groups.

[0189] For example, to distort and orient the liquid crystal compound, the composition for forming the optical anisotropy layer 16A preferably contains a chiral reagent. The chiral reagent is added to distort and orient the liquid crystal compound; however, if the liquid crystal compound is an optically active compound with asymmetric carbon or similar structures within its molecule, the chiral reagent is not required. Furthermore, depending on the manufacturing method and the distortion angle, the addition of a chiral reagent may or may not be necessary.

[0190] As a chiral reagent, there are no particular structural limitations as long as it is a substance compatible with the liquid crystal compound to be used. Any of the known chiral reagents can also be used (e.g., "Handbook of Liquid Crystal Devices" edited by the 142nd Committee of the Japan Society for the Promotion of Science, Chapter 3, Item 4-3, TN and STN are chiral reagents, page 199, mid-1989).

[0191] There is no particular limit to the amount of chiral reagent used; the amount is adjusted to achieve the aforementioned torsion angle.

[0192] Compositions for forming optical anisotropic layers may also contain polymerization initiators. The polymerization initiator used is selected according to the form of polymerization reaction; for example, thermal polymerization initiators and photopolymerization initiators can be cited.

[0193] The content of polymerization initiator in the composition for forming optical anisotropic layers is preferably 0.01 to 20% by mass, more preferably 0.5 to 10% by mass, relative to the total solid content of the composition.

[0194] Other components that may be included in the composition for forming optical anisotropic layers, in addition to those mentioned above, include multifunctional monomers, orientation control agents (vertical orientation agents, horizontal orientation agents), surfactants, adhesive modifiers, plasticizers, and solvents.

[0195] Examples of coating methods for compositions used in forming optical anisotropic layers include curtain coating, dip coating, spin coating, printing coating, spray coating, slot coating, roller coating, sliding coating, doctor blade coating, gravure coating, and wire rod coating.

[0196] Next, the formed coating is oriented to orient the polymerizable liquid crystal compound within it. For example, when forming the first optical anisotropic layer 12A, the disk-shaped liquid crystal compound is horizontally oriented. Furthermore, when forming the second optical anisotropic layer 14A, the disk-shaped liquid crystal compound is vertically oriented, with its optical axis (the axis orthogonal to the disk surface) aligned in the same direction. Furthermore, when forming the third optical anisotropic layer 16A, the rod-shaped liquid crystal compound is twisted and oriented. Furthermore, when forming the fourth optical anisotropic layer 18A, the rod-shaped liquid crystal compound is vertically oriented.

[0197] Orientation processing can be performed by drying the coating at room temperature or by heating the coating. In the case of thermotropic liquid crystal compounds, the liquid crystal phase formed by orientation processing can generally be transferred according to changes in temperature or pressure. In the case of lyotropic liquid crystal compounds, transfer can also be achieved through compositional ratios such as solvent volume.

[0198] In addition, there are no particular restrictions on the conditions for heating the coating, 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.

[0199] Furthermore, after heating the coating film, and before the curing process (light irradiation treatment) described later, the coating film can be cooled as needed.

[0200] Next, the coating film after the polymeric liquid crystal compound has been oriented is subjected to a curing process.

[0201] There are no particular limitations on the method of curing the coating film after the polymeric liquid crystal compound has been oriented; for example, light irradiation and heat treatment can be cited. From the viewpoint of manufacturing adaptability, light irradiation is preferred, and ultraviolet irradiation is more preferred.

[0202] There are no particular restrictions on the irradiation conditions for light treatment, but 50–1000 mJ / cm² is preferred. 2 The amount of radiation.

[0203] There are no particular restrictions on the atmosphere during light irradiation treatment, but a nitrogen atmosphere is preferred.

[0204] <First Embodiment of a Circular Polarizer>

[0205] The first embodiment of the phase retardation film of the present invention can be combined with a polarizer to be used as a circular polarizer. Furthermore, a circular polarizer is an optical element that converts unpolarized light into circularly polarized light.

[0206] The circular polarizer of the present invention having the above structure is preferably used for anti-reflective applications in display devices such as liquid crystal display (LCD), plasma display panel (PDP), electroluminescent display (ELD), and cathode ray tube display (CRT).

[0207] A polarizer is any component that can convert natural light into specific linearly polarized light; for example, an absorption polarizer can be cited.

[0208] There are no particular restrictions on the type of polarizer; commonly used polarizers can be used, such as iodine-based polarizers, dye-based polarizers utilizing dichroic substances, and polyene-based polarizers. Iodine-based and dye-based polarizers are typically manufactured by adsorbing iodine or dichroic dyes onto polyvinyl alcohol and then stretching it.

[0209] In addition, protective films can be configured on one or both sides of the polarizer.

[0210] Figure 2 A schematic cross-sectional view of one embodiment of the circular polarizer 100A is shown. Furthermore, Figure 3 It is shown Figure 2A diagram showing the relationship between the absorption axis of polarizer 20 in the circular polarizer 100A and the in-plane slow axes of the second optical anisotropic layer 14A and the third optical anisotropic layer 16A. Additionally, Figure 3 The arrows in the intermediate polarizer 20 indicate the absorption axis, and the arrows in the second optical anisotropic layer 14A and the third optical anisotropic layer 16A indicate the in-plane slow axis in each layer.

[0211] and, Figure 4 It shows from Figure 2 The white arrows show the angular relationship between the absorption axis (dashed line) of polarizer 20 and the in-plane slow axes (solid lines) of the second optical anisotropy layer 14A and the third optical anisotropy layer 16A, respectively.

[0212] In addition, from Figure 2 When observed using the white arrow, the rotation angle of the slow axis within the plane is represented by a positive angle value in the counterclockwise direction and a negative angle value in the clockwise direction, with the absorption axis of polarizer 20 as the reference (0°). Furthermore, from... Figure 2 When observing the white arrow in the diagram, the direction of the liquid crystal compound's twist is determined by the in-plane slow axis on the surface of the front side (opposite to the polarizer 20 side) of the third optical anisotropy layer 16A, to determine whether it is right-hand twist (clockwise) or left-hand twist (counterclockwise).

[0213] like Figure 2 As shown, the circular polarizer 100A sequentially includes a polarizer 20, a first optical anisotropic layer 12A, a second optical anisotropic layer 14A, a third optical anisotropic layer 16A, and a fourth optical anisotropic layer 18A.

[0214] like Figures 3-4 As shown, the angle φa1 between the absorption axis of polarizer 20 and the in-plane slow axis of the second optical anisotropy layer 14A is 75°. More specifically, the in-plane slow axis of the second optical anisotropy layer 14A is rotated -75° (75° clockwise) relative to the absorption axis of polarizer 20. Furthermore, in Figures 3-4 The diagram shows the in-plane slow axis of the second optical anisotropy layer 14A located at -75°, but the invention is not limited to this arrangement; it is preferably within the range of -75 ± 13°. That is, the angle between the absorption axis of the polarizer 20 and the in-plane slow axis of the second optical anisotropy layer 14A is preferably within the range of 75 ± 13°.

[0215] In addition, such as Figure 3 As shown, in the second optical anisotropy layer 14A, the in-plane slow axis of the second optical anisotropy layer 14A on the surface 141A on the polarizer 20 side is parallel to the in-plane slow axis of the second optical anisotropy layer 14A on the surface 142A on the third optical anisotropy layer 16A side.

[0216] like Figures 3-4 As shown, the in-plane slow axis of the second optical anisotropy layer 14A is parallel to the in-plane slow axis of the third optical anisotropy layer 16A on the surface 161A on the side of the second optical anisotropy layer 14A.

[0217] In addition, Figures 3-4 The diagram shows the in-plane slow axis of the second optical anisotropy layer 14A parallel to the in-plane slow axis of the third optical anisotropy layer 16A on the surface 161A of the second optical anisotropy layer 14A. However, the invention is not limited to this arrangement; the angle between the in-plane slow axis of the second optical anisotropy layer 14A and the in-plane slow axis of the third optical anisotropy layer 16A on the surface 161A of the second optical anisotropy layer 14A can be within the range of 0 to 30°. Therefore, for example, from... Figure 2 When observing with the white arrow, with the in-plane slow axis of the second optical anisotropy layer 14A as the reference, the in-plane slow axis of the third optical anisotropy layer 16A on the surface 161A on the side of the second optical anisotropy layer 14A can be configured at a position of 30° clockwise or 30° counterclockwise.

[0218] As described above, the third optical anisotropy layer 16A is a layer formed by fixing a rod-shaped liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction. Therefore, as Figures 3-4 As shown, the in-plane slow axis of the third optical anisotropy layer 16A on the surface 161A on the side of the second optical anisotropy layer 14A and the in-plane slow axis of the third optical anisotropy layer 16A on the surface 162A on the side opposite to the second optical anisotropy layer 14A form the aforementioned twist angle (in addition, Figure 3 The angle φa2 between the in-plane slow axis of the third optical anisotropy layer 16A on the surface 161A on the side of the second optical anisotropy layer 14A and the in-plane slow axis of the third optical anisotropy layer 16A on the surface 162A opposite to the side of the second optical anisotropy layer 14A is 80°. More specifically, the twisting direction of the rod-shaped liquid crystal compound in the third optical anisotropy layer 16A is right-hand twist (clockwise), and its twisting angle is 80°. Therefore, the angle between the absorption axis of the polarizer 20 and the in-plane slow axis of the third optical anisotropy layer 16A on the surface 162A opposite to the side of the second optical anisotropy layer 14A is 5°.

[0219] In addition, Figures 3-4The diagram shows a twist angle of 80° for the rod-shaped liquid crystal compound in the third optical anisotropy layer 16A, but it is not limited to this arrangement. The twist angle of the rod-shaped liquid crystal compound is preferably in the range of 80 ± 30°. That is, the angle between the in-plane slow axis of the third optical anisotropy layer 16A on the surface 161A on the side of the second optical anisotropy layer 14A and the in-plane slow axis of the third optical anisotropy layer 16A on the surface 162A opposite to the side of the second optical anisotropy layer 14A is preferably in the range of 80 ± 30°.

[0220] As mentioned above, in Figures 3-4 In this method, when observing the circular polarizer 100A from the phase difference film 10A side, with the absorption axis of the polarizer 20 as the reference, the in-plane slow axis of the second optical anisotropy layer 14A is rotated 75° clockwise, and the twisting direction of the rod-shaped liquid crystal compound in the third optical anisotropy layer 16A is clockwise (right twist).

[0221] exist Figures 3-4 The text describes in detail that the twisting direction of the rod-shaped liquid crystal compound is clockwise, but it can also be counterclockwise as long as the specified angular relationship is met. More specifically, it can also be done as follows: when observing the circular polarizer 100A from the phase retardation film 10A side, with the absorption axis of the polarizer 20 as the reference, the in-plane slow axis of the second optical anisotropy layer 14A is rotated counterclockwise by 75°, and the twisting direction of the rod-shaped liquid crystal compound in the third optical anisotropy layer 16A is counterclockwise (left twist).

[0222] That is, in the circular polarizer of the first embodiment including the retardation film, when the circular polarizer is viewed from the retardation film side, with the absorption axis of the polarizer as a reference, the in-plane slow axis of the second optical anisotropy layer rotates clockwise within a range of 75±13° (preferably 75±10°), preferably with the in-plane slow axis of the third optical anisotropy layer on the surface of the fourth optical anisotropy layer as a reference, and the twisting direction of the rod-shaped liquid crystal compound in the third optical anisotropy layer is clockwise.

[0223] Furthermore, in the circular polarizer of the first embodiment including the retardation film, when the circular polarizer is viewed from the retardation film side, with the absorption axis of the polarizer as a reference, the in-plane slow axis of the second optical anisotropy layer rotates counterclockwise within a range of 75±13° (preferably 75±10°), preferably with the in-plane slow axis of the third optical anisotropy layer on the surface of the fourth optical anisotropy layer as a reference, the twisting direction of the rod-shaped liquid crystal compound in the third optical anisotropy layer is counterclockwise.

[0224] The aforementioned circular polarizer may have other components besides the phase difference film and polarizer.

[0225] Circular polarizers can have an adhesive layer between the phase retardation film and the polarizer.

[0226] As an adhesive layer, examples include the aforementioned known adhesive layers and bonding agent layers.

[0227] There are no particular limitations on the manufacturing method of the aforementioned circular polarizer; any well-known method can be cited.

[0228] For example, one method is to bond a polarizer to a phase retardation film through an adhesive layer.

[0229] <Second Embodiment of the Phase Difference Film>

[0230] Hereinafter, a second embodiment of the phase difference film of the present invention will be described with reference to the accompanying drawings. Figure 5 A schematic cross-sectional view showing a second embodiment of the phase difference film of the present invention is shown.

[0231] The phase retardation film 10B has a first optical anisotropic layer 12B, a second optical anisotropic layer 14B, a third optical anisotropic layer 16B and a fourth optical anisotropic layer 18B in sequence.

[0232] The first optical anisotropic layer 12B is the positive C-plate, the second optical anisotropic layer 14B is the positive A-plate, the third optical anisotropic layer 16B is a layer formed by fixing a disk-shaped liquid crystal compound LC that is twisted and oriented along a spiral axis extending in the thickness direction, and the fourth optical anisotropic layer 18B is the negative C-plate.

[0233] The following is a detailed description of each layer.

[0234] (First optical anisotropy layer 12B)

[0235] The first optical anisotropic layer 12B is a positive C-plate.

[0236] The thickness direction delay of the first optical anisotropic layer 12B at a wavelength of 550 nm is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably -100 to -5 nm, and more preferably -90 to -10 nm.

[0237] The structure of the first optical anisotropic layer 12B is not particularly limited as long as it is a positive C-plate. Examples include a layer formed by fixing vertically oriented rod-shaped liquid crystal compounds and a resin film. From the viewpoint of having better effects than the present invention, a layer formed by fixing vertically oriented rod-shaped liquid crystal compounds is preferred.

[0238] The vertical orientation of the rod-shaped liquid crystal compound means that the long axis of the rod-shaped liquid crystal compound is parallel to the thickness direction of the first optical anisotropic layer 12B. However, strict parallelism is not required, and the angle between the long axis of the rod-shaped liquid crystal compound and the thickness direction of the first optical anisotropic layer 12B is preferably in the range of 0 ± 20°, more preferably in the range of 0 ± 10°.

[0239] As a rod-shaped liquid crystal compound, known compounds can be used.

[0240] As a specific example of a rod-shaped liquid crystal compound, it is described in the first embodiment of the retardation film.

[0241] Rod-shaped liquid crystal compounds can have polymerizable groups.

[0242] The types of polymerizable groups that rod-shaped liquid crystal compounds can possess are as described above.

[0243] The first optical anisotropic layer 12B is preferably a layer formed by polymerization of a vertically oriented rod-shaped liquid crystal compound with polymerizable groups.

[0244] The thickness of the first optical anisotropic layer 12B is not particularly limited, but is preferably less than 10 μm, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0245] Furthermore, the thickness of the first optical anisotropic layer 12B refers to the average thickness of the first optical anisotropic layer 12B. The aforementioned average thickness is obtained by measuring the thickness of the first optical anisotropic layer 12B at any five or more points and then taking the arithmetic mean of these measurements.

[0246] (Second optical anisotropy layer 14B)

[0247] The second optical anisotropy layer 14B is the positive A plate.

[0248] The in-plane delay of the second optical anisotropic layer 14B at a wavelength of 550 nm is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably 120 to 240 nm, and more preferably 130 to 230 nm.

[0249] The retardation in the thickness direction of the second optical anisotropic layer 14B at a wavelength of 550 nm is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably 60 to 120 nm, and more preferably 65 to 115 nm.

[0250] The second optical anisotropy layer 14B can exhibit both forward wavelength dispersion (the characteristic that the in-plane delay decreases as the measurement wavelength increases) and reverse wavelength dispersion (the characteristic that the in-plane delay increases as the measurement wavelength increases). Furthermore, it is preferable to exhibit both forward and reverse wavelength dispersion in a wind-sensitive region.

[0251] The structure of the second optical anisotropic layer 14B is not particularly limited as long as it is a positive A plate. Examples include a layer formed by fixing uniformly oriented rod-shaped liquid crystal compounds and a stretched film. From the viewpoint of having better effects than the present invention, a layer formed by fixing uniformly oriented rod-shaped liquid crystal compounds is preferred.

[0252] In this specification, uniform orientation refers to the state in which the molecular axes of a liquid crystal compound (e.g., the long axis in the case of rod-shaped liquid crystal compounds) are aligned horizontally and in the same orientation relative to the layer surface (optical uniaxiality).

[0253] The level is not required to be a strict level, but rather refers to an orientation in which the tilt angle between the average molecular axis of the liquid crystal compound and the main surface of the layer is less than 20°.

[0254] Furthermore, the same orientation does not require that they be strictly the same orientation. Rather, it means that when the slow axis orientation is measured at any 20 locations in the plane, the maximum difference between the slow axis orientations at the 20 locations (the difference between the two slow axis orientations with the largest difference among the 20 slow axis orientations) is less than 10°.

[0255] As a specific example of a rod-shaped liquid crystal compound, it is described in the first embodiment of the retardation film.

[0256] Rod-shaped liquid crystal compounds can have polymerizable groups.

[0257] The types of polymerizable groups that rod-shaped liquid crystal compounds can possess are as described above.

[0258] The second optical anisotropic layer 14B is preferably a layer formed by polymerizing and fixing a rod-shaped liquid crystal compound having polymerizable groups.

[0259] The thickness of the second optical anisotropic layer 14B is not particularly limited, but is preferably less than 10 μm, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0260] Furthermore, the thickness of the second optical anisotropic layer 14B refers to the average thickness of the second optical anisotropic layer 14B. This average thickness is obtained by measuring the thickness of the second optical anisotropic layer 14B at any five or more points and then taking the arithmetic mean of these measurements.

[0261] (Third optical anisotropy layer 16B)

[0262] The third optical anisotropic layer 16B is a layer formed by fixing a disk-shaped liquid crystal compound LC that is twisted and oriented along a helical axis extending in the thickness direction.

[0263] When forming the third optical anisotropy layer 16B, it is preferable to use at least a disk-shaped liquid crystal compound and a chiral reagent.

[0264] The twist angle (twist angle of the orientation direction of the disk-shaped liquid crystal compound) is not particularly limited, and is mostly greater than 0° and less than 360°. From the viewpoint of better effect of the present invention, it is preferred to be in the range of 80±30° (in the range of 50 to 110°), and more preferably in the range of 80±20° (in the range of 60 to 100°).

[0265] In addition, regarding the measurement method of the torsion angle, the AxoScan (polarimeter) device from Axometrics was used, and the device analysis software from Axometrics was used for measurement.

[0266] Furthermore, the disk-shaped liquid crystal compound twisting orientation refers to the twisting of the disk-shaped liquid crystal compound from one main surface of the third optical anisotropy layer 16B to another main surface, with the thickness direction of the third optical anisotropy layer 16B as the axis. At the same time, the orientation direction (in-plane slow axis direction) of the disk-shaped liquid crystal compound varies depending on its position in the thickness direction of the third optical anisotropy layer 16B.

[0267] In the twisted orientation, the disk-shaped liquid crystal compound is vertically oriented. Furthermore, the vertical orientation of the disk-shaped liquid crystal compound means that the disk surface of the liquid crystal compound is parallel to the thickness direction of the third optical anisotropic layer 16B. However, strict parallelism is not required; the angle between the disk surface and the thickness direction of the third optical anisotropic layer 16B is preferably in the range of 0 ± 20°, more preferably in the range of 0 ± 10°.

[0268] The angle between the in-plane slow axis of the second optical anisotropic layer 14B and the in-plane slow axis of the third optical anisotropic layer 16B on the surface of the second optical anisotropic layer 14B is in the range of 0 to 30°, preferably in the range of 0 to 20°.

[0269] The value of the product Δnd of the refractive index anisotropy Δn of the third optical anisotropy layer 16B at a wavelength of 550nm and the thickness d of the third optical anisotropy layer 16B is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably 120 to 240nm, and more preferably 130 to 230nm.

[0270] Regarding the measurement method of Δnd mentioned above, the AxoScan (polarimeter) device from Axometrics Corporation was used, and the device analysis software from Axometrics Corporation was used for measurement.

[0271] There are no particular limitations on the type of disk-shaped liquid crystal compound used to form the third optical anisotropic layer 16B, and well-known compounds can be cited.

[0272] Disc-shaped liquid crystal compounds can have polymerizable groups.

[0273] The types of polymerizable groups that a disc-shaped liquid crystal compound can have are as described above.

[0274] The third optical anisotropy layer 16B is preferably a layer formed by polymerization of a disk-shaped liquid crystal compound having polymerizable groups. More specifically, it is more preferably a layer formed by polymerization of a disk-shaped liquid crystal compound having polymerizable groups with a twisted orientation.

[0275] The thickness of the third optical anisotropic layer 16B is not particularly limited, but is preferably less than 10 μm, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0276] Furthermore, the thickness of the third optical anisotropic layer 16B refers to the average thickness of the third optical anisotropic layer 16B. This average thickness is obtained by measuring the thickness of the third optical anisotropic layer 16B at any five or more points and then taking the arithmetic mean of these measurements.

[0277] (4th optical anisotropy layer 18B)

[0278] The fourth optical anisotropy layer 18B is a negative C plate.

[0279] The retardation in the thickness direction of the fourth optical anisotropic layer 18B at a wavelength of 550 nm is not particularly limited, but from the viewpoint of better performance of the present invention, it is preferably 5 to 100 nm, and more preferably 10 to 80 nm.

[0280] The fourth optical anisotropy layer 18B has no particular restrictions on its structure as long as it is a negative C plate. Examples include a layer formed by fixing a horizontally oriented disk-shaped liquid crystal compound and a resin film. From the viewpoint of having better effects than the present invention, a layer formed by fixing a horizontally oriented disk-shaped liquid crystal compound is preferred.

[0281] As a disc-shaped liquid crystal compound, known compounds can be used.

[0282] As a disk-shaped liquid crystal compound, for example, the disk-shaped liquid crystal compound exemplified in the second optical anisotropy layer 14A can be cited.

[0283] Disc-shaped liquid crystal compounds can have polymerizable groups.

[0284] The types of polymerizable groups that a disc-shaped liquid crystal compound can have are as described above.

[0285] There are no particular restrictions on the type of resin that makes up the resin film; for example, TAC (triacetyl cellulose) can be used.

[0286] The fourth optical anisotropic layer 18B is preferably a layer formed by polymerization of a horizontally oriented disk-shaped liquid crystal compound with polymerizable groups.

[0287] The thickness of the fourth optical anisotropy layer 18B is not particularly limited. When the fourth optical anisotropy layer 18B is a layer formed by fixing a horizontally oriented disk-shaped liquid crystal compound, it is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 2.0 μm.

[0288] When the fourth optical anisotropic layer 18B is a resin film, the thickness of the fourth optical anisotropic layer 18B is preferably 10 to 100 μm, more preferably 15 to 90 μm.

[0289] Furthermore, the thickness of the fourth optical anisotropic layer 18B refers to the average thickness of the fourth optical anisotropic layer 18B. This average thickness is obtained by measuring the thickness of the fourth optical anisotropic layer 18B at any five or more points and then taking the arithmetic mean of these measurements.

[0290] (Other components)

[0291] The phase retardation film 10B may also contain other components besides the first optical anisotropy layer 12B to the fourth optical anisotropy layer 18B mentioned above.

[0292] Other components can be cited as examples from the first embodiment of the phase retardation film described above.

[0293] There are no particular limitations on the manufacturing methods of the first optical anisotropic layer 12B to the fourth optical anisotropic layer 18B. The manufacturing methods of the first optical anisotropic layer 12A to the fourth optical anisotropic layer 18A mentioned above can be cited as examples.

[0294] <Second Embodiment of Circular Polarizer>

[0295] The second embodiment of the phase difference film of the present invention can be combined with a polarizer to be used as a circular polarizer.

[0296] The circular polarizer of the present invention having the above structure is preferably used for anti-reflective applications in display devices such as liquid crystal display (LCD), plasma display panel (PDP), electroluminescent display (ELD), and cathode ray tube display (CRT).

[0297] The polarizer is as described in the first embodiment.

[0298] Figure 6 A schematic cross-sectional view of one embodiment of the circular polarizer 100B is shown. Furthermore, Figure 7 It is shown Figure 6A diagram showing the relationship between the absorption axis of the polarizer 20 in the circular polarizer 100B and the in-plane slow axes of the second optical anisotropic layer 14B and the third optical anisotropic layer 16B. Additionally, Figure 7 The arrows in the intermediate polarizer 20 indicate the absorption axis, and the arrows in the second optical anisotropic layer 14B and the third optical anisotropic layer 16B indicate the in-plane slow axis in each layer.

[0299] and, Figure 8 It shows from Figure 6 The white arrows show the angular relationship between the absorption axis (dashed line) of polarizer 20 and the in-plane slow axes (solid lines) of the second optical anisotropic layer 14B and the third optical anisotropic layer 16B, respectively.

[0300] In addition, from Figure 6 When observed using the white arrow, the rotation angle of the slow axis within the plane is represented by a positive angle value in the counterclockwise direction and a negative angle value in the clockwise direction, with the absorption axis of polarizer 20 as the reference (0°). Furthermore, from... Figure 6 When observing the white arrow in the diagram, the direction of the twist is determined by the in-plane slow axis on the surface of the front side (opposite to the polarizer 20) of the third optical anisotropy layer 16B as a reference to determine whether it is a right twist (clockwise) or a left twist (counterclockwise).

[0301] like Figure 6 As shown, the circular polarizer 100B sequentially includes a polarizer 20, a first optical anisotropic layer 12B, a second optical anisotropic layer 14B, a third optical anisotropic layer 16B, and a fourth optical anisotropic layer 18B.

[0302] like Figures 7-8 As shown, the angle φb1 between the absorption axis of polarizer 20 and the in-plane slow axis of the second optical anisotropy layer 14B is 15°. More specifically, the in-plane slow axis of the second optical anisotropy layer 14B is rotated 15° (15° counterclockwise) relative to the absorption axis of polarizer 20. Furthermore, in Figures 7-8 The diagram shows the in-plane slow axis of the second optical anisotropy layer 14B positioned at 15°, but the invention is not limited to this configuration; preferably, the angle is within the range of 15 ± 13°. That is, the angle between the absorption axis of the polarizer 20 and the in-plane slow axis of the second optical anisotropy layer 14B is preferably within the range of 15 ± 13°.

[0303] In addition, such as Figure 7 As shown, in the second optical anisotropy layer 14B, the in-plane slow axis of the second optical anisotropy layer 14B on the surface 141B on the polarizer 20 side is parallel to the in-plane slow axis of the second optical anisotropy layer 14B on the surface 142B on the third optical anisotropy layer 16B side.

[0304] like Figures 7-8 As shown, the in-plane slow axis of the second optical anisotropy layer 14B is parallel to the in-plane slow axis of the third optical anisotropy layer 16B on the surface 161B on the side of the second optical anisotropy layer 14B.

[0305] In addition, Figures 7-8 The diagram shows the in-plane slow axis of the second optical anisotropy layer 14B parallel to the in-plane slow axis of the third optical anisotropy layer 16B on the surface 161B on the side of the second optical anisotropy layer 14B. However, the invention is not limited to this arrangement; the angle between the in-plane slow axis of the second optical anisotropy layer 14B and the in-plane slow axis of the third optical anisotropy layer 16B on the surface 161B on the side of the second optical anisotropy layer 14B can be within the range of 0 to 30°. Therefore, for example, from... Figure 6 When observing with the white arrow, with the in-plane slow axis of the second optical anisotropy layer 14B as the reference, the in-plane slow axis of the third optical anisotropy layer 16B on the surface 161B on the side of the second optical anisotropy layer 14B can be configured at a position of 30° clockwise or 30° counterclockwise.

[0306] As described above, the third optical anisotropic layer 16B is a layer formed by fixing a disk-shaped liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction. Therefore, as Figures 7-8 As shown, the in-plane slow axis of the third optical anisotropy layer 16B on the surface 161B on the polarizer 20 side and the in-plane slow axis of the third optical anisotropy layer 16B on the surface 162B on the side opposite to the polarizer 20 side form the aforementioned twist angle (in addition, Figure 7 The angle φb2 between the in-plane slow axis of the third optical anisotropy layer 16B on the surface 161B on the side of the second optical anisotropy layer 14B and the in-plane slow axis of the third optical anisotropy layer 16B on the surface 162B opposite to the side of the second optical anisotropy layer 14B is 80°. More specifically, the disk-shaped liquid crystal compound in the third optical anisotropy layer 16B is twisted to the right (clockwise) with a twist angle of 80°. Therefore, the angle between the absorption axis of the polarizer 20 and the in-plane slow axis of the third optical anisotropy layer 16B on the surface 162B opposite to the side of the second optical anisotropy layer 14B is 95°.

[0307] In addition, Figures 7-8The diagram shows a configuration where the twist angle of the disk-shaped liquid crystal compound in the third optical anisotropy layer 16B is 80°, but it is not limited to this configuration. The twist angle of the disk-shaped liquid crystal compound is preferably within the range of 80 ± 30°. That is, the angle between the in-plane slow axis of the third optical anisotropy layer 16B on the surface 161B on the side of the second optical anisotropy layer 14B and the in-plane slow axis of the third optical anisotropy layer 16B on the surface 162B opposite to the side of the second optical anisotropy layer 14B is preferably within the range of 80 ± 30°.

[0308] As mentioned above, in Figures 7-8 In this method, when observing the circular polarizer 100B from the phase difference film 10B side, with the absorption axis of the polarizer 20 as the reference, the in-plane slow axis of the second optical anisotropy layer 14B is rotated counterclockwise by 15°, and the twisting direction of the disk-shaped liquid crystal compound in the third optical anisotropy layer 16B is clockwise (right twist).

[0309] exist Figures 7-8 The text describes in detail that the twisting direction of the disk-shaped liquid crystal compound is clockwise, but it can also be counterclockwise as long as the specified angular relationship is met. More specifically, it can also be done as follows: when observing the circular polarizer 100B from the phase retardation film 10B side, with the absorption axis of the polarizer 20 as the reference, the in-plane slow axis of the second optical anisotropy layer 14B is rotated 15° clockwise, and the twisting direction of the disk-shaped liquid crystal compound in the third optical anisotropy layer 16B is counterclockwise (left twist).

[0310] That is, in the circular polarizer of the second embodiment including the retardation film, when the circular polarizer is viewed from the retardation film side, with the absorption axis of the polarizer as the reference, the in-plane slow axis of the second optical anisotropy layer rotates counterclockwise within a range of 15±13° (preferably 15±10°), preferably with the in-plane slow axis of the third optical anisotropy layer on the surface of the fourth optical anisotropy layer as the reference, and the twisting direction of the liquid crystal compound in the third optical anisotropy layer is clockwise.

[0311] Furthermore, in the circular polarizer of the second embodiment including the retardation film, when the circular polarizer is observed from the retardation film side, with the absorption axis of the polarizer as a reference, the in-plane slow axis of the second optical anisotropy layer rotates clockwise within a range of 15±13° (preferably 15±10°), preferably with the in-plane slow axis of the third optical anisotropy layer on the surface of the fourth optical anisotropy layer as a reference, and the twisting direction of the liquid crystal compound in the third optical anisotropy layer is counterclockwise.

[0312] The aforementioned circular polarizer may have other components besides the phase difference film and polarizer.

[0313] Circular polarizers can have an adhesive layer between the phase retardation film and the polarizer.

[0314] As an adhesive layer, examples include the aforementioned known adhesive layers and bonding agent layers.

[0315] There are no particular limitations on the manufacturing method of the aforementioned circular polarizer; any well-known method can be cited.

[0316] For example, one method is to bond a polarizer to a phase retardation film through an adhesive layer.

[0317] <Third Embodiment of the Phase Difference Film>

[0318] Hereinafter, a third embodiment of the phase difference film of the present invention will be described with reference to the accompanying drawings. Figure 9 A schematic cross-sectional view showing a third embodiment of the phase difference film of the present invention is shown.

[0319] The phase retardation film 10C has a first optical anisotropic layer 12C, a second optical anisotropic layer 14C, a third optical anisotropic layer 16C and a fourth optical anisotropic layer 18C in sequence, with the second optical anisotropic layer 14C and the third optical anisotropic layer 16C stacked in layers separated by an adhesive layer 22.

[0320] exist Figure 9 In the first optical anisotropic layer 12C, the second optical anisotropic layer 14C is in direct contact with the third optical anisotropic layer 16C, the second optical anisotropic layer 14C is stacked with the third optical anisotropic layer 16C through an adhesive layer 22, and the third optical anisotropic layer 16C is in direct contact with the fourth optical anisotropic layer 18C.

[0321] In addition, Figure 9 In this configuration, the first optical anisotropic layer 12C and the second optical anisotropic layer 14C are in direct contact, but an adhesive layer can also be disposed between them, and the first optical anisotropic layer 12C and the second optical anisotropic layer 14C are stacked with the adhesive layer in between.

[0322] Furthermore, in Figure 9 In this process, the third optical anisotropic layer 16C and the fourth optical anisotropic layer 18C are in direct contact, but an adhesive layer can also be disposed between them, and the third optical anisotropic layer 16C and the fourth optical anisotropic layer 18C are stacked with the adhesive layer in between.

[0323] Furthermore, in Figure 9 In the middle, the second optical anisotropic layer 14C and the third optical anisotropic layer 16C are stacked with an adhesive layer 22 in between, but the second optical anisotropic layer 14C and the third optical anisotropic layer 16C can also be in direct contact.

[0324] In the third embodiment of the phase retardation film of the present invention, at least one of the following requirements 1 to 4 is satisfied. From the viewpoint of superior effect of the present invention, it is preferable to satisfy all requirements 1 to 4.

[0325] Requirement 1: The difference between the average refractive index of the first optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer side of the first optical anisotropic layer is less than 0.10;

[0326] Requirement 2: At least one of the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the first optical anisotropic layer of the second optical anisotropic layer, and the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer of the second optical anisotropic layer, is 0.10 or less;

[0327] Requirement 3: At least one of the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the second optical anisotropic layer, and the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the fourth optical anisotropic layer, is 0.10 or less;

[0328] Requirement 4: The difference between the average refractive index of the fourth optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer side of the fourth optical anisotropic layer is less than 0.10.

[0329] The following is based on Figure 9 Taking the phase difference film as an example, the requirements 1 to 4 will be explained.

[0330] Requirement 1 stipulates that the difference between the average refractive index of the first optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer side of the first optical anisotropic layer is 0.10 or less. Figure 9 In this context, the layer in contact with the surface of the second optical anisotropy layer 14C on the side of the first optical anisotropy layer 12C is the second optical anisotropy layer 14C itself. Therefore, in Figure 9 If the difference between the average refractive index of the first optical anisotropic layer 12C and the average refractive index of the second optical anisotropic layer 14C is less than 0.10, then condition 1 is satisfied.

[0331] The difference mentioned above is the value obtained by subtracting the smaller value from the larger value of the two average refractive indices. When the two values ​​are the same, the difference is 0.

[0332] In addition, Figure 9In the case where the first optical anisotropic layer and the second optical anisotropic layer are in direct contact, but the first optical anisotropic layer and the second optical anisotropic layer are stacked with an adhesive layer in between, and the first optical anisotropic layer is in contact with the adhesive layer, if the difference between the average refractive index of the first optical anisotropic layer and the average refractive index of the adhesive layer is less than 0.10, then condition 1 is satisfied.

[0333] Requirement 2 stipulates that at least one of the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer on the side of the first optical anisotropic layer, and the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer on the side of the third optical anisotropic layer, is 0.10 or less. Figure 9 In this structure, the layer in contact with the surface of the second optical anisotropy layer 14C on the side of the first optical anisotropy layer 12C is the first optical anisotropy layer 12C itself. Furthermore, the layer in contact with the surface of the second optical anisotropy layer 14C on the side of the third optical anisotropy layer 16C is the adhesive layer 22. Therefore, in... Figure 9 If at least one of the difference between the average refractive index of the second optical anisotropic layer 14C and the average refractive index of the first optical anisotropic layer 12C, and the difference between the average refractive index of the second optical anisotropic layer 14C and the average refractive index of the adhesive layer 22 is less than 0.10, then condition 2 is satisfied.

[0334] The difference mentioned above is the value obtained by subtracting the smaller value from the larger value of the two average refractive indices. When the two values ​​are the same, the difference is 0.

[0335] In addition, Figure 9 In the case where the second optical anisotropic layer and the third optical anisotropic layer are stacked with an adhesive layer in between, but when the second optical anisotropic layer and the third optical anisotropic layer are in direct contact, if at least one of the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the first optical anisotropic layer, and the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the third optical anisotropic layer is 0.10 or less, then condition 2 is satisfied.

[0336] Furthermore, in Figure 9In the case where the first optical anisotropic layer and the second optical anisotropic layer are in direct contact, but the first optical anisotropic layer and the second optical anisotropic layer are stacked in a manner separated by an adhesive layer, and the second optical anisotropic layer is in contact with the adhesive layer, if at least one of the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the adhesive layer that is in contact with the surface of the second optical anisotropic layer on the side of the first optical anisotropic layer, and the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the adhesive layer that is in contact with the surface of the second optical anisotropic layer on the side of the third optical anisotropic layer, is 0.10 or less, then condition 2 is satisfied.

[0337] Furthermore, when the first optical anisotropic layer and the second optical anisotropic layer are stacked with an adhesive layer in between, the second optical anisotropic layer is in contact with the adhesive layer, and the second optical anisotropic layer is in direct contact with the third optical anisotropic layer, if at least one of the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the adhesive layer, and the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the third optical anisotropic layer is 0.10 or less, then condition 2 is satisfied.

[0338] Requirement 3 stipulates that at least one of the differences between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the second optical anisotropic layer, and the differences between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the fourth optical anisotropic layer, is 0.10 or less. Figure 9 In this structure, the layer in contact with the surface of the third optical anisotropy layer 16C on the side of the second optical anisotropy layer 14C is the adhesive layer 22. Furthermore, the layer in contact with the surface of the third optical anisotropy layer 16C on the side of the fourth optical anisotropy layer 18C is the fourth optical anisotropy layer 18C itself. Therefore, in... Figure 9 If at least one of the differences between the average refractive index of the third optical anisotropic layer 16C and the average refractive index of the adhesive layer 22, and the differences between the average refractive index of the third optical anisotropic layer 16C and the average refractive index of the fourth optical anisotropic layer 18C, is less than 0.10, then condition 3 is satisfied.

[0339] The difference mentioned above is the value obtained by subtracting the smaller value from the larger value of the two average refractive indices. When the two values ​​are the same, the difference is 0.

[0340] In addition, Figure 9In the case where the second optical anisotropic layer and the third optical anisotropic layer are stacked with an adhesive layer in between, but when the second optical anisotropic layer and the third optical anisotropic layer are in direct contact, if at least one of the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the second optical anisotropic layer, and the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the fourth optical anisotropic layer is 0.10 or less, then condition 3 is satisfied.

[0341] Furthermore, in Figure 9 In the case where the third optical anisotropic layer and the fourth optical anisotropic layer are in direct contact, but the third optical anisotropic layer and the fourth optical anisotropic layer are stacked in a manner separated by an adhesive layer, and the third optical anisotropic layer is in contact with the adhesive layer, if at least one of the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the adhesive layer that is in contact with the surface of the third optical anisotropic layer on the side of the second optical anisotropic layer, and the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the adhesive layer that is in contact with the surface of the third optical anisotropic layer on the side of the fourth optical anisotropic layer, is 0.10 or less, then condition 3 is satisfied.

[0342] Furthermore, when the third optical anisotropic layer and the fourth optical anisotropic layer are stacked with an adhesive layer in between, the third optical anisotropic layer is in contact with the adhesive layer, and the third optical anisotropic layer is in direct contact with the second optical anisotropic layer, if at least one of the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the adhesive layer, and the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the second optical anisotropic layer is 0.10 or less, then condition 3 is satisfied.

[0343] Requirement 4 stipulates that the difference between the average refractive index of the fourth optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer side of the fourth optical anisotropic layer is 0.10 or less. Figure 9 In this context, the layer that contacts the surface of the third optical anisotropy layer 16C on the side of the fourth optical anisotropy layer 18C is the third optical anisotropy layer 16C itself. Therefore, in Figure 9 If the difference between the average refractive index of the fourth optical anisotropic layer 18C and the average refractive index of the third optical anisotropic layer 16C is less than 0.10, then condition 4 is satisfied.

[0344] The difference mentioned above is the value obtained by subtracting the smaller value from the larger value of the two average refractive indices. When the two values ​​are the same, the difference is 0.

[0345] In addition, Figure 9In the case where the fourth optical anisotropic layer is in direct contact with the third optical anisotropic layer, but the fourth optical anisotropic layer is stacked with the third optical anisotropic layer in between, and the fourth optical anisotropic layer is in contact with the adhesive layer, if the difference between the average refractive index of the fourth optical anisotropic layer and the average refractive index of the adhesive layer is less than 0.10, then condition 4 is satisfied.

[0346] (Optical anisotropic layer)

[0347] In the third embodiment of the retardation film, the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C are all different layers. Examples of different layers include layers with different types of liquid crystal compounds used to form the optical anisotropic layer, layers with different orientation morphologies or orientation directions of the liquid crystal compounds in the optical anisotropic layer, and layers with different optical properties (e.g., in-plane retardation and retardation in the thickness direction) of the optical anisotropic layer.

[0348] The first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C are preferably layers formed by fixing an oriented liquid crystal compound, and more preferably layers formed by fixing a liquid crystal compound having polymerizable groups through polymerization.

[0349] There are no particular restrictions on the types of liquid crystal compounds. Generally, liquid crystal compounds can be classified into rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds according to their shape.

[0350] The liquid crystal compound preferably has polymerizable groups. That is, the liquid crystal compound is preferably a polymerizable liquid crystal compound. Examples of polymerizable groups in a polymerizable liquid crystal compound include acryloyl, methacryloyl, epoxy, and vinyl groups.

[0351] Examples of achievable orientation states for liquid crystal compounds include uniform orientation, vertical orientation, mixed orientation, twisted orientation, and tilted orientation. Twisted orientation, in particular, refers to an orientation in which the liquid crystal compound is twisted from one main surface of the optically anisotropic layer to another, about the thickness direction of the optically anisotropic layer as the rotation axis. In twisted orientation, the twist angle (the twist angle of the orientation direction of the liquid crystal compound) is typically greater than 0° and less than 360°.

[0352] At least one of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C can be the aforementioned A plate, which can be a negative A plate or a positive A plate.

[0353] Furthermore, at least one of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C can be the aforementioned C plate, a negative C plate, or a positive C plate.

[0354] Furthermore, at least one of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C may be a layer formed by fixing a twisted liquid crystal compound (a layer formed by fixing a twisted liquid crystal compound along a helical axis extending in the thickness direction).

[0355] The liquid crystal compound used to fix the layer formed by the twisted orientation of the liquid crystal compound is preferably a rod-shaped liquid crystal compound.

[0356] The thickness of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C is not particularly limited, but is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 3.0 μm.

[0357] Furthermore, the thickness of each of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C refers to the average thickness of each layer. This average thickness is calculated by measuring the thickness of each layer at any five or more points and then taking the arithmetic mean of the measurements.

[0358] One preferred embodiment of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C is as follows: the first optical anisotropic layer 12C is a negative C-plate, the second optical anisotropic layer 14C is a negative A-plate, the third optical anisotropic layer 16C is a layer formed by fixing a rod-shaped liquid crystal compound twisted and oriented along a helical axis extending in the thickness direction, and the fourth optical anisotropic layer 18C is a positive C-plate. The angle between the in-plane slow axis of the second optical anisotropic layer 14C and the in-plane slow axis of the third optical anisotropic layer 16C on the surface of the second optical anisotropic layer 14C is in the range of 0° to 30°. This embodiment (hereinafter also referred to as "preferred embodiment 1") corresponds to the embodiment described in the first embodiment of the retardation film described above, and the preferred embodiment of each layer is the same as that of each layer described in the first embodiment.

[0359] Furthermore, as one of the other preferred embodiments of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C, the following embodiment can be provided: the first optical anisotropic layer 12C is a positive C-plate, the second optical anisotropic layer 14C is a positive A-plate, the third optical anisotropic layer 16C is a layer formed by fixing a disk-shaped liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction, the fourth optical anisotropic layer 18C is a negative C-plate, and the angle between the in-plane slow axis of the second optical anisotropic layer 14C and the in-plane slow axis of the third optical anisotropic layer 16C on the surface of the second optical anisotropic layer 14C is in the range of 0° to 30°. This embodiment (hereinafter also referred to as "preferred embodiment 2") corresponds to the embodiment described in the second embodiment of the retardation film described above, and the preferred embodiment of each layer is the same as that of each layer described in the second embodiment.

[0360] (Adhesive layer)

[0361] As an adhesive layer, the adhesive layer (adhesive layer and bonding agent layer) described in the first embodiment of the phase difference film above can be cited as an example.

[0362] More specifically, the adhesive layer is a layer formed using an adhesive. Examples of adhesives include water-based adhesives, solvent-based adhesives, emulsion-based adhesives, solvent-free adhesives, active energy radiation-cured adhesives, and thermosetting adhesives. Examples of active energy radiation-cured adhesives include electron beam-cured adhesives, ultraviolet-cured adhesives, and visible light-cured adhesives, with ultraviolet-cured adhesives being preferred. That is, the adhesive layer is preferably a layer formed using an ultraviolet-cured adhesive.

[0363] As a specific example of an active energy ray-curable adhesive, (meth)acrylate adhesives can be cited. As curing components in (meth)acrylate adhesives, for example, compounds having (meth)acryloyl groups and compounds having vinyl groups can be cited.

[0364] There is no particular limitation on the thickness of the adhesive layer, but it is preferably 0.1 to 5 μm, and more preferably 0.5 to 2 μm.

[0365] An adhesive layer refers to a layer formed using an adhesive. Examples of adhesives include rubber-based adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, polyacrylamide adhesives, and cellulose adhesives, with acrylic adhesives (pressure-sensitive adhesives) being preferred.

[0366] As an acrylic adhesive, a copolymer of (meth)acrylates with alkyl groups of 20 or fewer carbon atoms, such as methyl, ethyl or butyl, in the ester portion is preferred, and a (meth)acrylate monomer having a functional group such as (meth)acrylate or (meth)acrylate hydroxyethyl ester.

[0367] There is no particular limitation on the thickness of the adhesive layer, but it is preferably 1 to 30 μm, and more preferably 5 to 20 μm.

[0368] There are no particular limitations on the manufacturing methods of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C. The manufacturing methods of the first optical anisotropic layer 12A to the fourth optical anisotropic layer 18A mentioned above can be cited as examples.

[0369] More specifically, in order to form a state in which two optically anisotropic layers are in direct contact, for example, after coating an optically anisotropic layer forming composition containing a liquid crystal compound having polymerizable groups on a substrate (preferably containing a raw material (e.g., a photo-alignment polymer) that gives orientation control to the surface of the optically anisotropic layer) to form an optically anisotropic layer, another optically anisotropic layer is formed by coating the formed optically anisotropic layer with an optically anisotropic layer containing a liquid crystal compound having polymerizable groups. This can form a state in which two optically anisotropic layers are in direct contact.

[0370] Furthermore, in order to form a configuration of two optical anisotropic layers separated by an adhesive layer, for example, the aforementioned configuration can be formed by bonding two additionally prepared optical anisotropic layers together separated by an adhesive layer.

[0371] As described above, the phase retardation film of the present invention can be formed by combining a coating method and a bonding method using a composition for forming an optical anisotropic layer containing a liquid crystal compound having polymerizable groups.

[0372] Similar to the first and second embodiments of the phase retardation film described above, the third embodiment of the phase retardation film can be combined with a polarizer to be used as a circular polarizer.

[0373] In the case where the third embodiment of the phase retardation film is the preferred embodiment 1 described above, it is preferable to combine the third embodiment of the phase retardation film and the polarizer in the same layer configuration as the first embodiment of the circular polarizer described above.

[0374] Furthermore, in the case where the third embodiment of the phase retardation film is the preferred embodiment 2 described above, it is preferable to combine the third embodiment of the phase retardation film and the polarizer in the same layer configuration as the second embodiment of the circular polarizer described above.

[0375] In the third embodiment of combining the phase retardation film and the polarizer, the two can be stacked with the aforementioned adhesive layer in between.

[0376] In the third embodiment of the phase retardation film and the polarizer, which are stacked with an adhesive layer in between, the difference between the average refractive index of the optical anisotropic layer in the phase retardation film adjacent to the adhesive layer and the average refractive index of the adhesive layer is preferably 0.10 or less.

[0377] <Fourth Embodiment of the Phase Difference Film>

[0378] Hereinafter, a fourth embodiment of the phase difference film of the present invention will be described with reference to the accompanying drawings. Figure 10 A schematic cross-sectional view showing a fourth embodiment of the phase difference film of the present invention is shown.

[0379] The phase retardation film 10D sequentially comprises a first optical anisotropic layer 12D, a second optical anisotropic layer 14D, a third optical anisotropic layer 16D, and a fourth optical anisotropic layer 18D. The second optical anisotropic layer 14D and the third optical anisotropic layer 16D are stacked with an adhesive layer 22 in between. The adhesive layer 22 is in contact with the second optical anisotropic layer 14D and the third optical anisotropic layer 16D.

[0380] exist Figure 10 In this configuration, the second optical anisotropic layer 14D and the third optical anisotropic layer 16D are stacked with an adhesive layer 22 in between. However, this configuration is not limited to this one. It is permissible as long as at least one of the first optical anisotropic layer and the second optical anisotropic layer, the second optical anisotropic layer and the third optical anisotropic layer, and the third optical anisotropic layer and the fourth optical anisotropic layer are stacked with an adhesive layer in between.

[0381] In the fourth embodiment of the phase difference film of the present invention, the following requirement 5 is satisfied.

[0382] Requirement 5: The difference between the average refractive index of the adhesive layer and the average refractive index of the optical anisotropic layer adjacent to the adhesive layer is less than 0.10.

[0383] The following is based on Figure 10 Taking the phase retardation film as an example, the above points will be explained.

[0384] exist Figure 10 In this configuration, the second optical anisotropic layer 14D and the third optical anisotropic layer 16D are stacked with an adhesive layer 22 in between. In this configuration, the adhesive layer is adjacent to both the second optical anisotropic layer 14D and the third optical anisotropic layer 16D. Therefore, the difference between the average refractive index of the adhesive layer and the average refractive index of the second optical anisotropic layer 14D is 0.10 or less, and the difference between the average refractive index of the adhesive layer and the average refractive index of the third optical anisotropic layer 16D is 0.10 or less.

[0385] Furthermore, when the first optical anisotropic layer 12D and the second optical anisotropic layer 14D are stacked with an adhesive layer 22 in between, and the two optical anisotropic layers (the first optical anisotropic layer 12D and the second optical anisotropic layer 14D) are in contact with the adhesive layer 22, if the difference between the average refractive index of the adhesive layer and the average refractive index of the first optical anisotropic layer 12D is 0.10 or less, and the difference between the average refractive index of the adhesive layer and the average refractive index of the second optical anisotropic layer 14D is 0.10 or less, then condition 5 above is satisfied.

[0386] Furthermore, the third optical anisotropic layer 16D and the fourth optical anisotropic layer 18D are stacked with an adhesive layer 22 in between. When the two optical anisotropic layers (the third optical anisotropic layer 16D and the fourth optical anisotropic layer 18D) are in contact with the adhesive layer 22, if the difference between the average refractive index of the adhesive layer and the average refractive index of the third optical anisotropic layer 16D is less than 0.10, and the difference between the average refractive index of the adhesive layer and the average refractive index of the fourth optical anisotropic layer 18D is less than 0.10, then the above-mentioned requirement 5 is satisfied.

[0387] One of the preferred embodiments of the fourth implementation of the phase retardation film is as follows: the second optical anisotropic layer and the third optical anisotropic layer are stacked with an adhesive layer in between, the difference between the average refractive index of the adhesive layer and the average refractive index of the second optical anisotropic layer is 0.08 or less, and the difference between the average refractive index of the adhesive layer and the average refractive index of the third optical anisotropic layer is 0.08 or less.

[0388] Furthermore, as one of the other preferred embodiments of the retardation film, the following approach can be taken: satisfying all requirements 1 to 4 described in the third embodiment of the retardation film.

[0389] (Optical anisotropic layer)

[0390] In the fourth embodiment of the retardation film, the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D are all different layers. Examples of different layers include layers with different types of liquid crystal compounds used to form the optical anisotropic layer, layers with different orientation morphologies or orientation directions of the liquid crystal compounds in the optical anisotropic layer, and layers with different optical properties (e.g., in-plane retardation and retardation in the thickness direction) of the optical anisotropic layer.

[0391] The first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D are preferably layers formed by fixing an oriented liquid crystal compound, and more preferably layers formed by fixing a liquid crystal compound having polymerizable groups through polymerization.

[0392] There are no particular restrictions on the types of liquid crystal compounds. Generally, liquid crystal compounds can be classified into rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds according to their shape.

[0393] The liquid crystal compound preferably has polymerizable groups. That is, the liquid crystal compound is preferably a polymerizable liquid crystal compound. Examples of polymerizable groups in a polymerizable liquid crystal compound include acryloyl, methacryloyl, epoxy, and vinyl groups.

[0394] Examples of achievable orientation states for liquid crystal compounds include uniform orientation, vertical orientation, mixed orientation, twisted orientation, and tilted orientation. Twisted orientation, in particular, refers to an orientation in which the liquid crystal compound is twisted from one main surface of the optically anisotropic layer to another, about the thickness direction of the optically anisotropic layer as the rotation axis. In twisted orientation, the twist angle (the twist angle of the orientation direction of the liquid crystal compound) is typically greater than 0° and less than 360°.

[0395] At least one of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D can be the aforementioned A plate, which can be a negative A plate or a positive A plate.

[0396] Furthermore, at least one of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D can be the aforementioned C plate, a negative C plate, or a positive C plate.

[0397] Furthermore, at least one of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D may be a layer formed by fixing a twisted liquid crystal compound (a layer formed by fixing a twisted liquid crystal compound along a helical axis extending in the thickness direction).

[0398] The liquid crystal compound used to fix the layer formed by the twisted orientation of the liquid crystal compound is preferably a rod-shaped liquid crystal compound.

[0399] The thickness of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D is not particularly limited, but is preferably 10 μm or less, more preferably 0.1 to 5.0 μm, and even more preferably 0.3 to 3.0 μm.

[0400] Furthermore, the thickness of each of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D refers to the average thickness of each layer. This average thickness is calculated by taking the arithmetic mean of the thicknesses of any five or more points in each layer.

[0401] One preferred embodiment of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D is as follows: the first optical anisotropic layer 12D is a negative C-plate, the second optical anisotropic layer 14D is a negative A-plate, the third optical anisotropic layer 16D is a layer formed by fixing a rod-shaped liquid crystal compound twisted and oriented along a helical axis extending in the thickness direction, the fourth optical anisotropic layer 18D is a positive C-plate, and the angle between the in-plane slow axis of the second optical anisotropic layer 14D and the in-plane slow axis of the third optical anisotropic layer 16D on the surface of the second optical anisotropic layer 14D is in the range of 0° to 30°. This embodiment (hereinafter also referred to as "preferred embodiment 3") corresponds to the embodiment described in the first embodiment of the retardation film described above, and the preferred embodiment of each layer is the same as that of each layer described in the first embodiment.

[0402] Furthermore, as one of the other preferred embodiments of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D, the following embodiment can be provided: the first optical anisotropic layer 12D is a positive C-plate, the second optical anisotropic layer 14D is a positive A-plate, the third optical anisotropic layer 16D is a layer formed by fixing a disk-shaped liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction, the fourth optical anisotropic layer 18D is a negative C-plate, and the angle between the in-plane slow axis of the second optical anisotropic layer 14D and the in-plane slow axis of the third optical anisotropic layer 16D on the surface of the second optical anisotropic layer 14D is in the range of 0° to 30°. This embodiment (hereinafter also referred to as "preferred embodiment 4") corresponds to the embodiment described in the second embodiment of the retardation film described above, and the preferred embodiment of each layer is the same as the preferred embodiment of each layer described in the second embodiment.

[0403] (Adhesive layer)

[0404] As an adhesive layer, the adhesive layer (adhesive layer and bonding agent layer) described in the third embodiment of the phase difference film above can be cited as an example.

[0405] There are no particular limitations on the manufacturing methods of the first optical anisotropic layer 12D to the fourth optical anisotropic layer 18D. The manufacturing methods of the first optical anisotropic layer 12C to the fourth optical anisotropic layer 18C mentioned above can be cited as examples.

[0406] Similar to the first and second embodiments of the phase retardation film described above, the fourth embodiment of the phase retardation film can be combined with a polarizer to be used as a circular polarizer.

[0407] In the case where the fourth embodiment of the phase retardation film is the preferred embodiment 1 described above, it is preferable to combine the fourth embodiment of the phase retardation film and the polarizer in the same layer configuration as the third embodiment of the circular polarizer described above.

[0408] Furthermore, in the case where the fourth embodiment of the phase retardation film is the preferred embodiment 2 described above, it is preferable to combine the fourth embodiment of the phase retardation film and the polarizer in the same layer configuration as the fourth embodiment of the circular polarizer described above.

[0409] In the fourth embodiment of combining the phase retardation film and the polarizer, the two can be stacked with the aforementioned adhesive layer in between.

[0410] In the fourth embodiment of the polarizer and the phase retardation film stacked with an adhesive layer in between, the difference between the average refractive index of the optical anisotropic layer in the phase retardation film adjacent to the adhesive layer and the average refractive index of the adhesive layer is preferably 0.10 or less.

[0411] <Uses>

[0412] The aforementioned phase retardation film can be used for various applications. For example, the optical properties of each optical anisotropy layer can be adjusted, and it can be used as a so-called λ / 4 plate or λ / 2 plate.

[0413] In addition, a λ / 4 plate refers to a plate that has the function of converting linearly polarized light of a specific wavelength into circularly polarized light (or converting circularly polarized light into linearly polarized light). More specifically, it is a plate whose in-plane delay Re at a specified wavelength λnm is represented by λ / 4 (or an odd multiple thereof).

[0414] The in-plane delay (Re(550)) of the λ / 4 plate at a wavelength of 550nm can have an error of about 25nm centered on the ideal value (137.5nm), for example, preferably 110-160nm, more preferably 120-150nm.

[0415] Furthermore, the λ / 2 plate refers to an optically anisotropic film whose in-plane retardation Re(λ) at a specific wavelength λnm satisfies Re(λ)≈λ / 2. This formula can be implemented at any wavelength in the visible light region (e.g., 550nm). Preferably, the in-plane retardation Re(550) at a wavelength of 550nm satisfies the following relationship.

[0416] 210nm≤Re(550)≤300nm

[0417] <Display Device>

[0418] The phase difference film (first to fourth embodiments) and circular polarizer (first and second embodiments) of the present invention are preferably applicable to display devices.

[0419] The display device of the present invention includes a display element and the aforementioned phase difference film or circular polarizer.

[0420] The display device of the present invention preferably includes a display element and a surface protective film containing a hard coating in addition to the aforementioned phase difference film or circular polarizer.

[0421] When the phase retardation film of the present invention is applied to a display device, it is preferably used as the circular polarizer described above. In this case, the circular polarizer is disposed on the visual recognition side, and the polarizer in the circular polarizer is disposed on the visual recognition side. If the display device also has a surface protective film, the surface protective film is disposed closer to the visual recognition side than the polarizer. That is, the surface protective film, polarizer, phase retardation film, and display element are disposed sequentially from the visual recognition side.

[0422] There are no particular limitations on display elements; examples include organic electroluminescent display elements and liquid crystal display elements.

[0423] <Other Structures>

[0424] From the viewpoint of improving the light resistance of display elements, the hard coating of the adhesive layer or substrate and the surface protective film of the display device of the present invention, which are closer to the visual recognition side than the display element, may also contain an ultraviolet absorber. The ultraviolet absorber is not particularly limited, and various known ultraviolet absorbers can be used. For example, the ultraviolet absorber described in International Publication No. WO2021 / 006097 can be used.

[0425] The transmittance of the laminate that is closer to the visual recognition side than the display element is preferably less than 1% at a wavelength of 380 nm, 20-70% at 410 nm, and more than 90% in the range above 450 nm.

[0426] The transmittance at a wavelength of 410 nm is further preferably 40-50%.

[0427] Example

[0428] The following examples and comparative examples further illustrate the features of the present invention. Regarding the materials, amounts, proportions, processing contents, and processing steps shown in the following examples, appropriate modifications can be made without departing from the spirit of the invention. Therefore, the scope of the present invention should not be interpreted as limited by the specific examples shown below.

[0429] <Example 1>

[0430] (Preparation of cellulose acylated membranes)

[0431] The following composition was added to a mixing vessel and stirred, then heated at 90°C for 10 minutes. The resulting composition was then filtered through filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm to prepare a concentrated solution. The solids content of the concentrated solution was 23.5% by mass, and the solvent was dichloromethane / methanol / butanol in a mass ratio of 8:1:18:1.

[0432]

[0433] [Chemical Formula 1]

[0434]

[0435] [Chemical Formula 2]

[0436]

[0437] The concentrated liquid prepared in the above manner was cast using a roller film casting machine. After the concentrated liquid was cast from the mold and brought into contact with a metal support cooled to 0°C, the resulting sheet (film) was peeled off. The roller was made of SUS steel.

[0438] After the film obtained from casting is peeled from the rollers, it is dried for 20 minutes at 30–40°C using a tenter frame that clamps both ends of the film and conveys it. Subsequently, the film is post-dried by zone heating while being conveyed by rollers. The resulting film is then knurled and wound up.

[0439] The resulting cellulose acylated membrane has a thickness of 40 μm, an in-plane retardation of 1 nm at a wavelength of 550 nm, and a thickness retardation of 26 nm at a wavelength of 550 nm.

[0440] In this way, an optically anisotropic layer (1a) was made from a cellulose acylate film corresponding to the first optically anisotropic layer.

[0441] After passing the cellulose acylated membrane through a dielectric heating roller at 60°C to raise the membrane surface temperature to 40°C, an alkaline solution of the following composition is applied using a bar coater at a coating rate of 14 ml / m. 2 The coating was applied to the membrane strip and conveyed for 10 seconds beneath a steam-type far-infrared heater manufactured by Noritake Co., Limited, which was heated to 110°C. Then, 3 ml / m² of pure water was similarly coated using a bar coater. 2 Next, after three cycles of water washing based on a jet coating machine and dehydration based on an air knife, the product is conveyed to a drying zone at 70°C for 10 seconds to dry, thereby producing an alkali-saponified cellulose acylate membrane.

[0442]

[0443]

[0444] (Formation of the orientation film)

[0445] Using a #14 wire rod, the following orientation film coating solution 1 was continuously coated onto the alkali-saponified surface of the cellulose acylate membrane. Then, the resulting coating was dried with warm air at 60°C for 60 seconds, and then dried with warm air at 100°C for 120 seconds to obtain the orientation film 1.

[0446]

[0447] (Modified polyvinyl alcohol)

[0448] [Chemical Formula 3]

[0449]

[0450] (Formation of the optical anisotropic layer (1b))

[0451] The oriented film 1, produced in the above manner, was continuously subjected to friction treatment. At this time, the length direction of the elongated film (cellulose acylated film) was parallel to the conveying direction, and the angle between the length direction of the film (conveying direction) and the rotation axis of the friction roller was set to 76°. With the length direction of the film (conveying direction) set to 90°, when viewed from the film side and using a positive value to represent the clockwise direction with the film width direction as a reference (0°), the rotation axis of the friction roller was located at -14°. In other words, when viewed from the film side, the position of the rotation axis of the friction roller was 76° clockwise from the length direction of the film.

[0452] Using a die coater, an optical anisotropic layer forming composition (1b) containing a disk-shaped liquid crystal compound with the following composition was coated onto the alignment film that had undergone the above-described friction treatment, thus forming a composition layer. Then, to dry the solvent and ripen the disk-shaped liquid crystal compound, the resulting composition layer was heated with warm air at 110°C for 2 minutes. Next, the resulting composition layer was subjected to UV irradiation (500 mJ / cm²) at 80°C. 2 The orientation of the disk-shaped liquid crystal compound was fixed to form an optical anisotropy layer (1b), which is equivalent to the second optical anisotropy layer.

[0453] The thickness of the optical anisotropic layer (1b) is 1.1 μm. Furthermore, the retardation at a wavelength of 550 nm is 168 nm. It was confirmed that the average tilt angle of the disk-shaped liquid crystal compound relative to the film surface is 90°, and it is perpendicularly oriented relative to the film surface. Moreover, the in-plane slow axis angle of the optical anisotropic layer (1b) is parallel to the rotation axis of the friction roller. If the width direction of the film is set to 0° (counterclockwise in the length direction is set to 90°, and clockwise is set to -90°), then when viewed from the optical anisotropic layer (1b) side, the in-plane slow axis direction of the optical anisotropic layer (1b) is -14°.

[0454]

[0455] Disc-shaped liquid crystal compound 1

[0456] [Chemical Formula 4]

[0457]

[0458] Disc-shaped liquid crystal compound 2

[0459] [Chemical Formula 5]

[0460]

[0461] Orientation film interface orientation agent 1

[0462] [Chemical Formula 6]

[0463]

[0464] Fluorine-containing compound A (in the following formula, a and b represent the content (mass%) of each repeating unit relative to all repeating units, where a represents 90% by mass and b represents 10% by mass).

[0465] [Chemical Formula 7]

[0466]

[0467] Fluorine compound B (the values ​​in each repeating unit represent the content (mass%) relative to all repeating units; the content of the repeating unit on the left is 32.5% by mass, and the content of the repeating unit on the right is 67.5% by mass).

[0468] [Chemical Formula 8]

[0469]

[0470] Fluorine compound C (the values ​​in each repeating unit represent the content (mass%) relative to all repeating units; the content of the repeating unit on the left is 25% by mass, the content of the repeating unit in the middle is 25% by mass, and the content of the repeating unit on the right is 50% by mass).

[0471] [Chemical Formula 9]

[0472]

[0473] Through the above steps, a laminate (1a-1b) consisting of an optical anisotropic layer (1a) and an optical anisotropic layer (1b) was fabricated.

[0474] (Formation of the optical anisotropic layer (1d))

[0475] Using a die coater, an optical anisotropic layer forming composition containing a rod-shaped liquid crystal compound with the following composition was coated onto the cellulose acylate film prepared above (1d), forming a composition layer. Then, holding both ends of the film, a cooling plate (9°C) was placed on the side of the film where the coating was formed, with a distance of 5 mm between the cooling plate and the film, and a heater (75°C) was placed on the opposite side of the film where the coating was formed, with a distance of 5 mm between the heater and the film, and the film was dried for 2 minutes.

[0476] Next, the resulting membrane was heated at 60°C for 1 minute under warm air, while nitrogen purging was performed to bring the oxygen concentration to below 100 ppm by volume, and the membrane was irradiated with a 365nm UV-LED at an irradiation dose of 100 mJ / cm². 2 The ultraviolet light was then used to anneal the resulting coating at 120°C for 1 minute with warm air, thereby forming an optical anisotropic layer (1d) corresponding to the fourth optical anisotropic layer.

[0477] At room temperature, the obtained optical anisotropic layer (1d) was irradiated with UV light (ultra-high pressure mercury lamp; UL750; manufactured by HOYA) passing through a wire grating polarizer, producing a light intensity of 7.9 mJ / cm². 2 (Wavelength: 313nm), thus forming a composition layer with orientation control capability on the surface.

[0478] Furthermore, the thickness of the formed optically anisotropic layer (1d) is 0.6 μm. The in-plane retardation Re at 550 nm is 0 nm, and the thickness-direction retardation Rth at 550 nm is -75 nm. It was confirmed that the average tilt angle of the long axis of the rod-shaped liquid crystal compound relative to the film surface is 90°, and it is perpendicular to the film surface.

[0479]

[0480]

[0481] Rod-shaped liquid crystal compound (A) (The following is a mixture of compounds)

[0482] [Chemical Formula 10]

[0483]

[0484] Polymerization initiator S-1

[0485] [Chemical Formula 11]

[0486]

[0487] Photoacid generator D-1

[0488] [Chemical Formula 12]

[0489]

[0490] Polymer M-1

[0491] [Chemical Formula 13]

[0492]

[0493] Vertical Orientation Agent S01

[0494] [Chemical Formula 14]

[0495]

[0496] Photooriented polymer A-1 (The values ​​listed in each repeating unit represent the content (mass%) of each repeating unit relative to all repeating units, starting from the repeating units on the left: 43 mass%, 27 mass%, and 30 mass%. The weight-average molecular weight is 69,800.)

[0497] [Chemical Formula 15]

[0498]

[0499] Surfactant B-1 (weight-average molecular weight 2200).

[0500] [Chemical Formula 16]

[0501]

[0502] (Formation of the optical anisotropic layer (1c))

[0503] Next, using a die coater, an optical anisotropic layer forming composition (1c) containing a rod-shaped liquid crystal compound with the following composition was coated onto the optical anisotropic layer (1d) prepared above, and heated with warm air at 80°C for 60 seconds. Then, the resulting composition layer was subjected to UV irradiation (500 mJ / cm²) at 80°C. 2 The orientation of the liquid crystal compound is fixed, forming an optical anisotropy layer (1c) that is equivalent to the third optical anisotropy layer.

[0504] The thickness of the optical anisotropic layer (1c) is 1.2 μm, the Δnd at a wavelength of 550 nm is 164 nm, and the twist angle of the liquid crystal compound is 81°. If the width direction of the film is set to 0° (and the length direction is set to 90°), then when viewed from the optical anisotropic layer (1c) side, the angle on the air side in the in-plane slow axis direction (the orientation axis angle of the liquid crystal compound) is 14°, and the angle on the side in contact with the optical anisotropic layer (1d) is 95°.

[0505] In addition, the in-plane slow axis direction of the optical anisotropic layer is based on the width direction of the substrate (0°). When viewing the substrate from the surface side of the optical anisotropic layer, clockwise (right turn) indicates negative and counterclockwise (left turn) indicates positive.

[0506]

[0507] Left-handed tortuous chiral reagent (L1) (Bu represents butyl.)

[0508] [Chemical Formula 17]

[0509]

[0510] Through the above steps, a laminate (1c-1d) was fabricated by directly stacking an optically anisotropic layer (1d) and an optically anisotropic layer (1c) on a strip-shaped cellulose acylate membrane. The refractive index difference between the average refractive index of the optically anisotropic layer (1c) and the average refractive index of the optically anisotropic layer (1d) is within 0.05.

[0511] With the angle between the in-plane slow axis of the optical anisotropic layer (1b) and the in-plane slow axis of the surface side of the optical anisotropic layer (1c) being 0°, a UV-curable adhesive was used to continuously bond the surface side of the optical anisotropic layer (1b) formed on the optical anisotropic layer (1a) made of the elongated cellulose acylate film prepared above and the surface side of the optical anisotropic layer (1c-1d) formed on the elongated cellulose acylate film prepared above.

[0512] Furthermore, as a UV-curable adhesive, an adhesive with a high-refractive-index monomer added to an acrylic compound was used, and the refractive index after curing was controlled at 1.58. The refractive index difference between the average refractive index of the optical anisotropic layer adjacent to the adhesive layer and the average refractive index of the adhesive layer is within 0.05.

[0513] Next, the cellulose acylate film on the optical anisotropic layer (1d) side is peeled off, exposing the surface of the optical anisotropic layer (1d) that is in contact with the cellulose acylate film. In this way, an optical film (1a-1b-1c-1d) is obtained, on which an optical anisotropic layer (1a) made of a strip-shaped cellulose acylate film is sequentially stacked with an optical anisotropic layer (1b), an optical anisotropic layer (1c), and an optical anisotropic layer (1d).

[0514] (Fabrication of linear polarizers)

[0515] The surface of the support for the cellulose triacetate membrane TJ25 (manufactured by FUJIFILM Corporation: 25 μm thickness) was subjected to alkali saponification treatment. Specifically, the support was immersed in a 1.5-fold specified sodium hydroxide aqueous solution at 55°C for 2 minutes, then washed in a water bath at room temperature, and neutralized with 0.1-fold specified sulfuric acid at 30°C. After neutralization, the support was washed in a water bath at room temperature and then dried with warm air at 100°C to obtain the polarizer protective film.

[0516] A 60 μm thick roll-shaped polyvinyl alcohol (PVA) film was continuously stretched along its length in an iodine aqueous solution and then dried to obtain a 13 μm thick polarizer. The transmittance of the polarizer's visibility-corrected monomer was 43%. At this point, the absorption axis of the polarizer was aligned with its length.

[0517] A linear polarizer was fabricated by attaching the polarizer protective film to one side of the polarizer using the PVA adhesive described below.

[0518] (Preparation of PVA adhesive)

[0519] The PVA adhesive was prepared as follows: 100 parts by mass of polyvinyl alcohol resin with acetylacetyl groups (average degree of polymerization: 1200, degree of saponification: 98.5 mol%, degree of acetylacetylation: 5 mol%) and 20 parts by mass of hydroxymethyl melamine were dissolved in pure water at a temperature of 30°C, and the concentration of solid components was adjusted to 3.7% by mass in the aqueous solution.

[0520] (Fabrication of a circular polarizer)

[0521] Using a UV-curable adhesive, the surface of the optical anisotropy layer (1a) of the strip-shaped optical film (1a-1b-1c-1d) prepared above is continuously bonded to the surface of the polarizer of the strip-shaped linear polarizer prepared above (the side opposite to the polarizer protective film).

[0522] In this manner, a circular polarizer (P1) was fabricated using optical films (1a-1b-1c-1d) and linear polarizers. At this time, a polarizer protective film, a polarizer, an optical anisotropic layer (1a), an optical anisotropic layer (1b), an optical anisotropic layer (1c), and an optical anisotropic layer (1d) are sequentially stacked. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1b) is 76°. Furthermore, the angle between the in-plane slow axis of the optical anisotropic layer (1b) and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1b) is 0°. The twist angle of the liquid crystal compound in the optical anisotropic layer (1c) is 81°. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1d) is 5°.

[0523] <Example 2>

[0524] Similar to Example 1 above, a long strip of cellulose acylate film was prepared. The orientation film coating solution 2 with the following composition was continuously coated onto the alkali-saponified surface using a #14 wire rod. The resulting coating film was dried with warm air at 60°C for 60 seconds, and then dried with warm air at 100°C for 120 seconds to obtain the orientation film 2.

[0525]

[0526] Polyvinyl alcohol

[0527] [Chemical Formula 18]

[0528]

[0529] (Formation of the optical anisotropic layer (2a))

[0530] Using a die coater, an optical anisotropic layer forming composition (2a) containing a disk-shaped liquid crystal compound with the following composition was coated onto the alignment film 2, forming a composition layer. Then, to dry the solvent and ripen the disk-shaped liquid crystal compound, the resulting composition layer was heated with warm air at 110°C for 2 minutes. Next, the resulting composition layer was subjected to UV irradiation (500 mJ / cm²) at 80°C. 2 The orientation of the liquid crystal compound is fixed, forming an optical anisotropy layer (2a) that is equivalent to the first optical anisotropy layer.

[0531] The thickness of the optical anisotropic layer (2a) is 0.3 μm. Furthermore, the in-plane retardation at 550 nm is 0 nm, and the thickness-direction retardation at 550 nm is 40 nm. It was confirmed that the average tilt angle of the disk-shaped liquid crystal compound relative to the film surface is 0°, and that it is horizontally oriented relative to the film surface.

[0532]

[0533] Polymer (A) (where the values ​​recorded in each repeating unit represent the content (mass%) of each repeating unit relative to all repeating units.)

[0534] [Chemical Formula 19]

[0535]

[0536] (Formation of the optical anisotropic layer (1b))

[0537] The optical anisotropic layer (2a) fabricated as described above was continuously subjected to friction treatment. At this time, the length direction of the elongated film was parallel to the conveying direction, and the angle between the length direction of the film (conveying direction) and the rotation axis of the friction roller was set to 76°. With the length direction of the film (conveying direction) set to 90°, when viewed from the film side and using a positive value to represent the clockwise direction with the film width direction as a reference (0°), the rotation axis of the friction roller was located at -14°. In other words, the position of the rotation axis of the friction roller was the position of rotating 76° clockwise with the length direction of the film as a reference.

[0538] Using a die coater, the aforementioned optical anisotropic layer forming composition (1b) was coated onto the aforementioned friction-treated optical anisotropic layer (2a), forming a composition layer. Then, to dry the solvent and ripen the orientation of the disk-shaped liquid crystal compound, the resulting composition layer was heated with warm air at 110°C for 2 minutes. Next, the resulting composition layer was subjected to UV irradiation (500 mJ / cm²) at 80°C. 2 The orientation of the liquid crystal compound is fixed, forming an optical anisotropy layer (1b) that is equivalent to the second optical anisotropy layer.

[0539] The thickness of the optical anisotropic layer (1b) is 1.1 μm. Furthermore, the retardation at a wavelength of 550 nm is 168 nm. It was confirmed that the average tilt angle of the disk-shaped liquid crystal compound relative to the film surface is 90°, and it is perpendicularly oriented relative to the film surface. Moreover, the in-plane slow axis angle of the optical anisotropic layer (1b) is parallel to the rotation axis of the friction roller. If the width direction of the film is set to 0° (counterclockwise in the length direction is set to 90°, and clockwise is set to -90°), then when viewed from the optical anisotropic layer (1b) side, the in-plane slow axis direction of the optical anisotropic layer (1b) is -14°.

[0540] Through the above steps, a laminate (2a-1b) was fabricated, in which an optically anisotropic layer (2a) and an optically anisotropic layer (1b) are stacked on a cellulose acylate membrane. The refractive index difference between the average refractive index of the optically anisotropic layer (2a) and the average refractive index of the optically anisotropic layer (1b) is within 0.05.

[0541] With the angle between the in-plane slow axis of the optical anisotropic layer (1b) and the in-plane slow axis of the surface side of the optical anisotropic layer (1c) being 0°, a UV-curable adhesive was used to continuously bond the surface side of the optical anisotropic layer (1b) of the laminate (2a-1b) formed on the elongated cellulose acylate film prepared above to the surface side of the optical anisotropic layer (1c) of the laminate (1c-1d) formed on the elongated cellulose acylate film prepared in Example 1.

[0542] Furthermore, as a UV-curable adhesive, an adhesive with a high-refractive-index monomer added to an acrylic compound was used, and the refractive index after curing was controlled at 1.58. The refractive index difference between the average refractive index of the optical anisotropic layer adjacent to the adhesive layer and the average refractive index of the adhesive layer is within 0.05.

[0543] Next, the cellulose acylate film and the alignment film 2 on the optical anisotropic layer (2a) side are peeled off, exposing the surface of the optical anisotropic layer (2a) that is in contact with the alignment film 2. In this way, an optical film (2a-1b-1c-1d) is obtained, in which an optical anisotropic layer (1d), an optical anisotropic layer (1c), an optical anisotropic layer (1b), and an optical anisotropic layer (2a) are sequentially stacked on a strip-shaped cellulose acylate film.

[0544] (Fabrication of a circular polarizer)

[0545] Using a UV-curable adhesive that controls the refractive index to 1.53 after curing, the surface of the optical anisotropic layer (2a) of the strip-shaped optical film (2a-1b-1c-1d) prepared above was continuously bonded to the surface of the polarizer (the side opposite to the polarizer protective film) of the strip-shaped linear polarizer prepared in Example 1. The refractive index difference between the average refractive index of adjacent optical anisotropic layers and the average refractive index of the adhesive layer is 0.08 or less.

[0546] Next, the cellulose acylate film on the optical anisotropic layer (1d) side is peeled off, exposing the surface of the optical anisotropic layer (1d) that is in contact with the cellulose acylate film.

[0547] In this manner, a circular polarizer (P2) was fabricated using an optical film (2a-1b-1c-1d) and a linear polarizer. At this point, a polarizer protective film, a polarizer, an optical anisotropic layer (2a), an optical anisotropic layer (1b), an optical anisotropic layer (1c), and an optical anisotropic layer (1d) are sequentially stacked. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1b) is 76°. The angle between the in-plane slow axis of the optical anisotropic layer (1b) and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1b) is 0°. The twist angle of the liquid crystal compound in the optical anisotropic layer (1c) is 81°. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1d) is 5°.

[0548] <Example 3>

[0549] (Formation of the optical anisotropy layer (3a))

[0550] In the formation of the optical anisotropic layer (1d) in Example 1, in addition to changing the thickness of the composition layer, an optical anisotropic layer (3a) with orientation control capability on the surface, equivalent to the first optical anisotropic layer, was also formed.

[0551] Furthermore, the thickness of the formed optical anisotropic layer (3a) is 0.4 μm. The in-plane retardation at a wavelength of 550 nm is 0 nm, and the thickness direction retardation at a wavelength of 550 nm is -45 nm. It was confirmed that the average tilt angle of the long axis of the rod-shaped liquid crystal compound relative to the film surface is 90°, and it is perpendicular to the film surface.

[0552] (Formation of the optical anisotropic layer (3b))

[0553] Next, using a die coater, an optical anisotropic layer forming composition (3b) containing a rod-shaped liquid crystal compound with the following composition was coated onto the optical anisotropic layer (3a) prepared above, and heated with warm air at 80°C for 60 seconds. Then, the resulting composition layer was subjected to UV irradiation (500 mJ / cm²) at 80°C. 2 The orientation of the liquid crystal compound is fixed, forming an optical anisotropy layer (3b) that is equivalent to the second optical anisotropy layer.

[0554] The thickness of the optical anisotropic layer (3b) is 1.2 μm. Furthermore, the in-plane retardation at a wavelength of 550 nm is 168 nm. It was confirmed that the average tilt angle of the long axis of the rod-shaped liquid crystal compound relative to the film surface is 0°, and it is horizontally oriented (uniformly oriented) relative to the film surface. Moreover, if the width direction of the film is set to 0° (counterclockwise in the length direction is set to 90°, and clockwise to -90°), then when viewed from the optical anisotropic layer (3b) side, the in-plane slow axis direction of the optical anisotropic layer (3b) is 104°.

[0555]

[0556]

[0557] Through the above steps, a laminate (3a-3b) was fabricated in which an optically anisotropic layer (3a) and an optically anisotropic layer (3b) are directly stacked on a strip-shaped cellulose acylate membrane. The refractive index difference between the average refractive index of the optically anisotropic layer (3a) and the average refractive index of the optically anisotropic layer (3b) is within 0.05.

[0558] Furthermore, when the surface of the optical anisotropic layer (3a) in contact with the optical anisotropic layer (3b) is confirmed by the above method, the presence of a photo-oriented polymer can be confirmed.

[0559] (Formation of the optical anisotropic layer (3d))

[0560] In the formation of the optical anisotropic layer (2a) in Example 2, an optical anisotropic layer (3d) corresponding to the fourth optical anisotropic layer was formed in the same way, except that the thickness of the composition layer was changed.

[0561] The thickness of the optical anisotropic layer (3a) is 0.4 μm. Furthermore, the in-plane retardation at 550 nm is 0 nm, and the thickness-direction retardation at 550 nm is 55 nm. It was confirmed that the average tilt angle of the disk-shaped liquid crystal compound relative to the film surface is 0°, and that it is horizontally oriented relative to the film surface.

[0562] (Formation of the optical anisotropic layer (3c))

[0563] The optical anisotropic layer (3d) fabricated as described above was continuously subjected to friction treatment. At this time, the length direction of the elongated film is parallel to the conveying direction, and the angle formed between the length direction of the film (conveying direction) and the rotation axis of the friction roller is set to 85°. Setting the length direction of the film (conveying direction) to 90°, and viewing from the film side, if a positive value is represented by clockwise rotation with the film width direction as the reference (0°), then the rotation axis of the friction roller is 5°. In other words, the position of the rotation axis of the friction roller is 85° counterclockwise from the length direction of the film.

[0564] Using a die coater, the optical anisotropic layer forming composition (3c) described below was coated onto the above-mentioned friction-treated optical anisotropic layer (3d), forming a composition layer. Then, to dry the solvent and ripen the disk-shaped liquid crystal compound, the resulting composition layer was heated with warm air at 110°C for 2 minutes. Next, the resulting composition layer was subjected to UV irradiation (500 mJ / cm²) at 80°C. 2 The orientation of the liquid crystal compound is fixed, forming an optical anisotropy layer (3c) that is equivalent to the third optical anisotropy layer.

[0565] The thickness of the optical anisotropic layer (3c) is 1.1 μm, the Δnd at a wavelength of 550 nm is 164 nm, and the twist angle of the liquid crystal compound is 81°. If the width direction of the film is set to 0° (and the length direction to 90°), then when viewed from the optical anisotropic layer (3c) side, the angle on the air side in the in-plane slow axis direction is 76°, and the angle on the side in contact with the optical anisotropic layer (3d) is -5°.

[0566] In addition, the in-plane slow axis direction of the optical anisotropic layer is referenced to the width direction of the substrate (0°). When observing the circular polarizer from the surface side of the optical anisotropic layer, clockwise (right turn) indicates negative and counterclockwise (left turn) indicates positive.

[0567]

[0568] Right-handed tortuous chiral reagent (L2)

[0569] [Chemical Formula 20]

[0570]

[0571] Through the above steps, a laminate (3c-3d) was fabricated by stacking an optically anisotropic layer (3d) and an optically anisotropic layer (3c) on a cellulose acylate membrane. The refractive index difference between the average refractive index of the optically anisotropic layer (3c) and the average refractive index of the optically anisotropic layer (3d) is within 0.05.

[0572] With the angle between the in-plane slow axis of the optical anisotropic layer (3b) and the in-plane slow axis of the surface side of the optical anisotropic layer (3c) being 0°, a UV-curable adhesive was used to continuously bond the surface side of the optical anisotropic layer (3b) of the laminate (3a-3b) formed on the elongated cellulose acylate film prepared above and the surface side of the optical anisotropic layer (3c-3d) formed on the elongated cellulose acylate film prepared above.

[0573] Furthermore, as a UV-curable adhesive, an adhesive with a high-refractive-index monomer added to an acrylic compound was used, and the refractive index after curing was controlled at 1.58. The refractive index difference between the average refractive index of the optical anisotropic layer adjacent to the adhesive layer and the average refractive index of the adhesive layer is within 0.05.

[0574] Next, the cellulose acylate film on the optical anisotropic layer (3a) side is peeled off, exposing the surface of the optical anisotropic layer (3a) that is in contact with the cellulose acylate film. In this way, an optical film (3a-3b-3c-3d) is obtained, in which an optical anisotropic layer (3d), an optical anisotropic layer (3c), an optical anisotropic layer (3b), and an optical anisotropic layer (3a) are sequentially stacked on a strip-shaped cellulose acylate film.

[0575] (Fabrication of a circular polarizer)

[0576] Using a UV-curable adhesive that controls the refractive index to 1.53 after curing, the surface of the optical anisotropic layer (3a) of the strip-shaped optical film (3a-3b-3c-3d) prepared above was continuously bonded to the surface of the polarizer of the strip-shaped linear polarizer prepared in Example 1 (the side opposite to the polarizer protective film). The refractive index difference between the average refractive index of adjacent optical anisotropic layers and the average refractive index of the adhesive layer is 0.08 or less.

[0577] Next, the cellulose acylate film on the optical anisotropic layer (3d) side is peeled off, exposing the surface of the optical anisotropic layer (3d) that is in contact with the cellulose acylate film.

[0578] In this manner, a circular polarizer (P3) was fabricated using optical films (3a-3b-3c-3d) and linear polarizers. At this point, a polarizer protective film, a polarizer, an optical anisotropic layer (3a), an optical anisotropic layer (3b), an optical anisotropic layer (3c), and an optical anisotropic layer (3d) are sequentially stacked. The angle between the absorption axis of the polarizer and the slow axis of the optical anisotropic layer (3b) is 14°. The angle between the in-plane slow axis of the optical anisotropic layer (3b) and the in-plane slow axis of the optical anisotropic layer (3c) on the surface of the optical anisotropic layer (3b) is 0°. The twist angle of the liquid crystal compound in the optical anisotropic layer (3c) is 81°. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (3c) on the surface of the optical anisotropic layer (3d) is 95°.

[0579] In the circular polarizer (P3), when the circular polarizer (P3) is observed from the optical anisotropic layer side, with the absorption axis of the polarizer as the reference, the in-plane slow axis of the optical anisotropic layer (3b) is rotated counterclockwise by 14°, and the twisting direction of the liquid crystal compound in the optical anisotropic layer (3c) is clockwise.

[0580] Furthermore, when observing the circular polarizer (P3) from the optical anisotropic layer side, the twisting direction of the liquid crystal compound is determined to be clockwise or counterclockwise based on the in-plane slow axis on the surface of the optical anisotropic layer (3d) side (the surface directly in front) of the optical anisotropic layer (3c).

[0581] <Example 4>

[0582] (Formation of the optical anisotropy layer (4a))

[0583] Using a die coater, an optical anisotropic layer forming composition (4a) containing a disk-shaped liquid crystal compound with the following composition was coated onto a cellulose triacetate membrane TG40 (manufactured by FUJIFILM Corporation: 40 μm thick), forming a composition layer. Then, holding both ends of the membrane, a cooling plate (9°C) was placed on the side of the membrane where the coating was formed, with a distance of 5 mm between the cooling plate and the membrane, and a heater (110°C) was placed on the opposite side of the membrane where the coating was formed, with a distance of 5 mm between the heater and the membrane, and the membrane was dried for 90 seconds.

[0584] Next, the resulting membrane was heated at 116°C for 1 minute under warm air, while nitrogen purging was performed to bring the oxygen concentration to below 100 ppm by volume, and the membrane was irradiated with a 365nm UV-LED at an irradiation dose of 150 mJ / cm². 2 The ultraviolet light was then used to anneal the resulting coating at 115°C for 25 seconds with warm air, thereby forming an optical anisotropic layer (4a) corresponding to the first optical anisotropic layer.

[0585] At room temperature, the obtained optical anisotropic layer (4a) was irradiated with UV light (ultra-high pressure mercury lamp; UL750; manufactured by HOYA) passing through a wire grating polarizer, producing a light intensity of 7.9 mJ / cm². 2 (Wavelength: 313nm), thus giving the surface the ability to control orientation.

[0586] Furthermore, the thickness of the formed optical anisotropic layer (4a) is 1.0 μm. The in-plane retardation Re at a wavelength of 550 nm is 0 nm, and the thickness-direction retardation Rth at a wavelength of 550 nm is 40 nm. It was confirmed that the average tilt angle of the disk-shaped liquid crystal compound relative to the film surface is 0°, and it is horizontally oriented relative to the film surface.

[0587]

[0588]

[0589] Disc-shaped liquid crystal compound 3

[0590] [Chemical Formula 21]

[0591]

[0592] Polymerizable monomer 1

[0593] [Chemical Formula 22]

[0594]

[0595] Photooriented polymer A-2 (the letters in each repeating unit indicate the content (mass%) of each repeating unit relative to all repeating units, starting from the left-hand repeating unit: 37 mass%, 37 mass%, 26 mass%. The weight-average molecular weight is 73,000.)

[0596] [Chemical Formula 23]

[0597]

[0598] (Formation of the optical anisotropic layer (4b))

[0599] Next, using a die coater, an optical anisotropic layer forming composition (4b) containing a disk-shaped liquid crystal compound with the following composition was coated onto the optical anisotropic layer (4a) prepared above, and heated with warm air at 95°C for 120 seconds. Then, the resulting composition layer was subjected to UV irradiation (100 mJ / cm²) at 95°C. 2 The orientation of the liquid crystal compound is fixed, forming an optical anisotropy layer (4b) that is equivalent to the second optical anisotropy layer.

[0600] The thickness of the optical anisotropic layer (4b) is 1.5 μm, and the Δnd at a wavelength of 550 nm is 153 nm. The average tilt angle of the disk surface of the disk-shaped liquid crystal compound relative to the film surface was confirmed to be 90°, and it is perpendicular to the film surface.

[0601] Furthermore, the angle of the in-plane slow axis of the optical anisotropic layer (4b) is parallel to the rotation axis of the friction roller. If the width direction of the film is set to 0° (the counterclockwise direction of the length direction is set to 90° and the clockwise direction is set to -90°), then when viewed from the side of the optical anisotropic layer (4b), the in-plane slow axis direction of the optical anisotropic layer (4b) is -14°.

[0602]

[0603] Fluorine compound D (the values ​​in each repeating unit represent the content (mass%) relative to all repeating units; the content of the repeating unit on the left is 52% by mass, and the content of the repeating unit on the right is 48% by mass).

[0604] [Chemical Formula 24]

[0605]

[0606] Fluorine compound E (the content of the repeating unit on the left is 36% by mass, and the content of the repeating unit on the right is 64% by mass).

[0607] [Chemical Formula 25]

[0608]

[0609] Defoamer 1

[0610] [Chemical Formula 26]

[0611]

[0612] Through the above steps, a laminate (4a-4b) was prepared by directly stacking an optically anisotropic layer (4a) and an optically anisotropic layer (4b) on a cellulose acylate membrane TG40.

[0613] The difference in refractive index between the average refractive index of the optical anisotropic layer (4a) and the average refractive index of the optical anisotropic layer (4b) is less than 0.05.

[0614] (Formation of the optical anisotropic layer (4d))

[0615] In the formation of the optical anisotropic layer (1d) in Example 1, an optical anisotropic layer (4d) corresponding to the fourth optical anisotropic layer was formed in the same way, except that the thickness of the composition layer was changed.

[0616] Furthermore, the thickness of the formed optically anisotropic layer (4d) is 0.7 μm. The in-plane retardation Re at 550 nm is 0 nm, and the thickness-direction retardation Rth at 550 nm is -85 nm. It was confirmed that the average tilt angle of the long axis of the rod-shaped liquid crystal compound relative to the film surface is 90°, and it is perpendicular to the film surface.

[0617] (Formation of the optical anisotropic layer (4c))

[0618] Next, when forming the optical anisotropic layer (1c) of Example 1 on the optical anisotropic layer (4d) prepared above, the optical anisotropic layer (4c) corresponding to the third optical anisotropic layer is formed in the same way, except that the thickness of the composition layer is changed.

[0619] The thickness of the optical anisotropic layer (4c) is 1.25 μm, the Δnd at a wavelength of 550 nm is 170 nm, and the twist angle of the liquid crystal compound is 85°. If the width direction of the film is set to 0° (and the length direction is set to 90°), then when viewed from the optical anisotropic layer (4c) side, the angle on the air side in the in-plane slow axis direction (the orientation axis angle of the liquid crystal compound) is 10°, and the angle on the side in contact with the optical anisotropic layer (4d) is 95°.

[0620] In addition, the in-plane slow axis direction of the optical anisotropic layer is based on the width direction of the substrate (0°). When viewing the substrate from the surface side of the optical anisotropic layer, clockwise (right turn) indicates negative and counterclockwise (left turn) indicates positive.

[0621] Through the above steps, a laminate (4c-4d) was fabricated by directly stacking an optically anisotropic layer (4d) and an optically anisotropic layer (4c) on a strip-shaped cellulose acylate membrane. The refractive index difference between the average refractive index of the optically anisotropic layer (4c) and the average refractive index of the optically anisotropic layer (4d) is within 0.05.

[0622] With the in-plane slow axis relative to the surface side of the optically anisotropic layer (4c) of the laminate (4c-4d) being +4°, the surface side of the optically anisotropic layer (4b) of the laminate (4a-4b) and the surface side of the optically anisotropic layer (4c) of the laminate (4c-4d) formed on the cellulose acylate film TG40 prepared above are continuously bonded together using a UV-curable adhesive.

[0623] In addition, the in-plane slow axis direction of the optical anisotropic layer is based on the width direction of the substrate (0°). When observing the stack from the surface side of the optical anisotropic layer (4a), clockwise (right turn) indicates negative and counterclockwise (left turn) indicates positive.

[0624] As a UV-curable adhesive, this adhesive utilizes a high-refractive-index monomer added to an acrylic compound, with the cured refractive index controlled at 1.58. The refractive index difference between the average refractive index of the optical anisotropic layer adjacent to the adhesive layer and the average refractive index of the adhesive layer is within 0.05.

[0625] Next, the cellulose acylate film and the optical anisotropic layer (4a) on the optical anisotropic layer (4a) side are peeled off, exposing the surface of the optical anisotropic layer (4a) that is in contact with the cellulose acylate film. In this way, an optical film (4a-4b-4c-4d) is obtained, in which optical anisotropic layers (4d), (4c), (4b), and (4a) are sequentially stacked on a strip-shaped cellulose acylate film.

[0626] (Fabrication of a circular polarizer)

[0627] Using a UV-curable adhesive with a cured refractive index controlled at 1.53 using the same method as described above, the surface of the optical anisotropic layer (4a) of the strip-shaped optical film (4a-4b-4c-4d) prepared above was continuously bonded to the surface of the polarizer of the strip-shaped linear polarizer prepared in Example 1 (the side opposite to the polarizer protective film). The refractive index difference between the average refractive index of adjacent optical anisotropic layers and the average refractive index of the adhesive layer is 0.08 or less.

[0628] Next, the cellulose acylate film on the optical anisotropic layer (4d) side is peeled off, exposing the surface of the optical anisotropic layer (4d) that is in contact with the cellulose acylate film.

[0629] In this manner, a circular polarizer (P4) was fabricated using optical films (4a-4b-4c-4d) and linear polarizers. At this point, a polarizer protective film, a polarizer, an optical anisotropic layer (4a), an optical anisotropic layer (4b), an optical anisotropic layer (4c), and an optical anisotropic layer (4d) are sequentially stacked. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (4b) is 76°. The angle between the in-plane slow axis of the optical anisotropic layer (4b) and the in-plane slow axis of the optical anisotropic layer (4c) on the surface of the optical anisotropic layer (4b) is 4°. The twist angle of the liquid crystal compound in the optical anisotropic layer (4c) is 85°. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (4c) on the surface of the optical anisotropic layer (4d) is 5°.

[0630] <Example 5>

[0631] The optical anisotropic layer (1a), which is made of a cellulose acylate film equivalent to the first optical anisotropic layer of Example 1, was replaced with cellulose acetate TJ25 (manufactured by FUJIFILM Corporation: 25 μm thick) (optical anisotropic layer (5a)). Otherwise, optical anisotropic layers (1b), (1c), (1d) and a circular polarizer were fabricated by the same method as in Example 1.

[0632] <Example 6>

[0633] The optical anisotropic layer (1a) made of a cellulose acylate film equivalent to the first optical anisotropic layer of Example 1 was replaced with the following optical anisotropic layer (6a). Otherwise, the optical anisotropic layer (1b), optical anisotropic layer (1c), optical anisotropic layer (1d) and circular polarizer were fabricated by the same method as in Example 1.

[0634] (Preparation of cellulose acylated membranes)

[0635] The following composition was added to a mixing vessel and stirred, then heated at 90°C for 10 minutes. The resulting composition was then filtered through filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm to prepare a concentrated solution. The solids content of the concentrated solution was 19.0% by mass, and the solvent was dichloromethane / methanol = 87 / 13 (mass ratio).

[0636]

[0637] Polarizer durability improver

[0638] [Chemical Formula 27]

[0639]

[0640] UV absorber

[0641] [Chemical Formula 28]

[0642]

[0643] Delay enhancer

[0644] [Chemical Formula 29]

[0645]

[0646] The concentrated liquid prepared as described above was cast using a belt film casting machine. After the concentrated liquid was cast from the die and brought into contact with a metal support set at 20°C, the resulting sheet (film) was peeled off. The belt material was made of SUS.

[0647] After the film obtained by casting was peeled from the tape with a solvent content of about 20% by mass, it was dried while being stretched laterally by 1.1 times while conveying the film, with a residual solvent content of 3-15%. Then, it was further dried by conveying it between the rollers of a heat treatment device to produce a cellulose acylated film with a thickness of 25 μm.

[0648] The resulting cellulose acylated film has an in-plane retardation of 1 nm at a wavelength of 550 nm and a thickness retardation of 30 nm at a wavelength of 550 nm.

[0649] <Example 7>

[0650] Using adhesive A described below instead of the UV-curable adhesive used in Example 6, optical anisotropic layers (6a), (1b), (1c), (1d), and a circular polarizer were fabricated from a cellulose acylate film corresponding to the first optical anisotropic layer.

[0651] Using adhesive A, the surface side of the optically anisotropic layer (1b) of the laminate (6a-1b) formed on the elongated cellulose acylate film prepared in Example 6 and the surface side of the optically anisotropic layer (1c-1d) formed on the elongated cellulose acylate film prepared in Example 1 were continuously bonded together with adhesive A in such a way 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) of the laminate (1c-1d) formed on the elongated cellulose acylate film prepared in Example 1 was continuously bonded together with adhesive A.

[0652] The aforementioned adhesive A controls the refractive index to 1.54, forming an adhesive layer with a thickness of 15 μm. The average refractive index difference between the adjacent optical anisotropic layers and the adhesive along the axial direction is within 0.08.

[0653] Next, the cellulose acylate film on the optical anisotropic layer (1d) side is peeled off, exposing the surface of the optical anisotropic layer (1d) that is in contact with the cellulose acylate film. In this way, an optical film (6a-1b-1c-1d) is obtained, on which an optical anisotropic layer (6a) made of a strip-shaped cellulose acylate film is sequentially stacked with an optical anisotropic layer (1b), an optical anisotropic layer (1c), and an optical anisotropic layer (1d).

[0654] (Fabrication of a circular polarizer)

[0655] Using the PVA adhesive described above, the surface of the optical anisotropy layer (6a) of the strip-shaped optical film (6a-1b-1c-1d) prepared above is continuously bonded to the surface of the polarizer of the strip-shaped linear polarizer prepared above (the side opposite to the polarizer protective film).

[0656] In this manner, a circular polarizer (P7) was fabricated using an optical film (6a-1b-1c-1d) and a linear polarizer. At this time, a polarizer protective film, a polarizer, an optical anisotropic layer (6a), an optical anisotropic layer (1b), an optical anisotropic layer (1c), and an optical anisotropic layer (1d) are sequentially stacked. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1b) is 76°. Furthermore, the angle between the in-plane slow axis of the optical anisotropic layer (1b) and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1b) is 0°. The twist angle of the liquid crystal compound in the optical anisotropic layer (1c) is 81°. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1d) is 5°.

[0657] <Example 8>

[0658] Using adhesive B described below instead of the UV-curable adhesive used in Example 6, optical anisotropic layers (6a), (1b), (1c), (1d), and a circular polarizer were made of a cellulose acylate film corresponding to the first optical anisotropic layer.

[0659] Using adhesive B, the surface side of the optically anisotropic layer (1b) of the laminate (6a-1b) formed on the elongated cellulose acylate film prepared in Example 6 and the surface side of the optically anisotropic layer (1c-1d) formed on the elongated cellulose acylate film prepared in Example 1 were continuously bonded together with an adhesive B in such a way 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) of the laminate (1c-1d) formed on the elongated cellulose acylate film prepared in Example 1 was continuously bonded together with an adhesive B.

[0660] The aforementioned adhesive B contains UV-2 as an ultraviolet absorber as described in International Publication No. WO2021 / 006097, and controls the refractive index to 1.54, forming an adhesive layer with a thickness of 25 μm. The average difference between the refractive index of the adjacent optical anisotropic layers and the refractive index of the adhesive along the axial direction is within 0.08.

[0661] Next, the cellulose acylate film on the optical anisotropic layer (1d) side is peeled off, exposing the surface of the optical anisotropic layer (1d) that is in contact with the cellulose acylate film. In this way, an optical film (6a-1b-1c-1d) is obtained, on which an optical anisotropic layer (6a) made of a strip-shaped cellulose acylate film is sequentially stacked with an optical anisotropic layer (1b), an optical anisotropic layer (1c), and an optical anisotropic layer (1d).

[0662] (Fabrication of a circular polarizer)

[0663] Using the PVA adhesive described above, the surface of the optical anisotropy layer (6a) of the strip-shaped optical film (6a-1b-1c-1d) prepared above is continuously bonded to the surface of the polarizer of the strip-shaped linear polarizer prepared above (the side opposite to the polarizer protective film).

[0664] In this manner, a circular polarizer (P7) was fabricated using an optical film (6a-1b-1c-1d) and a linear polarizer. At this time, a polarizer protective film, a polarizer, an optical anisotropic layer (6a), an optical anisotropic layer (1b), an optical anisotropic layer (1c), and an optical anisotropic layer (1d) are sequentially stacked. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1b) is 76°. Furthermore, the angle between the in-plane slow axis of the optical anisotropic layer (1b) and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1b) is 0°. The twist angle of the liquid crystal compound in the optical anisotropic layer (1c) is 81°. The angle between the absorption axis of the polarizer and the in-plane slow axis of the optical anisotropic layer (1c) on the surface of the optical anisotropic layer (1d) is 5°. Furthermore, the transmittance of the circular polarizer (P7) at 380 nm was less than 1%. Additionally, the transmittance was measured using a UV-3150 spectrophotometer manufactured by SHIMADZU CORPORATION.

[0665] <Comparative Example 1>

[0666] Similar to the method described in Example 1 of Japanese Patent No. 5960743, an optical film was prepared in which an optical anisotropic layer (h1) made of a vertically oriented disk-shaped liquid crystal compound and an optical anisotropic layer (h2) made of a twistedly oriented disk-shaped liquid crystal compound were sequentially and directly stacked on a strip-shaped cellulose acylate film.

[0667] At this point, if the in-plane retardation of the optical anisotropic layer (h1) at a wavelength of 550 nm is 181 nm, and the width direction of the film is set to 0° (and the length direction to 90°), then when viewed from the optical anisotropic layer (h1) side, the in-plane slow axis direction is -13°. Furthermore, if the Δnd of the optical anisotropic layer (h2) at a wavelength of 550 nm is 172 nm, the twist angle of the liquid crystal compound is 81°, and the width direction of the film is set to 0° (and the length direction to 90°), then when viewed from the optical anisotropic layer (h2) side, the air side of the in-plane slow axis direction is -94°, and the side in contact with the cellulose acylate film is -13°.

[0668] Using a UV-curable adhesive, the surface of the cellulose acylate film (h1-h2) formed on the elongated cellulose acylate film prepared above is continuously bonded to the surface of the polarizer (the opposite side of the polarizer protective film) of the elongated linear polarizer prepared above. In this way, a circular polarizer (PH) is produced.

[0669] <Fabrication of Organic EL Display Devices>

[0670] (Installed on a display device)

[0671] The GALAXY S4, manufactured by Samsung Electronics Co., Ltd., which is equipped with an organic EL panel, was disassembled, and the circular polarizer was peeled off. The circular polarizers prepared in Examples 1 to 6 and Comparative Example 1 were then attached to the display device using a pressure-sensitive adhesive with the polarizer protective film disposed on the outside.

[0672] <Measurement of Refractive Index>

[0673] Samples were prepared by transferring the optical anisotropic layers used in the various embodiments and comparative examples onto glass using an adhesive. The reflectance spectra of the optical anisotropic layers were measured using a reflectance spectrophotometer FE3000 (manufactured by Otsuka Electronics Co., Ltd.), and the average refractive index was calculated from the obtained reflectance spectra. In calculating the average refractive index, assuming that the refractive indices at the two interfaces of the optical anisotropic layer are equal, the reflectance spectra were fitted to the following Cauchy dispersion using the least squares method to obtain the average refractive index n at a wavelength of 550 nm. Here, C1, C2, and C3 are parameters of the n-Cauchy model, λ is the wavelength, and k is the attenuation coefficient. Furthermore, the thickness of the samples for which the reflectance spectra were measured was measured using a scanning electron microscope (manufactured by Hitachi High-Tech Corporation, S-4800), and this value was used as the thickness during fitting.

[0674] Furthermore, as mentioned above, the average refractive index calculated above is equivalent to the average refractive index ((nx+ny) / 2) expressed by the above formula (N1).

[0675] [Formula 1]

[0676]

[0677] k = 0

[0678] In addition, the average refractive index of the adhesive layer and the bonding agent layer was also measured using the same method as described above.

[0679] [Evaluation of display performance]

[0680] (Front view)

[0681] The fabricated organic EL display device was displayed in black and observed from the front under bright light, and the color was evaluated according to the following criteria. The results are shown in Table 1 below.

[0682] A: The coloring cannot be confirmed at all, or it can be confirmed but very little. (Allowed)

[0683] B: The coloring is confirmed, but the reflected light is low, so there are no problems with its use. (Permitted)

[0684] C: It can be confirmed that the coloring is too strong and the reflected light is too large, so it cannot be allowed.

[0685] (Direction of tilt)

[0686] The fabricated organic EL display device was subjected to a black display, and a fluorescent lamp was projected from a 45° polar angle under bright light. The reflected light was observed from all directions. The azimuth dependence of hue variation was evaluated against the following criteria. The results are shown in Table 1 below.

[0687] A: Color difference cannot be confirmed at all, or it can be confirmed but is very minor. (Permitted)

[0688] B: A slight color difference is noticeable, but it's within acceptable limits. Reflected light is minimal, and there are no issues with use. (Permitted)

[0689] C: The color difference is confirmed, and the reflected light is also large, which is unacceptable.

[0690] [Table 1]

[0691]

[0692] The results shown in Table 1 confirm that the retardation film of the present invention, when used as a circular polarizer in an organic EL display device, can suppress the coloring of black in both the front and tilt directions. On the other hand, the retardation film of the comparative example, when used as a circular polarizer in an organic EL display device, exhibits poor suppression of black coloring in the tilt direction.

[0693] Furthermore, Examples 7 and 8 demonstrate the effects of the present invention in the same way as Example 6.

[0694] Symbol Explanation

[0695] 10A, 10B, 10C, 10D - Phase retardation film; 12A, 12B, 12C, 12D - First optical anisotropic layer; 14A, 14B, 14C, 14D - Second optical anisotropic layer; 16A, 16B, 16C, 16D - Third optical anisotropic layer; 18A, 18B, 18C, 18D - Fourth optical anisotropic layer; 20 - Polarizer; 22 - Adhesive layer; 100A, 100B - Circular polarizer.

Claims

1. A phase retardation film, wherein, It sequentially comprises a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer, and a fourth optical anisotropic layer. The first optical anisotropic layer is a C-plate. The second optical anisotropic layer is plate A. The third optical anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction. The fourth optical anisotropic layer is a C-plate. When the first optical anisotropy layer is a negative C-plate, the second optical anisotropy layer is a negative A-plate, the liquid crystal compound in the third optical anisotropy layer is a rod-shaped liquid crystal compound, and the fourth optical anisotropy layer is a positive C-plate. When the first optical anisotropy layer is a positive C-plate, the second optical anisotropy layer is a positive A-plate, the liquid crystal compound in the third optical anisotropy layer is a disk-shaped liquid crystal compound, and the fourth optical anisotropy layer is a negative C-plate. The angle between the in-plane slow axis of the second optical anisotropy layer and the in-plane slow axis of the third optical anisotropy layer on the surface of the second optical anisotropy layer is in the range of 0 to 30°.

2. The phase retardation film according to claim 1, wherein, The twist angle of the liquid crystal compound is in the range of 80±30°.

3. The phase retardation film according to claim 1 or 2, wherein, The absolute value of the retardation in the thickness direction of the first optical anisotropic layer at a wavelength of 550 nm is 5 to 100 nm.

4. The phase retardation film according to claim 1 or 2, wherein, The second optical anisotropic layer has an in-plane retardation of 120–240 nm at a wavelength of 550 nm.

5. The phase retardation film according to claim 1 or 2, wherein, The product of the refractive index anisotropy Δn of the third optical anisotropy layer at a wavelength of 550 nm and the thickness d of the third optical anisotropy layer, Δnd, is 120–240 nm.

6. The phase retardation film according to claim 1 or 2, wherein, The absolute value of the retardation in the thickness direction of the fourth optical anisotropic layer at a wavelength of 550 nm is 5 to 100 nm.

7. A phase retardation film, wherein, It sequentially comprises a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer, and a fourth optical anisotropic layer. The first optical anisotropic layer is in direct contact with the second optical anisotropic layer or is laminated with an adhesive layer in between. The second optical anisotropic layer is in direct contact with the third optical anisotropic layer or is laminated with an adhesive layer in between. The third optical anisotropic layer is in direct contact with the fourth optical anisotropic layer or is laminated with an adhesive layer in between. The first optical anisotropic layer is a negative C-plate, the second optical anisotropic layer is a negative A-plate, the third optical anisotropic layer is a layer formed by fixing a liquid crystal compound twisted and oriented along a helical axis extending in the thickness direction, and the fourth optical anisotropic layer is a positive C-plate. At least one of the following requirements 1 to 4 must be met: Requirement 1: The difference between the average refractive index of the first optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer side of the first optical anisotropic layer is less than 0.10; Requirement 2: At least one of the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer on the side of the first optical anisotropic layer, and the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer on the side of the third optical anisotropic layer, is 0.10 or less; Requirement 3: At least one of the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the second optical anisotropic layer, and the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the fourth optical anisotropic layer, is 0.10 or less; Requirement 4: The difference between the average refractive index of the fourth optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer side of the fourth optical anisotropic layer is less than 0.

10.

8. A phase retardation film, wherein, It sequentially comprises a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer, and a fourth optical anisotropic layer. The first optical anisotropic layer is a C-plate. The second optical anisotropic layer is plate A. The third optical anisotropic layer is a layer formed by fixing a liquid crystal compound that is twisted and oriented along a helical axis extending in the thickness direction. The fourth optical anisotropic layer is a C-plate. At least one of the first optical anisotropic layer and the second optical anisotropic layer, the second optical anisotropic layer and the third optical anisotropic layer, and the third optical anisotropic layer and the fourth optical anisotropic layer is stacked with an adhesive layer between them. The difference between the average refractive index of the adhesive layer and the average refractive index of the optical anisotropic layer adjacent to the adhesive layer is less than 0.

10.

9. The phase retardation film according to claim 7 or 8, wherein, The second optical anisotropic layer and the third optical anisotropic layer are stacked together with an adhesive layer in between. The difference between the average refractive index of the adhesive layer and the average refractive index of the second optical anisotropic layer is less than 0.

08. The difference between the average refractive index of the adhesive layer and the average refractive index of the third optical anisotropic layer is less than 0.

08.

10. The phase retardation film according to claim 8, wherein, All of the following requirements 1 to 4 must be met: Requirement 1: The difference between the average refractive index of the first optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer side of the first optical anisotropic layer is less than 0.10; Requirement 2: At least one of the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer on the side of the first optical anisotropic layer, and the difference between the average refractive index of the second optical anisotropic layer and the average refractive index of the layer in contact with the surface of the second optical anisotropic layer on the side of the third optical anisotropic layer, is 0.10 or less; Requirement 3: At least one of the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the second optical anisotropic layer, and the difference between the average refractive index of the third optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer on the side of the fourth optical anisotropic layer, is 0.10 or less; Requirement 4: The difference between the average refractive index of the fourth optical anisotropic layer and the average refractive index of the layer in contact with the surface of the third optical anisotropic layer side of the fourth optical anisotropic layer is less than 0.

10.

11. A circular polarizer comprising a polarizer and a phase difference film according to any one of claims 1 to 10.

12. A display device comprising a phase retardation film according to any one of claims 1 to 10.

13. A display device comprising the circular polarizer of claim 11.

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